Fail cleanly when the registry path has no directory

SpotBugs flagged a null passed to Files.createTempFile: the null check guarded
only createDirectories, while the temporary file creation would still have
dereferenced it. The path is resolved absolute so this is practically
unreachable, but bailing out with a log line is cheaper than the latent NPE.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hpa6bjie5qkeNG62y6FmXm

docs/PROJECT_CONTEXT.md

@@ -52,7 +52,7 @@ JavaFX ObservableList / UI state
 
 ## Configuration and Layout Persistence
 
-- The current `preferences.xml` configuration version is 7. Version 6 introduced optional managed leaf-column widths below `guiOptions`, identified by stable table and column IDs. Parent-column widths remain derived from their leaf columns.
+- Configuration and layout live in the `preferences.xml` of the **active operator profile**; see "Operator Profiles and Per-Profile Persistence" below. The current `preferences.xml` configuration version is 7. Version 6 introduced optional managed leaf-column widths below `guiOptions`, identified by stable table and column IDs. Parent-column widths remain derived from their leaf columns.
 - `GUIstationMapClusteringEnabled` is a layout preference below `guiOptions`. It defaults to `true`, is selectively autosaved and controls only screen-based clustering of nearby map markers. Missing or malformed values retain the enabled default for backward compatibility.
 - Stored widths take precedence. Without a usable entry, a managed column is sized once when meaningful table data first becomes available. Message and similar free-text columns use a flexible initial width instead of following the longest value.
 - Main-window and separate-monitor DXCluster/QSO tables use distinct layout IDs even though they share the underlying message stores.
@@ -61,6 +61,27 @@ JavaFX ObservableList / UI state
 - Full and selective writes are synchronized and replace `preferences.xml` atomically. Missing, unknown or malformed width entries do not prevent loading and fall back to initial sizing.
 - Older configuration files require no migration. Older KST4Contest versions can ignore the additional elements; a complete rewrite by such a version may discard column widths without invalidating the remaining file.
 
+## Operator Profiles and Per-Profile Persistence
+
+- One operator profile owns one `preferences.xml` and one worked-station database. Everything else under `~/.praktiKST/` stays global: CSS, audio files, DEM and terrain packages, the error log and the version-info feed.
+- The **root profile** is the historic flat installation: `preferences.xml` and `praktiKST.db` directly below the application directory. It is never moved, and it always uses the common station database, because that database is the installation's own.
+- Additional profiles live under `profiles/<profileId>/`. `profileId` is a stable, file-system-safe slug assigned once; renaming a profile changes only its display name and never moves a directory.
+- The registry `profiles.xml` is created lazily. An installation that has only the flat layout gets no registry and no `profiles/` directory; the root profile is synthesised in memory. Startup with no or exactly one profile therefore asks nothing and writes nothing, and a downgrade to an older release is a no-op.
+- The registry stores `profileId`, `displayName`, `rootProfile` and `sharedWorkedDatabase`, never a path. Both file names are derived in `OperatorProfilePaths` alone, so a stored path cannot drift apart from the flag that produced it.
+- `sharedWorkedDatabase` resolves to a path, not to a schema change: a sharing profile points at the flat `praktiKST.db`, an owning profile at its own file. There is no owner column, and no SQL statement in `DBController` knows about profiles.
+- A profile database is created **empty**. The bundled `/praktiKST.db` resource carries several thousand foreign callsigns and `user_version = 0`; seeding an additional profile from it would show a new operator foreign data and trigger the full callsign-normalization rebuild. Only the root installation is seeded from the resource. `preferences.xml` of a new profile *is* seeded from `/praktiKSTpreferences.xml`, because its defaults are what a first installation gets.
+- Worked-state semantics are unchanged and now apply per database file: normalized base callsign as key, worked state shared across suffix variants, three-day expiry, manual reset.
+- `stn_loginCallSign` and `stn_loginCallSignRaw` default to empty. The preferences reader treats an empty element as "not set" and falls back to the field default, so a non-empty default would make a profile created without credentials come up carrying a compiled-in callsign.
+- Passwords remain plaintext per profile. Profiles separate configuration; they are explicitly not an access-control boundary. This is documented in both manuals.
+
+### Runtime profile switching
+
+- A switch tears the current runtime down through `Kst4ContestApplication.shutdownRuntime()` and builds a **new** `Kst4ContestApplication` instance. Reusing the instance is not possible: many controls are inline-initialised instance fields, so a second `start()` would re-parent mounted nodes and register every listener twice. The approach is only sound because the class holds no mutable static state.
+- `Platform.setImplicitExit(false)` is required, because closing every window during a switch would otherwise end the process. All exits therefore run through `ApplicationRuntimeLauncher.exitApplication()`, including the main window's close handler; JavaFX calls `stop()` only on the instance it launched itself.
+- `shutdownRuntime()` is idempotent and must release everything that outlives a disconnect: the ON4KST supervisor thread, the sked reminder scheduler, the reachability executor, the PSTRotator retry scheduler, the map tile proxy, the station map bridge listeners and its coalescing animation, both view timers and every owned stage. Several of these were real leaks before; they only became visible once a second runtime could exist.
+- `ApplicationConstants.sessionRuntimeUniqueId` must not be regenerated during a switch, so UDP readers started earlier still recognise their own poison pill.
+- The layout autosave is flushed and then cancelled before a switch, so a pending debounced write cannot land after the profile changed.
+
 ## External Interfaces
 
 Treat current implementation/tests and authoritative upstream documentation as source of truth before modifying any interface.
@@ -114,6 +135,8 @@ CR/LF framing, XML framing, ports/transports, callsign normalization and frequen
 ### Terrain data providers
 
 - The active terrain profile provider is Open-Meteo using Copernicus GLO-90 data.
+- The terrain profile cache lives in its own global database `~/.praktiKST/terrainprofilecache.db`. It is deliberately not part of an operator profile: terrain profiles are pure geometry derived from two locators and a sample count, and at a multi operator station both operators share one location, so a per-profile copy would only double the traffic against the terrain service.
+- Cached entries are separated by owner identity through the primary key (`owner_callsign_raw` + `owner_locator6`). Earlier versions stored a single owner identity in a meta table and dropped the whole cache whenever the configured callsign or locator changed; with several operator profiles that would discard every computed profile on each switch. The old `TerrainProfileCache*` tables inside `praktiKST.db` are left in place and are still readable by older releases; the new file starts empty and refills itself.
 - `OfflineDemImportService` only prepares a local directory and copies manually selected Copernicus GLO-30 GeoTIFF files into it. Importing files does not activate an offline provider or change the active calculation chain.
 
 ### ON4KST session and authentication

github_docs/de-Changelog.md

@@ -8,6 +8,41 @@ Die veröffentlichten Stable-Versionen und ihre Programmpakete stehen unter [Git
 
 ---
 
+## v1.50 (in Entwicklung)
+
+**Operator-Profile**
+
+Mehrere Operateure an einem Rechner können jetzt eigene Rufzeichen, Locators und Layouts verwenden, ohne sich gegenseitig die Konfiguration zu überschreiben. Damit ist [Issue #57](https://github.com/praktimarc/kst4contest/issues/57) umgesetzt.
+
+### Neu
+
+- **Operator-Profile:** Jedes Profil hat seine eigene `preferences.xml` und damit eigene fachliche Einstellungen und einen eigenen Layoutstand. Verwaltet werden Profile im neuen Reiter **Profiles** des Einstellungsfensters: anlegen, duplizieren, umbenennen, löschen und aktivieren.
+
+- **Gemeinsame oder eigene gearbeitete Stationen:** Pro Profil wird entschieden, ob es eine eigene Worked-Datenbank bekommt oder die gemeinsame Stationsdatenbank benutzt. Eine Multi-OP-Station mit einem einzigen Stationslog teilt den Worked-Status, zwei OMs mit verschiedenen Rufzeichen an einem Rechner trennen ihn.
+
+- **Profilwahl beim Start:** Mit nur einem Profil fragt KST4Contest beim Start nichts und verhält sich unverändert. Ab zwei Profilen erscheint eine kleine Auswahl mit vorausgewähltem letzten Profil; Enter oder Doppelklick starten sofort. Der Aufrufparameter `--profile=<Name>` überspringt die Auswahl.
+
+- **Profilwechsel im laufenden Betrieb:** **File → Switch operator profile...** trennt die Verbindung und baut die Oberfläche mit den Einstellungen des gewählten Profils neu auf, ohne Programmneustart.
+
+### Geändert
+
+- **Zwischenspeicher der Geländeprofile getrennt:** Berechnete Geländeprofile liegen jetzt in der eigenen, gemeinsam genutzten Datei `terrainprofilecache.db` und werden nach Besitzer getrennt gespeichert. Bisher wurde der gesamte Zwischenspeicher gelöscht, sobald sich Rufzeichen oder Locator änderten; bei einem Profilwechsel wäre damit jedes berechnete Profil verloren gegangen.
+
+- **Rufzeichen-Vorgabe ist leer:** Fehlt in der `preferences.xml` ein Login-Rufzeichen, bleibt das Feld jetzt leer, statt auf ein im Programm hinterlegtes Rufzeichen zurückzufallen. Ein neu angelegtes Profil startet damit bewusst ohne Anmeldedaten.
+
+### Behoben
+
+- **Freigegebene Hintergrundressourcen:** Der ON4KST-Überwachungsthread, der Sked-Erinnerungs-Scheduler, der Reachability-Executor, der PSTRotator-Wiederholungs-Scheduler und der Kachel-Proxy der Karte werden beim Schließen des Chatcontrollers freigegeben. Bisher liefen sie bis zum Programmende weiter.
+
+### Hinweise zur Aktualisierung
+
+- Bestehende Installationen werden **nicht** verändert: `preferences.xml` und `praktiKST.db` bleiben genau dort liegen, wo sie sind, und werden zum Profil **Default**. Es wird keine Datei verschoben oder kopiert.
+- Eine Profil-Registry entsteht erst beim Anlegen des zweiten Profils. Wer nur ein Profil benutzt, merkt von der Änderung nichts.
+- Eine Rückkehr zu einer älteren KST4Contest-Version bleibt möglich; sie findet ihre Dateien unverändert vor.
+- Passwörter stehen weiterhin im Klartext in der `preferences.xml` des jeweiligen Profils. Profile trennen die Konfiguration, sie sind kein Zugriffsschutz.
+
+---
+
 ## v1.43.1 (2026-09-03)
 
 **Korrigierte Versionsmetadaten**

github_docs/de-DX-Cluster-Server.md

@@ -240,24 +240,6 @@ Prüfe zuerst, welche Frequenzen für die betreffende Station innerhalb der letz
 
 Ist kein aktueller Stationskontext vorhanden, prüfe die Auswahl unter **Fallback band for relative QRG detection**. Das Fallback wird nur benötigt, wenn sich das Band weder aus einer vollständigen Frequenz noch aus dem aktuellen Kontext des Absenders ergibt.
 
-### Das Logprogramm läuft in einer eigenen Sandbox
-
-Ein Logprogramm, das als Flatpak oder über eine Wine-Umgebung wie Bottles gestartet wird, benutzt die Netzwerkrechte dieser Sandbox. Teilt die Sandbox das Netzwerk des Rechners nicht, ist `127.0.0.1` darin nicht das `127.0.0.1`, auf dem KST4Contest lauscht. Die Verbindung wird dann abgewiesen, obwohl KST4Contest den Port korrekt meldet.
-
-Bei einem Flatpak-Logprogramm lassen sich die Rechte so prüfen:
-
-```bash
-flatpak info --show-permissions <Anwendungs-ID>
-```
-
-Im Abschnitt `[Context]` muss `shared=network` stehen. Nachträglich vergeben lässt es sich mit:
-
-```bash
-flatpak override --user --share=network <Anwendungs-ID>
-```
-
-Das Gleiche gilt, wenn KST4Contest selbst als Flatpak läuft. Dessen veröffentlichtes Manifest enthält `--share=network` bereits, ein lauschender Port ist daher vom Rechner selbst und von anderen Anwendungen darauf erreichbar.
-
 ### Der Spot wird vom Logger ausgeblendet
 
 Verwende ein Spotter-Rufzeichen, das nicht mit dem eigenen Contest-Rufzeichen identisch ist. Abhängig vom Logger können eigene Spots gefiltert oder besonders behandelt werden.

github_docs/de-Konfiguration.md

@@ -878,6 +878,61 @@ Anzeige und Herleitung: [Gearbeitete Rufzeichen, neue Bänder und neue Großfeld
 
 ---
 
+## Operator-Profile (ab v1.50)
+
+Mehrere Operateure an einem Rechner brauchen unterschiedliche Rufzeichen, Locators und Layouts. Ein Operator-Profil bündelt genau das: **jedes Profil hat seine eigene `preferences.xml` und damit seine eigenen fachlichen Einstellungen und seinen eigenen Layoutstand.**
+
+### Wo die Profile liegen
+
+| Profil | Einstellungen | Gearbeitete Stationen |
+|---|---|---|
+| **Default** | `~/.praktiKST/preferences.xml` | `~/.praktiKST/praktiKST.db` |
+| weitere Profile | `~/.praktiKST/profiles/<Profil-ID>/preferences.xml` | je nach Einstellung gemeinsam oder `~/.praktiKST/profiles/<Profil-ID>/praktiKST.db` |
+
+Unter Windows entsprechend unterhalb von `%USERPROFILE%\.praktiKST\`.
+
+Alle übrigen Daten bleiben gemeinsam: Klangdateien, Farbschemata, DEM- und Terrainpakete, der Zwischenspeicher der Geländeprofile (`terrainprofilecache.db`), das Fehlerprotokoll und die Versionsinformationen.
+
+Das Profil **Default** benutzt weiterhin genau die Dateien, die eine bestehende Installation schon hat. **Bei der Aktualisierung auf v1.50 wird keine Datei verschoben, kopiert oder umgeschrieben.** Wer eine ältere KST4Contest-Version wieder installiert, findet seine Konfiguration und seine gearbeiteten Stationen unverändert vor.
+
+### Gemeinsame oder eigene gearbeitete Stationen
+
+Beim Anlegen eines Profils wird entschieden, woher dessen Worked-, NOT-QRV- und Großfeld-Daten kommen:
+
+- **Eigene gearbeitete Stationen** (Vorgabe): Das Profil bekommt eine eigene, zunächst leere Datenbank. Sinnvoll, wenn sich zwei OMs mit verschiedenen Rufzeichen einen Rechner teilen.
+- **Gemeinsame Stationsdatenbank**: Das Profil benutzt `~/.praktiKST/praktiKST.db`, also dieselbe Datenbank wie das Profil **Default**. Das ist der Fall der **Multi-OP-Station**: es gibt nur ein Stationslog, also soll auch der Worked-Status für alle Operateure derselbe sein.
+
+Ein Wechsel zwischen beiden Einstellungen verschiebt keine Daten. Bereits gesammelte Worked-Daten bleiben dort liegen, wo sie entstanden sind. Der Drei-Tage-Ablauf und die Reset-Schaltfläche wirken jeweils auf die Datenbank des gerade aktiven Profils.
+
+### Profile verwalten
+
+Der Reiter **Profiles** im Einstellungsfenster zeigt alle Profile mit Name, Art der Worked-Daten und letzter Benutzung.
+
+- **New profile...** legt ein Profil an. Es startet **ohne Rufzeichen und ohne Passwort**; beides wird anschließend im Reiter **Station** eingetragen.
+- **Duplicate...** übernimmt die komplette Konfiguration des gewählten Profils — Antenne, Locator, Layout, Beacon, Integrationen — **außer Rufzeichen und Passwort**. Gearbeitete Stationen werden nie mitkopiert.
+- **Rename...** ändert nur den angezeigten Namen. Verzeichnisse und Dateien bleiben unberührt.
+- **Delete...** entfernt das Profilverzeichnis endgültig. Das Profil **Default** und das gerade aktive Profil lassen sich nicht löschen. Bei einem Profil mit gemeinsamer Stationsdatenbank bleibt diese unangetastet.
+- **Change worked stations...** schaltet zwischen gemeinsamer und eigener Datenbank um.
+- **Switch to selected profile...** wechselt das Profil im laufenden Betrieb.
+
+### Profilwahl beim Start
+
+- Solange nur **ein** Profil existiert, fragt KST4Contest beim Start **nichts** und startet wie bisher. Es wird auch keine Profil-Registry angelegt. Erst das Anlegen des zweiten Profils erzeugt `~/.praktiKST/profiles.xml`.
+- Ab **zwei** Profilen erscheint beim Start eine kleine Auswahl. Das zuletzt benutzte Profil ist vorausgewählt, **Enter** oder ein Doppelklick starten sofort.
+- Der Aufrufparameter `--profile=<Name>` überspringt die Auswahl und startet direkt das genannte Profil. Erlaubt sind die Profil-ID und der angezeigte Name, Groß- und Kleinschreibung spielen keine Rolle. Ein unbekannter Name führt zu einem Hinweis und danach zur normalen Auswahl — der Start wird nie verweigert.
+
+### Profil im laufenden Betrieb wechseln
+
+**File → Switch operator profile...** oder die Schaltfläche im Reiter **Profiles** wechseln ohne Programmneustart. Nach einer Sicherheitsabfrage wird die ON4KST-Verbindung getrennt und die Oberfläche mit den Einstellungen und dem Layout des gewählten Profils neu aufgebaut. Der Layoutstand des bisherigen Profils wird vorher gesichert; noch nicht mit **Save Settings** bestätigte fachliche Änderungen gehen dabei verloren.
+
+Sobald mehr als ein Profil existiert, zeigt die Titelzeile des Hauptfensters zusätzlich den Profilnamen.
+
+### Hinweis zu Passwörtern
+
+Das ON4KST-Passwort steht wie bisher im Klartext in der `preferences.xml` des jeweiligen Profils. Auf einem gemeinsam genutzten Rechner kann jeder, der Zugriff auf das Benutzerkonto hat, die Passwörter aller Profile lesen. Profile trennen die Konfiguration, sie sind **kein** Zugriffsschutz.
+
+---
+
 ## Dark Mode (ab v1.26)
 
 Der Dark Mode wird über **Windows → Use dark mode design** aktiviert. Mit **Windows → Use default mode design** wird wieder das normale helle Farbschema geladen.

github_docs/en-Changelog.md

@@ -8,6 +8,41 @@ Published Stable versions and their application packages are available under [Gi
 
 ---
 
+## v1.50 (in development)
+
+**Operator profiles**
+
+Several operators sharing one computer can now use their own callsigns, locators and layouts without overwriting each other's configuration. This implements [Issue #57](https://github.com/praktimarc/kst4contest/issues/57).
+
+### New
+
+- **Operator profiles:** every profile has its own `preferences.xml`, and therefore its own settings and its own window layout. Profiles are managed on the new **Profiles** tab of the settings window: create, duplicate, rename, delete and activate.
+
+- **Shared or own worked stations:** each profile decides whether it gets its own worked database or uses the common station database. A multi operator station with a single station log shares the worked state; two operators with different callsigns on one computer keep it apart.
+
+- **Choosing a profile at startup:** with only one profile, KST4Contest asks nothing at startup and behaves exactly as before. From two profiles on, a small selection appears with the last used profile preselected; Enter or a double click start immediately. The `--profile=<name>` argument skips the selection.
+
+- **Switching profiles while running:** **File > Switch operator profile...** closes the connection and rebuilds the user interface with the settings of the selected profile, without restarting the program.
+
+### Changed
+
+- **The terrain profile cache is separate:** computed terrain profiles now live in their own shared file `terrainprofilecache.db` and are stored per owner. Previously the whole cache was dropped whenever the callsign or locator changed, which would have discarded every computed profile on each profile switch.
+
+- **The default login callsign is empty:** if `preferences.xml` has no login callsign, the field now stays empty instead of falling back to a callsign compiled into the program. A newly created profile therefore deliberately starts without credentials.
+
+### Fixed
+
+- **Background resources are released:** the ON4KST supervisor thread, the sked reminder scheduler, the reachability executor, the PSTRotator retry scheduler and the map tile proxy are released when the chat controller is closed. They used to keep running until the program ended.
+
+### Upgrade notes
+
+- Existing installations are **not** modified: `preferences.xml` and `praktiKST.db` stay exactly where they are and become the **Default** profile. No file is moved or copied.
+- A profile registry only appears when the second profile is created. Anyone using a single profile will not notice the change.
+- Going back to an older KST4Contest release stays possible; it finds its files unchanged.
+- Passwords are still stored in clear text in each profile's `preferences.xml`. Profiles separate configuration; they are not an access control mechanism.
+
+---
+
 ## v1.43.1 (2026-09-03)
 
 **Corrected version metadata**

github_docs/en-Configuration.md

@@ -935,6 +935,61 @@ Display and derivation: [Worked Callsigns, New Bands and New Grid Squares](en-Fe
 
 ---
 
+## Operator Profiles (from v1.50)
+
+Several operators sharing one computer need different callsigns, locators and layouts. An operator profile bundles exactly that: **every profile has its own `preferences.xml`, and therefore its own settings and its own window layout.**
+
+### Where the profiles live
+
+| Profile | Settings | Worked stations |
+|---|---|---|
+| **Default** | `~/.praktiKST/preferences.xml` | `~/.praktiKST/praktiKST.db` |
+| additional profiles | `~/.praktiKST/profiles/<profile ID>/preferences.xml` | shared, or `~/.praktiKST/profiles/<profile ID>/praktiKST.db` |
+
+On Windows the same files live below `%USERPROFILE%\.praktiKST\`.
+
+Everything else stays shared: audio files, colour schemes, DEM and terrain packages, the terrain profile cache (`terrainprofilecache.db`), the error log and the version information.
+
+The **Default** profile keeps using exactly the files an existing installation already has. **Upgrading to v1.50 moves, copies and rewrites nothing.** Anyone reinstalling an older KST4Contest release finds their configuration and their worked stations unchanged.
+
+### Shared or own worked stations
+
+When a profile is created you decide where its worked, NOT-QRV and grid data come from:
+
+- **Own worked stations** (default): the profile gets its own, initially empty database. This is what two operators with different callsigns sharing a private computer want.
+- **Common station database**: the profile uses `~/.praktiKST/praktiKST.db`, the same database as the **Default** profile. This is the **multi operator station** case: there is only one station log, so the worked state should be the same for every operator.
+
+Switching between the two settings moves no data. Worked data already collected stays where it was created. The three day expiry and the reset button always act on the database of the currently active profile.
+
+### Managing profiles
+
+The **Profiles** tab in the settings window lists all profiles with their name, the kind of worked data they use and when they were last used.
+
+- **New profile...** creates a profile. It starts **without callsign and password**; both are entered afterwards on the **Station** tab.
+- **Duplicate...** copies the complete configuration of the selected profile - antenna, locator, layout, beacon, integrations - **except callsign and password**. Worked stations are never copied.
+- **Rename...** changes the displayed name only. Folders and files are untouched.
+- **Delete...** removes the profile folder permanently. The **Default** profile and the currently active profile cannot be deleted. For a profile using the common station database, that database is left untouched.
+- **Change worked stations...** switches between the common and an own database.
+- **Switch to selected profile...** changes the profile while the application is running.
+
+### Choosing a profile at startup
+
+- As long as only **one** profile exists, KST4Contest asks **nothing** at startup and starts exactly as before. No profile registry is created either; only creating the second profile writes `~/.praktiKST/profiles.xml`.
+- From **two** profiles on, a small selection appears at startup. The last used profile is preselected, and **Enter** or a double click start immediately.
+- The `--profile=<name>` argument skips the selection and starts the named profile directly. Both the profile ID and the displayed name are accepted, case insensitively. An unknown name produces a note and then the normal selection - startup is never refused.
+
+### Switching profiles while running
+
+**File > Switch operator profile...**, or the button on the **Profiles** tab, switches without restarting the program. After a confirmation the ON4KST connection is closed and the user interface is rebuilt with the settings and layout of the selected profile. The layout of the previous profile is saved first; settings not yet confirmed with **Save Settings** are lost.
+
+Once more than one profile exists, the main window title also shows the profile name.
+
+### A note about passwords
+
+As before, the ON4KST password is stored in clear text in the `preferences.xml` of each profile. On a shared computer, anyone with access to the user account can read the passwords of all profiles. Profiles separate configuration; they are **not** an access control mechanism.
+
+---
+
 ## Dark Mode (from v1.26)
 
 Enable Dark Mode through **Windows → Use dark mode design**. Use **Windows → Use default mode design** to restore the normal light colour scheme.

github_docs/en-DX-Cluster-Server.md

@@ -240,24 +240,6 @@ First check which frequencies were detected for the station during the previous
 
 If no current station context exists, check **Fallback band for relative QRG detection**. The fallback is used only when the band cannot be determined from a complete frequency or the sender's current context.
 
