feat(agent-model): add per-agent model override with default-reset UX and runtime sync (#651)

electron/api/routes/agents.ts

@@ -7,10 +7,11 @@ import {
   listAgentsSnapshot,
   removeAgentWorkspaceDirectory,
   resolveAccountIdForAgent,
+  updateAgentModel,
   updateAgentName,
 } from '../../utils/agent-config';
 import { deleteChannelAccountConfig } from '../../utils/channel-config';
-import { syncAllProviderAuthToRuntime } from '../../services/providers/provider-runtime-sync';
+import { syncAgentModelOverrideToRuntime, syncAllProviderAuthToRuntime } from '../../services/providers/provider-runtime-sync';
 import type { HostApiContext } from '../context';
 import { parseJsonBody, sendJson } from '../route-utils';
 
@@ -151,6 +152,26 @@ export async function handleAgentRoutes(
       return true;
     }
 
+    if (parts.length === 2 && parts[1] === 'model') {
+      try {
+        const body = await parseJsonBody<{ modelRef?: string | null }>(req);
+        const agentId = decodeURIComponent(parts[0]);
+        const snapshot = await updateAgentModel(agentId, body.modelRef ?? null);
+        try {
+          await syncAllProviderAuthToRuntime();
+          // Ensure this agent's runtime model registry reflects the new model override.
+          await syncAgentModelOverrideToRuntime(agentId);
+        } catch (syncError) {
+          console.warn('[agents] Failed to sync runtime after updating agent model:', syncError);
+        }
+        scheduleGatewayReload(ctx, 'update-agent-model');
+        sendJson(res, 200, { success: true, ...snapshot });
+      } catch (error) {
+        sendJson(res, 500, { success: false, error: String(error) });
+      }
+      return true;
+    }
+
     if (parts.length === 3 && parts[1] === 'channels') {
       try {
         const agentId = decodeURIComponent(parts[0]);