diff --git a/.changeset/web-first-prompt-fixes.md b/.changeset/web-first-prompt-fixes.md
new file mode 100644
index 000000000..fa34159ab
--- /dev/null
+++ b/.changeset/web-first-prompt-fixes.md
@@ -0,0 +1,5 @@
+---
+"@moonshot-ai/kimi-code": patch
+---
+
+web: Fix an occasional "another turn is active" error when sending the first message of a new conversation, and show a starting state while it is being sent.
diff --git a/apps/kimi-web/src/App.vue b/apps/kimi-web/src/App.vue
index e46e8a2fc..26dfcaefc 100644
--- a/apps/kimi-web/src/App.vue
+++ b/apps/kimi-web/src/App.vue
@@ -739,6 +739,7 @@ function openPr(url: string): void {
       :search-files="client.searchFiles"
       :upload-image="client.uploadImage"
       :sending="client.isSending.value"
+      :starting="client.isStartingFirstPrompt.value"
       :fast-moon="client.fastMoon.value"
       :file-reload-key="client.activeSessionId.value"
       :session-loading="client.sessionLoading.value"
diff --git a/apps/kimi-web/src/components/chat/ChatDock.vue b/apps/kimi-web/src/components/chat/ChatDock.vue
index 8da9067d2..ab84330a3 100644
--- a/apps/kimi-web/src/components/chat/ChatDock.vue
+++ b/apps/kimi-web/src/components/chat/ChatDock.vue
@@ -20,6 +20,10 @@ import Pill from '../ui/Pill.vue';
 const props = defineProps<{
   sessionId?: string;
   running?: boolean;
+  /** True while the empty-composer first prompt is being created + submitted.
+   *  Covers the gap where draft-session creation already selected the new
+   *  session (empty state → dock) before the first prompt is submitted. */
+  starting?: boolean;
   queued?: QueuedPromptView[];
   searchFiles?: (q: string) => Promise<FileItem[]>;
   uploadImage?: (file: Blob, name?: string) => Promise<{ fileId: string; name: string; mediaType: string } | null>;
@@ -256,6 +260,7 @@ defineExpose({ loadForEdit, loadAttachmentsForEdit, focus });
       :models="models"
       :starred-ids="starredIds"
       :skills="skills"
+      :starting="starting"
       @submit="emit('submit', $event)"
       @steer="emit('steer', $event)"
       @command="emit('command', $event)"
diff --git a/apps/kimi-web/src/components/chat/Composer.vue b/apps/kimi-web/src/components/chat/Composer.vue
index 92031302e..2b3968788 100644
--- a/apps/kimi-web/src/components/chat/Composer.vue
+++ b/apps/kimi-web/src/components/chat/Composer.vue
@@ -35,6 +35,9 @@ import Tooltip from '../ui/Tooltip.vue';
 
 const props = withDefaults(defineProps<{
   running?: boolean;
+  /** True while the empty-composer first prompt is being created + submitted.
+   *  Disables the textarea and swaps the send button for a spinner. */
+  starting?: boolean;
   /** Active session id — scopes the persisted unsent draft (per session). */
   sessionId?: string;
   queued?: QueuedPromptView[];
@@ -59,6 +62,7 @@ const props = withDefaults(defineProps<{
   hideContext?: boolean;
 }>(), {
   running: false,
+  starting: false,
   queued: () => [],
   searchFiles: undefined,
   uploadImage: undefined,
@@ -68,11 +72,13 @@ const props = withDefaults(defineProps<{
 });
 
 const placeholder = computed(() =>
-  props.running
-    ? t('composer.placeholderRunning')
-    : props.goalMode
-      ? t('status.goalPlaceholder')
-      : t('composer.placeholder')
+  props.starting
+    ? t('composer.starting')
+    : props.running
+      ? t('composer.placeholderRunning')
+      : props.goalMode
+        ? t('status.goalPlaceholder')
+        : t('composer.placeholder')
 );
 
