W14: F8 cross-host differential battery (test-only) — CHECKLIST COMPLETE

Committed replacement for the review's ephemeral 130-probe corpus:
spec/tests/differential-probes.txt (49 probes: F-1 int/float display, K18
overflow, F-3 apply + dict order, S-4 float printing, strings,
collections, special forms, error normalization) evaluated on the native
server (epoch protocol printer) and the SHIPPED WASM kernel
(eval_wasm_probes.js via guest sx-serialize), diffed by
scripts/test-differential.sh with a KNOWN_DIVERGENT heal-detecting ledger.

Result: 46/49 agree. All 3 divergences share one root cause, verified
live: bare sx_server's `apply` does not spread its argument list —
(apply + (list 1 2 3)) errors "Expected number, got list", (apply str l)
returns the serialized list; the WASM kernel spreads correctly and the
test runner masks the bug with its own apply binding (F-7 class).

Finding refinement: F-1's float-display divergence (0.3 vs
0.30000000000000004) is a K.eval JS-boundary artifact — guest-serialized
output agrees across hosts; the battery therefore compares guest
serialization.

This completes the W14 checklist: 7 pin suites, 6 gate scripts/runners,
2 harness capabilities, C9 label cleanup, adapter-dom render coverage.

Test-only: no semantics edits, no push.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

plans/agent-briefings/sx-gate-loop.md

@@ -104,10 +104,40 @@ Pin each confirmed-and-fixed finding with a minimal repro. Add suites to
       baseline identities updated in the same commit
 
 ### F. Differential battery
-- [ ] F8 — cross-host differential battery (same source, all hosts agree)
+- [x] F8 — cross-host differential battery: `spec/tests/differential-probes.txt`
+      (49 probes) × native server vs shipped WASM kernel via
+      `scripts/test-differential.sh` + `eval_wasm_probes.js`. 46 agree,
+      3 ledgered KNOWN_DIVERGENT (F-3: bare-server `apply` does not spread —
+      runner masks it, F-7 class). Refinement: the F-1 float-display
+      divergence is a K.eval JS-boundary artifact — guest `sx-serialize`
+      output AGREES across hosts
+
+**CHECKLIST COMPLETE 2026-07-04** — all W14 items delivered. Open handoffs:
+sx_render.ml regen drift (Blocked, hosts lane), adapter-dom depth tests,
+3 WASM load-error bisects (hash-table/r7rs/sets), CI wiring of the four
+gate scripts (D3 maintainer decision).
 
 ## Progress log (newest first)
 
+- 2026-07-04 — **F8 differential battery — CHECKLIST COMPLETE**. Committed
+  replacement for the review's ephemeral 130-probe corpus:
+  `spec/tests/differential-probes.txt` (49 probes across F-1 int/float
+  display, K18 overflow, F-3 apply + dict order, S-4 float printing,
+  strings/collections/special forms/error cases) evaluated on the native
+  server (epoch protocol) and the shipped WASM kernel
+  (`eval_wasm_probes.js`, guest `sx-serialize`), diffed by
+  `scripts/test-differential.sh` with a KNOWN_DIVERGENT ledger (heal →
+  red → delete entry). Result: 46/49 agree; 3 divergences, all one root
+  cause — **bare sx_server's `apply` does not spread its arg list**
+  ((apply + (list 1 2 3)) → "Expected number, got list"; WASM spreads
+  correctly; the test runner masks it with its own apply — F-7 class).
+  Finding refinement: F-1's float-display divergence (0.3 vs 0.3000…4) is
+  purely a K.eval JS-boundary artifact — guest-serialized output agrees.
+  W14 delivered: 7 pin suites (spec/tests/test-gate-pins.sx, 29 tests),
+  4 gate scripts (protocol-gate 11, env-parity 7, harness-parity 12,
+  wasm-corpus 83-file, suite-baseline 273-pin, differential 49-probe),
+  2 harness capabilities (C22 log-first, C21 perform-mode), C9 label
+  cleanup, adapter-dom render coverage. Test-only throughout.
 - 2026-07-04 — **C9 empty-suite labels (item E.3) — section E COMPLETE**.
   The sweep found the defect much wider than the finding: SIX files carried
   suite-less top-level deftests (test-chars 43, test-import-bind 14,