feat: helper locks GBRAIN_DATABASE_URL at startup, defends against config rewrites

The wireup helper previously read ~/.gbrain/config.json on every gbrain
subprocess invocation. On Garry's Mac, multiple concurrent test runs and
agent integrations were rewriting that file mid-sync, redirecting the
wireup at the wrong brain partway through a 4-min initial import.

This commit adds a `--database-url <url>` flag to the helper and locks
the URL at startup. Precedence:
  1. --database-url flag                       (explicit caller intent)
  2. GBRAIN_DATABASE_URL / DATABASE_URL env    (CI / manual override)
  3. read once from ~/.gbrain/config.json      (default)

Whichever wins gets exported as GBRAIN_DATABASE_URL for every child
`gbrain` invocation. Per gbrain's loadConfig at src/core/config.ts:53,
env-var URLs override the file URL — so a process that flips config.json
between two of our gbrain calls can't redirect us. Defense-in-depth:
once the URL is locked, the wireup completes against the original brain
even under hostile filesystem conditions.

setup-gbrain/SKILL.md.tmpl Step 7 now reads the URL out of config.json
once (via python3 inline) and passes it explicitly with --database-url,
so even the very first wireup call is decoupled from config.json mutability.

Three new test cases cover the lock behavior:
  - --database-url flag is exported to child gbrain calls
  - falls back to ~/.gbrain/config.json when no flag and no env
  - flag overrides env GBRAIN_DATABASE_URL and config.json values

The fake gbrain in the test suite now records GBRAIN_DATABASE_URL alongside
each call so tests can assert the helper exported the locked URL.

Total test count: 13 → 16 passing.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -23,6 +23,8 @@ gbrain search "ethos" --source gstack-brain-{user} | head -5
 
 `bin/gstack-gbrain-source-wireup` is the new helper. It derives a per-user source id from `~/.gstack/.git`'s origin URL (with multi-fallback to `~/.gstack-brain-remote.txt` and a `--source-id` flag), creates a detached `git worktree` at `~/.gstack-brain-worktree/`, registers it as a federated source on gbrain, runs initial backfill, and supports `--strict` (Step 7 strictness), `--uninstall` (full teardown including future-launchd plist), and `--probe` (read-only state inspection). All idempotent. The helper depends on `jq` (transitive via `gstack-gbrain-detect`).
 
+The helper locks the database URL at startup (precedence: `--database-url` flag > `GBRAIN_DATABASE_URL`/`DATABASE_URL` env > read once from `~/.gbrain/config.json`) and exports it as `GBRAIN_DATABASE_URL` for every child `gbrain` invocation. This means external rewrites of `~/.gbrain/config.json` mid-sync (e.g., a concurrent `gbrain init --non-interactive` running in another workspace) cannot redirect the wireup at a different brain. Per gbrain's `loadConfig()`, env-var URLs override the file. Step 7 of `/setup-gbrain` reads the URL out of `config.json` once and passes it explicitly via `--database-url`, so the wireup is robust against config flips during the seconds-to-minutes sync window.
+
 `/setup-gbrain` Step 7 now invokes the helper with `--strict` after `gstack-brain-init`. `/gstack-upgrade` invokes the helper without `--strict` via `gstack-upgrade/migrations/v1.12.3.0.sh` so missing/old gbrain is a benign skip during batch upgrade. `bin/gstack-brain-restore` invokes the helper after the initial clone so a 2nd Mac gets the wireup automatically. `bin/gstack-brain-uninstall` invokes `--uninstall` plus removes legacy `consumers.json`.
 
 `bin/gstack-brain-init` drops 60 lines of dead consumer-registration code (the HTTP POST block, the `consumers.json` writer, the chore commit). `bin/gstack-brain-restore` drops the 18-line `consumers.json` token-rehydration block (the only consumer that used it never had real tokens). `bin/gstack-brain-consumer` is marked deprecated in its header docstring; removal in v1.13.0.0 after one cycle of grace.

bin/gstack-gbrain-source-wireup

@@ -8,7 +8,9 @@
 #
 # Usage:
 #   gstack-gbrain-source-wireup [--strict] [--source-id <id>] [--no-pull]
+#                               [--database-url <url>]
 #   gstack-gbrain-source-wireup --uninstall [--source-id <id>]
+#                               [--database-url <url>]
 #   gstack-gbrain-source-wireup --probe
 #   gstack-gbrain-source-wireup --help
 #
@@ -25,6 +27,14 @@
 #   GSTACK_BRAIN_NO_SYNC — skip the gbrain sync step (tests; helper still
 #                          ensures source registration)
 #
+# Defense against external rewrites of ~/.gbrain/config.json:
+# At helper startup we capture the database URL ONCE — from --database-url,
+# from GBRAIN_DATABASE_URL/DATABASE_URL env, or from ~/.gbrain/config.json —
+# and export it as GBRAIN_DATABASE_URL for every child `gbrain` invocation.
+# That env var overrides whatever's in config.json (per gbrain's loadConfig
+# at src/core/config.ts:53), so a process that flips config.json mid-sync
+# can't redirect us at a different brain mid-stream.
+#
 # Depends on: jq (transitive via gstack-gbrain-detect).
 
