refactor(code-runtime): remove subprocess backend

.agents/notes/implemented/feature/2026-06-15-code-mode.md

@@ -20,7 +20,7 @@ Three decisions, each elaborated in its own section below:
 
 1. **Code Mode is a first-class presentation mode of `ToolRegistry`** (`dsh-tools`), selected by a validated `mode` config: `'native'` (the default, contributing the visible capability schemas), `'code'` (the registry contributes only its reserved `run_code` transport plus a generated SDK `.d.ts` in the system prompt), or `'both'` (native schemas and the transport + SDK). The registry shapes its canonical contribution at the source; the cooperative prompt-assembly result remains authoritative, and the logged request header records exactly that returned presentation.
 2. **Code execution is a capability seam** — `packages/code-runtime/` contains the interface package `@deepseek-ai/dsh-code-runtime`, which owns `ctx.codeRuntime` ([capability seams](../architecture/2026-06-13-capability-seams.md); consumer = `dsh-tools`, with core-consumes-a-seam precedent in `agent-loop` → `dsh-llm`). The runtime knows nothing about tools: it is handed a program and named async bindings, runs the program, and reports `{ value, logs, error? }`. Language and substrate are backend properties, so a future Python or container backend is another implementation package, not a redesign.
-3. **Two implementations preserve one fresh-worker contract**: `@deepseek-ai/dsh-code-runtime-worker` runs the worker in the harness process, while `@deepseek-ai/dsh-code-runtime-subprocess` passes a bundled eval runner to `ctx.subprocess` for another execution world. Both execute host-stripped TypeScript in a fresh Node worker with an empty environment, bridged bindings, configurable heap/output/time caps, and hard termination. Their trust posture is bash-equivalent by design; stronger isolation comes from the mounted execution world.
+3. **The shipped implementation is `@deepseek-ai/dsh-code-runtime-worker`**: one fresh Node worker thread per run, executing the model's TypeScript after type-strip, with bindings bridged over the message port, an empty environment, configurable heap/output/time caps, and hard termination. Its trust posture is bash-equivalent by design — no unsafe-acknowledgement flags — because the harness already ships `dsh-bash-local`, which executes arbitrary model-written shell commands with strictly *more* ambient authority.
 
 This note owns Code Mode's presentation, composition, isolation, and settlement foundation. The later [typed tool-return Agent Note](2026-07-20-code-mode-typed-tool-returns.md) owns the generated output map, canonical binding values, `ToolCallError`, and the lossless outer-output boundary.
 
@@ -64,7 +64,7 @@ Each sub-dispatch appends a log-only `tool/code-dispatch-start` event at pool en
 - `CodeBindingNamespace = { global: string; functions: Record<string, (args: unknown) => Promise<CodeJsonValue>>; errorClass?: { name: string; memberNameProperty: string } }` — the runtime exposes each namespace as a global object of async functions inside the program; the optional descriptor asks the runtime to inject a real program-visible rejection class without teaching the seam consumer-specific names. `CodeJsonValue` is this dependency-light seam's structural lossless-JSON type, so binding arguments and resolutions cross the implementation's serialization boundary whole.
 - `CodeRunResult = { value?: CodeJsonValue; logs: string[]; error?: CodeRunFailure }` — program execution outcomes resolve as the `error` field. `run()` may reject only for caller/seam misuse (for example a duplicate binding namespace); consumers still contain a non-conforming backend rejection at their own error boundary.
 - `CodeRunFailure = { kind: 'exception' | 'timeout' | 'abort' | 'worker-exit' | 'invalid-output' | 'output-limit'; message: string }` — orthogonal outcomes reported independently per [defensive patterns](../../../../docs/defensive-patterns.md); a timed-out run is not an exception, an abort is not a timeout, a lossy completion is not an overflow, and a substrate exit is none of them.
-- Two readonly backend descriptors, informational not gating: `language` (what the program must be written in — `'typescript'` for both shipped backends; a Python backend would pair with its own SDK generator) and `isolation` (`'worker-thread'` for both shipped backends; the subprocess provider may add a container boundary). `dsh-tools` requires `language === 'typescript'` in the MVP — its codegen emits TS — and fails the assembly loudly otherwise, the same misconfiguration idiom as `toolOrder` violations (as when `mode` is non-native with no `ctx.codeRuntime` loaded at all).
+- Two readonly backend descriptors, informational not gating: `language` (what the program must be written in — `'typescript'` for the shipped backend; a Python backend would say so, and pair with its own SDK generator on the presentation side) and `isolation` (`'worker-thread'` for the shipped backend; `'process'`, `'container'`, … for future ones). `dsh-tools` requires `language === 'typescript'` in the MVP — its codegen emits TS — and fails the assembly loudly otherwise, the same misconfiguration idiom as `toolOrder` violations (as when `mode` is non-native with no `ctx.codeRuntime` loaded at all).
 
