name: idea-implement
description: Stage 3 of the /idea pipeline — write the code and tests for an already-approved plan, respecting the hexagonal layout, CSV persistence conventions, and JUnit 5 + AssertJ testing style from exercise_1/CLAUDE.md. Use when the orchestrator invokes this, when the user says "implement the plan" / "let's build it", or when .claude/idea/current.md has Status: planned and Approved: yes. Appends a file-log to the state and hands off to idea-verify.
Idea — Stage 3: Implement
Turn the approved plan into working code + tests, without drifting from it.
Inputs
- State file
.claude/idea/current.md. Read Clarify and Plan. If Status ≠ planned or Approved ≠ yes, stop and route back to the correct stage.
- Architectural conventions in
exercise_1/CLAUDE.md.
Non-negotiable conventions
domain/ and application/ stay free of Spring and I/O imports. If you're tempted to @Autowired something in a domain class, it belongs behind a port instead.- Money is
BigDecimal, never double / float.
- Dates are
LocalDate, ISO-8601 (yyyy-MM-dd) on the wire.
- CSV adapter: UTF-8, header row,
yyyy-MM-dd dates, dot decimal, no thousands separators, one CSV per aggregate.
- Inbound web: Spring MVC, thin controllers. Templates read from the domain; they don't compute domain logic.
- Tests use AssertJ (
assertThat(...)) — never JUnit's assertEquals. Write the test before or alongside the production code, not after.
Parallelism opportunity
If the plan hits independent hex layers (domain + out-adapter + in-adapter) AND the interfaces between them are pinned down in the plan, fan out with Agent subagents — one per layer. Each subagent gets:
- The relevant section of the plan.
- The port signatures they consume/produce.
- A clear "write the code and tests in this layer only, do not touch others" instruction.
Don't fan out when the plan is thin or the layers haven't been pinned — subagents that have to re-derive shape will disagree.
For small features or single-layer changes, just do it sequentially.
Log as you go
Each time you finish a coherent chunk (e.g. a new aggregate, a repository adapter, a controller), append a one-line entry to the Implementation section of the state file:
- 2026-04-23 added Debt aggregate + DebtTest (domain/)
- 2026-04-23 wired CsvDebtRepository + round-trip test (adapter/out/csv/)
This is what makes resumption painless. If the session dies mid-stage, the next agent reads the log and knows what's already built.
Self-check before exit
Before marking this stage done, quickly scan for:
- Dead
private methods.
- Single-impl interfaces or ports without a second caller in sight — drop them.
- Spring imports that crept into
domain/.
double/float on money fields.@Disabled or TODO-ridden tests.
Fix anything found. Don't defer cleanup to stage 4.
On exit
Update the state file:
Implementation section: final file log + any notes worth preserving (non-obvious decisions, deferred follow-ups).Status: implemented.- Update
Updated:.
Tell the user one sentence: "Implemented — running verify next." Then hand off to idea-verify.
Don't
- Don't add dependencies not already in the project without flagging first and getting agreement.
- Don't silently expand scope beyond the plan. If you hit something adjacent that needs fixing, note it in the
Implementation section as a follow-up and ask whether to include it now.
- Don't commit here. Commits happen after verify.
