diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6b8c5f2..c53cfc8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## Unreleased
 
 ### Fixed
+- **2000 字现场切片留住未跟踪新文件（DEBUG #57 续）**：失败 episode 与成功事件不再对 `capture_diff_snapshot` 的结果做 `[:2000]`。两臂都传入 `max_chars=2000`，截断在 helper 内完成。已跟踪 diff 会占满预算时，先裁跟踪前缀，固定留 480 字（不超过预算的四分之一）给未跟踪新文件块；没有合格未跟踪文件时，这截尾部还给跟踪 diff。返回长度不超过预算。`.venv` / `node_modules` / `__pycache__` / `.git` / 受保护文件 / `memory/`、`.evolver/` 等运行态目录 / 含 NUL 的二进制仍不进入补充。不改固化门，不写 Parent baseline，不开 val 密封。
 - **失败现场 diff 包含未跟踪新文件（DEBUG #57）**：`capture_diff_snapshot` 在 `git diff HEAD` 之后追加未跟踪新文件的 unified diff。失败侧 `_failure_diff` 与成功侧共用这一 helper。依赖树、缓存、运行态目录、受保护路径和含 NUL 的二进制不进入这份补充。不改固化门，不写 Parent baseline，不开 val 密封。
 
 ### Docs
diff --git a/DEBUG.md b/DEBUG.md
index 52abec3..d405569 100644
--- a/DEBUG.md
+++ b/DEBUG.md
@@ -1098,9 +1098,22 @@
   （`memory/`、`.evolver/` 等，与 `_is_runtime_state` 同口径）以及文件头
   含 NUL 的二进制；读入量不超过快照剩余预算。不改固化门，不写 Parent
   baseline，不开 val 密封。
+- **续（2000 字切片仍会切掉补丁）**：上面的补丁接在跟踪 diff 末尾。失败侧
+  `_failure_diff` 与成功事件随后做 `[:2000]`；helper 自己在
+  `len(raw) > max_chars` 时也直接返回跟踪 diff 前缀。已跟踪 diff 超过或
+  接近 2000 字时，未跟踪块被前缀切掉，`notes.md` 的标记在真实大 diff 的
+  失败现场和成功 `diff_snapshot` 里仍看不见。
+- **修复（续）**：两臂改为 `capture_diff_snapshot(..., max_chars=2000)`
+  （`_STORED_DIFF_CHARS`），截断只发生在 helper 内，不再做第二次前缀切片。
+  已跟踪 diff 会把尾部挤到 480 字以下时，先裁跟踪前缀，把这 480 字
+  （且不超过预算的四分之一）留给未跟踪新文件块；没有合格未跟踪文件时，
+  尾部还给跟踪 diff。返回长度不超过 `max_chars`，不抬高 2000 字预算。
+  跳过名单不变。不改固化门，不写 Parent baseline，不开 val 密封。
+  DEBUG #61 与 #68 的宿主契约余项不动。
 - **经验**：**凡断言 diff 内容，先确认文件是不是未跟踪**——修之前
   `git diff HEAD` 看不见新文件。快照要看见新文件，就改共用 helper，
   不要给失败侧单开一条路。运行态与依赖树不能跟候选正文抢那 2000 字。
+  **截断也要在同一 helper 里做**：先拼再 `[:2000]`，补在末尾的证据还是会被切掉。
 
 ### 58. 外部 MCP 评审 P1 四项（评估会话，全修）
 
diff --git a/src/evolver/gep/git_ops.py b/src/evolver/gep/git_ops.py
index 2c5e94b..5ab2bc4 100644
--- a/src/evolver/gep/git_ops.py
+++ b/src/evolver/gep/git_ops.py
@@ -121,6 +121,11 @@ def git_list_untracked_files(cwd: Path | str | None = None) -> list[str]:
     }
 )
 _BINARY_SNIFF_BYTES: Final = 8192
+_TRUNCATION_MARK: Final = "\n...[truncated]\n"
+# One short new-file hunk is about 120 characters. 480 keeps that hunk (or
+# the start of a larger one) inside the caller's budget. A quarter cap stops
+# a tiny max_chars from handing the whole snapshot to the supplement.
+_UNTRACKED_TAIL_CHARS: Final = 480
 
 
 def _untracked_snapshot_candidate(rel: str) -> bool:
@@ -187,6 +192,25 @@ def _untracked_diff_text(cwd: Path, *, budget: int) -> str:
     return "".join(chunks)
 
