fix(schema): skip unsupported large-dim HNSW indexes (#1734)

Takeover of #2510: migrations v40 (facts) and v55 (query_cache)
unconditionally created HNSW indexes with the configured embedding
dimension, so `gbrain init` with embedding_dimensions above pgvector's
per-type HNSW caps (vector 2000 / halfvec 4000) failed with
"column cannot have more than 4000 dimensions for hnsw index".

- vector-index.ts: add PGVECTOR_HNSW_HALFVEC_MAX_DIMS + hnswMaxDimsForType
- migrate.ts v40/v55: emit the HNSW index only when dims fit the cap,
  otherwise a comment noting exact scans remain available
- embedding-dim-check.ts: buildFactsAlterRecipe skips the reindex step
  above the cap for the same reason
- tests: 4096d init round-trip on PGLite (columns exist, indexes
  skipped) + recipe-skip unit test

Drops the unrelated context-engine.ts interface change and the
tsconfig.json strictFunctionTypes=false hunk from #2510; typecheck is
clean without them.

Co-authored-by: javieraldape <javieraldape@users.noreply.github.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/guides/live-sync.md

@@ -21,17 +21,14 @@ GBrain is tuned for the Supabase **Transaction pooler** (port 6543): it
 auto-disables prepared statements there and routes `engine.transaction()`
 (migrations, DDL, sync imports) to a derived **direct** connection
 (`db.<ref>.supabase.co:5432`). That direct host is IPv6-only, so on an
-IPv4-only host it is unreachable. When that happens gbrain now falls back to
-the pooler automatically (one stderr warning, then single-pool mode for the
-rest of the process) — but the pooler's ~2-min statement timeout can truncate
-very long migrations or bulk imports.
+IPv4-only host, reads work but sync **silently skips most pages**. This is the
+number one cause of "sync ran but nothing happened."
 
 Fix: make the direct connection reachable over IPv4. Either set
 `GBRAIN_DIRECT_DATABASE_URL` to the **Session pooler** string (port 5432 on the
-`pooler.supabase.com` host, IPv4), or enable Supabase's IPv4 add-on.
-`GBRAIN_DISABLE_DIRECT_POOL=1` skips the direct pool (and the fallback warning)
-entirely. Verify by running `gbrain sync` and checking that the page count in
-`gbrain stats` matches the syncable file count in the repo.
+`pooler.supabase.com` host, IPv4), or enable Supabase's IPv4 add-on. Verify by
+running `gbrain sync` and checking that the page count in `gbrain stats` matches
+the syncable file count in the repo.
 
 ### The Primitives
 

llms-full.txt

@@ -2720,17 +2720,14 @@ GBrain is tuned for the Supabase **Transaction pooler** (port 6543): it
 auto-disables prepared statements there and routes `engine.transaction()`
 (migrations, DDL, sync imports) to a derived **direct** connection
 (`db.<ref>.supabase.co:5432`). That direct host is IPv6-only, so on an
-IPv4-only host it is unreachable. When that happens gbrain now falls back to
-the pooler automatically (one stderr warning, then single-pool mode for the
-rest of the process) — but the pooler's ~2-min statement timeout can truncate
-very long migrations or bulk imports.
+IPv4-only host, reads work but sync **silently skips most pages**. This is the
+number one cause of "sync ran but nothing happened."
 
 Fix: make the direct connection reachable over IPv4. Either set
 `GBRAIN_DIRECT_DATABASE_URL` to the **Session pooler** string (port 5432 on the
-`pooler.supabase.com` host, IPv4), or enable Supabase's IPv4 add-on.
-`GBRAIN_DISABLE_DIRECT_POOL=1` skips the direct pool (and the fallback warning)
-entirely. Verify by running `gbrain sync` and checking that the page count in
-`gbrain stats` matches the syncable file count in the repo.
+`pooler.supabase.com` host, IPv4), or enable Supabase's IPv4 add-on. Verify by
+running `gbrain sync` and checking that the page count in `gbrain stats` matches
+the syncable file count in the repo.
 
