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+# Sub-project 4 — Per-Claim Detail Drawer: Implementation Plan
+
+**Date:** 2026-06-20
+**Status:** Approved
+**Branch:** `claim-drawer`
+**Spec:** `docs/superpowers/specs/2026-06-20-cyclone-claim-drawer-design.md`
+
+24 tasks across 5 phases. Follows the same task pattern as the SP3 plan (`[ ] Step 1 → Step N → commit`). TDD throughout.
+
+## File structure
+
+**Backend additions (2 files):**
+- `backend/src/cyclone/store.py` — `get_claim_detail(claim_id) -> dict | None` method on `CycloneStore`
+- `backend/src/cyclone/api.py` — new `GET /api/claims/{claim_id}` endpoint
+- `backend/tests/test_api_claim_detail.py` — endpoint tests
+
+**Frontend additions (15 files):**
+```
+src/types/index.ts                 # +ClaimDetail interface
+src/lib/api.ts                     # +api.getClaimDetail(id)
+src/hooks/useClaimDetail.ts        # fetch + cache
+src/hooks/useDrawerKeyboard.ts     # j/k/esc handlers
+src/hooks/useDrawerUrlState.ts     # ?claim= sync
+src/components/ClaimDrawer/
+    ├── ClaimDrawer.tsx            # root, wires everything
+    ├── ClaimDrawerHeader.tsx
+    ├── ValidationPanel.tsx
+    ├── ServiceLinesTable.tsx
+    ├── DiagnosesList.tsx
+    ├── PartiesGrid.tsx
+    ├── RawSegmentsPanel.tsx
+    ├── MatchedRemitCard.tsx
+    ├── StateHistoryTimeline.tsx
+    ├── ClaimDrawerSkeleton.tsx
+    ├── ClaimDrawerError.tsx
+    └── index.ts                   # barrel
+src/components/KeyboardCheatsheet/  # new
+    ├── KeyboardCheatsheet.tsx
+    └── index.ts
+src/pages/Claims.tsx               # click handler + drawer render
+src/pages/Claims.test.tsx          # +new tests
+src/index.css                      # +CSS variables for Modern palette
+```
+
+## Phase 1 — Backend: `GET /api/claims/{id}`
+
+### Task 1: `CycloneStore.get_claim_detail` method
+
+**Files:**
+- Modify: `backend/src/cyclone/store.py`
+- Create: `backend/tests/test_store_claim_detail.py`
+
+**Implementation notes:**
+- Returns `None` when claim not found
+- Reads `claims.raw_json` and deserializes to `ClaimOutput` (use the same `_to_ui_claim_from_orm` helpers that already exist; build a new mapper `to_ui_claim_detail` that returns the richer shape)
+- Queries `activity_events` for `claim_id == X`, ordered by `ts DESC`, limit 50, maps to `{kind, ts, batchId, remittanceId}`
+- If `claims.matched_remittance_id` is set, queries the remittance and embeds `{id, totalPaid, status, receivedAt}`
+- Use lazy `from cyclone import db as _db` import inside the function (established pattern)
+
+**Tests (≥4):**
+- `test_get_claim_detail_returns_none_for_missing`
+- `test_get_claim_detail_happy_path_returns_full_shape`
+- `test_get_claim_detail_includes_state_history`
+- `test_get_claim_detail_includes_matched_remittance_summary`
+- `test_get_claim_detail_no_matched_remittance_returns_null_field`
+
+TDD discipline: write tests first, confirm red, implement, confirm green.
