Collab Phase 5: Durable Flush Worker from Drafts to RERUM with Conflict Acks

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Summary

Create server-side durable flush pipeline that coalesces draft operations and commits to RERUM with optimistic locking.

Scope

• Batch and coalesce queued operations by line.
• Persist through existing Line/Page update flow.
• Use optimistic locking for overwrite conflict detection.
• Emit durable events: queued, started, persisted, conflict, failed.
• Return durable revision metadata in ack payload.

Acceptance Criteria

• Multiple rapid edits are coalesced into fewer durable writes.
• 409 conflicts are emitted as durable conflict events with context.
• Persisted acknowledgements include durable revision references.
• Backpressure limits prevent unbounded growth.

Dependencies

• Depends on draft intake issue.
• Contract: docs/collaboration/websocket-collaboration-contract.md

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Dependency map for execution planning:

Depends on:

• Collab Phase 3: Draft Buffer API and Operation Intake for Deferred Persistence #510
• Collaboration Contract v1.0 Ratification for Services, Interfaces, and RERUM #512

Blocks:

• Collab Phase 7: Conflict Resolution UX and Collaboration Observability Dashboards TPEN-interfaces#557

Related to:

• Collab Phase 6: Idempotent Overwrite and Conflict Payload Enhancements for Deferred Commit Clients rerum_server_nodejs#266

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Phase Documentation Addendum

• This phase implements durable flush lifecycle aligned to Contract sections 9 and 10.
• Required validation: coalesced writes, durable revision acknowledgements, conflict event emission.
• Exit artifacts: flush worker sequence diagram and conflict examples.