docs(session-title): record contracts and generated catalogs

2026-07-21 01:54:00 +08:00
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+# 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
+2026-07-21-log-backed-session-titles.md: a2cef52bf88f03eef804e3d7f2bf83288ba49b2e
+2026-07-21-log-backed-session-titles.zh.md: ea6ecc6e66d1afac772cdd93936c6ed49d5409a2
@@ -0,0 +1,60 @@
+# Agent Note: Log-backed session titles
+
+Status: implemented
+
+English | [中文](2026-07-21-log-backed-session-titles.zh.md)
+
+## Problem
+
+A session needs a short human-facing title before an editor, terminal, or query consumer can present it usefully. The cheapest implementation can derive one from the first prompt, while higher-quality implementations may call a model over the first prompt or the whole conversation. Those strategies have different latency, cost, routing, and retry behavior, but every consumer needs one durable source of truth.
+
+Session identity metadata is immutable, the event log is the replay and fork boundary, and every event must remain turn-enclosed. A model-generated title often finishes after the main turn closes, so writing it synchronously would delay the agent response while writing it as mutable metadata would bypass ordinary persistence, replay, and lineage semantics. Concurrent prompts, provider HMR, cancellation, and ignored abort signals also make an unfenced background result capable of overwriting a newer title.
+
+## Decision
+
+The [`session-title` capability family](../../../../packages/session-title/README.md) owns title state and generation policy. `@deepseek-ai/dsh-session-title` provides `ctx.sessionTitle`, a deterministic first-message fallback, and a registry for at most one optional asynchronous provider. `@deepseek-ai/dsh-session-title-llm` owns the common auxiliary-model request policy; separate first-message and all-user-messages plugins choose input cadence. The shared agent spine mounts only the fallback service with explicit example limits, leaving both model providers opt-in.
+
+### Event ownership and folding
+
+Every accepted revision is a log-only `session/title` event. Its payload contains normalized non-empty text, the exact eligible human `user/message` seqs used to derive it, and either fallback provenance or the registered provider id plus optional provider/model route. `foldSessionTitle()` selects the latest event and adds that event's seq and timestamp as `SessionTitleSnapshot`. Title events never enter `session.surface` or `deriveMessages()`.
+
+The core session package exposes `ctx.sessions.appendOutOfBand()` only for plugin event types whose owners also declaration-merge an `OutOfBandSessionEventMap` marker. An open turn receives the log-only event directly and owns its normal checkpoint. A closed log receives `turn/start → event → turn/end` under the plugin's trigger, followed by an awaited flush. Once the synthetic turn opens, target-append failure still attempts to close and flush it; detach is deferred until the sequence settles. Session titles contribute the `session-title` zero-step trigger and opt `session/title` into this seam.
+
+### Input and asynchronous timing
+
+Only text blocks from human-source `user/message` events are eligible. Empty, control-only, and non-text prompts wait for the next eligible message. The service schedules the first fallback without awaiting it from the prompt path, normalizes whitespace and control sequences, applies the configured word and UTF-8 byte limits without splitting a code point, and records the first message seq.
+
+Automatic provider work waits until the corresponding `request/header` records the main request's exact provider/model route, then runs independently of the agent response. A completion joins whichever turn is open at acceptance time or uses the zero-step append path. Explicit `refresh(session, signal?)` materializes any missing fallback and awaits the registered provider; without a provider it returns the fallback.
+
+The first-message provider schedules once when a fresh session first creates its fallback. An automatic failure does not reschedule on later prompts; `refresh()` is the retry path. The all-messages provider schedules after every eligible human prompt and passes all eligible messages through that revision, including seeded history. Its newer revision aborts and supersedes older pending or active work.
+
+### Registration, routing, and failure policy
+
+`register(provider)` validates one branded stable id, cadence, and generation function, then returns an effect disposer. A second live registration throws immediately. Provider disposal and session disposal abort pending and active work. Every session-local generation has a monotonic revision and exact registration identity; acceptance rechecks revision, registration, session liveness, and cancellation, so a provider that ignores its abort signal cannot commit stale output.
+
+Model providers require explicit word, CJK-character, input-byte, output-token, and timeout limits. Optional `provider` and `model` overrides are a pair; without them the helper uses the exact route from the logged main request header. Selected messages are framed as JSON under one fixed language-aware instruction. Oversized input is rejected rather than truncated because truncation would make the recorded source seqs falsely imply complete use.
+
+Automatic provider failures are nonfatal warnings and retain the latest title. Explicit refresh failures reject to the caller. Output must be non-empty text with unique ordered seqs drawn from the fixed request; the service normalizes and byte-limits it before durable acceptance.
+
+### Forks and consumers
+
+A fork inherits seed title events unchanged, like the rest of its source log. The first-message provider does not automatically retitle a fork. The all-messages provider may append a child-owned revision after a later child prompt, using inherited and new eligible messages.
+
+`ctx.sessionQuery.readTitle()` folds one live-preferred or persisted log without loading titles during `listSessions()`. ACP maps the event to `session_info_update` during both live streaming and load replay, using the event timestamp for `updatedAt`. The TUI uses the latest title as its header subtitle and sets the terminal window title to `<session title> — <configured product title>` after terminal-safe rendering.
+
+## Alternatives considered
+
+- **Mutable `SessionHeader` or side metadata** — rejected because it creates a second persistence mutation protocol, weakens immutable identity metadata, makes crash atomicity backend-specific, and gives forks ambiguous copy-versus-reference behavior. The append-only log already owns replayable latest-wins state.
+- **Await title generation before returning the agent response** — rejected because auxiliary provider latency and failure would sit on the main interaction's critical path. The deterministic fallback gives immediate useful state while a better title may arrive later.
+- **Put titles in derived history or the request prefix** — rejected because UI metadata would consume tokens, change cache identity, and make the main model observe its own label. A log-only event remains reconstructable without becoming model-visible.
+- **Permit multiple registered providers and resolve precedence after completion** — rejected because completion order is not product precedence and would make retries, HMR, and provenance nondeterministic. A deployment that needs a composite policy can register one provider that owns that policy.
+- **Silently truncate oversized auxiliary input** — rejected because the provider result would claim exact source-message provenance while receiving only partial text. Keeping the prior title and warning preserves truthful attribution.
+- **Index titles in `listSessions()` immediately** — rejected because the existing lightweight metadata list would need per-backend derived-index synchronization. Exact `readTitle()` establishes the read contract without precommitting search or indexing policy.
+
+## Consequences
+
+- Titles survive JSONL and SQLite persistence, replay through ACP, and follow fork inheritance without a separate mutable record.
+- A fallback appears without an auxiliary call; deployments choose whether better titles justify model cost and whether later prompts should retitle a session.
+- Late accepted titles consume event seqs and may create a balanced zero-step turn, so transcript and persistence fixtures expose the update even though model history and KV-cache identity do not change.
+- One provider and monotonic per-session revisions make disposal, supersession, and stale-result rejection explicit, at the cost of leaving multi-strategy precedence to a composite provider.
+- Manual rename, deletion, generated-versus-user precedence, search, and list indexing remain outside the capability.
@@ -0,0 +1,60 @@
+# Agent Note: 基于日志的会话标题
+
+Status: implemented
+
+[English](2026-07-21-log-backed-session-titles.md) | 中文
+
+## 问题
+
+会话需要一个面向用户的简短标题，编辑器、终端或查询消费方才能有效呈现它。成本最低的实现可以从第一条提示词派生标题，质量更高的实现则可以让模型处理第一条提示词或整个对话。这些策略在延迟、成本、路由和重试行为上各有不同，但所有消费方都需要一个持久的真源。
+
+会话身份元数据不可变，事件日志是回放和 fork 的边界，而且每个事件都必须包围在轮次内。模型生成的标题往往在主轮次结束后才完成，因此同步写入会延迟 agent（智能体）响应，而作为可变元数据写入则会绕过常规的持久化、回放和沿袭语义。并发提示词、提供方 HMR（热模块替换）、取消以及被忽略的中止信号，还可能让未受版本校验约束的后台结果覆盖更新的标题。
+
+## 决策
+
+[`session-title` 功能包族](../../../../packages/session-title/README.md)负责标题状态和生成策略。`@deepseek-ai/dsh-session-title` 提供 `ctx.sessionTitle`、确定性的首消息回退方案，以及一个至多接受单个可选异步提供方的注册表。`@deepseek-ai/dsh-session-title-llm` 负责通用的辅助模型请求策略；首消息插件和全部用户消息插件分别选择输入调度方式。共享 agent 主干只挂载带显式示例限制的回退服务，两种模型提供方均需按需启用。
+
+### 事件归属与折叠
+
+每个已接受的修订都是纯日志 `session/title` 事件。其载荷包含规范化后的非空文本、用于派生标题的所有合格且来源为人类的 `user/message` 的准确 seq，以及回退来源信息，或已注册的提供方 id 加可选的提供方和模型路由。`foldSessionTitle()` 选择最新事件，并将该事件的 seq 和时间戳加入 `SessionTitleSnapshot`。标题事件永远不会进入 `session.surface` 或 `deriveMessages()`。
+
+核心会话包通过 `ctx.sessions.appendOutOfBand()` 暴露这一接口，但只允许所属插件同时通过声明合并向 `OutOfBandSessionEventMap` 添加标记的插件事件类型使用。开放轮次会直接接收纯日志事件，并负责其常规检查点。已关闭的日志会在该插件的触发器下接收 `turn/start → event → turn/end`，随后等待刷写完成。合成轮次一旦开启，即使目标追加失败，系统仍会尝试将其关闭并刷写；整个序列完成前会延迟 detach。会话标题提供 `session-title` 零步骤触发器，并让 `session/title` 使用这一服务边界。
+
+### 输入与异步时序
+
+只有人类来源的 `user/message` 事件中的文本块才符合条件。空提示词、仅含控制字符的提示词和非文本提示词会等待下一条合格消息。服务从提示词路径调度首个回退标题而不等待其完成，随后规范化空白和控制序列，应用已配置的单词数和 UTF-8 字节限制且不拆分代码点，并记录第一条消息的 seq。
+
+自动提供方工作会等待相应的 `request/header` 记录主请求的准确提供方和模型路由，然后独立于 agent 响应运行。完成结果在被接受时加入当时开放的轮次，否则使用零步骤追加路径。显式调用 `refresh(session, signal?)` 会生成尚缺的回退标题并等待已注册的提供方；没有提供方时则返回回退标题。
+
+首消息提供方仅在新会话首次创建回退标题时调度一次。自动执行失败后，后续提示词不会重新调度；`refresh()` 是重试路径。全部消息提供方会在每条合格且由人类发出的提示词后调度，并传入截至该修订的所有合格消息，包括预置历史记录。较新的修订会中止并取代更早的待执行或活跃工作。
+
+### 注册、路由与失败策略
+
+`register(provider)` 会验证一个带品牌类型的稳定 id、执行时机和生成函数，然后返回 effect 资源释放函数。第二个活跃注册会立即抛出错误。提供方和会话执行 dispose（资源释放）时，都会中止待执行和活跃工作。每项会话本地生成都有单调递增的修订号和对应的注册身份；接受结果时会重新检查修订号、注册、会话活跃状态和取消状态，因此即使提供方忽略中止信号，也无法提交陈旧输出。
+
+模型提供方必须显式配置单词数、CJK 字符数、输入字节数、输出 token 数和超时限制。可选的 `provider` 和 `model` 覆盖项必须成对提供；两者均未提供时，辅助组件会使用主请求已记录请求头中的准确路由。系统在一条固定且能区分语言的指令下，将选中的消息封装为 JSON。过大输入会被拒绝而不是截断，因为截断会让记录的源消息 seq 错误地表示这些消息已被完整使用。
+
+自动提供方故障只会发出非致命警告，并保留最新标题。显式刷新失败则会向调用方返回拒绝。输出必须是非空文本，并包含来自固定请求、唯一且有序的 seq；服务会在持久接受前对其进行规范化并施加字节限制。
+
+### Fork 与消费方
+
+与源日志的其他部分相同，fork 会原样继承作为种子的标题事件。首消息提供方不会自动为 fork 重新生成标题。全部消息提供方可以在子会话出现后续提示词后追加一项归子会话所有的修订，并使用继承的合格消息和新增的合格消息。
+
+`ctx.sessionQuery.readTitle()` 会折叠一份实时优先或已持久化的日志，而不会在 `listSessions()` 期间加载标题。ACP（Agent Client Protocol）会在实时流式输出和加载回放期间把该事件映射到 `session_info_update`，并使用事件时间戳作为 `updatedAt`。TUI 使用最新标题作为其标题栏副标题，并在完成终端安全渲染后，将终端窗口标题设置为 `<session title> — <configured product title>`。
+
+## 考虑过的替代方案
+
+- **可变 `SessionHeader` 或独立元数据**：不予采纳，因为这会创建第二套持久化变更协议，削弱不可变身份元数据，让崩溃原子性因后端而异，并使 fork 的复制或引用行为产生歧义。仅追加日志已经负责可回放的后写覆盖状态。
+- **返回 agent 响应前等待标题生成**：不予采纳，因为辅助提供方的延迟和故障会进入主交互的关键路径。确定性回退方案可以立即提供可用状态，质量更高的标题则可稍后到达。
+- **将标题放入派生历史记录或请求前缀**：不予采纳，因为 UI 元数据会消耗 token、改变缓存标识，并让主模型观察到自己的标签。纯日志事件既保持可重建，又不会变得对模型可见。
+- **允许注册多个提供方，并在完成后解析优先级**：不予采纳，因为完成顺序并不等于产品优先级，而且会让重试、HMR 和来源信息变得不确定。需要组合策略的部署可以注册一个自行负责该策略的提供方。
+- **静默截断过大的辅助输入**：不予采纳，因为提供方结果会声明准确的源消息来源信息，实际却只接收了部分文本。保留原有标题并发出警告，可以保持归因真实。
+- **立即在 `listSessions()` 中索引标题**：不予采纳，因为现有的轻量元数据列表将需要逐后端同步派生索引。精确的 `readTitle()` 建立了读取契约，而没有提前锁定搜索或索引策略。
+
+## 后果
+
+- 标题可以在 JSONL 和 SQLite 持久化中存续，通过 ACP 回放，并遵循 fork 继承语义，而无需单独的可变记录。
+- 回退标题无需辅助调用即可出现；部署方可以自行决定更优标题是否值得模型成本，以及后续提示词是否需要重新生成会话标题。
+- 延迟接受的标题会占用事件 seq，并可能创建平衡的零步骤轮次，因此 transcript（文本记录）和持久化 fixture（测试前置数据）会呈现该更新，尽管模型历史和 KV 缓存标识保持不变。
+- 单个提供方和每会话单调递增的修订号让释放、取代和陈旧结果拒绝行为明确可见，但多策略优先级必须由复合提供方负责。
+- 手动重命名、删除、生成标题与用户标题的优先级、搜索和列表索引不在此功能范围内。
@@ -0,0 +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
+architecture.md: ed17122d220145edbaafe56c02b4c0e21024316f
+architecture.zh.md: a69f3119ee4122b0f855cc1551d258f538e630ca
@@ -1,10 +1,12 @@
 # DeepSeek Harness Architecture

+English | [中文](architecture.zh.md)
+
 The **DeepSeek Harness SDK** builds agent harnesses on Cordis. The principle is simple: **everything is a plugin**. The shipped loop is one plugin, not a privileged kernel.

 ## Overview

-A harness is one [Cordis](cordis-primer.md) context. Packages add services (`ctx.llm`, `ctx.tools`, `ctx.sessions`), typed events (`agent/request`, `tools/pre-execute`, `session/event`), and disposable prompt, tool, provider, adapter, and listener registrations.
+A harness is one [Cordis](cordis-primer.md) context. Packages add services (`ctx.llm`, `ctx.tools`, `ctx.sessions`, `ctx.sessionTitle`), typed events (`agent/request`, `tools/pre-execute`, `session/event`), and disposable registrations.

 `packages/core/` groups the default agent flow; surrounding capabilities are equally first-class Cordis plugins.

