deepseek-harness/packages/subagent/subagent-cursor/tests/subagent-cursor.spec.ts

import { PassThrough } from 'node:stream'
import { Context } from '@deepseek-ai/cordis'
import Loader from '@deepseek-ai/cordis-plugin-loader'
import { describe, expect, it, vi } from 'vitest'
import type { Agent } from '@deepseek-ai/dsh-agent'
import type { InvariantInstaller } from '@deepseek-ai/dsh-invariants'
import type { ContentBlock } from '@deepseek-ai/dsh-llm'
import SubagentRuntime, { type SubagentStopReason } from '@deepseek-ai/dsh-subagent'
import { MAX_TIMER_DELAY_MS } from '@deepseek-ai/dsh-timeout'
import type {
  SubprocessHandle,
  SubprocessOutcome,
} from '@deepseek-ai/dsh-subprocess'
import LocalSubprocessRuntime from '@deepseek-ai/dsh-subprocess-local'
import * as cursor from '../src/index.ts'
import * as invariant from '../src/invariant.ts'
import {
  assertDirectlySpawnable,
  cursorAgentArgv,
  DEFAULT_DISPOSE_GRACE_MS,
  disposeCursorChild,
  startCursorRun,
  textTask,
  type CursorRunSpec,
} from '../src/run.ts'
import { CursorStreamWire } from '../src/wire.ts'

type JsonObject = Record<string, unknown>

const EXECUTABLE = '/opt/cursor/cursor-agent'

const fakeParent = {
  id: 'parent',
  session: { header: { cwd: process.cwd() } },
} as unknown as Agent

function request(
  prompt: ContentBlock[] = [{ type: 'text', text: 'do the task' }],
  signal = new AbortController().signal,
) {
  return { prompt, parent: fakeParent, signal }
}

async function nextTask(): Promise<void> {
  await new Promise<void>((resolve) => { setImmediate(resolve) })
}

function initEvent(overrides: JsonObject = {}): JsonObject {
  return {
    type: 'system',
    subtype: 'init',
    apiKeySource: 'env',
    cwd: process.cwd(),
    session_id: 'chat-1',
    model: 'cursor-model',
    permissionMode: 'default',
    ...overrides,
  }
}

function assistantEvent(content: unknown): JsonObject {
  return {
    type: 'assistant',
    message: { role: 'assistant', content },
    session_id: 'chat-1',
  }
}

function resultEvent(overrides: JsonObject = {}): JsonObject {
  return {
    type: 'result',
    subtype: 'success',
    duration_ms: 12,
    duration_api_ms: 10,
    is_error: false,
    result: 'the final answer',
    session_id: 'chat-1',
    ...overrides,
  }
}

/** Writes stream-json events the way the real CLI writes its stdout. */
class StreamPeer {
  constructor(private readonly output: PassThrough) {}

  send(...events: readonly JsonObject[]): void {
    this.output.write(`${events.map(event => JSON.stringify(event)).join('\n')}\n`)
  }

  raw(text: string): void {
    this.output.write(text)
  }
}

interface FakeChildOptions {
  readonly pid?: number
  readonly exitOnTerminate?: boolean
  readonly doneError?: Error
}

interface FakeChild {
  readonly handle: SubprocessHandle
  readonly peer: StreamPeer
  readonly fromChild: PassThrough
  readonly toChild: PassThrough
  readonly settle: (outcome?: SubprocessOutcome) => void
  readonly fail: (error: Error) => void
  readonly terminate: () => void
  readonly waitForExit: (signal?: AbortSignal) => Promise<boolean>
}

