Paul HittandClaude Opus 4.8
79c2734f86
The last client. A recipient mints a batch of random tokens per contact, uploads only their hashes, and hands the tokens over inside the ratchet; a sender spends one per message; revoking one contact is dropping one batch, and nobody else notices. The batch rides the existing `delivery_key` envelope rather than a new control kind, because a receiver recognises control traffic by KIND first and falls back to the `ctl` flag only for kinds it has never heard of — and this engine reads that flag with `optBoolean`, which does not coerce the number §6.10 calls for. A `delivery_tokens` kind would have arrived on the phones already out there as a bubble full of raw JSON. Replenishment is counted rather than requested, for the same reason: a "running low" message would have been another new kind. The issuer can count on its own, because every message it receives from a contact spent one of their capabilities, and it mints afresh at half a batch. A refused capability means the batch was revoked, so the rest is discarded and the same envelopes are re-sent on the shared key — they are addressed to the device, not to the authorisation. That is not a way around revocation, and the code says so: revoking moves a sender back onto §14.4's key, it does not silence them. One bug the tests found. `consumeControl` read the peer's delivery key first and bailed with `loadDelivery() ?: return`, so a device that had not published a key of ITS own yet — every device before `ensureDeliveryKey` runs — silently dropped everything in the envelope, capabilities included. Capabilities have their own store and no such dependency, so they are handled before that early return. Verified against a locally-run relay carrying the §21 work as well as by the unit suite: 126 capability hashes on the relay after the live run, so the path is exercised rather than mocked past. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Flamenet Messenger — Android
The Android app, and the two libraries under it.
engine/ the protocol: X3DH, Double Ratchet, sealed sender, safety numbers,
key transparency. Plain Kotlin/JVM — no Android in it at all.
client/ the relay transport: HTTP, auth, the §8 routes.
app/ the Compose app.
interop/ the cross-engine driver; not shipped.
engine and client are deliberately plain JVM libraries. The protocol has
nothing to do with Android, and keeping it off the platform means their tests
run anywhere a JVM does — no SDK, no emulator, no device, which is also what
lets them gate in CI on Linux:
./gradlew :engine:test :client:test
The app's own unit tests need the Android SDK but still no emulator (Robolectric):
./gradlew :app:testDebugUnitTest
Where it stands
PARITY.md is the definition of done for this app — read that, not this. Every row there names the iOS file it came from so it can be re-checked rather than trusted. Headlines as of 2026-08-28: messaging, groups, attachments, voice notes, stories, calls, sealed sender, key transparency and the encrypted vault are built and tested; a cross-platform round trip against iOS was verified on 2026-08-26.
⚠️ This file said "Nothing here is an app yet" until 2026-08-28, above a tree containing the finished app — the README described the repository as it was when the engine landed and nothing updated it as the app grew around it. If a claim here ever disagrees with PARITY.md or with the tree, believe those, and fix this.
Why the engine came first, and is held to the vectors
An Android client needs the protocol implemented a third time, and the third
implementation is the one that finds the places where the specification says
less than the two existing engines quietly agreed on — but only if it is
written against the spec and the published vectors rather than against a
reading of our own Swift and JavaScript. So the engine is held to
test/vectors/protocol-v1.json in
flamenet-e2e — the same file the
other two engines are checked against, read from that repository rather than
copied here, because a copied vector file drifts and a drifting vector file
stops being a check. PublishedVectorsTest looks for it beside this checkout
and fails loudly if it cannot find it; FLAMENET_VECTORS overrides the search.
Two implementations that agree may both be wrong in the same way, especially when one was written while reading the other. The audit-path ordering in §19 is the worked example: a top-down reading of a bottom-up path produces the correct root for every left-spine index, so it passes any test that only checks index 0. The vector file pins a right-descending index for that reason, and the Kotlin tests assert both that the published path verifies and that the same path reversed does not.
If this engine ever disagrees with the file, the interesting question is which of the three is wrong — not this one by default.
Contributing and security
- CONTRIBUTING.md — building (JDK 21,
JAVA_HOMEis not optional on a Mac), the test gate, and the platform traps that cost an hour each. - PARITY.md — what iOS does, what this does, and what is left. It is the definition of done for this app.
- SECURITY.md — threat model and where to send a vulnerability report. Not an issue tracker matter: security@flamenetmessenger.com.