gstack/setup-gbrain/SKILL.md.tmpl

---
name: setup-gbrain
preamble-tier: 2
version: 1.0.0
description: |
  Set up gbrain for this coding agent: install the CLI, initialize a
  local PGLite or Supabase brain, register MCP, capture per-remote trust
  policy. One command from zero to "gbrain is running, and this agent
  can call it." Use when: "setup gbrain", "connect gbrain", "start
  gbrain", "install gbrain", "configure gbrain for this machine". (gstack)
triggers:
  - setup gbrain
  - install gbrain
  - connect gbrain
  - start gbrain
  - configure gbrain
allowed-tools:
  - Bash
  - Read
  - Write
  - Edit
  - Glob
  - Grep
  - AskUserQuestion
---

{{PREAMBLE}}

# /setup-gbrain — Coding-Agent Onboarding for gbrain

You are setting up gbrain (https://github.com/garrytan/gbrain), a persistent
knowledge base, on the user's local Mac so that this coding agent (typically
Claude Code) can call it as both a CLI and an MCP tool.

**Scope honesty:** This skill's MCP registration step (5a) uses
`claude mcp add` and targets Claude Code specifically. Other local hosts
(Cursor, Codex CLI, etc.) will still get the gbrain CLI on PATH — they can
register `gbrain serve` in their own MCP config manually after setup.

**Audience:** local-Mac users. openclaw/hermes agents typically run in cloud
docker containers with their own gbrain; "sharing" a brain between them and
local Claude Code is only possible through shared Postgres (Supabase).

## User-invocable
When the user types `/setup-gbrain`, run this skill. Three shortcut modes:

- `/setup-gbrain` — full flow (default)
- `/setup-gbrain --repo` — only flip the per-remote policy for the current repo
- `/setup-gbrain --switch` — only migrate the engine (PGLite ↔ Supabase)
- `/setup-gbrain --resume-provision <ref>` — re-enter a previously interrupted
  Supabase auto-provision at the polling step
- `/setup-gbrain --cleanup-orphans` — list + delete in-flight Supabase projects

Parse the invocation args yourself — these are prose hints to the skill, not
implemented as a dispatcher binary.

---

## Step 1: Detect current state

```bash
~/.claude/skills/gstack/bin/gstack-gbrain-detect
```

Capture the JSON output. It contains: `gbrain_on_path`, `gbrain_version`,
`gbrain_config_exists`, `gbrain_engine`, `gbrain_doctor_ok`,
`gstack_brain_sync_mode`, `gstack_brain_git`.

Skip downstream steps that are already done. Report the detected state in
one line so the user knows what you found:

> "Detected: gbrain v0.18.2 on PATH, engine=postgres, doctor=ok,
>  sync=artifacts-only. Nothing to install; jumping to the policy check."

Branch on the `--repo`, `--switch`, `--resume-provision`, `--cleanup-orphans`
invocation flags here and skip to the matching step.

---

## Step 2: Pick a path (AskUserQuestion)

Only fire this if Step 1 shows no existing working config AND no shortcut
flag was passed. The question title: "Where should your brain live?"

Options (present based on detected state):

- **1 — Supabase, I already have a connection string.** Cloud-agent users
  whose openclaw/hermes provisioned one already. Paste the Session Pooler
  URL from the Supabase dashboard (Settings → Database → Connection Pooler
  → Session). *Trust-surface caveat to include in the prompt:* "Pasting this
  URL gives your local Claude Code full read/write access to every page your
  cloud agent can see. If that's not the trust level you want, pick PGLite
  local instead and accept the brains are disjoint."
- **2a — Supabase, auto-provision a new project.** You'll need a Supabase
  Personal Access Token (~90 seconds). Best choice for a shared team brain.
- **2b — Supabase, create manually.** Walk through supabase.com signup
  yourself; paste the URL back when ready.
- **3 — PGLite local.** Zero accounts, ~30 seconds. Isolated brain on this
  Mac only. Best for try-first.
- **Switch** (only if Step 1 detected an existing engine): "You already have
  a `<engine>` brain. Migrate it to the other engine?" → runs
  `gbrain migrate --to <other>` wrapped in `timeout 180s` (D9).

Do NOT silently pick; fire the AskUserQuestion.

