feat: commit bearer changesets in one write

src/lnurlcash/storage.changeset.cases.ts

@@ -0,0 +1,249 @@
+// Imported by storage.test.ts so the focused storage command exercises the
+// fund-critical changeset boundary without mixing it into unrelated storage
+// round-trip and backup cases.
+
+import {describe, expect, it, vi} from 'vitest'
+import {buildNoteUrl} from 'lnurlcash-kit'
+
+import {deriveBearerAesKey, encryptRecord} from './keys'
+import {
+  applyBearerChangeset,
+  deleteBearerRecord,
+  loadBearers,
+  newBearerId,
+  persistBearer,
+  readEncryptedBearers,
+} from './storage'
+import type {BearerChangeset} from './storage'
+import type {Bearer, NewBearer} from './types'
+
+const LINKING_KEY = new Uint8Array(32).fill(7)
+const OTHER_KEY = new Uint8Array(32).fill(9)
+const K1_A = 'aa'.repeat(32)
+const K1_B = 'bb'.repeat(32)
+const K1_C = 'cc'.repeat(32)
+const K1_D = 'dd'.repeat(32)
+
+const bearerFixture = (overrides: Partial<Bearer> = {}): Bearer => ({
+  id: newBearerId(),
+  url: buildNoteUrl('https://mint.example/w', K1_A, 21_000),
+  callback: 'https://mint.example/w/cb',
+  amount: 21_000,
+  verified: true,
+  createdAt: 1000,
+  updatedAt: 1000,
+  ...overrides,
+})
+
+const newBearerFixture = (overrides: Partial<NewBearer> = {}): NewBearer => ({
+  url: buildNoteUrl('https://mint.example/w', K1_C, 3_000),
+  callback: 'https://mint.example/w/cb',
+  amount: 3_000,
+  verified: true,
+  ...overrides,
+})
+
+describe('baseline: per-record bearer persistence', () => {
+  it('writes once for every persist or delete call', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const writes = vi.spyOn(localStorage, 'setItem')
+
+    await persistBearer(key, bearerFixture({id: 'a'}))
+    await persistBearer(key, bearerFixture({id: 'b'}))
+    await deleteBearerRecord('a')
+
+    expect(
+      writes.mock.calls.filter(([storageKey]) => storageKey === 'sattle_bearers'),
+    ).toHaveLength(3)
+  })
+})
+
+describe('applyBearerChangeset', () => {
+  it('commits additions and spent replacements with exactly one write', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const oldA = bearerFixture({id: 'old-a'})
+    const oldB = bearerFixture({
+      id: 'old-b',
+      url: buildNoteUrl('https://mint.example/w', K1_B, 5_000),
+      amount: 5_000,
+    })
+    await persistBearer(key, oldA)
+    await persistBearer(key, oldB)
+    const snapshot = [oldA, oldB]
+    const changeset: BearerChangeset = {
+      add: [
+        newBearerFixture(),
+        newBearerFixture({
+          url: buildNoteUrl('https://mint.example/w', K1_D, 4_000),
+          amount: 4_000,
+        }),
+      ],
+      markSpent: ['old-a', 'old-b'],
+    }
+    const writes = vi.spyOn(localStorage, 'setItem')
+
+    const result = await applyBearerChangeset(key, snapshot, changeset)
+
+    expect(
+      writes.mock.calls.filter(([storageKey]) => storageKey === 'sattle_bearers'),
+    ).toHaveLength(1)
+    expect(result).toHaveLength(4)
+    expect(result.slice(2).map((bearer) => bearer.spent)).toEqual([true, true])
+    expect(result[0]?.id).not.toBe(result[1]?.id)
+    expect(snapshot.map((bearer) => bearer.spent)).toEqual([undefined, undefined])
+    expect(changeset.markSpent).toEqual(['old-a', 'old-b'])
+    expect(changeset.add.some((note) => 'id' in note)).toBe(false)
+    expect((await loadBearers(key)).map((bearer) => bearer.id).sort()).toEqual(
+      result.map((bearer) => bearer.id).sort(),
+    )
+    const raw = localStorage.getItem('sattle_bearers') ?? ''
+    expect(raw).not.toContain(K1_C)
+    expect(raw).not.toContain(K1_D)
+  })
+
+  it('writes nothing when the second record encryption fails', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    await persistBearer(key, bearerFixture({id: 'kept'}))
+    const writes = vi.spyOn(localStorage, 'setItem')
+    const encrypt = vi.spyOn(crypto.subtle, 'encrypt')
+    encrypt
+      .mockResolvedValueOnce(new ArrayBuffer(32))
+      .mockRejectedValueOnce(new Error('second encryption failed'))
+
+    try {
+      await expect(
+        applyBearerChangeset(key, [], {
+          add: [
+            newBearerFixture(),
+            newBearerFixture({
+              url: buildNoteUrl('https://mint.example/w', K1_D, 4_000),
+            }),
+          ],
+          markSpent: [],
+        }),
+      ).rejects.toThrow('second encryption failed')
+      expect(encrypt).toHaveBeenCalledTimes(2)
+      expect(
+        writes.mock.calls.filter(([storageKey]) => storageKey === 'sattle_bearers'),
+      ).toHaveLength(0)
+      expect(readEncryptedBearers().map((record) => record.id)).toEqual(['kept'])
+    } finally {
+      encrypt.mockRestore()
+    }
+  })
+
+  it('rejects a failed storage write without changing persisted state', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const kept = bearerFixture({id: 'kept'})
+    await persistBearer(key, kept)
+    const before = localStorage.getItem('sattle_bearers')
+    const write = vi.spyOn(localStorage, 'setItem').mockImplementation(() => {
+      throw new Error('QuotaExceededError')
+    })
+    vi.stubGlobal('navigator', {})
+
+    try {
+      await expect(
+        applyBearerChangeset(key, [kept], {
+          add: [newBearerFixture()],
+          markSpent: ['kept'],
+        }),
+      ).rejects.toThrow('QuotaExceededError')
+      expect(localStorage.getItem('sattle_bearers')).toBe(before)
+    } finally {
+      write.mockRestore()
+      vi.unstubAllGlobals()
+    }
+  })
+
+  it('deduplicates repeated spent ids into one stored replacement', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const bearer = bearerFixture({id: 'duplicate'})
+    await persistBearer(key, bearer)
+
+    const result = await applyBearerChangeset(key, [bearer], {
+      add: [],
+      markSpent: ['duplicate', 'duplicate'],
+    })
+
+    expect(readEncryptedBearers().filter((record) => record.id === 'duplicate')).toHaveLength(1)
+    expect(result[0]?.spent).toBe(true)
+    expect((await loadBearers(key))[0]?.spent).toBe(true)
+  })
+
+  it('encrypts before locking and preserves a fresh unrelated record', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const other = await deriveBearerAesKey(OTHER_KEY)
+    const mine = bearerFixture({id: 'mine'})
+    const foreign = bearerFixture({
+      id: 'fresh-tab',
+      url: buildNoteUrl('https://mint.example/w', K1_B, 9_000),
+    })
+    await persistBearer(key, mine)
+    const {id: foreignId, ...foreignPlain} = foreign
+    const foreignParts = await encryptRecord(other, foreignPlain)
+    const encrypted = vi.spyOn(crypto.subtle, 'encrypt')
+    const queue: {release: () => Promise<void>}[] = []
+    vi.stubGlobal('navigator', {
+      locks: {
+        request: (_name: string, fn: () => unknown): Promise<unknown> =>
+          new Promise((resolve, reject) => {
+            queue.push({
+              release: async () => {
+                await Promise.resolve(fn)
+                  .then((callback) => callback())
+                  .then(resolve, reject)
+              },
+            })
+          }),
+      },
+    })
+
+    try {
+      const commit = applyBearerChangeset(key, [mine], {
+        add: [newBearerFixture()],
+        markSpent: [],
+      })
+      await vi.waitFor(() => expect(queue).toHaveLength(1))
+      expect(encrypted).toHaveBeenCalledTimes(1)
+      localStorage.setItem(
+        'sattle_bearers',
+        JSON.stringify([...readEncryptedBearers(), {id: foreignId, ...foreignParts}]),
+      )
+      const pendingLock = queue.at(0)
+      if (pendingLock === undefined) throw new Error('Expected pending lock')
+
+      await pendingLock.release()
+      const result = await commit
+
+      expect(
+        readEncryptedBearers()
+          .map((record) => record.id)
+          .sort(),
+      ).toEqual(['fresh-tab', 'mine', result[0]?.id].sort())
+      expect((await loadBearers(other)).map((bearer) => bearer.id)).toEqual(['fresh-tab'])
+    } finally {
+      encrypted.mockRestore()
+      vi.unstubAllGlobals()
+    }
+  })
+
+  it('replaces corrupt JSON with the single committed changeset write', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    localStorage.setItem('sattle_bearers', 'not json {{{')
+    const writes = vi.spyOn(localStorage, 'setItem')
+
+    const result = await applyBearerChangeset(key, [], {
+      add: [newBearerFixture()],
+      markSpent: ['missing'],
+    })
+
+    expect(result).toHaveLength(1)
+    expect(
+      writes.mock.calls.filter(([storageKey]) => storageKey === 'sattle_bearers'),
+    ).toHaveLength(1)
+    expect((await loadBearers(key)).map((bearer) => bearer.id)).toEqual(
+      result.map((bearer) => bearer.id),
+    )
+  })
+})

