feat(cli): overhaul thinking UI (#18725)

packages/core/src/utils/sessionUtils.ts

@@ -51,15 +51,24 @@ export function convertSessionToClientHistory(
         parts: ensurePartArray(msg.content),
       });
     } else if (msg.type === 'gemini') {
+      const modelParts: Part[] = [];
+
+      // Add thoughts if present
+      if (msg.thoughts && msg.thoughts.length > 0) {
+        for (const thought of msg.thoughts) {
+          const thoughtText = thought.subject
+            ? `**${thought.subject}** ${thought.description}`
+            : thought.description;
+          modelParts.push({
+            text: thoughtText,
+            thought: true,
+          } as Part);
+        }
+      }
+
       const hasToolCalls = msg.toolCalls && msg.toolCalls.length > 0;
 
       if (hasToolCalls) {
-        const modelParts: Part[] = [];
-
-        // TODO: Revisit if we should preserve more than just Part metadata (e.g. thoughtSignatures)
-        // currently those are only required within an active loop turn which resume clears
-        // by forcing a new user text prompt.
-
         // Preserve original parts to maintain multimodal integrity
         if (msg.content) {
           modelParts.push(...ensurePartArray(msg.content));
@@ -114,14 +123,14 @@ export function convertSessionToClientHistory(
         }
       } else {
         if (msg.content) {
-          const parts = ensurePartArray(msg.content);
+          modelParts.push(...ensurePartArray(msg.content));
+        }
 
-          if (parts.length > 0) {
-            clientHistory.push({
-              role: 'model',
-              parts,
-            });
-          }
+        if (modelParts.length > 0) {
+          clientHistory.push({
+            role: 'model',
+            parts: modelParts,
+          });
         }
       }
     }