diff --git a/crates/oxide_test262/src/main.rs b/crates/oxide_test262/src/main.rs
index 264e805f..247adf2f 100644
--- a/crates/oxide_test262/src/main.rs
+++ b/crates/oxide_test262/src/main.rs
@@ -17,7 +17,8 @@ mod report;
 mod test262_log;
 use oxide_log::{Level, LogConfig, Output, SUBSYSTEM_COUNT};
 use report::{
-    first_line, format_fail_categories, format_fail_list, FailRecord, MAX_FAIL_MSG_CHARS, MAX_FAIL_RECORD_BYTES,
+    append_fail_log, first_line, format_fail_categories, format_fail_list, parse_fail_log, FailRecord,
+    MAX_FAIL_MSG_CHARS, MAX_FAIL_RECORD_BYTES,
 };
 
 // 记录当前正在执行的测试路径（thread-local）；每个测试执行前写入，
@@ -137,6 +138,13 @@ struct RunStats {
     categories: Vec<String>, // 类别 id 表（FailRecord.category_id 索引）
     fail_records: Vec<FailRecord>,
     fail_record_bytes: usize, // 累计 message 字节（OOM cap）
+    // supervise 模式异常计数：spawn 失败 / try_wait 错误 / 心跳写失败（子进程侧
+    // 累计后经心跳第 6 字段回传）。
+    spawn_errors: usize,
+    wait_errors: usize,
+    hb_write_errors: usize,
+    /// 超时/崩溃清单：(index, elapsed_ms)；elapsed_ms=0 表示非超时崩溃。
+    timeout_crashes: Vec<(usize, u64)>,
 }
 
 impl RunStats {
@@ -156,6 +164,10 @@ impl RunStats {
             self.fail_records.push(FailRecord { category_id: id, ..rec });
         }
         self.fail_record_bytes += other.fail_record_bytes;
+        self.spawn_errors += other.spawn_errors;
+        self.wait_errors += other.wait_errors;
+        self.hb_write_errors += other.hb_write_errors;
+        self.timeout_crashes.extend(other.timeout_crashes);
     }
 
     /// 把单个测试结果记入运行累计；失败同时追加逐路径失败记录（含类别）。
@@ -949,11 +961,10 @@ fn run_chunked(args: &[String], skip_until: usize, end_index: usize, chunk_size:
 }
 
 /// 监督模式下子进程写入、父进程轮询的一条心跳记录。
-/// `index` 是子进程即将运行的全局测试下标（`START`）或其完成窗口的
-/// 结束下标（`DONE`）；计数始终覆盖 `index` *之前* 已完成的测试，
-/// 因此进行中的测试不会被计入。`categories` 为子进程失败分类计数快照
-/// （首行之后按 `类别\t计数` 逐行写出），使父进程在 supervise 下也能按
-/// 根因拆分失败。
+/// `COMPLETED`：每个测试完成后写，`index` 为刚完成的全局测试下标，计数覆盖
+/// ≤ index 的全部测试；`DONE`：窗口尾，`index` 为窗口结束下标。
+/// `categories` 为子进程失败分类计数快照（首行之后按 `类别\t计数` 逐行写出）；
+/// `hb_write_errors` 为子进程侧心跳/旁路写失败累计，经第 6 字段回传父进程。
 struct Heartbeat {
     phase: String,
     index: usize,
@@ -961,35 +972,57 @@ struct Heartbeat {
     fail: usize,
     skip: usize,
     categories: HashMap<String, usize>,
+    hb_write_errors: usize, // 子进程侧写失败累计（第 6 字段）
 }
 
