diff --git a/extension/package.json b/extension/package.json
index c134f48..228b803 100644
--- a/extension/package.json
+++ b/extension/package.json
@@ -2,7 +2,7 @@
     "name": "gravity-bridge",
     "displayName": "Gravity Bridge",
     "description": "Antigravity ↔ Discord 브리지 연동 확장",
-    "version": "0.3.7",
+    "version": "0.3.8",
     "publisher": "variet",
     "engines": {
         "vscode": "^1.100.0"
diff --git a/extension/src/extension.ts b/extension/src/extension.ts
index 740fbe5..779d661 100644
--- a/extension/src/extension.ts
+++ b/extension/src/extension.ts
@@ -38,6 +38,7 @@ let sdk: any;
 let statusBar: vscode.StatusBarItem;
 let bridgePath: string;
 let projectName: string;
+let workspaceUri: string = '';  // filesystem path of the workspace folder (for session filtering)
 let isActive = false;
 let deterministicPort = 0;  // derived from projectName, consistent across restarts
 let watcher: fs.FSWatcher | null = null;
@@ -1448,23 +1449,41 @@ function setupMonitor() {
             }
 
             // ── Filter to sessions owned by THIS window ──
-            // Each window claims sessions it sees first via writeRegistration().
-            // Only process sessions registered to THIS projectName (or unclaimed ones).
+            // PRIMARY: Use trajectoryMetadata.workspaces URI to match sessions to this workspace.
+            // FALLBACK: Use bridge/register/ files for sessions without metadata.
+            // This prevents cross-window session grabbing when multiple AG instances run.
             let bestSession: any = null;
             let bestSessionId = '';
             let bestModTime = '';
             const regDir = path.join(bridgePath, 'register');
+            const normalizedWorkspace = workspaceUri.replace(/\\/g, '/').toLowerCase();
             for (const [sid, data] of Object.entries(allTraj.trajectorySummaries) as [string, any][]) {
-                // Check if this session is claimed by another project
-                const regFile = path.join(regDir, `${sid}.json`);
-                if (fs.existsSync(regFile)) {
-                    try {
-                        const reg = JSON.parse(fs.readFileSync(regFile, 'utf-8'));
-                        if (reg.project_name && reg.project_name !== projectName) {
-                            // Session belongs to another window — skip
-                            continue;
-                        }
-                    } catch { }
+                // PRIMARY FILTER: Check workspace URI from trajectoryMetadata
+                const trajMeta = data.trajectoryMetadata;
+                if (trajMeta?.workspaces?.length > 0 && normalizedWorkspace) {
+                    const sessionWorkspaceRaw = trajMeta.workspaces[0]?.workspaceFolderAbsoluteUri || '';
+                    // Convert file:///c:/Users/... URI to c:/Users/... path for comparison
+                    const sessionWorkspace = sessionWorkspaceRaw
+                        .replace(/^file:\/\/\//, '')
+                        .replace(/%3A/gi, ':')
+                        .replace(/\\/g, '/')
+                        .toLowerCase();
+                    if (sessionWorkspace && !sessionWorkspace.includes(normalizedWorkspace) && !normalizedWorkspace.includes(sessionWorkspace)) {
+                        // Session belongs to a different workspace — skip
+                        continue;
+                    }
+                } else {
+                    // FALLBACK: Check registration file (for sessions without metadata)
+                    const regFile = path.join(regDir, `${sid}.json`);
+                    if (fs.existsSync(regFile)) {
+                        try {
+                            const reg = JSON.parse(fs.readFileSync(regFile, 'utf-8'));
+                            if (reg.project_name && reg.project_name !== projectName) {
+                                // Session belongs to another window — skip
+                                continue;
+                            }
+                        } catch { }
+                    }
                 }
 
                 const modTime = data.lastModifiedTime || '';
@@ -2669,7 +2688,10 @@ export async function activate(context: vscode.ExtensionContext) {
 
     // Project detection
     projectName = detectProjectName();
-    console.log(`Gravity Bridge: project "${projectName}"`);
+    // Store workspace folder path for session filtering (prevents cross-window session grabbing)
+    const folders = vscode.workspace.workspaceFolders;
+    workspaceUri = folders && folders.length > 0 ? folders[0].uri.fsPath : '';
+    console.log(`Gravity Bridge: project "${projectName}" workspace="${workspaceUri}"`);
 
     // Bridge path
     const config = vscode.workspace.getConfiguration('gravityBridge');