 const emit = defineEmits<{
@@ -913,6 +919,7 @@ function selectModel(modelId: string): void {
             v-model="text"
             class="ph"
             :placeholder="placeholder"
+            :disabled="starting"
             rows="1"
             @keydown="handleKeydown"
             @compositionstart="handleCompositionStart"
@@ -1131,10 +1138,13 @@ function selectModel(modelId: string): void {
           </Tooltip>
           <button
             class="send"
+            :class="{ 'is-starting': starting }"
             :aria-label="sendLabel"
+            :disabled="starting"
             @click="handleSubmit()"
           >
-            <Icon name="send" size="sm" />
+            <Spinner v-if="starting" size="sm" />
+            <Icon v-else name="send" size="sm" />
           </button>
         </div>
 
@@ -1520,6 +1530,25 @@ function selectModel(modelId: string): void {
   transform: scale(0.92);
 }
 
+.send:disabled {
+  cursor: not-allowed;
+  opacity: 0.88;
+}
+
+.send:disabled:active {
+  transform: none;
+}
+
+/* Spinner-on-accent: recolor the ring so the arc reads on the accent fill.
+   Spinner.vue styles are scoped, so pierce them with :deep(). */
+.send.is-starting :deep(.ui-spinner) {
+  color: var(--color-text-on-accent);
+}
+
+.send.is-starting :deep(.ui-spinner__track) {
+  stroke: rgba(255, 255, 255, 0.32);
+}
+
 .send svg {
   flex: none;
   width: var(--p-ic-lg);
diff --git a/apps/kimi-web/src/components/chat/ConversationPane.vue b/apps/kimi-web/src/components/chat/ConversationPane.vue
index 88fdc5dce..7c7f47511 100644
--- a/apps/kimi-web/src/components/chat/ConversationPane.vue
+++ b/apps/kimi-web/src/components/chat/ConversationPane.vue
@@ -12,6 +12,7 @@ import Composer from './Composer.vue';
 import ChatDock from './ChatDock.vue';
 import ConversationToc, { type ConversationTocItem } from './ConversationToc.vue';
 import Icon from '../ui/Icon.vue';
+import Spinner from '../ui/Spinner.vue';
 import Tooltip from '../ui/Tooltip.vue';
 import { getVisibleWorkspaces } from '../../lib/workspacePicker';
 import { safeRemove, STORAGE_KEYS } from '../../lib/storage';
@@ -48,6 +49,9 @@ const props = defineProps<{
   /** Cache-buster that remounts the chat pane when the active session changes. */
   fileReloadKey?: string | number;
   sending?: boolean;
+  /** True while the empty-composer first prompt is being created + submitted.
+   *  Drives the empty-session "starting conversation…" loading state. */
+  starting?: boolean;
   fastMoon?: boolean;
   /** Mobile shell: compact chrome. */
   mobile?: boolean;
@@ -1134,10 +1138,14 @@ defineExpose({ loadComposerForEdit, focusComposer });
             <!-- Empty session: Composer rendered in the centre of the pane -->
             <div class="empty-spacer" />
             <div class="empty-hint">
-              <span class="empty-hint-title">{{ t('composer.emptyConversationTitle') }}</span>
-              <span class="empty-hint-text">{{ t('composer.emptyConversation') }}</span>
-              <!-- Workspace picker: choose where this new conversation starts. -->
-              <div v-if="hasWorkspaces" class="ws-pick" :style="wsPickStyle">
+              <span class="empty-hint-title" :class="{ 'is-starting': starting }">
+                <Spinner v-if="starting" size="sm" />
