feat(chat): view context — tell the assistant what you're looking at

An eye next to the paperclip shares what the user has open with their next
message: the page, the folder being browsed, the file open in the viewer and
any highlighted passage (line numbers where a source view exists), plus which
entity a detail page is about. The bag is client-authored {label, value} pairs
in English — the backend only clamps (chars, never bytes), neutralizes the
harness tag and renders one <system-extra> block per message, deduped
consecutively so it appears exactly when the view changed. On by default,
per-device toggle, hover/tap to preview, a chip on every sent message;
docs/view-context.md for users, an updated harness.md clause for the model.

web/lib/chat-session.js

@@ -3,6 +3,25 @@ import { LightElement } from './base.js';
 import { InboxCardsMixin } from './inbox-cards.js';
 import { t } from './i18n.js';
 import { isSessionExpired, isNativeShell, notifySessionExpired, probeSession } from './session-expiry.js';
+import { getViewContext, subscribe as subscribeViewContext } from './view-context.js';
+
+// Whether what the user is looking at rides along with their messages. A UI
+// preference about this person on this browser, so `localStorage` rather than a
+// round-trip through `user_config` — and shared by both chat surfaces, so the
+// eye means the same thing in the copilot and in the mobile chat.
+//
+// Default **on**: off by default is the same as not shipping the feature for
+// everyone who never opens a settings panel. The eye in the composer is what
+// makes that honest — always visible, always showing the literal pairs it is
+// about to send (blueprint §3).
+const VIEW_CONTEXT_PREF_KEY = 'view-context-enabled';
+
+function readViewContextPref() {
+  // Anything but the explicit opt-out reads as on, so a corrupt or absent value
+  // fails towards the documented default rather than towards silence.
+  try { return localStorage.getItem(VIEW_CONTEXT_PREF_KEY) !== 'off'; }
+  catch { return true; }
+}
 
 // Slash commands handled entirely server-side: they reply with a `Done` and never
 // echo back as a `user_message`, so they are the only commands rendered
@@ -68,6 +87,13 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
     // Approvals and questions raised by those tasks: `{ approvals, clarifications }`,
     // each item carrying the `job_id` / `job_title` that asked.
     _taskInbox:          { state: true },
+    // View context — what the user is looking at (see `lib/view-context.js`).
+    // `_viewContextEnabled` is the eye's on/off state; `_viewContext` is a live
+    // mirror of the store, so the eye's panel shows what would be sent *now*
+    // without anybody having to send a message; `_viewContextOpen` is that panel.
+    _viewContextEnabled: { state: true },
+    _viewContext:        { state: true },
+    _viewContextOpen:    { state: true },
   };
 
   // Live events whose arrival implies a turn is in flight (used to restore the
@@ -128,12 +154,21 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
     this._taskTimer         = null;
     // Timers that drop a finished task from the strip after a grace period.
     this._taskDropTimers    = new Map();
+    this._viewContextEnabled = readViewContextPref();
+    this._viewContext        = getViewContext();
+    this._viewContextOpen    = false;
+    this._unsubViewContext   = null;
     this._onAuthRestored    = this._onAuthRestored.bind(this);
   }
 
   async connectedCallback() {
     super.connectedCallback();
     window.addEventListener('auth-restored', this._onAuthRestored);
+    // Keep the eye's panel honest between messages: the store changes as the
+    // user navigates and selects, and the whole point of the control is that it
+    // answers "what would you send right now?".
+    this._viewContext      = getViewContext();
+    this._unsubViewContext = subscribeViewContext((items) => { this._viewContext = items; });
     // Fire-and-forget: availability of a transcription provider determines
     // whether the mic button is rendered at all.
     this._checkTranscribe();
@@ -146,6 +181,8 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
   disconnectedCallback() {
     super.disconnectedCallback?.();
     window.removeEventListener('auth-restored', this._onAuthRestored);
+    this._unsubViewContext?.();
+    this._unsubViewContext = null;
     this._stopTaskClock();
     for (const timer of this._taskDropTimers.values()) clearTimeout(timer);
     this._taskDropTimers.clear();
@@ -864,10 +901,14 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
         // rendered optimistically (only slash commands are, and those are never
         // echoed). `message_id` is the real chat_history row id.
         this._push({
-          kind:        'user',
-          content:     msg.content,
-          attachments: msg.attachments ?? [],
-          message_id:  msg.message_id,
+          kind:         'user',
+          content:      msg.content,
+          attachments:  msg.attachments ?? [],
+          // Sanitized server-side and echoed to every client, so the chip in the
+          // bubble shows what actually went out — not what this browser meant to
+          // send — and matches what a reload rebuilds from the REST history.
+          view_context: msg.view_context ?? [],
+          message_id:   msg.message_id,
         });
         break;
 
@@ -1034,6 +1075,12 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
       ({ name, path, mimetype, filesize }));
     this._attachments = [];
 
+    // What the sender has on screen, read here because here is the last moment
+    // it is still true: the store is live, and by the time the echo comes back
+    // the user may have navigated away. The eye off means the field is *absent*
+    // from the payload, not an empty list — absent is what says "not shared".
+    const view_context = this._viewContextEnabled ? getViewContext() : [];
+
     // Sending implies the reader wants to follow the conversation: always land at
     // the latest, even if they had scrolled up to read before sending.
     this._forceScrollToBottom();
@@ -1045,10 +1092,12 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
     // event (for a custom command, carrying the typed form as its content), placing
     // it correctly (e.g. after the current round's tools when injected mid-turn).
     if (SYSTEM_SLASH_COMMANDS.has(content.split(/\s+/)[0])) {
-      this._push({ kind: 'user', content, attachments });
+      this._push({ kind: 'user', content, attachments, view_context });
     }
     this._waiting = true;
-    this._ws.send(JSON.stringify({ content, attachments }));
+    const payload = { content, attachments };
+    if (view_context.length) payload.view_context = view_context;
+    this._ws.send(JSON.stringify(payload));
   }
 
   // ── Attachments ────────────────────────────────────────────────────────────
@@ -1087,6 +1136,20 @@ export class ChatSession extends InboxCardsMixin(LightElement) {
     this._attachments = this._attachments.filter((_, idx) => idx !== i);
   }
 
+  // ── View context ───────────────────────────────────────────────────────────
+
+  /**
+   * Flip whether what the user is looking at rides along with their messages.
+   * Global rather than per-conversation: it is a preference about the person,
+   * not about one chat.
+   */
+  _toggleViewContext() {
+    this._viewContextEnabled = !this._viewContextEnabled;
+    try {
+      localStorage.setItem(VIEW_CONTEXT_PREF_KEY, this._viewContextEnabled ? 'on' : 'off');
+    } catch { /* a browser refusing storage still honours the toggle for this session */ }
+  }
+
   /** Handler for a paste event: uploads any files on the clipboard. */
   _onPaste(e) {
     const files = e.clipboardData?.files;