System details:

Positron and OS details:

Positron Version: 2026.05.0 build 114
Code - OSS Version: 1.109.2
Commit: d54bd5b7cee7fcf6104bae2b9181204af01673b9
Date: 2026-04-23T07:53:16.620Z
Electron: 39.3.0
Chromium: 142.0.7444.265
Node.js: 22.21.1
V8: 14.2.231.22-electron.0
OS: Darwin arm64 25.4.0

Session details:

Describe the issue:

Positron starts notebook kernels too aggressively.

Steps to reproduce the issue:

Repro 1

• Enable Quarto inline output.
• Open 4 Quarto file.
• Close Positron.
• Reopen Positron.
• Without doing anything else, check the list of running sessions (in e.g. the Sessions view).

Positron has started 4 Quarto notebook kernels on boot.

Repro 2

• Enable the Positron notebook editor.
• Open any text file.
• Open an ipynb file from Explorer with a single click.
• Observe that a Positron notebook editor appears, in Preview Editor mode, and a kernel is started.
• Click on the text file again.
• The Positron notebook editor disappears and we need to shut down the kernel.

This is what a preview editor with a kernel looks like:

Expected or desired behavior:

No

• No session is started for an editor that has never been focused in the current Positron session.
• No session is started for preview editors.

Yes

• A session is started when an editor is opened or switched to, so long as it is not a preview editor
• A session is started for a preview editor at the moment it becomes a real editor through user interaction (typing, running code, double clicking tab, etc.)