lean-session

A procedure for starting and checking a live Lean session. Lean is a programming language that checks mathematical proofs, and the session connects a terminal watcher, a browser dashboard, and the VS Code proof view.

In plain words
What is it for?
Use it to start the proof workspace, open its three live views, check their status, or repair a session that is not updating.
Why use it?
It removes uncertainty about whether saved proof changes were compiled and whether each live view is updating. It also provides steps for restarting parts that stop responding.

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

Made for: Claude Code, Codex.

Per session 154 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,538 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 $0.00154 $0.01538
Opus 5 $0.00077 $0.00769
Sonnet 5 $0.00031 $0.00308
Haiku 4.5 $0.00015 $0.00154

Measured 2d ago against content hash bc757b0c58a6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

lean-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.

.claude/skills/lean-session/SKILL.md · 135 lines

How it starts

The opening of the file, as written. The whole thing — 135 lines — stays where its author put it; the contents beside it link to each section on GitHub.

lean-session

Brings up the three live views and proves that each one is actually alive. Repository root: /path/to/lean-interact.

The user asked for all three views explicitly. They are not redundant; each answers a different question:

View Answers Where
Terminal watcher, tools/live.py did the last save compile, and how fast tmux pane
VS Code infoview, Lean 4 extension what is the goal state right here VS Code
Browser dashboard, tools/dashboard.py where do we stand overall browser tab

All three read the same contract: .live/status.json, schema 1.


Start

tools/session.sh --help     # read this FIRST: it is authoritative on panes, flags, port
tools/session.sh            # start everything

tools/session.sh starts the watcher, starts the dashboard, and opens Scratch/Current.lean in VS Code. macOS does not put the code CLI on PATH by default; the script uses /Applications/Visual Studio Code.app/Contents/Resources/app/bin/code.

Take the tmux session name and the dashboard port from the script's --help or from its startup output. Do not assume a port number - report the one the script actually printed.

Confirm it is alive - all three checks, every time

Do not report "session started" on the strength of the launcher exiting 0.

1. The watcher is drawing. Touch the live file and confirm the status file moves:

touch Scratch/Current.lean
sleep 3
jq '{state, finished_at, elapsed_s, counts}' .live/status.json

finished_at must be within the last few seconds. If it is not, the watcher is not polling - see Troubleshooting.

2. The dashboard port is listening.

tmux ls                              # the session exists
lsof -nP -iTCP:<port> -sTCP:LISTEN   # something is bound to the port

Then tell the user the exact URL, http://127.0.0.1:<port>/, so it can be clicked.

3. VS Code has the file open with the Lean 4 extension active. The infoview appears once the cursor is inside a proof. If the extension is still loading Mathlib's oleans, the infoview says so; that is normal on the first open and takes a minute.

Read the full file on GitHub · 135 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 · 135 lines · 154 tokens per session scan A bc757b0c58a6

Subscribe to this mod's changes

lean-session is a skill published in the GitHub repository nasqret/lean-interact (10 stars, last pushed 24d ago), licensed MIT. It adds 154 tokens to every session and 1,538 once invoked, about $0.0008 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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