AIDiveTL;DR and verdict
When Claude Code ignores a rule, the reflex is a louder line in CLAUDE.md. The docs say why that fails: Claude treats those files as context, not enforced configuration, and to block an action you use a hook instead. s4 The retro loop goes the other way: fewer lines, and a check that cannot be ignored.
In our run, one Claude Code session built a credit-note feature on a small invoicing API and shipped a numbering bug with its own tests green. A retro on that session, told what failed, proposed what would have prevented it. We approved four changes by hand: a pre-commit hook, a test, one standards line and one comment at the source. A fresh session given the same request then shipped the numbers gapless.
The verdict:
- Run a retro after a session that went wrong, before you clear it, or on the old session's log.
- Do not run it on autopilot. It only proposes, and nothing changes until you pick a candidate. s2
- Trace every candidate to a moment of the transcript, and drop the ones you cannot trace.
- Route each survivor to the right carrier: a check for a mechanical failure, a standards line for a judgement call, a comment at the source for a navigation gap.
- The checks you add are code you now maintain. The retro does not audit the checks it proposed last month. s2
The pack below holds the checklist, the hook script and the numbering test from our run.
Sourced synthesis
What the retro is. It is a skill in Matt Pocock's collection. It is user-invoked only (disable-model-invocation: true), and it looks for candidates in seven categories: Navigation, Automated checks, Coding standards, Global AGENTS.md, Tool economy, No-ops and Information access. s1 Its last step only presents the candidates, in order of severity. s1 It graduated into the Claude Code plugin in v1.3.0. s22
How to install it. The install line is claude plugin install mattpocock-skills@claude-plugins-official. s25 One trap: an issue reported the retro command missing when installing through the official marketplace. s24 The marketplace entry now pins a newer commit. s26 On our machine the local marketplace was still on the old pin, so we ran the marketplace update first, then the install, then checked the command in a new session.
Why the log, not the code. Claude Code stores transcripts as JSONL at ~/.claude/projects/<project>/<session-id>.jsonl, and claude --resume <transcript-path> resumes a session from that file. s8 The format is internal and changes between versions, so do not build scripts on it. s8 The retention is 30 days and configurable with cleanupPeriodDays. s8
The retro is noisy until you trace it. The docs tell you to discard any candidate you cannot trace to a specific moment. s2 They also warn that the model tends to forget the struggles from the middle of the session and invents generic advice to satisfy the categories. s2 An open issue counts 17 retro runs across 12 sessions, 15 of them followed by the user asking the agent to prove the candidates were needed, and asks for zero survivors to count as a complete retro. s7
Route each survivor. A repo with no guardrail, meaning no pre-commit hook and no CI job running its lint, typecheck or test command, is itself a finding. s1 A mechanical violation gets a deterministic check, full stop. s1 Steering files should be used incredibly sparingly, usually only for navigation pointers to other files. s1 A developer running a lessons loop in production reaches the same ladder: a rule that slips back becomes a test, a lint rule or a hook. s6
Keep CLAUDE.md small. The docs target under 200 lines per CLAUDE.md file, because longer files consume more context and reduce adherence. s4 Their test for each line: would removing it cause Claude to make mistakes? If not, cut it. s9 The bloat failure mode, an ignored rule that gets a louder rule and a longer file, is described by one developer. s10
Close the loop. The docs say to treat CLAUDE.md like code: review it when things go wrong, prune it regularly, and test changes by observing whether Claude's behavior actually shifts. s9 /doctor prompt-audit needs Claude Code v2.1.283 or later, reports findings with proposed edits, and changes nothing until you ask. s4 It runs through the bundled claude-api skill, so it is unavailable while that skill is turned off. s4 And an open issue describes the retro implementing approved changes and then forgetting the commit. s23
What we saw on our run. The first retro opened with "This session was smooth", because the session never learned that it had failed. Only after we reported the failure as the argument did it find the cause, a number taken before validation. Details in the measurements below.
Code
Each file is the real one from our run, or the script we used to run it. Edit the paths to match your repo.
retro-checklist.md is the page's checklist as a file: the seven gestures, the trace question word for word, the four carriers, the commit reminder and the prompt-audit path trap.
retro-checklist.md
# The retro checklist
Run it after a session that went wrong, before you clear it, or later on the old session's log.
## The seven gestures
1. Install: `claude plugin marketplace update claude-plugins-official`, then `claude plugin install mattpocock-skills@claude-plugins-official --scope project`. Open a NEW session, type a slash, check that the retro command is listed.
2. Run your real task in a plain session. Let it finish. Keep the session open.
3. Run the retro in that session, then run it again with what failed written after it, as its argument. The retro reads the session log, and a session that never learned it failed will call itself smooth.
4. Trace every candidate. Type this, word for word:
> For each candidate, quote the moment of this session's transcript that backs it; drop any candidate you cannot trace to a specific moment.
Zero survivors is a valid retro. Weaker survivors are a judgement call: you decide.
5. Approve one survivor at a time, each into its carrier (below). One change per turn, read the diff after each.
6. Run the prompt audit WITH a path, apply its edits if any, then commit the files yourself. The retro proposes and edits, it does not commit.
7. Re-run the same task in a fresh session and watch what it reads first and whether the failure happens again.
## The four carriers
| What failed | Carrier | Example from our run |
| --- | --- | --- |
| A mechanical failure | A deterministic check: a pre-commit hook, a test, a lint rule, a CI job | `pre-commit.sh` (typecheck, then tests) and `numbering.test.ts` |
| A judgement call | One line in `CODING_STANDARDS.md`, read by the reviewer | `CODING_STANDARDS.md` |
| A navigation gap | A comment at the source, or one CLAUDE.md pointer if a comment cannot do it | A doc comment above `nextId` |
| Nothing the above can hold | Do not write a rule | Both retros declined a CLAUDE.md line |
## Traps
- Commit reminder: the retro can implement what you approve and then leave the files uncommitted. Stage the approved files and commit them yourself.
- A new hook checks the working tree, not the commit. If the tree still holds the bug, the hook refuses the commit. Fix the code first, then commit.
- A cherry-pick does not run the pre-commit hook.
- Prompt-audit path trap: `/doctor prompt-audit` with no path audited the user-level files under `~/.claude`, not the repo, and said nothing about the new files. Give it the path: `/doctor prompt-audit CODING_STANDARDS.md`.
- The retro has no dry-run mode. Try a proposed check against the repo before you let it block merges.
- Do not wire the retro to a session-end hook. Keep a human on the approval.
- Keep the transcript format out of your scripts: it is internal and changes between versions.
pre-commit.sh is the hook we approved. It runs the typecheck, then the tests, and blocks the commit if either fails. Save it as .githooks/pre-commit, make it executable and run git config core.hooksPath .githooks.
pre-commit.sh
#!/bin/sh
set -e
pnpm typecheck
pnpm test
numbering.test.ts is the vitest test we approved. It locks one rule: a rejected credit-note request burns no number.
numbering.test.ts
import { describe, expect, it } from "vitest";
import { seedCustomer, seedOpenInvoice, testApp } from "./helpers";
describe("credit note numbering", () => {
it("does not burn a number on a rejected request", async () => {
const app = testApp();
const customerId = await seedCustomer(app);
const id = await seedOpenInvoice(app, { customerId, unitPrice: 10_000 });
await app.handle("POST", `/invoices/${id}/pay`);
const url = `/invoices/${id}/credit-notes`;
const first = await app.handle("POST", url, { amount: 4_000 });
expect(first.body).toMatchObject({ number: "CN-0001" });
const rejected = await app.handle("POST", url, { amount: 6_001 });
expect(rejected.status).not.toBe(201);
const next = await app.handle("POST", url, { amount: 6_000 });
expect(next.status).toBe(201);
expect(next.body).toMatchObject({ number: "CN-0002" });
});
});
CODING_STANDARDS.md is the one standards line we approved, the file a reviewer reads.
