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 agentmods add rules/joinwell52-ai/fcop/fcop-protocolgit clone --depth 1 https://github.com/joinwell52-AI/FCoPWhat 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 | $0.33974 | $0.33974 |
| Opus 5 | $0.16987 | $0.16987 |
| Sonnet 5 | $0.06795 | $0.06795 |
| Haiku 4.5 | $0.03397 | $0.03397 |
Grade E, and why
fcop-protocol scanned grade E with 2 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- Host-neutral reminder / 宿主中立提示: The conventions below describe FCoP itself (a file-based coordination protocol), not anything specific to Cursor. The `.mdc` wrapper and `alwaysApply` frontmatter are a Cursor-specifi Reaches for credential fileshighPrivilege escalation
SSH keys, cloud credentials, git-credentials, .npmrc, /etc/shadow: reading these is how a config file becomes a credential leak.
- PM 在 TASK 文档里写 G6 描述："cached diff 对 `\.env|\.aws/credentials` 0 命中" Copies of this mod
1 near-identical copy found in the catalogue:
- fcop-protocol — 97% identical, 20 lines differ
How it starts
The opening of the file, as written. The whole thing — 2,329 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FCoP Protocol · 协议解释 / Protocol Commentary
本文件是 FCoP 的协议解释——把
fcop-rules.mdc里那 10 条协议规则 （Rule 0–9）落到实际场景里：文件怎么命名、YAML 怎么写、目录怎么组织、 巡检怎么触发。两个文件同为alwaysApply: true，但当本文件与 协议规则冲突时，以fcop-rules.mdc为准。This file is the protocol commentary on
fcop-rules.mdc— how each rule (0–9) actually applies in practice: file naming, YAML shape, directory layout, patrol triggers. Both files arealwaysApply: true. In case of conflict,fcop-rules.mdcwins.
v1.0 final（fcop_protocol_version 1.9.0）：Rule 9 的完整 commentary 已补入文末"Rule 9 Commentary"节。七大核心概念的规范性定义 见
spec/archived/fcop-runtime-protocol-v1.0.md（英文）/.zh.md（中文）。v1.0 final (fcop_protocol_version 1.9.0): Full Rule 9 commentary is now in the "Rule 9 Commentary" section at the end of this file. Normative definitions of the seven core concepts:
spec/archived/fcop-runtime-protocol-v1.0.md(EN) /.zh.md(ZH).
Core Principle / 核心原则
AI agents must not talk only inside their heads — they must land it as a file.
AI 角色之间不能只在脑子里说话，必须落成文件。
This is the overall principle of the entire protocol. Every specific rule below — file naming, YAML frontmatter, subtask batches, collaboration rules — can be understood as "this principle landing in a specific scenario". The principle itself was not designed top-down; it was surfaced by an agent during an unrelated task and then adopted in reverse as the overall rule.
本条为整份协议的总则。下面所有的具体规定——文件命名、YAML 元数据、分包任务、 协作规则——都可以被理解为"这条原则在不同场景下的具体落地"。这条总则不是自上 而下设计出来的，是某次无关任务中由 agent 自发升华得出、后被反向收回为总则。
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.
- yesterday First seen · 2,329 lines · 33,974 tokens per session scan E 9c6e83e14434
fcop-protocol is a cursor rule published in the GitHub repository joinwell52-AI/FCoP (2 stars, last pushed 6d ago), licensed MIT. It adds 33,974 tokens to every session, about $0.1699 per session on Opus 5. A static security scan graded it E with 2 findings (hidden instructions, reaches for credential files). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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