Postgres Adopt

The engine is the brain's foundation: PGLite is the zero-config floor, Postgres is where concurrency, multi-machine access, and 1000+ pages live. This skill answers "which one am I on?", prefers Postgres when the operator wants it, and moves data safely — never by flipping config.

Contract

This skill guarantees:

• Detection is engine-free and read-only: gbrain engine status --json answers with the database down (that is the point of the command).
• Engine changes NEVER happen by editing config. Moving data uses gbrain migrate --to <supabase|pglite> — which brings its own guardrails (quiesce mutex, resume manifest, non-empty-target guard, and a config flip only on a fully clean run). This skill wraps it; it never reimplements it.
• Provisioning consent is explicit: the docker rung needs --allow-docker, creating a database on a local server needs --allow-create-db. Headless mutation of infrastructure the operator didn't opt into never happens.

Step 1 — Detect

gbrain engine status --json

Branch on the output:

• effective_engine: "postgres" and (optionally) --probe says ok → report healthy, done.
• effective_engine: "postgres" but the probe fails → this is an ACCESS problem, not an adoption problem: route to db-repair.
• config_file_engine differs from effective_engine → an env URL is overriding the config file; tell the operator which one wins — the signal is db_url_source (env:GBRAIN_DATABASE_URL / env:DATABASE_URL means env wins; env.note additionally fires when both env URLs are set or the cwd-.env shadow guard excluded one).
• thin_client: true → the brain lives on a remote server; engine choices belong to that host. Stop.
• effective_engine: null (no brain) → Step 2.
• effective_engine: "pglite" with data → Step 3.

Step 2 — Fresh install, Postgres-first

gbrain init --prefer-postgres

The ladder tries, in order: an env URL → Supabase Management-API discovery (SUPABASE_ACCESS_TOKEN, plus SUPABASE_PROJECT_REF on multi-project accounts and SUPABASE_DB_PASSWORD for the connection string) → a local Postgres (only when PGHOST/PGPORT/PGUSER/PGPASSWORD are set or --local-postgres is passed) → docker → PGLite. Each unusable rung prints a one-line note and falls through; nothing is silent.

• Ask the operator BEFORE adding --allow-docker (it creates and owns a gbrain-postgres container that survives reboots) or --allow-create-db (it runs CREATE DATABASE on their local server).
• --json reports {engine, ladder_rung, url_source} — relay which rung won.
• If the ladder lands on PGLite, that is a fine outcome: say so, and note the upgrade path below is available whenever they want it.

Step 3 — Existing PGLite brain: migrate, don't flip

Confirm with the operator first (this copies every page/fact into the target and, only on a fully clean run, flips the config). Then:

gbrain migrate --to supabase --url <postgres-connection-string>

• A partial run leaves you on PGLite and exits non-zero; re-running the same command resumes from its manifest. Never "fix" a partial by editing config.
• After a clean run: gbrain doctor on the new engine; the old brain.pglite/ dir is preserved (doctor's pglite_leftovers tracks it).
• gbrain doctor's pglite_scale check warns at 1000+ pages — that warning is this skill's cue.

The tradeoff (say it when recommending)

Postgres wins on concurrency, multi-machine access, and scale. PGLite keeps the per-turn bootstrap hook lane (hook injection is PGLite-only today — docs/guides/bootstrap.md); on Postgres, ambient context rides MCP-every-session and the pull protocol instead. Recommend Postgres when the operator has concurrent agents, multiple machines, or a 1000+ page brain; otherwise PGLite is genuinely fine.

Anti-Patterns

• NEVER gbrain config set engine ... — it is refused by design; an engine flip without a data migration splits the brain across two stores.
• NEVER pick Postgres over a healthy PGLite brain without the migrate path.
• NEVER run the docker rung without the operator's explicit yes.
• NEVER paste or echo SUPABASE_ACCESS_TOKEN / passwords into output.

Output Format

Detection reports in one line; changes report in 2-4:

Engine: <pglite|postgres> (source: <db_url_source>)   [probe: ok, 42ms]
Action: <none | init rung that won | migrate --to supabase result>
Next:   <upgrade note, or "healthy — nothing to do">

Quote gbrain engine status output as-is (it is already redacted); name the winning ladder rung when an install ran; after a migration, include the target's gbrain doctor verdict.