Paul HittandClaude Opus 5
3b195c730c
A sticker is a content envelope carrying an id, never an image: sending the picture would cost an upload and a download of bytes both ends already ship with, on every sticker. This is about sixty bytes. Recognised before the text path on both sides, because a sticker is renderable but is NOT text - it draws as a glyph with no bubble, and falling through would render it as an empty message. An unknown pack or id has to degrade to the pack's fallback rather than break, which is what the envelope format exists for. The pack is one JSON manifest read by both clients, so there is a single source of truth for what exists. docs/STICKERS.md says plainly what the first cut is: the glyphs are Unicode, because real sticker art is a design job, not a code one. The protocol, picker, rendering, fallback and tests are real and finished; swapping in artwork is a change to the manifest plus an image loader, not to any of that. It is not a claim to have drawn a sticker set. Emoji are deliberately NOT this. They go into the text of an ordinary message and are indistinguishable from any other character once sent - no new kind, no new field, nothing for the receiver to understand. That picker is a keyboard convenience, not a protocol feature. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Flamenet Messenger — Android
Nothing here is an app yet. This is the engine, and it is deliberately first.
An Android client needs the protocol implemented a third time. That 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 comes first, it is a
plain Kotlin/JVM library with no Android in it at all, and it is held to
engine/test/vectors/protocol-v1.json — the same file the other two engines
are checked against, read from that one location rather than copied here.
./gradlew :engine:test
No Android SDK, no emulator, no device. It runs anywhere a JVM does, which is also what lets it run in CI on Linux.
What the engine covers today
| Area | Spec | State |
|---|---|---|
| Safety numbers | §7 | Done — fingerprints and conversation ordering match the published vectors |
| Key transparency verification | §19 | Done — RFC 6962 leaf/node hashing, unbalanced split, bottom-up audit paths |
| Byte helpers | — | Unsigned comparison, constant-time equality |
What it does not cover
Listed rather than left to be discovered, because a table of green ticks with the hard parts quietly missing is worse than no table:
| Area | Spec | State |
|---|---|---|
| X25519 / Ed25519 | §3 | Not started — needs a provider that works on both JVM and Android |
| X3DH key agreement | §4 | Not started |
| Double Ratchet | §6 | Not started |
| Sealed sender | §12 | Not started |
| ML-KEM-768 hybrid | §11 | Not started |
| ML-DSA-65 identities | §20 | Not started |
| Relay client | §8 | Not started |
| The app itself | — | Not started |
Until those exist, Android is honestly marked "not started" on the website, and a conversation gets the protocol's guarantees only when both ends are iOS.
Why the vectors matter more than the code
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.