fix(perf): wire engine selection through openRepo to fix query benchmarks

scripts/lib/fork-engine.ts

@@ -76,7 +76,7 @@ export function forkWorker(scriptPath, envKey, workerName, argv = [], timeoutMs
 		console.error(`\n[fork] Spawning ${workerName} worker (pid isolation)...`);
 
 		const child = fork(scriptPath, argv, {
-			env: { ...process.env, [envKey]: workerName },
+			env: { ...process.env, [envKey]: workerName, CODEGRAPH_ENGINE: workerName },
 			stdio: ['ignore', 'pipe', 'inherit', 'ipc'],
 		});
 

src/db/connection.ts

@@ -360,7 +360,7 @@ function openRepoNative(customDbPath?: string): { repo: Repository; close(): voi
  */
 export function openRepo(
   customDbPath?: string,
-  opts: { repo?: Repository } = {},
+  opts: { repo?: Repository; engine?: 'native' | 'wasm' | 'auto' } = {},
 ): { repo: Repository; close(): void } {
   if (opts.repo != null) {
     if (!(opts.repo instanceof Repository)) {
@@ -371,8 +371,12 @@ export function openRepo(
     return { repo: opts.repo, close() {} };
   }
 
+  // Respect explicit engine selection: opts.engine > CODEGRAPH_ENGINE env > auto.
+  // This ensures --engine wasm and benchmark workers bypass the native path.
+  const engine = opts.engine || process.env.CODEGRAPH_ENGINE || 'auto';
+
   // Try native rusqlite path first (Phase 6.14)
-  if (isNativeAvailable()) {
+  if (engine !== 'wasm' && isNativeAvailable()) {
     try {
       return openRepoNative(customDbPath);
     } catch (e) {
@@ -412,8 +416,11 @@ export function openReadonlyWithNative(customPath?: string): {
 } {
   const db = openReadonlyOrFail(customPath);
 
+  // Respect explicit engine selection, consistent with openRepo().
+  const engine = process.env.CODEGRAPH_ENGINE || 'auto';
+
   let nativeDb: NativeDatabase | undefined;
-  if (isNativeAvailable()) {
+  if (engine !== 'wasm' && isNativeAvailable()) {
     try {
       const dbPath = findDbPath(customPath);
       const native = getNative();

tests/benchmarks/regression-guard.test.ts

@@ -65,8 +65,19 @@ const SKIP_VERSIONS = new Set(['3.8.0']);
  * - 3.9.0:1-file rebuild — native incremental path re-runs graph-wide phases
  *   (structureMs, AST, CFG, dataflow) on single-file rebuilds. Documented in
  *   BUILD-BENCHMARKS.md Notes section with phase-level breakdown.
+ *
+ * - 3.9.0:fnDeps depth {1,3,5} — openRepo() always routed queries through the
+ *   native NAPI path regardless of engine selection, so both "wasm" and "native"
+ *   benchmark workers measured native rusqlite open/close overhead (~27ms vs
+ *   ~10ms with direct better-sqlite3). Fixed by wiring CODEGRAPH_ENGINE through
+ *   openRepo(); v3.10.0 benchmarks will reflect the corrected measurements.
  */
-const KNOWN_REGRESSIONS = new Set(['3.9.0:1-file rebuild']);
+const KNOWN_REGRESSIONS = new Set([
+  '3.9.0:1-file rebuild',
+  '3.9.0:fnDeps depth 1',
+  '3.9.0:fnDeps depth 3',
+  '3.9.0:fnDeps depth 5',
+]);
 
 /**
  * Maximum minor-version gap allowed for comparison. When the nearest
@@ -332,6 +343,38 @@ describe('Benchmark regression guard', () => {
     'INCREMENTAL_BENCHMARK_DATA',
   );
 
+  // Warn when KNOWN_REGRESSIONS entries are stale (more than 1 minor version
+  // behind the current package version).  This makes the stale-exemption
+  // problem self-detecting rather than requiring manual bookkeeping.
+  test('KNOWN_REGRESSIONS entries are not stale', () => {
+    // eslint-disable-next-line @typescript-eslint/no-require-imports
+    const pkgVersion: string = JSON.parse(
+      fs.readFileSync(path.join(ROOT, 'package.json'), 'utf8'),
+    ).version;
+    const stale: string[] = [];
+    for (const entry of KNOWN_REGRESSIONS) {
+      const colonIdx = entry.indexOf(':');
+      if (colonIdx === -1) continue;
+      const entryVersion = entry.slice(0, colonIdx);
+      const gap = minorGap(entryVersion, pkgVersion);
+      if (gap > 1) {
+        stale.push(
+          `${entry} (version ${entryVersion} is ${gap} minor versions behind ${pkgVersion})`,
+        );
+      }
+    }
+    if (stale.length > 0) {
+      console.warn(
+        `[regression-guard] Stale KNOWN_REGRESSIONS entries — remove after verifying corrected data:\n  ${stale.join('\n  ')}`,
+      );
+    }
+    expect(
+      stale.length,
+      `KNOWN_REGRESSIONS has ${stale.length} stale entries (>1 minor version behind ${pkgVersion}). ` +
+        `Remove them after verifying the corrected benchmark data has landed:\n  ${stale.join('\n  ')}`,
+    ).toBe(0);
+  });
+
   // Validate newest-first ordering assumption for all history arrays
   test('build history is sorted newest-first', () => {
     assertNewestFirst(buildHistory, 'Build benchmark');