CODING_STANDARDS.md
# Coding standards
- Take a sequence number (`nextId`) only once every validation has passed, so a rejected request leaves the sequence gapless.
retro-output.md is the full text of both retro passes and both trace answers from our session.
retro-output.md
# Retro output, session A (cb5884fb-bd6f-4684-8866-d0adc12ac26e)
## 1. `/retro` (resumed headless, 2026-10-23 10:39:44, $0.0658, 17.5 s, 5 turns)
Prompt typed: `/retro` -> transcript records `<command-name>/mattpocock-skills:retro</command-name>`. Tool calls: Skill(mattpocock-skills:writing-for-agents), Bash(ls -a; ls .github; ls .git/hooks | grep -v sample; cat tsconfig.json), Bash(find .claude -type f; cat .claude/settings*.json).
Verbatim:
> This session was smooth. The pass came out clean on the first typecheck and test run, and I found no `AGENTS.md`/`CLAUDE.md` or `CODING_STANDARDS.md` to prune. The candidates below are in order of severity.
>
> **1. No guardrail runs the checks (automated checks)**
> - `package.json` already has `test` and `typecheck`, but nothing runs them: there's no `.github/` workflow and no pre-commit hook.
> - This session only stayed green because I ran both by hand. An agent, or a person, can commit a type error or a failing test.
> - **Fix:** add a CI job running `pnpm typecheck && pnpm test`, plus a pre-commit hook running the same. Neither needs prose.
>
> **2. The migration rule is the one convention that could be missed (automated checks)**
> - The README says "any change to the stored shape bumps `schemaVersion` and adds a migration".
> - I found it only because I read `README.md` while working out the design. If I'd skipped it, nothing would have failed. Adding a field to `StoreData` without a migration still typechecks.
> - **Fix:** a test that fails when someone changes the stored shape without bumping the version. For example, snapshot the output of `migrate({})` and assert the snapshot's `schemaVersion` equals `CURRENT_SCHEMA_VERSION`. This is a deterministic check, so it should replace the README sentence rather than add to it.
>
> **3. Adding a counter or store collection touches five places (navigation)**
> - Adding credit notes meant editing `types.ts`, `json-store.ts` (the `empty()` function), `migrations.ts` (the migration, plus the fallback defaults at the bottom of `migrate`), `context.ts`, and a new repo file.
> - The `{ customer: 0, invoice: 0, invoiceNumber: 0 }` literal is duplicated in `json-store.ts` and `migrations.ts`. I had to find both with `grep`.
> - **Fix:** have `migrate` build its defaults from one shared `emptyData()`. That removes a hidden dependency rather than documenting it. A pointer in a steering file would cost context on every turn and go stale, so I wouldn't write one.
>
> **4. Nothing for the reviewer to enforce (coding standards)**
> - There's no `CODING_STANDARDS.md`. The README's conventions are mostly mechanical: integer cents, domain functions that don't mutate their input, and which error type maps to which status.
> - A reviewer agent would have no judgement-call rules to apply. I wouldn't add any until a real review miss shows one is needed.
>
> **5. Tool economy and information access: nothing to change**
> - My one failed Bash call (a rejected heredoc) cost a retry, but that was my command and not the tooling.
> - I had everything I needed, since the tests call `createApp().handle` directly with no server or logs to tee.
>
> I'd start with 1 and 2. They're small, mechanical, and would catch the likeliest future mistake. Want me to add the CI workflow, the pre-commit hook and the schema-version test?
## 2. Trace step (same session, 10:40:33, $0.0322, 17.1 s, 1 turn)
Prompt: "For each candidate, quote the moment of this session's transcript that backs it; drop any candidate you cannot trace to a specific moment."
Verbatim:
> Two of the five candidates have no support in the transcript, and I got a detail wrong in a third. Here is each one against what actually happened.
>
> **1. No guardrail: kept**
> - The moment is my `ls -a; ls .github 2>/dev/null; ls .git/hooks | grep -v sample` command. The listing shows `.claude .git .gitignore data node_modules package.json … vitest.config.ts`. There is no `.github`, and the hooks `grep` printed nothing.
> - It isn't a mistake I made, since my own `pnpm typecheck` and `pnpm test` run came back clean. It's a repo-state finding: the checks exist as scripts and nothing runs them.
>
> **2. Migration rule has no check: dropped**
> - I can't point to a moment where I missed or nearly missed a migration. I read `migrations.ts` in my first big `cat`, before I'd seen the README. I would have found the migration step either way, so my claim that I found it only through the README was wrong.
> - "Nothing would have failed if I'd skipped it" is a hypothetical, not something that happened.
>
> **3. Five places to touch for a new collection: kept, but weaker than I said**
> - The moment is my batch of edits to `types.ts`, `json-store.ts`, `migrations.ts` and `context.ts`. Two of them changed the same literal, `{ customer: 0, invoice: 0, invoiceNumber: 0 }`, which now reads `…, creditNote: 0`. It appears in both `json-store.ts` and the fallback in `migrate`.
> - I said I "had to find both with `grep`". That's wrong. I never ran one, since the `grep` was in the command that was rejected. I already knew both locations from reading the files, and the edits went through without friction.
> - The duplicated literal is real but caused no trouble. I'd rate it low severity.
>
> **4. No `CODING_STANDARDS.md`: dropped**
> - The only moment is the `git ls-files` output showing the file doesn't exist. No review step happened in this session and no reviewer missed anything.
> - "I wouldn't add any until a real review miss shows one is needed" was my own opinion, not something the session showed.
>
> **5. Tool economy: dropped as a finding**
> - The moment is my first Bash call being rejected with `Contains brace with quote character (expansion obfuscation)`. It cost one retry, and I switched to Write and Edit.
> - It was a one-off, and I can't tell from the transcript whether the harness or my heredoc-in-Python approach was at fault. I don't think it justifies a change.
>
> That leaves candidate 1 as the only solid finding and candidate 3 as a minor one. For 1, I can add a CI workflow and a pre-commit hook that both run `pnpm typecheck && pnpm test`.
## 3. Second `/retro`, with the defect reported by the developer (same session, 10:41:10, $0.0491, 23.1 s, 1 turn, no tool call; it skipped the writing-for-agents reload)
Prompt: `/retro Finance tested this build after the session: they sent a credit note that was too big (rejected, fine), and the next valid credit note came out CN-0004 where CN-0002 was due. Rejected requests burn credit-note numbers. Don't fix the code; run the retro on this session with that failure in mind.`
Verbatim:
> I'm skipping the style-guide reload because it's already in this session. The cause is in my own code, and I traced each finding to a specific moment.
>
> **What happened**
> - In `issueCreditNote` (`src/http/handlers/invoices.ts`) I call `ctx.store.nextId("creditNote")` first and `createCreditNote(...)` second. `nextId` persists the counter immediately, and `createCreditNote` is what throws the 409 for an over-limit amount. So a rejected request still burns a number.
> - I copied the order from the existing `/issue` handler, which I had read. It does `const n = ctx.store.nextId("invoiceNumber"); const issued = issue(current, ...)`, and `issue()` throws if the invoice isn't a draft. So issuing a non-draft invoice probably burns an `INV-` number the same way. I haven't run that, only read it.
>
> **1. A test that would have caught it: I wrote the scenario and skipped the assertion (automated checks)**
> - The moment is the test I wrote: "rejects bad amounts (400) and amounts above what is left (409)".
> ```
> await app.handle("POST", ..., { amount: 8_000 });
> expect((await app.handle("POST", ..., { amount: 1_001 })).status).toBe(409);
> expect((await app.handle("POST", ..., { amount: 1_000 })).status).toBe(201);
> ```
> That is exactly Finance's sequence: accept, reject, accept. I only checked status codes, never the number on the last note, which comes out as `CN-0003`.
> - The "numbers credit notes sequentially" test only covers two successful requests in a row.
> - **Fix:** add a test that each numbered sequence (`INV-`, `CN-`) stays gapless after rejected requests. Run it over both sequences, which also exposes the `/issue` case.
> - **Rule:** when a test reaches a failure path, assert the state afterwards, not just the status code.
>
> **2. `nextId` looks pure but isn't (navigation)**
> - In `json-store.ts`, `nextId(kind)` runs `this.update(...)`, so every call writes to the counter and persists it. The `Store` type in `json-store.ts` has only the signature `nextId(kind: keyof Counters): number;`, with no comment about the side effect.
> - Nothing at the call site tells you to allocate only after validation. This is a gotcha no config reveals, so a short doc comment on `nextId` is worth its cost. Something like: "Consumes the number even if the caller then fails; call it only after validation."