@@ -38,6 +40,7 @@ A harness is one [Cordis](cordis-primer.md) context. Packages add services (`ctx
 | `ctx.workflows` | [`workflow/`](../packages/workflow/README.md) | script-driven multi-agent orchestration |
 | `ctx.sessionPersistence` | [`session-persistence/`](../packages/session-persistence/README.md) | durable storage for session logs |
 | `ctx.sessionQuery` | [`session-query/`](../packages/session-query/README.md) | live-preferred logical-corpus exact reads and relationship traces |
+| `ctx.sessionTitle` | [`session-title/`](../packages/session-title/README.md) | log-backed fallback titles and one optional asynchronous provider |

 ## Event

@@ -45,9 +48,9 @@ Events form the service extension API; see the exhaustive [events catalog](cordi

 ### Event Domains

- **Session events** are durable, replayable facts: boundaries, messages, tool activity, steering, compaction, and tool-owned records append to the log and flow through `session/event`.
- **Agent events** carry the live `Agent` handle for status, diagnostics, prompt admission, request shaping, result validation, and continuation policy.
- **Capability events** belong to their owning seam; `tools/*`, `llm/*`, `system-prompt/*`, `fs/*`, and `subagent/*` attach policy and adapters without importing the loop.
+- **Session events** are durable facts appended to the log and emitted through `session/event`.
+- **Agent events** carry the live `Agent` for status, prompt admission, request shaping, validation, and continuation.
+- **Capability events** let owning seams attach policy and adapters without importing the loop.

 ### Interception Semantics

@@ -57,9 +60,9 @@ Waterfall events behave like around-middleware: a listener delegates by calling

 The shipped loop drains prompt-to-checkpoint work through plugin-visible services and events.

-A **session** is an append-only log. Each ordinary **turn** claims one queued `send()` item; injection claims none. A claimed `send()` successor awaits the preceding claimed ordinary turn's checkpoint but may share its `running` interval ([decision](../.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.md)). A turn ends when model and plugins stop it. A **step** is one model request plus tools. Below ([sequence companion](agent-lifecycle.md)), quotes mark durable events; other names are extension points.
+A **session** is an append-only log. Each ordinary **turn** claims one queued `send()` item; injection claims none. Successors await the preceding claimed turn's checkpoint but may share its `running` interval ([decision](../.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.md)). A turn ends when model and plugins stop it. A **step** is one model request plus tools. Below ([sequence companion](agent-lifecycle.md)), quotes mark durable events.

-No id mints `<config-id>-session-<uuid>`; `sessionId` resumes/creates; `resumeSessionId` needs history. Resume restores lineage, seeds, and delegation depth pre-publication. Failures emit `agent-loop/config-start-failed(sessionId, error)`; front doors reject; teardown stays silent.
+No id mints `<config-id>-session-<uuid>`; `sessionId` resumes/creates and `resumeSessionId` needs history. Resume restores lineage and delegation depth before publication. Setup failures emit `agent-loop/config-start-failed`; teardown stays silent.