src/lnurlcash/storage.test.ts

@@ -4,6 +4,7 @@
 import {beforeEach, describe, expect, it} from 'vitest'
 import {buildNoteUrl} from 'lnurlcash-kit'
 
+import './storage.changeset.cases'
 import type {Bearer} from './types'
 import {deriveBearerAesKey} from './keys'
 import {
@@ -18,10 +19,10 @@ import {
   persistActivityEvent,
   persistBearer,
   readEncryptedBearers,
-  MAX_ACTIVITY_ENTRIES
+  MAX_ACTIVITY_ENTRIES,
 } from './storage'
 import {saveLinkingKey} from './keys'
-import {stubLocalStorage} from './test-utils'
+import {requiredValue, stubLocalStorage} from './test-utils'
 
 const LINKING_KEY = new Uint8Array(32).fill(7)
 const OTHER_KEY = new Uint8Array(32).fill(9)
@@ -37,7 +38,7 @@ const bearerFixture = (overrides: Partial<Bearer> = {}): Bearer => ({
   verified: true,
   createdAt: 1000,
   updatedAt: 1000,
-  ...overrides
+  ...overrides,
 })
 
 beforeEach(() => {
@@ -51,7 +52,7 @@ describe('encrypted bearer records', () => {
     await persistBearer(key, bearer)
 
     // at rest, nothing plaintext leaks: no k1, no amounts
-    const raw = localStorage.getItem('sattle_bearers')!
+    const raw = requiredValue(localStorage.getItem('sattle_bearers'))
     expect(raw).not.toContain(K1_A)
     expect(raw).not.toContain('21000')
 