---

## Step 3: Install gbrain CLI (if missing)

Only if `gbrain_on_path=false`:

```bash
~/.claude/skills/gstack/bin/gstack-gbrain-install
```

The installer runs D5 detect-first (probes `~/git/gbrain`, `~/gbrain` first),
then D19 PATH-shadow validation (post-link `gbrain --version` must match
install-dir `package.json`). On D19 failure the installer exits 3 with a
clear remediation menu; surface the full output to the user and STOP. Do not
continue the skill — the environment is broken until the user fixes PATH.

---

## Step 4: Initialize the brain

Path-specific.

### Path 1 (Supabase, existing URL)

Source the secret-read helper, collect URL with `read -s` + redacted preview:

```bash
. ~/.claude/skills/gstack/bin/gstack-gbrain-lib.sh
read_secret_to_env GBRAIN_POOLER_URL "Paste Session Pooler URL: " \
  --echo-redacted 's#://[^@]*@#://***@#'
```

Then validate structurally:

```bash
printf '%s' "$GBRAIN_POOLER_URL" | ~/.claude/skills/gstack/bin/gstack-gbrain-supabase-verify -
```

If the verify exit code is 3 (direct-connection URL), the verifier's own
message explains the fix; surface it and re-prompt for a Session Pooler URL.

On success, hand off to gbrain via env var (D10, never argv):

```bash
GBRAIN_DATABASE_URL="$GBRAIN_POOLER_URL" gbrain init --non-interactive --json
```

Then `unset GBRAIN_POOLER_URL GBRAIN_DATABASE_URL` immediately. The URL is
now persisted in `~/.gbrain/config.json` at mode 0600 by gbrain itself.

### Path 2a (Supabase, auto-provision — D7)

Show the D11 PAT scope disclosure verbatim BEFORE collecting the token:

> *This Supabase Personal Access Token grants full read/write/delete access
> to every project in your Supabase account, not just the `gbrain` one we're
> about to create. Supabase doesn't currently support scoped tokens. We use
> this PAT only to: create one project, poll it until healthy, read the
> Session Pooler URL — then discard it from process memory. The token
> remains valid on Supabase's side until you manually revoke it at
> https://supabase.com/dashboard/account/tokens — we recommend revoking
> immediately after setup completes.*

Then:

```bash
. ~/.claude/skills/gstack/bin/gstack-gbrain-lib.sh
read_secret_to_env SUPABASE_ACCESS_TOKEN "Paste PAT: "
```

Ask the D17 tier prompt via AskUserQuestion: "Which Supabase tier?" Present
Free (2-project limit, pauses after 7d inactivity) vs Pro ($25/mo, no
pauses, recommended for real use). Explain that tier is **org-level** (per
the Management API contract) — user picks their org based on its current
tier. Pro may require them to upgrade the org first at supabase.com.

List orgs, pick one (AskUserQuestion if multiple):

```bash
orgs=$(~/.claude/skills/gstack/bin/gstack-gbrain-supabase-provision list-orgs --json)
```

If the `.orgs` array is empty, surface: "Your Supabase account has no
organizations. Create one at https://supabase.com/dashboard, then re-run
`/setup-gbrain`." STOP.

Ask the user for a region (default `us-east-1`; valid values are the 18
enum values in the Supabase Management API — list a few common ones, let
them pick "Other" for a full list).

Generate the DB password (never shown to the user):

```bash
export DB_PASS=$(openssl rand -base64 24)
```

Set up a SIGINT trap (D12 basic recovery):

```bash
trap 'echo ""; echo "gstack-gbrain: interrupted. In-flight ref: $INFLIGHT_REF"; \
      echo "Resume: /setup-gbrain --resume-provision $INFLIGHT_REF"; \
      echo "Delete: https://supabase.com/dashboard/project/$INFLIGHT_REF"; \
      unset SUPABASE_ACCESS_TOKEN DB_PASS; exit 130' INT TERM
```

Create + wait + fetch:

```bash
result=$(~/.claude/skills/gstack/bin/gstack-gbrain-supabase-provision \
  create gbrain "$REGION" "$ORG_SLUG" --json)
INFLIGHT_REF=$(echo "$result" | jq -r .ref)
~/.claude/skills/gstack/bin/gstack-gbrain-supabase-provision wait "$INFLIGHT_REF" --json
pooler=$(~/.claude/skills/gstack/bin/gstack-gbrain-supabase-provision \
  pooler-url "$INFLIGHT_REF" --json)
GBRAIN_DATABASE_URL=$(echo "$pooler" | jq -r .pooler_url)
export GBRAIN_DATABASE_URL
gbrain init --non-interactive --json
unset SUPABASE_ACCESS_TOKEN DB_PASS GBRAIN_DATABASE_URL INFLIGHT_REF
trap - INT TERM
```

After success, emit the PAT revocation reminder:

> "Setup complete. Revoke the PAT you pasted at
> https://supabase.com/dashboard/account/tokens — we've already discarded
> it from memory and don't need it again. The gbrain project will continue
> working because it uses its own embedded database password."

