diff --git a/USING_GBRAIN_WITH_GSTACK.md b/USING_GBRAIN_WITH_GSTACK.md
index 49781d7b8..f2b4a48ce 100644
--- a/USING_GBRAIN_WITH_GSTACK.md
+++ b/USING_GBRAIN_WITH_GSTACK.md
@@ -253,7 +253,8 @@ Gbrain itself ships with these that gstack wraps:
 | `SUPABASE_API_BASE` | `gstack-gbrain-supabase-provision` | Override the Management API host. Used by tests to point at a mock server. |
 | `GBRAIN_INSTALL_DIR` | `gstack-gbrain-install` | Override default install path (`~/gbrain`) |
 | `GSTACK_HOME` | every bin helper | Override `~/.gstack` state dir. Heavy test use. |
-| `OPENAI_API_KEY` | `gbrain embed` subprocess | Required for embeddings during `gbrain sync` / `/sync-gbrain`. Without it, pages are imported structurally (symbol tables, chunks) but semantic search degrades — you'll see `[gbrain] embedding failed for code file ... OpenAI embedding requires OPENAI_API_KEY` in the sync log. |
+| `VOYAGE_API_KEY` | `gbrain embed` subprocess; gstack PGLite init | When set, gstack inits PGLite with `voyage-code-3` (1024-dim), Voyage's code-specialized embedding model. Beats `voyage-4-large` and OpenAI `text-embedding-3-large` head-to-head on this codebase's symbol queries. See CHANGELOG v1.43.1.0 for the A/B numbers. |
+| `OPENAI_API_KEY` | `gbrain embed` subprocess | Used for embeddings during `gbrain sync` / `/sync-gbrain` when `VOYAGE_API_KEY` is not set (gbrain's auto-selected fallback, `text-embedding-3-large` 1536-dim). Without either key, pages are imported structurally (symbol tables, chunks) but semantic search degrades — you'll see `[gbrain] embedding failed for code file ...` in the sync log. |
 | `ANTHROPIC_API_KEY` | `claude-agent-sdk`, paid evals | Required for `bun run test:evals` and any direct `query()` call against Claude. |
 | `GSTACK_OPENAI_API_KEY` | `lib/conductor-env-shim.ts` | Conductor-injected fallback. Promoted to `OPENAI_API_KEY` when the canonical name is empty. |
 | `GSTACK_ANTHROPIC_API_KEY` | `lib/conductor-env-shim.ts` | Same pattern as above for Anthropic. |
@@ -347,7 +348,7 @@ Embeddings probably failed during import. Symbol queries (`code-def`, `code-refs
 [gbrain] embedding failed for code file <name>: OpenAI embedding requires OPENAI_API_KEY
 ```
 
-The fix is to put `OPENAI_API_KEY` in the process env before re-running. On a bare Mac shell, source it from `~/.zshrc` before calling. In Conductor, set `GSTACK_OPENAI_API_KEY` at the workspace level — `lib/conductor-env-shim.ts` promotes it to canonical automatically when imported. Re-run `/sync-gbrain --code-only` to backfill embeddings on already-imported pages.
+The fix is to put a provider API key in the process env before re-running. `VOYAGE_API_KEY` is preferred for code (gstack defaults PGLite to `voyage-code-3` when set); otherwise `OPENAI_API_KEY` falls back to `text-embedding-3-large`. On a bare Mac shell, source the key from `~/.zshrc` before calling. In Conductor, the `lib/conductor-env-shim.ts` shim promotes `GSTACK_ANTHROPIC_API_KEY` / `GSTACK_OPENAI_API_KEY` to their canonical names automatically; for `VOYAGE_API_KEY`, set it directly in your Conductor workspace env. Re-run `/sync-gbrain --code-only` to backfill embeddings on already-imported pages.
 
 ### `gbrain sync` blocked at a commit hash — `FILE_TOO_LARGE`