feat(chat): support agentId to auto-select persona

WORKLOG.md

@@ -1,5 +1,19 @@
 # Worklog
 
+## 2026-07-08
+
+### nx2/blocks/chat — agent-id as a plain attribute (feat/chat-agent-id branch, PR #462)
+
+Reviewer consensus (sharanyavinod + mhaack) on #462: `agentId` should not be a reactive Lit property since it is not used for rendering. Keeping it reactive re-renders `<nx-chat>` on `agent-id` changes for no benefit today.
+
+- Removed `agentId: { type: String, attribute: 'agent-id' }` from `static properties`.
+- Read the value once in `connectedCallback` via `getAttribute('agent-id')` and forward it to the controller's `setAgentId`.
+- Dropped the `agentId` branch from `updated(changed)` (no longer observed).
+- Controller plumbing unchanged: `setAgentId` stores `_agentId`, sent as `agentId` in the request body only when set.
+- Documented the `agent-id` attribute and its request-body contract in `docs/chat-ui-component.md`.
+
+If we later drive rendering from the agent id, reintroduce it as a reactive property then (per the review thread).
+
 ## 2026-06-26
 
 ### nx2/blocks/chat/chat.js — skill selection preserves pending attachments (feat/da-skill-attachment-fix)
@@ -14,7 +28,6 @@ Post-review follow-up (fe049a9b):
 - Renamed loop variable `i` → `item` in `_onSlashSelect` callbacks
 - Added regression tests in `test/nx2/blocks/chat/chat.test.js` (8 tests, all pass)
 
-
 ## 2026-06-23
 
 ### nx2/blocks/shared/dialog — configurable panel sizing (dialog-css-vars branch)

docs/chat-ui-component.md

@@ -22,6 +22,12 @@ The component manages its own controller internally. No external wiring needed.
 | `thinking` | `Boolean` | Agent is processing. Disables input.                                   |
 | `context`  | `Object`  | Page context: `{ org, site, path, view }`. Required — set by the host view. `view` must be `browse` or `edit`. |
 
+## Attributes in
+
+| Attribute  | Type     | Description                                                                                     |
+| ---------- | -------- | ----------------------------------------------------------------------------------------------- |
+| `agent-id` | `String` | Optional. Selects a specific agent/persona. Read once on mount and forwarded to the agent as `agentId` in the request body. Not a reactive property — set it before mount; later changes are not observed. |
+
 **Message shape:**
 
 ```js
@@ -30,7 +36,7 @@ The component manages its own controller internally. No external wiring needed.
 { role: 'tool', ... }  // filtered from display automatically
 ```
 
-**Request body:** The controller POSTs `{ messages, pageContext, imsToken, room, sessionId }` to the agent. `sessionId` is a UUID scoped to the current conversation session — it resets when the user clears the chat. Selection context is embedded on individual user messages (see [Selection context](#selection-context)) rather than as a top-level request field.
+**Request body:** The controller POSTs `{ messages, pageContext, imsToken, room, sessionId }` to the agent (plus `agentId` when the `agent-id` attribute is set). `sessionId` is a UUID scoped to the current conversation session — it resets when the user clears the chat. Selection context is embedded on individual user messages (see [Selection context](#selection-context)) rather than as a top-level request field.
 
 ## Methods
 

nx2/blocks/chat/chat-controller.js

@@ -88,6 +88,10 @@ export default class ChatController {
     this._room = null;
   }
 
+  setAgentId(id) {
+    this._agentId = id;
+  }
+
   _pageContextForAgent() {
     const { org, site, path, view } = this._context ?? {};
     return org && site ? { org, site, path: path ?? '', view } : undefined;
@@ -370,6 +374,7 @@ export default class ChatController {
         pageContext,
         imsToken: accessToken?.token ?? null,
         room,
+        ...(this._agentId ? { agentId: this._agentId } : {}),
         sessionId: this._sessionId,
         ...(this._requestedSkills?.length ? { requestedSkills: this._requestedSkills } : {}),
         ...(this._pendingAttachments?.length ? { attachments: this._pendingAttachments } : {}),

nx2/blocks/chat/chat.js

@@ -211,6 +211,8 @@ class NxChat extends LitElement {
       },
     });
     if (this._context) this._controller.setContext(this._context);
+    const agentId = this.getAttribute('agent-id');
+    if (agentId) this._controller.setAgentId(agentId);
 
     this._unsubscribeHash = hashChange.subscribe((state) => {
       if (!this._explicitContext) this._applyContext(state);