diff --git a/apps/shared/OpenClawKit/Sources/OpenClawProtocol/GatewayModels.swift b/apps/shared/OpenClawKit/Sources/OpenClawProtocol/GatewayModels.swift
index 9b3b25ddca87..60578baa9dea 100644
--- a/apps/shared/OpenClawKit/Sources/OpenClawProtocol/GatewayModels.swift
+++ b/apps/shared/OpenClawKit/Sources/OpenClawProtocol/GatewayModels.swift
@@ -616,9 +616,9 @@ public struct SendParams: Codable, Sendable {
         message: String?,
         mediaurl: String?,
         mediaurls: [String]?,
-        buffer: String?,
-        filename: String?,
-        contenttype: String?,
+        buffer: String? = nil,
+        filename: String? = nil,
+        contenttype: String? = nil,
         asvoice: Bool?,
         gifplayback: Bool?,
         channel: String?,
diff --git a/scripts/protocol-gen-swift.ts b/scripts/protocol-gen-swift.ts
index ea5f92926f25..5150cffb885f 100644
--- a/scripts/protocol-gen-swift.ts
+++ b/scripts/protocol-gen-swift.ts
@@ -42,6 +42,7 @@ const STRICT_LITERAL_STRUCTS = new Set([
 ]);
 
 const DEFAULTED_OPTIONAL_INIT_PARAM_ENTRIES: readonly [string, readonly string[]][] = [
+  ["SendParams", ["buffer", "filename", "contentType"]],
   ["SessionOperationEvent", ["agentId"]],
   ["SessionsCompactionListParams", ["agentId"]],
   ["SessionsCompactionGetParams", ["agentId"]],
diff --git a/src/agents/tools/gateway-tool.test.ts b/src/agents/tools/gateway-tool.test.ts
index 500e09594949..f7126c9ef63d 100644
--- a/src/agents/tools/gateway-tool.test.ts
+++ b/src/agents/tools/gateway-tool.test.ts
@@ -11,11 +11,13 @@ const {
   extractDeliveryInfoMock,
   formatDoctorNonInteractiveHintMock,
   isRestartEnabledMock,
+  callGatewayToolMock,
   removeRestartSentinelFileMock,
   scheduleGatewaySigusr1RestartMock,
   writeRestartSentinelMock,
 } = vi.hoisted(() => ({
   isRestartEnabledMock: vi.fn(() => true),
+  callGatewayToolMock: vi.fn(async () => ({ ok: true })),
   extractDeliveryInfoMock: vi.fn(() => ({
     deliveryContext: {
       channel: "slack",
@@ -31,8 +33,14 @@ const {
   writeRestartSentinelMock: vi.fn(async (_payload: RestartSentinelPayload) => "/tmp/restart"),
   removeRestartSentinelFileMock: vi.fn(async (_path: string | null | undefined) => undefined),
   scheduleGatewaySigusr1RestartMock: vi.fn((_opts?: ScheduleGatewayRestartArgs) => ({
-    scheduled: true,
+    ok: true,
+    pid: 123,
+    signal: "SIGUSR1" as const,
     delayMs: 250,
+    mode: "emit" as const,
+    coalesced: false,
+    cooldownMsApplied: 0,
+    emitHooksQueued: true,
   })),
 }));
 
@@ -67,7 +75,7 @@ vi.mock("../../logging/subsystem.js", () => ({
 }));
 
 vi.mock("./gateway.js", () => ({
-  callGatewayTool: vi.fn(),
+  callGatewayTool: callGatewayToolMock,
   readGatewayCallOptions: vi.fn(() => ({})),
 }));
 
@@ -110,7 +118,18 @@ describe("gateway tool restart continuation", () => {
     writeRestartSentinelMock.mockResolvedValue("/tmp/restart");
     removeRestartSentinelFileMock.mockClear();
     scheduleGatewaySigusr1RestartMock.mockReset();
-    scheduleGatewaySigusr1RestartMock.mockReturnValue({ scheduled: true, delayMs: 250 });
+    scheduleGatewaySigusr1RestartMock.mockReturnValue({
+      ok: true,
+      pid: 123,
+      signal: "SIGUSR1",
+      delayMs: 250,
+      mode: "emit",
+      coalesced: false,
+      cooldownMsApplied: 0,
+      emitHooksQueued: true,
+    });
+    callGatewayToolMock.mockReset();
+    callGatewayToolMock.mockResolvedValue({ ok: true });
   });
 
