perf: skip re-verifying and re-decrypting already-unwrapped envelopes - #702
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A chat envelope costs ~5 EC multiplications to verify and decrypt. With R relays each message was unwrapped R times (the handlers continued past alreadyStored), every history load re-unwrapped every stored envelope, and two node-message copies arriving within the dedup read's round trip were both decrypted. - ChatRoomNotifier caches unwraps per outer envelope id: relay re-deliveries of an envelope this notifier already verified only advance the cursor (and re-surface the cached inner event if state lost it), and history loads reuse cached unwraps. Envelopes persisted by the background isolate are NOT in the cache and still get unwrapped on first sight, preserving the pinned background-handoff behaviour and the verify-before-persist security property. - DisputeChatNotifier applies the same skip via a set of locally verified outer ids. - MostroService._onData adds a synchronous seen-id check ahead of the async hasItem, closing the two-relay decrypt race.
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WalkthroughThe change adds envelope verification deduplication to chat and dispute notifiers. Chat processing caches unwrap futures across live and historical paths. Dispute processing reserves envelope IDs. Tests cover duplicate, concurrent, persisted, and forged envelopes. ChangesEnvelope deduplication
Merge Risk: 🟠 High · up to The optimization can make valid chat or dispute messages unavailable when an invalid duplicate wins a delivery race, and it can prevent retrying persistence after a storage failure. These recovery paths should be fixed before merging. Sequence Diagram(s)sequenceDiagram
participant Relay
participant ChatRoomNotifier
participant UnwrapCache
participant EventStorage
Relay->>ChatRoomNotifier: Deliver kind-14 envelope
ChatRoomNotifier->>UnwrapCache: Reserve or reuse outer envelope ID
UnwrapCache-->>ChatRoomNotifier: Return verified inner event
ChatRoomNotifier->>EventStorage: Persist verified envelope
ChatRoomNotifier-->>Relay: Update chat state
Suggested reviewers: Poem
🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
Full details: Docstring CoverageExplanation No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0 files. (3 skipped: 3 unsupported.) ✨ Finishing Touches🧪 Generate unit tests (beta)
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The optimization is well reasoned and the payoff is the largest of this batch. I measured chatUnwrap at 32.2 ms on the JIT VM, so with 3 relays that is ~96.7 ms of pure EC math per delivered message, and a 50-message history load was ~1.6 s of it.
I also want to confirm the two things I checked hardest, because both hold:
- The background-handoff invariant is preserved. I wrote the missing test: an envelope persisted by the background isolate — on disk but never in this notifier's _unwrapCache — still goes through the full chatUnwrap. The skip gate is alreadyStored && cachedUnwrap != null, and the cache is only populated after a successful unwrap, so nothing enters it unverified.
- _seenEventIds in MostroService is not a new trust hole. My first read was that marking an id before verification would let a forged copy dedup away the real one, but main already reserves the id via putItem (mostro_service.dart:125) before decrypting. The synchronous set only closes the await gap without changing the semantics. Good catch on that race.
Ordering is also fine — the skip path appends without sorting, but ChatRoom's constructor (chat_room.dart:11) sorts on every construction.
flutter analyze is clean apart from the two pre-existing stale-mock errors, and the full suite shows no new failures against main.
One thing needs to change before this can merge.
The cursor advances from an unverified event
Both skip paths advance the persisted cursor before any signature check:
// chat_room_notifier.dart:197-199
unawaited(
ref.read(chatCursorStoreProvider).advance(orderId, event.createdAt!),
);
// dispute_chat_notifier.dart:232-236
unawaited(
ref.read(disputeChatCursorStoreProvider).advance(disputeId, event.createdAt!),
);
The only gate ahead of them is event.pubkey != chatKeys.sign.public. That is not a secret: K_sign.public is the author field of every message in the conversation and is visible to any relay or observer, as is the envelope id. So anyone able to publish to a relay the victim reads can replay a real, already-accepted envelope id with the right claimed author, garbage content and an invalid signature, and move the cursor.
The only gate ahead of them is event.pubkey != chatKeys.sign.public. That is not a secret: K_sign.public is the author field of every message in the conversation and is visible to any relay or observer, as is the envelope id. So anyone able to publish to a relay the victim reads can replay a real, already-accepted envelope id with the right claimed author, garbage content and an invalid signature, and move the cursor.
