refactor: deduplicate label assignment and simplify line budget logic

- Hoist label assignment before the skip/emit branch in getTree walk
- Precompute lineLimit once instead of recalculating reserve on every
  addLine call

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: piotrski

packages/agent-react-devtools/src/__tests__/component-tree.test.ts

@@ -489,7 +489,6 @@ describe('ComponentTree', () => {
       // With noHost, div is skipped so Header is at depth 1, Deep at depth 2
       const filtered = tree.getTree({ noHost: true, maxDepth: 1 });
       expect(filtered.map((n) => n.displayName)).toEqual(['App', 'Header']);
->>>>>>> ff2ef20 (test: add tests for tree truncation and host filtering)
     });
   });
 });

packages/agent-react-devtools/src/component-tree.ts

@@ -410,14 +410,20 @@ export class ComponentTree {
       if (!node) return;
       if (maxDepth !== undefined && depth > maxDepth) return;
 
+      // Assign label for every node (even skipped hosts) so IDs stay stable
+      const label = `@c${labelCounter++}`;
+      this.labelToId.set(label, node.id);
+      this.idToLabel.set(node.id, label);
+
       // Check if this host node should be filtered out
       const skipThis = noHost && node.type === 'host' && !isSignificantHost(node);
 
-      if (!skipThis) {
-        const label = `@c${labelCounter++}`;
-        this.labelToId.set(label, node.id);
-        this.idToLabel.set(node.id, label);
-
+      if (skipThis) {
+        // Promote children to the effective parent at the same depth
+        for (const childId of node.children) {
+          walk(childId, depth, effectiveParentId);
+        }
+      } else {
         const treeNode: TreeNode = {
           id: node.id,
           label,
@@ -435,16 +441,6 @@ export class ComponentTree {
         for (const childId of node.children) {
           walk(childId, depth + 1, node.id);
         }
-      } else {
-        // Labels are still assigned for skipped host nodes so IDs stay stable
-        const label = `@c${labelCounter++}`;
-        this.labelToId.set(label, node.id);
-        this.idToLabel.set(node.id, label);
-
-        // Skip this node: promote children to the effective parent at the same depth
-        for (const childId of node.children) {
-          walk(childId, depth, effectiveParentId);
-        }
       }
     };
 

packages/agent-react-devtools/src/formatters.ts

@@ -93,13 +93,15 @@ export function formatTree(nodes: TreeNode[], hintOrOpts?: string | FormatTreeOp
 
   const lines: string[] = [];
   let truncated = false;
+  // Reserve lines for truncation message (+1) and optional summary footer
+  const lineLimit = maxLines !== undefined
+    ? maxLines - (totalCount !== undefined ? 1 : 0) - 1
+    : Infinity;
 
   function addLine(line: string): boolean {
-    // Reserve lines for truncation message and summary footer
-    const reserve = (totalCount !== undefined ? 1 : 0) + 1; // +1 for truncation line
-    if (maxLines !== undefined && lines.length >= maxLines - reserve) {
+    if (lines.length >= lineLimit) {
       truncated = true;
-      return false; // signal: stop adding
+      return false;
     }
     lines.push(line);
     return true;