   it("does not expose system-event continuations to the agent tool", async () => {
@@ -187,9 +206,62 @@ describe("gateway tool restart continuation", () => {
     const restartArgs = requireScheduledRestartArgs();
     expect(restartArgs.delayMs).toBe(250);
     expect(restartArgs.reason).toBe("continue after reboot");
+    expect(restartArgs.sessionKey).toBe("agent:main:main");
     expect(typeof restartArgs.emitHooks?.beforeEmit).toBe("function");
     expect(typeof restartArgs.emitHooks?.afterEmitRejected).toBe("function");
-    expect(result?.details).toEqual({ scheduled: true, delayMs: 250 });
+    expect(result?.details).toMatchObject({
+      ok: true,
+      delayMs: 250,
+      coalesced: false,
+      emitHooksQueued: true,
+      continuationQueued: true,
+    });
+  });
+
+  it("uses the runtime session, not model-supplied params, for scheduler ownership and sentinel routing (#86742)", async () => {
+    const tool = createGatewayTool({
+      agentSessionKey: "agent:main:session-A",
+      config: {},
+    });
+
+    await tool.execute?.("tool-call-1", {
+      action: "restart",
+      sessionKey: "agent:main:session-B",
+      continuationMessage: "Reply after restart",
+    });
+
+    expect(requireScheduledRestartArgs().sessionKey).toBe("agent:main:session-A");
+    await requireScheduledRestartArgs().emitHooks?.beforeEmit?.();
+    expect(requireRestartSentinelPayload().sessionKey).toBe("agent:main:session-A");
+  });
+
+  it("reports continuationQueued=false when a coalesced restart belongs to another session (#86742)", async () => {
+    scheduleGatewaySigusr1RestartMock.mockReturnValue({
+      ok: true,
+      pid: 123,
+      signal: "SIGUSR1",
+      delayMs: 0,
+      mode: "emit",
+      coalesced: true,
+      cooldownMsApplied: 0,
+      emitHooksQueued: false,
+    });
+    const tool = createGatewayTool({
+      agentSessionKey: "agent:main:main",
+      config: {},
+    });
+
+    const result = await tool.execute?.("tool-call-1", {
+      action: "restart",
+      continuationMessage: "Reply after restart",
+    });
+
+    expect(writeRestartSentinelMock).not.toHaveBeenCalled();
+    expect(result?.details).toMatchObject({
+      coalesced: true,
+      emitHooksQueued: false,
+      continuationQueued: false,
+    });
   });
 
   it.each([-1, 1.5, "soon"])("rejects invalid restart delayMs value %s", async (delayMs) => {
@@ -278,4 +350,30 @@ describe("gateway tool restart continuation", () => {
 
     expect(removeRestartSentinelFileMock).toHaveBeenCalledWith("/tmp/restart");
   });
+
+  it("uses the runtime session for update.run continuation routing (#86742)", async () => {
+    const tool = createGatewayTool({
+      agentSessionKey: "agent:main:session-A",
+      config: {},
+    });
+
+    await tool.execute?.("tool-call-update", {
+      action: "update.run",
+      sessionKey: "agent:main:session-B",
+      continuationMessage: "Reply after update restart",
+      note: "Updating now",
+      restartDelayMs: 0,
+    });
+
+    expect(callGatewayToolMock).toHaveBeenCalledWith(
+      "update.run",
+      expect.objectContaining({ timeoutMs: expect.any(Number) }),
+      expect.objectContaining({
+        sessionKey: "agent:main:session-A",
+        continuationMessage: "Reply after update restart",
+        note: "Updating now",
+        restartDelayMs: 0,
+      }),
+    );
+  });
 });
diff --git a/src/agents/tools/gateway-tool.ts b/src/agents/tools/gateway-tool.ts
index 93d357d4d426..188f0f8fa3f3 100644
--- a/src/agents/tools/gateway-tool.ts
+++ b/src/agents/tools/gateway-tool.ts
@@ -395,8 +395,8 @@ export function createGatewayTool(opts?: {
           throw new Error("Gateway restart is disabled (commands.restart=false).");
         }
         const sessionKey =
-          normalizeOptionalString(params.sessionKey) ??
-          normalizeOptionalString(opts?.agentSessionKey);
+          normalizeOptionalString(opts?.agentSessionKey) ??
+          normalizeOptionalString(params.sessionKey);
         const delayMs = readNonNegativeIntegerParam(params, "delayMs");
         const reason = normalizeOptionalString(params.reason)?.slice(0, 200);
         const note = normalizeOptionalString(params.note);
@@ -429,6 +429,9 @@ export function createGatewayTool(opts?: {
         const scheduled = scheduleGatewaySigusr1Restart({
           delayMs,
           reason,
+          // Ownership and sentinel routing use the same trusted session identity,
+          // so model-supplied params cannot queue work into another session.
+          sessionKey,
           emitHooks: {
             beforeEmit: async () => {
               sentinelPath = await writeRestartSentinel(payload);
@@ -438,7 +441,10 @@ export function createGatewayTool(opts?: {
             },
           },
         });
-        return jsonResult(scheduled);
+        return jsonResult({
+          ...scheduled,
+          ...(payload.continuation ? { continuationQueued: scheduled.emitHooksQueued } : {}),
+        });
       }
 
