diff --git a/packages/core/src/sessions/clearSessionError.test.ts b/packages/core/src/sessions/clearSessionError.test.ts
new file mode 100644
index 000000000..dabc95aa3
--- /dev/null
+++ b/packages/core/src/sessions/clearSessionError.test.ts
@@ -0,0 +1,196 @@
+import type { AgentSession } from "@posthog/shared";
+import { describe, expect, it, vi } from "vitest";
+import { SessionService, type SessionServiceDeps } from "./sessionService";
+
+const TASK_ID = "task-1";
+const RUN_ID = "run-1";
+const REPO = "/repo";
+
+const noopLog = {
+  info: vi.fn(),
+  warn: vi.fn(),
+  error: vi.fn(),
+  debug: vi.fn(),
+};
+
+function makeSession(overrides: Partial<AgentSession> = {}): AgentSession {
+  return {
+    taskRunId: RUN_ID,
+    taskId: TASK_ID,
+    taskTitle: "Task",
+    channel: "agent-event:run-1",
+    events: [],
+    startedAt: Date.now(),
+    status: "error",
+    isPromptPending: false,
+    isCompacting: false,
+    pendingPermissions: new Map(),
+    promptStartedAt: null,
+    pausedDurationMs: 0,
+    messageQueue: [],
+    optimisticItems: [],
+    initialPrompt: [{ type: "text", text: "do the thing" }],
+    ...overrides,
+  };
+}
+
+function createService(session?: AgentSession) {
+  const sessions: Record<string, AgentSession> = {};
+  if (session) sessions[session.taskRunId] = session;
+
+  const store = {
+    getSessions: () => sessions,
+    getSessionByTaskId: (taskId: string) =>
+      Object.values(sessions).find((s) => s.taskId === taskId),
+    setSession: (s: AgentSession) => {
+      sessions[s.taskRunId] = s;
+    },
+    updateSession: (taskRunId: string, updates: Partial<AgentSession>) => {
+      const s = sessions[taskRunId];
+      if (s) Object.assign(s, updates);
+    },
+    clearTailOptimisticItems: vi.fn(),
+    appendOptimisticItem: vi.fn(),
+    replaceOptimisticWithEvent: vi.fn(),
+    clearMessageQueue: vi.fn(),
+  };
+
+  const deps = {
+    store,
+    log: noopLog,
+    notifyPromptComplete: vi.fn(),
+    notifyPermissionRequest: vi.fn(),
+    getPersistedConfigOptions: () => undefined,
+    setPersistedConfigOptions: vi.fn(),
+    trpc: {
+      agent: {
+        onSessionIdleKilled: {
+          subscribe: () => ({ unsubscribe: vi.fn() }),
+        },
+        cancel: {
+          mutate: vi.fn().mockResolvedValue(undefined),
+        },
+        getPreviewConfigOptions: {
+          query: vi.fn().mockResolvedValue([]),
+        },
+      },
+    },
+  } as unknown as SessionServiceDeps;
+
+  const service = new SessionService(deps);
+
+  // Replace the private helpers clearSessionError delegates to so the test can
+  // assert the session-intent args in isolation, without standing up the full
+  // agent.start/createTaskRun/subscribe chain inside createNewLocalSession.
+  const createSpy = vi.fn().mockResolvedValue(undefined);
+  const teardownSpy = vi.fn().mockResolvedValue(undefined);
+  const authSpy = vi.fn().mockResolvedValue({
+    apiHost: "https://us.posthog.com",
+    projectId: 1,
+    client: {},
+  });
+  // biome-ignore lint/suspicious/noExplicitAny: spy on private methods
+  const anyService = service as any;
+  anyService.createNewLocalSession = createSpy;
+  anyService.teardownSession = teardownSpy;
+  anyService.getAuthCredentials = authSpy;
+
+  return { service, createSpy, teardownSpy, sessions };
+}
+
+describe("clearSessionError preserves session intent on retry", () => {
+  it("forwards the caller overrides (adapter/model/executionMode/reasoningLevel)", async () => {
+    const { service, createSpy } = createService(makeSession());
+
+    await service.clearSessionError(TASK_ID, REPO, {
+      adapter: "codex",