### Path 2b (Supabase, manual)

Walk the user through the supabase.com steps:
1. Login at https://supabase.com/dashboard
2. Click "New Project," name it `gbrain`, pick a region, copy the generated
   database password (you'll need it for paste-back? no — it's embedded in
   the pooler URL we collect next)
3. Wait ~2 min for the project to initialize
4. Settings → Database → Connection Pooler → Session → copy the URL (port
   6543)

Then follow the same secret-read + verify + init flow as Path 1.

### Path 3 (PGLite local)

```bash
gbrain init --pglite --json
```

Done. No network, no secrets.

### Switch (from detect's existing-engine state)

```bash
# Going PGLite → Supabase, collect URL first (Path 1 flow), then:
timeout 180s gbrain migrate --to supabase --url "$URL" --json
# Going Supabase → PGLite:
timeout 180s gbrain migrate --to pglite --json
```

If `timeout` returns 124 (exit code for timeout): surface D9 message
("Migration didn't complete in 3 minutes — another gstack session may be
holding a lock on the source brain. Close other workspaces and re-run
`/setup-gbrain --switch`. Your original brain is untouched."). STOP.

---

## Step 5: Verify gbrain doctor

```bash
doctor=$(gbrain doctor --json)
status=$(echo "$doctor" | jq -r .status)
```

If status is `ok` or `warnings`, proceed. Anything else → surface the full
doctor output and STOP.

---

## Step 5a: Register gbrain as Claude Code MCP (D18)

Only if `which claude` resolves. Ask: "Give Claude Code a typed tool surface
for gbrain? (recommended yes)"

If yes, register at **user scope** with an **absolute path** to the gbrain
binary. User scope makes the MCP available in every Claude Code session on
this machine, not just the current workspace. Absolute path avoids PATH
resolution issues when Claude Code spawns `gbrain serve` as a subprocess.

```bash
GBRAIN_BIN=$(command -v gbrain)
[ -z "$GBRAIN_BIN" ] && GBRAIN_BIN="$HOME/.bun/bin/gbrain"
claude mcp add --scope user gbrain -- "$GBRAIN_BIN" serve
claude mcp list | grep gbrain  # verify: should show "✓ Connected"
```

If the user already had a local-scope registration from an earlier run,
remove it first so both scopes don't conflict:
```bash
claude mcp remove gbrain 2>/dev/null || true
```

If `claude` is not on PATH: emit "MCP registration skipped — this skill is
Claude-Code-targeted; register `gbrain serve` in your agent's MCP config
manually." Continue to step 6.

**Heads-up for the user:** an already-open Claude Code session will not
pick up the new MCP tools until restart. Tell them: "Restart any open
Claude Code sessions to see `mcp__gbrain__*` tools — they're loaded at
session start, not mid-session."

---

## Step 6: Per-remote policy (D3 triad, gated repo-import)

If we're in a git repo with an `origin` remote, check the policy:

```bash
current_tier=$(~/.claude/skills/gstack/bin/gstack-gbrain-repo-policy get)
```

Branches:
- `read-write` → import this repo: `gbrain import "$(pwd)" --no-embed` then
  `gbrain embed --stale &` in the background.
- `read-only` → skip import entirely (this tier is enforced by the future
  auto-import hook + by gbrain resolver injection, not here).
- `deny` → do nothing.
- `unset` → AskUserQuestion: "How should `<normalized-remote>` interact with
  gbrain?"
  - `read-write` — agent can search AND write new pages from this repo
  - `read-only` — agent can search but never write
  - `deny` — no interaction at all
  - `skip-for-now` — don't persist, ask next time

  On answer (other than skip-for-now):
  ```bash
  ~/.claude/skills/gstack/bin/gstack-gbrain-repo-policy set "$REMOTE" "$TIER"
  ```
  Then import iff `read-write`.

If outside a git repo OR no origin remote: skip this step with a note.