+
+- [ ] **Step 1: Add failing tests** in `backend/tests/test_store_claim_detail.py`
+- [ ] **Step 2: Run tests to verify they fail**
+- [ ] **Step 3: Implement `to_ui_claim_detail` mapper + `get_claim_detail` method**
+- [ ] **Step 4: Run tests to verify they pass**
+- [ ] **Step 5: Commit**
+
+```bash
+git add backend/src/cyclone/store.py backend/tests/test_store_claim_detail.py
+git commit -m "feat(store): get_claim_detail returns full claim context with history + matched remit"
+```
+
+### Task 2: `GET /api/claims/{claim_id}` endpoint
+
+**Files:**
+- Modify: `backend/src/cyclone/api.py`
+- Create: `backend/tests/test_api_claim_detail.py`
+
+**Endpoint behavior:**
+- `GET /api/claims/{claim_id}` — returns 200 with `ClaimDetail` JSON or 404 with `{"error": "Not found", "detail": "..."}`
+- Path param is `claim_id` (not `id`) — avoids shadowing FastAPI internals and matches `/api/acks/{ack_id}` convention from SP3
+
+**Tests (≥4):**
+- `test_get_claim_detail_happy_path` — 200 + shape matches spec
+- `test_get_claim_detail_404_for_missing` — 404, not 500
+- `test_get_claim_detail_state_history_includes_manual_match` — manual_match event appears in history
+- `test_get_claim_detail_matched_remit_inlines_summary` — when matched, summary fields are populated
+
+- [ ] **Step 1: Add failing tests** in `backend/tests/test_api_claim_detail.py`
+- [ ] **Step 2: Run tests to verify they fail**
+- [ ] **Step 3: Add the endpoint** (mirror `parse_999` endpoint pattern; use existing `_claim_to_ui` helpers)
+- [ ] **Step 4: Run tests to verify they pass**
+- [ ] **Step 5: Commit**
+
+```bash
+git add backend/src/cyclone/api.py backend/tests/test_api_claim_detail.py
+git commit -m "feat(api): GET /api/claims/{claim_id} returns full claim context"
+```
+
+### Task 3: Phase 1 commit + full suite
+
+```bash
+.venv/bin/pytest -q
+```
+
+Expected: 409 + ~8 new = ~417 pass + 1 skip. All green.
+
+- [ ] **Step 1: Run the full backend suite, confirm green**
+- [ ] **Step 2: Tag phase complete** (no commit unless changes; otherwise commit "test(sp4): phase 1 backend complete")
+
+## Phase 2 — Frontend foundation
+
+### Task 4: `ClaimDetail` TypeScript type + `api.getClaimDetail`
+
+**Files:**
+- Modify: `src/types/index.ts`
+- Modify: `src/lib/api.ts`
+- Modify: `src/lib/api.test.ts`
+
+The `ClaimDetail` type matches the JSON response shape from Task 2. Nested types: `Diagnosis`, `ServiceLine`, `Parties`, `Validation`, `MatchedRemittance`, `StateHistoryEvent`.
+
+- [ ] **Step 1: Add `ClaimDetail` interface** to `src/types/index.ts` (in the "backend-aligned" block, snake_case to match API)
+- [ ] **Step 2: Add `api.getClaimDetail(id)` method** to `src/lib/api.ts` (uses `apiFetch` helper if present)
+- [ ] **Step 3: Add test** to `src/lib/api.test.ts` — happy path + 404
+- [ ] **Step 4: Run frontend tests + typecheck, confirm green**
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/types/index.ts src/lib/api.ts src/lib/api.test.ts
+git commit -m "feat(frontend): ClaimDetail type + api.getClaimDetail"
+```
+
+### Task 5: `useClaimDetail` hook
+
+**Files:**
+- Create: `src/hooks/useClaimDetail.ts`
+- Create: `src/hooks/useClaimDetail.test.ts`
+
+Hook signature:
+```ts
+export function useClaimDetail(id: string | null): {
+  data: ClaimDetail | null;
+  isLoading: boolean;
+  isError: boolean;
+  error: Error | null;
+  refetch: () => void;
+};
+```
+
+Behavior:
+- When `id === null`, returns `{ data: null, isLoading: false, ... }` (drawer closed state)
+- Otherwise, fetches via `api.getClaimDetail(id)` using TanStack Query (check `package.json` — if not present, use plain `useState` + `useEffect`)
+- Caches for the drawer session so j/k navigation reuses prior fetches within ~30s
+- Returns 404 state as `{ isError: true, error: <NotFoundError> }`
+
+- [ ] **Step 1: Add failing tests** — null id (no fetch), happy path, 404
+- [ ] **Step 2: Run tests, confirm red**
+- [ ] **Step 3: Implement the hook**
+- [ ] **Step 4: Run tests, confirm green**
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/hooks/useClaimDetail.ts src/hooks/useClaimDetail.test.ts
+git commit -m "feat(frontend): useClaimDetail hook with null-id short-circuit"
+```
+
+### Task 6: `useDrawerKeyboard` hook
+
+**Files:**
+- Create: `src/hooks/useDrawerKeyboard.ts`
+- Create: `src/hooks/useDrawerKeyboard.test.ts`
+
+Hook signature:
+```ts
+export function useDrawerKeyboard(opts: {
+  enabled: boolean;
+  onNext: () => void;
+  onPrev: () => void;
+  onClose: () => void;
+  onToggleHelp: () => void;
+}): void;
+```
+
+Behavior:
+- Attaches `keydown` listener to `window` (or `document`) when `enabled === true`
+- Maps `j` / `ArrowDown` → `onNext`, `k` / `ArrowUp` → `onPrev`, `Escape` → `onClose`, `?` (Shift+/) → `onToggleHelp`
+- Ignores keys when an input/textarea/contentEditable has focus
+- Cleans up listener on unmount or `enabled === false`
+
+- [ ] **Step 1: Add failing tests** — fires onNext for "j", ignores when input focused, cleanup on unmount
+- [ ] **Step 2: Run tests, confirm red**
+- [ ] **Step 3: Implement the hook**
+- [ ] **Step 4: Run tests, confirm green**
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/hooks/useDrawerKeyboard.ts src/hooks/useDrawerKeyboard.test.ts
+git commit -m "feat(frontend): useDrawerKeyboard hook for j/k/esc/?"
