Investigate AI-agent analysis report on the causal-consistency 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

• Initial state: operationTime MUST be unset when ClientSession is first created
• First read MUST NOT send afterClusterTime to server — verify command structure before any operation
• First read/write SHOULD update operationTime even on error — test both success and error paths
• findOne followed by any read MUST include operationTime in afterClusterTime — test propagation across
  multiple reads
• Write followed by findOne MUST include operationTime in afterClusterTime, including error cases — test
  write→read causal chain (PR #1930,
  DRIVERS-3274)
• Read in a non-causally-consistent session MUST NOT include afterClusterTime — test explicit
  causalConsistency=false
• Causally consistent read against a pre-3.6 server MUST NOT send afterClusterTime — test backwards compatibility
• With default server ReadConcern, readConcern MUST NOT include a level field
• With custom ReadConcern, readConcern MUST merge ReadConcern value and afterClusterTime
• Messages to pre-cluster-time servers MUST NOT include $clusterTime
• advanceOperationTime MUST advance only if new value is greater
• advanceOperationTime MUST NOT validate the operationTime value

Ambiguities

• causalConsistency default inheritance: "Currently inherited from the global default which is defined to be true.
  In the future it might be inherited from client settings." — Vague. Should explicitly state what "global default"
  means and freeze the current behavior.
• Unacknowledged writes + causal consistency: Spec accepts the limitation but states "Drivers MUST document that
  causally consistent reads are not causally consistent with unacknowledged writes." The trade-off is not well
  justified for users.
• Reference to ReadConcern spec for supported commands list: Creates maintenance coupling. Should include an inline
  list or a stable link.

Inconsistencies

• Unacknowledged writes and operationTime: Spec says "do not wait for a response" for unacknowledged writes but
  also says drivers "MUST save the operationTime in the ClientSession whether the operation succeeded or not."
  Saving operationTime requires a response, which contradicts the "no response" statement.
  → DRIVERS-3480 / PR #1938
• Default for implicit sessions: "For implicit sessions, the value of this property MUST be set to false" conflicts
  with "If no value is supplied for causalConsistency the value will be inherited."

Notes

• Tests exist only as prose in the "Test Plan" section — no structured YAML fixtures. Requires manual per-driver
  implementation.
• Spec references Sessions Specification (required reading) and ReadConcern spec for the list of commands that support
  causal consistency.
• DRIVERS-1083 /
  DRIVERS-2097 (Backlog): prose tests 6 and 7 always succeed as
  written — known issue predating this analysis.
• DRIVERS-1374 (Implementing): remove outdated prose test.