       const gatewayOpts = readGatewayCallOptions(params);
@@ -449,8 +455,8 @@ export function createGatewayTool(opts?: {
         restartDelayMs: number | undefined;
       } => {
         const sessionKey =
-          normalizeOptionalString(params.sessionKey) ??
-          normalizeOptionalString(opts?.agentSessionKey);
+          normalizeOptionalString(opts?.agentSessionKey) ??
+          normalizeOptionalString(params.sessionKey);
         const note = normalizeOptionalString(params.note);
         const restartDelayMs = readNonNegativeIntegerParam(params, "restartDelayMs");
         return { sessionKey, note, restartDelayMs };
diff --git a/src/auto-reply/reply/commands-session-restart.test.ts b/src/auto-reply/reply/commands-session-restart.test.ts
index 7d281046ed8c..40f44efefcb8 100644
--- a/src/auto-reply/reply/commands-session-restart.test.ts
+++ b/src/auto-reply/reply/commands-session-restart.test.ts
@@ -180,6 +180,18 @@ describe("handleRestartCommand", () => {
     }
   });
 
+  it("threads sessionKey into scheduleGatewaySigusr1Restart so cross-session coalescing is rejected (#86742)", async () => {
+    const handler = () => {};
+    process.on("SIGUSR1", handler);
+    try {
+      await handleRestartCommand(restartCommandParams(), true);
+      const scheduledArgs = mocks.scheduleGatewaySigusr1Restart.mock.calls.at(-1)?.[0];
+      expect(scheduledArgs?.sessionKey).toBe("agent:main:telegram:direct:123:thread:thread-1");
+    } finally {
+      process.removeListener("SIGUSR1", handler);
+    }
+  });
+
   it("rejects authorized non-owner restart commands", async () => {
     const result = await handleRestartCommand(
       restartCommandParams({
diff --git a/src/auto-reply/reply/commands-session.ts b/src/auto-reply/reply/commands-session.ts
index d3e086ad8214..10a27451c4da 100644
--- a/src/auto-reply/reply/commands-session.ts
+++ b/src/auto-reply/reply/commands-session.ts
@@ -706,6 +706,10 @@ export const handleRestartCommand: CommandHandler = async (params, allowTextComm
     let sentinelPath: string | null = null;
     scheduleGatewaySigusr1Restart({
       reason: "/restart",
+      // Sibling session-routing guard: /restart writes a session-scoped sentinel
+      // with continuation, so the scheduler must own the pending slot under the
+      // same key to avoid cross-session continuation overwrite (#86742).
+      sessionKey: sentinelPayload?.sessionKey,
       emitHooks: sentinelPayload
         ? {
             beforeEmit: async () => {
diff --git a/src/infra/infra-runtime.test.ts b/src/infra/infra-runtime.test.ts
index ad23e017e97f..bb1d3549d48d 100644
--- a/src/infra/infra-runtime.test.ts
+++ b/src/infra/infra-runtime.test.ts
@@ -324,6 +324,179 @@ describe("infra runtime", () => {
       }
     });
 
