diff --git a/src/agents/bash-process-registry.e2e.test.ts b/src/agents/bash-process-registry.e2e.test.ts
index 29f47a3f6c3e..4606c3d77e9e 100644
--- a/src/agents/bash-process-registry.e2e.test.ts
+++ b/src/agents/bash-process-registry.e2e.test.ts
@@ -5,7 +5,10 @@ import {
   addSession,
   appendOutput,
   drainSession,
+  getSession,
+  killAllSessions,
   listFinishedSessions,
+  listRunningSessions,
   markBackgrounded,
   markExited,
   resetProcessRegistryForTests,
@@ -114,4 +117,43 @@ describe("bash process registry", () => {
     markExited(session, 0, null, "completed");
     expect(listFinishedSessions()).toHaveLength(1);
   });
+
+  it("killAllSessions kills running children and clears registries", () => {
+    const killFnA = vi.fn();
+    const killFnB = vi.fn();
+    const childA = {
+      pid: 100,
+      kill: killFnA,
+      removeAllListeners: vi.fn(),
+    } as unknown as ChildProcessWithoutNullStreams;
+    const session = createProcessSessionFixture({
+      id: "kill-test",
+      command: "sleep 60",
+      child: childA,
+      maxOutputChars: 1000,
+    });
+    addSession(session);
+    markBackgrounded(session);
+
+    const bgSession = createProcessSessionFixture({
+      id: "kill-test-bg",
+      command: "sleep 120",
+      child: {
+        pid: 200,
+        kill: killFnB,
+        removeAllListeners: vi.fn(),
+      } as unknown as ChildProcessWithoutNullStreams,
+      maxOutputChars: 1000,
+    });
+    addSession(bgSession);
+
+    killAllSessions();
+
+    expect(killFnA).toHaveBeenCalledWith("SIGKILL");
+    expect(killFnB).toHaveBeenCalledWith("SIGKILL");
+    expect(getSession("kill-test")).toBeUndefined();
+    expect(getSession("kill-test-bg")).toBeUndefined();
+    expect(listRunningSessions()).toHaveLength(0);
+    expect(listFinishedSessions()).toHaveLength(0);
+  });
 });
diff --git a/src/agents/bash-process-registry.ts b/src/agents/bash-process-registry.ts
index 0e84065c7f2f..f6469842abfa 100644
--- a/src/agents/bash-process-registry.ts
+++ b/src/agents/bash-process-registry.ts
@@ -268,6 +268,25 @@ export function clearFinished() {
   finishedSessions.clear();
 }
 
+/**
+ * Kill all running sessions and clean up resources.
+ * Called during gateway shutdown to prevent orphaned child processes.
+ */
+export function killAllSessions(): void {
+  for (const session of runningSessions.values()) {
+    if (session.child && !session.exited) {
+      try {
+        session.child.kill("SIGKILL");
+      } catch {
+        // Process already exited
+      }
+    }
+  }
+  runningSessions.clear();
+  finishedSessions.clear();
+  stopSweeper();
+}
+
 export function resetProcessRegistryForTests() {
   runningSessions.clear();
   finishedSessions.clear();
diff --git a/src/gateway/server-close.ts b/src/gateway/server-close.ts
index da9f5a39e97d..b1981ad14e37 100644
--- a/src/gateway/server-close.ts
+++ b/src/gateway/server-close.ts
@@ -1,10 +1,12 @@
 import type { Server as HttpServer } from "node:http";
 import type { WebSocketServer } from "ws";
+import { killAllSessions } from "../agents/bash-process-registry.js";
 import type { CanvasHostHandler, CanvasHostServer } from "../canvas-host/server.js";
 import { type ChannelId, listChannelPlugins } from "../channels/plugins/index.js";
 import { stopGmailWatcher } from "../hooks/gmail-watcher.js";
 import type { HeartbeatRunner } from "../infra/heartbeat-runner.js";
 import type { PluginServicesHandle } from "../plugins/services.js";
+import { getProcessSupervisor } from "../process/supervisor/index.js";
 
