diff --git a/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.i18n.yaml b/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.i18n.yaml
index 055804b569..70618612a2 100644
--- a/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.i18n.yaml
+++ b/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.i18n.yaml
@@ -1,6 +1,6 @@
 # Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
-#   pnpm run verify-translation-pairing --write
-2026-07-19-gui-layering-and-rpc-protocol.md: 63db4786adcc007d09b7a58824a59f4d1e1e8be1
-2026-07-19-gui-layering-and-rpc-protocol.zh.md: b3037ceb8c172925581d2862ea675e53a7f8c54e
+#   pnpm run verify-translation-pairing --write .agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md
+2026-07-19-gui-layering-and-rpc-protocol.md: b9718da4725316c64686adef24827e2984d8723d
+2026-07-19-gui-layering-and-rpc-protocol.zh.md: 2add148054e8f97c65600cd719fb4f8e0283f52d
diff --git a/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md b/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md
index 63db4786ad..b9718da472 100644
--- a/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md
+++ b/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.md
@@ -165,7 +165,7 @@ One example row (the table structure is the reading key):
 |---|---|---|---|
 | `session.list` | `{ cursor?: string }` (cursor is a reserved seat, unimplemented) | `{ items: SessionSummary[] }` | persisted sessions, updatedAt descending; v1 builds no index |
 
-The remaining methods (`session.create`/`session.history`/`session.prompt`/`session.cancel`/`host.describe`) are not re-copied here — signatures are the source of truth; see `api/sessions.ts`, `api/host.ts`, and `RpcMethodMap`.
+The remaining methods (`session.create`/`session.history`/`session.rename`/`session.prompt`/`session.cancel`/`host.describe`) are not re-copied here — signatures are the source of truth; see `api/sessions.ts`, `api/host.ts`, and `RpcMethodMap`.
 
 ### Frames (server→client, named unions)
 
@@ -187,7 +187,7 @@ The remaining frame types are not re-copied here; the full unions are `MuxFrame`
 - **Cold sessions resume implicitly**: when `history`/`prompt` hits an unattached session the impl auto-resumes, deduplicating concurrent triggers with an in-flight table; attachment status is not exposed to clients (`running` already covers it).
 - **Approvals/questions**: the requested frame mints a stable rpcId on acceptance; first answer wins, and the host's in-memory pending table (keyed by rpcId) is the only referee; after a mux reopen, still-pending requested frames replay after the subscribed frame (rpcId reused verbatim — refresh recovery). The audit events `approval/asked`/`decided` continue through the durable log — frames = the live control plane, events = the durable audit. **Status**: the contract and frame types are shipped; the host-side pending table/wire answerer is unimplemented (`respond` in `api-proxy.ts` is a stub, always `not-pending`); PendingCard v1 is display-only.
 - **No protocol version**: client and host release bound together; `host.describe` has no protocolVersion field; introduce one when an independently released client appears.
-- **Reserved-seam discipline**: the map holds only implemented methods; an unknown method fails loud at envelope parse (`bad-request`) — no not-implemented fallback code. The reservation list (implementing = copy the signature into the domain interface + add the map row + add the schema pair): `session.fork`, `prompt.mode` gaining `'inject'`, `task.list`, `host.listModels`, describe gaining `hostInstanceId`.
+- **Reserved-seam discipline**: the map holds only implemented methods; an unknown method fails loud at envelope parse (`bad-request`) — no not-implemented fallback code. The reservation list (implementing = copy the signature into the domain interface + add the map row + add the schema pair): `session.fork`, `prompt.mode` gaining `'inject'`, `task.list`, `host.listModels`, describe gaining `hostInstanceId`. (`session.rename` graduated from this list: it appends a user-source `session/title` event.)
 
