diff --git a/gitnexus/src/core/ingestion/import-resolvers/standard.ts b/gitnexus/src/core/ingestion/import-resolvers/standard.ts
index f8aae96250..47e2dabb2e 100644
--- a/gitnexus/src/core/ingestion/import-resolvers/standard.ts
+++ b/gitnexus/src/core/ingestion/import-resolvers/standard.ts
@@ -128,7 +128,21 @@ export const resolveImportPath = (
 
   if (importPath.startsWith('.')) {
     const resolved = tryResolveWithExtensions(basePath, allFiles);
-    return cache(resolved);
+    if (resolved) return cache(resolved);
+
+    // TypeScript ESM: imports use .js/.jsx/.mjs/.cjs but source files are
+    // .ts/.tsx/.mts/.cts. Strip the JS-family extension and re-resolve.
+    // NOTE: This fallback only applies to relative imports. Path alias imports
+    // (e.g. @/utils.js via tsconfig paths) do not yet strip .js extensions —
+    // that is a known limitation tracked for follow-up.
+    if (language === SupportedLanguages.TypeScript || language === SupportedLanguages.JavaScript) {
+      const stripped = stripJsExtension(basePath);
+      if (stripped !== null) {
+        return cache(tryResolveWithExtensions(stripped, allFiles));
+      }
+    }
+
+    return cache(null);
   }
 
   // ---- Generic package/absolute import resolution (suffix matching) ----
@@ -182,3 +196,19 @@ export function resolveStandard(
 export function createStandardStrategy(language: SupportedLanguages): ImportResolverStrategy {
   return (raw, fp, ctx) => resolveStandard(raw, fp, ctx, language);
 }
+
+// ============================================================================
+// ESM extension helpers
+// ============================================================================
+
+/** JS-family extensions that TypeScript ESM maps to TS equivalents. */
+const JS_EXTENSION_PATTERN = /\.(js|jsx|mjs|cjs)$/;
+
+/**
+ * Strip a JS-family extension from a path, returning the stem.
+ * Returns `null` if the path does not end with a JS-family extension.
+ */
+export function stripJsExtension(path: string): string | null {
+  const match = JS_EXTENSION_PATTERN.exec(path);
+  return match ? path.slice(0, -match[0].length) : null;
+}
diff --git a/gitnexus/src/core/ingestion/import-resolvers/utils.ts b/gitnexus/src/core/ingestion/import-resolvers/utils.ts
index 8d915eb7fb..c4d36556c3 100644
--- a/gitnexus/src/core/ingestion/import-resolvers/utils.ts
+++ b/gitnexus/src/core/ingestion/import-resolvers/utils.ts
@@ -9,8 +9,12 @@ export const EXTENSIONS = [
   // TypeScript/JavaScript
   '.tsx',
   '.ts',
+  '.mts',
+  '.cts',
   '.jsx',
   '.js',
+  '.mjs',
+  '.cjs',
   '.vue',
   '/index.tsx',
   '/index.ts',
diff --git a/gitnexus/test/integration/resolvers/typescript-esm-js-extension.test.ts b/gitnexus/test/integration/resolvers/typescript-esm-js-extension.test.ts
new file mode 100644
index 0000000000..4760825637
--- /dev/null
+++ b/gitnexus/test/integration/resolvers/typescript-esm-js-extension.test.ts
@@ -0,0 +1,62 @@
+/**
+ * Integration test: TypeScript ESM .js extension imports produce CALLS edges.
+ *
+ * Verifies the full pipeline: .js import → resolveImportPath strips .js →
+ * resolves to .ts → scope-resolver emits CALLS edge.
