fix(server): one-shot initializers no longer race

apps/desktop/src/backend/DesktopServerExposure.test.ts

@@ -2,7 +2,9 @@ import * as NodeFileSystem from "@effect/platform-node/NodeFileSystem";
 import * as NodeHttpClient from "@effect/platform-node/NodeHttpClient";
 import * as NodeServices from "@effect/platform-node/NodeServices";
 import { assert, describe, it } from "@effect/vitest";
+import * as Deferred from "effect/Deferred";
 import * as Effect from "effect/Effect";
+import * as Fiber from "effect/Fiber";
 import * as FileSystem from "effect/FileSystem";
 import * as Layer from "effect/Layer";
 import * as Sink from "effect/Sink";
@@ -305,6 +307,55 @@ describe("DesktopServerExposure", () => {
     );
   });
 
+  it.effect("keeps a Tailscale Serve change made while a mode change is saving", () =>
+    Effect.gen(function* () {
+      const modeWriteStarted = yield* Deferred.make<void>();
+      const releaseModeWrite = yield* Deferred.make<void>();
+      const settingsLayer = Layer.effect(
+        DesktopAppSettings.DesktopAppSettings,
+        Effect.gen(function* () {
+          const settings = yield* DesktopAppSettings.DesktopAppSettings;
+          return DesktopAppSettings.DesktopAppSettings.of({
+            ...settings,
+            // Hold the mode write the way a slow disk would.
+            setServerExposureMode: (mode) =>
+              Deferred.succeed(modeWriteStarted, undefined).pipe(
+                Effect.andThen(Deferred.await(releaseModeWrite)),
+                Effect.andThen(settings.setServerExposureMode(mode)),
+              ),
+          });
+        }),
+      ).pipe(Layer.provide(DesktopAppSettings.layerTest()));
+
+      return yield* withHarness(
+        lanNetworkInterfaces,
+        Effect.gen(function* () {
+          const serverExposure = yield* DesktopServerExposure.DesktopServerExposure;
+          yield* serverExposure.configureFromSettings({ port: 4173 });
+
+          const modeChange = yield* serverExposure
+            .setMode("network-accessible")
+            .pipe(Effect.forkChild({ startImmediately: true }));
+          yield* Deferred.await(modeWriteStarted);
+          const tailscaleChange = yield* serverExposure
+            .setTailscaleServeEnabled({ enabled: true, port: 8443 })
+            .pipe(Effect.forkChild({ startImmediately: true }));
+          yield* Deferred.succeed(releaseModeWrite, undefined);
+          yield* Fiber.join(modeChange);
+          yield* Fiber.join(tailscaleChange);
+
+          const state = yield* serverExposure.getState;
+          assert.equal(state.mode, "network-accessible");
+          assert.equal(state.tailscaleServeEnabled, true);
+          assert.equal(state.tailscaleServePort, 8443);
+        }),
+        {},
+        undefined,
+        settingsLayer,
+      );
+    }),
+  );
+
   it.effect("keeps LAN and Tailscale endpoints distinct when Tailscale is enumerated first", () =>
     withHarness(
       { ...tailnetNetworkInterfaces, ...lanNetworkInterfaces },

apps/desktop/src/backend/DesktopServerExposure.ts

@@ -17,6 +17,7 @@ import * as Layer from "effect/Layer";
 import * as Option from "effect/Option";
 import * as Ref from "effect/Ref";
 import * as Schema from "effect/Schema";
+import * as Semaphore from "effect/Semaphore";
 import * as HttpClient from "effect/http/HttpClient";
 import * as ChildProcessSpawner from "effect/process/ChildProcessSpawner";
 
@@ -419,6 +420,10 @@ export const make = Effect.gen(function* () {
   const httpClient = yield* HttpClient.HttpClient;
   const desktopSettings = yield* DesktopAppSettings.DesktopAppSettings;
   const stateRef = yield* Ref.make(initialRuntimeState());
+  // Each change reads the runtime state, persists settings, then writes the
+  // state back. Run them one at a time so a change never writes over another
+  // with values it read before that change persisted.
+  const changePermit = yield* Semaphore.make(1);
 
