diff --git a/web/src/components/AgentChatComponent.vue b/web/src/components/AgentChatComponent.vue
index 190090f5..cc8c831e 100644
--- a/web/src/components/AgentChatComponent.vue
+++ b/web/src/components/AgentChatComponent.vue
@@ -220,127 +220,215 @@
             </div>
 
             <div class="state-panel-body">
-              <section class="state-section">
-                <div class="state-section-header">
-                  <span class="state-section-title">待办</span>
+              <section
+                class="state-section"
+                :class="{ 'is-collapsed': !isStateSectionExpanded('todos') }"
+              >
+                <button
+                  type="button"
+                  class="state-section-header"
+                  :aria-expanded="isStateSectionExpanded('todos')"
+                  aria-controls="state-section-todos"
+                  @click="toggleStateSection('todos')"
+                >
+                  <span class="state-section-label">
+                    <span class="state-section-title">待办</span>
+                    <ChevronDown
+                      :size="15"
+                      class="state-section-chevron"
+                      :class="{ 'is-collapsed': !isStateSectionExpanded('todos') }"
+                    />
+                  </span>
                   <span v-if="totalTodoCount" class="state-section-meta">
                     {{ completedTodoCount }}/{{ totalTodoCount }} · {{ todoProgress }}%
                   </span>
-                </div>
-                <div v-if="currentTodos.length" class="todo-panel-list">
-                  <div
-                    v-for="(todo, index) in currentTodos"
-                    :key="`${todo.content}-${index}`"
-                    class="todo-item"
-                  >
-                    <div class="todo-item-icon" :class="todo.status || 'unknown'">
-                      <CheckCircleOutlined v-if="todo.status === 'completed'" />
-                      <SyncOutlined v-else-if="todo.status === 'in_progress'" spin />
-                      <ClockCircleOutlined v-else-if="todo.status === 'pending'" />
-                      <CloseCircleOutlined v-else-if="todo.status === 'cancelled'" />
-                      <QuestionCircleOutlined v-else />
-                    </div>
-                    <div class="todo-item-body">
-                      <span class="todo-item-text">{{ todo.content }}</span>
+                </button>
+                <div
+                  v-show="isStateSectionExpanded('todos')"
+                  id="state-section-todos"
+                  class="state-section-content"
+                >
+                  <div v-if="currentTodos.length" class="todo-panel-list">
+                    <div
+                      v-for="(todo, index) in currentTodos"
+                      :key="`${todo.content}-${index}`"
+                      class="todo-item"
+                    >
+                      <div class="todo-item-icon" :class="todo.status || 'unknown'">
+                        <CheckCircleOutlined v-if="todo.status === 'completed'" />
+                        <SyncOutlined v-else-if="todo.status === 'in_progress'" spin />
+                        <ClockCircleOutlined v-else-if="todo.status === 'pending'" />
+                        <CloseCircleOutlined v-else-if="todo.status === 'cancelled'" />
+                        <QuestionCircleOutlined v-else />
+                      </div>
+                      <div class="todo-item-body">
+                        <span class="todo-item-text">{{ todo.content }}</span>
+                      </div>
                     </div>
                   </div>
+                  <div v-else class="state-section-empty">暂无待办</div>
                 </div>
-                <div v-else class="state-section-empty">暂无待办</div>
               </section>
 
