Module report 

Cross-context coherence drift report schema.

Defines the per-context identity surfaces, the Skipped marker for unavailable contexts, and the drift-diagnostic records emitted by crate::coherence::probes::CoherenceProbe. All comparison logic in this file is pure Rust with no I/O so it can be unit-tested deterministically without booting Chrome.

Feature flag

The coherence module is default-on and is always compiled as part of the stygian-browser crate.

Separation of hard failures vs known limitations

Drift is classified into two severity bands:

• DriftSeverity::Hard — user-agent, platform, languages, and navigator.webdriver MUST be identical across all contexts. Drift here is a strong anti-bot detection signal.
• DriftSeverity::KnownLimitation — fields like hardwareConcurrency and deviceMemory are documented to differ between Document and Worker contexts in some browsers. Drift here is a known limitation, not a stealth regression.

Reports always carry both bands; callers can filter on DriftSeverity to surface regressions only.

Structs

CoherenceDriftReport

Aggregate coherence drift report covering top-level, iframe, and (best-effort) worker contexts.

DriftDiagnostic

Single drift record describing one field that disagreed across two contexts.

IdentitySurface

Identity surface probed in a single browser context.

Enums

ContextKind

Logical browser context in which an identity surface was observed.

ContextObservation

Result of probing a single context: either an observed IdentitySurface or a Skipped marker describing why the probe could not run.

ContextPair

Pair of contexts to compare.

DriftSeverity

Drift severity classification.

Functions

build_report

Build a CoherenceDriftReport from three ContextObservations by running diff_surfaces for every applicable pair.

diff_surfaces

Compare a and b (both Observed) and emit a Vec<DriftDiagnostic> covering every disagreed field. Returns an empty vec when a == b.

field_severity

Severity for a given field name.

signature_field_names

Fields that contribute to surface_signature. Exposed for callers that need to extend the contract.

surface_signature

Compute a deterministic signature hash from an IdentitySurface.