# First Safe Change — an offline fixture before Lab 001 **Status:** `candidate` supplemental route. **Learner run:** `not_run`. This is the default novice sandbox between Chapter 2 and Lab 001. It gives you one deliberately incomplete README, one permitted local edit, and one narrow checker before you work in a project of your own. It is not Chapter 23, a new Skill, a Git exercise, or evidence that a model completed anything. If this is your first time opening a project folder or running a checker, that is exactly why this route exists. You do not need to install anything, create an account, or risk a real project to learn the first loop. We will keep the target small enough that you can see every relevant file and decide whether the check actually answers the question. ## Problem Lab 001 asks for a disposable project, a real command source, and a bounded README change. Those are good production-facing constraints, but they can make the first practical step feel circular: a new reader may not yet have a safe project or know which command source to trust. ## Concept A fixture separates *practising the method* from *finding a suitable project*. It is synthetic, local, and disposable. The only intended content change is a README correction; the checker reads that file and reports a small result. That makes the acceptance condition visible without requiring an account, network access, installation, Git, commit, push, publication, or personal data. ## Decision Use the project-owned [First Safe Change fixture](../../examples/lab-001-v1/README-EN.md) when you do not already have a disposable local project. Copy the entire fixture into `.work/` or another throwaway directory, so its seeded mistake remains available for the next reader. ## Action First make a private working copy. In your file manager, copy the entire `examples/lab-001-v1` folder to a throwaway location and call the copy `first-safe-change`. Do not edit the repository's original fixture: its seeded mistake is the starting point for the next reader. Then choose one of two checks: 1. **No-runtime check (the default).** Open `seed/README.md` and `expected/acceptance.json` in the copied folder. Before editing, the README is missing two required preview details. After the one permitted README edit, check that the README visibly contains all three strings named under `required_readme_strings` in the acceptance file. 2. **Optional local checker.** Use this only when Python 3 already works on your computer. Open a terminal in the copied folder and run: ```powershell python .\seed\verify_readme.py ``` The first optional checker result should be `FIRST_SAFE_CHANGE_FAILED`: that is the intentional starting state, not a broken installation. Then use the task card in the fixture README to inspect `seed/README.md`, propose the smallest change, and edit **only** that README after you approve the plan. Repeat the same manual check or optional local command. A passing optional local result is `FIRST_SAFE_CHANGE_OK`. If Python is unavailable, do not install a runtime or substitute another command just for this route. Use the no-runtime check and record `check: manual required_readme_strings 3/3`. If you cannot make a disposable local copy at all, stop and use the text-only First Win instead; do not pretend that a GitHub web view is a local sandbox. ## Evidence Keep only a modest receipt: ```text sandbox: baseline: FIRST_SAFE_CHANGE_FAILED allowed_change: seed/README.md only diff: check: manual required_readme_strings 3/3 | FIRST_SAFE_CHANGE_OK external_actions: none unverified: - learner completion - model behavior - transfer ``` The checker can establish only that this fixed synthetic README matches the fixture's declared strings at one local moment. A pass is not a Git result, browser result, account-permission result, security review, or learning result. ## Failure and boundary case Do not edit the checker, the acceptance file, or a different path to obtain a pass. If the proposed fix requires an install, network request, secret, account, repository operation, or a second file, stop. Those actions belong to a new decision, not to this fixture. ## Reflection 1. Which part of the acceptance condition was observable before any edit? 2. What does the final diff prove that a confident completion message does not? 3. Which real-project fact will you need to establish before repeating this pattern in Lab 001? ## Continue Continue with [Lab 001 — Make one safe README change](../labs/lab-001-first-safe-task-EN.md). Its default novice setup now points back to this fixture, then adds the project-specific source, sandbox-identity, and recovery checks that a real local task needs. ## Status and limits This route is `candidate` and `not_run` as a learner route. Its committed test checks fixture shape and the checker's declared pass/fail behavior; it does not observe a learner, invoke Codex or another model, compare products, establish transfer, or validate a real project command.