For `/setup-gbrain --repo` invocations, execute ONLY Step 6 and exit.

---

## Step 7: Offer gstack-brain-sync + wire it into gbrain

Separate AskUserQuestion: "Also sync your gstack session memory (learnings,
plans, retros) to a private git repo that gbrain can index across machines?"

Options:
- Yes, full sync (everything allowlisted)
- Yes, artifacts-only (plans, designs, retros — skip behavioral data)
- No thanks

If yes:

```bash
~/.claude/skills/gstack/bin/gstack-brain-init
~/.claude/skills/gstack/bin/gstack-config set gbrain_sync_mode artifacts-only
# or "full" if user picked yes-full
```

Then wire the brain repo into gbrain so its content is searchable from any
gbrain client (this Claude Code session, future Macs, optional cloud agents).
The helper creates a `git worktree` of `~/.gstack/`, registers it as a
federated source on the user's gbrain (Supabase or PGLite), and runs an
initial `gbrain sync`. Local-Mac only. No cloud agent required. Subsequent
skill runs trigger incremental sync via the existing skill-end push hook.

Capture the database URL out of `~/.gbrain/config.json` first and pass it
explicitly so the wireup is robust against any other process rewriting
`~/.gbrain/config.json` mid-sync (e.g., concurrent `gbrain init` runs
elsewhere on the machine):

```bash
GBRAIN_URL=$(python3 -c "
import json, os, sys
try:
    c = json.load(open(os.path.expanduser('~/.gbrain/config.json')))
    print(c.get('database_url', ''))
except Exception:
    pass
")
~/.claude/skills/gstack/bin/gstack-gbrain-source-wireup --strict \
  ${GBRAIN_URL:+--database-url "$GBRAIN_URL"}
```

`--strict` exits non-zero on missing prereqs (gbrain not installed, < 0.18.0,
or no `~/.gstack/.git` yet) so the user sees the failure rather than silently
ending up with an unwired brain. On non-zero exit, surface the helper's
output and STOP per skill rules — search-across-machines won't work until
the prereq is fixed.

---

## Step 7.5: Transcript & memory ingest gate

After memory sync is wired (Step 7) but before persisting the CLAUDE.md
config (Step 8), offer to bring this Mac's coding-agent transcripts +
curated `~/.gstack/` artifacts into gbrain so the retrieval surface
(per-skill manifests, salience block) has data to surface.

Run the probe to size the operation:
```bash
~/.claude/skills/gstack/bin/gstack-memory-ingest --probe
```

Read the output. If `Total files in window: 0`, skip — there's nothing
to ingest. Set `gstack-config set transcript_ingest_mode incremental`
silently and continue to Step 8.

If `New (never ingested)` is < 200 AND total bytes are < 100MB: silent
bulk via `gstack-memory-ingest --bulk --quiet`. Set
`transcript_ingest_mode=incremental` and continue.

Otherwise (the "many transcripts on disk" path): AskUserQuestion with
the exact counts AND the value promise. Default scope is **current repo
only, last 90 days**:

> "Found <N_repo> transcripts in THIS repo (<repo-slug>) over the last
> 90 days, plus <N_other> across other repos on this machine (<bytes>
> total if all ingested). Ingest THIS repo's transcripts into gbrain?
>
> What you get after this: every gstack skill auto-loads recent salience
> from your past sessions in this repo, so the agent finds your prior
> work without you describing it. You can query 'what was I doing on
> day X' and get a real answer. Per-session pages are searchable,
> taggable, and deletable. Secret scanning runs before any push.
>
> What stays the same: nothing leaves your machine unless gbrain sync
> is enabled (Step 7). Per-repo trust policies still apply.
>
> Multi-Mac note: if you HAVE enabled brain sync (Step 7), these
> transcript pages will sync across your Macs. Caveat: deleting a
> transcript page later removes it from gbrain but git history retains
> it in prior commits. Use `gstack-transcript-prune` to delete in bulk;
> use `git filter-repo` on the brain remote for hard-delete from
> history."

Options:
- A) Yes — this repo, last 90 days (recommended; ~est min)
- B) Yes — this repo, ALL history
- C) Yes — this repo + other repos on this machine
- D) Skip historical, track new from now (`transcript_ingest_mode=incremental`)
- E) Never ingest transcripts (`transcript_ingest_mode=off`)

After answer:
```bash
~/.claude/skills/gstack/bin/gstack-config set transcript_ingest_mode <choice>
~/.claude/skills/gstack/bin/gstack-gbrain-sync --full --no-brain-sync
```
(`--no-brain-sync` because Step 7 already wired that path; this just
runs the code import + memory ingest stages. Brain-sync will run on the
next preamble hook.)