function fakeChild(options: FakeChildOptions = {}): FakeChild {
  const fromChild = new PassThrough()
  const toChild = new PassThrough()
  const peer = new StreamPeer(fromChild)
  let exited = false
  let resolveDone!: (outcome: SubprocessOutcome) => void
  let rejectDone!: (error: Error) => void
  const done = new Promise<SubprocessOutcome>((resolve, reject) => {
    resolveDone = resolve
    rejectDone = reject
  })
  const settle = (
    outcome: SubprocessOutcome = { exitCode: 0, signal: null },
  ): void => {
    if (exited) return
    exited = true
    resolveDone(outcome)
  }
  const fail = (error: Error): void => {
    if (exited) return
    exited = true
    rejectDone(error)
  }
  if (options.doneError !== undefined) fail(options.doneError)
  const terminate = vi.fn(() => {
    if (options.exitOnTerminate !== false) settle()
  })
  const waitForExit = vi.fn(async (signal?: AbortSignal) => {
    if (exited) return true
    if (signal === undefined) {
      await done.catch(() => {})
      return true
    }
    return await new Promise<boolean>((resolve) => {
      const onAbort = (): void => { resolve(false) }
      signal.addEventListener('abort', onAbort, { once: true })
      void done.then(
        () => {
          signal.removeEventListener('abort', onAbort)
          resolve(true)
        },
        () => {
          signal.removeEventListener('abort', onAbort)
          resolve(true)
        },
      )
    })
  })
  const handle: SubprocessHandle = {
    pid: options.pid ?? 4321,
    stdin: toChild,
    stdout: fromChild,
    stderr: undefined,
    collected: {},
    done,
    terminate,
    waitForExit,
  }
  return {
    handle,
    peer,
    fromChild,
    toChild,
    settle,
    fail,
    terminate,
    waitForExit,
  }
}

function runSpec(
  child: FakeChild,
  overrides: Partial<CursorRunSpec> = {},
): CursorRunSpec {
  return {
    cwd: process.cwd(),
    executable: EXECUTABLE,
    env: {},
    disposeGraceMs: DEFAULT_DISPOSE_GRACE_MS,
    force: false,
    trust: false,
    spawn: () => child.handle,
    ...overrides,
  }
}

async function publishRun(
  child = fakeChild(),
  signal = new AbortController().signal,
  specOverrides: Partial<CursorRunSpec> = {},
) {
  const starting = startCursorRun(request(undefined, signal), runSpec(child, specOverrides))
  await nextTask()
  child.peer.send(initEvent())
  return { child, run: await starting }
}

function startedWire(): { readonly child: FakeChild; readonly wire: CursorStreamWire } {
  const child = fakeChild()
  const wire = new CursorStreamWire(child.handle.stdout!)
  wire.start()
  return { child, wire }
}

describe('task admission and command construction', () => {
  it('accepts one or more text blocks and rejects empty, non-text, or option-shaped tasks', () => {
    expect(textTask([{ type: 'text', text: 'a' }, { type: 'text', text: 'b' }])).toBe('ab')
    expect(() => textTask([])).toThrow('must contain only text blocks')
    expect(() => textTask([{ type: 'reasoning', text: 'x' }]))
      .toThrow('must contain only text blocks')
    expect(() => textTask([{ type: 'text', text: '  ' }])).toThrow('must not be empty')
    expect(() => textTask([{ type: 'text', text: '--force me' }]))
      .toThrow('must not begin with "-"')
  })

  it('refuses a Windows batch shim so task text never reaches a shell', () => {
    expect(assertDirectlySpawnable('C:\\bin\\cursor-agent.exe', 'win32'))
      .toBe('C:\\bin\\cursor-agent.exe')
    expect(assertDirectlySpawnable('/usr/bin/cursor-agent', 'linux'))
      .toBe('/usr/bin/cursor-agent')
    // A shim is only unusable where it needs cmd.exe.
    expect(assertDirectlySpawnable('/usr/bin/cursor-agent.cmd', 'linux'))
      .toBe('/usr/bin/cursor-agent.cmd')
    for (const shim of ['C:\\bin\\cursor-agent.cmd', 'C:\\bin\\cursor-agent.BAT']) {
      expect(() => assertDirectlySpawnable(shim, 'win32')).toThrow('is a batch shim')
    }
    // The omitted platform reads the host, so the expectation follows it.
    const underHostPlatform = (): string => assertDirectlySpawnable('C:\\bin\\cursor-agent.cmd')
    if (process.platform === 'win32') {
      expect(underHostPlatform).toThrow('is a batch shim')
    } else {
      expect(underHostPlatform()).toBe('C:\\bin\\cursor-agent.cmd')
    }
  })

  it('builds the fixed print-mode argv and adds only selected permissions', () => {
    const base = { executable: EXECUTABLE, cwd: '/work', force: false, trust: false }
    expect(cursorAgentArgv(base, 'ship it')).toEqual([
      EXECUTABLE,
      '--print',
      '--output-format',
      'stream-json',
      '--workspace',
      '/work',
      'ship it',
    ])
    expect(cursorAgentArgv({ ...base, force: true, trust: true }, 'ship it')).toEqual([
      EXECUTABLE,
      '--print',
      '--output-format',
      'stream-json',
      '--workspace',
      '/work',
      '--force',
      '--trust',
      'ship it',
    ])
  })
})

