c4bc6e0e38
abort() only kills the in-flight step, so a queued-but-not-yet-started prompt
ran to completion after a cancel and a prompt accepted right after could be
batched into the cancelled turn (the loop merges queued messages into one turn).
This closes TODO(rfc010-cancel-prestep) with a distinct cancel() verb.
cancel() clears the queued + steering FIFOs, aborts the in-flight step, and
drives a turn-scoped marker on the LoopHandle that the driver checks at EVERY
point a turn could start or continue:
- right after the idle wait (window 1): drop the about-to-run turn and settle
whenIdle() waiters directly (no running→idle transition fires, and no
agent/status is emitted, so an ACP listener can't see a spurious idle that
resolves a freshly-queued prompt as cancelled);
- after the synchronous setStatus('running') emit (window 2): a running listener
can cancel in the gap before runTurn;
- in the step-start window (before runStep, after setAbort): a synchronous
turn-start/step-start listener can cancel before any AbortController exists;
- at the continuation gate: a cancel during the continuation waterfall (the
finished step's controller already cleared) ends the turn aborted.
The marker is ARMED only when there is something to cancel (running, an
in-flight step, or queued/steering work) — an idle no-op cancel cannot leave it
set to drop a later prompt — and RESET unconditionally once per loop iteration,
so it governs exactly one turn and never leaks onto the next prompt (even when a
send() lands in the cancelled turn's flush window).
ACP session/cancel now maps to agent.cancel() (keeping the synchronous
settlePrompt). Teardown/disconnect still use abort('disposed') until PR D, so
the ACP README narrows the remaining best-effort window to teardown only.
Tests (agent-loop/cancel.spec.ts) cover every window unit-level (the F1 hang
guard: a whenIdle() waiter registered before a pre-step cancel resolves; the F2
leak guard: idle cancel then a prompt runs; mid-step, continuation, both
pre-step windows, turn-start-listener, steering-cleared, marker-reset). ACP
turns.spec.ts adds the through-bridge tests with NO intervening whenIdle (idle
cancel→prompt runs; mid-stream cancel→immediate next prompt runs) and updates
the stale pre-step test to the queue-aware guarantee. The existing cancel
snapshot golden is byte-identical (it drives the new cancel() path end-to-end
through the real subprocess), so no new golden is needed. 100% coverage.
Packages
Harness packages, all under the @deepseek-ai/dsh-* scope. Each package is a Cordis plugin (microkernel-style): it exports either a default Service subclass or a functional plugin that gets registered via ctx.plugin(), declares its ctx key/events where applicable through declaration merging, and exposes extension points through ctx.effect(), ctx.on(), and ctx.waterfall().
Dependency graph
dsh-llm (no harness deps — pure vocabulary)
dsh-bash (no harness deps — abstract executor seam)
dsh-session ← dsh-llm
dsh-system-prompt ← dsh-llm
dsh-agent ← dsh-llm, dsh-session
dsh-tools ← dsh-llm, dsh-system-prompt, dsh-agent
dsh-bash-local ← dsh-bash (BashExecutor impl)
dsh-tool-bash ← dsh-bash, dsh-tools (bash tool schemas)
dsh-llm-deepseek ← dsh-llm (DeepSeek adapter)
dsh-llm-pi-ai ← dsh-llm (pi-ai-backed adapter)
dsh-agent-loop ← dsh-llm, dsh-session, dsh-system-prompt, dsh-tools, dsh-agent
dsh-invariants ← dsh-llm, dsh-session, dsh-agent (dev-mode contract checks)
dsh-acp ← dsh-agent, dsh-llm, dsh-session, dsh-session-persistence (ACP JSON-RPC bridge)
dsh-ui-stdio ← dsh-agent, dsh-llm, dsh-session (stdio readline UI plugin)
dsh-llm-replay ← dsh-llm, dsh-session (record/replay adapter for keyless snapshot tests)
The rule: plugins depend on interfaces, never on the concrete loop. dsh-agent-loop is swappable — UI/hook/tool plugins keep working against the dsh-agent vocabulary if the loop is replaced. A swappable capability splits into interface / implementation / consumer packages (the bash trio is the template — see capability seams).
What goes where
| Package | Role | ctx key |
|---|---|---|
llm/ |
Abstract LLM service + content-block vocabulary + chunk assembler | ctx.llm |
session/ |
Event-sourced session log + in-memory store | ctx.sessions |
system-prompt/ |
Prompt-section + tool-schema assembly registry | ctx.systemPrompt |
tools/ |
Tool registry + tools/execute waterfall |
ctx.tools |
agent/ |
Agent interface, registry, agent/* event vocabulary |
ctx.agents |
agent-loop/ |
THE concrete loop plugin: ReactLoopAgent + the loop driver |
ctx.agentLoop |
bash/ |
Abstract bash executor seam (interface + vocabulary) | ctx.bash |
bash-local/ |
Local-subprocess BashExecutor implementation |
(registers ctx.bash) |
tool-bash/ |
Model-facing bash/bash_output/bash_kill tool schemas |
(registers on ctx.tools) |
llm-deepseek/ |
DeepSeek API adapter (hand-rolled fetch/SSE) | (registers on ctx.llm) |
llm-pi-ai/ |
DeepSeek adapter via @earendil-works/pi-ai (design twin) |
(registers on ctx.llm) |
invariants/ |
Dev-mode event-contract invariants + session-log freeze | (listens on session/*, agent/*) |
acp/ |
Agent Client Protocol bridge: serves the agent to an ACP editor over JSON-RPC stdio | (drives ctx.agents/ctx.sessions) |
ui-stdio/ |
Minimal stdio (readline) UI plugin: renders agent/* events, feeds stdin lines to the agent |
(drives ctx.agents) |
llm-replay/ |
Record/replay adapter: short-circuits llm/stream with chunks from a recorded session JSONL (keyless snapshot tests) |
(listens on llm/stream) |
Each package has its own README.md with purpose, service API, events, extension points, and deliberate non-goals (TODOs).
Conventions (applied across all harness packages)
- Registrations are effects: every contribution (adapter, tool, section, agent, event listener) goes through
ctx.effect()/ctx.on(), so disposal and HMR clean up automatically. Everyregister()returns the disposer. - Declaration merging for events and ctx: services declare their events in
declare module 'cordis' { interface Events { ... } }and their ctx key ininterface Context. - Waterfall semantics:
ctx.waterfalllisteners receive(...args, next)and MUST callnext()to delegate; returning without it short-circuits (the veto mechanism). - Extensible unions:
ContentBlockMap,MessageSourceMap,FinishReasonMap,TurnTriggerMap,TurnEndReasonMap, andSessionEventMapuse the merge-extensible-map pattern so plugins can add variants via declaration merging. - ESM everywhere; imports use package names across package boundaries,
.tsextensions within a package. - Tests: vitest, colocated under
packages/<name>/tests/*.spec.ts. Every registry needs an HMR-safety test. Err on the side of more tests.