 ### Turn Flow

@@ -107,15 +110,15 @@ forever:
    checkpoint persistence and notify idle/running status
 ```

-Each step assembles ordered prompt sections, tool schemas, and `{{name}}` variables; unknown or valueless references fail the turn. `dsh-system-prompt` owns the harness identity and default persona, which an agent scope may shadow. The loop supplies `model` and `cwd` ([prompt ownership](../.agents/notes/implemented/architecture/2026-07-05-prompt-variables-and-tool-guidance-ownership.md)).
+Each step assembles ordered prompt sections, tool schemas, and variables; unknown references fail the turn. `dsh-system-prompt` owns identity and persona, while the loop supplies `model` and `cwd` ([prompt ownership](../.agents/notes/implemented/architecture/2026-07-05-prompt-variables-and-tool-guidance-ownership.md)).

-Tool-time context—including async `agent.inject()` notices and post-tool `additionalContexts`—settles, then follows recorded results. Steering drains before `agent/post-step`, which observes durable output, results, context, and steering before signal closure. Leftovers become queued input. Terminal `agent/turn-stop` runs after continuation and steering folding, stays authoritative through turn close and flush, and discards later steering but preserves queued prompts.
+Tool-time context settles after recorded results. Steering drains before `agent/post-step`; leftovers become queued input. Terminal `agent/turn-stop` runs after continuation and steering folding, stays authoritative through flush, and discards later steering while preserving queued prompts.

 Pruning precedes summaries; overflow retries require durable progress. Bounded transient retries compose on `agent/request-error`; cancellation wins ([compaction](../.agents/notes/implemented/architecture/2026-07-10-after-call-compaction-pressure-and-overflow-recovery.md), [retry](../.agents/notes/implemented/architecture/2026-06-21-bounded-llm-request-recovery.md)).

 ### Failure Boundaries

-The turn is the containment boundary. Adapter failures close the step, entering `agent/request-error` with the exact `Error`, `LlmFailure`, and retry history. Retry opens a numbered step; success clears history; exhaustion stores the failure on `turn/end`. Failed chunks commit no message or tool.
+The turn is the containment boundary. Adapter failures close the step and enter `agent/request-error` with exact failure facts. Retry opens a numbered step; exhaustion stores the failure on `turn/end`. Failed chunks commit no message or tool.

 Other failures use `agent/error`. Cancellation and disposal beat recovery; undispatched model tool calls receive synthetic `tool/call` and `ABORTED` result pairs before `turn/end`. `cancel()` clears queues and aborts active work; disposal awaits quiescence before unregistering.

@@ -123,11 +126,11 @@ Every session event is turn-enclosed. Reloading preserves an interrupted tail an

 ### Agent Handles

-`ctx.agents` owns live agents and returns `AgentHandle { agent, dispose() }`. Plugins drive `Agent` through `send()`, `steer()`, `inject()`, `cancel()`, and `whenIdle()`. The caller fiber and factory provider structurally co-own programmatic lifecycles; the consumer handle is the only other teardown capability. All owners await one disposer.
+`ctx.agents` owns live agents and returns `AgentHandle { agent, dispose() }`. Plugins use `send()`, `steer()`, `inject()`, `cancel()`, and `whenIdle()`. The caller fiber, factory provider, and consumer handle co-own teardown through one awaited disposer.

 ### Agent Scope

-Every live agent owns a scoped `agent.ctx`. Its registrations shadow globals, receive only that agent's dispatches, and unwind with it; async effects such as background-task cleanup are awaited. `CreateAgentOptions.setup(agentCtx)` composes the scope before publication. Typed resolvers derive carrier checks from merged `Events` signatures and `scopeTarget` ([semantic gates](../.agents/notes/implemented/process/2026-07-14-typescript-program-backed-semantic-gates.md)). See [agent scope](../.agents/notes/implemented/architecture/2026-07-08-agent-scope-contexts.md) and [subagent composition controls](../.agents/notes/implemented/feature/2026-07-12-subagent-persona-tool-filter-and-depth.md). `AgentLoop` runs drivers inside `ctx.agents.withInitiator()`; private orchestration derives `agent.session`; other identities stay explicit ([decision](../.agents/notes/implemented/architecture/2026-07-15-agent-initiator-scope.md)).
+Every live agent owns a scoped `agent.ctx`. Registrations shadow globals, receive only that agent's dispatches, and unwind with it; async cleanup is awaited. `CreateAgentOptions.setup(agentCtx)` composes before publication. Typed resolvers derive carrier checks from merged `Events` signatures and `scopeTarget` ([semantic gates](../.agents/notes/implemented/process/2026-07-14-typescript-program-backed-semantic-gates.md)). See [agent scope](../.agents/notes/implemented/architecture/2026-07-08-agent-scope-contexts.md) and [subagent composition](../.agents/notes/implemented/feature/2026-07-12-subagent-persona-tool-filter-and-depth.md). `AgentLoop` propagates its initiator; private orchestration derives `agent.session`, while other identities stay explicit ([decision](../.agents/notes/implemented/architecture/2026-07-15-agent-initiator-scope.md)).

 ## State

@@ -139,11 +142,13 @@ The session log is the source of truth. `deriveMessages()` projects session even

 Durability is a plugin concern. Backends buffer synchronous `session/event` notifications; the loop awaits a turn-end checkpoint. `SessionPersistence` stores `SessionEvent` directly and metadata in `SessionHeader`; JSONL defaults to checksummed Zstandard, with SQLite under one contract.

+Plugin-owned log-only events may opt into `ctx.sessions.appendOutOfBand()`: they join an open turn or receive a balanced, flushed zero-step turn. `session/title` uses that path as a latest-wins fold with source-message seqs and provenance. Its first-message fallback is immediate; at most one optional provider may replace it asynchronously without delaying the agent response. Forks inherit logged titles unchanged ([decision](../.agents/notes/implemented/feature/2026-07-21-log-backed-session-titles.md)).
+
 ### Model Content

 Messages contain typed blocks (`text`, `reasoning`, `tool-call`, `tool-result`) derived from merge-extensible `ContentBlockMap`; the same pattern types `MessageSource`, `FinishReason`, `TurnTrigger`, and `TurnEndReason`. New block types coordinate adapters, UI bridges, compaction pricing, token metering, and persistence as one repo-wide contract; replay measurement types live in [token-meter.md](core-data-structures/token-meter.md).

-Streaming uses raw chunks and `BlockAssembler`. One `LlmAdapter.stream()` is one provider attempt; adapters report facts, while recovery policy lives on `agent/request-error`. The loop logs chunks and successful provenance/replay state. Remote adapters stop stalled transport with per-read idle watchdogs. Replay state reaches targets only when routes share an adapter instance ([contract](core-data-structures/llm-streaming.md)).
+Streaming uses raw chunks and `BlockAssembler`. One `LlmAdapter.stream()` is one provider attempt; adapters report facts, while recovery lives on `agent/request-error`. The loop logs chunks and successful provenance/replay state. Remote adapters use per-read idle watchdogs. Replay state reaches targets only when routes share an adapter instance ([contract](core-data-structures/llm-streaming.md)).

 ## Extension And Composition

@@ -151,13 +156,13 @@ Streaming uses raw chunks and `BlockAssembler`. One `LlmAdapter.stream()` is one

 A swappable capability usually splits into **interface / implementation / consumer**: the interface owns its `ctx` key and events, an implementation registers a backend, and a consumer exposes model behavior through tools or prompts. Bash is the reference; the [capability graph](capability-seams.md) shows every family.

-Some seams bend the template deliberately: LLM combines interface and consumer because adapters implement it; filesystem wraps provider primitives with policy; web keeps search/fetch provider registries behind one service; skills and subagents use named providers. Subagents spawn fresh, fork a completed-turn prefix, or use ACP children ([subagent.md](core-data-structures/subagent.md)).
+Some seams bend the template: LLM combines interface and consumer; filesystem wraps providers with policy; web, skills, and subagents own registries. Session titles pair a built-in fallback with a single-provider registry and shared LLM helper. Subagents spawn fresh, fork a completed-turn prefix, or use ACP children ([subagent.md](core-data-structures/subagent.md)).

 `dsh-workspace-context` composes baselines on `agent/session-prefix` and appends `ctx.fs`-discovered nested changes on `tools/post-execute`; its [decision](../.agents/notes/implemented/feature/2026-06-24-workspace-context.md) records isolation. `dsh-paths` owns shared paths.

 ### Bundles And Apps

-`dsh-agent-spine-demo` bundles the default spine ([README](../packages/examples/agent-spine-demo/README.md)). `dsh-tui-demo` owns the interactive full-screen terminal; `dsh-cli-demo` runs one persisted headless turn with format-pure stdout; `dsh-acp-demo` adds stdout-pure ACP over JSON-RPC ([ui/](../packages/ui/README.md)). `dsh-jsonrpc-agent` boots external `cordis.yml`; the Python SDK supplies its default only without an explicit config channel and drives `dsh-jsonrpc` over line-delimited JSON-RPC ([Python SDK](../python/README.md)). Deployments remain thin leaves with swappable backends and optional product tools ([examples/](../examples/AGENTS.md), [runnable wirings](cookbook/extension-cookbook.md#runnable-wirings), [graph atlas](graph-atlas.md)).
+`dsh-agent-spine-demo` bundles the default spine, including fallback-only session titles; model title providers remain opt-in ([README](../packages/examples/agent-spine-demo/README.md)). `dsh-tui-demo` owns the terminal; `dsh-cli-demo` runs one persisted headless turn; `dsh-acp-demo` adds stdout-pure ACP ([ui/](../packages/ui/README.md)). `dsh-jsonrpc-agent` boots external `cordis.yml`; the Python SDK supplies a default only without an explicit config and drives line-delimited JSON-RPC ([Python SDK](../python/README.md)). Deployments remain thin leaves with swappable backends and optional tools ([examples/](../examples/AGENTS.md), [runnable wirings](cookbook/extension-cookbook.md#runnable-wirings), [graph atlas](graph-atlas.md)).

 ### Where New Behavior Goes

@@ -175,6 +180,7 @@ New behavior should attach to a documented extension point; changing the shipped
 | Add a session-stable request prefix outside history | compose it on `agent/session-prefix`, once per loop instance; logged on the request header |
 | Add UI or editor integration | drive `ctx.agents` and render from `session/event` |
 | Add durable session state | add a `SessionEventMap` member and render/replay from the log |
+| Add asynchronous session-title generation | register the sole provider on `ctx.sessionTitle` |
 | Fork a live session | use `ctx.sessions.fork(source, boundary?, childSessionId?)` |
 | Scope a tool, prompt section, or listener to ONE agent | register it through that agent's `agent.ctx` (see Agent Scope) |

@@ -0,0 +1,195 @@
+# DeepSeek Harness 架构
+
+[English](architecture.md) | 中文
+
+**DeepSeek Harness SDK** 基于 Cordis 构建 agent harness（智能体框架）。设计准则很简单：**一切皆插件**。已交付的循环只是一个插件，并非拥有特权的内核。
+
+## 概览
+
+一个 harness 对应一个 [Cordis](cordis-primer.md) 上下文。各包（package）会添加服务（`ctx.llm`、`ctx.tools`、`ctx.sessions`、`ctx.sessionTitle`）、类型化事件（`agent/request`、`tools/pre-execute`、`session/event`）和可释放的注册项。
+
+`packages/core/` 汇集默认的 agent 流程；外围功能同样都是一等的 Cordis 插件。
+
+### 默认服务
+
+| ctx 键 | 包 | 职责 |
+|---|---|---|
+| — | [`dsh-scope`](../packages/core/scope/README.md) | 作用域上下文注册原语（库） |
+| `ctx.sessions` | `dsh-session` | 内存中的事件溯源会话 |
+| `ctx.systemPrompt` | `dsh-system-prompt` | 有序提示词片段、工具 schema 和提示词变量 |
+| `ctx.tools` | `dsh-tools` | 工具注册表和[执行流水线](tool-execution-pipeline.md) |
+| `ctx.agents` | `dsh-agent` | 活跃 agent、委托创建、`agent/*` 事件和进程内发起方作用域 |
+| `ctx.agentLoop` | `dsh-agent-loop` | 实体 `Agent` 驱动器 |
+
+### 功能服务
+
+| ctx 键 | 包族 | 职责 |
+|---|---|---|
+| `ctx.llm` | [`llm/`](../packages/llm/README.md) | 适配器注册表和模型流式调用 |
+| `ctx.tokenMeter` | [`llm/token-meter`](../packages/llm/token-meter/README.md) | 感知回放的单实例请求压力和会话表面压力 |
+| `ctx.bash` | [`bash/`](../packages/bash/README.md) | 前台和后台命令执行 |
+| `ctx.sandbox` | [`sandbox/`](../packages/sandbox/README.md) | 同一执行环境内的进程限制（argv 包装、逐调用策略） |
+| `ctx.sandboxPolicy` | [`sandbox/`](../packages/sandbox/README.md) | 共享沙箱策略归属点 |
+| `ctx.codeRuntime` | [`code-runtime/`](../packages/code-runtime/README.md) | 执行模型编写的程序 |
+| `ctx.fs` | [`fs/`](../packages/fs/README.md) | 文件系统提供方原语和策略事件 |
+| `ctx.skills` | [`skill/`](../packages/skill/README.md) | skill（技能）提供方注册表和渐进式披露 |
+| `ctx.web` | [`web/`](../packages/web/README.md) | 搜索与抓取提供方注册表 |
+| `ctx.compact`，`ctx.toolResultPrune` | [`compact/`](../packages/compact/README.md)/[`compact-tool-result-prune`](../packages/compact/compact-tool-result-prune/README.md) | 摘要压缩（compaction）；可选的无模型结果裁剪 |
+| `ctx.subagents` | [`subagent/`](../packages/subagent/README.md) | 具名委托提供方 |
+| `ctx.tasks` | [`tasks/`](../packages/tasks/README.md) | 后台任务注册表和通用 `task_*` 控制工具 |
+| `ctx.workflows` | [`workflow/`](../packages/workflow/README.md) | 脚本驱动的多 agent 编排 |
+| `ctx.sessionPersistence` | [`session-persistence/`](../packages/session-persistence/README.md) | 会话日志的持久存储 |
+| `ctx.sessionQuery` | [`session-query/`](../packages/session-query/README.md) | 实时优先的逻辑语料精确读取和关系追踪 |
+| `ctx.sessionTitle` | [`session-title/`](../packages/session-title/README.md) | 基于日志的回退标题和单个可选异步提供方 |
+
+## 事件
+
+事件构成服务的扩展 API；完整清单见[事件目录](cordis-catalog/events.md)和[生产方与消费方映射](event-producer-consumer.md)。
+
+### 事件域
+
+- **会话事件**是追加到日志并通过 `session/event` 发出的持久事实。
+- **Agent 事件**携带活跃 `Agent`，用于状态、提示词准入、请求塑形、验证和续跑。
+- **功能事件**让所属服务边界无需导入循环即可附加策略和适配器。
+
+### 拦截语义
+
+waterfall（瀑布式事件）的行为类似环绕中间件：监听器调用 `next()` 即表示委托，直接返回而不调用它则会否决或接管。完整规则见 [Cordis waterfall 语义](cordis-primer.md#cordis-waterfall-semantics)。
+
+## 默认循环生命周期
+
+已交付的循环通过插件可见的服务和事件，持续处理从提示词到检查点的工作。
+
+**会话**是仅追加日志。每个普通**轮次**领取一项已排队的 `send()` 输入；注入不领取输入。后续轮次会等待上一项已领取轮次的检查点，但可以与其共用同一个 `running` 区间（[决策](../.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.md)）。模型和插件停止轮次时，该轮次结束。一个**步骤**包含一次模型请求及其工具。下文（[时序配套文档](agent-lifecycle.md)）用引号标记持久事件。
+
+未提供 id 时会生成 `<config-id>-session-<uuid>`；`sessionId` 用于恢复或创建会话，而 `resumeSessionId` 要求已有历史。恢复流程在发布前还原沿袭关系和委托深度。设置失败会发出 `agent-loop/config-start-failed`；拆卸过程保持静默。
+
+### 轮次流程
+
+```text
+choose declarative identity and fresh/resume path
+  -> prepare private session + agent.ctx -> await unpublished setup
+  -> enter session + agent -> session/created -> agent/created
+  -> enable driving -> agent/session-start(source) -> start driver
+forever:
+  wait for a queued message
+  emit agent/status(running)
+  TURN:
+    'turn/start'
+    claimed message -> agent/prompt-submit
+      allowed prompt -> 'user/message' plus injected context
+      blocked prompt -> 'prompt/blocked' -> 'turn/end'(rejected)
+    STEP loop:
+      drain steering
+      assemble system prompt and tool schemas
+      agent/session-prefix (first step)
+      agent/pre-step
+      snapshot the derived messages (the reconstruction boundary)
+      'step/start'
+      agent/request (config only) -> log request/header -> llm/stream (frozen)
+      on final adapter-path or terminal in-band failure:
+        'step/end'
+        agent/request-error(original error, failure facts, immutable prior failures, signal)
+        retry in the next numbered step or preserve the original error
+      otherwise:
+        'assistant/chunk'
+        agent/step-result
+        'assistant/message' (transformed content or empty success anchor after step-result rejection)
+        schedule tool calls by ctx.tools.executionMode:
+          exclusive -> one-call barrier
+          parallel -> rolling pool, <= maxParallelToolCalls in flight; reclassify before start
+          each start -> 'tool/call' -> ordered tools/pre-execute -> concurrent tools/execute
+          each model-order result -> ordered tools/post-execute -> 'tool/result'
+        append accepted tool-batch context after all recorded results, then steering
+        agent/post-step
+        'step/end'
+        agent/turn-continuation
+        agent/turn-stop (terminal policy)
+        stop unless tools or continuation policy ask for another step
+    'turn/end'
+    checkpoint persistence and notify idle/running status
+```
+
+每个步骤都会组装有序提示词片段、工具 schema 和变量；未知引用会使该轮次失败。`dsh-system-prompt` 负责身份和角色设定，循环则提供 `model` 和 `cwd`（[提示词归属](../.agents/notes/implemented/architecture/2026-07-05-prompt-variables-and-tool-guidance-ownership.md)）。
+
+工具执行阶段的上下文会在结果记录后稳定。steering（中途引导）在 `agent/post-step` 前排空；余留内容会成为排队输入。终止型 `agent/turn-stop` 在续跑判断和 steering 折叠后执行，在整个刷写期间保持最终决定权，并丢弃后续 steering，同时保留排队提示词。
+
+裁剪先于摘要；溢出重试必须取得持久进展。有界的瞬态重试在 `agent/request-error` 上组合；取消优先（[压缩](../.agents/notes/implemented/architecture/2026-07-10-after-call-compaction-pressure-and-overflow-recovery.md)、[重试](../.agents/notes/implemented/architecture/2026-06-21-bounded-llm-request-recovery.md)）。
+
+### 失败边界
+
+轮次是故障隔离边界。适配器故障会关闭步骤，并携带准确的故障事实进入 `agent/request-error`。重试会开启一个有编号的步骤；重试耗尽后，故障存入 `turn/end`。失败分片不会提交任何消息或工具。
+
+其他故障使用 `agent/error`。取消和 dispose（资源释放）优先于恢复；尚未分派的模型工具调用会收到合成的 `tool/call` 与 `ABORTED` 结果对，然后才出现 `turn/end`。`cancel()` 会清空队列并中止活跃工作；资源释放会等待系统停稳后再注销。
+
+每个会话事件都包围在轮次内。重新加载会保留中断的日志尾部，并用合成的 `interrupted` 轮次结束事件将其闭合。持久轮次关闭后的故障只通过 `agent/error` 报告，因为此时已没有安全的轮次内位置。每个轮次有一个 `TurnEndReason`；各变体由 [TurnEndReasonMap](core-data-structures/session.md#why-a-turn-ended-turnendreasonmap) 统一定义。
+
+### Agent 句柄
+
+`ctx.agents` 拥有活跃 agent，并返回 `AgentHandle { agent, dispose() }`。插件使用 `send()`、`steer()`、`inject()`、`cancel()` 和 `whenIdle()`。调用方 fiber、工厂提供方和消费方句柄通过同一个需等待完成的 disposer 共同拥有拆卸过程。
+
+### Agent 作用域
+
+每个活跃 agent 都拥有一个作用域化的 `agent.ctx`。注册项会遮蔽全局项，只接收发往该 agent 的分派，并随 agent 一同撤销；系统会等待异步清理。`CreateAgentOptions.setup(agentCtx)` 在发布前完成组合。类型化解析器从合并后的 `Events` 签名和 `scopeTarget` 推导载体检查（[语义门禁](../.agents/notes/implemented/process/2026-07-14-typescript-program-backed-semantic-gates.md)）。参见 [agent 作用域](../.agents/notes/implemented/architecture/2026-07-08-agent-scope-contexts.md)和 [subagent 组合](../.agents/notes/implemented/feature/2026-07-12-subagent-persona-tool-filter-and-depth.md)。`AgentLoop` 会传播其发起方；私有编排会派生 `agent.session`，其他身份则保持显式（[决策](../.agents/notes/implemented/architecture/2026-07-15-agent-initiator-scope.md)）。
+
+## 状态
+
+### 会话日志
+
+会话日志是真源。`deriveMessages()` 将会话事件投影为发送给模型的 `Message[]`；原始 `assistant/chunk` 事件留在日志中，以保证回放和 UI 保真。回放、fork、恢复、transcript（文本记录）渲染、遥测和持久化均派生自同一个事件流。
+
+**模型可见 ⟺ 已记录**：日志可以重建每个请求，包括由请求头会话前缀置于开头的 `step/start` 时消息，以及通过折叠 `request/header` 得到的请求头；开发期不变量会断言这一点（[可重建性](../.agents/notes/implemented/architecture/2026-07-05-reconstructable-requests.md)）。
+
+持久性由插件负责。后端会缓冲同步的 `session/event` 通知；循环等待轮次结束检查点。`SessionPersistence` 直接存储 `SessionEvent`，并将元数据存入 `SessionHeader`；JSONL 默认采用带校验和的 Zstandard，SQLite 则遵循同一契约。
+
+插件所属的纯日志事件可选择使用 `ctx.sessions.appendOutOfBand()`：事件会加入开放轮次，或获得一个平衡且已刷写的零步骤轮次。`session/title` 采用该路径并以后写覆盖方式折叠，同时记录源消息 seq 和来源信息。其首消息回退标题会立即产生；至多一个可选提供方可以异步替换该标题，而不会延迟 agent 响应。fork 会原样继承已记录的标题（[决策](../.agents/notes/implemented/feature/2026-07-21-log-backed-session-titles.md)）。
+
+### 模型内容
+
+消息包含类型化块（`text`、`reasoning`、`tool-call`、`tool-result`），这些块从可合并扩展的 `ContentBlockMap` 派生；`MessageSource`、`FinishReason`、`TurnTrigger` 和 `TurnEndReason` 也采用同一模式定义类型。新增块类型会将适配器、UI 桥接、压缩计价、token 计量和持久化协调成一项全仓库契约；回放计量类型见 [token-meter.md](core-data-structures/token-meter.md)。
+
+流式输出使用原始分片和 `BlockAssembler`。一次 `LlmAdapter.stream()` 调用代表一次提供方尝试；适配器报告事实，恢复逻辑则位于 `agent/request-error`。循环会记录分片及成功结果的来源信息和回放状态。远程适配器使用逐次读取空闲看门狗。只有当路由共用同一个适配器实例时，回放状态才会到达目标（[契约](core-data-structures/llm-streaming.md)）。
+
+## 扩展与组合
+
+### 功能模式
+
+可替换功能通常拆分为**接口／实现／消费方**：接口拥有自己的 `ctx` 键和事件，实现负责注册后端，消费方通过工具或提示词暴露模型行为。Bash 是参考实现；[功能图](capability-seams.md)展示了所有包族。
+
+有些服务边界会调整这一模板：LLM（大语言模型）合并接口和消费方；文件系统以策略包装提供方；web、skill 和 subagent 拥有注册表。会话标题将内置回退方案与单提供方注册表和共享 LLM 辅助组件配对。subagent 可以通过 spawn 创建全新实例、fork 一个已完成轮次的前缀，或使用 ACP（Agent Client Protocol）子 agent（[subagent.md](core-data-structures/subagent.md)）。
+
+`dsh-workspace-context` 在 `agent/session-prefix` 上组合基线，并在通过 `ctx.fs` 发现嵌套变更后，于 `tools/post-execute` 追加这些变更；其[决策](../.agents/notes/implemented/feature/2026-06-24-workspace-context.md)记录了隔离方式。`dsh-paths` 负责共享路径。
+
+### 组合包与应用
+
+`dsh-agent-spine-demo` 组合默认主干，其中包含仅提供回退行为的会话标题；模型标题提供方保持按需启用（[README](../packages/examples/agent-spine-demo/README.md)）。`dsh-tui-demo` 负责终端；`dsh-cli-demo` 运行一个持久化的无界面轮次；`dsh-acp-demo` 添加保持 stdout 纯净的 ACP（[ui/](../packages/ui/README.md)）。`dsh-jsonrpc-agent` 启动外部 `cordis.yml`；Python SDK 仅在没有显式配置时提供默认项，并驱动按行分隔的 JSON-RPC（[Python SDK](../python/README.md)）。部署保持为轻量叶节点，使用可替换后端和可选工具（[examples/](../examples/AGENTS.md)、[可运行接线](cookbook/extension-cookbook.md#runnable-wirings)、[图谱](graph-atlas.md)）。
+
+### 新行为的归属位置
+
+新行为应附加到已有文档记录的扩展点；修改已交付的循环时，必须同步更新本架构图。
+
+| 目标 | 机制 |
+|---|---|
+| 添加模型提供方 | 在 `ctx.llm` 上注册适配器 |
+| 添加面向模型的功能 | 在 `ctx.tools` 上注册工具；schema 会进入提示词组装流程 |
+| 添加命令执行 | 实现并注册 `ctx.bash` 后端 |
+| 添加长时间运行或后台功能 | 在 `ctx.tasks` 上注册工作；通用 `task_*` 工具负责收集或停止 |
+| 添加文件系统访问或策略 | 实现 `ctx.fs` 提供方，或监听 `fs/*` 策略事件 |
+| 限制生成的进程 | 使用 `ctx.sandbox` 后端；消费方在生成进程前包装 argv |
+| 拦截提示词、请求、模型完成或失败、工具使用或续跑 | 监听相应的 `agent/*` 或 `tools/*` 事件；使用串行 `agent/turn-stop` 实现单调终止 |
+| 添加历史记录之外的会话稳定请求前缀 | 在 `agent/session-prefix` 上组合，每个循环实例一次；记录在请求头中 |
+| 添加 UI 或编辑器集成 | 驱动 `ctx.agents` 并从 `session/event` 渲染 |
+| 添加持久会话状态 | 添加一个 `SessionEventMap` 成员，并从日志渲染和回放 |
+| 添加异步会话标题生成 | 在 `ctx.sessionTitle` 上注册唯一提供方 |
+| fork 活跃会话 | 使用 `ctx.sessions.fork(source, boundary?, childSessionId?)` |
+| 将工具、提示词片段或监听器限定到单个 agent | 通过该 agent 的 `agent.ctx` 注册（参见 Agent 作用域） |
+
+[扩展实操手册（cookbook）](cookbook/extension-cookbook.md)提供插件骨架和功能到服务边界的映射；分步指南涵盖[包](cookbook/adding-a-package.md)、[工具](cookbook/adding-a-tool.md)、[LLM 适配器](cookbook/adding-an-llm-adapter.md)和 [vendored 包](cookbook/adding-a-vendored-package.md)。
+
+## 快速参考
+- [术语表](glossary.md)中的领域术语
+- [core-data-structures/](core-data-structures/core.md) 中的类型定义
+- [事件](cordis-catalog/events.md)中的准确事件与服务签名
+- [服务](cordis-catalog/services.md)目录
+- [包索引](../packages/README.md)中的包契约
+- [Agent Note（agent 决策记录）](../.agents/notes/README.md)
@@ -34,6 +34,10 @@ flowchart LR
  pkg_hooks_codex["hooks-codex"]
  pkg_acp["acp"]
  svc_sessionQuery["ctx.sessionQuery<br/>Exact session-history reads and traces"]
+  pkg_session_title["session-title"]
+  svc_sessionTitle["ctx.sessionTitle<br/>Log-backed session titles"]
+  pkg_session_title_first_message_llm["session-title-first-message-llm"]
+  pkg_session_title_all_messages_llm["session-title-all-messages-llm"]
  pkg_system_prompt["system-prompt"]
  svc_systemPrompt["ctx.systemPrompt<br/>System prompt assembly registry"]
  pkg_tools["tools"]
@@ -130,6 +134,9 @@ flowchart LR
  pkg_session_persistence_jsonl --> svc_sessionPersistence
  pkg_session_persistence_sqlite --> svc_sessionPersistence
  pkg_session_query --> svc_sessionQuery
+  pkg_session_title --> svc_sessionTitle
+  pkg_session_title_all_messages_llm --> svc_sessionTitle
+  pkg_session_title_first_message_llm --> svc_sessionTitle
  pkg_skill --> svc_skills
  pkg_skill_local --> svc_skills
  pkg_spill --> svc_spillStore
@@ -224,6 +231,7 @@ flowchart LR
 | `ctx.sessions` | `core` | [`session`](../packages/core/session) | - | [`agent-loop`](../packages/core/agent-loop), [`agent`](../packages/core/agent), [`cli-demo`](../packages/examples/cli-demo), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-query`](../packages/session-query/session-query), [`subagent-inprocess`](../packages/subagent/subagent-inprocess), [`invariants`](../packages/support/invariants) | - | Owns append-only Session instances and emits the durable session event feed. |
 | `ctx.sessionPersistence` | `seam` | [`session-persistence`](../packages/session-persistence/session-persistence) | [`session-persistence-jsonl`](../packages/session-persistence/session-persistence-jsonl), [`session-persistence-sqlite`](../packages/session-persistence/session-persistence-sqlite) | [`agent-loop`](../packages/core/agent-loop), [`tool-bash`](../packages/bash/tool-bash), [`hooks-claude`](../packages/hooks/hooks-claude), [`hooks-codex`](../packages/hooks/hooks-codex), [`acp`](../packages/ui/acp), [`session-query`](../packages/session-query/session-query) | - | Backends persist the same SessionEvent vocabulary; apps choose a backend at composition time. |
 | `ctx.sessionQuery` | `seam` | [`session-query`](../packages/session-query/session-query) | - | - | - | Resolves live and optional persisted logs into one logical corpus for exact reads and relationship traces. |
+| `ctx.sessionTitle` | `seam` | [`session-title`](../packages/session-title/session-title) | [`session-title-first-message-llm`](../packages/session-title/session-title-first-message-llm), [`session-title-all-messages-llm`](../packages/session-title/session-title-all-messages-llm) | - | - | Owns the deterministic fallback, latest-title fold, and sole optional asynchronous provider registration. |
 | `ctx.systemPrompt` | `core` | [`system-prompt`](../packages/core/system-prompt) | - | [`agent-loop`](../packages/core/agent-loop), [`tools`](../packages/core/tools), [`tool-fs`](../packages/fs/tool-fs), [`tool-web`](../packages/web/tool-web) | - | Collects prompt sections and model-facing tool schemas for each step. |
 | `ctx.tools` | `core` | [`tools`](../packages/core/tools) | - | [`agent-loop`](../packages/core/agent-loop), [`tool-ask-user`](../packages/ui/tool-ask-user), [`tool-bash`](../packages/bash/tool-bash), [`tool-cordis`](../packages/cordis/tool-cordis), [`tool-fs`](../packages/fs/tool-fs), [`tool-skill`](../packages/skill/tool-skill), [`tool-subagent`](../packages/subagent/tool-subagent), [`tool-todo`](../packages/todo/tool-todo), [`tool-web`](../packages/web/tool-web), [`acp`](../packages/ui/acp) | - | Registers capabilities, owns Code Mode transport, and routes calls through pre-policy, monotonic guards, around dispatch, post-policy, and final-result observation. |
 | `ctx.userInteraction` | `seam` | [`user-interaction`](../packages/ui/user-interaction) | [`tui`](../packages/ui/tui), [`acp`](../packages/ui/acp) | [`tool-ask-user`](../packages/ui/tool-ask-user), [`tui`](../packages/ui/tui), [`acp`](../packages/ui/acp) | - | UI front doors provide the active human-answer provider; tool-ask-user pauses a tool call on the provider-neutral ask() promise. |
@@ -27,7 +27,7 @@ export interface AcpConfig {

 Depends on: `Stream` (`@agentclientprotocol/sdk`)

-Source: [`packages/ui/acp/src/index.ts:207`](../packages/ui/acp/src/index.ts)
+Source: [`packages/ui/acp/src/index.ts:209`](../packages/ui/acp/src/index.ts)

 ## `@deepseek-ai/dsh-acp-demo`

@@ -165,7 +165,7 @@ export interface SkillConfig {

 Depends on: [`AgentLoopConfig`](#deepseek-aidsh-agent-loop) · [`llmRetry`](../packages/llm/llm-retry/src/index.ts) · [`SkillLocal`](../packages/skill/skill-local/src/index.ts) · [`SkillRegistryConfig`](#deepseek-aidsh-skill) · [`SystemPromptConfig`](#deepseek-aidsh-system-prompt) · [`toolBash`](../packages/bash/tool-bash/src/index.ts) · [`ToolsConfig`](#deepseek-aidsh-tools) · [`toolSkill`](../packages/skill/tool-skill/src/index.ts) · [`toolTasks`](../packages/tasks/tool-tasks/src/index.ts) · [`workspaceContext`](../packages/context/workspace-context/src/index.ts)

-Source: [`packages/examples/agent-spine-demo/src/index.ts:60`](../packages/examples/agent-spine-demo/src/index.ts)
+Source: [`packages/examples/agent-spine-demo/src/index.ts:61`](../packages/examples/agent-spine-demo/src/index.ts)

 ## `@deepseek-ai/dsh-bash-local`

@@ -833,6 +833,50 @@ export interface Config {

 Source: [`packages/session-query/session-query/src/config.ts:9`](../packages/session-query/session-query/src/config.ts)

+## `@deepseek-ai/dsh-session-title`
+
+Requires: `sessions`
+
+```ts config-catalog
+/** Required deterministic fallback and accepted-title limits. */
+export interface Config {
+  /** Maximum whitespace-delimited words in the built-in fallback. */
+  readonly fallbackMaxWords: number
+  /** Maximum UTF-8 bytes in the built-in fallback. */
+  readonly fallbackMaxBytes: number
+  /** Maximum UTF-8 bytes in any accepted title. */
+  readonly maxTitleBytes: number
+}
+```
+
+Source: [`packages/session-title/session-title/src/index.ts:63`](../packages/session-title/session-title/src/index.ts)
+
+## `@deepseek-ai/dsh-session-title-all-messages-llm`
+
+Requires: `sessionTitle` · `llm`
+
+```ts config-catalog
+/** Required LLM policy; this plugin adds no defaults. */
+export type Config = SessionTitleLlmConfig
+```
+
+Depends on: [`SessionTitleLlmConfig`](../packages/session-title/session-title-llm/src/index.ts)
+
+Source: [`packages/session-title/session-title-all-messages-llm/src/index.ts:15`](../packages/session-title/session-title-all-messages-llm/src/index.ts)
+
+## `@deepseek-ai/dsh-session-title-first-message-llm`
+
+Requires: `sessionTitle` · `llm`
+
+```ts config-catalog
+/** Required LLM policy; this plugin adds no defaults. */
+export type Config = SessionTitleLlmConfig
+```
+
+Depends on: [`SessionTitleLlmConfig`](../packages/session-title/session-title-llm/src/index.ts)
+
+Source: [`packages/session-title/session-title-first-message-llm/src/index.ts:15`](../packages/session-title/session-title-first-message-llm/src/index.ts)
+
 ## `@deepseek-ai/dsh-skill`

