three defects, one shape: the code has two names for "which session is this",
and every guard checked the one no caller uses.
`fable` is the FIRST entry in the claude-code catalogue, so it is what
ModelSelector picks whenever it decides a conversation needs a default. On a
key without fable entitlement that lands as a 429, after a real mid-session
switch — the reported header read OPUSPLAN → FABLE.
1. the settings default was applied to RESUMED chats. the guard was
`!initialSessionId`, and no chat caller passes that when resuming — the id
arrives as `options.resumeSessionId`, and ChatPanelWrapper goes as far as
`resume ? undefined : sessionKey`. so a user's default model was written
over sessions that already had one. both names are checked now.
2. `hasStarted` was `!!preloadedMessages?.length`, which is FALSE for the
first frames of a resumed chat — before its messages arrive. ModelSelector
reads "not started" as permission to pick a default, so a reload reassigned
live sessions during that window. a session id is known on the first render
and a chat that has one is by definition not new.
3. harness lock. `crossesHarness` returned false when the current harness was
unknown, which reads as "nothing crosses" and is the opposite of what is
known — with no current harness, everything might. so a started session
offered a switch to opencode while its model was still resolving, a switch
that cannot work: it hands a `ses_…` id to `claude --resume` and dispatches
to the wrong sidecar. unknown is not permission; the strip locks until the
answer arrives.
the settings themselves were never wrong — chat.defaultModel reads
claude-code/opus on the affected server. nothing was ever reading it for the
sessions that got reassigned.
pastilhas
fe7fe49cee