I confirmed it with a test on this branch — a forged envelope with created_at far in the future and sig set to zeros:
cursor before: 2026-08-31 13:02:24.567068
cursor after: 2026-08-31 13:02:24.723823
clamp() caps the jump at now, and cachedSinceFor subtracts cursorOverlap (10 minutes), so the reachable effect is pushing the conversation's since to now - 10 min. Any message not yet fetched and older than that window is never requested again — silent message loss in the chat that carries payment coordination for a live trade.
On main this is unreachable: the old flow required a successful chatUnwrap (which verifies the outer integrity and the allowed signer) before the advance ran.
The fix is to delete both calls. They are no-ops for legitimate traffic: a re-delivery carries the same envelope id and therefore the same created_at, so _advanceSerialized returns early at if (current != null && !clamped.isAfter(current)) return;
(chat_cursor_store.dart:99). I verified that with a test — feeding the same envelope twice leaves the cursor unchanged — so the line only ever has an effect when created_at is forged. Removing it costs nothing and closes the hole.
Tests worth adding while the PR is open
The two current tests cover the performance property (debugUnwrapCount) but not the security ones, which are the load-bearing claims here. Both of these pass on this branch as-is except the second, which is the finding above:
test('an envelope stored by the background isolate is still verified', () async {
final event = await envelope('from background');
// On disk, but this notifier never verified it.
await eventStorage.putItem(event.id!, event.peerChatRecord(orderId));
await notifier.handleChatEvent(event);
expect(notifier.debugUnwrapCount, 1,
reason: 'an envelope this notifier never verified must be unwrapped, '
'even though it is already on disk');
expect(container.read(chatRoomProvider).messages, hasLength(1));
});
test('the cursor does not advance from an unverified envelope', () async {
final real = await envelope('legit');
await notifier.handleChatEvent(real);
final before = await cursorStore.cursorFor(orderId);
// Hostile relay: real envelope id, correct claimed author, bogus signature.
final forged = NostrEvent.deserialized('["EVENT","",${jsonEncode({
'id': real.id,
'pubkey': chatKeys.sign.public,
'created_at': DateTime.now()
.add(const Duration(days: 3650)).millisecondsSinceEpoch ~/ 1000,
'kind': 14,
'tags': <List<String>>[],
'content': 'undecryptable garbage',
'sig': '0' * 128,
})}]');
await notifier.handleChatEvent(forged);
expect(await cursorStore.cursorFor(orderId), before);
});
Non-blocking notes
- debugUnwrapCount is a public mutable field in production code. Acceptable for the test hook, same trade-off as elsewhere in this batch.
- _seenEventIds and _seenEventIdsLimit are declared mid-class immediately before _onData rather than with the other fields.
- The second commit turns if (wrapperEventId == null) return; into event.id!, which throws instead of returning — but it is inside the handler's try/catch, so it degrades to a logged error rather than a crash.
- Worth knowing for sequencing against #701: chatUnwrap is 32 ms, of which only ~5 ms is the NIP-44 decrypt (the rest is the two Schnorr verifications), so the conversation-key cache in #701 barely overlaps with this path. The two PRs are complementary and both are worth landing.
The skip paths added for the redundant-decrypt optimization advanced the persisted since cursor before any signature check. The only gate ahead of them was the claimed author, which is public — as is the envelope id — so anyone able to publish to a relay the victim reads could replay an already-accepted id with a forged created_at and push the cursor to the local clock, dropping every not-yet-fetched message older than the ten-minute overlap. Both advances are deleted. They were no-ops for legitimate traffic: a re-delivery carries the same id and therefore the same created_at, which the store already rejects as not newer. Also: - coalesce concurrent unwraps: the chat cache now keys on the in-flight future and the dispute reservation is taken synchronously, so two relays delivering the same envelope at once share one verification instead of each paying for it. A rejected unwrap is never cached, so a corrupted copy delivered first cannot lock out the valid event with the same id. - release the MostroService seen-id reservation when the durable one fails, so a transient storage error no longer discards every later redelivery of that event for the rest of the run. - move _seenEventIds up with the other fields. Tests: an envelope stored by the background isolate is still verified, the cursor does not advance from an unverified envelope, and concurrent deliveries share one unwrap.