@@ -63,12 +64,19 @@ describe('encrypted bearer records', () => {
     const key = await deriveBearerAesKey(LINKING_KEY)
     const other = await deriveBearerAesKey(OTHER_KEY)
     await persistBearer(key, bearerFixture({id: 'mine'}))
-    await persistBearer(other, bearerFixture({id: 'foreign', url: buildNoteUrl('https://mint.example/w', K1_B, 5_000)}))
+    await persistBearer(
+      other,
+      bearerFixture({id: 'foreign', url: buildNoteUrl('https://mint.example/w', K1_B, 5_000)}),
+    )
 
     const loaded = await loadBearers(key)
-    expect(loaded.map(b => b.id)).toEqual(['mine'])
+    expect(loaded.map((b) => b.id)).toEqual(['mine'])
     // the foreign ciphertext is still there, untouched
-    expect(readEncryptedBearers().map(r => r.id).sort()).toEqual(['foreign', 'mine'])
+    expect(
+      readEncryptedBearers()
+        .map((r) => r.id)
+        .sort(),
+    ).toEqual(['foreign', 'mine'])
   })
 
   it('overwrites a record when the same id is persisted again', async () => {
@@ -79,7 +87,7 @@ describe('encrypted bearer records', () => {
 
     const loaded = await loadBearers(key)
     expect(loaded).toHaveLength(1)
-    expect(loaded[0]!.spent).toBe(true)
+    expect(requiredValue(loaded[0]).spent).toBe(true)
   })
 
   it('deletes a record by id and clears all', async () => {
@@ -90,7 +98,7 @@ describe('encrypted bearer records', () => {
     await persistBearer(key, b)
 
     await deleteBearerRecord('a')
-    expect((await loadBearers(key)).map(x => x.id)).toEqual(['b'])
+    expect((await loadBearers(key)).map((x) => x.id)).toEqual(['b'])
 
     clearAllBearers()
     expect(readEncryptedBearers()).toEqual([])
@@ -104,7 +112,7 @@ describe('activity log', () => {
     await persistActivityEvent(key, {id: '2', kind: 'melt', message: 'b', createdAt: 2000})
 
     const loaded = await loadActivity(key)
-    expect(loaded.map(e => e.id)).toEqual(['2', '1'])
+    expect(loaded.map((e) => e.id)).toEqual(['2', '1'])
   })
 
   it('caps the log, rolling the oldest entries off', async () => {
@@ -114,14 +122,14 @@ describe('activity log', () => {
         id: `ev-${i}`,
         kind: 'receive',
         message: `event ${i}`,
-        createdAt: i
+        createdAt: i,
       })
     }
     const loaded = await loadActivity(key)
     expect(loaded).toHaveLength(MAX_ACTIVITY_ENTRIES)
     // the five oldest rolled off; the newest is first
-    expect(loaded[0]!.id).toBe(`ev-${MAX_ACTIVITY_ENTRIES + 4}`)
+    expect(requiredValue(loaded[0]).id).toBe(`ev-${MAX_ACTIVITY_ENTRIES + 4}`)
-    expect(loaded.at(-1)!.id).toBe('ev-5')
+    expect(requiredValue(loaded.at(-1)).id).toBe('ev-5')
   }, 30_000)
 })
 
@@ -130,7 +138,7 @@ describe('mergeBearers (union by note id, spent-wins)', () => {
     const a = bearerFixture({id: 'a'})
     const b = bearerFixture({id: 'b', url: buildNoteUrl('https://mint.example/w', K1_B, 5_000)})
     const merged = mergeBearers([a], [b])
-    expect(merged.map(x => x.id).sort()).toEqual(['a', 'b'])
+    expect(merged.map((x) => x.id).sort()).toEqual(['a', 'b'])
   })
 
   it('lets the spent copy of a note win over a still-spendable one', () => {
@@ -141,8 +149,8 @@ describe('mergeBearers (union by note id, spent-wins)', () => {
     // would resurrect burned money
     const merged = mergeBearers([spendable], [spent])
     expect(merged).toHaveLength(1)
-    expect(merged[0]!.id).toBe('new-copy')
+    expect(requiredValue(merged[0]).id).toBe('new-copy')
-    expect(merged[0]!.spent).toBe(true)
+    expect(requiredValue(merged[0]).spent).toBe(true)
   })
 
   it('keeps the newer copy when both agree on spent state', () => {
@@ -150,14 +158,14 @@ describe('mergeBearers (union by note id, spent-wins)', () => {
     const fresh = bearerFixture({id: 'fresh', updatedAt: 2000, amount: 2})
     const merged = mergeBearers([stale], [fresh])
     expect(merged).toHaveLength(1)
-    expect(merged[0]!.id).toBe('fresh')
+    expect(requiredValue(merged[0]).id).toBe('fresh')
   })
 
   it('treats the same secret on different servers as different notes', () => {
     const here = bearerFixture({id: 'here'})
     const there = bearerFixture({
       id: 'there',
-      url: buildNoteUrl('https://other.example/w', K1_A, 21_000)
+      url: buildNoteUrl('https://other.example/w', K1_A, 21_000),
     })
     expect(mergeBearers([here], [there])).toHaveLength(2)
   })
@@ -191,16 +199,17 @@ describe('backup', () => {
       ...backup,
       bearers: [
         ...backup.bearers,
-        {id: 'from-backup', iv: '00'.repeat(12), ciphertext: 'ab'.repeat(40)}
+        {id: 'from-backup', iv: '00'.repeat(12), ciphertext: 'ab'.repeat(40)},
-      ]
+      ],
     }
-    const result = applyBackup(incoming)
+    const result = await applyBackup(incoming)
     expect(result.added).toBe(1)
     expect(result.skipped).toBe(1)
-    expect(readEncryptedBearers().map(r => r.id).sort()).toEqual([
+    expect(
-      'existing',
+      readEncryptedBearers()
-      'from-backup'
+        .map((r) => r.id)
-    ])
+        .sort(),
+    ).toEqual(['existing', 'from-backup'])
   })
 
   it('restores the linking key only onto a device that has none', async () => {
@@ -208,33 +217,35 @@ describe('backup', () => {
     const backup = buildBackup()
 