 ## The client carrier: the AbstractApiClient class family (`fetch/client.ts`)
 
diff --git a/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.zh.md b/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.zh.md
index b3037ceb8c..2add148054 100644
--- a/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.zh.md
+++ b/.agents/notes/implemented/architecture/2026-07-19-gui-layering-and-rpc-protocol.zh.md
@@ -163,7 +163,7 @@ export type ResponseValue<K> =
 |---|---|---|---|
 | `session.list` | `{ cursor?: string }`（cursor 留座不实现） | `{ items: SessionSummary[] }` | 已持久化 session，updatedAt 倒序；v1 不建索引 |
 
-其余方法（`session.create`/`session.history`/`session.prompt`/`session.cancel`/`host.describe`）的参数与返回不在此复写——签名即事实源，见 `api/sessions.ts`、`api/host.ts` 与 `RpcMethodMap`。
+其余方法（`session.create`/`session.history`/`session.rename`/`session.prompt`/`session.cancel`/`host.describe`）的参数与返回不在此复写——签名即事实源，见 `api/sessions.ts`、`api/host.ts` 与 `RpcMethodMap`。
 
 ### 帧（server→client，具名 union）
 
@@ -185,7 +185,7 @@ export type ResponseValue<K> =
 - **冷 session 隐式 resume**：`history`/`prompt` 命中未 attach 的 session 时 impl 自动 resume，并发触发用在途表去重；attach 与否不对客暴露（`running` 已覆盖）。
 - **审批/问答**：requested 帧受理时 mint 稳定 rpcId；先到先赢，host 内存 pending 表（keyed by rpcId）是唯一裁判；mux 重开后在 subscribed 帧后重放仍 pending 的 requested 帧（rpcId 原样复用，刷新恢复）。审计事件 `approval/asked`/`decided` 照旧走 durable 日志——帧=live 控制面，事件=durable 审计。**现状**：契约与帧类型已 shipped，host 侧 pending 表/wire answerer 未实现（`api-proxy.ts` 的 `respond` 是 stub，恒回 `not-pending`）；PendingCard v1 只展示。
 - **不设协议版本**：client 与 host 绑定发布，`host.describe` 无 protocolVersion 字段；出现独立发布的 client 时再引入。
-- **预留接缝纪律**：map 只含已实现方法，未知 method 在信封 parse 即 fail loud（`bad-request`），不设 not-implemented 兜底码。预留清单（实现时把签名抄进域接口+map 加行+schema 加对即升格）：`session.fork`、`prompt.mode` 加 `'inject'`、`task.list`、`host.listModels`、describe 加 `hostInstanceId`。
+- **预留接缝纪律**：map 只含已实现方法，未知 method 在信封 parse 即 fail loud（`bad-request`），不设 not-implemented 兜底码。预留清单（实现时把签名抄进域接口+map 加行+schema 加对即升格）：`session.fork`、`prompt.mode` 加 `'inject'`、`task.list`、`host.listModels`、describe 加 `hostInstanceId`。（`session.rename` 已从本清单毕业：追加 user 来源的 `session/title` 事件。）
 
 ## 客户端载体：AbstractApiClient 类体系（`fetch/client.ts`）
 
diff --git a/packages/host/apiproxy/README.i18n.yaml b/packages/host/apiproxy/README.i18n.yaml
index 73b0845370..6f22ce2466 100644
--- a/packages/host/apiproxy/README.i18n.yaml
+++ b/packages/host/apiproxy/README.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/host/apiproxy/README.md
-README.md: ca4471454f5be5d3fcba38ce665d4fb3fbd85e74
-README.zh.md: 953539e1198a52b2bf7cdd9ca1b0d263cc2ae6f9
+README.md: b5f80dcb3a077a411db3b721737a9c16b56fcecf
+README.zh.md: 1c3c7486f7d500f8c2d36028d47f29b112d9b5ae
diff --git a/packages/host/apiproxy/README.md b/packages/host/apiproxy/README.md
index ca4471454f..b5f80dcb3a 100644
--- a/packages/host/apiproxy/README.md
+++ b/packages/host/apiproxy/README.md
@@ -12,7 +12,7 @@ The layering/protocol decisions are recorded in the [GUI layering and RPC protoc
 
 `session.history`'s tail page (`beforeSeq` absent) additionally carries an optional `projections` block — the watermark snapshot of every unit registered on `ctx.sessionProjections` (`@deepseek-ai/dsh-session-projection`), with `asOfSeq` = the last event seq the values reflect (`-1` on an empty log). The gateway also subscribes to the registry's change feed and mints a `session/projection` mux frame per changed unit (`{sessionId, key, value, seq}` — live push state, never logged; clients hold one generic per-session value store under higher-seq-wins). The carrier holds zero domain knowledge (each value passed its unit's own schema inside the registry; the wire schemas keep `values`/`value` wide); loadOlder pages never carry the block, and a composition without the registry serves histories without either surface.
 
