| name | snapshot-check |
| description | Verify — BEFORE any structural edit to the candidate's evidence-bank, project-instructions or changelog files — that a Convention 13 pre-edit snapshot exists in _resources/ under the dated naming convention, and that the _resources/ retention discipline (keep 3 most-recent good backups, _archive/ for older, _quarantine/ for truncated, RESTORE_INDEX.md current) holds. Use this skill at the START of any session step that will add or move a matrix row, change entry format, restructure a Section file or Examples_Master.md, restructure Project_Instructions_V*.md or either changelog, or run a multi-edit Python script across the bank. Also use when [Candidate First Name] says 'check the snapshots', 'is there a backup', or 'verify the restore index'. This is a blocking gate, not advisory: a structural edit without a pre-edit snapshot is unrecoverable if it truncates. |
Snapshot Check — Convention 13 pre-edit gate skill
Codifies Convention 13 (pre-major-edit snapshot + retention rule) of Project_Instructions.md (rev 2026-06-12). Wave 3 verification skill of the framework.
The 2026-05-28 Section 7 reconstruction recovered from a 2026-05-11 backup only because that backup happened to exist. This gate makes the snapshot a checked precondition rather than a remembered discipline. It blocks the edit if the snapshot is missing.
When to invoke
Before any session step that will:
- (a) add or move a matrix row in any
Examples_Section_5_*.md file;
- (b) modify the entry format used in any A / B / C / D section file;
- (c) restructure
Examples_Section_4_Master_Index.md, any Examples_Section_5_*.md, Examples_Section_6_Signature_Metrics.md, Examples_Section_7_Watchouts.md or Examples_Master.md;
- (d) restructure
Project_Instructions_V*.md or either changelog (Convention 15 scope);
- (e) apply a multi-edit Python script across the bank.
Trivial edits are exempt — single proof-point amendment, single tag tweak, changelog appends, prose copy-edits inside an existing entry.
Checks — run all four
Load references/snapshot-rules.md, then:
- Snapshot exists. For every file about to be edited, a same-day snapshot exists in
_resources/ named [Original_filename]_backup_YYYY-MM-DD_pre-{kebab-descriptor}.md and its descriptor names this structural change. If missing → STOP: take the snapshot now, then proceed. (The fix is one cp; the gate exists so it cannot be skipped, not to create ceremony.)
- Snapshot is good. The snapshot is byte-identical to the current file (verbatim copy taken before any edit). A snapshot shorter than the live file is itself suspect — quarantine and retake.
- Retention discipline holds for the touched base files: at most the 3 most-recent good backups in
_resources/ root; older in _resources/_archive/; any *TRUNCATED* file in _resources/_quarantine/ (never a restore source).
RESTORE_INDEX.md is current — it names the known-good latest backup for every touched base file. The newest backup by timestamp is not necessarily the newest good one.
Output format
A per-file table (file / snapshot found / good / retention OK / index OK), then verdict: Proceed or Blocked — [action]. Blocked is resolved in-session (take snapshot, fix retention, update index), then re-run.
