version: 0.18.0 feature_pitch: headline: "Multi-source brains: one DB, many repos. Federated and isolated sources coexist." description: | v0.17.0 introduces sources as a first-class primitive. A single gbrain backend can now hold multiple knowledge repos (wiki, gstack, yc-media, garrys-list, etc.) with clean scoping. Every page, file, and ingest_log row is scoped to a sources(id) row. Slugs are unique PER source, not globally — so two sources can both have topics/ai and they're different pages.

Per-source federation controls whether a source participates in
unqualified default search. `federated=true` (the default source
post-upgrade) joins the cross-source recall pool. `federated=false`
is isolation — only searched when explicitly named via `--source`.
This supports both "unified knowledge brain" (wiki + gstack, both
federated) and "purpose-separated brains" (yc-media + garrys-list,
both isolated) at the same time.

Per-directory default via `.gbrain-source` dotfile walk-up +
`GBRAIN_SOURCE` env var. Matches how kubectl / terraform / git
scope context. `cd ~/yc-media && gbrain query "X"` just works.

recipe: docs/guides/multi-source-brains.md tiers: null

v0.17.0 Migration: Multi-source brains

Audience: host agents reading this after gbrain apply-migrations has run. v0.17.0 installs a schema primitive for multi-source and exposes a sources CLI subcommand. Existing single-source brains keep working unchanged — they live under a seeded default source that preserves all prior behavior.

Mechanical migration: automatic, no action required

gbrain upgrade chains to gbrain apply-migrations --yes, which runs:

migration v16 — creates the sources table, seeds default with {"federated": true} config, inherits your pre-v0.17 sync.repo_path and sync.last_commit into the default row.
migration v17 — adds pages.source_id TEXT NOT NULL DEFAULT 'default' REFERENCES sources(id). Swaps the global UNIQUE(slug) constraint for composite UNIQUE(source_id, slug). Engine upserts simultaneously re-target ON CONFLICT (source_id, slug) so the constraint swap and the write path land atomically.

Both migrations are idempotent. Safe to re-run.

Later point releases (v0.17.1 and v0.18.0) will layer:

v0.17.1: ACL enforcement via a caller-identity primitive (the JSONB slot for access_policy ships now; enforcement waits for identity to be designed).
v0.18.0: Session ingest (.jsonl transcripts, raised size cap, session PageType) AND per-source retention/TTL at the same time.

What's new for agents

`sources` CLI subcommand

gbrain sources add <id> --path <p> [--name <n>] [--federated|--no-federated]
gbrain sources list [--json]
gbrain sources remove <id> [--yes] [--dry-run] [--keep-storage]
gbrain sources rename <id> <new-display-name>
gbrain sources default <id>
gbrain sources attach <id>    # write .gbrain-source in CWD
gbrain sources detach         # remove .gbrain-source
gbrain sources federate <id>
gbrain sources unfederate <id>

Source id rules: [a-z0-9](?:[a-z0-9-]{0,30}[a-z0-9])? — start + end with alnum, optional interior hyphens, max 32 chars. Immutable after creation (rename only changes the display name). Used as the stable citation key in [source:slug] references.

Per-directory default

Running gbrain sources attach gstack inside ~/.gstack/ writes a .gbrain-source file containing the single word gstack. Any gbrain command run from that directory (or any subdirectory) auto- selects gstack as the default source. gbrain sources detach removes the dotfile.

Resolution priority for the source a command targets:

Explicit --source <id> flag.
GBRAIN_SOURCE env var.
.gbrain-source dotfile in CWD or any ancestor.
Registered source whose local_path contains CWD (longest prefix wins — nested ~/gstack + ~/gstack/plans resolves to plans when deeper).
Brain-level default set via gbrain sources default <id>.
Literal default (backward-compat fallback).

Federation semantics

federated=true (only the default source has this out of the box, by migration): appears in unqualified gbrain search "X" results.
federated=false (new sources default to this): only appears when --source <id> is passed.

Interactive gbrain sources add prompts for federation; non- interactive uses --federated / --no-federated. Flip later with gbrain sources federate <id> / unfederate <id>.

Citation contract (for agents)

When agents get multi-source search results they MUST cite pages in [source-id:slug] form. Example:

You told me about the distillation protocol — see [wiki:topics/ai] and [gstack:plans/multi-repo] for where this came from.

Citations are keyed on sources.id (immutable), never sources.name (mutable display). If a user renames a source via gbrain sources rename, existing citations stay valid.

What's NOT in v0.17.0 yet

The following land in later Steps of this release cycle (already on the branch but gated until the matching code ships):

ingest_log.source_id — lands with Step 5 sync rewrite.
links.resolution_type + qualified [[source:slug]] wikilink parsing — lands with Step 4 link-extraction rewrite.
files.page_slug → page_id FK rewrite + file_migration_ledger
- storage object prefixing — lands with Step 7 storage backfill.
Source-aware search dedup — lands with Step 3.
gbrain sources import-from-github <url> — deferred to a patch release after the plumbing stabilizes.

Existing callers continue to work against the default source. No agent behavioral change is required; the new capabilities are opt-in via the new sources CLI surface.

Host-repo actions

None required. If your host agent manages the brain via the standard gbrain sync flow, it continues to target the default source and sees no behavioral change. To start using multi-source:

# Register a new source
gbrain sources add gstack --path ~/.gstack --no-federated

# Pin that directory to it so no --source flag is needed
cd ~/.gstack
gbrain sources attach gstack

# Ingest
gbrain sync --source gstack

Or see docs/guides/multi-source-brains.md for the full three canonical scenarios (unified, purpose-separated, mixed).

v0.18.0