tts_source_revision_mismatch 409: stale expected_script_revision_id

tts_source_revision_mismatch is a 409 from the Sume script-source API. It is the optimistic-concurrency error: the accepted script revision is not the one your request assumed. It has four triggers in the code, and the fix is always to read the current revision and decide again. All of these come back in Sume's standard error envelope with an HTTP status and a stable code, so branch on the code, not the message text.

The accept call, POST /v1/tts-1.0/source, takes script_texts and an optional expected_script_revision_id. If you pass it and the thread's current accepted revision is a different one, the answer is 409 with the message "Accepted revision changed." Pass null to say "I expect there is no accepted revision yet."

The four triggers

Safe update loop

The pattern is read, change, accept with the id you read, and on 409 start over. It stops two writers from silently replacing each other's script. Accepted revisions are immutable, so the previous revision and the jobs generated from it are untouched.

curl -s "https://api.sume.com/v1/tts-1.0/source" \
  -H "x-api-key: $SUME_API_KEY" -H "content-type: application/json" \
  -d "{\"script_texts\": [\"Hello there. Second sentence.\"], \"thread_id\": \"$THREAD\", \"expected_script_revision_id\": \"$REV\"}"

Cost

A 409 is raised before dispatch, so it creates no job and no charge. The jobs you already generated from the older revision keep their receipts; verify-spine can re-adopt unchanged sentences when you pass explicit sentence_ids.