diff --git a/src/ai/tools.ts b/src/ai/tools.ts
index 4c463d7..f4ce836 100644
--- a/src/ai/tools.ts
+++ b/src/ai/tools.ts
@@ -201,5 +201,5 @@ export async function applyProposal(ctrl: Controller, p: Proposal): Promise<bool
   if (p.kind === 'remove') return (await ctrl.remove(p.nodeId)) !== null
   const node = await ctrl.node(p.nodeId, true)
   const patch = patchForPath(node.data ?? {}, parsePath(p.path), p.after)
-  return (await ctrl.setData(node.id, patch, { version: node.version })) !== null
+  return (await ctrl.saveData(node.id, node.data ?? {}, patch)) !== null
 }
diff --git a/src/controller.ts b/src/controller.ts
index 2614222..89dc4d9 100644
--- a/src/controller.ts
+++ b/src/controller.ts
@@ -615,6 +615,31 @@ export class Controller {
     return this.apply([op], { coalesce: opts.coalesce })
   }
 
+  /**
+   * Save a dialog's patch. `base` is the data the dialog started from, `patch` the keys it changed.
+   *
+   * Do NOT send the dialog's `node.version`: every other edit to the node (style chips, drag handles,
+   * inline text, moving/inserting a child) bumps it while the dialog is open, so the save would 409
+   * against the user's own earlier edits. Instead compare per key against the *current* node: only a
+   * key someone changed since the dialog opened is a real conflict. `set` merges top-level keys, so
+   * the untouched keys are safe to leave alone.
+   */
+  async saveData(id: string, base: Record<string, unknown>, patch: Record<string, unknown>) {
+    let fresh: CmsNode
+    try {
+      fresh = await this.node(id, true)
+    } catch (e) {
+      this.fail(e)
+      return null
+    }
+    const clash = Object.keys(patch).filter((k) => JSON.stringify(fresh.data?.[k] ?? null) !== JSON.stringify(base[k] ?? null))
+    if (clash.length) {
+      this.toast('error', `Someone else changed ${clash.join(', ')} - reopen it and retry`)
+      return null
+    }
+    return this.setData(id, patch)
+  }
+
   async insert(parent: string, type: string, opts: { index?: number; handle?: string; data?: Record<string, unknown> } = {}) {
     const res = await this.apply([{ op: 'insert', parent, type, ...opts }])
     const created = res?.results[0]?.node
@@ -1111,7 +1136,7 @@ export class Controller {
     const msg =
       e instanceof EditError || e instanceof ApiError
         ? e.status === 409
-          ? 'Someone else changed this node - reopen it and retry'
+          ? `Conflict: ${e.message} - reopen it and retry`
           : e.status === 401 || e.status === 403
             ? `Not allowed (${e.status}): ${e.message}`
             : e.message
diff --git a/src/editors/builtin.tsx b/src/editors/builtin.tsx
index cdb6c6b..6a4291d 100644
--- a/src/editors/builtin.tsx
+++ b/src/editors/builtin.tsx
@@ -27,7 +27,7 @@ function Properties({ node, schema, ctrl, close }: EditorProps) {
   const changed = Object.keys(patch).length > 0
   const save = async () => {
     setSaving(true)
-    const res = await ctrl.setData(node.id, patch, { version: node.version })
+    const res = await ctrl.saveData(node.id, node.data ?? {}, patch)
     setSaving(false)
     if (res) close()
   }
@@ -70,7 +70,7 @@ function RawJson({ node, ctrl, close }: EditorProps) {
       <JsonArea value={node.data ?? {}} onChange={setDraft} />
       {Object.keys(patch).length > 0 && (
         <footer className="cms-actions">
-          <button className="cms-btn cms-btn--primary" onClick={async () => (await ctrl.setData(node.id, patch, { version: node.version })) && close()}>
+          <button className="cms-btn cms-btn--primary" onClick={async () => (await ctrl.saveData(node.id, node.data ?? {}, patch)) && close()}>
             <Icon name="save" size={16} /> Save
           </button>
         </footer>
diff --git a/test/assistant.test.ts b/test/assistant.test.ts
index 72ea609..d4a88dd 100644
--- a/test/assistant.test.ts
+++ b/test/assistant.test.ts
@@ -8,8 +8,10 @@ const node = { id: 'n1', dataType: 'hero', version: 3, data: { title: 'Hello wro
 