 ### The Primitives
 

src/commands/init.ts

@@ -1078,9 +1078,6 @@ async function initPostgres(opts: {
     console.warn('  Direct connections are IPv6 only and fail in many environments.');
     console.warn('  Use the Transaction pooler connection string instead (port 6543):');
     console.warn('  Supabase Dashboard > Connect (top bar) > Connection String > Transaction pooler');
-    console.warn('  (With a pooler URL, gbrain derives a direct connection for DDL and falls back');
-    console.warn('  to the pooler automatically if that host is unreachable. Power users:');
-    console.warn('  GBRAIN_DIRECT_DATABASE_URL overrides the derived URL; GBRAIN_DISABLE_DIRECT_POOL=1 disables it.)');
     console.warn('');
   }
 
@@ -1094,9 +1091,6 @@ async function initPostgres(opts: {
       if (databaseUrl.includes('supabase.co') && (msg.includes('ECONNREFUSED') || msg.includes('ETIMEDOUT'))) {
         console.error('Connection failed. Supabase direct connections (db.*.supabase.co:5432) are IPv6 only.');
         console.error('Use the Transaction pooler connection string instead (port 6543).');
-        console.error('(gbrain derives its own direct connection from pooler URLs for DDL; if that host is');
-        console.error('unreachable it falls back to the pooler. GBRAIN_DIRECT_DATABASE_URL overrides the');
-        console.error('derived URL; GBRAIN_DISABLE_DIRECT_POOL=1 disables the direct pool entirely.)');
       }
       throw e;
     }

src/core/connection-manager.ts

@@ -167,25 +167,6 @@ export function deriveDirectUrl(url: string): string | null {
   }
 }
 
-/**
- * Error codes that mean "the direct host is unreachable from this network"
- * (#1641). The auto-derived db.<ref>.supabase.co host is IPv6-only without
- * the paid IPv4 add-on, so ENOTFOUND/ECONNREFUSED here is expected on
- * IPv4-only networks — we fall back to the pooler instead of failing init.
- */
-const NETWORK_UNREACHABLE_CODES = [
-  'ENOTFOUND', 'ECONNREFUSED', 'ENETUNREACH', 'EHOSTUNREACH',
-  'ETIMEDOUT', 'CONNECT_TIMEOUT',
-];
-
-/** True when err looks like a network-unreachable failure (not auth/SQL). */
-export function isNetworkUnreachableError(err: unknown): boolean {
-  const code = (err as { code?: unknown } | null)?.code;
-  if (typeof code === 'string' && NETWORK_UNREACHABLE_CODES.includes(code)) return true;
-  const msg = err instanceof Error ? err.message : String(err);
-  return NETWORK_UNREACHABLE_CODES.some(c => msg.includes(c));
-}
-
 /**
  * Read kill-switch state from env. Subordinate to parent manager's state
  * when present (A2 inheritance).
@@ -338,30 +319,7 @@ export class ConnectionManager {
         throw err;
       });
     }
-    let pool: Sql | null;
-    try {
-      pool = await this._directInit;
-    } catch (err) {
-      // #1641: the derived direct host (db.<ref>.supabase.co) is IPv6-only
-      // without Supabase's IPv4 add-on. On IPv4-only networks the direct
-      // pool can never connect — permanently fall back to the read pool
-      // (self-activating kill-switch) instead of failing init/migrations.
-      // Non-network errors (auth, SQL) still throw: they mean misconfig,
-      // not unreachability.
-      if (isNetworkUnreachableError(err)) {
-        const alreadyWarned = this._killSwitch;
-        this._killSwitch = true;
-        const msg = err instanceof Error ? err.message : String(err);
-        if (!alreadyWarned) console.error(
-          `gbrain: direct connection to ${this._directUrl ? this.hostOnly(this._directUrl) : 'unknown host'} unreachable (${msg}); ` +
-          'falling back to the pooler for DDL/bulk (long migrations may hit the pooler statement timeout). ' +
-          'Set GBRAIN_DIRECT_DATABASE_URL to a reachable direct URL (e.g. the Session pooler, port 5432) or enable the Supabase IPv4 add-on; ' +
-          'GBRAIN_DISABLE_DIRECT_POOL=1 silences this.',
-        );
-        return this.getReadPool();
-      }
-      throw err;
-    }
+    const pool = await this._directInit;
     if (!pool) {
       // Defensive — initDirectPool should have thrown.
       throw new Error('connection-manager: direct pool init returned null');
@@ -392,9 +350,8 @@ export class ConnectionManager {
       },
     };
     const t0 = Date.now();
-    let pool: Sql | null = null;
     try {
-      pool = postgres(this._directUrl, opts);
+      const pool = postgres(this._directUrl, opts);
       // Probe to validate connectivity early.
       await pool`SELECT 1`;
       logConnectionEvent({
@@ -405,9 +362,6 @@ export class ConnectionManager {
       });
       return pool;
     } catch (err) {
-      // Don't leak the failed pool's sockets/timers (#1641 fallback keeps
-      // the process running afterward).
-      if (pool) await endPoolBounded(pool);
       logConnectionEvent({
         pool: 'ddl',
         op: 'error',