 ```ts config-catalog
@@ -1277,7 +1321,7 @@ export interface TuiConfig {
 }
 ```

-Source: [`packages/ui/tui/src/index.ts:102`](../packages/ui/tui/src/index.ts)
+Source: [`packages/ui/tui/src/index.ts:103`](../packages/ui/tui/src/index.ts)

 ## `@deepseek-ai/dsh-tui-demo`

@@ -1560,6 +1604,7 @@ Imported as libraries by other packages; a `cordis.yml` cannot load them.
 - `@deepseek-ai/dsh-retention` ([`packages/util/retention/src/index.ts`](../packages/util/retention/src/index.ts))
 - `@deepseek-ai/dsh-scope` ([`packages/core/scope/src/index.ts`](../packages/core/scope/src/index.ts))
 - `@deepseek-ai/dsh-scripts` ([`packages/sdk/scripts/src/index.ts`](../packages/sdk/scripts/src/index.ts))
+- `@deepseek-ai/dsh-session-title-llm` ([`packages/session-title/session-title-llm/src/index.ts`](../packages/session-title/session-title-llm/src/index.ts))
 - `@deepseek-ai/dsh-subagent-inprocess` ([`packages/subagent/subagent-inprocess/src/index.ts`](../packages/subagent/subagent-inprocess/src/index.ts))
 - `@deepseek-ai/dsh-subagent-subprocess` ([`packages/subagent/subagent-subprocess/src/index.ts`](../packages/subagent/subagent-subprocess/src/index.ts))
 - `@deepseek-ai/dsh-telemetry` ([`packages/sdk/telemetry/src/index.ts`](../packages/sdk/telemetry/src/index.ts))
@@ -672,6 +672,13 @@ Live-preferred logical-corpus exact-read and relationship-tracing service.
 */
 listSessions(): Promise<SessionRecord[]>

+/**
+ * Fold the latest log-backed title from one live-preferred logical session.
+ * @param sessionId - live or persisted session id to read.
+ * @returns latest title snapshot, or `undefined` when the log has no title event.
+ */
+async readTitle(sessionId: SessionId): Promise<SessionTitleSnapshot | undefined>
+
 /**
 * List lightweight raw-log event records for one logical session.
 * @param sessionId - live-preferred session id to read.
@@ -703,9 +710,9 @@ async traceEvent(request: SessionEventTraceRequest): Promise<SessionEventTrace>
 async readEvent(request: SessionEventReadRequest): Promise<SessionEventWindow>
 ```

-Types: [SessionEventReadRequest](../core-data-structures/session-query.md) · [SessionEventRecord](../core-data-structures/session-query.md) · [SessionEventTrace](../core-data-structures/session-query.md) · [SessionEventTraceRequest](../core-data-structures/session-query.md) · [SessionEventWindow](../core-data-structures/session-query.md) · [SessionId](../core-data-structures/core.md) · [SessionLineageTrace](../core-data-structures/session-query.md) · [SessionRecord](../core-data-structures/session-query.md)
+Types: [SessionEventReadRequest](../core-data-structures/session-query.md) · [SessionEventRecord](../core-data-structures/session-query.md) · [SessionEventTrace](../core-data-structures/session-query.md) · [SessionEventTraceRequest](../core-data-structures/session-query.md) · [SessionEventWindow](../core-data-structures/session-query.md) · [SessionId](../core-data-structures/core.md) · [SessionLineageTrace](../core-data-structures/session-query.md) · [SessionRecord](../core-data-structures/session-query.md) · [SessionTitleSnapshot](../core-data-structures/session-title.md)

-Source: [`packages/session-query/session-query/src/index.ts:38`](../../packages/session-query/session-query/src/index.ts)
+Source: [`packages/session-query/session-query/src/index.ts:40`](../../packages/session-query/session-query/src/index.ts)

 ## `ctx.sessions` — `SessionStore`

@@ -801,6 +808,28 @@ announce(session: Session): void
 */
 async flush(session: Session): Promise<void>

+/**
+ * Append one plugin-declared log-only event without borrowing the agent
+ * loop's lifecycle. An open turn receives the event directly and remains
+ * responsible for its ordinary checkpoint. A closed log receives one
+ * zero-step turn around the event, followed by an awaited flush.
+ *
+ * Once the synthetic `turn/start` commits, this method always attempts its
+ * matching `turn/end` and flush, including when the target append fails.
+ * Detachment requested by an event or flush listener is deferred until that
+ * sequence settles, so publication cannot switch from a live scoped session
+ * to an unobserved bare `Session` halfway through the update.
+ *
+ * @param session - exact live session that owns the target log.
+ * @param type - event type opted into {@link OutOfBandSessionEventMap} by its owner.
+ * @param data - typed JSON payload for the target event.
+ * @param trigger - plugin-owned turn trigger used only when the log is closed.
+ * @returns the accepted target event with its assigned sequence and timestamp.
+ * @throws when the session is detached, another out-of-band append is active,
+ *   event acceptance fails, the synthetic turn cannot close, or flushing fails.
+ */
+async appendOutOfBand<T extends OutOfBandSessionEventType>( session: Session, type: T, data: SessionEventMap[T], trigger: TurnTrigger, ): Promise<SessionEvent<T>>
+
 /**
 * Look up a live session.
 * @param id - the session id to look up.
@@ -830,9 +859,43 @@ list(): Session[]
 fork(source: SessionForkSource, boundary?: number, childSessionId?: SessionId): Session
 ```

-Types: [CreateSessionOptions](../core-data-structures/persistence.md) · [Session](../core-data-structures/session.md) · [SessionId](../core-data-structures/core.md)
+Types: [CreateSessionOptions](../core-data-structures/persistence.md) · [OutOfBandSessionEventType](../core-data-structures/session.md) · [Session](../core-data-structures/session.md) · [SessionEvent](../core-data-structures/core.md) · [SessionEventMap](../core-data-structures/session.md) · [SessionId](../core-data-structures/core.md) · [TurnTrigger](../core-data-structures/session.md)

-Source: [`packages/core/session/src/index.ts:553`](../../packages/core/session/src/index.ts)
+Source: [`packages/core/session/src/index.ts:554`](../../packages/core/session/src/index.ts)
+
+## `ctx.sessionTitle` — `SessionTitleService`
+
+Log-backed title fold plus asynchronous fallback generation.
+
+```ts cordis-catalog
+/**
+ * Read the latest folded title from one live or replayed session.
+ * @param session - session whose log is the title source of truth.
+ * @returns latest title snapshot, or `undefined` before eligible input.
+ */
+get(session: Session): SessionTitleSnapshot | undefined
+
+/**
+ * Explicitly retry the registered provider, or materialize the built-in
+ * fallback when no provider is registered.
+ * @param session - exact live session to refresh.
+ * @param signal - optional caller cancellation.
+ * @returns latest accepted title, or `undefined` when no eligible text exists.
+ */
+async refresh(session: Session, signal?: AbortSignal): Promise<SessionTitleSnapshot | undefined>
+
+/**
+ * Register the sole optional title provider. Disposal aborts its pending and
+ * active work before another provider may register.
+ * @param provider - provider identity, cadence, and generation function.
+ * @returns exact Cordis effect disposer for HMR-safe unregistration.
+ */
+register(provider: SessionTitleProvider): () => void
+```
+
+Types: [Session](../core-data-structures/session.md) · [SessionTitleProvider](../core-data-structures/session-title.md) · [SessionTitleSnapshot](../core-data-structures/session-title.md)
+
+Source: [`packages/session-title/session-title/src/index.ts:233`](../../packages/session-title/session-title/src/index.ts)

 ## `ctx.skills` — `SkillService`

@@ -21,6 +21,7 @@ Everything else is documented on a **sub-page**, not here. The rule that draws t
 | [session.md](session.md) | the full `SessionEventMap` variant catalog, `TurnTrigger`/`TurnEndReason`, `deriveMessages()`, the turn-enclosure invariant |
 | [persistence.md](persistence.md) | the durability seam: `SessionPersistence`, JSONL + SQLite backends, `session/flush`, crash recovery, `SessionHeader` |
 | [session-query.md](session-query.md) | logical records, bounded exact-event reads, and relationship traces |
+| [session-title.md](session-title.md) | durable title snapshots, source provenance, and the asynchronous provider contract |
 | [system-prompt.md](system-prompt.md) | per-assembly context, tool-provider results, prompt sections, and cooperative assembly |
 | [tools.md](tools.md) | `ToolDefinition` full fields, the schema DSL, `ToolExecution`/`ToolResult`, tool-presentation UI types, and the guarded execution pipeline |
 | [user-interaction.md](user-interaction.md) | the UI-backed human question/answer seam: `AskUserQuestionRequest`, answer/options vocabulary, provider API, error taxonomy |
@@ -0,0 +1,118 @@
+# Session Titles
+
+Durable latest-wins title state and the optional asynchronous provider vocabulary owned by [`@deepseek-ai/dsh-session-title`](../../packages/session-title/session-title). The package README owns timing, fallback, failure, and fork behavior; the generated [persistence catalog](../persistence-catalog.md) owns the complete `session/title` event declaration.
+
+Source: [`packages/session-title/session-title/src/index.ts`](../../packages/session-title/session-title/src/index.ts)
+
+## Durable title state
+
+`SessionTitleProviderId` is recorded for provider-produced revisions. `SessionTitleEventData` carries exact human-message provenance, while `SessionTitleSnapshot` adds the durable event envelope facts selected by `foldSessionTitle()`.
+
+```ts type-equiv
+/** Identifies one session-title provider registration. */
+type SessionTitleProviderId = Branded<'SessionTitleProviderId'>
+```
+
+```ts type-equiv
+/** Exact auxiliary model route that produced a title. */
+interface SessionTitleModelProvenance {
+  /** Registered LLM provider route. */
+  readonly provider: string
+  /** Provider model id. */
+  readonly model: string
+}
+```
+
+```ts type-equiv
+/** Durable ownership record for an accepted session title. */
+type SessionTitleSource =
+  | { readonly kind: 'fallback' }
+  | {
+    readonly kind: 'provider'
+    readonly provider: SessionTitleProviderId
+    readonly model?: SessionTitleModelProvenance
+  }
+```
+
+```ts type-equiv
+/** Payload of the log-only `session/title` event. */
+interface SessionTitleEventData {
+  /** Normalized non-empty title text. */
+  readonly title: string
+  /** Exact human `user/message` seqs used to derive this title. */
+  readonly messageSeqs: number[]
+  /** Built-in fallback or registered-provider provenance. */
+  readonly source: SessionTitleSource
+}
+```
+
+```ts type-equiv
+/** Latest folded title plus the title event's durable envelope facts. */
+interface SessionTitleSnapshot extends SessionTitleEventData {
+  /** Seq of the latest `session/title` event. */
+  readonly eventSeq: number
+  /** Timestamp of the latest `session/title` event. */
+  readonly updatedAt: number
+}
+```
+
+## Provider input and output
+
+The service snapshots eligible messages through one revision. A provider returns only seqs from that request; service-owned acceptance verifies ordering, normalizes the title, enforces the byte limit, and appends provenance.
+
+```ts type-equiv
+/** One eligible human text message exposed to title providers. */
+interface SessionTitleUserMessage {
+  /** Source `user/message` event seq. */
+  readonly seq: number
+  /** Exact concatenated text-block content. */
+  readonly text: string
+}
+```
+
+```ts type-equiv
+/** Automatic generation cadence owned by a registered provider. */
+type SessionTitleAutomaticMode = 'first-message' | 'all-user-messages'
+```
+
+```ts type-equiv
+/** Immutable input supplied to one title-provider call. */
+interface SessionTitleProviderRequest {
+  /** Live session being titled. */
+  readonly session: Session
+  /** All eligible human messages through this generation revision. */
+  readonly messages: readonly SessionTitleUserMessage[]
+  /** Exact current logged main-request route, when one has been recorded. */
+  readonly route?: SessionTitleModelProvenance
+  /** Cancellation for supersession, disposal, timeout composition, or the explicit caller. */
+  readonly signal: AbortSignal
+}
+```
+
+```ts type-equiv
+/** Provider output before service-owned normalization and durable acceptance. */
+interface SessionTitleProviderResult {
+  /** Proposed title text. */
+  readonly title: string
+  /** Exact seqs from `request.messages` used by this result. */
+  readonly messageSeqs: readonly number[]
+  /** Auxiliary LLM route, when generation used a model. */
+  readonly model?: SessionTitleModelProvenance
+}
+```
+
+```ts type-equiv
+/** One optional asynchronous title implementation registered with the service. */
+interface SessionTitleProvider {
+  /** Stable provider identity recorded in title provenance. */
+  readonly id: SessionTitleProviderId
+  /** When new human prompts start automatic generation. */
+  readonly automatic: SessionTitleAutomaticMode
+  /**
+   * Produce one title revision.
+   * @param request - message snapshot, current route, session, and cancellation.
+   * @returns proposed title plus exact input seqs and optional model provenance.
+   */
+  generate(request: SessionTitleProviderRequest): Promise<SessionTitleProviderResult>
+}
+```
@@ -94,6 +94,20 @@ interface SessionEventMap {
 }
 ```