> - Keep it as a comment on `nextId`, not a steering-file line. It matters only to someone calling `nextId`, and it can't go stale there.
>
> **3. The gapless-numbering convention isn't written down (coding standards)**
> - The README's "Conventions" list has cents, immutability, error-to-status mapping, and migrations. It says nothing about invoice or credit-note numbers being gapless, though the request ("numbered `CN-0001`, `CN-0002`...") implies it.
> - This is partly a judgement call: reviewers need to know that numbers are allocated after validation. One README line would do. Finding 1's test is the deterministic check; the README line explains why the test exists.
>
> **4. Missing CI, from the first retro: still real, but it wouldn't have helped here**
> - My own typecheck and tests passed, so a CI job would also have passed. I'm keeping it as a separate, unrelated finding, not as a cause of this failure.
>
> **5. My summary stated the rules but didn't test them**
> - I told you "Rules I chose" and flagged the two-update void risk, but never exercised a rejection followed by a success. The summary read as complete when that path was untested. This is a process gap, and finding 1 is the fix.
>
> I'd start with 1 and 2. I haven't touched the code, as you asked.
## 4. Trace step on the second retro (same session, 10:41:43, $0.0498, 33.4 s, 1 turn)
Prompt: same trace prompt as section 2.
Verbatim:
> I traced each candidate again. Two survive on firm evidence, two survive but with a gap I should state, and one is dropped.
>
> **1. Test asserts status but not the number: kept, firm**
> - The moment is the test I wrote in `test/credit-notes.test.ts`:
> ```
> await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 8_000 });
> expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 1_001 })).status).toBe(409);
> expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 1_000 })).status).toBe(201);
> ```
> That is accept, reject, accept, with only status codes checked. By my reading of the handler, the last note comes out as `CN-0003`. I derived that and haven't run it.
> - The adjacent test, "numbers credit notes sequentially…", covers two successes in a row and never a rejection.
> - The cause, which I only read and haven't run, is this in the handler I wrote:
> ```
> const id = ctx.store.nextId("creditNote");
> const note = createCreditNote(invoice, existing, amount, …
> ```
> That order matches the existing issue handler, which I read:
> ```
> const n = ctx.store.nextId("invoiceNumber");
> const issued = issue(current, `INV-…`, ctx.now());
> ```
> and `issue()` throws `ConflictError` for non-drafts. So the `INV-` sequence very likely has the same leak. I haven't run that either.
>
> **2. `nextId` has no warning about its side effect: kept, firm on the facts**
> - The moment is the `Store` type I read in `json-store.ts`. `update` has a comment ("Apply a change and persist it (when file-backed)."), while `nextId(kind: keyof Counters): number;` has none. Its implementation calls `this.update(...)`, so it persists immediately.
> - The `/issue` call site I copied has no comment either.
> - I can't show that a comment would have changed what I did, because I never weighed the ordering at all. I copied it. The comment is a bet on the next caller, not a proven fix.
>
> **3. Gapless numbering isn't written in the README: kept, weaker**
> - The moment is the `README.md` output I read before writing the handler. Its Conventions list covers cents, no mutation, error-to-status mapping and `schemaVersion`. It has no line about numbers.
> - So the agent doing the implementation, meaning me, read the conventions and found nothing on this.
> - I overstated one thing last turn. Your request said "numbered `CN-0001`, `CN-0002`...", and I said that implies gapless numbers. That was my inference, not your words. Finance has now confirmed it as a requirement, but nothing in the original request stated it.
>
> **4. No CI or pre-commit hook: kept, unrelated to this failure**
> - The moment is my `ls -a; ls .github 2>/dev/null; ls .git/hooks | grep -v sample` output, which showed no `.github` and no hooks.
> - It wouldn't have caught this. My own run ended `Tests 42 passed (42)`, and CI would have passed too.
>
> **5. "My summary stated rules without testing them": dropped**
> - I can quote the summary ("Rules I chose", plus the line about the void being two separate store updates). But it describes my behaviour, not a change to the environment, and finding 1 already covers the underlying gap. Keeping it would count one moment twice.
>
> The order of importance is 1, 2, then 3. Finding 4 stays on the list but belongs to a separate piece of work. I still haven't changed any code.
doctor-prompt-audit.md is the prompt audit run with no path, then with a path. It shows the path trap.
doctor-prompt-audit.md
# `/doctor prompt-audit` (no path) on the ledgerly copy, session 26612b59-9edd-493b-a397-fb54300fa037
# Prompt audit: Claude Code configuration for ledgerly
**Assumptions**
- **Target model:** Claude Sonnet 5.5, the model running this session. A skill that writes prompts for other models (`prompt-master`) is audited for its Claude-facing text only.
- **Scope:** only the Claude Code configuration that loads into this project, as you specified. I proposed no edits to plugin files.
- **Settings and secrets:** I did not read `.claude/settings.json`, `.mcp.json` or `~/.claude.json`.
- **Edits are not applied.** Every edit below touches `~/.claude/`, so it **affects all projects**.
- **Dependency not verified:** I could not verify that `~/.claude` is under git, so I used no `git blame`. No hunk below relies on history.
**Inventory**
- **Project files:** none. The project root has no `CLAUDE.md`, `CLAUDE.local.md`, `AGENTS.md` or `.claude/` instruction files. The ancestors `/path/to/work` and `/private/tmp` have none either.
- **Managed policy:** no managed-policy `CLAUDE.md` exists.
- **User level:**
- `~/.claude/CLAUDE.md`, which imports `~/.claude/RTK.md`.
- `~/.claude/rules/context7.md`.
- 27 skills under `~/.claude/skills/*/SKILL.md`.
- There are no `commands/`, `agents/` or `output-styles/` folders.
- **Plugins:** `caveman`, `marketing`, `cowork-plugin-management` and `gleam-reels` are installed. I did not audit them in depth, and they have no findings or edits.
- **Coverage gap:** I read `CLAUDE.md`, `RTK.md`, the rule, `context7-mcp`, most of `prompt-master`, the relevant parts of `graphify`, and the top of `agent-reach`. I covered the other skills (Cloudflare, HyperFrames, browser, media) with signal greps and frontmatter only. I did not read their `references/` subfiles.
- **Possible mismatch:** this session's skill list shows none of the `~/.claude/skills/*` entries. These files may not be loading in this project, so the skill findings may not affect it.
## Findings of the first run
The audit without a path found no project instruction files and went on to audit the user-level files under the home folder instead: six proposed edits and four flags, all about files outside this repository, none applied. That part is left out of this copy because it concerns one developer's personal configuration, not the project.
# Second run: `/doctor prompt-audit CODING_STANDARDS.md` (session 9b5f0cd5-1701-498e-8d05-0355c7f1ece6)
## Prompt audit: `CODING_STANDARDS.md`
**Assumptions**
- **Scope:** only `CODING_STANDARDS.md`, which the request names. The inventory found no `CLAUDE.md`, `AGENTS.md`, rule files, skills, commands or subagents in the repo. `.claude/settings.json` exists but I did not read it, per the audit rules.
- **Target model:** Claude Sonnet 5.5, the model running this audit. The file is read by the coding agent, not by application code.
- **Group 4 (request config and architecture):** not applicable. The file is an agent instruction file and has no request-building code.
**Result: the file is clean.** It has one line, so there is nothing to change and the proposed diff is empty.
**Inventory:** `CODING_STANDARDS.md` has one rule at line 3: "Take a sequence number (`nextId`) only once every validation has passed, so a rejected request leaves the sequence gapless."
**Checks**
| Group | Findings |
|---|---|
| 1 Dated prompt text | 0. The rule has no emphasis, hedging, scaffold or step list. It states a reason, so it is context the model can't know, not a prohibition without provenance. |
| 2 Brittle config files | 0. `git blame` puts the line in `adaa593`, the retro commit that followed the credit-note session. It encodes a failure that actually happened, not a one-off stumble. |
| 3 Tool descriptions | Not applicable. |
| 4 Request config and architecture | Not applicable. |
Group 2 also covers stale facts. `nextId` is still defined (`src/store/json-store.ts:11,52`) and the sequence kinds it names still exist. No other instruction file ranks on the same point, so there is no conflict.