-/// 用单行心跳头 + 失败类别行覆写心跳文件。错误被忽略：漏写心跳只是把停滞
-/// 检测推迟一个轮询间隔。假定单 worker（监督器强制 `OXIDE_TEST262_WORKERS=1`）；
-/// 多 worker 时运行下标有歧义且文件存在竞争。
+/// 用单行心跳头（phase index pass fail skip hb_write_errors）+ 失败类别行覆写心跳文件。
+///
+/// 经 `{path}.tmp` 临时文件再 rename 原子落盘（同目录 POSIX 原子替换；不 fsync，
+/// SIGKILL 下 page cache 幸存，ponytail）。写失败返回 Err 并清理临时文件，由调用方
+/// 自增 hb_write_errors 随下一心跳回传父进程。
+///
+/// # 边界与前提
+/// - 假定单 worker（监督器强制 `OXIDE_TEST262_WORKERS=1`）；多 worker 时运行下标
+///   有歧义且对同一路径的覆写存在竞争。
+///
+/// # 副作用
+/// - 覆写 `path`；失败时可能残留 `path.tmp`（调用方或 supervise 清理兜底）。
+#[expect(clippy::too_many_arguments)]
 fn write_heartbeat(
     path: &Path, phase: &str, index: usize, pass: usize, fail: usize, skip: usize, categories: &HashMap<String, usize>,
-) {
-    let mut content = format!("{phase} {index} {pass} {fail} {skip}\n");
+    hb_write_errors: usize,
+) -> std::io::Result<()> {
+    let mut content = format!("{phase} {index} {pass} {fail} {skip} {hb_write_errors}\n");
     for (cat, count) in categories {
         // 类别文本内的制表符/换行会破坏行格式，写盘前压平。
         let cat = cat.replace(['\t', '\n', '\r'], " ");
         content.push_str(&format!("{cat}\t{count}\n"));
     }
-    let _ = std::fs::write(path, content);
+    let tmp = format!("{}.tmp", path.display());
+    if let Err(e) = std::fs::write(&tmp, content) {
+        let _ = std::fs::remove_file(&tmp);
+        return Err(e);
+    }
+    std::fs::rename(&tmp, path)
 }
 
-/// 读取最新心跳（含失败类别行）。任何缺失/残缺/畸形内容均返回 `None`，
-/// 使轮询循环可直接在下一拍重试。
+/// 读取最新心跳（含失败类别行与第 6 字段写失败计数）。任何缺失/残缺/畸形内容
+/// 均返回 `None`，使轮询循环可直接在下一拍重试。
+///
+/// # 边界与前提
+/// - 旧 5 字段 `START` 格式宽容映射为 `COMPLETED(index - 1)`：旧 START(j) 计数
+///   覆盖 < j 的测试，与 COMPLETED(j-1) 语义等价；index=0 时 saturating_sub 防下溢。
 fn read_heartbeat(path: &Path) -> Option<Heartbeat> {
     let content = std::fs::read_to_string(path).ok()?;
     let mut lines = content.lines();
     let line = lines.next()?;
     let mut parts = line.split_whitespace();
     let phase = parts.next()?.to_string();
-    let index = parts.next()?.parse().ok()?;
+    let index: usize = parts.next()?.parse().ok()?;
     let pass = parts.next()?.parse().ok()?;
     let fail = parts.next()?.parse().ok()?;
     let skip = parts.next()?.parse().ok()?;
+    let hb_write_errors = parts.next().and_then(|s| s.parse().ok()).unwrap_or(0);
     let mut categories = HashMap::new();
     for l in lines {
         if let Some((cat, count)) = l.split_once('\t') {
@@ -998,6 +1031,11 @@ fn read_heartbeat(path: &Path) -> Option<Heartbeat> {
             }
         }
     }
+    let (phase, index) = if phase == "START" {
+        ("COMPLETED".into(), index.saturating_sub(1))
+    } else {
+        (phase, index)
+    };
     Some(Heartbeat {
         phase,
         index,
@@ -1005,37 +1043,62 @@ fn read_heartbeat(path: &Path) -> Option<Heartbeat> {
         fail,
         skip,
         categories,
+        hb_write_errors,
     })
 }
 
