openclaw - 💡(How to fix) Fix Agent prefers system crontab over built-in cron tool — needs system prompt guidance [1 participants]

wujiaming88 · 2026-03-25T07:44:30Z

[openclaw] Problem When a user asks an agent to set up a scheduled task e.g., "remind me every day at 8am" , the agent consistently uses exec "crontab -e ..."… ## Fix / Workaround ## Current Workaround ## Problem When a user asks an agent to set up a scheduled task (e.g., "remind me every day at 8am"), the agent consistently uses `exec("crontab -e ...")` instead of the built-in `cron.add` tool. This leads to: - **Environment issues**: crontab runs with minimal PATH/HOME, causing `openclaw` CLI commands to fail silently - **No delivery**: system crontab has no integration with OpenClaw delivery (announce/webhook), so users never receive notifications - **Management fragmentation**: tasks split between `crontab -l` and `openclaw cron list` - **Shell compatibility**: scripts may fail due to sh vs bash differences (e.g., `set -o pipefail`) ## Root Cause 1. **No system prompt guidance**: OpenClaw injects the `cron.add` tool schema but does not include any instruction telling the model to prefer it over `exec + crontab` 2. **LLM training bias**: Models have seen millions of `crontab` examples vs near-zero OpenClaw cron examples, so `crontab` is the default instinct 3. **exec is a universal escape hatch**: The model can accomplish "set a timer" via `exec` using familiar Linux knowledge, bypassing the purpose-built tool ## Expected Behavior When a user requests a scheduled task, the agent should: 1. Use `cron.add` (built-in cron tool) by default 2. NOT use `exec("crontab ...")` for scheduling ## Suggested Fix ### Option A: Auto-inject system prompt guidance (minimal, recommended) When cron tools are available, automatically include in the system prompt: ``` For scheduled tasks, reminders, and recurring jobs, use the built-in cron tool (cron.add / cron.update / cron.remove). Do not use exec with system crontab. ``` This is zero-config for users and solves the problem at the source. ### Option B: exec-layer detection (defense in depth) Detect `crontab` in exec commands and either: - Warn the agent: "Detected crontab usage. Consider using the built-in cron.add tool instead." - Or block with a redirect message ### Option C: Improve cron tool schema description Add to the cron.add tool description: ``` "This is the recommended way to create scheduled tasks. Do not use system crontab via exec." ``` ### Ideal: Combine A + C Auto-inject guidance in system prompt AND improve tool schema description. This provides both proactive guidance and in-context reinforcement. ## Current Workaround Users must manually add guidance to their AGENTS.md or TOOLS.md: ```markdown ## Scheduling Rules - Always use OpenClaw built-in cron (cron.add), never use system crontab - Set delivery.mode="announce" with channel and target for notifications - Always specify timezone with --tz ``` ## Environment - OpenClaw v2026.3.13 - Multiple agents affected (any agent with exec + cron tools available) - Models tested: Claude Opus 4.6 (Bedrock)

openclaw2026-03-25 07:44:30

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openclaw/openclaw#54341•Fetched 2026-04-08 01:28:44

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Error Message

Warn the agent: "Detected crontab usage. Consider using the built-in cron.add tool instead."

Root Cause

No system prompt guidance: OpenClaw injects the cron.add tool schema but does not include any instruction telling the model to prefer it over exec + crontab
LLM training bias: Models have seen millions of crontab examples vs near-zero OpenClaw cron examples, so crontab is the default instinct
exec is a universal escape hatch: The model can accomplish "set a timer" via exec using familiar Linux knowledge, bypassing the purpose-built tool

Fix Action

Fix / Workaround

Current Workaround

Code Example

For scheduled tasks, reminders, and recurring jobs, use the built-in cron tool 
(cron.add / cron.update / cron.remove). Do not use exec with system crontab.

---

"This is the recommended way to create scheduled tasks. Do not use system crontab via exec."

---

## Scheduling Rules
- Always use OpenClaw built-in cron (cron.add), never use system crontab
- Set delivery.mode="announce" with channel and target for notifications
- Always specify timezone with --tz

RAW_BUFFERClick to expand / collapse

Problem

When a user asks an agent to set up a scheduled task (e.g., "remind me every day at 8am"), the agent consistently uses exec("crontab -e ...") instead of the built-in cron.add tool.