+### `OutOfBandSessionEventMap` — narrow late-append opt-in
+
+`SessionEventMap` membership alone does not authorize an event outside the agent loop's ordinary lifecycle. An event owner declaration-merges the same key into this empty marker map before `ctx.sessions.appendOutOfBand()` accepts it; the derived type additionally excludes every surface event. An accepted update joins an open turn or receives a balanced, flushed zero-step turn.
+
+```ts type-equiv
+/**
+ * Marker map for plugin-owned log-only events accepted by
+ * `SessionStore.appendOutOfBand()`. A plugin extends this map with the same key
+ * it adds to {@link SessionEventMap}; surface and lifecycle events stay
+ * ineligible unless their owner explicitly opts them into this narrow seam.
+ */
+interface OutOfBandSessionEventMap {}
+```
+
 ### `TodoItem` — one todo-list entry

 The unit of the `todo/write` event's whole-list snapshot. Deliberately minimal — a `content` line and a three-state `status` (no id, priority, or `activeForm`): the list is replaced wholesale on every write, so entries need no stable identity, and the status triple is exactly the ACP `PlanEntryStatus`, so a UI bridge can map a todo list onto an ACP `plan` 1:1 (synthesizing the priority ACP additionally requires). See the [todo_write Agent Note](../../.agents/notes/implemented/feature/2026-06-29-todo-write-tool.md).
@@ -501,7 +515,7 @@ interface TurnEndReasonMap {

 ## The turn-enclosure invariant

-Every session event lives **inside** a turn (between a `turn/start` and its `turn/end`). The loop appends queued `user/message` events *after* `turn/start`, and an idle `agent.inject()` wraps its `context/message` in a one-shot `injection` turn. This makes the turn the single durability/replay boundary: a backend can treat anything after the last `turn/end` as an interrupted-crash tail without risking the loss of legitimately-recorded between-turn context. The `dsh-invariants` plugin enforces it in dev (a message event outside an open turn throws). See [the turn-enclosure invariant Agent Note](../../.agents/notes/implemented/architecture/2026-06-15-turn-enclosure-invariant.md).
+Every session event lives **inside** a turn (between a `turn/start` and its `turn/end`). The loop appends queued `user/message` events *after* `turn/start`, an idle `agent.inject()` wraps its `context/message` in a one-shot `injection` turn, and `appendOutOfBand()` similarly wraps an eligible log-only event when no turn is open. This makes the turn the single durability/replay boundary: a backend can treat anything after the last `turn/end` as an interrupted-crash tail without risking the loss of legitimately-recorded between-turn context. The `dsh-invariants` plugin enforces it in dev (a message event outside an open turn throws). See [the turn-enclosure invariant Agent Note](../../.agents/notes/implemented/architecture/2026-06-15-turn-enclosure-invariant.md).