-/// 把心跳快照并入累计统计（含失败类别）。
+/// 把心跳快照并入累计统计（含失败类别与子进程侧写失败计数）。
 fn merge_heartbeat(stats: &mut RunStats, hb: &Heartbeat) {
     stats.pass += hb.pass;
     stats.fail += hb.fail;
     stats.skip += hb.skip;
+    stats.hb_write_errors += hb.hb_write_errors;
     for (cat, count) in &hb.categories {
         *stats.fail_categories.entry(cat.clone()).or_insert(0) += count;
     }
 }
 
+/// 把 supervise 旁路失败行文件并入统计：逐行重建 FailRecord（类别经本表 id
+/// 重映射 + push_fail_record 的 cap 逻辑）。
+///
+/// # 注意事项
+/// - 失败计数（fail_categories）已由对应心跳合并覆盖，此处只补 fail_records，
+///   不得再累计计数，避免双计。worker 循环先写心跳后追加旁路，故"无心跳退出"
+///   分支旁路必为空（防御性 no-op）。
+fn merge_fail_log(stats: &mut RunStats, hb_path: &Path) {
+    let content = match std::fs::read_to_string(hb_path.with_extension("fails")) {
+        Ok(c) => c,
+        Err(_) => return,
+    };
+    for (index, cat, subkey, message) in parse_fail_log(&content) {
+        stats.push_fail_record(index, cat, subkey, message);
+    }
+}
+
 /// 记一笔超时/崩溃结果：默认计入 skip，`--no-skip` 下计入 fail（归入
 /// `timeout/crash` 类别，父进程无法进一步拆分根因）。
-fn record_timeout_or_crash(stats: &mut RunStats, no_skip: bool) {
+///
+/// # 副作用
+/// - 把 `(index, elapsed_ms)` 追加进 timeout_crashes 清单（elapsed_ms=0 表示
+///   非超时崩溃：spawn 失败 / 中途退出 / waiterr / 无心跳），供收尾逐路径报告。
+fn record_timeout_or_crash(stats: &mut RunStats, no_skip: bool, index: usize, elapsed_ms: u64) {
     if no_skip {
         stats.fail += 1;
         *stats.fail_categories.entry("timeout/crash".into()).or_insert(0) += 1;
     } else {
         stats.skip += 1;
     }
+    stats.timeout_crashes.push((index, elapsed_ms));
 }
 
 /// 在监督下运行一个窗口 `[wstart, wend)`，返回经过多次子进程重启
 /// 聚合的 `RunStats`（含失败类别）。
 ///
 /// 单 worker 子进程运行常规 in-process 路径（预热 kernel + harness 前缀缓存）
-/// 并在每个测试前发出心跳。若运行下标停滞超过 `timeout`，子进程被杀死、
-/// 按路径报告肇事者，并由全新子进程从 `culprit + 1` 续跑。子进程在测试中途
-/// 崩溃也经同路径恢复。超时/崩溃默认计为 skip，`--no-skip` 下计为失败。
+/// 并在每个测试完成后发出心跳（COMPLETED）。若运行下标停滞超过 `timeout`，
+/// 子进程被杀死、按路径报告肇事者，并由全新子进程从肇事者之后续跑；子进程
+/// 在测试中途崩溃也经同路径恢复，恢复基于最后完成下标，无漏项。子进程死亡后
+/// 读取旁路失败行并入 fail_records。超时/崩溃默认计为 skip，`--no-skip` 下计为失败。
 #[expect(clippy::too_many_arguments)]
 fn supervise_window(
     exe: &Path, args: &[String], no_skip: bool, wstart: usize, wend: usize, timeout: Duration, startup_grace: Duration,
@@ -1054,6 +1117,8 @@ fn supervise_window(
 
     while cur < wend {
         let _ = std::fs::remove_file(&hb_path);
+        let _ = std::fs::remove_file(format!("{}.tmp", hb_path.display()));
+        let _ = std::fs::remove_file(hb_path.with_extension("fails"));
         let max_tests = wend - cur;
 