+      model: "gpt-5.5",
+      executionMode: "auto",
+      reasoningLevel: "high",
+    });
+
+    expect(createSpy).toHaveBeenCalledTimes(1);
+    // createNewLocalSession(taskId, taskTitle, repoPath, auth, initialPrompt,
+    //   executionMode, adapter, model, reasoningLevel)
+    const [, , , , , executionMode, adapter, model, reasoningLevel] =
+      createSpy.mock.calls[0];
+    expect(adapter).toBe("codex");
+    expect(model).toBe("gpt-5.5");
+    expect(executionMode).toBe("auto");
+    expect(reasoningLevel).toBe("high");
+  });
+
+  it("recovers adapter/model/executionMode from a previously-live session when no overrides are given", async () => {
+    const session = makeSession({
+      status: "error",
+      idleKilled: true,
+      adapter: "codex",
+      configOptions: [
+        {
+          id: "model",
+          name: "Model",
+          type: "select",
+          currentValue: "gpt-5.5",
+          options: [],
+          category: "model",
+        },
+        {
+          id: "mode",
+          name: "Approval Preset",
+          type: "select",
+          currentValue: "auto",
+          options: [],
+          category: "mode",
+        },
+        {
+          id: "reasoning_effort",
+          name: "Reasoning Level",
+          type: "select",
+          currentValue: "high",
+          options: [],
+          category: "thought_level",
+        },
+      ],
+    });
+    const { service, createSpy } = createService(session);
+
+    await service.clearSessionError(TASK_ID, REPO);
+
+    expect(createSpy).toHaveBeenCalledTimes(1);
+    const [, , , , , executionMode, adapter, model, reasoningLevel] =
+      createSpy.mock.calls[0];
+    expect(adapter).toBe("codex");
+    expect(model).toBe("gpt-5.5");
+    expect(executionMode).toBe("auto");
+    expect(reasoningLevel).toBe("high");
+  });
+
+  it("keeps the retry placeholder when fresh session creation fails", async () => {
+    const session = makeSession();
+    const { service, createSpy, teardownSpy, sessions } =
+      createService(session);
+    createSpy.mockRejectedValueOnce(new Error("still broken"));
+
+    await expect(service.clearSessionError(TASK_ID, REPO)).rejects.toThrow(
+      "still broken",
+    );
+
+    expect(teardownSpy).not.toHaveBeenCalled();
+    expect(sessions[RUN_ID]).toBe(session);
+  });
+
+  it("recovers a Codex placeholder with no explicit model as Codex default", async () => {
+    const session = makeSession({
+      adapter: "codex",
+      configOptions: [],
+    });
+    const { service, createSpy } = createService(session);
+
+    await service.clearSessionError(TASK_ID, REPO);
+
+    expect(createSpy).toHaveBeenCalledTimes(1);
+    const [, , , , , , adapter, model] = createSpy.mock.calls[0];
+    expect(adapter).toBe("codex");
+    expect(model).toBeUndefined();
+  });
+});
diff --git a/packages/core/src/sessions/sessionService.ts b/packages/core/src/sessions/sessionService.ts
index 28993a584..523445f39 100644
--- a/packages/core/src/sessions/sessionService.ts
+++ b/packages/core/src/sessions/sessionService.ts
@@ -7,6 +7,7 @@ import type {
   SessionConfigOption,
   SessionUpdate,
 } from "@agentclientprotocol/sdk";
+import { inferAdapterFromModelId } from "@posthog/core/task-detail/modelAdapter";
 import {
   type AcpMessage,
   type Adapter,
@@ -17,6 +18,7 @@ import {
   getBackoffDelay,
   getCloudUrlFromRegion,
   getConfigOptionByCategory,
+  getCurrentModeFromConfigOptions,
   isFatalSessionError,
   isJsonRpcNotification,
   isJsonRpcRequest,
@@ -831,9 +833,18 @@ export class SessionService {
     const events = convertStoredEntriesToEvents(rawEntries);
 
