- spill-policy reserves the spill notice's byte cost inside maxInlineBytes, so the replacement (preview + notice) never exceeds the documented model-facing cap. When the notice alone fills the budget the preview is empty; when even a notice-only replacement is not smaller than the original, the inline result is kept (spilling would only add bytes). - retention TextRetainer trims an oversized single suffix chunk to the last suffixCap bytes on push, so tail/headTail retention stays bounded by suffixCap instead of retaining and re-copying the whole chunk in finish() — this is the spill preview path, which pushes the whole result as one chunk.
spill/ - spill storage capability family
The tool-output spill capability seam: an abstract storage interface, a local filesystem implementation, and the tool-result policy that uses it. All product packages.
| Package | Role | ctx key |
|---|---|---|
spill/ |
Abstract spill storage seam (saveText — persist oversized tool text to a session-scoped path) |
ctx.spillFiles |
spill-local/ |
Local-filesystem backend: private, session-scoped files with traversal-safe names | (registers on ctx.spillFiles) |
spill-policy/ |
tools/post-execute policy: replaces oversized plain-text results with a preview + spill path |
(no service surface) |
The interface lives at spill/spill/. The split mirrors bash/fs: the seam owns storage only, spill-local owns the filesystem mechanics, and spill-policy owns WHEN to spill and the model-facing notice. Preview mechanics stay in util/retention — the policy composes the two without either owning the other's job.
See the tool output spill RFC for the design rationale, including why final-result spill is separate from tool-owned early spill (bash streams, subagent rollouts) and why creation belongs to the runtime spill seam rather than the model-facing write tool.