diff --git a/lib/units/websocket/index.ts b/lib/units/websocket/index.ts
index 93118d2d81..946afe2896 100644
--- a/lib/units/websocket/index.ts
+++ b/lib/units/websocket/index.ts
@@ -25,6 +25,7 @@ import {TransactionManager} from '../../wire/transmanager.js'
 import {ClientDispatcher} from './support/clientDispatcher.js'
 import {DeviceOwnership} from './support/deviceOwnership.js'
 import {OwnershipCache} from './support/ownershipCache.js'
+import {parseLogcatFilters} from './support/logcatFilters.js'
 import {
     UpdateAccessTokenMessage,
     DeleteUserMessage,
@@ -891,10 +892,20 @@ export default (async (options: Options) => {
                 }
             })
 
-            socket.on('logcat.start', (serial: string, rc: string, data: any) =>
-                runTx(serial, rc, LogcatStartMessage, {filters: data.filters}))
-            socket.on('logcat.startIos', (serial: string, rc: string, data: any) =>
-                runTx(serial, rc, LogcatStartMessage, {filters: data.filters}))
+            const startLogcat = (serial: string, rc: string, data: unknown) => {
+                const filters = parseLogcatFilters((data as {filters?: unknown} | null)?.filters)
+                if (!filters) {
+                    socket.emit('tx.done', rc, {
+                        source: serial,
+                        success: false,
+                        data: 'invalid_logcat_filters'
+                    })
+                    return
+                }
+                return runTx(serial, rc, LogcatStartMessage, {filters})
+            }
+            socket.on('logcat.start', startLogcat)
+            socket.on('logcat.startIos', startLogcat)
             socket.on('logcat.stop', (serial: string, rc: string) =>
                 runTx(serial, rc, LogcatStopMessage, {}))
             socket.on('logcat.stopIos', (serial: string, rc: string) =>
diff --git a/lib/units/websocket/support/logcatFilters.ts b/lib/units/websocket/support/logcatFilters.ts
new file mode 100644
index 0000000000..e6b49137d1
--- /dev/null
+++ b/lib/units/websocket/support/logcatFilters.ts
@@ -0,0 +1,29 @@
+export interface LogcatFilter {
+    tag: string
+    priority: number
+}
+
+const isLogcatFilter = (value: unknown): value is LogcatFilter => {
+    if (!value || typeof value !== 'object') {
+        return false
+    }
+    const filter = value as Partial<LogcatFilter>
+    return typeof filter.tag === 'string' &&
+        typeof filter.priority === 'number' &&
+        Number.isInteger(filter.priority) &&
+        filter.priority >= 0 &&
+        filter.priority <= 0xffffffff
+}
+
+// The UI sends one {tag, priority} filter, while the protobuf field is repeated.
+// Keep accepting arrays for older clients, and reject malformed payloads before
+// protobuf-ts tries to merge them into the repeated field.
+export const parseLogcatFilters = (value: unknown): LogcatFilter[] | null => {
+    if (isLogcatFilter(value)) {
+        return [value]
+    }
+    if (Array.isArray(value) && value.every(isLogcatFilter)) {
+        return value
+    }
+    return null
+}
diff --git a/test/unit/units/websocket/logcatFilters.test.ts b/test/unit/units/websocket/logcatFilters.test.ts
new file mode 100644
index 0000000000..e5bf92a7ad
--- /dev/null
+++ b/test/unit/units/websocket/logcatFilters.test.ts
@@ -0,0 +1,28 @@
+import {describe, expect, it} from 'vitest'
+import {parseLogcatFilters} from '../../../../lib/units/websocket/support/logcatFilters.ts'
+
+describe('parseLogcatFilters', () => {
+    it('wraps the single filter sent by the UI in the repeated protobuf field', () => {
+        expect(parseLogcatFilters({tag: '*', priority: 2})).toEqual([
+            {tag: '*', priority: 2}
+        ])
+    })
+
+    it('preserves filter arrays sent by older clients', () => {
+        const filters = [
+            {tag: 'ActivityManager', priority: 4},
+            {tag: 'System.err', priority: 6}
+        ]
+        expect(parseLogcatFilters(filters)).toEqual(filters)
+    })
+
+    it('accepts an empty filter array', () => {
+        expect(parseLogcatFilters([])).toEqual([])
+    })
+
+    it('rejects malformed filters before protobuf serialization', () => {
+        expect(parseLogcatFilters({tag: '*', priority: 'verbose'})).toBeNull()
+        expect(parseLogcatFilters([{tag: '*', priority: 2}, {tag: 1, priority: 3}])).toBeNull()
+        expect(parseLogcatFilters(undefined)).toBeNull()
+    })
+})