-Session titles ride the generic projection pair like every other domain — the history-tail `projections` block plus `session/projection` frames under the `title` key (the bespoke `session/title` frame is retired). Titles do not join `session.list`; cold sessions remain metadata-only there until opening or resuming attaches their logs.
+Session titles ride the generic projection pair like every other domain — the history-tail `projections` block plus `session/projection` frames under the `title` key (the bespoke `session/title` frame is retired). Titles do not join `session.list`; cold sessions remain metadata-only there until opening or resuming attaches their logs. `session.rename` accepts an explicit user title (resuming a cold session first), delegating to `ctx.sessionTitle.rename` — the accepted `session/title` event pins the title against automatic regeneration — and returns the normalized title plus its event seq so a client settles its `title` projection cell ahead of the push frame; a title that normalizes to empty returns `title-invalid`.
 
 Session model routing is a session-domain contract. `session.models` returns the selected provider/model/reasoning target with provider-grouped advisory models, exact-route reasoning metadata, and provider-local lookup failures. `session.selectModel` validates the optional adapter-owned reasoning effort and replaces the complete target selected for the next prompt-assembly boundary. Catalog membership is not validation: an adapter may resolve an unlisted model, while an unavailable route or unsupported effort returns `model-unavailable`.
 
diff --git a/packages/host/apiproxy/README.zh.md b/packages/host/apiproxy/README.zh.md
index 953539e119..1c3c7486f7 100644
--- a/packages/host/apiproxy/README.zh.md
+++ b/packages/host/apiproxy/README.zh.md
@@ -12,7 +12,7 @@
 
 `session.history` 的尾页（不带 `beforeSeq`）额外携带一个可选的 `projections` 块——`ctx.sessionProjections`（`@deepseek-ai/dsh-session-projection`）上每个已注册单元的水位线快照，`asOfSeq` = 这些值共同反映到的最后一个事件 seq（空日志为 `-1`）。网关还订阅注册表的变更流，为每个状态发生变化的单元铸造一个 `session/projection` mux 帧（`{sessionId, key, value, seq}`——实时推送状态，绝不入日志；客户端按 seq 高者胜维护一个按会话的通用值仓）。载体不持有任何领域知识（每个值在注册表内部已过其单元自己的 schema；协议 schema 对 `values`/`value` 保持宽松）；loadOlder 页永不携带该块，未装注册表的组合则两个面都不提供。
 
-会话标题与其他所有领域一样搭乘这对通用投影机制——历史尾页的 `projections` 块外加 `title` 键下的 `session/projection` 帧（专设的 `session/title` 帧已下线）。标题不会加入 `session.list`；冷会话在其中仍只有元数据，直到打开或恢复操作附加其日志。
+会话标题与其他所有领域一样搭乘这对通用投影机制——历史尾页的 `projections` 块外加 `title` 键下的 `session/projection` 帧（专设的 `session/title` 帧已下线）。标题不会加入 `session.list`；冷会话在其中仍只有元数据，直到打开或恢复操作附加其日志。`session.rename` 接受用户显式标题（冷会话先恢复），委托给 `ctx.sessionTitle.rename`——被接受的 `session/title` 事件将标题钉住、不再被自动生成覆盖——并返回规范化后的标题及其事件 seq，让 client 在推送帧到达前就结算自己的 `title` 投影格；规范化后为空的标题返回 `title-invalid`。
 
