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Agent skill

Sandbox Fallback Execution

by HKUDS in HKUDS/OpenSpace

Fallback workflow for executing Python code when executecodesandbox fails

MITAuto-check passed

Install Sandbox Fallback Execution

skills CLI
$ npx skills add HKUDS/OpenSpace --skill sandbox-fallback-execution -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install HKUDS/OpenSpace sandbox-fallback-execution --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/HKUDS/OpenSpace.git skills-src && mkdir -p .claude/skills && cp -r skills-src/benchmarks/gdpval/skills/sandbox-fallback-execution .claude/skills/sandbox-fallback-execution && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
sandbox-fallback-execution
GitHub stars
7.8k
Token cost
~740 tokens
SKILL.md length
280 words
Files
2
Skills in repo
199
Repo updated
First seen
Licence
MIT

At a glance

Fallback workflow for executing Python code when executecodesandbox fails

  • Works in 4 steps: Detect Sandbox Failure → Install Required Dependencies (If Needed) → Execute Python via Heredoc → …
  • SKILL.md covers When to Use This Skill, Pattern Overview, Step-by-Step Instructions and Complete Example, plus 3 more sections
  • Calls pip and python3

What it does

Sandbox Fallback Execution is an agent skill from HKUDS/OpenSpace. Fallback workflow for executing Python code when executecodesandbox fails

Its SKILL.md is about 740 tokens, which your agent loads only when the skill is triggered. The skill folder holds 1 other file.

It works with Python. The repository describes itself as: "OpenSpace: The Skill Management Layer for AI Agents" -- https://open-space.cloud/. The licence is MIT.

Example prompts

  • “/sandbox-fallback-execution”

Requirements

  • Python 3

Workflow steps

4 steps, taken from the step headings in SKILL.md.

  1. Detect Sandbox Failure
  2. Install Required Dependencies (If Needed)
  3. Execute Python via Heredoc
  4. Verify and Iterate

What it can do on your machine

Read from SKILL.md and the folder at commit 3827781. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • pip
    • python3

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use pip, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Sandbox Fallback Execution loads about 740 tokens when it runs. Until then it costs about 26 tokens; SKILL.md has 280 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~26
When it runs · the whole SKILL.md, loaded when a task matches
~740

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from HKUDS/OpenSpace at commit 3827781, republished under its MIT licence (© HKUDS). 280 words, ~740 tokens.

Download SKILL.mdSave it as .claude/skills/sandbox-fallback-execution/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.
name
sandbox-fallback-execution
description
Fallback workflow for executing Python code when execute_code_sandbox fails

Sandbox Fallback Execution

When to Use This Skill

Use this pattern when execute_code_sandbox fails with unknown errors, timeouts, or persistent execution failures. This fallback bypasses sandbox restrictions by using run_shell with a Python heredoc script.

Pattern Overview

execute_code_sandbox fails → run_shell with pip install → Python heredoc execution

Step-by-Step Instructions

Step 1: Detect Sandbox Failure

Monitor for these failure indicators from execute_code_sandbox:

  • Unknown or unexplained errors
  • Repeated execution failures (>2 attempts)
  • Timeout errors
  • Environment/package availability issues
Step 2: Install Required Dependencies (If Needed)

Use run_shell to install any required Python packages:

bash
pip install <package_name>

For multiple packages:

bash
pip install package1 package2 package3
Step 3: Execute Python via Heredoc

Run Python code using a heredoc script with run_shell:

bash
python3 << 'EOF'
# Your Python code here
import sys
print("Hello from fallback execution")
EOF

Key heredoc syntax notes:

  • Use << 'EOF' (quoted) to prevent shell variable expansion
  • Use << EOF (unquoted) if you need shell variable interpolation
  • Close with EOF on its own line
Step 4: Verify and Iterate
  • Check stdout/stderr for success indicators
  • If errors persist, inspect output and adjust the script
  • Capture any generated artifacts (files, outputs) for verification

Complete Example

Scenario: Need to create a Word document but execute_code_sandbox keeps failing.

bash
# Step 1: Install required package
pip install python-docx

# Step 2: Execute Python script via heredoc
python3 << 'EOF'
from docx import Document

doc = Document()
doc.add_heading('Proposal Document', 0)
doc.add_paragraph('This is the proposal content.')
doc.save('proposal.docx')
print("Document created successfully")
EOF

