Consolidates the persisted-plaintext-decrypt-cache pattern (already used by watch
history) into a shared factory, persistedPlaintextCache.js, and adds a DM cache
on top of it. watchHistoryDecryptCache now delegates to the factory (same public
API; tests unchanged).
decryptDirectMessageEvent now also consults/writes a persisted cache keyed by the
immutable DM event id (JSON of the decrypt result; flushed once per
listDirectMessages batch; cleared on logout alongside the in-memory cache). DM
events never change, so a reload re-decrypts only messages it has not seen and
skips the (serialized, slow) nip-07 extension for the rest.
Harness (dm-repro, now cold/warm): 20 DMs -> COLD nip04.decrypt 50, WARM 0 —
reloads cost zero extension decrypt calls. Also excludes the actor's own key from
NIP-04 remote candidates (decrypting against self is always wasted). DM unit +
integration and watch-history cache tests green.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
The DM-repro harness (fake nip-07 extension) showed legacy DM history made ~12
extension decrypt round-trips PER message (20 DMs -> 241 calls: nip44.decrypt
121 + nip04.decrypt 120). At a real ~100ms extension latency that's ~24s, which
is why DM history "looked broken" — it was just catastrophically slow.
Two causes in decryptLegacyDm:
- It raced EVERY (decryptor x remote-pubkey) combination in parallel. That looked
like a latency win, but the nip-07 extension serializes calls, so racing N
combinations just queued N slow round-trips per message.
- orderDecryptors ranked nip44 first (by candidate priority), so every kind-4
(always NIP-04) message burned a failing nip44 extension call first.
Fix: order nip04 first for legacy DMs (preferLegacy) and try candidates
SEQUENTIALLY, stopping at the first success. With the right scheme and remote
party tried first, it's ~1-3 calls/message instead of ~12. Harness after: 20 DMs
-> 60 calls, zero nip44 attempts (was 241). DM unit + integration tests green.
Adds scripts/perf/dm-repro.mjs (seeds kind-4 DMs, logs in via the fake extension,
calls listDirectMessages, reports decrypted count + extension call counts).
Co-Authored-By: Claude Opus 4.8 <[email protected]>