+                <span>{{ starting ? t('conversation.starting') : t('composer.emptyConversationTitle') }}</span>
+              </span>
+              <span v-if="!starting" class="empty-hint-text">{{ t('composer.emptyConversation') }}</span>
+              <!-- Workspace picker: choose where this new conversation starts.
+                   Hidden while starting — a workspace is already committed. -->
+              <div v-if="hasWorkspaces && !starting" class="ws-pick" :style="wsPickStyle">
                 <div ref="wsPickMeasureRef" class="ws-pick-measure" aria-hidden="true">
                   <button type="button" class="ws-pick-btn" tabindex="-1">
                     <Icon name="folder" size="sm" />
@@ -1198,7 +1206,7 @@ defineExpose({ loadComposerForEdit, focusComposer });
                 </div>
               </div>
               <button
-                v-else
+                v-else-if="!starting"
                 type="button"
                 class="empty-add-workspace"
                 @click="emit('addWorkspace')"
@@ -1225,6 +1233,7 @@ defineExpose({ loadComposerForEdit, focusComposer });
               :models="models"
               :starred-ids="starredIds"
               :skills="skills"
+              :starting="starting"
               hide-context
               @submit="handleComposerSubmit"
               @steer="emit('steer', $event)"
@@ -1286,6 +1295,7 @@ defineExpose({ loadComposerForEdit, focusComposer });
         :style="chatDockStyle"
         :session-id="sessionId"
         :running="running"
+        :starting="starting"
         :queued="queued"
         :search-files="searchFiles"
         :upload-image="uploadImage"
@@ -1449,6 +1459,13 @@ defineExpose({ loadComposerForEdit, focusComposer });
   font-optical-sizing: auto;
   font-weight: 600;
 }
+.empty-hint-title.is-starting {
+  display: inline-flex;
+  align-items: center;
+  gap: 9px;
+  color: var(--dim);
+  font-weight: 400;
+}
 .empty-hint-text {
   display: inline-block;
   font-size: var(--text-base);
diff --git a/apps/kimi-web/src/composables/client/useWorkspaceState.ts b/apps/kimi-web/src/composables/client/useWorkspaceState.ts
index 9fe107d34..0c7af8804 100644
--- a/apps/kimi-web/src/composables/client/useWorkspaceState.ts
+++ b/apps/kimi-web/src/composables/client/useWorkspaceState.ts
@@ -82,6 +82,17 @@ const pendingQuestionActions = reactive<Record<string, 'answer' | 'dismiss'>>({}
 const pendingApprovalActions = reactive<Record<string, true>>({});
 /** Task ids with an in-flight cancel, keyed by taskId. */
 const pendingTaskCancellations = reactive<Record<string, true>>({});
+/**
+ * Workspace ids whose empty-session first prompt is currently being created +
+ * submitted. The empty-composer path (`startSessionAndSendPrompt`) awaits
+ * `createDraftSession` (addWorkspace + createSession + selectSession) before
+ * the session id exists, so the per-session `inFlightPromptSessions` guard
+ * cannot cover that window — a second Enter / send-button click during it
+ * would otherwise fire a second concurrent POST and trip the daemon's
+ * `turn.agent_busy` race. Module-level singleton — matches the other
+ * `pending*Actions` guards above.
+ */
+const startingFirstPromptWorkspaces = reactive(new Set<string>());
 