 export function createGatewayCloseHandler(params: {
   bonjourStop: (() => Promise<void>) | null;
@@ -68,6 +70,8 @@ export function createGatewayCloseHandler(params: {
       await params.pluginServices.stop().catch(() => {});
     }
     await stopGmailWatcher();
+    getProcessSupervisor().cancelAll("manual-cancel");
+    killAllSessions();
     params.cron.stop();
     params.heartbeatRunner.stop();
     for (const timer of params.nodePresenceTimers.values()) {
diff --git a/src/process/supervisor/supervisor.test.ts b/src/process/supervisor/supervisor.test.ts
index 79d184672a5d..569dd46d8b6b 100644
--- a/src/process/supervisor/supervisor.test.ts
+++ b/src/process/supervisor/supervisor.test.ts
@@ -99,4 +99,31 @@ describe("process supervisor", () => {
     expect(streamed).toBe("streamed");
     expect(exit.stdout).toBe("");
   });
+
+  it("cancelAll terminates all active runs", async () => {
+    const supervisor = createProcessSupervisor();
+    const a = await supervisor.spawn({
+      sessionId: "s-all-1",
+      backendId: "test",
+      scopeKey: "scope:x",
+      mode: "child",
+      argv: [process.execPath, "-e", "setTimeout(() => {}, 10_000)"],
+      timeoutMs: 10_000,
+      stdinMode: "pipe-closed",
+    });
+    const b = await supervisor.spawn({
+      sessionId: "s-all-2",
+      backendId: "test",
+      scopeKey: "scope:y",
+      mode: "child",
+      argv: [process.execPath, "-e", "setTimeout(() => {}, 10_000)"],
+      timeoutMs: 10_000,
+      stdinMode: "pipe-closed",
+    });
+
+    supervisor.cancelAll();
+    const [exitA, exitB] = await Promise.all([a.wait(), b.wait()]);
+    expect(exitA.reason === "manual-cancel" || exitA.reason === "signal").toBe(true);
+    expect(exitB.reason === "manual-cancel" || exitB.reason === "signal").toBe(true);
+  });
 });
diff --git a/src/process/supervisor/supervisor.ts b/src/process/supervisor/supervisor.ts
index 3c6834003f0e..59496345ffe9 100644
--- a/src/process/supervisor/supervisor.ts
+++ b/src/process/supervisor/supervisor.ts
@@ -58,6 +58,12 @@ export function createProcessSupervisor(): ProcessSupervisor {
     }
   };
 
+  const cancelAll = (reason: TerminationReason = "manual-cancel") => {
+    for (const runId of Array.from(active.keys())) {
+      cancel(runId, reason);
+    }
+  };
+
   const spawn = async (input: SpawnInput): Promise<ManagedRun> => {
     const runId = input.runId?.trim() || crypto.randomUUID();
     if (input.replaceExistingScope && input.scopeKey?.trim()) {
@@ -273,6 +279,7 @@ export function createProcessSupervisor(): ProcessSupervisor {
     spawn,
     cancel,
     cancelScope,
+    cancelAll,
     reconcileOrphans: async () => {
       // Deliberate no-op: this supervisor uses in-memory ownership only.
       // Active runs are not recovered after process restart in the current model.
diff --git a/src/process/supervisor/types.ts b/src/process/supervisor/types.ts
index 04c571b08b2d..c6190fd0488e 100644
--- a/src/process/supervisor/types.ts
+++ b/src/process/supervisor/types.ts
@@ -91,6 +91,7 @@ export interface ProcessSupervisor {
   spawn(input: SpawnInput): Promise<ManagedRun>;
   cancel(runId: string, reason?: TerminationReason): void;
   cancelScope(scopeKey: string, reason?: TerminationReason): void;
+  cancelAll(reason?: TerminationReason): void;
   reconcileOrphans(): Promise<void>;
   getRecord(runId: string): RunRecord | undefined;
 }