Bug: Cron job system events are ignored during heartbeat execution

Summary

When a Cron job with sessionTarget: "main" and wakeMode: "now" triggers, the system event injected via enqueueSystemEvent() is completely ignored by the heartbeat runner. Instead of processing the Cron reminder, the AI reads HEARTBEAT.md and responds with HEARTBEAT_OK, causing the user to never receive the scheduled reminder.

Environment

• OpenClaw version: (latest main branch)
• OS: Windows 11
• Node.js: 22.x

Steps to Reproduce

1. Create a one-shot Cron job:

   Tell AI: "1 minute later, remind me to eat"
   

2. AI creates a job like:

   {
     "schedule": { "kind": "at", "atMs": ... },
     "payload": { "kind": "systemEvent", "text": "🍽️ Reminder: Time to eat!" },
     "sessionTarget": "main",
     "wakeMode": "now",
     "enabled": true
   }

3. When the Cron job triggers, the user receives HEARTBEAT_OK instead of the reminder

Root Cause Analysis

Issue 1: Cron events skipped when HEARTBEAT.md is empty

File: src/infra/heartbeat-runner.ts (lines 506-520)

const isExecEventReason = opts.reason === "exec-event";
// ...
if (isHeartbeatContentEffectivelyEmpty(heartbeatFileContent) && !isExecEventReason) {
  return { status: "skipped", reason: "empty-heartbeat-file" };  // ← Cron events skipped!
}

The code only exempts exec-event from the empty file check, but Cron events (cron:xxx) are not exempted.

Issue 2: Cron system events are never read (CRITICAL)

File: src/infra/heartbeat-runner.ts (lines 544-545)

const isExecEvent = opts.reason === "exec-event";
const pendingEvents = isExecEvent ? peekSystemEvents(sessionKey) : [];
//                                  ↑ Only exec-event reads system events!

When reason is cron:xxx, pendingEvents is always an empty array, so the system event injected by enqueueSystemEvent() is completely ignored.

Issue 3: AI uses standard heartbeat prompt instead of Cron prompt

Because pendingEvents is empty for Cron events, the AI receives the standard HEARTBEAT_PROMPT:

"Read HEARTBEAT.md if it exists... If nothing needs attention, reply HEARTBEAT_OK."

Instead of being told about the reminder, the AI reads HEARTBEAT.md and responds with HEARTBEAT_OK.

Suggested Fix

// src/infra/heartbeat-runner.ts

// Line ~509: Add Cron check for empty file exemption
const isExecEventReason = opts.reason === "exec-event";
const isCronReason = opts.reason?.startsWith("cron:");

// Line ~514: Exempt Cron events from empty file skip
if (isHeartbeatContentEffectivelyEmpty(heartbeatFileContent) && !isExecEventReason && !isCronReason) {
  // ...
}

// Line ~544-545: Read system events for Cron too
const isExecEvent = opts.reason === "exec-event";
const isCronEvent = opts.reason?.startsWith("cron:");
const shouldCheckEvents = isExecEvent || isCronEvent;
const pendingEvents = shouldCheckEvents ? peekSystemEvents(sessionKey) : [];

// Line ~548: Use appropriate prompt for Cron events
const hasCronEvents = isCronEvent && pendingEvents.length > 0;
const CRON_EVENT_PROMPT = 
  `A scheduled reminder has been triggered. The reminder message is shown in the system events above. ` +
  `Please relay this reminder to the user in a helpful way.`;

const prompt = hasExecCompletion 
  ? EXEC_EVENT_PROMPT 
  : hasCronEvents 
    ? CRON_EVENT_PROMPT
    : resolveHeartbeatPrompt(cfg, heartbeat);

Additional Issues Found

Issue 4: enabled defaults to undefined instead of true

File: src/cron/service/jobs.ts (line 97)

The tool description says "enabled defaults to true", but the code doesn't apply this default:

enabled: input.enabled,  // ← Should be: input.enabled !== false

Issue 5: wakeMode defaults to next-heartbeat for one-shot jobs

File: src/cron/normalize.ts (lines 121-124)

For reminder-type one-shot jobs (schedule.kind: "at"), wakeMode should default to "now" to ensure immediate delivery:

if (!next.wakeMode) {
  const isOneShot = isRecord(next.schedule) && next.schedule.kind === "at";
  next.wakeMode = isOneShot ? "now" : "next-heartbeat";
}

Impact

• Severity: High
• Affected Feature: Cron reminders with sessionTarget: "main"
• User Impact: Scheduled reminders never reach the user

Workaround

Use sessionTarget: "isolated" with payload.kind: "agentTurn" instead, which bypasses the heartbeat mechanism entirely.