The Kernel · 9 December 2025
Reading crash-free sessions without vanity
Crash-free sessions are a store metric with a well-cut suit. They tell you the process did not die. They do not tell you the person finished the job they opened the app to do. Mobile Session Diagnostics exists because product teams keep pasting the store number into an App Analytics review as if it were retention.
Pair vitals with a job event
We ask for two series on the same week: crash-free (and ANR where you have it) beside the first server-side job completion — order committed, issue filed, article unlocked. If vitals are calm and jobs are not, you do not have a stability win. You have a quiet failure after the process stayed alive: a blocked SDK, a dead-end screen, a payment retry that never returned.
Cold start is the other vanity trap. A faster launch that dumps people into a permission wall will still look pretty in a lab. The ledger wants the time from process start to first completed job, even if that number is unflattering.
What we mark in the margin
Students bring a week of store consoles and a week of product events. The exercise is to write one sentence that a support lead would recognise. “Sessions are calm; order confirm still fires on a layout nobody reaches after 3-D Secure” is a sentence. “Stability is excellent” is a slogan.
This is unfashionable because it refuses to let engineering and product keep separate scoreboards. Instrumentation as a craft, on the studio’s other page, is the doctrine underneath: birthplace, owner, and a reason to exist.