-### The Logger Runs in Its Own Sandbox
-
-A logging programme started as a Flatpak, or through a Wine environment such as Bottles, uses the network permissions of that sandbox. If the sandbox does not share the host network, `127.0.0.1` inside it is not the `127.0.0.1` on which KST4Contest is listening, and the connection is refused even though KST4Contest reports the port correctly.
-
-For a Flatpak logger, check its permission with:
-
-```bash
-flatpak info --show-permissions <application id>
-```
-
-The `[Context]` section has to contain `shared=network`. It can be granted with:
-
-```bash
-flatpak override --user --share=network <application id>
-```
-
-The same applies when KST4Contest itself runs as a Flatpak. Its published manifest already contains `--share=network`, so a listening port is reachable from the host and from other applications on the same computer.
-
 ### The Logger Hides the Spot
 
 Try a spotter callsign which differs from the contest callsign. Depending on the logger, spots from the local callsign may be filtered or handled specially. KST4Contest itself does not require the two callsigns to differ.

src/main/java/kst4contest/controller/ActiveOperatorProfile.java

@@ -0,0 +1,48 @@
+package kst4contest.controller;
+
+import kst4contest.model.OperatorProfileSelection;
+
+/**
+ * Holds the operator profile the current runtime works with.
+ *
+ * <p>The state is deliberately static, which is safe here for reasons that did not apply
+ * to the former static database connection: the value is immutable, it holds no live
+ * resource, and it is set on the JavaFX Application Thread before anything reads it -
+ * during startup, and again during a profile switch after the previous runtime has been
+ * shut down completely.</p>
+ */
+public final class ActiveOperatorProfile {
+
+    private static volatile OperatorProfileSelection currentSelection;
+
+    private ActiveOperatorProfile() {
+        // Utility class.
+    }
+
+    /**
+     * Returns the active profile selection.
+     *
+     * @return the active selection, or null when startup has not resolved one yet
+     */
+    public static OperatorProfileSelection get() {
+        return currentSelection;
+    }
+
+    /**
+     * Sets the active profile selection.
+     *
+     * @param selection selection to activate
+     */
+    public static void set(final OperatorProfileSelection selection) {
+        currentSelection = selection;
+    }
+
+    /**
+     * Returns whether a profile has already been resolved for this runtime.
+     *
+     * @return true if a selection is present
+     */
+    public static boolean isInitialized() {
+        return currentSelection != null;
+    }
+}

src/main/java/kst4contest/controller/ChatController.java

@@ -1083,9 +1083,35 @@ public class ChatController implements ThreadStatusCallback, PstRotatorEventList
 				rotatorClient.stop();
 				rotatorClient = null;
 			}
+
+			releaseBackgroundExecutors();
 		}
 	}
 
+	/**
+	 * Stops the background executors that live as long as this controller.
+	 *
+	 * <p>These are not bound to one ON4KST session, so disconnecting leaves them running
+	 * on purpose. When the controller itself is discarded they have to go, otherwise a
+	 * discarded controller stays reachable through its own threads.</p>
+	 */
+	private void releaseBackgroundExecutors() {
+
+		on4KstConnectionManager.shutdown();
+		skedReminderService.shutdown();
+
+		if (reachabilityService != null) {
+			reachabilityService.shutdown();
+		}
+
+		if (pendingRotatorRetry != null) {
+			pendingRotatorRetry.cancel(false);
+			pendingRotatorRetry = null;
+		}
+
+		rotatorCommandScheduler.shutdownNow();
+	}
+
 	private void cancelTimer(Timer timer) {
 		if (timer != null) {
 			timer.cancel();
@@ -2866,9 +2892,35 @@ private ObservableList<String>
 	 * @param setOwnChatMemberObject
 	 */
 	public ChatController(ChatMember setOwnChatMemberObject,StatusUpdateListener listener) {
+		this(setOwnChatMemberObject,
+				listener,
+				ChatPreferences.PREFERENCES_FILE,
+				DBController.DATABASE_FILE,
+				true);
+	}
+
+	/**
+	 * Creates a chat controller bound to the files of one operator profile.
+	 *
+	 * <p>Both file names are resolved below the application directory. This is the only
+	 * place where the active operator profile enters the controller; everything below
+	 * works on the resulting {@link ChatPreferences} and {@link DBController} instances
+	 * without knowing about profiles at all.</p>
+	 *
+	 * @param setOwnChatMemberObject          chat member object representing the local station
+	 * @param listener                        callback for thread status updates
+	 * @param preferencesRelativeFileName     preferences file name relative to the application directory
+	 * @param workedDatabaseRelativeFileName  worked-station database file name relative to the application directory
+	 * @param seedWorkedDatabaseFromResource  true to seed a missing database from the bundled template
+	 */
+	public ChatController(ChatMember setOwnChatMemberObject,
+			StatusUpdateListener listener,
+			String preferencesRelativeFileName,
+			String workedDatabaseRelativeFileName,
+			boolean seedWorkedDatabaseFromResource) {
 		super();
 
-        chatPreferences = new ChatPreferences();
+        chatPreferences = new ChatPreferences(preferencesRelativeFileName);
         chatPreferences.readPreferencesFromXmlFile();
 //        this.statusListener = listener;
 		lstNotify_QSOSniffer_sniffedCallSignList =
@@ -2930,7 +2982,7 @@ private ObservableList<String>
 			}
 		});
 
-		dbHandler = new DBController();
+		dbHandler = new DBController(workedDatabaseRelativeFileName, seedWorkedDatabaseFromResource);
 		reachabilityService = new ReachabilityService(this);
 		rebuildWorkedGrossFieldCacheFromDatabase();
 

src/main/java/kst4contest/controller/DBController.java

@@ -6,9 +6,13 @@ import java.sql.PreparedStatement;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.Objects;
 
 import kst4contest.ApplicationConstants;
 import kst4contest.model.ChatMember;
@@ -52,34 +56,128 @@ public class DBController {
 	 */
 	private static final long EXPIRATION_CLEANUP_MIN_INTERVAL_IN_MILLISECONDS = 60L * 1000L;
 
-	private static final DBController dbcontroller = new DBController();
+	/**
-	private static Connection connection;
+	 * Lazily created controller for the root installation database. It is created on
-	private static String DB_PATH = ApplicationFileUtils.getFilePath(ApplicationConstants.APPLICATION_NAME, DATABASE_FILE);
+	 * first use only, because an eagerly created instance would open a database file
+	 * before the application knows which operator profile is active.
+	 */
+	private static volatile DBController defaultInstance;
+
+	private Connection connection;
+
+	/**
+	 * File name of this database relative to the application directory, for example
+	 * "praktiKST.db" or "profiles/OP2/praktiKST.db".
+	 */
+	private final String databaseRelativeFileName;
+
+	/**
+	 * Absolute path of the database file, resolved once during construction.
+	 */
+	private final String databaseFilePath;
+
+	/**
+	 * True if a missing database file should be seeded from the shipped template.
+	 */
+	private final boolean seedFromResource;
+
+	/**
+	 * Shutdown hook of this instance. It is remembered so it can be deregistered when
+	 * the connection is closed. Without that, every operator profile switch would leave
+	 * another hook behind that keeps a dead connection alive until the process ends.
+	 */
+	private Thread databaseShutdownHook;
 
 	/**
 	 * Remembers the last timestamp at which the expiration cleanup had been executed.
 	 */
 	private long lastExpirationCleanupExecutionEpochMs = 0L;
 
+	/**
+	 * Creates a controller for the worked-station database of the root installation.
+	 */
 	public DBController() {
-		initDBConnection();
+		this(DATABASE_FILE, true);
-	}
-
-	public static DBController getInstance() {
-		return dbcontroller;
 	}
 
 	/**
-	 * Closes the database connection if it is still open.
+	 * Creates a controller for the worked-station database of one operator profile.
+	 *
+	 * @param databaseRelativeFileName file name relative to the application directory
+	 * @param seedFromResource         true to copy the shipped template database when the file
+	 *                                 does not exist yet, false to create an empty database and
+	 *                                 let the schema creation build all required tables
+	 */
+	public DBController(final String databaseRelativeFileName, final boolean seedFromResource) {
+		this.databaseRelativeFileName =
+				Objects.requireNonNull(databaseRelativeFileName, "databaseRelativeFileName");
+		this.seedFromResource = seedFromResource;
+		this.databaseFilePath = ApplicationFileUtils.getFilePath(
+				ApplicationConstants.APPLICATION_NAME,
+				databaseRelativeFileName
+		);
+
+		initDBConnection();
+	}
+
+	/**
+	 * Returns a controller for the root installation database, creating it on first use.
+	 *
+	 * @return the shared controller for the root installation database
+	 */
+	public static synchronized DBController getInstance() {
+
+		if (defaultInstance == null) {
+			defaultInstance = new DBController();
+		}
+
+		return defaultInstance;
+	}
+
+	/**
+	 * Returns the absolute path of the database file this controller works on.
+	 *
+	 * @return absolute database file path
+	 */
+	public String getDatabaseFilePath() {
+		return databaseFilePath;
+	}
+
+	/**
+	 * Closes the database connection if it is still open and deregisters the shutdown
+	 * hook of this instance.
 	 */
 	public synchronized void closeDBConnection() {
+
+		closeConnectionQuietly();
+
+		if (databaseShutdownHook != null) {
+			try {
+				Runtime.getRuntime().removeShutdownHook(databaseShutdownHook);
+			} catch (IllegalStateException shutdownAlreadyInProgress) {
+				// Expected while the JVM is shutting down; the hook is running anyway.
+			}
+
+			databaseShutdownHook = null;
+		}
+	}
+
+	/**
+	 * Closes the connection without touching the shutdown hook. This is also the body of
+	 * the shutdown hook itself.
+	 */
+	private synchronized void closeConnectionQuietly() {
+
 		try {
 			if (connection != null && !connection.isClosed()) {
 				connection.close();
+				System.out.println("Connection to Database closed: " + databaseFilePath);
 			}
 		} catch (SQLException e) {
 			e.printStackTrace();
 		}
+
+		connection = null;
 	}
 
 	/**
@@ -91,22 +189,17 @@ public class DBController {
 		System.out.println("DBH: initiate new db connection");
 
 		try {
-			ApplicationFileUtils.copyResourceIfRequired(
-					ApplicationConstants.APPLICATION_NAME,
-					DATABASE_RESOURCE,
-					DATABASE_FILE
-			);
-
 			if (connection != null && !connection.isClosed()) {
 				return;
 			}
 
+			prepareDatabaseFile();
+
 			System.out.println("Creating Connection to Database...");
 
-			DB_PATH = ApplicationFileUtils.getFilePath(ApplicationConstants.APPLICATION_NAME, DATABASE_FILE);
+			connection = DriverManager.getConnection("jdbc:sqlite:" + databaseFilePath);
-			connection = DriverManager.getConnection("jdbc:sqlite:" + DB_PATH);
 
-			System.out.println("[DBH, Info]: Path = " + DB_PATH);
+			System.out.println("[DBH, Info]: Path = " + databaseFilePath);
 
 			if (!connection.isClosed()) {
 				System.out.println("...Connection established");
@@ -115,25 +208,50 @@ public class DBController {
 			throw new RuntimeException(e);
 		}
 
-		Runtime.getRuntime().addShutdownHook(new Thread() {
+		databaseShutdownHook = new Thread(this::closeConnectionQuietly,
-			public void run() {
+				"DBController-shutdown-" + databaseRelativeFileName);
-				try {
+		Runtime.getRuntime().addShutdownHook(databaseShutdownHook);
-					if (connection != null && !connection.isClosed()) {
-						connection.close();
-
-						if (connection.isClosed()) {
-							System.out.println("Connection to Database closed");
-						}
-					}
-				} catch (SQLException e) {
-					e.printStackTrace();
-				}
-			}
-		});
 
 		ensureChatMemberTableCompatibility();
 	}
 
+	/**
+	 * Makes sure the database file can be opened.
+	 *
+	 * <p>The database of the root installation is seeded from the shipped template so
+	 * existing installations keep their historic content. A database that belongs to an
+	 * additional operator profile is created empty on purpose: the shipped template
+	 * carries several thousand foreign callsigns and an outdated schema version, which
+	 * would present a new operator with foreign data and trigger the full callsign
+	 * normalization rebuild. The required tables are created by
+	 * {@link #ensureChatMemberTableCompatibility()} in both cases.</p>
+	 */
+	private synchronized void prepareDatabaseFile() {
+
+		if (seedFromResource) {
+			ApplicationFileUtils.copyResourceIfRequired(
+					ApplicationConstants.APPLICATION_NAME,
+					DATABASE_RESOURCE,
+					databaseRelativeFileName
+			);
+
+			return;
+		}
+
+		Path parentDirectory = Path.of(databaseFilePath).getParent();
+
+		if (parentDirectory == null) {
+			return;
+		}
+
+		try {
+			Files.createDirectories(parentDirectory);
+		} catch (IOException e) {
+			throw new RuntimeException(
+					"[DBH, ERROR:] Could not create database directory " + parentDirectory, e);
+		}
+	}
+
 	/**
 	 * Ensures that the ChatMember table exists, that all required columns are
 	 * available for newer software versions, that existing old callsign keys are

src/main/java/kst4contest/controller/On4KstConnectionManager.java

@@ -139,6 +139,20 @@ final class On4KstConnectionManager {
         scheduler.execute(() -> openConnection(token));
     }
 
+    /**
+     * Stops the supervisor thread of this manager for good.
+     *
+     * <p>{@link #stopByUser()} only ends the current ON4KST session; the periodic
+     * session monitor keeps running. That is correct while the application lives, but a
+     * manager belonging to a discarded runtime must release its thread, otherwise every
+     * operator profile switch would leave another supervisor behind holding the dead
+     * controller.</p>
+     */
+    void shutdown() {
+        scheduler.shutdownNow();
+        LOGGER.fine("ON4KST connection supervisor shut down");
+    }
+
     /**
      * Stops the current session and invalidates every scheduled callback or reconnect
      * belonging to it.

