From 60b71d639bfcce6baf7007a3720355c6babbc73b Mon Sep 17 00:00:00 2001
From: marcone tenorio <marconetsf@gmail.com>
Date: Mon, 11 May 2026 10:33:44 +0200
Subject: [PATCH 1/4] fix(ethercat): prevent slave name collisions across
 masters [DOPE-281]

- Source slave name from <Type> (short, e.g. "EL1809") instead of the long <Name LcId> descriptor.
- Auto-suffix _NN at creation when the base collides with any existing slave in any master.
- Reject rename to a name already taken by another slave, matching the pattern used by POU/datatype/master renames.
- Re-add the long ESI descriptor as a subtitle below the slave header now that the title shows the short form.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../__tests__/unique-slave-name.test.ts       |  59 ++++++++
 .../shared/ethercat/unique-slave-name.ts      |  44 ++++++
 .../ethercat/ethercat-device-editor.tsx       |   3 +
 .../editor/device/ethercat/index.tsx          |  19 ++-
 .../store/__tests__/shared-slice.test.ts      | 126 ++++++++++++++++++
 src/frontend/store/slices/shared/slice.ts     |   7 +
 6 files changed, 256 insertions(+), 2 deletions(-)
 create mode 100644 src/backend/shared/ethercat/__tests__/unique-slave-name.test.ts
 create mode 100644 src/backend/shared/ethercat/unique-slave-name.ts

diff --git a/src/backend/shared/ethercat/__tests__/unique-slave-name.test.ts b/src/backend/shared/ethercat/__tests__/unique-slave-name.test.ts
new file mode 100644
index 000000000..70122fe78
--- /dev/null
+++ b/src/backend/shared/ethercat/__tests__/unique-slave-name.test.ts
@@ -0,0 +1,59 @@
+import { collectAllSlaveNames, generateUniqueSlaveName } from '../unique-slave-name'
+
+describe('collectAllSlaveNames', () => {
+  it('returns empty set when remoteDevices is undefined', () => {
+    expect(collectAllSlaveNames(undefined)).toEqual(new Set())
+  })
+
+  it('returns empty set when there are no remote devices', () => {
+    expect(collectAllSlaveNames([])).toEqual(new Set())
+  })
+
+  it('returns empty set when remote devices have no ethercat config', () => {
+    expect(collectAllSlaveNames([{}, { ethercatConfig: undefined }])).toEqual(new Set())
+  })
+
+  it('returns empty set when ethercat config has no devices array', () => {
+    expect(collectAllSlaveNames([{ ethercatConfig: {} }])).toEqual(new Set())
+  })
+
+  it('collects names from a single master', () => {
+    const result = collectAllSlaveNames([
+      { ethercatConfig: { devices: [{ name: 'EL1809' }, { name: 'EL2008' }] } },
+    ])
+    expect(result).toEqual(new Set(['EL1809', 'EL2008']))
+  })
+
+  it('collects names across multiple masters and deduplicates', () => {
+    const result = collectAllSlaveNames([
+      { ethercatConfig: { devices: [{ name: 'EL1809' }, { name: 'EL2008' }] } },
+      { ethercatConfig: { devices: [{ name: 'EL1809' }, { name: 'EL3104' }] } },
+    ])
+    expect(result).toEqual(new Set(['EL1809', 'EL2008', 'EL3104']))
+  })
+})
+
+describe('generateUniqueSlaveName', () => {
+  it('returns base when not taken', () => {
+    expect(generateUniqueSlaveName('EL1809', [])).toBe('EL1809')
+    expect(generateUniqueSlaveName('EL1809', ['EL2008'])).toBe('EL1809')
+  })
+
+  it('returns _01 suffix on first collision', () => {
+    expect(generateUniqueSlaveName('EL1809', ['EL1809'])).toBe('EL1809_01')
+  })
+
+  it('skips taken suffixes and picks the next free one', () => {
+    expect(generateUniqueSlaveName('EL1809', ['EL1809', 'EL1809_01', 'EL1809_02'])).toBe('EL1809_03')
+  })
+
+  it('pads single digits to two digits and widens past 99', () => {
+    const taken = new Set<string>(['EL1809'])
+    for (let i = 1; i <= 99; i++) taken.add(`EL1809_${String(i).padStart(2, '0')}`)
+    expect(generateUniqueSlaveName('EL1809', taken)).toBe('EL1809_100')
+  })
+
+  it('accepts a Set directly as the existing argument', () => {
+    expect(generateUniqueSlaveName('EL1809', new Set(['EL1809']))).toBe('EL1809_01')
+  })
+})
diff --git a/src/backend/shared/ethercat/unique-slave-name.ts b/src/backend/shared/ethercat/unique-slave-name.ts
new file mode 100644
index 000000000..cf14680cf
--- /dev/null
+++ b/src/backend/shared/ethercat/unique-slave-name.ts
@@ -0,0 +1,44 @@
+/**
+ * Helpers to ensure EtherCAT slave names are unique within a project.
+ *
+ * Slaves with the same name across different masters used to collide in the
+ * UI's name-keyed slices (tabs/editor/file). Dedup happens at creation time
+ * by appending `_01`, `_02`, … to the base name when it clashes with any
+ * existing slave in any master.
+ */
+
+type RemoteDeviceForNameCollection = {
+  ethercatConfig?: {
+    devices?: Array<{ name: string }>
+  }
+}
+
+/**
+ * Collect every EtherCAT slave name currently configured across all masters.
+ */
+export function collectAllSlaveNames(remoteDevices: RemoteDeviceForNameCollection[] | undefined): Set<string> {
+  const names = new Set<string>()
+  if (!remoteDevices) return names
+
+  for (const rd of remoteDevices) {
+    for (const dev of rd.ethercatConfig?.devices ?? []) {
+      names.add(dev.name)
+    }
+  }
+  return names
+}
+
+/**
+ * Return `base` if unused, otherwise the first `${base}_NN` (two-digit padded)
+ * not present in `existing`. Pad widens past 99 automatically.
+ */
+export function generateUniqueSlaveName(base: string, existing: Iterable<string>): string {
+  const taken = new Set(existing)
+  let candidate = base
+  let i = 0
+  while (taken.has(candidate)) {
+    i++
+    candidate = `${base}_${String(i).padStart(2, '0')}`
+  }
+  return candidate
+}
diff --git a/src/frontend/components/_features/[workspace]/editor/device/ethercat/ethercat-device-editor.tsx b/src/frontend/components/_features/[workspace]/editor/device/ethercat/ethercat-device-editor.tsx
index 05155f4bd..dcbd6caf7 100644
--- a/src/frontend/components/_features/[workspace]/editor/device/ethercat/ethercat-device-editor.tsx
+++ b/src/frontend/components/_features/[workspace]/editor/device/ethercat/ethercat-device-editor.tsx
@@ -224,6 +224,9 @@ const EtherCATDeviceEditor = () => {
       {/* Header */}
       <div className='mb-4 shrink-0'>
         <h2 className='text-lg font-semibold text-neutral-1000 dark:text-neutral-100'>{device.name}</h2>
+        {esiDevice?.name && esiDevice.name !== device.name && (
+          <p className='mt-0.5 text-xs text-neutral-500 dark:text-neutral-400'>{esiDevice.name}</p>
+        )}
       </div>
 