 set -euo pipefail
@@ -36,25 +46,54 @@ GSTACK_HOME="${GSTACK_HOME:-$HOME/.gstack}"
 WORKTREE="${GSTACK_BRAIN_WORKTREE:-$HOME/.gstack-brain-worktree}"
 REMOTE_FILE="$HOME/.gstack-brain-remote.txt"
 PLIST_PATH="$HOME/Library/LaunchAgents/com.gstack.brain-sync.plist"
+GBRAIN_CONFIG="$HOME/.gbrain/config.json"
 
 # ---- arg parse ----
 MODE="wireup"
 STRICT=0
 NO_PULL=0
 SOURCE_ID=""
+DATABASE_URL_ARG=""
 
 while [ $# -gt 0 ]; do
   case "$1" in
-    --uninstall)   MODE="uninstall"; shift ;;
-    --probe)       MODE="probe"; shift ;;
-    --strict)      STRICT=1; shift ;;
-    --no-pull)     NO_PULL=1; shift ;;
-    --source-id)   SOURCE_ID="$2"; shift 2 ;;
-    --help|-h)     sed -n '2,28p' "$0" | sed 's/^# \{0,1\}//'; exit 0 ;;
-    *)             echo "Unknown flag: $1" >&2; exit 1 ;;
+    --uninstall)     MODE="uninstall"; shift ;;
+    --probe)         MODE="probe"; shift ;;
+    --strict)        STRICT=1; shift ;;
+    --no-pull)       NO_PULL=1; shift ;;
+    --source-id)     SOURCE_ID="$2"; shift 2 ;;
+    --database-url)  DATABASE_URL_ARG="$2"; shift 2 ;;
+    --help|-h)       sed -n '2,40p' "$0" | sed 's/^# \{0,1\}//'; exit 0 ;;
+    *)               echo "Unknown flag: $1" >&2; exit 1 ;;
   esac
 done
 
+# ---- lock the database URL at startup ----
+# Precedence: --database-url flag > existing GBRAIN_DATABASE_URL/DATABASE_URL
+# env > read once from ~/.gbrain/config.json. Whichever wins gets exported as
+# GBRAIN_DATABASE_URL so every child `gbrain` invocation uses THAT brain even
+# if config.json is rewritten by another process during the wireup.
+_locked_url=""
+if [ -n "$DATABASE_URL_ARG" ]; then
+  _locked_url="$DATABASE_URL_ARG"
+elif [ -n "${GBRAIN_DATABASE_URL:-}" ]; then
+  _locked_url="$GBRAIN_DATABASE_URL"
+elif [ -n "${DATABASE_URL:-}" ]; then
+  _locked_url="$DATABASE_URL"
+elif [ -f "$GBRAIN_CONFIG" ]; then
+  _locked_url=$(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
+" 2>/dev/null)
+fi
+if [ -n "$_locked_url" ]; then
+  export GBRAIN_DATABASE_URL="$_locked_url"
+fi
+
 prefix() { sed 's/^/gstack-gbrain-source-wireup: /' >&2; }
 warn()   { echo "$*" | prefix; }
 die()    { warn "$*"; exit "${2:-1}"; }

setup-gbrain/SKILL.md

@@ -1370,8 +1370,22 @@ 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
-~/.claude/skills/gstack/bin/gstack-gbrain-source-wireup --strict
+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,

setup-gbrain/SKILL.md.tmpl

@@ -372,8 +372,22 @@ 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
-~/.claude/skills/gstack/bin/gstack-gbrain-source-wireup --strict
+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,

test/gstack-gbrain-source-wireup.test.ts

@@ -42,7 +42,12 @@ function makeFakeGbrain(opts: {
   const script = `#!/bin/bash
 LOG="${gbrainCallLog}"
 STATE="${gbrainStateFile}"
-echo "gbrain $@" >> "$LOG"
+# Record the call AND any GBRAIN_DATABASE_URL that the parent passed via env.
+# Format: "gbrain <args> [GBRAIN_DATABASE_URL=<url>]" so tests can assert
+# the wireup helper exported the locked URL into our env.
+LINE="gbrain $@"
+[ -n "\${GBRAIN_DATABASE_URL:-}" ] && LINE="\$LINE [GBRAIN_DATABASE_URL=\$GBRAIN_DATABASE_URL]"
+echo "\$LINE" >> "$LOG"
 