describe('package contracts', () => {
  it('registers one fixed descriptor, validates config, and unregisters on HMR', async () => {
    const ctx = new Context()
    await ctx.plugin(SubagentRuntime)
    await ctx.plugin(LocalSubprocessRuntime)
    const fiber = await ctx.plugin(cursor, {})
    expect(ctx.subagents.getProvider('cursor')).toMatchObject({
      name: 'cursor',
      capabilities: {
        outputSchema: false,
        depthLimit: false,
        toolFilter: false,
        persona: false,
      },
      inheritsParentContext: false,
    })
    expect(ctx.subagents.list()).toEqual(['cursor'])
    await fiber.dispose()
    expect(ctx.subagents.list()).toEqual([])

    for (const disposeGraceMs of [0, -1, Number.NaN, Number.POSITIVE_INFINITY]) {
      await expect(ctx.plugin(cursor, { disposeGraceMs }))
        .rejects.toThrow('disposeGraceMs must be a positive finite number')
    }
    await expect(ctx.plugin(cursor, { disposeGraceMs: MAX_TIMER_DELAY_MS + 1 }))
      .rejects.toThrow(`disposeGraceMs must be no greater than ${MAX_TIMER_DELAY_MS}`)
    await ctx.fiber.dispose()
  })

  it('requires a parent session cwd before resolving or spawning anything', async () => {
    const ctx = new Context()
    await ctx.plugin(SubagentRuntime)
    await ctx.plugin(LocalSubprocessRuntime)
    const resolveExecutable = vi.spyOn(ctx.subprocess, 'resolveExecutable')
    const spawn = vi.spyOn(ctx.subprocess, 'spawn')
    await ctx.plugin(cursor, {})

    await expect(ctx.subagents.start('cursor', {
      prompt: [{ type: 'text', text: 'task' }],
      parent: {
        id: 'parent-without-cwd',
        session: { header: {} },
      } as unknown as Agent,
      signal: new AbortController().signal,
    })).rejects.toThrow(
      'subagent-cursor: no working directory for the child — delegate from a parent session that has one',
    )
    expect(resolveExecutable).not.toHaveBeenCalled()
    expect(spawn).not.toHaveBeenCalled()
    await ctx.fiber.dispose()
  })

  it('keeps the namespace export shape and package-owned empty invariant', async () => {
    expect('default' in cursor).toBe(false)
    expect(cursor.name).toBe('subagent-cursor')
    expect(cursor.inject).toEqual(['subagents', 'subprocess'])
    const loader = Object.create(Loader.prototype) as Loader
    expect(loader.unwrapExports(cursor)).toBe(cursor)

    const dispose = vi.fn()
    const register = vi.fn((
      _packageName: string,
      _installer: InvariantInstaller,
    ) => dispose)
    const ctx = { invariants: { register } } as unknown as Context
    await expect(invariant.apply(ctx)).resolves.toBe(dispose)
    expect(register).toHaveBeenCalledWith(
      '@deepseek-ai/dsh-subagent-cursor',
      expect.any(Function),
    )
    const install = register.mock.calls[0]![1]
    await install(new Context(), (message) => { throw new Error(message) })
    expect(invariant.name).toBe('subagent-cursor-invariant')
    expect(invariant.inject).toEqual(['invariants'])
  })
})

describe('CursorStreamWire', () => {
  it('gates on init, keeps the terminal answer, and ignores unrelated events', async () => {
    const { child, wire } = startedWire()
    wire.start()
    child.peer.send(initEvent())
    await expect(wire.ready()).resolves.toEqual({
      sessionId: 'chat-1',
      model: 'cursor-model',
    })
    child.peer.send(
      { type: 'user', message: { role: 'user', content: [{ type: 'text', text: 'task' }] } },
      { type: 'tool_call', subtype: 'started', call_id: 'c1', tool_call: {} },
      { type: 'system', subtype: 'usage', tokens: 12 },
      assistantEvent([{ type: 'text', text: 'thinking out loud' }]),
      { type: 'newer_cli_event', payload: 1 },
    )
    await nextTask()
    expect(wire.collectOutput()).toEqual([{ type: 'text', text: 'thinking out loud' }])
    child.peer.send(resultEvent())
    await expect(wire.awaitResult()).resolves.toEqual({
      output: [{ type: 'text', text: 'the final answer' }],
      stopReason: 'completed',
    })
  })

