修复：完善流式输出滚动跟随

web-ui/src/pages/ProjectPage.test.ts

@@ -2,7 +2,7 @@
 
 import { defineComponent, h } from 'vue'
 import { flushPromises, shallowMount } from '@vue/test-utils'
-import { beforeEach, describe, expect, it, vi } from 'vitest'
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import type { AgentEvent } from '../api'
 import ProjectPage from './ProjectPage.vue'
 
@@ -13,6 +13,7 @@ let outputResizeCallback: ResizeObserverCallback | null = null
 const observeOutputMock = vi.fn()
 const unobserveOutputMock = vi.fn()
 const disconnectOutputObserverMock = vi.fn()
+const mountedWrappers: Array<{ unmount: () => void }> = []
 
 /**
  * JSDOM 不提供 ResizeObserver，这里保留组件注册的回调，模拟流式 Markdown
@@ -139,7 +140,7 @@ function mountProject(runStatus: 'RUNNING' | 'INTERRUPTED', options: ProjectFixt
     throw new Error(`未处理的测试请求：${url}`)
   })
 
-  return shallowMount(ProjectPage, {
+  const wrapper = shallowMount(ProjectPage, {
     global: {
       stubs: {
         'el-button': ElButtonStub,
@@ -151,8 +152,16 @@ function mountProject(runStatus: 'RUNNING' | 'INTERRUPTED', options: ProjectFixt
       }
     }
   })
+  mountedWrappers.push(wrapper)
+  return wrapper
 }
 
+afterEach(() => {
+  // ProjectPage 会注册全局滚动监听；每个用例结束后必须卸载，避免前一个实例
+  // 修改下一用例的 followsLatestOutput 状态，造成测试假阳性或假阴性。
+  while (mountedWrappers.length) mountedWrappers.pop()!.unmount()
+})
+
 describe('ProjectPage 模型切换', () => {
   beforeEach(() => {
     // Vitest 会把钩子返回的函数当作清理回调，因此这里不能直接返回 mockReset() 的返回值。
@@ -280,12 +289,112 @@ describe('ProjectPage 项目工作区', () => {
     expect(scrollTo).toHaveBeenCalledWith({ top: 1800, behavior: 'auto' })
     expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
 
+    // 箭头点击后如果输出容器先发生尺寸变化，必须保留程序滚动目标，
+    // 不能因 ResizeObserver 的再次滚动把“持续跟随”状态提前结束。
+    Object.defineProperty(document.documentElement, 'scrollHeight', { configurable: true, value: 1900 })
+    outputResizeCallback!([], {} as ResizeObserver)
+
     // 大文档滚动可能先派发尚未到达目标底部的中间事件，不能把程序滚动误判为用户再次上滚。
     Object.defineProperty(window, 'scrollY', { configurable: true, value: 1190 })
     window.dispatchEvent(new Event('scroll'))
     await wrapper.vm.$nextTick()
     expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
 
