fallback-code-execution

A fallback procedure for running Python code through a file and a shell command when the main sandbox executor fails repeatedly. It includes guidance for saving the script, handling dependencies, and adding diagnostics.

In plain words
What is it for?
Use it after repeated sandbox failures to create a Python script, install or record needed packages, run it from the shell, and capture useful error output.
Why use it?
It avoids repeatedly retrying a broken execution environment when the code itself appears valid. Running a saved script through the shell can provide a more reliable path to execution.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/hkuds/openspace/fallback-code-execution
Any agent
npx skills add HKUDS/OpenSpace --skill fallback-code-execution
Clone the repo
git clone --depth 1 https://github.com/HKUDS/OpenSpace

Made for: Claude Code, Codex.

Per session 19 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 645 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What 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.

ModelPer sessionOnce invoked
Fable 5 $0.00019 $0.00645
Opus 5 $0.00010 $0.00322
Sonnet 5 $0.00004 $0.00129
Haiku 4.5 $0.00002 $0.00064

Measured yesterday against content hash 5c05b68b15d1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fallback-code-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 yesterday.

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.

benchmarks/gdpval/skills/fallback-code-execution/SKILL.md · 72 lines

How it starts

The opening of the file, as written. The whole thing — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fallback Code Execution Workflow

Overview

This skill defines a robust workaround for executing code (specifically Python) when the primary execute_code_sandbox tool fails repeatedly with unknown or transient errors. Instead of continuing to retry the failing tool, the agent switches to a manual file-write and shell-execution pattern.

Trigger Conditions

Activate this workflow when:

  1. execute_code_sandbox fails 2 or more times consecutively for the same logic.
  2. Error messages are generic, unknown, or indicate environment issues rather than syntax errors.
  3. The code logic itself is verified correct but the execution environment is unstable.

Procedure

Step 1: Write Script to File

Use the write_file tool to save the Python script to a specific path in the workspace.

  • Path: Choose a descriptive name ending in .py (e.g., scripts/generate_report.py).
  • Content: Ensure the script includes necessary error handling and print statements for debugging.
  • Dependencies: If the script requires external libraries, ensure a requirements.txt is updated or installed via shell beforehand.

Example:

tool: write_file
path: workspace/scripts/process_data.py
content: |
  import sys
  # ... script logic ...
  print("Success")

Step 2: Execute via Shell

Use the run_shell tool to execute the script using the system Python interpreter.

  • Command: python3 <path_to_script> or python <path_to_script>.
  • Working Directory: Ensure the shell command runs from the workspace root or the directory containing the script.
  • Capture Output: Store stdout and stderr for verification.

Example:

tool: run_shell
command: python3 scripts/process_data.py

Step 3: Verify Execution

  1. Check Exit Code: Ensure the shell command returned exit code 0.
  2. Check Output: Verify expected files were created or expected stdout messages appeared.
  3. Handle Errors: If the shell execution fails, inspect the stderr output. This often provides more detailed tracebacks than the sandbox tool.

Read the full file on GitHub · 72 lines

Files

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.

Changes

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.

  1. yesterday First seen · 72 lines · 19 tokens per session scan A 5c05b68b15d1

Subscribe to this mod's changes

fallback-code-execution is a skill published in the GitHub repository HKUDS/OpenSpace (7,479 stars, last pushed 19d ago), licensed MIT. It adds 19 tokens to every session and 645 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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