         let mut child = match Command::new(exe)
@@ -1072,7 +1137,8 @@ fn supervise_window(
             Ok(child) => child,
             Err(err) => {
                 eprintln!("  window {window_id}: failed to spawn child at index {cur}: {err}");
-                record_timeout_or_crash(&mut stats, no_skip);
+                stats.spawn_errors += 1;
+                record_timeout_or_crash(&mut stats, no_skip, cur, 0);
                 cur += 1;
                 continue;
             }
@@ -1088,23 +1154,27 @@ fn supervise_window(
                     match read_heartbeat(&hb_path) {
                         Some(hb) if hb.phase == "DONE" => {
                             merge_heartbeat(&mut stats, &hb);
+                            merge_fail_log(&mut stats, &hb_path);
                             cur = wend;
                         }
                         Some(hb) => {
                             merge_heartbeat(&mut stats, &hb);
+                            let culprit = hb.index + 1;
+                            merge_fail_log(&mut stats, &hb_path);
                             eprintln!(
                                 "  [warn] window {window_id}: child exited ({status}) mid-test #{}: {}",
-                                hb.index,
-                                describe(hb.index)
+                                culprit,
+                                describe(culprit)
                             );
-                            record_timeout_or_crash(&mut stats, no_skip);
-                            cur = hb.index + 1;
+                            record_timeout_or_crash(&mut stats, no_skip, culprit, 0);
+                            cur = culprit;
                         }
                         None => {
                             eprintln!(
                                 "  [warn] window {window_id}: child exited ({status}) with no heartbeat at index {cur}; skipping one"
                             );
-                            record_timeout_or_crash(&mut stats, no_skip);
+                            merge_fail_log(&mut stats, &hb_path);
+                            record_timeout_or_crash(&mut stats, no_skip, cur, 0);
                             cur += 1;
                         }
                     }
@@ -1113,8 +1183,11 @@ fn supervise_window(
                 Ok(None) => {}
                 Err(err) => {
                     eprintln!("  window {window_id}: try_wait error: {err}");
+                    stats.wait_errors += 1;
                     let _ = child.kill();
                     let _ = child.wait();
+                    merge_fail_log(&mut stats, &hb_path);
+                    record_timeout_or_crash(&mut stats, no_skip, cur, 0);
                     cur += 1;
                     break;
                 }
@@ -1134,19 +1207,21 @@ fn supervise_window(
             };
 
             if elapsed > deadline {
+                // 先杀再读：心跳与旁路失败行都须在子进程死亡后取最终状态。
+                let _ = child.kill();
+                let _ = child.wait();
                 let hb = read_heartbeat(&hb_path);
-                let culprit = hb.as_ref().map(|h| h.index).unwrap_or(cur);
+                let culprit = hb.as_ref().map(|h| h.index + 1).unwrap_or(cur);
                 if let Some(h) = &hb {
                     merge_heartbeat(&mut stats, h);
                 }
+                merge_fail_log(&mut stats, &hb_path);
                 eprintln!(
                     "  [timeout] window {window_id}: TIMEOUT ({}s) on test #{culprit}: {}",
                     deadline.as_secs(),
                     describe(culprit)
                 );
-                let _ = child.kill();
-                let _ = child.wait();
-                record_timeout_or_crash(&mut stats, no_skip);
+                record_timeout_or_crash(&mut stats, no_skip, culprit, elapsed.as_millis() as u64);
                 cur = culprit + 1;
                 break;
             }
@@ -1156,6 +1231,8 @@ fn supervise_window(
     }
 
     let _ = std::fs::remove_file(&hb_path);
+    let _ = std::fs::remove_file(format!("{}.tmp", hb_path.display()));
+    let _ = std::fs::remove_file(hb_path.with_extension("fails"));
     stats
 }
 
