diff --git a/.github/workflows/presubmit.yaml b/.github/workflows/presubmit.yaml
index dc152e2bec8..74035893d23 100644
--- a/.github/workflows/presubmit.yaml
+++ b/.github/workflows/presubmit.yaml
@@ -36,10 +36,15 @@ jobs:
         with:
           fetch-depth: 300
           persist-credentials: false
+      - name: Fetch base branch for linter diff
+        run: git fetch origin ${{ github.base_ref }}:refs/remotes/origin/${{ github.base_ref }}
       - name: Use Node.js 24
         uses: actions/setup-node@249970729cb0ef3589644e2896645e5dc5ba9c38 # v6.5.0
         with:
           node-version: 24
       - run: npm install
-      - run: npm run lint
+      - run: node ./bin/linter.mjs
         name: Run monorepo linter
+        env:
+          STRICT: "true"
+          GIT_DIFF_ARG: "origin/${{ github.base_ref }}...HEAD"
diff --git a/bin/linter.mjs b/bin/linter.mjs
index bd9a976ca94..acf3a27be8a 100755
--- a/bin/linter.mjs
+++ b/bin/linter.mjs
@@ -26,7 +26,13 @@ const tsconfigCache = new Map();
 // --- Main Runner (Entry Point) ---
 async function run() {
   try {
-    const changedTsFiles = getChangedFiles();
+    const isStrict = Boolean(process.env.STRICT);
+    let changedTsFiles;
+    if (isStrict) {
+      changedTsFiles = getChangedFilesStrict();
+    } else {
+      changedTsFiles = getChangedFiles();
+    }
 
     if (changedTsFiles.length === 0) {
       console.log('No TypeScript files changed. Skipping checks.');
@@ -63,19 +69,60 @@ function runGit(args, options = {}) {
   });
 }
 
+function getChangedFilesStrict() {
+  const gitDiffArg = process.env.GIT_DIFF_ARG;
+
+  if (!gitDiffArg) {
+    throw new Error(
+      'Strict mode is enabled, but GIT_DIFF_ARG environment variable was not provided. ' +
+      'Please set the GIT_DIFF_ARG environment variable.'
+    );
+  }
+
+  console.log(`Strict mode enabled. Comparing using GIT_DIFF_ARG: ${gitDiffArg}`);
+
+  const args = gitDiffArg.trim().split(/\s+/);
+
+  try {
+    runGit(['diff', '--quiet', ...args]);
+  } catch (err) {
+    if (err.status !== 1) {
+      throw new Error(
+        `Strict mode error: git diff --quiet ${gitDiffArg} failed with exit code ${err.status}.\n` +
+        `Ensure that the git reference '${gitDiffArg}' exists locally and that you have fetched the required commits/branches.\n` +
+        `Details: ${String(err.stderr || err.message || '').trim()}`
+      );
+    }
+  }
+
+  const output = runGit([
+    'diff',
+    '--name-only',
+    '--diff-filter=ACMRT',
+    ...args,
+    '--',
+    '*.ts',
+  ]);
+  return output
+    .split('\n')
+    .map(f => f.trim())
+    .filter(f => f.length > 0 && existsSync(f));
+}
+
 /**
- * Returns a list of changed TypeScript files comparing against target branches/references.
+ * Returns a list of changed TypeScript files comparing against target branches/references when not in strict mode.
  */
 function getChangedFiles() {
-  const base = process.env.GITHUB_BASE_REF || 'main';
-  const refsToTry = [
-    base,
-    `upstream/${base}`,
-    `origin/${base}`,
-    'FETCH_HEAD',
-    'HEAD~1',
-    'HEAD^',
-  ];
+  let currentBranch = '';
+  try {
+    currentBranch = runGit(['rev-parse', '--abbrev-ref', 'HEAD']).trim();
+  } catch {
+    // Continue with fallback refs if branch detection fails
+  }
+
+  const refsToTry = (currentBranch === 'main')
+    ? ['origin/main', 'upstream/main', 'HEAD~1']
+    : ['upstream/main', 'origin/main', 'main'];
 
   for (const ref of refsToTry) {
     try {
@@ -83,36 +130,21 @@ function getChangedFiles() {
         'diff',
         '--name-only',
         '--diff-filter=ACMRT',
-        ref,
+        `${ref}...HEAD`,
         '--',
         '*.ts',
       ]);
+      console.log(`Comparing against base reference: ${ref}`);
       return output
         .split('\n')
         .map(f => f.trim())
         .filter(f => f.length > 0 && existsSync(f));
     } catch {
-      // Continue to the next fallback ref
+      // Continue to next ref if this one fails/does not exist
     }
   }
 
-  // Fallback to checking uncommitted working tree changes against HEAD if all specific refs fail
-  try {
-    const output = runGit([
-      'diff',
-      '--name-only',
-      '--diff-filter=ACMRT',
-      'HEAD',
-      '--',
-      '*.ts',
-    ]);
-    return output
-      .split('\n')
-      .map(f => f.trim())
-      .filter(f => f.length > 0 && existsSync(f));
-  } catch {
-    return [];
-  }
+  throw new Error(`Failed to determine changed files. Tried refs: ${refsToTry.join(', ')}`);
 }
 
 // --- ESLint Checker ---