Borrowing it
Nothing to install: this file belongs to thesanjeetc/Parselbox. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/thesanjeetc/Parselbox/main/CLAUDE.mdgit clone --depth 1 https://github.com/thesanjeetc/ParselboxWrote 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/instructions/thesanjeetc/parselbox/claude-md)<a href="https://agentmods.dev/instructions/thesanjeetc/parselbox/claude-md"><img src="https://agentmods.dev/badge/instructions/thesanjeetc/parselbox/claude-md/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/instructions/thesanjeetc/parselbox/claude-md"><img src="https://agentmods.dev/badge/instructions/thesanjeetc/parselbox/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00987 | $0.00987 |
| Opus 5 | $0.00494 | $0.00494 |
| Sonnet 5 | $0.00197 | $0.00197 |
| Haiku 4.5 | $0.00099 | $0.00099 |
Grade A, and why
Parselbox CLAUDE.md 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 9d 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 — 45 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
Parselbox: a secure Python sandbox for AI agents — one execute_code MCP tool; external systems (MCP servers, REST/GraphQL, shells, host functions) appear as native Python objects inside it. Single process: Deno + Pyodide, no containers. It is an execution layer that plugs into any harness — harness-scope features (planning, memory, orchestration) are out of scope.
Architecture (host ↔ sandbox)
Host (Python, holds credentials) Deno subprocess (permission-jailed)
main.py Parselbox orchestrator sandbox/main.ts entry, registers "exec"
rpc.py JSON-lines RPC over stdio <--> sandbox/rpc.ts counterpart
bridge/ tools: http, graphql, shell, sandbox/sandbox.ts PyodideManager (mounts, timeout,
mcp (OAuth), toolkit (sbx.*) packages, watcher, restart)
mcp.py exposes execute_code (FastMCP) sandbox/serve.ts @api routes, uploads, live reload
view.py display() → MCP Apps renderer sandbox/wasi.ts WASI preview1 shim — .wasm commands
context.py dispatches callbacks to bridges via require() and as bash() commands
models.py Callback / ExecutionResult / Mount sandbox/filesystem.ts just-bash (pure-JS bash) + watcher
prompt.py agent guide (served by sbx.help()) sandbox/setup.ts Pyodide boot + snapshot cache
hooks.py lifecycle + MCP elicitation sandbox/bootstrap.py runs INSIDE Pyodide: sbx toolkit,
namespace proxies, tasks, js/require/bash
Two RPC flows: host→sandbox exec (run code), sandbox→host callback (a namespace proxy call → bridge executes with real creds → result returns). Tool calls made in sandbox code therefore run on the host; secrets never enter the sandbox.
Commands
uv sync— setup (Deno ≥2.x must be installed separately)make test— coverage + pytest overtests/(excludes bench); boots real sandboxes, ~7 minuv run pytest tests/test_foo.py -q— run one file;make bench— benchmarksmake check— the CI gate:deno lint+ruff+ruff format --check, thenmake test. CI runs the same lint/format hooks via pre-commit.
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.
- 9d ago First seen · 45 lines · 987 tokens per session scan A 54b5d0c25557
Parselbox CLAUDE.md is an instructions file published in the GitHub repository thesanjeetc/Parselbox (4 stars, last pushed 12d ago), licensed MIT. It adds 987 tokens to every session, about $0.0049 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 2026-08-31.
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