diff --git a/internal/cloud/server-agent-chat.test.ts b/internal/cloud/server-agent-chat.test.ts
index d5023898..e71ec0cb 100644
--- a/internal/cloud/server-agent-chat.test.ts
+++ b/internal/cloud/server-agent-chat.test.ts
@@ -299,12 +299,25 @@ test("cloud api /v1/agent/chat supports short submit and result polling", async
     assert.equal(accepted.accepted, true);
     assert.equal(accepted.shortConnection, true);
     assert.equal(accepted.traceId, traceId);
+    assert.equal(accepted.turnId, traceId);
+    assert.equal(accepted.userMessageId, "msg_server-test-short-submit_user");
+    assert.equal(accepted.assistantMessageId, "msg_server-test-short-submit_agent");
     assert.equal(accepted.resultUrl, `/v1/agent/chat/result/${traceId}`);
 
+    const acceptedTurn = await fetch(`http://127.0.0.1:${port}/v1/agent/turns/${encodeURIComponent(traceId)}`, { headers: { cookie: manualSession.cookie } });
+    assert.equal(acceptedTurn.status, 200);
+    const acceptedTurnPayload = await acceptedTurn.json();
+    assert.equal(acceptedTurnPayload.turnId, traceId);
+    assert.equal(acceptedTurnPayload.userMessageId, accepted.userMessageId);
+    assert.equal(acceptedTurnPayload.assistantMessageId, accepted.assistantMessageId);
+
     const payload = await pollAgentResult(port, traceId);
     validateCodeAgentChatSchema(payload);
     assert.equal(payload.status, "completed");
     assert.equal(payload.traceId, traceId);
+    assert.equal(payload.turnId, traceId);
+    assert.equal(payload.userMessageId, accepted.userMessageId);
+    assert.equal(payload.assistantMessageId, accepted.assistantMessageId);
     assert.equal(payload.sandbox, "danger-full-access");
     assert.match(payload.reply.content, new RegExp(workspace.replace(/[.*+?^${}()|[\]\\]/gu, "\\$&")));
   } finally {
@@ -588,10 +601,23 @@ test("cloud api /v1/agent/chat delegates v0.2 turns to AgentRun v0.1 over adapte
     assert.equal(submit.status, 202);
     const accepted = await submit.json();
     assert.equal(accepted.shortConnection, true);
+    assert.equal(accepted.turnId, traceId);
+    assert.equal(accepted.userMessageId, "msg_server-test-agentrun-adapter_user");
+    assert.equal(accepted.assistantMessageId, "msg_server-test-agentrun-adapter_agent");
+
+    const acceptedTurn = await fetch(`http://127.0.0.1:${port}/v1/agent/turns/${encodeURIComponent(traceId)}`, { headers: { cookie: "hwlab_session=test-stub-session" } });
+    assert.equal(acceptedTurn.status, 200);
+    const acceptedTurnPayload = await acceptedTurn.json();
+    assert.equal(acceptedTurnPayload.turnId, traceId);
+    assert.equal(acceptedTurnPayload.userMessageId, accepted.userMessageId);
+    assert.equal(acceptedTurnPayload.assistantMessageId, accepted.assistantMessageId);
 
     const payload = await pollAgentResult(port, traceId);
     validateCodeAgentChatSchema(payload);
     assert.equal(payload.status, "completed");
+    assert.equal(payload.turnId, traceId);
+    assert.equal(payload.userMessageId, accepted.userMessageId);
+    assert.equal(payload.assistantMessageId, accepted.assistantMessageId);
     assert.equal(payload.provider, "deepseek");
     assert.equal(payload.backend, "agentrun-v01/deepseek");
     assert.equal(payload.infrastructureBackend, "agentrun-v01/deepseek");
diff --git a/internal/cloud/server-code-agent-http.ts b/internal/cloud/server-code-agent-http.ts
index a4cd7aea..bfd6897b 100644
--- a/internal/cloud/server-code-agent-http.ts
+++ b/internal/cloud/server-code-agent-http.ts
@@ -1,3 +1,5 @@
+// SPEC: PJ2026-010403 API契约 draft-2026-06-17-r0; PJ2026-0102 Agent编排 draft-2026-06-17-r0.
+// Responsibility: Code Agent HTTP turn admission, lifecycle compatibility wrappers, and session evidence projection.
 
