study-session

A guided study session for understanding existing code. It tests whether a developer can explain a subsystem's design, rules, and failure cases, either in a deep session or a short retention check.

In plain words
What is it for?
Use it to learn or revisit one subsystem, explain how it works from memory, answer probing questions, and measure retained understanding.
Why use it?
It addresses the loss of understanding that can happen when coding agents change code on a developer's behalf.

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/mryll/skills/study-session
Any agent
npx skills add mryll/skills --skill study-session
Clone the repo
git clone --depth 1 https://github.com/mryll/skills

Made for: Claude Code, Codex.

Per session 117 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,670 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 $0.00117 $0.01670
Opus 5 $0.00059 $0.00835
Sonnet 5 $0.00023 $0.00334
Haiku 4.5 $0.00012 $0.00167

Measured 2d ago against content hash 839b8c6b1afd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

study-session 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/study-session/SKILL.md · 75 lines

How it starts

The opening of the file, as written. The whole thing — 75 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Study Session — recover and measure the theory of a subsystem

A session over real code in the repo. The user reads and explains; you probe and grade. The goal is Naur's "theory": the user can defend the subsystem's design, invariants, and failure modes without help. Two modes:

  • Deep (45-60 min): learn or repair one subsystem/unit. Default for not-assessed, practiced, or code-changed targets.
  • Checkpoint (10-15 min): measure retention of a due unit — one cold reconstruction + one transfer scenario. Default when the row's next-due date expired.

Core principle: cold evidence is graded separately from learning. What the user produces BEFORE your corrections is what gets measured; what they learn after counts as learning, never as certification.

Finding the comprehension map

The map's schema (columns, status vocabularies, event format, spacing rule) lives in the user's knowledge wiki — this skill defers to it. To locate the map:

  1. Resolve the wiki root: follow the ~/.claude/work-wiki symlink if present; otherwise ask once and offer to create that symlink.
  2. Glob **/projects/*-comprension.md (or the wiki's declared comprehension-map convention) with kind: comprehension-map frontmatter; match the current repo/workspace (git remote or basename) against each map's repo/paths column — one project may span several repos.
  3. Exactly one match → use it. None → derive the path from the project name per the wiki's convention, confirm with the user, create from the wiki's schema template. Several → ask.

No wiki or schema at all → offer a minimal inline map: | Subsystem | Repo/paths | Current evidence | Scope | Last passed | Next due | Gaps | with outcome (not-assessed | practiced | partial | defensible) and validity (current | evidence-expired | code-changed | code-currentness-unknown) vocabularies.

Target selection (risk-first)

Propose ONE target with a one-line reason, in this priority order — the user can override:

  1. Relevant code changed since the row's last evidence SHA (code-changed).
  2. An open gap implicated by a recent MR or incident.
  3. High-blast-radius unit overdue.
  4. Any other overdue unit.
  5. Untested low-risk units.

Read the full file on GitHub · 75 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 · 75 lines · 117 tokens per session scan A 839b8c6b1afd

Subscribe to this mod's changes

study-session is a skill published in the GitHub repository mryll/skills (3 stars, last pushed 13d ago), licensed MIT. It adds 117 tokens to every session and 1,670 once invoked, about $0.0006 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 2026-08-31.

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