feat(composer): show where the context window went, in the composer

apps/desktop/renderer/composer/RunComposer.tsx

@@ -13,6 +13,7 @@ import {
   parseTransportError,
   type CompleteAttachment,
   type ComposerConnectorsPort,
+  type ContextPillView,
   type ProviderKeysPort,
   type RunStartRequest,
   type StartRunError,
@@ -112,6 +113,14 @@ export interface RunComposerProps {
    * frame. Host-bound (list + write); omitted ⇒ the zone is absent.
    */
   readonly filing?: RunComposerFiling;
+  /**
+   * The context meter's view, built by the cockpit from the two `/context`
+   * reads and handed down the `renderComposer` ctx. `null` when nothing has
+   * been measured — the composer then renders no meter, which is the honest
+   * state. Mirrors the web binder's prop of the same name; the two hosts share
+   * the mapping, not the fetch.
+   */
+  readonly context?: ContextPillView | null;
 }
 
 /**
@@ -149,6 +158,7 @@ export function RunComposer(props: RunComposerProps): ReactElement {
     conversationId = null,
     conversationModel = null,
     filing,
+    context,
   } = props;
 
   // The last run-create failure, surfaced inline above the composer. The
@@ -347,6 +357,9 @@ export function RunComposer(props: RunComposerProps): ReactElement {
       <AssistantComposer
         connectors={{ servers: [...servers], loading: serversLoading }}
         skills={{ skills: [...skills], loading: skillsLoading }}
+        // Context meter — built once by the cockpit, so this binder and the web
+        // one draw the same number for the same conversation.
+        context={context}
         attachmentAdapter={attachmentAdapter}
         dictationPort={desktopDictationPort}
         filePicker={filePicker}

apps/desktop/renderer/destinationBinders.tsx

@@ -57,6 +57,7 @@ import {
   type ProjectDetail,
   type ProjectDetailProfile,
   type ProjectSummary,
+  type ContextPillView,
   type RunEmptyComposerCtx,
   type RunStartRequest,
   type WorkspaceStageHost,
@@ -1557,6 +1558,9 @@ export function RunBinder({
       // What this chat last ran with — the composer's model-pill seed of last
       // resort, derived by the cockpit from the run list it already fetched.
       readonly conversationModel?: string | null;
+      // The context meter, built ONCE by the cockpit from the two `/context`
+      // reads so both hosts draw the same number for the same conversation.
+      readonly context?: ContextPillView | null;
     }) => (
       <RunComposer
         dispatch={ctx.dispatch}
@@ -1577,6 +1581,7 @@ export function RunBinder({
         // sends through the cockpit's dispatch, which owns the run target.
         conversationId={conversationId}
         conversationModel={ctx.conversationModel}
+        context={ctx.context}
         // Same binding as the empty composer's — one filing state per chat, so
         // the pill reads the same before and after the first message.
         filing={filing}

apps/frontend/src/features/run/RunComposer.tsx

@@ -28,6 +28,7 @@ import {
 import {
   AssistantComposer,
   parseTransportError,
+  type ContextPillView,
   type RunStartRequest,
   type StartRunError,
 } from "@0x-copilot/chat-surface";
@@ -68,6 +69,9 @@ export interface RunComposerCtx {
   readonly onCancel: () => void;
   /** Newly authenticated connector to enable in the run-scoped Tools state. */
   readonly autoActivateConnectorId?: string | null;
+  /** The context meter's view, built by the cockpit from the two `/context`
+   *  reads. `null` when nothing has been measured — render no meter. */
+  readonly context?: ContextPillView | null;
 }
 
 export interface RunComposerProps {
@@ -172,6 +176,10 @@ export function RunComposer({
         onOpenSkillsSettings={noop}
         onOpenMcpSettings={noop}
         toolsTrigger={toolsTrigger}
+        // Context meter. The cockpit reads both `/context` endpoints once and
+        // hands the built view down the ctx, so this binder and the desktop one
+        // cannot fetch it differently. `undefined` renders no meter.
+        context={ctx.context}
         models={models}
         selectedModel={selectedModel}
         onModelChange={onModelChange}

apps/frontend/src/features/run/RunRoute.tsx

@@ -39,6 +39,7 @@ import {
   RunDestination,
   buildRunCreateBody,
   useTransport,
+  type ContextPillView,
   type RunEmptyComposerCtx,
   type RunStartRequest,
 } from "@0x-copilot/chat-surface";
@@ -355,6 +356,9 @@ export function RunRoute({
       // WC-P3 — cockpit-owned run state + cancel; RunComposer swaps send↔Stop.
       readonly running: boolean;
       readonly onCancel: () => void;
+      // The context meter, built ONCE by the cockpit from the two `/context`
+      // reads so both hosts draw the same number for the same conversation.
+      readonly context?: ContextPillView | null;
     }) => (
       <RunComposer
         ctx={ctx}

packages/chat-surface/src/composer/AssistantComposer.tsx

@@ -30,6 +30,8 @@ import {
 } from "./useWorkspaceFolderGrants";
 import { WorkspaceFolderBar } from "./WorkspaceFolderBar";
 import type { ThinkingDepth } from "./depth";
+import { ContextPill } from "./ContextPill";
+import type { ContextPillView } from "./contextPillView";
 import { ModelPill } from "./ModelPill";
 import type { ProviderKeysPort } from "../settings/data/providerKeys";
 import type { KeyFormConnected } from "../onboarding/KeyForm";
@@ -186,6 +188,19 @@ export interface AssistantComposerProps {
    * above the overflow-hidden composer frame.
    */
   toolsTrigger?: ReactNode;
+  /**
+   * Context meter for the right cluster — "how full is the window, and who
+   * filled it". Built by `buildContextPillView` from the two read APIs; the
+   * host owns the fetch, this package owns the drawing.
+   *
+   * `null`/omitted renders NOTHING, which is the honest state for a
+   * conversation nobody has measured yet: no skeleton, no spinner, no zeroed
+   * meter. A zeroed meter is a claim.
+   */
+  context?: ContextPillView | null;
+  /** Open the full context report (`by_call` / `by_subagent` / the per-turn
+   *  occupancy series). Host-owned navigation; omitted renders no link. */
+  onOpenContextReport?: () => void;
   /** PR 8.0.1 — display name of the active model, surfaced in the
    *  composer footer hint row. */
   activeModelLabel?: string;
@@ -340,6 +355,8 @@ export const AssistantComposer = forwardRef<
     // been migrated) but the composer no longer surfaces it — the model
     // name lives in <ModelPill> only (Phase 9 dedup).
     activeModelLabel: _activeModelLabel,
+    context,
+    onOpenContextReport,
     models,
     selectedModel,
     onModelChange,
@@ -691,6 +708,18 @@ export const AssistantComposer = forwardRef<
                 {dictation.message}
               </span>
             ) : null}
+            {/* Context meter, LEFT of the model pill — the model sets the
+                denominator, so reading rightward gives "60% free · of Opus 5's
+                window". It is also the one control here that answers a
+                question asked immediately before pressing send.
+                Absent (not disabled, not zeroed) until something is measured. */}
+            {context != null ? (
+              <ContextPill
+                view={context}
+                disabled={controlsDisabled}
+                onOpenReport={onOpenContextReport}
+              />
+            ) : null}
             {models && selectedModel !== undefined && onModelChange ? (
               <ModelPill
                 models={models}