Rubric / Performance
Time to first byte
performance.ttfb_ms
weight 1heuristic
Time-to-first-byte is under 800ms from a US-East origin. Measured as a single sample of total fetch time from one location, so treat it as directional.
Definition
Check ID
performance.ttfb_ms
Category
Performance
Weight
1
Counts toward the score
Yes.
Evaluated by
A fixed rule whose threshold AgentSpeed chose. Reproducible; another rubric may reasonably disagree.
Chosen parameter
threshold = 800ms
Standard maturity
established
Canonical spec
Introduced in
r2026.04.1
Retired in
Still active.
History
Every change to the instrument— including the versions that changed this check
Machine-readable
/rubric.json— this check, and every other, as data
How often this check is right
No rate published. Too few labelled cases to publish a rate: 1 flagged case (30 needed to publish), 1 defective case (30 needed to publish). The counts are the honest answer here. The matrix behind performance.ttfb_ms is 4 labelled cases — reported here rather than turned into a percentage that would read as more certain than the evidence is.
Corpus v1, measured under rubric r2026.11.0. Full method and every other check at /rubric/accuracy.
How to fix it
Agents time out aggressively. Use edge caching for anonymous requests to cut TTFB below 800ms.
Does your site pass this check?
Free scan, 30 seconds, no signup — this check and the other 35, with the exact evidence for each verdict.
Scan my site →