+    // 点击后浏览器可能先派发仍接近旧位置的事件；即使距离底部小于通用阈值，
+    // 也不能提前结束程序滚动跟踪，否则紧接着的布局滚动会再次显示箭头。
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1180 })
+    window.dispatchEvent(new Event('scroll'))
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1170 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
+
+    // 用户上滚事件先于 scroll 到达时，必须立即取消跟随，不能被尺寸观察器抢回底部。
+    window.dispatchEvent(new WheelEvent('wheel', { deltaY: -24 }))
+    scrollTo.mockClear()
+    Object.defineProperty(document.documentElement, 'scrollHeight', { configurable: true, value: 2100 })
+    outputResizeCallback!([], {} as ResizeObserver)
+    await wrapper.vm.$nextTick()
+    expect(scrollTo).not.toHaveBeenCalled()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+
+    // 已取消的程序滚动可能仍会派发到达底部的延迟事件，不能借此错误恢复跟随。
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1500 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+
+    // 用户明确向下滚动并抵达底部时，仍应恢复持续跟随。
+    window.dispatchEvent(new WheelEvent('wheel', { deltaY: 32 }))
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
+
+    // 在输入控件内使用方向键不应改变页面的自动跟随状态。
+    const modelInput = document.createElement('input')
+    document.body.appendChild(modelInput)
+    modelInput.dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowUp', bubbles: true }))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
+    modelInput.remove()
+
+    // 控件内部的图标/子节点事件也不应触发页面滚动状态切换。
+    const control = document.createElement('button')
+    const icon = document.createElement('span')
+    control.appendChild(icon)
+    document.body.appendChild(control)
+    window.dispatchEvent(new WheelEvent('wheel', { deltaY: -24 }))
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1100 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+    icon.dispatchEvent(new KeyboardEvent('keydown', { key: 'ArrowDown', bubbles: true }))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+    control.remove()
+
+    // 空格键同样会向下翻页，回到底部后应恢复持续跟随。
+    window.dispatchEvent(new WheelEvent('wheel', { deltaY: -24 }))
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1100 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+    window.dispatchEvent(new KeyboardEvent('keydown', { key: ' ' }))
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1500 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
+
+    // 滚动条拖动期间，旧程序滚动到达底部不能提前恢复跟随；释放后向下拖到底部才恢复。
+    Object.defineProperty(document.documentElement, 'clientWidth', { configurable: true, value: 1000 })
+    window.dispatchEvent(new WheelEvent('wheel', { deltaY: -24 }))
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1100 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+    window.dispatchEvent(new MouseEvent('mousedown', { clientX: 1000, clientY: 300 }))
+    window.dispatchEvent(new MouseEvent('mousemove', { clientX: 1000, clientY: 100 }))
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1500 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+    window.dispatchEvent(new MouseEvent('mouseup', { clientX: 1000 }))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+
+    // 向下拖动滚动条并释放到底部时才恢复跟随。
+    window.dispatchEvent(new MouseEvent('mousedown', { clientX: 1000, clientY: 100 }))
+    window.dispatchEvent(new MouseEvent('mousemove', { clientX: 1000, clientY: 300 }))
+    window.dispatchEvent(new MouseEvent('mouseup', { clientX: 1000, clientY: 300 }))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
+
+    // 触摸滚动/滚动条拖动没有 wheel 事件，也必须能取消跟随。
+    window.dispatchEvent(new TouchEvent('touchmove'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(true)
+    await wrapper.get('.back-to-bottom').trigger('click')
+
     // 点击箭头代表重新进入持续跟随模式；同一批 Markdown 的平滑渲染继续增高时也必须跟随。
     scrollTo.mockClear()
     Object.defineProperty(document.documentElement, 'scrollHeight', { configurable: true, value: 2000 })
@@ -294,6 +403,17 @@ describe('ProjectPage 项目工作区', () => {
 
     expect(scrollTo).toHaveBeenCalledWith({ top: 2000 })
 
+    // 即使新内容只让底部前移 20px，也必须记录程序目标，防止中间 scroll 事件误停跟随。
+    scrollTo.mockClear()
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1380 })
+    Object.defineProperty(document.documentElement, 'scrollHeight', { configurable: true, value: 2000 })
+    outputResizeCallback!([], {} as ResizeObserver)
+    expect(scrollTo).toHaveBeenCalledWith({ top: 2000 })
+    Object.defineProperty(window, 'scrollY', { configurable: true, value: 1370 })
+    window.dispatchEvent(new Event('scroll'))
+    await wrapper.vm.$nextTick()
+    expect(wrapper.find('.back-to-bottom').exists()).toBe(false)
+
     // 尺寸变化后的新流事件到达时仍应保持跟随，而不是重新显示箭头。
     scrollTo.mockClear()
     streamCallback!([{

