The google provider called response.text after a chat completion and
passed the resulting string downstream unchanged. When Gemini's content
filter, recitation guard, or max_tokens ceiling fired, response.text
quietly returned "" — which the planner then reported as "no JSON block
found", masking the real cause. Empirically this failed in 45 ms on a
simple Quiz mission.
Introduces providers/errors.py with a small ProviderError hierarchy
(Blocked / Truncated / Auth / RateLimit / Capability). google.py now
inspects response.candidates[0].finish_reason and raises the matching
structured error; the non-streaming path maps it to 422/502/429 via a
new except-branch in main.py, and the streaming path surfaces the kind
as the SSE error type. Capability is wired but not yet used — it lands
with the tool-schema passthrough in the next commit.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
EventSourceResponse from sse-starlette adds its own 'data:' prefix,
so we should yield dicts with a 'data' key instead of pre-formatted
SSE strings. This was causing 'data: data:' double prefixes and
backticks appearing in chat messages.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