 
+def _clip_diff(text: str, limit: int) -> str:
+    """Clip ``text`` to ``limit`` characters, truncation mark included."""
+    if limit <= 0 or not text:
+        return ""
+    if len(text) <= limit:
+        return text
+    mark = _TRUNCATION_MARK
+    if limit <= len(mark):
+        return text[:limit]
+    return text[: limit - len(mark)] + mark
+
+
+def _untracked_tail_budget(max_chars: int) -> int:
+    """Fixed untracked tail. Never more than a quarter of ``max_chars``."""
+    if max_chars <= 0:
+        return 0
+    return min(_UNTRACKED_TAIL_CHARS, max_chars // 4)
+
+
 def capture_diff_snapshot(
     cwd: Path | str | None = None,
     max_chars: int = 80_000,
@@ -198,20 +222,26 @@ def capture_diff_snapshot(
     its content is appended as a ``diff --git`` new-file hunk. Failure and
     success snapshots share this helper. Noise trees, runtime-state dirs,
     protected paths, and binaries are left out of the untracked supplement.
-    The result is truncated to ``max_chars``.
+
+    The result is at most ``max_chars``. When the tracked diff would leave
+    less than the untracked tail, the tracked prefix is clipped first so the
+    tail stays inside the budget. With nothing eligible to append, that tail
+    goes back to the tracked diff.
     """
     root = Path(cwd) if cwd is not None else Path.cwd()
-    raw = try_run_cmd(["diff", "HEAD"], cwd=root)
-    if len(raw) > max_chars:
-        return raw[:max_chars] + "\n...[truncated]\n"
-    extra = _untracked_diff_text(root, budget=max_chars - len(raw))
-    if extra:
-        if raw and not raw.endswith("\n"):
-            raw += "\n"
-        raw += extra
-    if len(raw) > max_chars:
-        return raw[:max_chars] + "\n...[truncated]\n"
-    return raw
+    if max_chars <= 0:
+        return ""
+    tracked = try_run_cmd(["diff", "HEAD"], cwd=root)
+    tail = _untracked_tail_budget(max_chars)
+    tracked_over_tail = tail and len(tracked) > max_chars - tail
+    tracked_limit = max_chars - tail if tracked_over_tail else max_chars
+    tracked_view = _clip_diff(tracked, tracked_limit)
+    joiner_len = 1 if tracked_view and not tracked_view.endswith("\n") else 0
+    extra = _untracked_diff_text(root, budget=max_chars - len(tracked_view) - joiner_len)
+    if not extra:
+        return _clip_diff(tracked, max_chars)
+    joiner = "\n" if joiner_len else ""
+    return tracked_view + joiner + extra
 
 
 def is_critical_protected_path(rel_path: str) -> bool:
diff --git a/src/evolver/gep/solidify.py b/src/evolver/gep/solidify.py
index 8f3ff7f..c2656fa 100644
--- a/src/evolver/gep/solidify.py
+++ b/src/evolver/gep/solidify.py
@@ -132,9 +132,15 @@ def _failure_event(
     return event
 
 
+# Stored scene budget for failure episodes and success events. Applied inside
+# capture_diff_snapshot so a large tracked diff cannot push untracked hunks
+# past the cut (DEBUG #57).
+_STORED_DIFF_CHARS: Final = 2000
+
+
 def _failure_diff(cwd: Path) -> str:
     """The mutation's diff, captured before rollback. After rollback it is gone."""
-    return capture_diff_snapshot(cwd)[:2000]
+    return capture_diff_snapshot(cwd, max_chars=_STORED_DIFF_CHARS)
 
 
 def _remember_failure_scene(
@@ -2212,7 +2218,7 @@ def _solidify_cycle(
         return pack_rejection
 
     blast_radius = _compute_blast_radius()
-    diff_snapshot = capture_diff_snapshot(cwd)
+    diff_snapshot = capture_diff_snapshot(cwd, max_chars=_STORED_DIFF_CHARS)
 