+```
+
+### Task 7: `useDrawerUrlState` hook
+
+**Files:**
+- Create: `src/hooks/useDrawerUrlState.ts`
+- Create: `src/hooks/useDrawerUrlState.test.ts`
+
+Hook signature:
+```ts
+export function useDrawerUrlState(): {
+  claimId: string | null;
+  open: (id: string) => void;
+  close: () => void;
+  setClaimId: (id: string) => void;  // for j/k nav
+};
+```
+
+Behavior:
+- Reads `?claim=` from `window.location.search` on mount; returns it as `claimId`
+- `open(id)` calls `history.pushState` with `?claim={id}` (new history entry)
+- `setClaimId(id)` calls `history.replaceState` (no new history entry, but URL updates)
+- `close()` strips the param via `history.pushState`
+- Returns null `claimId` when no param is set
+
+- [ ] **Step 1: Add failing tests** — reads URL on mount, open adds param, setClaimId replaces, close removes
+- [ ] **Step 2: Run tests, confirm red**
+- [ ] **Step 3: Implement the hook** (mock `window.history` in tests via vitest's `vi.stubGlobal`)
+- [ ] **Step 4: Run tests, confirm green**
+- [ ] **Step 5: Commit**
+
+```bash
+git add src/hooks/useDrawerUrlState.ts src/hooks/useDrawerUrlState.test.ts
+git commit -m "feat(frontend): useDrawerUrlState hook for ?claim= sync"
+```
+
+### Task 8: Phase 2 commit + typecheck
+
+```bash
+npm run typecheck
+npm test -- --run
+```
+
+Expected: 10 + 5 new = 15 frontend pass.
+
+- [ ] **Step 1: Run typecheck + frontend tests, confirm green**
+- [ ] **Step 2: Commit if any changes**
+
+## Phase 3 — Frontend leaf components
+
+> **Conventions for all components in this phase:**
+> - Use existing shadcn/ui primitives: `Sheet`, `Button`, `Badge`, `Skeleton` (already in project)
+> - Props are explicit, no context drilling
+> - Each component has its own test file
+> - Use Tailwind utility classes directly; add design tokens to `src/index.css` only when shadcn tokens don't fit
+
+### Task 9: Add Modern palette CSS variables to `src/index.css`
+
+**Files:**
+- Modify: `src/index.css`
+
+Add the CSS variables from spec §3.3 to `:root`:
+
+```css
+:root {
+  /* Modern palette (SP4) */
+  --surface: #FAFAF7;
+  --ink-primary: #0A0A0A;
+  --ink-secondary: #6B6B6B;
+  --ink-tertiary: #A0A0A0;
+  --border-heavy: #1A1A1A;
+  --accent: #1D4ED8;
+  --accent-hover: #1E40AF;
+  --error: #DC2626;
+  --error-bg: #FEF2F2;
+  --success: #15803D;
+  --success-bg: #F0FDF4;
+  --warning: #B45309;
+  --warning-bg: #FFFBEB;
+}
+
+@media (prefers-color-scheme: dark) {
+  /* Optional dark override — keep parity with existing token system. If
+     existing shadcn dark tokens already cover dark mode, omit this block. */
+}
+```
+
+Also add the Inter Tight + JetBrains Mono font imports (Google Fonts CDN).