 import { createHash, randomUUID } from "node:crypto";
 
@@ -85,9 +87,11 @@ export async function handleCodeAgentChatHttp(request, response, options) {
   }
 
   const traceId = safeTraceId(getHeader(request, "x-trace-id") || params.traceId) || `trc_${randomUUID()}`;
+  const lifecycle = codeAgentTurnLifecycleFields(traceId, params);
   const chatParams = {
     ...params,
     traceId,
+    ...lifecycle,
     ownerUserId: options.actor?.id ?? params.ownerUserId,
     ownerRole: options.actor?.role ?? params.ownerRole
   };
@@ -113,6 +117,7 @@ export async function handleCodeAgentChatHttp(request, response, options) {
       shortConnection: true,
       controlSemantics: "submit-and-poll",
       traceId,
+      ...lifecycle,
       workspaceId: workspaceClaim?.workspace?.id ?? null,
       workspaceRevision: workspaceClaim?.workspace?.revision ?? null,
       conversationId: safeConversationId(nativeSessionChatParams.conversationId) || null,
@@ -702,6 +707,7 @@ function submitCodeAgentChatTurn({ params, options, traceId }) {
     accepted: true,
     status: "running",
     traceId,
+    ...codeAgentTurnLifecycleFields(traceId, params),
     conversationId: safeConversationId(params.conversationId) || null,
     sessionId: safeSessionId(params.sessionId) || null,
     threadId: safeOpaqueId(params.threadId) || null,
@@ -1276,6 +1282,7 @@ function forbiddenTurnSnapshot(traceId) {
 function codeAgentTurnStatusPayload({ traceId, result, snapshot, resultPollError, refreshError, options }) {
   const resultObject = result && typeof result === "object" ? result : null;
   const snapshotObject = snapshot && typeof snapshot === "object" ? snapshot : null;
+  const lifecycle = codeAgentTurnLifecycleFields(traceId, resultObject ?? snapshotObject ?? {});
   const events = Array.isArray(snapshotObject?.events) ? snapshotObject.events : Array.isArray(resultObject?.runnerTrace?.events) ? resultObject.runnerTrace.events : [];
   const lastEvent = events.at(-1) ?? null;
   const status = normalizeTurnStatus(
@@ -1300,6 +1307,7 @@ function codeAgentTurnStatusPayload({ traceId, result, snapshot, resultPollError
     running: found ? running : false,
     terminal: found ? terminal : false,
     traceId,
+    ...lifecycle,
     conversationId: safeConversationId(resultObject?.conversationId ?? snapshotObject?.conversationId) || null,
     sessionId: safeSessionId(resultObject?.sessionId ?? resultObject?.session?.sessionId ?? snapshotObject?.sessionId) || null,
     threadId: safeOpaqueId(resultObject?.threadId ?? resultObject?.session?.threadId ?? snapshotObject?.threadId) || null,
@@ -2219,6 +2227,7 @@ function codeAgentConversationMessagesEvidence(payload = {}, params = {}, traceI
   const userText = boundedConversationMessageText(params.message ?? params.prompt ?? payload.userMessage ?? payload.prompt);
   if (!userText) return [];
   const resolvedTraceId = safeTraceId(traceId) || null;
+  const lifecycle = codeAgentTurnLifecycleFields(resolvedTraceId, payload);
   const session = payload.session && typeof payload.session === "object" ? payload.session : null;
   const sessionReuse = payload.sessionReuse && typeof payload.sessionReuse === "object" ? payload.sessionReuse : null;
   const conversationId = safeConversationId(payload.conversationId ?? session?.conversationId ?? sessionReuse?.conversationId ?? params.conversationId) || null;
@@ -2226,14 +2235,15 @@ function codeAgentConversationMessagesEvidence(payload = {}, params = {}, traceI
   const threadId = safeOpaqueId(session?.threadId ?? sessionReuse?.threadId ?? payload.threadId ?? params.threadId) || null;
   const createdAt = payload.createdAt ?? payload.reply?.createdAt ?? new Date().toISOString();
   const updatedAt = payload.updatedAt ?? createdAt;
-  const traceSuffix = codeAgentMessageTraceSuffix(resolvedTraceId);
   const userMessage = {
-    id: `msg_${traceSuffix}_user`,
+    id: lifecycle.userMessageId,
+    messageId: lifecycle.userMessageId,
     role: "user",
     title: "用户",
     text: userText,
     status: "sent",
     traceId: resolvedTraceId,
+    turnId: lifecycle.turnId,
     conversationId,
     sessionId,
     threadId,
@@ -2256,12 +2266,14 @@ function codeAgentConversationMessagesEvidence(payload = {}, params = {}, traceI
   );
   const agentStatus = codeAgentConversationAgentMessageStatus(payload);
   const agentMessage = {
-    id: `msg_${traceSuffix}_agent`,
+    id: lifecycle.assistantMessageId,
+    messageId: lifecycle.assistantMessageId,
     role: "agent",
     title: agentStatus === "failed" ? "Code Agent 返回阻塞" : agentStatus === "running" ? "Code Agent 处理中" : "Code Agent 回复",
     text: agentText || (agentStatus === "running" ? "" : "Code Agent 请求已结束，请查看 Trace 详情。"),
     status: agentStatus,
     traceId: resolvedTraceId,
+    turnId: lifecycle.turnId,
     conversationId,
     sessionId,
     threadId,
@@ -2306,6 +2318,31 @@ function codeAgentMessageTraceSuffix(traceId) {
   return text.replace(/^trc_/u, "").replace(/[^A-Za-z0-9_.:-]/gu, "_").slice(0, 48) || "trace";
 }
 
