CLAIM-2026-09-04-01

In a session trace of one 800-line backend change, Sonar recorded 512 model round-trips, a context window peaking at 458,700 tokens, 152.8 million cache-read tokens ("the re-billed transcript") and an approximate session cost of $41.

Why it matters

It is the first published per-PR trace precise enough to separate what an agent reads from what it re-reads. The re-billed transcript, not the context window, is the quantity a deployer has to be able to account for.

Sources

• sonar2026smarter