* fix(shadow_eval): tell a tool-call shadow reply apart from an empty one
Both arrive at the attempt row as the same 'shadow router returned an empty
response', because _chat_final_text returns empty for a tool-final turn by
design and for a reply that genuinely carried no text. Those are different
things: an arm that chose a tool where the real model wrote prose is a
divergence a text judge cannot score, and the sampling side already drops the
real arm's tool-final turns for exactly that reason, so the shadow side reads
as a fault where the real side reads as a filter. A job that is almost all
'empty response' gives no way to tell a tool-happy arm from a broken one.
The error now names which of the two happened, and carries the finish_reason
and the routed model so the row says what the arm was doing. Every varying
part sits behind the first semicolon: operators read these by grouping on the
error text, and interpolating the model into the leading sentence would make
each row its own group.
The outcome stays 'error'. Whether a tool-call reply should instead be its own
non-judged outcome, excluded from the loss rate the way the real arm's
tool-final turns already are, needs the four aggregation predicates that spell
judged as outcome != 'error' rewritten, and a decision on how to surface the
new bucket. That is a separate change.
* fix(shadow_eval): read the tool name of a custom tool call
A custom tool call carries its name under custom.name with no function key,
so every one of them reported as tool=unnamed.
* feat(shadow_eval): judge tool calls instead of dropping the turn
A turn where either arm called a tool was discarded before it could be
compared: the real arm's at sampling, the shadow arm's as an error row. On
agentic traffic that is most of the traffic, so a job set to sample 10% was
sampling 10% of the prose-only slice. Tool calls now serialize to text on
every surface and are judged like any other response, and the judge is told
a tool call is not a defect so it scores the choice rather than the shape.
* feat(shadow_eval): show the judge what tools were available
Both arms were offered the same tools, but the judge only ever saw the
chosen call in isolation, with no way to tell whether a better tool existed
or the arguments matched what the tool expects. Threads the request's tool
definitions (name and description only) into the judge prompt, capped and
omitted entirely on turns that offered none.
* fix(shadow_eval): read a custom tool definition's name from custom, not function
A chat-completions custom tool definition nests name and description under
custom, mirroring how a custom tool call nests them (openai.types.chat.
ChatCompletionCustomToolParam). Reading only function rendered every one as
unnamed, telling the judge nothing about what it was.
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