diff --git a/areal/api/cli_args.py b/areal/api/cli_args.py
index 50b619ea80..76a48d1261 100644
--- a/areal/api/cli_args.py
+++ b/areal/api/cli_args.py
@@ -2624,6 +2624,10 @@ class AgentConfig:
         default="qwen3",
         metadata={"help": "Parser for reasoning content (<think> tags)."},
     )
+    chat_template_kwargs: dict[str, Any] = field(
+        default_factory=dict,
+        metadata={"help": "Default chat template arguments for proxy requests."},
+    )
     chat_template_type: str = field(
         default="hf",
         metadata={
diff --git a/areal/experimental/openai/proxy/proxy_rollout_server.py b/areal/experimental/openai/proxy/proxy_rollout_server.py
index 9eb8994bb7..531d02d3d6 100644
--- a/areal/experimental/openai/proxy/proxy_rollout_server.py
+++ b/areal/experimental/openai/proxy/proxy_rollout_server.py
@@ -900,6 +900,42 @@ async def _call_client_create(
             raise HTTPException(status_code=500, detail=message) from e
         kwargs["messages"] = prepared_messages
 
+    defaults = dict(
+        getattr(_engine.config.agent, "chat_template_kwargs", {}) if _engine else {}
+    )
+    extra_body = dict(kwargs.get("extra_body") or {})
+    session_template = session_data.metadata.get("chat_template_kwargs") or {}
+    thinking_keys = ("thinking_option", "enable_thinking", "thinking")
+    template_kwargs = {}
+    for layer in (
+        defaults,
+        session_template,
+        extra_body.get("chat_template_kwargs") or {},
+        kwargs.pop("chat_template_kwargs", None) or {},
+    ):
+        effective = {
+            key: value
+            for key, value in layer.items()
+            if key not in thinking_keys or value is not None
+        }
+        # Thinking aliases share precedence, even when their names differ.
+        if any(key in effective for key in thinking_keys):
+            for key in thinking_keys:
+                template_kwargs.pop(key, None)
+        template_kwargs.update(effective)
+    session_thinking = {
+        key: value
+        for key, value in session_template.items()
+        if key in thinking_keys and value is not None
+    }
+    if session_thinking:
+        for key in thinking_keys:
+            template_kwargs.pop(key, None)
+        template_kwargs.update(session_thinking)
+    if template_kwargs:
+        extra_body["chat_template_kwargs"] = template_kwargs
+        kwargs["extra_body"] = extra_body
+
     dropped_args = []
     for k, v in kwargs.items():
         if k not in areal_client_allowed_args:
diff --git a/docs/en/cli_reference.md b/docs/en/cli_reference.md
index 5e5925dea1..6f5c5dc4c1 100644
--- a/docs/en/cli_reference.md
+++ b/docs/en/cli_reference.md
@@ -948,6 +948,7 @@ Consolidates proxy settings (mode, parsers, export) with agent-service orchestra
 | `mode`                      | string                     | `"inline"`          | OpenAI proxy mode: 'inline' (in-process), 'subproc' (subprocess), or 'online' (external user sessions for online RL training). `inline` mode runs the provided agent workflow directly in the same process. `subproc` mode launches a separate process to run the agent. `online` mode waits for external users to complete sessions via the proxy gateway URL, enabling online RL training. **Choices:** `inline`, `subproc`, `online`                                                          |
 | `tool_call_parser`          | string                     | `"qwen"`            | Parser for tool calls in model output.                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
 | `reasoning_parser`          | string                     | `"qwen3"`           | Parser for reasoning content (<think> tags).                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
+| `chat_template_kwargs`      | `dict`                     | `{}`                | Default chat template arguments for proxy requests.                                                                                                                                                                                                                                                                                                                                                                                                                                              |
 | `chat_template_type`        | string                     | `"hf"`              | Chat template type: 'hf' (standard) or 'concat' (multi-turn concatenation). **Choices:** `hf`, `concat`                                                                                                                                                                                                                                                                                                                                                                                          |
 | `engine_max_tokens`         | integer \| None            | `None`              | Maximum total tokens for the engine (prompt + completion).                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | `turn_discount`             | float                      | `1.0`               | Discount factor for reward propagation in 'individual' export. Concat leaves keep their own branch-local outcome reward.                                                                                                                                                                                                                                                                                                                                                                         |
diff --git a/docs/zh/cli_reference.md b/docs/zh/cli_reference.md
index 8ce06cfab6..5c0b911a74 100644
--- a/docs/zh/cli_reference.md
+++ b/docs/zh/cli_reference.md
@@ -946,6 +946,7 @@ Consolidates proxy settings (mode, parsers, export) with agent-service orchestra
 | `mode`                      | string                     | `"inline"`          | OpenAI proxy mode: 'inline' (in-process), 'subproc' (subprocess), or 'online' (external user sessions for online RL training). `inline` mode runs the provided agent workflow directly in the same process. `subproc` mode launches a separate process to run the agent. `online` mode waits for external users to complete sessions via the proxy gateway URL, enabling online RL training. **Choices:** `inline`, `subproc`, `online`                                                          |
 | `tool_call_parser`          | string                     | `"qwen"`            | Parser for tool calls in model output.                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
 | `reasoning_parser`          | string                     | `"qwen3"`           | Parser for reasoning content (<think> tags).                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
+| `chat_template_kwargs`      | `dict`                     | `{}`                | Default chat template arguments for proxy requests.                                                                                                                                                                                                                                                                                                                                                                                                                                              |
 | `chat_template_type`        | string                     | `"hf"`              | Chat template type: 'hf' (standard) or 'concat' (multi-turn concatenation). **Choices:** `hf`, `concat`                                                                                                                                                                                                                                                                                                                                                                                          |
 | `engine_max_tokens`         | integer \| None            | `None`              | Maximum total tokens for the engine (prompt + completion).                                                                                                                                                                                                                                                                                                                                                                                                                                       |
 | `turn_discount`             | float                      | `1.0`               | Discount factor for reward propagation in 'individual' export. Concat leaves keep their own branch-local outcome reward.                                                                                                                                                                                                                                                                                                                                                                         |