 ## Plugin-contributed log-only events

@@ -29,8 +29,8 @@ This matrix shows which packages dispatch each harness-owned event and which pac
 | `fs/write-intent` | `waterfall` | [`packages/fs/fs/src/index.ts:54`](../packages/fs/fs/src/index.ts) | [`tool-fs`](../packages/fs/tool-fs) (`waterfall`) | [`fs-policy`](../packages/fs/fs-policy) |
 | `llm/stream` | `waterfall` | [`packages/llm/llm/src/index.ts:44`](../packages/llm/llm/src/index.ts) | [`llm`](../packages/llm/llm) (`waterfall`) | [`invariants`](../packages/support/invariants), [`llm-replay`](../packages/support/llm-replay) |
 | `session/created` | `emit` | [`packages/core/session/src/index.ts:47`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`invariants`](../packages/support/invariants), [`jsonrpc`](../packages/ui/jsonrpc), [`session-persistence`](../packages/session-persistence/session-persistence) |
-| `session/disposed` | `emit` | [`packages/core/session/src/index.ts:57`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`agent-loop`](../packages/core/agent-loop), [`session-persistence`](../packages/session-persistence/session-persistence) |
-| `session/event` | `emit` | [`packages/core/session/src/index.ts:69`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`acp`](../packages/ui/acp), [`cli-demo`](../packages/examples/cli-demo), [`invariants`](../packages/support/invariants), [`jsonrpc`](../packages/ui/jsonrpc), [`session-persistence`](../packages/session-persistence/session-persistence), [`token-meter`](../packages/llm/token-meter), [`tui`](../packages/ui/tui), [`workspace-context`](../packages/context/workspace-context) |
+| `session/disposed` | `emit` | [`packages/core/session/src/index.ts:57`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`agent-loop`](../packages/core/agent-loop), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-title`](../packages/session-title/session-title) |
+| `session/event` | `emit` | [`packages/core/session/src/index.ts:69`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`acp`](../packages/ui/acp), [`cli-demo`](../packages/examples/cli-demo), [`invariants`](../packages/support/invariants), [`jsonrpc`](../packages/ui/jsonrpc), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-title`](../packages/session-title/session-title), [`token-meter`](../packages/llm/token-meter), [`tui`](../packages/ui/tui), [`workspace-context`](../packages/context/workspace-context) |
 | `session/flush` | `parallel` | [`packages/core/session/src/index.ts:79`](../packages/core/session/src/index.ts) | [`session`](../packages/core/session) (`events.dispatch`) | [`session-persistence`](../packages/session-persistence/session-persistence) |
 | `subagent/end` | `emit` | [`packages/subagent/subagent/src/index.ts:139`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`events.dispatch`) | [`hooks-claude`](../packages/hooks/hooks-claude), [`jsonrpc`](../packages/ui/jsonrpc) |
 | `subagent/provider-added` | `emit` | [`packages/subagent/subagent/src/index.ts:113`](../packages/subagent/subagent/src/index.ts) | [`subagent`](../packages/subagent/subagent) (`emit`) | [`tool-subagent`](../packages/subagent/tool-subagent) |
@@ -97,6 +97,12 @@ flowchart TD
  subgraph group_session_query["packages/session-query"]
    pkg_session_query["session-query"]
  end
+  subgraph group_session_title["packages/session-title"]
+    pkg_session_title["session-title"]
+    pkg_session_title_all_messages_llm["session-title-all-messages-llm"]
+    pkg_session_title_first_message_llm["session-title-first-message-llm"]
+    pkg_session_title_llm["session-title-llm"]
+  end
  subgraph group_support["packages/support"]
    pkg_acp_snapshot["acp-snapshot"]
    pkg_agent_loop_testkit["agent-loop-testkit"]
@@ -194,6 +200,9 @@ flowchart TD
  pkg_spill --> pkg_llm
  pkg_spill --> pkg_session
  pkg_session_persistence --> pkg_session
+  pkg_session_title --> pkg_brand
+  pkg_session_title --> pkg_llm
+  pkg_session_title --> pkg_session
  pkg_llm_replay --> pkg_llm
  pkg_llm_replay --> pkg_session
  pkg_sandbox_local --> pkg_llm
@@ -227,6 +236,10 @@ flowchart TD
  pkg_session_query --> pkg_llm
  pkg_session_query --> pkg_session
  pkg_session_query --> pkg_session_persistence
+  pkg_session_query --> pkg_session_title
+  pkg_session_title_llm --> pkg_llm
+  pkg_session_title_llm --> pkg_session_title
+  pkg_session_title_llm --> pkg_timeout
  pkg_invariants --> pkg_agent
  pkg_invariants --> pkg_llm
  pkg_invariants --> pkg_scope
@@ -263,6 +276,12 @@ flowchart TD
  pkg_fs_sandbox --> pkg_fs_local
  pkg_fs_sandbox --> pkg_sandbox
  pkg_fs_sandbox --> pkg_sandbox_policy
+  pkg_session_title_all_messages_llm --> pkg_llm
+  pkg_session_title_all_messages_llm --> pkg_session_title
+  pkg_session_title_all_messages_llm --> pkg_session_title_llm
+  pkg_session_title_first_message_llm --> pkg_llm
+  pkg_session_title_first_message_llm --> pkg_session_title
+  pkg_session_title_first_message_llm --> pkg_session_title_llm
  pkg_permission --> pkg_bash
  pkg_permission --> pkg_sandbox
  pkg_permission --> pkg_sandbox_policy
@@ -347,6 +366,7 @@ flowchart TD
  pkg_acp --> pkg_sandbox
  pkg_acp --> pkg_session
  pkg_acp --> pkg_session_persistence
+  pkg_acp --> pkg_session_title
  pkg_acp --> pkg_system_prompt
  pkg_acp --> pkg_tools
  pkg_acp --> pkg_user_approval
@@ -407,6 +427,7 @@ flowchart TD
  pkg_tui --> pkg_llm
  pkg_tui --> pkg_llm_retry
  pkg_tui --> pkg_session
+  pkg_tui --> pkg_session_title
  pkg_tui --> pkg_tools
  pkg_tui --> pkg_user_interaction
  pkg_agent_spine_demo --> pkg_agent
@@ -416,6 +437,7 @@ flowchart TD
  pkg_agent_spine_demo --> pkg_llm
  pkg_agent_spine_demo --> pkg_llm_retry
  pkg_agent_spine_demo --> pkg_session
+  pkg_agent_spine_demo --> pkg_session_title
  pkg_agent_spine_demo --> pkg_skill
  pkg_agent_spine_demo --> pkg_skill_local
  pkg_agent_spine_demo --> pkg_system_prompt
@@ -505,6 +527,7 @@ flowchart TD
 | [`web-search-perplexity`](../packages/web/web-search-perplexity) | `web` | [`web`](../packages/web/web) |
 | [`spill`](../packages/spill/spill) | `spill` | [`brand`](../packages/util/brand), [`llm`](../packages/llm/llm), [`session`](../packages/core/session) |
 | [`session-persistence`](../packages/session-persistence/session-persistence) | `session-persistence` | [`session`](../packages/core/session) |
+| [`session-title`](../packages/session-title/session-title) | `session-title` | [`brand`](../packages/util/brand), [`llm`](../packages/llm/llm), [`session`](../packages/core/session) |
 | [`llm-replay`](../packages/support/llm-replay) | `support` | [`llm`](../packages/llm/llm), [`session`](../packages/core/session) |
 | [`sandbox-local`](../packages/sandbox/sandbox-local) | `sandbox` | [`llm`](../packages/llm/llm), [`sandbox`](../packages/sandbox/sandbox) |
 | [`sandbox-policy`](../packages/sandbox/sandbox-policy) | `sandbox` | [`sandbox`](../packages/sandbox/sandbox), [`session`](../packages/core/session) |
@@ -518,7 +541,8 @@ flowchart TD
 | [`hook-protocol`](../packages/hooks/hook-protocol) | `hooks` | [`bash`](../packages/bash/bash), [`session`](../packages/core/session) |
 | [`session-persistence-jsonl`](../packages/session-persistence/session-persistence-jsonl) | `session-persistence` | [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence) |
 | [`session-persistence-sqlite`](../packages/session-persistence/session-persistence-sqlite) | `session-persistence` | [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence) |
-| [`session-query`](../packages/session-query/session-query) | `session-query` | [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence) |
+| [`session-query`](../packages/session-query/session-query) | `session-query` | [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-title`](../packages/session-title/session-title) |
+| [`session-title-llm`](../packages/session-title/session-title-llm) | `session-title` | [`llm`](../packages/llm/llm), [`session-title`](../packages/session-title/session-title), [`timeout`](../packages/util/timeout) |
 | [`invariants`](../packages/support/invariants) | `support` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope), [`session`](../packages/core/session) |
 | [`user-approval`](../packages/ui/user-approval) | `ui` | [`agent`](../packages/core/agent), [`brand`](../packages/util/brand), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope), [`session`](../packages/core/session), [`system-prompt`](../packages/core/system-prompt) |
 | [`user-interaction`](../packages/ui/user-interaction) | `ui` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm) |
@@ -528,6 +552,8 @@ flowchart TD
 | [`tools`](../packages/core/tools) | `core` | [`agent`](../packages/core/agent), [`code-runtime`](../packages/code-runtime/code-runtime), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope), [`session`](../packages/core/session), [`system-prompt`](../packages/core/system-prompt), [`user-approval`](../packages/ui/user-approval) |
 | [`bash-sandbox`](../packages/bash/bash-sandbox) | `bash` | [`bash`](../packages/bash/bash), [`bash-local`](../packages/bash/bash-local), [`sandbox`](../packages/sandbox/sandbox), [`sandbox-policy`](../packages/sandbox/sandbox-policy) |
 | [`fs-sandbox`](../packages/fs/fs-sandbox) | `fs` | [`fs`](../packages/fs/fs), [`fs-local`](../packages/fs/fs-local), [`sandbox`](../packages/sandbox/sandbox), [`sandbox-policy`](../packages/sandbox/sandbox-policy) |
+| [`session-title-all-messages-llm`](../packages/session-title/session-title-all-messages-llm) | `session-title` | [`llm`](../packages/llm/llm), [`session-title`](../packages/session-title/session-title), [`session-title-llm`](../packages/session-title/session-title-llm) |
+| [`session-title-first-message-llm`](../packages/session-title/session-title-first-message-llm) | `session-title` | [`llm`](../packages/llm/llm), [`session-title`](../packages/session-title/session-title), [`session-title-llm`](../packages/session-title/session-title-llm) |
 | [`permission`](../packages/ui/permission) | `ui` | [`bash`](../packages/bash/bash), [`sandbox`](../packages/sandbox/sandbox), [`sandbox-policy`](../packages/sandbox/sandbox-policy), [`session`](../packages/core/session), [`user-approval`](../packages/ui/user-approval) |
 | [`agent-loop`](../packages/core/agent-loop) | `core` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`scope`](../packages/core/scope), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
 | [`tool-bash`](../packages/bash/tool-bash) | `bash` | [`agent`](../packages/core/agent), [`bash`](../packages/bash/bash), [`home`](../packages/util/home), [`llm`](../packages/llm/llm), [`sandbox`](../packages/sandbox/sandbox), [`sandbox-policy`](../packages/sandbox/sandbox-policy), [`session-persistence`](../packages/session-persistence/session-persistence), [`system-prompt`](../packages/core/system-prompt), [`tasks`](../packages/tasks/tasks), [`tools`](../packages/core/tools), [`user-approval`](../packages/ui/user-approval) |
@@ -542,7 +568,7 @@ flowchart TD
 | [`tool-cordis`](../packages/cordis/tool-cordis) | `cordis` | [`scope`](../packages/core/scope), [`tools`](../packages/core/tools) |
 | [`hooks-codex`](../packages/hooks/hooks-codex) | `hooks` | [`agent`](../packages/core/agent), [`hook-protocol`](../packages/hooks/hook-protocol), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`tools`](../packages/core/tools) |
 | [`agent-loop-testkit`](../packages/support/agent-loop-testkit) | `support` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools) |
-| [`acp`](../packages/ui/acp) | `ui` | [`agent`](../packages/core/agent), [`bash`](../packages/bash/bash), [`llm`](../packages/llm/llm), [`llm-retry`](../packages/llm/llm-retry), [`permission`](../packages/ui/permission), [`sandbox`](../packages/sandbox/sandbox), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools), [`user-approval`](../packages/ui/user-approval), [`user-interaction`](../packages/ui/user-interaction) |
+| [`acp`](../packages/ui/acp) | `ui` | [`agent`](../packages/core/agent), [`bash`](../packages/bash/bash), [`llm`](../packages/llm/llm), [`llm-retry`](../packages/llm/llm-retry), [`permission`](../packages/ui/permission), [`sandbox`](../packages/sandbox/sandbox), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`session-title`](../packages/session-title/session-title), [`system-prompt`](../packages/core/system-prompt), [`tools`](../packages/core/tools), [`user-approval`](../packages/ui/user-approval), [`user-interaction`](../packages/ui/user-interaction) |
 | [`tool-ask-user`](../packages/ui/tool-ask-user) | `ui` | [`agent`](../packages/core/agent), [`tools`](../packages/core/tools), [`user-interaction`](../packages/ui/user-interaction) |
 | [`workspace-context`](../packages/context/workspace-context) | `context` | [`agent`](../packages/core/agent), [`fs`](../packages/fs/fs), [`llm`](../packages/llm/llm), [`paths`](../packages/util/paths), [`session`](../packages/core/session), [`tools`](../packages/core/tools) |
 | [`repeat-tool-guard`](../packages/guard/repeat-tool-guard) | `guard` | [`agent`](../packages/core/agent), [`tools`](../packages/core/tools) |
@@ -554,8 +580,8 @@ flowchart TD
 | [`tool-subagent`](../packages/subagent/tool-subagent) | `subagent` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`subagent`](../packages/subagent/subagent), [`tasks`](../packages/tasks/tasks), [`tools`](../packages/core/tools) |
 | [`hooks-claude`](../packages/hooks/hooks-claude) | `hooks` | [`agent`](../packages/core/agent), [`hook-protocol`](../packages/hooks/hook-protocol), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`session-persistence`](../packages/session-persistence/session-persistence), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools) |
 | [`jsonrpc`](../packages/ui/jsonrpc) | `ui` | [`agent`](../packages/core/agent), [`llm`](../packages/llm/llm), [`llm-deepseek`](../packages/llm/llm-deepseek), [`scope`](../packages/core/scope), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent) |
-| [`tui`](../packages/ui/tui) | `ui` | [`agent`](../packages/core/agent), [`agent-loop`](../packages/core/agent-loop), [`llm`](../packages/llm/llm), [`llm-retry`](../packages/llm/llm-retry), [`session`](../packages/core/session), [`tools`](../packages/core/tools), [`user-interaction`](../packages/ui/user-interaction) |
-| [`agent-spine-demo`](../packages/examples/agent-spine-demo) | `examples` | [`agent`](../packages/core/agent), [`agent-loop`](../packages/core/agent-loop), [`home`](../packages/util/home), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`llm-retry`](../packages/llm/llm-retry), [`session`](../packages/core/session), [`skill`](../packages/skill/skill), [`skill-local`](../packages/skill/skill-local), [`system-prompt`](../packages/core/system-prompt), [`tasks`](../packages/tasks/tasks), [`tool-bash`](../packages/bash/tool-bash), [`tool-skill`](../packages/skill/tool-skill), [`tool-tasks`](../packages/tasks/tool-tasks), [`tools`](../packages/core/tools), [`workspace-context`](../packages/context/workspace-context) |
+| [`tui`](../packages/ui/tui) | `ui` | [`agent`](../packages/core/agent), [`agent-loop`](../packages/core/agent-loop), [`llm`](../packages/llm/llm), [`llm-retry`](../packages/llm/llm-retry), [`session`](../packages/core/session), [`session-title`](../packages/session-title/session-title), [`tools`](../packages/core/tools), [`user-interaction`](../packages/ui/user-interaction) |
+| [`agent-spine-demo`](../packages/examples/agent-spine-demo) | `examples` | [`agent`](../packages/core/agent), [`agent-loop`](../packages/core/agent-loop), [`home`](../packages/util/home), [`invariants`](../packages/support/invariants), [`llm`](../packages/llm/llm), [`llm-retry`](../packages/llm/llm-retry), [`session`](../packages/core/session), [`session-title`](../packages/session-title/session-title), [`skill`](../packages/skill/skill), [`skill-local`](../packages/skill/skill-local), [`system-prompt`](../packages/core/system-prompt), [`tasks`](../packages/tasks/tasks), [`tool-bash`](../packages/bash/tool-bash), [`tool-skill`](../packages/skill/tool-skill), [`tool-tasks`](../packages/tasks/tool-tasks), [`tools`](../packages/core/tools), [`workspace-context`](../packages/context/workspace-context) |
 | [`workflow-workerthread`](../packages/workflow/workflow-workerthread) | `workflow` | [`agent`](../packages/core/agent), [`brand`](../packages/util/brand), [`llm`](../packages/llm/llm), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`tools`](../packages/core/tools), [`workflow`](../packages/workflow/workflow) |
 | [`subagent-fork`](../packages/subagent/subagent-fork) | `subagent` | [`agent`](../packages/core/agent), [`session`](../packages/core/session), [`subagent`](../packages/subagent/subagent), [`subagent-inprocess`](../packages/subagent/subagent-inprocess) |
 | [`subagent-spawn`](../packages/subagent/subagent-spawn) | `subagent` | [`subagent`](../packages/subagent/subagent), [`subagent-inprocess`](../packages/subagent/subagent-inprocess) |
@@ -79,7 +79,7 @@ export type SessionEvent<T extends SessionEventType = SessionEventType> = {
 }[T]
 ```

-Sources: [`packages/core/session/src/types.ts:267`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:274`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:304`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:336`](../packages/core/session/src/types.ts)
+Sources: [`packages/core/session/src/types.ts:275`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:288`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:318`](../packages/core/session/src/types.ts) · [`packages/core/session/src/types.ts:350`](../packages/core/session/src/types.ts)

 ## Events

@@ -376,6 +376,22 @@ Source: [`packages/core/session/src/types.ts:263`](../packages/core/session/src/

 Source: [`packages/sandbox/sandbox-policy/src/session-mode.ts:34`](../packages/sandbox/sandbox-policy/src/session-mode.ts)

+### `session/*`
+
+#### `session/title` — log-only
+
+```ts persistence-catalog
+/**
+ * Latest-wins session title snapshot. Log-only: it never enters the model
+ * surface or derived history.
+ */
+'session/title': SessionTitleEventData
+```
+
+Types: [SessionTitleEventData](core-data-structures/session-title.md)
+
+Source: [`packages/session-title/session-title/src/index.ts:89`](../packages/session-title/session-title/src/index.ts)
+
 ### `steering/*`

 #### `steering/message` — surface
@@ -29,6 +29,7 @@ Packages live at `packages/<group>/<pkg>/`; groups are containers, while names r
 | [`hooks/`](hooks/README.md) | Hook bridges + the shared Claude Code / Codex wire-protocol library | Product — stable surface |
 | [`session-persistence/`](session-persistence/README.md) | Persistence capability family: the seam + JSONL/SQLite backends | Product — stable surface |
 | [`session-query/`](session-query/README.md) | Session retrieval: logical corpus, bounded reads, lineage, and event relationships | Product — stable surface |
+| [`session-title/`](session-title/README.md) | Log-backed session titles: fallback service, shared LLM policy, and opt-in providers | Product — stable surface |
 | [`sdk/`](sdk/README.md) | Project SDK tooling | Product — stable surface |
 | [`ui/`](ui/README.md) | Editor/client integration surfaces: ACP bridge, JSON-RPC SDK server, user-approval/user-interaction seams, ask-user tool | Product — stable surface |
 | [`examples/`](examples/README.md) | Demo bundles (agent-spine + TUI/one-shot CLI/ACP/JSON-RPC bins) the leaves load | Support — example infra |
@@ -343,6 +343,10 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
        signature: 'listSessions(): Promise<SessionRecord[]>',
        jsDoc: '/**\n * List the complete logical corpus using live-preferred records.\n * @returns deterministic newest-first cloned session records.\n */',
      },
+      {
+        signature: 'async readTitle(sessionId: SessionId): Promise<SessionTitleSnapshot | undefined>',
+        jsDoc: '/**\n * Fold the latest log-backed title from one live-preferred logical session.\n * @param sessionId - live or persisted session id to read.\n * @returns latest title snapshot, or `undefined` when the log has no title event.\n */',
+      },
      {
        signature: 'async listEvents(sessionId: SessionId): Promise<SessionEventRecord[]>',
        jsDoc: '/**\n * List lightweight raw-log event records for one logical session.\n * @param sessionId - live-preferred session id to read.\n * @returns event records in ascending seq order.\n */',
@@ -385,6 +389,10 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
        signature: 'async flush(session: Session): Promise<void>',
        jsDoc: '/**\n * Dispatch the awaited `session/flush` durability checkpoint for `session`,\n * with the carrier captured at {@link enter}. THE flush entry point: the\n * store owns the carrier, so callers (the loop\'s turn-end checkpoint, idle\n * injection, teardown drains) must come through here rather than dispatch a\n * raw `ctx.parallel(\'session/flush\', …)` — one owner, one spelling, and the\n * scoped-dispatch invariant can pin it.\n * @param session - the session whose buffered events must reach durable storage.\n * @returns resolves when every flush listener has settled; after all settle,\n *   rejects with the first registered listener failure if any listener failed.\n */',
      },
+      {
+        signature: 'async appendOutOfBand<T extends OutOfBandSessionEventType>( session: Session, type: T, data: SessionEventMap[T], trigger: TurnTrigger, ): Promise<SessionEvent<T>>',
+        jsDoc: '/**\n * Append one plugin-declared log-only event without borrowing the agent\n * loop\'s lifecycle. An open turn receives the event directly and remains\n * responsible for its ordinary checkpoint. A closed log receives one\n * zero-step turn around the event, followed by an awaited flush.\n *\n * Once the synthetic `turn/start` commits, this method always attempts its\n * matching `turn/end` and flush, including when the target append fails.\n * Detachment requested by an event or flush listener is deferred until that\n * sequence settles, so publication cannot switch from a live scoped session\n * to an unobserved bare `Session` halfway through the update.\n *\n * @param session - exact live session that owns the target log.\n * @param type - event type opted into {@link OutOfBandSessionEventMap} by its owner.\n * @param data - typed JSON payload for the target event.\n * @param trigger - plugin-owned turn trigger used only when the log is closed.\n * @returns the accepted target event with its assigned sequence and timestamp.\n * @throws when the session is detached, another out-of-band append is active,\n *   event acceptance fails, the synthetic turn cannot close, or flushing fails.\n */',
+      },
      {
        signature: 'get(id: SessionId): Session | undefined',
        jsDoc: '/**\n * Look up a live session.\n * @param id - the session id to look up.\n * @returns the session, or undefined when no live session has that id.\n */',
@@ -399,6 +407,24 @@ export const SERVICE_API: readonly ServiceApiEntry[] = [
      },
    ],
  },
+  {
+    key: 'sessionTitle',
+    summary: 'Log-backed title fold plus asynchronous fallback generation.',
+    methods: [
+      {
+        signature: 'get(session: Session): SessionTitleSnapshot | undefined',
+        jsDoc: '/**\n * Read the latest folded title from one live or replayed session.\n * @param session - session whose log is the title source of truth.\n * @returns latest title snapshot, or `undefined` before eligible input.\n */',
+      },
+      {
+        signature: 'async refresh(session: Session, signal?: AbortSignal): Promise<SessionTitleSnapshot | undefined>',
+        jsDoc: '/**\n * Explicitly retry the registered provider, or materialize the built-in\n * fallback when no provider is registered.\n * @param session - exact live session to refresh.\n * @param signal - optional caller cancellation.\n * @returns latest accepted title, or `undefined` when no eligible text exists.\n */',
+      },
+      {
+        signature: 'register(provider: SessionTitleProvider): () => void',
+        jsDoc: '/**\n * Register the sole optional title provider. Disposal aborts its pending and\n * active work before another provider may register.\n * @param provider - provider identity, cadence, and generation function.\n * @returns exact Cordis effect disposer for HMR-safe unregistration.\n */',
+      },
+    ],
+  },
  {
    key: 'skills',
    summary: 'Registry of skill providers.',
@@ -1227,6 +1253,14 @@ export const TYPE_API: readonly TypeApiEntry[] = [
    name: 'MessageSourceMap',
    declaration: 'export interface MessageSourceMap {\n    user: {\n        kind: \'user\';\n    };\n    plugin: {\n        kind: \'plugin\';\n        plugin: string;\n    };\n}',
  },
+  {
+    name: 'OutOfBandSessionEventMap',
+    declaration: 'export interface OutOfBandSessionEventMap {\n}',
+  },
+  {
+    name: 'OutOfBandSessionEventType',
+    declaration: 'export type OutOfBandSessionEventType = Exclude<Extract<SessionEventType, keyof OutOfBandSessionEventMap>, SurfaceEventType>;',
+  },
  {
    name: 'PresetOption',
    declaration: 'export interface PresetOption {\n    value: string;\n    name: string;\n    description?: string;\n}',
@@ -1351,6 +1385,46 @@ export const TYPE_API: readonly TypeApiEntry[] = [
    name: 'SessionRecord',
    declaration: 'export interface SessionRecord {\n    header: SessionHeader;\n    live: boolean;\n    persisted: boolean;\n}',
  },
+  {
+    name: 'SessionTitleAutomaticMode',
+    declaration: 'export type SessionTitleAutomaticMode = \'first-message\' | \'all-user-messages\';',
+  },
+  {
+    name: 'SessionTitleEventData',
+    declaration: 'export interface SessionTitleEventData {\n    readonly title: string;\n    readonly messageSeqs: number[];\n    readonly source: SessionTitleSource;\n}',
+  },
+  {
+    name: 'SessionTitleModelProvenance',
+    declaration: 'export interface SessionTitleModelProvenance {\n    readonly provider: string;\n    readonly model: string;\n}',
+  },
+  {
+    name: 'SessionTitleProvider',
+    declaration: 'export interface SessionTitleProvider {\n    readonly id: SessionTitleProviderId;\n    readonly automatic: SessionTitleAutomaticMode;\n    generate(request: SessionTitleProviderRequest): Promise<SessionTitleProviderResult>;\n}',
+  },
+  {
+    name: 'SessionTitleProviderId',
+    declaration: 'export type SessionTitleProviderId = Branded<\'SessionTitleProviderId\'>;',
+  },
+  {
+    name: 'SessionTitleProviderRequest',
+    declaration: 'export interface SessionTitleProviderRequest {\n    readonly session: Session;\n    readonly messages: readonly SessionTitleUserMessage[];\n    readonly route?: SessionTitleModelProvenance;\n    readonly signal: AbortSignal;\n}',
+  },
+  {
+    name: 'SessionTitleProviderResult',
+    declaration: 'export interface SessionTitleProviderResult {\n    readonly title: string;\n    readonly messageSeqs: readonly number[];\n    readonly model?: SessionTitleModelProvenance;\n}',
+  },
+  {
+    name: 'SessionTitleSnapshot',
+    declaration: 'export interface SessionTitleSnapshot extends SessionTitleEventData {\n    readonly eventSeq: number;\n    readonly updatedAt: number;\n}',
+  },
+  {
+    name: 'SessionTitleSource',
+    declaration: 'export type SessionTitleSource = {\n    readonly kind: \'fallback\';\n} | {\n    readonly kind: \'provider\';\n    readonly provider: SessionTitleProviderId;\n    readonly model?: SessionTitleModelProvenance;\n};',
+  },
+  {
+    name: 'SessionTitleUserMessage',
+    declaration: 'export interface SessionTitleUserMessage {\n    readonly seq: number;\n    readonly text: string;\n}',
+  },
  {
    name: 'SkillCandidate',
    declaration: 'export interface SkillCandidate extends SkillSummary {\n    readonly rank: number;\n    readonly locator: unknown;\n    readonly path?: string;\n    readonly metadata?: Readonly<Record<string, unknown>>;\n}',
@@ -15,4 +15,4 @@ The session log, system-prompt assembly, tool registry, agent vocabulary, and co

 `agent-loop` is the one concrete implementation of the `agent` seam and lives here because it is the harness's default product loop. It runs each driver inside `ctx.agents.withInitiator()`. Extension plugins depend on `agent`, including when they need the initiating Agent, and never on `agent-loop` directly, so the loop stays swappable.

-The default composition that wires this spine into a runnable agent lives in [`examples/agent-spine-demo`](../examples/agent-spine-demo/README.md): one bundle plugin that loads the control spine plus selected default capabilities (`timer` + `llm` + sessions + system-prompt + tools + agents + invariants + the local [skill family](../skill/README.md) + `tool-bash` + workspace-context + `agent-loop`) and forwards `agent-loop`'s `agents` list as its own config. It sits in `examples/` — ready-to-run demo/reference bundles — not in `core/`: `core/` ships the swappable spine pieces, while a demo bundle picks one concrete composition of them and adds a front door.
+The default composition that wires this spine into a runnable agent lives in [`examples/agent-spine-demo`](../examples/agent-spine-demo/README.md): one bundle plugin that loads the control spine plus selected default capabilities (`timer` + `llm` + sessions + fallback session titles + system-prompt + tools + agents + invariants + the local [skill family](../skill/README.md) + `tool-bash` + workspace-context + `agent-loop`) and forwards `agent-loop`'s `agents` list as its own config. It sits in `examples/` — ready-to-run demo/reference bundles — not in `core/`: `core/` ships the swappable spine pieces, while a demo bundle picks one concrete composition of them and adds a front door.
@@ -10,6 +10,7 @@ Creates and holds event-sourced `Session` instances. Persistence is intentionall

 - `ctx.sessions.create(id?, { seed?, meta? }?)` validates and detaches durable seed/header data, fills the version and id, defaults `createdAt` to now, publishes the session, and binds it to the calling fiber. Persisted reconstruction supplies its original `createdAt`, `seedLength`, and `delegationDepth`.
 - `ctx.sessions.flush(session)` dispatches the awaited parallel durability checkpoint through the session's captured scope. Every listener starts and the call waits for all to settle before reporting failure; unpublished, detached, and stale objects reject.
+- `ctx.sessions.appendOutOfBand(session, type, data, trigger)` accepts only plugin event types opted into `OutOfBandSessionEventMap`. It appends directly inside an open turn; otherwise it atomically opens a zero-step plugin turn, appends, closes, and flushes. A target failure still closes and flushes the synthetic turn, and detach is deferred until the sequence settles.
 - `ctx.sessions.fork(source, boundary?, childSessionId?): Session` — Resolve a live session object or id, select a seed through the inclusive `boundary` event seq (default: current last event), require that boundary to be `turn/end`, and create a live child session with lineage metadata.
 - `ctx.sessions.get(id: SessionId): Session | undefined`
 - `ctx.sessions.list(): Session[]`
@@ -62,7 +63,7 @@ Durable values need one accepted representation, not a check followed by a secon

 The append-only log's event types, enumerated member by member — payloads, surface badges, provenance — in the generated [persistence log event catalog](../../../docs/persistence-catalog.md). Token accounting reads per-step `assistant/chunk { type: 'usage' }` records and treats `assistant/message.usage` as the committed-step fallback when no usage chunk exists; failed model-request attempts have no assistant message. Provider/model/replay provenance rides on `assistant/message`; an operational error's step is on `turn/end.reason` for `kind: 'error'`, with structured provider facts for a final model-request failure.

-Merge-extensible via `SessionEventMap` — a plugin declaration-merges its own types (the compaction seam's `compact/*`, bounded recovery's non-surface `llm/retry`, the hook bridges' `hook/*`); merged members appear in the same catalog.
+Merge-extensible via `SessionEventMap` — a plugin declaration-merges its own types (the compaction seam's `compact/*`, bounded recovery's non-surface `llm/retry`, the hook bridges' `hook/*`); merged members appear in the same catalog. `OutOfBandSessionEventMap` is a separate empty-by-default marker map: an event owner must merge the same key there before `appendOutOfBand()` accepts that log-only type, while surface and lifecycle types remain excluded.

 Also defines `TurnTriggerMap` and `TurnEndReasonMap` (merge-extensible sum types for typed turn boundaries — `kind`-tagged instead of strings). A final model-request error retains one structured `LlmFailure`; other turn errors retain message/code, and both identify the failed step.

@@ -4,7 +4,7 @@ Pre-composed plugin bundles a thin leaf `cordis.yml` loads instead of assembling

 | Package | npm name | Role |
 |---|---|---|
-| `agent-spine-demo/` | `@deepseek-ai/dsh-agent-spine-demo` | The executor-less/UI-less agent spine as one bundle plugin (`timer` + `llm` + sessions + system-prompt + tools + skills + agents + invariants + `tool-bash` + workspace-context + `tool-skill` + `agent-loop`) |
+| `agent-spine-demo/` | `@deepseek-ai/dsh-agent-spine-demo` | The executor-less/UI-less agent spine as one bundle plugin (`timer` + `llm` + sessions + fallback titles + system-prompt + tools + skills + agents + invariants + `tool-bash` + workspace-context + `tool-skill` + `agent-loop`) |
 | `tui-demo/` | `@deepseek-ai/dsh-tui-demo` | Full-screen terminal app: the spine + JSONL persistence + `dsh-tui` + a pre-created `main` agent, with a boot `bin` |
 | `cli-demo/` | `@deepseek-ai/dsh-cli-demo` | Headless one-shot app: the spine + JSONL persistence + a pre-created `main` agent, with text and DSH-native JSON output |
 | `acp-demo/` | `@deepseek-ai/dsh-acp-demo` | ACP server app: the spine + JSONL persistence + the [`acp`](../ui/acp/README.md) bridge (no stdout logger), with a boot `bin` |
@@ -12,6 +12,7 @@ Read this package for the whole plugin tree and its composition order.
@cordisjs/plugin-timer            timer service (writes nothing to stdout)
@deepseek-ai/dsh-llm              abstract LLM service + content-block vocabulary
@deepseek-ai/dsh-session          event-sourced session log + store
+@deepseek-ai/dsh-session-title    log-backed title service + deterministic fallback
@deepseek-ai/dsh-system-prompt    prompt-section + tool-schema assembly
@deepseek-ai/dsh-tools            registry + guarded pre/around/post/final-result pipeline
@deepseek-ai/dsh-skill            skill provider registry
@@ -33,6 +34,7 @@ Read this package for the whole plugin tree and its composition order.
 The spine is everything COMMON to every front door. The swappable and front-door-coupled pieces stay out, picked by whatever loads the bundle:

 - **the LLM adapter** — the bundle ships the abstract `llm` service; the leaf registers a concrete adapter on `ctx.llm` (`llm-deepseek`, `llm-pi-ai`, `llm-replay`).
+- **model-backed session-title providers** — the bundle mounts the fallback service with fixed example limits (5 words, 40 fallback bytes, 80 accepted-title bytes); a leaf may opt into exactly one first-message or all-messages LLM provider.
 - **the bash executor** — the bundle ships `tool-bash` (the consumer schema); the leaf provides `ctx.bash` (`bash-local` or a sandboxed impl).
 - **non-local skill providers** — the bundle ships the skill registry, the local filesystem provider, and the `skill` tool; deployments can add other providers such as embedded or remote catalogs as siblings.
 - **presentation + per-app infra** — the terminal TUI or ACP front door and `hmr`. These form the coupled front-door cluster that the app packages ([`dsh-tui-demo`](../tui-demo/README.md), [`dsh-acp-demo`](../acp-demo/README.md)) bake in. `timer` is in the spine because it is common and stdout-silent; front doors own stdout and remain outside.
@@ -47,7 +49,7 @@ import type { Config } from '@deepseek-ai/dsh-agent-spine-demo'
 // workspaceContext requires { maxBytes } or false; the other owner schemas supply defaults.
 ```

