Problem

V2 change streams (featureFlagChangeStreamPreciseShardTargeting) can observe migrateLastChunkFromShard on a live stream, but resumeAfter that token fails:

ChangeStreamFatalError: cannot resume stream; the resume token was not found.

Repro: migrate_last_chunk_from_shard_event.js (excluded from CI — change_streams.yml).

Root cause

Chunk migration change-stream events are written to the donor shard oplog by buildMoveChunkOplogEntries. The resume token therefore points at an oplog entry on the donor.

On resume, ChangeStreamShardTargeterBase::initialize picks which shard cursors to open from placement history at the token's clusterTime. After migration, that placement is usually the recipient only — the donor is not opened.

ChangeStreamEnsureResumeTokenPresentStage never sees the token on an open cursor and fails with ChangeStreamFatalError: cannot resume stream; the resume token was not found.