execute-code-fallback

A backup procedure for running Python code when an e2b code sandbox is unavailable. It switches execution to a shell command instead.

In plain words
What is it for?
Use it after sandbox errors or timeouts to run Python from the shell, installing needed packages first when required.
Why use it?
It keeps code work moving when the normal isolated execution environment cannot connect or repeatedly fails.

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

Made for: Claude Code, Codex.

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 971 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 $0.00021 $0.00971
Opus 5 $0.00010 $0.00485
Sonnet 5 $0.00004 $0.00194
Haiku 4.5 $0.00002 $0.00097

Measured yesterday against content hash cb9bbd9a7fc1, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

execute-code-fallback 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/execute-code-fallback/SKILL.md · 138 lines

How it starts

The opening of the file, as written. The whole thing — 138 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Execute Code Fallback Pattern

When execute_code_sandbox fails due to e2b unavailability, immediately fall back to run_shell with embedded Python code. This ensures task continuity when the sandbox service is down.

When to Apply

Use this pattern when you observe:

  • execute_code_sandbox returns errors mentioning "e2b", "sandbox unavailable", or connection timeouts
  • Repeated sandbox execution failures (2+ attempts)
  • Error messages indicating the code execution environment is unreachable

Fallback Procedure

Step 1: Detect the Failure

Identify that execute_code_sandbox has failed. Common error indicators:

  • "e2b service unavailable"
  • "Sandbox connection failed"
  • "Execution environment not reachable"
  • Timeout errors during code execution

Step 2: Switch to run_shell with Embedded Python

Instead of:

execute_code_sandbox(code="...")

Use:

run_shell(command="python3 -c '...your Python code...'")

Step 3: Install Dependencies First (If Needed)

If your Python code requires external packages, install them first:

run_shell(command="pip install pandas requests matplotlib")

Then execute your main code:

run_shell(command="python3 << 'EOF'
import pandas as pd
import requests

# Your code here
print("Success")
EOF
")

Step 4: Use Heredoc for Multi-line Code

For complex Python scripts, use heredoc syntax for cleaner code:

run_shell(command="python3 << 'PYTHON_SCRIPT'
import json
import os

# Complex logic here
data = {'key': 'value'}
with open('output.json', 'w') as f:
    json.dump(data, f)

print('File created successfully')
PYTHON_SCRIPT
")

Complete Example

Scenario: You need to process a CSV file and generate a report.

Original approach (sandbox):

execute_code_sandbox(code="""
import pandas as pd
df = pd.read_csv('data.csv')
summary = df.describe()
print(summary)
""")

Fallback approach (run_shell):

# First install dependencies if needed
run_shell(command="pip install pandas --quiet")

# Then execute the code
run_shell(command="python3 << 'EOF'
import pandas as pd
df = pd.read_csv('data.csv')
summary = df.describe()
print(summary)
EOF
")

Read the full file on GitHub · 138 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 · 138 lines · 21 tokens per session scan A cb9bbd9a7fc1

Subscribe to this mod's changes

execute-code-fallback is a skill published in the GitHub repository HKUDS/OpenSpace (7,479 stars, last pushed 19d ago), licensed MIT. It adds 21 tokens to every session and 971 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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