A new beta header is added to the centralized header registry: token_efficient_tools → token-efficient-tools-2026-03-28. The whole registry was reorganized to use Object.freeze({ name, header }) records, making it easier to enable/disable individual betas server-side via stickyBetas.
Evidence
Beta header registry (search for "token-efficient-tools-2026-03-28").
Strings lifted out of the shipped bundle, so the claim above can be checked against them.