       {/* Tabs */}
diff --git a/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx b/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
index 2d2234a89..e5ebc40b0 100644
--- a/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
+++ b/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
@@ -3,6 +3,7 @@ import { collectUsedIecAddresses } from '@root/backend/shared/ethercat/collect-u
 import { createDefaultSlaveConfig } from '@root/backend/shared/ethercat/device-config-defaults'
 import { matchDevicesToRepository } from '@root/backend/shared/ethercat/device-matcher'
 import { enrichDeviceData } from '@root/backend/shared/ethercat/enrich-device-data'
+import { collectAllSlaveNames, generateUniqueSlaveName } from '@root/backend/shared/ethercat/unique-slave-name'
 import type { EtherCATMasterConfig } from '@root/backend/shared/types/PLC/open-plc'
 import { Modal, ModalContent, ModalTitle } from '@root/frontend/components/_molecules/modal'
 import { useOpenPLCStore } from '@root/frontend/store'
@@ -379,6 +380,9 @@ const EtherCATEditor = () => {
     const unmatched: ScannedDeviceMatch['device'][] = []
     const existingPositions = new Set(configuredDevices.map((d) => d.position))
     const usedAddresses = collectUsedIecAddresses(project.data.remoteDevices)
+    // Names already taken across every master — extended as we add each
+    // device so the batch can't collide with itself either.
+    const takenNames = collectAllSlaveNames(project.data.remoteDevices)
 
     for (const position of selectedScannedDevices) {
       // Skip devices already configured at this position
@@ -406,10 +410,17 @@ const EtherCATEditor = () => {
         for (const m of enriched.channelMappings ?? []) usedAddresses.add(m.iecLocation)
       }
 
