Document latency limits for voice simulations

[scott-lowe-vapi]

Summary

Voice simulations can now fail when the assistant responds too slowly. The feature shipped in VapiAI/vapi#21959 (API and worker), VapiAI/vapi#21962 (run results) and VapiAI/vapi#21963 (editor), tracked in TEST-140. The API reference already shows the new latencyExpectations and latencyEvaluations fields through the nightly spec update; this PR covers the guides.

• Simulations advanced: new Set latency limits section and card:
  • Dashboard and cURL setup;
  • the turn, model and voice metrics and the four aggregations, including that p95 equals max under 20 turns;
  • required versus optional limits;
  • when limits are skipped (chat mode, GPT-Live assistants under test) and that a voice run with no measured turns fails;
  • reading results in the run details and through results.latencyEvaluations;
  • two troubleshooting rows.
• Simulations overview: the scenario definition, the "how it works" paragraph and the Evals comparison table now mention latency limits next to structured outputs.
• Manage simulations: run results mention latency results and latencyEvaluations, "Design evaluations" points to latency limits, and the voice-or-chat table gains a "Gate on response latency" row.
• GPT-Live testing: notes that latency limits are skipped when the assistant under test uses GPT-Live.

Every behavior described was checked against the merged code: field names, the default of a required median turn latency of 1,200 ms, the 1 to 60,000 ms range, the 20-limit maximum and the skip rules.

Not included

A "What's new" changelog entry. The weekly changelog files look curated by one author (e.g. #1280), so I left the entry to the next weekly post. Happy to add it here instead.

Testing

fern check with the pinned CLI 5.112.0 (node scripts/fern/run.cjs check): 0 errors. The 14 warnings are pre-existing discriminator warnings in the API spec. The preview link from CI is the place to check rendering.

🤖 Generated with Claude Code

[lightsage-app]

Lightsage docs evals

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Docs URL: https://vapi-preview-01a11374-b04e-771e-a168-40438c9b76a6.docs.buildwithfern.com
Commit: d95a911
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[stephenvapiai]

Two suggested wording changes for the latency limits section. Each suggestion can be accepted independently.

[github-actions]

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