learn

A command that records a useful lesson from a surprise, incident, or code review finding. It saves the lesson in a learning inbox for later review.

In plain words
What is it for?
Use it to document what happened, why it matters, the smallest rule change that could prevent a repeat, and the affected file paths.
Why use it?
It prevents important discoveries from being forgotten or remaining only in conversation.

Command

Install

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.

agentmods
npx agentmods add commands/tacoda/keystone/learn
Clone the repo
git clone --depth 1 https://github.com/tacoda/keystone
Per session 16 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 555 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00016 $0.00555
Opus 5 $0.00008 $0.00278
Sonnet 5 $0.00003 $0.00111
Haiku 4.5 $0.00002 $0.00056

Measured 2d ago against content hash 1730469b6500, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

learn 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 2d 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.

.charter/commands/learn.md · 57 lines

How it starts

The opening of the file, as written. The whole thing — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.

learn

Capture a learning candidate from a surprise, an incident, or a review finding. Writes to .charter/learning/inbox/ for later synthesis. Read .charter/learning/README.md.

Activities

Write a candidate to .charter/learning/inbox/<timestamp>-<slug>.md where:

  • <timestamp> is YYYY-MM-DD-HHMM in UTC
  • <slug> is a short kebab-case description of the insight

The candidate file uses this shape:

---
captured: <ISO date>
source: <what triggered this — review finding, surprise during implementation, etc.>
proposed-layer: <corpus/principles | guides/idioms/<stack> | guides/process | sensor>
proposed-globs:                       # optional; see below
  - "src/billing/**"
  - "tests/billing/**"
---

## What happened

<concrete observation — code, output, or interaction>

## Why it matters

<the principle, idiom, or rule this implies>

## Proposed change

<the smallest charter edit that would prevent the next incident>

proposed-globs: — record the paths the lesson came from

When the surprise happened in a specific region of the codebase, list the paths in proposed-globs:. These are the touched files (or their parent directories' globs) from the interaction that produced the candidate. Synthesize uses this as signal when deciding the guide's actual globs:.

  • If the lesson is cross-cutting (would apply to any file in any stack), omit the field. Synthesize will default to no globs: on the promoted guide.
  • If the lesson is regional, list the patterns that match the affected files. Prefer existing region globs from corpus/state/CODEBASE_STATE.md over hand-invented patterns — globs should reflect the real codebase, not the abstraction the rule is about.
  • Never set proposed-globs: wider than where the surprise actually occurred. Synthesize narrows on user confirmation; widening at learn-time loses the evidence.

Gate

Learn writes only to the inbox. Promotion into corpus / guides happens in synthesize, not here. Capture liberally; prune aggressively later.

Read the full file on GitHub · 57 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. 2d ago First seen · 57 lines · 16 tokens per session scan A 1730469b6500

Subscribe to this mod's changes

learn is a command published in the GitHub repository tacoda/keystone (44 stars, last pushed 2mo ago), licensed MIT. It adds 16 tokens to every session and 555 once invoked, about $0.0001 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 2026-08-30.