refactor: unify delegation strategy into single DelegationExecutor

.changeset/unify-delegation-strategy.md

@@ -0,0 +1,5 @@
+---
+"@perstack/runtime": patch
+---
+
+Unify delegation strategy into single DelegationExecutor class

packages/runtime/src/helpers/checkpoint.test.ts

@@ -1,7 +1,6 @@
 import type { Checkpoint, RunSetting } from "@perstack/core"
 import { describe, expect, it, vi } from "vitest"
 import {
-  buildDelegateToState,
   buildDelegationReturnState,
   createInitialCheckpoint,
   createNextStepCheckpoint,
@@ -218,86 +217,3 @@ describe("@perstack/runtime: buildDelegationReturnState", () => {
     warnSpy.mockRestore()
   })
 })
-
-describe("@perstack/runtime: buildDelegateToState", () => {
-  const baseSetting = {
-    jobId: "job-123",
-    runId: "run-123",
-    model: "claude-sonnet-4-20250514",
-    providerConfig: { providerName: "anthropic" as const, apiKey: "test-key" },
-    expertKey: "parent-expert",
-    input: { text: "parent query" },
-    experts: {},
-    reasoningBudget: "low",
-    maxSteps: 100,
-    maxRetries: 3,
-    timeout: 30000,
-    startedAt: 1000,
-    updatedAt: 2000,
-    perstackApiBaseUrl: "https://api.perstack.dev",
-    env: {},
-  } satisfies RunSetting
-  const resultCheckpoint: Checkpoint = {
-    id: "parent-checkpoint-id",
-    jobId: "job-123",
-    runId: "run-123",
-    expert: { key: "parent-expert", name: "parent", version: "1.0.0" },
-    stepNumber: 3,
-    status: "stoppedByDelegate",
-    messages: [
-      { id: "m1", type: "userMessage", contents: [{ id: "c1", type: "textPart", text: "hello" }] },
-    ],
-    usage: {
-      inputTokens: 100,
-      outputTokens: 50,
-      reasoningTokens: 0,
-      totalTokens: 150,
-      cachedInputTokens: 0,
-    },
-    delegateTo: [
-      {
-        expert: { key: "child-expert", name: "child", version: "2.0.0" },
-        toolCallId: "tool-call-456",
-        toolName: "delegateToChild",
-        query: "please do this",
-      },
-    ],
-  }
-  const currentExpert = { key: "parent-expert", name: "parent", version: "1.0.0" }
-
-  it("builds correct setting for delegate target", () => {
-    const result = buildDelegateToState(baseSetting, resultCheckpoint, currentExpert)
-    expect(result.setting.expertKey).toBe("child-expert")
-    expect(result.setting.input).toEqual({ text: "please do this" })
-  })
-
-  it("builds checkpoint with delegate target expert and delegatedBy", () => {
-    const result = buildDelegateToState(baseSetting, resultCheckpoint, currentExpert)
-    expect(result.checkpoint.status).toBe("init")
-    expect(result.checkpoint.messages).toEqual([])
-    expect(result.checkpoint.expert).toEqual({
-      key: "child-expert",
-      name: "child",
-      version: "2.0.0",
-    })
-    expect(result.checkpoint.delegatedBy).toEqual({
-      expert: { key: "parent-expert", name: "parent", version: "1.0.0" },
-      toolCallId: "tool-call-456",
-      toolName: "delegateToChild",
-      checkpointId: "parent-checkpoint-id",
-      runId: "run-123",
-    })
-  })
-
-  it("preserves usage from result checkpoint", () => {
-    const result = buildDelegateToState(baseSetting, resultCheckpoint, currentExpert)
-    expect(result.checkpoint.usage).toEqual(resultCheckpoint.usage)
-  })
-
-  it("throws when delegateTo is missing", () => {
-    const checkpointWithoutDelegateTo = { ...resultCheckpoint, delegateTo: undefined }
-    expect(() =>
-      buildDelegateToState(baseSetting, checkpointWithoutDelegateTo, currentExpert),
-    ).toThrow("delegateTo is required")
-  })
-})

packages/runtime/src/helpers/checkpoint.ts

@@ -97,49 +97,3 @@ export function buildDelegationReturnState(
     },
   }
 }
-
-export function buildDelegateToState(
-  currentSetting: RunSetting,
-  resultCheckpoint: Checkpoint,
-  currentExpert: Pick<Expert, "key" | "name" | "version">,
-): DelegationStateResult {
-  const { delegateTo } = resultCheckpoint
-  if (!delegateTo || delegateTo.length === 0) {
-    throw new Error("delegateTo is required for buildDelegateToState")
-  }
-  const firstDelegation = delegateTo[0]
-  const { expert, toolCallId, toolName, query } = firstDelegation
-  return {
-    setting: {
-      ...currentSetting,
-      expertKey: expert.key,
-      input: {
-        text: query,
-      },
-    },
-    checkpoint: {
-      ...resultCheckpoint,
-      status: "init",
-      messages: [],
-      expert: {
-        key: expert.key,
-        name: expert.name,
-        version: expert.version,
-      },
-      delegatedBy: {
-        expert: {
-          key: currentExpert.key,
-          name: currentExpert.name,
-          version: currentExpert.version,
-        },
-        toolCallId,
-        toolName,
-        checkpointId: resultCheckpoint.id,
-        runId: currentSetting.runId,
-      },
-      usage: resultCheckpoint.usage,
-      pendingToolCalls: undefined,
-      partialToolResults: undefined,
-    },
-  }
-}