fix: handle ambiguous prompt transport failures

packages/ui/src/lib/opencode/client.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, mock, test } from 'bun:test';
+import { beforeEach, describe, expect, mock, test } from 'bun:test';
 
 type ConfigResponse = { data: Record<string, unknown> };
 
@@ -6,6 +6,15 @@ type ConfigResponse = { data: Record<string, unknown> };
 
 const configResolvers: Array<(response: ConfigResponse) => void> = [];
 let configCalls = 0;
+const promptAsyncCalls: unknown[][] = [];
+const promptAsyncResults: Array<unknown> = [];
+
+const promptAsyncMock = mock(async (...args: unknown[]) => {
+  promptAsyncCalls.push(args);
+  const next = promptAsyncResults.shift();
+  if (next instanceof Error) throw next;
+  return next ?? { response: new Response(null, { status: 200 }) };
+});
 
 mock.module('@opencode-ai/sdk/v2', () => ({
   createOpencodeClient: mock(() => ({
@@ -17,6 +26,9 @@ mock.module('@opencode-ai/sdk/v2', () => ({
         });
       }),
     },
+    session: {
+      promptAsync: promptAsyncMock,
+    },
   })),
 }));
 
@@ -47,6 +59,11 @@ mock.module('@/lib/startupTrace', () => ({
 
 const { opencodeClient } = await import(`./client?cache-test=${Date.now()}`);
 
+beforeEach(() => {
+  promptAsyncCalls.length = 0;
+  promptAsyncResults.length = 0;
+});
+
 describe('opencodeClient getConfig cache', () => {
   test('cleared stale in-flight requests do not repopulate cache or delete newer in-flight requests', async () => {
     const first = opencodeClient.getConfig('/workspace/project');
@@ -72,3 +89,54 @@ describe('opencodeClient getConfig cache', () => {
     expect(configCalls).toBe(2);
   });
 });
+
+describe('opencodeClient prompt retry behavior', () => {
+  const sendPrompt = (providerID = 'anthropic') => opencodeClient.sendMessage({
+    id: 'ses_1',
+    providerID,
+    modelID: 'claude-sonnet',
+    text: 'hello',
+  });
+
+  test('does not retry 504 prompt responses because the POST may already be accepted', async () => {
+    promptAsyncResults.push({ response: new Response('gateway timeout', { status: 504 }) });
+
+    let error: unknown = null;
+    try {
+      await sendPrompt('anthropic-504');
+    } catch (caught) {
+      error = caught;
+    }
+
+    expect(promptAsyncCalls.length).toBe(1);
+    expect(error instanceof Error ? error.message : String(error)).toContain('Failed to send message (504)');
+  });
+
+  test('does not retry transport failures because the tunnel may have lost only the response', async () => {
+    promptAsyncResults.push(new TypeError('Failed to fetch'));
+
+    let error: unknown = null;
+    try {
+      await sendPrompt('anthropic-network');
+    } catch (caught) {
+      error = caught;
+    }
+
+    expect(promptAsyncCalls.length).toBe(1);
+    expect(error instanceof Error ? error.message : String(error)).toContain('Failed to fetch');
+  });
+
+  test('does not retry 503 prompt responses because proxy errors can be ambiguous too', async () => {
+    promptAsyncResults.push({ response: new Response('starting', { status: 503 }) });
+
+    let error: unknown = null;
+    try {
+      await sendPrompt('anthropic-503');
+    } catch (caught) {
+      error = caught;
+    }
+
+    expect(promptAsyncCalls.length).toBe(1);
+    expect(error instanceof Error ? error.message : String(error)).toContain('Failed to send message (503)');
+  });
+});