Tianyi Cui
e6fad266a6
Define the in-file RFC contract in docs/rfc/README.md § The file format: the header block (`# RFC: <title>` plus a dateless Status enum cross-checked against the lifecycle folder), the per-lifecycle body skeleton (a Problem opener everywhere; Proposal/Alternatives considered/ Acceptance criteria/Risks in proposed/; present-tense Decision/ Consequences with proposal-era headings banned in implemented/; the frozen proposal shape in rejected/), and a mandatory Alternatives considered section with a date-fenced grandfather comment for pre-format RFCs whose alternatives are not reconstructible from the record. Enforce it with a new doc-sync gate, scripts/verify-rfc-format.ts, and normalize all 112 RFCs to it: ~15 Status-line spellings collapse to the enum, 29 Context openers become Problem, the 39 legacy-format XXX debt markers are resolved and banned from reappearing, proposal-era sections in implemented RFCs are rewritten to shipped reality (including the web/fs/subagent seam RFCs' migration plans and test checklists, closing the doc-tiers deferred-work item on the web seam), every RFC gains an Alternatives considered section or the grandfather comment, and the bilingual pair is re-mirrored and re-recorded. Move the generated index tables out of README.md into a fully generated docs/rfc/INDEX.md — gen-rfc-index now writes the whole file, and verify-rfc-classification checks its freshness and rejects index-shaped rows in the curated README — which makes room for the format contract to live in the README front door instead of a separate FORMAT.md. The decision record, and the first RFC written in the new format, is docs/rfc/implemented/process/2026-07-05-uniform-rfc-format.md.
38 lines
6.3 KiB
Markdown
38 lines
6.3 KiB
Markdown
# RFC: Prune the unimplemented subagent seam vocabulary
|
|
|
|
Status: rejected — the deferred capability vocabulary (`outputSchema`/`structured`, `toolFilter`, `sendMessage`/`resume`) is intentionally reserved surface: the seam advertises the full intended contract ahead of its implementations by design, so providers and consumers grow into a stable shape rather than re-negotiating it per capability. The consumer-evidence analysis below stands as the record of what is currently unimplemented.
|
|
|
|
## Problem
|
|
|
|
The [subagent seam](../../implemented/feature/2026-06-21-subagent-capability-seam.md) shipped a two-tier capability design: start-time capability flags checked by the service, and optional runtime methods on `SubagentRun`. Three start-time features and both optional runtime methods have zero implementations and zero callers:
|
|
|
|
- **`outputSchema`/`structured` and `toolFilter`** (`SubagentCapabilities`, `SubagentStartRequest`, `SubagentResult` in `packages/subagent/subagent/src/types.ts`): every real provider declares `outputSchema: false, toolFilter: false` (`packages/subagent/subagent-spawn/src/index.ts`, `packages/subagent/subagent-fork/src/index.ts`, `packages/subagent/subagent-acp/src/index.ts`); the sole production `ctx.subagents.start` caller (`packages/subagent/tool-subagent/src/index.ts`) builds `{ prompt, parent, signal?, agentOptions? }` and structurally cannot set either; `structured` is produced only by the test mock (`packages/support/subagent-mock`) for its own spec. The service's capability check carries two assert rows whose only exercisers are the rejection tests.
|
|
- **`SubagentRun.sendMessage` / `SubagentRun.resume`** (same file): implemented by NO provider — not even the mock; the spawn spec asserts their *absence*.
|
|
|
|
The only reason `dsh-subagent` depends on `dsh-tools` at all is `outputSchema`'s `SchemaSpec` type. Three subsequent subagent workstreams (per-session snapshot replay, the fork seed boundary, the ACP backend) landed around this surface without growing a single consumer.
