checkpoint

checkpoint is a skill for Claude Code, Codex from jovesun-lab/arcgram. It costs 103 tokens per session (903 once invoked), scanned A, original, Apache-2.0.

A checker that tests whether an Arcgram diagram’s logic is connected and well-formed. Arcgram is a diagram format that represents flows with nodes and edges, or links between nodes.

In plain words
What is it for?
Use it to validate flow diagrams, find dangling edges or orphan nodes, check decision branches, and identify disconnected parts of a process.
Why use it?
It finds broken links, isolated steps, missing decision branches, and other structural problems without judging whether the underlying idea is correct.

Skill for Claude CodeCodex

Part of the arcgram plugin — 4 skills shipped together

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/jovesun-lab/arcgram/checkpoint
Any agent
npx skills add jovesun-lab/arcgram --skill checkpoint
Clone the repo
git clone --depth 1 https://github.com/jovesun-lab/arcgram

Made for: Claude Code, Codex.

Or install arcgram, the plugin that ships this one along with the rest of its 4 skills.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for checkpoint

README.md
[![agentmods](https://agentmods.dev/badge/skills/jovesun-lab/arcgram/checkpoint.svg)](https://agentmods.dev/skills/jovesun-lab/arcgram/checkpoint)
Your own site
<a href="https://agentmods.dev/skills/jovesun-lab/arcgram/checkpoint"><img src="https://agentmods.dev/badge/skills/jovesun-lab/arcgram/checkpoint.svg" alt="Measured on agentmods" height="20"></a>
Per session 103 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 903 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 $0.00103 $0.00903
Opus 5 $0.00051 $0.00451
Sonnet 5 $0.00021 $0.00181
Haiku 4.5 $0.00010 $0.00090

Measured 4d ago against content hash 9609bb1f6dff, 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 4d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (checkpoint-selftest.mjs, checkpoint.mjs), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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/checkpoint/SKILL.md · 78 lines

How it starts

The opening of the file, as written. The whole thing — 78 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Checkpoint - Arcgram logic self-check validator

One input: a diagram (treated as a spec). One question: is the flow logic well-formed and coherent? Returns typed findings; marks, never blocks.

Sibling to Reconcile: Checkpoint checks structure from the diagram alone; Reconcile checks values across diagram + code. Run both -> the diagram is a faithful, current spec.

It checks the graph's logic structure - not drawing quality (the engine auto-handles overlaps/spacing/routing) and not semantic correctness (whether the logic is right - a human call).

Red line: reads only the semantic field values id, f, t, kind, role, type (plus optional status, flag). Never a coordinate, color, size, or spacing. The judge: am I reading a semantic string, or a rendered visual quantity?

Findings

Tier A - structural integrity (always on). Domain-agnostic graph theory.

finding means
dangling-edge an edge points at an id that is not a node
orphan-node a node has no edge (chain broken) - except a declared type:'open'
missing-branch a decision (kind:'diamond') lacks its Y or N branch
disconnected-island a cluster with no edge to the main flow
duplicate-id a node id used more than once
missing-field a node has no id, or an edge no f/t
missing-meta-version ARCGRAM_META.version absent
empty-diagram no nodes - reported uncovered, never falsely "clean"

Tier B - justification coherence (auto-on for a thinking flow). Does it read as reasoning: every action traces back to a goal, every goal reaches an action, every decision sits on a justification path. Auto-on when the diagram has a decision diamond (kind:'diamond', = the engine's _isThinkflow); no-diamond diagrams skip it. Override --tier-b / --no-tier-b. Roles: goal/action/decision (coherence-bearing) + constraint/evidence/state/output (recognized). No resolvable role -> [?] uncovered, never guessed. cat is not read.

Read the full file on GitHub · 78 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 4d ago First seen · 78 lines · 103 tokens per session scan A 9609bb1f6dff

Subscribe to this mod's changes

checkpoint is a skill published in the GitHub repository jovesun-lab/arcgram (9 stars, last pushed 16d ago), licensed Apache-2.0. It adds 103 tokens to every session and 903 once invoked, about $0.0005 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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