-              <section class="state-section">
-                <div class="state-section-header">
-                  <span class="state-section-title">附件/文件</span>
+              <section
+                class="state-section"
+                :class="{ 'is-collapsed': !isStateSectionExpanded('files') }"
+              >
+                <button
+                  type="button"
+                  class="state-section-header"
+                  :aria-expanded="isStateSectionExpanded('files')"
+                  aria-controls="state-section-files"
+                  @click="toggleStateSection('files')"
+                >
+                  <span class="state-section-label">
+                    <span class="state-section-title">附件/文件</span>
+                    <ChevronDown
+                      :size="15"
+                      class="state-section-chevron"
+                      :class="{ 'is-collapsed': !isStateSectionExpanded('files') }"
+                    />
+                  </span>
                   <span class="state-section-meta">{{ currentStateFiles.length }}</span>
-                </div>
-                <div v-if="currentStateFiles.length" class="state-list">
-                  <div v-for="file in currentStateFiles" :key="file.key" class="state-list-item">
-                    <FileTypeIcon
-                      :name="file.name || file.path"
-                      :size="18"
-                      class="state-list-item-icon"
-                    />
-                    <div class="state-list-item-body">
-                      <div class="state-list-item-title">{{ file.name }}</div>
-                      <div class="state-list-item-meta">{{ file.meta || file.path }}</div>
+                </button>
+                <div
+                  v-show="isStateSectionExpanded('files')"
+                  id="state-section-files"
+                  class="state-section-content"
+                >
+                  <div v-if="currentStateFiles.length" class="state-list">
+                    <div v-for="file in currentStateFiles" :key="file.key" class="state-list-item">
+                      <FileTypeIcon
+                        :name="file.name || file.path"
+                        :size="18"
+                        class="state-list-item-icon"
+                      />
+                      <div class="state-list-item-body">
+                        <div class="state-list-item-title">{{ file.name }}</div>
+                        <div class="state-list-item-meta">{{ file.meta || file.path }}</div>
+                      </div>
                     </div>
                   </div>
+                  <div v-else class="state-section-empty">暂无附件或文件</div>
                 </div>
-                <div v-else class="state-section-empty">暂无附件或文件</div>
               </section>
 
-              <section class="state-section">
-                <div class="state-section-header">
-                  <span class="state-section-title">产物</span>
+              <section
+                class="state-section"
+                :class="{ 'is-collapsed': !isStateSectionExpanded('artifacts') }"
+              >
+                <button
+                  type="button"
+                  class="state-section-header"
+                  :aria-expanded="isStateSectionExpanded('artifacts')"
+                  aria-controls="state-section-artifacts"
+                  @click="toggleStateSection('artifacts')"
+                >
+                  <span class="state-section-label">
+                    <span class="state-section-title">产物</span>
+                    <ChevronDown
+                      :size="15"
+                      class="state-section-chevron"
+                      :class="{ 'is-collapsed': !isStateSectionExpanded('artifacts') }"
+                    />
+                  </span>
                   <span class="state-section-meta">{{ currentArtifactFiles.length }}</span>
+                </button>
+                <div
+                  v-show="isStateSectionExpanded('artifacts')"
+                  id="state-section-artifacts"
+                  class="state-section-content"
+                >
+                  <div v-if="currentArtifactFiles.length" class="state-list">
+                    <button
+                      v-for="file in currentArtifactFiles"
+                      :key="file.path"
+                      type="button"
+                      class="state-list-item state-list-item--button"
+                      :title="`打开 ${file.name}`"
+                      @click="openPanelPreview(file)"
+                    >
+                      <FileTypeIcon
+                        :name="file.name || file.path"
+                        :size="18"
+                        class="state-list-item-icon"
+                      />
+                      <div class="state-list-item-body">
+                        <div class="state-list-item-title">{{ file.name }}</div>
+                        <div class="state-list-item-meta">{{ file.meta }}</div>
+                      </div>
+                    </button>
+                  </div>
+                  <div v-else class="state-section-empty">暂无产物</div>
                 </div>
-                <div v-if="currentArtifactFiles.length" class="state-list">
-                  <button
-                    v-for="file in currentArtifactFiles"
-                    :key="file.path"
-                    type="button"
-                    class="state-list-item state-list-item--button"
-                    :title="`打开 ${file.name}`"
-                    @click="openPanelPreview(file)"
-                  >
-                    <FileTypeIcon
-                      :name="file.name || file.path"
-                      :size="18"
-                      class="state-list-item-icon"
-                    />
-                    <div class="state-list-item-body">
-                      <div class="state-list-item-title">{{ file.name }}</div>
-                      <div class="state-list-item-meta">{{ file.meta }}</div>
-                    </div>
-                  </button>
-                </div>
-                <div v-else class="state-section-empty">暂无产物</div>
               </section>
 
