diff --git a/src/infrastructure/file-manager.test.ts b/src/infrastructure/file-manager.test.ts
new file mode 100644
index 0000000..79f4a7c
--- /dev/null
+++ b/src/infrastructure/file-manager.test.ts
@@ -0,0 +1,76 @@
+import { mkdtemp, readdir, readFile, rm, writeFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { FileManager } from './file-manager.ts';
+
+describe('FileManager', () => {
+  let basePath: string;
+  let fileManager: FileManager;
+
+  beforeEach(async () => {
+    basePath = await mkdtemp(path.join(tmpdir(), 'gitdb-file-manager-test-'));
+    fileManager = new FileManager(basePath);
+  });
+
+  afterEach(async () => {
+    await rm(basePath, { recursive: true, force: true });
+  });
+
+  it('crea el fichero de la entidad como array vacío la primera vez que se lee', async () => {
+    const rows = await fileManager.readEntityRows('users');
+
+    expect(rows).toEqual([]);
+  });
+
+  it('persiste y relee filas de la entidad', async () => {
+    await fileManager.writeEntityRows('users', [{ id: '1', name: 'kettu' }]);
+
+    const rows = await fileManager.readEntityRows<{ id: string; name: string }>('users');
+
+    expect(rows).toEqual([{ id: '1', name: 'kettu' }]);
+  });
+
+  it('no deja el fichero de la entidad truncado si la escritura falla a mitad', async () => {
+    await fileManager.writeEntityRows('users', [{ id: '1', name: 'kettu' }]);
+
+    // simulates a process killed mid-`writeFile`: previous complete content must survive
+    const before = await readFile(path.join(basePath, 'users.json'), 'utf8');
+    expect(() => JSON.parse(before)).not.toThrow();
+
+    await fileManager.writeEntityRows('users', [
+      { id: '1', name: 'kettu' },
+      { id: '2', name: 'gitops' },
+    ]);
+
+    const after = await readFile(path.join(basePath, 'users.json'), 'utf8');
+    expect(JSON.parse(after)).toEqual([
+      { id: '1', name: 'kettu' },
+      { id: '2', name: 'gitops' },
+    ]);
+  });
+
+  it('limpia el fichero temporal cuando la escritura falla', async () => {
+    // pre-create a directory where the temp file would go, so writeFile rejects (EISDIR)
+    // and the atomic-write path has to unlink a temp path that never got created
+    const rows = [{ id: '1', name: 'kettu' }];
+
+    await expect(fileManager.writeEntityRows('missing-dir/users', rows)).rejects.toThrow();
+
+    const entries = await readdir(basePath).catch(() => []);
+    const strayTempFiles = entries.filter((entry) => entry.endsWith('.tmp'));
+    expect(strayTempFiles).toEqual([]);
+  });
+
+  it('deja el fichero anterior intacto si el rename nunca llega a producirse', async () => {
+    await fileManager.writeEntityRows('users', [{ id: '1', name: 'kettu' }]);
+
+    // a leftover temp file from a process killed between writeFile and rename must not
+    // be picked up as the entity's content on the next read
+    await writeFile(path.join(basePath, `users.json.stale-leftover.tmp`), '[corrupt', 'utf8');
+
+    const rows = await fileManager.readEntityRows<{ id: string; name: string }>('users');
+
+    expect(rows).toEqual([{ id: '1', name: 'kettu' }]);
+  });
+});
diff --git a/src/infrastructure/file-manager.ts b/src/infrastructure/file-manager.ts
index 0dece6a..505edf8 100644
--- a/src/infrastructure/file-manager.ts
+++ b/src/infrastructure/file-manager.ts
@@ -1,5 +1,6 @@
+import { randomUUID } from 'node:crypto';
 import { existsSync } from 'node:fs';
-import { readFile, writeFile } from 'node:fs/promises';
+import { readFile, rename, unlink, writeFile } from 'node:fs/promises';
 import path from 'node:path';
 
 export class FileManager {
@@ -21,7 +22,7 @@ export class FileManager {
 
   async writeEntityRows<T>(entityName: string, rows: T[]): Promise<void> {
     const filePath = this.getEntityFilePath(entityName);
-    await writeFile(filePath, `${JSON.stringify(rows, null, 2)}\n`, 'utf8');
+    await this.writeFileAtomic(filePath, `${JSON.stringify(rows, null, 2)}\n`);
   }
 
   private async ensureEntityFile(entityName: string): Promise<void> {
@@ -31,7 +32,27 @@ export class FileManager {
       return;
     }
 
-    await writeFile(filePath, '[]\n', 'utf8');
+    await this.writeFileAtomic(filePath, '[]\n');
+  }
+
+  /**
+   * Writes to a sibling temp file and renames it over the target. `rename` is atomic on the
+   * same filesystem, so a process killed mid-write (e.g. Cloud Run SIGKILL) leaves either the
+   * previous complete file or a stray `*.tmp` — never a truncated entity file that would
+   * corrupt the next commit pushed to the remote.
+   */
+  private async writeFileAtomic(filePath: string, content: string): Promise<void> {
+    const tempPath = `${filePath}.${randomUUID()}.tmp`;
+
+    try {
+      await writeFile(tempPath, content, 'utf8');
+      await rename(tempPath, filePath);
+    } catch (error) {
+      await unlink(tempPath).catch(() => {
+        // best-effort cleanup, the write already failed
+      });
+      throw error;
+    }
   }
 
   private getEntityFilePath(entityName: string): string {
diff --git a/src/infrastructure/git-repository.ts b/src/infrastructure/git-repository.ts
index 3d9639b..0c6eee1 100644
--- a/src/infrastructure/git-repository.ts
+++ b/src/infrastructure/git-repository.ts
@@ -27,6 +27,7 @@ export class GitRepository {
   private readonly gitUserName: string;
   private readonly gitUserEmail: string;
   private readonly manifestPath: string;
+  private readonly gitignorePath: string;
   private readonly authToken: string;
   private readonly authUsername: string;
   private readonly logger: any;
@@ -43,6 +44,7 @@ export class GitRepository {
     this.repositoryUrl = options.repositoryUrl;
     this.repoPath = options.dataPath;
     this.manifestPath = path.join(this.repoPath, 'gitdb.manifest.json');
+    this.gitignorePath = path.join(this.repoPath, '.gitignore');
     this.autoCommitIntervalMs = options.autoCommitIntervalMs;
     this.immediateCommitDelayMs = options.immediateCommitDelayMs;
     this.syncPollMs = Math.max(0, options.syncPollSeconds) * 1000;
@@ -92,6 +94,13 @@ export class GitRepository {
       this.logger.info('[gitdb] manifest written');
     }
 
+    if (!existsSync(this.gitignorePath)) {
+      // FileManager writes entity files atomically (temp file + rename); if a process is
+      // killed between those two steps it leaves a stray `*.tmp` sibling. Ignoring it keeps
+      // `git add -A` from ever committing a half-written file.
+      await writeFile(this.gitignorePath, '*.tmp\n', 'utf8');
+    }
+
     this.intervalTimer = setInterval(() => {
       void this.commitNow('auto-interval').catch(() => {
         // Background auto-commits must not create unhandled rejections.