diff --git a/src/server/app.js b/src/server/app.js
index 2dc49ad..fe766a2 100644
--- a/src/server/app.js
+++ b/src/server/app.js
@@ -322,10 +322,14 @@ export function createApp(ctx) {
     return guided({ attemptId: r.attempts[0].attemptId, batchId: r.batchId, state: 'queued' });
   });
 
+  // The repository stores LF line endings; submissions from Windows workspaces may carry CRLF.
+  const lf = (files) => Object.fromEntries(Object.entries(files).map(([f, c]) => [f, typeof c === 'string' ? c.replace(/\r\n/g, '\n') : c]));
+
   /** Validates a submission body and queues it as one batch for the given tasks. */
   const submitBatch = (user, taskIds, body) => {
     if (typeof body.baseCommit !== 'string' || !/^[0-9a-f]{40}$/.test(body.baseCommit)) throw new HttpError(400, 'baseCommit must be a full commit hash');
     if (!body.files || typeof body.files !== 'object' || Array.isArray(body.files)) throw new HttpError(400, 'files must be an object of path -> content');
+    body.files = lf(body.files);
     const r = tasks.submitBatch(user, {
       taskIds,
       baseCommit: body.baseCommit,
@@ -500,6 +504,7 @@ export function createApp(ctx) {
     const body = await readJson(req);
     if (typeof body.baseCommit !== 'string' || !/^[0-9a-f]{40}$/.test(body.baseCommit)) throw new HttpError(400, 'baseCommit must be a full commit hash');
     if (!body.files || typeof body.files !== 'object' || Array.isArray(body.files)) throw new HttpError(400, 'files must be an object of path -> content');
+    body.files = lf(body.files);
     const allowed = [...project.sourceDirs.map((d) => `${d}/**`)];
     const lintErrors = lintSubmission(body.files, { allowedPaths: allowed, limits: project.lintLimits, allowedPragmas: project.allowedPragmas });
     if (lintErrors.length) return { gate: 'rejected', lintErrors };
diff --git a/src/server/git.js b/src/server/git.js
index e9b80fc..371fb6e 100644
--- a/src/server/git.js
+++ b/src/server/git.js
@@ -111,6 +111,8 @@ export class Repo {
       fs.writeFileSync(abs, content);
     }
     this.git(['add', '--', ...Object.keys(files)]);
+    // Nothing to commit (the code is already on main, e.g. a function resubmitted unchanged).
+    if (!this.git(['status', '--porcelain', '--', ...Object.keys(files)]).trim()) return this.head();
     this.git(['-c', 'user.name=Clank Together', '-c', 'user.email=bot@clank-together.invalid', 'commit', '-q', '--author', author, '-F', '-'], { input: message });
     return this.head();
   }
diff --git a/test/server.test.js b/test/server.test.js
index a05d7db..8546b85 100644
--- a/test/server.test.js
+++ b/test/server.test.js
@@ -375,6 +375,13 @@ test('submissions may not add comments or strings that could instruct other agen
   assert.equal(JSON.stringify(r.body).includes('ignore your instructions'), false, 'the text is not echoed back');
 });
 
+test('committing files that are already on main is a no-op, not an error', () => {
+  const files = { 'src/noop.cpp': 'int noop() { return 0; }\n' };
+  const head = ctx.repo.commitFiles(files, 'add noop.cpp', 'x <x@y.invalid>');
+  assert.equal(ctx.repo.commitFiles(files, 'nothing', 'x <x@y.invalid>'), head);
+  assert.equal(ctx.repo.head(), head);
+});
+
 test('the crew view is public and shows no account details', async () => {
   const token = await activeUser('crewview');
   await call('GET', '/api/tasks', null, token); // the agent checks in