-              <section class="state-section">
-                <div class="state-section-header">
-                  <span class="state-section-title">子智能体</span>
-                  <span class="state-section-meta">{{ displaySubagentRuns.length }}</span>
-                </div>
-                <div v-if="displaySubagentRuns.length" class="state-list">
-                  <div
-                    v-for="(run, index) in displaySubagentRuns"
-                    :key="run.id || `${run.subagent_type || 'subagent'}-${index}`"
-                    class="state-list-item"
-                    :class="{ 'is-clickable': run.child_thread_id }"
-                    @click="run.child_thread_id && openSubagentThread(run)"
-                  >
-                    <img
-                      v-if="getSubagentIconSrc(run)"
-                      class="state-subagent-icon"
-                      :src="getSubagentIconSrc(run)"
-                      :alt="`${getSubagentRunName(run)}图标`"
+              <section
+                class="state-section"
+                :class="{ 'is-collapsed': !isStateSectionExpanded('subagents') }"
+              >
+                <button
+                  type="button"
+                  class="state-section-header"
+                  :aria-expanded="isStateSectionExpanded('subagents')"
+                  aria-controls="state-section-subagents"
+                  @click="toggleStateSection('subagents')"
+                >
+                  <span class="state-section-label">
+                    <span class="state-section-title">子智能体</span>
+                    <ChevronDown
+                      :size="15"
+                      class="state-section-chevron"
+                      :class="{ 'is-collapsed': !isStateSectionExpanded('subagents') }"
                     />
-                    <span v-else class="state-subagent-icon" aria-hidden="true"></span>
-                    <div class="state-list-item-body">
-                      <div class="state-list-item-title state-subagent-title">
-                        <span>{{ getSubagentRunName(run) }}</span>
-                        <CheckCircleOutlined
-                          v-if="run.status === 'completed'"
-                          class="state-subagent-status-icon state-subagent-completed-icon"
-                        />
-                        <CloseCircleOutlined
-                          v-else-if="run.status === 'failed'"
-                          class="state-subagent-status-icon state-subagent-failed-icon"
-                        />
-                        <SyncOutlined
-                          v-else-if="run.status === 'running'"
-                          spin
-                          class="state-subagent-status-icon state-subagent-running-icon"
-                        />
-                      </div>
-                      <div class="state-list-item-meta">
-                        {{ run.description || getSubagentRunMeta(run) }}
+                  </span>
+                  <span class="state-section-meta">{{ displaySubagentRuns.length }}</span>
+                </button>
+                <div
+                  v-show="isStateSectionExpanded('subagents')"
+                  id="state-section-subagents"
+                  class="state-section-content"
+                >
+                  <div v-if="displaySubagentRuns.length" class="state-list">
+                    <div
+                      v-for="(run, index) in displaySubagentRuns"
+                      :key="run.id || `${run.subagent_type || 'subagent'}-${index}`"
+                      class="state-list-item"
+                      :class="{ 'is-clickable': run.child_thread_id }"
+                      @click="run.child_thread_id && openSubagentThread(run)"
+                    >
+                      <img
+                        v-if="getSubagentIconSrc(run)"
+                        class="state-subagent-icon"
+                        :src="getSubagentIconSrc(run)"
+                        :alt="`${getSubagentRunName(run)}图标`"
+                      />
+                      <span v-else class="state-subagent-icon" aria-hidden="true"></span>
+                      <div class="state-list-item-body">
+                        <div class="state-list-item-title state-subagent-title">
+                          <span>{{ getSubagentRunName(run) }}</span>
+                          <CheckCircleOutlined
+                            v-if="run.status === 'completed'"
+                            class="state-subagent-status-icon state-subagent-completed-icon"
+                          />
+                          <CloseCircleOutlined
+                            v-else-if="run.status === 'failed'"
+                            class="state-subagent-status-icon state-subagent-failed-icon"
+                          />
+                          <SyncOutlined
+                            v-else-if="run.status === 'running'"
+                            spin
+                            class="state-subagent-status-icon state-subagent-running-icon"
+                          />
+                        </div>
+                        <div class="state-list-item-meta">
+                          {{ run.description || getSubagentRunMeta(run) }}
+                        </div>
                       </div>
                     </div>
                   </div>
+                  <div v-else class="state-section-empty">暂无子智能体运行</div>
                 </div>
-                <div v-else class="state-section-empty">暂无子智能体运行</div>
               </section>
             </div>
           </div>
@@ -351,7 +439,8 @@
     <SubagentThreadModal
       v-model:open="subagentThreadModal.open"
       :child-thread-id="subagentThreadModal.childThreadId"
-      :subagent-name="subagentThreadModal.subagentName"
+      :subagent-name="activeSubagentThreadName"
+      :subagent-avatar="activeSubagentThreadAvatar"
     />
   </div>
 </template>
@@ -370,7 +459,7 @@ import {
   onDeactivated
 } from 'vue'
 import { message } from 'ant-design-vue'
-import { RefreshCw, SquareCheck } from 'lucide-vue-next'
+import { ChevronDown, RefreshCw, SquareCheck } from 'lucide-vue-next'
 import { formatFileSize } from '@/utils/file_utils'
 import FileTypeIcon from '@/components/common/FileTypeIcon.vue'
 import { generatePixelAvatar } from '@/utils/pixelAvatar'
@@ -480,6 +569,12 @@ const threadFilesMap = ref({})
 const threadAttachmentsMap = ref({})
 const attachmentUploadModalOpen = ref(false)
 const isRefreshingState = ref(false)
+const collapsedStateSections = reactive({
+  todos: false,
+  files: false,
+  artifacts: false,
+  subagents: false
+})
 const threadConfigNoticeMap = ref({})
 const threadPendingConfigNoticeMap = ref({})
 const threadConfigSnapshotMap = ref({})
@@ -787,14 +882,20 @@ const currentSubagentOptionBySlug = computed(() => {
 const subagentThreadModal = reactive({
   open: false,
   childThreadId: '',
-  subagentName: ''
+  subagentName: '',
+  subagentAvatar: ''
 })
 const openSubagentThread = (run) => {
   if (!run?.child_thread_id) return
   subagentThreadModal.childThreadId = String(run.child_thread_id)
   subagentThreadModal.subagentName = getSubagentRunName(run)
+  subagentThreadModal.subagentAvatar = getSubagentIconSrc(run)
   subagentThreadModal.open = true
 }
+const isStateSectionExpanded = (key) => !collapsedStateSections[key]
+const toggleStateSection = (key) => {
+  collapsedStateSections[key] = !collapsedStateSections[key]
+}
 const currentStateFiles = computed(() => {
   const files = []
   const seenPaths = new Set()
@@ -988,6 +1089,25 @@ const displaySubagentRuns = computed(() => {
   return merged
 })
 
