deepseek-harness/packages/spill/spill/README.md

@deepseek-ai/dsh-spill

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The SpillStore (ctx.spillStore) defines WHAT a spill backend does — persist a tool's oversized text and return a model-facing locator plus retrieval guidance — without saying HOW.

This package is one third of the spill capability, split so each concern evolves (and swaps) independently:

Package	Role
@deepseek-ai/dsh-spill (this)	Service Definition: abstract service + vocabulary types
@deepseek-ai/dsh-spill-local	Service Provider: private session-scoped files on the host filesystem
@deepseek-ai/dsh-spill-policy	Consumer: the tool-result policy that spills oversized final results

The split mirrors the shell/fs seams. A future remote or virtual backend (e.g. a spill://… URI, a database key, or a backend-specific retrieval tool) implements this Service Definition without touching the policy plugin.

Service API (ctx.spillStore)

Member	Semantics
saveText(input)	Persist input.content verbatim; resolves with a SpillRef (opaque locator, exact bytes written, and retrieval hint). Rejects on a real storage failure (permissions, ENOSPC, backend unavailable) — the caller decides how to degrade.

Storage is grouped by the request's owner session as a save-time namespace; the backend chooses its own private representation and may derive names from — never trust as a path — the caller's suggestedName. The seam owns storage only: NO retention policy (that is @deepseek-ai/dsh-output-retention), NO tool-result replacement (that is @deepseek-ai/dsh-spill-policy), NO retrieval/search API (the backend's retrievalHint tells the model what to do with the locator).

Vocabulary

SaveTextSpill (owner, source, suggestedName, content) is the request; SpillRef (locator, bytes, retrievalHint) is the result. SpillLocator is branded and rendered to the model as an opaque string — a local path for dsh-spill-local, but a future backend may return a URI, key, or command token without changing policy/tool consumers. SpillOwner.sessionId is the save-time storage namespace: forked sessions inherit existing locators from the seeded log without copying or re-owning them, and new spills after the fork use the child session id. SpillSource records the producing toolName, callId, and label for backend naming and inspection, not access control. See src/types.ts for the full contracts.

See the tool output spill Agent Note for the design rationale, including why creation belongs to the runtime spill seam rather than the model-facing write tool.

Model Experience

Indirectly, through spill consumers that render a backend locator and retrieval guidance.

KV Cache effect

No direct invalidation; the named consumer owns any request-prefix changes.

Known Limitations and Deferred Work

• The seam has no retrieval or deletion API — consumers can only render the backend's locator and guidance; lifecycle and access semantics remain backend-specific.
• Storage is not access control — SpillOwner namespaces writes but does not authorize reads of a locator; each backend and retrieval consumer must enforce its own boundary.