If A/D/E, ingest is incremental from this point on; preamble-boundary
hook runs `gstack-gbrain-sync --incremental --quiet` on every skill
start (cheap mtime fast-path).

Reference doc for users: `setup-gbrain/memory.md` (linked from CLAUDE.md
Step 8).

---

## Step 8: Persist `## GBrain Configuration` in CLAUDE.md

Find-and-replace (or append) this section in CLAUDE.md:

```markdown
## GBrain Configuration (configured by /setup-gbrain)
- Engine: {pglite|postgres}
- Config file: ~/.gbrain/config.json (mode 0600)
- Setup date: {today}
- MCP registered: {yes/no}
- Memory sync: {off|artifacts-only|full}
- Current repo policy: {read-write|read-only|deny|unset}
```

**After Step 9 (smoke test) passes, also write the `## GBrain Search Guidance`
block** so the coding agent learns when to prefer `gbrain` over Grep. This
block is gated on the smoke test passing — write the Configuration block
first (so the user knows what state they're in even if the smoke test fails),
then return here after Step 9 and write the guidance block only if smoke
test succeeded.

When Step 9 passes, find-and-replace (or append) this block. Use HTML-comment
delimiters so removal regex is unambiguous and never eats user content. The
block content is machine-AGNOSTIC — no engine type, no page counts, no
last-sync time. Machine state stays in the Configuration block above.

```markdown
## GBrain Search Guidance (configured by /sync-gbrain)
<!-- gstack-gbrain-search-guidance:start -->

GBrain is set up and synced on this machine. The agent should prefer gbrain
over Grep when the question is semantic or when you don't know the exact
identifier yet. Two indexed corpora available via the `gbrain` CLI:
- This repo's code (registered as `gstack-code-<repo>` source).
- `~/.gstack/` curated memory (registered as `gstack-brain-<user>` source via
  the existing federation pipeline).

Prefer gbrain when:
- "Where is X handled?" / semantic intent, no exact string yet:
    `gbrain search "<terms>"` or `gbrain query "<question>"`
- "Where is symbol Y defined?" / symbol-based code questions:
    `gbrain code-def <symbol>` or `gbrain code-refs <symbol>`
- "What calls Y?" / "What does Y depend on?":
    `gbrain code-callers <symbol>` / `gbrain code-callees <symbol>`
- "What did we decide last time?" / past plans, retros, learnings:
    `gbrain search "<terms>" --source gstack-brain-<user>`

Grep is still right for known exact strings, regex, multiline patterns, and
file globs. The brain auto-syncs incrementally on every gstack skill start.
Run `/sync-gbrain` to force-refresh, `/sync-gbrain --full` for full reindex.

<!-- gstack-gbrain-search-guidance:end -->
```

If Step 9 smoke test fails, skip the guidance block write entirely. The user's
next `/sync-gbrain` run will re-evaluate capability and write the block when
the round-trip works.

---

## Step 9: Smoke test

```bash
SLUG="setup-gbrain-smoke-test-$(date +%s)"
echo "Set up on $(date). Smoke test for /setup-gbrain." | gbrain put "$SLUG"
gbrain search "smoke test" | grep -i "$SLUG"
```

Confirms the round trip. On failure, surface `gbrain doctor --json` output
and STOP with a NEEDS_CONTEXT escalation.

---

## Step 10: GREEN/YELLOW/RED verdict block (idempotent doctor output)

After Steps 1-9 complete, summarize. Re-running `/setup-gbrain` on a
configured Mac is a first-class doctor path: every step detects existing
state, repairs only what's missing, and reports here.

```bash
~/.claude/skills/gstack/bin/gstack-gbrain-detect 2>/dev/null || true
~/.claude/skills/gstack/bin/gstack-config get transcript_ingest_mode 2>/dev/null || echo "off"
~/.claude/skills/gstack/bin/gstack-config get gbrain_sync_mode 2>/dev/null || echo "off"
[ -f ~/.gstack/.gbrain-sync-state.json ] && cat ~/.gstack/.gbrain-sync-state.json || echo "{}"
```

