7c400e9c02
Collapse docs/adr/ and docs/rfc/ into a single docs/rfc/ with proposed/, implemented/, and rejected/ subfolders. Every file is renamed to yyyy-mm-dd-topic-title.md, where the date is when the topic was first proposed (from git history). ADRs and RFCs that covered exactly the same topic are merged (property-based testing, session persistence); the umbrella RFC 005 stays split across its three implemented decisions, and RFC 006's deferred part-3 (API extractor reports) splits into its own proposed RFC. All cross-references become machine-checkable relative links instead of bare "ADR NNNN" / "RFC NNN" prose. Add a verify-md-links doc-sync gate (scripts/verify-md-links.ts) that checks every relative Markdown cross-link resolves, wired into doc-sync alongside verify-md-wrap. This makes the reorganization self-verifying: the same change that rewrote ~forty inter-doc links adds the check that proves none dangle. Document the cross-link convention in a new docs/AGENTS.md and record the gate as an implemented RFC. doc-sync, typecheck, lint, and the full test suite (667) all pass.
27 lines
2.6 KiB
Markdown
27 lines
2.6 KiB
Markdown
# RFC: Structured error taxonomy
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Status: implemented (accepted 2026-06-14)
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<!-- XXX: legacy ADR/RFC body format, not yet normalized to a unified RFC template. -->
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## Context
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Failures crossed seams as bare strings. A tool error flattened to a text block — name, code, and stack lost — so a future sandbox/retry plugin couldn't tell ENOENT from EACCES, and the model got less actionable feedback than it could. A non-Error throw degraded further: the loop wrapped it in `new Error(String(x))`, dropping any code. And `LlmError` was the only typed error in the system, with no shared base, so there was nothing for a consumer to `instanceof` against generically.
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This is the last of the runtime-validation / error-taxonomy pieces and the one the user was most skeptical of, so it was deliberately built **last and in isolation**: the earlier PRs (arg validation, dev invariants) threw plain `Error`s with a `code` field, decoupled from any shared base, so this change is a pure upgrade and is independently revertible without unpicking them.
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## Decision
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A single `HarnessError extends Error` base in `dsh-llm` (the leaf package every other imports — no new dependency edge): a stable `code` distinct from `message`, `cause` chaining via `ErrorOptions`, and `name` defaulting to the subclass. `isHarnessError` narrows at seams.
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- `LlmError`, `ToolArgsError` (dsh-tools), and `InvariantError` (dsh-invariants) now extend it, keeping their existing codes.
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- `ToolExecutionResult` gains optional `error: { name, code }`, populated in the registry's catch when the thrown value is a `HarnessError`. The agent loop forwards it onto the `tool/result` session event (which gained the same optional field), so the structured failure survives into the log for retry/sandbox plugins and replay. The model-facing text block is unchanged.
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- The loop's `toError` wraps a non-Error throw in a `HarnessError` (`code: 'UNKNOWN'`, original chained as `cause`) instead of a bare `Error`, so even a bad throw carries a routable code into the session `error` event (which already surfaced `code`).
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## Consequences
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- Errors are machine-routable end-to-end: a plugin can branch on `error.code` rather than substring-matching a message.
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- One base class is imported widely, but it lives in the package everyone already depends on, so the cost is a single import, not a new edge.
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- `deriveMessages` does not surface `error` into model history — the model still sees the text block; the structured field is for code and replay.
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- Reverting this PR returns the earlier errors to plain `Error`+`code` form; nothing else in the stack depends on the shared base.
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