diff --git a/.github/workflows/dco.yml b/.github/workflows/dco.yml
index c9553b7..c2e60b2 100644
--- a/.github/workflows/dco.yml
+++ b/.github/workflows/dco.yml
@@ -10,7 +10,12 @@ permissions:
 jobs:
   dco:
     name: DCO Check
-    # DCO 的 Signed-off-by 是对人类贡献者的来源认证，Dependabot 生成的 commit 无法携带签名。
+    # DCO 的 Signed-off-by 是对**人类**贡献者的来源认证；机器生成的 commit 无从签名。
+    # 原先这里只放过 dependabot[bot]，于是 release-please 开的 release PR 永远红：
+    # 它的提交作者是 github-actions[bot]（用 GitHub API 建提交，不走本地 git，
+    # 工作流里的 GIT_AUTHOR_* 环境变量对它无效），既没有也**不可能有** Signed-off-by。
+    # 净效果 = 分支保护要求 DCO 的仓库里，自动发版路径结构上不可用（#115/#120/#132 都撞在这）。
+    # 现在按"提交作者"而不是"PR 作者"判，豁免名单见脚本里的 BOT_AUTHOR_EMAILS。
     if: github.actor != 'dependabot[bot]'
     runs-on: ubuntu-latest
     steps:
@@ -21,19 +26,36 @@ jobs:
 
       - name: Verify Signed-off-by
         shell: bash
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
         run: |
           set -euo pipefail
-          base_sha="${{ github.event.pull_request.base.sha }}"
-          head_sha="${{ github.event.pull_request.head.sha }}"
-          if [[ -z "$base_sha" || -z "$head_sha" ]]; then
+          # 只豁免"我们自己的自动化"产出的提交；人的提交缺签名照样红。
+          BOT_AUTHOR_EMAILS="41898282+github-actions[bot]@users.noreply.github.com 49699333+dependabot[bot]@users.noreply.github.com"
+          if [[ -z "${BASE_SHA:-}" || -z "${HEAD_SHA:-}" ]]; then
             echo "::error::Could not determine PR base/head SHA"
             exit 1
           fi
           fails=0
+          checked=0
+          skipped=0
           while IFS= read -r commit; do
+            author_email=$(git log -1 --format='%ae' "$commit")
+            is_bot=no
+            for bot in $BOT_AUTHOR_EMAILS; do
+              if [[ "$author_email" == "$bot" ]]; then is_bot=yes; fi
+            done
+            if [[ "$is_bot" == yes ]]; then
+              skipped=$((skipped + 1))
+              echo "跳过机器提交 $commit（作者 $author_email —— 自动化无法签名）"
+              continue
+            fi
+            checked=$((checked + 1))
             if ! git log -1 --format='%B' "$commit" | grep -q 'Signed-off-by:'; then
-              echo "::error::Commit $commit is missing 'Signed-off-by:' trailer (run: git commit -s)"
+              echo "::error::Commit $commit 缺 'Signed-off-by:' 尾注（本地补签：git commit --amend -s）"
               fails=1
             fi
-          done < <(git rev-list "$base_sha..$head_sha")
+          done < <(git rev-list "$BASE_SHA..$HEAD_SHA")
+          echo "DCO：人类提交 $checked 条、机器提交豁免 $skipped 条、失败=$fails"
           exit $fails
diff --git a/tests/test_dco_bot_exemption.py b/tests/test_dco_bot_exemption.py
new file mode 100644
index 0000000..322cb63
--- /dev/null
+++ b/tests/test_dco_bot_exemption.py
@@ -0,0 +1,104 @@
+"""DCO 检查的豁免范围：只放过"自动化自己产的提交"，人的提交缺签名照样红。
+
+为什么要改：release-please 用 GitHub API 建提交（作者 = github-actions[bot]，
+工作流里设的 GIT_AUTHOR_* 对它无效），所以它的 release PR **永远不可能**有 Signed-off-by；
+分支保护又要求 DCO 通过 —— 于是自动发版路径结构上不可用（#115 / #120 / #132 都撞在这）。
+
+这道测试的作用是把"豁免"钉在它能豁免的地方：混合提交里只要有一条人写的没签名就必须红。
+"""
+
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+import yaml
+
+_ROOT = Path(__file__).resolve().parent.parent
+_WF = _ROOT / ".github" / "workflows" / "dco.yml"
+
+HUMAN = ("Re Serendipity", "human@example.com")
+BOT = ("github-actions[bot]", "41898282+github-actions[bot]@users.noreply.github.com")
