diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
index d4a96b45e6..8437420340 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.test.ts
@@ -1117,6 +1117,42 @@ describe("Codex app-server provider", () => {
     });
   });
 
+  test("starts a session without a model on the project's Codex model and effort", async () => {
+    const cwd = "/workspace/project";
+    const appServer = createFakeCodexAppServer({
+      "config/read": (params) => ({
+        config:
+          (params as { cwd?: unknown }).cwd === cwd
+            ? { model: "project-model", model_reasoning_effort: "high" }
+            : { model: "global-model", model_reasoning_effort: "low" },
+      }),
+      getUserSavedConfig: () => ({
+        config: { model: "global-model", modelReasoningEffort: "low" },
+      }),
+    });
+    const session = new CodexAppServerAgentSession(
+      createConfig({ cwd, model: undefined }),
+      null,
+      createTestLogger(),
+      async () => appServer.child,
+    );
+
+    try {
+      await session.startTurn("use project defaults");
+
+      await expect(appServer.waitForRequest("thread/start")).resolves.toMatchObject({
+        model: "project-model",
+      });
+      await expect(appServer.waitForTurnStart()).resolves.toMatchObject({
+        model: "project-model",
+        effort: "high",
+      });
+      appServer.assertNoErrors();
+    } finally {
+      await session.close();
+    }
+  });
+
   test("preserves cwd-resolved Codex writable roots under an explicit workflow mode", async () => {
     const appServer = createFakeCodexAppServer({
       "config/read": () => ({
diff --git a/packages/server/src/server/agent/providers/codex-app-server-agent.ts b/packages/server/src/server/agent/providers/codex-app-server-agent.ts
index 55d7886df8..ac927a8656 100644
--- a/packages/server/src/server/agent/providers/codex-app-server-agent.ts
+++ b/packages/server/src/server/agent/providers/codex-app-server-agent.ts
@@ -3100,10 +3100,32 @@ const CodexNotificationSchema = z.union([
     ),
 ]);
 
+// config/read resolves the effective layered config, including a trusted project's
+// .codex/config.toml when given its cwd; getUserSavedConfig predates it.
 async function readCodexConfiguredDefaults(
   client: CodexAppServerClient,
   logger: Logger,
+  cwd: string | null,
 ): Promise<CodexConfiguredDefaults> {
+  let configReadDefaults: CodexConfiguredDefaults = {};
+  try {
+    const response = toObjectRecord(await client.request("config/read", { cwd }));
+    const config = toObjectRecord(response?.config);
+    const modelValue = typeof config?.model === "string" ? config.model : undefined;
+    const thinkingOptionValue =
+      typeof config?.model_reasoning_effort === "string" ? config.model_reasoning_effort : null;
+    configReadDefaults = {
+      model: normalizeCodexModelId(modelValue),
+      thinkingOptionId: normalizeCodexThinkingOptionId(thinkingOptionValue),
+    };
+  } catch (error) {
+    logger.debug({ error }, "Failed to read Codex config defaults");
+  }
+
+  if (configReadDefaults.model && configReadDefaults.thinkingOptionId) {
+    return configReadDefaults;
+  }
+
   let savedConfigDefaults: CodexConfiguredDefaults = {};
   try {
     const response = toObjectRecord(await client.request("getUserSavedConfig", {}));
@@ -3119,26 +3141,7 @@ async function readCodexConfiguredDefaults(
     logger.debug({ error }, "Failed to read Codex saved config defaults");
   }
 
-  if (savedConfigDefaults.model && savedConfigDefaults.thinkingOptionId) {
-    return savedConfigDefaults;
-  }
-
-  let configReadDefaults: CodexConfiguredDefaults = {};
-  try {
-    const response = toObjectRecord(await client.request("config/read", {}));
-    const config = toObjectRecord(response?.config);
-    const modelValue = typeof config?.model === "string" ? config.model : undefined;
-    const thinkingOptionValue =
-      typeof config?.model_reasoning_effort === "string" ? config.model_reasoning_effort : null;
-    configReadDefaults = {
-      model: normalizeCodexModelId(modelValue),
-      thinkingOptionId: normalizeCodexThinkingOptionId(thinkingOptionValue),
-    };
-  } catch (error) {
-    logger.debug({ error }, "Failed to read Codex config defaults");
-  }
-
-  return mergeCodexConfiguredDefaults(savedConfigDefaults, configReadDefaults);
+  return mergeCodexConfiguredDefaults(configReadDefaults, savedConfigDefaults);
 }
 
 interface CodexSkillPromptBlock {
@@ -5119,7 +5122,11 @@ export class CodexAppServerAgentSession implements AgentSession {
     let model = this.config.model;
     let thinkingOptionId = normalizeCodexThinkingOptionId(this.config.thinkingOptionId);
     if (!model || !thinkingOptionId) {
-      configuredDefaults = await readCodexConfiguredDefaults(this.client, this.logger);
+      configuredDefaults = await readCodexConfiguredDefaults(
+        this.client,
+        this.logger,
+        this.config.cwd ?? null,
+      );
     }
     if (!model) {
       model = configuredDefaults.model;
@@ -7323,7 +7330,7 @@ export class CodexAppServerAgentClient implements AgentClient {
       const parsedResponse = CodexModelListResponseSchema.safeParse(rawResponse);
       const models = parsedResponse.success ? (parsedResponse.data.data ?? []) : [];
       const configuredDefaults = await runProviderRefreshActivity(context, "config/read", () =>
-        readCodexConfiguredDefaults(client!, this.logger),
+        readCodexConfiguredDefaults(client!, this.logger, null),
       );
       const configuredDefaultModelId = configuredDefaults.model;
       const configuredDefaultThinkingOptionId = configuredDefaults.thinkingOptionId;