checkpoint

A command that saves current Lean proof progress as a verified Git commit. Git is a system for recording changes to code over time.

In plain words
What is it for?
Use it before continuing proof work to verify the project, count remaining sorries, and save the current state without pushing it online.
Why use it?
It creates a known working checkpoint after checking the project build, custom axioms, and remaining unfinished proofs.

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/frenzymath/archon/checkpoint
Clone the repo
git clone --depth 1 https://github.com/frenzymath/Archon
Per session 9 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 510 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 $0.00009 $0.00510
Opus 5 $0.00005 $0.00255
Sonnet 5 $0.00002 $0.00102
Haiku 4.5 $0.00001 $0.00051

Measured 3d ago against content hash 0a6528e34f13, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

checkpoint 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 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.

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.

src/archon/.archon-src/skills/lean4/commands/checkpoint.md · 80 lines

What it actually says

Lean4 Checkpoint

Creates a verified checkpoint of your current proof progress.

Usage

/lean4:checkpoint
/lean4:checkpoint "optional custom message"

Inputs

Arg Required Description
message No Custom commit message suffix

Actions

  1. Verify Build - Run lake build to ensure code compiles (this is a project-wide gate — runs full lake build, not file-level)
  2. Check Axioms - Verify no unwanted custom axioms:
    bash "$LEAN4_SCRIPTS/check_axioms_inline.sh" src/*.lean
    
  3. Count Sorries - Report current sorry count:
    ${LEAN4_PYTHON_BIN:-python3} "$LEAN4_SCRIPTS/sorry_analyzer.py" . --format=summary
    
  4. Stage and Commit - Stage changes and create commit:
    git add -A && git status --short
    git commit -m "checkpoint(lean4): [summary]"
    
  5. Report Status - Show what was saved

Output

## Checkpoint Created

**Commit:** [hash] - [message]
**Build:** ✓ passing
**Sorries:** [N] remaining
**Axioms:** [status]

**Next steps:**
- Continue with `/lean4:prove`
- Push manually when ready: `git push`

Safety

  • Does NOT push to remote (manual only)
  • Does NOT create PRs (manual only)
  • Does NOT amend commits (each checkpoint = new commit)
  • Will NOT create checkpoint if build fails

Rollback

git reset --soft HEAD~1   # Undo last, keep staged
git reset HEAD~1          # Undo last, keep unstaged
git reset HEAD~N          # Undo last N commits

Warning: Only use reset before pushing.

See Also

  • /lean4:prove - Guided cycle-by-cycle proving
  • /lean4:review - Read-only code review
  • /lean4:refactor - Strategy-level proof simplification
  • Examples
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 First seen · 80 lines · 9 tokens per session scan A 0a6528e34f13

Subscribe to this mod's changes

checkpoint is a command published in the GitHub repository frenzymath/Archon (213 stars, last pushed 16d ago), licensed Apache-2.0. It adds 9 tokens to every session and 510 once invoked, about $0.0000 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.