Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/hkuds/openspace/fallback-python-executionnpx skills add HKUDS/OpenSpace --skill fallback-python-executiongit clone --depth 1 https://github.com/HKUDS/OpenSpaceWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00018 | $0.00615 |
| Opus 5 | $0.00009 | $0.00308 |
| Sonnet 5 | $0.00004 | $0.00123 |
| Haiku 4.5 | $0.00002 | $0.00061 |
Grade A, and why
fallback-python-execution scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Fallback Python Execution Pattern
When to Use
Use this pattern when:
execute_code_sandboxreturns unknown errors or fails repeatedlyshell_agentcannot successfully execute Python code- You need to create files (spreadsheets, documents, data files) via Python
- Direct delegated approaches prove unreliable in the current environment
Core Technique
Instead of delegating Python execution to agents, use this two-step inline approach:
- Write Python code to a
.pyfile usingwrite_file - Execute the file using
run_shellwithpython <script.py>
Step-by-Step Instructions
Step 1: Write Python Code to File
Use write_file to create a Python script with all necessary code inline:
write_file
path: /path/to/script.py
content: |
import pandas as pd
# Your complete Python code here
df = pd.DataFrame({...})
df.to_excel('output.xlsx', index=False)
Step 2: Execute via run_shell
Run the script directly:
run_shell
command: python /path/to/script.py
Step 3: Verify and Clean Up
- Check the output for success/errors
- Verify the expected files were created
- Optionally remove the temporary script if no longer needed
Why This Works
This approach is more reliable because:
- Avoids agent interpretation layers that can introduce errors
- Provides direct control over execution environment
- Gives clear error output for debugging
- Bypasses sandbox delegation issues
Example: Excel File Creation
# Step 1: Write the script
write_file:
path: create_report.py
content: |
import pandas as pd
from openpyxl import Workbook
# Create data
data = {'Column1': [1, 2, 3], 'Column2': ['A', 'B', 'C']}
df = pd.DataFrame(data)
# Save to Excel
df.to_excel('report.xlsx', index=False)
print('Excel file created successfully')
# Step 2: Execute
run_shell:
command: python create_report.py
Tips
- Include error handling in your Python code for better debugging
- Use absolute paths when possible to avoid working directory issues
- Add print statements to track execution progress
- Keep scripts self-contained with all imports at the top
- For complex tasks, break into multiple scripts if needed
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2d ago First seen · 100 lines · 18 tokens per session scan A b7cc2b24da5e
fallback-python-execution is a skill published in the GitHub repository HKUDS/OpenSpace (7,479 stars, last pushed 20d ago), licensed MIT. It adds 18 tokens to every session and 615 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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