Sensible Slack by Mike Turley

Adds quality-of-life improvements to the Slack web interface. The primary feature is preventing the Threads view from automatically marking messages as read. All features can be individually toggled from the extension popup.

Manual Thread Read Control

Prevents the Threads page from automatically marking threads as read as you scroll past them. Instead:

• Automatic subscriptions.thread.mark API calls are intercepted at the XHR level and suppressed with fake success responses, so Slack doesn't retry.
• A "Mark as read" button appears on each thread with unread messages, letting you explicitly dismiss them.
• Threads viewed on other pages (channels, DMs) are still marked as read normally.

Quick Message Actions

Adds a secondary toolbar on message hover with shortcuts that are normally buried in menus:

• Copy link — One-click permalink copy to clipboard.
• Open thread in new tab — Opens the message's thread in a new tab with the thread panel automatically expanded.
• Open in split view — Opens the thread's split view (the native Slack feature that's normally several clicks deep).
• Mark unread — Marks the message as unread without right-clicking or opening a menu.

Each action can be individually enabled or disabled in the popup settings.

How it works

A content script running in the page's MAIN world wraps XMLHttpRequest.prototype before Slack's scripts load. When you're on the Threads page, mark-as-read requests are redirected to a blob URL returning {"ok":true}, preventing Slack from knowing the request was blocked. The intercepted request parameters (token, timestamps, URL) are captured and stored per-thread so they can be replayed exactly when you click "Mark as read".

Pairing with a Redirect Blocker

Slack's web client often tries to redirect you to the desktop app when you open a Slack link. This extension pairs well with a separate extension that blocks that redirect behavior, like Slack Redirect.