+    it("reports emitHooksQueued=false for hookless coalesced restart requests", () => {
+      const first = scheduleGatewaySigusr1Restart({ delayMs: 1_000, reason: "first" });
+      const second = scheduleGatewaySigusr1Restart({ delayMs: 1_000, reason: "second" });
+
+      expect(first.coalesced).toBe(false);
+      expect(first.emitHooksQueued).toBe(false);
+      expect(second.coalesced).toBe(true);
+      expect(second.emitHooksQueued).toBe(false);
+    });
+
+    it("rejects coalesced emit hooks from a different session and reports emitHooksQueued=false (#86742)", async () => {
+      const sessionAHooks = vi.fn(async () => {});
+      const sessionBHooks = vi.fn(async () => {});
+      const emitSpy = vi.spyOn(process, "emit");
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        const first = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "session-A",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit: sessionAHooks },
+        });
+        const second = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "session-B",
+          sessionKey: "agent:main:session-B",
+          emitHooks: { beforeEmit: sessionBHooks },
+        });
+
+        expect(first.coalesced).toBe(false);
+        expect(first.emitHooksQueued).toBe(true);
+        expect(second.coalesced).toBe(true);
+        expect(second.emitHooksQueued).toBe(false);
+
+        await vi.advanceTimersByTimeAsync(1_000);
+
+        // Session A's hook ran (it owns the pending slot); session B's hook is dropped,
+        // which the caller already observed via emitHooksQueued=false.
+        expect(sessionAHooks).toHaveBeenCalledTimes(1);
+        expect(sessionBHooks).not.toHaveBeenCalled();
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
+    it("allows same-session coalesced restart to replace its own preparation hook (#86742)", async () => {
+      const firstHooks = vi.fn(async () => {});
+      const latestHooks = vi.fn(async () => {});
+      const emitSpy = vi.spyOn(process, "emit");
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        const first = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "first",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit: firstHooks },
+        });
+        const second = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "second",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit: latestHooks },
+        });
+
+        expect(first.emitHooksQueued).toBe(true);
+        expect(second.coalesced).toBe(true);
+        expect(second.emitHooksQueued).toBe(true);
+
+        await vi.advanceTimersByTimeAsync(1_000);
+
+        // Same session: latest hooks take ownership (existing debounce semantics).
+        expect(firstHooks).not.toHaveBeenCalled();
+        expect(latestHooks).toHaveBeenCalledTimes(1);
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
+    it("rejects earlier reschedule hooks from a different session (#86742)", async () => {
+      const sessionAHooks = vi.fn(async () => {});
+      const sessionBHooks = vi.fn(async () => {});
+      const emitSpy = vi.spyOn(process, "emit");
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        const first = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "session-A",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit: sessionAHooks },
+        });
+        const second = scheduleGatewaySigusr1Restart({
+          delayMs: 0,
+          reason: "session-B",
+          sessionKey: "agent:main:session-B",
+          emitHooks: { beforeEmit: sessionBHooks },
+        });
+
+        expect(first.coalesced).toBe(false);
+        expect(first.emitHooksQueued).toBe(true);
+        expect(second.coalesced).toBe(true);
+        expect(second.emitHooksQueued).toBe(false);
+        expect(second.delayMs).toBe(0);
+
+        await vi.advanceTimersByTimeAsync(0);
+
+        expect(sessionAHooks).toHaveBeenCalledTimes(1);
+        expect(sessionBHooks).not.toHaveBeenCalled();
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
+    it("rejects coalesced emit hooks from a different session while preparation is in flight (#86742)", async () => {
+      // Pins the CWE-200 in-flight preparation race: pendingRestartSessionKey
+      // must stay alive through await beforeEmit(), otherwise a coalesced
+      // different-session caller slips past updatePendingRestartEmitHooks
+      // and chains its own hooks while preparation runs.
+      let releaseSessionAPrep: () => void = () => {};
+      const sessionAPrepBlocked = new Promise<void>((resolve) => {
+        releaseSessionAPrep = resolve;
+      });
+      const sessionAHooks = vi.fn(async () => {
+        await sessionAPrepBlocked;
+      });
+      const sessionBHooks = vi.fn(async () => {});
+      const emitSpy = vi.spyOn(process, "emit");
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        const first = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "session-A",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit: sessionAHooks },
+        });
+        // Advance the scheduled timer so session A's beforeEmit starts and
+        // pendingRestartPreparing becomes true; the hook awaits forever until
+        // we resolve sessionAPrepBlocked below.
+        await vi.advanceTimersByTimeAsync(1_000);
+        await Promise.resolve();
+        expect(sessionAHooks).toHaveBeenCalledTimes(1);
+
+        // Session B coalesces *during* session A's beforeEmit await window.
+        const second = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "session-B",
+          sessionKey: "agent:main:session-B",
+          emitHooks: { beforeEmit: sessionBHooks },
+        });
+
+        expect(first.emitHooksQueued).toBe(true);
+        expect(second.coalesced).toBe(true);
+        expect(second.emitHooksQueued).toBe(false);
+
+        releaseSessionAPrep();
+        await Promise.resolve();
+        await Promise.resolve();
+
+        // Session B's hook must NOT run — the guard kept session A as owner
+        // through the in-flight preparation window.
+        expect(sessionBHooks).not.toHaveBeenCalled();
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
     it("keeps existing preparation hook when a hookless restart coalesces", async () => {
       const beforeEmit = vi.fn(async () => {});
       const emitSpy = vi.spyOn(process, "emit");
@@ -595,6 +768,39 @@ describe("infra runtime", () => {
       }
     });
 
