Tianyi Cui
7702a33531
Applies the documentation standard to its biggest offender. Every rule survives as one to three lines plus a link to its durable home; the stories, duplicate statements, and re-narrations go: - Situational clusters evict to new homes: docs/testing.md (tiers, with-key policy, real-over-mock, world-verification, real-entry-path guards), docs/defensive-patterns.md (the bug-class rules), and docs/cookbook/responding-to-pr-review-on-a-stack.md (the stacked-PR review procedure). - Doc-authoring rules consolidate into docs/AGENTS.md § Writing rules (current-state-never-history, md-wrap, ts-block compilation, @mode, catalog same-change, pair same-change). - packages/README.md drops to the group table + the extension-vs-bundle dependency rule; the hand ASCII graph yields to the generated module-graph.md; group READMEs are the canonical per-package map. - packages/AGENTS.md keeps only its packages-specific rules (export shape, ctx.get, real-Loader coverage); examples/AGENTS.md repoints its with-key-policy link; rfc/README.md loses a narrated-history aside; dsh-code-review / dsh-find-simplifications / verify-md-wrap references follow the moved content. - Budget manifest ratchets: AGENTS.md 8200 -> 1500 (now 1,495 words), packages/README.md 1900 -> 600, packages/AGENTS.md 600 -> 450; the two new eviction docs join the budget set (testing 800, defensive 550); docs/AGENTS.md raises 1000 -> 1250 for the absorbed writing rules (the one justified increase). The doc-tiers RFC's deferred list prunes the two items this change ships.
37 lines
5.2 KiB
Markdown
37 lines
5.2 KiB
Markdown
# RFC: Keep one public stop primitive
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Status: implemented (proposed 2026-06-20; accepted in amended form — `whenIdle()` retained)
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> **Implementation note (scope narrowed from the original proposal).** This RFC proposed removing BOTH `abort()` and `whenIdle()` from the public `Agent` handle. Only `abort()` was removed. Validating the premise against the code ([AGENTS.md "RFCs are proposals, not golden truth"](../../../../AGENTS.md)) found `whenIdle()` to be a **load-bearing quiescence primitive**, not dead surface: it is the settle signal in several ACP tests (`packages/ui/acp/tests/{edges,turns,dispose}.spec.ts`) and is backed by a deliberate loop contract (settle waiters without a status transition; handle the replacement-turn race). The RFC's suggested migration — have consumers observe the `running`→`idle` transition by hand — is exactly the brittle hand-rolled path [the defensive patterns](../../../defensive-patterns.md) warns against ("Async state is not synchronous state"). Deleting a clean primitive to push every consumer onto that is a net loss, so `whenIdle()` stays. `abort()` was genuinely dead public surface (no production caller; the loop aborts its own `AbortController` directly), so it was removed as proposed. The text below is amended to describe what shipped.
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## Problem
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The public `Agent` handle exposed two overlapping ways to stop in-flight work: `abort(reason?)` and `cancel(reason?)`. `abort()` killed only the in-flight step and left queued work alone; `cancel()` clears queued and steering work, aborts the running step, and handles the pre-step race. In production, ACP uses `cancel()` for `session/cancel`, while lifecycle owners tear down agents through `AgentHandle.dispose()`. No production caller needed bare `abort()`.
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The `abort()`/`cancel()` distinction is real — `abort()` preserves queued prompts and steering while `cancel()` drops them — but no shipping code called the public `abort()` verb. The loop's own stop paths (`cancel()` and disposal) abort the current `AbortController` directly rather than routing through `Agent.abort()`. Most tests that called `abort()` interrupt an empty queue and switch to `cancel(reason)`; the steering re-delivery test that deliberately depends on queue preservation drives the in-flight `AbortController` directly, because `cancel()` would drop the queued steering it is trying to prove survives a step abort. The no-argument `abort()` default reason (`'aborted'`) is deleted with the verb rather than preserved by accident; `cancel()` keeps its own `'cancelled'` default.
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The extra surface area made the loop carry a public verb that is mostly a teardown internal: `abort()` had to be documented as distinct from queue-aware cancellation even though a UI cancellation almost always wants the broader operation.
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## Proposal
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Keep `cancel()` as the only public *stop* primitive on `Agent`. Lifecycle owners use `AgentHandle.dispose()` to stop and unregister an agent; non-owners use `cancel()` to abandon current and queued work. The implementation keeps a private abort controller, but it is not part of the plugin-facing `Agent` contract.
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`whenIdle()` is **retained** as the public quiescence-observation primitive (resolve once the agent settles out of `running`, resolve immediately when already idle, await the loop exit when disposed). It is not a stop verb; it is how a non-owner observes the stop *completing* without disposing the agent. Its live consumers are ACP and agent tests that await settlement through this public seam (`packages/ui/acp/tests`, `packages/core/agent-loop/tests`); the production ACP bridge owns its agents and tears them down through `AgentHandle.dispose()`, so `packages/ui/acp/src` itself has no `whenIdle()` call.
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Delete public `abort()`, the tests that exercise it as standalone API, and the docs that describe step-only abort as an embedding feature. Empty-queue abort tests migrate to `cancel(reason)` where they still prove cancellation behavior; tests whose subject is the loop's internal `AbortController` behavior drive that controller directly via an in-package typed cast to the private field; tests that only pin the removed no-arg `abort()` default go away with the method. The disposer remains async and still waits for the loop to stop.
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## Acceptance criteria
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- `Agent` exposes no public `abort()`; `cancel()`, `whenIdle()`, and `steer()` remain part of the surface.
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- ACP cancellation continues to call `cancel()`.
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- Agent teardown continues to await quiescence through handle disposal, and `whenIdle()` still resolves on quiescence for non-owner observers.
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- Tests cover cancellation and disposal as the two supported stop paths.
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## What we give up
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A future plugin cannot abort only the current model/tool step while preserving queued prompts through the public interface. If that use case becomes real, it should return with a named consumer and a narrower contract. Today it is latent generality that keeps a private loop mechanic public.
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## Related
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This RFC only removes the redundant stop verb. Mid-turn steering remains an intentional message path; quiescence observation remains via `whenIdle()`. The resulting public surface is `send()`, `steer()`, `inject()`, `cancel()`, `whenIdle()`, status, options, session, and identity.
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