|
|
|
|
## Proposal
|
|
|
|
Remove `outputSchema`/`structured`, `toolFilter`, `sendMessage`, and `resume` from the seam; shrink `SubagentCapabilities` to `{ depthLimit }`; drop the two capability-assert rows, the all-false flags on the three providers, the mock's structured branch and its `capabilities`/`structured` config knobs, and the tests that exist to pin the removed surface (the two rejection rows, the spawn absence test, the mock structured specs). Drop the `dsh-tools` peer/dev dependency from `packages/subagent/subagent/package.json`. Update the [subagent.md](../../../core-data-structures/subagent.md) pastes and the type-equiv manifest, and the README rows in `packages/subagent/subagent`, `packages/subagent/subagent-spawn`, `packages/subagent/subagent-fork`, and `packages/support/subagent-mock`. The implementing PR amends the seam RFC's capability catalog per [implemented/AGENTS.md](../../implemented/AGENTS.md).
|
|
|
|
**Keep** `depthLimit`/`maxDepth` and the capability-check mechanism itself — with eyes open about its current reach. The in-process backend genuinely enforces the cap (`SubagentDepthError` in `packages/subagent/subagent-inprocess/src/index.ts`), but no production request sets `maxDepth` (`tool-subagent` exposes no knob for it), so on the shipped tool path the guard is dormant and recursion is uncapped. The alternative — remove the depth machinery too, on the argument that a dormant guard reads like a safety property while providing none — was considered and rejected: recursion is the seam RFC's named risk, the enforcement is real working code rather than vocabulary awaiting an implementation, and the honest completion is wiring a default cap through `tool-subagent` (a few-line feature) rather than deleting the only existing guard. One live capability row also keeps the two-tier design demonstrated rather than merely remembered.
|
|
|
|
Adjacent surface examined and deliberately left alone: `SubagentService.getProvider()`/`list()` have test-harness consumers only, but the [prune-dead-seam-methods implementation note](../../implemented/simplification/2026-06-20-prune-dead-seam-methods.md) records precisely this shape being removed from the bash executor and reverted — a test harness IS a consumer for a one-line accessor over an already-tracked map. `SubagentRunEndInfo.lastAssistantMessage` is a recorded keep (the [subagent-observe-enrich RFC](../../implemented/feature/2026-06-30-subagent-observe-enrich.md)'s review dropped `agentType` and kept it deliberately, as the only final-message channel for out-of-process children); its currently-unwired bridge forwarding is a gap to close or a consumer to document, not surface for this RFC to cut.
|
|
|
|
This is the seam-vocabulary echo of [prune dead methods from the persistence seam](../../implemented/simplification/2026-06-20-prune-dead-seam-methods.md): members every implementation must declare for nobody — weaker even, since here zero implementations exist.
|
|
|
|
## Alternatives considered
|
|
|
|
### Why not keep it?
|
|
|
|
The two-kinds-of-capability design is the seam RFC's headline, and re-adding `outputSchema` later touches several files. But the design survives with `depthLimit` as its live example and the RFCs as its record, and the seam RFC itself concedes the shipped `toolFilter` shape is wrong (real enforcement needs a `tools/pre-execute` deny in the child's context, not schema filtering) — that deny primitive exists on the interception seams, so re-adding against a real implementing provider will pin a better contract than the current speculative one.
|
|
|
|
## Acceptance criteria
|
|
|
|
- The removed spellings appear only in this RFC and the amended seam RFCs; `SubagentCapabilities` is `{ depthLimit: boolean }`; the `dsh-tools` dependency edge is gone (`hygiene` green).
|
|
- Depth-enforcement tests are unchanged and green.
|
|
|
|
## Risks
|
|
|
|
The subagent lifecycle events carry `lastAssistantMessage` on the end payload — that enrichment lives in the service module, not the seam vocabulary this RFC shrinks, and the observe-enrich RFC records dropping an `agentType` sibling for lacking a consumer: the judgment this RFC extends. The CC hooks bridge, the first outside consumer of those lifecycle events, reads only the event payloads and touches none of the surface removed here; the observe-enrich RFC's deferred control-flow redesign names implementing `resume` as its own future work — exactly the re-add trigger this RFC's pattern anticipates.
|