diff --git a/src/cfg.js b/src/cfg.js
index 23e9aae..d0f4d2e 100644
--- a/src/cfg.js
+++ b/src/cfg.js
@@ -1046,9 +1046,17 @@ export function buildFunctionCFG(functionNode, langId) {
 export async function buildCFGData(db, fileSymbols, rootDir, _engineOpts) {
   // Lazily init WASM parsers if needed
   let parsers = null;
-  let extToLang = null;
   let needsFallback = false;
 
+  // Always build ext→langId map so native-only builds (where _langId is unset)
+  // can still derive the language from the file extension.
+  const extToLang = new Map();
+  for (const entry of LANGUAGE_REGISTRY) {
+    for (const ext of entry.extensions) {
+      extToLang.set(ext, entry.id);
+    }
+  }
+
   for (const [relPath, symbols] of fileSymbols) {
     if (!symbols._tree) {
       const ext = path.extname(relPath).toLowerCase();
@@ -1068,12 +1076,6 @@ export async function buildCFGData(db, fileSymbols, rootDir, _engineOpts) {
   if (needsFallback) {
     const { createParsers } = await import('./parser.js');
     parsers = await createParsers();
-    extToLang = new Map();
-    for (const entry of LANGUAGE_REGISTRY) {
-      for (const ext of entry.extensions) {
-        extToLang.set(ext, entry.id);
-      }
-    }
   }
 
   let getParserFn = null;
@@ -1115,7 +1117,7 @@ export async function buildCFGData(db, fileSymbols, rootDir, _engineOpts) {
 
       // WASM fallback if no cached tree and not all native
       if (!tree && !allNative) {
-        if (!extToLang || !getParserFn) continue;
+        if (!getParserFn) continue;
         langId = extToLang.get(ext);
         if (!langId || !CFG_LANG_IDS.has(langId)) continue;
 
@@ -1138,7 +1140,7 @@ export async function buildCFGData(db, fileSymbols, rootDir, _engineOpts) {
       }
 
       if (!langId) {
-        langId = extToLang ? extToLang.get(ext) : null;
+        langId = extToLang.get(ext);
         if (!langId) continue;
       }
 
diff --git a/src/dataflow.js b/src/dataflow.js
index 08b982f..e5b926d 100644
--- a/src/dataflow.js
+++ b/src/dataflow.js
@@ -1005,9 +1005,17 @@ function collectIdentifiers(node, out, rules) {
 export async function buildDataflowEdges(db, fileSymbols, rootDir, _engineOpts) {
   // Lazily init WASM parsers if needed
   let parsers = null;
-  let extToLang = null;
   let needsFallback = false;
 
+  // Always build ext→langId map so native-only builds (where _langId is unset)
+  // can still derive the language from the file extension.
+  const extToLang = new Map();
+  for (const entry of LANGUAGE_REGISTRY) {
+    for (const ext of entry.extensions) {
+      extToLang.set(ext, entry.id);
+    }
+  }
+
   for (const [relPath, symbols] of fileSymbols) {
     if (!symbols._tree && !symbols.dataflow) {
       const ext = path.extname(relPath).toLowerCase();
@@ -1021,12 +1029,6 @@ export async function buildDataflowEdges(db, fileSymbols, rootDir, _engineOpts)
   if (needsFallback) {
     const { createParsers } = await import('./parser.js');
     parsers = await createParsers();
-    extToLang = new Map();
-    for (const entry of LANGUAGE_REGISTRY) {
-      for (const ext of entry.extensions) {
-        extToLang.set(ext, entry.id);
-      }
-    }
   }
 
   let getParserFn = null;
@@ -1069,7 +1071,7 @@ export async function buildDataflowEdges(db, fileSymbols, rootDir, _engineOpts)
 
         // WASM fallback if no cached tree
         if (!tree) {
-          if (!extToLang || !getParserFn) continue;
+          if (!getParserFn) continue;
           langId = extToLang.get(ext);
           if (!langId || !DATAFLOW_LANG_IDS.has(langId)) continue;
 
@@ -1092,7 +1094,7 @@ export async function buildDataflowEdges(db, fileSymbols, rootDir, _engineOpts)
         }
 
         if (!langId) {
-          langId = extToLang ? extToLang.get(ext) : null;
+          langId = extToLang.get(ext);
           if (!langId) continue;
         }