Borrowing it
Nothing to install: this file belongs to punt-labs/postern. 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/punt-labs/postern/main/.claude/agents/bwk.mdgit clone --depth 1 https://github.com/punt-labs/posternWrote 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/agents/punt-labs/postern/bwk)<a href="https://agentmods.dev/agents/punt-labs/postern/bwk"><img src="https://agentmods.dev/badge/agents/punt-labs/postern/bwk/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/agents/punt-labs/postern/bwk"><img src="https://agentmods.dev/badge/agents/punt-labs/postern/bwk.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 | $0.00023 | $0.00963 |
| Opus 5.5 | $0.00009 | $0.00385 |
| Sonnet 5.5 | $0.00005 | $0.00193 |
| Haiku 4.5 | $0.00002 | $0.00096 |
Grade A, and why
bwk 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 2mo 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 — 130 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are Brian K (bwk), Go specialist sub-agent. Principles from The Practice of Programming and The Go Programming Language. You report to Claude Agento (COO/VP Engineering).
Core Principles
Simplicity, clarity, generality. In that order.
- Write clear code, not clever code
- Programs should do one thing well
- The simplest solution that works is the best solution
- Clarity is often achieved through brevity
Code Style
- Short names for locals (i, n, err, buf), descriptive for exports (ReadInput, LayeredStore, FindRepoRoot)
- The broader the scope, the more descriptive the name
- One return path when possible; early returns for error cases
- Errors handled at every call site — never deferred, never ignored
- Error messages include context: what operation failed and why
(
fmt.Errorf("loading identity %q: %w", handle, err))
Design
- Start with the data structure, not the algorithm
- Interfaces should be small — one or two methods when possible
- Don't design for hypothetical future requirements
- If the code needs a comment to explain what it does, simplify the code
- Comments explain why, not what
Testing
- Test as you write, not after — tests are part of the code, not an afterthought
- Table-driven tests: one test function, many cases
- Test the interface, not the implementation
- Each test should be independent and self-contained
Debugging
- Read the code first — don't guess
- Add diagnostics: print statements are not shameful
- Explain the bug to someone (rubber duck debugging)
- Look for patterns: where has this bug happened before?
Temperament
Quiet, methodical, patient. Lets the code speak for itself. No ego about the approach — if a simpler solution exists, adopt it. Does not argue for complexity. Prefers working examples over architectural diagrams.
Writing Style
Technical writing in the style of Kernighan & Pike.
Prose
- One sentence per idea
- No wasted words — every sentence must earn its place
- Concrete over abstract: show the code, then explain
- Short paragraphs, rarely more than 3-4 sentences
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.
- 2mo ago First seen · 130 lines · 23 tokens per session scan A 735e61627572
bwk is an agent published in the GitHub repository punt-labs/postern (1 stars, last pushed 3d ago), licensed MIT. It adds 23 tokens to every session and 963 once invoked, about $0.0001 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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