diff --git a/src/infra/heartbeat-events-filter.test.ts b/src/infra/heartbeat-events-filter.test.ts
index dab2250dd0e..9cff6652537 100644
--- a/src/infra/heartbeat-events-filter.test.ts
+++ b/src/infra/heartbeat-events-filter.test.ts
@@ -1,21 +1,93 @@
 import { describe, expect, it } from "vitest";
-import { buildCronEventPrompt, buildExecEventPrompt } from "./heartbeat-events-filter.js";
+import {
+  buildCronEventPrompt,
+  buildExecEventPrompt,
+  isCronSystemEvent,
+  isExecCompletionEvent,
+} from "./heartbeat-events-filter.js";
 
 describe("heartbeat event prompts", () => {
-  it("builds user-relay cron prompt by default", () => {
-    const prompt = buildCronEventPrompt(["Cron: rotate logs"]);
-    expect(prompt).toContain("Please relay this reminder to the user");
+  it.each([
+    {
+      name: "builds user-relay cron prompt by default",
+      events: ["Cron: rotate logs"],
+      expected: ["Cron: rotate logs", "Please relay this reminder to the user"],
+      unexpected: ["Handle this reminder internally", "Reply HEARTBEAT_OK."],
+    },
+    {
+      name: "builds internal-only cron prompt when delivery is disabled",
+      events: ["Cron: rotate logs"],
+      opts: { deliverToUser: false },
+      expected: ["Cron: rotate logs", "Handle this reminder internally"],
+      unexpected: ["Please relay this reminder to the user"],
+    },
+    {
+      name: "falls back to bare heartbeat reply when cron content is empty",
+      events: ["", "   "],
+      expected: ["Reply HEARTBEAT_OK."],
+      unexpected: ["Handle this reminder internally"],
+    },
+    {
+      name: "uses internal empty-content fallback when delivery is disabled",
+      events: ["", "   "],
+      opts: { deliverToUser: false },
+      expected: ["Handle this internally", "HEARTBEAT_OK when nothing needs user-facing follow-up"],
+      unexpected: ["Please relay this reminder to the user"],
+    },
+  ])("$name", ({ events, opts, expected, unexpected }) => {
+    const prompt = buildCronEventPrompt(events, opts);
+    for (const part of expected) {
+      expect(prompt).toContain(part);
+    }
+    for (const part of unexpected) {
+      expect(prompt).not.toContain(part);
+    }
   });
 
-  it("builds internal-only cron prompt when delivery is disabled", () => {
-    const prompt = buildCronEventPrompt(["Cron: rotate logs"], { deliverToUser: false });
-    expect(prompt).toContain("Handle this reminder internally");
-    expect(prompt).not.toContain("Please relay this reminder to the user");
-  });
-
-  it("builds internal-only exec prompt when delivery is disabled", () => {
-    const prompt = buildExecEventPrompt({ deliverToUser: false });
-    expect(prompt).toContain("Handle the result internally");
-    expect(prompt).not.toContain("Please relay the command output to the user");
+  it.each([
+    {
+      name: "builds user-relay exec prompt by default",
+      opts: undefined,
+      expected: ["Please relay the command output to the user", "If it failed"],
+      unexpected: ["Handle the result internally"],
+    },
+    {
+      name: "builds internal-only exec prompt when delivery is disabled",
+      opts: { deliverToUser: false },
+      expected: ["Handle the result internally"],
+      unexpected: ["Please relay the command output to the user"],
+    },
+  ])("$name", ({ opts, expected, unexpected }) => {
+    const prompt = buildExecEventPrompt(opts);
+    for (const part of expected) {
+      expect(prompt).toContain(part);
+    }
+    for (const part of unexpected) {
+      expect(prompt).not.toContain(part);
+    }
+  });
+});
+
+describe("heartbeat event classification", () => {
+  it.each([
+    { value: "exec finished: ok", expected: true },
+    { value: "Exec Finished: failed", expected: true },
+    { value: "cron finished", expected: false },
+  ])("classifies exec completion events for %j", ({ value, expected }) => {
+    expect(isExecCompletionEvent(value)).toBe(expected);
+  });
+
+  it.each([
+    { value: "Cron: rotate logs", expected: true },
+    { value: "  Cron: rotate logs  ", expected: true },
+    { value: "", expected: false },
+    { value: "   ", expected: false },
+    { value: "HEARTBEAT_OK", expected: false },
+    { value: "heartbeat_ok: already handled", expected: false },
+    { value: "heartbeat poll: noop", expected: false },
+    { value: "heartbeat wake: noop", expected: false },
+    { value: "exec finished: ok", expected: false },
+  ])("classifies cron system events for %j", ({ value, expected }) => {
+    expect(isCronSystemEvent(value)).toBe(expected);
   });
 });