refactor: hide subagent implementation helpers

packages/subagent/subagent-inprocess/README.md

@@ -26,7 +26,7 @@ After fulfillment, the caller owns the run. Provider-plugin unload does not revo
 
 `InProcessRunOptions` is `{ seed?: SessionEvent[] }`. Spawn omits it. Fork supplies a balanced completed-turn prefix and records its length so the result reader never mistakes a seeded parent message for child output.
 
-`depthOf(agent)` reads `AgentOptions.subagentDepth`, treating absence as top-level depth zero and rejecting malformed stored values. `SubagentDepthError` reports an attempted child depth above `maxDepth`; an unrepresentable depth above the safe-integer domain is a `RangeError`.
+Depth enforcement is internal to `startInProcessRun`: it reads `AgentOptions.subagentDepth`, treats absence as top-level depth zero, rejects malformed stored values, and reports an attempted child depth above `maxDepth`. An unrepresentable depth above the safe-integer domain is a `RangeError`.
 
 ## Structured output
 

packages/subagent/subagent-inprocess/src/index.ts

@@ -36,7 +36,7 @@ declare module '@deepseek-ai/dsh-agent' {
  * @param agent - the agent whose options carry the depth.
  * @returns its non-negative safe-integer depth.
  */
-export function depthOf(agent: Agent): number {
+function depthOf(agent: Agent): number {
   const depth = agent.options.subagentDepth
   if (depth === undefined) return 0
   if (!Number.isSafeInteger(depth) || depth < 0 || Object.is(depth, -0)) {
@@ -46,7 +46,7 @@ export function depthOf(agent: Agent): number {
 }
 
 /** Thrown when starting a child would exceed the requested depth cap. */
-export class SubagentDepthError extends Error {
+class SubagentDepthError extends Error {
   constructor(public readonly attemptedDepth: number, public readonly maxDepth: number) {
     super(`subagent depth ${attemptedDepth} exceeds maxDepth ${maxDepth}`)
     this.name = 'SubagentDepthError'

packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts

@@ -10,7 +10,7 @@ import AgentLoop from '@deepseek-ai/dsh-agent-loop'
 import * as Invariants from '@deepseek-ai/dsh-invariants'
 import SubagentService from '@deepseek-ai/dsh-subagent'
 import { MockAdapter, textResponse } from '../../../core/agent-loop/tests/mock-adapter.ts'
-import { depthOf, SubagentDepthError, startInProcessRun } from '../src/index.ts'
+import { startInProcessRun } from '../src/index.ts'
 
 type Script = ConstructorParameters<typeof MockAdapter>[0]
 
@@ -37,19 +37,6 @@ function text(blocks: readonly { type: string; text?: string }[]): string {
   return blocks.filter(block => block.type === 'text').map(block => block.text).join('')
 }
 
-describe('depthOf', () => {
-  it('reads zero for a top-level agent and an explicit child depth', async () => {
-    const { parent } = await setup([])
-    expect(depthOf(parent)).toBe(0)
-    expect(depthOf({ options: { subagentDepth: 3 } } as unknown as Agent)).toBe(3)
-  })
-
-  it.each([Number.NaN, 1.5, -1, -0, Number.MAX_SAFE_INTEGER + 1])('rejects malformed depth %s', (value) => {
-    expect(() => depthOf({ options: { subagentDepth: value } } as unknown as Agent))
-      .toThrow('non-negative safe integer')
-  })
-})
-
 describe('startInProcessRun', () => {
   it('returns only after publication, drives a fresh child, and disposes it', async () => {
     const { ctx, parent } = await setup([textResponse('driver answer')])
@@ -58,7 +45,7 @@ describe('startInProcessRun', () => {
     const result = await run.result
     expect(result.stopReason).toBe('completed')
     expect(text(result.output)).toBe('driver answer')
-    expect(depthOf(ctx.agents.get(run.id)!)).toBe(1)
+    expect(ctx.agents.get(run.id)!.options.subagentDepth).toBe(1)
     await run.dispose()
     await run.dispose()
     expect(ctx.agents.get(run.id)).toBeUndefined()
@@ -83,7 +70,12 @@ describe('startInProcessRun', () => {
     await expect(startInProcessRun({ ...request(parent), maxDepth: -1 }, {}))
       .rejects.toThrow('non-negative safe integer')
     await expect(startInProcessRun({ ...request(parent), maxDepth: 0 }, {}))
-      .rejects.toBeInstanceOf(SubagentDepthError)
+      .rejects.toMatchObject({ name: 'SubagentDepthError' })
+    for (const value of [Number.NaN, 1.5, -1, -0, Number.MAX_SAFE_INTEGER + 1]) {
+      const malformed = { options: { subagentDepth: value } } as unknown as Agent
+      await expect(startInProcessRun(request(malformed), {}))
+        .rejects.toThrow('agent subagentDepth must be a non-negative safe integer')
+    }
     const maxParent = { options: { subagentDepth: Number.MAX_SAFE_INTEGER } } as unknown as Agent
     await expect(startInProcessRun(request(maxParent), {})).rejects.toBeInstanceOf(RangeError)
   })