feat(post): add topic-based signup experiment

[rebelchris]

Changes

Logged-out post readers currently see a generic signup offer. Add an inline offer that connects signup to the article’s topic: “Get more posts about React,” with up to two related-post previews and the existing signup options.

• Use the first non-empty article tag, including the underlying article on shared posts. Display the backend topic title with a raw-tag fallback.
• Render in classic and redesigned post layouts, including mobile; suppress the generic sidebar card for the treatment. Preserve existing behavior for the control and posts without tags.
• Fetch previews only when the offer enters view, using the batched GraphQL transport. Keep signup usable if recommendations fail.
• Use a centered layout inspired by the onboarding signup hero and auth banner, with a primary Google button and quieter secondary options.
• This changes the signup offer only; it does not automatically follow topics after registration.

Events

Type	event_name	value
New target type	impression	target_type: post topic signup, target_id: current article ID, extra: { origin: "post topic signup", tag }; once on visibility
New placement	click	target_type: post, target_id: preview article ID, extra: { origin: "post topic signup", tag }

Existing signup tracking keeps AuthTriggers.PostPage. Analytics taxonomy update is pending.

Experiment

New GrowthBook flag: post_topic_signup, default false. Eligible readers are auth-ready, logged-out visitors viewing a post with a topic. Treatment replaces the sidebar offer with an inline topic-based offer; control retains the existing post_signup_widget behavior.

Experiment configuration and enrolment approval are pending. No rollout has been enabled and no experiments-channel announcement has been sent.

Important

Do not merge until experiment enrolment is approved.

Manual Testing

Visually checked the actual signup components in a local isolated preview at 390px and 1020px, both with and without sample related-post data. The offer uses centered copy and a bounded form, a soft theme-aware accent background, and the existing single-primary provider button hierarchy. Related-post cards stack on phones and sit side by side on wider screens.

Full-page, extension/companion, and physical-device sanity checks remain pending.

Validation

• Changed-file ESLint and git diff --check: passed.
• node ./scripts/typecheck-strict-changed.js: passed.
• Focused shared tests: 38 passed across signup widget, auth widget, classic post content, and redesigned post content.
• pnpm --filter webapp test: 93 suites / 722 tests passed.
• Full webapp typecheck: 12 existing test-fixture errors. Verified the unchanged HEAD in a temporary baseline checkout produces identical diagnostics.

Preview domain

https://codex-post-topic-signup.preview.app.daily.dev

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Project	Deployment	Actions	Updated
daily-webapp	Ready	Preview	Sep 18, 2026 10:56am UTC