diff --git a/src/ipc.test.ts b/src/ipc.test.ts
new file mode 100644
index 0000000..6531f9a
--- /dev/null
+++ b/src/ipc.test.ts
@@ -0,0 +1,73 @@
+import fs from 'fs';
+import os from 'os';
+import path from 'path';
+
+import { afterEach, describe, expect, it } from 'vitest';
+
+import { claimIpcFile, quarantineClaimedIpcFiles } from './ipc.js';
+
+const tempDirs: string[] = [];
+
+function makeTempDir(): string {
+  const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'ejclaw-ipc-'));
+  tempDirs.push(dir);
+  return dir;
+}
+
+afterEach(() => {
+  for (const dir of tempDirs.splice(0, tempDirs.length)) {
+    fs.rmSync(dir, { recursive: true, force: true });
+  }
+});
+
+describe('ipc file claiming', () => {
+  it('claims IPC files into a hidden processing directory before handling', () => {
+    const baseDir = makeTempDir();
+    const messagesDir = path.join(baseDir, 'messages');
+    fs.mkdirSync(messagesDir, { recursive: true });
+
+    const filePath = path.join(messagesDir, 'message.json');
+    fs.writeFileSync(filePath, '{"type":"message"}');
+
+    const claimedPath = claimIpcFile(filePath);
+
+    expect(claimedPath).toBe(
+      path.join(messagesDir, '.processing', 'message.json'),
+    );
+    expect(fs.existsSync(filePath)).toBe(false);
+    expect(fs.existsSync(claimedPath!)).toBe(true);
+  });
+
+  it('returns null when the IPC file was already claimed or deleted', () => {
+    const baseDir = makeTempDir();
+    const missingPath = path.join(baseDir, 'messages', 'missing.json');
+
+    expect(claimIpcFile(missingPath)).toBeNull();
+  });
+});
+
+describe('ipc claimed-file quarantine', () => {
+  it('moves stranded claimed files into the error directory without reprocessing', () => {
+    const baseDir = makeTempDir();
+    const messagesDir = path.join(baseDir, 'messages');
+    const processingDir = path.join(messagesDir, '.processing');
+    const errorDir = path.join(baseDir, 'errors');
+
+    fs.mkdirSync(processingDir, { recursive: true });
+    fs.mkdirSync(errorDir, { recursive: true });
+
+    const claimedPath = path.join(processingDir, 'message.json');
+    fs.writeFileSync(claimedPath, '{"type":"message"}');
+
+    const movedPaths = quarantineClaimedIpcFiles(
+      messagesDir,
+      errorDir,
+      'group-message-stale',
+    );
+
+    expect(movedPaths).toHaveLength(1);
+    expect(fs.existsSync(claimedPath)).toBe(false);
+    expect(fs.existsSync(movedPaths[0])).toBe(true);
+    expect(path.dirname(movedPaths[0])).toBe(errorDir);
+  });
+});
diff --git a/src/ipc.ts b/src/ipc.ts
index 4f4ba41..3bb6954 100644
--- a/src/ipc.ts
+++ b/src/ipc.ts
@@ -35,6 +35,68 @@ export interface IpcDeps {
 }
 
 let ipcWatcherRunning = false;
+const IPC_PROCESSING_DIRNAME = '.processing';
+
+function buildIpcErrorPath(
+  errorDir: string,
+  prefix: string,
+  fileName: string,
+): string {
+  return path.join(errorDir, `${prefix}-${Date.now()}-${fileName}`);
+}
+
+export function claimIpcFile(filePath: string): string | null {
+  const processingDir = path.join(
+    path.dirname(filePath),
+    IPC_PROCESSING_DIRNAME,
+  );
+  fs.mkdirSync(processingDir, { recursive: true });
+
+  const claimedPath = path.join(processingDir, path.basename(filePath));
+  try {
+    fs.renameSync(filePath, claimedPath);
+    return claimedPath;
+  } catch (err) {
+    if ((err as NodeJS.ErrnoException).code === 'ENOENT') {
+      return null;
+    }
+    throw err;
+  }
+}
+
+export function quarantineClaimedIpcFiles(
+  ipcDir: string,
+  errorDir: string,
+  prefix: string,
+): string[] {
+  const processingDir = path.join(ipcDir, IPC_PROCESSING_DIRNAME);
+  if (!fs.existsSync(processingDir)) {
+    return [];
+  }
+
+  const movedPaths: string[] = [];
+  for (const file of fs.readdirSync(processingDir).filter((f) =>
+    f.endsWith('.json'),
+  )) {
+    const claimedPath = path.join(processingDir, file);
+    const errorPath = buildIpcErrorPath(errorDir, prefix, file);
+    fs.renameSync(claimedPath, errorPath);
+    movedPaths.push(errorPath);
+  }
+
+  return movedPaths;
+}
+
+function moveClaimedIpcFileToError(
+  claimedPath: string,
+  errorDir: string,
+  prefix: string,
+): void {
+  fs.renameSync(
+    claimedPath,
+    buildIpcErrorPath(errorDir, prefix, path.basename(claimedPath)),
+  );
+}
 