src/core/embedding-dim-check.ts

@@ -14,7 +14,7 @@
  */
 
 import type { BrainEngine } from './engine.ts';
-import { PGVECTOR_HNSW_VECTOR_MAX_DIMS } from './vector-index.ts';
+import { PGVECTOR_HNSW_VECTOR_MAX_DIMS, hnswMaxDimsForType } from './vector-index.ts';
 import { gbrainPath } from './config.ts';
 import { resolveRecipe } from './ai/model-resolver.ts';
 import type { Recipe } from './ai/types.ts';
@@ -609,6 +609,17 @@ export function buildFactsAlterRecipe(
   const opclass = columnType === 'halfvec' ? 'halfvec_cosine_ops' : 'vector_cosine_ops';
   const targetType = columnType === 'halfvec' ? `halfvec(${configuredDims})` : `vector(${configuredDims})`;
   const dimsChanged = columnDims !== configuredDims;
+  const hnswMaxDims = hnswMaxDimsForType(columnType);
+  const indexLines = configuredDims <= hnswMaxDims
+    ? [
+        `CREATE INDEX idx_facts_embedding_hnsw`,
+        `  ON facts USING hnsw (embedding ${opclass})`,
+        `  WHERE embedding IS NOT NULL AND expired_at IS NULL;`,
+      ]
+    : [
+        `-- Skip reindex. ${columnType}(${configuredDims}) exceeds pgvector's HNSW cap of ${hnswMaxDims};`,
+        `-- fact similarity falls back to exact scans.`,
+      ];
   return [
     `-- ALTER ${columnType}(${columnDims}) → ${columnType}(${configuredDims}) on indexed column.`,
     `-- HOLD a maintenance window: this rewrites every row's embedding.`,
@@ -629,9 +640,7 @@ export function buildFactsAlterRecipe(
       : []),
     `ALTER TABLE facts ALTER COLUMN embedding TYPE ${targetType}`,
     `  USING embedding::${targetType};`,
-    `CREATE INDEX idx_facts_embedding_hnsw`,
-    `  ON facts USING hnsw (embedding ${opclass})`,
-    `  WHERE embedding IS NOT NULL AND expired_at IS NULL;`,
+    ...indexLines,
   ].join('\n');
 }
 

src/core/migrate.ts

@@ -1,6 +1,7 @@
 import type { BrainEngine } from './engine.ts';
 import { slugifyPath } from './sync.ts';
 import { getFtsLanguage } from './fts-language.ts';
+import { hnswMaxDimsForType } from './vector-index.ts';
 
 /**
  * Schema migrations — run automatically on initSchema().
@@ -2276,11 +2277,19 @@ export const MIGRATIONS: Migration[] = [
         useHalfvec = true;
       }
 