src/main/java/kst4contest/controller/OperatorProfileManagementService.java

@@ -0,0 +1,312 @@
+package kst4contest.controller;
+
+import kst4contest.ApplicationConstants;
+import kst4contest.model.ChatPreferences;
+import kst4contest.model.OperatorProfile;
+import kst4contest.utils.ApplicationFileUtils;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+import java.util.stream.Stream;
+
+/**
+ * Creates, renames, duplicates and removes operator profiles.
+ *
+ * <p>Kept free of user interface code so the behaviour can be tested without a JavaFX
+ * runtime. All methods work on the registry and on the files below the application
+ * directory.</p>
+ */
+public class OperatorProfileManagementService {
+
+    private static final Logger LOGGER =
+            Logger.getLogger(OperatorProfileManagementService.class.getName());
+
+    private final OperatorProfileStore profileStore;
+
+    public OperatorProfileManagementService() {
+        this(new OperatorProfileStore());
+    }
+
+    public OperatorProfileManagementService(final OperatorProfileStore profileStore) {
+        this.profileStore = profileStore;
+    }
+
+    /**
+     * Lists all profiles, including the implicit root profile of a plain installation.
+     *
+     * @return the known profiles, never empty
+     */
+    public List<OperatorProfile> listProfiles() {
+
+        List<OperatorProfile> knownProfiles = profileStore.loadProfiles();
+
+        if (knownProfiles.isEmpty()) {
+            knownProfiles = new ArrayList<>();
+            knownProfiles.add(profileStore.buildImplicitRootProfile());
+        }
+
+        return knownProfiles;
+    }
+
+    /**
+     * Creates a new operator profile with its own preferences file.
+     *
+     * <p>Creating the first additional profile is also the moment the registry appears:
+     * the root profile is written alongside, so both are selectable afterwards.</p>
+     *
+     * @param displayName          name entered by the operator
+     * @param sharedWorkedDatabase true to use the common station worked database
+     * @return the created profile, or null when it could not be stored
+     */
+    public OperatorProfile createProfile(final String displayName, final boolean sharedWorkedDatabase) {
+
+        List<OperatorProfile> knownProfiles = listProfiles();
+        Set<String> takenProfileIds = new LinkedHashSet<>();
+
+        for (OperatorProfile existingProfile : knownProfiles) {
+            takenProfileIds.add(existingProfile.getProfileId());
+        }
+
+        OperatorProfile createdProfile = new OperatorProfile(
+                OperatorProfilePaths.toProfileId(displayName, takenProfileIds),
+                displayName == null || displayName.isBlank() ? "New profile" : displayName.trim(),
+                false,
+                sharedWorkedDatabase);
+
+        knownProfiles.add(createdProfile);
+
+        if (!profileStore.saveProfiles(knownProfiles, createdProfile.getProfileId())) {
+            return null;
+        }
+
+        createPreferencesFile(createdProfile, null);
+
+        return createdProfile;
+    }
+
+    /**
+     * Creates a copy of an existing profile.
+     *
+     * <p>The preferences are taken over completely except for the login credentials:
+     * callsign and password are cleared on purpose, because a duplicate is meant for
+     * another operator. Antenna, locator, layout and integration settings are exactly
+     * what the operator does not want to enter twice.</p>
+     *
+     * <p>The worked-station database is never copied.</p>
+     *
+     * @param sourceProfile profile to copy
+     * @param displayName   name of the new profile
+     * @return the created profile, or null when it could not be stored
+     */
+    public OperatorProfile duplicateProfile(final OperatorProfile sourceProfile, final String displayName) {
+
+        if (sourceProfile == null) {
+            return null;
+        }
+
+        List<OperatorProfile> knownProfiles = listProfiles();
+        Set<String> takenProfileIds = new LinkedHashSet<>();
+
+        for (OperatorProfile existingProfile : knownProfiles) {
+            takenProfileIds.add(existingProfile.getProfileId());
+        }
+
+        OperatorProfile createdProfile = new OperatorProfile(
+                OperatorProfilePaths.toProfileId(displayName, takenProfileIds),
+                displayName == null || displayName.isBlank() ? "Copy" : displayName.trim(),
+                false,
+                sourceProfile.isSharedWorkedDatabase());
+
+        knownProfiles.add(createdProfile);
+
+        if (!profileStore.saveProfiles(knownProfiles, createdProfile.getProfileId())) {
+            return null;
+        }
+
+        createPreferencesFile(createdProfile, sourceProfile);
+
+        return createdProfile;
+    }
+
+    /**
+     * Changes the visible name of a profile. The identifier and all paths stay as they are.
+     *
+     * @param profile        profile to rename
+     * @param newDisplayName new name
+     * @return true if the registry was updated
+     */
+    public boolean renameProfile(final OperatorProfile profile, final String newDisplayName) {
+
+        if (profile == null || newDisplayName == null || newDisplayName.isBlank()) {
+            return false;
+        }
+
+        List<OperatorProfile> knownProfiles = listProfiles();
+
+        for (OperatorProfile currentProfile : knownProfiles) {
+            if (currentProfile.getProfileId().equals(profile.getProfileId())) {
+                currentProfile.setDisplayName(newDisplayName.trim());
+            }
+        }
+
+        return profileStore.saveProfiles(knownProfiles, profileStore.loadLastUsedProfileId().orElse(null));
+    }
+
+    /**
+     * Switches a profile between the common station database and its own one.
+     *
+     * @param profile              profile to change
+     * @param sharedWorkedDatabase true to use the common station worked database
+     * @return true if the registry was updated
+     */
+    public boolean setSharedWorkedDatabase(final OperatorProfile profile, final boolean sharedWorkedDatabase) {
+
+        if (profile == null || profile.isRootProfile()) {
+            return false;
+        }
+
+        List<OperatorProfile> knownProfiles = listProfiles();
+
+        for (OperatorProfile currentProfile : knownProfiles) {
+            if (currentProfile.getProfileId().equals(profile.getProfileId())) {
+                currentProfile.setSharedWorkedDatabase(sharedWorkedDatabase);
+            }
+        }
+
+        return profileStore.saveProfiles(knownProfiles, profileStore.loadLastUsedProfileId().orElse(null));
+    }
+
+    /**
+     * Removes a profile and its directory.
+     *
+     * <p>The root profile can never be removed, because its files are the installation
+     * itself. A profile using the common station database keeps that database untouched;
+     * only its own directory is deleted.</p>
+     *
+     * @param profile profile to remove
+     * @return true if the profile was removed
+     */
+    public boolean deleteProfile(final OperatorProfile profile) {
+
+        if (profile == null || profile.isRootProfile()) {
+            return false;
+        }
+
+        List<OperatorProfile> remainingProfiles = new ArrayList<>();
+
+        for (OperatorProfile currentProfile : listProfiles()) {
+            if (!currentProfile.getProfileId().equals(profile.getProfileId())) {
+                remainingProfiles.add(currentProfile);
+            }
+        }
+
+        if (!profileStore.saveProfiles(remainingProfiles,
+                profileStore.loadLastUsedProfileId().orElse(null))) {
+            return false;
+        }
+
+        deleteProfileDirectory(profile);
+
+        return true;
+    }
+
+    /**
+     * Returns the absolute directory of a profile.
+     *
+     * @param profile profile to resolve
+     * @return absolute profile directory
+     */
+    public String getProfileDirectory(final OperatorProfile profile) {
+        return ApplicationFileUtils.getFilePath(
+                ApplicationConstants.APPLICATION_NAME,
+                OperatorProfilePaths.profileRelativeDirectory(profile));
+    }
+
+    /**
+     * Creates the preferences file of a new profile.
+     *
+     * <p>The file is either seeded from the bundled template or copied from the source
+     * profile. In both cases the login credentials are cleared, so a new profile never
+     * carries another operator's callsign or password.</p>
+     *
+     * @param createdProfile profile that needs a preferences file
+     * @param sourceProfile  profile to copy the preferences from, or null for the template
+     */
+    private void createPreferencesFile(final OperatorProfile createdProfile,
+            final OperatorProfile sourceProfile) {
+
+        String createdRelativeFileName = OperatorProfilePaths.preferencesRelativeFileName(createdProfile);
+
+        if (sourceProfile != null) {
+            copyPreferencesFile(
+                    OperatorProfilePaths.preferencesRelativeFileName(sourceProfile),
+                    createdRelativeFileName);
+        }
+
+        // Seeds from the bundled template when nothing was copied, and always resolves
+        // the preferences of the new profile.
+        ChatPreferences createdPreferences = new ChatPreferences(createdRelativeFileName);
+        createdPreferences.readPreferencesFromXmlFile();
+
+        createdPreferences.setStn_loginCallSign("");
+        createdPreferences.setStn_loginPassword("");
+
+        createdPreferences.writePreferencesToXmlFile();
+    }
+
+    private void copyPreferencesFile(final String sourceRelativeFileName,
+            final String targetRelativeFileName) {
+
+        Path sourcePath = Path.of(ApplicationFileUtils.getFilePath(
+                ApplicationConstants.APPLICATION_NAME, sourceRelativeFileName));
+        Path targetPath = Path.of(ApplicationFileUtils.getFilePath(
+                ApplicationConstants.APPLICATION_NAME, targetRelativeFileName));
+
+        if (!Files.isRegularFile(sourcePath)) {
+            return;
+        }
+
+        try {
+            Path targetDirectory = targetPath.getParent();
+
+            if (targetDirectory != null) {
+                Files.createDirectories(targetDirectory);
+            }
+
+            Files.copy(sourcePath, targetPath);
+        } catch (IOException e) {
+            LOGGER.log(Level.WARNING,
+                    "Could not copy the preferences of the source profile, using the defaults instead", e);
+        }
+    }
+
+    private void deleteProfileDirectory(final OperatorProfile profile) {
+
+        Path profileDirectory = Path.of(getProfileDirectory(profile));
+
+        if (!Files.isDirectory(profileDirectory)) {
+            return;
+        }
+
+        try (Stream<Path> containedPaths = Files.walk(profileDirectory)) {
+            List<Path> deepestFirst = containedPaths
+                    .sorted(Comparator.reverseOrder())
+                    .toList();
+
+            for (Path currentPath : deepestFirst) {
+                Files.deleteIfExists(currentPath);
+            }
+        } catch (IOException e) {
+            LOGGER.log(Level.WARNING,
+                    "Could not remove the directory of the deleted operator profile", e);
+        }
+    }
+}

src/main/java/kst4contest/controller/OperatorProfilePaths.java

@@ -0,0 +1,199 @@
+package kst4contest.controller;
+
+import kst4contest.model.ChatPreferences;
+import kst4contest.model.OperatorProfile;
+import kst4contest.model.OperatorProfileSelection;
+
+import java.util.Collection;
+import java.util.Locale;
+
+/**
+ * Derives the file names of an operator profile.
+ *
+ * <p>This is the single place that knows how a profile maps onto files. The registry
+ * stores only the shared/own flag, never a path, so the two can never drift apart.</p>
+ */
+public final class OperatorProfilePaths {
+
+    /**
+     * Directory below the application directory that holds the additional profiles.
+     */
+    public static final String PROFILES_DIRECTORY = "profiles";
+
+    /**
+     * Identifier of the profile that uses the historic flat installation layout.
+     */
+    public static final String ROOT_PROFILE_ID = "default";
+
+    /**
+     * Maximum length of a generated profile identifier.
+     */
+    private static final int MAX_PROFILE_ID_LENGTH = 32;
+
+    private OperatorProfilePaths() {
+        // Utility class.
+    }
+
+    /**
+     * Builds the profile descriptor of the historic flat installation.
+     *
+     * @param displayName name to show for the root profile
+     * @return the root profile descriptor
+     */
+    public static OperatorProfile buildRootProfile(final String displayName) {
+        return new OperatorProfile(ROOT_PROFILE_ID, displayName, true, true);
+    }
+
+    /**
+     * Returns the profile directory relative to the application directory.
+     *
+     * @param profile profile to resolve
+     * @return relative directory name
+     */
+    public static String profileRelativeDirectory(final OperatorProfile profile) {
+        return PROFILES_DIRECTORY + "/" + profile.getProfileId();
+    }
+
+    /**
+     * Returns the preferences file name relative to the application directory.
+     *
+     * @param profile profile to resolve
+     * @return relative preferences file name
+     */
+    public static String preferencesRelativeFileName(final OperatorProfile profile) {
+
+        if (profile.isRootProfile()) {
+            return ChatPreferences.PREFERENCES_FILE;
+        }
+
+        return profileRelativeDirectory(profile) + "/" + ChatPreferences.PREFERENCES_FILE;
+    }
+
+    /**
+     * Returns the worked-station database file name relative to the application directory.
+     *
+     * <p>A profile using the common station database always resolves to the historic flat
+     * file, which is what a multi operator station wants: the existing contest state stays
+     * the shared one.</p>
+     *
+     * @param profile profile to resolve
+     * @return relative database file name
+     */
+    public static String workedDatabaseRelativeFileName(final OperatorProfile profile) {
+
+        if (profile.isRootProfile() || profile.isSharedWorkedDatabase()) {
+            return DBController.DATABASE_FILE;
+        }
+
+        return profileRelativeDirectory(profile) + "/" + DBController.DATABASE_FILE;
+    }
+
+    /**
+     * Resolves a profile descriptor into the runtime selection used during startup.
+     *
+     * @param profile profile to resolve
+     * @return resolved selection
+     */
+    public static OperatorProfileSelection resolve(final OperatorProfile profile) {
+
+        boolean usesSharedStationDatabase = profile.isRootProfile() || profile.isSharedWorkedDatabase();
+
+        return new OperatorProfileSelection(
+                profile,
+                preferencesRelativeFileName(profile),
+                workedDatabaseRelativeFileName(profile),
+                usesSharedStationDatabase
+        );
+    }
+
+    /**
+     * Derives a stable, file system safe identifier from a display name.
+     *
+     * <p>The identifier becomes a directory name and is never changed afterwards, so a
+     * later rename of the profile does not move any file.</p>
+     *
+     * @param displayName name entered by the operator
+     * @param takenProfileIds identifiers that are already in use
+     * @return an identifier that is not yet taken
+     */
+    public static String toProfileId(final String displayName, final Collection<String> takenProfileIds) {
+
+        StringBuilder sanitized = new StringBuilder();
+
+        if (displayName != null) {
+            String foldedDisplayName = foldGermanUmlauts(displayName.toUpperCase(Locale.ROOT));
+
+            for (char currentCharacter : foldedDisplayName.toCharArray()) {
+                boolean isAcceptable = (currentCharacter >= 'A' && currentCharacter <= 'Z')
+                        || (currentCharacter >= '0' && currentCharacter <= '9')
+                        || currentCharacter == '-';
+
+                if (isAcceptable) {
+                    sanitized.append(currentCharacter);
+                } else if (sanitized.length() > 0 && sanitized.charAt(sanitized.length() - 1) != '_') {
+                    sanitized.append('_');
+                }
+            }
+        }
+
+        while (sanitized.length() > 0 && sanitized.charAt(sanitized.length() - 1) == '_') {
+            sanitized.setLength(sanitized.length() - 1);
+        }
+
+        if (sanitized.length() > MAX_PROFILE_ID_LENGTH) {
+            sanitized.setLength(MAX_PROFILE_ID_LENGTH);
+        }
+
+        String candidate = sanitized.toString();
+
+        if (candidate.isEmpty() || ROOT_PROFILE_ID.equalsIgnoreCase(candidate)) {
+            candidate = "OP";
+        }
+
+        if (!isProfileIdTaken(candidate, takenProfileIds)) {
+            return candidate;
+        }
+
+        int suffix = 2;
+
+        while (isProfileIdTaken(candidate + "_" + suffix, takenProfileIds)) {
+            suffix++;
+        }
+
+        return candidate + "_" + suffix;
+    }
+
+    /**
+     * Folds German umlauts so a name like "Muller" written with an umlaut still produces a
+     * readable identifier instead of a placeholder character.
+     *
+     * @param upperCaseText already upper-cased text
+     * @return text with umlauts replaced by their base letters
+     */
+    private static String foldGermanUmlauts(final String upperCaseText) {
+        return upperCaseText
+                .replace("\u00C4", "A")
+                .replace("\u00D6", "O")
+                .replace("\u00DC", "U")
+                .replace("\u00DF", "SS");
+    }
+
+    private static boolean isProfileIdTaken(final String candidate, final Collection<String> takenProfileIds) {
+
+        if (ROOT_PROFILE_ID.equalsIgnoreCase(candidate)) {
+            return true;
+        }
+
+        if (takenProfileIds == null) {
+            return false;
+        }
+
+        for (String takenProfileId : takenProfileIds) {
+            if (candidate.equalsIgnoreCase(takenProfileId)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}

src/main/java/kst4contest/controller/OperatorProfileStore.java

@@ -0,0 +1,386 @@
+package kst4contest.controller;
+
+import kst4contest.ApplicationConstants;
+import kst4contest.model.OperatorProfile;
+import kst4contest.utils.ApplicationFileUtils;
+
+import org.w3c.dom.Document;
+import org.w3c.dom.Element;
+import org.w3c.dom.Node;
+import org.w3c.dom.NodeList;
+
+import javax.xml.XMLConstants;
+import javax.xml.parsers.DocumentBuilder;
+import javax.xml.parsers.DocumentBuilderFactory;
+import javax.xml.transform.OutputKeys;
+import javax.xml.transform.Transformer;
+import javax.xml.transform.TransformerFactory;
+import javax.xml.transform.dom.DOMSource;
+import javax.xml.transform.stream.StreamResult;
+
+import java.io.File;
+import java.io.OutputStream;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * Reads and writes the operator profile registry.
+ *
+ * <p>The registry file is created lazily. As long as an installation has only the
+ * historic flat layout, no registry exists and none is written, so a single operator
+ * installation behaves exactly as before. The file appears when the second profile is
+ * created; at that moment the root profile is materialised as well.</p>
+ *
+ * <p>A missing, unreadable or malformed registry is never fatal. It is logged and
+ * treated like an installation without additional profiles.</p>
+ */
+public class OperatorProfileStore {
+
+    private static final Logger LOGGER = Logger.getLogger(OperatorProfileStore.class.getName());
+
+    /**
+     * Name of the registry file inside the application directory.
+     */
+    public static final String PROFILES_REGISTRY_FILE = "profiles.xml";
+
+    private static final String TAG_ROOT = "praktiKSTProfiles";
+    private static final String TAG_REGISTRY_VERSION = "registryVersion";
+    private static final String TAG_LAST_USED_PROFILE_ID = "lastUsedProfileId";
+    private static final String TAG_PROFILE = "profile";
+    private static final String TAG_PROFILE_ID = "profileId";
+    private static final String TAG_DISPLAY_NAME = "displayName";
+    private static final String TAG_ROOT_PROFILE = "rootProfile";
+    private static final String TAG_SHARED_WORKED_DATABASE = "sharedWorkedDatabase";
+    private static final String TAG_LAST_USED_EPOCH_MS = "lastUsedEpochMs";
+
+    private static final int REGISTRY_VERSION = 1;
+
+    private final String registryFilePath;
+
+    /**
+     * Creates a store working on the registry of the current installation.
+     */
+    public OperatorProfileStore() {
+        this(ApplicationFileUtils.getFilePath(
+                ApplicationConstants.APPLICATION_NAME, PROFILES_REGISTRY_FILE));
+    }
+
+    /**
+     * Creates a store working on an explicit registry file.
+     *
+     * @param registryFilePath absolute path of the registry file
+     */
+    public OperatorProfileStore(final String registryFilePath) {
+        this.registryFilePath = registryFilePath;
+    }
+
+    /**
+     * Returns whether a registry file exists at all.
+     *
+     * @return true if the installation already has more than the historic flat layout
+     */
+    public boolean isRegistryPresent() {
+        return new File(registryFilePath).isFile();
+    }
+
+    /**
+     * Builds the in-memory descriptor of the historic flat installation.
+     *
+     * <p>Nothing is written. This keeps a single operator installation untouched.</p>
+     *
+     * @return the implicit root profile
+     */
+    public OperatorProfile buildImplicitRootProfile() {
+        return OperatorProfilePaths.buildRootProfile("Default");
+    }
+
+    /**
+     * Reads all stored profiles.
+     *
+     * @return the stored profiles, or an empty list when no usable registry exists
+     */
+    public List<OperatorProfile> loadProfiles() {
+
+        List<OperatorProfile> loadedProfiles = new ArrayList<>();
+        Document document = readRegistryDocument();
+
+        if (document == null) {
+            return loadedProfiles;
+        }
+
+        NodeList profileNodes = document.getElementsByTagName(TAG_PROFILE);
+
+        for (int profileIndex = 0; profileIndex < profileNodes.getLength(); profileIndex++) {
+            Node currentNode = profileNodes.item(profileIndex);
+
+            if (currentNode.getNodeType() != Node.ELEMENT_NODE) {
+                continue;
+            }
+
+            Element profileElement = (Element) currentNode;
+            String profileId = readText(profileElement, TAG_PROFILE_ID);
+
+            if (profileId == null || profileId.isBlank()) {
+                LOGGER.log(Level.WARNING, "Skipping operator profile entry without an identifier");
+                continue;
+            }
+
+            OperatorProfile loadedProfile = new OperatorProfile();
+            loadedProfile.setProfileId(profileId.trim());
+            loadedProfile.setDisplayName(readText(profileElement, TAG_DISPLAY_NAME));
+            loadedProfile.setRootProfile(readBoolean(profileElement, TAG_ROOT_PROFILE, false));
+            loadedProfile.setSharedWorkedDatabase(
+                    readBoolean(profileElement, TAG_SHARED_WORKED_DATABASE, true));
+            loadedProfile.setLastUsedEpochMs(readLong(profileElement, TAG_LAST_USED_EPOCH_MS));
+
+            if (loadedProfile.getDisplayName() == null || loadedProfile.getDisplayName().isBlank()) {
+                loadedProfile.setDisplayName(loadedProfile.getProfileId());
+            }
+
+            // The root profile always uses the common station database, because its
+            // database is the historic flat file itself.
+            if (loadedProfile.isRootProfile()) {
+                loadedProfile.setSharedWorkedDatabase(true);
+            }
+
+            loadedProfiles.add(loadedProfile);
+        }
+
+        return loadedProfiles;
+    }
+
+    /**
+     * Reads the identifier of the profile that was activated last.
+     *
+     * @return the identifier, or empty when unknown
+     */
+    public Optional<String> loadLastUsedProfileId() {
+
+        Document document = readRegistryDocument();
+
+        if (document == null) {
+            return Optional.empty();
+        }
+
+        Element rootElement = document.getDocumentElement();
+
+        if (rootElement == null) {
+            return Optional.empty();
+        }
+
+        String lastUsedProfileId = readText(rootElement, TAG_LAST_USED_PROFILE_ID);
+
+        if (lastUsedProfileId == null || lastUsedProfileId.isBlank()) {
+            return Optional.empty();
+        }
+
+        return Optional.of(lastUsedProfileId.trim());
+    }
+
+    /**
+     * Writes the complete registry.
+     *
+     * @param profiles          profiles to store
+     * @param lastUsedProfileId identifier of the profile that was activated last, may be null
+     * @return true if the registry was written
+     */
+    public boolean saveProfiles(final List<OperatorProfile> profiles, final String lastUsedProfileId) {
+
+        try {
+            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
+            DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
+            Document document = documentBuilder.newDocument();
+
+            Element rootElement = document.createElement(TAG_ROOT);
+            document.appendChild(rootElement);
+
+            appendTextElement(document, rootElement, TAG_REGISTRY_VERSION, String.valueOf(REGISTRY_VERSION));
+
+            if (lastUsedProfileId != null && !lastUsedProfileId.isBlank()) {
+                appendTextElement(document, rootElement, TAG_LAST_USED_PROFILE_ID, lastUsedProfileId);
+            }
+
+            for (OperatorProfile currentProfile : profiles) {
+                Element profileElement = document.createElement(TAG_PROFILE);
+                rootElement.appendChild(profileElement);
+
+                appendTextElement(document, profileElement, TAG_PROFILE_ID, currentProfile.getProfileId());
+                appendTextElement(document, profileElement, TAG_DISPLAY_NAME, currentProfile.getDisplayName());
+                appendTextElement(document, profileElement, TAG_ROOT_PROFILE,
+                        String.valueOf(currentProfile.isRootProfile()));
+                appendTextElement(document, profileElement, TAG_SHARED_WORKED_DATABASE,
+                        String.valueOf(currentProfile.isRootProfile() || currentProfile.isSharedWorkedDatabase()));
+                appendTextElement(document, profileElement, TAG_LAST_USED_EPOCH_MS,
+                        String.valueOf(currentProfile.getLastUsedEpochMs()));
+            }
+
+            return writeDocumentAtomically(document);
+        } catch (Exception e) {
+            LOGGER.log(Level.SEVERE, "Could not write the operator profile registry", e);
+            return false;
+        }
+    }
+
+    /**
+     * Records that a profile has been activated.
+     *
+     * <p>Does nothing when no registry exists, so a single operator installation is not
+     * turned into a multi profile installation by merely starting the application.</p>
+     *
+     * @param profileId identifier of the activated profile
+     * @return true if the registry was updated
+     */
+    public boolean recordLastUsed(final String profileId) {
+
+        if (!isRegistryPresent()) {
+            return false;
+        }
+
+        List<OperatorProfile> storedProfiles = loadProfiles();
+
+        if (storedProfiles.isEmpty()) {
+            return false;
+        }
+
+        for (OperatorProfile currentProfile : storedProfiles) {
+            if (currentProfile.getProfileId().equalsIgnoreCase(profileId)) {
+                currentProfile.setLastUsedEpochMs(System.currentTimeMillis());
+            }
+        }
+
+        return saveProfiles(storedProfiles, profileId);
+    }
+
+    /**
+     * Returns the absolute path of the registry file.
+     *
+     * @return absolute registry path
+     */
+    public String getRegistryFilePath() {
+        return registryFilePath;
+    }
+
+    private Document readRegistryDocument() {
+
+        File registryFile = new File(registryFilePath);
+
+        if (!registryFile.isFile()) {
+            return null;
+        }
+
+        try {
+            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
+            documentBuilderFactory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
+
+            return documentBuilderFactory.newDocumentBuilder().parse(registryFile);
+        } catch (Exception e) {
+            LOGGER.log(Level.WARNING,
+                    "Could not read the operator profile registry, continuing without additional profiles", e);
+            return null;
+        }
+    }
+
+    private static String readText(final Element parentElement, final String tagName) {
+
+        NodeList matchingNodes = parentElement.getElementsByTagName(tagName);
+
+        if (matchingNodes.getLength() == 0) {
+            return null;
+        }
+
+        return matchingNodes.item(0).getTextContent();
+    }
+
+    private static boolean readBoolean(final Element parentElement,
+            final String tagName,
+            final boolean defaultValue) {
+
+        String rawValue = readText(parentElement, tagName);
+
+        if (rawValue == null || rawValue.isBlank()) {
+            return defaultValue;
+        }
+
+        return Boolean.parseBoolean(rawValue.trim());
+    }
+
+    private static long readLong(final Element parentElement, final String tagName) {
+
+        String rawValue = readText(parentElement, tagName);
+
+        if (rawValue == null || rawValue.isBlank()) {
+            return 0L;
+        }
+
+        try {
+            return Long.parseLong(rawValue.trim());
+        } catch (NumberFormatException e) {
+            return 0L;
+        }
+    }
+
+    private static void appendTextElement(final Document document,
+            final Element parentElement,
+            final String tagName,
+            final String textContent) {
+
+        Element createdElement = document.createElement(tagName);
+        createdElement.setTextContent(textContent == null ? "" : textContent);
+        parentElement.appendChild(createdElement);
+    }
+
+    /**
+     * Writes the registry through a temporary file so a crash can never leave a
+     * half-written registry behind. This mirrors the established preferences writer.
+     *
+     * @param document document to write
+     * @return true if the registry file was replaced
+     */
+    private boolean writeDocumentAtomically(final Document document) {
+
+        Path targetPath = Path.of(registryFilePath).toAbsolutePath();
+        Path parentDirectory = targetPath.getParent();
+
+        if (parentDirectory == null) {
+            LOGGER.log(Level.SEVERE,
+                    "The operator profile registry path has no directory: {0}", registryFilePath);
+            return false;
+        }
+
+        try {
+            Files.createDirectories(parentDirectory);
+
+            // The temporary file has to live next to the target so the final move can be
+            // atomic; both must be on the same file system.
+            Path temporaryPath = Files.createTempFile(
+                    parentDirectory, PROFILES_REGISTRY_FILE, ".tmp");
+
+            Transformer transformer = TransformerFactory.newInstance().newTransformer();
+            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
+            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
+
+            try (OutputStream outputStream = Files.newOutputStream(temporaryPath)) {
+                transformer.transform(new DOMSource(document), new StreamResult(outputStream));
+            }
+
+            try {
+                Files.move(temporaryPath, targetPath,
+                        StandardCopyOption.REPLACE_EXISTING, StandardCopyOption.ATOMIC_MOVE);
+            } catch (AtomicMoveNotSupportedException atomicMoveUnsupported) {
+                Files.move(temporaryPath, targetPath, StandardCopyOption.REPLACE_EXISTING);
+            }
+
+            return true;
+        } catch (Exception e) {
+            LOGGER.log(Level.SEVERE, "Could not store the operator profile registry", e);
+            return false;
+        }
+    }
+}

