The session_level_signals body field the feed surfaces carry: a session
state snapshot (surface navigation trail, video counters, ranking-session
window). app_session_navigation is the foreground surface trail — the
screens the session brought to front, the request's own surface last — read
from the navigation state, so a session that showed a prompt before the feed
reports both ([save-credentials, feed_timeline], the 451 launch); the
ranking-session window derives from the request clock (local hour, day,
weekend); the video counters are zero because the library shows no media.
Key order mirrors the 448 capture.
The 451 build (extendedSessionSignals, the profile's launchWire) inserts
the app-session and container-module block at its recorded positions. Its
structure — the counts, the transition map, the hop count, the surface count
and the navigation depth — derives from the trail. The dwell figures — the
dwell shares and the top share, the switch velocity, the gap statistics, the
two entropies, the three hashes and the phase/output-volume levels — are the
session's own measurements of user dwell: the shares, the gaps and the
velocity are computed from the request trail and clock, while the app's
formulas for the hashes, the entropies and the two levels are not observable
yet and keep the zero the one-surface block sends.
The
session_level_signalsbody field the feed surfaces carry: a session state snapshot (surface navigation trail, video counters, ranking-session window).app_session_navigationis the foreground surface trail — the screens the session brought to front, the request's own surface last — read from the navigation state, so a session that showed a prompt before the feed reports both ([save-credentials, feed_timeline], the 451 launch); the ranking-session window derives from the request clock (local hour, day, weekend); the video counters are zero because the library shows no media. Key order mirrors the 448 capture.The 451 build (
extendedSessionSignals, the profile'slaunchWire) inserts the app-session and container-module block at its recorded positions. Its structure — the counts, the transition map, the hop count, the surface count and the navigation depth — derives from the trail. The dwell figures — the dwell shares and the top share, the switch velocity, the gap statistics, the two entropies, the three hashes and the phase/output-volume levels — are the session's own measurements of user dwell: the shares, the gaps and the velocity are computed from the request trail and clock, while the app's formulas for the hashes, the entropies and the two levels are not observable yet and keep the zero the one-surface block sends.