Files
gbrain/test
Garry TanandClaude Opus 4.7 306fc0e1ef fix(init): error on existing-brain dim mismatch + embedding-migration recipe
Adds A4 hard-error path: when `gbrain init --embedding-dimensions N` is
run against an existing brain whose `content_chunks.embedding` column is
a different `vector(M)`, init exits 1 with an inline four-step ALTER
recipe and a pointer to docs/embedding-migrations.md.

This kills the silent-corruption pattern surfaced by issue #673: the
v0.27 schema seeded `('embedding_dimensions', '1536')` regardless of the
flag, so users got a config saying 768 but a column at 1536 — first
sync write blew up with "expected 1536, got 768."

A4's contract:
  1. Connect to engine BEFORE saveConfig so we can read the live column type
  2. If column exists AND dim != requested, exit 1 (loud failure)
  3. If column doesn't exist (fresh init) OR dim matches, proceed normally

Recipe in docs/embedding-migrations.md (and inlined in init's error
output) covers all four destructive steps codex's plan-review caught:
  1. DROP INDEX IF EXISTS idx_chunks_embedding (HNSW won't survive ALTER)
  2. ALTER TABLE content_chunks ALTER COLUMN embedding TYPE vector(N)
  3. UPDATE content_chunks SET embedding = NULL, embedded_at = NULL
  4. CREATE INDEX HNSW *only if N <= 2000* (pgvector cap)

Step 4 is conditional: dims > 2000 (e.g. Voyage 4 Large 2048d) cannot
be HNSW-indexed in pgvector; the recipe explicitly says "Skip reindex"
in that case so the user doesn't paste a CREATE INDEX that crashes.

Helper `readContentChunksEmbeddingDim` and message builder
`embeddingMismatchMessage` live in src/core/embedding-dim-check.ts so
doctor 8b (next commit) can reuse the same source of truth.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-05-06 18:01:18 -07:00
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