@@ -1275,6 +1352,29 @@ fn run_supervised(args: &[String], skip_until: usize, end_index: usize, no_skip:
     if !fail_list.is_empty() {
         print!("{fail_list}");
     }
+    let anomalies = stats.spawn_errors + stats.wait_errors + stats.hb_write_errors;
+    if anomalies > 0 {
+        println!("  --- supervise anomalies ---");
+        if stats.spawn_errors > 0 {
+            println!("    spawn errors   : {}", stats.spawn_errors);
+        }
+        if stats.wait_errors > 0 {
+            println!("    wait errors    : {}", stats.wait_errors);
+        }
+        if stats.hb_write_errors > 0 {
+            println!("    hb write errors: {}", stats.hb_write_errors);
+        }
+    }
+    if !stats.timeout_crashes.is_empty() {
+        println!("  --- TIMEOUT/CRASH list ({}) ---", stats.timeout_crashes.len());
+        for (idx, elapsed_ms) in &stats.timeout_crashes {
+            let path = paths
+                .get(*idx)
+                .map(|p| p.display().to_string())
+                .unwrap_or_else(|| format!("#{idx}"));
+            println!("    {idx}  {elapsed_ms}ms  {path}");
+        }
+    }
     println!("═══════════════════════════════════════");
 
     stats.fail == 0
@@ -1598,17 +1698,6 @@ fn run_tests() -> bool {
                                 test262_debug!("running: {}", path_str);
                                 eprintln!("  [{tid:?}] running: {path_str}");
                             }
-                            if let Some(hb) = heartbeat_ref {
-                                write_heartbeat(
-                                    hb,
-                                    "START",
-                                    i,
-                                    stats.pass,
-                                    stats.fail,
-                                    stats.skip,
-                                    &stats.fail_categories,
-                                );
-                            }
 
                             let result = process_path(
                                 &paths_ref[i],
@@ -1620,6 +1709,30 @@ fn run_tests() -> bool {
                                 &harness_cache,
                             );
                             stats.record(i, &result);
+                            // COMPLETED 心跳：先写心跳再追加旁路失败行（崩溃恢复
+                            // 无漏项、无双计的写序契约）。
+                            if let Some(hb) = heartbeat_ref {
+                                if let Err(e) = write_heartbeat(
+                                    hb,
+                                    "COMPLETED",
+                                    i,
+                                    stats.pass,
+                                    stats.fail,
+                                    stats.skip,
+                                    &stats.fail_categories,
+                                    stats.hb_write_errors,
+                                ) {
+                                    stats.hb_write_errors += 1;
+                                    eprintln!("  [warn] heartbeat write failed at #{i}: {e}");
+                                }
+                                if let TestOutcome::Fail(msg) = &result.outcome {
+                                    let cat = categorize_fail(msg);
+                                    if let Err(e) = append_fail_log(&hb.with_extension("fails"), i, &cat, "", msg) {
+                                        stats.hb_write_errors += 1;
+                                        eprintln!("  [warn] fail log append failed at #{i}: {e}");
+                                    }
+                                }
+                            }
                             if verbose {
                                 match &result.outcome {
                                     TestOutcome::Pass(_) => println!("PASS {}", paths_ref[i].display()),
@@ -1665,7 +1778,19 @@ fn run_tests() -> bool {
     }
 
     if let Some(hb) = &heartbeat_path {
-        write_heartbeat(hb, "DONE", end_index, stats.pass, stats.fail, stats.skip, &stats.fail_categories);
+        if let Err(e) = write_heartbeat(
+            hb,
+            "DONE",
+            end_index,
+            stats.pass,
+            stats.fail,
+            stats.skip,
+            &stats.fail_categories,
+            stats.hb_write_errors,
+        ) {
+            stats.hb_write_errors += 1;
+            eprintln!("  [warn] final DONE heartbeat write failed: {e}");
+        }
     }
 
