The 12 tests in `agents::pool::pipeline::merge::tests` share a
process-wide `server_start_time` (a `OnceLock` captured the first time
the merge subsystem runs) and the global merge-job CRDT log. Default
cargo parallelism has caught at least one interleaving on the merge
gate's Docker scheduler where `stale_running_merge_job_is_cleared_and_retry_succeeds`
flakes — `delete_merge_job` from one test lands while another is mid-
assertion. Couldn't reproduce locally despite many tries.
Each test now acquires a poison-tolerant `std::sync::Mutex` at entry,
so the 12 tests run serially relative to each other while the rest of
the suite (2862 tests) stays parallel. Module-level
`#![allow(clippy::await_holding_lock)]` covers the deliberate sync
guard across `.await`s.
Targeted isolation — not a global `--test-threads=1`.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Timmy
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