Standardize headers

src/analytics/identifiers/session.ts

@@ -18,6 +18,16 @@ export function getInitialSessionId() {
   return sessionId
 }
 
+/**
+ * Gets the current session ID. Freshness depends on `useSessionId` being
+ * mounted, which handles refreshing this value between foreground/background
+ * transitions. Since that's mounted in `analytics/index.tsx`, this value can
+ * generally be trusted to be up to date.
+ */
+export function getSessionId() {
+  return device.get(['nativeSessionId'])
+}
+
 export function useSessionId() {
   const [id, setId] = useState(() => sessionId)
 

src/analytics/identifiers/session.web.ts

@@ -21,6 +21,16 @@ export function getInitialSessionId() {
   return sessionId
 }
 
+/**
+ * Gets the current session ID. Freshness depends on `useSessionId` being
+ * mounted, which handles refreshing this value between foreground/background
+ * transitions. Since that's mounted in `analytics/index.tsx`, this value can
+ * generally be trusted to be up to date.
+ */
+export function getSessionId() {
+  return window.sessionStorage.getItem(SESSION_ID_KEY)
+}
+
 export function useSessionId() {
   const [id, setId] = useState(() => sessionId)
 

src/analytics/utils.ts

@@ -2,6 +2,7 @@ import {useMemo} from 'react'
 
 import {BSKY_SERVICE} from '#/lib/constants'
 import {type SessionAccount} from '#/state/session'
+import {getDeviceId, getSessionId} from '#/analytics/identifiers'
 import {
   type MergeableMetadata,
   type SessionMetadata,
@@ -31,3 +32,20 @@ export function accountToSessionMetadata(
     }
   }
 }
+
+/**
+ * Get anonymous identifiers and construct headers we use for requests that may
+ * trigger experiment exposures in our backend. These values are used for A/B
+ * test bucketing, in addition to the user DID, if the request is
+ * authenticated. They ensure we can attribute exposures to a specific device
+ * and session, even for unauthenticated requests.
+ *
+ * These headers must stay in sync with our appview.
+ * @see https://github.com/bluesky-social/atproto/blob/39cf199df5847d3fd4a60d8cdeb604a0e07f9784/packages/bsky/src/feature-gates/utils.ts#L7-L8
+ */
+export function getAnalyticsHeaders() {
+  return {
+    'X-Bsky-Device-Id': getDeviceId(),
+    'X-Bsky-Session-Id': getSessionId(),
+  }
+}

src/lib/api/feed/custom.ts

@@ -9,7 +9,7 @@ import {
   getAppLanguageAsContentLanguage,
   getContentLanguages,
 } from '#/state/preferences/languages'
-import {getDeviceId} from '#/analytics/identifiers'
+import {getAnalyticsHeaders} from '#/analytics/utils'
 import {type FeedAPI, type FeedAPIResponse} from './types'
 import {createBskyTopicsHeader, isBlueskyOwnedFeed} from './utils'
 
@@ -66,7 +66,7 @@ export class CustomFeedAPI implements FeedAPI {
             headers: isBlueskyOwned
               ? {
                   ...createBskyTopicsHeader(this.userInterests),
-                  'X-Bsky-Stable-Id': getDeviceId(),
+                  ...getAnalyticsHeaders(),
                   'Accept-Language': contentLangs,
                 }
               : {