diff --git a/src/agents/cli-runner.test.ts b/src/agents/cli-runner.test.ts
new file mode 100644
index 000000000..5a215f7c8
--- /dev/null
+++ b/src/agents/cli-runner.test.ts
@@ -0,0 +1,56 @@
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+import { runCliAgent } from "./cli-runner.js";
+
+const runCommandWithTimeoutMock = vi.fn();
+const runExecMock = vi.fn();
+
+vi.mock("../process/exec.js", () => ({
+  runCommandWithTimeout: (...args: unknown[]) =>
+    runCommandWithTimeoutMock(...args),
+  runExec: (...args: unknown[]) => runExecMock(...args),
+}));
+
+describe("runCliAgent resume cleanup", () => {
+  beforeEach(() => {
+    runCommandWithTimeoutMock.mockReset();
+    runExecMock.mockReset();
+  });
+
+  it("kills stale resume processes for codex sessions", async () => {
+    runExecMock.mockResolvedValue({ stdout: "", stderr: "" });
+    runCommandWithTimeoutMock.mockResolvedValueOnce({
+      stdout: "ok",
+      stderr: "",
+      code: 0,
+      signal: null,
+      killed: false,
+    });
+
+    await runCliAgent({
+      sessionId: "s1",
+      sessionFile: "/tmp/session.jsonl",
+      workspaceDir: "/tmp",
+      prompt: "hi",
+      provider: "codex-cli",
+      model: "gpt-5.2-codex",
+      timeoutMs: 1_000,
+      runId: "run-1",
+      cliSessionId: "thread-123",
+    });
+
+    if (process.platform === "win32") {
+      expect(runExecMock).not.toHaveBeenCalled();
+      return;
+    }
+
+    expect(runExecMock).toHaveBeenCalledTimes(1);
+    const args = runExecMock.mock.calls[0] ?? [];
+    expect(args[0]).toBe("pkill");
+    const pkillArgs = args[1] as string[];
+    expect(pkillArgs[0]).toBe("-f");
+    expect(pkillArgs[1]).toContain("codex");
+    expect(pkillArgs[1]).toContain("resume");
+    expect(pkillArgs[1]).toContain("thread-123");
+  });
+});
diff --git a/src/agents/cli-runner.ts b/src/agents/cli-runner.ts
index 8394a070e..9bc7e2528 100644
--- a/src/agents/cli-runner.ts
+++ b/src/agents/cli-runner.ts
@@ -11,7 +11,7 @@ import type { ClawdbotConfig } from "../config/config.js";
 import type { CliBackendConfig } from "../config/types.js";
 import { shouldLogVerbose } from "../globals.js";
 import { createSubsystemLogger } from "../logging.js";
-import { runCommandWithTimeout } from "../process/exec.js";
+import { runCommandWithTimeout, runExec } from "../process/exec.js";
 import { resolveUserPath } from "../utils.js";
 import { resolveSessionAgentIds } from "./agent-scope.js";
 import { resolveCliBackendConfig } from "./cli-backends.js";
@@ -32,6 +32,37 @@ import {
 const log = createSubsystemLogger("agent/claude-cli");
 const CLI_RUN_QUEUE = new Map<string, Promise<unknown>>();
 
+function escapeRegex(value: string): string {
+  return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
+}
+
+async function cleanupResumeProcesses(
+  backend: CliBackendConfig,
+  sessionId: string,
+): Promise<void> {
+  if (process.platform === "win32") return;
+  const resumeArgs = backend.resumeArgs ?? [];
+  if (resumeArgs.length === 0) return;
+  if (!resumeArgs.some((arg) => arg.includes("{sessionId}"))) return;
+  const commandToken = path.basename(backend.command ?? "").trim();
+  if (!commandToken) return;
+
+  const resumeTokens = resumeArgs.map((arg) =>
+    arg.replaceAll("{sessionId}", sessionId),
+  );
+  const pattern = [commandToken, ...resumeTokens]
+    .filter(Boolean)
+    .map((token) => escapeRegex(token))
+    .join(".*");
+  if (!pattern) return;
+
+  try {
+    await runExec("pkill", ["-f", pattern]);
+  } catch {
+    // ignore missing pkill or no matches
+  }
+}
+
 function enqueueCliRun<T>(key: string, task: () => Promise<T>): Promise<T> {
   const prior = CLI_RUN_QUEUE.get(key) ?? Promise.resolve();
   const chained = prior.catch(() => undefined).then(task);
@@ -602,6 +633,10 @@ export async function runCliAgent(params: {
         return next;
       })();
 
+      if (useResume && cliSessionIdToSend) {
+        await cleanupResumeProcesses(backend, cliSessionIdToSend);
+      }
+
       const result = await runCommandWithTimeout([backend.command, ...args], {
         timeoutMs: params.timeoutMs,
         cwd: workspaceDir,