     const storedAdapter = this.d.adapterStore.getAdapter(taskRunId);
-    const resolvedAdapter = adapter ?? storedAdapter;
     const persistedConfigOptions = this.d.getPersistedConfigOptions(taskRunId);
 
+    // Infer the adapter from the persisted model as a safety net. A missing
+    // adapter on reconnect would cause the local agent to default to Claude
+    // even for Codex/OpenAI sessions.
+    const persistedModelForAdapter =
+      getConfigOptionByCategory(persistedConfigOptions, "model")?.currentValue;
+    const resolvedAdapter =
+      adapter ??
+      storedAdapter ??
+      inferAdapterFromModelId(persistedModelForAdapter);
+
     const previous = this.d.store.getSessions()[taskRunId];
 
     const session = createBaseSession(taskRunId, taskId, taskTitle);
@@ -1207,7 +1218,20 @@ export class SessionService {
     }
 
     const { customInstructions: startCustomInstructions } = this.d.settings;
-    const preferredModel = model ?? this.d.DEFAULT_GATEWAY_MODEL;
+
+    // Infer the adapter from the model id when the caller did not supply one.
+    // Without this, a GPT/Codex model paired with an undefined adapter causes
+    // the local agent process to default to Claude and silently ignore the
+    // selected model, falling back to the Claude default (Opus).
+    const resolvedAdapter = adapter ?? inferAdapterFromModelId(model);
+
+    // Use the gateway default only when the caller did not pick a model AND the
+    // adapter is Claude (or still unknown). Codex resolves its own default
+    // server-side via Agent.run, so passing no model is correct there.
+    const preferredModel =
+      model ??
+      (resolvedAdapter === "codex" ? undefined : this.d.DEFAULT_GATEWAY_MODEL);
+
     const result = await this.d.trpc.agent.start.mutate({
       taskId,
       taskRunId: taskRun.id,
@@ -1215,7 +1239,7 @@ export class SessionService {
       apiHost: auth.apiHost,
       projectId: auth.projectId,
       permissionMode: executionMode,
-      adapter,
+      adapter: resolvedAdapter,
       customInstructions: startCustomInstructions || undefined,
       effort: effortLevelSchema.safeParse(reasoningLevel).success
         ? (reasoningLevel as EffortLevel)
@@ -1226,7 +1250,7 @@ export class SessionService {
     const session = createBaseSession(taskRun.id, taskId, taskTitle);
     session.channel = result.channel;
     session.status = "connected";
-    session.adapter = adapter;
+    session.adapter = resolvedAdapter;
     const configOptions = result.configOptions as
       | SessionConfigOption[]
       | undefined;
@@ -1238,8 +1262,8 @@ export class SessionService {
     }
 
     // Persist the adapter
-    if (adapter) {
-      this.d.adapterStore.setAdapter(taskRun.id, adapter);
+    if (resolvedAdapter) {
+      this.d.adapterStore.setAdapter(taskRun.id, resolvedAdapter);
     }
 
     // Store the initial prompt on the session so retry/reset flows can
@@ -1256,7 +1280,7 @@ export class SessionService {
       task_id: taskId,
       execution_type: "local",
       initial_mode: executionMode,
-      adapter,
+      adapter: resolvedAdapter,
     });
 
