fix: reject stale plans before preview and apply

[lloydrichards]

Goals/Scope

Ensure that Apply uses the repository state represented by Plan. Review the baseline checks before composition and each write, including the preview path.

Description

Plan records the canonical repository root and fingerprints of inspected text files. Preview and Apply now return StalePlanFailure when those paths change. File preview seeds an isolated memory filesystem and uses the same guarded Apply path. Tests cover drift, root changes, partial writes, and host file preservation.

---

• closes Ensure Apply executes the repository state represented by Plan #175

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Project	Deployment	Actions	Updated
stack-effect-docs	Ready	Preview	Sep 27, 2026 10:11am UTC

[changeset-bot]

🦋 Changeset detected

Latest commit: 7d85ff9

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

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stack-effect	Patch

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[lloydrichards]

@pullfrog please review

[pullfrog]

Caution

File preview now rejects valid greenfield Plans and BOM-prefixed text files as stale. These false positives block --dry-run --show-files and valid incremental file previews.

Reviewed changes across the Plan baseline contract, repository capture and freshness checks, guarded Apply, virtual file preview, CLI serialization, integration tests, and supporting documentation:

• Repository authority: Plans now carry canonical roots and path fingerprints, with typed stale errors for drift.
• Execution and preview: Apply validates state before composition and each write; file preview seeds a private filesystem and reruns guarded Apply.
• Coverage and documentation: Added drift, partial-write, and host-preservation tests and recorded the contract in OKF.

  ^{｜ Fix all ➔ ｜ Fix 👍s ➔ ｜ View workflow run ｜ Using GPT Sol ｜ 𝕏}

[lloydrichards]

@pullfrog please review the latest head, including the greenfield and BOM preview fixes.

[pullfrog]

✅ No new issues found.

Reviewed changes since the prior Pullfrog review, including the greenfield and BOM preview fixes and their VFS compatibility update:

• Preserved preview bytes: Seeded fingerprinted files with raw bytes so BOM-prefixed files remain valid.
• Restored greenfield previews: Adapted the missing-root baseline to the initialized virtual root and checked host state before and after seeding.
• Verified coverage: Added regressions for both cases; bun run test --filter=@repo/scaffold and bun run type-check pass.

  ^{｜ View workflow run ｜ Using GPT Sol ｜ 𝕏}