 会话模型路由属于会话领域契约。`session.models` 返回选中的提供方／模型／推理（reasoning）目标，以及按提供方分组的建议性模型、精确路由推理元数据和逐提供方查询失败记录。`session.selectModel` 校验由适配器持有的可选推理强度，并替换将在下一提示词组装边界使用的完整目标。目录成员关系不构成校验：适配器可以解析未列出的模型，而不可用路由或不受支持的推理强度会返回 `model-unavailable`。
 
diff --git a/packages/host/apiproxy/package.json b/packages/host/apiproxy/package.json
index 8cbdb91cf4..8b4a895774 100644
--- a/packages/host/apiproxy/package.json
+++ b/packages/host/apiproxy/package.json
@@ -51,6 +51,7 @@
     "@deepseek-ai/dsh-session-persistence": "workspace:^",
     "@deepseek-ai/dsh-session-projection": "workspace:^",
     "@deepseek-ai/dsh-session-projection-cache": "workspace:^",
+    "@deepseek-ai/dsh-session-title": "workspace:^",
     "@deepseek-ai/dsh-skill": "workspace:^",
     "@deepseek-ai/dsh-tools": "workspace:^",
     "@deepseek-ai/dsh-user-approval": "workspace:^",
diff --git a/packages/host/apiproxy/src/api-proxy.ts b/packages/host/apiproxy/src/api-proxy.ts
index f178bfefd0..8ed681e239 100644
--- a/packages/host/apiproxy/src/api-proxy.ts
+++ b/packages/host/apiproxy/src/api-proxy.ts
@@ -36,6 +36,8 @@ import type {} from '@deepseek-ai/dsh-session-projection-cache'
 import { GoalError } from '@deepseek-ai/dsh-goal'
 import type { GoalRef as CoreGoalRef } from '@deepseek-ai/dsh-goal'
 // Type-only edges: resolve `ctx.get('commands')`, the `commands/change` event, and `ctx.get('skills')`.
+// Type-only edge: resolves `ctx.get('sessionTitle')` for the rename impl.
+import type {} from '@deepseek-ai/dsh-session-title'
 import type {} from '@deepseek-ai/dsh-commands'
 import type {} from '@deepseek-ai/dsh-skill'
 import type { CallId } from '@deepseek-ai/dsh-llm/brand'
@@ -1049,6 +1051,26 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
         }
       },
 
+      async rename(request) {
+        const { sessionId, title } = request.payload
+        const found = await agentFor(sessionId)
+        if ('error' in found) return err(request, found.error)
+        const titles = ctx.get('sessionTitle')
+        if (titles === undefined) {
+          return err(request, { code: 'internal', message: 'session-title service is absent: this deployment does not mount @deepseek-ai/dsh-session-title in its composition (cordis.yml or explicit assembly)', details: {} })
+        }
+        try {
+          const accepted = titles.rename(found.agent.session, title)
+          return ok(request, { title: accepted.title, seq: accepted.eventSeq })
+        } catch (error: unknown) {
+          return err(request, {
+            code: 'title-invalid',
+            message: `rename rejected for session "${sessionId}": ${String(error)}`,
+            details: { sessionId },
+          })
+        }
+      },
+
       async prompt(request) {
         const { sessionId, mode, content } = request.payload
         const found = await agentFor(sessionId)
diff --git a/packages/host/apiproxy/src/api/rpc-map.ts b/packages/host/apiproxy/src/api/rpc-map.ts
index 5394691248..8b26b1fc2a 100644
--- a/packages/host/apiproxy/src/api/rpc-map.ts
+++ b/packages/host/apiproxy/src/api/rpc-map.ts
@@ -23,6 +23,7 @@ export interface RpcMethodMap {
   'session.history': SessionsApi['history']
   'session.models': SessionsApi['models']
   'session.selectModel': SessionsApi['selectModel']
+  'session.rename': SessionsApi['rename']
   'session.prompt': SessionsApi['prompt']
   'session.cancel': SessionsApi['cancel']
   'host.describe': HostApi['describe']
diff --git a/packages/host/apiproxy/src/api/rpc.schema.ts b/packages/host/apiproxy/src/api/rpc.schema.ts
index 58d3a17126..db5435a757 100644
--- a/packages/host/apiproxy/src/api/rpc.schema.ts
+++ b/packages/host/apiproxy/src/api/rpc.schema.ts
@@ -49,6 +49,7 @@ export const rpcErrorSchema: z.ZodType<RpcError> = z.discriminatedUnion('code',
   z.object({ code: z.literal('agent-busy'), message: z.string(), details: z.object({ reason: z.string() }) }),
   z.object({ code: z.literal('command-error'), message: z.string(), details: z.object({}) }),
   z.object({ code: z.literal('unknown-command'), message: z.string(), details: z.object({}) }),
+  z.object({ code: z.literal('title-invalid'), message: z.string(), details: z.object({ sessionId: z.string() }) }),
   z.object({ code: z.literal('internal'), message: z.string(), details: z.object({}) }),
 ]) as unknown as z.ZodType<RpcError>
 
