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postern: Instructions file for Claude Code

CLAUDE.md

postern CLAUDE.md is an instructions file for Claude Code from punt-labs/postern. It costs 3,246 tokens per session, scanned A, original, MIT.

Project instructions for Postern, a tool that exposes a running Pharo Smalltalk environment through HTTP. Pharo is a Smalltalk programming environment; HTTP lets clients send requests to it.

In plain words
What is it for?
Developing Postern’s HTTP evaluation server, dashboard, documentation, authentication, compilation, testing, inspection, and commit workflows.
Why use it?
They give the coding agent the architecture and contributor rules needed to work safely on the project.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions CLAUDE.md; mentions subagents; mentions AGENTS.md.

This is punt-labs/postern's own configuration. It tells Claude Code how to work on postern 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 postern configures →

not rated 1repo changed 3d ago A scan 3,246 tokens original MIT
View source ↗ punt-labs/postern
Reuse

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.

Copy the file
curl -O https://raw.githubusercontent.com/punt-labs/postern/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/punt-labs/postern

Made for: Claude Code.

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README.md
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Per session 3,246 This file is loaded in full into every session.
When invoked 3,246 The same file — it is already loaded in full.
Security scan A 1 finding. 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 $0.03246 $0.03246
Opus 5.5 $0.01298 $0.01298
Sonnet 5.5 $0.00649 $0.00649
Haiku 4.5 $0.00325 $0.00325

Measured 3d ago against content hash c9e6966d63f1, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

postern CLAUDE.md scanned grade A with 1 finding 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 3d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

2. From any tool (curl, the Pharo IDE, another agent), drive `/repl` to
CLAUDE.md · 281 lines

How it starts

The opening of the file, as written. The whole thing — 281 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Postern

Postern is a remote driver for a live Pharo Smalltalk image. It exposes the running image as an HTTP server: clients send Smalltalk to /repl, read live documentation from /help, and drive compile / test / inspect / commit loops without going through the Pharo GUI. Postern was carved out of punt-labs/claude-agent-sdk-smalltalk in early 2026 and ships independently. It has zero Claude dependency by design — agent integration happens at the HTTP boundary, not in the Smalltalk image.

This file covers the contributor workflow for developing Postern. For agents using Postern's runtime (bootstrap, /help flow, /repl usage, eval token handling), read AGENTS.md.

The public-facing description is in README.md. Architecture and engineering conventions live below.

What Postern Is

A single product, three packages plus a baseline:

  1. Postern-Core — the HTTP eval server. PosternServer (Zinc-backed) binds to localhost:8422 (or $EVAL_PORT), routes /repl, /health, and /help/*, enforces auth on /repl when configured, and converts LF line endings to CR before passing source to the Pharo compiler.
  2. Postern-Dashboard — PosternDashboard Morphic UI showing live request traffic, status, and request/response bodies. Optional; loaded by the default group but never required by Postern-Core.
  3. Postern-IcebergExtensions — repairs Iceberg reference-commit drift after CLI git operations. Optional; loaded by the default group.
  4. BaselineOfPostern — Metacello baseline declaring all three packages plus their *-Tests siblings. Three groups: default (Core + Dashboard + IcebergExtensions), tests, all.

Loading from another image:

Metacello new
  baseline: 'Postern';
  repository: 'github://punt-labs/postern:main';
  load.

Architecture

  • HTTP eval server — PosternServer is Zinc-backed (Pharo's built-in HTTP). Loopback-only by default. startOn: and startOn:withAuth: bind to localhost; startPublicOn: binds to all interfaces and always requires a token. /health and /help are unauthenticated; /repl uses an X-Eval-Token header read from .tmp/eval-token.
  • Live /help system — help content is generated from the loaded image, not static markdown. /help/api, /help/browse, /help/pharo, /help/dispatch, /help/lint, /help/git, /help/testing, /help/safety, /help/makefile, /help/lessons. Each section reflects the actual loaded packages; updating the image updates the help.
  • Eval pipeline — POST /repl body is text/plain Smalltalk. Server normalises line endings, evaluates in OpalCompiler, returns printString of the result. Errors return the exception's description. No streaming.
  • Iceberg sync — Postern-IcebergExtensions adds a repairAfterCli helper for the case where you've committed via CLI (make targets, git directly) and Iceberg's reference commit has drifted.
  • Dashboard — Morphic; opens from World menu or via PosternDashboard open. Subscribes to Postern-Core announcements to render request traffic.

Read the full file on GitHub · 281 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. 3d ago Changed · +2 lines · +54 tokens per session c9e6966d63f1
  2. 2mo ago First seen · 279 lines · 3,192 tokens per session scan A 6350faf8c265

Subscribe to this mod's changes

postern CLAUDE.md is an instructions file published in the GitHub repository punt-labs/postern (1 stars, last pushed 3d ago), licensed MIT. It adds 3,246 tokens to every session, about $0.0130 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Backend and APIsClaude Codecodex-clipharopharo-smalltalksmalltalk
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