The kernel-on-sx loop documented six candidate reflective API files
gated on the two-consumer rule. This plan opens that block by
selecting Tcl's existing uplevel/upvar machinery as the second
consumer for env.sx specifically (the highest-fit candidate).
Discovery: Kernel and Tcl have identical scope-chain semantics but
diverge on mutable-vs-functional update. Solution: adapter-cfg
pattern, same as lib/guest/match.sx. Canonical wire shape with
mutable defaults for Kernel; Tcl provides its own cfg keeping
the functional model.
Roadmap: env.sx extracted, both consumers migrated, all tests green.
The other five candidate files (combiner, evaluator, hygiene,
quoting, short-circuit) stay deferred — Tcl has no operatives.
giles
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