src/main/java/kst4contest/controller/SkedReminderService.java

@@ -33,6 +33,24 @@ public final class SkedReminderService {
         this.controller = controller;
     }
 
+    /**
+     * Cancels every armed reminder and stops the scheduler thread.
+     *
+     * <p>Called when the runtime that owns this service is torn down, so a discarded
+     * runtime does not keep a thread and pending reminders alive.</p>
+     */
+    public void shutdown() {
+
+        for (List<ScheduledFuture<?>> remindersOfOneCall : scheduledByCallRaw.values()) {
+            for (ScheduledFuture<?> armedReminder : remindersOfOneCall) {
+                armedReminder.cancel(false);
+            }
+        }
+
+        scheduledByCallRaw.clear();
+        scheduler.shutdownNow();
+    }
+
     /**
      * Arms reminders for one sked. Existing reminders for this call are cancelled.
      *

src/main/java/kst4contest/model/ChatPreferences.java

@@ -79,7 +79,26 @@ public class ChatPreferences {
 	 * TODO: delete this from the kst4contest.view/Main.java!
 	 */
 	public ChatPreferences() {
-		ApplicationFileUtils.copyResourceIfRequired(ApplicationConstants.APPLICATION_NAME, PREFERENCE_RESOURCE, PREFERENCES_FILE);
+		this(PREFERENCES_FILE);
+	}
+
+	/**
+	 * Creates preferences bound to one operator profile.
+	 *
+	 * <p>The file name is resolved below the application directory, so both
+	 * "preferences.xml" for the root installation and "profiles/OP2/preferences.xml"
+	 * for an additional operator profile are valid. A missing file is seeded from the
+	 * bundled template, which gives a new profile the same clean defaults a first-ever
+	 * installation gets.</p>
+	 *
+	 * @param applicationRelativeFileName preferences file name relative to the application directory
+	 */
+	public ChatPreferences(final String applicationRelativeFileName) {
+		ApplicationFileUtils.copyResourceIfRequired(ApplicationConstants.APPLICATION_NAME, PREFERENCE_RESOURCE, applicationRelativeFileName);
+		this.storeAndRestorePreferencesFileName = ApplicationFileUtils.getFilePath(
+				ApplicationConstants.APPLICATION_NAME,
+				applicationRelativeFileName
+		);
 
 //        lstNotify_QSOSniffer_sniffedCallSignList.add("DF0GEB");
 
@@ -168,8 +187,14 @@ public class ChatPreferences {
 	int stn_pstRotatorPort = 12000;
 
 	boolean stn_loginAFKState = false; //always start as here
-	String stn_loginCallSign = "do5amf";
+	/*
-	String stn_loginCallSignRaw = "do5amf"; //for example: do5amf instead of logincallsign do5amf-2
+	 * The login credentials default to empty on purpose. A missing or empty value in
+	 * preferences.xml means "not configured yet", and falling back to a real callsign
+	 * would let an operator transmit under someone else's call. This matters for every
+	 * additional operator profile, whose preferences are created without credentials.
+	 */
+	String stn_loginCallSign = "";
+	String stn_loginCallSignRaw = ""; //for example: do5amf instead of logincallsign do5amf-2
 	String stn_loginPassword = "";
 	String stn_loginNameMainCat = "KST4Contest";
 	String stn_loginNameSecondCat = "KST4ContestSHF";

src/main/java/kst4contest/model/OperatorProfile.java

@@ -0,0 +1,133 @@
+package kst4contest.model;
+
+import java.util.Objects;
+
+/**
+ * Descriptor of one operator profile.
+ *
+ * <p>A profile always owns its own preferences file. Whether it also owns its own
+ * worked-station database is decided by {@link #isSharedWorkedDatabase()}: a multi
+ * operator contest station keeps one common log and therefore shares the database,
+ * while two operators sharing a private computer usually want their worked data kept
+ * apart.</p>
+ *
+ * <p>The descriptor deliberately carries no file paths. They are derived in exactly one
+ * place, {@link kst4contest.controller.OperatorProfilePaths}, so a stored path can never
+ * drift apart from the flag that produced it.</p>
+ */
+public class OperatorProfile {
+
+    /**
+     * Stable identifier of the profile. It is assigned once and never changes, so
+     * renaming a profile never moves a directory.
+     */
+    private String profileId;
+
+    /**
+     * Name shown in the profile picker and in the settings window.
+     */
+    private String displayName;
+
+    /**
+     * True for the profile that uses the historic flat installation layout directly.
+     */
+    private boolean rootProfile;
+
+    /**
+     * True if this profile uses the common station worked-station database.
+     */
+    private boolean sharedWorkedDatabase;
+
+    /**
+     * Timestamp of the last activation, used to preselect an entry in the picker.
+     */
+    private long lastUsedEpochMs;
+
+    public OperatorProfile() {
+        // Default constructor for stepwise construction while reading the registry.
+    }
+
+    public OperatorProfile(final String profileId,
+            final String displayName,
+            final boolean rootProfile,
+            final boolean sharedWorkedDatabase) {
+        this.profileId = profileId;
+        this.displayName = displayName;
+        this.rootProfile = rootProfile;
+        this.sharedWorkedDatabase = sharedWorkedDatabase;
+    }
+
+    public String getProfileId() {
+        return profileId;
+    }
+
+    public void setProfileId(final String profileId) {
+        this.profileId = profileId;
+    }
+
+    public String getDisplayName() {
+        return displayName;
+    }
+
+    public void setDisplayName(final String displayName) {
+        this.displayName = displayName;
+    }
+
+    public boolean isRootProfile() {
+        return rootProfile;
+    }
+
+    public void setRootProfile(final boolean rootProfile) {
+        this.rootProfile = rootProfile;
+    }
+
+    public boolean isSharedWorkedDatabase() {
+        return sharedWorkedDatabase;
+    }
+
+    public void setSharedWorkedDatabase(final boolean sharedWorkedDatabase) {
+        this.sharedWorkedDatabase = sharedWorkedDatabase;
+    }
+
+    public long getLastUsedEpochMs() {
+        return lastUsedEpochMs;
+    }
+
+    public void setLastUsedEpochMs(final long lastUsedEpochMs) {
+        this.lastUsedEpochMs = lastUsedEpochMs;
+    }
+
+    @Override
+    public boolean equals(final Object other) {
+
+        if (this == other) {
+            return true;
+        }
+
+        if (!(other instanceof OperatorProfile)) {
+            return false;
+        }
+
+        return Objects.equals(profileId, ((OperatorProfile) other).profileId);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(profileId);
+    }
+
+    /**
+     * Returns the display name so the descriptor can be shown in a list control directly.
+     *
+     * @return the display name, or the profile id when no name was set
+     */
+    @Override
+    public String toString() {
+
+        if (displayName == null || displayName.isBlank()) {
+            return String.valueOf(profileId);
+        }
+
+        return displayName;
+    }
+}

src/main/java/kst4contest/model/OperatorProfileSelection.java

@@ -0,0 +1,70 @@
+package kst4contest.model;
+
+import kst4contest.ApplicationConstants;
+import kst4contest.utils.ApplicationFileUtils;
+
+import java.util.Objects;
+
+/**
+ * Resolved runtime view of the active operator profile.
+ *
+ * <p>This is the only profile information the rest of the application needs: two file
+ * names relative to the application directory plus the flag whether a missing
+ * worked-station database may be seeded from the bundled template. Everything else is
+ * derived from the descriptor.</p>
+ */
+public class OperatorProfileSelection {
+
+    private final OperatorProfile profile;
+    private final String preferencesRelativeFileName;
+    private final String workedDatabaseRelativeFileName;
+    private final boolean seedWorkedDatabaseFromResource;
+
+    public OperatorProfileSelection(final OperatorProfile profile,
+            final String preferencesRelativeFileName,
+            final String workedDatabaseRelativeFileName,
+            final boolean seedWorkedDatabaseFromResource) {
+        this.profile = Objects.requireNonNull(profile, "profile");
+        this.preferencesRelativeFileName =
+                Objects.requireNonNull(preferencesRelativeFileName, "preferencesRelativeFileName");
+        this.workedDatabaseRelativeFileName =
+                Objects.requireNonNull(workedDatabaseRelativeFileName, "workedDatabaseRelativeFileName");
+        this.seedWorkedDatabaseFromResource = seedWorkedDatabaseFromResource;
+    }
+
+    public OperatorProfile getProfile() {
+        return profile;
+    }
+
+    public String getPreferencesRelativeFileName() {
+        return preferencesRelativeFileName;
+    }
+
+    public String getWorkedDatabaseRelativeFileName() {
+        return workedDatabaseRelativeFileName;
+    }
+
+    public boolean isSeedWorkedDatabaseFromResource() {
+        return seedWorkedDatabaseFromResource;
+    }
+
+    /**
+     * Returns the absolute preferences path, for display in the settings window.
+     *
+     * @return absolute path of the preferences file
+     */
+    public String getPreferencesAbsolutePath() {
+        return ApplicationFileUtils.getFilePath(
+                ApplicationConstants.APPLICATION_NAME, preferencesRelativeFileName);
+    }
+
+    /**
+     * Returns the absolute worked-station database path, for display in the settings window.
+     *
+     * @return absolute path of the worked-station database
+     */
+    public String getWorkedDatabaseAbsolutePath() {
+        return ApplicationFileUtils.getFilePath(
+                ApplicationConstants.APPLICATION_NAME, workedDatabaseRelativeFileName);
+    }
+}

src/main/java/kst4contest/view/ApplicationRuntimeLauncher.java

@@ -0,0 +1,106 @@
+package kst4contest.view;
+
+import kst4contest.controller.ActiveOperatorProfile;
+import kst4contest.controller.OperatorProfilePaths;
+import kst4contest.controller.OperatorProfileStore;
+import kst4contest.model.OperatorProfile;
+
+import javafx.application.Platform;
+import javafx.stage.Stage;
+
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+/**
+ * Owns the lifecycle of the running application.
+ *
+ * <p>Switching the operator profile tears the current runtime down completely and builds
+ * a fresh one in the same process. Rebinding the existing windows is not an option: the
+ * user interface is built from the chat controller outwards, with several hundred
+ * references to the active preferences, and many controls are instance fields created
+ * once. A new {@link Kst4ContestApplication} instance gets fresh controls, which is safe
+ * here because the class keeps no mutable static state.</p>
+ */
+public final class ApplicationRuntimeLauncher {
+
+    private static final Logger LOGGER = Logger.getLogger(ApplicationRuntimeLauncher.class.getName());
+
+    private static Kst4ContestApplication currentRuntime;
+
+    private ApplicationRuntimeLauncher() {
+        // Utility class.
+    }
+
+    /**
+     * Registers the runtime that is currently live.
+     *
+     * @param runtime the running application instance
+     */
+    public static void setCurrent(final Kst4ContestApplication runtime) {
+        currentRuntime = runtime;
+    }
+
+    /**
+     * Returns the runtime that is currently live.
+     *
+     * @return the running application instance, or null before the first startup
+     */
+    public static Kst4ContestApplication getCurrent() {
+        return currentRuntime;
+    }
+
+    /**
+     * Shuts the application down.
+     *
+     * <p>JavaFX only calls {@code stop()} on the instance it launched itself, so an exit
+     * after a profile switch has to release the resources explicitly.</p>
+     */
+    public static void exitApplication() {
+
+        if (currentRuntime != null) {
+            currentRuntime.shutdownRuntime();
+        }
+
+        Platform.exit();
+        System.exit(0);
+    }
+
+    /**
+     * Replaces the running runtime with one bound to another operator profile.
+     *
+     * @param targetProfile profile to activate
+     * @return true if the new runtime was built
+     */
+    public static boolean switchProfile(final OperatorProfile targetProfile) {
+
+        if (targetProfile == null) {
+            return false;
+        }
+
+        new OperatorProfileStore().recordLastUsed(targetProfile.getProfileId());
+
+        if (currentRuntime != null) {
+            currentRuntime.shutdownRuntime();
+        }
+
+        ActiveOperatorProfile.set(OperatorProfilePaths.resolve(targetProfile));
+
+        Kst4ContestApplication nextRuntime = new Kst4ContestApplication();
+
+        try {
+            nextRuntime.start(new Stage());
+        } catch (Exception e) {
+            // The previous runtime is already gone, so there is nothing left to return to.
+            LOGGER.log(Level.SEVERE, "Could not start the selected operator profile", e);
+            Kst4ContestApplication.alertWindowEvent(
+                    "The operator profile could not be started: " + e.getMessage()
+                            + "\n\nKST4Contest has to be closed.");
+            Platform.exit();
+            System.exit(1);
+            return false;
+        }
+
+        setCurrent(nextRuntime);
+        return true;
+    }
+}

src/main/java/kst4contest/view/CommandLineOptions.java

@@ -0,0 +1,102 @@
+package kst4contest.view;
+
+import java.util.List;
+
+/**
+ * Command line options of the application.
+ *
+ * <p>The parsed value is additionally kept in a process wide holder. JavaFX only knows
+ * the parameters of the {@code Application} instance it launched itself, so an instance
+ * created during a profile switch would see no parameters at all. Parsing once at
+ * startup and remembering the result avoids that entirely.</p>
+ */
+public class CommandLineOptions {
+
+    /**
+     * Command line switch selecting the operator profile to start with.
+     */
+    public static final String PROFILE_ARGUMENT = "--profile";
+
+    /**
+     * System property used as an alternative to the command line switch.
+     */
+    public static final String PROFILE_SYSTEM_PROPERTY = "kst4contest.profile";
+
+    private static volatile CommandLineOptions rememberedOptions = new CommandLineOptions(null);
+
+    private final String requestedProfileName;
+
+    public CommandLineOptions(final String requestedProfileName) {
+        this.requestedProfileName = requestedProfileName;
+    }
+
+    /**
+     * Parses the raw application arguments.
+     *
+     * <p>Unknown arguments are ignored on purpose. A typo in a command line must never
+     * keep an operator out of the application shortly before a contest.</p>
+     *
+     * @param rawArguments raw arguments, may be null
+     * @return the parsed options
+     */
+    public static CommandLineOptions parse(final List<String> rawArguments) {
+
+        String requestedProfileName = null;
+
+        if (rawArguments != null) {
+            for (int argumentIndex = 0; argumentIndex < rawArguments.size(); argumentIndex++) {
+                String currentArgument = rawArguments.get(argumentIndex);
+
+                if (currentArgument == null) {
+                    continue;
+                }
+
+                if (currentArgument.startsWith(PROFILE_ARGUMENT + "=")) {
+                    requestedProfileName = currentArgument.substring(PROFILE_ARGUMENT.length() + 1);
+                } else if (PROFILE_ARGUMENT.equals(currentArgument)
+                        && argumentIndex + 1 < rawArguments.size()) {
+                    requestedProfileName = rawArguments.get(argumentIndex + 1);
+                    argumentIndex++;
+                }
+            }
+        }
+
+        if (requestedProfileName == null || requestedProfileName.isBlank()) {
+            requestedProfileName = System.getProperty(PROFILE_SYSTEM_PROPERTY);
+        }
+
+        if (requestedProfileName != null && requestedProfileName.isBlank()) {
+            requestedProfileName = null;
+        }
+
+        return new CommandLineOptions(
+                requestedProfileName == null ? null : requestedProfileName.trim());
+    }
+
+    /**
+     * Stores the parsed options for the lifetime of the process.
+     *
+     * @param options options to remember
+     */
+    public static void remember(final CommandLineOptions options) {
+        rememberedOptions = options == null ? new CommandLineOptions(null) : options;
+    }
+
+    /**
+     * Returns the options parsed at application startup.
+     *
+     * @return the remembered options, never null
+     */
+    public static CommandLineOptions remembered() {
+        return rememberedOptions;
+    }
+
+    /**
+     * Returns the operator profile requested on the command line.
+     *
+     * @return the requested profile name, or null when none was given
+     */
+    public String getRequestedProfileName() {
+        return requestedProfileName;
+    }
+}

src/main/java/kst4contest/view/Kst4ContestApplication.java

@@ -15,6 +15,7 @@ import java.util.logging.SimpleFormatter;
 import java.util.function.Consumer;
 import java.util.function.Predicate;
 
+import javafx.animation.Animation;
 import javafx.animation.KeyFrame;
 import javafx.animation.Timeline;
 import javafx.collections.FXCollections;
@@ -70,6 +71,12 @@ import javafx.stage.Screen;
 import kst4contest.logic.BandOpportunityResolver;
 import kst4contest.utils.ApplicationFileUtils;
 import kst4contest.view.map.StationMapBridge;
+import kst4contest.controller.ActiveOperatorProfile;
+import kst4contest.controller.OperatorProfileStore;
+import kst4contest.controller.OperatorProfileManagementService;
+import kst4contest.controller.OperatorProfilePaths;
+import kst4contest.model.OperatorProfile;
+import kst4contest.model.OperatorProfileSelection;
 import kst4contest.view.map.StationMapView;
 import kst4contest.view.map.OfflineDemImportService;
 import kst4contest.controller.WorkedGrossFieldCache;
@@ -5500,6 +5507,9 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 		});
 
 
+		MenuItem menuItemFileSwitchProfile = new MenuItem("Switch operator profile...");
+		menuItemFileSwitchProfile.setOnAction(event -> showOperatorProfileSwitchDialog());
+
 		MenuItem m10 = new MenuItem("Exit + disconnect");
 		m10.setOnAction(new EventHandler<ActionEvent>() {
 			public void handle(ActionEvent event) {
@@ -5510,6 +5520,7 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 		// add menu items to menu
 		fileMenu.getItems().add(menuItemFileConnect);
 		fileMenu.getItems().add(menuItemFileDisconnect);
+		fileMenu.getItems().add(menuItemFileSwitchProfile);
 		fileMenu.getItems().add(m10);
 
 		Menu optionsMenu = new Menu("Options");
@@ -6096,6 +6107,17 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 	FlowPane flwPane_textSnippets;
     FlowPane flwpne_StatusBar;
 
+	/**
+	 * True once this runtime released its resources. Shutdown must stay idempotent
+	 * because it is reached both through the JavaFX stop() callback and explicitly.
+	 */
+	private boolean runtimeShutdownDone;
+
+	/**
+	 * The primary stage of this runtime, remembered so shutdown can close it.
+	 */
+	private Stage ownPrimaryStage;
+
 	Stage clusterAndQSOMonStage;
 //	Stage stage_selectedCallSignInfoStage;
 	ChatMember selectedCallSignInfoStageChatMember;
@@ -6227,29 +6249,264 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 		return txMessageButtons;
 	}
 