+    it("preserves a session-owned preparation hook when a hookless forced restart pulls a pending timer earlier (#86742)", async () => {
+      const emitSpy = vi.spyOn(process, "emit");
+      const beforeEmit = vi.fn(async () => {});
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        const pending = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          reason: "session-A",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit },
+        });
+        const forced = scheduleGatewaySigusr1Restart({
+          delayMs: 1_000,
+          preservePendingEmitHooksOnDeferralBypass: true,
+          reason: "gateway.restart.safe",
+          skipDeferral: true,
+        });
+
+        expect(pending.emitHooksQueued).toBe(true);
+        expect(forced.coalesced).toBe(false);
+        expect(forced.emitHooksQueued).toBe(false);
+
+        await vi.advanceTimersByTimeAsync(1_000);
+
+        expect(beforeEmit).toHaveBeenCalledTimes(1);
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+        expect(peekGatewaySigusr1RestartReason()).toBe("gateway.restart.safe");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
     it("bypasses an active restart deferral when a forced restart arrives", async () => {
       const emitSpy = vi.spyOn(process, "emit");
       const staleBeforeEmit = vi.fn(async () => {});
@@ -625,6 +831,76 @@ describe("infra runtime", () => {
       }
     });
 
+    it("clears a session-owned preparation hook when a forced update owns the sentinel (#86742)", async () => {
+      const emitSpy = vi.spyOn(process, "emit");
+      const beforeEmit = vi.fn(async () => {});
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        setPreRestartDeferralCheck(() => 5);
+        scheduleGatewaySigusr1Restart({
+          delayMs: 0,
+          reason: "session-A",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit },
+        });
+        await vi.advanceTimersByTimeAsync(0);
+        expect(emitSpy).not.toHaveBeenCalledWith("SIGUSR1");
+
+        const forced = scheduleGatewaySigusr1Restart({
+          delayMs: 0,
+          reason: "update.run",
+          skipDeferral: true,
+        });
+
+        expect(forced.coalesced).toBe(false);
+        expect(forced.emitHooksQueued).toBe(false);
+        expect(beforeEmit).not.toHaveBeenCalled();
+        await Promise.resolve();
+        await Promise.resolve();
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+        expect(peekGatewaySigusr1RestartReason()).toBe("update.run");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
+    it("preserves a session-owned preparation hook when a hookless forced restart bypasses active deferral (#86742)", async () => {
+      const emitSpy = vi.spyOn(process, "emit");
+      const beforeEmit = vi.fn(async () => {});
+      const handler = () => {};
+      process.on("SIGUSR1", handler);
+      try {
+        setPreRestartDeferralCheck(() => 5);
+        const pending = scheduleGatewaySigusr1Restart({
+          delayMs: 0,
+          reason: "session-A",
+          sessionKey: "agent:main:session-A",
+          emitHooks: { beforeEmit },
+        });
+        await vi.advanceTimersByTimeAsync(0);
+        expect(emitSpy).not.toHaveBeenCalledWith("SIGUSR1");
+
+        const forced = scheduleGatewaySigusr1Restart({
+          delayMs: 0,
+          preservePendingEmitHooksOnDeferralBypass: true,
+          reason: "gateway.restart.safe",
+          skipDeferral: true,
+        });
+
+        expect(pending.emitHooksQueued).toBe(true);
+        expect(forced.coalesced).toBe(false);
+        expect(forced.emitHooksQueued).toBe(false);
+        expect(beforeEmit).toHaveBeenCalledTimes(1);
+        await Promise.resolve();
+        await Promise.resolve();
+        expect(emitSpy).toHaveBeenCalledWith("SIGUSR1");
+        expect(peekGatewaySigusr1RestartReason()).toBe("gateway.restart.safe");
+      } finally {
+        process.removeListener("SIGUSR1", handler);
+      }
+    });
+
     it("emits SIGUSR1 after the default deferral timeout while work is still pending", async () => {
       const emitSpy = vi.spyOn(process, "emit");
       const handler = () => {};
diff --git a/src/infra/restart-coordinator.test.ts b/src/infra/restart-coordinator.test.ts
index 3226245b2a23..bc9b2fbcc18c 100644
--- a/src/infra/restart-coordinator.test.ts
+++ b/src/infra/restart-coordinator.test.ts
@@ -145,6 +145,7 @@ describe("safe gateway restart coordinator", () => {
     expect(result.preflight.safe).toBe(false);
     expect(scheduleGatewaySigusr1Restart).toHaveBeenCalledWith({
       delayMs: 0,
+      preservePendingEmitHooksOnDeferralBypass: true,
       reason: "test.skip-deferral",
       skipDeferral: true,
     });
diff --git a/src/infra/restart-coordinator.ts b/src/infra/restart-coordinator.ts
index 8e69f9110b94..8b3af949844a 100644
--- a/src/infra/restart-coordinator.ts
+++ b/src/infra/restart-coordinator.ts
@@ -164,6 +164,7 @@ export function requestSafeGatewayRestart(
   const restart = scheduleGatewaySigusr1Restart({
     delayMs: opts.delayMs ?? 0,
     reason: opts.reason ?? "gateway.restart.safe",
+    ...(skipDeferral ? { preservePendingEmitHooksOnDeferralBypass: true } : {}),
     ...(skipDeferral ? { skipDeferral: true } : {}),
   });
   const status = restart.coalesced
diff --git a/src/infra/restart.ts b/src/infra/restart.ts
index 9f3085179492..15b1d4c6619a 100644
--- a/src/infra/restart.ts
+++ b/src/infra/restart.ts
@@ -47,6 +47,7 @@ let pendingRestartTimer: ReturnType<typeof setTimeout> | null = null;
 let pendingRestartDueAt = 0;
 let pendingRestartReason: string | undefined;
 let pendingRestartEmitHooks: RestartEmitHooks | undefined;
+let pendingRestartSessionKey: string | undefined;
 let pendingRestartSkipDeferral = false;
 let pendingRestartPreparing = false;
 const activeDeferralPolls = new Set<ReturnType<typeof setInterval>>();
@@ -67,10 +68,41 @@ function clearPendingScheduledRestart(): void {
   pendingRestartDueAt = 0;
   pendingRestartReason = undefined;
   pendingRestartEmitHooks = undefined;
+  pendingRestartSessionKey = undefined;
   pendingRestartSkipDeferral = false;
   pendingRestartPreparing = false;
 }
 