   // Cache the `tailscale status` spawn for the TTL. On macOS, the Mac App
   // Store Tailscale CLI lives inside Tailscale's sandbox container, so each
@@ -492,7 +497,7 @@ export const make = Effect.gen(function* () {
       state: toContractState(resolved.state),
       requiresRelaunch: change.changed || requiresBackendRelaunch(previous, resolved.state),
     };
-  });
+  }, changePermit.withPermit);
 
   const setTailscaleServeEnabled = Effect.fn("desktop.serverExposure.setTailscaleServeEnabled")(
     function* (input: { readonly enabled: boolean; readonly port?: number }) {
@@ -527,6 +532,7 @@ export const make = Effect.gen(function* () {
         requiresRelaunch: result.changed,
       };
     },
+    changePermit.withPermit,
   );
 
   const getAdvertisedEndpoints = Effect.gen(function* () {

apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.test.ts

@@ -1656,6 +1656,150 @@ function makeCodexReplayTranscript(input: {
   };
 }
 
+function withReplayRequestId(
+  entry: CodexReplay.CodexAppServerReplayEntry,
+  id: number,
+): CodexReplay.CodexAppServerReplayEntry {
+  return entry.type !== "runtime_exit" && Predicate.isObject(entry.frame)
+    ? { ...entry, frame: { ...entry.frame, id } }
+    : entry;
+}
+
+describe("CodexAdapterV2 session initialize", () => {
+  const openReplaySession = (
+    transcript: CodexReplay.CodexAppServerReplayTranscript,
+    beforeEmitInbound?: CodexReplay.CodexAppServerReplayDriver["beforeEmitInbound"],
+  ) =>
+    Effect.gen(function* () {
+      const driver = yield* CodexReplay.makeReplayDriver(
+        transcript,
+        beforeEmitInbound === undefined ? {} : { beforeEmitInbound },
+      );
+      let initializeRequests = 0;
+      const adapter = CodexAdapterV2.makeCodexAdapterV2({
+        instanceId: CodexAdapterV2.CODEX_DEFAULT_INSTANCE_ID,
+        settings: DEFAULT_CODEX_SETTINGS,
+        environment: {},
+        clientFactory: {
+          open: (openInput) =>
+            Layer.build(CodexReplay.layerReplayWithDriver(driver)).pipe(
+              Effect.flatMap((context) =>
+                Effect.service(CodexClient.CodexAppServerClient).pipe(Effect.provide(context)),
+              ),
+              Effect.map(
+                (client) =>
+                  ({
+                    ...client,
+                    request: (method, params) =>
+                      Effect.sync(() => {
+                        if (method === "initialize") initializeRequests++;
+                      }).pipe(Effect.andThen(client.request(method, params))),
+                  }) satisfies CodexClient.CodexAppServerClient["Service"],
+              ),
+              Effect.mapError(
+                (cause) =>
+                  new ProviderAdapterOpenSessionError({
+                    driver: CodexAdapterV2.CODEX_DRIVER_KIND,
+                    providerSessionId: openInput.providerSessionId,
+                    cause,
+                  }),
+              ),
+            ),
+        },
+        fileSystem: yield* FileSystem.FileSystem,
+        idAllocator: yield* IdAllocator.IdAllocatorV2,
+        serverConfig: yield* makeReplayServerConfig(transcript.scenario).pipe(Effect.orDie),
+      });
+      const runtime = yield* adapter.openSession({
+        threadId: ThreadId.make(`thread-${transcript.scenario}`),
+        providerSessionId: ProviderSessionId.make(`provider-session-${transcript.scenario}`),
+        modelSelection: CODEX_TEST_MODEL_SELECTION,
+        runtimePolicy: CODEX_TEST_RUNTIME_POLICY,
+      });
+      return {
+        ensureThread: (threadId: string) =>
+          runtime.ensureThread({
+            threadId: ThreadId.make(threadId),
+            modelSelection: CODEX_TEST_MODEL_SELECTION,
+            runtimePolicy: CODEX_TEST_RUNTIME_POLICY,
+          }),
+        initializeRequests: () => initializeRequests,
+      };
+    });
+
+  const replayPreamble = (nativeThreadId: string) =>
+    codexReplayPreamble({ nativeThreadId, nativeTurnId: "unused", prompt: "unused" });
+
+  it.effect("sends one initialize when two threads start on a fresh session at once", () =>
+    Effect.gen(function* () {
+      const initializeAwaitingResponse = yield* Deferred.make<void>();
+      const releaseInitialize = yield* Deferred.make<void>();
+      // The transcript allows exactly one handshake: a second `initialize`
+      // frame fails the replay, as Codex rejects it with "Already initialized".
+      const session = yield* openReplaySession(
+        makeCodexReplayTranscript({
+          scenario: "concurrent-initialize",
+          entries: [
+            ...replayPreamble("concurrent-first").slice(0, 5),
+            ...replayPreamble("concurrent-second")
+              .slice(3, 5)
+              .map((entry) => withReplayRequestId(entry, 3)),
+          ],
+        }),
+        (entry) =>
+          entry.label === "initialize"
+            ? Deferred.succeed(initializeAwaitingResponse, undefined).pipe(
+                Effect.andThen(Deferred.await(releaseInitialize)),
+              )
+            : Effect.void,
+      );
+
+      const first = yield* session
+        .ensureThread("thread-concurrent-first")
+        .pipe(Effect.forkChild({ startImmediately: true }));
+      yield* Deferred.await(initializeAwaitingResponse);
+      // The second thread arrives while the handshake is still unanswered.
+      const second = yield* session
+        .ensureThread("thread-concurrent-second")
+        .pipe(Effect.forkChild({ startImmediately: true }));
+      yield* Deferred.succeed(releaseInitialize, undefined);
+
+      const providerThreads = [yield* Fiber.join(first), yield* Fiber.join(second)];
+      assert.equal(session.initializeRequests(), 1);
+      assert.sameMembers(
+        providerThreads.map((providerThread) => providerThread.nativeThreadRef?.nativeId),
+        ["concurrent-first", "concurrent-second"],
+      );
+    }).pipe(Effect.scoped, Effect.provide(Layer.merge(IdAllocator.layer, NodeServices.layer))),
+  );
+
+  it.effect("retries initialize after a failed handshake", () =>
+    Effect.gen(function* () {
+      const preamble = replayPreamble("initialize-retry");
+      const entries: Array<CodexReplay.CodexAppServerReplayEntry> = [
+        ...preamble.slice(0, 1),
+        {
+          type: "emit_inbound",
+          label: "initialize",
+          frame: { id: 1, error: { code: -32603, message: "Codex is not ready." } },
+        },
+        ...preamble.slice(0, 2).map((entry) => withReplayRequestId(entry, 2)),
+        ...preamble.slice(2, 3),
+        ...preamble.slice(3, 5).map((entry) => withReplayRequestId(entry, 3)),
+      ];
+      const session = yield* openReplaySession(
+        makeCodexReplayTranscript({ scenario: "initialize-retry", entries }),
+      );
+
+      const failure = yield* session.ensureThread("thread-initialize-retry").pipe(Effect.flip);
+      assert.equal(failure._tag, "ProviderAdapterEnsureThreadError");
+      const providerThread = yield* session.ensureThread("thread-initialize-retry");
+      assert.equal(providerThread.nativeThreadRef?.nativeId, "initialize-retry");
+      assert.equal(session.initializeRequests(), 2);
+    }).pipe(Effect.scoped, Effect.provide(Layer.merge(IdAllocator.layer, NodeServices.layer))),
+  );
+});
+
 describe("CodexAdapterV2 post-settle continuation", () => {
   const awaitUntil = (predicate: () => boolean, label: string): Effect.Effect<void> =>
     Effect.gen(function* () {