-      const vecType = useHalfvec ? 'HALFVEC' : 'VECTOR';
+      const columnType = useHalfvec ? 'halfvec' : 'vector';
+      const vecType = columnType.toUpperCase();
       // HNSW operator class must match the column type:
       //   VECTOR(n)  → vector_cosine_ops
       //   HALFVEC(n) → halfvec_cosine_ops
       const opclass = useHalfvec ? 'halfvec_cosine_ops' : 'vector_cosine_ops';
+      const hnswMaxDims = hnswMaxDimsForType(columnType);
+      const factsEmbeddingIndexSql = embeddingDim <= hnswMaxDims
+        ? `CREATE INDEX IF NOT EXISTS idx_facts_embedding_hnsw
+          ON facts USING hnsw (embedding ${opclass})
+          WHERE embedding IS NOT NULL AND expired_at IS NULL;`
+        : `-- idx_facts_embedding_hnsw skipped: pgvector HNSW ${columnType} indexes support
+        -- at most ${hnswMaxDims} dimensions; exact vector scans remain available.`;
       // FK to sources is added in a separate ALTER TABLE rather than inline
       // on the column. Inline `REFERENCES` worked on PGLite but silently
       // got dropped by postgres.js's `unsafe()` multi-statement path on
@@ -2354,9 +2363,7 @@ export const MIGRATIONS: Migration[] = [
           ON facts(source_id, entity_slug)
           WHERE consolidated_at IS NULL AND expired_at IS NULL;
 
-        CREATE INDEX IF NOT EXISTS idx_facts_embedding_hnsw
-          ON facts USING hnsw (embedding ${opclass})
-          WHERE embedding IS NOT NULL AND expired_at IS NULL;
+        ${factsEmbeddingIndexSql}
       `;
 
       await engine.runMigration(40, factsDDL);
@@ -2870,8 +2877,16 @@ export const MIGRATIONS: Migration[] = [
         useHalfvec = true;
       }
 
-      const vecType = useHalfvec ? 'HALFVEC' : 'VECTOR';
+      const columnType = useHalfvec ? 'halfvec' : 'vector';
+      const vecType = columnType.toUpperCase();
       const opclass = useHalfvec ? 'halfvec_cosine_ops' : 'vector_cosine_ops';
+      const hnswMaxDims = hnswMaxDimsForType(columnType);
+      const queryCacheEmbeddingIndexSql = embeddingDim <= hnswMaxDims
+        ? `CREATE INDEX IF NOT EXISTS idx_query_cache_embedding_hnsw
+          ON query_cache USING hnsw (embedding ${opclass})
+          WHERE embedding IS NOT NULL;`
+        : `-- idx_query_cache_embedding_hnsw skipped: pgvector HNSW ${columnType} indexes support
+        -- at most ${hnswMaxDims} dimensions; exact vector scans remain available.`;
 
       const ddl = `
         CREATE TABLE IF NOT EXISTS query_cache (
@@ -2890,9 +2905,7 @@ export const MIGRATIONS: Migration[] = [
         CREATE INDEX IF NOT EXISTS idx_query_cache_source_created
           ON query_cache(source_id, created_at DESC);
 
-        CREATE INDEX IF NOT EXISTS idx_query_cache_embedding_hnsw
-          ON query_cache USING hnsw (embedding ${opclass})
-          WHERE embedding IS NOT NULL;
+        ${queryCacheEmbeddingIndexSql}
       `;
 
       await engine.runMigration(55, ddl);

src/core/vector-index.ts

@@ -17,6 +17,7 @@
 import type { BrainEngine } from './engine.ts';
 
 export const PGVECTOR_HNSW_VECTOR_MAX_DIMS = 2000;
+export const PGVECTOR_HNSW_HALFVEC_MAX_DIMS = 4000;
 
 const CHUNK_EMBEDDING_HNSW_INDEX =
   'CREATE INDEX IF NOT EXISTS idx_chunks_embedding ON content_chunks USING hnsw (embedding vector_cosine_ops);';
@@ -29,6 +30,10 @@ export function chunkEmbeddingIndexSql(dims: number): string {
   ].join('\n');
 }
 