 function fakeCtrl() {
   const setData = vi.fn(async () => ({}))
+  const saveData = vi.fn(async () => ({}))
   return {
     setData,
+    saveData,
     ctrl: {
       store: { get: () => ({ selected: 'n1', blocks: [{ id: 'n1', type: 'hero', depth: 0 }] }) },
       block: (id: string) => (id === 'n1' ? { id } : undefined),
@@ -19,6 +21,7 @@ function fakeCtrl() {
       schema: async () => schema,
       labelFor: () => 'Hero',
       setData,
+      saveData,
     } as any,
   }
 }
@@ -80,10 +83,10 @@ describe('runAgent + tools', () => {
 })
 
 describe('applyProposal', () => {
-  it('rebuilds the nested patch from the fresh node and saves with its version', async () => {
-    const { ctrl, setData } = fakeCtrl()
+  it('rebuilds the nested patch from the fresh node and saves it through the key-level conflict check', async () => {
+    const { ctrl, saveData } = fakeCtrl()
     await applyProposal(ctrl, { id: 1, kind: 'set', nodeId: 'n1', label: 'Hero', path: 'links.0.text', before: 'a', after: 'b' })
-    expect(setData).toHaveBeenCalledWith('n1', { links: [{ text: 'b' }] }, { version: 3 })
+    expect(saveData).toHaveBeenCalledWith('n1', node.data, { links: [{ text: 'b' }] })
   })
 })
 
diff --git a/test/editor.test.tsx b/test/editor.test.tsx
index ce7e2d7..fd6ec2c 100644
--- a/test/editor.test.tsx
+++ b/test/editor.test.tsx
@@ -100,7 +100,7 @@ describe('on-page editor against the mock CMS', () => {
     expect(h.cms.graph.node('s1').data).toMatchObject({ title: 'Hello', tone: 'dark', padded: true })
     expect(byId('s1').querySelector('.sec__title')!.textContent).toBe('Hello')
     const edit = h.editor.ctrl.store.get().log.find((l) => l.url === '/api/edit')!
-    expect((edit.request as any).ops[0]).toMatchObject({ op: 'set', id: 's1', data: { title: 'Hello' }, version: 1 })
+    expect((edit.request as any).ops[0]).toMatchObject({ op: 'set', id: 's1', data: { title: 'Hello' } })
   })
 
   it('array editors save through the dialog as a minimal diff, and invalid data blocks Save', async () => {
@@ -126,6 +126,25 @@ describe('on-page editor against the mock CMS', () => {
     expect(Object.keys(op.ops[0].data)).toEqual(['links']) // companyName, usps, social... untouched
   })
 
+  it('edits to OTHER fields of the node while the dialog is open do not conflict (the dialog does not pin a version)', async () => {
+    h = await setup()
+    await selectBlock('s1')
+    await h.press('Properties')
+    // style chip / drag handle / inline edit on the same node bump its version under the open dialog
+    await h.editor.ctrl.setData('s1', { tone: 'accent' })
+    await h.editor.ctrl.setData('s1', { padded: false })
+    const input = h.shadow.querySelector<HTMLInputElement>('[data-path="title"] input')!
+    const set = Object.getOwnPropertyDescriptor(HTMLInputElement.prototype, 'value')!.set!
+    await act(async () => {
+      set.call(input, 'Mine')
+      input.dispatchEvent(new Event('input', { bubbles: true }))
+    })
+    await act(async () => void h.shadow.querySelector<HTMLElement>('.cms-btn--primary')!.click())
+    await h.settle()
+    expect(h.cms.graph.node('s1').data).toMatchObject({ title: 'Mine', tone: 'accent', padded: false })
+    expect(h.editor.ctrl.store.get().toast?.kind).not.toBe('error')
+  })
+
   it('a stale version shows a conflict instead of overwriting', async () => {
     h = await setup()
     await selectBlock('s1')