diff --git a/CHANGELOG.md b/CHANGELOG.md
index cf33ae7d512..fe3b27bf2d0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -134,6 +134,7 @@ Docs: https://docs.openclaw.ai
 - Providers/Google: add model-level `cacheRetention` support for direct Gemini system prompts by creating, reusing, and refreshing `cachedContents` automatically on Google AI Studio runs. (#51372) Thanks @rafaelmariano-glitch.
 - Windows/restart: fall back to the installed Startup-entry launcher when the scheduled task was never registered, so `/restart` can relaunch the gateway on Windows setups where `schtasks` install fell back during onboarding. (#58943) Thanks @imechZhangLY.
 - Exec/heartbeat: use the canonical `exec-event` wake reason for `notifyOnExit` so background exec completions still trigger follow-up turns when `HEARTBEAT.md` is empty or comments-only. (#41479) Thanks @rstar327.
+- Heartbeat: skip wake delivery when the target session lane is already busy so the pending event is retried instead of getting drained too early. (#40526) Thanks @lucky7323.
 
 ## 2026.4.2
 
diff --git a/src/infra/heartbeat-runner.skips-busy-session-lane.test.ts b/src/infra/heartbeat-runner.skips-busy-session-lane.test.ts
new file mode 100644
index 00000000000..1feed8e530b
--- /dev/null
+++ b/src/infra/heartbeat-runner.skips-busy-session-lane.test.ts
@@ -0,0 +1,130 @@
+import { afterAll, beforeAll, beforeEach, describe, expect, it, vi } from "vitest";
+import * as replyModule from "../auto-reply/reply.js";
+import { getActivePluginRegistry, setActivePluginRegistry } from "../plugins/runtime.js";
+import { createOutboundTestPlugin, createTestRegistry } from "../test-utils/channel-plugins.js";
+import { type HeartbeatDeps, runHeartbeatOnce } from "./heartbeat-runner.js";
+import { resetSystemEventsForTest, enqueueSystemEvent } from "./system-events.js";
+import {
+  seedMainSessionStore,
+  withTempHeartbeatSandbox,
+} from "./heartbeat-runner.test-utils.js";
+import type { OpenClawConfig } from "../config/config.js";
+
+vi.mock("jiti", () => ({ createJiti: () => () => ({}) }));
+
+let previousRegistry: ReturnType<typeof getActivePluginRegistry> | null = null;
+
+const noopOutbound = {
+  deliveryMode: "direct" as const,
+  sendText: async () => ({ channel: "telegram" as const, messageId: "1", chatId: "1" }),
+  sendMedia: async () => ({ channel: "telegram" as const, messageId: "1", chatId: "1" }),
+};
+
+beforeAll(() => {
+  previousRegistry = getActivePluginRegistry();
+  const telegramPlugin = createOutboundTestPlugin({ id: "telegram", outbound: noopOutbound });
+  const registry = createTestRegistry([
+    { pluginId: "telegram", plugin: telegramPlugin, source: "test" },
+  ]);
+  setActivePluginRegistry(registry);
+});
+
+afterAll(() => {
+  if (previousRegistry) setActivePluginRegistry(previousRegistry);
+});
+
+beforeEach(() => {
+  resetSystemEventsForTest();
+});
+
+describe("heartbeat runner skips when target session lane is busy", () => {
+  it("returns requests-in-flight when session lane has queued work", async () => {
+    await withTempHeartbeatSandbox(async ({ storePath, replySpy }) => {
+      const cfg: OpenClawConfig = {
+        agents: {
+          defaults: {
+            heartbeat: { every: "30m" },
+            model: { primary: "test/model" },
+          },
+        },
+        channels: {
+          telegram: {
+            enabled: true,
+            token: "fake",
+            allowFrom: ["123"],
+          },
+        },
+      } as unknown as OpenClawConfig;
+
+      const sessionKey = await seedMainSessionStore(storePath, cfg, {