Best Practices

  1. Quote the heredoc delimiter ('EOF') to avoid unintended shell expansion of Python code
  2. Install packages first before running the script to ensure availability
  3. Print status messages in your script for easier debugging
  4. Save outputs to files when possible for verification
  5. Keep scripts focused - break complex tasks into multiple heredoc executions if needed

Troubleshooting

IssueSolution
pip not foundTry pip3 or python3 -m pip install
Script hangsAdd timeout to run_shell command
Permission errorsCheck file paths are writable
Import errorsVerify package was installed successfully
  • run_shell: Execute shell commands directly
  • execute_code_sandbox: Primary Python execution tool (try first)
  • shell_agent: For more complex multi-step shell tasks

© HKUDS, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file in benchmarks/gdpval/skills/sandbox-fallback-execution of HKUDS/OpenSpace.

  • SKILL.md
  • .skill_id

Open the folder on GitHubat commit 3827781

Compare with similar skills

Sandbox Fallback Execution next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Sandbox Fallback Execution compared with similar skills
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Sandbox Fallback Execution this skillHKUDS/OpenSpace7.8k—~740Automated safety check: PassMIT
MCP Server Builderanthropics/skills180k63 repos~2.3kAutomated safety check: PassApache-2.0
PDF Processinganthropics/skills180k48 repos~2kAutomated safety check: PassProprietary
NotebookLM Research AssistantPleasePrompto/notebooklm-skill7.8k14 repos~2.4kAutomated safety check: NotesMIT
Manim Video Productionbrowser-use/video-use28k6 repos~3kAutomated safety check: PassMIT
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT

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Works with

Questions about Sandbox Fallback Execution

What does Sandbox Fallback Execution do?

Fallback workflow for executing Python code when executecodesandbox fails. Sandbox Fallback Execution is an agent skill from HKUDS/OpenSpace.

How do I install Sandbox Fallback Execution in Claude Code?

Run `npx skills add HKUDS/OpenSpace --skill sandbox-fallback-execution -a claude-code`. Or copy the skill folder (benchmarks/gdpval/skills/sandbox-fallback-execution in HKUDS/OpenSpace) into .claude/skills/sandbox-fallback-execution in your project. Claude Code loads it when a task matches its description.

How do I install Sandbox Fallback Execution in Codex?

Run `npx skills add HKUDS/OpenSpace --skill sandbox-fallback-execution -a codex`. Or copy the skill folder (benchmarks/gdpval/skills/sandbox-fallback-execution in HKUDS/OpenSpace) into .agents/skills/sandbox-fallback-execution in your project. Codex loads it when a task matches its description.

Can I use Sandbox Fallback Execution in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add HKUDS/OpenSpace --skill sandbox-fallback-execution -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/sandbox-fallback-execution, .gemini/skills/sandbox-fallback-execution, .github/skills/sandbox-fallback-execution and .opencode/skills/sandbox-fallback-execution in your project.

What does Sandbox Fallback Execution need to run?

Going by SKILL.md and its folder, Sandbox Fallback Execution needs the command-line tools its instructions call (pip and python3). Our summary lists: Python 3.

Does Sandbox Fallback Execution access the network?

SKILL.md contains no URLs. Its commands use pip, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Sandbox Fallback Execution safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Sandbox Fallback Execution use?

Sandbox Fallback Execution is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Sandbox Fallback Execution use?

About 740 tokens (SKILL.md is roughly 3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Sandbox Fallback Execution?

Skills that share tags, products or a category with Sandbox Fallback Execution: MCP Server Builder (anthropics/skills, 180k stars), PDF Processing (anthropics/skills, 180k stars), NotebookLM Research Assistant (PleasePrompto/notebooklm-skill, 7.8k stars) and Manim Video Production (browser-use/video-use, 28k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Sandbox Fallback Execution?

HKUDS (a GitHub organization) maintains it in HKUDS/OpenSpace, which has 7,750 GitHub stars. The repository holds 199 skills in this directory. The repository was last updated on August 12, 2026.

Source: HKUDS/OpenSpace on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.