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Tianyi Cui 4dafad4db6 Add RFCs for the remaining quality-proposal ideas

Eight proposals grouped by category, each with problem statement,
concrete plan, and risks: property-based testing over the
protocol-shaped core (chunk streams, event logs, schema DSL);
mutation testing as the counterweight to the 100%-coverage gate;
deterministic tests + a universal replay-invariant fixture + nightly
race stress; architectural conformance (dependency-cruiser rules and
the LlmAdapter conformance kit); runtime arg validation at the model
boundary with a structured error taxonomy and dev-mode invariants;
doc-sync enforcement (typechecked doc snippets, API reports);
supply-chain checks and nightly vendor-drift verification against the
manifest; and deep-readonly public surfaces (logged-vs-in-flight
mutability boundary). AGENTS.md points at docs/adr and docs/rfc.

2026-06-11 15:27:07 +08:00

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RFC 005: Runtime validation at the model boundary, error taxonomy, dev-mode invariants

Status: proposed

Problem

Three gaps where compile-time guarantees stop:

Tool args are model-generated JSON — defineTool's InferArgs<S> claim is only as true as the model's output. Today a malformed call reaches execute untyped-in-practice.
Tool errors flatten to a text block; name/code/stack are lost, so future sandbox/retry plugins can't distinguish ENOENT from EACCES, and the model gets less actionable feedback than it could.
Loop ordering invariants (seq monotonicity, step/turn event nesting, turn-number continuity) are asserted only where tests look.

Proposal

Schema validation in defineTool: before execute, validate parsed args against the SchemaSpec (the converter already encodes the structure — a small interpreter walks it: presence of required keys, primitive type checks, enum membership, recursion into objects/arrays). On mismatch, return an isError ToolExecutionResult describing the violation — the model can self-correct. Raw-registered tools (MCP) keep validating their own input.
Structured error taxonomy: per-package error classes extending a common HarnessError (name, code, cause chaining). ToolExecutionResult gains optional error: { name, code } alongside the model-facing text. The loop's errorData consumes it; session error events carry the code. This also properly fixes the non-Error-throw message degradation found in review.
Dev-mode invariants: a dsh-invariants debug plugin (everything is a plugin — it's just listeners) asserting, when enabled: session seq strictly increases; step/start precedes its chunks; turn/start/turn/end pair and nest; tool/call has a matching tool/result; status transitions are legal. Enabled in tests and the demo; off in production. Doubles as executable documentation of the event contract.

Plan

2 first (taxonomy is a dependency of 1's error shape), then 1, then 3. Property tests (RFC 001) then close the loop: generated args ↔ validator ↔ InferArgs agreement.

Risks

Validator/InferArgs drift — covered by the RFC 001 composition property. Validation cost per call is negligible next to a model call.

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