Draft changelog: Sep 24, 2026 updates

[mintlify]

Summary

Adds a changelog entry for product changes merged since the Sep 21, 2026 entry.

Changes

• New features: OAuth 2.0 webhook signature header, expires_at on X Activity API subscriptions, Livestream API access form
• Updates: is_moderator on broadcast.chat, broadcast scopes in OAuth 1.0a token exchange, source removed from tweet.fields
• No bug fixes shipped this period

Context

Sourced from PRs #436, #441, #443, #445, #448, #450 and the Livestream access form commits.

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Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 24, 2026, 2:14 AM

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