+      // Prefer the short product code from <Type> (e.g. "EL1809") over the
+      // long localized name from <Name LcId="1033"> — the long form is
+      // verbose and identical for any two units of the same model.
+      const baseName = bestMatch.esiDevice.type.name || bestMatch.esiDevice.name || match.device.name
+      const uniqueName = generateUniqueSlaveName(baseName, takenNames)
+      takenNames.add(uniqueName)
+
       newDevices.push({
         id: uuidv4(),
         position: match.device.position,
-        name: bestMatch.esiDevice.name || match.device.name,
+        name: uniqueName,
         esiDeviceRef: {
           repositoryItemId: bestMatch.repositoryItemId,
           deviceIndex: bestMatch.deviceIndex,
@@ -473,10 +484,14 @@ const EtherCATEditor = () => {
       const nextPosition =
         configuredDevices.length > 0 ? Math.max(...configuredDevices.map((d) => d.position ?? 0)) + 1 : 1
 
+      // Prefer the short product code from <Type> over the long localized name.
+      const baseName = device.type.name || device.name
+      const uniqueName = generateUniqueSlaveName(baseName, collectAllSlaveNames(project.data.remoteDevices))
+
       const newDevice: ConfiguredEtherCATDevice = {
         id: uuidv4(),
         position: nextPosition,
-        name: device.name,
+        name: uniqueName,
         esiDeviceRef: ref,
         vendorId: repoItem.vendor.id,
         productCode: device.type.productCode,
diff --git a/src/frontend/store/__tests__/shared-slice.test.ts b/src/frontend/store/__tests__/shared-slice.test.ts
index d4dd285b2..6769e929a 100644
--- a/src/frontend/store/__tests__/shared-slice.test.ts
+++ b/src/frontend/store/__tests__/shared-slice.test.ts
@@ -773,6 +773,132 @@ describe('createSharedSlice', () => {
     })
   })
 
