fix: enable reasoning for third-party OpenAI-compatible proxies (#194)

### Summary

Fixes #188.

The issue was that when a user configured:
- OpenAI-compatible protocol
- A third-party proxy (e.g. univibe)
- A reasoning-capable model ID (e.g. )

would return because it only enabled reasoning for **official OpenAI
API**. This caused the synthesized PiModel to have , and the gateway
would reject the request or return empty content, resulting in and the
UI showing completed but with an empty preview.

### The fix

Extend the heuristic: for third-party OpenAI-compatible gateways, still
check if the model ID matches a known reasoning model pattern (same
patterns already used for OpenRouter). This enables for Claude 4,
o1/o3/gpt-5, qwq, deepseek-r, etc when proxied through OpenAI-compatible
endpoints.

### Testing

- Added test cases covering the issue scenario
- Existing tests still pass
- Fix verified by the issue author's log: the model on will now
correctly get

Closes #188.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Signed-off-by: Sun-sunshine06 <Sun-sunshine06@users.noreply.github.com>
Co-authored-by: Sun-sunshine06 <Sun-sunshine06@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: Sun-sunshine06

packages/providers/src/index.test.ts

@@ -555,4 +555,47 @@ describe('inferReasoning', () => {
   it('returns false when wire is undefined', () => {
     expect(inferReasoning(undefined, 'gpt-4o', 'https://api.openai.com/v1')).toBe(false);
   });
+
+  it('returns true for third-party openai-chat with reasoning model ID (issue #188)', () => {
+    // univibe/custom proxy with Claude 4 model
+    expect(inferReasoning('openai-chat', 'claude-opus-4-6', 'https://api.univibe.cc/openai')).toBe(
+      true,
+    );
+    expect(
+      inferReasoning('openai-chat', 'claude-sonnet-4-6', 'https://api.univibe.cc/openai'),
+    ).toBe(true);
+    // OpenRouter-style paths on custom proxy
+    expect(
+      inferReasoning('openai-chat', 'anthropic/claude-opus-4-6', 'https://my-proxy.example/v1'),
+    ).toBe(true);
+    // OpenAI-style namespaced paths on custom proxy
+    expect(inferReasoning('openai-chat', 'openai/o3-mini', 'https://my-proxy.example/v1')).toBe(
+      true,
+    );
+    expect(inferReasoning('openai-chat', 'openai/gpt-5.1', 'https://my-proxy.example/v1')).toBe(
+      true,
+    );
+    // o1 on custom proxy
+    expect(inferReasoning('openai-chat', 'o1-mini', 'https://my-proxy.example/v1')).toBe(true);
+    // qwen/qwq on custom proxy
+    expect(
+      inferReasoning('openai-chat', 'qwen/qwq-32b-preview', 'https://my-proxy.example/v1'),
+    ).toBe(true);
+  });
+
+  it('returns false for third-party openai-chat with non-reasoning model ID', () => {
+    expect(
+      inferReasoning(
+        'openai-chat',
+        'qwen3.6-plus',
+        'https://dashscope.aliyuncs.com/compatible-mode/v1',
+      ),
+    ).toBe(false);
+    expect(inferReasoning('openai-chat', 'deepseek-chat', 'https://api.deepseek.com/v1')).toBe(
+      false,
+    );
+    expect(inferReasoning('openai-chat', 'glm-4.6v', 'https://open.bigmodel.cn/api/paas/v4')).toBe(
+      false,
+    );
+  });
 });

packages/providers/src/index.ts

@@ -189,6 +189,24 @@ function isReasoningModelId(modelId: string): boolean {
   return /^(o[134]|gpt-5)/i.test(modelId);
 }
 
+/**
+ * Matches reasoning-capable model IDs commonly proxied through OpenAI-compatible
+ * gateways (OpenRouter, univibe, sub2api, etc). This pattern matches the same
+ * set that OPENROUTER_REASONING_MODEL_RE uses for OpenRouter, but applies to
+ * custom openai-chat wire endpoints as well.
+ */
+const REASONING_MODEL_ID_PATTERN = new RegExp(
+  [
+    ':thinking$',
+    '(^|/)claude-(?:opus|sonnet)-4',
+    '^(?:openai/)?(?:o1|o3|o4|gpt-5)(?:[-.].*)?$',
+    '^minimax/minimax-m\\d',
+    '^deepseek/deepseek-r\\d',
+    '^qwen/qwq',
+  ].join('|'),
+  'i',
+);
+
 export function inferReasoning(
   wire: GenerateOptions['wire'],
   modelId: string,
@@ -201,7 +219,14 @@ export function inferReasoning(
     case 'openai-codex-responses':
       return true;
     case 'openai-chat':
-      return isOpenAIOfficial(baseUrl) && isReasoningModelId(modelId);
+      // For official OpenAI, check both base URL and model ID pattern
+      if (isOpenAIOfficial(baseUrl)) {
+        return isReasoningModelId(modelId);
+      }
+      // For third-party OpenAI-compatible gateways, heuristically match
+      // common reasoning model IDs — many gateways still require the
+      // reasoning flag to get extended thinking output.
+      return REASONING_MODEL_ID_PATTERN.test(modelId);
     default:
       return false;
   }