+const activeSubagentThreadRun = computed(() => {
+  if (!subagentThreadModal.childThreadId) return null
+  return (
+    displaySubagentRuns.value.find(
+      (run) => String(run?.child_thread_id || '') === subagentThreadModal.childThreadId
+    ) || null
+  )
+})
+const activeSubagentThreadName = computed(() =>
+  activeSubagentThreadRun.value
+    ? getSubagentRunName(activeSubagentThreadRun.value)
+    : subagentThreadModal.subagentName
+)
+const activeSubagentThreadAvatar = computed(() =>
+  activeSubagentThreadRun.value
+    ? getSubagentIconSrc(activeSubagentThreadRun.value) || subagentThreadModal.subagentAvatar
+    : subagentThreadModal.subagentAvatar
+)
+
 // 首次运行的子智能体：前端按后端同样的哈希推算 child_thread_id，缓存到映射里供面板/轨迹定位。
 watch(
   onGoingConvMessages,
@@ -2858,13 +2978,45 @@ watch(currentChatId, (threadId, oldThreadId) => {
   display: flex;
   flex-direction: column;
   gap: 8px;
+
+  &.is-collapsed {
+    gap: 0;
+  }
 }
 
 .state-section-header {
+  width: 100%;
   display: flex;
   align-items: center;
   justify-content: space-between;
   gap: 8px;
+  padding: 2px 0;
+  border: none;
+  border-radius: 6px;
+  background: transparent;
+  color: inherit;
+  font: inherit;
+  text-align: left;
+  cursor: pointer;
+
+  &:hover {
+    .state-section-title,
+    .state-section-chevron {
+      color: var(--gray-900);
+    }
+  }
+
+  &:focus-visible {
+    outline: 2px solid var(--main-200);
+    outline-offset: 2px;
+  }
+}
+
+.state-section-label {
+  min-width: 0;
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
 }
 
 .state-section-title {
@@ -2873,6 +3025,22 @@ watch(currentChatId, (threadId, oldThreadId) => {
   color: var(--gray-800);
 }
 
