Mobile UA exposes more than 8 CPU cores — a phone SoC does not
br.mobile_cores_high · convicts
What it catches
Core-count realism for a mobile UA. A real phone (a 'Mobile' token) exposes at most ~8 CPU cores to navigator.hardwareConcurrency — mobile SoCs are octa-core at most (big. THRESHOLD > 9, CALIBRATED against real browserforge mobile fingerprints (FP-audit 2026-07-03): coherent-Android hardwareConcurrency is 8 (dominant) + a real 9-tail (~1.4%) + a lone 12 (likely cross-sample), iPhone 4 — so an earlier > 8 FALSE-FIRED on real 9-core Android (the SECOND latent FP the calibration caught); > 9 clears real 8-9-core phones while the 12-core test host still leaks (12 > 9).LITTLE 4+4 / 1+3+4), and iOS caps lower (A-series 6). A 'Mobile' UA reporting hardwareConcurrency > 9 is a desktop wearing a phone UA that never shrank the core count. CRUCIAL: Playwright/CDP device emulation sets the UA + screen + touch + DPR but does NOT spoof hardwareConcurrency (it reads the REAL host), so even a FULL device emulation (KS_DEVICE=Pixel) on a many-core host LEAKS the host core count — this catches the emulated Android node, not just the UA-only spoof. FP-SAFE: no current phone exposes > 8 web cores, and the check is gated on the 'Mobile' token (phones/iPhones, NOT M-series iPads which run desktop-mode Safari without the token and can have 8-10 cores). EXPERIMENTAL (w0.5). The RED counter is spoofing navigator.hardwareConcurrency <= 8, which main-only is caught by the worker realm (the collector's Blob-worker hw probe → worker_divergence) and whose worker-scope escalation trips worker_constructor_tampered / worker_source_rewritten — so a coherent low core count needs a real <=8-core device, realm-backed like the model ratchet. GROUNDED LIVE: KS_DEVICE='Pixel 5' on a 12-core host FIRES mobile_cores_high (hardware_concurrency 12 under a phone UA); a real phone (<=8) does not fire by construction.
Signals it reads
browser.mobile_cores_high
How it fires
present
Bypassed by 10
Frontier evaders that reach the detector uncaught (scored only suspicious, defeating every convicting tell) — this check is not one that stops them. The red-team frontier this detection still has to convict.