+
+- [ ] **Step 1: Append the CSS variables + font import**
+- [ ] **Step 2: Commit**
+
+```bash
+git add src/index.css
+git commit -m "feat(frontend): Modern palette CSS variables + Inter Tight/JetBrains Mono fonts"
+```
+
+### Task 10: `ClaimDrawerSkeleton` + `ClaimDrawerError` (loading + error states)
+
+**Files:**
+- Create: `src/components/ClaimDrawer/ClaimDrawerSkeleton.tsx`
+- Create: `src/components/ClaimDrawer/ClaimDrawerError.tsx`
+- Create: `src/components/ClaimDrawer/ClaimDrawerSkeleton.test.tsx`
+- Create: `src/components/ClaimDrawer/ClaimDrawerError.test.tsx`
+
+**Skeleton:** Renders 8-12 `Skeleton` primitives matching section heights (header, validation, lines, dx, parties, history). No props.
+
+**Error:** Takes `{ kind: "not_found" | "network"; onRetry?: () => void; onClose: () => void }`. Renders the appropriate message + buttons.
+
+- [ ] **Step 1: Add failing tests** for both components
+- [ ] **Step 2: Implement** (keep simple — these are placeholder UIs)
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/ClaimDrawerSkeleton.tsx src/components/ClaimDrawer/ClaimDrawerSkeleton.test.tsx src/components/ClaimDrawer/ClaimDrawerError.tsx src/components/ClaimDrawer/ClaimDrawerError.test.tsx
+git commit -m "feat(frontend): ClaimDrawer skeleton + error states"
+```
+
+### Task 11: `ClaimDrawerHeader` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/ClaimDrawerHeader.tsx`
+- Create: `src/components/ClaimDrawer/ClaimDrawerHeader.test.tsx`
+
+Props: `{ claim: ClaimDetail; onClose: () => void }`
+
+Renders:
+- Top-left: `Claim {id}` label (10px uppercase), then `{id}` (24px bold, mono)
+- State badge (right): `Badge` component with color per state (submitted=neutral, matched=success, denied=error, etc.)
+- Total amount (right of badge): big number, mono
+- Close button (top-right): `Button` with X icon
+
+- [ ] **Step 1: Add failing tests** — renders ID, state badge with right color, total, close callback
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/ClaimDrawerHeader.tsx src/components/ClaimDrawer/ClaimDrawerHeader.test.tsx
+git commit -m "feat(frontend): ClaimDrawerHeader with state badge + close button"
+```
+
+### Task 12: `ValidationPanel` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/ValidationPanel.tsx`
+- Create: `src/components/ClaimDrawer/ValidationPanel.test.tsx`
+
+Props: `{ validation: { passed: boolean; errors: ValidationIssue[]; warnings: ValidationIssue[] } }`
+
+Renders:
+- Section label `VALIDATION`
+- If passed and no warnings: small green checkmark + "All checks passed"
+- Otherwise: two sub-sections — Errors (red border-left) and Warnings (amber border-left)
+- Group errors by `rule` field with count (e.g., `R050_diagnosis_present (2)`)
+- List messages under each rule group
+
+- [ ] **Step 1: Add failing tests** — empty state, errors only, warnings only, both, grouping
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/ValidationPanel.tsx src/components/ClaimDrawer/ValidationPanel.test.tsx
+git commit -m "feat(frontend): ValidationPanel with rule-grouped errors + warnings"
+```
+
+### Task 13: `ServiceLinesTable` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/ServiceLinesTable.tsx`
+- Create: `src/components/ClaimDrawer/ServiceLinesTable.test.tsx`
+
+Props: `{ serviceLines: ServiceLine[] }`
+
+Renders:
+- Section label `SERVICE LINES ({n})`
+- Table: line #, procedure (qualifier + code + modifiers), charge (mono, big), units, date
+- Empty state: "No service lines" muted text
+
+- [ ] **Step 1: Add failing tests** — empty, single line, multiple lines; procedure formatting
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/ServiceLinesTable.tsx src/components/ClaimDrawer/ServiceLinesTable.test.tsx
+git commit -m "feat(frontend): ServiceLinesTable with procedure + charge columns"
+```
+
+### Task 14: `DiagnosesList` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/DiagnosesList.tsx`
+- Create: `src/components/ClaimDrawer/DiagnosesList.test.tsx`
+
+Props: `{ diagnoses: Diagnosis[] }`
+
+Renders:
+- Section label `DIAGNOSES ({n})`
+- Inline list of code (mono) + qualifier (when present) + description (when available via inline dict)