**One thing outside the audit:** the rule is violated in the code. `src/http/handlers/invoices.ts:44` calls `ctx.store.nextId("invoiceNumber")` before `issue()` runs. `issue()` throws `ConflictError` for any non-draft invoice (`src/domain/invoice.ts:42-44`). Issuing an already-issued, paid or void invoice therefore consumes an invoice number and leaves a gap. The fix is to validate first, or to pass an allocator into `issue()` the way `createCreditNote` takes `allocate`. I didn't check `customers.ts:8` or `credit-note.ts`.
This is a code bug, not a prompt problem, and the rule is working as intended. Keep it, and consider an enforcing test: `test/numbering.test.ts` may only cover credit notes. I haven't edited anything.
doctor-prompt-audit.md on GitHub
run-session.sh runs one headless Claude Code turn in an isolated, project-only setup with an allow-list. Edit the env line to your own.
run-session.sh
#!/usr/bin/env bash
# Usage: run-session.sh <workdir> <out.json> <prompt> [resume-session-id]
# One headless Claude Code turn with an isolated project-only setup and an allow-list.
set -uo pipefail
W="$1"; OUT="$2"; PROMPT="$3"; SID="${4:-}"
source ./env.sh # your own env: unset CLAUDE* variables, optionally CLAUDE_CODE_DISABLE_AUTO_MEMORY=1
ALLOWED="Read,Edit,Write,MultiEdit,Glob,Grep,Skill,TodoWrite,Task,Agent,Bash(node:*),Bash(npm:*),Bash(pnpm:*),Bash(npx vitest:*),Bash(npx tsc:*),Bash(tsc:*),Bash(git status:*),Bash(git diff:*),Bash(git log:*),Bash(git add:*),Bash(git commit:*),Bash(git checkout -b:*),Bash(ls:*),Bash(cat:*),Bash(mkdir:*),Bash(head:*),Bash(tail:*),Bash(grep:*),Bash(wc:*),Bash(gh:*)"
DIS="AskUserQuestion,EnterPlanMode,ExitPlanMode,EnterWorktree,ExitWorktree,WebFetch,WebSearch"
ARGS=(-p "$PROMPT")
[ -n "$SID" ] && ARGS+=(--resume "$SID")
cd "$W" || exit 1
T0=$(date +%s)
claude "${ARGS[@]}" --model claude-sonnet-5-5 --permission-mode acceptEdits --output-format json \
--allowedTools "$ALLOWED" --disallowedTools "$DIS" --setting-sources project --strict-mcp-config \
> "$OUT" 2> "$OUT.stderr" < /dev/null
RC=$?
echo "rc=$RC wall=$(( $(date +%s) - T0 ))s" | tee "$OUT.wall"
python3 -c "import json,sys;d=json.load(open(sys.argv[1]));print({k:d.get(k) for k in ('session_id','total_cost_usd','duration_ms','num_turns','is_error','subtype')})" "$OUT"
oracle.sh runs the hidden finance test, five requirements checked from outside the session, against a working copy. Point it at your own hidden tests.
oracle.sh
#!/usr/bin/env bash
# Usage: oracle.sh <workdir> <out.json> -- the hidden finance test for the credit-note task, run from OUTSIDE the work copy.
H=/path/to/hidden-tests
W="$1"; OUT="$2"
cd "$H" && env -u CLAUDECODE WORK="$W" BASE="$(git -C "$W" rev-list --max-parents=0 HEAD | head -1)" TASK=F2 \
"$H/node_modules/.bin/vitest" run --reporter=json --outputFile="$OUT" > "$OUT.log" 2>&1
python3 - "$OUT" <<'PY'
import json,sys
j=json.load(open(sys.argv[1]))
for tr in j["testResults"]:
for a in tr["assertionResults"]:
print(a["status"].upper(), a["title"]);
if a["status"]!="passed": print(" ", " ".join(a.get("failureMessages") or [])[:500].replace("\n"," | "))
PY
sessionA-F2.diff is the code of the session that shipped the bug, with the fix.
sessionA-F2.diff
diff --git a/README.md b/README.md
index 890f13c..ae1e4f9 100644
--- a/README.md
+++ b/README.md
@@ -27,4 +27,8 @@ pnpm typecheck # tsc --noEmit
## Invoice lifecycle
-`draft` → (`issue`) → `open` → (`pay`) → `paid`; `draft`/`open` → (`void`) → `void`.
+`draft` → (`issue`) → `open` → (`pay`) → `paid`; `draft`/`open`/`paid` → (`void`) → `void`.
+
+Credit notes (`POST`/`GET /invoices/:id/credit-notes`, numbered `CN-0001`, ...) can be issued against
+`open` or `paid` invoices, up to the invoice total minus earlier credit notes. Open invoices' credits
+reduce the outstanding report. Voiding a paid invoice issues a credit note for whatever is left.
diff --git a/src/domain/credit-note.ts b/src/domain/credit-note.ts
new file mode 100644
index 0000000..9a48b40
--- /dev/null
+++ b/src/domain/credit-note.ts
@@ -0,0 +1,43 @@
+import { ConflictError, ValidationError } from "./errors";
+import { computeTotals, type Invoice } from "./invoice";
+import { assertCents, type Cents, type Currency, sum } from "./money";
+
+export type CreditNote = {
+ id: string;
+ /** CN-0001, ... */
+ number: string;
+ invoiceId: string;
+ currency: Currency;
+ /** cents, always positive */
+ amount: Cents;
+ createdAt: string;
+};
+
+export function parseCreditNoteAmount(body: unknown): Cents {
+ if (typeof body !== "object" || body === null) {
+ throw new ValidationError("body must be an object");
+ }
+ return assertCents((body as Record<string, unknown>).amount, "amount", { min: 1 });
+}
+
+/** What is still creditable on an invoice: its total minus the credit notes already issued. */
+export function remainingCredit(invoice: Invoice, notes: CreditNote[]): Cents {
+ return computeTotals(invoice).total - sum(notes.map((n) => n.amount));
+}
+
+export function createCreditNote(
+ invoice: Invoice,
+ existing: CreditNote[],
+ amount: Cents,
+ ids: { id: string; number: string },
+ now: Date,
+): CreditNote {
+ if (invoice.status !== "open" && invoice.status !== "paid") {
+ throw new ConflictError(`invoice ${invoice.id} is ${invoice.status}, only open or paid invoices can be credited`);
+ }
+ const remaining = remainingCredit(invoice, existing);
+ if (amount > remaining) {
+ throw new ConflictError(`credit note of ${amount} exceeds the ${remaining} still creditable on invoice ${invoice.id}`);
+ }
+ return { ...ids, invoiceId: invoice.id, currency: invoice.currency, amount, createdAt: now.toISOString() };
+}
diff --git a/src/domain/invoice.ts b/src/domain/invoice.ts
index 5b69fc9..1a3967b 100644
--- a/src/domain/invoice.ts
+++ b/src/domain/invoice.ts
@@ -52,8 +52,9 @@ export function markPaid(invoice: Invoice, now: Date): Invoice {
return { ...invoice, status: "paid", paidAt: now.toISOString() };
}
+/** Paid invoices can be voided too, but the caller must credit what is left on them first. */
export function voidInvoice(invoice: Invoice, now: Date): Invoice {
- if (invoice.status === "paid" || invoice.status === "void") {
+ if (invoice.status === "void") {
throw new ConflictError(`invoice ${invoice.id} is ${invoice.status} and cannot be voided`);
}
return { ...invoice, status: "void", voidedAt: now.toISOString() };
diff --git a/src/http/context.ts b/src/http/context.ts
index c0a89d3..38d7ffa 100644
--- a/src/http/context.ts
+++ b/src/http/context.ts
@@ -1,5 +1,6 @@