This leads to:

Environment issues: crontab runs with minimal PATH/HOME, causing openclaw CLI commands to fail silently
No delivery: system crontab has no integration with OpenClaw delivery (announce/webhook), so users never receive notifications
Management fragmentation: tasks split between crontab -l and openclaw cron list
Shell compatibility: scripts may fail due to sh vs bash differences (e.g., set -o pipefail)

Root Cause

No system prompt guidance: OpenClaw injects the cron.add tool schema but does not include any instruction telling the model to prefer it over exec + crontab
LLM training bias: Models have seen millions of crontab examples vs near-zero OpenClaw cron examples, so crontab is the default instinct
exec is a universal escape hatch: The model can accomplish "set a timer" via exec using familiar Linux knowledge, bypassing the purpose-built tool

Expected Behavior

When a user requests a scheduled task, the agent should:

Use cron.add (built-in cron tool) by default
NOT use exec("crontab ...") for scheduling

Suggested Fix

Option A: Auto-inject system prompt guidance (minimal, recommended)

When cron tools are available, automatically include in the system prompt:

For scheduled tasks, reminders, and recurring jobs, use the built-in cron tool 
(cron.add / cron.update / cron.remove). Do not use exec with system crontab.

This is zero-config for users and solves the problem at the source.

Option B: exec-layer detection (defense in depth)

Detect crontab in exec commands and either:

Warn the agent: "Detected crontab usage. Consider using the built-in cron.add tool instead."
Or block with a redirect message

Option C: Improve cron tool schema description

Add to the cron.add tool description:

"This is the recommended way to create scheduled tasks. Do not use system crontab via exec."

Ideal: Combine A + C

Auto-inject guidance in system prompt AND improve tool schema description. This provides both proactive guidance and in-context reinforcement.

Current Workaround

Users must manually add guidance to their AGENTS.md or TOOLS.md:

## Scheduling Rules
- Always use OpenClaw built-in cron (cron.add), never use system crontab
- Set delivery.mode="announce" with channel and target for notifications
- Always specify timezone with --tz

Environment

OpenClaw v2026.3.13
Multiple agents affected (any agent with exec + cron tools available)
Models tested: Claude Opus 4.6 (Bedrock)

extent analysis

Fix Plan

To address the issue, we will implement Option A: Auto-inject system prompt guidance and Option C: Improve cron tool schema description. This approach provides both proactive guidance and in-context reinforcement.

Step-by-Step Solution

Auto-inject system prompt guidance:

Add the following text to the system prompt when cron tools are available:

For scheduled tasks, reminders, and recurring jobs, use the built-in cron tool 
(cron.add / cron.update / cron.remove). Do not use exec with system crontab.

Example code snippet (in Python):

def generate_system_prompt():
    prompt = ""
    # ... other prompt generation logic ...
    if cron_tools_available:
        prompt += "For scheduled tasks, reminders, and recurring jobs, use the built-in cron tool (cron.add / cron.update / cron.remove). Do not use exec with system crontab."
    return prompt

Improve cron tool schema description:

Update the cron.add tool description to include:

"This is the recommended way to create scheduled tasks. Do not use system crontab via exec."

Example code snippet (in Python):

def get_cron_tool_description():
    return {
        "name": "cron.add",
        "description": "This is the recommended way to create scheduled tasks. Do not use system crontab via exec."
    }

Verification

To verify that the fix worked, test the following scenarios:

Create a new scheduled task using the agent.
Verify that the agent uses the built-in cron.add tool instead of exec("crontab ...").
Check that the task is successfully created and notifications are delivered as expected.

Extra Tips

Regularly review and update the system prompt guidance to ensure it remains relevant and effective.
Consider implementing Option B: exec-layer detection as an additional defense mechanism to detect and prevent crontab usage via exec.

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openclaw - 💡(How to fix) Fix Agent prefers system crontab over built-in cron tool — needs system prompt guidance [1 participants]

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Error Message

Root Cause

Fix Action

Fix / Workaround

Current Workaround

Code Example

Problem

Root Cause

Expected Behavior

Suggested Fix

Option A: Auto-inject system prompt guidance (minimal, recommended)

Option B: exec-layer detection (defense in depth)

Option C: Improve cron tool schema description

Ideal: Combine A + C

Current Workaround

Environment

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Fix Plan

Step-by-Step Solution

Verification

Extra Tips

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openclaw - 💡(How to fix) Fix Agent prefers system crontab over built-in cron tool — needs system prompt guidance [1 participants]

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GitHub issue graph ai analysis

Error Message

Root Cause

Fix Action

Fix / Workaround

Current Workaround

Code Example

Problem

Root Cause

Expected Behavior

Suggested Fix

Option A: Auto-inject system prompt guidance (minimal, recommended)

Option B: exec-layer detection (defense in depth)

Option C: Improve cron tool schema description

Ideal: Combine A + C

Current Workaround

Environment

extent analysis

Fix Plan

Step-by-Step Solution

Verification

Extra Tips

Still need to ship something?

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