-The bundle FORWARDS each field to the child that owns it: `agents` and `maxParallelToolCalls` to `agent-loop` (`agents` defaults to `[]`; the cap defaults there), so each app supplies its own pre-created agents — TUI and headless apps pre-create `main`, while the ACP app creates agents on demand at `session/new`; `llmRetry` to the bounded retry policy; `persona` and `toolOrder` to `dsh-system-prompt`; `tools` to the tool registry for its presentation mode; `skills.registry`, `skills.local`, and `skills.tool` to the skill registry, local provider, and model-facing consumer; the required `workspaceContext` choice to `dsh-workspace-context` (`{ maxBytes }` enables loading and `false` disables it); and `toolBash`/`toolTasks` to the two model-facing tool plugins the bundle owns. Set `skills.enabled: false` to omit both the local provider and model-facing skill tool, and set `toolTasks: false` to retain the task service for foreground producers without exposing `task_output` / `task_list` / `task_kill`. It resolves `dshHome` once through [`@deepseek-ai/dsh-home`](../../util/home/README.md) and forwards that absolute value to tool-bash's managed environment and enabled local skill discovery. An absent top-level `dshHome` adopts `skills.local.dshHome`; supplying both with different resolved paths fails loudly. `toolBash.enableRunInBackground` controls only the bash producer; independently loaded producers keep their own config. Workspace instructions register before the skill catalog so their session-prefix message renders first. App packages use `pickSpineConfig()` to copy only these bundle-owned fields.
+The bundle FORWARDS each field to the child that owns it: `agents` and `maxParallelToolCalls` to `agent-loop` (`agents` defaults to `[]`; the cap defaults there), so each app supplies its own pre-created agents — TUI and headless apps pre-create `main`, while the ACP app creates agents on demand at `session/new`; `llmRetry` to the bounded retry policy; `persona` and `toolOrder` to `dsh-system-prompt`; `tools` to the tool registry for its presentation mode; `skills.registry`, `skills.local`, and `skills.tool` to the skill registry, local provider, and model-facing consumer; the required `workspaceContext` choice to `dsh-workspace-context` (`{ maxBytes }` enables loading and `false` disables it); and `toolBash`/`toolTasks` to the two model-facing tool plugins the bundle owns. The session-title fallback limits are fixed example composition policy rather than bundle config. Set `skills.enabled: false` to omit both the local provider and model-facing skill tool, and set `toolTasks: false` to retain the task service for foreground producers without exposing `task_output` / `task_list` / `task_kill`. It resolves `dshHome` once through [`@deepseek-ai/dsh-home`](../../util/home/README.md) and forwards that absolute value to tool-bash's managed environment and enabled local skill discovery. An absent top-level `dshHome` adopts `skills.local.dshHome`; supplying both with different resolved paths fails loudly. `toolBash.enableRunInBackground` controls only the bash producer; independently loaded producers keep their own config. Workspace instructions register before the skill catalog so their session-prefix message renders first. App packages use `pickSpineConfig()` to copy only these bundle-owned fields.

 ## Why a code bundle, not a shared YAML include

@@ -1,9 +1,9 @@
 # session-query/ — session retrieval capability family

-Trusted exact reads and relationship traces over live and durable session logs. The family contains one interface package that owns `ctx.sessionQuery`, logical-corpus precedence, surface classification, bounded event reads, lineage, and direct event relationships.
+Trusted exact reads and relationship traces over live and durable session logs. The family contains one interface package that owns `ctx.sessionQuery`, logical-corpus precedence, title folding, surface classification, bounded event reads, lineage, and direct event relationships.

 | Package | Role | ctx key |
 |---|---|---|
-| [`session-query/`](session-query/README.md) | Logical-corpus exact-read and relationship-tracing service | `ctx.sessionQuery` |
+| [`session-query/`](session-query/README.md) | Logical-corpus title, event, lineage, and relationship reads | `ctx.sessionQuery` |

 The family is independent of compaction: it reads canonical lineage, surface operations, and logged provenance but does not participate in compaction policy or execution. Full-text search remains a proposed SQLite package rather than a speculative provider seam in this interface package.
@@ -5,12 +5,13 @@ Exact session-history retrieval and relationship tracing through `ctx.sessionQue
 ## Reads

 - `listSessions()` reads current persistence metadata, merges live records with live precedence, and returns cloned records in deterministic newest-first order.
+- `readTitle(sessionId)` loads one live-preferred or persisted log and folds its latest `session/title` event into a `SessionTitleSnapshot`; it returns `undefined` when the known session has no title.
 - `listEvents(sessionId)` loads the live-preferred raw log and classifies each event as `current`, `shadowed`, or `log-only` with the shared `dsh-session` surface fold.
 - `readEvent(request)` returns a cloned header, the full target event, and a bounded raw-seq window. `before` and `after` default to zero and may not exceed `readWindowMax`.
 - `traceSession(sessionId)` reads the corpus once and returns immediate-to-outward ancestors plus deterministic recursive descendant trees. `complete: false` identifies the first missing parent; a target-connected cycle fails with `SESSION_QUERY_INVALID_LINEAGE`.
 - `traceEvent(request)` loads the logical log once and returns direct positional replacements and direct logged provenance. `replacementChain` follows positional replacers to the final replacement; provenance links remain non-transitive.

-Persistence is optional and may mount or unmount dynamically. Cross-corpus listing and lineage tracing fail with `SESSION_QUERY_PERSISTENCE_FAILED` while mounted persistence is unreadable. An event read or trace targeting a known live session does not consult persistence, so durable backend health cannot make current in-memory history unreadable. Persisted event operations list before loading and reject a metadata mismatch rather than combining inconsistent observations.
+Persistence is optional and may mount or unmount dynamically. Cross-corpus listing and lineage tracing fail with `SESSION_QUERY_PERSISTENCE_FAILED` while mounted persistence is unreadable. A title, event read, or trace targeting a known live session does not consult persistence, so durable backend health cannot make current in-memory state unreadable. Persisted title and event operations list before loading and reject a metadata mismatch rather than combining inconsistent observations. `listSessions()` remains lightweight and does not load logs or index titles.

 `listEvents()` and `traceEvent()` run the same one-pass `dsh-session` surface fold. A loaded log is valid only when event seqs are zero-based and contiguous, surface markers obey event-type eligibility, provenance arrays are nonempty and duplicate-free, references name earlier events, and each positional replacement names and cites every surface node it removes; every violation fails with `SESSION_QUERY_INVALID_SURFACE`.

