[Idea] Public composer-keymap & sent-message-history APIs for plugins (use case: shell-style ↑ history recall)

[Chaiyahang]

English below / 中文在后。

Summary

I'd like to build a plugin (dsh-command-history) that gives the Web GUI composer a shell-style input history recall: press ↑ in an empty composer to refill the previous message you sent, ↓ to go forward — exactly like a terminal.

While prototyping against 0.2.1-rc.x, I found the write path is already there (inputActions.setDraft), but two capabilities have no first-class plugin API, so the feature is only reachable through host internals / DOM hacks that would break on upgrades. This is a request for stable public surfaces.

Gap 1 — Composer keymap registration (context-scoped)

dsh-client-ui-conversation owns a Lexical editor whose keymap "registers the fixed send, newline, complementary-delivery, command-menu, and reference-menu rows … and leaves every other key to the editor." There's no documented way for a third-party plugin to register a composer-focused key binding (e.g. bare ArrowUp only when the draft is empty / caret at the first line).

ctx.shortcuts is for global, app-wide chords (and rejects modifier-only / is unsuitable for a bare ArrowUp), so the only route today is a capture-phase keydown listener fighting the Lexical editor (IME, multiline, caret-edge detection) — fragile.

Ask: a public, composer-scoped keymap hook — e.g. a registerable row in the composer's existing key arbitration, or an observeComposerKey-style extension point that receives { key, isEmpty, caretAtStart } and can consume the event.

Gap 2 — Readable sent-message history for a session

The data clearly exists (conversation assembly, UiConversation.userText, the session projection / inbox), but there's no public API that hands a plugin the list of user-sent message texts for the current session. Consuming the internal conversation event feed is complex and not a stable third-party surface.

Ask: a read-only, session-scoped API such as ctx.uiConversation.sentUserMessages(sessionId) (or a useSentMessages hook) returning an ordered, de-duplicatable list of the user's own submitted texts — enough to drive history navigation.

Why this is worth a stable surface

History recall is a tiny feature with broad appeal, and both gaps are reusable far beyond it: Gap 1 enables any composer-level interaction plugin; Gap 2 enables "resend / edit last", templates, analytics, and more. Today both force brittle internal coupling.

Happy to help validate a design or test a preview build.

---

概要（中文）

我想做一个插件（dsh-command-history），给 Web GUI 输入框加上类似终端的输入历史回溯：输入框为空时按 ↑ 回填上一条你发过的消息，↓ 往回翻——和 shell 里完全一样。

在 0.2.1-rc.x 上试做时发现：写回输入框已有现成能力（inputActions.setDraft），但有两项能力没有一等公民的插件 API，只能靠怼 host 内部 / DOM 实现，升级即可能失效。因此来申请稳定的公开接口。

缺口 1 — 输入框键位注册（限定输入框聚焦场景）

dsh-client-ui-conversation 的 Lexical 编辑器键位"注册了发送、换行、互补投递、命令菜单、引用菜单等固定行……其余按键一律交给编辑器"。第三方插件没有公开途径去注册输入框内的键位（例如"仅当草稿为空 / 光标在首行时的裸 ↑"）。

ctx.shortcuts 面向全局 app 级快捷键（且拒绝纯修饰键、不适合裸 ↑），所以今天唯一的办法是在编辑器上挂 capture 阶段 keydown 硬抢，和 Lexical 较劲（输入法、多行、光标边界判定）——很脆。

诉求： 一个限定输入框作用域的公开键位钩子——比如可注册进 composer 既有键位仲裁的一行，或 observeComposerKey 式扩展点，回调带 { key, isEmpty, caretAtStart } 且可消费事件。

缺口 2 — 可读取的会话"已发消息"历史

数据显然存在（conversation 装配、UiConversation.userText、会话投影 / inbox），但没有公开 API 把当前会话里用户发过的消息文本列表交给插件。消费内部事件流复杂且不是稳定的第三方接口。

诉求： 一个只读、会话作用域的 API，例如 ctx.uiConversation.sentUserMessages(sessionId)（或 useSentMessages hook），返回有序、可去重的用户自己提交文本列表，足以驱动历史导航即可。

为什么值得做成稳定接口

历史回溯本身小，但很通用；两个缺口的复用价值远超它：缺口 1 能支撑任何输入框级交互插件；缺口 2 能支撑"重发 / 编辑上一条"、模板、用量统计等。目前两者都迫使插件和内部实现脆性耦合。

乐意协助敲定设计或测试预览版。