fix(node): chat is bounded in size and in rate

2026-09-13T18:28:52Z

A chat message is the plainest member-supplied write there is: the node stores it in `chat.db`, where nothing expires it — retention is a manual command (§6.6) — relays it to every other connected member, and has the hub write a notification for every member of the group. Nothing bounded any of it. The only ceiling was the DataChannel frame, 64 MB once the handshake is done, so one member in a loop filled the operator's disk and saturated everyone else's connection, and the node's answer to each message was `ack`. Uploads, the other member-supplied write, have carried a filename allowlist, strict chunk ordering, a no-overwrite rule and a 4 GB cap since C5a — because somebody asked what one member costs the others on that path. Nobody had asked it on this one. Two bounds, for the two halves of the question: **64 KB of ciphertext** for what one message may cost, and **60 a minute per account per group** for how often one member may impose it. Both are checked before anything is stored or relayed; a refusal names itself and is audited, so "why is my disk full" has an answer. The rate is keyed by account, not by connection: a second tab does not make anyone type faster, and keying on the session would hand a script one budget per socket it opens. No node-wide ceiling beside it, deliberately. The link-preview limiter has one because a preview spends the *node's* egress and its third-party quota, which is one shared thing; a chat message spends the sender's own group, and a node-wide ceiling would let a busy group silence a quiet one — this same defect one level up. The last test in the new file is that property: a member at their limit has not spent anybody else's. Two things stay open on purpose and are named rather than quietly done: retention still keeps everything, because a default that deletes people's history is not a review's call; and the composer still offers to send an oversized message, so this is §6.4's pattern with only the node half built. §6.6 gains the rule, §13.5b the label — AV20, with AV21–AV23 registering the three fixes this week that closed the same kind of gap elsewhere. Co-Authored-By: Claude Opus 5 Claude-Session: https://claude.ai/code/session_01UMxEQadpzPkYLFf5CYKhpW

meshbay.git/packages/meshbay-node/tests/test_chat_is_bounded.py, branch 0.14

fix(node): chat is bounded in size and in rate