fix(web): generate model-backed session titles

packages/host/runtime/README.md

@@ -1,6 +1,6 @@
 # @deepseek-ai/dsh-host-runtime
 
-Host runtime assembly for `dsh`: `bootHost` composes the core plugin spine (LLM service + DeepSeek adapter, sessions with JSONL persistence and deterministic fallback titles, system prompt, tools, agents, agent loop, local bash), `createApiProxy` implements the [`dsh-host-apiproxy`](../apiproxy/README.md) contract over that composition, and `startHost` is the one-step shell seam returning `{ api, handler, defaults, ctx, dispose }`.
+Host runtime assembly for `dsh`: `bootHost` composes the core plugin spine (LLM service + DeepSeek adapter, sessions with JSONL persistence, immediate fallback titles and first-message model summaries, system prompt, tools, agents, agent loop, local bash), `createApiProxy` implements the [`dsh-host-apiproxy`](../apiproxy/README.md) contract over that composition, and `startHost` is the one-step shell seam returning `{ api, handler, defaults, ctx, dispose }`.
 
 Which plugins mount and with what defaults is decided only here — shells must not `ctx.plugin` to alter the assembly. `RunningHost.ctx` is a formal seam with exactly two sanctioned uses: mounting protocol front-door plugins (e.g. a future `dsh acp`) and headless session-event subscription; consuming clients must not bypass `api` through it.
 
@@ -12,7 +12,8 @@ Which plugins mount and with what defaults is decided only here — shells must
 | `provider` | `'deepseek'` | Default provider route injected as agentOptions on create/resume and reported by `host.describe`. |
 | `model` | `'deepseek-v4-flash'` | Default model id, same single source as `provider`. |
 | `cwd` | `process.cwd()` | Default project directory for a session whose create request omits `cwd`. |
-| `sessionTitle` | 5 words / 40 fallback bytes / 80 accepted bytes | Deterministic fallback-title limits. The host mounts no asynchronous title provider, so title creation adds no model call. |
+| `sessionTitle` | 5 words / 40 fallback bytes / 80 accepted bytes | Deterministic fallback and accepted-title limits. |
+| `sessionTitleLlm` | 5 words / 10 CJK chars / 4,096 input bytes / 64 output tokens / 60 s | First-message model-title policy. An omitted route inherits the logged main-request provider and model. |
 
 ## ApiProxy implementation notes
 
@@ -20,11 +21,11 @@ Unary methods take the narrow `RpcRequest<P>` and echo `request.rpcId`; a prompt
 
 ## Model Experience
 
-Indirectly, through the model-facing plugins bootHost mounts and the provider/model defaults injected into created and resumed agents.
+Indirectly, through the non-blocking first-message title request owned by [`dsh-session-title-llm`](../../session-title/session-title-llm/README.md) and the other model-facing plugins `bootHost` mounts.
 
 #### KV Cache effect
 
-No direct invalidation; the mounted model-facing plugins own their request-prefix changes.
+No main-request invalidation; the auxiliary title request has its own cache behavior and the conversation prefix remains unchanged.
 
 ## Known Limitations and Deferred Work
 

packages/host/runtime/package.json

@@ -50,6 +50,7 @@
     "@deepseek-ai/dsh-session-persistence": "workspace:^",
     "@deepseek-ai/dsh-session-persistence-jsonl": "workspace:^",
     "@deepseek-ai/dsh-session-title": "workspace:^",
+    "@deepseek-ai/dsh-session-title-first-message-llm": "workspace:^",
     "@deepseek-ai/dsh-skill": "workspace:^",
     "@deepseek-ai/dsh-skill-local": "workspace:^",
     "@deepseek-ai/dsh-spill-local": "workspace:^",

packages/host/runtime/src/boot.ts

@@ -9,6 +9,8 @@ import Timer from '@cordisjs/plugin-timer'
 import LlmService from '@deepseek-ai/dsh-llm'
 import SessionStore from '@deepseek-ai/dsh-session'
 import SessionTitleService, { type Config as SessionTitleConfig } from '@deepseek-ai/dsh-session-title'
+import * as SessionTitleFirstMessageLlm from '@deepseek-ai/dsh-session-title-first-message-llm'
+import type { Config as SessionTitleLlmConfig } from '@deepseek-ai/dsh-session-title-first-message-llm'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry from '@deepseek-ai/dsh-tools'
 import AgentRegistry from '@deepseek-ai/dsh-agent'
@@ -46,6 +48,15 @@ const DEFAULT_SESSION_TITLE_CONFIG: SessionTitleConfig = {
   maxTitleBytes: 80,
 }
 
