fix pre-step lifecycle regressions

packages/core/agent-loop/src/agent.ts

@@ -217,6 +217,7 @@ export class ReactLoopAgent implements Agent {
           await this.loopCtx.serial(agentCarrier(this), 'agent/turn-stopping', this, turn, signal)
           signal.throwIfAborted()
         }
+        if (turnEnds && this.inbox.nextStep.length === 0) break
         decision = await this.preStep('next-step', { turn, step: phase.step + 1 })
         if (decision.kind === 'reject') {
           turnEnds = { kind: 'blocked' }

packages/core/agent-loop/tests/contract-regressions.spec.ts

@@ -292,7 +292,6 @@ describe('abort during tool execution ends the turn', () => {
         { type: 'finish', reason: { kind: 'tool-calls' } },
       ] satisfies StreamChunk[],
       textResponse('later turn'),
-      textResponse('context accepted'),
     ])
     const ctx = await harness(adapter)
     const agent = ctx.agentLoop.create(SessionId('a-historical-tool-pair'), { provider: 'mock', model: 'mock' })
@@ -338,7 +337,7 @@ describe('abort during tool execution ends the turn', () => {
         ? [event.data.content]
         : [])[0])
       .toEqual([{ type: 'text', text: 'new turn context' }])
-    expect(JSON.stringify(adapter.requests[2]?.messages)).toContain('new turn context')
+    expect(JSON.stringify(adapter.requests[1]?.messages)).toContain('new turn context')
   })
 })
 

packages/core/agent-loop/tests/loop.spec.ts

@@ -313,11 +313,12 @@ describe('agent loop', () => {
     const steering = agent.session.events.find(e =>
       e.type === 'user/message' && JSON.stringify(e.data.content).includes('change of plans'))
     expect(steering).toBeDefined()
-    // Steering enters history before the second step's request derives it.
+    // The entered batch is appended after the second step opens and before its
+    // request derives history.
     const steeringSeq = steering!.seq
     const secondStepStart = agent.session.events.filter(e => e.type === 'step/start')[1]
     expect(secondStepStart).toBeDefined()
-    expect(steeringSeq).toBeLessThan(secondStepStart!.seq)
+    expect(steeringSeq).toBeGreaterThan(secondStepStart!.seq)
 
     // the second model request saw the steering content
     const secondRequest = adapter.requests[1]

packages/core/agent-loop/tests/request-reconstruction.spec.ts

@@ -590,14 +590,18 @@ describe('request stability across the loop', () => {
 
     adapter.requests.forEach((request, index) => {
       const stepStart = stepStarts[index]!
-      // Messages: the derivation over the log prefix strictly before this
-      // step's step/start — rebuilt here through a completely fresh Session.
-      const rebuilt = new Session(SessionId(`rebuild-${index}`), structuredClone(events.slice(0, stepStart.seq)))
+      const firstChunk = events.find(e =>
+        e.type === 'assistant/chunk'
+        && e.data.turn === stepStart.data.turn
+        && e.data.step === stepStart.data.step,
+      )!
+      // Messages: the entered batch is logged after step/start, so rebuild the
+      // complete dispatch prefix through a completely fresh Session.
+      const rebuilt = new Session(SessionId(`rebuild-${index}`), structuredClone(events.slice(0, firstChunk.seq)))
       expect(structuredClone(request.messages)).toEqual(rebuilt.deriveMessages())
 
       // Header: the latest request/header snapshot up to this step's dispatch
       // (its header event sits between step/start and the first chunk).
-      const firstChunk = events.find(e => e.type === 'assistant/chunk' && e.seq > stepStart.seq)!
       const header = foldRequestHeader(events.slice(0, firstChunk.seq))!
       expect(request.model).toBe(header.config.model)
       expect(request.reasoningEffort).toBe(header.config.reasoningEffort)