+  // =========================================================================
+  // ethercatDeviceActions
+  // =========================================================================
+  describe('ethercatDeviceActions', () => {
+    function addEthercatBus(name: string, slaves: Array<{ id: string; name: string }>) {
+      store.getState().projectActions.createRemoteDevice({
+        data: { name, protocol: 'ethercat' },
+      })
+      store.getState().projectActions.updateEthercatConfig(name, {
+        masterConfig: { networkInterface: 'eth0', cycleTimeUs: 1000, watchdogTimeoutCycles: 3 },
+        devices: slaves as never,
+      })
+      for (const slave of slaves) {
+        store
+          .getState()
+          .editorActions.addModel({ type: 'plc-remote-device', meta: { name: slave.name, protocol: 'ethercat' } })
+        store.getState().fileActions.addFile({ name: slave.name, type: 'ethercat-device', filePath: name })
+        store.getState().tabsActions.updateTabs({
+          name: slave.name,
+          elementType: { type: 'ethercat-device', busName: name, deviceId: slave.id },
+        })
+      }
+    }
+
+    // -----------------------------------------------------------------------
+    // delete
+    // -----------------------------------------------------------------------
+    describe('delete', () => {
+      beforeEach(() => {
+        addEthercatBus('bus1', [{ id: 'slave-1', name: 'EK1100' }])
+      })
+
+      it('removes the slave from project, files, tabs and editor', () => {
+        store.getState().editorActions.setEditor({
+          type: 'plc-remote-device',
+          meta: { name: 'EK1100', protocol: 'ethercat' },
+        })
+
+        const result = store.getState().ethercatDeviceActions.delete('bus1', 'slave-1')
+        expect(result).toEqual({ ok: true })
+
+        const state = store.getState()
+        const bus = state.project.data.remoteDevices?.find((d) => d.name === 'bus1')
+        expect(bus?.ethercatConfig?.devices).toHaveLength(0)
+        expect(state.files['EK1100']).toBeUndefined()
+        expect(state.tabs.some((t) => t.name === 'EK1100')).toBe(false)
+        expect(state.editor.type).toBe('available')
+      })
+
+      it('returns error when the bus does not exist', () => {
+        const result = store.getState().ethercatDeviceActions.delete('missing-bus', 'slave-1')
+        expect(result).toEqual({ ok: false, message: 'Bus not found' })
+      })
+
+      it('returns error when the slave id does not exist', () => {
+        const result = store.getState().ethercatDeviceActions.delete('bus1', 'missing-slave')
+        expect(result).toEqual({ ok: false, message: 'EtherCAT device not found' })
+      })
+
+      it('does not clear the editor when a different slave is active', () => {
+        store.getState().editorActions.setEditor({
+          type: 'plc-remote-device',
+          meta: { name: 'other-device', protocol: 'ethercat' },
+        })
+        store.getState().ethercatDeviceActions.delete('bus1', 'slave-1')
+        expect(store.getState().editor.meta.name).toBe('other-device')
+      })
+    })
+
+    // -----------------------------------------------------------------------
+    // rename
+    // -----------------------------------------------------------------------
+    describe('rename', () => {
+      beforeEach(() => {
+        addEthercatBus('bus1', [
+          { id: 'slave-1', name: 'EK1100' },
+          { id: 'slave-2', name: 'EL1809' },
+        ])
+        addEthercatBus('bus2', [{ id: 'slave-3', name: 'EL1809_01' }])
+      })
+
+      it('renames the slave across project, files and tabs', () => {
+        const result = store.getState().ethercatDeviceActions.rename('bus1', 'slave-1', 'EK1100-renamed')
+        expect(result).toEqual({ ok: true })
+
+        const state = store.getState()
+        const bus = state.project.data.remoteDevices?.find((d) => d.name === 'bus1')
+        const slave = bus?.ethercatConfig?.devices?.find((d) => d.id === 'slave-1')
+        expect(slave?.name).toBe('EK1100-renamed')
+        expect(state.files['EK1100-renamed']).toBeDefined()
+        expect(state.files['EK1100']).toBeUndefined()
+        expect(state.tabs.some((t) => t.name === 'EK1100-renamed')).toBe(true)
+      })
+
+      it('rejects renaming to a name already used by another slave in the same bus', () => {
+        const result = store.getState().ethercatDeviceActions.rename('bus1', 'slave-1', 'EL1809')
+        expect(result.ok).toBe(false)
+        expect(result.message).toContain('EL1809')
+        const state = store.getState()
+        const bus = state.project.data.remoteDevices?.find((d) => d.name === 'bus1')
+        expect(bus?.ethercatConfig?.devices?.find((d) => d.id === 'slave-1')?.name).toBe('EK1100')
+      })
+
+      it('rejects renaming to a name already used by a slave on a different bus', () => {
+        const result = store.getState().ethercatDeviceActions.rename('bus1', 'slave-2', 'EL1809_01')
+        expect(result.ok).toBe(false)
+        expect(result.message).toContain('EL1809_01')
+      })
+
+      it('allows renaming to the same name (no-op)', () => {
+        const result = store.getState().ethercatDeviceActions.rename('bus1', 'slave-1', 'EK1100')
+        expect(result).toEqual({ ok: true })
+      })
+
+      it('returns error when the bus does not exist', () => {
+        const result = store.getState().ethercatDeviceActions.rename('missing-bus', 'slave-1', 'X')
+        expect(result).toEqual({ ok: false, message: 'Bus not found' })
+      })
+
+      it('returns error when the slave id does not exist', () => {
+        const result = store.getState().ethercatDeviceActions.rename('bus1', 'missing-slave', 'X')
+        expect(result).toEqual({ ok: false, message: 'EtherCAT device not found' })
+      })
+    })
+  })
+
   // =========================================================================
   // snapshotActions
   // =========================================================================
diff --git a/src/frontend/store/slices/shared/slice.ts b/src/frontend/store/slices/shared/slice.ts
index e7b98103a..f1a9b765f 100644
--- a/src/frontend/store/slices/shared/slice.ts
+++ b/src/frontend/store/slices/shared/slice.ts
@@ -1,6 +1,7 @@
 import { produce } from 'immer'
 import { StateCreator } from 'zustand'
 
+import { collectAllSlaveNames } from '../../../../backend/shared/ethercat/unique-slave-name'
 import type { PLCVariable } from '../../../../middleware/shared/ports/types'
 import { parseIecStringToVariables } from '../../../utils/generate-iec-string-to-variables'
 import { generateIecVariablesToString } from '../../../utils/generate-iec-variables-to-string'
@@ -345,6 +346,12 @@ const createSharedSlice: StateCreator<SharedRootState, [], [], SharedSlice> = (s
       if (!device) return { ok: false, message: 'EtherCAT device not found' }
 
       const oldName = device.name
+      // Reject if another slave (any master) already owns the target name.
+      // Same-name rename is a no-op the UI short-circuits before us, but we
+      // still allow it here so the action stays idempotent.
+      if (newName !== oldName && collectAllSlaveNames(state.project.data.remoteDevices).has(newName)) {
+        return { ok: false, message: `An EtherCAT slave named "${newName}" already exists in this project` }
+      }
       const updatedDevices = devices.map((d) => (d.id === deviceId ? { ...d, name: newName } : d))
       state.projectActions.updateEthercatConfig(busName, {
         masterConfig: remoteDevice.ethercatConfig?.masterConfig ?? {