     eprintln!();
@@ -1838,7 +1963,8 @@ mod tests {
         }
     }
 
-    /// 心跳写读往返：类别行随心跳头一起持久化并完整还原（含制表符/换行压平）。
+    /// 心跳写读往返：类别行随心跳头一起持久化并完整还原（含制表符/换行压平），
+    /// 第 6 字段 hb_write_errors 同步往返。
     #[test]
     fn heartbeat_round_trips_categories() {
         let dir = std::env::temp_dir();
@@ -1846,13 +1972,14 @@ mod tests {
         let mut categories = HashMap::new();
         categories.insert("vm: not defined".to_string(), 3);
         categories.insert("compile: unsupported".to_string(), 1);
-        write_heartbeat(&path, "DONE", 42, 30, 4, 8, &categories);
+        write_heartbeat(&path, "DONE", 42, 30, 4, 8, &categories, 3).expect("心跳写失败");
         let hb = read_heartbeat(&path).expect("心跳应可读回");
         assert_eq!(hb.phase, "DONE");
         assert_eq!(hb.index, 42);
         assert_eq!(hb.pass, 30);
         assert_eq!(hb.fail, 4);
         assert_eq!(hb.skip, 8);
+        assert_eq!(hb.hb_write_errors, 3);
         assert_eq!(hb.categories.get("vm: not defined"), Some(&3));
         assert_eq!(hb.categories.get("compile: unsupported"), Some(&1));
         let _ = std::fs::remove_file(&path);
@@ -1865,7 +1992,7 @@ mod tests {
         let path = dir.join(format!("oxide_t262_hb_test2_{}.txt", std::process::id()));
         let mut categories = HashMap::new();
         categories.insert("vm: other (multi\nline\tmessage)".to_string(), 2);
-        write_heartbeat(&path, "START", 7, 1, 2, 3, &categories);
+        write_heartbeat(&path, "COMPLETED", 7, 1, 2, 3, &categories, 0).expect("心跳写失败");
         let hb = read_heartbeat(&path).expect("心跳应可读回");
         assert_eq!(hb.fail, 2);
         assert_eq!(hb.categories.len(), 1);
@@ -1960,4 +2087,128 @@ mod tests {
         let payload: Box<dyn std::any::Any + Send> = Box::new(42u32);
         assert_eq!(panic_payload_str(&payload), "engine panic (non-string payload)");
     }
+
+    /// 心跳第 6 字段（hb_write_errors）写读往返。
+    #[test]
+    fn heartbeat_round_trips_write_errors_field() {
+        let dir = std::env::temp_dir();
+        let path = dir.join(format!("oxide_t262_hb_test_wr_{}.txt", std::process::id()));
+        let categories = HashMap::new();
+        write_heartbeat(&path, "COMPLETED", 9, 5, 1, 2, &categories, 5).expect("心跳写失败");
+        let hb = read_heartbeat(&path).expect("心跳应可读回");
+        assert_eq!(hb.phase, "COMPLETED");
+        assert_eq!(hb.index, 9);
+        assert_eq!(hb.hb_write_errors, 5);
+        let _ = std::fs::remove_file(&path);
+    }
+
+    /// 旧 5 字段 START 心跳宽容映射：START(j) → COMPLETED(j-1)；j=0 不溢出。
+    #[test]
+    fn read_heartbeat_maps_legacy_start_to_completed() {
+        let dir = std::env::temp_dir();
+        let path = dir.join(format!("oxide_t262_hb_test_legacy_{}.txt", std::process::id()));
+        std::fs::write(&path, "START 7 1 2 3\n").expect("写原始心跳行失败");
+        let hb = read_heartbeat(&path).expect("心跳应可读回");
+        assert_eq!(hb.phase, "COMPLETED");
+        assert_eq!(hb.index, 6);
+        std::fs::write(&path, "START 0 0 0 0\n").expect("写原始心跳行失败");
+        let hb = read_heartbeat(&path).expect("心跳应可读回");
+        assert_eq!(hb.index, 0, "saturating_sub 防下溢");
+        let _ = std::fs::remove_file(&path);
+    }
+
+    /// 原子写：写后目标文件内容完整、无 `.tmp` 残留。
+    #[test]
+    fn write_heartbeat_atomic_no_tmp_leftover() {
+        let dir = std::env::temp_dir();
+        let path = dir.join(format!("oxide_t262_hb_test_atomic_{}.txt", std::process::id()));
+        let categories = HashMap::new();
+        write_heartbeat(&path, "DONE", 10, 3, 2, 1, &categories, 0).expect("心跳写失败");
+        let content = std::fs::read_to_string(&path).expect("心跳应可读回");
+        assert!(content.starts_with("DONE 10 3 2 1 0\n"), "内容应为 6 字段头，实际:\n{content}");
+        let tmp = format!("{}.tmp", path.display());
+        assert!(!Path::new(&tmp).exists(), "tmp 文件不应残留");
+        let _ = std::fs::remove_file(&path);
+    }
+
+    /// 超时/崩溃记账：计数（no_skip 转 fail）与 timeout_crashes 入列。
+    #[test]