import type { Store } from "../store/json-store";
import { customerRepo } from "../store/customer-repo";
+import { creditNoteRepo } from "../store/credit-note-repo";
import { invoiceRepo } from "../store/invoice-repo";
export type AppContext = {
@@ -7,8 +8,9 @@ export type AppContext = {
now: () => Date;
customers: ReturnType<typeof customerRepo>;
invoices: ReturnType<typeof invoiceRepo>;
+ creditNotes: ReturnType<typeof creditNoteRepo>;
};
export function createContext(store: Store, now: () => Date = () => new Date()): AppContext {
- return { store, now, customers: customerRepo(store), invoices: invoiceRepo(store) };
+ return { store, now, customers: customerRepo(store), invoices: invoiceRepo(store), creditNotes: creditNoteRepo(store) };
}
diff --git a/src/http/handlers/invoices.ts b/src/http/handlers/invoices.ts
index 09959e1..17b3910 100644
--- a/src/http/handlers/invoices.ts
+++ b/src/http/handlers/invoices.ts
@@ -1,3 +1,4 @@
+import { type CreditNote, createCreditNote, parseCreditNoteAmount, remainingCredit } from "../../domain/credit-note";
import { ValidationError } from "../../domain/errors";
import { type Invoice, type InvoiceStatus, issue, markPaid, voidInvoice } from "../../domain/invoice";
import { parseNewInvoice } from "../../domain/validation";
@@ -51,8 +52,33 @@ export function invoiceRoutes(router: Router, ctx: AppContext): void {
return { status: 200, body: invoiceView(ctx.invoices.save(paid)) };
});
+ /** Voiding a paid invoice credits whatever is left on it, so the books stay balanced. */
router.on("POST", "/invoices/:id/void", ({ params }) => {
- const voided = voidInvoice(ctx.invoices.get(params.id), ctx.now());
+ const current = ctx.invoices.get(params.id);
+ const now = ctx.now();
+ const voided = voidInvoice(current, now);
+ if (current.status === "paid") {
+ const left = remainingCredit(current, ctx.creditNotes.listForInvoice(current.id));
+ if (left > 0) issueCreditNote(current, left);
+ }
return { status: 200, body: invoiceView(ctx.invoices.save(voided)) };
});
+
+ router.on("POST", "/invoices/:id/credit-notes", ({ params, body }) => {
+ const invoice = ctx.invoices.get(params.id);
+ const amount = parseCreditNoteAmount(body);
+ return { status: 201, body: issueCreditNote(invoice, amount) };
+ });
+
+ router.on("GET", "/invoices/:id/credit-notes", ({ params }) => {
+ const invoice = ctx.invoices.get(params.id);
+ return { status: 200, body: ctx.creditNotes.listForInvoice(invoice.id) };
+ });
+
+ function issueCreditNote(invoice: Invoice, amount: number): CreditNote {
+ const existing = ctx.creditNotes.listForInvoice(invoice.id);
+ const id = ctx.store.nextId("creditNote");
+ const note = createCreditNote(invoice, existing, amount, { id: `cn_${id}`, number: `CN-${String(id).padStart(4, "0")}` }, ctx.now());
+ return ctx.creditNotes.insert(note);
+ }
}
diff --git a/src/http/handlers/reports.ts b/src/http/handlers/reports.ts
index 19262c9..c84089a 100644
--- a/src/http/handlers/reports.ts
+++ b/src/http/handlers/reports.ts
@@ -1,4 +1,5 @@
-import { computeTotals, isOverdue } from "../../domain/invoice";
+import { remainingCredit } from "../../domain/credit-note";
+import { isOverdue } from "../../domain/invoice";
import type { Currency } from "../../domain/money";
import type { AppContext } from "../context";
import type { Router } from "../router";
@@ -11,8 +12,8 @@ export function reportRoutes(router: Router, ctx: AppContext): void {
let count = 0;
let overdue = 0;
for (const invoice of ctx.invoices.list({ status: "open" })) {
- const { total } = computeTotals(invoice);
- totals[invoice.currency] = (totals[invoice.currency] ?? 0) + total;
+ const owed = remainingCredit(invoice, ctx.creditNotes.listForInvoice(invoice.id));
+ totals[invoice.currency] = (totals[invoice.currency] ?? 0) + owed;
count += 1;
if (isOverdue(invoice, now)) overdue += 1;
}
diff --git a/src/store/credit-note-repo.ts b/src/store/credit-note-repo.ts
new file mode 100644
index 0000000..c922142
--- /dev/null
+++ b/src/store/credit-note-repo.ts
@@ -0,0 +1,14 @@
+import type { CreditNote } from "../domain/credit-note";
+import type { Store } from "./json-store";
+
+export function creditNoteRepo(store: Store) {
+ return {
+ listForInvoice(invoiceId: string): CreditNote[] {
+ return store.read().creditNotes.filter((n) => n.invoiceId === invoiceId);
+ },
+ insert(note: CreditNote): CreditNote {
+ store.update((d) => ({ ...d, creditNotes: [...d.creditNotes, note] }));
+ return note;
+ },
+ };
+}
diff --git a/src/store/json-store.ts b/src/store/json-store.ts
index b404c51..99205b7 100644
--- a/src/store/json-store.ts
+++ b/src/store/json-store.ts
@@ -13,9 +13,10 @@ export type Store = {
function empty(): StoreData {
return {
schemaVersion: CURRENT_SCHEMA_VERSION,
- counters: { customer: 0, invoice: 0, invoiceNumber: 0 },
+ counters: { customer: 0, invoice: 0, invoiceNumber: 0, creditNote: 0 },
customers: [],
invoices: [],
+ creditNotes: [],
};
}
diff --git a/src/store/migrations.ts b/src/store/migrations.ts
index c8b73a9..91d4f99 100644
--- a/src/store/migrations.ts
+++ b/src/store/migrations.ts
@@ -1,6 +1,6 @@
import type { StoreData } from "./types";
-export const CURRENT_SCHEMA_VERSION = 1;
+export const CURRENT_SCHEMA_VERSION = 2;
type RawData = Record<string, unknown> & { schemaVersion?: number };
type Migration = (data: RawData) => RawData;
@@ -21,9 +21,18 @@ const v0ToV1: Migration = (data) => {
};
};
+/** v1 -> v2: credit notes (a `creditNotes` list and a `creditNote` counter). */
+const v1ToV2: Migration = (data) => ({
+ ...data,
+ schemaVersion: 2,
+ counters: { creditNote: 0, ...(data.counters as Record<string, number> | undefined) },
+ creditNotes: (data.creditNotes as unknown[] | undefined) ?? [],
+});
+
/** migrations[n] upgrades a file from version n to n + 1. */
const migrations: Record<number, Migration> = {
0: v0ToV1,
+ 1: v1ToV2,
};
export function migrate(raw: unknown): StoreData {
@@ -43,8 +52,9 @@ export function migrate(raw: unknown): StoreData {
}
return {
schemaVersion: CURRENT_SCHEMA_VERSION,
- counters: (data.counters as StoreData["counters"]) ?? { customer: 0, invoice: 0, invoiceNumber: 0 },
+ counters: (data.counters as StoreData["counters"]) ?? { customer: 0, invoice: 0, invoiceNumber: 0, creditNote: 0 },
customers: (data.customers as StoreData["customers"]) ?? [],
invoices: (data.invoices as StoreData["invoices"]) ?? [],
+ creditNotes: (data.creditNotes as StoreData["creditNotes"]) ?? [],
};
}
diff --git a/src/store/types.ts b/src/store/types.ts
index 222b191..a9d7277 100644
--- a/src/store/types.ts
