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ironcurtain: Instructions file for GitHub Copilot

.github/copilot-instructions.md

ironcurtain copilot-instructions.md is an instructions file for GitHub Copilot from provos/ironcurtain. It costs 850 tokens per session, scanned A, original, Apache-2.0.

Review rules for IronCurtain, a security runtime that checks every AI-agent tool call against policy before sending it to an MCP server. MCP servers are services that provide tools an agent can call.

In plain words
What is it for?
Use it when reviewing policy-engine changes, MCP forwarding, trusted-server exceptions, platform support, or code that handles tool-call security.
Why use it?
It helps reviewers catch security bypasses, platform mistakes, and incorrect handling of trusted servers at the boundary where agent requests are approved.

Instructions file for GitHub Copilot

Written for GitHub Copilot: a Copilot instructions file.

This is provos/ironcurtain's own configuration. It tells GitHub Copilot how to work on ironcurtain itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything ironcurtain configures →

not rated 615repo +1 yesterday A scan 850 tokens original Apache-2.0
View source ↗ provos/ironcurtain ironcurtain.dev
Reuse

Borrowing it

Nothing to install: this file belongs to provos/ironcurtain. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/provos/ironcurtain/master/.github/copilot-instructions.md
Clone the repo
git clone --depth 1 https://github.com/provos/ironcurtain

Made for: GitHub Copilot.

Wrote 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.

agentmods badge for ironcurtain copilot-instructions.md

README.md
[![agentmods](https://agentmods.dev/badge/instructions/provos/ironcurtain/copilot-instructions/github.svg)](https://agentmods.dev/instructions/provos/ironcurtain/copilot-instructions)
Your own site
<a href="https://agentmods.dev/instructions/provos/ironcurtain/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/provos/ironcurtain/copilot-instructions/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.

agentmods 80×15 button for ironcurtain copilot-instructions.md

Your own site · 80×15
<a href="https://agentmods.dev/instructions/provos/ironcurtain/copilot-instructions"><img src="https://agentmods.dev/badge/instructions/provos/ironcurtain/copilot-instructions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 850 This file is loaded in full into every session.
When invoked 850 The same file — it is already loaded in full.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00850 $0.00850
Opus 5.5 $0.00340 $0.00340
Sonnet 5.5 $0.00170 $0.00170
Haiku 4.5 $0.00085 $0.00085

Measured 1mo ago against content hash 717b57c86929, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

ironcurtain copilot-instructions.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 1mo 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.

.github/copilot-instructions.md · 48 lines

How it starts

The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.

IronCurtain Copilot Review Instructions

IronCurtain is a secure agent runtime that mediates between an AI agent and MCP servers. Every tool call passes through a trusted process that evaluates it against policy rules before forwarding. The policy engine and MCP proxy are the security boundary.

Platform Support

IronCurtain runs on macOS and Linux. Windows is only supported under WSL2 — native Windows is not a target platform.

Security Invariants

  • Every tool call MUST pass through policyEngine.evaluate() before forwarding to a real MCP server. Any code path that skips evaluation is a security bypass.
  • Trusted servers are an intentional exception to annotation requirements. Servers in the trustedServers set (currently only the memory MCP server) bypass structural invariants and compiled rules via an early return in evaluate(). This is by design: trusted server tools have no filesystem paths or URLs, so structural invariants (protected paths, sandbox containment, domain gate) are not applicable and would require fake annotations. Trust is verified by matching both the server name AND the expected entrypoint path (MEMORY_SERVER_ENTRY), not name alone. The normal flow (annotation lookup → evaluate → forward → audit) still runs; only prepareToolArgs is skipped when no annotation exists.
  • Path containment checks MUST use resolveRealPath() (symlink resolution) before comparison. Raw path.resolve() is a symlink-escape vulnerability.
  • isWithinDirectory() appends a trailing / before startsWith(). Without it, /tmp/sandbox-evil matches /tmp/sandbox.
  • Multi-role evaluation uses most-restrictive-wins (deny > escalate > allow). Least-restrictive is a privilege escalation.
  • Unknown tools (without annotations) MUST be denied, unless the server is in the trustedServers set.
  • The auto-approver can only return approve or escalate, never deny. Error paths must return escalate (fail-open to human).
  • SERVER_CREDENTIALS must be deleted from process.env immediately after parsing to prevent child process leakage.
  • Audit logging must occur for every tool call outcome. No code path should skip it.

Read the full file on GitHub · 48 lines

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. 1mo ago First seen · 48 lines · 850 tokens per session scan A 717b57c86929

Subscribe to this mod's changes

ironcurtain copilot-instructions.md is an instructions file published in the GitHub repository provos/ironcurtain (615 stars, last pushed yesterday), licensed Apache-2.0. It adds 850 tokens to every session, about $0.0034 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.

Securityagentmcpmodel-context-protocolpolicysandbox
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