 type SyncSessionResult = 'ok' | 'not-found' | 'failed';
 
@@ -815,12 +826,22 @@ export function useWorkspaceState(rawState: ExtendedState, deps: UseWorkspaceSta
     text: string,
     attachments?: PromptAttachment[],
   ): Promise<void> {
+    // Guard the whole "create draft session + submit first prompt" flow: the
+    // session id doesn't exist until `createDraftSession` resolves, so the
+    // per-session `inFlightPromptSessions` guard can't cover this window. A
+    // second Enter / send-button click in that window would otherwise fire a
+    // concurrent first POST for the same new session and trip the daemon's
+    // `turn.agent_busy` race.
+    if (startingFirstPromptWorkspaces.has(workspaceId)) return;
+    startingFirstPromptWorkspaces.add(workspaceId);
     try {
       const sid = await createDraftSession(workspaceId);
       if (!sid) return;
       await submitPromptInternal(sid, text, attachments);
     } catch (err) {
       pushOperationFailure('startSessionAndSendPrompt', err);
+    } finally {
+      startingFirstPromptWorkspaces.delete(workspaceId);
     }
   }
 
@@ -837,6 +858,11 @@ export function useWorkspaceState(rawState: ExtendedState, deps: UseWorkspaceSta
     skillName: string,
     args?: string,
   ): Promise<void> {
+    // Same reentry window as startSessionAndSendPrompt (see the guard there):
+    // draft-session creation selects the new session before the activation,
+    // so concurrent first actions must be dropped here.
+    if (startingFirstPromptWorkspaces.has(workspaceId)) return;
+    startingFirstPromptWorkspaces.add(workspaceId);
     try {
       const sid = await createDraftSession(workspaceId);
       if (!sid) return;
@@ -862,6 +888,7 @@ export function useWorkspaceState(rawState: ExtendedState, deps: UseWorkspaceSta
           : rawState.defaultModel) ?? undefined;
       await persistSessionProfile(
         {
+          model,
           planMode,
           swarmMode,
           permissionMode: rawState.permission,
@@ -872,6 +899,8 @@ export function useWorkspaceState(rawState: ExtendedState, deps: UseWorkspaceSta
       await modelProvider.activateSkill(skillName, args, sid);
     } catch (err) {
       pushOperationFailure('startSessionAndActivateSkill', err);
+    } finally {
+      startingFirstPromptWorkspaces.delete(workspaceId);
     }
   }
 
@@ -888,12 +917,17 @@ export function useWorkspaceState(rawState: ExtendedState, deps: UseWorkspaceSta
     workspaceId: string,
     prompt?: string,
   ): Promise<void> {
+    // Same reentry window as startSessionAndSendPrompt (see the guard there).
+    if (startingFirstPromptWorkspaces.has(workspaceId)) return;
+    startingFirstPromptWorkspaces.add(workspaceId);
     try {
       const sid = await createDraftSession(workspaceId);
       if (!sid) return;
       await sideChat.openSideChatOn(sid, prompt);
     } catch (err) {
       pushOperationFailure('startSessionAndOpenSideChat', err);
+    } finally {
+      startingFirstPromptWorkspaces.delete(workspaceId);
     }
   }
 
@@ -2186,6 +2220,14 @@ export function useWorkspaceState(rawState: ExtendedState, deps: UseWorkspaceSta
     searchFiles,
     loadOlderMessages,
     refreshSessionSidecars,
+    /** True while any empty-composer first prompt is being created + submitted
+     *  (the window covered by startingFirstPromptWorkspaces). Drives the
+     *  empty-session "starting conversation…" loading state. Intentionally
+     *  keyed by the lock set itself rather than the current activeWorkspaceId:
+     *  createDraftSession can swap activeWorkspaceId to a registered id
+     *  mid-flight, and a workspace-keyed read would prematurely re-enable the
+     *  composer and reopen the duplicate first-submit race. */
+    isStartingFirstPrompt: () => startingFirstPromptWorkspaces.size > 0,
   };
 }
 
diff --git a/apps/kimi-web/src/composables/useKimiWebClient.ts b/apps/kimi-web/src/composables/useKimiWebClient.ts
index 0e2b7adf5..e1af68eb8 100644
--- a/apps/kimi-web/src/composables/useKimiWebClient.ts
+++ b/apps/kimi-web/src/composables/useKimiWebClient.ts
@@ -1685,6 +1685,11 @@ const isSending = computed<boolean>(() => {
   return rawState.sendingBySession[sid] ?? false;
 });
 
+// True while the empty-composer first prompt for the active workspace is being
+// created + submitted (before the session id exists). Drives the empty-session
+// "starting conversation…" loading state in ConversationPane / Composer.
+const isStartingFirstPrompt = computed<boolean>(() => workspaceState.isStartingFirstPrompt());
+
 const sideChat = useSideChat(rawState, {
   pushOperationFailure,
   nextOptimisticMsgId,
@@ -2520,6 +2525,7 @@ export function useKimiWebClient() {
     questions,
     activity,
     isSending,
+    isStartingFirstPrompt,
     fastMoon: appearance.fastMoon,
 