 export function startIpcWatcher(deps: IpcDeps): void {
   if (ipcWatcherRunning) {
@@ -72,6 +134,30 @@ export function startIpcWatcher(deps: IpcDeps): void {
       const isMain = folderIsMain.get(sourceGroup) === true;
       const messagesDir = path.join(ipcBaseDir, sourceGroup, 'messages');
       const tasksDir = path.join(ipcBaseDir, sourceGroup, 'tasks');
+      const errorDir = path.join(ipcBaseDir, 'errors');
+      fs.mkdirSync(errorDir, { recursive: true });
+
+      for (const quarantinedPath of quarantineClaimedIpcFiles(
+        messagesDir,
+        errorDir,
+        `${sourceGroup}-message-stale`,
+      )) {
+        logger.warn(
+          { sourceGroup, quarantinedPath },
+          'Quarantined previously claimed IPC message after restart',
+        );
+      }
+
+      for (const quarantinedPath of quarantineClaimedIpcFiles(
+        tasksDir,
+        errorDir,
+        `${sourceGroup}-task-stale`,
+      )) {
+        logger.warn(
+          { sourceGroup, quarantinedPath },
+          'Quarantined previously claimed IPC task after restart',
+        );
+      }
 
       // Process messages from this group's IPC directory
       try {
@@ -81,8 +167,10 @@ export function startIpcWatcher(deps: IpcDeps): void {
             .filter((f) => f.endsWith('.json'));
           for (const file of messageFiles) {
             const filePath = path.join(messagesDir, file);
+            const claimedPath = claimIpcFile(filePath);
+            if (!claimedPath) continue;
             try {
-              const data = readJsonFile(filePath);
+              const data = readJsonFile(claimedPath);
               if (!data || typeof data !== 'object')
                 throw new Error('Invalid JSON');
               const msg = data as {
@@ -122,17 +210,16 @@ export function startIpcWatcher(deps: IpcDeps): void {
                   );
                 }
               }
-              fs.unlinkSync(filePath);
+              fs.unlinkSync(claimedPath);
             } catch (err) {
               logger.error(
                 { file, sourceGroup, err },
                 'Error processing IPC message',
               );
-              const errorDir = path.join(ipcBaseDir, 'errors');
-              fs.mkdirSync(errorDir, { recursive: true });
-              fs.renameSync(
-                filePath,
-                path.join(errorDir, `${sourceGroup}-${file}`),
+              moveClaimedIpcFileToError(
+                claimedPath,
+                errorDir,
+                `${sourceGroup}-message-error`,
               );
             }
           }
@@ -152,8 +239,10 @@ export function startIpcWatcher(deps: IpcDeps): void {
             .filter((f) => f.endsWith('.json'));
           for (const file of taskFiles) {
             const filePath = path.join(tasksDir, file);
+            const claimedPath = claimIpcFile(filePath);
+            if (!claimedPath) continue;
             try {
-              const data = readJsonFile(filePath);
+              const data = readJsonFile(claimedPath);
               if (!data || typeof data !== 'object')
                 throw new Error('Invalid JSON');
               // Pass source group identity to processTaskIpc for authorization
@@ -163,17 +252,16 @@ export function startIpcWatcher(deps: IpcDeps): void {
                 isMain,
                 deps,
               );
-              fs.unlinkSync(filePath);
+              fs.unlinkSync(claimedPath);
             } catch (err) {
               logger.error(
                 { file, sourceGroup, err },
                 'Error processing IPC task',
               );
-              const errorDir = path.join(ipcBaseDir, 'errors');
-              fs.mkdirSync(errorDir, { recursive: true });
-              fs.renameSync(
-                filePath,
-                path.join(errorDir, `${sourceGroup}-${file}`),
+              moveClaimedIpcFileToError(
+                claimedPath,
+                errorDir,
+                `${sourceGroup}-task-error`,
               );
             }
           }