Borrowing it
Nothing to install: this file belongs to srnichols/plan-forge. 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/srnichols/plan-forge/master/.github/instructions/architecture-principles.instructions.mdgit clone --depth 1 https://github.com/srnichols/plan-forgeWrote 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/srnichols/plan-forge/architecture-principles)<a href="https://agentmods.dev/instructions/srnichols/plan-forge/architecture-principles"><img src="https://agentmods.dev/badge/instructions/srnichols/plan-forge/architecture-principles/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/srnichols/plan-forge/architecture-principles"><img src="https://agentmods.dev/badge/instructions/srnichols/plan-forge/architecture-principles.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 | $0.04487 | $0.04487 |
| Opus 5.5 | $0.01795 | $0.01795 |
| Sonnet 5.5 | $0.00897 | $0.00897 |
| Haiku 4.5 | $0.00449 | $0.00449 |
Grade A, and why
plan-forge architecture-principles.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 11d 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 — 321 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Architecture-First Engineering Principles
Priority: CRITICAL — Read before ANY code changes Applies to: ALL files
AI Agent Instructions
┌─────────────────────────────────────────────────────────────────────────────┐
│ STOP! Before writing ANY code, you MUST: │
│ │
│ 1. ✅ Read this file (architecture-principles.instructions.md) │
│ 2. ✅ Follow the Decision Framework below │
│ 3. ✅ Apply Separation of Concerns │
│ 4. ✅ Consider TDD for business logic │
│ 5. ✅ Check existing patterns first (DON'T reinvent) │
│ │
│ 🚨 RED FLAGS that MUST stop you: │
│ ❌ "quick fix" → STOP, find proper solution │
│ ❌ "copy-paste" → STOP, create reusable abstraction │
│ ❌ "skip types" → STOP, add proper types │
│ ❌ "we'll refactor later" → STOP, do it right now │
└─────────────────────────────────────────────────────────────────────────────┘
The 5 Questions Before Writing ANY Code
1. Does this code BELONG in this file/layer?
| Layer | Responsibility |
|---|---|
| Controllers / Routes | HTTP handling only — no business logic |
| Services | Business logic only — no data access |
| Repositories / Data Access | Database queries only — no business rules |
| Components / Views | UI rendering only — no side effects |
2. Does a PATTERN already exist for this?
- Search existing codebase for similar functionality
- Check
.github/instructions/*.instructions.mdfiles - Follow existing patterns — don't create new approaches
3. Will this SCALE appropriately?
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.
- 11d ago Changed · +18 lines · +615 tokens per session 55bceda13e7d
- 1mo ago First seen · 303 lines · 3,872 tokens per session scan A 6e436d950221
plan-forge architecture-principles.instructions.md is an instructions file published in the GitHub repository srnichols/plan-forge (6 stars, last pushed today), licensed MIT. It adds 4,487 tokens to every session, about $0.0179 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 2026-08-31.
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