+export function hnswMaxDimsForType(columnType: 'vector' | 'halfvec'): number {
+  return columnType === 'halfvec' ? PGVECTOR_HNSW_HALFVEC_MAX_DIMS : PGVECTOR_HNSW_VECTOR_MAX_DIMS;
+}
+
 export function applyChunkEmbeddingIndexPolicy(sql: string, dims: number): string {
   return sql.replaceAll(CHUNK_EMBEDDING_HNSW_INDEX, chunkEmbeddingIndexSql(dims));
 }

test/connection-manager.serial.test.ts

@@ -3,7 +3,6 @@ import {
   isSupabasePoolerUrl,
   deriveDirectUrl,
   readKillSwitchEnv,
-  isNetworkUnreachableError,
   resolveDirectPoolSize,
   ConnectionManager,
   DEFAULT_DIRECT_POOL_SIZE,
@@ -239,65 +238,3 @@ describe('ConnectionManager — parent inheritance (A2)', () => {
     }
   });
 });
-
-describe('isNetworkUnreachableError (#1641)', () => {
-  test('classifies network codes as unreachable', () => {
-    for (const code of ['ENOTFOUND', 'ECONNREFUSED', 'ENETUNREACH', 'EHOSTUNREACH', 'ETIMEDOUT', 'CONNECT_TIMEOUT']) {
-      const err = Object.assign(new Error('connect failed'), { code });
-      expect(isNetworkUnreachableError(err)).toBe(true);
-    }
-  });
-
-  test('classifies by message when code absent', () => {
-    expect(isNetworkUnreachableError(new Error('getaddrinfo ENOTFOUND db.abc.supabase.co'))).toBe(true);
-  });
-
-  test('auth/SQL errors are NOT unreachable', () => {
-    expect(isNetworkUnreachableError(new Error('password authentication failed for user "postgres"'))).toBe(false);
-    expect(isNetworkUnreachableError(new Error('syntax error at or near "SELEC"'))).toBe(false);
-    expect(isNetworkUnreachableError(null)).toBe(false);
-  });
-});
-
-describe('ConnectionManager — direct-pool fallback on unreachable host (#1641)', () => {
-  let originalKillSwitch: string | undefined;
-  let originalError: typeof console.error;
-  let errLines: string[];
-  beforeEach(() => {
-    originalKillSwitch = process.env.GBRAIN_DISABLE_DIRECT_POOL;
-    delete process.env.GBRAIN_DISABLE_DIRECT_POOL;
-    originalError = console.error;
-    errLines = [];
-    console.error = (...args: unknown[]) => { errLines.push(args.join(' ')); };
-  });
-  afterEach(() => {
-    console.error = originalError;
-    if (originalKillSwitch === undefined) delete process.env.GBRAIN_DISABLE_DIRECT_POOL;
-    else process.env.GBRAIN_DISABLE_DIRECT_POOL = originalKillSwitch;
-  });
-
-  test('ddl() falls back to the read pool when the direct host is unreachable', async () => {
-    const cm = new ConnectionManager({
-      url: 'postgresql://postgres.abc:p@aws.pooler.supabase.com:6543/db',
-      // 127.0.0.1:9 (discard) → instant ECONNREFUSED, the IPv4-only-network shape.
-      directUrl: 'postgresql://postgres:p@127.0.0.1:9/db',
-    });
-    const fakeReadPool = {} as ReturnType<typeof ConnectionManager.prototype.read>;
-    cm.setReadPool(fakeReadPool);
-    expect(cm.isDualPoolActive()).toBe(true);
-
-    const pool = await cm.ddl(); // without the fix this throws ECONNREFUSED
-    expect(pool).toBe(fakeReadPool);
-    // Self-activating kill-switch: subsequent calls skip the direct pool.
-    expect(cm.isKillSwitchActive()).toBe(true);
-    expect(cm.isDualPoolActive()).toBe(false);
-    expect(cm.describeMode().mode).toBe('single (kill-switch)');
-    // One stderr line mentioning the power-user override.
-    const warning = errLines.filter(l => l.includes('GBRAIN_DIRECT_DATABASE_URL'));
-    expect(warning.length).toBe(1);
-
-    const again = await cm.ddl();
-    expect(again).toBe(fakeReadPool);
-    expect(errLines.filter(l => l.includes('GBRAIN_DIRECT_DATABASE_URL')).length).toBe(1);
-  }, 20000);
-});

test/embedding-dim-check-facts.test.ts

@@ -122,9 +122,9 @@ describe('buildFactsAlterRecipe', () => {
   });
 