 Requests contain every runtime input; implementations own validated timeout and cap defaults. The registry looks up the optional runtime only when Code Mode is assembled, so native mode does not depend on one. Missing or language-incompatible runtimes fail loudly. Alternate substrates or languages can replace the implementation behind the same seam, paired with the appropriate SDK generator.
 
@@ -79,11 +79,9 @@ Requests contain every runtime input; implementations own validated timeout and
 5. **Enforce independent budgets.** `computeMs` meters worker busy time, allowing slow awaited tools without excusing a hot loop. `maxWallMs` bounds total elapsed time, including unresolved waits. `maxOutputBytes` bounds only the combined serialized outer logs, completion, or diagnostic; intermediate binding values have no byte cap. Expiry, cancellation, and completion terminate the worker, and heap exits or outer overflow are explicit failures.
 6. **Dispose to quiescence**: the service's own disposal terminates in-flight workers and *awaits* their exits before resolving, per [defensive patterns](../../../../docs/defensive-patterns.md).
 
-`@deepseek-ai/dsh-code-runtime-subprocess` preserves those program, binding, output, and worker-budget semantics across another process world. It passes a dependency-free eval runner directly through the subprocess provider and carries binding traffic over bounded newline-delimited UTF-8 JSON frames on raw pipes. The heap-bounded worker rejects expanded completion wires before MessagePort transfer; terminal settlement asks the launcher to reap its controller and keeps process-group escalation armed until `waitForExit()` confirms whole-tree quiescence. The [portable execution-world decision](../architecture/2026-07-28-portable-execution-world-consumers.md) owns why this generic backend replaces provider-specific Code Runtime packages; `dsh-code-runtime-worker` remains the single-process and single-file-distribution path.
-
 ### Trust posture
 
-The runtimes provide containment, not an independent security boundary: model code can reach Node APIs and has the authority of its mounted execution world. Code Mode uses the same `tools/pre-execute` policy gate as bash and adds an empty worker environment, heap limits, a separate isolate, and hard termination of the program itself. Deployments that need a hard multi-tenant boundary mount container-class filesystem/subprocess providers for both code and bash.
+The worker runtime provides containment, not a security boundary: model code can reach Node APIs and has authority comparable to the bash tool. `worker.terminate()` stops the thread but not OS processes it spawned. Code Mode uses the same `tools/pre-execute` policy gate as bash and adds an empty environment, heap limits, a separate isolate, and hard termination of the program itself. Deployments that need a hard multi-tenant boundary need a container-class backend for both code and bash; the runtime's isolation descriptor lets them distinguish that backend.
 
