igneum-pow: the invention lane's known-failed test for the per-load bias fix (tests/v6_window_bits.rs: the sound form accepts under drawn eras 0 to 7 with 0 window-bit refusals; the no-era bit-0 refusal on seed 3 stands); 2 of 2 on igneum-build-2 at 11:41 UTC against 0ab27582's fix

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

igneum-pow/tests/v6_window_bits.rs

@@ -0,0 +1,46 @@
+//! Class v6 invention lane (8 October 2026): the per-load acceptance's value-level bias test must not judge the era
+//! window's fixed top index bits. Known-failed first: at counter-asic-4 5984ffab every per-load form under every drawn
+//! era was refused with "index bit 26 (or 27) at load site s set in 0 (or 16,384) of 16,384" (0 of 256 seeds on 11
+//! forms, build-1, 11:0x UK); with the window bits skipped the sound form accepts under an era as it does without one.
+//! Offered by the invention lane (tools/attack/v6-invention/v6_window_bits.rs.offered on class-v6-invention), landed
+//! here by the research lane against 0ab27582's fix.
+use igneum_pow::accept::Reject;
+use igneum_pow::generator::{attempts_class, LoadClass};
+use igneum_pow::seed::seed_words_from_bytes;
+
+fn era_class(name: &str, n: u32) -> LoadClass {
+    let era_seed = seed_words_from_bytes(format!("igneum-era-test/{n}").as_bytes());
+    let mut bytes = Vec::new();
+    for w in era_seed {
+        bytes.extend_from_slice(&w.to_le_bytes());
+    }
+    LoadClass::era(LoadClass::parse(name).unwrap(), &bytes, &igneum_pow::generator::V3_ALLOWED)
+}
+
+#[test]
+fn per_load_bias_test_skips_the_era_window_bits() {
+    let mut accepted = 0usize;
+    let mut window_bit_rejections = 0usize;
+    for i in 0..8u32 {
+        let class = era_class("mx8+shl4096x1", i);
+        let label = format!("igneum-v6inv/{i}");
+        for (_, verdict) in attempts_class(&label, label.as_bytes(), class) {
+            match verdict {
+                Ok(()) => accepted += 1,
+                Err(Reject::BiasedIndexBit { bit, ones, .. }) if bit >= 26 && (ones == 0 || ones == 16_384) => window_bit_rejections += 1,
+                Err(_) => {}
+            }
+        }
+    }
+    assert_eq!(window_bit_rejections, 0, "a window's fixed top bit was judged as biased");
+    assert!(accepted >= 4, "the sound per-load form accepted on {accepted} of 8 seeds under drawn eras (0 before the fix)");
+}
+
+#[test]
+fn per_load_bias_test_still_refuses_a_biased_real_bit_without_an_era() {
+    let class = LoadClass::parse("mx8+shl4096x1").unwrap();
+    let label = "igneum-v6inv/3";
+    let v = attempts_class(label, label.as_bytes(), class);
+    assert!(v.iter().all(|(_, r)| r.is_err()), "seed 3 exhausted the cap on the no-era census (0 of 32) and must still");
+    assert!(v.iter().any(|(_, r)| matches!(r, Err(Reject::BiasedIndexBit { bit: 0, .. }))), "a bit-0 refusal on seed 3 stands");
+}