diff --git a/packages/host/apiproxy/src/api/rpc.ts b/packages/host/apiproxy/src/api/rpc.ts
index fd99d015ee..8daf898693 100644
--- a/packages/host/apiproxy/src/api/rpc.ts
+++ b/packages/host/apiproxy/src/api/rpc.ts
@@ -48,6 +48,7 @@ export interface RpcErrorDetailsMap {
   'command-error': {}
   /** A leading-/ prompt named no registered command; the message names the token. */
   'unknown-command': {}
+  'title-invalid': { sessionId: SessionId }
   'internal': {}
 }
 
diff --git a/packages/host/apiproxy/src/api/sessions.schema.ts b/packages/host/apiproxy/src/api/sessions.schema.ts
index 81c42b8a56..29dd88c89b 100644
--- a/packages/host/apiproxy/src/api/sessions.schema.ts
+++ b/packages/host/apiproxy/src/api/sessions.schema.ts
@@ -73,6 +73,18 @@ export const sessionCreateValueSchema = z.object({
   sessionId: sessionIdSchema,
 }) satisfies z.ZodType<Wire<ResponseValue<'session.create'>>>
 
+/** session.rename request payload (raw title; host-side normalization decides acceptance). */
+export const sessionRenameRequestSchema = z.object({
+  sessionId: sessionIdSchema,
+  title: z.string(),
+}) satisfies z.ZodType<Wire<RequestPayload<'session.rename'>>>
+
+/** session.rename response value (the normalized accepted title and its event seq). */
+export const sessionRenameValueSchema = z.object({
+  title: z.string().min(1),
+  seq: z.number().int().nonnegative(),
+}) satisfies z.ZodType<Wire<ResponseValue<'session.rename'>>>
+
 /** session.history request payload (beforeSeq/maxMessages page backwards from the window tail). */
 export const sessionHistoryRequestSchema = z.object({
   sessionId: sessionIdSchema,
diff --git a/packages/host/apiproxy/src/api/sessions.ts b/packages/host/apiproxy/src/api/sessions.ts
index f952c7c542..3a824c8261 100644
--- a/packages/host/apiproxy/src/api/sessions.ts
+++ b/packages/host/apiproxy/src/api/sessions.ts
@@ -208,6 +208,16 @@ export interface SessionsApi {
   }>):
   Promise<RpcResponse<{ selected: ModelTarget }>>
 