+	/**
+	 * Resolves the operator profile this runtime works with.
+	 *
+	 * <p>Only executed on the very first launch. A profile switch sets the profile before
+	 * building the new runtime, so the resolution is skipped there.</p>
+	 *
+	 * <p>An installation with no or exactly one profile is resolved without asking
+	 * anything, which keeps the single operator startup exactly as it was.</p>
+	 *
+	 * @return true if the application may continue starting up
+	 */
+	private boolean resolveOperatorProfileIfRequired() {
+
+		if (ActiveOperatorProfile.isInitialized()) {
+			return true;
+		}
+
+		OperatorProfileBootstrap bootstrap = new OperatorProfileBootstrap();
+		OperatorProfileSelection resolvedProfile = bootstrap.resolveAtStartup(
+				new OperatorProfileStore(),
+				CommandLineOptions.remembered(),
+				OperatorProfilePickerDialog::showAndSelect);
+
+		if (bootstrap.getStartupWarning() != null) {
+			Alert startupWarning = new Alert(AlertType.WARNING);
+			startupWarning.setTitle("Operator profile");
+			startupWarning.setHeaderText("The requested operator profile was not found.");
+			startupWarning.setContentText(bootstrap.getStartupWarning());
+			startupWarning.showAndWait();
+		}
+
+		if (resolvedProfile == null) {
+			Platform.exit();
+			System.exit(0);
+			return false;
+		}
+
+		ActiveOperatorProfile.set(resolvedProfile);
+		return true;
+	}
+
+	/**
+	 * Returns the window title suffix naming the active operator profile.
+	 *
+	 * <p>Empty for the historic single profile installation, so nothing changes visually
+	 * for operators who never create a second profile.</p>
+	 *
+	 * @return the suffix to append to a window title, never null
+	 */
+	private String buildOperatorProfileTitleSuffix() {
+
+		OperatorProfileSelection activeProfile = ActiveOperatorProfile.get();
+
+		if (activeProfile == null || activeProfile.getProfile().isRootProfile()) {
+			return "";
+		}
+
+		return " - " + activeProfile.getProfile().getDisplayName();
+	}
+
+	/**
+	 * Lets the operator pick another profile and rebuilds the runtime for it.
+	 *
+	 * <p>Offers to create a second profile when only one exists, because the menu entry
+	 * is the discoverable place to find the feature at all.</p>
+	 */
+	private void showOperatorProfileSwitchDialog() {
+
+		OperatorProfileStore profileStore = new OperatorProfileStore();
+		List<OperatorProfile> selectableProfiles = profileStore.loadProfiles();
+
+		if (selectableProfiles.size() < 2) {
+			Alert noProfilesYet = new Alert(AlertType.INFORMATION);
+			noProfilesYet.setTitle("Operator profiles");
+			noProfilesYet.setHeaderText("Only one operator profile is configured.");
+			noProfilesYet.setContentText(
+					"Additional profiles are created in the settings window on the "
+							+ "\"Profiles\" tab. Each profile keeps its own settings and layout, "
+							+ "and can either share the station worked database or use its own.");
+			noProfilesYet.showAndWait();
+			return;
+		}
+
+		OperatorProfileSelection activeProfile = ActiveOperatorProfile.get();
+		String activeProfileId = activeProfile == null ? null : activeProfile.getProfile().getProfileId();
+
+		Optional<OperatorProfile> chosenProfile =
+				OperatorProfilePickerDialog.showAndSelect(selectableProfiles, activeProfileId);
+
+		if (chosenProfile.isEmpty()) {
+			return;
+		}
+
+		if (chosenProfile.get().getProfileId().equalsIgnoreCase(activeProfileId)) {
+			return;
+		}
+
+		requestOperatorProfileSwitch(chosenProfile.get());
+	}
+
+	/**
+	 * Confirms and performs a switch to another operator profile.
+	 *
+	 * <p>Shared by the File menu and the profile settings tab, so both ask the same
+	 * question before giving up the running session.</p>
+	 *
+	 * @param targetProfile profile to activate
+	 */
+	private void requestOperatorProfileSwitch(OperatorProfile targetProfile) {
+
+		if (targetProfile == null || !confirmOperatorProfileSwitch(targetProfile)) {
+			return;
+		}
+
+		ApplicationRuntimeLauncher.switchProfile(targetProfile);
+	}
+
+	/**
+	 * Asks whether the running session may be given up for a profile switch.
+	 *
+	 * @param targetProfile profile the operator selected
+	 * @return true if the switch may proceed
+	 */
+	private boolean confirmOperatorProfileSwitch(OperatorProfile targetProfile) {
+
+		Alert confirmation = new Alert(AlertType.CONFIRMATION);
+		confirmation.setTitle("Switch operator profile");
+		confirmation.setHeaderText("Switch to \"" + targetProfile.getDisplayName() + "\"?");
+		confirmation.setContentText(
+				"The ON4KST connection is closed and all windows are rebuilt with the "
+						+ "settings and layout of the selected profile.\n\n"
+						+ "Unsaved settings of the current profile are lost. Window sizes, "
+						+ "divider and column widths are saved automatically.");
+
+		ButtonType switchButton = new ButtonType("Switch profile", ButtonBar.ButtonData.OK_DONE);
+		ButtonType cancelButton = new ButtonType("Cancel", ButtonBar.ButtonData.CANCEL_CLOSE);
+		confirmation.getButtonTypes().setAll(switchButton, cancelButton);
+
+		return confirmation.showAndWait().orElse(cancelButton) == switchButton;
+	}
+
 	@Override
 	public void stop() {
-		System.out.println("[Main.java, Info:] Stage is closing, killing all resources");
+		shutdownRuntime();
-		if (layoutAutosave != null) {
+		System.exit(0);
-			layoutAutosave.flushPending();
 	}
-		timer_buildWindowTitle.purge();
+
-		timer_buildWindowTitle.cancel();
+	/**
+	 * Releases every resource this runtime owns, without terminating the process.
+	 *
+	 * <p>Separated from {@link #stop()} so the same teardown can be reused when the
+	 * operator switches to another profile and a fresh runtime is built afterwards.
+	 * The method is idempotent and tolerates a runtime that never connected, because a
+	 * switch may happen before the first login.</p>
+	 */
+	public void shutdownRuntime() {
+
+		if (runtimeShutdownDone) {
+			return;
+		}
+
+		runtimeShutdownDone = true;
+
+		System.out.println("[Main.java, Info:] Stage is closing, killing all resources");
+
+		if (layoutAutosave != null) {
+			// Flush before cancelling, otherwise a pending debounced write would either
+			// be lost or land after a profile switch.
+			layoutAutosave.flushPending();
+			layoutAutosave.cancelPending();
+		}
+
+		cancelViewTimer(timer_buildWindowTitle);
+		timer_buildWindowTitle = null;
 
 //		timer_chatMemberTableSortTimer.purge();
 //		timer_chatMemberTableSortTimer.cancel();
 
-		timer_updatePrivatemessageTable.purge();
+		cancelViewTimer(timer_updatePrivatemessageTable);
-		timer_updatePrivatemessageTable.cancel();
+		timer_updatePrivatemessageTable = null;
+
+		stopAnimation(userListRefreshCoalescer);
+		userListRefreshCoalescer = null;
+		stopAnimation(skedWarnBlinkTimeline);
+		skedWarnBlinkTimeline = null;
+		stopAnimation(bandUpgradeBlinkTimeline);
+		bandUpgradeBlinkTimeline = null;
+
+		if (stationMapBridge != null) {
+			stationMapBridge.uninstall();
+			stationMapBridge = null;
+		}
+
+		if (stationMapView != null) {
+			stationMapView.dispose();
+			stationMapView = null;
+		}
+
+		closeOwnedStages();
 
 		try {
-			chatcontroller.disconnect("CLOSEALL");
+			if (chatcontroller != null) {
+				chatcontroller.disconnect(ApplicationConstants.DISCSTRING_DISCONNECT_AND_CLOSE);
+			}
 		} catch (Exception e) {
 			System.out.println("[Main.java, Warning:] Exception during disconnect: " + e.getMessage());
 		}
+	}
 
-//	    Platform.exit();
+	/**
-		System.exit(0);
+	 * Cancels a timer created during user interface construction.
+	 *
+	 * @param timerToCancel timer to cancel, may be null when startup did not get that far
+	 */
+	private static void cancelViewTimer(Timer timerToCancel) {
+
+		if (timerToCancel == null) {
+			return;
+		}
+
+		timerToCancel.purge();
+		timerToCancel.cancel();
+	}
+
+	/**
+	 * Stops a JavaFX animation if it exists.
+	 *
+	 * @param animationToStop animation to stop, may be null
+	 */
+	private static void stopAnimation(Animation animationToStop) {
+
+		if (animationToStop != null) {
+			animationToStop.stop();
+		}
+	}
+
+	/**
+	 * Closes every window this runtime opened, so no stale window survives a profile
+	 * switch. The map window is closed by its own dispose method.
+	 */
+	private void closeOwnedStages() {
+
+		for (Stage ownedStage : new Stage[] {
+				settingsStage, clusterAndQSOMonStage, stage_updateStage, ownPrimaryStage }) {
+
+			if (ownedStage != null) {
+				try {
+					ownedStage.close();
+				} catch (Exception e) {
+					System.out.println("[Main.java, Warning:] Could not close a window: " + e.getMessage());
+				}
+			}
+		}
+
+		settingsStage = null;
+		clusterAndQSOMonStage = null;
+		stage_updateStage = null;
+		ownPrimaryStage = null;
 	}
 
 	private void requestLayoutSave() {
@@ -6644,9 +6901,36 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 		};
 	}
 
+	@Override
+	public void init() {
+
+		Parameters applicationParameters = getParameters();
+
+		CommandLineOptions.remember(CommandLineOptions.parse(
+				applicationParameters == null ? null : applicationParameters.getRaw()));
+	}
+
 	@Override
 	public void start(Stage primaryStage) throws InterruptedException, IOException, URISyntaxException {
 
+		if (!resolveOperatorProfileIfRequired()) {
+			return;
+		}
+
+		ownPrimaryStage = primaryStage;
+
+		/*
+		 * A profile switch closes every window of the old runtime before the new one
+		 * exists. With the JavaFX default that would end the process, so the application
+		 * takes over the exit decision and closing the main window is handled explicitly.
+		 */
+		Platform.setImplicitExit(false);
+		primaryStage.setOnCloseRequest(closeRequest -> {
+			closeRequest.consume();
+			ApplicationRuntimeLauncher.exitApplication();
+		});
+		ApplicationRuntimeLauncher.setCurrent(this);
+
 		GuiUtils.applyApplicationIcon(primaryStage);
 
 		VBox pnl_inputAndSendButtons = new VBox(); //gets the sendtext field, send button and the timeline
@@ -6681,8 +6965,15 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 		ApplicationFileUtils.copyResourceIfRequired(ApplicationConstants.APPLICATION_NAME, STYLE_DEFAULTCSSDAY_RESOURCE, STYLE_DEFAULTCSSDAY_FILE);
 		ApplicationFileUtils.copyResourceIfRequired(ApplicationConstants.APPLICATION_NAME, STYLE_DEFAULTCSSEVENING_RESOURCE, STYLE_DEFAULTCSSEVENING_FILE);
 		ChatMember ownChatMemberObject = new ChatMember();
+		OperatorProfileSelection activeOperatorProfile = ActiveOperatorProfile.get();
 
-		chatcontroller = new ChatController(ownChatMemberObject, this); // instantiate the Chatcontroller with the user object
+		// instantiate the Chatcontroller with the user object and the files of the active profile
+		chatcontroller = new ChatController(
+				ownChatMemberObject,
+				this,
+				activeOperatorProfile.getPreferencesRelativeFileName(),
+				activeOperatorProfile.getWorkedDatabaseRelativeFileName(),
+				activeOperatorProfile.isSeedWorkedDatabaseFromResource());
 		layoutAutosave = new LayoutAutosave(chatcontroller.getChatPreferences());
 		messageVariableResolver = new MessageVariableResolver(chatcontroller.getChatPreferences());
 		chatcontroller.setStatusListener(this); //callback interface for updating Thread events in visual
@@ -7200,7 +7491,7 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 			txt_ownqrgSecondCategory.setFocusTraversable(false);
 			txt_ownqrgSecondCategory.setTooltip(new Tooltip("Enter frequency for second chat-category here by hand! <fixme>"));
 
-			primaryStage.setTitle(chatcontroller.getChatPreferences().getChatState());
+			primaryStage.setTitle(chatcontroller.getChatPreferences().getChatState() + buildOperatorProfileTitleSuffix());
 
 			timer_buildWindowTitle = new Timer();
 			timer_buildWindowTitle.scheduleAtFixedRate(new TimerTask() {
@@ -7255,7 +7546,7 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 							chatcontroller.getChatPreferences().setChatState(chatState);
 						}
 
-						primaryStage.setTitle(chatcontroller.getChatPreferences().getChatState());
+						primaryStage.setTitle(chatcontroller.getChatPreferences().getChatState() + buildOperatorProfileTitleSuffix());
 
 //						System.out.println(chatcontroller.getChatPreferences().getChatState());
 					});
@@ -11751,6 +12042,14 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 		Tab tbInternalDB = new Tab("Workedstn database", vbxInternalDB);
 		Tab tbGui = new Tab("GUI", vbxGuiOptions);
 
+		/*
+		 * Appended last on purpose so no established tab position shifts. Contest
+		 * operators navigate these tabs by muscle memory.
+		 */
+		Tab tbProfiles = new Tab("Profiles", new OperatorProfileSettingsPane(
+				new OperatorProfileManagementService(),
+				this::requestOperatorProfileSwitch));
+
 
 		/**
 		 * Automatic update of tab contents out of the database
@@ -11766,7 +12065,7 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 
 
 		tabPaneOptions.getTabs().addAll(tbStationSettings, tbLogSynchSet, tbTRXSynchSet, tbAirScoutSettings, tbNotify,
-				tbShorts, tbBeacon, tbMsgHandling, tbInternalDB, tbGui);
+				tbShorts, tbBeacon, tbMsgHandling, tbInternalDB, tbGui, tbProfiles);
 
 		optionsPanel.setLeft(tabPaneOptions);
 
@@ -12178,10 +12477,12 @@ public class Kst4ContestApplication extends Application implements StatusUpdateL
 			if (res.get().equals(ButtonType.CANCEL)) {
 //				event.consume();
 			} else {
-				System.out.println("closewindowevent: Platform.exit");
+				System.out.println("closewindowevent: exiting the application");
 
-
+				// Routed through the launcher so the runtime that is actually live
-				Platform.exit();
+				// releases its resources. After a profile switch that is no longer the
+				// instance JavaFX would call stop() on.
+				ApplicationRuntimeLauncher.exitApplication();
 			}
 		}
 //        }

src/main/java/kst4contest/view/OperatorProfileBootstrap.java

@@ -0,0 +1,107 @@
+package kst4contest.view;
+
+import kst4contest.controller.OperatorProfilePaths;
+import kst4contest.controller.OperatorProfileStore;
+import kst4contest.model.OperatorProfile;
+import kst4contest.model.OperatorProfileSelection;
+
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Decides which operator profile the application starts with.
+ *
+ * <p>The class contains no user interface code so the decision can be tested headless.
+ * Asking the operator is delegated to an {@link OperatorProfileChoiceRequester}, and a
+ * problem worth telling the operator about is reported through
+ * {@link #getStartupWarning()} instead of being shown here.</p>
+ *
+ * <p>The most important property of this logic is what it does <em>not</em> do: an
+ * installation with no or exactly one profile is resolved without asking anything and
+ * without touching a single file, so a single operator start stays exactly as fast and
+ * as quiet as it was before profiles existed.</p>
+ */
+public class OperatorProfileBootstrap {
+
+    private String startupWarning;
+
+    /**
+     * Resolves the operator profile to start with.
+     *
+     * @param store           registry to read the profiles from
+     * @param commandLineOptions parsed command line options
+     * @param choiceRequester requester used when the operator has to choose
+     * @return the resolved selection, or null when the operator chose to quit
+     */
+    public OperatorProfileSelection resolveAtStartup(final OperatorProfileStore store,
+            final CommandLineOptions commandLineOptions,
+            final OperatorProfileChoiceRequester choiceRequester) {
+
+        startupWarning = null;
+
+        List<OperatorProfile> availableProfiles = store.loadProfiles();
+        String requestedProfileName = commandLineOptions == null
+                ? null
+                : commandLineOptions.getRequestedProfileName();
+
+        if (requestedProfileName != null) {
+            OperatorProfile requestedProfile = findProfile(availableProfiles, requestedProfileName);
+
+            if (requestedProfile != null) {
+                return OperatorProfilePaths.resolve(requestedProfile);
+            }
+
+            startupWarning = "The operator profile \"" + requestedProfileName
+                    + "\" is unknown. KST4Contest continues with the normal profile selection.";
+        }
+
+        if (availableProfiles.isEmpty()) {
+            // No registry at all: the historic flat installation is the only profile.
+            return OperatorProfilePaths.resolve(store.buildImplicitRootProfile());
+        }
+
+        if (availableProfiles.size() == 1) {
+            return OperatorProfilePaths.resolve(availableProfiles.get(0));
+        }
+
+        String preselectedProfileId = store.loadLastUsedProfileId().orElse(null);
+        Optional<OperatorProfile> chosenProfile =
+                choiceRequester.requestProfileChoice(availableProfiles, preselectedProfileId);
+
+        return chosenProfile.map(OperatorProfilePaths::resolve).orElse(null);
+    }
+
+    /**
+     * Returns a message that should be shown to the operator after startup.
+     *
+     * @return the warning text, or null when startup was unremarkable
+     */
+    public String getStartupWarning() {
+        return startupWarning;
+    }
+
+    /**
+     * Finds a profile by identifier or display name, ignoring case.
+     *
+     * @param availableProfiles profiles to search
+     * @param requestedName     identifier or display name entered by the operator
+     * @return the matching profile, or null
+     */
+    private static OperatorProfile findProfile(final List<OperatorProfile> availableProfiles,
+            final String requestedName) {
+
+        for (OperatorProfile currentProfile : availableProfiles) {
+            if (requestedName.equalsIgnoreCase(currentProfile.getProfileId())) {
+                return currentProfile;
+            }
+        }
+
+        for (OperatorProfile currentProfile : availableProfiles) {
+            if (requestedName.equalsIgnoreCase(currentProfile.getDisplayName())) {
+                return currentProfile;
+            }
+        }
+
+        return null;
+    }
+}

src/main/java/kst4contest/view/OperatorProfileChoiceRequester.java

@@ -0,0 +1,26 @@
+package kst4contest.view;
+
+import kst4contest.model.OperatorProfile;
+
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Asks the operator which profile to start with.
+ *
+ * <p>The startup logic depends on this interface rather than on a dialog, so the
+ * decision which profile to use can be tested without a JavaFX runtime.</p>
+ */
+@FunctionalInterface
+public interface OperatorProfileChoiceRequester {
+
+    /**
+     * Requests a profile choice.
+     *
+     * @param selectableProfiles  profiles to choose from, never empty
+     * @param preselectedProfileId identifier to preselect, may be null
+     * @return the chosen profile, or empty when the operator wants to quit
+     */
+    Optional<OperatorProfile> requestProfileChoice(List<OperatorProfile> selectableProfiles,
+            String preselectedProfileId);
+}

