Skill · Code & Agents
Legacy Code Navigator
Explore first, pin current behaviour with tests, then make the smallest reviewed change in code nobody fully understands.
When to use
- You have to change code that nobody on the team fully understands.
- The area has few or no tests and no documentation.
- Earlier AI-assisted edits in this area caused regressions.
When not to use
- A modern codebase with good test coverage. Normal agent workflows are fine there.
- A planned rewrite. That needs an architecture plan; the Refactor Planner skill covers a gradual restructure.
Example
User: A PHP checkout from more than ten years ago needs a discount-code field. There are no tests.
Result (excerpt):
TRACE: 1. checkout.php:handlePost → 2. lib/cart.php:calculateTotal → 3. lib/tax.php:applyVat → 4. lib/order.php:createOrder
HISTORY: calculateTotal rounds to cents twice: evidence, git log -S "round(" finds a commit titled "fix cents mismatch on invoices". Deliberate; keep it.
PINNED BEHAVIOUR: golden file of calculateTotal output for 6 saved carts · ran on unchanged code: 6/6 match
PLAN (awaiting approval)
- checkout.php: read and pass discount_code
- lib/cart.php: apply the discount before applyVat
- lib/order.php: store discount_code
Blast radius: invoice PDFs and the monthly VAT export, which recalculates from order lines
Rollback: revert one commit; the new column is nullable
Noticed, not fixed: lib/tax.php:88 falls back to a hard-coded VAT rate when the config lookup failsIllustrative example written by Meevra; your model's wording will differ.
What is inside
The full skill has these sections. The ones marked “in the pack” come with the download.
- When to use on this page
- When not to use on this page
- Inputs to ask for in the pack
- Workflow in the pack
- Output format in the pack
- Example on this page
- Model notes (Oct 2026) in the pack
- Troubleshooting in the pack
Get Legacy Code Navigator
The full skill is a SKILL.md folder you install once and reuse: the workflow, the checklist and the answer format written out, with notes for each model. It comes in the Code & Agents pack (5 prompts · 15 skills · 1 free), with a QUICKSTART, setup notes in every item and 12 months of updates.
All-Access 39 € vs 7 packs × 12 € = 84 € · less than buying 4 or more packs one by one
Stuck? Email support@meevra.com — we'll help you set it up.