[wedamija]

We're adding comments to Investigations, and this is one of a series of frontend PRs that build the feature. Comments show in an Activity section at the bottom of the page, and block comments open in a thread drawer. Everything is behind the investigations flag.

This PR adds posting comments:

• A composer under the Activity feed. Enter sends the comment.
• The metadata line shows the comment count ("Comment" when there are none) before the viewers. Clicking it moves focus to the composer; on archived investigations it scrolls to Activity.
• Archived investigations do not show the composer.

Stacked on #127498. The next PR adds edit and delete.

[github-actions]

Story previews

Preview the stories changed in this PR on the Vercel deployment:

• app/views/investigations/detail/index.stories.tsx

_{Preview deployment: https://sentry-hdgbc242w.sentry.dev}

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[billyvg]

🤖 AI review by Claude, an AI agent. I'm reviewing this stack at @billyvg's request and wrote the inline comments below. @wedamija, Billy will also go through these comments and the code, so please treat this as a first pass, not a final review.

One small correctness issue (the header count tops out at 100) and two minor UX notes.

[billyvg]

Visual QA

Screenshots from Scraps stories (fixture data, 1440×900, light theme). "Before" is the #127498 head with the same story and data.

Story coverage: the header comment button goes into TopBar.Slot, and stories have no top bar, so it never rendered. I added a small story top bar that renders the page's slots, plus POST …/comments/ in the fixture and archived states. That's in a local commit that isn't pushed yet. Comments posted in stories come from a fixed persona (Ada Lovelace), so the frames never show the signed-in account.

before	after

Header button with the count (no before frame, since stories had no top bar):

typing shows Comment	after Enter

The header button scrolls the composer into view and focuses it:

archived page	archived Activity

Checked in the browser:

• The button reads "5 comments" and focuses the composer.
• Enter posts the comment: the count goes to 6 and the composer clears.
• Archived: no composer, and the button reads "Comment" and is disabled.