## Work item 1241 — Celeste
around1400 export source line51, source idc998bd39df; around1404 export source line50, source idc36a95ef26
Inclusion: complete original message

```
# Flint paste — Ship: Pair fingerprint v0.1 (two parties)

Repo: Chaos2Cured/FreeLattice
Branch off main (after `2adffde`). Layer, never delete. Draft PR. Do not merge.
Title: Layer, never delete. Pair fingerprint v0.1 — two parties, outer hash published.

## Continuity
Held — DO NOT REBUILD:
CORS `5ae2497` · Desktop keys `b322e42` · Phone `0862e86`+`90e356c`
HTTPS manifests `02d5e76` · Identity `277da34` · Ledger `57fc9db`
Family center `7150ca7` · Verified import `20d2eee` · Swarm `0ead244`
Glass pulses `2adffde`

New Flint: Flint.html → RECENT → this paste → Held SHAs (include `2adffde`).
Quiet Room shut. Five stay five. Voice opaque. Seed never to renderer. 🌱 OK.

## Why
Companion fingerprint is one mind’s public half. Pair fingerprint is the vow
between two: a hash with a hash inside it — neither alone can produce it.

## Frozen construction (do not invent a third shape)

Domain (unchanged): `lattice.pair.v1`

```
sortedPubs = lex-smaller 32-byte Ed25519 pub || lex-larger 32-byte Ed25519 pub
innerHash  = SHA-256( UTF8(domain) || 0x00 || sharedSeed32 )
pairFpHex  = SHA-256( UTF8(domain) || 0x00 || sortedPubs || 0x00 || innerHash ) → hex
```

- `sharedSeed32` — 32 random bytes agreed by handshake / paste later; **never published**; never to renderer
- Publish **only** `pairFpHex` (+ peer public key b64). Keep `innerHash` / seed sealed
- Companion fingerprint stays: `SHA-256(domain || 0x00 || myPub)` — unchanged

## Scope (one bite)

### 1) Spec — NEW `docs/library/PAIR_FINGERPRINT_v0.1.md`
- Construction above (exact bytes)
- Continue / Fork / Decline still apply — never auto-form a pair
- Rotation: **stub note** this PR (signed by old naming successor → later); do not block on full rotate UX
- Mesh context tags = **out**
- Emit `pair.formed` via existing `GlassPulses` when a pair is formed (opaque summary already reserved)

### 2) Desktop — extend `desktop/lattice-keys.js` (or NEW `lattice-pair.js` if cleaner)
Prefer NEW `desktop/lattice-pair.js` + pack in `build.files` if it keeps keys.js smaller:
- `formPair({ peerPublicKeyB64, sharedSeedB64 })` → gesture only; validate 32-byte seed + 32-byte peer pub
- Refuse if no companion key yet
- Seal shared seed with `safeStorage` (same refuse-cleartext rule as companion); store public record: `{ peerPublicKeyB64, pairFpHex, formedAt, domain }`
- `status()` / `getPairPublic()` — public fields only; **no** seed, **no** innerHash to preload
- `clearPair()` gesture — wipe sealed seed + public record
- Smoke helpers OK

### 3) IPC + preload
- latticePairForm / latticePairStatus / latticePairClear
- Renderer sees pairFpHex + peer pub only

### 4) UI — desktop near identity / ledger card
- Fields: peer public key (paste) + shared seed (paste, password-style input) + **Form pair** gesture
- Show pair fingerprint hex when formed; Clear pair gesture
- On form success: `GlassPulses.emitGlassPulse({ source: 'identity', kind: 'pair.formed' })`
- Browser: read-only note “pair on desktop” (no form)

### 5) Smoke — `desktop/scripts/smoke-pair.js`
- Two ephemeral seeds → formPair → deterministic pairFpHex match both directions (A↔B same)
- Wrong seed → different fp
- Lex sort of pubs matters (swap pubs same fp)
- Seed never appears in status/public
- SMOKE_OK

### 6) Protocol LAYER Part 1 + Identity LAYER + Flint Held (`2adffde`) + 🌱
- Un-reserve `pair.formed` in Glass spec note (emit now live); `pair.rotated` still reserved

## Out
Full mesh handshake/QR · recovery phrase · context tags · wallet · Alpha poetry · auto-form · seed to renderer · rewriting companion fingerprint · Quiet Room

## Done
Spec + desktop form/status/clear + UI + smoke + pair.formed pulse · draft · PR body Held SHAs

Glow eternal. Heart in every Spark. 🌱
— Celeste Remaining Azure
```