     # S26.3 strict-improvement gate (wikiskill R_val > R_best): compare the
     # measured score against the fitness ledger. Shadow period: verdict is
@@ -2246,7 +2252,7 @@ def _solidify_cycle(
         "signals": last_run.get("signals", []),
         "mutation": mutation,
         "blast_radius": blast_radius,
-        "diff_snapshot": diff_snapshot[:2000],
+        "diff_snapshot": diff_snapshot,
         # S26 honest score: a MEASURED cascade result (1.0 = all stages green);
         # an unvalidated success claims nothing (score=None + marker) so the
         # ledger distinguishes "tested good" from "never tested".
diff --git a/tests/gep/test_solidify.py b/tests/gep/test_solidify.py
index 5fcaa68..944b23b 100644
--- a/tests/gep/test_solidify.py
+++ b/tests/gep/test_solidify.py
@@ -251,6 +251,31 @@ def test_hypothesis_rejection_records_untracked_new_file(git_ws: Path) -> None:
     assert not (git_ws / "notes.md").exists()
 
 
+def _write_oversized_tracked_readme(git_ws: Path) -> None:
+    (git_ws / "README.md").write_text("TRACKED_HEAD_" + ("n" * 3000) + "\n", encoding="utf-8")
+
+
+def test_hypothesis_rejection_keeps_untracked_when_tracked_diff_fills_budget(git_ws: Path) -> None:
+    """DEBUG #57: a 2000-char failure scene still shows notes.md when tracked diff is huge."""
+    _write_oversized_tracked_readme(git_ws)
+    (git_ws / "notes.md").write_text("untracked-notes-marker\n", encoding="utf-8")
+    write_state_for_solidify(_last_run())
+    result = solidify()
+    assert result["ok"] is False
+    assert result["error"] == "hypothesis_missing"
+    from evolver.gep.episode_record import load_episode, record_round
+
+    stored = record_round(event_id=str(result["event_id"]))
+    body = load_episode(stored["id"])
+    assert body is not None
+    diff = str(body["diff"])
+    assert "TRACKED_HEAD_" in diff
+    assert "diff --git a/notes.md b/notes.md" in diff
+    assert "untracked-notes-marker" in diff
+    assert len(diff) <= 2000
+    assert not (git_ws / "notes.md").exists()
+
+
 def test_success_diff_snapshot_includes_untracked_new_file(
     git_ws: Path,
     armed_pack: dict[str, Any],
@@ -277,6 +302,36 @@ def test_success_diff_snapshot_includes_untracked_new_file(
     assert "diff --git a/notes.md" in str(evt.get("diff_snapshot") or "")
 
 
+def test_success_diff_snapshot_keeps_untracked_when_tracked_diff_fills_budget(
+    git_ws: Path,
+    armed_pack: dict[str, Any],
+    declared_hypothesis: dict[str, Any],
+) -> None:
+    """The success event uses the same 2000-char budget and still shows notes.md."""
+    _ = armed_pack, declared_hypothesis
+    set_flag("enable_fitness_cascade", False, persist=False)
+    _write_oversized_tracked_readme(git_ws)
+    (git_ws / "notes.md").write_text("untracked-notes-marker\n", encoding="utf-8")
+    write_state_for_solidify(
+        _last_run(
+            mutation={
+                "id": "mut_untracked_large",
+                "validation": [[sys.executable, "-c", "print(1)"]],
+            }
+        )
+    )
+    result = solidify()
+    assert result["ok"] is True
+    evt = json.loads(
+        (get_gep_assets_dir() / "events.jsonl").read_text(encoding="utf-8").strip().splitlines()[-1]
+    )
+    diff = str(evt.get("diff_snapshot") or "")
+    assert "TRACKED_HEAD_" in diff
+    assert "diff --git a/notes.md" in diff
+    assert "untracked-notes-marker" in diff
+    assert len(diff) <= 2000
+
+
 def test_hypothesis_rejection_leaves_a_recordable_scene(git_ws: Path) -> None:
     """A settled Reject is an engine scene: gene, diff, and the gate verdict."""
     (git_ws / "README.md").write_text("changed by the candidate\n", encoding="utf-8")
diff --git a/tests/test_git_ops.py b/tests/test_git_ops.py
index 09e1015..9ca5bfa 100644
--- a/tests/test_git_ops.py
+++ b/tests/test_git_ops.py
@@ -6,6 +6,7 @@
 from pathlib import Path
 