src/main/java/kst4contest/view/OperatorProfilePickerDialog.java

@@ -0,0 +1,143 @@
+package kst4contest.view;
+
+import kst4contest.model.OperatorProfile;
+
+import javafx.geometry.Insets;
+import javafx.scene.Scene;
+import javafx.scene.control.Button;
+import javafx.scene.control.Label;
+import javafx.scene.control.ListCell;
+import javafx.scene.control.ListView;
+import javafx.scene.input.KeyCode;
+import javafx.scene.input.MouseButton;
+import javafx.scene.layout.HBox;
+import javafx.scene.layout.Priority;
+import javafx.scene.layout.VBox;
+import javafx.stage.Modality;
+import javafx.stage.Stage;
+
+import java.util.List;
+import java.util.Optional;
+
+/**
+ * Asks the operator which profile to start with.
+ *
+ * <p>The dialog is shown only when more than one profile exists. It is intentionally
+ * minimal, because it stands between the operator and a contest: the last used profile
+ * is preselected, the list has the focus, and Enter or a double click start immediately.</p>
+ */
+public final class OperatorProfilePickerDialog {
+
+    private OperatorProfilePickerDialog() {
+        // Utility class.
+    }
+
+    /**
+     * Shows the picker and waits for the operator's choice.
+     *
+     * @param selectableProfiles   profiles to choose from
+     * @param preselectedProfileId identifier of the profile to preselect, may be null
+     * @return the chosen profile, or empty when the operator wants to quit
+     */
+    public static Optional<OperatorProfile> showAndSelect(final List<OperatorProfile> selectableProfiles,
+            final String preselectedProfileId) {
+
+        Stage dialogStage = new Stage();
+        GuiUtils.applyApplicationIcon(dialogStage);
+        dialogStage.initModality(Modality.APPLICATION_MODAL);
+        dialogStage.setTitle("Select operator profile");
+
+        ListView<OperatorProfile> profileListView = new ListView<>();
+        profileListView.getItems().addAll(selectableProfiles);
+        profileListView.setCellFactory(listView -> new OperatorProfileListCell());
+        VBox.setVgrow(profileListView, Priority.ALWAYS);
+
+        selectPreselectedProfile(profileListView, selectableProfiles, preselectedProfileId);
+
+        OperatorProfile[] chosenProfile = new OperatorProfile[1];
+
+        Button startButton = new Button("Start");
+        startButton.setDefaultButton(true);
+        startButton.setOnAction(event -> {
+            chosenProfile[0] = profileListView.getSelectionModel().getSelectedItem();
+            dialogStage.close();
+        });
+
+        Button quitButton = new Button("Quit");
+        quitButton.setCancelButton(true);
+        quitButton.setOnAction(event -> {
+            chosenProfile[0] = null;
+            dialogStage.close();
+        });
+
+        profileListView.setOnMouseClicked(event -> {
+            if (event.getButton() == MouseButton.PRIMARY && event.getClickCount() == 2) {
+                startButton.fire();
+            }
+        });
+
+        profileListView.setOnKeyPressed(event -> {
+            if (event.getCode() == KeyCode.ENTER) {
+                startButton.fire();
+            }
+        });
+
+        HBox buttonRow = new HBox(10, startButton, quitButton);
+        buttonRow.setPadding(new Insets(10, 0, 0, 0));
+
+        VBox dialogContent = new VBox(8,
+                new Label("More than one operator profile is configured."),
+                profileListView,
+                buttonRow);
+        dialogContent.setPadding(new Insets(15));
+
+        dialogStage.setScene(new Scene(dialogContent, 380, 280));
+        profileListView.requestFocus();
+        dialogStage.showAndWait();
+
+        return Optional.ofNullable(chosenProfile[0]);
+    }
+
+    private static void selectPreselectedProfile(final ListView<OperatorProfile> profileListView,
+            final List<OperatorProfile> selectableProfiles,
+            final String preselectedProfileId) {
+
+        int profileIndexToSelect = 0;
+
+        if (preselectedProfileId != null) {
+            for (int profileIndex = 0; profileIndex < selectableProfiles.size(); profileIndex++) {
+                if (preselectedProfileId.equalsIgnoreCase(
+                        selectableProfiles.get(profileIndex).getProfileId())) {
+                    profileIndexToSelect = profileIndex;
+                    break;
+                }
+            }
+        }
+
+        profileListView.getSelectionModel().select(profileIndexToSelect);
+        profileListView.scrollTo(profileIndexToSelect);
+    }
+
+    /**
+     * Renders a profile with its name and the kind of worked data it uses.
+     */
+    private static final class OperatorProfileListCell extends ListCell<OperatorProfile> {
+
+        @Override
+        protected void updateItem(final OperatorProfile profile, final boolean empty) {
+
+            super.updateItem(profile, empty);
+
+            if (empty || profile == null) {
+                setText(null);
+                return;
+            }
+
+            String workedDataDescription = profile.isRootProfile() || profile.isSharedWorkedDatabase()
+                    ? "shared station worked database"
+                    : "own worked database";
+
+            setText(profile.getDisplayName() + "\n" + workedDataDescription);
+        }
+    }
+}

src/main/java/kst4contest/view/OperatorProfileSettingsPane.java

@@ -0,0 +1,488 @@
+package kst4contest.view;
+
+import kst4contest.controller.ActiveOperatorProfile;
+import kst4contest.controller.OperatorProfileManagementService;
+import kst4contest.controller.OperatorProfilePaths;
+import kst4contest.model.OperatorProfile;
+import kst4contest.model.OperatorProfileSelection;
+
+import javafx.beans.property.SimpleStringProperty;
+import javafx.geometry.Insets;
+import javafx.scene.control.Alert;
+import javafx.scene.control.Alert.AlertType;
+import javafx.scene.control.Button;
+import javafx.scene.control.ButtonBar;
+import javafx.scene.control.ButtonType;
+import javafx.scene.control.Dialog;
+import javafx.scene.control.Label;
+import javafx.scene.control.RadioButton;
+import javafx.scene.control.TableColumn;
+import javafx.scene.control.TableView;
+import javafx.scene.control.TextField;
+import javafx.scene.control.TextInputDialog;
+import javafx.scene.control.ToggleGroup;
+import javafx.scene.layout.GridPane;
+import javafx.scene.layout.HBox;
+import javafx.scene.layout.Priority;
+import javafx.scene.layout.VBox;
+import javafx.util.Pair;
+
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.format.DateTimeFormatter;
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Consumer;
+
+/**
+ * Settings tab that manages the operator profiles.
+ *
+ * <p>Every profile keeps its own settings and window layout. Whether it also keeps its
+ * own worked stations is chosen per profile, because a multi operator contest station
+ * shares one log while two operators on a private computer usually do not.</p>
+ */
+public class OperatorProfileSettingsPane extends VBox {
+
+    private static final DateTimeFormatter LAST_USED_FORMATTER =
+            DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm").withZone(ZoneId.systemDefault());
+
+    private final OperatorProfileManagementService managementService;
+    private final Consumer<OperatorProfile> profileActivationRequest;
+
+    private final TableView<OperatorProfile> profileTable = new TableView<>();
+    private final Label activeProfileLabel = new Label();
+    private final Label preferencesPathLabel = new Label();
+    private final Label workedDatabasePathLabel = new Label();
+
+    public OperatorProfileSettingsPane(final OperatorProfileManagementService managementService,
+            final Consumer<OperatorProfile> profileActivationRequest) {
+
+        this.managementService = managementService;
+        this.profileActivationRequest = profileActivationRequest;
+
+        setSpacing(10);
+        setPadding(new Insets(15));
+
+        getChildren().addAll(
+                buildActiveProfileHeader(),
+                buildProfileTable(),
+                buildButtonRows(),
+                buildExplanationLabel());
+
+        refreshActiveProfileHeader();
+        refreshProfileTable();
+    }
+
+    private GridPane buildActiveProfileHeader() {
+
+        GridPane headerGrid = new GridPane();
+        headerGrid.setHgap(10);
+        headerGrid.setVgap(4);
+
+        headerGrid.add(new Label("Active profile:"), 0, 0);
+        headerGrid.add(activeProfileLabel, 1, 0);
+        headerGrid.add(new Label("Settings file:"), 0, 1);
+        headerGrid.add(preferencesPathLabel, 1, 1);
+        headerGrid.add(new Label("Worked stations:"), 0, 2);
+        headerGrid.add(workedDatabasePathLabel, 1, 2);
+
+        return headerGrid;
+    }
+
+    private TableView<OperatorProfile> buildProfileTable() {
+
+        TableColumn<OperatorProfile, String> nameColumn = new TableColumn<>("Profile");
+        nameColumn.setCellValueFactory(cellData ->
+                new SimpleStringProperty(cellData.getValue().getDisplayName()));
+        nameColumn.setPrefWidth(200);
+
+        TableColumn<OperatorProfile, String> workedDataColumn = new TableColumn<>("Worked stations");
+        workedDataColumn.setCellValueFactory(cellData ->
+                new SimpleStringProperty(describeWorkedDataMode(cellData.getValue())));
+        workedDataColumn.setPrefWidth(200);
+
+        TableColumn<OperatorProfile, String> lastUsedColumn = new TableColumn<>("Last used");
+        lastUsedColumn.setCellValueFactory(cellData ->
+                new SimpleStringProperty(describeLastUsed(cellData.getValue())));
+        lastUsedColumn.setPrefWidth(140);
+
+        profileTable.getColumns().add(nameColumn);
+        profileTable.getColumns().add(workedDataColumn);
+        profileTable.getColumns().add(lastUsedColumn);
+        profileTable.setPlaceholder(new Label("No operator profile configured."));
+
+        VBox.setVgrow(profileTable, Priority.ALWAYS);
+
+        return profileTable;
+    }
+
+    private VBox buildButtonRows() {
+
+        Button newProfileButton = new Button("New profile...");
+        newProfileButton.setOnAction(event -> createProfile());
+
+        Button duplicateProfileButton = new Button("Duplicate...");
+        duplicateProfileButton.setOnAction(event -> duplicateSelectedProfile());
+
+        Button renameProfileButton = new Button("Rename...");
+        renameProfileButton.setOnAction(event -> renameSelectedProfile());
+
+        Button deleteProfileButton = new Button("Delete...");
+        deleteProfileButton.setOnAction(event -> deleteSelectedProfile());
+
+        Button changeWorkedDataButton = new Button("Change worked stations...");
+        changeWorkedDataButton.setOnAction(event -> changeWorkedDataModeOfSelectedProfile());
+
+        Button switchProfileButton = new Button("Switch to selected profile...");
+        switchProfileButton.setOnAction(event -> activateSelectedProfile());
+
+        HBox managementRow = new HBox(8,
+                newProfileButton, duplicateProfileButton, renameProfileButton, deleteProfileButton);
+        HBox activationRow = new HBox(8, changeWorkedDataButton, switchProfileButton);
+
+        return new VBox(8, managementRow, activationRow);
+    }
+
+    private Label buildExplanationLabel() {
+
+        Label explanation = new Label(
+                "Each profile has its own settings and window layout. A profile can either share the "
+                        + "common station worked stations, which is what a multi operator station wants, "
+                        + "or keep its own. Duplicating a profile copies everything except callsign and "
+                        + "password, and never copies worked stations.");
+        explanation.setWrapText(true);
+
+        return explanation;
+    }
+
+    private void refreshActiveProfileHeader() {
+
+        OperatorProfileSelection activeProfile = ActiveOperatorProfile.get();
+
+        if (activeProfile == null) {
+            activeProfileLabel.setText("unknown");
+            return;
+        }
+
+        activeProfileLabel.setText(activeProfile.getProfile().getDisplayName());
+        preferencesPathLabel.setText(activeProfile.getPreferencesAbsolutePath());
+        workedDatabasePathLabel.setText(activeProfile.getWorkedDatabaseAbsolutePath());
+    }
+
+    private void refreshProfileTable() {
+
+        List<OperatorProfile> knownProfiles = managementService.listProfiles();
+        OperatorProfile previouslySelected = profileTable.getSelectionModel().getSelectedItem();
+
+        profileTable.getItems().setAll(knownProfiles);
+
+        if (previouslySelected != null && knownProfiles.contains(previouslySelected)) {
+            profileTable.getSelectionModel().select(previouslySelected);
+        } else if (!knownProfiles.isEmpty()) {
+            profileTable.getSelectionModel().select(0);
+        }
+    }
+
+    private void createProfile() {
+
+        Optional<Pair<String, Boolean>> enteredProfile =
+                showProfileCreationDialog("New operator profile", "");
+
+        if (enteredProfile.isEmpty()) {
+            return;
+        }
+
+        OperatorProfile createdProfile = managementService.createProfile(
+                enteredProfile.get().getKey(), enteredProfile.get().getValue());
+
+        if (createdProfile == null) {
+            showError("The profile could not be created. The profile registry could not be written.");
+            return;
+        }
+
+        refreshProfileTable();
+        profileTable.getSelectionModel().select(createdProfile);
+
+        showInformation("The profile \"" + createdProfile.getDisplayName() + "\" was created without "
+                + "callsign and password. Enter them on the Station tab after switching to it.");
+    }
+
+    private void duplicateSelectedProfile() {
+
+        OperatorProfile selectedProfile = requireSelectedProfile();
+
+        if (selectedProfile == null) {
+            return;
+        }
+
+        TextInputDialog nameDialog =
+                new TextInputDialog("Copy of " + selectedProfile.getDisplayName());
+        nameDialog.setTitle("Duplicate operator profile");
+        nameDialog.setHeaderText("Name of the new profile");
+        nameDialog.setContentText(
+                "Everything is copied except callsign and password. Worked stations are never copied.");
+
+        Optional<String> enteredName = nameDialog.showAndWait();
+
+        if (enteredName.isEmpty() || enteredName.get().isBlank()) {
+            return;
+        }
+
+        OperatorProfile duplicatedProfile =
+                managementService.duplicateProfile(selectedProfile, enteredName.get());
+
+        if (duplicatedProfile == null) {
+            showError("The profile could not be duplicated.");
+            return;
+        }
+
+        refreshProfileTable();
+        profileTable.getSelectionModel().select(duplicatedProfile);
+    }
+
+    private void renameSelectedProfile() {
+
+        OperatorProfile selectedProfile = requireSelectedProfile();
+
+        if (selectedProfile == null) {
+            return;
+        }
+
+        TextInputDialog nameDialog = new TextInputDialog(selectedProfile.getDisplayName());
+        nameDialog.setTitle("Rename operator profile");
+        nameDialog.setHeaderText("New name of the profile");
+        nameDialog.setContentText("Files and folders of the profile are not touched.");
+
+        Optional<String> enteredName = nameDialog.showAndWait();
+
+        if (enteredName.isEmpty() || enteredName.get().isBlank()) {
+            return;
+        }
+
+        managementService.renameProfile(selectedProfile, enteredName.get());
+        refreshProfileTable();
+        refreshActiveProfileHeader();
+    }
+
+    private void deleteSelectedProfile() {
+
+        OperatorProfile selectedProfile = requireSelectedProfile();
+
+        if (selectedProfile == null) {
+            return;
+        }
+
+        if (selectedProfile.isRootProfile()) {
+            showError("The default profile uses the files of the installation itself "
+                    + "and cannot be deleted.");
+            return;
+        }
+
+        if (isActiveProfile(selectedProfile)) {
+            showError("The profile currently in use cannot be deleted. Switch to another "
+                    + "profile first.");
+            return;
+        }
+
+        Alert confirmation = new Alert(AlertType.CONFIRMATION);
+        confirmation.setTitle("Delete operator profile");
+        confirmation.setHeaderText("Delete the profile \"" + selectedProfile.getDisplayName() + "\"?");
+        confirmation.setContentText(
+                "The following folder is removed permanently:\n"
+                        + managementService.getProfileDirectory(selectedProfile)
+                        + "\n\n"
+                        + (selectedProfile.isSharedWorkedDatabase()
+                                ? "The common station worked stations are not touched."
+                                : "The worked stations of this profile are deleted as well."));
+
+        ButtonType deleteButton = new ButtonType("Delete profile", ButtonBar.ButtonData.OK_DONE);
+        ButtonType cancelButton = new ButtonType("Cancel", ButtonBar.ButtonData.CANCEL_CLOSE);
+        confirmation.getButtonTypes().setAll(deleteButton, cancelButton);
+
+        if (confirmation.showAndWait().orElse(cancelButton) != deleteButton) {
+            return;
+        }
+
+        if (!managementService.deleteProfile(selectedProfile)) {
+            showError("The profile could not be deleted.");
+        }
+
+        refreshProfileTable();
+    }
+
+    private void changeWorkedDataModeOfSelectedProfile() {
+
+        OperatorProfile selectedProfile = requireSelectedProfile();
+
+        if (selectedProfile == null) {
+            return;
+        }
+
+        if (selectedProfile.isRootProfile()) {
+            showError("The default profile always uses the common station worked stations, "
+                    + "because that database is the one of the installation itself.");
+            return;
+        }
+
+        Optional<Boolean> chosenMode = showWorkedDataModeDialog(selectedProfile);
+
+        if (chosenMode.isEmpty() || chosenMode.get() == selectedProfile.isSharedWorkedDatabase()) {
+            return;
+        }
+
+        managementService.setSharedWorkedDatabase(selectedProfile, chosenMode.get());
+        refreshProfileTable();
+
+        if (isActiveProfile(selectedProfile)) {
+            showInformation("The change takes effect after switching to this profile again.");
+        }
+    }
+
+    private void activateSelectedProfile() {
+
+        OperatorProfile selectedProfile = requireSelectedProfile();
+
+        if (selectedProfile == null) {
+            return;
+        }
+
+        if (isActiveProfile(selectedProfile)) {
+            showInformation("This profile is already active.");
+            return;
+        }
+
+        profileActivationRequest.accept(selectedProfile);
+    }
+
+    private Optional<Pair<String, Boolean>> showProfileCreationDialog(final String title,
+            final String initialName) {
+
+        Dialog<Pair<String, Boolean>> creationDialog = new Dialog<>();
+        creationDialog.setTitle(title);
+        creationDialog.setHeaderText("Name and worked stations of the new profile");
+
+        ButtonType createButton = new ButtonType("Create profile", ButtonBar.ButtonData.OK_DONE);
+        ButtonType cancelButton = new ButtonType("Cancel", ButtonBar.ButtonData.CANCEL_CLOSE);
+        creationDialog.getDialogPane().getButtonTypes().setAll(createButton, cancelButton);
+
+        TextField nameField = new TextField(initialName);
+        nameField.setPromptText("for example DN9APW");
+
+        ToggleGroup workedDataGroup = new ToggleGroup();
+
+        RadioButton ownDatabaseOption = new RadioButton("Own worked stations for this profile");
+        ownDatabaseOption.setToggleGroup(workedDataGroup);
+        ownDatabaseOption.setSelected(true);
+
+        RadioButton sharedDatabaseOption =
+                new RadioButton("Share the common station worked stations (multi operator station)");
+        sharedDatabaseOption.setToggleGroup(workedDataGroup);
+
+        VBox dialogContent = new VBox(8,
+                new Label("Profile name"),
+                nameField,
+                new Label("Worked stations"),
+                ownDatabaseOption,
+                sharedDatabaseOption);
+        dialogContent.setPadding(new Insets(10));
+
+        creationDialog.getDialogPane().setContent(dialogContent);
+
+        creationDialog.setResultConverter(pressedButton -> {
+            if (pressedButton != createButton || nameField.getText().isBlank()) {
+                return null;
+            }
+
+            return new Pair<>(nameField.getText().trim(), sharedDatabaseOption.isSelected());
+        });
+
+        return creationDialog.showAndWait();
+    }
+
+    private Optional<Boolean> showWorkedDataModeDialog(final OperatorProfile profile) {
+
+        Dialog<Boolean> modeDialog = new Dialog<>();
+        modeDialog.setTitle("Worked stations");
+        modeDialog.setHeaderText("Worked stations of \"" + profile.getDisplayName() + "\"");
+
+        ButtonType applyButton = new ButtonType("Apply", ButtonBar.ButtonData.OK_DONE);
+        ButtonType cancelButton = new ButtonType("Cancel", ButtonBar.ButtonData.CANCEL_CLOSE);
+        modeDialog.getDialogPane().getButtonTypes().setAll(applyButton, cancelButton);
+
+        ToggleGroup workedDataGroup = new ToggleGroup();
+
+        RadioButton ownDatabaseOption = new RadioButton("Own worked stations for this profile");
+        ownDatabaseOption.setToggleGroup(workedDataGroup);
+
+        RadioButton sharedDatabaseOption =
+                new RadioButton("Share the common station worked stations (multi operator station)");
+        sharedDatabaseOption.setToggleGroup(workedDataGroup);
+
+        sharedDatabaseOption.setSelected(profile.isSharedWorkedDatabase());
+        ownDatabaseOption.setSelected(!profile.isSharedWorkedDatabase());
+
+        Label pathHint = new Label("Switching does not move any data. Worked stations already "
+                + "collected under the other setting stay where they are.");
+        pathHint.setWrapText(true);
+
+        VBox dialogContent = new VBox(8, ownDatabaseOption, sharedDatabaseOption, pathHint);
+        dialogContent.setPadding(new Insets(10));
+
+        modeDialog.getDialogPane().setContent(dialogContent);
+        modeDialog.setResultConverter(pressedButton ->
+                pressedButton == applyButton ? sharedDatabaseOption.isSelected() : null);
+
+        return modeDialog.showAndWait();
+    }
+
+    private OperatorProfile requireSelectedProfile() {
+
+        OperatorProfile selectedProfile = profileTable.getSelectionModel().getSelectedItem();
+
+        if (selectedProfile == null) {
+            showInformation("Select a profile in the table first.");
+        }
+
+        return selectedProfile;
+    }
+
+    private static boolean isActiveProfile(final OperatorProfile profile) {
+
+        OperatorProfileSelection activeProfile = ActiveOperatorProfile.get();
+
+        return activeProfile != null
+                && activeProfile.getProfile().getProfileId().equals(profile.getProfileId());
+    }
+
+    private static String describeWorkedDataMode(final OperatorProfile profile) {
+
+        if (profile.isRootProfile() || profile.isSharedWorkedDatabase()) {
+            return "common station database";
+        }
+
+        return "own database";
+    }
+
+    private static String describeLastUsed(final OperatorProfile profile) {
+
+        if (profile.getLastUsedEpochMs() <= 0L) {
+            return "";
+        }
+
+        return LAST_USED_FORMATTER.format(Instant.ofEpochMilli(profile.getLastUsedEpochMs()));
+    }
+
+    private static void showInformation(final String message) {
+        Alert information = new Alert(AlertType.INFORMATION);
+        information.setTitle("Operator profiles");
+        information.setContentText(message);
+        information.showAndWait();
+    }
+
+    private static void showError(final String message) {
+        Alert error = new Alert(AlertType.ERROR);
+        error.setTitle("Operator profiles");
+        error.setContentText(message);
+        error.showAndWait();
+    }
+}

src/main/java/kst4contest/view/map/StationMapBridge.java

@@ -2,6 +2,7 @@ package kst4contest.view.map;
 
 import javafx.animation.PauseTransition;
 import javafx.application.Platform;
+import javafx.beans.value.ChangeListener;
 import javafx.collections.ListChangeListener;
 import javafx.scene.control.TableView;
 import javafx.util.Duration;
@@ -54,6 +55,16 @@ public final class StationMapBridge {
 
     private final PauseTransition refreshCoalescer = new PauseTransition(Duration.seconds(1.0));
 