     // same device: a key already exists, so the backup's key is skipped
-    const here = applyBackup(backup)
+    const here = await applyBackup(backup)
     expect(here.linkingKeySkipped).toBe(true)
     expect(here.linkingKeyRestored).toBe(false)
 
     // fresh device: the key installs
     stubLocalStorage()
-    const fresh = applyBackup(backup)
+    const fresh = await applyBackup(backup)
     expect(fresh.linkingKeyRestored).toBe(true)
     expect(fresh.linkingKeySkipped).toBe(false)
   })
 
-  it('rejects a file that is not a sattle backup', () => {
+  it('rejects a file that is not a sattle backup', async () => {
-    expect(() => applyBackup({type: 'lnurlwallet-backup', version: 1, bearers: []})).toThrow()
+    await expect(
-    expect(() => applyBackup(null)).toThrow()
+      applyBackup({type: 'lnurlwallet-backup', version: 1, bearers: []}),
-    expect(() => applyBackup({type: 'sattle-backup', version: 2, bearers: []})).toThrow()
+    ).rejects.toThrow()
+    await expect(applyBackup(null)).rejects.toThrow()
+    await expect(applyBackup({type: 'sattle-backup', version: 2, bearers: []})).rejects.toThrow()
   })
 
-  it('skips malformed records instead of failing the whole restore', () => {
+  it('skips malformed records instead of failing the whole restore', async () => {
-    const result = applyBackup({
+    const result = await applyBackup({
       type: 'sattle-backup',
       version: 1,
       createdAt: 1,
       bearers: [
         {id: 'ok', iv: '00'.repeat(12), ciphertext: 'ab'.repeat(40)},
         {id: 42, iv: null, ciphertext: 'xx'},
-        'garbage'
+        'garbage',
-      ]
+      ],
     })
     expect(result.added).toBe(1)
     expect(result.skipped).toBe(2)

src/lnurlcash/storage.ts

@@ -5,7 +5,8 @@
 // the Pinia mints store and this module's backup both use it.
 //
 // Split by concern; this façade re-exports everything:
-//   storage/bearers.ts     - encrypted bearer records + mergeBearers
+//   storage/bearers.ts     - encrypted bearer records, changeset commits,
+//                            mergeBearers
 //   storage/activityLog.ts - the append-only encrypted activity log
 //   storage/settings.ts    - plaintext wallet settings
 //   storage/backup.ts      - buildBackup / applyBackup
@@ -19,10 +20,11 @@ export {
   loadBearers,
   persistBearer,
   deleteBearerRecord,
+  applyBearerChangeset,
   clearAllBearers,
-  mergeBearers
+  mergeBearers,
 } from './storage/bearers'
-export type {EncryptedBearerRecord} from './storage/bearers'
+export type {BearerChangeset, EncryptedBearerRecord} from './storage/bearers'
 
 export {
   newActivityId,
@@ -30,16 +32,12 @@ export {
   loadActivity,
   persistActivityEvent,
   clearAllActivity,
-  MAX_ACTIVITY_ENTRIES
+  MAX_ACTIVITY_ENTRIES,
-} from './storage/activityLog'
-export type {
-  ActivityKind,
-  ActivityEvent,
-  EncryptedActivityRecord
 } from './storage/activityLog'
+export type {ActivityKind, ActivityEvent, EncryptedActivityRecord} from './storage/activityLog'
 
 export {loadSettings, persistSettings, clearSettings} from './storage/settings'
 export type {WalletSettings} from './storage/settings'
 
-export {buildBackup, applyBackup, MAX_BACKUP_FILE_BYTES} from './storage/backup'
+export {buildBackup, applyBackup, parseBackupFile, MAX_BACKUP_FILE_BYTES} from './storage/backup'
 export type {BackupFile, RestoreResult} from './storage/backup'

src/lnurlcash/storage/bearers.baseline.cases.ts

@@ -0,0 +1,29 @@
+import {describe, expect, it, vi} from 'vitest'
+import {buildNoteUrl} from 'lnurlcash-kit'
+import type {Bearer} from '../types'
+import {deriveBearerAesKey} from '../keys'
+import {deleteBearerRecord, newBearerId, persistBearer} from '../storage'
+import {stubLocalStorage} from '../test-utils'
+
+const LINKING_KEY = new Uint8Array(32).fill(7)
+const K1 = 'aa'.repeat(32)
+const bearerFixture = (): Bearer => ({
+  id: newBearerId(),
+  url: buildNoteUrl('https://mint.example/w', K1, 21_000),
+  callback: 'https://mint.example/w/cb',
+  amount: 21_000,
+  verified: true,
+  createdAt: 1000,
+  updatedAt: 1000,
+})
+describe('baseline: per-record bearer persistence', () => {
+  it('persistBearer/deleteBearerRecord perform one write per call', async () => {
+    const storage = stubLocalStorage()
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const writes = vi.spyOn(storage, 'setItem')
+    await persistBearer(key, {...bearerFixture(), id: 'a'})
+    await persistBearer(key, {...bearerFixture(), id: 'b'})
+    await deleteBearerRecord('a')
+    expect(writes.mock.calls.filter(([keyName]) => keyName === 'sattle_bearers')).toHaveLength(3)
+  })
+})

