Bug type

Regression (worked before, now fails)

Beta release blocker

No

Summary

When using deepseek-v4-pro with thinking:disabled via extra_body, conversations intermittently fail with:

400 The reasoning_content in the thinking mode must be passed back to the API.

The error occurs because DeepSeek occasionally returns reasoning_content in its response even when thinking is disabled. OpenClaw stores this in the conversation history, and on the next request, DeepSeek rejects the payload because reasoning_content from previous messages must be passed back consistently.

Steps to reproduce

Configure extra_body: {thinking: {type: "disabled"}} for deepseek-v4-pro
Have a multi-turn conversation
DeepSeek intermittently returns reasoning_content in a response
The next message in the conversation fails with 400
Restarting the gateway clears the in-memory session cache and temporarily resolves it
Configuration (both files have extra_body set correctly)

models.json:
"id": "deepseek-v4-pro"
"extra_body": {"thinking": {"type": "disabled"}}

openclaw.json (agents.defaults.models):
"deepseek/deepseek-v4-pro": {
"params": {
"thinking": false,
"extra_body": {"thinking": {"type": "disabled"}}
}
}

Expected behavior

OpenClaw should strip reasoning_content from assistant messages in the conversation history before sending to DeepSeek when thinking is disabled. Alternatively, detect reasoning_content in history and auto-enable thinking mode for consistency.

Actual behavior

400 The reasoning_content in the thinking mode must be passed back to the API.

OpenClaw version

OpenClaw: 2026.3.28 (f9b1079)

Operating system

Debian 12 (bookworm), kernel 5.19.17

Install method

docker

Model

deepseek-v4-pro

Provider / routing chain

deepseek

Additional provider/model setup details

No response

Logs, screenshots, and evidence

{"event":"embedded_run_agent_end","isError":true,
"error":"400 The reasoning_content in the thinking mode must be passed back to the API.",
"model":"deepseek-v4-pro","provider":"deepseek"}

Two occurrences within 4 minutes (13:05 and 13:09 UTC, 2026-04-29).

Impact and severity

No response

Additional information

Environment
OpenClaw: 2026.3.28 (f9b1079)
Provider: deepseek
Model: deepseek-v4-pro
Channel: feishu / websocket
Workaround

Restarting the gateway clears in-memory session cache and stops error recurrence until DeepSeek returns reasoning_content again.