Symptom

Two ERROR records appear whenever a client cancels a request, and alerts fire.

Evidence what you'll see

Running v1.x with a stateless Streamable HTTP server
Later requests work fine

Cause

When a client disconnects mid-request, the server logs ERROR records. On 1.x the error path also sends a log notification after the transport closes. PR #2257 (merged 2026-03-09, in v2.0) removed that log notification; a request to backport it to 1.x (#3142) was closed as not planned. The "Error handling POST request" ERROR log is tracked in open issue #1648 and is still in the v2 code.

Fix steps

0 of 3 done

Step 1Confirm later requests still work, which means it is only log noise.
Step 2Filter the "Error handling POST request" record (and, on 1.x, the log notification record) in your logging config. This is the workaround on both 1.x and v2.
Step 3Optional: upgrading to v2 drops the log notification record (PR #2257), but the ERROR log from #1648 stays, so keep the filter.

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Verify the fix worked

With the filter in place, a cancelled request no longer sets off ERROR alerts, and later requests still work.

Did this fix it?

Sources and credit

Summarized in our own words from these public reports. Credit goes to their authors.

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