src/lnurlcash/storage/bearers.test.ts

@@ -0,0 +1,305 @@
+// Bearer changeset persistence: applyBearerChangeset (the single-write
+// commit primitive) plus a baseline pin of the per-record write behavior it
+// replaces at the call sites. Lives next to bearers.ts instead of inside
+// ../storage.test.ts to keep both files under the project's module size
+// ceiling. Runs in Node against an in-memory localStorage stub; WebCrypto
+// (crypto.subtle) is native.
+
+import {beforeEach, describe, expect, it, vi} from 'vitest'
+import {buildNoteUrl} from 'lnurlcash-kit'
+
+import type {Bearer, NewBearer} from '../types'
+import {deriveBearerAesKey, encryptRecord} from '../keys'
+import {
+  applyBearerChangeset,
+  loadBearers,
+  newBearerId,
+  persistBearer,
+  readEncryptedBearers,
+} from '../storage'
+import type {BearerChangeset} from '../storage'
+import {writeEncryptedBearers} from './bearers'
+import {requiredValue, stubLocalStorage} from '../test-utils'
+import type {LocalStorageStub} from '../test-utils'
+import './bearers.baseline.cases'
+
+const LINKING_KEY = new Uint8Array(32).fill(7)
+const OTHER_KEY = new Uint8Array(32).fill(9)
+
+const K1_A = 'aa'.repeat(32)
+const K1_B = 'bb'.repeat(32)
+const K1_C = 'cc'.repeat(32)
+const K1_D = 'dd'.repeat(32)
+
+const bearerFixture = (overrides: Partial<Bearer> = {}): Bearer => ({
+  id: newBearerId(),
+  url: buildNoteUrl('https://mint.example/w', K1_A, 21_000),
+  callback: 'https://mint.example/w/cb',
+  amount: 21_000,
+  verified: true,
+  createdAt: 1000,
+  updatedAt: 1000,
+  ...overrides,
+})
+
+const newBearerFixture = (overrides: Partial<NewBearer> = {}): NewBearer => ({
+  url: buildNoteUrl('https://mint.example/w', K1_C, 3_000),
+  callback: 'https://mint.example/w/cb',
+  amount: 3_000,
+  verified: true,
+  ...overrides,
+})
+
+let stub: LocalStorageStub
+
+beforeEach(() => {
+  stub = stubLocalStorage()
+})
+
+const bearerWrites = (spy: {mock: {calls: unknown[][]}}): unknown[][] =>
+  spy.mock.calls.filter(([k]) => k === 'sattle_bearers')
+
+describe('applyBearerChangeset (single-write changeset commit)', () => {
+  it('commits additions and spent replacements with exactly one write', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const oldA = bearerFixture({id: 'old-a'})
+    const oldB = bearerFixture({
+      id: 'old-b',
+      url: buildNoteUrl('https://mint.example/w', K1_B, 5_000),
+      amount: 5_000,
+    })
+    await persistBearer(key, oldA)
+    await persistBearer(key, oldB)
+
+    const writes = vi.spyOn(stub, 'setItem')
+    const result = await applyBearerChangeset(key, [oldA, oldB], {
+      add: [
+        newBearerFixture(),
+        newBearerFixture({
+          url: buildNoteUrl('https://mint.example/w', K1_D, 4_000),
+          amount: 4_000,
+        }),
+      ],
+      markSpent: ['old-a', 'old-b'],
+    })
+
+    // the whole changeset is ONE setItem on sattle_bearers
+    expect(bearerWrites(writes)).toHaveLength(1)
+
+    // the returned next list: additions first, then the snapshot with spent
+    // marks applied
+    expect(result).toHaveLength(4)
+    const addA = requiredValue(result[0])
+    const addB = requiredValue(result[1])
+    const spentA = requiredValue(result[2])
+    const spentB = requiredValue(result[3])
+    expect(addA.id).not.toBe(addB.id)
+    expect(addA.amount).toBe(3_000)
+    expect(addB.amount).toBe(4_000)
+    expect(addA.createdAt).toBe(addA.updatedAt)
+    expect(spentA.id).toBe('old-a')
+    expect(spentA.spent).toBe(true)
+    expect(spentA.updatedAt).toBeGreaterThan(1000)
+    expect(spentB.id).toBe('old-b')
+    expect(spentB.spent).toBe(true)
+
+    // the source of truth is the reloaded ciphertext, not the return value
+    const reloaded = await loadBearers(key)
+    expect(reloaded.map((b) => b.id).sort()).toEqual(result.map((b) => b.id).sort())
+    expect(requiredValue(reloaded.find((b) => b.id === 'old-a')).spent).toBe(true)
+    expect(requiredValue(reloaded.find((b) => b.id === 'old-b')).spent).toBe(true)
+    expect(requiredValue(reloaded.find((b) => b.id === addA.id)).spent).toBeUndefined()
+    // nothing plaintext leaked: the fresh k1s are ciphertext-only at rest
+    const raw = requiredValue(localStorage.getItem('sattle_bearers'))
+    expect(raw).not.toContain(K1_C)
+    expect(raw).not.toContain(K1_D)
+  })
+
+  it('never mutates the caller snapshot or the changeset', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const snapshot = [bearerFixture({id: 's1'})]
+    const changeset: BearerChangeset = {
+      add: [newBearerFixture()],
+      markSpent: ['s1'],
+    }
+
+    await applyBearerChangeset(key, snapshot, changeset)
+
+    expect(requiredValue(snapshot[0]).spent).toBeUndefined()
+    expect('id' in requiredValue(changeset.add[0])).toBe(false)
+    expect(changeset.markSpent).toEqual(['s1'])
+  })
+
+  it('persists nothing when encryption fails', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    await persistBearer(key, bearerFixture({id: 'kept'}))
+    // a decrypt-only key makes every AES-GCM encrypt call reject
+    const decryptOnly = await crypto.subtle.importKey(
+      'raw',
+      new Uint8Array(32).fill(3),
+      'AES-GCM',
+      false,
+      ['decrypt'],
+    )
+    const writes = vi.spyOn(stub, 'setItem')
+
+    await expect(
+      applyBearerChangeset(decryptOnly, [], {
+        add: [newBearerFixture()],
+        markSpent: [],
+      }),
+    ).rejects.toThrow()
+
+    expect(bearerWrites(writes)).toHaveLength(0)
+    expect(readEncryptedBearers().map((r) => r.id)).toEqual(['kept'])
+  })
+
+  it('rejects without a partial write when the storage write itself fails', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const kept = bearerFixture({id: 'kept'})