+  /**
+   * Renames a session: appends a `session/title` event with the `user`
+   * source, which pins the title against automatic regeneration. The
+   * normalized accepted title and the title event's seq return so the caller
+   * can settle its projection cell without waiting for the push frame. A
+   * title that normalizes to empty fails with `title-invalid`.
+   */
+  rename(request: RpcRequest<{ sessionId: SessionId; title: string }>):
+  Promise<RpcResponse<{ title: string; seq: number }>>
+
   /**
    * Sends a message. content is core's ContentBlock[] verbatim; mode maps 1:1 — queue→send, steer→steer.
    * A prompt whose content is exactly one text block starting with '/' is a slash command: the host
diff --git a/packages/host/apiproxy/src/fetch/client.ts b/packages/host/apiproxy/src/fetch/client.ts
index 8bcc6f7c3e..5940775499 100644
--- a/packages/host/apiproxy/src/fetch/client.ts
+++ b/packages/host/apiproxy/src/fetch/client.ts
@@ -20,6 +20,7 @@ import {
 import {
   sessionCancelValueSchema,
   sessionCreateValueSchema,
+  sessionRenameValueSchema,
   sessionHistoryValueSchema,
   sessionListValueSchema,
   sessionModelsValueSchema,
@@ -66,6 +67,7 @@ export interface IApiClient {
     history(payload: RequestPayload<'session.history'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.history'>>>
     models(payload: RequestPayload<'session.models'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.models'>>>
     selectModel(payload: RequestPayload<'session.selectModel'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.selectModel'>>>
+    rename(payload: RequestPayload<'session.rename'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.rename'>>>
     prompt(payload: RequestPayload<'session.prompt'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.prompt'>>>
     cancel(payload: RequestPayload<'session.cancel'>, signal?: AbortSignal): Promise<RpcResponse<ResponseValue<'session.cancel'>>>
   }
@@ -116,6 +118,7 @@ const UNARY_VALUE_SCHEMAS: { [K in keyof RpcMethodMap]: z.ZodType<Wire<ResponseV
   'session.history': sessionHistoryValueSchema,
   'session.models': sessionModelsValueSchema,
   'session.selectModel': sessionSelectModelValueSchema,
+  'session.rename': sessionRenameValueSchema,
   'session.prompt': sessionPromptValueSchema,
   'session.cancel': sessionCancelValueSchema,
   'host.describe': hostDescribeValueSchema,
@@ -327,6 +330,7 @@ export abstract class AbstractApiClient implements IApiClient {
     history: (payload, signal) => this.callUnary('session.history', payload, signal),
     models: (payload, signal) => this.callUnary('session.models', payload, signal),
     selectModel: (payload, signal) => this.callUnary('session.selectModel', payload, signal),
+    rename: (payload, signal) => this.callUnary('session.rename', payload, signal),
     prompt: (payload, signal) => this.callUnary('session.prompt', payload, signal),
     cancel: (payload, signal) => this.callUnary('session.cancel', payload, signal),
   }
diff --git a/packages/host/apiproxy/src/fetch/handler.ts b/packages/host/apiproxy/src/fetch/handler.ts
index e1340aad5b..c14e680119 100644
--- a/packages/host/apiproxy/src/fetch/handler.ts
+++ b/packages/host/apiproxy/src/fetch/handler.ts
@@ -17,6 +17,7 @@ import { clientRequestSchema, clientResponseSchema } from '../api/rpc.schema.ts'
 import {
   sessionCancelRequestSchema,
   sessionCreateRequestSchema,
+  sessionRenameRequestSchema,
   sessionHistoryRequestSchema,
   sessionListRequestSchema,
   sessionModelsRequestSchema,
@@ -68,6 +69,7 @@ const UNARY_ROUTES: UnaryRoutes = {
   'session.history': { schema: sessionHistoryRequestSchema, invoke: (api, r) => api.sessions.history(r) },
   'session.models': { schema: sessionModelsRequestSchema, invoke: (api, r) => api.sessions.models(r) },
   'session.selectModel': { schema: sessionSelectModelRequestSchema, invoke: (api, r) => api.sessions.selectModel(r) },
+  'session.rename': { schema: sessionRenameRequestSchema, invoke: (api, r) => api.sessions.rename(r) },
   'session.prompt': { schema: sessionPromptRequestSchema, invoke: (api, r) => api.sessions.prompt(r) },