+    fn record_timeout_or_crash_records_index_elapsed() {
+        let mut stats = RunStats::default();
+        record_timeout_or_crash(&mut stats, true, 3, 2500);
+        assert_eq!(stats.fail, 1);
+        assert_eq!(stats.fail_categories.get("timeout/crash"), Some(&1));
+        assert_eq!(stats.timeout_crashes, vec![(3, 2500)]);
+        record_timeout_or_crash(&mut stats, false, 4, 0);
+        assert_eq!(stats.skip, 1);
+        assert_eq!(stats.timeout_crashes, vec![(3, 2500), (4, 0)]);
+    }
+
+    /// merge 合并异常计数器：spawn/wait/hb 求和、timeout_crashes 拼接。
+    #[test]
+    fn runstats_merge_sums_error_counters() {
+        let mut a = RunStats {
+            spawn_errors: 1,
+            wait_errors: 2,
+            hb_write_errors: 3,
+            timeout_crashes: vec![(0, 100)],
+            ..RunStats::default()
+        };
+        let b = RunStats {
+            spawn_errors: 4,
+            wait_errors: 5,
+            hb_write_errors: 6,
+            timeout_crashes: vec![(1, 200)],
+            ..RunStats::default()
+        };
+        a.merge(b);
+        assert_eq!(a.spawn_errors, 5);
+        assert_eq!(a.wait_errors, 7);
+        assert_eq!(a.hb_write_errors, 9);
+        assert_eq!(a.timeout_crashes, vec![(0, 100), (1, 200)]);
+    }
+
+    /// 旁路失败行往返：append 后 parse 恢复全部字段；残缺/畸形尾行静默跳过。
+    #[test]
+    fn fail_log_round_trips_and_skips_truncated() {
+        let dir = std::env::temp_dir();
+        let path = dir.join(format!("oxide_t262_fails_test_{}.log", std::process::id()));
+        append_fail_log(&path, 3, "vm: not callable", "", "x is not callable").expect("追加失败");
+        append_fail_log(&path, 4, "compile: unsupported", "foo", "a\tb\nc").expect("追加失败");
+        let mut content = std::fs::read_to_string(&path).expect("读取失败");
+        content.push_str("5\tvm: x\n"); // 残缺：仅 2 字段（SIGKILL 半写形态）
+        content.push_str("x\tb\tc\td\n"); // 畸形：index 非数字
+        std::fs::write(&path, content).expect("写回失败");
+        let content = std::fs::read_to_string(&path).expect("读取失败");
+        let rows = parse_fail_log(&content);
+        assert_eq!(rows.len(), 2, "残缺/畸形行应被跳过，实际 {rows:?}");
+        assert_eq!(
+            rows[0],
+            (3, "vm: not callable".to_string(), "".to_string(), "x is not callable".to_string())
+        );
+        assert_eq!(rows[1], (4, "compile: unsupported".to_string(), "foo".to_string(), "a b c".to_string()));
+        let _ = std::fs::remove_file(&path);
+    }
+
+    /// merge_fail_log 重建 fail_records：类别经 id 表重映射、消息 cap；
+    /// fail_categories 保持空（计数不双计契约）。
+    #[test]
+    fn merge_fail_log_reconstructs_fail_records() {
+        let dir = std::env::temp_dir();
+        let hb_path = dir.join(format!("oxide_t262_hb_test_mrg_{}.txt", std::process::id()));
+        let sidecar = hb_path.with_extension("fails");
+        append_fail_log(&sidecar, 2, "vm: not callable", "", "x is not callable").expect("追加失败");
+        append_fail_log(&sidecar, 7, "compile: unsupported", "", "y").expect("追加失败");
+        let mut stats = RunStats::default();
+        merge_fail_log(&mut stats, &hb_path);
+        assert_eq!(stats.fail_records.len(), 2);
+        assert_eq!(stats.fail_records[0].index, 2);
+        assert_eq!(stats.categories[stats.fail_records[0].category_id as usize], "vm: not callable");
+        assert_eq!(stats.fail_records[0].message, "x is not callable");
+        assert_eq!(stats.fail_records[1].index, 7);
+        assert_eq!(stats.categories[stats.fail_records[1].category_id as usize], "compile: unsupported");
+        assert!(stats.fail_categories.is_empty(), "计数不双计：fail_categories 必须保持空");
+        let _ = std::fs::remove_file(&sidecar);
+        let _ = std::fs::remove_file(&hb_path);
+    }
 }
diff --git a/crates/oxide_test262/src/report.rs b/crates/oxide_test262/src/report.rs
index f7c4863b..3a822c28 100644
--- a/crates/oxide_test262/src/report.rs
+++ b/crates/oxide_test262/src/report.rs
@@ -2,7 +2,7 @@
 //! 全部为纯函数/String builder（可单测），不持有全局状态。
 
