What
When the model you are using is blocked and Claude Code has to fall back to another one (reason model_blocked), the error it raises (FallbackTriggeredError) now carries the block message the server sent (blockMessage).
- The text shown to you, both when compaction fails and in the normal query error, is that block message if there is one.
- Otherwise it reads " is currently unavailable. Learn more: https://www.anthropic.com/news/". Before, it was always just " is currently unavailable." with no link.
A related gate, tengu_off_switch_query, appears nearby; nothing has been read about it.
Why
If a model is switched off or retired, you see the explanation given for it, or at least a link to look for one, instead of an unexplained "unavailable".
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
Where the server's explanation comes from is not stated.