~x-ai/grok-latest → B (2:5)

B replaces ad-hoc URL combinators (engine.rs + per-host normalize paths) with a graph/DFA-based canonicalization API wired through registry, which is core identity infrastructure lasting across the product. A is a correct but narrow fix: rank-history thread_post_index becomes strictly 0-based with expect() and tests, removing optional 1-based/unwrap_or(0) mismatch—valuable polish, not system-level design.