learn

A memory tool for saving paper-specific facts in a project file. These facts can include variable names, coding or analysis conventions, design decisions, formatting preferences, and references.

In plain words
What is it for?
Use it whenever the user states a rule to remember or repeats a correction, so later research and writing tasks follow that fact.
Why use it?
The agent can apply the same project rules in later tasks instead of forgetting them or asking again. It is useful when a correction or convention needs to persist across the paper's workflow.

Skill for Claude CodeCodex

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 skills/matthewdigiuseppe/mstack/learn
Any agent
npx skills add matthewdigiuseppe/MStack --skill learn
Clone the repo
git clone --depth 1 https://github.com/matthewdigiuseppe/MStack

Made for: Claude Code, Codex.

Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 509 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 $0.00052 $0.00509
Opus 5 $0.00026 $0.00254
Sonnet 5 $0.00010 $0.00102
Haiku 4.5 $0.00005 $0.00051

Measured 2d ago against content hash 60dd71529763, 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.

skills/learn/SKILL.md · 60 lines

What it actually says

/mstack:learn

Stage: power Voice: memory

When to invoke

Whenever you find yourself telling Claude the same paper-specific fact twice. The convention belongs in the paper's memory, not in your head.

Argument

$ARGUMENTS — the fact to remember. Free-form text; this skill will normalize it.

Procedure

  1. Classify the fact into one of:

    • variable_name — naming convention for a key variable.
    • convention — analytical / coding convention specific to this paper.
    • decision — a design or framing decision (with rationale).
    • preference — output / formatting / style preference.
    • reference — pointer to an external resource specific to this paper.
    • other — free-form.
  2. Normalize. Strip whitespace; trim trailing punctuation; capitalize the sentence.

  3. Append a JSON line to .mstack/learnings.jsonl:

    {"date":"YYYY-MM-DD","kind":"<class>","fact":"<normalized fact>"}
    
  4. Echo back what was written so the user can confirm.

  5. Hint at scope. If the fact looks like it generalizes across papers (a methodological habit, a tooling preference, a writing rule), tell the user to consider also adding it to their global memory (~/.claude/CLAUDE.md) rather than only here.

Outputs

  • .mstack/learnings.jsonl — one new line.
  • Summary: the new line + scope hint if applicable.

Anti-patterns to refuse

  • Storing transient state. "Currently working on table 3" is conversation context, not memory. Don't write it.
  • Storing what's already in code. If the convention is encoded in a script, the script is the memory.

When to call other skills

  • If the fact crosses papers, suggest writing to global memory rather than just here.
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 · 60 lines · 52 tokens per session scan A 60dd71529763

Subscribe to this mod's changes

learn is a skill published in the GitHub repository matthewdigiuseppe/MStack (14 stars, last pushed 6d ago), licensed MIT. It adds 52 tokens to every session and 509 once invoked, about $0.0003 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.

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