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fix(chat): thread UI-selected model into the chat workflow #638

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fix(chat): thread UI-selected model into the chat workflow #638

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fix(chat): thread UI-selected model into the chat workflow
arpitgupta1214 Jun 3, 2026
ea0da82
test(chat): trim workflow model tests to one case each
arpitgupta1214 Jun 3, 2026
d5e63a0
docs(chat): trim model-selection comments to one-liners
arpitgupta1214 Jun 3, 2026
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24 changes: 24 additions & 0 deletions lib/chat/__tests__/handleChatWorkflowStream.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -289,6 +289,30 @@ describe("handleChatWorkflowStream", () => {
expect(startArgs.modelId).toBe("anthropic/claude-haiku-4.5");
});

it("prefers validated.model over a persisted chat.model_id", async () => {
vi.mocked(validateChatWorkflow).mockResolvedValue({
messages: [],
chatId: CHAT_ID,
sessionId: SESSION_ID,
accountId: ACCOUNT_ID,
orgId: null,
authToken: "test-key",
model: "openai/gpt-5.4-mini",
});
vi.mocked(selectChats).mockResolvedValue([
{
id: CHAT_ID,
session_id: SESSION_ID,
active_stream_id: null,
model_id: "anthropic/claude-opus-4.6",
} as never,
]);
mockStartedRun();
await handleChatWorkflowStream(makeRequest());
const startArgs = vi.mocked(start).mock.calls[0]?.[1]?.[0] as { modelId: string };
expect(startArgs.modelId).toBe("openai/gpt-5.4-mini");
});

// Bundle A.4 — forward the Privy JWT from the validated body into
// AgentContext.recoupAccessToken so the sandbox env-builder can
// surface it as `RECOUP_ACCESS_TOKEN`.
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9 changes: 9 additions & 0 deletions lib/chat/__tests__/validateChatWorkflow.test.ts
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Expand Up @@ -78,6 +78,15 @@ describe("validateChatWorkflow", () => {
if (result instanceof NextResponse) return;
expect(result.recoupAccessToken).toBe("eyJ.test.jwt");
});

it("accepts and surfaces the gateway-format model selected in the UI", async () => {
const result = await validateChatWorkflow(
makeRequest({ ...validBody, model: "openai/gpt-5.4-mini" }),
);
expect(result).not.toBeInstanceOf(NextResponse);
if (result instanceof NextResponse) return;
expect(result.model).toBe("openai/gpt-5.4-mini");
});
});

describe("invalid body", () => {
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3 changes: 2 additions & 1 deletion lib/chat/handleChatWorkflowStream.ts
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Expand Up @@ -90,7 +90,8 @@ export async function handleChatWorkflowStream(request: NextRequest): Promise<Re
await updateSession(validated.sessionId, buildActiveLifecycleUpdate(session.sandbox_state));
void persistLatestUserMessage(validated.chatId, validated.messages as never);

const modelId = chat.model_id ?? DEFAULT_MODEL_ID;
// UI selection wins over the chat's persisted model, then the default.
const modelId = validated.model ?? chat.model_id ?? DEFAULT_MODEL_ID;

@cubic-dev-ai cubic-dev-ai Bot Jun 3, 2026

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P2: Whitespace-only model values are treated as valid overrides, bypassing fallback to persisted/default model.

Prompt for AI agents 
Check if this issue is valid — if so, understand the root cause and fix it. At lib/chat/handleChatWorkflowStream.ts, line 97:

<comment>Whitespace-only `model` values are treated as valid overrides, bypassing fallback to persisted/default model.</comment>

<file context>
@@ -90,7 +90,11 @@ export async function handleChatWorkflowStream(request: NextRequest): Promise<Re
+  // persisted model_id, then the default. Without this the workflow
+  // always billed DEFAULT_MODEL_ID since model_id is null until a
+  // chat is explicitly PATCHed.
+  const modelId = validated.model ?? chat.model_id ?? DEFAULT_MODEL_ID;
   const recoupOrgId = session.clone_url
     ? (extractOrgId(session.clone_url) ?? undefined)
</file context>
Suggested change
const modelId = validated.model ?? chat.model_id ?? DEFAULT_MODEL_ID;
const requestedModelId = validated.model?.trim();
const modelId = requestedModelId ? requestedModelId : chat.model_id ?? DEFAULT_MODEL_ID;

const recoupOrgId = session.clone_url
? (extractOrgId(session.clone_url) ?? undefined)
: undefined;
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2 changes: 2 additions & 0 deletions lib/chat/validateChatWorkflow.ts
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Expand Up @@ -22,6 +22,8 @@ export const chatWorkflowBodySchema = z.object({
* field shape.
*/
recoupAccessToken: z.string().min(1).max(8192).optional(),
/** Gateway-format model id selected in the chat UI (e.g. `"openai/gpt-5.4-mini"`). */
model: z.string().min(1).max(256).optional(),
});

export type ChatWorkflowBody = z.infer<typeof chatWorkflowBodySchema>;
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