implement-change

wb <args>    # wb not on PATH: python <this skill's directory>/../../lib/wb.py <args>

Steps

1. Read the plan's own slices, not the whole document: sdd get <KEY> --section steps and --section files. No sdd.json? Run plan-change first. A failed audit blocks every command here by design — fix the plan, do not work around it.

   Picking work back up mid-way? status <KEY> says which planned files are already changed and what is left, without re-reading the plan.

2. Check where you are. flow show reports the branch this work starts from, whether the current branch is protected, and any validation branch the commits will later be carried onto. flow start <KEY> --title "..." prints the branch name and base to use.
3. Implement one step at a time, in order, touching only the listed files. Follow the repo's existing patterns. Nothing tidied, renamed or upgraded along the way: the plan's file list is the scope, and it was reviewed.
4. Write the tests the plan named. sdd get <KEY> --section tests. Each entry says what must hold — assert that, not that a function was called. impl verify fails, naming it, on any target the branch never changed.
5. Check the scope. impl check <KEY> after each step or two: planned files ok/pending, companion (a test, lockfile or generated file tied to a planned one), other (another plan's), overlap. It fails on a file nothing accounts for; with hooks on, that edit is refused before it lands.
6. Verify. impl verify <KEY> runs the plan's verify commands and writes .workflow/<KEY>/evidence.md. It refuses anything that is not a known test, build or lint runner — run those yourself and say so. The first time a command appears in a checkout nothing runs: approve <KEY> then shows the commands and a token. Show it to the user; never approve on their behalf. The evidence is bound to the tree it saw, so verify last, then commit. For a bug fix, impl verify <KEY> --regression: each regression target runs on the commit the branch left, with the new tests carried in, and must fail there, then pass here. Report the result either way.
7. Report honestly. If verification fails, say so with the failing line. Fix the code, never the evidence.

Do not re-run sdd audit to confirm your work: it checks the plan, not the code. Re-run it when you change the plan — that now passes, reporting which citations have drifted. impl check and impl verify are the checks for this stage.

When the plan is wrong

It happens, and it is not a reason to improvise. Stop, say what the plan assumed and what the code actually does, update sdd.json, re-run sdd audit <KEY>, then continue. A deviation that goes through the plan is a correction; one that does not is an unreviewed change wearing a reviewed plan's name.

A missed file: sdd amend <KEY> <path> --why "..." --lines N (--new to create it) re-audits in place; if the tier rises, add what the audit asks.

Rules

• Smallest diff that satisfies the step. No opportunistic refactors.
• A file outside the plan stops the work. Not a warning — impl check exits non-zero, and the critical zones it names raise the bar further.
• Never weaken a test to make it pass. If an existing test now fails, either the change is wrong or the test encoded the old behaviour; say which, with the file and line.

Next: write-commit, then draft-pr. If the flow has a validation branch, flow carry <KEY> --to <branch> lists the commits to cherry-pick, oldest first, measured against origin/<source> after a fetch. It prints the commands; pass --execute only when the user asked you to run them.