  it('reads events split across chunks and skips blank lines', async () => {
    const { child, wire } = startedWire()
    const frame = JSON.stringify(initEvent())
    child.peer.raw(`\n  \n${frame.slice(0, 10)}`)
    await nextTask()
    child.peer.raw(`${frame.slice(10)}\n`)
    await expect(wire.ready()).resolves.toMatchObject({ sessionId: 'chat-1' })
    expect(wire.collectOutput()).toEqual([])
  })

  it('reports an absent model rather than inventing one', async () => {
    const { child, wire } = startedWire()
    child.peer.send(initEvent({ model: 42 }))
    await expect(wire.ready()).resolves.toEqual({
      sessionId: 'chat-1',
      model: undefined,
    })
  })

  it('keeps the last non-empty assistant message and drops non-text blocks', async () => {
    const { child, wire } = startedWire()
    child.peer.send(
      initEvent(),
      assistantEvent([{ type: 'text', text: 'first' }]),
      assistantEvent([{ type: 'image', source: {} }]),
      assistantEvent([]),
      assistantEvent([{ type: 'text', text: 'second' }, { type: 'image', source: {} }]),
    )
    await nextTask()
    expect(wire.collectOutput()).toEqual([{ type: 'text', text: 'second' }])
  })

  it('fails closed on every unusable terminal result', async () => {
    for (const [overrides, detail] of [
      [{ subtype: 'error' }, 'terminal result subtype error'],
      [{ subtype: 7 }, 'terminal result subtype unknown'],
      [{ is_error: true }, 'success result was marked as an error'],
      [{ result: 12 }, 'success result was marked as an error'],
      [{ result: '   ' }, 'success result was marked as an error'],
    ] as const) {
      const { child, wire } = startedWire()
      child.peer.send(initEvent(), resultEvent(overrides))
      await expect(wire.awaitResult()).rejects.toThrow(detail)
    }
  })

  it('refuses a result that arrives without an announced session', async () => {
    const { child, wire } = startedWire()
    child.peer.send(resultEvent())
    await expect(wire.ready()).rejects.toThrow('without announcing a session')
    await expect(wire.awaitResult()).rejects.toThrow('without announcing a session')
  })

  it('treats malformed stdout as a protocol failure', async () => {
    for (const [line, detail] of [
      ['not json at all', 'a stdout line that is not JSON'],
      ['[1,2]', 'an invalid event'],
      ['null', 'an invalid event'],
      [JSON.stringify({ type: 'system', subtype: 'init', session_id: '' }), 'an invalid init session id'],
      [JSON.stringify({ type: 'assistant', message: 'text' }), 'an invalid assistant message'],
      [JSON.stringify(assistantEvent('not an array')), 'an invalid assistant message content'],
    ] as const) {
      const { child, wire } = startedWire()
      child.peer.raw(`${line}\n`)
      await expect(wire.awaitResult()).rejects.toThrow(detail)
    }
  })

  it('fails pending gates on stream error, end of stream, and close', async () => {
    const broken = startedWire()
    broken.child.fromChild.emit('error', new Error('stdout broke'))
    await expect(broken.wire.awaitResult()).rejects.toThrow('stdout broke')

    const ended = startedWire()
    ended.child.fromChild.end()
    await expect(ended.wire.awaitResult()).rejects.toThrow('ended without a terminal result')

    const closed = startedWire()
    closed.wire.close()
    closed.wire.close()
    await expect(closed.wire.ready()).rejects.toThrow('event stream closed')

    // A completed run keeps its result across teardown and end of stream.
    const done = startedWire()
    done.child.peer.send(initEvent(), resultEvent())
    await expect(done.wire.awaitResult()).resolves.toMatchObject({ stopReason: 'completed' })
    done.wire.close()
    done.child.fromChild.end()
    await expect(done.wire.awaitResult()).resolves.toMatchObject({ stopReason: 'completed' })
  })

  it('is safe to close before it is started', async () => {
    const child = fakeChild()
    const wire = new CursorStreamWire(child.handle.stdout!)
    wire.close()
    await expect(wire.ready()).rejects.toThrow('event stream closed')
  })
})