From 018f7fed905677b7ba3d4d19e6d7f910fa3f3936 Mon Sep 17 00:00:00 2001
From: marcone tenorio <marconetsf@gmail.com>
Date: Mon, 11 May 2026 10:58:20 +0200
Subject: [PATCH 2/4] fix(ethercat): move slave-name dedup helper to
 frontend/utils [DOPE-281]
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The helper was misplaced under backend/shared/ethercat/, which made the
store import violate the layer rule "Store must not import from Backend
Shared". Move it to frontend/utils/ alongside next-name.ts and
ethercat-status.ts — the conventional location for pure helpers shared
between store and components.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../_features/[workspace]/editor/device/ethercat/index.tsx      | 2 +-
 src/frontend/store/slices/shared/slice.ts                       | 2 +-
 .../utils}/__tests__/unique-slave-name.test.ts                  | 0
 .../shared/ethercat => frontend/utils}/unique-slave-name.ts     | 0
 4 files changed, 2 insertions(+), 2 deletions(-)
 rename src/{backend/shared/ethercat => frontend/utils}/__tests__/unique-slave-name.test.ts (100%)
 rename src/{backend/shared/ethercat => frontend/utils}/unique-slave-name.ts (100%)

diff --git a/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx b/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
index e5ebc40b0..6fbfdd169 100644
--- a/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
+++ b/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
@@ -3,11 +3,11 @@ import { collectUsedIecAddresses } from '@root/backend/shared/ethercat/collect-u
 import { createDefaultSlaveConfig } from '@root/backend/shared/ethercat/device-config-defaults'
 import { matchDevicesToRepository } from '@root/backend/shared/ethercat/device-matcher'
 import { enrichDeviceData } from '@root/backend/shared/ethercat/enrich-device-data'
-import { collectAllSlaveNames, generateUniqueSlaveName } from '@root/backend/shared/ethercat/unique-slave-name'
 import type { EtherCATMasterConfig } from '@root/backend/shared/types/PLC/open-plc'
 import { Modal, ModalContent, ModalTitle } from '@root/frontend/components/_molecules/modal'
 import { useOpenPLCStore } from '@root/frontend/store'
 import { cn } from '@root/frontend/utils/cn'
+import { collectAllSlaveNames, generateUniqueSlaveName } from '@root/frontend/utils/unique-slave-name'
 import type {
   ConfiguredEtherCATDevice,
   ESIDeviceRef,
diff --git a/src/frontend/store/slices/shared/slice.ts b/src/frontend/store/slices/shared/slice.ts
index 942749670..c640a8fff 100644
--- a/src/frontend/store/slices/shared/slice.ts
+++ b/src/frontend/store/slices/shared/slice.ts
@@ -1,12 +1,12 @@
 import { produce } from 'immer'
 import { StateCreator } from 'zustand'
 
-import { collectAllSlaveNames } from '../../../../backend/shared/ethercat/unique-slave-name'
 import type { PLCVariable } from '../../../../middleware/shared/ports/types'
 import { parseIecStringToVariables } from '../../../utils/generate-iec-string-to-variables'
 import { generateIecVariablesToString } from '../../../utils/generate-iec-variables-to-string'
 import { syncNodesWithVariables, syncNodesWithVariablesFBD } from '../../../utils/graphical/sync-nodes-with-variables'
 import { toast } from '../../../utils/toast'
+import { collectAllSlaveNames } from '../../../utils/unique-slave-name'
 import type { FBDFlowType } from '../fbd'
 import type { FileSliceDataObject } from '../file'
 import type { HistorySnapshot } from '../history'
diff --git a/src/backend/shared/ethercat/__tests__/unique-slave-name.test.ts b/src/frontend/utils/__tests__/unique-slave-name.test.ts
similarity index 100%
rename from src/backend/shared/ethercat/__tests__/unique-slave-name.test.ts
rename to src/frontend/utils/__tests__/unique-slave-name.test.ts
diff --git a/src/backend/shared/ethercat/unique-slave-name.ts b/src/frontend/utils/unique-slave-name.ts
similarity index 100%
rename from src/backend/shared/ethercat/unique-slave-name.ts
rename to src/frontend/utils/unique-slave-name.ts

From 189c134a94b4e882a59aac2e577a44b5d4d341e6 Mon Sep 17 00:00:00 2001
From: marcone tenorio <marconetsf@gmail.com>
Date: Mon, 11 May 2026 11:04:16 +0200
Subject: [PATCH 3/4] style(ethercat): apply prettier to unique-slave-name test