+function armPendingRestartTimer(requestedDueAt: number, nowMs: number): void {
+  pendingRestartTimer = setTimeout(
+    () => {
+      const scheduledReason = pendingRestartReason;
+      const scheduledSkipDeferral = pendingRestartSkipDeferral;
+      pendingRestartTimer = null;
+      pendingRestartDueAt = 0;
+      pendingRestartReason = undefined;
+      pendingRestartSkipDeferral = false;
+      pendingRestartPreparing = true;
+      const pendingCheck = preRestartCheck;
+      if (scheduledSkipDeferral || !pendingCheck) {
+        void emitPreparedGatewayRestart(undefined, scheduledReason);
+        return;
+      }
+      const cfg = getRuntimeConfig();
+      const deferralTimeoutMs = resolveGatewayRestartDeferralTimeoutMs(
+        cfg.gateway?.reload?.deferralTimeoutMs,
+      );
+      deferGatewayRestartUntilIdle({
+        getPendingCount: pendingCheck,
+        maxWaitMs: deferralTimeoutMs,
+        reason: scheduledReason,
+        timeoutIntent: { force: true, ...(scheduledReason ? { reason: scheduledReason } : {}) },
+      });
+    },
+    Math.max(0, requestedDueAt - nowMs),
+  );
+}
+
 function clearActiveDeferralPolls(): void {
   for (const poll of activeDeferralPolls) {
     clearInterval(poll);
@@ -440,10 +472,34 @@ export function resolveGatewayRestartDeferralTimeoutMs(timeoutMs: unknown): numb
   return Math.floor(timeoutMs);
 }
 
-function updatePendingRestartEmitHooks(hooks?: RestartEmitHooks): void {
-  if (hooks) {
-    pendingRestartEmitHooks = hooks;
+function canReplacePendingRestartEmitHooks(
+  hooks: RestartEmitHooks | undefined,
+  sessionKey: string | undefined,
+): boolean {
+  if (!hooks) {
+    return true;
   }
+  return pendingRestartSessionKey === undefined || pendingRestartSessionKey === sessionKey;
+}
+
+// Returns true when the new hooks took ownership of the pending restart slot.
+// Coalesced callers from a different sessionKey are rejected to prevent the
+// cross-session continuation overwrite documented in #86742 (CWE-200).
+function updatePendingRestartEmitHooks(
+  hooks: RestartEmitHooks | undefined,
+  sessionKey: string | undefined,
+): boolean {
+  if (!canReplacePendingRestartEmitHooks(hooks, sessionKey)) {
+    return false;
+  }
+  if (!hooks) {
+    return false;
+  }
+  pendingRestartEmitHooks = hooks;
+  if (sessionKey !== undefined) {
+    pendingRestartSessionKey = sessionKey;
+  }
+  return true;
 }
 