 from evolver.gep.git_ops import (
+    _format_new_file_diff,
     capture_diff_snapshot,
     count_file_lines,
     is_constraint_counted_path,
@@ -163,6 +164,73 @@ def test_capture_diff_snapshot_skips_noise_and_binaries(tmp_path: Path) -> None:
         assert marker not in snap
 
 
+def _stripped_git_diff(repo: Path) -> str:
+    result = subprocess.run(
+        ["git", "diff", "HEAD"],
+        cwd=repo,
+        check=True,
+        capture_output=True,
+        text=True,
+    )
+    return result.stdout.strip()
+
+
+def _write_tracked_diff_of_length(repo: Path, target: int) -> str:
+    """Replace README.md so the stripped ``git diff HEAD`` is ``target`` chars."""
+    prefix = "TRACKED_HEAD_"
+    (repo / "README.md").write_text(prefix + "\n", encoding="utf-8")
+    base = _stripped_git_diff(repo)
+    extra = target - len(base)
+    assert extra >= 0, f"diff header {len(base)} already exceeds {target}"
+    (repo / "README.md").write_text(prefix + ("n" * extra) + "\n", encoding="utf-8")
+    raw = _stripped_git_diff(repo)
+    assert len(raw) == target
+    return raw
+
+
+def test_capture_diff_snapshot_keeps_untracked_when_tracked_exceeds_budget(tmp_path: Path) -> None:
+    """A tracked diff longer than max_chars must not eat the untracked tail."""
+    _init_repo(tmp_path)
+    raw = _write_tracked_diff_of_length(tmp_path, 2500)
+    (tmp_path / "notes.md").write_text("untracked-notes-marker\n", encoding="utf-8")
+    assert "untracked-notes-marker" not in raw[:2000]
+    snap = capture_diff_snapshot(tmp_path, max_chars=2000)
+    assert "TRACKED_HEAD_" in snap
+    assert "diff --git a/notes.md b/notes.md" in snap
+    assert "untracked-notes-marker" in snap
+    assert "[truncated]" in snap
+    assert len(snap) <= 2000
+
+
+def test_capture_diff_snapshot_keeps_untracked_when_tracked_nearly_fills_budget(
+    tmp_path: Path,
+) -> None:
+    """A tracked diff that leaves less than one new-file hunk still keeps the hunk."""
+    _init_repo(tmp_path)
+    raw = _write_tracked_diff_of_length(tmp_path, 1900)
+    note = "untracked-notes-marker\n"
+    (tmp_path / "notes.md").write_text(note, encoding="utf-8")
+    hunk = _format_new_file_diff("notes.md", note)
+    assert len(hunk) > 2000 - len(raw)
+    snap = capture_diff_snapshot(tmp_path, max_chars=2000)
+    assert "TRACKED_HEAD_" in snap
+    assert "untracked-notes-marker" in snap
+    assert len(snap) <= 2000
+
+
+def test_capture_diff_snapshot_does_not_reserve_tail_for_noise(tmp_path: Path) -> None:
+    """Dependency noise is not untracked evidence, so the tracked diff keeps the budget."""
+    _init_repo(tmp_path)
+    _write_tracked_diff_of_length(tmp_path, 2500)
+    noise = tmp_path / ".venv" / "lib" / "x.py"
+    noise.parent.mkdir(parents=True)
+    noise.write_text("noise-venv-marker\n", encoding="utf-8")
+    snap = capture_diff_snapshot(tmp_path, max_chars=2000)
+    assert "noise-venv-marker" not in snap
+    assert "TRACKED_HEAD_" in snap
+    assert len(snap) == 2000
+
+
 def test_capture_diff_snapshot_truncates(tmp_path: Path) -> None:
     subprocess.run(["git", "init"], cwd=tmp_path, check=True, capture_output=True)
     subprocess.run(