     if (initialPrompt?.length) {
@@ -3025,13 +3049,27 @@ export class SessionService {
    * initialPrompt saved from the original creation attempt), creates
    * a fresh session and re-sends the prompt instead of reconnecting
    * to an empty session.
+   *
+   * Optional overrides let callers (e.g. the "Retry" button) explicitly pin
+   * the adapter/model/mode for the fresh session. When no overrides are given
+   * the values are recovered from the errored session's adapter +
+   * configOptions so a retry does not silently revert to Claude/Opus.
    */
-  async clearSessionError(taskId: string, repoPath: string): Promise<void> {
+  async clearSessionError(
+    taskId: string,
+    repoPath: string,
+    overrides?: {
+      adapter?: Adapter;
+      model?: string;
+      executionMode?: ExecutionMode;
+      reasoningLevel?: string;
+    },
+  ): Promise<void> {
     this.localRepoPaths.set(taskId, repoPath);
     const session = this.d.store.getSessionByTaskId(taskId);
     if (session?.initialPrompt?.length) {
       const { taskTitle, initialPrompt } = session;
-      await this.teardownSession(session.taskRunId);
+      const oldTaskRunId = session.taskRunId;
       const authStatus = await this.getAuthCredentialsStatus();
       if (authStatus.kind === "restoring") {
         throw new Error("Authentication is still restoring. Please wait.");
@@ -3041,13 +3079,42 @@ export class SessionService {
           "Unable to reach server. Please check your connection.",
         );
       }
+
+      // Recover session intent from the errored session when the caller did
+      // not supply overrides, so retry preserves the user's original picks
+      // instead of resetting to defaults.
+      const recoveredModel =
+        overrides?.model ??
+        getConfigOptionByCategory(session.configOptions, "model")?.currentValue;
+      const recoveredAdapter =
+        overrides?.adapter ??
+        session.adapter ??
+        inferAdapterFromModelId(recoveredModel);
+      const recoveredMode =
+        overrides?.executionMode ??
+        getCurrentModeFromConfigOptions(session.configOptions);
+      const recoveredReasoning =
+        overrides?.reasoningLevel ??
+        getConfigOptionByCategory(
+          session.configOptions,
+          "thought_level",
+        )?.currentValue;
+
+      // Create the new session before tearing down the old one. If creation
+      // fails the caller can retry from the preserved placeholder instead of
+      // being left with no session at all.
       await this.createNewLocalSession(
         taskId,
         taskTitle,
         repoPath,
         authStatus.auth,
         initialPrompt,
+        recoveredMode,
+        recoveredAdapter,
+        recoveredModel,
+        recoveredReasoning,
       );
+      await this.teardownSession(oldTaskRunId);
       return;
     }
     await this.reconnectInPlace(taskId, repoPath);
diff --git a/packages/core/src/task-detail/modelAdapter.test.ts b/packages/core/src/task-detail/modelAdapter.test.ts
new file mode 100644
index 000000000..c60062a46
--- /dev/null
+++ b/packages/core/src/task-detail/modelAdapter.test.ts
@@ -0,0 +1,25 @@
+import { describe, expect, it } from "vitest";
+import { inferAdapterFromModelId } from "./modelAdapter";
+
+describe("inferAdapterFromModelId", () => {
+  it.each(["gpt-5.5", "gpt-5.4", "o3", "o4-mini", "codex-mini"])(
+    "maps OpenAI model %s to Codex",
+    (model) => {
+      expect(inferAdapterFromModelId(model)).toBe("codex");
+    },
+  );
+
+  it.each(["claude-opus-4-8", "claude-sonnet-4-5"])(
+    "maps Anthropic model %s to Claude",
+    (model) => {
+      expect(inferAdapterFromModelId(model)).toBe("claude");
+    },
+  );
+
+  it.each([undefined, null, "", "fable", "custom-model"])(
+    "leaves ambiguous model %s unchanged",
+    (model) => {
+      expect(inferAdapterFromModelId(model)).toBeUndefined();
+    },
+  );
+});
diff --git a/packages/core/src/task-detail/modelAdapter.ts b/packages/core/src/task-detail/modelAdapter.ts
new file mode 100644
index 000000000..714d8599f
--- /dev/null
+++ b/packages/core/src/task-detail/modelAdapter.ts
@@ -0,0 +1,20 @@
+import type { Adapter } from "@posthog/shared";
+
+const CODEX_MODEL_PATTERNS = [/^gpt-/i, /^o\d/i, /^codex-/i];
+const CLAUDE_MODEL_PATTERNS = [/^claude-/i];
+
+export function inferAdapterFromModelId(
+  modelId: string | null | undefined,
+): Adapter | undefined {
+  if (!modelId) return undefined;
+  const normalized = modelId.trim();
+  if (!normalized) return undefined;
+
+  if (CODEX_MODEL_PATTERNS.some((pattern) => pattern.test(normalized))) {
+    return "codex";
+  }
+  if (CLAUDE_MODEL_PATTERNS.some((pattern) => pattern.test(normalized))) {
+    return "claude";
+  }
+  return undefined;
+}