As far as I can tell, the trace links are now missing from the histogram output, when they were there before.

Old histogram json, that has the trace links we expect.
https://isolateserver.appspot.com/browse?namespace=default-gzip&digest=021042ab2fcd03c9a9b3d5abcdf9946686471561&as=chartjson-output.json

New histogram json, that has "traceUrls" diagnostics, but they don't reference anything in the histogram set.
https://isolateserver.appspot.com/browse?namespace=default-gzip&digest=062f01903d4afd439769b9a5b080839d68f9b2ac&as=chartjson-output.json

BTW this is also tracked in Catapult at https://github.com/catapult-project/catapult/issues/4243

I briefly broke this last week, see https://github.com/catapult-project/catapult/issues/4232. However, it should be fixed at head.

Closing this out since there isn't much we can do here. Data isn't there in the broken range, so we can't recover in Pinpoint.

Can't we just bail out early if the trace links aren't present? That way we could finish the bisects, and they just wouldn't have trace links, right?

That's what I tried out originally, and then we ran into the same issue missing story tags diagnostics. Missing urls is totally fine, that just won't show up in the UI. Missing diagnostics like story tags isn't since we can't find the histogram at that point.

Yes, Simon's fix for ignoring DiagnosticRef will work for functional bisects, but if the story tags are missing, we can't find the metric, so we're hosed for perf bisects.