@@ -6,8 +6,8 @@ Four layers, importable separately:

 - **`launchAcpTestAgent` (launcher)** — boots an unbuilt ACP agent from a temp cwd, pins tsx to the repo tsconfig, connects the SDK client over a raw-byte stdout tee, collects session updates and stderr, surfaces asynchronous spawn failures through its startup lifecycle, fails closed on unhandled permission requests, and owns graceful or signalled shutdown. Shutdown waits for process exit, inherited stdio closure, and ACP parser exhaustion before resolving or propagating a child error, so captures are complete and callers can remove owned paths after either outcome. Snapshot and ordinary e2e suites share this process boundary; a test supplies only agent paths, cwd, environment overrides, and any permission policy.
 - **`runScenario` (harness)** — boots the real agent bin as a subprocess via tsx (unbuilt, Loader path), drives it over ACP JSON-RPC stdio from a deterministic `input.json` script, tees raw stdout for the expected-output and purity checks, and harvests every persisted session JSONL (parent + subagent children, primary-first) after a graceful stdin-EOF shutdown. Parameterized by `AgentUnderTest` (`binScript`, `configPath`, `tsconfigPath` — absolute paths; the subprocess cwd is a temp dir outside the repo). Startup failures preserve captured agent stderr in the rejected diagnostic.
- **Normalizers** — pure functions turning the two captured surfaces into stable text: `normalizeStdout` (JSON-RPC ids → first-seen sequence; UUIDs/cwd → tokens; doubles as the stdout-purity check), `normalizeSessionLog` (times zeroed, `seq` kept), `scrubSystemPrompts` (prompt text → `{{system}}`), `scrubToolSchemas` (schema bulk → `{{tools}}`), and `scrubRequestHeaders` (all header bulk → `{{system}}`/`{{tools}}`/`{{messagePrefix}}` outside each pin, structure kept — [pinned-header Agent Note](../../../.agents/notes/implemented/testing/2026-07-06-pin-request-header-content-in-one-scenario.md)).
- **`defineAcpSnapshotSuite` (factory)** — registers the whole describe/it tree for a scenario table: per-scenario expected-output and re-persisted-log comparisons, record/refresh fixture write-back, rejection of structured `UNKNOWN_TOOL` results, the per-header-class pin (`system-prompt.expected.md` plus `tool-schemas.expected.json`) with its live uniformity guard, and the fixture guard block (no orphan scenario dirs, required files present, exactly one pin per class, every JSONL prompt/schema-scrubbed, non-pinning fixtures fully header-scrubbed). Each scenario directory's `session.jsonl` plus contiguous `session.<n>.jsonl` siblings are the ordered primary/child inventory; the scenario table does not duplicate their count. Must be called at vitest collection time.
+- **Normalizers** — pure functions turning the two captured surfaces into stable text: `normalizeStdout` (JSON-RPC ids → first-seen sequence; UUIDs/cwd → tokens; `session_info_update.updatedAt` → `{{updatedAt}}`; doubles as the stdout-purity check), `normalizeSessionLog` (times zeroed, `seq` kept), `scrubSystemPrompts` (prompt text → `{{system}}`), `scrubToolSchemas` (schema bulk → `{{tools}}`), and `scrubRequestHeaders` (all header bulk → `{{system}}`/`{{tools}}`/`{{messagePrefix}}` outside each pin, structure kept — [pinned-header Agent Note](../../../.agents/notes/implemented/testing/2026-07-06-pin-request-header-content-in-one-scenario.md)).
+- **`defineAcpSnapshotSuite` (factory)** — registers the whole describe/it tree for a scenario table: per-scenario expected-output and re-persisted-log comparisons, record/refresh fixture write-back, rejection of structured `UNKNOWN_TOOL` results, the per-header-class pin (`system-prompt.expected.md` plus `tool-schemas.expected.json`) with its live uniformity guard, and the fixture guard block (no orphan scenario dirs, required files present, exactly one pin per class, every JSONL prompt/schema-scrubbed, non-pinning fixtures fully header-scrubbed). Refresh preserves existing volatile fields by event position and gives a newly inserted `session/title` its preceding event's time, so feature-driven insertions do not churn the remainder of a fixture. Each scenario directory's `session.jsonl` plus contiguous `session.<n>.jsonl` siblings are the ordered primary/child inventory; the scenario table does not duplicate their count. Must be called at vitest collection time.

 A consuming `*.snapshot.ts` is the scenario table plus one factory call:

@@ -4,12 +4,12 @@ Integrations that expose the agent to an external editor or client. These are **

 | Package | Role | ctx key |
 |---|---|---|
-| `acp/` | Agent Client Protocol bridge: serves the agent to an ACP editor (Zed) over JSON-RPC stdio | (drives `ctx.agents`/`ctx.sessions`) |
+| `acp/` | Agent Client Protocol bridge: serves agents and live/replayed title updates to an ACP editor over JSON-RPC stdio | (drives `ctx.agents`/`ctx.sessions`) |
 | `user-approval/` | One-shot user-approval mechanism, closed outcome vocabulary, audit events, and per-session approval policy | `ctx.approval` |
 | `permission/` | User-facing permission presets (`workspace-write`/`danger-full-access`): one product-level select bundling the sandbox-mode and approval-policy knobs, written through to their session events | `ctx.permission` |
 | `user-interaction/` | Abstract human question/answer seam used by UI-backed confirmation tools | `ctx.userInteraction` |
 | `tool-ask-user/` | Model-facing `ask_user_question` tool over `ctx.userInteraction` | (registers on `ctx.tools`) |
-| `tui/` | Interactive pi-tui terminal channel for TTY sessions; renders `session/event`, tool presentation intents, and answers `ctx.userInteraction` | (drives `ctx.agents`) |
+| `tui/` | Interactive pi-tui terminal channel; renders session titles/events and tool intents, and answers `ctx.userInteraction` | (drives `ctx.agents`) |
 | `jsonrpc/` | Stdio JSON-RPC server for out-of-process SDK clients | (drives `ctx.agents`) |
 | `app-boot/` | Shared boot glue for the app bins: `.env` loading, fail-loud Loader guards, snapshot-aware config resolution, the settle-the-tree boot sequence | (library for the bins) |

@@ -27,10 +27,10 @@ The `initialize` handshake reports a fixed server identity (`agentInfo: { name:
 |---|---|---|
 | `initialize` | static | negotiate `protocolVersion`; advertise baseline prompt capabilities (`text`, plus `resource_link` rendered as text) and `loadSession: true` |
 | `session/new` | `ctx.agents.create({ sessionId, meta:{cwd} })` | creates a new session/agent; N concurrent sessions are allowed, keyed by id; `cwd` must be absolute (it becomes the session's workspace — see Per-session cwd); non-empty `additionalDirectories` and `mcpServers` rejected |
-| `session/load` | `ctx.agents.resume(...)` | reserves the id, verifies the persisted cwd, resumes, and replays user, assistant, and tool events |
+| `session/load` | `ctx.agents.resume(...)` | reserves the id, verifies the persisted cwd, resumes, and replays user, assistant, tool, and title events |
 | `session/prompt` | `agent.send()` | supports ACP `text` and `resource_link` blocks; rejects image/audio/embedded resource and empty prompts; one in-flight prompt PER session (independent); settles on the OWNING turn's end (a turn that ends in `error` rejects the RPC) |
 | `session/cancel` | `agent.cancel()` | the queue-aware cancel: aborts a running step, clears queued + steering work, and drops a turn about to start, then settles the prompt `cancelled` — for ONLY that session (a cancel never touches another session's stream or prompt) |
-| `session/update` | `session/event` | streams user replay, assistant text/reasoning, retry/failure attempt markers, and tool render intents |
+| `session/update` | `session/event` | streams user replay, assistant text/reasoning, retry/failure attempt markers, tool render intents, and `session_info_update` title revisions |
 | `elicitation/create` | `ctx.userInteraction.ask()` | maps `ask_user_question` questions to ACP form elicitations; option descriptions are shown in enum titles, `multi_select` uses ACP array enums, optionless requests use a required `custom` field, and a non-empty custom answer overrides any selected choice |
 | `session/request_permission` | `approval/request` listener | answers one-shot allow/reject requests for bridge-owned calls; foreign or call-less requests delegate and fail closed if unanswered — see "Permission prompts" |
 | `session/set_config_option` | agent-scoped request target / `ctx.permission.set()` | per-session provider+model and permission-preset switching over [session config options](https://agentclientprotocol.com/protocol/session-config-options) — see "Session config options" |
@@ -49,6 +49,8 @@ The shared [`ctx.tasks` runtime](../../tasks/tasks/) fences access to predictabl

 ACP updates are append-only, so `llm/retry` emits a visible separator that marks preceding partial model output discarded before the next attempt streams. A terminal model-request failure emits the same discarded-output warning; replay derives both markers from the durable events.

+A log-only `session/title` event maps to ACP `session_info_update` with `title` and the event timestamp as `updatedAt`. The same mapping runs for live events and `session/load` replay, so an asynchronously generated late title and a restored persisted title have one wire representation without entering model history.
+
 ## Per-session cwd

 `session/new` records the request's absolute cwd in the session header. Before constructing an agent, `session/load` uses persisted metadata to require an absolute request cwd that matches the stored one. Bash defaults to that workspace; an explicit relative workdir resolves against it, and multiple sessions may use different workspaces. `additionalDirectories` remains unsupported.
@@ -112,7 +114,7 @@ Append-only; newly visible content follows the reusable request prefix and does

 #### What the model sees

-When optional consumers are loaded, ACP form answers become the exact JSON shape documented by `dsh-tool-ask-user`. Failures become `Error: ACP user questions must come from an agent-owned request`, `Error: ACP user question has no matching session`, `Error: ACP elicitation request failed`, `Error: ask_user_question was cancelled by the user`, `Error: ask_user_question returned no answer`, or `Error: ask_user_question was aborted before the user answered`. Permission decisions control whether another tool yields success or denial. ACP tool cards, terminal output, diffs, and streamed session updates are UI-only.
+When optional consumers are loaded, ACP form answers become the exact JSON shape documented by `dsh-tool-ask-user`. Failures become `Error: ACP user questions must come from an agent-owned request`, `Error: ACP user question has no matching session`, `Error: ACP elicitation request failed`, `Error: ask_user_question was cancelled by the user`, `Error: ask_user_question returned no answer`, or `Error: ask_user_question was aborted before the user answered`. Permission decisions control whether another tool yields success or denial. ACP tool cards, terminal output, diffs, title updates, and other streamed session updates are UI-only.

 #### Token effect

@@ -8,7 +8,7 @@ Interactive terminals on macOS, Linux, and Windows are supported. Windows uses p

 This package owns interactive terminal presentation and input only. It injects `agents`, `tools`, and `userInteraction`, then drives an agent created or resumed by app or developer code. Agent lifecycle, persistence, and the model-facing [`ask_user_question`](../tool-ask-user/README.md) tool remain separate composition entries.

-The TUI rebuilds resumed history from the active session surface, renders Markdown responses and reasoning, applies each tool's `presentCall` / `presentResult` intent to terminal, diff, or generic cards, keeps the latest `todo/write` plan above the editor, and presents `ctx.userInteraction` questions as keyboard-driven overlays. A durable `llm/retry` event retracts the failed step's live chunks and renders the scheduled retry count, delay, and failure in the transcript; success, exhaustion, and cancellation then settle through ordinary session events. The footer totals each logged model step's usage once, including failed attempts, while treating committed-message usage as a fallback for logs without a usage chunk. Surface replacement events rebuild the transcript so compacted history does not reappear.
+The TUI rebuilds resumed history from the active session surface, renders Markdown responses and reasoning, applies each tool's `presentCall` / `presentResult` intent to terminal, diff, or generic cards, keeps the latest `todo/write` plan above the editor, and presents `ctx.userInteraction` questions as keyboard-driven overlays. The latest logged session title becomes the header subtitle, with `welcome` before a title exists, and the terminal window title becomes `<session title> — <configured title>`. A durable `llm/retry` event retracts the failed step's live chunks and renders the scheduled retry count, delay, and failure in the transcript; success, exhaustion, and cancellation then settle through ordinary session events. The footer totals each logged model step's usage once, including failed attempts, while treating committed-message usage as a fallback for logs without a usage chunk. Surface replacement events rebuild the transcript so compacted history does not reappear.

 Before model output, session events, tool presenters, questions, configuration, or diagnostics reach pi-tui's ANSI-aware renderers or the terminal title, the TUI renders C0 and C1 controls other than line feeds as visible `\xNN` text. Those sources cannot add terminal control sequences; the TUI and pi-tui retain ownership of terminal rendering and styling.

@@ -18,7 +18,7 @@ While the agent is running, editor submissions call `agent.steer()`; otherwise t

 | Key | Default | Meaning |
 |---|---|---|
-| `welcome` | `ready.` | Header subtitle |
+| `welcome` | `ready.` | Header subtitle until the session has a logged title. |
 | `sessionId` | `main` | Exact shared agent/session identity driven by the terminal |
 | `showReasoning` | `true` | Render reasoning blocks |
 | `maxToolOutputLines` | `12` | Collapsed tool-card output limit |
@@ -27,7 +27,7 @@ While the agent is running, editor submissions call `agent.steer()`; otherwise t
 | `questionDialogMaxHeight` | `20` | Question-overlay maximum rows |
 | `showHardwareCursor` | `false` | Show the hardware cursor at pi-tui's IME marker |
 | `color` | `true` | Apply the built-in ANSI palette (see [Color](#color)) |
-| `title` | `DeepSeek Harness` | Terminal window title |
+| `title` | `DeepSeek Harness` | Product suffix for the terminal window title. |

 ```yaml
 - id: terminal
@@ -55,7 +55,7 @@ Each non-empty editor submission becomes one text block, sent with `agent.send()

 #### Token effect

-Submitted text is retained under the agent loop's normal session-history and compaction rules. Headers, cards, Markdown rendering, status lines, plans, and help text add no tokens.
+Submitted text is retained under the agent loop's normal session-history and compaction rules. Headers, the logged title, cards, Markdown rendering, status lines, plans, and help text add no tokens.

 #### KV Cache effect

@@ -83,8 +83,11 @@ export const LINK_MAP: Record<string, string> = {
  ScopeKey: 'scope.md',
  Scoped: 'scope.md',
  EpochHeader: 'session.md',
+  OutOfBandSessionEventType: 'session.md',
  Session: 'session.md',
+  SessionEventMap: 'session.md',
  TurnEndReason: 'session.md',
+  TurnTrigger: 'session.md',
  SessionEventReadRequest: 'session-query.md',
  SessionEventRecord: 'session-query.md',
  SessionEventTrace: 'session-query.md',
@@ -92,6 +95,8 @@ export const LINK_MAP: Record<string, string> = {
  SessionEventWindow: 'session-query.md',
  SessionLineageTrace: 'session-query.md',
  SessionRecord: 'session-query.md',
+  SessionTitleProvider: 'session-title.md',
+  SessionTitleSnapshot: 'session-title.md',
  SkillDefinition: 'skills.md',
  SkillLookupOptions: 'skills.md',
  SkillProvider: 'skills.md',
@@ -73,6 +73,7 @@ const GROUP_ORDER = [
  'hooks',
  'session-persistence',
  'session-query',
+  'session-title',
  'support',
  'ui',
 ]
@@ -127,6 +128,14 @@ const SERVICE_ROLES: ServiceRole[] = [
    mode: 'seam',
    note: 'Resolves live and optional persisted logs into one logical corpus for exact reads and relationship traces.',
  },
+  {
+    key: 'sessionTitle',
+    pkg: 'session-title',
+    title: 'Log-backed session titles',
+    mode: 'seam',
+    implementations: ['session-title-first-message-llm', 'session-title-all-messages-llm'],
+    note: 'Owns the deterministic fallback, latest-title fold, and sole optional asynchronous provider registration.',
+  },
  {
    key: 'systemPrompt',
    pkg: 'system-prompt',
@@ -34,6 +34,7 @@ const GROUP_ORDER = [
  'hooks',
  'session-persistence',
  'session-query',
+  'session-title',
  'support',
  'ui',
 ]
@@ -41,6 +41,10 @@ const LINK_MAP: Record<string, string> = {
  TodoItem: 'session.md',
  TurnTrigger: 'session.md',
  TurnEndReason: 'session.md',
+  SessionTitleEventData: 'session-title.md',
+  SessionTitleModelProvenance: 'session-title.md',
+  SessionTitleProviderId: 'session-title.md',
+  SessionTitleSource: 'session-title.md',
 }

 /** One log event, extracted from a `SessionEventMap` declaration. */
@@ -43,6 +43,7 @@
    { "doc": "docs/core-data-structures/token-meter.md", "symbol": "TokenSurfaceNode", "source": "packages/llm/token-meter/src/types.ts" },

    { "doc": "docs/core-data-structures/session.md", "symbol": "SessionEventMap", "source": "packages/core/session/src/types.ts" },
+    { "doc": "docs/core-data-structures/session.md", "symbol": "OutOfBandSessionEventMap", "source": "packages/core/session/src/types.ts" },
    { "doc": "docs/core-data-structures/session.md", "symbol": "EpochHeader", "source": "packages/core/session/src/types.ts" },
    { "doc": "docs/core-data-structures/session.md", "symbol": "TodoItem", "source": "packages/core/session/src/types.ts" },
    { "doc": "docs/core-data-structures/session.md", "symbol": "SessionEvent", "source": "packages/core/session/src/types.ts" },
@@ -71,6 +72,17 @@
    { "doc": "docs/core-data-structures/session-query.md", "symbol": "SessionEventTraceRequest", "source": "packages/session-query/session-query/src/types.ts" },
    { "doc": "docs/core-data-structures/session-query.md", "symbol": "SessionEventTrace", "source": "packages/session-query/session-query/src/types.ts" },

+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleProviderId", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleModelProvenance", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleSource", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleEventData", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleSnapshot", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleUserMessage", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleAutomaticMode", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleProviderRequest", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleProviderResult", "source": "packages/session-title/session-title/src/index.ts" },
+    { "doc": "docs/core-data-structures/session-title.md", "symbol": "SessionTitleProvider", "source": "packages/session-title/session-title/src/index.ts" },
+
    { "doc": "docs/core-data-structures/tools.md", "symbol": "ToolDefinition", "source": "packages/core/tools/src/index.ts" },
    { "doc": "docs/core-data-structures/tools.md", "symbol": "SchemaProp", "source": "packages/core/tools/src/schema.ts" },
    { "doc": "docs/core-data-structures/tools.md", "symbol": "SchemaSpec", "source": "packages/core/tools/src/schema.ts" },