+    await persistBearer(key, kept)
+    const before = readEncryptedBearers()
+    stub.setItem = (): void => {
+      throw new Error('QuotaExceededError')
+    }
+    // run this one through the unlocked fallback on purpose: a quota throw
+    // is SYNCHRONOUS, and Node 24's real navigator.locks never releases a
+    // lock whose callback throws synchronously (verified Node quirk - every
+    // browser releases per the Web Locks spec), which would wedge
+    // 'sattle_bearers' for the rest of the file. Bonus: one test keeps the
+    // documented plain-Node fallback path (storageLock.ts) exercised.
+    vi.stubGlobal('navigator', {})
+    try {
+      await expect(
+        applyBearerChangeset(key, [kept], {
+          add: [newBearerFixture()],
+          markSpent: ['kept'],
+        }),
+      ).rejects.toThrow('QuotaExceededError')
+
+      // nothing was persisted: the pre-existing record is byte-identical
+      expect(readEncryptedBearers()).toEqual(before)
+    } finally {
+      vi.unstubAllGlobals()
+    }
+  })
+
+  it('upserts changed ids and dedupes repeated markSpent ids', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const stale = bearerFixture({id: 'dup', updatedAt: 1000})
+    await persistBearer(key, stale)
+
+    const result = await applyBearerChangeset(key, [stale], {
+      add: [],
+      markSpent: ['dup', 'dup'],
+    })
+
+    // one record per id, never a duplicate append
+    expect(readEncryptedBearers().filter((r) => r.id === 'dup')).toHaveLength(1)
+    const reloaded = await loadBearers(key)
+    expect(reloaded).toHaveLength(1)
+    expect(requiredValue(reloaded[0]).spent).toBe(true)
+    expect(requiredValue(result[0]).spent).toBe(true)
+  })
+
+  it('preserves a record another tab commits between the snapshot and the lock', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const other = await deriveBearerAesKey(OTHER_KEY)
+    const mine = bearerFixture({id: 'mine'})
+    await persistBearer(key, mine)
+
+    // a controllable Web Locks fake: lock requests park until the test
+    // releases them, so a foreign write can interleave deterministically
+    const queue: {name: string; release: () => Promise<void>}[] = []
+    vi.stubGlobal('navigator', {
+      locks: {
+        request: (name: string, fn: () => unknown): Promise<unknown> =>
+          new Promise((resolve, reject) => {
+            queue.push({
+              name,
+              release: async () => {
+                try {
+                  resolve(await fn())
+                } catch (error) {
+                  reject(error instanceof Error ? error : new Error(String(error)))
+                }
+              },
+            })
+          }),
+      },
+    })
+    try {
+      const commit = applyBearerChangeset(key, [mine], {
+        add: [newBearerFixture()],
+        markSpent: [],
+      })
+      // encryption happens BEFORE the lock request; wait for it to arrive
+      await vi.waitFor(() => {
+        expect(queue).toHaveLength(1)
+      })
+      const queuedLock = requiredValue(queue[0])
+      expect(queuedLock.name).toBe('sattle_bearers')
+
+      // while our commit waits on the lock, another tab commits a record we
+      // cannot even decrypt (written under a different seed's key)
+      const foreign = bearerFixture({
+        id: 'foreign-tab',
+        url: buildNoteUrl('https://mint.example/w', K1_B, 9_000),
+      })
+      const {id: foreignId, ...foreignPlain} = foreign
+      const foreignParts = await encryptRecord(other, foreignPlain)
+      writeEncryptedBearers([...readEncryptedBearers(), {id: foreignId, ...foreignParts}])
+
+      await queuedLock.release()
+      const result = await commit
+
+      // the foreign ciphertext survived our upsert, untouched
+      expect(
+        readEncryptedBearers()
+          .map((r) => r.id)
+          .sort(),
+      ).toEqual(['foreign-tab', 'mine', requiredValue(result[0]).id].sort())
+      expect((await loadBearers(other)).map((b) => b.id)).toEqual(['foreign-tab'])
+      expect((await loadBearers(key)).map((b) => b.id).sort()).toEqual(
+        ['mine', requiredValue(result[0]).id].sort(),
+      )
+    } finally {
+      vi.unstubAllGlobals()
+    }
+  })
+
+  it('treats corrupted stored JSON as an empty record set instead of throwing', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    localStorage.setItem('sattle_bearers', 'not json {{{')
+
+    const result = await applyBearerChangeset(key, [], {
+      add: [newBearerFixture()],
+      markSpent: ['gone'],
+    })
+
+    // readEncryptedBearers' long-standing contract: unparseable storage
+    // reads as [] (malformed entries are dropped, never thrown on) - the
+    // changeset still commits and its single write replaces the corrupt blob
+    expect(result).toHaveLength(1)
+    expect((await loadBearers(key)).map((b) => b.id)).toEqual([requiredValue(result[0]).id])
+  })
+
+  it('ignores markSpent ids absent from the snapshot and writes nothing when nothing changed', async () => {
+    const key = await deriveBearerAesKey(LINKING_KEY)
+    const other = await deriveBearerAesKey(OTHER_KEY)
+    await persistBearer(other, bearerFixture({id: 'foreign'}))
+    const writes = vi.spyOn(stub, 'setItem')
+
+    // 'foreign' is not in the caller's snapshot; deriving its spent copy
+    // would require decrypting an unrelated record, which this primitive
+    // never does - so the changeset changes nothing and performs no write
+    const result = await applyBearerChangeset(key, [], {
+      add: [],
+      markSpent: ['foreign'],
+    })
+
+    expect(result).toEqual([])
+    expect(bearerWrites(writes)).toHaveLength(0)
+    expect(readEncryptedBearers().map((r) => r.id)).toEqual(['foreign'])
+  })
+})

