ShadowFrog is a suite of coding-agent skills that maintains a file-backed knowledge base of tacit information about a codebase, such as fragile dependencies, untested invariants, and hard-to-notice edge cases. It helps coding agents preserve lessons from code reading, experiments, and conversations across future work. The catalogue contains skills that create, update, explore, organize, and view this shadow knowledge base.
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 skills add microsoft/ShadowFrog --skill shadow-frog-initgit clone --depth 1 https://github.com/microsoft/ShadowFrogWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/microsoft/shadowfrog/shadow-frog-init)<a href="https://agentmods.dev/skills/microsoft/shadowfrog/shadow-frog-init"><img src="https://agentmods.dev/badge/skills/microsoft/shadowfrog/shadow-frog-init/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/microsoft/shadowfrog/shadow-frog-init"><img src="https://agentmods.dev/badge/skills/microsoft/shadowfrog/shadow-frog-init.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00063 | $0.01894 |
| Opus 5.5 | $0.00025 | $0.00758 |
| Sonnet 5.5 | $0.00013 | $0.00379 |
| Haiku 4.5 | $0.00006 | $0.00189 |
Grade A, and why
shadow-frog-init scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 29d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 253 lines — stays where its author put it; the contents beside it link to each section on GitHub.
ShadowFrog Init
Creates .shadow/ directory with symbol-organized shadow files for every
source file. Run once per repo. If .shadow/ exists, ask user to reset or skip.
Primary: Python Helper Script
The companion script shadow-init.py lives in the same directory as
this SKILL.md file. To find and run it:
# Project install (Copilot CLI):
python3 .github/skills/shadow-frog-init/shadow-init.py [options]
# Or for Claude Code:
python3 .claude/skills/shadow-frog-init/shadow-init.py [options]
Run from the repo/worktree root. The helper auto-detects it with
git rev-parse --show-toplevel. If Git cannot resolve or access the root
(for example, inside a container), use --root to bypass detection:
# If auto-detect fails, pass the root explicitly:
python3 .github/skills/shadow-frog-init/shadow-init.py --root "$(pwd)"
Options
| Flag | Effect |
|---|---|
--root DIR |
Repository root (default: auto-detect via git) |
--reset |
Delete existing .shadow/ and recreate |
--dry-run |
Show what would be created without writing |
What it does
The helper discovers sources with git ls-files, applies
.shadow/.shadowignore, extracts symbols, and creates symbol-organized
per-file shadows plus _index.md, _prefs.md, _meta/state.json, and
.shadowignore. It reports file/symbol counts and detected languages.
After creating .shadow/, complete Post-init steps.
The helper does not choose the version-control mode.
Fallback: Manual Init
If the Python script fails (wrong Python version, missing file, etc.), follow these steps manually, then complete Post-init steps.
1. Check preconditions
git rev-parse --is-inside-work-tree # must be a git repo
test -d .shadow && echo "exists" # if exists, ask user: reset or skip
2. Discover source files
git ls-files --cached --others --exclude-standard
Include patterns (auto-detect from repo contents):
*.py, *.js, *.ts, *.tsx, *.jsx, *.java, *.go, *.rs, *.rb,
*.cpp, *.c, *.h, *.cs, *.swift, *.kt, *.scala, *.php,
*.sh, *.bash, *.zsh, *.yaml, *.yml, *.toml, *.json,
Makefile, Dockerfile, docker-compose*.yml
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.
- 29d ago Changed · +2 lines 8cae8ac804eb
- 1mo ago Changed · -17 lines f872e93bcbc2
- 1mo ago First seen · 268 lines · 63 tokens per session scan A 2c2a8e053895
shadow-frog-init is a skill published in the GitHub repository microsoft/ShadowFrog (30 stars, last pushed 6d ago), licensed MIT. It adds 63 tokens to every session and 1,894 once invoked, about $0.0003 per session on Opus 5.5. 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.
Other skills, from other repositories
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memory
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ha-data-stores
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