apps/server/src/orchestration-v2/Adapters/CodexAdapterV2.ts

@@ -1687,21 +1687,28 @@ export function makeCodexAdapterV2(adapterOptions: CodexAdapterV2Options): Provi
             ),
           );
         const initialized = yield* Ref.make(false);
-        const ensureInitialized = Effect.gen(function* () {
-          const alreadyInitialized = yield* Ref.get(initialized);
-          if (alreadyInitialized) {
-            return;
-          }
+        // Threads share this app-server, and Codex rejects a second
+        // `initialize`. Callers wait for an in-flight handshake instead of
+        // starting their own; a failed handshake leaves the flag unset so the
+        // next caller retries.
+        const initializePermit = yield* Semaphore.make(1);
+        const ensureInitialized = initializePermit.withPermit(
+          Effect.gen(function* () {
+            const alreadyInitialized = yield* Ref.get(initialized);
+            if (alreadyInitialized) {
+              return;
+            }
 
-          yield* client.request("initialize", {
-            // Codex uses the client name as the request originator, so sessions
-            // identify themselves exactly like the provider probe.
-            clientInfo: buildCodexInitializeParams().clientInfo,
-            capabilities: CODEX_CLIENT_CAPABILITIES,
-          });
-          yield* client.notify("initialized", undefined);
-          yield* Ref.set(initialized, true);
-        });
+            yield* client.request("initialize", {
+              // Codex uses the client name as the request originator, so sessions
+              // identify themselves exactly like the provider probe.
+              clientInfo: buildCodexInitializeParams().clientInfo,
+              capabilities: CODEX_CLIENT_CAPABILITIES,
+            });
+            yield* client.notify("initialized", undefined);
+            yield* Ref.set(initialized, true);
+          }),
+        );
         const now = yield* DateTime.now;
         const session = providerSession({
           providerSessionId: input.providerSessionId,