diff --git a/src/benchflow/agents/registry.py b/src/benchflow/agents/registry.py
index 8e2eedf2..97b4dfa5 100644
--- a/src/benchflow/agents/registry.py
+++ b/src/benchflow/agents/registry.py
@@ -932,6 +932,10 @@ class AgentConfig:
             'printf \',"base_url":"%s"\' "$LLM_BASE_URL"; fi; '
             'if [ -n "$LLM_API_VERSION" ]; then '
             'printf \',"api_version":"%s"\' "$LLM_API_VERSION"; fi; '
+            'if [ -n "$LLM_REASONING_EFFORT" ]; then '
+            'printf \',"reasoning_effort":"%s",'
+            '"litellm_extra_body":{"reasoning_effort":"%s"}\' '
+            '"$LLM_REASONING_EFFORT" "$LLM_REASONING_EFFORT"; fi; '
             "printf '}}'; } > ~/.openhands/agent_settings.json && "
             "openhands acp --always-approve --override-with-envs"
         ),
diff --git a/src/benchflow/providers/litellm_config.py b/src/benchflow/providers/litellm_config.py
index 47b5247d..18c0bda6 100644
--- a/src/benchflow/providers/litellm_config.py
+++ b/src/benchflow/providers/litellm_config.py
@@ -18,9 +18,13 @@
 AZURE_API_VERSION_ENV = "AZURE_API_VERSION"
 AZURE_DEFAULT_API_VERSION = "preview"
 BEDROCK_THINKING_EFFORT_ENV = "BENCHFLOW_BEDROCK_THINKING_EFFORT"
+PROVIDER_REASONING_EFFORT_ENV = "BENCHFLOW_REASONING_EFFORT"
 LITELLM_MODEL_ALIAS_ENV = "BENCHFLOW_LITELLM_MODEL_ALIAS"
 LITELLM_MODEL_VIA_ENV = "BENCHFLOW_LITELLM_MODEL_VIA_ENV"
 LITELLM_MASTER_KEY_ENV = "BENCHFLOW_LITELLM_MASTER_KEY"
+_PROVIDER_REASONING_EFFORTS = frozenset(
+    {"none", "minimal", "low", "medium", "high", "xhigh", "max"}
+)
 
 # Per-token USD prices for models LiteLLM's built-in ``model_cost`` does not
 # already know (custom OpenAI-compatible endpoints such as private vLLM servers
@@ -164,6 +168,20 @@ def _registered_api_key_ref(cfg: ProviderConfig) -> str | None:
     return None
 
 
+def _provider_reasoning_effort(env: dict[str, str]) -> str | None:
+    """Return an explicitly requested gateway-side reasoning effort."""
+    raw = (
+        env.get(PROVIDER_REASONING_EFFORT_ENV) or env.get("LLM_REASONING_EFFORT") or ""
+    )
+    effort = raw.strip().lower()
+    if not effort:
+        return None
+    if effort not in _PROVIDER_REASONING_EFFORTS:
+        allowed = ", ".join(sorted(_PROVIDER_REASONING_EFFORTS))
+        raise ValueError(f"{PROVIDER_REASONING_EFFORT_ENV} must be one of: {allowed}")
+    return effort
+
+
 def _bedrock_thinking_effort(model: str, env: dict[str, str]) -> str | None:
     if not _BEDROCK_ADAPTIVE_THINKING_RE.search(model):
         return None
@@ -213,6 +231,9 @@ def _route_registered_provider(
             "api_base": api_base,
             "api_version": env.get(AZURE_API_VERSION_ENV, AZURE_DEFAULT_API_VERSION),
         }
+        effort = _provider_reasoning_effort(env)
+        if effort:
+            params["reasoning_effort"] = effort
         return LiteLLMRoute(
             requested_model=model,
             model_alias=safe_model_alias(model),
diff --git a/tests/test_agent_registry.py b/tests/test_agent_registry.py
index a5e73346..adddbe3c 100644
--- a/tests/test_agent_registry.py
+++ b/tests/test_agent_registry.py
@@ -202,6 +202,16 @@ def test_openhands_launch_cmd_writes_optional_azure_api_version(self):
         assert ',"api_version":"%s"' in cfg.launch_cmd
         assert '"$LLM_API_VERSION"' in cfg.launch_cmd
 
+    def test_openhands_launch_cmd_writes_optional_reasoning_effort(self):
+        """Guards PR #911 against OpenHands silently using default high effort."""
+        cfg = AGENTS["openhands"]
+        assert 'if [ -n "$LLM_REASONING_EFFORT" ]' in cfg.launch_cmd
+        assert ',"reasoning_effort":"%s",' in cfg.launch_cmd
+        assert '"litellm_extra_body":{"reasoning_effort":"%s"}' in cfg.launch_cmd
+        assert (
+            '"$LLM_REASONING_EFFORT" "$LLM_REASONING_EFFORT"' in cfg.launch_cmd
+        )
+
     def test_harvey_lab_installs_python_deps_in_venv(self):
         """Guards the v0.5 stress failure where pip hit PEP 668 in Ubuntu."""
         cfg = AGENTS["harvey-lab-harness"]
diff --git a/tests/test_litellm_config.py b/tests/test_litellm_config.py
index 6679c097..cd8f52ec 100644
--- a/tests/test_litellm_config.py
+++ b/tests/test_litellm_config.py
@@ -49,6 +49,20 @@ def test_azure_openai_route_uses_resource_and_preview_version():
     assert route.litellm_params["api_version"] == "preview"
 
 
+def test_azure_openai_route_honors_openhands_reasoning_effort_env():
+    """Guards PR #911 against proxy-alias capability guessing."""
+    route = resolve_litellm_route(
+        "azure-foundry-openai/gpt-5.6-sol",
+        {
+            "AZURE_API_KEY": "key",
+            "AZURE_RESOURCE": "benchflow",
+            "LLM_REASONING_EFFORT": "xhigh",
+        },
+    )
+
+    assert route.litellm_params["reasoning_effort"] == "xhigh"
+
+
 def test_azure_anthropic_route_uses_azure_ai_anthropic_surface():
     route = resolve_litellm_route(
         "azure-foundry-anthropic/claude-opus-4-5",