Conciseness

The ~40-line body is lean and assumes Claude's competence throughout — a trigger table, terse numbered procedures, and bare commands ("Run `git status`, `git branch` — confirm you are on correct branch") with zero padding or explanation of concepts Claude already knows. Every line instructs; matches the level-5 anchor.

Actionability

There are concrete commands (`cat .opencastle/SESSION-CHECKPOINT.md`, `git log --oneline -20`) and specific rules ("if stale (>1 session old)", "remove rows for questions the user has since answered"), but the central instruction — "Write .opencastle/SESSION-CHECKPOINT.md from the canonical CHECKPOINT-TEMPLATE.md" — depends on a template file that is not in the bundle, so the checkpoint's canonical format is unavailable and Claude must invent it. This is a key missing detail, matching the level-3 anchor rather than level 4's "minor gaps".

Workflow Clarity

Both workflows are clearly sequenced with explicit validation checkpoints and error recovery: "Verify: `cat .opencastle/SESSION-CHECKPOINT.md`; confirm listed files exist", branch confirmation via `git status`/`git branch`, staleness checks, and a recovery loop ("If checkpoint missing or corrupt: Rebuild from `git log --oneline -20`, tracker state"). The trigger table acts as a checklist. This matches the level-5 anchor; level 4 would imply missing some of these checkpoints, and none are absent.

Progressive Disclosure

The body is short (<50 lines) and well-sectioned, which alone would support a high score, but its single reference — "the canonical [CHECKPOINT-TEMPLATE.md](./CHECKPOINT-TEMPLATE.md)" — points to a file that does not exist anywhere in the skill directory. The one clearly-signaled reference is therefore broken and the promised detailed material is unreachable, fitting the level-3 anchor's "references present but not clearly signaled / content that should be separate is inline" better than level 4's "minor organization gaps".

Specificity

"Saves, restores session state including task progress, file changes, delegation history" names the domain, two concrete actions, and three specific state categories. It is more concrete than the level-3 anchor ("names domain and 1-2 concrete actions") because of the enumerated state items, but stops short of level 5's "multiple specific concrete actions; comprehensive coverage" — only two verbs (saves, restores) carry the whole capability list.

Completeness

The description explicitly answers both questions: what ("Saves, restores session state including task progress, file changes, delegation history") and when ("Use when saving progress, resuming interrupted work, picking up where you left off, or checkpointing current work") with four concrete trigger phrases. This matches the level-5 anchor directly, and neither the what nor the when clause is vague.

Trigger Term Quality

"saving progress", "resuming interrupted work", "picking up where you left off", "checkpointing current work" are phrases users would naturally say. Not level 5 because closely related natural terms like "restore session", "session recovery", or "handoff" are absent from the trigger clause, leaving a few common variations uncovered.

Distinctiveness Conflict Risk

Session checkpointing is a fairly distinct niche with dedicated trigger terms ("checkpointing", "resuming interrupted work"). Not level 5 because phrases like "saving progress" and "picking up where you left off" could plausibly fire for generic progress-tracking or context-handoff skills, creating minor overlap risk.