+ */
+import { describe, it, expect, beforeAll, afterAll } from 'vitest';
+import path from 'path';
+import fs from 'node:fs';
+import os from 'node:os';
+import { getRelationships, runPipelineFromRepo, type PipelineResult } from './helpers.js';
+
+function writeFixtureRepo(root: string, files: Record<string, string>): void {
+  for (const [relPath, content] of Object.entries(files)) {
+    const fullPath = path.join(root, relPath);
+    fs.mkdirSync(path.dirname(fullPath), { recursive: true });
+    fs.writeFileSync(fullPath, content, 'utf8');
+  }
+}
+
+describe('TypeScript ESM .js extension → CALLS edges', () => {
+  let result: PipelineResult;
+  let repoDir: string | undefined;
+
+  beforeAll(async () => {
+    repoDir = fs.mkdtempSync(path.join(os.tmpdir(), 'gn-ts-esm-js-ext-'));
+    writeFixtureRepo(repoDir, {
+      'src/utils.ts': `
+export function estimateTokens(text: string): number {
+  return Math.ceil(text.length / 4);
+}
+`,
+      'src/index.ts': `
+import { estimateTokens } from './utils.js';
+
+export function processText(text: string): number {
+  return estimateTokens(text);
+}
+`,
+    });
+    result = await runPipelineFromRepo(repoDir, () => {});
+  }, 60000);
+
+  afterAll(() => {
+    if (repoDir !== undefined) fs.rmSync(repoDir, { recursive: true, force: true });
+  });
+
+  it('emits CALLS edge from processText → estimateTokens via .js import', () => {
+    const calls = getRelationships(result, 'CALLS');
+    const edge = calls.find((c) => c.source === 'processText' && c.target === 'estimateTokens');
+    expect(edge).toBeDefined();
+    expect(edge!.targetFilePath).toBe('src/utils.ts');
+  });
+
+  it('emits IMPORTS edge from index.ts → utils.ts', () => {
+    const imports = getRelationships(result, 'IMPORTS');
+    const edge = imports.find(
+      (e) => e.sourceFilePath === 'src/index.ts' && e.targetFilePath === 'src/utils.ts',
+    );
+    expect(edge).toBeDefined();
+  });
+});
diff --git a/gitnexus/test/unit/esm-extension-resolution.test.ts b/gitnexus/test/unit/esm-extension-resolution.test.ts
new file mode 100644
index 0000000000..69dc652cf3
--- /dev/null
+++ b/gitnexus/test/unit/esm-extension-resolution.test.ts
@@ -0,0 +1,153 @@
+/**
+ * Unit tests for TypeScript ESM .js extension resolution.
+ *
+ * TypeScript ESM requires imports to use .js extensions even when source
+ * files are .ts. The resolver must map .js → .ts (and .jsx → .tsx,
+ * .mjs → .mts, .cjs → .cts) when the literal .js file does not exist.
+ */
+
+import { describe, it, expect } from 'vitest';
+import { resolveImportPath } from '../../src/core/ingestion/import-resolvers/standard.js';
+import { stripJsExtension } from '../../src/core/ingestion/import-resolvers/standard.js';
+import { buildSuffixIndex } from '../../src/core/ingestion/import-resolvers/utils.js';
+import { SupportedLanguages } from 'gitnexus-shared';
+
+function makeCtx(files: string[]) {
+  // Match production normalization: only replace backslashes with forward slashes
+  const normalized = files.map((f) => f.replace(/\\/g, '/'));
+  const allFilesSet = new Set(files);
+  const index = buildSuffixIndex(normalized, files);
+  const cache = new Map<string, string | null>();
+  return { files, normalized, allFilesSet, index, cache };
+}
+
+function resolve(
+  currentFile: string,
+  importPath: string,
+  language: SupportedLanguages,
+  ctx: ReturnType<typeof makeCtx>,
+): string | null {
+  return resolveImportPath(
+    currentFile,
+    importPath,
+    ctx.allFilesSet,
+    ctx.files,
+    ctx.normalized,
+    ctx.cache,
+    language,
+    null,
+    ctx.index,
+  );
+}
+
+describe('TypeScript ESM .js extension resolution', () => {
+  it('resolves ./utils.js to ./utils.ts when .js does not exist', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/utils.ts']);
+    const result = resolve('src/index.ts', './utils.js', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/utils.ts');
+  });
+
+  it('resolves ./component.jsx to ./component.tsx', () => {
+    const ctx = makeCtx(['src/app.ts', 'src/component.tsx']);
+    const result = resolve('src/app.ts', './component.jsx', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/component.tsx');
+  });
+
+  it('resolves ./config.mjs to ./config.mts', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/config.mts']);
+    const result = resolve('src/index.ts', './config.mjs', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/config.mts');