+++ b/src/store/types.ts
@@ -1,7 +1,8 @@
+import type { CreditNote } from "../domain/credit-note";
import type { Customer } from "../domain/customer";
import type { Invoice } from "../domain/invoice";
-export type Counters = { customer: number; invoice: number; invoiceNumber: number };
+export type Counters = { customer: number; invoice: number; invoiceNumber: number; creditNote: number };
/** The shape of the JSON file at CURRENT_SCHEMA_VERSION. */
export type StoreData = {
@@ -9,4 +10,5 @@ export type StoreData = {
counters: Counters;
customers: Customer[];
invoices: Invoice[];
+ creditNotes: CreditNote[];
};
diff --git a/test/credit-notes.test.ts b/test/credit-notes.test.ts
new file mode 100644
index 0000000..f841a3c
--- /dev/null
+++ b/test/credit-notes.test.ts
@@ -0,0 +1,94 @@
+import { describe, expect, it } from "vitest";
+import { openStore } from "../src/store/json-store";
+import { migrate } from "../src/store/migrations";
+import { seedCustomer, seedOpenInvoice, testApp } from "./helpers";
+
+async function setup(opts: { unitPrice?: number; discount?: number } = {}) {
+ const app = testApp();
+ const customerId = await seedCustomer(app);
+ const id = await seedOpenInvoice(app, { customerId, unitPrice: opts.unitPrice ?? 10_000, discount: opts.discount });
+ return { app, id };
+}
+
+describe("credit notes", () => {
+ it("numbers credit notes sequentially and lists them per invoice", async () => {
+ const { app, id } = await setup();
+ const first = await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 2_500 });
+ const second = await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 1_000 });
+ expect(first.status).toBe(201);
+ expect(first.body).toMatchObject({ number: "CN-0001", invoiceId: id, amount: 2_500, currency: "EUR" });
+ expect(second.body).toMatchObject({ number: "CN-0002" });
+ const list = await app.handle("GET", `/invoices/${id}/credit-notes`);
+ expect((list.body as { number: string }[]).map((n) => n.number)).toEqual(["CN-0001", "CN-0002"]);
+ });
+
+ it("rejects bad amounts (400) and amounts above what is left (409)", async () => {
+ const { app, id } = await setup({ discount: 1_000 });
+ for (const amount of [0, -5, 1.5, "10", undefined]) {
+ expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount })).status).toBe(400);
+ }
+ await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 8_000 });
+ expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 1_001 })).status).toBe(409);
+ expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 1_000 })).status).toBe(201);
+ });
+
+ it("refuses drafts and unknown invoices", async () => {
+ const app = testApp();
+ const customerId = await seedCustomer(app);
+ const draft = await app.handle("POST", "/invoices", {
+ customerId,
+ currency: "EUR",
+ lines: [{ description: "x", quantity: 1, unitPrice: 100 }],
+ });
+ const id = (draft.body as { id: string }).id;
+ expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 10 })).status).toBe(409);
+ expect((await app.handle("GET", "/invoices/inv_999/credit-notes")).status).toBe(404);
+ });
+
+ it("reduces the outstanding report for open invoices", async () => {
+ const { app, id } = await setup();
+ await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 4_000 });
+ const report = await app.handle("GET", "/reports/outstanding");
+ expect(report.body).toMatchObject({ totals: { EUR: 6_000 }, count: 1 });
+ });
+
+ it("voids a paid invoice by crediting what is left", async () => {
+ const { app, id } = await setup();
+ await app.handle("POST", `/invoices/${id}/pay`);
+ await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 3_000 });
+ const res = await app.handle("POST", `/invoices/${id}/void`);
+ expect(res.status).toBe(200);
+ expect(res.body).toMatchObject({ status: "void" });
+ const notes = (await app.handle("GET", `/invoices/${id}/credit-notes`)).body as { amount: number }[];
+ expect(notes.map((n) => n.amount)).toEqual([3_000, 7_000]);
+ });
+
+ it("voids a fully credited paid invoice without another note", async () => {
+ const { app, id } = await setup();
+ await app.handle("POST", `/invoices/${id}/pay`);
+ await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 10_000 });
+ expect((await app.handle("POST", `/invoices/${id}/void`)).status).toBe(200);
+ const notes = (await app.handle("GET", `/invoices/${id}/credit-notes`)).body as unknown[];
+ expect(notes).toHaveLength(1);
+ });
+
+ it("refuses credit notes on void invoices and double voids", async () => {
+ const { app, id } = await setup();
+ await app.handle("POST", `/invoices/${id}/pay`);
+ await app.handle("POST", `/invoices/${id}/void`);
+ expect((await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 1 })).status).toBe(409);
+ expect((await app.handle("POST", `/invoices/${id}/void`)).status).toBe(409);
+ });
+
+ it("migrates a v1 file by adding the credit note list and counter", () => {
+ const data = migrate({
+ schemaVersion: 1,
+ counters: { customer: 1, invoice: 1, invoiceNumber: 1 },
+ customers: [],
+ invoices: [],
+ });
+ expect(data.creditNotes).toEqual([]);
+ expect(data.counters).toEqual({ customer: 1, invoice: 1, invoiceNumber: 1, creditNote: 0 });
+ expect(openStore().nextId("creditNote")).toBe(1);
+ });
+});
diff --git a/test/invoice.test.ts b/test/invoice.test.ts
index 85202f2..4ad9677 100644
--- a/test/invoice.test.ts
+++ b/test/invoice.test.ts
@@ -53,9 +53,10 @@ describe("invoice domain", () => {
expect(() => markPaid(draft({ status: "void" }), NOW)).toThrow(ConflictError);
});
- it("voids drafts and open invoices, never paid ones", () => {
+ it("voids drafts, open and paid invoices, never void ones", () => {
expect(voidInvoice(draft(), NOW).status).toBe("void");
- expect(() => voidInvoice(draft({ status: "paid" }), NOW)).toThrow(ConflictError);
+ expect(voidInvoice(draft({ status: "paid" }), NOW).status).toBe("void");
+ expect(() => voidInvoice(draft({ status: "void" }), NOW)).toThrow(ConflictError);
});
it("knows when an open invoice is overdue", () => {
sessionB-F2.diff is the code of the fresh session that re-ran the same request.
sessionB-F2.diff
diff --git a/README.md b/README.md
index 890f13c..3aa7a58 100644
--- a/README.md
+++ b/README.md
@@ -28,3 +28,5 @@ pnpm typecheck # tsc --noEmit
## Invoice lifecycle
`draft` → (`issue`) → `open` → (`pay`) → `paid`; `draft`/`open` → (`void`) → `void`.
+A `paid` invoice is voided by crediting whatever is left on it (credit notes `CN-0001`, ..., via
+`POST /invoices/:id/credit-notes` `{ "amount": cents }`; list with `GET`), then it becomes `void`.