Inline a single-element array literal that exceeded the explicit-wrap
heuristic but fits within the 120-char width.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 src/frontend/utils/__tests__/unique-slave-name.test.ts | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/src/frontend/utils/__tests__/unique-slave-name.test.ts b/src/frontend/utils/__tests__/unique-slave-name.test.ts
index 70122fe78..b338f1dde 100644
--- a/src/frontend/utils/__tests__/unique-slave-name.test.ts
+++ b/src/frontend/utils/__tests__/unique-slave-name.test.ts
@@ -18,9 +18,7 @@ describe('collectAllSlaveNames', () => {
   })
 
   it('collects names from a single master', () => {
-    const result = collectAllSlaveNames([
-      { ethercatConfig: { devices: [{ name: 'EL1809' }, { name: 'EL2008' }] } },
-    ])
+    const result = collectAllSlaveNames([{ ethercatConfig: { devices: [{ name: 'EL1809' }, { name: 'EL2008' }] } }])
     expect(result).toEqual(new Set(['EL1809', 'EL2008']))
   })
 

From 7679a9f50137bb891a2764f583ef0bd26f03d6c0 Mon Sep 17 00:00:00 2001
From: marcone tenorio <marconetsf@gmail.com>
Date: Mon, 18 May 2026 09:41:14 +0200
Subject: [PATCH 4/4] fix(ethercat): harden short device name fallback
 [DOPE-281]

The previous chain assumed <Type> always carried text, but the ESI
schema only requires its ProductCode/RevisionNo attributes. Vendors
emitting self-closing <Type/> were silently dropping to the long
localized <Name>, defeating the readability win of short product codes.

Introduce getShortDeviceName with a tiered fallback that validates
<Type> shape, extracts SKU-shaped tokens from <Name>, and falls back
to the canonical (productCode, revisionNo) identity when nothing
readable is available. Also clarify the unique-slave-name padStart
docstring and document the rename guard as the sole rejecting
enforcement point for slave-name uniqueness across masters.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 .../editor/device/ethercat/index.tsx          |   9 +-
 src/frontend/store/slices/shared/slice.ts     |   7 +-
 .../utils/__tests__/short-device-name.test.ts | 102 ++++++++++++++++++
 src/frontend/utils/short-device-name.ts       |  46 ++++++++
 src/frontend/utils/unique-slave-name.ts       |   3 +-
 5 files changed, 157 insertions(+), 10 deletions(-)
 create mode 100644 src/frontend/utils/__tests__/short-device-name.test.ts
 create mode 100644 src/frontend/utils/short-device-name.ts

diff --git a/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx b/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
index 6fbfdd169..2e25f5e1c 100644
--- a/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
+++ b/src/frontend/components/_features/[workspace]/editor/device/ethercat/index.tsx
@@ -7,6 +7,7 @@ import type { EtherCATMasterConfig } from '@root/backend/shared/types/PLC/open-p
 import { Modal, ModalContent, ModalTitle } from '@root/frontend/components/_molecules/modal'
 import { useOpenPLCStore } from '@root/frontend/store'
 import { cn } from '@root/frontend/utils/cn'
+import { getShortDeviceName } from '@root/frontend/utils/short-device-name'
 import { collectAllSlaveNames, generateUniqueSlaveName } from '@root/frontend/utils/unique-slave-name'
 import type {
   ConfiguredEtherCATDevice,
@@ -410,10 +411,7 @@ const EtherCATEditor = () => {
         for (const m of enriched.channelMappings ?? []) usedAddresses.add(m.iecLocation)
       }
 
-      // Prefer the short product code from <Type> (e.g. "EL1809") over the
-      // long localized name from <Name LcId="1033"> — the long form is
-      // verbose and identical for any two units of the same model.
-      const baseName = bestMatch.esiDevice.type.name || bestMatch.esiDevice.name || match.device.name
+      const baseName = getShortDeviceName(bestMatch.esiDevice)
       const uniqueName = generateUniqueSlaveName(baseName, takenNames)
       takenNames.add(uniqueName)
 
@@ -484,8 +482,7 @@ const EtherCATEditor = () => {
       const nextPosition =
         configuredDevices.length > 0 ? Math.max(...configuredDevices.map((d) => d.position ?? 0)) + 1 : 1
 
-      // Prefer the short product code from <Type> over the long localized name.
-      const baseName = device.type.name || device.name
+      const baseName = getShortDeviceName(device)
       const uniqueName = generateUniqueSlaveName(baseName, collectAllSlaveNames(project.data.remoteDevices))
 
       const newDevice: ConfiguredEtherCATDevice = {
diff --git a/src/frontend/store/slices/shared/slice.ts b/src/frontend/store/slices/shared/slice.ts
index c640a8fff..e86e7bdb2 100644
--- a/src/frontend/store/slices/shared/slice.ts
+++ b/src/frontend/store/slices/shared/slice.ts
@@ -346,9 +346,10 @@ const createSharedSlice: StateCreator<SharedRootState, [], [], SharedSlice> = (s
       if (!device) return { ok: false, message: 'EtherCAT device not found' }
 
