Explain unclosed Mustache tag errors in scorer templates#203
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Explain unclosed Mustache tag errors in scorer templates#203paultancre-bt wants to merge 1 commit into
paultancre-bt wants to merge 1 commit into
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renderMessages surfaced the raw mustache error ("Unclosed tag at 216"),
whose number is a character offset users read as a line number. Convert
it to line/column plus a nearby snippet, matching the proxy renderer.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Braintrust eval report
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LLM-judge scorer templates render through
renderMessages, which calls rawmustache.render. When a scorer template has an unclosed tag, users get the bareUnclosed tag at 216— where the number is a character offset that reads as a line number. This is the error that surfaces in playground eval traces (the scorer step fails after the task prompt already succeeded).This mirrors the enrichment we added to the api-ts proxy renderer: convert the offset to line/column and append the nearby template text, e.g.:
Unclosed tag at 57 (line 3, column 21, near "…{output}}\nExpected: {{expected…"). Check for an unclosed {{ }} tag or {{#section}} block in the template.Non-string message content is still rendered exactly as before; only the error path changed. Test added in
render-messages.test.ts.Note: the Python side uses
chevron(different error format) and is unaffected.