diff --git a/src/domain/credit-note.ts b/src/domain/credit-note.ts
new file mode 100644
index 0000000..e2047c3
--- /dev/null
+++ b/src/domain/credit-note.ts
@@ -0,0 +1,39 @@
+import { ConflictError, ValidationError } from "./errors";
+import { computeTotals, type Invoice } from "./invoice";
+import { assertCents, type Cents, type Currency, sum } from "./money";
+
+export type CreditNote = {
+ id: string;
+ /** CN-0001, CN-0002, ... */
+ number: string;
+ invoiceId: string;
+ currency: Currency;
+ /** cents, always > 0 */
+ amount: Cents;
+ createdAt: string;
+};
+
+/** What can still be credited on an invoice: its total minus the credit notes already issued. */
+export function remainingCredit(invoice: Invoice, notes: CreditNote[]): Cents {
+ return computeTotals(invoice).total - sum(notes.map((n) => n.amount));
+}
+
+/** Checks a credit-note request against the invoice and returns the amount. Throws before any number is taken. */
+export function parseCreditAmount(body: unknown, invoice: Invoice, notes: CreditNote[]): Cents {
+ if (typeof body !== "object" || body === null) {
+ throw new ValidationError("body must be an object");
+ }
+ const amount = assertCents((body as Record<string, unknown>).amount, "amount", { min: 1 });
+ if (invoice.status !== "paid") {
+ throw new ConflictError(`invoice ${invoice.id} is ${invoice.status}, only paid invoices can be credited`);
+ }
+ const remaining = remainingCredit(invoice, notes);
+ if (amount > remaining) {
+ throw new ConflictError(`amount ${amount} exceeds the ${remaining} left to credit on invoice ${invoice.id}`);
+ }
+ return amount;
+}
+
+export function creditNumber(n: number): string {
+ return `CN-${String(n).padStart(4, "0")}`;
+}
diff --git a/src/domain/invoice.ts b/src/domain/invoice.ts
index 5b69fc9..60be8ac 100644
--- a/src/domain/invoice.ts
+++ b/src/domain/invoice.ts
@@ -52,8 +52,9 @@ export function markPaid(invoice: Invoice, now: Date): Invoice {
return { ...invoice, status: "paid", paidAt: now.toISOString() };
}
-export function voidInvoice(invoice: Invoice, now: Date): Invoice {
- if (invoice.status === "paid" || invoice.status === "void") {
+/** A paid invoice can be voided only once it is fully credited (`fullyCredited`). */
+export function voidInvoice(invoice: Invoice, now: Date, opts: { fullyCredited?: boolean } = {}): Invoice {
+ if ((invoice.status === "paid" && !opts.fullyCredited) || invoice.status === "void") {
throw new ConflictError(`invoice ${invoice.id} is ${invoice.status} and cannot be voided`);
}
return { ...invoice, status: "void", voidedAt: now.toISOString() };
diff --git a/src/http/context.ts b/src/http/context.ts
index c0a89d3..4b26d92 100644
--- a/src/http/context.ts
+++ b/src/http/context.ts
@@ -1,4 +1,5 @@
import type { Store } from "../store/json-store";
+import { creditNoteRepo } from "../store/credit-note-repo";
import { customerRepo } from "../store/customer-repo";
import { invoiceRepo } from "../store/invoice-repo";
@@ -7,8 +8,15 @@ export type AppContext = {
now: () => Date;
customers: ReturnType<typeof customerRepo>;
invoices: ReturnType<typeof invoiceRepo>;
+ creditNotes: ReturnType<typeof creditNoteRepo>;
};
export function createContext(store: Store, now: () => Date = () => new Date()): AppContext {
- return { store, now, customers: customerRepo(store), invoices: invoiceRepo(store) };
+ return {
+ store,
+ now,
+ customers: customerRepo(store),
+ invoices: invoiceRepo(store),
+ creditNotes: creditNoteRepo(store),
+ };
}
diff --git a/src/http/handlers/invoices.ts b/src/http/handlers/invoices.ts
index 09959e1..d393c34 100644
--- a/src/http/handlers/invoices.ts
+++ b/src/http/handlers/invoices.ts
@@ -1,3 +1,4 @@
+import { type CreditNote, creditNumber, parseCreditAmount, remainingCredit } from "../../domain/credit-note";
import { ValidationError } from "../../domain/errors";
import { type Invoice, type InvoiceStatus, issue, markPaid, voidInvoice } from "../../domain/invoice";
import { parseNewInvoice } from "../../domain/validation";
@@ -51,8 +52,39 @@ export function invoiceRoutes(router: Router, ctx: AppContext): void {
return { status: 200, body: invoiceView(ctx.invoices.save(paid)) };
});
+ router.on("POST", "/invoices/:id/credit-notes", ({ params, body }) => {
+ const invoice = ctx.invoices.get(params.id);
+ const amount = parseCreditAmount(body, invoice, ctx.creditNotes.listForInvoice(invoice.id));
+ return { status: 201, body: ctx.creditNotes.insert(newCreditNote(ctx, invoice, amount)) };
+ });
+
+ router.on("GET", "/invoices/:id/credit-notes", ({ params }) => {
+ const invoice = ctx.invoices.get(params.id);
+ return { status: 200, body: ctx.creditNotes.listForInvoice(invoice.id) };
+ });
+
router.on("POST", "/invoices/:id/void", ({ params }) => {
- const voided = voidInvoice(ctx.invoices.get(params.id), ctx.now());
+ const current = ctx.invoices.get(params.id);
+ if (current.status !== "paid") {
+ return { status: 200, body: invoiceView(ctx.invoices.save(voidInvoice(current, ctx.now()))) };
+ }
+ // Paid invoice: credit whatever is left, then void it.
+ const left = remainingCredit(current, ctx.creditNotes.listForInvoice(current.id));
+ if (left > 0) ctx.creditNotes.insert(newCreditNote(ctx, current, left));
+ const voided = voidInvoice(current, ctx.now(), { fullyCredited: true });
return { status: 200, body: invoiceView(ctx.invoices.save(voided)) };
});
}
+
+/** Takes the next number: call only once the amount has been validated. */
+function newCreditNote(ctx: AppContext, invoice: Invoice, amount: number): CreditNote {
+ const n = ctx.store.nextId("creditNote");
+ return {
+ id: `cn_${n}`,
+ number: creditNumber(n),
+ invoiceId: invoice.id,
+ currency: invoice.currency,
+ amount,
+ createdAt: ctx.now().toISOString(),
+ };
+}
diff --git a/src/store/credit-note-repo.ts b/src/store/credit-note-repo.ts
new file mode 100644
index 0000000..c922142
--- /dev/null
+++ b/src/store/credit-note-repo.ts
@@ -0,0 +1,14 @@
+import type { CreditNote } from "../domain/credit-note";
+import type { Store } from "./json-store";
+
+export function creditNoteRepo(store: Store) {
+ return {
+ listForInvoice(invoiceId: string): CreditNote[] {
+ return store.read().creditNotes.filter((n) => n.invoiceId === invoiceId);
+ },
+ insert(note: CreditNote): CreditNote {
+ store.update((d) => ({ ...d, creditNotes: [...d.creditNotes, note] }));
+ return note;
+ },
+ };
+}
diff --git a/src/store/json-store.ts b/src/store/json-store.ts
index e1daef5..03df910 100644
--- a/src/store/json-store.ts
+++ b/src/store/json-store.ts
@@ -14,9 +14,10 @@ export type Store = {
function empty(): StoreData {
return {
schemaVersion: CURRENT_SCHEMA_VERSION,
- counters: { customer: 0, invoice: 0, invoiceNumber: 0 },
+ counters: { customer: 0, invoice: 0, invoiceNumber: 0, creditNote: 0 },
customers: [],
invoices: [],
+ creditNotes: [],
};
}
diff --git a/src/store/migrations.ts b/src/store/migrations.ts
index c8b73a9..e8545db 100644
--- a/src/store/migrations.ts
+++ b/src/store/migrations.ts
@@ -1,6 +1,6 @@
import type { StoreData } from "./types";
-export const CURRENT_SCHEMA_VERSION = 1;
+export const CURRENT_SCHEMA_VERSION = 2;
type RawData = Record<string, unknown> & { schemaVersion?: number };
type Migration = (data: RawData) => RawData;
@@ -21,9 +21,18 @@ const v0ToV1: Migration = (data) => {
};
};
+/** v1 -> v2: credit notes (`creditNotes` list and `counters.creditNote`). */
+const v1ToV2: Migration = (data) => ({
+ ...data,
+ schemaVersion: 2,
+ counters: { ...(data.counters as object), creditNote: 0 },
+ creditNotes: [],
+});
+
/** migrations[n] upgrades a file from version n to n + 1. */
const migrations: Record<number, Migration> = {
0: v0ToV1,
+ 1: v1ToV2,
};
export function migrate(raw: unknown): StoreData {
@@ -43,8 +52,9 @@ export function migrate(raw: unknown): StoreData {
}
return {
schemaVersion: CURRENT_SCHEMA_VERSION,
- counters: (data.counters as StoreData["counters"]) ?? { customer: 0, invoice: 0, invoiceNumber: 0 },
+ counters: (data.counters as StoreData["counters"]) ?? { customer: 0, invoice: 0, invoiceNumber: 0, creditNote: 0 },
customers: (data.customers as StoreData["customers"]) ?? [],
invoices: (data.invoices as StoreData["invoices"]) ?? [],
+ creditNotes: (data.creditNotes as StoreData["creditNotes"]) ?? [],
};
}
diff --git a/src/store/types.ts b/src/store/types.ts
index 222b191..a9d7277 100644
--- a/src/store/types.ts
+++ b/src/store/types.ts
@@ -1,7 +1,8 @@
+import type { CreditNote } from "../domain/credit-note";
import type { Customer } from "../domain/customer";
import type { Invoice } from "../domain/invoice";
-export type Counters = { customer: number; invoice: number; invoiceNumber: number };
+export type Counters = { customer: number; invoice: number; invoiceNumber: number; creditNote: number };
/** The shape of the JSON file at CURRENT_SCHEMA_VERSION. */
export type StoreData = {
@@ -9,4 +10,5 @@ export type StoreData = {