   'session.cancel': { schema: sessionCancelRequestSchema, invoke: (api, r) => api.sessions.cancel(r) },
   'host.describe': { schema: hostDescribeRequestSchema, invoke: (api, r) => api.host.describe(r) },
diff --git a/packages/host/apiproxy/tests/api-proxy-rename.spec.ts b/packages/host/apiproxy/tests/api-proxy-rename.spec.ts
new file mode 100644
index 0000000000..5bdac4fb11
--- /dev/null
+++ b/packages/host/apiproxy/tests/api-proxy-rename.spec.ts
@@ -0,0 +1,110 @@
+/**
+ * sessions.rename delegation through the composed SessionTitleService. The
+ * agent factory is a structural stub whose createAgent forwards seed/meta into
+ * the real SessionStore, and whose resume never runs (every source here is
+ * already attached).
+ */
+
+import { describe, expect, it } from 'vitest'
+import { Context } from 'cordis'
+import SessionStore from '@deepseek-ai/dsh-session'
+import AgentRegistry from '@deepseek-ai/dsh-agent'
+import type { Agent, AgentHandle, CreateAgentOptions } from '@deepseek-ai/dsh-agent'
+import { createUserMessage } from '@deepseek-ai/dsh-llm'
+import SessionTitleService from '@deepseek-ai/dsh-session-title'
+import UserInteractionService from '@deepseek-ai/dsh-user-interaction'
+import type { Session, SessionId } from '@deepseek-ai/dsh-session'
+import type { RpcRequest } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { RpcId } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
+import { createApiProxy } from '@deepseek-ai/dsh-host-apiproxy'
+
+const sid = (id: string): SessionId => id as SessionId
+
+let nextRpc = 1
+function request<P>(payload: P): RpcRequest<P> {
+  return { rpcId: RpcId(`fr-${String(nextRpc++)}`), payload }
+}
+
+async function composed(withTitles = true): Promise<Context> {
+  const ctx = new Context()
+  await ctx.plugin(SessionStore)
+  await ctx.plugin(AgentRegistry)
+  await ctx.plugin(UserInteractionService)
+  if (withTitles) {
+    await ctx.plugin(SessionTitleService, { fallbackMaxWords: 5, fallbackMaxBytes: 40, maxTitleBytes: 40 })
+  }
+  // Store-backed structural factory: create builds the session with the
+  // forwarded seed/meta (the store validates the balanced prefix) and
+  // registers an idle agent stub over it.
+  ctx.agents.setFactory({
+    createAgent: (ownerCtx: Context, options: CreateAgentOptions): Promise<AgentHandle> => {
+      const session = ctx.sessions.create(options.sessionId, {
+        ...options.seed === undefined ? {} : { seed: [...options.seed] },
+        ...options.meta === undefined ? {} : { meta: options.meta },
+      })
+      const agent = { id: session.id, session, status: 'idle', ctx: ownerCtx } as Agent
+      ctx.agents.register(agent)
+      return Promise.resolve({ agent, dispose: () => Promise.resolve() })
+    },
+    resume: () => Promise.reject(new Error('resume must not run: every source is attached')),
+  })
+  return ctx
+}
+
+/** Register one live agent whose log holds `turns` completed turns. */
+function liveAgent(ctx: Context, id: string, turns: number): Session {
+  const session = ctx.sessions.create(sid(id), { meta: { cwd: '/proj' } })
+  for (let turn = 1; turn <= turns; turn++) {
+    session.append('turn/start', { turn, trigger: { kind: 'message', source: { kind: 'user' } } })
+    session.append('user/message', createUserMessage({
+      content: [{ type: 'text', text: `prompt ${String(turn)}` }],
+      source: { kind: 'user' },
+    }), { surfaceOp: 'append' })
+    session.append('turn/end', { turn, reason: { kind: 'completed' } })
+  }
+  ctx.agents.register({ id: session.id, session, status: 'idle', ctx } as Agent)
+  return session
+}
+
+const api = (ctx: Context) => createApiProxy(ctx, { provider: 'p', model: 'm', cwd: '/tmp', workspaceRoot: '/tmp' })
+
+describe('sessions.rename', () => {
+  it('accepts through the composed title service: normalized user-source event, echoed seq', async () => {
+    const ctx = await composed()
+    const source = liveAgent(ctx, 'session-rename', 1)
+
+    const renamed = await api(ctx).sessions.rename(request({ sessionId: source.id, title: '  new   name  ' }))
+    expect(renamed.result.ok).toBe(true)
+    if (!renamed.result.ok) return
+    expect(renamed.result.value.title).toBe('new name')