describe('run lifecycle and quiescence', () => {
  it('spawns the fixed command, publishes after init, and disposes once', async () => {
    const child = fakeChild()
    const spawn = vi.fn(() => child.handle)
    const starting = startCursorRun(
      request(),
      runSpec(child, { spawn, force: true, trust: true, disposeGraceMs: 40, env: { CURSOR_API_KEY: 'fake' } }),
    )
    await nextTask()
    expect(spawn).toHaveBeenCalledWith(expect.objectContaining({
      argv: [
        EXECUTABLE,
        '--print',
        '--output-format',
        'stream-json',
        '--workspace',
        process.cwd(),
        '--force',
        '--trust',
        'do the task',
      ],
      cwd: process.cwd(),
      graceMs: 40,
      env: { CURSOR_API_KEY: 'fake' },
    }))
    child.peer.send(initEvent())
    const run = await starting
    expect(run.id).toMatch(/^[0-9a-f-]{36}$/)
    expect(run.localAgent).toBeUndefined()

    child.peer.send(resultEvent())
    await expect(run.result).resolves.toEqual({
      output: [{ type: 'text', text: 'the final answer' }],
      stopReason: 'completed',
    })
    const first = run.dispose()
    expect(run.dispose()).toBe(first)
    await first
    expect(child.terminate).toHaveBeenCalledTimes(1)
  })

  it('closes stdin so an unattended prompt cannot stall the child', async () => {
    const { child, run } = await publishRun()
    expect(child.toChild.writableEnded).toBe(true)
    child.peer.send(resultEvent())
    await run.result
    await run.dispose()
  })

  it('settles a cancelled run as aborted with the output collected so far', async () => {
    const controller = new AbortController()
    const child = fakeChild({ exitOnTerminate: false })
    const { run } = await publishRun(child, controller.signal)
    child.peer.send(assistantEvent([{ type: 'text', text: 'partial work' }]))
    await nextTask()
    controller.abort(new Error('parent stopped waiting'))
    await expect(run.result).resolves.toEqual({
      output: [{ type: 'text', text: 'partial work' }],
      stopReason: 'aborted',
    })
    child.settle({ exitCode: null, signal: 'SIGTERM' })
    await run.dispose()
  })

  it('flattens a child exit and a protocol failure after publication', async () => {
    const exited = await publishRun()
    exited.child.settle({ exitCode: 2, signal: null })
    await expect(exited.run.result).resolves.toEqual({
      output: [],
      stopReason: 'error',
    })
    await exited.run.dispose()

    const onError = vi.fn<(error: Error, stopReason: SubagentStopReason) => void>()
    const malformed = await publishRun(fakeChild(), new AbortController().signal, { onError })
    malformed.child.peer.raw('garbage\n')
    await expect(malformed.run.result).resolves.toMatchObject({ stopReason: 'error' })
    expect(onError).toHaveBeenCalledTimes(1)
    const [reported, reportedReason] = onError.mock.calls[0]!
    expect(reported.message).toContain('not JSON')
    expect(reportedReason).toBe('error')
    await malformed.run.dispose()
  })

  it('rejects before spawn when the request is already aborted', async () => {
    const controller = new AbortController()
    controller.abort()
    const child = fakeChild()
    const spawn = vi.fn(() => child.handle)
    await expect(startCursorRun(request(undefined, controller.signal), runSpec(child, { spawn })))
      .rejects.toThrow('aborted before cursor-agent startup')
    expect(spawn).not.toHaveBeenCalled()
  })

  it('rolls the child back when startup fails or is aborted before publication', async () => {
    const failed = fakeChild()
    const failing = startCursorRun(request(), runSpec(failed))
    await nextTask()
    failed.peer.raw('not json\n')
    await expect(failing).rejects.toThrow('not JSON')
    expect(failed.terminate).toHaveBeenCalledTimes(1)

    const controller = new AbortController()
    const aborted = fakeChild()
    const aborting = startCursorRun(request(undefined, controller.signal), runSpec(aborted))
    await nextTask()
    controller.abort()
    await expect(aborting).rejects.toThrow('aborted before run publication')
    expect(aborted.terminate).toHaveBeenCalledTimes(1)

    const exited = fakeChild()
    const exiting = startCursorRun(request(), runSpec(exited))
    await nextTask()
    exited.settle({ exitCode: 3, signal: null })
    await expect(exiting).rejects.toThrow('exited before the run settled')