counters: Counters;
customers: Customer[];
invoices: Invoice[];
+ creditNotes: CreditNote[];
};
diff --git a/test/invoice.test.ts b/test/invoice.test.ts
index 85202f2..97ef4d9 100644
--- a/test/invoice.test.ts
+++ b/test/invoice.test.ts
@@ -53,9 +53,10 @@ describe("invoice domain", () => {
expect(() => markPaid(draft({ status: "void" }), NOW)).toThrow(ConflictError);
});
- it("voids drafts and open invoices, never paid ones", () => {
+ it("voids drafts and open invoices, paid ones only when fully credited", () => {
expect(voidInvoice(draft(), NOW).status).toBe("void");
expect(() => voidInvoice(draft({ status: "paid" }), NOW)).toThrow(ConflictError);
+ expect(voidInvoice(draft({ status: "paid" }), NOW, { fullyCredited: true }).status).toBe("void");
});
it("knows when an open invoice is overdue", () => {
diff --git a/test/numbering.test.ts b/test/numbering.test.ts
index a97d189..1fa4dd8 100644
--- a/test/numbering.test.ts
+++ b/test/numbering.test.ts
@@ -20,3 +20,34 @@ describe("credit note numbering", () => {
expect(next.body).toMatchObject({ number: "CN-0002" });
});
});
+
+describe("credit notes and voiding", () => {
+ it("lists credit notes and voids a paid invoice by crediting the rest", async () => {
+ const app = testApp();
+ const customerId = await seedCustomer(app);
+ const id = await seedOpenInvoice(app, { customerId, unitPrice: 10_000 });
+ await app.handle("POST", `/invoices/${id}/pay`);
+ await app.handle("POST", `/invoices/${id}/credit-notes`, { amount: 2_500 });
+
+ const voided = await app.handle("POST", `/invoices/${id}/void`);
+ expect(voided.status).toBe(200);
+ expect(voided.body).toMatchObject({ status: "void" });
+
+ const list = await app.handle("GET", `/invoices/${id}/credit-notes`);
+ expect((list.body as { number: string; amount: number }[]).map((n) => [n.number, n.amount])).toEqual([
+ ["CN-0001", 2_500],
+ ["CN-0002", 7_500],
+ ]);
+ });
+
+ it("rejects bad amounts and unpaid invoices", async () => {
+ const app = testApp();
+ const customerId = await seedCustomer(app);
+ const id = await seedOpenInvoice(app, { customerId });
+ const url = `/invoices/${id}/credit-notes`;
+ expect((await app.handle("POST", url, { amount: 100 })).status).toBe(409);
+ await app.handle("POST", `/invoices/${id}/pay`);
+ expect((await app.handle("POST", url, { amount: 0 })).status).toBe(400);
+ expect((await app.handle("POST", url, {})).status).toBe(400);
+ });
+});
diff --git a/test/store.test.ts b/test/store.test.ts
index a1bf345..82cc59f 100644
--- a/test/store.test.ts
+++ b/test/store.test.ts
@@ -31,7 +31,7 @@ describe("store", () => {
writeFileSync(
file,
JSON.stringify({
- counters: { customer: 1, invoice: 1, invoiceNumber: 0 },
+ counters: { customer: 1, invoice: 1, invoiceNumber: 0, creditNote: 0 },
customers: [{ id: "cus_1", name: "Acme", email: "a@acme.io", createdAt: "2025-01-01T00:00:00.000Z" }],
invoices: [{ id: "inv_1", customer: { id: "cus_1", name: "Acme" }, status: "draft" }],
}),
Do this Monday
- Update the official marketplace, install the skills pack at project scope, and check that the retro command shows up in a new session.
- Run your real task in a plain session. Let it finish and keep the session open.
- Run the retro in that session, then run it again with the failure you found written after it.
- Ask the trace question: "For each candidate, quote the moment of this session's transcript that backs it; drop any candidate you cannot trace to a specific moment."
- Approve survivors one at a time into their carrier: a check for a mechanical failure, a standards line for a judgement call, a comment at the source for a navigation gap.
- Run
/doctor prompt-auditwith a path to the files you touched, apply its edits, then commit the files yourself. - Re-run the same task in a fresh session and watch the failure not happen.
Measurements
These are small runs on one invented invoicing API (Node and TypeScript, TypeScript, vitest) with Claude Code 2.1.294. They are a demonstration, not a benchmark. The hidden finance test is five checks written before the run.
| Step | Result |
|---|---|
| Credit-note task, attempt 1 | Clean: 40 passed, hidden finance test 5/5 (discarded, not the defect session) |
| Credit-note task, attempt 2 | 42 passed, typecheck exit 0, hidden finance test 4/5. Got CN-0004 where CN-0002 was due |
| First retro, no failure reported | 5 ranked items, opened with "This session was smooth" |
| Trace on the first retro | 2 survivors, 3 dropped |
| Second retro, failure reported | 5 candidates |
| Trace on the second retro | 4 survivors, 1 dropped |
| Approved by hand | 4 changes: hook, test, standards line, comment at the source. No CLAUDE.md line |
| First commit attempt | Hook blocked it: 1 failed, 42 passed (43). The tree still held the buggy code |
| After the one-line fix | Suite 43/43, hidden finance test 5/5, commits went through |
| Fresh session B, same request | 37 passed, typecheck exit 0, hidden finance test 5/5, numbers gapless after a rejected request |
Read these with care:
- Of the two plain runs we made on this task, one shipped the bug before the retro. After the retro we have a single re-run, so this is n=1.
- Session B read the standards file, the hook and the red numbering test before it wrote code. It was handed the lesson. Its pass shows the loop working as designed, not an independent replication.
- The retro never found the bug on its own. Its first pass found a missing guardrail that, in its own words, would not have caught this bug.
- The new hook checks the working tree. A
git cherry-pickof the retro commit onto the base did not run it. - With no path, the prompt audit read the user-level files and said nothing about the new ones. With the path of the standards file it answered that the file was clean.
- The older issue route in that repo leaks invoice numbers the same way. We left it, it is out of scope for this session.
Go further
Read the person who runs a lessons loop for real. One developer re-injects a dated lessons file at session start and turns a rule that keeps slipping into a test, a lint rule or a hook, with a CLAUDE.md kept to a short router. s6
Read the issues before you rely on the retro. Issue 1173 is the case for the trace step. s7 Issue 1311 is the forgotten commit. s23 Issue 1158 is the missing command on the official marketplace. s24
Learn where logs live and how long they last. The sessions page covers the transcript path, resuming by path and the 30-day cleanup. s8
Auto memory is the automatic alternative. We left it out. One writer's rant argues that it writes silently, is unversioned and keeps trivia next to durable rules, which is why we keep a human approving each line. s11 Treat that as one opinion, and test it on your own setup.
/insights is the weekly companion. It builds an HTML report over up to 200 sessions with friction points and suggestions. s14 One field report turned 64 sessions into 5 CLAUDE.md lines, 2 skills and hooks. s12 We did not run it here.
Anthropic's own loop is manual. Its harness post describes tuning by reading the evaluator's logs, finding where its judgment diverged and updating the prompt. s13 We found no official retro command or post on the first page of the engineering index. s27
Why we did not automate it. A session-end trigger would be glue we wrote ourselves and did not test. Session-end hooks cannot block termination and have a default timeout of 1.5 seconds, and the retro skill is user-invoked only. s5 s1 The retro's own docs say it only proposes and that nothing changes until you pick a candidate. s2 We kept the human in the loop.
What we left out of scope. The same ordering bug exists in the older invoice-issue route of that repo, and a retro on it would be its own run. We also did not add a CI job, because our copy had no remote and a workflow would never have run.
FAQ
Why did the retro call my session smooth? It reads the session log, and the session never learned it had failed: its tests and typecheck were green. Run it again with what failed written after the command, as its argument.
Does the retro change my files? It only proposes. Nothing changes until you pick a candidate. s2 Once you approve, the changes may be implemented but not committed, so commit them yourself. s23
Can I run it on a session I already cleared?
Yes, if the log is still on disk. Transcripts live under ~/.claude/projects/ and are cleaned after 30 days by default, and claude --resume <transcript-path> opens one. s8
Why did my new hook block the commit? It runs your typecheck and tests on the working tree. If the tree still holds the bug the test now catches, the commit is refused. Fix the code first, then commit.
Why no CLAUDE.md line? Both of our retro passes declined one, saying a pointer would cost context on every turn and go stale. The docs target under 200 lines and say CLAUDE.md is context, not enforced configuration. s4