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/tw-haiven/haiven-mcp-server/backend-rulesgit clone --depth 1 https://github.com/tw-haiven/haiven-mcp-serverWrote 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/rules/tw-haiven/haiven-mcp-server/backend-rules)<a href="https://agentmods.dev/rules/tw-haiven/haiven-mcp-server/backend-rules"><img src="https://agentmods.dev/badge/rules/tw-haiven/haiven-mcp-server/backend-rules.svg" alt="Measured on agentmods" 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 | $0.00004 | $0.00127 |
| Opus 5 | $0.00002 | $0.00063 |
| Sonnet 5 | $0.00001 | $0.00025 |
| Haiku 4.5 | $0.00000 | $0.00013 |
Grade A, and why
backend-rules 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 5d 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.
What it actually says
- Our backend is in Python and in the app/ subfolder. The app needs to be started from that directory.
- The backend tests are in app/tests/
- When running tests or the application, the virtual environment in app/.venv first needs to be activated
- We're using constructor dependency injections to make our code more testable. Pass dependencies in via constructors, do not initialise them inside of a class.
- When we wrap up a backend change, make sure to remind me to start up the whole application, to make sure that it's all well-integrated.
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.
- 5d ago First seen · 11 lines · 4 tokens per session scan A fefd7cda29ea
backend-rules is a cursor rule published in the GitHub repository tw-haiven/haiven-mcp-server (0 stars, last pushed 9mo ago), licensed Apache-2.0. It adds 4 tokens to every session and 127 once invoked, about $0.0000 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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