    // A failed spawn reports pid -1, so rollback has no tree to signal.
    const broken = fakeChild({ pid: -1, doneError: new Error('spawn observer failed') })
    await expect(startCursorRun(request(), runSpec(broken)))
      .rejects.toThrow('spawn observer failed')
    expect(broken.terminate).not.toHaveBeenCalled()
  })

  it('reports a startup failure whose cleanup also failed as an aggregate', async () => {
    const child = fakeChild()
    child.handle.waitForExit = vi.fn(() => Promise.reject(new Error('tree never exited')))
    const starting = startCursorRun(request(), runSpec(child))
    await nextTask()
    child.peer.raw('not json\n')
    const failure = await starting.catch((error: unknown) => error)
    expect(failure).toBeInstanceOf(AggregateError)
    expect((failure as AggregateError).message)
      .toContain('startup failed and cursor-agent cleanup also failed')
  })

  it('keeps overlapping runs isolated', async () => {
    const first = await publishRun()
    const second = await publishRun()
    first.child.peer.send(resultEvent({ result: 'first answer' }))
    second.child.peer.send(resultEvent({ subtype: 'error' }))
    await expect(first.run.result).resolves.toMatchObject({
      output: [{ type: 'text', text: 'first answer' }],
      stopReason: 'completed',
    })
    await expect(second.run.result).resolves.toMatchObject({ stopReason: 'error' })
    await first.run.dispose()
    await second.run.dispose()
  })

  it('uses the registered provider config, the resolved executable, and logs flattened errors', async () => {
    const ctx = new Context()
    await ctx.plugin(SubagentRuntime)
    await ctx.plugin(LocalSubprocessRuntime)
    const child = fakeChild()
    const resolveExecutable = vi.spyOn(ctx.subprocess, 'resolveExecutable')
      .mockResolvedValue(EXECUTABLE)
    const spawn = vi.spyOn(ctx.subprocess, 'spawn').mockReturnValue(child.handle)
    const warnings: string[] = []
    ctx.logger.warn = ((message: unknown) => {
      warnings.push(String(message))
    }) as typeof ctx.logger.warn
    await ctx.plugin(cursor, {
      env: { CURSOR_API_KEY: 'fake' },
      disposeGraceMs: 25,
      force: true,
    })
    const starting = ctx.subagents.start('cursor', {
      prompt: [{ type: 'text', text: 'task' }],
      parent: fakeParent,
      signal: new AbortController().signal,
    })
    await nextTask()
    child.peer.send(initEvent())
    const run = await starting
    child.settle({ exitCode: 1, signal: null })
    await expect(run.result).resolves.toMatchObject({ stopReason: 'error' })
    expect(resolveExecutable).toHaveBeenCalledWith(
      'cursor-agent',
      { CURSOR_API_KEY: 'fake' },
      expect.any(AbortSignal),
    )
    expect(spawn).toHaveBeenCalledTimes(1)
    const spawned = spawn.mock.calls[0]![0]
    expect(spawned.argv).toContain('--force')
    expect(spawned.env).toEqual({ CURSOR_API_KEY: 'fake' })
    expect(spawned.graceMs).toBe(25)
    expect(spawned.cwd).toBe(process.cwd())
    expect(warnings).toEqual([
      expect.stringContaining('subagent-cursor: child run failed (error):'),
    ])
    await run.dispose().catch(() => {})
    await ctx.fiber.dispose()
  })
})

describe('disposeCursorChild', () => {
  it('closes the stream, terminates, and waits for the managed tree', async () => {
    const child = fakeChild()
    const wire = new CursorStreamWire(child.handle.stdout!)
    wire.start()
    await disposeCursorChild(wire, child.handle)
    expect(child.terminate).toHaveBeenCalledTimes(1)
    expect(child.waitForExit).toHaveBeenCalledTimes(1)
  })

  it('does not finish disposal before the managed tree exits', async () => {
    const child = fakeChild({ exitOnTerminate: false })
    const wire = new CursorStreamWire(child.handle.stdout!)
    let settled = false
    const disposing = disposeCursorChild(wire, child.handle).then(() => { settled = true })
    await nextTask()
    expect(settled).toBe(false)
    child.settle()
    await disposing
    expect(settled).toBe(true)
  })

  it('skips signalling a failed spawn and contains its observer rejection', async () => {
    const child = fakeChild({ pid: -1, doneError: new Error('spawn failed') })
    const wire = new CursorStreamWire(child.handle.stdout!)
    await expect(disposeCursorChild(wire, child.handle)).resolves.toBeUndefined()
    expect(child.terminate).not.toHaveBeenCalled()
  })

  it('reports a direct-child observer failure from a live tree', async () => {
    const child = fakeChild({ exitOnTerminate: false })
    const wire = new CursorStreamWire(child.handle.stdout!)
    const disposing = disposeCursorChild(wire, child.handle)
    child.fail(new Error('observer failed'))
    await expect(disposing).rejects.toThrow('observer failed')
  })
})