Print the verdict block. Each row is `[OK]/[FIX]/[WARN]/[ERR]` — see
template below; substitute your detect outputs:

```
gbrain status: GREEN

  CLI ............. OK   <gbrain version>
  Engine .......... OK   <pglite|supabase> at <path>
  doctor .......... OK
  MCP ............. OK   registered (user scope)
  Repo policy ..... OK   <read-write|read-only|deny>
  Code import ..... OK   <last_imported_head>
  Memory sync ..... OK   <gbrain_sync_mode> to <remote>
  Transcripts ..... OK   <N> sessions, last ingest <when>
  CLAUDE.md ....... OK
  Smoke test ...... OK   put → search → delete round-trip

Run `/setup-gbrain` again any time gbrain feels off; it's safe and idempotent.
```

If any row is YELLOW or RED, the verdict line says so and the failing rows
surface a one-line "next action" (e.g.,
`Engine .......... ERR  PGLite corrupt — run \`gbrain restore-from-sync\` (V1.5)`).
For V1, restore-from-sync is a V1.5 P0 cross-repo TODO; until it ships,
the user's brain remote (with brain-sync enabled) holds curated artifacts
as markdown + git, recoverable manually via `gbrain import` from a clone.

---

## `/setup-gbrain --cleanup-orphans` (D20)

Re-collect a PAT (Step 4 path-2a scope disclosure), then:

```bash
# List user's Supabase projects (user has to pipe this through their own
# shell to review; we don't rely on a stored PAT).
export SUPABASE_ACCESS_TOKEN="<collected from read_secret_to_env>"
projects=$(curl -s -H "Authorization: Bearer $SUPABASE_ACCESS_TOKEN" \
  https://api.supabase.com/v1/projects)
```

Parse the response, identify any project named starting with `gbrain` whose
`ref` doesn't match the user's active `~/.gbrain/config.json` pooler URL.
For each orphan, AskUserQuestion per project: "Delete orphan project
`<ref>` (`<name>`, created `<created_at>`)?" — NEVER batch; per-project
confirm is a one-way door.

On confirmed delete:
```bash
curl -s -X DELETE -H "Authorization: Bearer $SUPABASE_ACCESS_TOKEN" \
  https://api.supabase.com/v1/projects/$REF
```

Never delete the active brain without a second explicit confirmation.

At end: `unset SUPABASE_ACCESS_TOKEN`. Revocation reminder.

---

## Telemetry (D4)

The preamble's Telemetry block logs skill success/failure at exit. When
emitting the event, add these enumerated categorical values to the
telemetry payload (SAFE — no free-form secrets, never the URL or PAT):

- `scenario`: `supabase-existing` | `supabase-auto-provision` |
  `supabase-manual` | `pglite-local` | `switch-to-supabase` |
  `switch-to-pglite` | `repo-flip-only` | `cleanup-orphans` |
  `resume-provision`
- `install_performed`: `yes` | `no` (D5 reuse) | `skipped` (pre-existing)
- `mcp_registered`: `yes` | `no` | `claude-missing`
- `trust_tier_set`: `read-write` | `read-only` | `deny` |
  `skip-for-now` | `n/a` (outside git repo)

Never pass `SUPABASE_ACCESS_TOKEN`, `DB_PASS`, `GBRAIN_POOLER_URL`,
`GBRAIN_DATABASE_URL`, or any `postgresql://` substring to the telemetry
invocation. The CI grep test in `test/skill-validation.test.ts` enforces
this at build time.

---

## Important Rules

- **One rule for every secret.** PAT, DB_PASS, pooler URL: env-var only,
  never argv, never logged, never persisted to disk by us. The only file
  that holds the pooler URL long-term is `~/.gbrain/config.json`, written
  by gbrain's own `init` at mode 0600 — that's gbrain's discipline, not
  ours.
- **STOP points are hard.** Gbrain doctor not healthy, D19 PATH shadow, D9
  migrate timeout, smoke test failure — each is a STOP. Do not paper over.
- **Concurrent-run lock.** At skill start, `mkdir ~/.gstack/.setup-gbrain.lock.d`
  (atomic). If the mkdir fails, abort with: "Another `/setup-gbrain` instance
  is running. Wait for it, or `rm -rf ~/.gstack/.setup-gbrain.lock.d` if
  you're sure it's stale." Release on normal exit AND in the SIGINT trap.
- **CLAUDE.md is the audit trail.** Always update it in Step 8 after a
  successful setup.