feat(homepage): 'What's Happening Now' activity feed widget

[mekarpeles]

Summary

Adds a mobile-first "What's Happening Now" activity feed to the Open Library homepage, showing recent public reading log activity in a sliding 3-card window.

• API: GET /api/internal/activity.json — paginated, filters to patrons with public_readlog: yes, Solr-enriched with title/cover/author
• Lit component: <ol-activity-feed> — 3 stacked cards, auto-advances every 15s, manual right-arrow advance, "More →" link to /trending when exhausted. Uses design system CSS tokens (--primary-blue, --border-radius-*, etc.) for all interactive elements.
• Template: home/activity_feed.html wired into home/index.html between the welcome section and trending carousel
• Follow button: optimistic update via POST /people/{key}/follows, redirects anonymous users to login

Closes

Closes #12861

Related

• Update "Trending Now" cards to display patron Follow Card (if reading log public) #10241 — trending cards with patron follow pattern
• Add Social Activity Feed to My Books page #10242 — social activity feed on My Books
• feat(community): Weekly Prompt homepage widget — staff-curated book discovery #12858 — weekly prompt widget (comparable Lit architecture)

Files changed

File	Change
openlibrary/fastapi/internal/api.py	New GET /api/internal/activity.json endpoint
openlibrary/components/lit/OLActivityFeed.js	New <ol-activity-feed> Lit component
openlibrary/components/lit/index.js	Export the new component
openlibrary/templates/home/activity_feed.html	New homepage partial
openlibrary/templates/home/index.html	Wire in the partial

API response shape

{
  "activity": [
    {
      "type": "shelf_change",
      "shelf_id": 2,
      "shelf_label": "is Currently Reading",
      "username": "jsmith",
      "avatar_url": "https://...",
      "work_key": "/works/OL123W",
      "title": "The Great Gatsby",
      "cover_id": 12345,
      "author": "F. Scott Fitzgerald",
      "updated": "2026-06-04T12:00:00"
    }
  ],
  "page": 1
}

Verification

JS build: webpack compiled with 0 errors (make js)
Linting: ruff ✅, eslint ✅, codespell ✅

⚠️ Docker note: End-to-end browser verification was blocked by a pre-existing Python 3.14 regression in master — except A, B: Python 2 syntax in core/db.py (and other files) causes a SyntaxError on startup. This is unrelated to our 5 changed files. Tracking in #12861 comment.

Checklist

• API endpoint follows FastAPI patterns in internal/api.py
• Component uses design system tokens (no hardcoded brand colors)
• Privacy: only shows public_readlog: yes patrons
• Follow button redirects anon users to login
• Fallback images for broken avatars/covers
• webpack 0 errors
• pre-commit clean (eslint, ruff, codespell)
• Browser verification (blocked: see Docker note above)

[Copilot]

Pull request overview

Adds a new “What’s Happening Now” homepage section powered by a Lit web component and a new internal FastAPI endpoint, intended to show recent public reading-log activity in a rotating 3-card feed.

Changes:

• Added a homepage partial (home/activity_feed.html) and wired it into the homepage template.
• Introduced GET /api/internal/activity.json to return recent public reading-log activity enriched with Solr work metadata.
• Added and exported a new Lit component <ol-activity-feed> that fetches/paginates and renders the activity cards, including a Follow action.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
openlibrary/templates/home/index.html	Inserts the new activity-feed partial into the homepage layout.
openlibrary/templates/home/activity_feed.html	Defines the homepage section wrapper and instantiates <ol-activity-feed>.
openlibrary/fastapi/internal/api.py	Adds the new activity feed JSON endpoint and response models.
openlibrary/components/lit/OLActivityFeed.js	Implements the Lit activity feed component, auto-advance behavior, and follow button logic.
openlibrary/components/lit/index.js	Exports the new Lit component.

[mekarpeles]

Hi — I'm Pierre, an AI-assisted PR health agent running on behalf of @mekarpeles.

Resolved a merge conflict in openlibrary/fastapi/internal/api.py:

Master had added:

from openlibrary.core.bestbook import Bestbook
from openlibrary.core.follows import PubSub

This branch added:

from openlibrary.core.bookshelves import Bookshelves

Resolution: kept all three imports in alphabetical order. All three are actively used in the file (verified before resolving). This was a pure import-ordering conflict with no semantic ambiguity.

Safeguards: Confirmed all commits authored by @mekarpeles. Zero unresolved review threads. Used git push --force-with-lease.

To reverse: git reset --hard e090359ef then git push --force-with-lease.