 async function emitPreparedGatewayRestart(
@@ -452,6 +508,10 @@ async function emitPreparedGatewayRestart(
   intent?: GatewayRestartIntent,
 ): Promise<void> {
   let nextHooks = hooks ?? pendingRestartEmitHooks;
+  // Keep pendingRestartSessionKey alive across the await beforeEmit() window:
+  // a different-session caller that coalesces while preparation runs would
+  // otherwise slip past the updatePendingRestartEmitHooks session guard and
+  // chain its own hooks (#86742, the CWE-200 in-flight preparation race).
   if (!hooks) {
     pendingRestartEmitHooks = undefined;
   }
@@ -475,6 +535,9 @@ async function emitPreparedGatewayRestart(
     nextHooks = pendingRestartEmitHooks;
     pendingRestartEmitHooks = undefined;
   }
+  if (!hooks) {
+    pendingRestartSessionKey = undefined;
+  }
 
   const emitted = emitGatewayRestart(reasonOverride, intent);
   if (!emitted) {
@@ -716,6 +779,10 @@ export type ScheduledRestart = {
   mode: "emit" | "signal" | "supervisor";
   coalesced: boolean;
   cooldownMsApplied: number;
+  // True iff the caller's emitHooks own the pending restart slot. Coalesced
+  // requests from a different sessionKey are rejected to protect the existing
+  // session's continuation (#86742).
+  emitHooksQueued: boolean;
 };
 
 export function scheduleGatewaySigusr1Restart(opts?: {
@@ -723,6 +790,8 @@ export function scheduleGatewaySigusr1Restart(opts?: {
   reason?: string;
   audit?: RestartAuditInfo;
   emitHooks?: RestartEmitHooks;
+  preservePendingEmitHooksOnDeferralBypass?: boolean;
+  sessionKey?: string;
   skipDeferral?: boolean;
   skipCooldown?: boolean;
 }): ScheduledRestart {
@@ -744,6 +813,8 @@ export function scheduleGatewaySigusr1Restart(opts?: {
     : Math.max(0, lastRestartEmittedAt + RESTART_COOLDOWN_MS - nowMs);
   const requestedDueAt = nowMs + delayMs + cooldownMsApplied;
   const skipDeferral = opts?.skipDeferral === true;
+  let nextPendingEmitHooks = opts?.emitHooks;
+  let nextPendingSessionKey = opts?.sessionKey;
 
   if (hasUnconsumedRestartSignal()) {
     if (shouldPreferRestartReason(reason, emittedRestartReason)) {
@@ -765,6 +836,8 @@ export function scheduleGatewaySigusr1Restart(opts?: {
       mode,
       coalesced: true,
       cooldownMsApplied,
+      // SIGUSR1 already emitted; the new caller's hooks cannot run for this cycle.
+      emitHooksQueued: false,
     };
   }
 
