nx_srcfmt_gate.nx

nx_srcfmt_gate.nx -- GATE for LN9, the canonical source formatter (lang.plan rung LN9, symbol srcfmt_emit). The done-rule: idempotent over the tokenizer stream, fmt(fmt(x)) == fmt(x); comments and string literals preserved; the formatted corpus builds byte-identical. This gate proves the deterministic half in-process (it IMPORTS nx_srcfmt, so nx_gate_bite mutating nx_srcfmt.nx and rebuilding the gate exercises the real subject) and the build-neutrality half on a hermetic fixture by forking the live compiler; the WHOLE-CORPUS build-neutrality is the lane's sweep (nx_srcfmt runs it over every .nx as a sibling in the tree so imports resolve; a /tmp copy fails expand_imports for a reason unrelated to the formatter -- measured 2026-08-23) and its count is published, not sampled here. The load-bearing non-vacuity tooth is T9: it proves the ORACLE inside the formatter actually distinguishes two different token streams -- the oracle is what makes "a formatter that changes a program is impossible" true, so a vacuous oracle would make every other tooth meaningless. Data captures in /tmp/nxsf/, the one runnable under _build/ (NAS /tmp is noexec). Usage: nx_srcfmt_gate [compiler_elf] (CWD = the tree root, like nx_cc_equiv_gate) license_tier: ORIGINAL No hw writes (Rule 26).