The context browser read the system row's item count from
`header.systemTokens`, a field only the post-#37 metadata wire shape
carries — but a host still running the pre-#37 view (a stale watch
build, an app not restarted since the upgrade) delivers content-bearing
epochs where the system TEXT rides the value instead. The row then read
0 项 while the ≈tokens figure still rendered, because the two come from
independent projections. Diagnosed against a real session: the cached
projection row was pre-#37 shaped, holding a 6261-char system string
(≈1570 tokens shown, count 0).
`headersOf` now normalizes both generations: unpriced legacy entries get
the meter's own heuristic, priced entries and new-shape values keep the
zero-copy pass-through. The heuristic (ceil(chars/4) + 4) moves to
shared/estimate.ts so the host fold and the client boundary price
identically. Regression tests cover the boundary matrix and the browser
row through the real call path; the #37 slimming itself is untouched.
Bowen Liang
07aae76261