+    /*
+     * The listeners are kept so install() can be undone. Without that, the coalescing
+     * animation and the registered listeners would keep a discarded runtime reachable
+     * after an operator profile switch.
+     */
+    private ListChangeListener<ChatMember> chatMemberListListener;
+    private ChangeListener<ChatMember> selectedChatMemberListener;
+    private ChangeListener<Number> antennaDirectionListener;
+    private ListChangeListener<Predicate<ChatMember>> filterPredicateListener;
+
     public StationMapBridge(ChatController chatController,
                             TableView<ChatMember> chatMemberTable,
                             StationMapView stationMapView,
@@ -81,25 +92,59 @@ public final class StationMapBridge {
 
         stationMapView.setOnResetView(this::handleMapReset);
 
-        chatController.getLst_chatMemberSortedFilteredList().addListener(
+        chatMemberListListener = change -> scheduleRefresh();
-                (ListChangeListener<ChatMember>) change -> scheduleRefresh()
+        chatController.getLst_chatMemberSortedFilteredList().addListener(chatMemberListListener);
-        );
 
-        chatController.getScoreService().selectedChatMemberProperty().addListener(
+        selectedChatMemberListener = (obs, oldValue, newValue) -> requestImmediateRefresh();
-                (obs, oldValue, newValue) -> requestImmediateRefresh()
+        chatController.getScoreService().selectedChatMemberProperty()
-        );
+                .addListener(selectedChatMemberListener);
 
-        chatController.getChatPreferences().getActualQTF().addListener(
+        antennaDirectionListener = (obs, oldValue, newValue) -> scheduleRefresh();
-                (obs, oldValue, newValue) -> scheduleRefresh()
+        chatController.getChatPreferences().getActualQTF().addListener(antennaDirectionListener);
-        );
 
-        chatController.getLst_chatMemberListFilterPredicates().addListener(
+        filterPredicateListener = change -> requestImmediateRefresh();
-                (ListChangeListener<Predicate<ChatMember>>) change -> requestImmediateRefresh()
+        chatController.getLst_chatMemberListFilterPredicates().addListener(filterPredicateListener);
-        );
 
         requestImmediateRefresh();
     }
 
+    /**
+     * Removes everything {@link #install()} registered and stops the coalescing timer.
+     *
+     * <p>Needed when the runtime owning this bridge is discarded, for example during an
+     * operator profile switch. A running {@link PauseTransition} would otherwise keep
+     * firing into a dead user interface.</p>
+     */
+    public void uninstall() {
+
+        refreshCoalescer.stop();
+
+        stationMapView.setOnCallsignRawSelected(null);
+        stationMapView.setOnTriggerClusterSpot(null);
+        stationMapView.setOnResetView(null);
+
+        if (chatMemberListListener != null) {
+            chatController.getLst_chatMemberSortedFilteredList().removeListener(chatMemberListListener);
+            chatMemberListListener = null;
+        }
+
+        if (selectedChatMemberListener != null) {
+            chatController.getScoreService().selectedChatMemberProperty()
+                    .removeListener(selectedChatMemberListener);
+            selectedChatMemberListener = null;
+        }
+
+        if (antennaDirectionListener != null) {
+            chatController.getChatPreferences().getActualQTF().removeListener(antennaDirectionListener);
+            antennaDirectionListener = null;
+        }
+
+        if (filterPredicateListener != null) {
+            chatController.getLst_chatMemberListFilterPredicates().removeListener(filterPredicateListener);
+            filterPredicateListener = null;
+        }
+    }
+
     private void handleMapReset() {
         Runnable resetAction = () -> {
             /*

src/main/java/kst4contest/view/map/StationMapView.java

@@ -244,6 +244,25 @@ public final class StationMapView {
         stage.hide();
     }
 
+    /**
+     * Releases every resource this map window owns.
+     *
+     * <p>The tile proxy is a local server socket with its own thread pool. It used to
+     * live until the process ended, which was harmless while the map existed exactly
+     * once per process. A runtime that is discarded, for example during an operator
+     * profile switch, has to hand it back.</p>
+     */
+    public void dispose() {
+
+        if (tileProxyServer != null) {
+            tileProxyServer.stop();
+            tileProxyServer = null;
+        }
+
+        webEngine.load(null);
+        stage.close();
+    }
+
     public boolean isShowing() {
         return stage.isShowing();
     }

src/main/java/kst4contest/view/map/TerrainProfileCacheRepository.java

@@ -1,9 +1,11 @@
 package kst4contest.view.map;
 
 import kst4contest.ApplicationConstants;
-import kst4contest.controller.DBController;
 import kst4contest.utils.ApplicationFileUtils;
 
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.PreparedStatement;
@@ -15,30 +17,44 @@ import java.util.Locale;
 import java.util.Optional;
 
 /**
- * Persistent terrain profile cache stored in the application's existing SQLite database.
+ * Persistent terrain profile cache, stored globally in its own SQLite database.
  *
- * The cache is intentionally owner-bound:
+ * <p>Terrain profiles are pure geometry derived from two locators and a sample count.
- * if the configured own callsign or own locator changes, all cached terrain
+ * They do not belong to one operator, so the cache is deliberately not part of an
- * profiles are cleared automatically.
+ * operator profile: at a multi operator station both operators share one location, and
+ * duplicating the cache would double the traffic against an external terrain service.</p>
+ *
+ * <p>Entries are separated by owner identity through the primary key instead. Earlier
+ * versions kept a single owner identity and dropped the whole cache whenever the
+ * configured callsign or locator changed; with several operator profiles that would
+ * discard every computed profile on each switch.</p>
  */
 public final class TerrainProfileCacheRepository {
 
-    private static final String META_KEY_OWNER_CALLSIGN_RAW = "terrain_cache_owner_callsign_raw";
+    /**
-    private static final String META_KEY_OWNER_LOCATOR6 = "terrain_cache_owner_locator6";
+     * File name of the global terrain profile cache below the application directory.
+     */
+    public static final String TERRAIN_CACHE_DATABASE_FILE = "terrainprofilecache.db";
 
     private final String databasePath;
 
     public TerrainProfileCacheRepository() {
-        ApplicationFileUtils.copyResourceIfRequired(
-                ApplicationConstants.APPLICATION_NAME,
-                DBController.DATABASE_RESOURCE,
-                DBController.DATABASE_FILE
-        );
-
         this.databasePath = ApplicationFileUtils.getFilePath(
                 ApplicationConstants.APPLICATION_NAME,
-                DBController.DATABASE_FILE
+                TERRAIN_CACHE_DATABASE_FILE
         );
+
+        // SQLite only creates the database file itself, not the directory holding it.
+        Path applicationDirectory = Path.of(databasePath).getParent();
+
+        if (applicationDirectory != null) {
+            try {
+                Files.createDirectories(applicationDirectory);
+            } catch (IOException exception) {
+                System.err.println("[StationMap] Terrain cache directory could not be created: "
+                        + exception.getMessage());
+            }
+        }
     }
 
     public synchronized Optional<TerrainProfileData> load(String ownerCallsignRaw,
@@ -183,60 +199,37 @@ public final class TerrainProfileCacheRepository {
                     """);
 
             statement.executeUpdate("""
-                    CREATE TABLE IF NOT EXISTS TerrainProfileCacheMeta (
+                    CREATE TABLE IF NOT EXISTS TerrainProfileCacheOwner (
-                        meta_key TEXT NOT NULL PRIMARY KEY,
+                        owner_callsign_raw TEXT NOT NULL,
-                        meta_value TEXT NOT NULL
+                        owner_locator6 TEXT NOT NULL,
+                        last_used_epoch_ms INTEGER NOT NULL,
+                        PRIMARY KEY (owner_callsign_raw, owner_locator6)
                     )
                     """);
         }
     }
 
+    /**
+     * Records that the given owner identity is in use.
+     *
+     * <p>Entries of other owners stay untouched. The cached profiles of an identity are
+     * separated by the primary key already, so a different callsign or locator simply
+     * misses the cache instead of invalidating everybody else's entries.</p>
+     */
     private void ensureOwnerIdentity(Connection connection,
                                      String currentOwnerCallsignRaw,
                                      String currentOwnerLocator6) throws Exception {
 
-        String normalizedOwnerCallsignRaw = normalize(currentOwnerCallsignRaw);
-        String normalizedOwnerLocator6 = normalize(currentOwnerLocator6);
-
-        String storedOwnerCallsignRaw = readMetaValue(connection, META_KEY_OWNER_CALLSIGN_RAW);
-        String storedOwnerLocator6 = readMetaValue(connection, META_KEY_OWNER_LOCATOR6);
-
-        boolean callsignChanged = storedOwnerCallsignRaw != null && !storedOwnerCallsignRaw.equals(normalizedOwnerCallsignRaw);
-        boolean locatorChanged = storedOwnerLocator6 != null && !storedOwnerLocator6.equals(normalizedOwnerLocator6);
-
-        if (callsignChanged || locatorChanged) {
-            clearTerrainCache(connection);
-        }
-
-        writeMetaValue(connection, META_KEY_OWNER_CALLSIGN_RAW, normalizedOwnerCallsignRaw);
-        writeMetaValue(connection, META_KEY_OWNER_LOCATOR6, normalizedOwnerLocator6);
-    }
-
-    private void clearTerrainCache(Connection connection) throws Exception {
-        try (Statement statement = connection.createStatement()) {
-            statement.executeUpdate("DELETE FROM TerrainProfileCache");
-        }
-    }
-
-    private String readMetaValue(Connection connection, String key) throws Exception {
-        try (PreparedStatement statement = connection.prepareStatement(
-                "SELECT meta_value FROM TerrainProfileCacheMeta WHERE meta_key = ?")) {
-            statement.setString(1, key);
-
-            try (ResultSet resultSet = statement.executeQuery()) {
-                return resultSet.next() ? resultSet.getString(1) : null;
-            }
-        }
-    }
-
-    private void writeMetaValue(Connection connection, String key, String value) throws Exception {
         try (PreparedStatement statement = connection.prepareStatement("""
-                INSERT INTO TerrainProfileCacheMeta (meta_key, meta_value)
+                INSERT INTO TerrainProfileCacheOwner (
-                VALUES (?, ?)
+                    owner_callsign_raw, owner_locator6, last_used_epoch_ms
-                ON CONFLICT(meta_key) DO UPDATE SET meta_value = excluded.meta_value
+                ) VALUES (?, ?, ?)
+                ON CONFLICT(owner_callsign_raw, owner_locator6) DO UPDATE SET
+                    last_used_epoch_ms = excluded.last_used_epoch_ms
                 """)) {
-            statement.setString(1, key);
+            statement.setString(1, normalize(currentOwnerCallsignRaw));
-            statement.setString(2, value == null ? "" : value);
+            statement.setString(2, normalize(currentOwnerLocator6));
+            statement.setLong(3, System.currentTimeMillis());
             statement.executeUpdate();
         }
     }

src/test/java/kst4contest/controller/DBControllerProfileDatabaseTest.java

@@ -0,0 +1,127 @@
+package kst4contest.controller;
+
+import kst4contest.model.ChatMember;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.sql.SQLException;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Verifies that one DBController instance works on exactly one database file, so two
+ * operator profiles can keep independent worked-station data inside the same process.
+ */
+class DBControllerProfileDatabaseTest {
+
+    private static final String USER_HOME_PROPERTY = "user.home";
+
+    @TempDir
+    Path temporaryHomeDirectory;
+
+    private String originalUserHome;
+
+    @BeforeEach
+    void redirectUserHomeToTemporaryDirectory() {
+        originalUserHome = System.getProperty(USER_HOME_PROPERTY);
+        System.setProperty(USER_HOME_PROPERTY, temporaryHomeDirectory.toString());
+    }
+
+    @AfterEach
+    void restoreUserHome() {
+        if (originalUserHome == null) {
+            System.clearProperty(USER_HOME_PROPERTY);
+        } else {
+            System.setProperty(USER_HOME_PROPERTY, originalUserHome);
+        }
+    }
+
+    @Test
+    void profileDatabaseIsCreatedEmptyAndKeepsWorkedDataSeparate() throws SQLException {
+
+        DBController firstProfileDatabase =
+                new DBController("profiles/OP1/praktiKST.db", false);
+        DBController secondProfileDatabase =
+                new DBController("profiles/OP2/praktiKST.db", false);
+
+        try {
+            // A profile database must not inherit the several thousand callsigns of the
+            // bundled template database.
+            assertTrue(firstProfileDatabase.fetchChatMemberWkdDataFromDB().isEmpty());
+            assertTrue(secondProfileDatabase.fetchChatMemberWkdDataFromDB().isEmpty());
+
+            assertNotEquals(firstProfileDatabase.getDatabaseFilePath(),
+                    secondProfileDatabase.getDatabaseFilePath());
+            assertTrue(Files.exists(Path.of(firstProfileDatabase.getDatabaseFilePath())));
+            assertTrue(Files.exists(Path.of(secondProfileDatabase.getDatabaseFilePath())));
+
+            ChatMember workedOnFirstProfile = new ChatMember();
+            workedOnFirstProfile.setCallSign("DL0XYZ");
+            workedOnFirstProfile.setQra("JO51IJ");
+            workedOnFirstProfile.setWorked(true);
+            workedOnFirstProfile.setWorked144(true);
+
+            firstProfileDatabase.storeChatMember(workedOnFirstProfile);
+
+            Map<String, ChatMember> firstProfileContent =
+                    firstProfileDatabase.fetchChatMemberWkdDataFromDB();
+            Map<String, ChatMember> secondProfileContent =
+                    secondProfileDatabase.fetchChatMemberWkdDataFromDB();
+
+            assertEquals(1, firstProfileContent.size());
+            assertTrue(firstProfileContent.get("DL0XYZ").isWorked144());
+            assertTrue(secondProfileContent.isEmpty(),
+                    "A worked station of one profile must not appear in the other profile");
+        } finally {
+            firstProfileDatabase.closeDBConnection();
+            secondProfileDatabase.closeDBConnection();
+        }
+    }
+
+    @Test
+    void twoProfilesPointingAtTheSameFileShareTheirWorkedData() throws SQLException {
+
+        DBController sharedStationDatabase = new DBController("praktiKST.db", false);
+        DBController sameSharedDatabaseAgain = new DBController("praktiKST.db", false);
+
+        try {
+            ChatMember workedAtTheStation = new ChatMember();
+            workedAtTheStation.setCallSign("DL0ABC");
+            workedAtTheStation.setWorked(true);
+            workedAtTheStation.setWorked432(true);
+
+            sharedStationDatabase.storeChatMember(workedAtTheStation);
+
+            Map<String, ChatMember> seenByTheOtherOperator =
+                    sameSharedDatabaseAgain.fetchChatMemberWkdDataFromDB();
+
+            assertTrue(seenByTheOtherOperator.containsKey("DL0ABC"),
+                    "Operators sharing one station database must see the same worked stations");
+            assertTrue(seenByTheOtherOperator.get("DL0ABC").isWorked432());
+        } finally {
+            sharedStationDatabase.closeDBConnection();
+            sameSharedDatabaseAgain.closeDBConnection();
+        }
+    }
+
+    @Test
+    void closingTheConnectionDeregistersTheShutdownHook() {
+
+        DBController profileDatabase = new DBController("profiles/OP3/praktiKST.db", false);
+        profileDatabase.closeDBConnection();
+
+        // A second close must stay harmless, and the hook must already be gone.
+        profileDatabase.closeDBConnection();
+
+        assertFalse(Files.notExists(Path.of(profileDatabase.getDatabaseFilePath())),
+                "The database file stays on disk after the connection was closed");
+    }
+}

src/test/java/kst4contest/controller/OperatorProfileManagementServiceTest.java

@@ -0,0 +1,177 @@
+package kst4contest.controller;
+
+import kst4contest.model.ChatPreferences;
+import kst4contest.model.OperatorProfile;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class OperatorProfileManagementServiceTest {
+
+    private static final String USER_HOME_PROPERTY = "user.home";
+
+    @TempDir
+    Path temporaryHomeDirectory;
+
+    private String originalUserHome;
+    private OperatorProfileManagementService managementService;
+
+    @BeforeEach
+    void redirectUserHomeToTemporaryDirectory() {
+        originalUserHome = System.getProperty(USER_HOME_PROPERTY);
+        System.setProperty(USER_HOME_PROPERTY, temporaryHomeDirectory.toString());
+        managementService = new OperatorProfileManagementService();
+    }
+
+    @AfterEach
+    void restoreUserHome() {
+        if (originalUserHome == null) {
+            System.clearProperty(USER_HOME_PROPERTY);
+        } else {
+            System.setProperty(USER_HOME_PROPERTY, originalUserHome);
+        }
+    }
+
+    @Test
+    void aPlainInstallationReportsExactlyOneImplicitRootProfile() {
+
+        List<OperatorProfile> knownProfiles = managementService.listProfiles();
+
+        assertEquals(1, knownProfiles.size());
+        assertTrue(knownProfiles.get(0).isRootProfile());
+        assertFalse(Files.exists(applicationFile("profiles.xml")),
+                "Merely listing profiles must not create a registry");
+    }
+
+    @Test
+    void creatingTheSecondProfileMaterialisesTheRegistryIncludingTheRootProfile() {
+
+        OperatorProfile createdProfile = managementService.createProfile("DN9APW", false);
+
+        assertNotNull(createdProfile);
+        assertEquals("DN9APW", createdProfile.getProfileId());
+        assertTrue(Files.exists(applicationFile("profiles.xml")));
+
+        List<OperatorProfile> knownProfiles = managementService.listProfiles();
+
+        assertEquals(2, knownProfiles.size());
+        assertTrue(knownProfiles.get(0).isRootProfile());
+        assertEquals("DN9APW", knownProfiles.get(1).getProfileId());
+
+        assertTrue(Files.exists(applicationFile("profiles/DN9APW/preferences.xml")));
+
+        // The historic files must stay exactly where an older release expects them.
+        assertFalse(Files.exists(applicationFile("profiles/default")));
+    }
+
+    @Test
+    void aNewProfileStartsWithoutLoginCredentials() {
+
+        OperatorProfile createdProfile = managementService.createProfile("DN9APW", false);
+
+        ChatPreferences createdPreferences =
+                preferencesAt(OperatorProfilePaths.preferencesRelativeFileName(createdProfile));
+
+        assertEquals("", createdPreferences.getStn_loginCallSign());
+        assertEquals("", createdPreferences.getStn_loginPassword());
+    }
+
+    @Test
+    void duplicatingKeepsTheStationSetupButClearsCallsignAndPassword() {
+
+        OperatorProfile sourceProfile = managementService.createProfile("Source", false);
+
+        ChatPreferences sourcePreferences =
+                preferencesAt(OperatorProfilePaths.preferencesRelativeFileName(sourceProfile));
+        sourcePreferences.setStn_loginCallSign("DM5M");
+        sourcePreferences.setStn_loginPassword("secret");
+        sourcePreferences.setStn_loginLocatorMainCat("JO51IJ");
+        sourcePreferences.setStn_antennaBeamWidthDeg(17.5);
+        assertTrue(sourcePreferences.writePreferencesToXmlFile());
+
+        OperatorProfile duplicatedProfile =
+                managementService.duplicateProfile(sourceProfile, "Copy of source");
+
+        assertNotNull(duplicatedProfile);
+
+        ChatPreferences duplicatedPreferences =
+                preferencesAt(OperatorProfilePaths.preferencesRelativeFileName(duplicatedProfile));
+
+        // The work worth keeping.
+        assertEquals("JO51IJ", duplicatedPreferences.getStn_loginLocatorMainCat());
+        assertEquals(17.5, duplicatedPreferences.getStn_antennaBeamWidthDeg());
+
+        // The identity that must not be inherited.
+        assertEquals("", duplicatedPreferences.getStn_loginCallSign());
+        assertEquals("", duplicatedPreferences.getStn_loginPassword());
+    }
+
+    @Test
+    void switchingBetweenSharedAndOwnWorkedDataChangesOnlyTheDatabasePath() {
+
+        OperatorProfile createdProfile = managementService.createProfile("DN9APW", false);
+
+        assertEquals("profiles/DN9APW/praktiKST.db",
+                OperatorProfilePaths.workedDatabaseRelativeFileName(createdProfile));
+
+        assertTrue(managementService.setSharedWorkedDatabase(createdProfile, true));
+
+        OperatorProfile reloadedProfile = managementService.listProfiles().get(1);
+
+        assertTrue(reloadedProfile.isSharedWorkedDatabase());
+        assertEquals("praktiKST.db",
+                OperatorProfilePaths.workedDatabaseRelativeFileName(reloadedProfile));
+        assertEquals("profiles/DN9APW/preferences.xml",
+                OperatorProfilePaths.preferencesRelativeFileName(reloadedProfile));
+    }
+
+    @Test
+    void deletingRemovesTheProfileDirectoryButNeverTheRootProfile() {
+
+        OperatorProfile createdProfile = managementService.createProfile("DN9APW", false);
+        assertTrue(Files.exists(applicationFile("profiles/DN9APW/preferences.xml")));
+
+        OperatorProfile rootProfile = managementService.listProfiles().get(0);
+        assertFalse(managementService.deleteProfile(rootProfile),
+                "The root profile is the installation itself and must not be removable");
+
+        assertTrue(managementService.deleteProfile(createdProfile));
+        assertFalse(Files.exists(applicationFile("profiles/DN9APW")));
+        assertEquals(1, managementService.listProfiles().size());
+    }
+
+    @Test
+    void renamingKeepsTheIdentifierAndTherebyAllPaths() {
+
+        OperatorProfile createdProfile = managementService.createProfile("DN9APW", false);
+
+        assertTrue(managementService.renameProfile(createdProfile, "Philipp portable"));
+
+        OperatorProfile renamedProfile = managementService.listProfiles().get(1);
+
+        assertEquals("Philipp portable", renamedProfile.getDisplayName());
+        assertEquals("DN9APW", renamedProfile.getProfileId());
+        assertEquals("profiles/DN9APW/preferences.xml",
+                OperatorProfilePaths.preferencesRelativeFileName(renamedProfile));
+    }
+
+    private ChatPreferences preferencesAt(final String relativeFileName) {
+        ChatPreferences preferences = new ChatPreferences(relativeFileName);
+        preferences.readPreferencesFromXmlFile();
+        return preferences;
+    }
+
+    private Path applicationFile(final String relativeFileName) {
+        return temporaryHomeDirectory.resolve(".praktiKST").resolve(relativeFileName);
+    }
+}

