fallback-file-ops

A fallback procedure for filesystem work when the usual sandbox or shell tools fail with an unknown error. It switches to explicit shell commands for creating folders and files, then checks that they were created.

In plain words
What is it for?
Use it to create nested project folders and files when the primary filesystem tools fail, and to verify the results.
Why use it?
It helps complete file operations after a tool reports success but does not actually create the requested files or directories.

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

Made for: Claude Code, Codex.

Per session 22 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 653 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 $0.00022 $0.00653
Opus 5 $0.00011 $0.00327
Sonnet 5 $0.00004 $0.00131
Haiku 4.5 $0.00002 $0.00065

Measured 3d ago against content hash fc4409471c8e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fallback-file-ops 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 3d 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.

benchmarks/gdpval/skills/fallback-file-ops/SKILL.md · 87 lines

How it starts

The opening of the file, as written. The whole thing — 87 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fallback File Operations

Purpose

When execute_code_sandbox or shell_agent fail with 'unknown error' on filesystem operations, fall back to run_shell with explicit mkdir and file write commands. This hybrid approach is more reliable for creating complex project structures.

When to Apply

  • execute_code_sandbox returns 'unknown error' on file/directory creation
  • shell_agent fails to write files or create nested directories
  • You need to create complex project structures with multiple levels

Procedure

Step 1: Detect Tool Failure

Monitor for these failure patterns:

  • Error message contains "unknown error"
  • File operations silently fail (file not created)
  • Directory creation returns success but directory doesn't exist

Step 2: Switch to run_shell

When failures occur, immediately switch to run_shell for filesystem operations:

# Create directory structure explicitly
run_shell: mkdir -p /path/to/nested/directory

# Write files using shell redirection or echo
run_shell: echo "content" > /path/to/file.txt

# Or use cat with heredoc for multi-line files
run_shell: cat > /path/to/file.txt << 'EOF'
line 1
line 2
EOF

Step 3: Verify Creation

After each operation, verify the file/directory was created:

run_shell: ls -la /path/to/created/item
run_shell: test -f /path/to/file && echo "File exists"
run_shell: test -d /path/to/dir && echo "Directory exists"

Step 4: Continue with Hybrid Approach

  • Use run_shell for all filesystem operations (mkdir, write, copy, move)
  • Continue using execute_code_sandbox or shell_agent for code execution, compilation, or other non-filesystem tasks
  • Document which tool handles which operation for clarity

Example: Creating Project Structure

# Failed attempt with execute_code_sandbox
execute_code_sandbox: create directory src/components

# Fallback with run_shell
run_shell: mkdir -p src/components
run_shell: mkdir -p src/utils
run_shell: mkdir -p tests/unit
run_shell: echo "// Component file" > src/components/Button.tsx
run_shell: echo "// Utility file" > src/utils/helpers.ts

Read the full file on GitHub · 87 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. 3d ago First seen · 87 lines · 22 tokens per session scan A fc4409471c8e

Subscribe to this mod's changes

fallback-file-ops is a skill published in the GitHub repository HKUDS/OpenSpace (7,486 stars, last pushed 21d ago), licensed MIT. It adds 22 tokens to every session and 653 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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