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Gracias por la revisión — todo corregido en The blocking finding: the cursor advanced from an unverified event Deleted both The dispute skip branch is now a plain Tests Both of yours are in, plus one more:
Codex's two P2s, also addressed
Your non-blocking notes
Verification
One gap I want to be explicit about: the dispute-side cursor fix has no dedicated test. The scaffolding in |
Resolve conflict in MostroService._onData: keep main's in-flight dedup (_inFlightEventIds) and mark-after-processing (_markEventProcessed), which supersedes this branch's _seenEventIds reservation. Main's design covers the same concurrent-relay-copy race without poisoning an event whose first processing attempt fails.
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Inline comments:
In `@lib/features/chat/notifiers/chat_room_notifier.dart`:
- Line 233: Update the successful-unwrap storage handling in the chat room
notifier so failures from eventStore.hasItem or eventStore.putItem invalidate
the fulfilled cache entry before returning. Ensure a later relay delivery can
retry persistence and cursor advancement, while preserving the existing error
logging and successful duplicate handling.
In `@lib/features/disputes/notifiers/dispute_chat_notifier.dart`:
- Line 234: Update the duplicate-event handling around _unwrappedOuterIds and
chatUnwrap so one same-ID event arriving while the first envelope is awaiting
verification is retained, then replayed after the initial unwrap fails instead
of being permanently dropped. Preserve normal duplicate suppression after
successful processing, and add a regression test covering invalid-signature
delivery followed by a valid same-ID copy.
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📒 Files selected for processing (3)
lib/features/chat/notifiers/chat_room_notifier.dartlib/features/disputes/notifiers/dispute_chat_notifier.darttest/features/chat/chat_room_notifier_redundant_decrypt_test.dart
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Two gaps in the per-envelope dedup, both raised in review: - A forged copy can reuse a valid envelope's id (the signature is not part of the id). It reserved the id, and the real copy arriving while it was being verified was dropped for good. A copy now awaits the in-flight one and, if that fails, is verified on its own. - In the P2P chat notifier a storage failure after a successful unwrap left the fulfilled cache entry in place, so a later delivery took the already-unwrapped shortcut and never retried the write or the cursor advance — the message was gone after a restart. The cached unwrap is now dropped when persistence fails. The dispute notifier's id set now means "fully processed" (verified, persisted, in state) instead of "reserved", with in-flight envelopes tracked separately.
2 participants
Summary
Item 3.3 of the performance plan. A chat envelope costs ~5 EC multiplications (two Schnorr verifications + NIP-44 decrypt) on the UI isolate. Three redundancy sources:
_onChatEventcheckedhasItembut deliberately continued tochatUnwrap— with R relays, R full unwraps per message._loadHistoricalMessagesre-verified and re-decrypted every stored envelope on every init/reload.stream.listen(_onData)doesn't await the handler, so two relay copies arriving within the SembasthasItemround trip both passed the check and were both decrypted.Changes
ChatRoomNotifier: unwraps cached per outer envelope id (bounded). A re-delivery of an envelope this notifier already verified only advances the cursor and re-surfaces the cached inner event if state lost it; history loads consult the cache first. The pinned security/handoff behaviours are preserved: an envelope persisted by the background isolate is not in the cache, so it is still unwrapped on first sight (the existing security-test pin for that path stays green), and nothing unverified is ever persisted (the verify-before-persist order is untouched —putItemremains conditional on!alreadyStored).DisputeChatNotifier: same skip via a set of locally verified outer ids.MostroService._onData: synchronous seen-id set checked before the asynchasItem, closing the two-relay decrypt race (disk dedup still guards across restarts).@visibleForTesting debugUnwrapCountonChatRoomNotifierpins the unwrap count.Test plan
test/features/chat/chat_room_notifier_redundant_decrypt_test.dart(RED onmain): a second relay delivery does not unwrap again; a history reload reuses the live unwrap — both with real crypto against the in-memory storechat_room_notifier_security_test.dart— all pins green, including "an event the background already persisted still reaches the UI" (which drove the cache-aware skip design)flutter test— 1195/1195flutter analyze— no new issues🤖 Generated with Claude Code
https://claude.ai/code/session_018fTxqxhpdL5siTgKZqwtur
Summary by CodeRabbit
Performance Improvements
Reliability
Tests