refactor(agent-loop): simplify observable state machine

packages/skill/tool-skill/tests/tool-skill.spec.ts

@@ -4,6 +4,8 @@ import { join } from 'node:path'
 import { tmpdir } from 'node:os'
 import { Context } from 'cordis'
 import { CallId, type Message } from '@deepseek-ai/dsh-llm'
+import { AgentMessageId } from '@deepseek-ai/dsh-agent'
+import { Session, SessionId } from '@deepseek-ai/dsh-session'
 import { createScope, type Scope } from '@deepseek-ai/dsh-scope'
 import SystemPrompt, { renderPrompt } from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry, { defineContentToolFixture } from '@deepseek-ai/dsh-tools'
@@ -35,7 +37,28 @@ async function setup(home: string, config: toolSkill.Config = {}): Promise<Conte
 }
 
 function agentForCwd(cwd: string): Agent {
-  return { session: { header: { cwd } } } as unknown as Agent
+  const id = SessionId(`tool-skill-${cwd}`)
+  const session = new Session(id, [], { version: 0, id, createdAt: 0, cwd })
+  return {
+    ctx: new Context(),
+    id,
+    options: {},
+    session,
+    status: 'idle',
+    send: () => AgentMessageId('stub'),
+    followup: () => AgentMessageId('stub'),
+    steer: () => AgentMessageId('stub'),
+    inject(content, options) {
+      session.append('user/message', {
+        content,
+        source: options?.source ?? { kind: 'user' },
+      }, { surfaceOp: 'append' })
+      return AgentMessageId('stub')
+    },
+    cancel() {},
+    retry() {},
+    whenIdle: () => Promise.resolve(),
+  }
 }
 
 async function composePrefix(ctx: Context, cwd: string, signal = new AbortController().signal): Promise<Message[]> {
@@ -43,11 +66,8 @@ async function composePrefix(ctx: Context, cwd: string, signal = new AbortContro
 }
 
 async function composePrefixForAgent(ctx: Context, agent: Agent, signal = new AbortController().signal): Promise<Message[]> {
-  const empty: Message[] = []
-  return await agentEvents(ctx, agent).waterfall(
-    'agent/session-prefix', empty, signal,
-    () => Promise.resolve(empty),
-  )
+  await agentEvents(ctx, agent).serial('agent/step', 1, 1, signal)
+  return agent.session.deriveMessages()
 }
 
 async function mintAgentScope(ctx: Context, cwd: string): Promise<{ agent: Agent; scope: Scope }> {
@@ -86,7 +106,7 @@ describe('dsh-tool-skill', () => {
     expect(ctx.tools.schemas().map(tool => tool.name)).toEqual(['skill'])
   })
 
-  it('forwards the session-prefix abort signal to skill discovery', async () => {
+  it('forwards the step abort signal to skill discovery', async () => {
     const home = await tempDir('tool-prefix-signal')
     const ctx = await setup(home)
     let seenSignal: AbortSignal | undefined
@@ -107,7 +127,7 @@ describe('dsh-tool-skill', () => {
     expect(seenSignal).toBe(controller.signal)
   })
 
-  it('contributes a stable name-and-description catalog through the session prefix', async () => {
+  it('injects a stable durable name-and-description catalog at the first step', async () => {
     const home = await tempDir('tool-catalog')
     const ctx = await setup(home, { catalogDescriptionMaxLength: 50 })
     ctx.skills.register({
@@ -126,10 +146,11 @@ describe('dsh-tool-skill', () => {
       provider: 'runtime',
       content: 'A body.',
     })
-    ctx.on('agent/session-prefix', async (_agent, _prefix, _signal, next): Promise<Message[]> => [
-      { role: 'user', content: [{ type: 'text', text: 'later contribution' }] },
-      ...await next(),
-    ])
+    ctx.on('agent/step', (agent) => {
+      agent.inject([{ type: 'text', text: 'later contribution' }], {
+        source: { kind: 'plugin', plugin: 'later-contribution' },
+      })
+    })
 
     const prefix = await composePrefix(ctx, '/workspace')
 
@@ -162,7 +183,7 @@ describe('dsh-tool-skill', () => {
     expect(renderPrompt(await ctx.systemPrompt.assemble({ agent: agentForCwd('/workspace') }))).not.toContain('<available_skills>')
   })
 
-  it('does not contribute a session-prefix message when no skills are available', async () => {
+  it('does not inject a catalog when no skills are available', async () => {
     const home = await tempDir('tool-empty-catalog')
     const ctx = await setup(home)