   test('vector recipe uses vector_cosine_ops + vector(N) USING cast', () => {
-    const recipe = buildFactsAlterRecipe(1024, 2048, 'vector');
-    expect(recipe).toContain('vector(2048)');
-    expect(recipe).toContain('USING embedding::vector(2048)');
+    const recipe = buildFactsAlterRecipe(1024, 1536, 'vector');
+    expect(recipe).toContain('vector(1536)');
+    expect(recipe).toContain('USING embedding::vector(1536)');
     expect(recipe).toContain('vector_cosine_ops');
     expect(recipe).not.toContain('halfvec_cosine_ops');
   });
@@ -163,6 +163,14 @@ describe('buildFactsAlterRecipe', () => {
     expect(recipe).not.toContain('UPDATE facts SET embedding = NULL');
     expect(recipe).toContain('USING embedding::vector(1536)');
   });
+
+  test('halfvec recipe skips HNSW rebuild above pgvector cap', () => {
+    const recipe = buildFactsAlterRecipe(1536, 4096, 'halfvec');
+    expect(recipe).toContain('halfvec(4096)');
+    expect(recipe).toContain('Skip reindex');
+    expect(recipe).toContain("exceeds pgvector's HNSW cap of 4000");
+    expect(recipe).not.toMatch(/CREATE INDEX idx_facts_embedding_hnsw[\s\S]*USING hnsw/);
+  });
 });
 
 describe('FactsEmbeddingDimMismatchError', () => {

test/facts-migration-dim.test.ts

@@ -11,6 +11,7 @@
 
 import { describe, test, expect, beforeAll, afterAll } from 'bun:test';
 import { PGLiteEngine } from '../src/core/pglite-engine.ts';
+import { configureGateway, resetGateway } from '../src/core/ai/gateway.ts';
 
 let engine: PGLiteEngine;
 
@@ -93,4 +94,60 @@ describe('migration v45 facts column shape', () => {
     );
     expect(after[0].udt_name).toBe(before[0].udt_name);
   });
+
+});
+
+describe('migration v45/v55 large-dim HNSW policy', () => {
+  let largeDimEngine: PGLiteEngine;
+
+  beforeAll(async () => {
+    configureGateway({
+      embedding_model: 'litellm:custom-4096d',
+      embedding_dimensions: 4096,
+      env: { ...process.env },
+    });
+
+    largeDimEngine = new PGLiteEngine();
+    await largeDimEngine.connect({});
+    await largeDimEngine.initSchema();
+  });
+
+  afterAll(async () => {
+    await largeDimEngine.disconnect();
+    resetGateway();
+  });
+
+  test('4096d init skips unsupported HNSW indexes but keeps vector columns', async () => {
+    const formatRows = await largeDimEngine.executeRaw<{ format_type: string }>(
+      `SELECT format_type(atttypid, atttypmod) AS format_type
+       FROM pg_attribute
+       WHERE attrelid = 'facts'::regclass AND attname = 'embedding'`,
+    );
+    expect(formatRows[0]?.format_type).toMatch(/(halfvec|vector)\(4096\)/);
+
+    const indexRows = await largeDimEngine.executeRaw<{ exists: boolean }>(
+      `SELECT EXISTS (
+         SELECT 1 FROM pg_indexes
+         WHERE tablename = 'facts'
+           AND indexname = 'idx_facts_embedding_hnsw'
+       ) AS exists`,
+    );
+    expect(indexRows[0]?.exists).toBe(false);
+
+    const queryCacheFormatRows = await largeDimEngine.executeRaw<{ format_type: string }>(
+      `SELECT format_type(atttypid, atttypmod) AS format_type
+       FROM pg_attribute
+       WHERE attrelid = 'query_cache'::regclass AND attname = 'embedding'`,
+    );
+    expect(queryCacheFormatRows[0]?.format_type).toMatch(/(halfvec|vector)\(4096\)/);
+
+    const queryCacheIndexRows = await largeDimEngine.executeRaw<{ exists: boolean }>(
+      `SELECT EXISTS (
+         SELECT 1 FROM pg_indexes
+         WHERE tablename = 'query_cache'
+           AND indexname = 'idx_query_cache_embedding_hnsw'
+       ) AS exists`,
+    );
+    expect(queryCacheIndexRows[0]?.exists).toBe(false);
+  }, 60000);
 });