fix(transport): honor compat.requiresReasoningContentOnAssistantMessages from config

KrasimirKralev · KrasimirKralev · commit c54c4f34334b · 2026-06-04T14:21:11.000+03:00
Addresses clawsweeper review on #89832 (P1 compatibility trap). getCompat() in openai-transport-stream resolved every compat field as "compat.X ?? detected.X" EXCEPT requiresReasoningContentOnAssistantMessages, which used detected.X alone. So a custom OpenAI-compatible proxy (not auto-detected as DeepSeek/Xiaomi) that set the flag in config would pass schema validation but be ignored by the active transport — a startup-success/runtime-failure trap. Now resolves compat.X ?? detected.X, matching openai-completions.ts:1333 and every sibling field. Exposes getCompat via the existing test-only testing export and adds a focused regression: a custom provider with the flag set resolves true (verified to fail against the pre-fix detected-only code); the same provider without the flag falls back to detection (false).
diff --git a/src/agents/openai-transport-stream.test.ts b/src/agents/openai-transport-stream.test.ts
@@ -10097,4 +10097,37 @@ describe("buildOpenAICompletionsParams sanitizes reasoning replay fields", () =>
     const assistant = getAssistantMessage(params);
     expect(assistant.reasoning_details).toEqual([reasoningDetail]);
   });
+
+  // issue #89660: a custom OpenAI-compatible proxy (not auto-detected as DeepSeek/
+  // Xiaomi/Kimi) can opt into the DeepSeek reasoning-content replay contract by
+  // setting compat.requiresReasoningContentOnAssistantMessages in config. getCompat
+  // must resolve `compat.X ?? detected.X` (matching every sibling field) instead of
+  // using `detected.X` alone, so the explicit config flag is honored in this transport.
+  const customReasoningProxyModel = {
+    id: "my-proxy/r1-pro",
+    name: "Custom Reasoning Proxy",
+    api: "openai-completions",
+    provider: "custom-openai-proxy",
+    baseUrl: "https://my-proxy.example.com/v1",
+    reasoning: true,
+    input: ["text"],
+    cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+    contextWindow: 200_000,
+    maxTokens: 8_192,
+  } satisfies Model<"openai-completions">;
+
+  it("honors compat.requiresReasoningContentOnAssistantMessages from config on a custom provider (#89660)", () => {
+    const resolved = testing.getCompat({
+      ...customReasoningProxyModel,
+      compat: { requiresReasoningContentOnAssistantMessages: true },
+    } as never);
+
+    expect(resolved.requiresReasoningContentOnAssistantMessages).toBe(true);
+  });
+
+  it("falls back to detection (false) for the same custom provider when the flag is absent", () => {
+    const resolved = testing.getCompat(customReasoningProxyModel as never);
+
+    expect(resolved.requiresReasoningContentOnAssistantMessages).toBe(false);
+  });
 });
diff --git a/src/agents/openai-transport-stream.ts b/src/agents/openai-transport-stream.ts
@@ -3432,6 +3432,7 @@ function getCompat(model: OpenAIModeModel): {
     visibleReasoningDetailTypes:
       compat.visibleReasoningDetailTypes ?? detected.visibleReasoningDetailTypes,
     requiresReasoningContentOnAssistantMessages:
+      compat.requiresReasoningContentOnAssistantMessages ??
       detected.requiresReasoningContentOnAssistantMessages,
     requiresNonEmptyUserOrAssistantMessage: detected.requiresNonEmptyUserOrAssistantMessage,
   };
@@ -4277,6 +4278,7 @@ function mapStopReason(reason: string | null) {
 }
 
 export const testing = {
+  getCompat,
   assertCodeModeResponsesToolSurface,
   buildOpenAIClientHeaders,
   buildOpenAISdkClientOptions,
