feat(cron): add default stagger controls for scheduled jobs

docs/automation/cron-jobs.md

@@ -115,11 +115,22 @@ Cron supports three schedule kinds:
 
 - `at`: one-shot timestamp via `schedule.at` (ISO 8601).
 - `every`: fixed interval (ms).
-- `cron`: 5-field cron expression with optional IANA timezone.
+- `cron`: 5-field cron expression (or 6-field with seconds) with optional IANA timezone.
 
 Cron expressions use `croner`. If a timezone is omitted, the Gateway host’s
 local timezone is used.
 
+To reduce top-of-hour load spikes across many gateways, OpenClaw applies a
+deterministic per-job stagger window of up to 5 minutes for recurring
+top-of-hour expressions (for example `0 * * * *`, `0 */2 * * *`). Fixed-hour
+expressions such as `0 7 * * *` remain exact.
+
+For any cron schedule, you can set an explicit stagger window with `schedule.staggerMs`
+(`0` keeps exact timing). CLI shortcuts:
+
+- `--stagger 30s` (or `1m`, `5m`) to set an explicit stagger window.
+- `--exact` to force `staggerMs = 0`.
+
 ### Main vs isolated execution
 
 #### Main session jobs (system events)
@@ -408,6 +419,19 @@ openclaw cron add \
   --to "+15551234567"
 ```
 
+Recurring cron job with explicit 30-second stagger:
+
+```bash
+openclaw cron add \
+  --name "Minute watcher" \
+  --cron "0 * * * * *" \
+  --tz "UTC" \
+  --stagger 30s \
+  --session isolated \
+  --message "Run minute watcher checks." \
+  --announce
+```
+
 Recurring isolated job (deliver to a Telegram topic):
 
 ```bash
@@ -465,6 +489,12 @@ openclaw cron edit <jobId> \
   --thinking low
 ```
 
+Force an existing cron job to run exactly on schedule (no stagger):
+
+```bash
+openclaw cron edit <jobId> --exact
+```
+
 Run history:
 
 ```bash

docs/automation/cron-vs-heartbeat.md

@@ -74,7 +74,9 @@ See [Heartbeat](/gateway/heartbeat) for full configuration.
 
 ## Cron: Precise Scheduling
 
-Cron jobs run at **exact times** and can run in isolated sessions without affecting main context.
+Cron jobs run at precise times and can run in isolated sessions without affecting main context.
+Recurring top-of-hour schedules are automatically spread by a deterministic
+per-job offset in a 0-5 minute window.
 
 ### When to use cron
 
@@ -87,7 +89,9 @@ Cron jobs run at **exact times** and can run in isolated sessions without affect
 
 ### Cron advantages
 
-- **Exact timing**: 5-field cron expressions with timezone support.
+- **Precise timing**: 5-field or 6-field (seconds) cron expressions with timezone support.
+- **Built-in load spreading**: recurring top-of-hour schedules are staggered by up to 5 minutes by default.
+- **Per-job control**: override stagger with `--stagger <duration>` or force exact timing with `--exact`.
 - **Session isolation**: Runs in `cron:<jobId>` without polluting main history.
 - **Model overrides**: Use a cheaper or more powerful model per job.
 - **Delivery control**: Isolated jobs default to `announce` (summary); choose `none` as needed.