EIS Writing

Author an EIS that follows the established format in docs/eis/. An EIS is a concrete, codebase-grounded implementation plan — not a design doc, not a PRD.

1. Naming & location

• Path: docs/eis/EIS-<###>-<kebab-slug>.md (three-digit zero-padded number).
• The number is the next unused integer. ls docs/eis/EIS-*.md to find the highest, then +1.
• Slug is lowercase kebab, 2–5 words, describes the feature (stripe-integration, security-hardening, api-auth-tenant-isolation).
• The raw EIS lives at docs/eis/. The directory docs/wiki/eis/ is ONLY for wiki summaries — never put the full spec there.

2. Required sections (in order)

Every existing EIS uses these. Use the same names.

1. # EIS-<###>: <Title Case Name> — H1 title.
2. ## Problem — what is wrong today, with file paths and line references. Often broken into numbered sub-problems (### 1. …). Cite real files.
3. ## Scope — a markdown table listing affected files + the issue/status for each. Columns vary (File | Issue | Severity or File | Status | Issue or File | Current Behavior | Gap), pick what fits.
4. ## Solution Design — the plan, broken into streams or numbered sub-sections, each with a short prose explanation and TypeScript code blocks showing the intended shape (imports, function signatures, key logic). Code is illustrative, not exhaustive.
5. ## Files to Create — table: File | Purpose. Omit if nothing new is created.
6. ## Files to Modify (with specific changes) — table: File | Change. The Change cell is a crisp imperative sentence per file.
7. ## Dependencies — bullet list: other EIS that must land first, env vars required, schema/migration concerns, external services.
8. ## Complexity: <S|M|L> — single letter, then bullets on scope size (file count, testing notes, risk areas).

Do not invent new top-level sections. If something doesn't fit, put it inside Solution Design as a numbered sub-section.

3. Template

# EIS-<###>: <Title>

## Problem

<1–2 paragraphs stating the gap. Then numbered sub-problems:>

### 1. <Sub-problem>
- `src/path/to/file.ts` — what it does wrong.
- Consequence (security, correctness, UX).

### 2. <Sub-problem>
- …

## Scope

| File | Issue | Severity |
|------|-------|----------|
| `src/…` | <what's broken> | High/Medium/Low |

## Solution Design

### 1. <Stream or fix name>

<Prose.>

```typescript
// Illustrative code for src/lib/foo.ts
export function foo() { … }

2. <Next stream>

…

Files to Create

File	Purpose
src/lib/new-thing.ts	<why>

Files to Modify (with specific changes)

File	Change
src/app/api/x/route.ts	<Imperative: "Add Zod validation via fooSchema.safeParse(body)">

Dependencies

• EIS-XXX must land first because …
• Requires env var FOO_SECRET.
• Schema migration: add column bar to Baz.

Complexity: M

• N new files (~X lines), M files modified.
• <Testing note>.
• <Risk note>.

## 4. Grounding rule (MANDATORY)

Before writing a single line of the EIS, you must have scanned the live codebase. Concretely:

- Use `Grep`/`Glob` to locate every file you will reference in Scope, Files to Create, and Files to Modify.
- Every file path in the EIS must exist (or be a believable new file under an existing directory).
- Every "currently does X" claim in Problem must be backed by lines you actually read.
- When Solution Design says "modify `functionName()` in `src/lib/foo.ts`", that function must exist there today (or the EIS must explicitly say it is being introduced).

If a natural-language request asks for something you cannot ground in the codebase, stop and ask the user to clarify — do not hand-wave paths.

## 5. Wiki companion rule

Every new EIS ships with a summary page plus an index update. When you create `docs/eis/EIS-<###>-<slug>.md`, also:

1. Create `docs/wiki/eis/EIS-<###>.md` — a 1-page wiki summary.
   - Wiki frontmatter (match the style already in `docs/wiki/eis/` — check an existing file or the wiki conventions first).
   - Short prose: what problem, what solution approach, complexity.
   - A link back to the raw source at `../../eis/EIS-<###>-<slug>.md`.
2. Update `docs/wiki/index.md` — add the new EIS to whatever list/section the index uses for EIS entries (mirror existing formatting).

Do not dump the full spec into the wiki file; the wiki is a navigable summary, the raw EIS is the source of truth.

## 6. Overlap check (before creating)

Read the titles + Problem sections of every existing `docs/eis/EIS-*.md`. If the NL description overlaps with an existing EIS (same files, same feature area, same gap):

- **Do not create a duplicate.**
- Either: extend the existing EIS (add a new sub-problem in Problem, new rows in Scope, new numbered Solution Design section). Return a clear diff of what you added.
- Or: abort and surface the conflict to the user — tell them which EIS overlaps and ask whether to extend it, supersede it, or proceed with a narrower scope.

Overlap signals: same `src/` files appear in the existing EIS's Scope table; same subsystem (auth, stripe, storefront, etc.); same issue numbers referenced.

## 7. Final checklist before returning

- [ ] Filename matches `EIS-<###>-<kebab-slug>.md`, number is next available.
- [ ] All 8 required sections present in order.
- [ ] Every file path referenced has been verified in the codebase.
- [ ] No duplicate of an existing EIS.
- [ ] Wiki summary at `docs/wiki/eis/EIS-<###>.md` created.
- [ ] `docs/wiki/index.md` updated.
- [ ] Complexity rating (S/M/L) set with justifying bullets.