The live MCP endpoint on 127.0.0.1 was a bypass of the collaboration
admission model. Its per-instance token authenticated only the ping probe
and shutdown, so document reads and writes were available to any local
process, and nothing validated Origin or Host — a page in a browser on the
same machine could reach it by DNS rebinding. During a session that is the
shared document, not just this user's file.
Every stateful call now requires the instance token, compared without an
early exit. Host must be a numeric loopback literal on the bound port, and
an Origin, when present, must match it; a request with no Origin still
works, which is what real CLI clients send. OPTIONS, initialize, and ping
stay tokenless so CLI discovery keeps working, and CollabGatePolicy is
untouched — this sits in front of it.
The `op` CLI did not send the token, so authenticating tool calls would
have returned 401 for every `op` invocation against a live editor. The
token was already in the port file next to the port; it is now resolved
with the port and travels as a header. Ping and shutdown keep their
existing tokenless wire contract.
Bootstrap cache: reads now degrade like writes already did. An unreadable
or corrupt cache leaves this start with no anti-rollback generation floor,
which is the position an absent cache has always left it in, and which the
threat model already accepts because deleting the file achieves the same
thing with no more privilege than corrupting it. Refusing bought no
security and cost the ability to collaborate at all. The tests state the
price plainly: with no floor the lower-generation document is accepted,
and `rollback_floor_armed` has to report it.
Threat model: correct an overstatement. Peer admission requires the remote
ticket's subject to equal the local account, so the product pairs only
devices of one account today. A relay operator reconstructs which devices
of an account sync and when — not a cross-account collaboration graph.
Also records that the relay reads exactly one field out of the ticket it
verifies, the expiry, which makes the identity disclosure gratuitous
rather than load-bearing, and states what a minimized credential would and
would not buy.
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