+.state-section-chevron {
+  flex-shrink: 0;
+  color: var(--gray-500);
+  transition:
+    transform 0.18s ease,
+    color 0.18s ease;
+
+  &.is-collapsed {
+    transform: rotate(-90deg);
+  }
+}
+
+.state-section-content {
+  min-width: 0;
+}
+
 .state-section-empty {
   padding: 10px 12px;
   border-radius: 10px;
diff --git a/web/src/components/SubagentThreadModal.vue b/web/src/components/SubagentThreadModal.vue
index 1b39caef..77594b1b 100644
--- a/web/src/components/SubagentThreadModal.vue
+++ b/web/src/components/SubagentThreadModal.vue
@@ -1,12 +1,23 @@
 <template>
   <a-modal
     :open="open"
-    :title="subagentName || '子智能体'"
     :footer="null"
     :width="800"
     :destroyOnClose="true"
     @cancel="$emit('update:open', false)"
   >
+    <template #title>
+      <div class="subagent-thread-modal-title">
+        <img
+          v-if="subagentAvatar"
+          class="subagent-thread-modal-avatar"
+          :src="subagentAvatar"
+          :alt="`${modalTitleName} icon`"
+        />
+        <span v-else class="subagent-thread-modal-avatar" aria-hidden="true"></span>
+        <span class="subagent-thread-modal-name">{{ modalTitleName }}</span>
+      </div>
+    </template>
     <div class="subagent-thread-modal-body">
       <div v-if="loading" class="subagent-thread-modal-state">正在加载子智能体消息...</div>
       <div v-else-if="error" class="subagent-thread-modal-state is-error">{{ error }}</div>
@@ -16,7 +27,7 @@
 </template>
 
 <script setup>
-import { ref, watch } from 'vue'
+import { computed, ref, watch } from 'vue'
 import { agentApi } from '@/apis'
 import { MessageProcessor } from '@/utils/messageProcessor'
 import ThreadMessageList from '@/components/ThreadMessageList.vue'
@@ -33,6 +44,10 @@ const props = defineProps({
   subagentName: {
     type: String,
     default: ''
+  },
+  subagentAvatar: {
+    type: String,
+    default: ''
   }
 })
 
@@ -42,6 +57,8 @@ const loading = ref(false)
 const error = ref('')
 const messages = ref([])
 
+const modalTitleName = computed(() => props.subagentName || '子智能体')
+
 // LangChain 内容块数组 → 纯文本（仅保留 text 块）
 const flattenContent = (content) => {
   if (typeof content === 'string') return content
@@ -86,6 +103,31 @@ watch(
 </script>
 
 <style lang="less" scoped>
+.subagent-thread-modal-title {
+  min-width: 0;
+  display: flex;
+  align-items: center;
+  gap: 10px;
+  padding-right: 24px;
+}
+
+.subagent-thread-modal-avatar {
+  width: 28px;
+  height: 28px;
+  flex-shrink: 0;
+  border: 1px solid var(--gray-150);
+  border-radius: 7px;
+  background: var(--gray-0);
+  object-fit: cover;
+}
+
+.subagent-thread-modal-name {
+  min-width: 0;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
 .subagent-thread-modal-body {
   max-height: 70vh;
   overflow-y: auto;
diff --git a/web/src/utils/__tests__/subagentThread.test.js b/web/src/utils/__tests__/subagentThread.test.js
new file mode 100644
index 00000000..dfe44789
--- /dev/null
+++ b/web/src/utils/__tests__/subagentThread.test.js
@@ -0,0 +1,30 @@
+import assert from 'node:assert/strict'
+
+import { makeChildThreadId } from '../subagentThread.js'
+
+const EXPECTED_THREAD_ID = 'subagent_198242794595efedd1850d5263f677c9b628052b1bfca0d5bc77499'
+
+const run = async () => {
+  assert.equal(await makeChildThreadId('thread-1', 'researcher', 'call-1'), EXPECTED_THREAD_ID)
+  assert.equal(await makeChildThreadId('', 'researcher', 'call-1'), '')
+
+  const originalCrypto = Object.getOwnPropertyDescriptor(globalThis, 'crypto')
+  try {
+    Object.defineProperty(globalThis, 'crypto', {
+      configurable: true,
+      value: {}
+    })
+
+    assert.equal(await makeChildThreadId('thread-1', 'researcher', 'call-1'), EXPECTED_THREAD_ID)
+  } finally {
+    if (originalCrypto) {
+      Object.defineProperty(globalThis, 'crypto', originalCrypto)
+    } else {
+      delete globalThis.crypto
+    }
+  }
+
+  console.log('subagentThread: all assertions passed')
+}
+
+await run()
diff --git a/web/src/utils/subagentThread.js b/web/src/utils/subagentThread.js
index 566f5ab4..0bfeab89 100644
--- a/web/src/utils/subagentThread.js
+++ b/web/src/utils/subagentThread.js
@@ -4,12 +4,100 @@
 const PREFIX = 'subagent_'
 const DIGEST_LENGTH = 64 - PREFIX.length
 