+function codeAgentTurnLifecycleFields(traceId, source = {}) {
+  const resolvedTraceId = safeTraceId(source?.traceId ?? traceId) || safeTraceId(traceId) || null;
+  const turnId = safeTurnId(source?.turnId) || resolvedTraceId;
+  const traceSuffix = codeAgentMessageTraceSuffix(resolvedTraceId);
+  return {
+    turnId,
+    userMessageId: safeMessageId(source?.userMessageId ?? source?.userMessage?.messageId) || codeAgentLifecycleMessageId(traceSuffix, "user"),
+    assistantMessageId: safeMessageId(source?.assistantMessageId ?? source?.assistantMessage?.messageId) || codeAgentLifecycleMessageId(traceSuffix, "agent")
+  };
+}
+
+function codeAgentLifecycleMessageId(traceSuffix, role) {
+  return `msg_${traceSuffix}_${role}`;
+}
+
+function safeTurnId(value) {
+  const text = textValue(value);
+  return /^turn_[A-Za-z0-9_.:-]+$/u.test(text) ? text : null;
+}
+
+function safeMessageId(value) {
+  const text = textValue(value);
+  return /^msg_[A-Za-z0-9_.:-]+$/u.test(text) ? text : null;
+}
+
 function codeAgentConversationAgentMessageStatus(payload = {}) {
   const status = textValue(payload.status ?? payload.agentRun?.terminalStatus ?? payload.commandState ?? payload.runStatus).toLowerCase();
   if (["completed", "done", "success", "active"].includes(status)) return "completed";
@@ -2831,6 +2868,7 @@ function compactCodeAgentChatResultPayload(payload, options = {}) {
   const { userBillingReservation, ...publicPayload } = payload;
   return {
     ...publicPayload,
+    ...codeAgentTurnLifecycleFields(publicPayload.traceId, publicPayload),
     ...(terminalEvidence ? { terminalEvidence: terminalEvidencePayload(terminalEvidence) } : {}),
     ...(publicPayload.runnerTrace && typeof publicPayload.runnerTrace === "object"
       ? { runnerTrace: compactRunnerTraceForResult(publicPayload.runnerTrace, limit) }
diff --git a/web/hwlab-cloud-web/src/stores/workbench.ts b/web/hwlab-cloud-web/src/stores/workbench.ts
index cbec4a71..7c677dcf 100644
--- a/web/hwlab-cloud-web/src/stores/workbench.ts
+++ b/web/hwlab-cloud-web/src/stores/workbench.ts
@@ -1,3 +1,6 @@
+// SPEC: PJ2026-010403 API契约 draft-2026-06-17-r0; PJ2026-010401 Web工作台 draft-2026-06-17-r0.
+// Responsibility: Workbench client state orchestration for session selection, turn admission, and trace lifecycle rendering.
+
 import { computed, ref } from "vue";
 import { defineStore } from "pinia";
 import { api } from "@/api";
@@ -377,6 +380,7 @@ export const useWorkbenchStore = defineStore("workbench", () => {
       return;
     }
     void refreshSessionStatusById(sessionId);
+    alignOptimisticTurnMessages(traceId, response.data);
     applyTurnStatusSnapshot(traceId, response.data);
     void refreshConversations(conversationId);
     subscribe(traceId, response.data);
@@ -656,6 +660,19 @@ export const useWorkbenchStore = defineStore("workbench", () => {
     messages.value = messages.value.map((message) => message.traceId === traceId && message.role === "agent" ? { ...message, ...patch, updatedAt: new Date().toISOString() } : message);
   }
 