       const oldName = device.name
-      // Reject if another slave (any master) already owns the target name.
-      // Same-name rename is a no-op the UI short-circuits before us, but we
-      // still allow it here so the action stays idempotent.
+      // Only *rejecting* enforcement of slave-name uniqueness — scan-bus add
+      // auto-suffixes instead. Tabs/editor/file slices are name-keyed and break
+      // silently on duplicates, so new write paths must replicate one strategy.
+      // Same-name rename is allowed (the action stays idempotent).
       if (newName !== oldName && collectAllSlaveNames(state.project.data.remoteDevices).has(newName)) {
         return { ok: false, message: `An EtherCAT slave named "${newName}" already exists in this project` }
       }
diff --git a/src/frontend/utils/__tests__/short-device-name.test.ts b/src/frontend/utils/__tests__/short-device-name.test.ts
new file mode 100644
index 000000000..9dc8fec67
--- /dev/null
+++ b/src/frontend/utils/__tests__/short-device-name.test.ts
@@ -0,0 +1,102 @@
+import { getShortDeviceName } from '../short-device-name'
+
+const make = (
+  overrides: Partial<{ typeName: string; name: string; productCode: string; revisionNo: string }> = {},
+) => ({
+  type: {
+    name: overrides.typeName ?? '',
+    productCode: overrides.productCode ?? '0x07212C52',
+    revisionNo: overrides.revisionNo ?? '0x00110000',
+  },
+  name: overrides.name ?? '',
+})
+
+describe('getShortDeviceName', () => {
+  describe('P1: <Type> text as short code', () => {
+    it('returns <Type> text when it looks like an SKU', () => {
+      expect(getShortDeviceName(make({ typeName: 'EL1809' }))).toBe('EL1809')
+    })
+
+    it('accepts SKUs with hyphens up to 24 chars', () => {
+      expect(getShortDeviceName(make({ typeName: 'EL2521-0124-0010' }))).toBe('EL2521-0124-0010')
+    })
+
+    it('trims surrounding whitespace before evaluating', () => {
+      expect(getShortDeviceName(make({ typeName: '  EL1809  ' }))).toBe('EL1809')
+    })
+
+    it('falls through to P2 when <Type> text contains internal whitespace', () => {
+      // P1 rejects (whitespace), P2 takes first token "EK1100" — SKU-shaped, returned
+      expect(getShortDeviceName(make({ typeName: 'Generic Coupler', name: 'EK1100 EtherCAT Coupler' }))).toBe('EK1100')
+    })
+
+    it('falls through to P3 when both P1 and P2 reject but <Type> text exists', () => {
+      // P1 rejects (whitespace), P2 rejects ("Generic" has no digit), P3 returns <Type> text
+      expect(getShortDeviceName(make({ typeName: 'Generic Coupler', name: 'Generic Coupler description' }))).toBe(
+        'Generic Coupler',
+      )
+    })
+
+    it('falls through when <Type> text is longer than 24 chars', () => {
+      expect(
+        getShortDeviceName(make({ typeName: 'ExtraLongDescriptiveTypeName123', name: 'EL1809 2Ch. Digital Input' })),
+      ).toBe('EL1809')
+    })
+  })
+
+  describe('P2: first token of <Name> as SKU', () => {
+    it('extracts SKU when it leads the long name', () => {
+      expect(getShortDeviceName(make({ name: 'EL1809 2Ch. Digital Input 24V, 3ms' }))).toBe('EL1809')
+    })
+
+    it('handles comma and semicolon separators', () => {
+      expect(getShortDeviceName(make({ name: 'EK1100,EtherCAT Coupler' }))).toBe('EK1100')
+    })
+
+    it('rejects digit-leading tokens like "2-Channel"', () => {
+      // P2 rejects, P3 unavailable, P4 returns the long name as-is
+      expect(getShortDeviceName(make({ name: '2-Channel Digital Input' }))).toBe('2-Channel Digital Input')
+    })
+
+    it('rejects pure-letter tokens like "EtherCAT"', () => {
+      expect(getShortDeviceName(make({ name: 'EtherCAT Generic Slave' }))).toBe('EtherCAT Generic Slave')
+    })
+
+    it('rejects tokens shorter than 3 chars even if SKU-shaped', () => {
+      expect(getShortDeviceName(make({ name: 'A1 short token here' }))).toBe('A1 short token here')
+    })
+
+    it('rejects tokens longer than 24 chars', () => {
+      const longToken = 'X' + '1'.repeat(24)