+        lastChannel: "telegram",
+        lastProvider: "telegram",
+        lastTo: "123",
+      });
+
+      enqueueSystemEvent("Exec completed (test-id, code 0) :: test output", {
+        sessionKey,
+      });
+
+      // main lane idle (0), session lane busy (1)
+      const getQueueSize = vi.fn((lane?: string) => {
+        if (!lane || lane === "main") return 0;
+        if (lane.startsWith("session:")) return 1;
+        return 0;
+      });
+
+      const result = await runHeartbeatOnce({
+        cfg,
+        deps: { getQueueSize, nowMs: () => Date.now() } as HeartbeatDeps,
+      });
+
+      expect(result.status).toBe("skipped");
+      if (result.status === "skipped") {
+        expect(result.reason).toBe("requests-in-flight");
+      }
+      expect(replySpy).not.toHaveBeenCalled();
+    });
+  });
+
+  it("proceeds normally when session lane is idle", async () => {
+    await withTempHeartbeatSandbox(async ({ storePath, replySpy }) => {
+      const cfg: OpenClawConfig = {
+        agents: {
+          defaults: {
+            heartbeat: { every: "30m" },
+            model: { primary: "test/model" },
+          },
+        },
+        channels: {
+          telegram: {
+            enabled: true,
+            token: "fake",
+            allowFrom: ["123"],
+          },
+        },
+      } as unknown as OpenClawConfig;
+
+      await seedMainSessionStore(storePath, cfg, {
+        lastChannel: "telegram",
+        lastProvider: "telegram",
+        lastTo: "123",
+      });
+
+      // Both lanes idle
+      const getQueueSize = vi.fn((_lane?: string) => 0);
+
+      replySpy.mockResolvedValue({
+        text: "HEARTBEAT_OK",
+        model: "test/model",
+      } as any);
+
+      const result = await runHeartbeatOnce({
+        cfg,
+        deps: { getQueueSize, nowMs: () => Date.now() } as HeartbeatDeps,
+      });
+
+      expect(replySpy).toHaveBeenCalled();
+      expect(result.status).toBe("ran");
+    });
+  });
+});
diff --git a/src/infra/heartbeat-runner.ts b/src/infra/heartbeat-runner.ts
index 9615e7f9bfb..791102c3376 100644
--- a/src/infra/heartbeat-runner.ts
+++ b/src/infra/heartbeat-runner.ts
@@ -48,6 +48,7 @@ import {
 } from "../routing/session-key.js";
 import { defaultRuntime, type RuntimeEnv } from "../runtime.js";
 import { escapeRegExp } from "../utils.js";
+import { resolveEmbeddedSessionLane } from "../agents/pi-embedded-runner.js";
 import { formatErrorMessage, hasErrnoCode } from "./errors.js";
 import { isWithinActiveHours } from "./heartbeat-active-hours.js";
 import {
@@ -634,6 +635,21 @@ export async function runHeartbeatOnce(opts: {
     return { status: "skipped", reason: preflight.skipReason };
   }
   const { entry, sessionKey, storePath } = preflight.session;
+
+  // Check the resolved session lane — if it is busy, skip to avoid interrupting
+  // an active streaming turn.  The wake-layer retry (heartbeat-wake.ts) will
+  // re-schedule this wake automatically.  See #14396 (closed without merge).
+  const sessionLaneKey = resolveEmbeddedSessionLane(sessionKey);
+  const sessionLaneSize = (opts.deps?.getQueueSize ?? getQueueSize)(sessionLaneKey);
+  if (sessionLaneSize > 0) {
+    emitHeartbeatEvent({
+      status: "skipped",
+      reason: "requests-in-flight",
+      durationMs: Date.now() - startedAt,
+    });
+    return { status: "skipped", reason: "requests-in-flight" };
+  }
+
   const previousUpdatedAt = entry?.updatedAt;
 
   // When isolatedSession is enabled, create a fresh session via the same