+  function alignOptimisticTurnMessages(traceId: string, lifecycle: AgentChatResponse): void {
+    const turnId = firstNonEmptyString(lifecycle.turnId, traceId);
+    const userMessageId = firstNonEmptyString(lifecycle.userMessageId);
+    const assistantMessageId = firstNonEmptyString(lifecycle.assistantMessageId);
+    if (!turnId && !userMessageId && !assistantMessageId) return;
+    messages.value = messages.value.map((message) => {
+      if (message.traceId !== traceId) return message;
+      if (message.role === "user" && userMessageId) return { ...message, id: userMessageId, messageId: userMessageId, turnId, updatedAt: new Date().toISOString() };
+      if (message.role === "agent" && assistantMessageId) return { ...message, id: assistantMessageId, messageId: assistantMessageId, turnId, updatedAt: new Date().toISOString() };
+      return turnId ? { ...message, turnId, updatedAt: new Date().toISOString() } : message;
+    });
+  }
+
   async function ensureWorkspace(): Promise<WorkspaceRecord | null> {
     if (workspace.value) return workspace.value;
     await hydrate();
@@ -879,7 +896,8 @@ function normalizeChatMessage(message: ChatMessage): ChatMessage {
   const text = message.role === "agent" && isTerminalMessageStatus(status)
     ? firstNonEmptyString(finalText, errorText, baseText) ?? ""
     : firstNonEmptyString(baseText, finalText, errorText) ?? "";
-  return { ...message, text, id: message.id ?? nextProtocolId("msg"), title: normalizeWorkbenchMessageTitle(message.role, message.title), createdAt: message.createdAt ?? new Date().toISOString(), status, runnerTrace, error: error ?? message.error ?? null, agentRun: agentRun ?? undefined };
+  const messageId = firstNonEmptyString((message as Record<string, unknown>).messageId, message.id) ?? nextProtocolId("msg");
+  return { ...message, text, id: messageId, messageId, title: normalizeWorkbenchMessageTitle(message.role, message.title), createdAt: message.createdAt ?? new Date().toISOString(), status, runnerTrace, error: error ?? message.error ?? null, agentRun: agentRun ?? undefined };
 }
 
 function activeTraceIdFromMessages(messages: ChatMessage[], turnStatusAuthority: Record<string, TurnStatusAuthority>): string | null {
diff --git a/web/hwlab-cloud-web/src/types/index.ts b/web/hwlab-cloud-web/src/types/index.ts
index e0e7cb5d..429e148d 100644
--- a/web/hwlab-cloud-web/src/types/index.ts
+++ b/web/hwlab-cloud-web/src/types/index.ts
@@ -1,3 +1,6 @@
+// SPEC: PJ2026-010403 API契约 draft-2026-06-17-r0; PJ2026-010401 Web工作台 draft-2026-06-17-r0.
+// Responsibility: Cloud Web API and Workbench state type contracts shared by stores and components.
+
 export type Tone = "ok" | "pending" | "blocked" | "error" | "warn" | "dev-live" | "dry-run";
 export type AuthState = "checking" | "login" | "authenticated";
 export type ProviderProfile = string;
@@ -167,6 +170,8 @@ export interface ChatMessage {
   createdAt: string;
   updatedAt?: string;
   traceId?: string | null;
+  turnId?: string | null;
+  messageId?: string | null;
   conversationId?: string | null;
   sessionId?: string | null;
   threadId?: string | null;
@@ -200,6 +205,9 @@ export interface AgentChatResponse {
   text?: string;
   summary?: string;
   traceId?: string;
+  turnId?: string | null;
+  userMessageId?: string | null;
+  assistantMessageId?: string | null;
   conversationId?: string;
   sessionId?: string;
   threadId?: string;