fix: forward reasoning_config to custom providers (vLLM, Ollama, etc.)

agent/transports/chat_completions.py

@@ -341,7 +341,16 @@ def build_kwargs(
                 if gh_reasoning is not None:
                     extra_body["reasoning"] = gh_reasoning
             else:
-                extra_body["reasoning"] = {"enabled": True, "effort": "medium"}
+                # Use the user-configured effort level when available,
+                # falling back to "medium" for known providers.  Custom
+                # providers (vLLM etc.) carry the user's reasoning_config
+                # effort so thinking_token_budget is respected.  See #20576.
+                _effort = "medium"
+                if reasoning_config and isinstance(reasoning_config, dict):
+                    _e = (reasoning_config.get("effort") or "").strip().lower()
+                    if _e in ("low", "medium", "high"):
+                        _effort = _e
+                extra_body["reasoning"] = {"enabled": True, "effort": _effort}
 
         if provider_name == "gemini":
             raw_thinking_config = _build_gemini_thinking_config(model, reasoning_config)

run_agent.py

@@ -8662,6 +8662,14 @@ def _supports_reasoning_extra_body(self) -> bool:
             opts = self._lmstudio_reasoning_options_cached()
             # "off-only" (or absent) means no real reasoning capability.
             return any(opt and opt != "off" for opt in opts)
+        # Custom provider (e.g. vLLM, Ollama, etc.): honor explicit
+        # reasoning_config from the user.  vLLM supports reasoning_effort
+        # and thinking_token_budget for thinking models; without this gate
+        # those parameters are silently dropped.  See #20576.
+        if (self.provider or "").strip().lower() == "custom":
+            if self.reasoning_config and isinstance(self.reasoning_config, dict):
+                return self.reasoning_config.get("enabled") is not False
+            return False
         if "openrouter" not in self._base_url_lower:
             return False
         if "api.mistral.ai" in self._base_url_lower: