From e47835c1e856731a1054a66bf3f31907613b7442 Mon Sep 17 00:00:00 2001
From: David Kaya <david@kaya.sk>
Date: Sun, 5 Apr 2026 21:37:01 +0200
Subject: [PATCH] fix(workflows): disable start/end palette buttons when node
 already exists

Prevents users from adding duplicate start or end nodes, which made the
workflow invalid with no way to recover since those node kinds are
protected from deletion.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 src/renderer/components/WorkflowEditor.tsx           |  9 ++++++++-
 .../components/workflow/WorkflowNodePalette.tsx      | 12 ++++++++++--
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/renderer/components/WorkflowEditor.tsx b/src/renderer/components/WorkflowEditor.tsx
index 9b1f1d2..66835f5 100644
--- a/src/renderer/components/WorkflowEditor.tsx
+++ b/src/renderer/components/WorkflowEditor.tsx
@@ -182,6 +182,13 @@ export function WorkflowEditor({
 
   const issues = validateWorkflowDefinition(activeWorkflow);
 
+  const disabledPaletteKinds = useMemo(() => {
+    const disabled = new Set<WorkflowNodeKind>();
+    if (activeWorkflow.graph.nodes.some((n) => n.kind === 'start')) disabled.add('start');
+    if (activeWorkflow.graph.nodes.some((n) => n.kind === 'end')) disabled.add('end');
+    return disabled;
+  }, [activeWorkflow.graph.nodes]);
+
   /* ── Change propagation ─────────────────────────────────── */
 
   function propagateActiveChange(updatedActive: WorkflowDefinition) {
@@ -482,7 +489,7 @@ export function WorkflowEditor({
       <div className="flex min-h-0 flex-1">
         {/* Left palette */}
         <div className="w-40 shrink-0 overflow-y-auto border-r border-[var(--color-border)] bg-[var(--color-surface-1)]">
-          <WorkflowNodePalette onAddNode={handleAddNode} />
+          <WorkflowNodePalette disabledKinds={disabledPaletteKinds} onAddNode={handleAddNode} />
         </div>
 
         {/* Center column: validation + canvas + settings */}
diff --git a/src/renderer/components/workflow/WorkflowNodePalette.tsx b/src/renderer/components/workflow/WorkflowNodePalette.tsx
index 3a46ebd..6788bde 100644
--- a/src/renderer/components/workflow/WorkflowNodePalette.tsx
+++ b/src/renderer/components/workflow/WorkflowNodePalette.tsx
@@ -4,6 +4,7 @@ import type { WorkflowNodeKind } from '@shared/domain/workflow';
 
 interface WorkflowNodePaletteProps {
   onAddNode: (kind: WorkflowNodeKind) => void;
+  disabledKinds?: ReadonlySet<WorkflowNodeKind>;
 }
 
 interface PaletteItem {
@@ -48,7 +49,7 @@ const paletteGroups: PaletteGroup[] = [
   },
 ];
 
-export function WorkflowNodePalette({ onAddNode }: WorkflowNodePaletteProps) {
+export function WorkflowNodePalette({ onAddNode, disabledKinds }: WorkflowNodePaletteProps) {
   return (
     <div className="space-y-4 p-3">
       <h4 className="text-[10px] font-semibold uppercase tracking-wider text-[var(--color-text-muted)]">
@@ -62,11 +63,18 @@ export function WorkflowNodePalette({ onAddNode }: WorkflowNodePaletteProps) {
           <div className="space-y-0.5">
             {group.items.map((item) => {
               const Icon = item.icon;
+              const disabled = disabledKinds?.has(item.kind) ?? false;
               return (
                 <button
-                  className="flex w-full items-center gap-2 rounded-lg px-2 py-1.5 text-left text-[12px] text-[var(--color-text-secondary)] transition-all duration-200 hover:bg-[var(--color-surface-3)] hover:text-[var(--color-text-primary)]"
+                  className={`flex w-full items-center gap-2 rounded-lg px-2 py-1.5 text-left text-[12px] transition-all duration-200 ${
+                    disabled
+                      ? 'cursor-not-allowed text-[var(--color-text-muted)] opacity-40'
+                      : 'text-[var(--color-text-secondary)] hover:bg-[var(--color-surface-3)] hover:text-[var(--color-text-primary)]'
+                  }`}
+                  disabled={disabled}
                   key={item.kind}
                   onClick={() => onAddNode(item.kind)}
+                  title={disabled ? `${item.label} node already exists` : undefined}
                   type="button"
                 >
                   <Icon className={`size-3.5 ${item.color}`} />