Draft changelog: streaming latency and webhook auth updates

[mintlify]

Summary

Adds a Sep 4, 2026 changelog entry covering product changes shipped since the Sep 1 entry.

Changes

• Lower streaming latency: P99 improved from ~6-7s to ~4-5s on Filtered Stream and volume streams
• Webhook management endpoints now accept OAuth 2.0 user context; X Activity API subscription update/delete endpoints now accept OAuth 2.0 and OAuth 1.0a user context

Context

Based on changes merged to main this week: the streaming latency figure update and the OpenAPI spec syncs adding user-context auth to webhook and activity subscription endpoints. Aug 26 changes were excluded as they predate the last changelog entry.

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Project	Status	Preview	Updated
x-corp	🟢 Ready	View Preview	Sep 4, 2026, 8:08 PM

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