id: "GW20-008"
title: "Retain saved Coordinates across checkpoint replacement and Git GC"
type: "feature"
status: "planned"
milestone: "v20.1.0"
category: "required"
workstream: "storage"
issue: "#964"
baseline_commit: "ceb58e656ec5bc85f0ae5991bf2a55599693bbb3"
feedback_sections: [7]
prerequisites: ["GW20-009"]

Feature

LLM prompt

Complete GW20-008: Retain saved Coordinates across checkpoint replacement and Git GC.
Read this entire task and its current GitHub issue before implementation.
Verify the current mainline and all prerequisite integrations.
Read AGENTS.md and the three TypeScript policy documents.
Use runtime-backed domain values and injected ports.
Keep parsing and codecs at the adapter boundary.
Preserve v20 APIs, stored identities, CRDT semantics, and failure meanings.
Use one coherent issue, PR, and mainline integration. Do not leave a broken intermediate state.
Problem to resolve:
A captured coordinate loses its checkpoint commit after checkpoint replacement and aggressive Git GC. Caller-created refs prevent the loss.
Acceptance checks:
A public retain operation keeps the complete coordinate support reachable across reopen and GC.
Provide named release and retention inspection with validated names and expected-old publication.
Several newer checkpoints do not change the retained historical answer.
Define transient capture and saved-coordinate lifetime explicitly. Capture alone does not imply permanent retention.
Release one saved name without deleting another owner's support.
Provide a named saved-coordinate lookup after reopen. Delegate reconstruction to the canonical validated restore boundary from #965.
Retention works for an existing valid captured basis. It does not require automatic cadence or first-basis creation.
Preserve all referenced checkpoint, frontier, and retained-root support. A saved name alone is not a retention witness.
Read these source paths:
src/domain/WarpWorldlineCoordinate.ts
src/domain/services/controllers/CheckpointController.ts
src/infrastructure/adapters/CborCheckpointStoreAdapter.ts
src/domain/utils/RefLayout.ts
Prerequisites: #965
Scope exclusions: Retain every historical checkpoint forever or tell applications to create private Git refs.
Run all tests and benchmarks in COPY-based Docker without host repository mounts.
Use the project guarded runner and the shared git-locks authority.
Lock host/heavy-work and the exact worker key together for expensive work.
Limit build caches to 20 GiB, test data to 4 GiB, and logs to 128 MiB.
Require 50 GiB free on host and Docker backing storage before heavy work.
Enforce disk accounting, CPU, memory, timeout, and child-process shutdown.
Do not start an unguarded workload. Do not bypass a resource refusal.
Require full touched-code coverage for refactors and an all-green manual SSJS scorecard.
Record source, image, command, fixtures, results, limits, and the regression witness.
Commit only your own files. Do not amend, rebase, force, push, or publish without authorization.
Report incomplete or blocked checks. Do not claim completion from a narrow green test.
Link the issue, coherent PR, and actual mainline integration when those actions are authorized.

1. Background Context

Source: FEEDBACK-git-warp.md, sections 7.
The report SHA-256 is 9b15209d51cd705059a9e6bfebf0f6681ff832924c1462b99ff3cfebde6bacae.
The report uses npm git-warp 20.0.0 and git-cas 6.5.11.
Its runtime results come from macOS host experiments. This planning task did not rerun them.
Source review baseline: ceb58e65.

Tracker: #964.

Read these source and test surfaces before work:

• src/domain/WarpWorldlineCoordinate.ts
• src/domain/services/controllers/CheckpointController.ts
• src/infrastructure/adapters/CborCheckpointStoreAdapter.ts
• src/domain/utils/RefLayout.ts

2. Problem Description

A captured coordinate loses its checkpoint commit after checkpoint replacement and aggressive Git GC. Caller-created refs prevent the loss.

2b. Proposed Solution

Add retain, named lookup, inspection, and release through storage-neutral ports. Reuse #965 for canonical reconstruction after reopen.

2c. Alternatives considered and rejected

Reject a private-import workaround. It does not provide a supported application contract.
Reject a documentation-only substitute when this task requires runtime behavior.
Keep larger storage and package redesigns under their existing issues.

2d. Acceptance Criteria

• A public retain operation keeps the complete coordinate support reachable across reopen and GC.
• Provide named release and retention inspection with validated names and expected-old publication.
• Several newer checkpoints do not change the retained historical answer.
• Define transient capture and saved-coordinate lifetime explicitly. Capture alone does not imply permanent retention.
• Release one saved name without deleting another owner's support.
• Provide a named saved-coordinate lookup after reopen. Delegate reconstruction to the canonical validated restore boundary from Export and restore Coordinates without private factories #965.
• Retention works for an existing valid captured basis. It does not require automatic cadence or first-basis creation.
• Preserve all referenced checkpoint, frontier, and retained-root support. A saved name alone is not a retention witness.

2e. Test Plan

Golden: Capture and retain a coordinate, create three newer checkpoints, close all runtimes, run GC in Docker, reopen, and read the old value.

Edges: Duplicate names; two names for one coordinate; foreign Lane; missing object; retain races; release races; strand support after its feature lands.

Known failure modes: preserve typed refusal, atomic publication, and complete evidence. Do not conceal unavailable support.

Fuzz and stress: use fixed fixture sizes and seeds. Apply the roadmap resource guards. Do not start an unbounded campaign.

3. Prerequisites

• Export and restore Coordinates without private factories #965 must be integrated. Saved-coordinate lookup delegates to canonical validated restoration after reopen.

4. Scope

In: A captured coordinate loses its checkpoint commit after checkpoint replacement and aggressive Git GC. Caller-created refs prevent the loss.

Out: Retain every historical checkpoint forever or tell applications to create private Git refs.

Safe intermediate state: one independently mergeable PR passes its relevant checks after its prerequisites.
Existing supported applications remain usable. Historical data remains intact.

5. Why now

This flaw blocks a supported Synapse store workflow or gives its operator incorrect guidance.
Resolve it within v20.1.0 without reducing the existing causal-history commitment.

6. Risks

Source inspection does not establish runtime or performance results.
Preserve historical identities, validation, and evidence. Do not weaken refusal to obtain a green result.
If the fix requires a breaking contract, record the conflict before activation. Do not hide it within a minor release.

7. Definition of Done

All acceptance checks have evidence from the exact candidate.
Relevant lint, typecheck, compatibility, and Docker checks pass.
The manual SSJS scorecard is green. Refactor coverage reaches 100% on touched code.
Record the issue, PR, and mainline integration commit. Record any external release gate.
A required check with missing evidence remains incomplete.

8. Stakeholders

James Ross: git-warp maintainer and acceptance owner.
Synapse store authors: applications need correct writes, reads, history, and operational guidance.
Library and CLI consumers: existing v20 contracts must remain usable.

9. Related Issues

• #474