+  });
+
+  it('resolves ./legacy.cjs to ./legacy.cts', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/legacy.cts']);
+    const result = resolve('src/index.ts', './legacy.cjs', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/legacy.cts');
+  });
+
+  it('prefers actual .js file when it exists', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/utils.js', 'src/utils.ts']);
+    const result = resolve('src/index.ts', './utils.js', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/utils.js');
+  });
+
+  it('resolves relative path with ../ and .js extension', () => {
+    const ctx = makeCtx(['src/helpers/token.ts', 'src/core/engine.ts']);
+    const result = resolve(
+      'src/core/engine.ts',
+      '../helpers/token.js',
+      SupportedLanguages.TypeScript,
+      ctx,
+    );
+    expect(result).toBe('src/helpers/token.ts');
+  });
+
+  it('works for JavaScript language too', () => {
+    const ctx = makeCtx(['src/index.js', 'src/utils.ts']);
+    const result = resolve('src/index.js', './utils.js', SupportedLanguages.JavaScript, ctx);
+    expect(result).toBe('src/utils.ts');
+  });
+
+  it('does NOT apply ESM fallback for non-TS/JS languages', () => {
+    const ctx = makeCtx(['src/main.py', 'src/utils.ts']);
+    const result = resolve('src/main.py', './utils.js', SupportedLanguages.Python, ctx);
+    expect(result).toBeNull();
+  });
+
+  it('returns null when neither .js nor .ts exists', () => {
+    const ctx = makeCtx(['src/index.ts']);
+    const result = resolve('src/index.ts', './missing.js', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBeNull();
+  });
+});
+
+describe('ESM extension resolution — .mjs/.cjs with competing siblings', () => {
+  it('resolves ./config.mjs to .ts when only .ts exists (no .mts)', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/config.ts']);
+    const result = resolve('src/index.ts', './config.mjs', SupportedLanguages.TypeScript, ctx);
+    // .ts wins because EXTENSIONS order tries .ts before .mts
+    expect(result).toBe('src/config.ts');
+  });
+
+  it('resolves ./config.mjs to .mts when both .ts and .mts exist', () => {
+    // Note: EXTENSIONS order is .tsx, .ts, .mts, .cts — so .ts wins over .mts.
+    // This is intentional for a source-analysis tool: we resolve to the first
+    // matching source file. In practice, having both config.ts and config.mts
+    // in the same directory is extremely rare.
+    const ctx = makeCtx(['src/index.ts', 'src/config.ts', 'src/config.mts']);
+    const result = resolve('src/index.ts', './config.mjs', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/config.ts');
+  });
+
+  it('resolves ./config.cjs to .cts when only .cts exists', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/config.cts']);
+    const result = resolve('src/index.ts', './config.cjs', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/config.cts');
+  });
+});
+
+describe('ESM extension resolution — directory index boundary', () => {
+  it('resolves ./dir.js to dir/index.ts when dir/ exists (bundler-mode)', () => {
+    // After stripping .js from "dir.js" → "dir", tryResolveWithExtensions probes
+    // "/index.ts" suffix. This matches bundler-mode behavior where bare directory
+    // imports resolve to index files. Intentional for source-analysis compatibility.
+    const ctx = makeCtx(['src/index.ts', 'src/dir/index.ts']);
+    const result = resolve('src/index.ts', './dir.js', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/dir/index.ts');
+  });
+
+  it('resolves ./dir/index.js to dir/index.ts', () => {
+    const ctx = makeCtx(['src/index.ts', 'src/dir/index.ts']);
+    const result = resolve('src/index.ts', './dir/index.js', SupportedLanguages.TypeScript, ctx);
+    expect(result).toBe('src/dir/index.ts');
+  });
+});
+
+describe('stripJsExtension', () => {
+  it('strips .js', () => expect(stripJsExtension('foo/bar.js')).toBe('foo/bar'));
+  it('strips .jsx', () => expect(stripJsExtension('foo/bar.jsx')).toBe('foo/bar'));
+  it('strips .mjs', () => expect(stripJsExtension('foo/bar.mjs')).toBe('foo/bar'));
+  it('strips .cjs', () => expect(stripJsExtension('foo/bar.cjs')).toBe('foo/bar'));
+  it('returns null for .ts', () => expect(stripJsExtension('foo/bar.ts')).toBeNull());
+  it('returns null for no extension', () => expect(stripJsExtension('foo/bar')).toBeNull());
+});