Preserve fractional-millisecond decoder evidence in timing evaluator

tools/speech-eval/native-validation/src/main.rs

@@ -60,6 +60,18 @@ fn file_hash(path: &Path) -> Result<String> {
     }
     Ok(format!("{:x}", state.finalize()))
 }
+fn validate_sample_coverage(samples: usize, duration_ms: u32) -> Result<()> {
+    let expected = duration_ms as usize * 16;
+    ensure!(
+        samples > 0
+            && samples <= 480000
+            && expected > 0
+            && expected <= 480000
+            && samples.abs_diff(expected) <= 16,
+        "Fixture source clock coverage differs beyond existing one-millisecond bound"
+    );
+    Ok(())
+}
 fn write_new(path: &Path, value: &Value) -> Result<()> {
     let mut file = fs::OpenOptions::new()
         .write(true)
@@ -174,16 +186,13 @@ fn run_case(
         let mut source_windows = Vec::new();
         for window in windows(metadata.audio_start_ms, metadata.audio_end_ms, max_windows)? {
             let pcm = decode_audio_aligned(&assets.tools, &path, window, &limits)?;
-            ensure!(
-                pcm.len() == window.duration_ms as usize * 16,
-                "Fixture source clock coverage differs"
-            );
+            validate_sample_coverage(pcm.len(), window.duration_ms)?;
             let sha = hash(
                 &pcm.iter()
                     .flat_map(|value| value.to_le_bytes())
                     .collect::<Vec<_>>(),
             );
-            let record = json!({"asset":id,"start_ms":window.start_ms,"duration_ms":window.duration_ms,"samples":pcm.len(),"pcm_sha256":sha});
+            let record = json!({"asset":id,"start_ms":window.start_ms,"duration_ms":window.duration_ms,"samples":pcm.len(),"nominal_samples":window.duration_ms as usize*16,"coverage_difference_samples":pcm.len() as i64-i64::from(window.duration_ms)*16,"pcm_sha256":sha});
             expected.entry(sha).or_default().push(record.clone());
             source_windows.push(record);
         }
@@ -487,6 +496,13 @@ mod tests {
         assert!(values.iter().all(|window| window.duration_ms <= 30000));
     }
     #[test]
+    fn fractional_millisecond_tail_preserves_real_samples() {
+        assert!(validate_sample_coverage(32618, 2039).is_ok());
+        assert!(validate_sample_coverage(32607, 2039).is_err());
+        assert!(validate_sample_coverage(0, 1).is_err());
+        assert!(validate_sample_coverage(480001, 30000).is_err());
+    }
+    #[test]
     #[ignore = "Requires the five hash-verified real media fixture files; no inference"]
     fn timing_mode_preflight_checks_all_real_frozen_sources_without_models() -> Result<()> {
         let root = Path::new(env!("CARGO_MANIFEST_DIR")).join("../../../fixtures/media");