Problem

Cron jobs with wakeMode: "now" and payload.kind: "systemEvent" fail to deliver when HEARTBEAT.md exists but is effectively empty (only comments/headers). The job state shows:

"lastError": "empty-heartbeat-file",
"lastStatus": "skipped"

Expected behavior

wakeMode: "now" should force immediate delivery regardless of HEARTBEAT.md state. The empty-file optimization makes sense for periodic heartbeats, but not for explicit wake requests.

Root cause

In src/infra/heartbeat-runner.ts:463-468, the empty-file check only bypasses for reason === "exec-event":

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

When a cron job with wakeMode: "now" runs (src/cron/service/timer.ts:153-161), it:

1. Calls enqueueSystemEvent(text, ...) at line 152
2. Calls runHeartbeatOnce({ reason: "cron:${job.id}" }) at line 161

The reason "cron:abc123" doesn't match "exec-event", so the bypass doesn't trigger - even though the job has pending system events to process (just like exec events do).

Related issues

Note: #2217 was closed as "inactive" but the bug was never fixed. #4098 is the most recent and comprehensive report of this issue. #2937 appears to be a separate channel delivery bug.