deepseek-harness/docs/rfc/implemented/simplification/2026-06-20-drop-unconsumed-llm-assembled-surfaces.md

RFC: Drop unconsumed assembled LLM convenience surfaces

Status: implemented

Problem

LlmService (packages/llm/llm/src/index.ts) exposes three call surfaces over a model:

• stream() — raw StreamChunks, dispatched through the llm/stream waterfall.
• streamBlocks() — a "convenience view" that runs the chunks through a BlockAssembler and yields completed ContentBlocks in stream order (index.ts:137-144).
• generate() — one fully-assembled GenerateResult, dispatched through a second llm/generate waterfall (index.ts:151-157).

The only production consumer of the LLM service is the agent loop, and it uses stream() exclusively — feeding raw chunks through its own BlockAssembler so it can log chunks for replay fidelity while assembling in parallel (packages/core/agent-loop/src/loop.ts, the ctx.llm.stream(req) step). Grepping streamBlocks and ctx.llm.generate across packages/*/src and examples/*/src finds no production callers. The references are the service methods, docs, and tests; adapter tests use generate() as a convenient driver, but they can hand-drain stream() through the same assembler helper without preserving a public production API.

This is the drop-mutable-session-summary pattern: assembled-view APIs with tested contracts, consumed by tests rather than production. They were built speculatively for consumers that do not care about token-level deltas, but the one real consumer cares about deltas precisely so it can persist high-fidelity replay data.

streamBlocks() drags a dedicated slice of BlockAssembler behind it: flushReady() and flushRemaining() (packages/llm/llm/src/assembler.ts:138-168) plus the flushed cursor field exist only to support incremental in-order yield. generate() drags GenerateResult, BlockAssembler.result(), and the llm/generate waterfall as a second interception surface over the same underlying stream. The loop's assembler usage is push() / message() / usage / finish — not streaming flush or one-shot service assembly.

Decision

stream() is the sole public LLM call surface. Remove streamBlocks, generate, its event/result types, and assembler helpers used only by that path. Adapter tests assemble the public stream through a local helper, while BlockAssembler retains only the operations with production consumers.

Alternatives considered

Keep generate() as a test-only convenience — rejected: adapter tests hand-draining stream() through the shared assembler exercise the same streaming path production uses, and a public method whose only callers are tests is exactly the dead-surface shape the drop-mutable-summary precedent retired. A future consumer that wants assembled blocks without deltas reintroduces a focused helper with that consumer.

Verification

streamBlocks, generate, llm/generate, and the assembler helpers they alone required are gone with no new dead exports; both real adapters are exercised through stream() and the shared assembler; the loop behaves identically (ACP snapshot goldens unchanged); and the README, architecture doc, and module docs carry no mention of the removed surfaces.

Consequences

• It removes public methods from a core vocabulary package. A future plugin that wants assembled blocks without deltas would need to call stream() and use BlockAssembler directly or reintroduce a focused helper with a real consumer. Given the pre-release "foundation over speculative future" stance (AGENTS.md), this is the right time to cut test-only public shape.
• Adapter tests get a little more explicit. They lose the ergonomic generate() wrapper, but that is useful pressure: tests exercise the same streaming path production uses.
• Waterfall users lose llm/generate. No production listener exists. Any future caching/retry/logging plugin should wrap llm/stream, which remains the single provider call path.

The size is modest, but it is a clean removal of speculative surface area from the LLM package, leaving one model-call contract for both production and tests.