Begin the coven evolution of cmd-chat (see docs/spec-collaborative-sandbox.md):
a Rust/ratatui client for the unchanged Python Sanic server, plus the
multi-user + zero-knowledge groundwork.
P0 — crypto parity (the spec's #1 risk), proven three ways:
- Hand-rolled SRP-6a (NG_2048, SHA-256, rfc5054 padding) matching pysrp
byte-for-byte, incl. the fixed b"chat" SRP identity and minimal-vs-256B
width quirks. Golden-vector unit test + offline selftest.
- Live handshake against the running server (H_AMK verified).
- Cross-language E2E: Python client decrypts a Rust-encrypted Fernet message.
P2 — multi-user coven (server):
- CMD_CHAT_MAX_USERS capacity cap (default 4, infra-for-more).
- Authoritative roster + user_joined broadcasts.
- Free the slot/username on ws disconnect (was held until 1h stale sweep).
Also: fix requirements.txt (was UTF-16, unparseable by pip).
coven/ : Rust crate (crypto.rs proven; main.rs spike CLI: selftest/handshake/srpm)
docs/ : full feature spec for the 6 requested features.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