 ### What the model sees
 
@@ -95,7 +93,7 @@ Deployments switching to `'code'` must update any native-only `toolOrder`. Assem
 
 ## Testing
 
-- **Runtime implementations:** Real-worker suites cover typed binding values and failures, every lossless JSON completion root, invalid and over-limit output, exact combined ledger and per-hop frame boundaries, compute and wall budgets, hostile binding traffic, empty environment, descendant lifetime cleanup, and disposal to quiescence. Built-package tests run both the direct worker entry and the subprocess composition under plain Node; the latter also has a Loader-driven `cordis.yml` test.
+- **Worker runtime:** Real-worker tests cover typed binding values and failures, every lossless JSON completion root, invalid and over-limit output, exact combined ledger boundaries, compute and wall budgets, hostile binding traffic, empty environment, and disposal to quiescence. A built-package test runs the worker entry under plain Node.
 - **Registry integration:** Tests cover code generation, all presentation modes, reserved-name and restriction rules, scoped visibility, authoritative assembly rewrites, `toolOrder`, runtime compatibility failures, full-pipeline sub-dispatch, parent-token correlation, serialization, cancellation and queue drain, JSON normalization, error propagation, log events, ordered context deferral across successful and failed programs, outer-block suppression, and HMR cleanup.
 - **With-key e2e:** A real model composes two bash calls in one program; another discovers nested workspace instructions through a Code Mode fs dispatch. The tests verify collapsed request headers, correlated dispatch events, resulting files, deferred context, and model behavior.
 - **Snapshot:** The `code-mode-turn`, `both-mode-turn`, and `code-mode-workspace-context` fixtures pin SDK text, header tool lists, dispatch events, deferred context, and result cards.
@@ -120,7 +118,7 @@ Deployments switching to `'code'` must update any native-only `toolOrder`. Assem
 
 ## Risks
 
-**A worker is not a hard security boundary.** Deliberate and documented (§Trust posture): posture equals the existing bash tool and gating uses the same seams. The subprocess implementation can run inside a container-class execution world, but its worker descriptor does not itself claim that boundary.
+**The worker is not a hard security boundary.** Deliberate and documented (§Trust posture): posture equals the existing bash tool, containment exceeds it, gating uses the same seams. Deployments needing more need a future `isolation: 'container'` backend — tracked as the seam's designed extension, not a TODO on this design.
 
 **`stripTypeScriptTypes` is marked experimental.** It is the same engine (amaro/swc) behind Node's own native `.ts` execution, exposed as an API across this repo's whole engines range. Mitigations: the runtime's unit suite pins the behaviors relied on (position preservation, erasable-only rejection message shape loosely), the call sits behind one private function, and `amaro`/`sucrase` are drop-in replacements if the API shifts. The erasable-only subset is a model-facing contract line, and the error path is a working feedback loop, not a dead end.
 
@@ -128,7 +126,7 @@ Deployments switching to `'code'` must update any native-only `toolOrder`. Assem
 
 **Registry scope growth.** `dsh-tools` absorbs codegen, a tool, a bridge, and an event. Contained by module boundaries inside the package (`ts-types.ts`, `code-mode.ts` beside `schema.ts`/`json-schema.ts`/`presentation.ts`) and by the seam: everything substrate-shaped lives behind `ctx.codeRuntime`.
 
-**Large lossless JSON values can exhaust memory.** Tool bindings snapshot lossless JSON before dispatch and return canonical JSON resolutions whole. The direct worker runtime applies no per-binding byte cap; the subprocess runtime bounds each transport frame with `maxFrameBytes`, but repeated or concurrent calls can still consume process or worker memory. The combined outer-output ledger for logs, the completion value, and a failure diagnostic is separately bounded by `maxOutputBytes`.
+**Large lossless JSON values can exhaust memory.** Tool bindings snapshot lossless JSON before dispatch and return canonical JSON resolutions whole. The runtime validates both sides of the worker port and applies no per-binding byte cap; structured-clone cost and process or worker memory are the practical bounds. The combined outer-output ledger for logs, the completion value, and a failure diagnostic is the only byte-capped boundary.
 
 **Serialized-only sub-dispatch.** `Promise.all` gains no wall-clock parallelism yet, only fewer round-trips; models may over-expect. The instructions state it; lifting it is tied to the same concurrency-safety metadata the native parallel-dispatch TODO needs.