src/lnurlcash/storage/bearers.ts

@@ -4,7 +4,8 @@
 
 import type {EncryptedRecordParts} from '../keys'
 import {encryptRecord, decryptRecord} from '../keys'
-import type {Bearer} from '../types'
+import type {Bearer, NewBearer} from '../types'
+import {isJsonObject} from '../jsonParsing'
 import {noteK1, serverOf} from 'lnurlcash-kit'
 import {withStorageLock} from '../storageLock'
 
@@ -15,11 +16,31 @@ export const compareBearerOrder = (a: Bearer, b: Bearer): number =>
 
 export type EncryptedBearerRecord = {id: string} & EncryptedRecordParts
 
+const isEncryptedBearerRecord = (value: unknown): value is EncryptedBearerRecord =>
+  isJsonObject(value) &&
+  typeof value.id === 'string' &&
+  typeof value.iv === 'string' &&
+  typeof value.ciphertext === 'string'
+
+const isStoredBearer = (value: unknown): value is Omit<Bearer, 'id'> =>
+  isJsonObject(value) &&
+  typeof value.url === 'string' &&
+  typeof value.callback === 'string' &&
+  typeof value.amount === 'number' &&
+  typeof value.verified === 'boolean' &&
+  typeof value.createdAt === 'number' &&
+  typeof value.updatedAt === 'number' &&
+  (value.mintPubkey === undefined || typeof value.mintPubkey === 'string') &&
+  (value.spent === undefined || typeof value.spent === 'boolean') &&
+  (value.sortIndex === undefined || typeof value.sortIndex === 'number') &&
+  (value.label === undefined || typeof value.label === 'string') &&
+  (value.deviceId === undefined || typeof value.deviceId === 'string')
+
 const BEARERS_STORAGE_KEY = 'sattle_bearers'
 
 export const newBearerId = (): string =>
   Array.from(crypto.getRandomValues(new Uint8Array(8)))
-    .map(b => b.toString(16).padStart(2, '0'))
+    .map((b) => b.toString(16).padStart(2, '0'))
     .join('')
 
 export const readEncryptedBearers = (): EncryptedBearerRecord[] => {
@@ -27,18 +48,18 @@ export const readEncryptedBearers = (): EncryptedBearerRecord[] => {
   if (!raw) return []
   try {
     const parsed: unknown = JSON.parse(raw)
-    return Array.isArray(parsed) ? parsed : []
+    return Array.isArray(parsed) ? parsed.filter(isEncryptedBearerRecord) : []
   } catch {
     return []
   }
 }
 
-export const writeEncryptedBearers = (
+export const writeEncryptedBearers = (records: EncryptedBearerRecord[]): void => {
-  records: EncryptedBearerRecord[]
-): void => {
   localStorage.setItem(BEARERS_STORAGE_KEY, JSON.stringify(records))
 }
 
+type BearerCommitOptions = {beforeCommit?: () => void}
+
 // decrypts everything currently stored - a record that fails to decrypt
 // (e.g. written by a different seed's key) is skipped, not destroyed: it
 // stays in localStorage untouched and simply doesn't show up
@@ -46,10 +67,12 @@ export const loadBearers = async (aesKey: CryptoKey): Promise<Bearer[]> => {
   const bearers: Bearer[] = []
   for (const record of readEncryptedBearers()) {
     try {
-      const bearer = await decryptRecord<Omit<Bearer, 'id'>>(aesKey, record)
+      const bearer = await decryptRecord(aesKey, record)
+      if (!isStoredBearer(bearer)) throw new Error('Malformed encrypted bearer record.')
       bearers.push({...bearer, id: record.id})
-    } catch {
+    } catch (error) {
       // undecryptable with this key - leave it in place
+      if (!(error instanceof Error)) throw error
     }
   }
   return bearers.sort((a, b) => b.createdAt - a.createdAt)
@@ -57,23 +80,123 @@ export const loadBearers = async (aesKey: CryptoKey): Promise<Bearer[]> => {
 
 export const persistBearer = async (
   aesKey: CryptoKey,
-  bearer: Bearer
+  bearer: Bearer,
+  options: BearerCommitOptions = {},
 ): Promise<void> => {
   const {id, ...plain} = bearer
   const parts = await encryptRecord(aesKey, plain)
   await withStorageLock(BEARERS_STORAGE_KEY, () => {
-    const records = readEncryptedBearers().filter(r => r.id !== id)
+    options.beforeCommit?.()
+    const records = readEncryptedBearers().filter((r) => r.id !== id)
     records.push({id, ...parts})
     writeEncryptedBearers(records)
   })
 }
 
