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Hermes-agent
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---
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sidebar_position: 11
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title: "Cron Internals"
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description: "How Hermes stores, schedules, edits, pauses, skill-loads, and delivers cron jobs"
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---
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# Cron Internals
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The cron subsystem provides scheduled task execution — from simple one-shot delays to recurring cron-expression jobs with skill injection and cross-platform delivery.
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## Key Files
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| File | Purpose |
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|------|---------|
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| `cron/jobs.py` | Job model, storage, atomic read/write to `jobs.json` |
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| `cron/scheduler.py` | Scheduler loop — due-job detection, execution, repeat tracking |
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| `tools/cronjob_tools.py` | Model-facing `cronjob` tool registration and handler |
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| `gateway/run.py` | Gateway integration — cron ticking in the long-running loop |
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| `hermes_cli/cron.py` | CLI `hermes cron` subcommands |
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## Scheduling Model
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Four schedule formats are supported:
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| Format | Example | Behavior |
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|--------|---------|----------|
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| **Relative delay** | `30m`, `2h`, `1d` | One-shot, fires after the specified duration |
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| **Interval** | `every 2h`, `every 30m` | Recurring, fires at regular intervals |
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| **Cron expression** | `0 9 * * *` | Standard 5-field cron syntax (minute, hour, day, month, weekday) |
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| **ISO timestamp** | `2025-01-15T09:00:00` | One-shot, fires at the exact time |
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The model-facing surface is a single `cronjob` tool with action-style operations: `create`, `list`, `update`, `pause`, `resume`, `run`, `remove`.
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## Job Storage
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Jobs are stored in `~/.hermes/cron/jobs.json` with atomic write semantics (write to temp file, then rename). Each job record contains:
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```json
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{
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"id": "a1b2c3d4e5f6",
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"name": "Daily briefing",
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"prompt": "Summarize today's AI news and funding rounds",
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"schedule": {
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"kind": "cron",
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"expr": "0 9 * * *",
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"display": "0 9 * * *"
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},
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"skills": ["ai-funding-daily-report"],
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"deliver": "telegram:-1001234567890",
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"repeat": {
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"times": null,
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"completed": 42
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},
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"state": "scheduled",
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"enabled": true,
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"next_run_at": "2025-01-16T09:00:00Z",
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"last_run_at": "2025-01-15T09:00:00Z",
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"last_status": "ok",
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"created_at": "2025-01-01T00:00:00Z",
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"model": null,
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"provider": null,
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"script": null
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}
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```
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### Job Lifecycle States
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| State | Meaning |
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|-------|---------|
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| `scheduled` | Active, will fire at next scheduled time |
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| `paused` | Suspended — won't fire until resumed |
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| `completed` | Repeat count exhausted or one-shot that has fired |
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| `running` | Currently executing (transient state) |
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### Backward Compatibility
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Older jobs may have a single `skill` field instead of the `skills` array. The scheduler normalizes this at load time — single `skill` is promoted to `skills: [skill]`.
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## Scheduler Runtime
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### Tick Cycle
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The scheduler runs on a periodic tick (default: every 60 seconds):
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```text
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tick()
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1. Acquire scheduler lock (prevents overlapping ticks)
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2. Load all jobs from jobs.json
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3. Filter to due jobs (next_run <= now AND state == "scheduled")
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4. For each due job:
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a. Set state to "running"
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b. Create fresh AIAgent session (no conversation history)
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c. Load attached skills in order (injected as user messages)
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d. Run the job prompt through the agent
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e. Deliver the response to the configured target
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f. Update run_count, compute next_run
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g. If repeat count exhausted → state = "completed"
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h. Otherwise → state = "scheduled"
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5. Write updated jobs back to jobs.json
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6. Release scheduler lock
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```
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### Gateway Integration
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In gateway mode, the scheduler runs in a dedicated background thread (`_start_cron_ticker` in `gateway/run.py`) that calls `scheduler.tick()` every 60 seconds alongside message handling.
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In CLI mode, cron jobs only fire when `hermes cron` commands are run or during active CLI sessions.
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### Fresh Session Isolation
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Each cron job runs in a completely fresh agent session:
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- No conversation history from previous runs
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- No memory of previous cron executions (unless persisted to memory/files)
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- The prompt must be self-contained — cron jobs cannot ask clarifying questions
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- The `cronjob` toolset is disabled (recursion guard)
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## Skill-Backed Jobs
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A cron job can attach one or more skills via the `skills` field. At execution time:
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1. Skills are loaded in the specified order
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2. Each skill's SKILL.md content is injected as context
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3. The job's prompt is appended as the task instruction
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4. The agent processes the combined skill context + prompt
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This enables reusable, tested workflows without pasting full instructions into cron prompts. For example:
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```
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Create a daily funding report → attach "ai-funding-daily-report" skill
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```
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### Script-Backed Jobs
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Jobs can also attach a Python script via the `script` field. The script runs *before* each agent turn, and its stdout is injected into the prompt as context. This enables data collection and change detection patterns:
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```python
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# ~/.hermes/scripts/check_competitors.py
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import requests, json
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# Fetch competitor release notes, diff against last run
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# Print summary to stdout — agent analyzes and reports
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```
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The script timeout defaults to 120 seconds. `_get_script_timeout()` resolves the limit through a three-layer chain:
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1. **Module-level override** — `_SCRIPT_TIMEOUT` (for tests/monkeypatching). Only used when it differs from the default.
