diff --git a/CLAUDE.md b/CLAUDE.md
index 54c7e7c525..4338c0e3ac 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1,6 +1,7 @@
 ## Code Style & Organization
 - Order method, fields and properties, first by accessibility and then by alphabetical order.
 - Don't add the Microsoft copyright header to new files.
+- Use `Uri.joinPath()` for constructing file paths to ensure platform-correct path separators (e.g., `Uri.joinPath(venvPath, 'share', 'jupyter', 'kernels')` instead of string concatenation with `/`)
 
 ## Testing
 - Unit tests use Mocha/Chai framework with `.unit.test.ts` extension
diff --git a/src/kernels/deepnote/deepnoteToolkitInstaller.node.ts b/src/kernels/deepnote/deepnoteToolkitInstaller.node.ts
index 38ca4b3f00..b9ee1113dd 100644
--- a/src/kernels/deepnote/deepnoteToolkitInstaller.node.ts
+++ b/src/kernels/deepnote/deepnoteToolkitInstaller.node.ts
@@ -65,6 +65,8 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
         const venvPath = this.getVenvPath(deepnoteFileUri);
         const venvKey = venvPath.fsPath;
 
+        logger.info(`Ensuring virtual environment at ${venvKey}`);
+
         // Wait for any pending installation for this venv to complete
         const pendingInstall = this.pendingInstallations.get(venvKey);
         if (pendingInstall) {
@@ -210,6 +212,7 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
                 logger.info('deepnote-toolkit installed successfully in venv');
 
                 // Install kernel spec so the kernel uses this venv's Python
+                // Install into the venv itself (not --user) so the Deepnote server can discover it
                 logger.info('Installing kernel spec for venv...');
                 try {
                     // Reuse the process service with system environment
@@ -219,7 +222,8 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
                             '-m',
                             'ipykernel',
                             'install',
-                            '--user',
+                            '--prefix',
+                            venvPath.fsPath,
                             '--name',
                             `deepnote-venv-${this.getVenvHash(deepnoteFileUri)}`,
                             '--display-name',
@@ -227,7 +231,14 @@ export class DeepnoteToolkitInstaller implements IDeepnoteToolkitInstaller {
                         ],
                         { throwOnStdErr: false }
                     );
-                    logger.info('Kernel spec installed successfully');
+                    const kernelSpecPath = Uri.joinPath(
+                        venvPath,
+                        'share',
+                        'jupyter',
+                        'kernels',
+                        `deepnote-venv-${this.getVenvHash(deepnoteFileUri)}`
+                    );
+                    logger.info(`Kernel spec installed successfully to ${kernelSpecPath.fsPath}`);
                 } catch (ex) {
                     logger.warn(`Failed to install kernel spec: ${ex}`);
                     // Don't fail the entire installation if kernel spec creation fails