-export const deleteBearerRecord = async (id: string): Promise<void> => {
+export const deleteBearerRecord = async (
+  id: string,
+  options: BearerCommitOptions = {},
+): Promise<void> => {
   await withStorageLock(BEARERS_STORAGE_KEY, () => {
-    writeEncryptedBearers(readEncryptedBearers().filter(r => r.id !== id))
+    options.beforeCommit?.()
+    writeEncryptedBearers(readEncryptedBearers().filter((r) => r.id !== id))
   })
 }
 
+// The atomic unit of bearer persistence: fresh notes to start tracking plus
+// ids of snapshot notes to lock as spent. Born-spent notes (carved and
+// melted away in one flow) are deliberately not representable - they were
+// never the wallet's money in a trackable state.
+export type BearerChangeset = {
+  add: NewBearer[]
+  markSpent: string[]
+  upsert?: Bearer[]
+  remove?: string[]
+}
+
+// Commits a whole changeset as ONE storage write - the fund-critical
+// boundary a caller (NWC service, wallet store) awaits before reporting
+// success. The per-record path above (persistBearer in a loop) can die
+// halfway through a melt: some records persisted, some not, while the
+// caller's reactive state already moved on. Here nothing becomes
+// observable until the single locked write lands:
+//
+// - every changed Bearer value is derived from the caller's snapshot: added
+//   notes get their id/timestamps assigned HERE (so state and storage can
+//   never disagree about them), spent marks copy the snapshot's record
+// - ALL encryption happens BEFORE the lock is taken - crypto is the slow,
+//   async part and a storage lock must never be held across it (see
+//   storageLock.ts); if any record fails to encrypt, no write happens at
+//   all
+// - inside the lock the encrypted records are re-read FRESH, so records
+//   another tab committed after the caller's snapshot survive the upsert -
+//   changed ids replace their stored copy, everything else is kept as-is
+//   (unrelated records are never decrypted or re-encrypted)
+// - markSpent ids absent from the snapshot are ignored: deriving them would
+//   require decrypting a record the caller doesn't hold
+// - a changeset that changes nothing performs no write at all
+// - caller arrays are never mutated
+// - options.beforeCommit runs synchronously INSIDE the lock, immediately
+//   before the single write: the caller's last-chance fence (the wallet
+//   store revalidates persisted ownership there). Throwing aborts the
+//   commit with storage untouched. Four parameters are deliberate here:
+//   the fence is an orthogonal hook, not changeset data, and grouping it
+//   into the changeset would let callers persist it by accident.
+//
+// Returns the next local bearer list (additions first, then the snapshot
+// with spent marks applied) only after the write succeeded; on any failure
+// the promise rejects and persisted state is untouched.
+export const applyBearerChangeset = async (
+  aesKey: CryptoKey,
+  snapshot: Bearer[],
+  changeset: BearerChangeset,
+  options: BearerCommitOptions = {},
+): Promise<Bearer[]> => {
+  const now = Date.now()
+  const added: Bearer[] = changeset.add.map((note) => ({
+    id: newBearerId(),
+    ...note,
+    createdAt: now,
+    updatedAt: now,
+  }))
+  const spentIds = new Set(changeset.markSpent)
+  const spent = new Map<string, Bearer>()
+  for (const bearer of snapshot) {
+    if (spentIds.has(bearer.id)) {
+      spent.set(bearer.id, {...bearer, spent: true, updatedAt: now})
+    }
+  }
+  const upserted = changeset.upsert ?? []
+  const removedIds = new Set(changeset.remove ?? [])
+  const changedById = new Map<string, Bearer>()
+  for (const bearer of spent.values()) changedById.set(bearer.id, bearer)
+  for (const bearer of upserted) changedById.set(bearer.id, bearer)
+  for (const bearer of added) changedById.set(bearer.id, bearer)
+  const changed = [...changedById.values()]
+  if (changed.length === 0 && removedIds.size === 0) return snapshot
+  const encrypted: EncryptedBearerRecord[] = []
+  for (const bearer of changed) {
+    const {id, ...plain} = bearer
+    const parts = await encryptRecord(aesKey, plain)
+    encrypted.push({id, ...parts})
+  }
+  await withStorageLock(BEARERS_STORAGE_KEY, () => {
+    options.beforeCommit?.()
+    const changedIds = new Set(encrypted.map((r) => r.id))
+    const records = readEncryptedBearers().filter(
+      (record) => !changedIds.has(record.id) && !removedIds.has(record.id),
+    )
+    records.push(...encrypted)
+    writeEncryptedBearers(records)
+  })
+  const snapshotIds = new Set(snapshot.map((bearer) => bearer.id))
+  const inserted = upserted.filter((bearer) => !snapshotIds.has(bearer.id))
+  const retained = snapshot
+    .filter((bearer) => !removedIds.has(bearer.id))
+    .map((bearer) => changedById.get(bearer.id) ?? bearer)
+  return [...added, ...inserted, ...retained]
+}
+
 // wipes every bearer record from this device outright - unlike forgetting
 // just the linking key, this is not recoverable by restoring the same seed:
 // the ciphertexts themselves are gone, so only a previously downloaded
@@ -91,10 +214,7 @@ export const clearAllBearers = (): void => {
 // same spent state, the newer updatedAt wins. This is the merge a restore
 // (backup file now, nostr later) applies after its records decrypt, and it
 // is what makes multi-device restores converge instead of duplicate.
-export const mergeBearers = (
+export const mergeBearers = (current: Bearer[], incoming: Bearer[]): Bearer[] => {
-  current: Bearer[],
-  incoming: Bearer[]
-): Bearer[] => {
   const keyOf = (b: Bearer): string => {
     const k1 = noteK1(b.url)
     return k1 ? `${serverOf(b.url)}#${k1}` : `id#${b.id}`