Bug type
Regression (worked before, now fails)
Beta release blocker
No
Summary
When a session approaches the context limit and auto-compaction triggers, OpenClaw's pre-compaction memory flush constructs a user message with empty string content (""). The Anthropic API rejects this with a 400 error, causing the session to reset unexpectedly
Steps to reproduce
Let a session run long enough to approach the auto-compaction threshold. The flush
triggers automatically — no user action required.
Expected behavior
The pre-compaction flush completes silently and the session continues or compacts cleanly.
Actual behavior
Telegram User sees: "Something went wrong while processing your request. Please try again,
or use /new to start a fresh session." — and the session is reset.
Root Cause (suspected by claude)
The flush prompt text exists in the session trajectory as a system message, but the
"messages" array passed to the API contains only an empty string. The flush prompt
content appears to not be serialized correctly before the API call.
OpenClaw version
2026.4.27
Operating system
Windows 11
Install method
No response
Model
Anthropic/claude-sonnet-4.6
Provider / routing chain
Telegram > Openclaw Gateway > anthropic/claude-sonnet-4.6
Additional provider/model setup details
No response
Logs, screenshots, and evidence
Impact and severity
This ends up causing issues in sessions that use a fair amount of context, i assume that there are a decent number of people hitting this problem. It happens to me multiple times a day and results in me needing to run /compact if that even works
Additional information
NOT_ENOUGH_INFO
Bug type
Regression (worked before, now fails)
Beta release blocker
No
Summary
When a session approaches the context limit and auto-compaction triggers, OpenClaw's pre-compaction memory flush constructs a user message with empty string content (""). The Anthropic API rejects this with a 400 error, causing the session to reset unexpectedly
Steps to reproduce
Let a session run long enough to approach the auto-compaction threshold. The flush
triggers automatically — no user action required.
Expected behavior
The pre-compaction flush completes silently and the session continues or compacts cleanly.
Actual behavior
Telegram User sees: "Something went wrong while processing your request. Please try again,
or use /new to start a fresh session." — and the session is reset.
Root Cause (suspected by claude)
The flush prompt text exists in the session trajectory as a system message, but the
"messages" array passed to the API contains only an empty string. The flush prompt
content appears to not be serialized correctly before the API call.
OpenClaw version
2026.4.27
Operating system
Windows 11
Install method
No response
Model
Anthropic/claude-sonnet-4.6
Provider / routing chain
Telegram > Openclaw Gateway > anthropic/claude-sonnet-4.6
Additional provider/model setup details
No response
Logs, screenshots, and evidence
Impact and severity
This ends up causing issues in sessions that use a fair amount of context, i assume that there are a decent number of people hitting this problem. It happens to me multiple times a day and results in me needing to run /compact if that even works
Additional information
NOT_ENOUGH_INFO