+/** Default first-message model-title policy for sessions created through the host. */
+const DEFAULT_SESSION_TITLE_LLM_CONFIG: SessionTitleLlmConfig = {
+  targetWords: 5,
+  targetCjkCharacters: 10,
+  maxInputBytes: 4_096,
+  maxOutputTokens: 64,
+  timeoutMs: 60_000,
+}
+
 /** Options for bootHost — the assembly-layer composition knobs. */
 export interface BootHostOptions {
   /** Root directory for JSONL session persistence. */
@@ -54,8 +65,10 @@ export interface BootHostOptions {
   provider?: string
   /** Default model id (defaults to 'deepseek-v4-flash', matching the demos). */
   model?: string
-  /** Deterministic fallback-title limits; no asynchronous title provider is mounted by the host. */
+  /** Deterministic fallback-title limits. */
   sessionTitle?: SessionTitleConfig
+  /** First-message model-title policy; omitted provider/model inherit the session's logged main-request route. */
+  sessionTitleLlm?: SessionTitleLlmConfig
   /**
    * Default project directory for sessions created without an explicit cwd
    * (defaults to the host process working directory). A session's cwd is its
@@ -100,6 +113,7 @@ export async function bootHost(options: BootHostOptions): Promise<HostHandle> {
   await ctx.plugin(LlmService)
   await ctx.plugin(SessionStore)
   await ctx.plugin(SessionTitleService, options.sessionTitle ?? DEFAULT_SESSION_TITLE_CONFIG)
+  await ctx.plugin(SessionTitleFirstMessageLlm, options.sessionTitleLlm ?? DEFAULT_SESSION_TITLE_LLM_CONFIG)
   await ctx.plugin(SystemPrompt, { persona: '' })
   await ctx.plugin(ToolRegistry)
   await ctx.plugin(AgentRegistry)

packages/host/runtime/tests/host-runtime.spec.ts

@@ -9,6 +9,7 @@ import type { GenerateOptions, StreamChunk } from '@deepseek-ai/dsh-llm'
 import { LlmAdapter } from '@deepseek-ai/dsh-llm'
 import type { SessionId } from '@deepseek-ai/dsh-session'
 import type { Config as SessionTitleConfig } from '@deepseek-ai/dsh-session-title'
+import type { Config as SessionTitleLlmConfig } from '@deepseek-ai/dsh-session-title-first-message-llm'
 import type { HostFrame, MuxFrame } from '@deepseek-ai/dsh-host-apiproxy/api'
 import type { RpcRequest, RpcResponse } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
 import { RpcId } from '@deepseek-ai/dsh-host-apiproxy/api/rpc'
@@ -21,6 +22,10 @@ class ScriptedAdapter extends LlmAdapter {
   }
 
   async * stream(options: GenerateOptions): AsyncIterable<StreamChunk> {
+    if ((options.tools?.length ?? 0) === 0) {
+      yield * textResponse('Durable append-only session titles')
+      return
+    }
     const entry = this.script.shift()
     if (!entry) throw new Error('ScriptedAdapter: script exhausted')
     if (entry === 'hang') {
@@ -96,6 +101,7 @@ afterEach(async () => {
 async function boot(
   script: (StreamChunk[] | 'hang')[] = [],
   sessionTitle?: SessionTitleConfig,
+  sessionTitleLlm?: SessionTitleLlmConfig,
 ): Promise<RunningHost> {
   host = await startHost({
     boot: {
@@ -103,6 +109,7 @@ async function boot(
       provider: 'scripted',
       model: 'test-model',
       ...(sessionTitle === undefined ? {} : { sessionTitle }),
+      ...(sessionTitleLlm === undefined ? {} : { sessionTitleLlm }),
     },
   })
   host.ctx.llm.registerAdapter(['scripted'], new ScriptedAdapter(script))
@@ -158,6 +165,63 @@ describe('sessions.create / list', () => {
 })
 
 describe('sessions.prompt / cancel', () => {
+  it.each([
+    { name: 'host default', config: undefined, target: '5 words', maxTokens: 64 },
+    {
+      name: 'configured policy',
+      config: {
+        targetWords: 3,
+        targetCjkCharacters: 8,
+        maxInputBytes: 2_048,
+        maxOutputTokens: 24,
+        timeoutMs: 2_000,
+      },
+      target: '3 words',
+      maxTokens: 24,
+    },
+  ] satisfies {
+    name: string
+    config: SessionTitleLlmConfig | undefined
+    target: string
+    maxTokens: number
+  }[])('replaces the fallback with a model-backed first-message title using the $name', async ({ config, target, maxTokens }) => {
+    const modelTitle = 'Durable append-only session titles'
+    const running = await boot([textResponse('pong')], undefined, config)
+    const { api, ctx } = running
+    const { sessionId } = expectOk(await api.sessions.create(request({})))
+    const agent = ctx.agents.get(sessionId) as Agent
+    const idle = waitForIdle(ctx, agent)
+    expectOk(await api.sessions.prompt(request({
+      sessionId,
+      mode: 'queue' as const,
+      content: [{ type: 'text' as const, text: 'Explain why append-only logs make session titles durable.' }],
+    })))
+    await idle
+
+    await vi.waitFor(() => {
+      expect(agent.session.events.filter(event => event.type === 'session/title').map(event => event.data))
+        .toEqual([
+          {
+            title: 'Explain why append-only logs make',
+            messageSeqs: [1],
+            source: { kind: 'fallback' },
+          },
+          {
+            title: modelTitle,
+            messageSeqs: [1],
+            source: {
+              kind: 'provider',
+              provider: 'session-title-first-message-llm',
+              model: { provider: 'scripted', model: 'test-model' },
+            },
+          },
+        ])
+    })
+    const titleRequest = agent.session.events.find(event => event.type === 'session/title-llm-request')
+    expect(titleRequest?.data.system).toContain(target)
+    expect(titleRequest?.data.maxTokens).toBe(maxTokens)
+  })
+
   it.each([
     { name: 'host default', config: undefined, expected: 'Show the Web UI durable' },
     {

packages/host/runtime/tsconfig.json

@@ -26,6 +26,9 @@
     {
       "path": "../../session-title/session-title"
     },
+    {
+      "path": "../../session-title/session-title-first-message-llm"
+    },
     {
       "path": "../../core/system-prompt"
     },