+const SHA256_K = [
+  0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
+  0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
+  0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+  0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
+  0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
+  0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+  0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
+  0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
+]
+
+const rightRotate = (value, shift) => ((value >>> shift) | (value << (32 - shift))) >>> 0
+
+const bytesToHex = (bytes) =>
+  Array.from(bytes)
+    .map((byte) => byte.toString(16).padStart(2, '0'))
+    .join('')
+
+const sha256Hex = (bytes) => {
+  const paddedLength = Math.ceil((bytes.length + 9) / 64) * 64
+  const padded = new Uint8Array(paddedLength)
+  padded.set(bytes)
+  padded[bytes.length] = 0x80
+
+  const view = new DataView(padded.buffer)
+  const bitLength = bytes.length * 8
+  view.setUint32(paddedLength - 8, Math.floor(bitLength / 0x100000000))
+  view.setUint32(paddedLength - 4, bitLength >>> 0)
+
+  const words = new Uint32Array(64)
+  const hash = [
+    0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19
+  ]
+
+  for (let offset = 0; offset < paddedLength; offset += 64) {
+    for (let index = 0; index < 16; index += 1) {
+      words[index] = view.getUint32(offset + index * 4)
+    }
+    for (let index = 16; index < 64; index += 1) {
+      const s0 =
+        rightRotate(words[index - 15], 7) ^
+        rightRotate(words[index - 15], 18) ^
+        (words[index - 15] >>> 3)
+      const s1 =
+        rightRotate(words[index - 2], 17) ^
+        rightRotate(words[index - 2], 19) ^
+        (words[index - 2] >>> 10)
+      words[index] = (words[index - 16] + s0 + words[index - 7] + s1) >>> 0
+    }
+
+    let [a, b, c, d, e, f, g, h] = hash
+    for (let index = 0; index < 64; index += 1) {
+      const s1 = rightRotate(e, 6) ^ rightRotate(e, 11) ^ rightRotate(e, 25)
+      const ch = (e & f) ^ (~e & g)
+      const temp1 = (h + s1 + ch + SHA256_K[index] + words[index]) >>> 0
+      const s0 = rightRotate(a, 2) ^ rightRotate(a, 13) ^ rightRotate(a, 22)
+      const maj = (a & b) ^ (a & c) ^ (b & c)
+      const temp2 = (s0 + maj) >>> 0
+
+      h = g
+      g = f
+      f = e
+      e = (d + temp1) >>> 0
+      d = c
+      c = b
+      b = a
+      a = (temp1 + temp2) >>> 0
+    }
+
+    hash[0] = (hash[0] + a) >>> 0
+    hash[1] = (hash[1] + b) >>> 0
+    hash[2] = (hash[2] + c) >>> 0
+    hash[3] = (hash[3] + d) >>> 0
+    hash[4] = (hash[4] + e) >>> 0
+    hash[5] = (hash[5] + f) >>> 0
+    hash[6] = (hash[6] + g) >>> 0
+    hash[7] = (hash[7] + h) >>> 0
+  }
+
+  return hash.map((word) => word.toString(16).padStart(8, '0')).join('')
+}
+
+const digestSha256Hex = async (bytes) => {
+  const subtle = globalThis.crypto?.subtle
+  if (typeof subtle?.digest === 'function') {
+    const buffer = await subtle.digest('SHA-256', bytes)
+    return bytesToHex(new Uint8Array(buffer))
+  }
+  return sha256Hex(bytes)
+}
+
 export async function makeChildThreadId(parentThreadId, agentSlug, toolCallId) {
   if (!parentThreadId || !agentSlug || !toolCallId) return ''
   const data = new TextEncoder().encode(`${parentThreadId}:${agentSlug}:${toolCallId}`)
-  const buffer = await crypto.subtle.digest('SHA-256', data)
-  const hex = Array.from(new Uint8Array(buffer))
-    .map((byte) => byte.toString(16).padStart(2, '0'))
-    .join('')
+  const hex = await digestSha256Hex(data)
   return `${PREFIX}${hex.slice(0, DIGEST_LENGTH)}`
 }