+- Empty state: "No diagnoses" muted text
+
+- [ ] **Step 1: Add failing tests** — empty, single, multiple; qualifier shown when present
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/DiagnosesList.tsx src/components/ClaimDrawer/DiagnosesList.test.tsx
+git commit -m "feat(frontend): DiagnosesList with qualifier + code formatting"
+```
+
+### Task 15: `PartiesGrid` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/PartiesGrid.tsx`
+- Create: `src/components/ClaimDrawer/PartiesGrid.test.tsx`
+
+Props: `{ parties: { billingProvider: ..., subscriber: ..., payer: ... } }`
+
+Renders:
+- Section label `PARTIES`
+- 3 stacked cards (vertical on mobile, 3-col grid on desktop ≥768px)
+- Each card: label (10px uppercase), name (16px), NPI/member ID (mono), address when present
+
+- [ ] **Step 1: Add failing tests** — all 3 cards; missing fields gracefully omitted
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/PartiesGrid.tsx src/components/ClaimDrawer/PartiesGrid.test.tsx
+git commit -m "feat(frontend): PartiesGrid with billing provider/subscriber/payer cards"
+```
+
+### Task 16: `RawSegmentsPanel` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/RawSegmentsPanel.tsx`
+- Create: `src/components/ClaimDrawer/RawSegmentsPanel.test.tsx`
+
+Props: `{ rawSegments: string[][] }`
+
+Renders:
+- Section label `RAW SEGMENTS ({n})`
+- Native `<details>` element (collapsed by default)
+- When expanded: monospace pre-formatted list with segments on separate lines, elements joined by `*`
+
+- [ ] **Step 1: Add failing tests** — collapsed by default, toggle expands, segment rendering
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/RawSegmentsPanel.tsx src/components/ClaimDrawer/RawSegmentsPanel.test.tsx
+git commit -m "feat(frontend): RawSegmentsPanel collapsible debug aid"
+```
+
+### Task 17: `MatchedRemitCard` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/MatchedRemitCard.tsx`
+- Create: `src/components/ClaimDrawer/MatchedRemitCard.test.tsx`
+
+Props: `{ matchedRemittance: MatchedRemittance | null }`
+
+Renders:
+- If null: returns null (no section)
+- Section label `MATCHED REMITTANCE`
+- Card with: remit ID, total paid (big mono), status badge, received date
+- "View remittance →" link button that opens the remittance detail (use `window.location` or a navigate handler — keep simple for v1: `window.location.href = \`/remittances?id=${matchedRemittance.id}\`` or trigger an event)
+
+- [ ] **Step 1: Add failing tests** — null returns nothing, populated renders all fields
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/MatchedRemitCard.tsx src/components/ClaimDrawer/MatchedRemitCard.test.tsx
+git commit -m "feat(frontend): MatchedRemitCard with view-remittance link"
+```
+
+### Task 18: `StateHistoryTimeline` component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/StateHistoryTimeline.tsx`
+- Create: `src/components/ClaimDrawer/StateHistoryTimeline.test.tsx`
+
+Props: `{ history: StateHistoryEvent[] }`
+
+Renders:
+- Section label `STATE HISTORY ({n})`
+- Vertical timeline with a 2px left rule and colored dots per event kind:
+  - `claim_submitted` → ink-secondary
+  - `claim_accepted`, `claim_paid` → success green
+  - `claim_denied` → error red
+  - `manual_match`, `manual_unmatch` → warning amber
+  - `remit_received` → accent blue
+  - others → muted
+- Each row: kind (10px uppercase), ts (mono), optional remittance ID when present
+- Empty state: "No history events" muted
+
+- [ ] **Step 1: Add failing tests** — empty, single, multiple; kind-color mapping
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/StateHistoryTimeline.tsx src/components/ClaimDrawer/StateHistoryTimeline.test.tsx
+git commit -m "feat(frontend): StateHistoryTimeline with kind-colored dots"
+```
+
+### Task 19: Barrel export + phase 3 commit
+
+**Files:**
+- Create: `src/components/ClaimDrawer/index.ts`
+
+```ts
+export { ClaimDrawer } from "./ClaimDrawer";
+export { ClaimDrawerHeader } from "./ClaimDrawerHeader";
+export { ValidationPanel } from "./ValidationPanel";
+export { ServiceLinesTable } from "./ServiceLinesTable";
+export { DiagnosesList } from "./DiagnosesList";