web-ui/src/pages/ProjectPage.vue

@@ -62,8 +62,17 @@ let loadVersion = 0
 let previousScrollY = 0
 let hasObservedScrollPosition = false
 let pendingFollowScrollTarget: number | null = null
+type UserScrollIntent = 'none' | 'up' | 'down'
+let userScrollIntent: UserScrollIntent = 'none'
+let touchStartY: number | null = null
+let scrollbarDragLastY: number | null = null
+let scrollbarDragDirection: 'none' | 'up' | 'down' = 'none'
+let scrollbarDragActive = false
 const folderInput = ref<HTMLInputElement | null>(null)
 const LATEST_OUTPUT_THRESHOLD = 48
+// 程序滚动只有真正抵达目标位置才算完成，不能复用用户回到底部的宽松阈值。
+// 否则浏览器派发的中间 scroll 事件会提前清除待跟随目标，后续输出就会停止跟随。
+const PROGRAMMATIC_SCROLL_THRESHOLD = 2
 
 const projectId = computed(() => String(route.params.id || ''))
 const waitingPlan = computed(() => pendingAsk.value?.kind === 'planning' && plan.value?.status === 'DRAFT')
@@ -131,6 +140,11 @@ async function load(id: string) {
   previousScrollY = window.scrollY
   hasObservedScrollPosition = false
   pendingFollowScrollTarget = null
+  userScrollIntent = 'none'
+  touchStartY = null
+  scrollbarDragLastY = null
+  scrollbarDragDirection = 'none'
+  scrollbarDragActive = false
   stopStream?.()
   stopStream = null
   project.value = null
@@ -480,17 +494,20 @@ function updateScrollState() {
   const completingFollowScroll = pendingFollowScrollTarget !== null
 
   if (completingFollowScroll) {
-    // 大文档滚动可能产生多个中间事件；抵达目标附近前，这些事件都属于同一次程序滚动。
+    // 大文档滚动可能产生多个中间事件；只有抵达程序滚动目标（允许极小的像素误差）
-    const reachedRequestedTarget = Math.abs(currentScrollY - pendingFollowScrollTarget!) <= LATEST_OUTPUT_THRESHOLD
+    // 才能结束跟踪，不能因为“接近底部”的用户阈值而提前清除目标。
-    if (reachedRequestedTarget || distanceFromBottom <= LATEST_OUTPUT_THRESHOLD) {
+    const reachedRequestedTarget = Math.abs(currentScrollY - pendingFollowScrollTarget!) <= PROGRAMMATIC_SCROLL_THRESHOLD
+    if (reachedRequestedTarget) {
       pendingFollowScrollTarget = null
       followsLatestOutput.value = true
     }
-  } else if (scrollingUp) {
+  } else if (scrollingUp && userScrollIntent !== 'down') {
     followsLatestOutput.value = false
-  } else if (distanceFromBottom <= LATEST_OUTPUT_THRESHOLD) {
+    userScrollIntent = 'up'
+  } else if (!scrollbarDragActive && distanceFromBottom <= LATEST_OUTPUT_THRESHOLD && userScrollIntent !== 'up') {
     // 用户主动回到底部后恢复跟随；仅内容高度增加时则保留原来的跟随意图。
     followsLatestOutput.value = true
+    userScrollIntent = 'none'
   }
   previousScrollY = currentScrollY
   hasObservedScrollPosition = true
@@ -506,7 +523,9 @@ function updateScrollState() {
 function moveViewportToLatestOutput(behavior?: ScrollBehavior) {
   const scrollHeight = document.documentElement.scrollHeight
   const targetScrollY = Math.max(0, scrollHeight - window.innerHeight)
-  pendingFollowScrollTarget = Math.abs(window.scrollY - targetScrollY) <= LATEST_OUTPUT_THRESHOLD
+  // 所有程序滚动（箭头点击、事件更新、ResizeObserver）统一只在真正抵达目标时
+  // 清除待跟随标记，避免近底部的中间 scroll 事件破坏持续跟随状态。
+  pendingFollowScrollTarget = Math.abs(window.scrollY - targetScrollY) <= PROGRAMMATIC_SCROLL_THRESHOLD
     ? null
     : targetScrollY
   hasObservedScrollPosition = true
@@ -518,9 +537,137 @@ function moveViewportToLatestOutput(behavior?: ScrollBehavior) {
 /** 点击悬浮箭头后立即回到最新输出，并重新启用后续输出跟随。 */
 function scrollToBottom() {
   followsLatestOutput.value = true
+  userScrollIntent = 'none'
+  touchStartY = null
+  // 点击箭头即使当前已经接近底部，也必须追踪这次程序滚动的完整过程，
+  // 防止浏览器先派发的中间 scroll 事件被误判成用户向上滚动。
   moveViewportToLatestOutput('auto')
 }
 
