Map constructs to observable evidence

Contract: references/interaction-contract.md. Calibration, templates, provenance: references/evidence-map.md.

Trigger

• A construct appearing in no trace field: helpfulness, trustworthiness, safety.
• A behavior spec's review questions needing observable signals.
• Scorers that exist but nobody can say what they are evidence of.

Do

1. For each construct, fill four columns before asking anything: success evidence, failure evidence, limitation (what this signal misses), gaming path (how to raise it without improving the outcome).
2. Require more than one proxy for any consequential outcome — several independent proxies make it harder to win the eval without improving the product.
3. Apply the usefulness test: closely connected to the outcome, covers its most important dimensions, hard to improve without improving real behavior.
4. Surface the most consequential blind spot explicitly and label it Not yet measurable rather than substituting a convenient proxy.
5. Mark evidence the system cannot currently produce. That list is what the trace schema has to be extended to cover.

Avoid

• Do not invent field names or schemas; that is the next skill.
• Do not write scoring logic or thresholds.
• Do not treat chain-of-thought or a self-reported rationale as behavioral evidence — it is a claim about behavior, not a record of it.
• Do not stop at success evidence. Failure evidence is what makes a scorer discriminate.

Check

• Every construct has success evidence, failure evidence, ≥1 limitation, ≥1 gaming path.
• Consequential constructs carry multiple independent signals.
• Blind spots stated rather than papered over; uncapturable evidence flagged.

Risk

• Weak proxies look precise. Latency, token count, and polish are easy to measure and routinely stand in for outcomes they do not track.
• Process-compliance evidence ("called the right tool") can diverge entirely from outcome evidence ("solved the user's problem"); mapping only one produces a confident, wrong conclusion.
• Proxies chosen from what is already logged encode last year's instrumentation as this year's construct.

Braintrust

Each signal must be locatable in a span. Signals about what the agent did come from tool-call spans, so they exist only if the agent is instrumented at that granularity. Signals about the output come from the top-level span. Signals you want to slice by are metadata, not evidence — do not conflate them: evidence is what you score, metadata is how you group scores. One signal, one scorer (references/platform-mechanics.md §5), so the multi-proxy requirement shows up as multiple columns; two signals in one scorer breaks the gaming-path analysis because you can no longer see which proxy moved. A Not yet measurable blind spot vanishes once numbers start appearing — record it in the dataset or experiment description, and where it matters to a gate, prefer a documented unimplemented placeholder over omitting the dimension and letting its absence read as a pass.