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2. **Environment variable** — `HERMES_CRON_SCRIPT_TIMEOUT`
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3. **Config** — `cron.script_timeout_seconds` in `config.yaml` (read via `load_config()`)
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4. **Default** — 120 seconds
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### Provider Recovery
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`run_job()` passes the user's configured fallback providers and credential pool into the `AIAgent` instance:
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- **Fallback providers** — reads `fallback_providers` (list) or `fallback_model` (legacy dict) from `config.yaml`, matching the gateway's `_load_fallback_model()` pattern. Passed as `fallback_model=` to `AIAgent.__init__`, which normalizes both formats into a fallback chain.
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- **Credential pool** — loads via `load_pool(provider)` from `agent.credential_pool` using the resolved runtime provider name. Only passed when the pool has credentials (`pool.has_credentials()`). Enables same-provider key rotation on 429/rate-limit errors.
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This mirrors the gateway's behavior — without it, cron agents would fail on rate limits without attempting recovery.
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## Delivery Model
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Cron job results can be delivered to any supported platform:
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| Target | Syntax | Example |
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|--------|--------|---------|
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| Origin chat | `origin` | Deliver to the chat where the job was created |
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| Local file | `local` | Save to `~/.hermes/cron/output/` |
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| Telegram | `telegram` or `telegram:<chat_id>` | `telegram:-1001234567890` |
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| Discord | `discord` or `discord:#channel` | `discord:#engineering` |
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| Slack | `slack` | Deliver to Slack home channel |
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| WhatsApp | `whatsapp` | Deliver to WhatsApp home |
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| Signal | `signal` | Deliver to Signal |
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| Matrix | `matrix` | Deliver to Matrix home room |
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| Mattermost | `mattermost` | Deliver to Mattermost home |
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| Email | `email` | Deliver via email |
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| SMS | `sms` | Deliver via SMS |
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| Home Assistant | `homeassistant` | Deliver to HA conversation |
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| DingTalk | `dingtalk` | Deliver to DingTalk |
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| Feishu | `feishu` | Deliver to Feishu |
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| WeCom | `wecom` | Deliver to WeCom |
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| Weixin | `weixin` | Deliver to Weixin (WeChat) |
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| BlueBubbles | `bluebubbles` | Deliver to iMessage via BlueBubbles |
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| QQ Bot | `qqbot` | Deliver to QQ (Tencent) via Official API v2 |
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For Telegram topics, use the format `telegram:<chat_id>:<thread_id>` (e.g., `telegram:-1001234567890:17585`).
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### Response Wrapping
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By default (`cron.wrap_response: true`), cron deliveries are wrapped with:
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- A header identifying the cron job name and task
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- A footer noting the agent cannot see the delivered message in conversation
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The `[SILENT]` prefix in a cron response suppresses delivery entirely — useful for jobs that only need to write to files or perform side effects.
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### Session Isolation
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Cron deliveries are NOT mirrored into gateway session conversation history. They exist only in the cron job's own session. This prevents message alternation violations in the target chat's conversation.
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## Recursion Guard
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Cron-run sessions have the `cronjob` toolset disabled. This prevents:
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- A scheduled job from creating new cron jobs
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- Recursive scheduling that could explode token usage
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- Accidental mutation of the job schedule from within a job
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## Locking
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The scheduler uses cross-process file-based locking (`fcntl.flock` on Unix, `msvcrt.locking` on Windows) to prevent overlapping ticks from executing the same due-job batch twice — even between the gateway's in-process ticker and a standalone `hermes cron` / manual `tick()` call. If the lock cannot be acquired, `tick()` returns 0 immediately.
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## CLI Interface
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The `hermes cron` CLI provides direct job management:
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```bash
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hermes cron list # Show all jobs
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hermes cron create # Interactive job creation (alias: add)
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hermes cron edit <job_id> # Edit job configuration
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hermes cron pause <job_id> # Pause a running job
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hermes cron resume <job_id> # Resume a paused job
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hermes cron run <job_id> # Trigger immediate execution
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hermes cron remove <job_id> # Delete a job
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```
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## Related Docs
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- [Cron Feature Guide](/user-guide/features/cron)
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- [Gateway Internals](./gateway-internals.md)
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- [Agent Loop Internals](./agent-loop.md)
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