diff --git a/gauss_cli/models.py b/gauss_cli/models.py
index 766d41d..0a437a8 100644
--- a/gauss_cli/models.py
+++ b/gauss_cli/models.py
@@ -28,6 +28,8 @@
     ("z-ai/glm-5",                      ""),
     ("moonshotai/kimi-k2.5",            ""),
     ("minimax/minimax-m2.5",            ""),
+    ("deepseek/deepseek-v4-pro",        ""),
+    ("deepseek/deepseek-v4-flash",      ""),
 ]
 
 _PROVIDER_MODELS: dict[str, list[str]] = {
@@ -79,6 +81,8 @@
         "claude-haiku-4-5-20251001",
     ],
     "deepseek": [
+        "deepseek-v4-pro",
+        "deepseek-v4-flash",
         "deepseek-chat",
         "deepseek-reasoner",
     ],
diff --git a/run_agent.py b/run_agent.py
index 5df7a9d..b51c719 100644
--- a/run_agent.py
+++ b/run_agent.py
@@ -2931,6 +2931,8 @@ def _build_api_kwargs(self, api_messages: list) -> dict:
             extra_body["provider"] = provider_preferences
         _is_nous = "nousresearch" in self.base_url.lower()
 
+        _is_deepseek = "deepseek.com" in self.base_url.lower()
+
         if self._supports_reasoning_extra_body():
             if self.reasoning_config is not None:
                 rc = dict(self.reasoning_config)
@@ -2938,14 +2940,42 @@ def _build_api_kwargs(self, api_messages: list) -> dict:
                 # enabled=false to it (would cause 400).
                 if _is_nous and rc.get("enabled") is False:
                     pass  # omit reasoning entirely for Nous when disabled
+                elif _is_deepseek:
+                    # DeepSeek uses {"thinking": {"type": "enabled/disabled"}}
+                    # in extra_body and reasoning_effort as a top-level param.
+                    reasoning_enabled = rc.pop("enabled", True)
+                    reasoning_effort = rc.pop("effort", "high")
+                    extra_body["thinking"] = {"type": "enabled" if reasoning_enabled else "disabled"}
+                    if reasoning_enabled:
+                        api_kwargs["reasoning_effort"] = reasoning_effort
+                    # Pass remaining keys through (e.g. user_id passthrough)
+                    if rc:
+                        extra_body.update(rc)
                 else:
                     extra_body["reasoning"] = rc
+            elif _is_deepseek:
+                # Default: enable thinking for DeepSeek with max effort
+                extra_body["thinking"] = {"type": "enabled"}
+                api_kwargs["reasoning_effort"] = "max"
             else:
                 extra_body["reasoning"] = {
                     "enabled": True,
                     "effort": "medium"
                 }
 
+        # Resolve reasoning_effort as a top-level parameter for DeepSeek.
+        # DeepSeek supports: "high" (default) and "max" (complex agents).
+        # Only set when thinking is enabled (not already set above).
+        if _is_deepseek and "reasoning_effort" not in api_kwargs:
+            effort = "high"
+            if self.reasoning_config and isinstance(self.reasoning_config, dict):
+                if self.reasoning_config.get("enabled") is not False:
+                    effort = self.reasoning_config.get("effort", "high")
+                else:
+                    effort = None  # thinking disabled, skip
+            if effort:
+                api_kwargs["reasoning_effort"] = effort
+
         # Nous Portal product attribution
         if _is_nous:
             extra_body["tags"] = ["product=gauss-agent"]
@@ -2960,11 +2990,14 @@ def _supports_reasoning_extra_body(self) -> bool:
 
         OpenRouter forwards unknown extra_body fields to upstream providers.
         Some providers/routes reject `reasoning` with 400s, so gate it to
-        known reasoning-capable model families and direct Nous Portal.
+        known reasoning-capable model families, direct Nous Portal, and
+        direct DeepSeek API endpoints (which use a different format).
         """
         base_url = (self.base_url or "").lower()
         if "nousresearch" in base_url:
             return True
+        if "deepseek.com" in base_url:
+            return True
         if "openrouter" not in base_url:
             return False
         if "api.mistral.ai" in base_url: