THE METHODS · CLAUDE CODE · Nº 490 · EDITION 2 · LAUNCHING SOON

LUND CARDS · THE METHODSNº 490

THE CARD AS TEXT · FOR EYES AND FOR MACHINES

THE CHECKPOINT CARD · The undo seat: a named snapshot before the change, the difference since, a way back file by file.

WAKES WHEN An agent is about to edit a lot of files and nobody has committed. · Something went wrong and someone wants to see exactly what changed since they last felt safe. · One file needs to go back to how it was; the rest should stay. · Someone wants to be sure a checkpoint is still what it was.

THE LOOP

Take a named checkpoint before the change
Diff: added, changed, removed since
Restore one file or all, after a dry run
Verify the checkpoint is intact

NEVER

Never overwrites a checkpoint
Never restores over current work unasked
Never copies a secret file into a checkpoint
Never claims a certainty it does not have

IT MAKES take — copy every text file under DIR into the store under NAME with a manifest of hashes; a file that looks like a secret is left out and named; diff — what changed since the checkpoint: ADDED, CHANGED, REMOVED, one line per file; restore — put one file, or every file, back as it was at NAME; without --yes it only prints what it would do; verify — check the checkpoint's own files against its manifest: CORRUPT if any hash moved; list — print every checkpoint with its date and file count.

THE LAW An undo is only an undo if it was taken before the change, is never overwritten, and can be verified. The machine restores only when told twice — once to say what it would do, once to do it — and it leaves added files where they are, because deleting is not its job.

IN THE BOX SKILL.md · CARD.md · ▣ scripts/checkpoint.py (machine) · ▣ scripts/evals.py (test runner) · tests/EVALS.json (9 tests) · references/ (schema + fictional demo) · START-HERE.md · system/ doors · MY-LEDGER.md · LICENSE-NOTE.md · card.svg · card.json · card.html · AUDIT.md · MANIFEST.md · WITNESS.md · SELFTEST.md.

PROOF SELFTEST 12/12 · witnessed in Claude 2026-10-14 on fictional fixtures · the test prompts in fresh chat, 9/9 · Edition 2.

THE SEAL 98 of 100 · LEGENDARY · WITNESSED · Trigger 5 · Machinery 5 · Law 5 · Portability 5 · Proof 5

IT CAN BE WRONG an AI reading a text file: it can be wrong and can invent a number, a rule, a name or a date; check what matters against your own records and the source; the risk is yours. LICENSE-NOTE.md rides in the packet and is the licence.

THE PUNCH · SHA-256 OF SKILL.MD · 6B3C3951EC09EC9BCBC795AC

THE FACE, FULL SIZE → · THE MACHINE FACE → · card.json →

THE CHECKPOINT CARD

The undo seat: a named snapshot before the change, the difference since, a way back file by file.

TAKE · DIFF · RESTORE · VERIFY · LIST

LEGENDARYWITNESSEDIN CLAUDE IN LUNDR IN CHATGPT

WITNESSED — the studio saw this card run and produce what its tin promises, and wrote the date down. What the marks mean →

THE SPEC SHEET · READ BEFORE YOU BUY · THE STANDARD EVERY CARD MEETS →

SEAL: 98 of 100 · LEGENDARY · WITNESSED
EDITION: E1 · witnessed 2026-10-14
MACHINE: scripts/checkpoint.py · 5 commands · selftest 12/12
RUNS: On your own computer. Standard library only, offline; no account, no key, no telemetry.
HOSTS: Claude · Claude Code · ChatGPT · Gemini · any AI that reads a file (START-HERE.md and system/ name each door)
LICENCE: One person, any number of their own AIs and computers · editions replace files · nothing renews · freeze, not loss
PUNCH: 6B3C3951EC09EC9BCBC795AC · sha-256 of SKILL.md · check any file against it →

CITE THIS CARDTHE CHECKPOINT CARD, Edition 2. Lund Studio LLC, Westminster, Colorado. https://lundr.tech/?view=checkpoint-card. Punch 6B3C3951EC09EC9BCBC795AC. Retrieved 2026-10-14.

What it is.

Use when an agent is about to change many files and you want a way back: a named checkpoint, the difference since, a restore of one file or all. Not for version control or for planning the change.

It carries a machine that shows its working: take — copy every text file under DIR into the store under NAME with a manifest of hashes; a file that looks like a secret is left out and named; diff — what changed since the checkpoint: ADDED, CHANGED, REMOVED, one line per file; restore — put one file, or every file, back as it was at NAME; without --yes it only prints what it would do; verify — check the checkpoint's own files against its manifest: CORRUPT if any hash moved; list — print every checkpoint with its date and file count — 12 checks in its selftest. It never overwrites a checkpoint; never restores over current work unasked; never copies a secret file into a checkpoint; never claims a certainty it does not have.

The law, written into the card.

It is in the card itself, so the AI follows it.

THE LAWAn undo is only an undo if it was taken before the change, is never overwritten, and can be verified. The machine restores only when told twice — once to say what it would do, once to do it — and it leaves added files where they are, because deleting is not its job.

The method.

Take a checkpoint with a name before the agent starts; the machine copies every text file and writes a manifest of hashes. Secret-looking files are left out and named.
Work. When something feels wrong, diff: ADDED, CHANGED and REMOVED since the checkpoint, one line per file.
Restore: first a dry run that prints what would change, then the same command with --yes. One file with --file, or every changed and removed file. Files added since are left in place.
Verify a checkpoint before trusting it: every copy against its hash; a moved hash is CORRUPT.
A checkpoint is never overwritten; a new name is a new checkpoint, and the list shows them all with their dates.

What you bring.

The folder the agent will work in.
A name for the moment before the change.
The habit of taking one before every big edit.

Planned as a separate seat, not in this box and not yet on sale: the checkpoints the studio takes before every cut of its own builds.

What it does once your AI has it.

take Copy every text file under DIR into the store under NAME with a manifest of hashes; a file that looks like a secret is left out and named
diff What changed since the checkpoint: ADDED, CHANGED, REMOVED, one line per file
restore Put one file, or every file, back as it was at NAME; without --yes it only prints what it would do
verify Check the checkpoint's own files against its manifest: CORRUPT if any hash moved
list Print every checkpoint with its date and file count

What it will never do.

It never overwrites a checkpoint; never restores over current work unasked; never copies a secret file into a checkpoint; never claims a certainty it does not have.

Where it hands off: Planning the change before it starts → THE PLAN CARD; Keeping a real history across days → the team's version control; Splitting the change across helpers → THE CREW CARD.

It is not a backup service. It is an AI reading a text file: it can be wrong, so check what matters against your own records and the source. The holder brings their own AI; no endorsement by Anthropic or any other AI company is claimed.

What’s in the buy.

SKILL.md — the card your AI reads: when it wakes, the loop, the never-lines, the hand-offs.
CARD.md — the whole card in ten sections: face, law, method, machine, what you bring, never, tests, seal, term.
scripts/checkpoint.py — the machine, Python standard library only; `selftest` proves it on its own fixtures.
tests/EVALS.json and scripts/evals.py — 9 test prompts and the offline runner that scores your AI's answers.
references/ — the data schema and FICTIONAL demo files, invented to show the machine, not real.
MY-LEDGER.md — your own record of what you asked and what you decided.
START-HERE.md, system/short-prompt.md, system/rules.md — the doors, for any AI with or without skills.
card.svg, card.json, card.html, AUDIT.md, MANIFEST.md, WITNESS.md, SELFTEST.md — the faces and the proof.
NOT IN THE BOX — any studio edition (planned, not yet on sale: the checkpoints the studio takes before every cut of its own builds). Also not in the box: any data you must bring, and advice of any kind (not a backup service).

PROOF · SELFTEST 12/12 · WITNESSED IN CLAUDE 2026-10-14 ON FICTIONAL FIXTURES · THE 9 TEST PROMPTS ASKED IN A FRESH CHAT HOLDING ONLY THE CARD · 9/9 · EDITION 2 · PUNCH 6B3C3951EC09EC9BCBC795AC

ON EVERY DOOR · A CARD FOR YOUR AI, A FILE FOR YOUR COMPUTER

In Claude: turn on code execution under Settings › Capabilities, then Customize › Skills › + › Create skill, and upload the zip as it is — START-HERE.md in the box walks you through it, and tells you how to keep the ledger. In ChatGPT, Gemini and the rest: a Project, a GPT or a Gem with the card’s files attached and the short door in the box pasted as its instructions. The words run anywhere an AI reads Markdown; the machines run wherever the host runs Python. Witnessed in Claude only. The host marks →

Take it.

Nº 490 — LAUNCHING SOON

Sold as is under the term printed. A card instructs an AI you operate; results depend on your model, your files and your judgement. Not medical, legal, tax or financial advice, never the person’s boss, and not a licence to practise. The terms →

ONE PAYMENT · NOTHING RENEWS ITSELF

OFFLINE · ONE LICENCE · PUNCH-CHECKABLE · THE STANDARD

One payment. The file is yours to keep and keeps working at its edition; new editions issued in the year after you buy reach you by email as replacement files. Tax is added at checkout where it applies. Nothing auto-renews.

A TERM, NOT A SUBSCRIPTION: NOTHING RENEWS ITSELF AND NOBODY IS CHARGED AGAIN. WHEN A TERM ENDS THE FILES STAY ON YOUR COMPUTER AND STAY READABLE — FREEZE, NOT LOSS.

THE MACHINE · IN THE OPEN · FROM THE CARD’S OWN SELFTEST.MD

checkpoint.py, every command showing its working.

A small Python program, standard library only. Your AI runs it; you can too. The block below is pasted from the card’s own SELFTEST.md, as printed when it was run from inside the packet.

`take`	copy every text file under DIR into the store under NAME with a manifest of hashes; a file that looks like a secret is left out and named
`diff`	what changed since the checkpoint: ADDED, CHANGED, REMOVED, one line per file
`restore`	put one file, or every file, back as it was at NAME; without --yes it only prints what it would do
`verify`	check the checkpoint's own files against its manifest: CORRUPT if any hash moved
`list`	print every checkpoint with its date and file count
`selftest`	12 checks that prove the machine; it must print selftest 12/12

THE SELFTEST, AS PRINTED

LEFT OUT (secret): .env
take before · 2 files · 2026-01-02 · store <tmp>
EXISTS: checkpoint before is already taken; a checkpoint is never overwritten — pick another name
would restore  README.md  (REMOVED since)
would restore  src/app.py  (CHANGED since)
restore before · 2 file(s) would change · nothing done · say --yes to do it
restored  src/app.py
restore before · 1 file(s) put back as at 2026-01-02 · the files added since were left in place
restored  README.md
restore before · 1 file(s) put back as at 2026-01-02 · the files added since were left in place
NOT IN CHECKPOINT: src/ghost.py was not in before
verify before · 2 files · intact
CORRUPT  src/app.py
verify before · 2 files · CORRUPT: 1
before                   2026-01-02  2 files
list · 1 checkpoints in <tmp>
ok   1  take copies the text files and writes a manifest of hashes
ok   2  a secret file is LEFT OUT of the checkpoint and named; a binary is skipped
ok   3  a second take under the same name is EXISTS: refused, never overwritten
ok   4  diff names the ADDED, CHANGED and REMOVED files
ok   5  restore without --yes only says what it would do and exits 1
ok   6  restore --file --yes puts one file back as it was
ok   7  restore --yes puts the removed file back and leaves the added file in place
ok   8  restoring a file the checkpoint never had is NOT IN CHECKPOINT, exit 1
ok   9  verify finds the checkpoint intact
ok   10  a checkpoint whose copy moved is CORRUPT, exit 1
ok   11  a name that was never taken is NO CHECKPOINT
ok   12  list prints the checkpoints with date and file count
selftest 12/12

THE RUN IS PASTED FROM THE CARD’S OWN SELFTEST.MD AS PRINTED. ITS FIXTURES ARE FICTIONAL, INVENTED FOR THE TEST; NO PRIVATE PERSON IS NAMED.

QUESTIONS AT THE TABLE

Asked before the wire.

What does it need from me?

The folder the agent will work in. A name for the moment before the change. The habit of taking one before every big edit. If something it needs is missing, it says what is missing and stops there.

Does it send anything anywhere?

No. The machine is a standard-library Python program that runs on your own computer and sends nothing anywhere; the words run wherever an AI reads Markdown. No server, no account, no key.

What is on the record?

The machine's selftest (12/12), run from inside the packet in Claude on 2026-10-14 on fictional fixtures and pasted into SELFTEST.md as printed; the twelve-check audit (AUDIT.md). Owed, and said so in WITNESS.md: Any run on real data. Every demo file is fictional. The punch on the face is the SHA-256 of SKILL.md, so a downloaded copy can be checked against this room.

Can it be wrong?

Yes — it is an AI reading a text file: it can be wrong and can invent a number, a rule, a name or a date; check what matters against your own records and the source; the risk is yours. LICENSE-NOTE.md rides in the packet and is the licence. It is not a backup service.

What will it never do?

It never overwrites a checkpoint; never restores over current work unasked; never copies a secret file into a checkpoint; never claims a certainty it does not have.

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