fix(server): settings saves no longer revert external edits to settings.json

apps/server/src/serverSettings.test.ts

@@ -488,6 +488,46 @@ it.layer(NodeServices.layer)("server settings", (it) => {
     }).pipe(Effect.provide(layerServerSettings())),
   );
 
+  it.effect("keeps an external settings edit that the watcher has not reloaded yet", () =>
+    Effect.gen(function* () {
+      const config = yield* ServerConfig.ServerConfig;
+      const fs = yield* FileSystem.FileSystem;
+      const serverSettings = yield* ServerSettingsModule.ServerSettingsService;
+      yield* serverSettings.getSettings;
+
+      yield* writeFileStringAtomically({
+        filePath: config.settingsPath,
+        contents: `{ "responseStreamingMode": "turn" }`,
+      });
+      yield* serverSettings.updateSettings({
+        observability: { otlpTracesUrl: "http://localhost:4318/v1/traces" },
+      });
+
+      const saved = yield* decodeServerSettingsJson(yield* fs.readFileString(config.settingsPath));
+      assert.equal(saved.responseStreamingMode, "turn");
+      assert.equal(saved.observability.otlpTracesUrl, "http://localhost:4318/v1/traces");
+    }).pipe(Effect.provide(layerServerSettings())),
+  );
+
+  it.effect("refuses to save over a settings file it cannot parse", () =>
+    Effect.gen(function* () {
+      const config = yield* ServerConfig.ServerConfig;
+      const fs = yield* FileSystem.FileSystem;
+      const serverSettings = yield* ServerSettingsModule.ServerSettingsService;
+      const raw = `{ "responseStreamingMode": "turn", `;
+      yield* fs.writeFileString(config.settingsPath, raw);
+
+      const error = yield* Effect.flip(
+        serverSettings.updateSettings({
+          observability: { otlpTracesUrl: "http://localhost:4318/v1/traces" },
+        }),
+      );
+
+      assert.equal(error.operation, "read-file");
+      assert.equal(yield* fs.readFileString(config.settingsPath), raw);
+    }).pipe(Effect.provide(layerServerSettings())),
+  );
+
   it.effect("creates provider instances atomically without overwriting a concurrent add", () =>
     Effect.gen(function* () {
       const serverSettings = yield* ServerSettingsModule.ServerSettingsService;

apps/server/src/serverSettings.ts

@@ -661,6 +661,7 @@ const make = Effect.gen(function* () {
     // A file that failed to decode must stay on disk for the user to repair;
     // the fold below only writes when it started from the file's real contents.
     let settingsFileTrusted = true;
+    let parseFailure = Option.none<unknown>();
 
     if (yield* readConfigExists) {
       const raw = yield* readRawConfig;
@@ -679,6 +680,7 @@ const make = Effect.gen(function* () {
         // The file may hold an opt-out we can no longer read; never resume threads on a guess.
         settings = { ...DEFAULT_SERVER_SETTINGS, continueThreadsAfterServerUpdate: false };
         if (failure._tag === "Failure") {
+          parseFailure = Option.some(Cause.squash(failure.cause));
           yield* Effect.logWarning("failed to parse settings.json, using defaults", {
             path: settingsPath,
             issues: Cause.pretty(failure.cause),
@@ -787,18 +789,24 @@ const make = Effect.gen(function* () {
         yield* secretStore.remove(move.from).pipe(Effect.ignore);
       }
     }
-    return migrated;
+    return { settings: migrated, parseFailure };
   });
 
-  const settingsCache = yield* Cache.makeWith<typeof cacheKey, ServerSettings, ServerSettingsError>(
-    () => loadSettingsFromDisk,
-    {
-      capacity: 1,
-      timeToLive: (exit) => (Exit.isSuccess(exit) ? Duration.infinity : Duration.zero),
-    },
-  );
+  const settingsCache = yield* Cache.makeWith<
+    typeof cacheKey,
+    { readonly settings: ServerSettings; readonly parseFailure: Option.Option<unknown> },
+    ServerSettingsError
+  >(() => loadSettingsFromDisk, {
+    capacity: 1,
+    timeToLive: (exit) => (Exit.isSuccess(exit) ? Duration.infinity : Duration.zero),
+  });
 
-  const getSettingsFromCache = Cache.get(settingsCache, cacheKey);
+  const getSettingsFromCache = Cache.get(settingsCache, cacheKey).pipe(
+    Effect.map((loaded) => loaded.settings),
+  );
+  const reloadSettings = Cache.invalidate(settingsCache, cacheKey).pipe(
+    Effect.andThen(Cache.get(settingsCache, cacheKey)),
+  );
 
   const materializeSettingsSecrets = (
     settings: ServerSettings,
@@ -1001,7 +1009,14 @@ const make = Effect.gen(function* () {
   ): Effect.Effect<ServerSettings, ServerSettingsError> =>
     writeSemaphore.withPermits(1)(
       Effect.gen(function* () {
-        const current = yield* getSettingsFromCache;
+        const { settings: current, parseFailure } = yield* reloadSettings;
+        if (Option.isSome(parseFailure)) {
+          return yield* new ServerSettingsError({
+            settingsPath,
+            operation: "read-file",
+            cause: parseFailure.value,
+          });
+        }
         const updated = yield* update(current);
         const persisted = yield* persistSettingsSecrets(current, updated);
         const next = yield* normalizeServerSettings(persisted.settings);
@@ -1021,7 +1036,7 @@ const make = Effect.gen(function* () {
             return materializedExit.value;
           }),
         );
-        yield* Cache.set(settingsCache, cacheKey, next);
+        yield* Cache.set(settingsCache, cacheKey, { settings: next, parseFailure: Option.none() });
         yield* emitChange(next);
         return resolveTextGenerationProvider(materialized);
       }),
@@ -1038,8 +1053,7 @@ const make = Effect.gen(function* () {
 
   const revalidateAndEmit = writeSemaphore.withPermits(1)(
     Effect.gen(function* () {
-      yield* Cache.invalidate(settingsCache, cacheKey);
-      const settings = yield* getSettingsFromCache;
+      const { settings } = yield* reloadSettings;
       yield* emitChange(settings);
     }),
   );
@@ -1128,8 +1142,7 @@ const make = Effect.gen(function* () {
 
     const startup = Effect.gen(function* () {
       yield* startWatcher;
-      yield* Cache.invalidate(settingsCache, cacheKey);
-      yield* getSettingsFromCache;
+      yield* reloadSettings;
     });
 
     const startupExit = yield* Effect.exit(startup);