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Tianyi Cui 066f94c7e0 docs: unwrap hard-wrapped Markdown to one line per paragraph

Hard line breaks mid-paragraph make docs harder to edit and diff — a
one-word change reflows and re-diffs the whole paragraph. Reflow all
tracked non-vendor Markdown (plus vendor/AGENTS.md) so each prose
paragraph is a single line; soft-wrapping is the editor's job. Fenced
code, tables, and list structure are preserved (wrapped list items fold
to one line per bullet). Documents the convention in AGENTS.md.

2026-06-13 20:27:04 +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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