+
+
+def _dco_script() -> str:
+    doc = yaml.safe_load(_WF.read_text(encoding="utf-8"))
+    steps = doc["jobs"]["dco"]["steps"]
+    step = next((s for s in steps if "Signed-off-by" in str(s.get("name") or "")), None)
+    assert step, "dco.yml 里找不到 Signed-off-by 校验步骤"
+    body = step["run"]
+    assert "BASE_SHA" in body and "HEAD_SHA" in body, (
+        "脚本又直接从 ${{ }} 模板取 SHA 了 —— 那样本测试无法注入，判据也就没法验"
+    )
+    return body
+
+
+def _git(cwd: Path, *args: str) -> str:
+    r = subprocess.run(["git", *args], cwd=str(cwd), capture_output=True, text=True, check=True)
+    return r.stdout.strip()
+
+
+def _repo_with(tmp: Path, commits: list[tuple[tuple[str, str], bool]]) -> tuple[Path, str, str]:
+    """建一个一次性仓库：commits = [(作者身份, 是否带 Signed-off-by)]，返回 (base, head)。"""
+    repo = tmp / "dco_repo"
+    repo.mkdir(parents=True)
+    _git(repo, "init", "-q")
+    _git(repo, "config", "user.name", "Test Base")
+    _git(repo, "config", "user.email", "base@example.com")
+    (repo / "seed.txt").write_text("seed\n", encoding="utf-8")
+    _git(repo, "add", ".")
+    _git(repo, "commit", "-q", "-m", "seed")
+    base = _git(repo, "rev-parse", "HEAD")
+    for (name, email), signed in commits:
+        (repo / f"f-{email}-{len(str(repo))}.txt").write_text("x\n", encoding="utf-8")
+        _git(repo, "add", ".")
+        msg = "some change" + ("\n\nSigned-off-by: " + f"{name} <{email}>" if signed else "")
+        _git(repo, "commit", "-q", "--author", f"{name} <{email}>", "-m", msg)
+    return repo, base, _git(repo, "rev-parse", "HEAD")
+
+
+def _run_dco(tmp: Path, commits: list[tuple[tuple[str, str], bool]]) -> subprocess.CompletedProcess[str]:
+    bash = shutil.which("bash")
+    if not bash:  # pragma: no cover - 无 bash 的机器上直接跳过，不给假绿
+        pytest.skip("本机没有 bash，无法执行从工作流里抽出的脚本")
+    repo, base, head = _repo_with(tmp, commits)
+    script = tmp / "dco.sh"
+    script.write_text(_dco_script(), encoding="utf-8", newline="\n")
+    env = {**os.environ, "BASE_SHA": base, "HEAD_SHA": head, "PATH": os.environ["PATH"]}
+    return subprocess.run(
+        [bash, str(script)],
+        cwd=str(repo),
+        capture_output=True,
+        text=True,
+        encoding="utf-8",
+        errors="replace",
+        env=env,
+        check=False,
+    )
+
+
+def test_human_commit_without_signoff_still_fails(tmp_path: Path) -> None:
+    res = _run_dco(tmp_path, [(HUMAN, False)])
+    assert res.returncode == 1, f"人写的提交没签名却被放行：{res.stdout}{res.stderr}"
+
+
+def test_human_commit_with_signoff_passes(tmp_path: Path) -> None:
+    res = _run_dco(tmp_path, [(HUMAN, True)])
+    assert res.returncode == 0, res.stdout + res.stderr
+
+
+def test_bot_release_commit_without_signoff_is_exempt(tmp_path: Path) -> None:
+    """这正是 release-please 的形状：作者是 bot、没有也签不出 Signed-off-by。"""
+    res = _run_dco(tmp_path, [(BOT, False)])
+    assert res.returncode == 0, f"自动化提交仍被判红，自动发版路径依旧不可用：{res.stdout[-300:]}"
+    assert "豁免 1" in res.stdout, f"没有把豁免显式记出来（审计要看得到放过了谁）：{res.stdout[-300:]}"
+
+
+def test_exemption_does_not_bypass_a_whole_pr(tmp_path: Path) -> None:
+    """混合：bot 提交 + 人提交（无签名）→ 必须红。这条是本豁免不是后门的关键证据。"""
+    res = _run_dco(tmp_path, [(BOT, False), (HUMAN, False)])
+    assert res.returncode == 1, f"有 bot 提交在场时人的缺签名被一起放过了：{res.stdout[-400:]}"
+    assert "豁免 1" in res.stdout