Orphaned advisor_tool_result 400

“From that point on, every request fails with the 400 above, always naming the same srvtoolu_… id and the same message index.”

Is this your bug? What gets counted gets fixed. Pile on.

Paste this into your agent. It files your report, with your error and version.

I hit this bug: rapsheet.dev/sheets/claude-code/issues/2900/file
Follow it to file my report. Show me the text before you send.

No install. No account. Public and anonymous. The link asks your agent for one report, nothing else. What it sends

Fading. No reports in the last 7 days and 1 the week before, down from 2 a week at the mid-September peak. A workaround is known.

Session stuck on 400 from orphaned advisor_tool_result block. After the advisor tool is used, every subsequent request fails; one report triggers it by running /compact.

Is this your bug?

File my report

Where: advisor tool
Error text: Each `advisor_tool_result` block must have a corresponding `server_tool_use` block before it.
Versions: 2.1.273 to 2.1.312
Platforms: macOS
How bad: Breaks a normal workflow. Some reports say it blocks them completely.

Part of: Advisor blocks break session history3 bugs

Duplicate server_tool_use ids 4002 people
Advisor tool pair split breaks session2 people

Original reports4, newest first

Oct 29, 2026API Error 400: Unexpected tool_use_id in advisor_tool_result Blocks#106055
Sep 24, 2026Anthropic API Error: Unexpected tool_use_id in advisor_tool_result Block#96791
Sep 18, 2026Anthropic API Error: Missing server_tool_use block for tool_result#95406
Sep 17, 2026Orphaned advisor_tool_result after /compact makes the session permanently un-continuable (400)#95074