1. Most turns: tracing where a function value is a Kept and where it is only a reference. That took about 15 read turns over emit_expr, emit_core_args, CheckLocal, run_code, check_core_free_call and the assignment target. The key facts were: a parameter that only runs its function is in state.run_code (and lowers to &impl AsyncFn), a name callee is never passed to check_core_expr, and an assignment target is.
2. What the brief could have handed me:
   • state.run_code as the test for “this name holds a Kept”.
   • The argument code calls emit_expr on its argument, so an emitter-wide .clone() also lands on lent arguments, run-only arguments and the closure-wrapper paths.
   • The struct-literal shorthand H { f } takes its own branch (kept_byte_fields is the model).
   • EmitWalk is built in one place, EmitWalk::fresh().

   I needed no ADRs or converter.

3. Checks run:
   • Three probe programs on the old binary using lower to see the Rust it writes, then run with the new one.
   • One build and two lower-std runs (the fixpoint check).
   • tests/compiler at both settings, the guard set, clippy and pre-push-check.
   • Nothing was clearly wasted. The extra cargo build I ran to check the fixpoint only recompiled once; an md5 of the lowered/ diff before and after lower-std was cheaper and enough.
   • Two probe rounds hit unrelated refusals (NK2605 on a field call, NK1131 on return h.f) and cost a rerun each.
4. One change: the brief’s Locations should name the positions where the fact must be taken out again or must not apply (callee, assignment target, lent or run-only argument, run_code parameter, shorthand field). The emitter sites alone are not enough, and finding these exceptions was most of the reading. builder.md could also say how to show “fails on the unfixed compiler” without a stash: nikaia lower with the old binary before the first build.

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