+    const event = source.events.findLast(item => item.type === 'session/title')
+    expect(event?.seq).toBe(renamed.result.value.seq)
+    expect(event?.data).toMatchObject({ title: 'new name', source: { kind: 'user' } })
+  })
+
+  it('maps an empty-normalizing title to title-invalid', async () => {
+    const ctx = await composed()
+    const source = liveAgent(ctx, 'session-rename-bad', 1)
+
+    const response = await api(ctx).sessions.rename(request({ sessionId: source.id, title: '   ' }))
+    expect(response.result.ok).toBe(false)
+    if (!response.result.ok) {
+      expect(response.result.error).toMatchObject({
+        code: 'title-invalid',
+        details: { sessionId: source.id },
+      })
+    }
+  })
+
+  it('answers internal when the composition mounts no session-title service', async () => {
+    const ctx = await composed(false)
+    const source = liveAgent(ctx, 'session-no-titles', 1)
+
+    const response = await api(ctx).sessions.rename(request({ sessionId: source.id, title: 'name' }))
+    expect(response.result.ok).toBe(false)
+    if (!response.result.ok) {
+      expect(response.result.error.code).toBe('internal')
+      expect(response.result.error.message).toMatch(/session-title service is absent/)
+    }
+  })
+})
diff --git a/packages/host/apiproxy/tests/client-handler.spec.ts b/packages/host/apiproxy/tests/client-handler.spec.ts
index d807557d00..4f56f17dfd 100644
--- a/packages/host/apiproxy/tests/client-handler.spec.ts
+++ b/packages/host/apiproxy/tests/client-handler.spec.ts
@@ -46,6 +46,7 @@ function scriptedApi(overrides: {
       selectModel: r => ok(r, {
         selected: { provider: r.payload.provider, model: r.payload.model },
       }),
+      rename: r => ok(r, { title: 'renamed', seq: 0 }),
       prompt: r => ok(r, { accepted: true as const }),
       cancel: r => ok(r, { accepted: true as const }),
       ...overrides.sessions,
diff --git a/packages/host/apiproxy/tests/fetch-carrier.spec.ts b/packages/host/apiproxy/tests/fetch-carrier.spec.ts
index d7528072f7..1e975d6008 100644
--- a/packages/host/apiproxy/tests/fetch-carrier.spec.ts
+++ b/packages/host/apiproxy/tests/fetch-carrier.spec.ts
@@ -67,6 +67,9 @@ function fakeApi(overrides: Partial<{ muxFrames: MuxFrame[]; hostFrames: HostFra
           },
         }
       },
+      async rename(request) {
+        return { rpcId: request.rpcId, result: { ok: true, value: { title: request.payload.title, seq: 0 } } }
+      },
       async prompt(request) {
         return { rpcId: request.rpcId, result: { ok: true, value: { accepted: true as const } } }
       },
@@ -224,6 +227,8 @@ describe('unary round trip (handler ⇄ client, no network)', () => {
         },
       },
     })
+    const renamed = await c.sessions.rename({ sessionId: 's' as never, title: 'named' })
+    expect(renamed.result).toMatchObject({ ok: true, value: { title: 'named', seq: 0 } })
     expect((await c.sessions.prompt({ sessionId: 's' as never, mode: 'queue', content: [{ type: 'text', text: 'x' }] })).result.ok).toBe(true)
     expect((await c.sessions.cancel({ sessionId: 's' as never })).result.ok).toBe(true)
     expect((await c.host.describe({})).result.ok).toBe(true)
diff --git a/packages/host/apiproxy/tsconfig.json b/packages/host/apiproxy/tsconfig.json
index 7e1e83e39b..908e2cb546 100644
--- a/packages/host/apiproxy/tsconfig.json
+++ b/packages/host/apiproxy/tsconfig.json
@@ -38,6 +38,9 @@
     {
       "path": "../../session-projection/session-projection"
     },
+    {
+      "path": "../../session-title/session-title"
+    },
     {
       "path": "../../session-projection/session-projection-cache"
     },
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 66ea5bea26..8c728eac97 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -2890,6 +2890,9 @@ importers:
       '@deepseek-ai/dsh-session-projection-cache':
         specifier: workspace:^
         version: link:../../session-projection/session-projection-cache
+      '@deepseek-ai/dsh-session-title':
+        specifier: workspace:^
+        version: link:../../session-title/session-title
       '@deepseek-ai/dsh-skill':
         specifier: workspace:^
         version: link:../../skill/skill