diff --git a/packages/app/src/utils/session-export.test.ts b/packages/app/src/utils/session-export.test.ts
index ff18a16b7fa3..c8a7b8b4f080 100644
--- a/packages/app/src/utils/session-export.test.ts
+++ b/packages/app/src/utils/session-export.test.ts
@@ -16,6 +16,23 @@ describe("sessionExportFilename", () => {
   test("falls back to id when title and slug are empty", () => {
     expect(sessionExportFilename({ id: "ses_123" })).toBe("ses_123.json")
   })
+
+  test("avoids Windows reserved device names", () => {
+    const reserved = [
+      "CON",
+      "PRN",
+      "AUX",
+      "NUL",
+      ...Array.from({ length: 9 }, (_, index) => `COM${index + 1}`),
+      ...Array.from({ length: 9 }, (_, index) => `LPT${index + 1}`),
+    ]
+
+    reserved.forEach((title) =>
+      expect(sessionExportFilename({ id: "ses_123", title })).toBe(`${title.toLowerCase()}-session.json`),
+    )
+    expect(sessionExportFilename({ id: "ses_123", title: "COM0" })).toBe("com0.json")
+    expect(sessionExportFilename({ id: "ses_123", title: "COM10" })).toBe("com10.json")
+  })
 })
 
 describe("fetchSessionExport", () => {
diff --git a/packages/app/src/utils/session-export.ts b/packages/app/src/utils/session-export.ts
index 6eb9f9ab6a7c..1889c9335bca 100644
--- a/packages/app/src/utils/session-export.ts
+++ b/packages/app/src/utils/session-export.ts
@@ -16,6 +16,8 @@ export type SessionExportClient = {
   }
 }
 
+const WINDOWS_RESERVED_NAME = /^(con|prn|aux|nul|com[1-9]|lpt[1-9])$/i
+
 export async function fetchSessionExport(input: {
   sessionID: string
   client: SessionExportClient
@@ -44,7 +46,8 @@ export function sessionExportFilename(session: { id: string; title?: string; slu
     .toLowerCase()
     .replace(/[^a-z0-9_-]+/gi, "-")
     .replace(/^-+|-+$/g, "")
-  return `${clean || session.id}.json`
+  const basename = clean || session.id
+  return `${WINDOWS_RESERVED_NAME.test(basename) ? `${basename}-session` : basename}.json`
 }
 
 export function downloadSessionExport(filename: string, data: unknown) {