Collab Phase 3: Draft Buffer API and Operation Intake for Deferred Persistence

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Summary

Add transient draft operation intake and storage so interfaces can submit collaborative edits without immediate durable RERUM writes.

Scope

• Add draft operation intake endpoint(s) for line text and bounds patches.
• Store coalesced transient draft state by project/page/line/user.
• Emit op accepted or rejected acknowledgements.
• Fanout accepted operations to websocket room members.
• Add validation and limits for payload size and queue depth.

Acceptance Criteria

• Draft operations are accepted and visible to collaborators in realtime.
• Duplicate retry submissions are deduplicated by idempotency key.
• No durable RERUM write occurs in this phase.
• Rejected operations return machine-readable reason.

Dependency

• Depends on websocket skeleton issue.

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Dependency map for execution planning:

Depends on:

• Collab Phase 1: Websocket Server Skeleton, Auth, and Presence Rooms #509
• Collaboration Contract v1.0 Ratification for Services, Interfaces, and RERUM #512

Blocks:

• Collab Phase 4: Deferred Commit Engine with Important-Moment and Long-Debounce Flush TPEN-interfaces#556
• Collab Phase 5: Durable Flush Worker from Drafts to RERUM with Conflict Acks #511

Related to:

• Collab Phase 2: Realtime Client and Presence UI (No Save Behavior Change Yet) TPEN-interfaces#555

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Phase Documentation Addendum

• This phase introduces draft intake contracts and coalesced temporary state, aligned to Contract sections 6 and 7.
• All modifications require permissions from the authorized user.
• Required validation: idempotency-key dedupe, payload validation, rejection reasons, no durable write side effects.
• Exit artifacts: op intake API examples and queue limit behavior notes.