@@ -776,7 +849,16 @@ export function scheduleGatewaySigusr1Restart(opts?: {
       );
       clearActiveDeferralPolls();
       pendingRestartReason = reason;
-      pendingRestartEmitHooks = opts?.emitHooks;
+      // Hookless forced restarts that own no sentinel may preserve an accepted
+      // pending hook; update/handoff callers rely on the default clear path.
+      const preservePendingHooks =
+        opts?.preservePendingEmitHooksOnDeferralBypass === true &&
+        opts?.emitHooks === undefined &&
+        pendingRestartSessionKey !== undefined;
+      if (!preservePendingHooks) {
+        pendingRestartEmitHooks = opts?.emitHooks;
+        pendingRestartSessionKey = opts?.sessionKey;
+      }
       void emitPreparedGatewayRestart(undefined, reason);
       return {
         ok: true,
@@ -787,6 +869,7 @@ export function scheduleGatewaySigusr1Restart(opts?: {
         mode,
         coalesced: false,
         cooldownMsApplied,
+        emitHooksQueued: opts?.emitHooks !== undefined,
       };
     }
     const shouldUpgradeToSkipDeferral = skipDeferral && !pendingRestartSkipDeferral;
@@ -794,10 +877,47 @@ export function scheduleGatewaySigusr1Restart(opts?: {
       !pendingRestartPreparing &&
       (requestedDueAt < pendingRestartDueAt || shouldUpgradeToSkipDeferral);
     if (shouldPullEarlier) {
+      const preservePendingHooks =
+        opts?.preservePendingEmitHooksOnDeferralBypass === true &&
+        opts?.emitHooks === undefined &&
+        pendingRestartSessionKey !== undefined;
+      if (
+        !preservePendingHooks &&
+        !canReplacePendingRestartEmitHooks(opts?.emitHooks, opts?.sessionKey)
+      ) {
+        restartLog.warn(
+          `restart continuation dropped: another session owns the pending restart (callerSessionKey=${opts?.sessionKey ?? "unspecified"} pendingSessionKey=${pendingRestartSessionKey ?? "unspecified"})`,
+        );
+        if (pendingRestartTimer) {
+          clearTimeout(pendingRestartTimer);
+        }
+        pendingRestartTimer = null;
+        pendingRestartDueAt = requestedDueAt;
+        pendingRestartReason = reason;
+        pendingRestartSkipDeferral = pendingRestartSkipDeferral || skipDeferral;
+        armPendingRestartTimer(requestedDueAt, nowMs);
+        return {
+          ok: true,
+          pid: process.pid,
+          signal: "SIGUSR1",
+          delayMs: Math.max(0, requestedDueAt - nowMs),
+          reason,
+          mode,
+          coalesced: true,
+          cooldownMsApplied,
+          emitHooksQueued: false,
+        };
+      }
+      const preservedEmitHooks = preservePendingHooks ? pendingRestartEmitHooks : undefined;
+      const preservedSessionKey = preservePendingHooks ? pendingRestartSessionKey : undefined;
       restartLog.warn(
         `restart request rescheduled earlier reason=${reason ?? "unspecified"} pendingReason=${pendingRestartReason ?? "unspecified"} oldDelayMs=${remainingMs} newDelayMs=${Math.max(0, requestedDueAt - nowMs)} ${formatRestartAudit(opts?.audit)}`,
       );
       clearPendingScheduledRestart();
+      if (preservePendingHooks) {
+        nextPendingEmitHooks = preservedEmitHooks;
+        nextPendingSessionKey = preservedSessionKey;
+      }
     } else {
       if (shouldPreferRestartReason(reason, pendingRestartReason)) {
         pendingRestartReason = reason;
@@ -806,7 +926,12 @@ export function scheduleGatewaySigusr1Restart(opts?: {
       restartLog.warn(
         `restart request coalesced (already scheduled) reason=${reason ?? "unspecified"} pendingReason=${pendingRestartReason ?? "unspecified"} delayMs=${remainingMs} ${formatRestartAudit(opts?.audit)}`,
       );
-      updatePendingRestartEmitHooks(opts?.emitHooks);
+      const emitHooksQueued = updatePendingRestartEmitHooks(opts?.emitHooks, opts?.sessionKey);
+      if (opts?.emitHooks && !emitHooksQueued) {
+        restartLog.warn(
+          `restart continuation dropped: another session owns the pending restart (callerSessionKey=${opts.sessionKey ?? "unspecified"} pendingSessionKey=${pendingRestartSessionKey ?? "unspecified"})`,
+        );
+      }
       return {
         ok: true,
         pid: process.pid,
@@ -816,41 +941,17 @@ export function scheduleGatewaySigusr1Restart(opts?: {
         mode,
         coalesced: true,
         cooldownMsApplied,
+        emitHooksQueued,
       };
     }
   }
 
   pendingRestartDueAt = requestedDueAt;
   pendingRestartReason = reason;
-  pendingRestartEmitHooks = opts?.emitHooks;
+  pendingRestartEmitHooks = nextPendingEmitHooks;
+  pendingRestartSessionKey = nextPendingSessionKey;
   pendingRestartSkipDeferral = skipDeferral;
-  pendingRestartTimer = setTimeout(
-    () => {
-      const scheduledReason = pendingRestartReason;
-      const scheduledSkipDeferral = pendingRestartSkipDeferral;
-      pendingRestartTimer = null;
-      pendingRestartDueAt = 0;
-      pendingRestartReason = undefined;
-      pendingRestartSkipDeferral = false;
-      pendingRestartPreparing = true;
-      const pendingCheck = preRestartCheck;
-      if (scheduledSkipDeferral || !pendingCheck) {
-        void emitPreparedGatewayRestart(undefined, scheduledReason);
-        return;
-      }
-      const cfg = getRuntimeConfig();
-      const deferralTimeoutMs = resolveGatewayRestartDeferralTimeoutMs(
-        cfg.gateway?.reload?.deferralTimeoutMs,
-      );
-      deferGatewayRestartUntilIdle({
-        getPendingCount: pendingCheck,
-        maxWaitMs: deferralTimeoutMs,
-        reason: scheduledReason,
-        timeoutIntent: { force: true, ...(scheduledReason ? { reason: scheduledReason } : {}) },
-      });
-    },
-    Math.max(0, requestedDueAt - nowMs),
-  );
+  armPendingRestartTimer(requestedDueAt, nowMs);
   return {
     ok: true,
     pid: process.pid,
@@ -860,6 +961,7 @@ export function scheduleGatewaySigusr1Restart(opts?: {
     mode,
     coalesced: false,
     cooldownMsApplied,
+    emitHooksQueued: opts?.emitHooks !== undefined,
   };
 }