+/** 判断事件是否发生在表单控件或可编辑元素内，避免控件内部操作误触发页面滚动状态。 */
+function isInteractiveTarget(target: EventTarget | null) {
+  const element = target instanceof Element ? target : null
+  return Boolean(element && (
+    (element instanceof HTMLElement && element.isContentEditable)
+    || element.closest('input, textarea, select, option, button, [contenteditable="true"]')
+  ))
+}
+
+/** 当前已经位于最新输出附近时恢复跟随，覆盖没有产生 scroll 事件的输入场景。 */
+function restoreFollowIfAtLatest() {
+  const distanceFromBottom = document.documentElement.scrollHeight - window.scrollY - window.innerHeight
+  if (distanceFromBottom <= LATEST_OUTPUT_THRESHOLD) {
+    followsLatestOutput.value = true
+    userScrollIntent = 'none'
+    return true
+  }
+  return false
+}
+
+/**
+ * 在浏览器派发 scroll 之前捕获用户的真实上滚意图。
+ *
+ * <p>输出区域持续变化时 ResizeObserver 也会触发程序滚动；如果只依赖 scroll
+ * 事件，程序滚动可能抢在用户的滚动事件之前执行，导致用户无法回看历史。</p>
+ */
+function handleUserWheel(event: WheelEvent) {
+  if (isInteractiveTarget(event.target)) return
+  if (event.deltaY !== 0) {
+    // 一旦用户开始滚轮操作，先取消尚未完成的程序滚动；否则其延迟 scroll
+    // 事件可能在用户上滚后再次把页面状态恢复到底部。
+    pendingFollowScrollTarget = null
+  }
+  if (event.deltaY < 0) {
+    followsLatestOutput.value = false
+    userScrollIntent = 'up'
+  } else if (event.deltaY > 0) {
+    userScrollIntent = 'down'
+    // 页面已经在底部附近时，浏览器可能不会再派发 scroll 事件。
+    restoreFollowIfAtLatest()
+  }
+}
+
+/** 拖动浏览器右侧滚动条时没有 wheel 事件，需要单独取消程序滚动目标。 */
+function handleUserScrollbarDrag(event: MouseEvent) {
+  const scrollbarStart = document.documentElement.clientWidth
+  if (event.clientX >= scrollbarStart) {
+    followsLatestOutput.value = false
+    pendingFollowScrollTarget = null
+    scrollbarDragLastY = event.clientY
+    scrollbarDragDirection = 'none'
+    scrollbarDragActive = true
+    // 鼠标按下时还无法判断拖动方向，先按上滚保护，释放时再依据实际起止位置修正。
+    userScrollIntent = 'up'
+  }
+}
+
+/** 根据滚动条指针的实际位移记录用户拖动方向，避免把程序 scroll 事件当成用户方向。 */
+function handleUserScrollbarMove(event: MouseEvent) {
+  if (!scrollbarDragActive || scrollbarDragLastY === null) return
+  if (event.clientY < scrollbarDragLastY) scrollbarDragDirection = 'up'
+  else if (event.clientY > scrollbarDragLastY) scrollbarDragDirection = 'down'
+  scrollbarDragLastY = event.clientY
+}
+
+/** 释放滚动条后按实际起止位置确认是否回到底部，结束本次滚动条交互会话。 */
+function handleUserMouseUp() {
+  if (!scrollbarDragActive) return
+  const distanceFromBottom = document.documentElement.scrollHeight - window.scrollY - window.innerHeight
+  scrollbarDragActive = false
+  scrollbarDragLastY = null
+  const draggedUp = scrollbarDragDirection === 'up'
+  scrollbarDragDirection = 'none'
+  if (!draggedUp && distanceFromBottom <= LATEST_OUTPUT_THRESHOLD) {
+    followsLatestOutput.value = true
+    userScrollIntent = 'none'
+  }
+}
+
+/** 记录触摸开始位置，供 touchmove 判断用户是向上还是向下拖动页面。 */
+function handleUserTouchStart(event: TouchEvent) {
+  touchStartY = event.touches[0]?.clientY ?? null
+}
+
+/** 触摸滚动同样要在 scroll 事件之前取消程序滚动，并记录用户滚动方向。 */
+function handleUserTouchMove(event: TouchEvent) {
+  if (isInteractiveTarget(event.target)) return
+  pendingFollowScrollTarget = null
+  const currentY = event.touches[0]?.clientY
+  if (touchStartY === null || currentY === undefined) {
+    // 无法读取触点坐标时按上滚处理，确保不会因延迟程序事件抢回底部。
+    followsLatestOutput.value = false
+    userScrollIntent = 'up'
+    return
+  }
+  const pageScrollDelta = touchStartY - currentY
+  if (pageScrollDelta < 0) {
+    followsLatestOutput.value = false
+    userScrollIntent = 'up'
+  } else if (pageScrollDelta > 0) {
+    userScrollIntent = 'down'
+    restoreFollowIfAtLatest()
+  }
+}
+
+/** 触摸手势结束后清理起始坐标，避免下一次无 touchstart 的异常事件复用旧坐标。 */
+function handleUserTouchEnd() {
+  touchStartY = null
+}
+
+/** 键盘 PageUp、Home、ArrowUp 同样代表用户主动回看历史，应立即暂停跟随。 */
+function handleUserKeydown(event: KeyboardEvent) {
+  if (isInteractiveTarget(event.target)) return
+  if (event.key === 'PageUp' || event.key === 'Home' || event.key === 'ArrowUp') {
+    followsLatestOutput.value = false
+    pendingFollowScrollTarget = null
+    userScrollIntent = 'up'
+  } else if (event.key === 'PageDown' || event.key === 'End' || event.key === 'ArrowDown' || event.key === ' ' || event.key === 'Spacebar') {
+    pendingFollowScrollTarget = null
+    userScrollIntent = 'down'
+    restoreFollowIfAtLatest()
+  }
+}
+
 watch(projectId, id => { if (id) void load(id) }, { immediate: true })
 watch(() => events.value.length, async () => {
   await nextTick()
@@ -543,6 +690,15 @@ onMounted(() => {
   if (outputContainer.value) outputResizeObserver.observe(outputContainer.value)
 
