See the [tool-output spill decision](../../.agents/notes/implemented/architecture/2026-07-08-tool-output-spill-files.md) for the boundary between storage, retention, and tool-owned output handling.
The subsystem reference — `SaveTextSpill`, owners/sources, the branded locator — is [docs/subsystems/spill.md](../../docs/subsystems/spill.md); rationale in the [tool output spill Agent Note](../../.agents/notes/implemented/architecture/2026-07-08-tool-output-spill-files.md).