Investigate AI-agent analysis report on the read-write-concern specification. This ticket tracks findings identified during a systematic review of the spec: missing test coverage, ambiguous normative language, and spec/test inconsistencies.

Missing Tests

• Commands supporting ReadConcern MUST raise an error when maxWireVersion < 4 and a non-default, non-local read
  concern is specified (§Errors)
• readConcern with atClusterTime in snapshot operations (§Snapshot Read Concern) — no test verifies
  atClusterTime sent or returned
• aggregate with write stage on 4.2+: linearizable MUST be rejected; other levels MUST work (§Read Concern)
• WriteConcern consistency: w=0 AND journal=true MUST raise an error — only one document test, no connection
  string test
• fsync field SHOULD be treated identically to journal for consistency validation (§FSync) — no test for fsync
• ReadConcern and WriteConcern inheritance: Client → Database → Collection (§Location Specification) — no operation
  test for inheritance chain
• RunCommand MUST NOT automatically apply ReadConcern or WriteConcern (§Generic Command Method)
• WriteConcernError parsing from server replies (§Errors) — no test for writeConcernError extraction from
  findAndModify or aggregate
• findAndModify with WriteConcern MUST omit writeConcern when maxWireVersion < 4 (§Find And Modify)

Ambiguities

• getLastErrorDefaults reference (§Server's Default WriteConcern): This MongoDB feature was removed (Changelog
  2024-10-30). The section referencing it is now outdated and confusing.
• mapReduce with write stage and ReadConcern: Spec lists mapReduce as supporting writes, but it's unclear whether
  ReadConcern is disallowed on mapReduce with a write stage (similar to aggregate).
• "On the Wire" inheritance rule: "If Client/Database/Collection has non-default RC, MUST include command's RC even
  if command specifies server default." This nuance is not clearly tested across all commands.

Inconsistencies

• No ReadConcern operation tests: All 4 operation test files (default-write-concern-*.yml) focus exclusively on
  WriteConcern. No unified tests verify ReadConcern is sent/omitted correctly in read operations.
• Snapshot level undertested: Added in 2021 but only basic validity is checked in document tests. No tests verify
  atClusterTime behavior or server response handling.
• w=-2 rejected but very large w not tested: Tests verify w=-2 is invalid, but no test covers values that
  could overflow in some languages.

Notes

• ~75 tests total across connection-string, document, and operation test directories.
• Operation tests are split by server version (2.6, 3.2, 3.4, 4.2) — well-structured but makes it unclear which tests
  apply to modern servers.