   window.addEventListener('scroll', updateScrollState, { passive: true })
+  window.addEventListener('wheel', handleUserWheel, { passive: true })
+  window.addEventListener('mousedown', handleUserScrollbarDrag)
+  window.addEventListener('mousemove', handleUserScrollbarMove)
+  window.addEventListener('mouseup', handleUserMouseUp)
+  window.addEventListener('touchstart', handleUserTouchStart, { passive: true })
+  window.addEventListener('touchmove', handleUserTouchMove, { passive: true })
+  window.addEventListener('touchend', handleUserTouchEnd, { passive: true })
+  window.addEventListener('touchcancel', handleUserTouchEnd, { passive: true })
+  window.addEventListener('keydown', handleUserKeydown)
   updateScrollState()
 })
 onBeforeUnmount(() => {
@@ -551,6 +707,15 @@ onBeforeUnmount(() => {
   outputResizeObserver?.disconnect()
   outputResizeObserver = null
   window.removeEventListener('scroll', updateScrollState)
+  window.removeEventListener('wheel', handleUserWheel)
+  window.removeEventListener('mousedown', handleUserScrollbarDrag)
+  window.removeEventListener('mousemove', handleUserScrollbarMove)
+  window.removeEventListener('mouseup', handleUserMouseUp)
+  window.removeEventListener('touchstart', handleUserTouchStart)
+  window.removeEventListener('touchmove', handleUserTouchMove)
+  window.removeEventListener('touchend', handleUserTouchEnd)
+  window.removeEventListener('touchcancel', handleUserTouchEnd)
+  window.removeEventListener('keydown', handleUserKeydown)
 })
 </script>