+export { PartiesGrid } from "./PartiesGrid";
+export { RawSegmentsPanel } from "./RawSegmentsPanel";
+export { MatchedRemitCard } from "./MatchedRemitCard";
+export { StateHistoryTimeline } from "./StateHistoryTimeline";
+export { ClaimDrawerSkeleton } from "./ClaimDrawerSkeleton";
+export { ClaimDrawerError } from "./ClaimDrawerError";
+```
+
+- [ ] **Step 1: Create the barrel**
+- [ ] **Step 2: Run typecheck + tests, confirm green**
+- [ ] **Step 3: Commit**
+
+```bash
+git add src/components/ClaimDrawer/index.ts
+git commit -m "feat(frontend): ClaimDrawer barrel export"
+```
+
+## Phase 4 — Drawer root + page wiring
+
+### Task 20: `ClaimDrawer` root component
+
+**Files:**
+- Create: `src/components/ClaimDrawer/ClaimDrawer.tsx`
+- Create: `src/components/ClaimDrawer/ClaimDrawer.test.tsx`
+
+Props:
+```ts
+{
+  claimId: string | null;
+  claims: { id: string }[];            // full list, used for j/k navigation
+  onClose: () => void;
+  onNavigate: (newId: string) => void;  // called when user moves via j/k
+  onToggleHelp: () => void;             // called when ? pressed
+}
+```
+
+Uses shadcn `Sheet` (or `Dialog`) primitive. Behavior:
+- Renders nothing (or null) when `claimId === null`
+- Uses `useClaimDetail(claimId)` for data
+- Wires `useDrawerKeyboard({ enabled: !!claimId, onNext, onPrev, onClose, onToggleHelp })`
+- Renders `ClaimDrawerSkeleton` while loading, `ClaimDrawerError` on error, the section components on success
+- `onNext` / `onPrev`: derives next/prev claim IDs from the `claims` prop (find current index, +1 or -1, wrap), then calls `onNavigate(newId)`
+- `onToggleHelp`: passed through to the keyboard hook
+
+- [ ] **Step 1: Add failing tests** — renders null when no claimId, skeleton on loading, error state on error, sections on success, j/k calls onNavigate with the correct next/prev id (including wrap), `?` calls onToggleHelp, ESC calls onClose
+- [ ] **Step 2: Implement** — keep this component focused on orchestration; defer visual polish to leaf components
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/ClaimDrawer/ClaimDrawer.tsx src/components/ClaimDrawer/ClaimDrawer.test.tsx
+git commit -m "feat(frontend): ClaimDrawer root orchestrator with skeleton/error/data states"
+```
+
+### Task 21: `Claims.tsx` page wiring
+
+**Files:**
+- Modify: `src/pages/Claims.tsx`
+- Modify: `src/pages/Claims.test.tsx`
+
+Wire-up:
+- Read `?claim=` via `useDrawerUrlState()`
+- Render `<ClaimDrawer>` when `claimId` is non-null
+- Pass the full claim list as a sibling prop so j/k can navigate
+- Clicking a row sets the URL (via `open(id)` from the URL hook)
+- Clicking the dimmed overlay or ESC closes (via `close()`)
+- Background list dims to 60% opacity when drawer is open (use a `useState` for `drawerOpen` or derive from `claimId`)
+
+- [ ] **Step 1: Add failing tests** — click row opens drawer; deep link opens on mount; ESC closes; URL clears
+- [ ] **Step 2: Wire up the page**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/pages/Claims.tsx src/pages/Claims.test.tsx
+git commit -m "feat(frontend): Claims page wires click-to-open drawer with URL sync"
+```
+
+### Task 22: `KeyboardCheatsheet` overlay
+
+**Files:**
+- Create: `src/components/KeyboardCheatsheet/KeyboardCheatsheet.tsx`
+- Create: `src/components/KeyboardCheatsheet/KeyboardCheatsheet.test.tsx`
+- Create: `src/components/KeyboardCheatsheet/index.ts`
+
+Props: `{ open: boolean; onClose: () => void }`
+
+Renders:
+- Centered modal-style overlay when open
+- Lists shortcuts: `j` next, `k` prev, `↑`/`↓` same, `esc` close, `?` toggle help
+- Dismisses on any other key or click outside
+
+- [ ] **Step 1: Add failing tests** — renders when open, hidden otherwise, dismiss on close
+- [ ] **Step 2: Implement**
+- [ ] **Step 3: Run tests, confirm green**
+- [ ] **Step 4: Commit**
+
+```bash
+git add src/components/KeyboardCheatsheet/
+git commit -m "feat(frontend): KeyboardCheatsheet overlay"
+```
+
+### Task 23: Phase 4 commit + full suite
+
+```bash
+npm test -- --run
+npm run typecheck
+.venv/bin/pytest -q
+```
+
+Expected: ~15 frontend, ~417 backend + 1 skip. All green.