     // Model + Provider reactive state
diff --git a/apps/kimi-web/src/i18n/locales/en/composer.ts b/apps/kimi-web/src/i18n/locales/en/composer.ts
index 0f9ea6603..8ab8f7b59 100644
--- a/apps/kimi-web/src/i18n/locales/en/composer.ts
+++ b/apps/kimi-web/src/i18n/locales/en/composer.ts
@@ -3,6 +3,7 @@ export default {
   send: 'Send ↵',
   queueLabel: 'Queue',
   placeholderRunning: 'Press Enter to queue · Ctrl+S to inject into the running turn',
+  starting: 'Sending…',
   queueAutoDrain: 'sends automatically when the current turn ends',
   queueNext: 'Up next',
   queueDragTitle: 'Drag to reorder',
diff --git a/apps/kimi-web/src/i18n/locales/en/conversation.ts b/apps/kimi-web/src/i18n/locales/en/conversation.ts
index c97cb4c4a..431d8d7ad 100644
--- a/apps/kimi-web/src/i18n/locales/en/conversation.ts
+++ b/apps/kimi-web/src/i18n/locales/en/conversation.ts
@@ -3,6 +3,7 @@ export default {
   toc: 'Conversation outline',
   newMessages: 'Latest messages',
   loading: 'Loading…',
+  starting: 'Starting conversation…',
   emptyWorkspaceHint: 'Send in {name}',
   switchWorkspace: 'Switch workspace',
   addWorkspace: 'New workspace',
diff --git a/apps/kimi-web/src/i18n/locales/zh/composer.ts b/apps/kimi-web/src/i18n/locales/zh/composer.ts
index 719f7adb7..b93217197 100644
--- a/apps/kimi-web/src/i18n/locales/zh/composer.ts
+++ b/apps/kimi-web/src/i18n/locales/zh/composer.ts
@@ -3,6 +3,7 @@ export default {
   send: '发送 ↵',
   queueLabel: '队列',
   placeholderRunning: '输入会加入队列 · Ctrl+S 立即插入运行中的回合',
+  starting: '正在发送…',
   queueAutoDrain: '当前回合结束后自动逐条发送',
   queueNext: '下一条',
   queueDragTitle: '拖拽排序',
diff --git a/apps/kimi-web/src/i18n/locales/zh/conversation.ts b/apps/kimi-web/src/i18n/locales/zh/conversation.ts
index 2ae2c2504..98af571e3 100644
--- a/apps/kimi-web/src/i18n/locales/zh/conversation.ts
+++ b/apps/kimi-web/src/i18n/locales/zh/conversation.ts
@@ -3,6 +3,7 @@ export default {
   toc: '对话目录',
   newMessages: '最新消息',
   loading: '加载中…',
+  starting: '正在创建对话…',
   emptyWorkspaceHint: '在 {name} 中发送',
   switchWorkspace: '切换工作区',
   addWorkspace: '添加工作区',
diff --git a/apps/kimi-web/test/workspace-state.test.ts b/apps/kimi-web/test/workspace-state.test.ts
index 045b6c024..ff28d0016 100644
--- a/apps/kimi-web/test/workspace-state.test.ts
+++ b/apps/kimi-web/test/workspace-state.test.ts
@@ -638,7 +638,7 @@ describe('useWorkspaceState — startSessionAndActivateSkill', () => {
     // Activation must NOT have started while /profile is still pending.
     await new Promise((r) => setTimeout(r, 0));
     expect(persistSessionProfile).toHaveBeenCalledWith(
-      { planMode: true, swarmMode: true, permissionMode: 'auto', thinking: 'high' },
+      { model: undefined, planMode: true, swarmMode: true, permissionMode: 'auto', thinking: 'high' },
       'sess_new',
     );
     expect(activateSkill).not.toHaveBeenCalled();