deepseek-harness/docs/rfc/implemented/simplification/2026-07-04-drop-inert-request-knobs.md

RFC: Drop GenerateOptions.prefill and ToolSchema.strict — request knobs with no working end-to-end path

Status: implemented

Problem

Two request-contract knobs rode the whole request pipeline, yet neither could do anything:

• prefill (packages/llm/llm/src/types.ts) had no production setter — the loop assembles model/system/tools/messages plus sessionId/signal, and the compaction backend adds only maxTokens — and BOTH adapters rejected it: packages/llm/llm-deepseek/src/serialize.ts and packages/llm/llm-pi-ai/src/adapter.ts each threw LlmError('UNSUPPORTED') on a non-undefined prefill. The field's entire observable behavior was two throws, each pinned by one adapter test. DeepSeek's chat-prefix completion is a Beta feature on a base URL neither adapter targets.
• strict (ToolSchema, same file) was threaded through DefineToolOptions/defineTool (packages/core/tools/src/schema.ts), the registry's schemas() allowlist (packages/core/tools/src/index.ts), the deepseek wire mapping (packages/llm/llm-deepseek/src/serialize.ts, whose wire-type note recorded that strict mode requires the /beta base URL the adapter does not use), a per-tool payload-patching pass in packages/llm/llm-pi-ai/src/adapter.ts, and a conditional Strict: row in the tool-catalog renderer (scripts/gen-tool-catalog.ts). No shipped tool set it — rg across every tool-* package src and examples/ found zero strict: producers; the only setters were dsh-tools unit tests.

Both knobs were adapter-symmetric, so removal shed them from both twins together — the twin-adapter design is untouched.

Decision

• prefill is removed from GenerateOptions, along with both adapters' UNSUPPORTED guards, the tests pinning the throws, the paste line in core.md, and the adapter README rows documenting the rejection. The cookbook's UNSUPPORTED guidance (adding-an-llm-adapter.md) states the rule generically — a GenerateOptions field your provider cannot honor throws LlmError(..., 'UNSUPPORTED') — instead of using prefill as the example. The content-block vocabulary RFC's consequences record prefill as producer-gated rather than as having a home, per implemented/AGENTS.md.
• strict is removed from ToolSchema, DefineToolOptions, defineTool, the schemas() allowlist, the deepseek serializer branch and its wire-type field, and the tool-catalog renderer's Strict: row. The pi-ai payload fixup is simplified to the unconditional scrub of pi-ai's own per-tool strict default (pi-ai stamps strict: false on every serialized tool; the hand-rolled twin sends no such field, so the scrub survives for wire parity, pinned by its serializer test). The setter tests and the core.md paste line are gone; both GenerateOptions and ToolSchema keep their rows in scripts/type-equiv.manifest.json, since each type survives minus a field.

This RFC deliberately does NOT touch temperature, stop, or maxTokens: those are honored end-to-end by both adapters and are the natural first targets of a request-mutating hook plugin on agent/request.

Alternatives considered

Why not keep them?

"An explicit UNSUPPORTED throw is honest contract behavior" — but a knob whose only implementation across both twins is rejection promises nothing, and deleting it upgrades the failure mode: an accidental setter becomes a compile error instead of a runtime throw. "Strict schema adherence is an officially documented provider feature with complete plumbing" — but a knob is not product surface until a shipped tool sets it AND an endpoint honors it; today neither is true. Each returns with its first real producer: prefill together with an adapter that implements chat-prefix completion (and a stated policy for adapters that do not), strict together with a tool that wants it and a beta-endpoint story.

Verification

rg prefill returns only RFC records (this one and the content-block vocabulary RFC's producer-gated consequence); a tool-schema-scoped rg strict returns only this RFC, the surviving pi-ai scrub, and unrelated prose such as strictEqual. Both adapters' contract tests pass without the guards, and the pi-ai fixup still scrubs the library's strict default — wire parity pinned by its serializer tests.

Consequences

The shipped hook bridges set no request fields at all, and a request-mutating plugin (an agent/request waterfall listener) reaches for temperature/stop (kept, working), not a field adapters reject. If chat-prefix completion or strict mode become product features, the re-add lands with the adapter/endpoint work, where the contract can say what actually happens rather than "everyone throws".