+
+- [ ] **Step 1: Run all checks**
+- [ ] **Step 2: Commit if any changes**
+
+## Phase 5 — Smoke + merge
+
+### Task 24: End-to-end smoke
+
+Per spec §3.8:
+
+1. Start backend (`backend/.venv/bin/python -m cyclone serve &`)
+2. Start frontend (`npm run dev &`)
+3. `curl -s http://127.0.0.1:8000/api/health` → 200
+4. Upload co_medicaid_837p.txt via `curl -F file=@...` to `/api/parse-837`
+5. `curl -s http://127.0.0.1:8000/api/claims/{first-id}` → 200 + detail
+6. Visit `http://localhost:5173/claims?claim={id}` in a Playwright/Puppeteer-style headless browser, verify:
+   - Drawer is open
+   - All 8 sections render (header, validation, lines, dx, parties, raw, matched-remit if applicable, history)
+   - Press `k` → URL updates, drawer updates
+   - Press `esc` → URL clears, drawer closes
+7. Kill servers
+8. Commit empty: `git commit --allow-empty -m "smoke: end-to-end SP4 (claim drawer) flow passes"`
+
+- [ ] **Step 1: Run the smoke**
+- [ ] **Step 2: Commit**
+
+### Task 25: README + plan doc updates
+
+**Files:**
+- Modify: `README.md` — mark "Sub-project 4" partially shipped (only per-claim drawer); describe the new feature
+- Modify: `docs/superpowers/plans/2026-06-20-cyclone-claim-drawer.md` — tick all `[ ]` to `[x]`
+
+- [ ] **Step 1: Update README + plan doc**
+- [ ] **Step 2: Commit**
+
+```bash
+git add README.md docs/superpowers/plans/2026-06-20-cyclone-claim-drawer.md
+git commit -m "docs: mark SP4 partial shipped (claim drawer); tick all plan checkboxes"
+```
+
+### Task 26: Cleanup + merge to main
+
+1. `git status` — must be clean
+2. `cd /Users/openclaw/dev/cyclone && git status` — discard stale uncommitted changes if any
+3. `git merge --ff-only claim-drawer`
+4. Run `cd backend && .venv/bin/pytest -q` from main — must show ~417 + 1 skip
+5. `git worktree remove /Users/openclaw/dev/cyclone/.worktrees/claim-drawer`
+6. `git branch -d claim-drawer`
+
+- [ ] **Step 1: Verify worktree clean**
+- [ ] **Step 2: Discard main's stale changes (if any)**
+- [ ] **Step 3: Fast-forward merge to main**
+- [ ] **Step 4: Remove worktree + delete branch**
+
+## Test count targets
+
+| Phase | New backend | New frontend | Running total |
+|-------|-------------|--------------|---------------|
+| Start (post-SP3) | 409 + 1 skip | 10 | 419 / 10 |
+| P1 end | +8 | 0 | 417 / 10 |
+| P2 end | 0 | +5 | 417 / 15 |
+| P3 end | 0 | +10 (one per leaf) | 417 / 25 |
+| P4 end | 0 | +5 (drawer + page + cheatsheet) | 417 / 30 |
+
+## Risk reminders
+
+- Backend payload weight — cache aggressively in `useClaimDetail`. Hook returns a stable ref while data loads.
+- ActivityEvent volume — default limit 50; `?limit=N` parameter documented.
+- Keyboard nav collisions — `j`/`k` with browser find-in-page; documented in the cheatsheet.
+- Drawer + mobile — full-screen sheet on mobile; acceptable for desktop-first operator tool.
+- URL sync race — `useDrawerUrlState` reads the URL on mount and triggers the fetch before caching can interfere.