src/test/java/kst4contest/controller/OperatorProfilePathsTest.java

@@ -0,0 +1,81 @@
+package kst4contest.controller;
+
+import kst4contest.model.OperatorProfile;
+import kst4contest.model.OperatorProfileSelection;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+import java.util.Set;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class OperatorProfilePathsTest {
+
+    @Test
+    void rootProfileKeepsTheHistoricFlatFileNames() {
+
+        OperatorProfileSelection resolved =
+                OperatorProfilePaths.resolve(OperatorProfilePaths.buildRootProfile("Default"));
+
+        // This is the downgrade guard: an older KST4Contest release reads exactly these
+        // two files. If this test ever fails, existing installations would silently lose
+        // their configuration and worked data when the operator reverts a version.
+        assertEquals("preferences.xml", resolved.getPreferencesRelativeFileName());
+        assertEquals("praktiKST.db", resolved.getWorkedDatabaseRelativeFileName());
+        assertTrue(resolved.isSeedWorkedDatabaseFromResource());
+    }
+
+    @Test
+    void additionalProfileWithSharedDatabaseUsesItsOwnPreferencesButTheStationDatabase() {
+
+        OperatorProfile sharedProfile = new OperatorProfile("OP2", "DN9APW", false, true);
+        OperatorProfileSelection resolved = OperatorProfilePaths.resolve(sharedProfile);
+
+        assertEquals("profiles/OP2/preferences.xml", resolved.getPreferencesRelativeFileName());
+        assertEquals("praktiKST.db", resolved.getWorkedDatabaseRelativeFileName());
+        assertTrue(resolved.isSeedWorkedDatabaseFromResource());
+    }
+
+    @Test
+    void additionalProfileWithOwnDatabaseIsFullySeparatedAndNotSeeded() {
+
+        OperatorProfile ownDatabaseProfile = new OperatorProfile("OP2", "DN9APW", false, false);
+        OperatorProfileSelection resolved = OperatorProfilePaths.resolve(ownDatabaseProfile);
+
+        assertEquals("profiles/OP2/preferences.xml", resolved.getPreferencesRelativeFileName());
+        assertEquals("profiles/OP2/praktiKST.db", resolved.getWorkedDatabaseRelativeFileName());
+
+        // Seeding would hand a new operator the several thousand callsigns of the
+        // bundled template database.
+        assertFalse(resolved.isSeedWorkedDatabaseFromResource());
+    }
+
+    @Test
+    void profileIdIsFileSystemSafe() {
+
+        assertEquals("DN9APW", OperatorProfilePaths.toProfileId("dn9apw", Set.of()));
+        assertEquals("DM5M_CONTEST", OperatorProfilePaths.toProfileId("DM5M Contest", Set.of()));
+        assertEquals("A_B", OperatorProfilePaths.toProfileId("a/../b", Set.of()));
+        assertEquals("MULLER", OperatorProfilePaths.toProfileId("Müller", Set.of()));
+        assertEquals("OP", OperatorProfilePaths.toProfileId("   ", Set.of()));
+        assertEquals("OP", OperatorProfilePaths.toProfileId(null, Set.of()));
+
+        String longName = "A".repeat(60);
+        assertEquals(32, OperatorProfilePaths.toProfileId(longName, Set.of()).length());
+    }
+
+    @Test
+    void profileIdNeverCollidesAndNeverClaimsTheRootIdentifier() {
+
+        assertEquals("DN9APW_2", OperatorProfilePaths.toProfileId("DN9APW", List.of("DN9APW")));
+        assertEquals("DN9APW_3",
+                OperatorProfilePaths.toProfileId("DN9APW", List.of("DN9APW", "DN9APW_2")));
+
+        // "default" is reserved for the historic flat installation.
+        assertNotEquals(OperatorProfilePaths.ROOT_PROFILE_ID,
+                OperatorProfilePaths.toProfileId("default", Set.of()));
+    }
+}

src/test/java/kst4contest/controller/OperatorProfileStoreTest.java

@@ -0,0 +1,117 @@
+package kst4contest.controller;
+
+import kst4contest.model.OperatorProfile;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class OperatorProfileStoreTest {
+
+    @TempDir
+    Path temporaryDirectory;
+
+    @Test
+    void missingRegistryIsNotAnErrorAndIsNotCreated() {
+
+        OperatorProfileStore store = storeAt("profiles.xml");
+
+        assertFalse(store.isRegistryPresent());
+        assertTrue(store.loadProfiles().isEmpty());
+        assertEquals(Optional.empty(), store.loadLastUsedProfileId());
+
+        // A single operator installation must stay untouched by merely starting up.
+        assertFalse(Files.exists(temporaryDirectory.resolve("profiles.xml")));
+    }
+
+    @Test
+    void profilesSurviveAWriteReadRoundTrip() {
+
+        OperatorProfileStore store = storeAt("profiles.xml");
+
+        OperatorProfile rootProfile = OperatorProfilePaths.buildRootProfile("DM5M station");
+        OperatorProfile secondProfile = new OperatorProfile("OP2", "DN9APW", false, false);
+        secondProfile.setLastUsedEpochMs(1757328000000L);
+
+        assertTrue(store.saveProfiles(List.of(rootProfile, secondProfile), "OP2"));
+        assertTrue(store.isRegistryPresent());
+
+        List<OperatorProfile> restored = store.loadProfiles();
+
+        assertEquals(2, restored.size());
+        assertEquals("default", restored.get(0).getProfileId());
+        assertEquals("DM5M station", restored.get(0).getDisplayName());
+        assertTrue(restored.get(0).isRootProfile());
+        assertTrue(restored.get(0).isSharedWorkedDatabase());
+
+        assertEquals("OP2", restored.get(1).getProfileId());
+        assertEquals("DN9APW", restored.get(1).getDisplayName());
+        assertFalse(restored.get(1).isRootProfile());
+        assertFalse(restored.get(1).isSharedWorkedDatabase());
+        assertEquals(1757328000000L, restored.get(1).getLastUsedEpochMs());
+
+        assertEquals(Optional.of("OP2"), store.loadLastUsedProfileId());
+    }
+
+    @Test
+    void atomicWriteLeavesNoTemporaryFileBehind() throws IOException {
+
+        OperatorProfileStore store = storeAt("profiles.xml");
+        store.saveProfiles(List.of(OperatorProfilePaths.buildRootProfile("Default")), "default");
+
+        try (var directoryEntries = Files.list(temporaryDirectory)) {
+            assertTrue(directoryEntries.noneMatch(entry -> entry.getFileName().toString().endsWith(".tmp")));
+        }
+    }
+
+    @Test
+    void malformedRegistryFallsBackToNoAdditionalProfiles() throws IOException {
+
+        Path registryFile = temporaryDirectory.resolve("profiles.xml");
+        Files.writeString(registryFile, "<praktiKSTProfiles><profile><profileId>OP2");
+
+        OperatorProfileStore store = storeAt("profiles.xml");
+
+        assertTrue(store.isRegistryPresent());
+        assertTrue(store.loadProfiles().isEmpty());
+        assertEquals(Optional.empty(), store.loadLastUsedProfileId());
+    }
+
+    @Test
+    void entriesWithoutAnIdentifierAreSkippedInsteadOfBreakingTheRegistry() throws IOException {
+
+        Path registryFile = temporaryDirectory.resolve("profiles.xml");
+        Files.writeString(registryFile,
+                "<praktiKSTProfiles>"
+                        + "<profile><displayName>broken</displayName></profile>"
+                        + "<profile><profileId>OP2</profileId><displayName>DN9APW</displayName>"
+                        + "<sharedWorkedDatabase>false</sharedWorkedDatabase></profile>"
+                        + "</praktiKSTProfiles>");
+
+        List<OperatorProfile> restored = storeAt("profiles.xml").loadProfiles();
+
+        assertEquals(1, restored.size());
+        assertEquals("OP2", restored.get(0).getProfileId());
+    }
+
+    @Test
+    void recordLastUsedDoesNothingWhenNoRegistryExists() {
+
+        OperatorProfileStore store = storeAt("profiles.xml");
+
+        assertFalse(store.recordLastUsed("default"));
+        assertFalse(store.isRegistryPresent());
+    }
+
+    private OperatorProfileStore storeAt(final String fileName) {
+        return new OperatorProfileStore(temporaryDirectory.resolve(fileName).toString());
+    }
+}

src/test/java/kst4contest/view/CommandLineOptionsTest.java

@@ -0,0 +1,46 @@
+package kst4contest.view;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+
+class CommandLineOptionsTest {
+
+    @Test
+    void profileArgumentIsAcceptedInBothSpellings() {
+        assertEquals("OP2", CommandLineOptions.parse(List.of("--profile=OP2")).getRequestedProfileName());
+        assertEquals("OP2", CommandLineOptions.parse(List.of("--profile", "OP2")).getRequestedProfileName());
+        assertEquals("DM5M Contest",
+                CommandLineOptions.parse(List.of("--profile", "DM5M Contest")).getRequestedProfileName());
+    }
+
+    @Test
+    void missingOrEmptyProfileArgumentsAreTreatedAsAbsent() {
+        assertNull(CommandLineOptions.parse(List.of()).getRequestedProfileName());
+        assertNull(CommandLineOptions.parse(null).getRequestedProfileName());
+        assertNull(CommandLineOptions.parse(List.of("--profile=")).getRequestedProfileName());
+        assertNull(CommandLineOptions.parse(List.of("--profile")).getRequestedProfileName());
+    }
+
+    @Test
+    void unrelatedArgumentsAreIgnoredInsteadOfFailing() {
+        assertEquals("OP2",
+                CommandLineOptions.parse(List.of("--verbose", "--profile=OP2", "somefile.adi"))
+                        .getRequestedProfileName());
+        assertNull(CommandLineOptions.parse(List.of("--verbose", "-x")).getRequestedProfileName());
+    }
+
+    @Test
+    void rememberedOptionsDefaultToEmptyInsteadOfNull() {
+        CommandLineOptions.remember(null);
+        assertNull(CommandLineOptions.remembered().getRequestedProfileName());
+
+        CommandLineOptions.remember(new CommandLineOptions("OP2"));
+        assertEquals("OP2", CommandLineOptions.remembered().getRequestedProfileName());
+
+        CommandLineOptions.remember(null);
+    }
+}

src/test/java/kst4contest/view/OperatorProfileBootstrapTest.java

@@ -0,0 +1,161 @@
+package kst4contest.view;
+
+import kst4contest.controller.OperatorProfilePaths;
+import kst4contest.controller.OperatorProfileStore;
+import kst4contest.model.OperatorProfile;
+import kst4contest.model.OperatorProfileSelection;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class OperatorProfileBootstrapTest {
+
+    @TempDir
+    Path temporaryDirectory;
+
+    @Test
+    void installationWithoutRegistryStartsSilentlyOnTheHistoricLayout() {
+
+        AtomicInteger pickerInvocations = new AtomicInteger();
+        OperatorProfileStore store = storeAt();
+
+        OperatorProfileSelection resolved = new OperatorProfileBootstrap().resolveAtStartup(
+                store, new CommandLineOptions(null), countingPicker(pickerInvocations, null));
+
+        assertNotNull(resolved);
+        assertEquals("preferences.xml", resolved.getPreferencesRelativeFileName());
+        assertEquals("praktiKST.db", resolved.getWorkedDatabaseRelativeFileName());
+
+        // Nothing may be asked, and nothing may be written.
+        assertEquals(0, pickerInvocations.get());
+        assertTrue(store.loadProfiles().isEmpty());
+    }
+
+    @Test
+    void singleProfileStartsWithoutAskingAnything() {
+
+        AtomicInteger pickerInvocations = new AtomicInteger();
+        OperatorProfileStore store = storeAt();
+        store.saveProfiles(List.of(OperatorProfilePaths.buildRootProfile("Default")), "default");
+
+        OperatorProfileSelection resolved = new OperatorProfileBootstrap().resolveAtStartup(
+                store, new CommandLineOptions(null), countingPicker(pickerInvocations, null));
+
+        assertNotNull(resolved);
+        assertEquals(0, pickerInvocations.get());
+    }
+
+    @Test
+    void twoProfilesAskTheOperatorAndPreselectTheLastUsedOne() {
+
+        OperatorProfileStore store = storeAt();
+        OperatorProfile secondProfile = new OperatorProfile("OP2", "DN9APW", false, false);
+        store.saveProfiles(
+                List.of(OperatorProfilePaths.buildRootProfile("Default"), secondProfile), "OP2");
+
+        AtomicInteger pickerInvocations = new AtomicInteger();
+        String[] observedPreselection = new String[1];
+
+        OperatorProfileSelection resolved = new OperatorProfileBootstrap().resolveAtStartup(
+                store,
+                new CommandLineOptions(null),
+                (profiles, preselectedProfileId) -> {
+                    pickerInvocations.incrementAndGet();
+                    observedPreselection[0] = preselectedProfileId;
+                    return Optional.of(profiles.get(1));
+                });
+
+        assertEquals(1, pickerInvocations.get());
+        assertEquals("OP2", observedPreselection[0]);
+        assertNotNull(resolved);
+        assertEquals("profiles/OP2/praktiKST.db", resolved.getWorkedDatabaseRelativeFileName());
+    }
+
+    @Test
+    void aValidProfileArgumentSkipsThePicker() {
+
+        OperatorProfileStore store = storeAt();
+        store.saveProfiles(
+                List.of(OperatorProfilePaths.buildRootProfile("Default"),
+                        new OperatorProfile("OP2", "DN9APW", false, false)),
+                "default");
+
+        AtomicInteger pickerInvocations = new AtomicInteger();
+        OperatorProfileBootstrap bootstrap = new OperatorProfileBootstrap();
+
+        OperatorProfileSelection byId = bootstrap.resolveAtStartup(
+                store, new CommandLineOptions("op2"), countingPicker(pickerInvocations, null));
+
+        assertEquals(0, pickerInvocations.get());
+        assertEquals("profiles/OP2/preferences.xml", byId.getPreferencesRelativeFileName());
+        assertNull(bootstrap.getStartupWarning());
+
+        OperatorProfileSelection byDisplayName = bootstrap.resolveAtStartup(
+                store, new CommandLineOptions("DN9APW"), countingPicker(pickerInvocations, null));
+
+        assertEquals(0, pickerInvocations.get());
+        assertEquals("profiles/OP2/preferences.xml", byDisplayName.getPreferencesRelativeFileName());
+    }
+
+    @Test
+    void anUnknownProfileArgumentWarnsAndFallsBackToTheNormalSelection() {
+
+        OperatorProfileStore store = storeAt();
+        store.saveProfiles(
+                List.of(OperatorProfilePaths.buildRootProfile("Default"),
+                        new OperatorProfile("OP2", "DN9APW", false, false)),
+                "default");
+
+        AtomicInteger pickerInvocations = new AtomicInteger();
+        OperatorProfileBootstrap bootstrap = new OperatorProfileBootstrap();
+
+        OperatorProfileSelection resolved = bootstrap.resolveAtStartup(
+                store, new CommandLineOptions("NOPE"), countingPicker(pickerInvocations, 0));
+
+        assertEquals(1, pickerInvocations.get());
+        assertNotNull(resolved);
+        assertNotNull(bootstrap.getStartupWarning());
+        assertTrue(bootstrap.getStartupWarning().contains("NOPE"));
+    }
+
+    @Test
+    void quittingInThePickerYieldsNoSelection() {
+
+        OperatorProfileStore store = storeAt();
+        store.saveProfiles(
+                List.of(OperatorProfilePaths.buildRootProfile("Default"),
+                        new OperatorProfile("OP2", "DN9APW", false, false)),
+                "default");
+
+        OperatorProfileSelection resolved = new OperatorProfileBootstrap().resolveAtStartup(
+                store, new CommandLineOptions(null), (profiles, preselected) -> Optional.empty());
+
+        assertNull(resolved);
+    }
+
+    private OperatorProfileChoiceRequester countingPicker(final AtomicInteger invocationCounter,
+            final Integer profileIndexToChoose) {
+        return (profiles, preselectedProfileId) -> {
+            invocationCounter.incrementAndGet();
+
+            if (profileIndexToChoose == null) {
+                return Optional.of(profiles.get(0));
+            }
+
+            return Optional.of(profiles.get(profileIndexToChoose));
+        };
+    }
+
+    private OperatorProfileStore storeAt() {
+        return new OperatorProfileStore(temporaryDirectory.resolve("profiles.xml").toString());
+    }
+}

src/test/java/kst4contest/view/map/TerrainProfileCacheRepositoryTest.java

@@ -0,0 +1,111 @@
+package kst4contest.view.map;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.List;
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Guards the property that made the terrain cache useless with several operator
+ * profiles: it used to drop every cached profile whenever the configured callsign or
+ * locator changed.
+ */
+class TerrainProfileCacheRepositoryTest {
+
+    private static final String USER_HOME_PROPERTY = "user.home";
+    private static final String PROVIDER_ID = "test-provider";
+    private static final int SAMPLE_COUNT = 3;
+
+    @TempDir
+    Path temporaryHomeDirectory;
+
+    private String originalUserHome;
+
+    @BeforeEach
+    void redirectUserHomeToTemporaryDirectory() {
+        originalUserHome = System.getProperty(USER_HOME_PROPERTY);
+        System.setProperty(USER_HOME_PROPERTY, temporaryHomeDirectory.toString());
+    }
+
+    @AfterEach
+    void restoreUserHome() {
+        if (originalUserHome == null) {
+            System.clearProperty(USER_HOME_PROPERTY);
+        } else {
+            System.setProperty(USER_HOME_PROPERTY, originalUserHome);
+        }
+    }
+
+    @Test
+    void profilesOfDifferentOwnersCoexistAndSurviveSwitchingBackAndForth() {
+
+        TerrainProfileCacheRepository repository = new TerrainProfileCacheRepository();
+
+        repository.save("DM5M", "JO51IJ", "DL0ABC", "JN49FK",
+                SAMPLE_COUNT, PROVIDER_ID, profileData("station-a"));
+
+        // Another operator profile with a different callsign and locator.
+        repository.save("DN9APW", "JN59AA", "DL0ABC", "JN49FK",
+                SAMPLE_COUNT, PROVIDER_ID, profileData("station-b"));
+
+        Optional<TerrainProfileData> firstOwnerEntry = repository.load(
+                "DM5M", "JO51IJ", "DL0ABC", "JN49FK", SAMPLE_COUNT, PROVIDER_ID);
+        Optional<TerrainProfileData> secondOwnerEntry = repository.load(
+                "DN9APW", "JN59AA", "DL0ABC", "JN49FK", SAMPLE_COUNT, PROVIDER_ID);
+
+        assertTrue(firstOwnerEntry.isPresent(),
+                "Working under a second operator identity must not discard the first one's cache");
+        assertTrue(secondOwnerEntry.isPresent());
+        assertEquals("station-a", firstOwnerEntry.get().sourceName());
+        assertEquals("station-b", secondOwnerEntry.get().sourceName());
+    }
+
+    @Test
+    void anUnknownOwnerSimplyMissesTheCacheInsteadOfClearingIt() {
+
+        TerrainProfileCacheRepository repository = new TerrainProfileCacheRepository();
+
+        repository.save("DM5M", "JO51IJ", "DL0ABC", "JN49FK",
+                SAMPLE_COUNT, PROVIDER_ID, profileData("station-a"));
+
+        assertTrue(repository.load("DL0XYZ", "JO60AA", "DL0ABC", "JN49FK",
+                SAMPLE_COUNT, PROVIDER_ID).isEmpty());
+
+        assertTrue(repository.load("DM5M", "JO51IJ", "DL0ABC", "JN49FK",
+                SAMPLE_COUNT, PROVIDER_ID).isPresent(),
+                "A cache miss of one owner must not remove the entries of another");
+    }
+
+    @Test
+    void theCacheLivesInItsOwnGlobalFileAndNotInTheWorkedStationDatabase() {
+
+        TerrainProfileCacheRepository repository = new TerrainProfileCacheRepository();
+        repository.save("DM5M", "JO51IJ", "DL0ABC", "JN49FK",
+                SAMPLE_COUNT, PROVIDER_ID, profileData("station-a"));
+
+        Path applicationDirectory = temporaryHomeDirectory.resolve(".praktiKST");
+
+        assertTrue(Files.exists(applicationDirectory.resolve("terrainprofilecache.db")));
+        assertFalse(Files.exists(applicationDirectory.resolve("praktiKST.db")),
+                "The terrain cache must not pull in the worked station database");
+    }
+
+    private static TerrainProfileData profileData(final String sourceName) {
+        return new TerrainProfileData(
+                List.of(
+                        new PathProfilePoint(0.0, 51.0, 10.0, 100.0),
+                        new PathProfilePoint(10.0, 51.1, 10.1, 220.0),
+                        new PathProfilePoint(20.0, 51.2, 10.2, 150.0)),
+                sourceName,
+                false);
+    }
+}