shrinkCluster keeps an oversize cluster's highest-importance member WHOLE on
purpose — an empty file section sends the agent to Read, the outcome explore
exists to prevent. What it lacked was a bound, and "never empty" quietly meant
"never bounded": on the reporting repo one file emitted 22,376 chars against a
9,181-char reservation (2.44x), past both the per-file budget and the spine
ceiling. That overshoot is what collapses `headroom` for every file below it.
The same rule has a second face. When the top member is bigger than the whole
response ceiling, the file does not overshoot — it is dropped entirely at the
renderCeiling check, so the agent gets nothing for a file it named.
renderCluster now takes a ceiling (1.5x what the file may spend — the same
multiple SPINE_CEILING already draws, and never below the cap, so a cluster
that fits is untouched). Past it the member is WINDOWED on whole lines rather
than emitted whole or dropped: leading window plus, on a flow cluster, a window
on the spine's call site. A partial window shorter than 12 lines is dropped
instead — a sliver in the session record forces the next call's dedup to shred
the block around it or re-send it — unless nothing else was emitted, where the
never-empty floor wins.
Measured on the new fixture, pre-fix vs post-fix:
monthly.ts 12,391 chars on a 3,334 budget (3.7x) → 4,941 (1.48x)
quarterly.ts dropped, no headroom left → 4,004 delivered
Also: the diagnostic now reports `spendable` (reservation + inherited slack)
alongside `reserved`. Every render bound reads the former, so reporting only
the latter makes an ordinary carry-forward read as a file spending over budget
— and it made the overshoot this issue is about unmeasurable. A windowed file
is now flagged `clipped` too, instead of presenting a window as the whole file.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Colby McHenryandClaude Opus 5
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