 # --version
 if [ "$1" = "--version" ]; then
@@ -286,6 +291,74 @@ describe('gstack-gbrain-source-wireup — wireup mode', () => {
   });
 });
 
+describe('gstack-gbrain-source-wireup — --database-url lock (defends against external config rewrites)', () => {
+  test('--database-url flag is exported as GBRAIN_DATABASE_URL to child gbrain calls', () => {
+    setupGstackRepo('git@github.com:user/gstack-brain-user.git');
+    makeFakeGbrain({});
+    const TARGET = 'postgresql://postgres.abc:pw@aws.pooler.supabase.com:5432/postgres';
+    const r = run(['--database-url', TARGET], { env: { GSTACK_BRAIN_NO_SYNC: '1' } });
+    expect(r.status).toBe(0);
+    const calls = gbrainCalls();
+    // every gbrain invocation should carry the locked URL
+    const writingCalls = calls.filter((c) => c.includes('sources') || c.includes('sync'));
+    expect(writingCalls.length).toBeGreaterThan(0);
+    for (const c of writingCalls) {
+      expect(c).toContain(`[GBRAIN_DATABASE_URL=${TARGET}]`);
+    }
+  });
+
+  test('falls back to ~/.gbrain/config.json database_url when no flag and no env', () => {
+    setupGstackRepo('git@github.com:user/gstack-brain-user.git');
+    makeFakeGbrain({});
+    const FILE_URL = 'postgresql://postgres.xyz:pw@aws.pooler.supabase.com:5432/postgres';
+    fs.mkdirSync(path.join(tmpHome, '.gbrain'), { recursive: true });
+    fs.writeFileSync(
+      path.join(tmpHome, '.gbrain', 'config.json'),
+      JSON.stringify({ engine: 'postgres', database_url: FILE_URL })
+    );
+    // Important: don't pass GBRAIN_DATABASE_URL or DATABASE_URL in env; helper
+    // should read from $HOME/.gbrain/config.json (HOME is tmpHome here).
+    const r = run([], {
+      env: {
+        GSTACK_BRAIN_NO_SYNC: '1',
+        GBRAIN_DATABASE_URL: '',
+        DATABASE_URL: '',
+      },
+    });
+    expect(r.status).toBe(0);
+    const calls = gbrainCalls();
+    const writingCalls = calls.filter((c) => c.includes('sources add'));
+    expect(writingCalls.length).toBe(1);
+    expect(writingCalls[0]).toContain(`[GBRAIN_DATABASE_URL=${FILE_URL}]`);
+  });
+
+  test('--database-url overrides env GBRAIN_DATABASE_URL and config.json', () => {
+    setupGstackRepo('git@github.com:user/gstack-brain-user.git');
+    makeFakeGbrain({});
+    const FLAG_URL = 'postgresql://postgres.flag:pw@a.b:5432/postgres';
+    const ENV_URL = 'postgresql://postgres.env:pw@x.y:5432/postgres';
+    const FILE_URL = 'postgresql://postgres.file:pw@p.q:5432/postgres';
+    fs.mkdirSync(path.join(tmpHome, '.gbrain'), { recursive: true });
+    fs.writeFileSync(
+      path.join(tmpHome, '.gbrain', 'config.json'),
+      JSON.stringify({ engine: 'postgres', database_url: FILE_URL })
+    );
+    const r = run(['--database-url', FLAG_URL], {
+      env: {
+        GSTACK_BRAIN_NO_SYNC: '1',
+        GBRAIN_DATABASE_URL: ENV_URL,
+      },
+    });
+    expect(r.status).toBe(0);
+    const calls = gbrainCalls();
+    const writingCalls = calls.filter((c) => c.includes('sources add'));
+    expect(writingCalls.length).toBe(1);
+    expect(writingCalls[0]).toContain(`[GBRAIN_DATABASE_URL=${FLAG_URL}]`);
+    expect(writingCalls[0]).not.toContain(ENV_URL);
+    expect(writingCalls[0]).not.toContain(FILE_URL);
+  });
+});
+
 describe('gstack-gbrain-source-wireup — uninstall mode', () => {
   test('after wireup: removes source + worktree', () => {
     setupGstackRepo('git@github.com:user/gstack-brain-user.git');