diff --git a/src/main/utils/pathDecoder.ts b/src/main/utils/pathDecoder.ts
index 077d5cde..5257b748 100644
--- a/src/main/utils/pathDecoder.ts
+++ b/src/main/utils/pathDecoder.ts
@@ -47,6 +47,16 @@ export function decodePath(encodedName: string): string {
     return '';
   }
 
+  // Legacy Windows format observed in some Claude installs: "C--Users-name-project"
+  // (no leading dash, drive separator encoded as "--").
+  const legacyWindowsRegex = /^([a-zA-Z])--(.+)$/;
+  const legacyWindowsMatch = legacyWindowsRegex.exec(encodedName);
+  if (legacyWindowsMatch) {
+    const drive = legacyWindowsMatch[1].toUpperCase();
+    const rest = legacyWindowsMatch[2].replace(/-/g, '/');
+    return `${drive}:/${rest}`;
+  }
+
   // Remove leading dash if present (indicates absolute path)
   const withoutLeadingDash = encodedName.startsWith('-') ? encodedName.slice(1) : encodedName;
 
@@ -96,6 +106,12 @@ export function isValidEncodedPath(encodedName: string): boolean {
     return false;
   }
 
+  // Support legacy Windows format: "C--Users-name-project"
+  // (no leading dash, drive separator encoded as "--").
+  if (/^[a-zA-Z]--[a-zA-Z0-9_.\s-]+$/.test(encodedName)) {
+    return true;
+  }
+
   // Must start with a dash (indicates absolute path)
   if (!encodedName.startsWith('-')) {
     return false;
diff --git a/test/main/ipc/guards.test.ts b/test/main/ipc/guards.test.ts
index 6af43df5..e6b264dd 100644
--- a/test/main/ipc/guards.test.ts
+++ b/test/main/ipc/guards.test.ts
@@ -21,6 +21,12 @@ describe('ipc guards', () => {
     expect(result.value).toBe('-C:-Users-test-project');
   });
 
+  it('accepts legacy Windows-style encoded project IDs', () => {
+    const result = validateProjectId('C--Users-test-project');
+    expect(result.valid).toBe(true);
+    expect(result.value).toBe('C--Users-test-project');
+  });
+
   it('rejects invalid project IDs', () => {
     const result = validateProjectId('../escape');
     expect(result.valid).toBe(false);
diff --git a/test/main/utils/pathDecoder.test.ts b/test/main/utils/pathDecoder.test.ts
index c0a4e50f..aba00925 100644
--- a/test/main/utils/pathDecoder.test.ts
+++ b/test/main/utils/pathDecoder.test.ts
@@ -75,6 +75,10 @@ describe('pathDecoder', () => {
     it('should decode Windows-style encoded path without adding leading slash', () => {
       expect(decodePath('-C:-Users-username-projectname')).toBe('C:/Users/username/projectname');
     });
+
+    it('should decode legacy Windows-style encoded path without leading dash', () => {
+      expect(decodePath('C--Users-username-projectname')).toBe('C:/Users/username/projectname');
+    });
   });
 
   describe('extractProjectName', () => {
@@ -145,6 +149,10 @@ describe('pathDecoder', () => {
       expect(isValidEncodedPath('-C:-Users-username-projectname')).toBe(true);
     });
 
+    it('should return true for legacy Windows-style encoded path', () => {
+      expect(isValidEncodedPath('C--Users-username-projectname')).toBe(true);
+    });
+
     it('should return false for misplaced colons', () => {
       expect(isValidEncodedPath('-Users-username:project')).toBe(false);
       expect(isValidEncodedPath('-C:-Users-name-project:extra')).toBe(false);