ZIm/crates/language_model/src
Bennet Bo Fenner 7be57baef0
agent: Fix issue with Anthropic thinking models (#33317)
cc @osyvokon 

We were seeing a bunch of errors in our backend when people were using
Claude models with thinking enabled.

In the logs we would see
> an error occurred while interacting with the Anthropic API:
invalid_request_error: messages.x.content.0.type: Expected `thinking` or
`redacted_thinking`, but found `text`. When `thinking` is enabled, a
final `assistant` message must start with a thinking block (preceeding
the lastmost set of `tool_use` and `tool_result` blocks). We recommend
you include thinking blocks from previous turns. To avoid this
requirement, disable `thinking`. Please consult our documentation at
https://docs.anthropic.com/en/docs/build-with-claude/extended-thinking

However, this issue did not occur frequently and was not easily
reproducible. Turns out it was triggered by us not correctly handling
[Redacted Thinking
Blocks](https://docs.anthropic.com/en/docs/build-with-claude/extended-thinking#thinking-redaction).

I could constantly reproduce this issue by including this magic string:
`ANTHROPIC_MAGIC_STRING_TRIGGER_REDACTED_THINKING_46C9A13E193C177646C7398A98432ECCCE4C1253D5E2D82641AC0E52CC2876CB
` in the request, which forces `claude-3-7-sonnet` to emit redacted
thinking blocks (confusingly the magic string does not seem to be
working for `claude-sonnet-4`). As soon as we hit a tool call Anthropic
would return an error.

Thanks to @osyvokon for pointing me in the right direction 😄!


Release Notes:

- agent: Fixed an issue where Anthropic models would sometimes return an
error when thinking was enabled
2025-06-24 16:23:59 +00:00
..
model language_model: Remove CloudModel enum (#31322) 2025-05-24 02:04:51 +00:00
fake_provider.rs Standardize on u64 for token counts (#32869) 2025-06-17 10:43:07 -04:00
language_model.rs agent: Fix issue with Anthropic thinking models (#33317) 2025-06-24 16:23:59 +00:00
rate_limiter.rs More resilient eval (#32257) 2025-06-09 18:07:22 +00:00
registry.rs Distinguish between missing models and registries in error messages (#32678) 2025-06-13 10:31:52 +00:00
request.rs agent: Fix issue with Anthropic thinking models (#33317) 2025-06-24 16:23:59 +00:00
role.rs language_model: Remove dependencies on individual model provider crates (#25503) 2025-02-24 16:41:35 -05:00
telemetry.rs Don't spawn Anthropic telemetry event when API key is missing (#32813) 2025-06-16 14:58:37 -04:00