+      expect(getShortDeviceName(make({ name: `${longToken} description` }))).toBe(`${longToken} description`)
+    })
+
+    it('accepts SKUs with mixed digits and hyphens (e.g. Omron R88D-1SN02H-ECT)', () => {
+      expect(getShortDeviceName(make({ name: 'R88D-1SN02H-ECT Servo Drive' }))).toBe('R88D-1SN02H-ECT')
+    })
+  })
+
+  describe('P3: <Type> text as last readable fallback', () => {
+    it('returns <Type> text when it has whitespace and P2 finds nothing usable', () => {
+      expect(getShortDeviceName(make({ typeName: 'Generic Coupler' }))).toBe('Generic Coupler')
+    })
+  })
+
+  describe('P4: long name as-is', () => {
+    it('returns the long name when both P1 and P2 reject', () => {
+      expect(getShortDeviceName(make({ name: 'Generic EtherCAT Slave' }))).toBe('Generic EtherCAT Slave')
+    })
+  })
+
+  describe('P5: canonical identity fallback', () => {
+    it('returns Device_{productCode}_{revisionNo} when no name is available', () => {
+      expect(getShortDeviceName(make({ productCode: '0x07212C52', revisionNo: '0x00110000' }))).toBe(
+        'Device_0x07212C52_0x00110000',
+      )
+    })
+
+    it('treats whitespace-only names as empty', () => {
+      expect(getShortDeviceName(make({ typeName: '   ', name: '   ' }))).toBe('Device_0x07212C52_0x00110000')
+    })
+  })
+})
diff --git a/src/frontend/utils/short-device-name.ts b/src/frontend/utils/short-device-name.ts
new file mode 100644
index 000000000..20ba5bc14
--- /dev/null
+++ b/src/frontend/utils/short-device-name.ts
@@ -0,0 +1,46 @@
+import type { ESIDeviceSummary } from '@root/middleware/shared/ports/esi-types'
+
+type ShortNameInput = Pick<ESIDeviceSummary, 'name' | 'type'>
+
+// SKU-shaped tokens: leading letter, ≥1 digit, only [A-Z0-9_-].
+// Rejects descriptive tokens that happen to contain a digit
+// (e.g. "2-Channel", "24V", "2Ch."), which are common when a vendor
+// puts the model code *after* the description in <Name LcId="1033">.
+const SKU_TOKEN = /^[A-Z][A-Z0-9_-]*\d[A-Z0-9_-]*$/i
+
+/**
+ * Pick a short, human-readable device name from an ESI device summary.
+ *
+ * The ESI schema doesn't require <Type> to carry text content (only the
+ * ProductCode/RevisionNo attributes), so vendors that emit a self-closing
+ * <Type/> leave us without a short code. This walks a fallback chain so
+ * the UI always renders something sensible, and worst-case falls back to
+ * the canonical (ProductCode, RevisionNo) identity that is unique by
+ * construction.
+ */
+export function getShortDeviceName(esiDevice: ShortNameInput): string {
+  const typeText = esiDevice.type.name.trim()
+  const longName = esiDevice.name.trim()
+
+  // P1: <Type> text if it already looks like a short code.
+  if (typeText && typeText.length <= 24 && !/\s/.test(typeText)) {
+    return typeText
+  }
+
+  // P2: first token of <Name> if it matches an SKU shape.
+  if (longName) {
+    const firstToken = longName.split(/[\s,;]/)[0]
+    if (firstToken.length >= 3 && firstToken.length <= 24 && SKU_TOKEN.test(firstToken)) {
+      return firstToken
+    }
+  }
+
+  // P3: <Type> text even if it's longer than a typical SKU.
+  if (typeText) return typeText
+
+  // P4: full long name as-is.
+  if (longName) return longName
+
+  // P5: canonical ETG identity — always unique, always deterministic.
+  return `Device_${esiDevice.type.productCode}_${esiDevice.type.revisionNo}`
+}
diff --git a/src/frontend/utils/unique-slave-name.ts b/src/frontend/utils/unique-slave-name.ts
index cf14680cf..64634d194 100644
--- a/src/frontend/utils/unique-slave-name.ts
+++ b/src/frontend/utils/unique-slave-name.ts
@@ -30,7 +30,8 @@ export function collectAllSlaveNames(remoteDevices: RemoteDeviceForNameCollectio
 
 /**
  * Return `base` if unused, otherwise the first `${base}_NN` (two-digit padded)
- * not present in `existing`. Pad widens past 99 automatically.
+ * not present in `existing`. Two-digit pad doesn't truncate, so 3+ digit
+ * indices pass through unchanged.
  */
 export function generateUniqueSlaveName(base: string, existing: Iterable<string>): string {
   const taken = new Set(existing)