Read a remembered Codex fast_mode as its service tier

The create-agent preferences convert the legacy key on read, keyed on the
built-in codex provider id, so the Codex draft shows the Fast selection the user
last used. Tagged COMPAT(featureValues) with the other legacy-option shims.

packages/app/src/create-agent-preferences/preferences.test.ts

@@ -80,7 +80,7 @@ describe("create agent preferences", () => {
         modelId: "gpt-5.5",
         modeId: "full-access",
         thinkingOptionId: "high",
-        options: { fast_mode: true },
+        options: { service_tier: "fast" },
       }),
     );
 
@@ -95,7 +95,7 @@ describe("create agent preferences", () => {
           model: "gpt-5.5",
           mode: "full-access",
           thinkingByModel: { "gpt-5.5": "high" },
-          options: { fast_mode: true },
+          options: { service_tier: "fast" },
         },
       },
     });
@@ -220,6 +220,37 @@ describe("create agent preferences", () => {
     });
   });
 
+  it("reads a remembered Codex fast_mode as the service tier it meant, so the draft shows Fast", () => {
+    expect(
+      parseFormPreferences({
+        provider: "codex",
+        providerPreferences: {
+          codex: { options: { fast_mode: true, sandbox_mode: "read-only" } },
+          claude: { options: { fast_mode: true } },
+        },
+      }),
+    ).toEqual({
+      provider: "codex",
+      providerPreferences: {
+        codex: { options: { service_tier: "fast", sandbox_mode: "read-only" } },
+        claude: { options: { fast_mode: true } },
+      },
+    });
+
+    expect(
+      parseFormPreferences({
+        providerPreferences: { codex: { featureValues: { fast_mode: false } } },
+      }),
+    ).toEqual({ providerPreferences: { codex: { options: { service_tier: "default" } } } });
+
+    // A tier already remembered wins over the key it replaced.
+    expect(
+      parseFormPreferences({
+        providerPreferences: { codex: { options: { fast_mode: true, service_tier: "default" } } },
+      }),
+    ).toEqual({ providerPreferences: { codex: { options: { service_tier: "default" } } } });
+  });
+
   it("keeps options that are not booleans or strings, such as a profile's sandbox settings", () => {
     const options = {
       sandbox_workspace_write: { network_access: true, writable_roots: ["/tmp"] },

packages/app/src/create-agent-preferences/preferences.ts

@@ -39,6 +39,24 @@ const providerPreferencesSchema: z.ZodType<ProviderPreferences> = z.preprocess(
   }),
 );
 
+// COMPAT(featureValues): added in v0.15.0, remove after 2027-05-01. Codex took `fast_mode`
+// before `service_tier`; the daemon converts the option on every agent and profile it touches,
+// and this is the one place the app reads a remembered value without the daemon in between. Keyed
+// on the built-in provider id: a custom provider extending Codex keeps the old key and the daemon
+// still converts it on create.
+function convertLegacyCodexOptions(
+  preferences: Record<string, ProviderPreferences>,
+): Record<string, ProviderPreferences> {
+  const codex = preferences.codex;
+  if (!codex?.options || !("fast_mode" in codex.options)) return preferences;
+  const { fast_mode: legacy, ...rest } = codex.options;
+  const options =
+    "service_tier" in rest || typeof legacy !== "boolean"
+      ? rest
+      : { ...rest, service_tier: legacy ? "fast" : "default" };
+  return { ...preferences, codex: { ...codex, options } };
+}
+
 const launchTargetSchema: z.ZodType<LaunchTarget> = z.discriminatedUnion("kind", [
   z.strictObject({ kind: z.literal("chat") }),
   z.strictObject({ kind: z.literal("terminal"), profileId: z.string() }),
@@ -46,7 +64,10 @@ const launchTargetSchema: z.ZodType<LaunchTarget> = z.discriminatedUnion("kind",
 
 export const FormPreferencesSchema = z.strictObject({
   provider: z.string().optional(),
-  providerPreferences: z.record(z.string(), providerPreferencesSchema).optional(),
+  providerPreferences: z
+    .record(z.string(), providerPreferencesSchema)
+    .transform(convertLegacyCodexOptions)
+    .optional(),
   // COMPAT(agentProfileFavoriteMigration): favourites were removed in v0.3.2.
   // Keep the legacy payload alive until every capable host has had a chance to
   // import it; ordinary preference writes must not erase it first.