fix: wire PatternEditor to mode-aware graph mutations

Replace the old disconnected-node addAgentNodeToGraph with the
mode-aware addAgentToGraph so new agents are automatically wired
into the graph topology. Replace the graph-nuking removeAgent
path with removeAgentFromGraph for surgical node removal. Split
emitChange into graph-preserving and mode-change paths so editing
agent properties no longer discards custom positions and edges.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/renderer/components/PatternEditor.tsx

@@ -18,6 +18,8 @@ import {
 import type { ApprovalCheckpointKind, ApprovalPolicy } from '@shared/domain/approval';
 import type { ModelDefinition } from '@shared/domain/models';
 import {
+  addAgentToGraph,
+  removeAgentFromGraph,
   resolvePatternGraph,
   syncPatternGraph,
   validatePatternDefinition,
@@ -35,7 +37,6 @@ import {
 } from '@shared/domain/tooling';
 
 import { ToggleSwitch } from '@renderer/components/ui';
-import { addAgentNodeToGraph } from '@renderer/lib/patternGraph';
 import { PatternGraphCanvas } from './pattern-graph/PatternGraphCanvas';
 import { PatternGraphInspector } from './pattern-graph/PatternGraphInspector';
 
@@ -143,6 +144,10 @@ export function PatternEditor({
   const graph = resolvePatternGraph(pattern);
 
   function emitChange(nextPattern: PatternDefinition) {
+    onChange({ ...nextPattern, graph: resolvePatternGraph(nextPattern) });
+  }
+
+  function emitModeChange(nextPattern: PatternDefinition) {
     onChange(syncPatternGraph(nextPattern));
   }
 
@@ -159,7 +164,7 @@ export function PatternEditor({
       model: 'gpt-5.4',
       reasoningEffort: 'high',
     };
-    const updatedGraph = addAgentNodeToGraph(graph, newAgent);
+    const updatedGraph = addAgentToGraph(graph, pattern.mode, newAgent);
     onChange({ ...pattern, agents: [...pattern.agents, newAgent], graph: updatedGraph });
   }
 
@@ -175,9 +180,11 @@ export function PatternEditor({
       return;
     }
 
-    emitChange({
+    const updatedGraph = removeAgentFromGraph(graph, pattern.mode, agentId);
+    onChange({
       ...pattern,
       agents: pattern.agents.filter((a) => a.id !== agentId),
+      graph: updatedGraph,
     });
     setSelectedNodeId(null);
   }
@@ -374,7 +381,7 @@ export function PatternEditor({
                         }`}
                         disabled={disabled}
                         key={mode}
-                        onClick={() => emitChange({ ...pattern, mode })}
+                        onClick={() => emitModeChange({ ...pattern, mode })}
                         type="button"
                       >
                         <div className="flex items-center gap-1.5">

src/renderer/lib/patternGraph.ts

@@ -246,32 +246,6 @@ export function removeEdge(graph: PatternGraph, removeEdgeId: string): PatternGr
   return { ...graph, edges: graph.edges.filter((e) => e.id !== removeEdgeId) };
 }
 
-/* ── Add disconnected agent node ───────────────────────────── */
-
-export function addAgentNodeToGraph(
-  graph: PatternGraph,
-  agent: PatternAgentDefinition,
-): PatternGraph {
-  const existingAgentNodes = graph.nodes.filter((n) => n.kind === 'agent');
-  const nextOrder = existingAgentNodes.length;
-
-  // Place new node below existing agent nodes
-  const maxY = existingAgentNodes.reduce((max, n) => Math.max(max, n.position.y), 0);
-  const avgX = existingAgentNodes.length > 0
-    ? Math.round(existingAgentNodes.reduce((sum, n) => sum + n.position.x, 0) / existingAgentNodes.length)
-    : 400;
-
-  const newNode: PatternGraphNode = {
-    id: `agent-node-${agent.id}`,
-    kind: 'agent',
-    agentId: agent.id,
-    order: nextOrder,
-    position: { x: avgX, y: maxY + 120 },
-  };
-
-  return { ...graph, nodes: [...graph.nodes, newNode] };
-}
-
 /* ── Sequential reorder ────────────────────────────────────── */
 
 export function swapSequentialOrder(

tests/renderer/patternGraph.test.ts

@@ -1,8 +1,7 @@
 import { describe, expect, test } from 'bun:test';
 
-import { createBuiltinPatterns, resolvePatternGraph, type PatternDefinition } from '@shared/domain/pattern';
+import { addAgentToGraph, createBuiltinPatterns, resolvePatternGraph, type PatternDefinition } from '@shared/domain/pattern';
 import {
-  addAgentNodeToGraph,
   addEdge,
   autoLayoutGraph,
   canMoveSequential,
@@ -208,20 +207,20 @@ describe('pattern graph mutation helpers', () => {
     expect(updated.edges.find((e) => e.id === firstEdge.id)).toBeUndefined();
   });
 
-  test('addAgentNodeToGraph places a disconnected agent node on the canvas', () => {
+  test('addAgentToGraph inserts a wired agent node for sequential mode', () => {
     const pattern = findPattern('sequential');
     const graph = resolvePatternGraph(pattern);
     const newAgent = { id: 'new-1', name: 'New Agent', description: '', instructions: '', model: 'gpt-5.4' };
 
-    const updated = addAgentNodeToGraph(graph, newAgent);
+    const updated = addAgentToGraph(graph, pattern.mode, newAgent);
     expect(updated.nodes.length).toBe(graph.nodes.length + 1);
 
     const newNode = updated.nodes.find((n) => n.agentId === 'new-1');
     expect(newNode).toBeDefined();
     expect(newNode!.kind).toBe('agent');
 
-    // No new edges added — node is disconnected
-    expect(updated.edges.length).toBe(graph.edges.length);
+    // New agent is wired into the chain, so edge count stays at agents+1
+    expect(updated.edges.length).toBe(graph.edges.length + 1);
   });
 });