 use crate::RunStats;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 /// 单条失败记录：路径用全局测试数组下标（8 字节），类别用 RunStats 内 id 表下标。
 /// 消息完整保留（单条 2 KiB cap + 全局 64 MiB cap），不截断到类别桶。
@@ -29,8 +29,7 @@ pub fn first_line(s: &str) -> &str {
     s.lines().next().unwrap_or("")
 }
 
-/// 压平 \t \n \r 为空格（后续 fail-log / 心跳旁路行的可解析保证）。
-#[cfg_attr(not(test), expect(dead_code))] // 心跳旁路行接入后使用
+/// 压平 \t \n \r 为空格（fail-log / 心跳旁路行 / 类别行的可解析保证）。
 pub fn escape_log_field(s: &str) -> String {
     s.replace(['\t', '\n', '\r'], " ")
 }
@@ -97,6 +96,42 @@ pub fn format_fail_list(stats: &RunStats, paths: &[PathBuf]) -> String {
     out
 }
 
+/// 把一条失败记录追加到 supervise 旁路文件（子进程 → 父进程通道）。
+/// 行格式 `index\tcategory\tsubkey\tmessage`，字段经 escape_log_field 压平。
+///
+/// # 注意事项
+/// - 追加写不做原子性：父进程只在子进程死亡后才读取，半写尾行由
+///   [`parse_fail_log`] 防御性跳过。
+pub fn append_fail_log(path: &Path, index: usize, category: &str, subkey: &str, message: &str) -> std::io::Result<()> {
+    use std::io::Write;
+    let mut f = std::fs::OpenOptions::new().create(true).append(true).open(path)?;
+    writeln!(
+        f,
+        "{}\t{}\t{}\t{}",
+        index,
+        escape_log_field(category),
+        escape_log_field(subkey),
+        escape_log_field(message)
+    )
+}
+
+/// 解析旁路失败行文件为 `(index, category, subkey, message)` 列表。
+///
+/// # 边界与前提
+/// - 残缺尾行（子进程被杀时半写）与畸形行（字段数不足 / index 非数字）静默跳过。
+pub fn parse_fail_log(content: &str) -> Vec<(usize, String, String, String)> {
+    let mut out = Vec::new();
+    for line in content.lines() {
+        let mut it = line.splitn(4, '\t');
+        let (Some(index), Some(cat), Some(subkey), Some(message)) = (it.next(), it.next(), it.next(), it.next()) else {
+            continue;
+        };
+        let Ok(index) = index.parse::<usize>() else { continue };
+        out.push((index, cat.to_string(), subkey.to_string(), message.to_string()));
+    }
+    out
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;