Parent design: MemoryVault — see Detailed Design §1 for the full architectural context.

This part ships the two foundational write primitives that every other part of MemoryVault depends on:

/memory save <kind> <slug> [--group <group>] [--always-load] — writes an entry at MemoryVault/<group>/<kind>/<slug>.md with YAML frontmatter (kind, status: active, created, updated, tags, optional supersedes). Body is free-form markdown. On save: file write is synchronous (<50ms target); embedding + vec-index update are async (don't block the agent or the user). The --always-load flag writes to MemoryVault/personal-private/_always-load/ and sets always_load: true frontmatter — entries flagged this way get injected at SessionStart per the recall-loop part.

/memory evolve <old-path> <new-content> <reason> — atomic archive-and-replace. Five steps: (1) Read the old entry; (2) write new entry with supersedes: <old-path> frontmatter pointing back; (3) atomically move old entry to MemoryVault/personal-private/_archive/<original-path>.YYYYMMDD.md via filesystem rename (single-syscall atomicity on macOS APFS); (4) update old entry's frontmatter status: superseded + superseded_by: <new-path> cross-link; (5) trigger vec-index update for both files. Recall filters skip status: superseded by default.

Tri-modal confidence routing (HIGH → auto-save / MEDIUM → interactive review / LOW → _inbox/) applies only when the reflection sidecar invokes these primitives — direct user invocation always writes immediately to the requested location.

The skill home is crickets/skills/memory/SKILL.md with full YAML frontmatter (name: memory, kind: skill, supported_hosts: [claude-code, antigravity], version: 0.1.0, install_scope: project) and tool allowlist [Read, Write, Edit, Glob, Grep] — no Bash. This part ships the skill scaffold + the save and evolve sub-command bodies only; recall/reflection/idea-ledger sub-commands stub for future parts. (Standalone Gemini CLI host removed from supported_hosts in v0.9.0 per ROADMAP item #15 / Gemini CLI host removal (crickets-hld).)

None — foundational. All other parts depend on this one. The only pre-existing dependencies are:

• sqlite-vec Python package (pip install sqlite-vec) — installed lazily on first save invocation; if missing, save still succeeds (file write is unconditional) but index update is deferred until the dep lands.
• Local sentence-transformers — the only embedding mode as of v0.9.2 (see local-only embeddings decision, 2026-05-20 — crickets-hld). Call is async (queued); first invocation downloads BGE-large (~1.3GB) lazily; subsequent calls are on-device + offline-capable. The save side is unconditional — file write never blocks on embedding state. Embedding implementation lives in the recall-loop part.

1. Smoke install green — bash crickets/scripts/smoke-install-bash.sh (+ .ps1) verifies the memory skill installs at the 2 host destinations (.claude/skills/, .agent/skills/); negative-existence assertions verify .agents/skills/ is NOT created (gemini-cli removed in v0.9.0).
2. validate-manifests.py clean — skill manifest parses with no errors; skill count increments.
3. /memory save end-to-end — invoke against a scratch vault; file lands at the expected path with correct frontmatter (kind, status: active, created, updated, tags, group); content matches the input.
4. --always-load flag — files written with the flag land in _always-load/ subdir with always_load: true frontmatter.
5. /memory evolve end-to-end — invoke against an existing entry; verify old entry is archived to _archive/<original-path>.YYYYMMDD.md with status: superseded + superseded_by cross-link; new entry has supersedes cross-link; both files exist on disk after the operation.
6. PII guardrails apply — crickets/scripts/check-no-pii.sh clean on toolkit-committed content (skill source + templates); pre-push hook runs clean.
7. All 3 OS CI workflows green on the commit that lands this part.

• This is the foundational part — every later part assumes these primitives exist + behave as specified above. If the spec needs amendment mid-execution, append to the parent design's Document History before re-running /design translate on this part.
• The skill body should document both sub-commands per the established pattern from crickets/skills/design/SKILL.md (which is the first toolkit skill with multi-sub-command bodies — use it as the reference shape).
• The vec-index file at MemoryVault/_meta/vec-index.db doesn't need to exist when save is first invoked; create on first call if absent.
• The _archive/ subdir doesn't need to exist for the first save; create lazily on first evolve.