diff --git a/CHANGELOG.md b/CHANGELOG.md
index 12980eb5..a27085b1 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,11 @@ All notable changes to vouch are documented here. Format follows
 ## [Unreleased]
 
 ### Fixed
+- **sandbox docker argv on Windows** (#582): omit `--user uid:gid` when
+  `os.getuid` / `os.getgid` are unavailable so sandboxed dual-solve no
+  longer raises `AttributeError` while building the docker command.
+- **`kb.session_transcript` handler test needs a KB** : `test_handler_returns_degraded_when_absent` now chdirs into a temp KB and points Claude/Codex search roots at empty dirs, so the handler can return the degraded payload instead of raising `KBNotFoundError`.
+)
 - **`kb.search` excludes retracted claims and archived pages** (#581):
   `search_kb` now drops `ARCHIVED` / `SUPERSEDED` / `REDACTED` claims and
   `ARCHIVED` pages the same way `kb.context` already does, so lifecycle
diff --git a/src/vouch/sandbox.py b/src/vouch/sandbox.py
index eb4f6883..66ea29bc 100644
--- a/src/vouch/sandbox.py
+++ b/src/vouch/sandbox.py
@@ -109,7 +109,15 @@ def _docker_argv(self, agent_argv: list[str], cwd: str | None) -> list[str]:
         args = [
             "docker", "run", "--rm", "-i",
             "--entrypoint", "",
-            "--user", f"{os.getuid()}:{os.getgid()}",
+        ]
+        # os.getuid/getgid are POSIX-only. On Windows (Docker Desktop) omit
+        # --user so argv construction does not AttributeError before docker
+        # runs (#582).
+        getuid = getattr(os, "getuid", None)
+        getgid = getattr(os, "getgid", None)
+        if callable(getuid) and callable(getgid):
+            args += ["--user", f"{getuid()}:{getgid()}"]
+        args += [
             "-w", str(workdir),
             "-e", f"HOME={self.container_home}",
             "-v", f"{self.sandbox_home}:{self.container_home}",
diff --git a/tests/test_sandbox.py b/tests/test_sandbox.py
index 37e93134..4ac16b9c 100644
--- a/tests/test_sandbox.py
+++ b/tests/test_sandbox.py
@@ -54,8 +54,14 @@ def test_docker_agent_runner_wraps_agent_with_worktree_and_home_mounts(
         argv = fr.calls[0]
         assert argv[:3] == ["docker", "run", "--rm"]
         assert "--entrypoint" in argv and "" in argv
-        assert "--user" in argv
-        assert f"{os.getuid()}:{os.getgid()}" in argv
+        # match sandbox._docker_argv: both must be callable, not merely present.
+        uid_ok = callable(getattr(os, "getuid", None))
+        gid_ok = callable(getattr(os, "getgid", None))
+        if uid_ok and gid_ok:
+            assert "--user" in argv
+            assert f"{os.getuid()}:{os.getgid()}" in argv
+        else:
+            assert "--user" not in argv
         assert "-w" in argv and str(worktree.resolve()) in argv
         assert "-e" in argv
         assert f"HOME={sandbox.CONTAINER_HOME}" in argv
@@ -72,6 +78,51 @@ def test_docker_agent_runner_wraps_agent_with_worktree_and_home_mounts(
         runner.close()
 
 
+@pytest.mark.parametrize(
+    "break_uid,break_gid",
+    [
+        pytest.param(True, False, id="getuid-missing"),
+        pytest.param(False, True, id="getgid-missing"),
+        pytest.param(True, True, id="both-missing"),
+        pytest.param("noncallable", False, id="getuid-noncallable"),
+        pytest.param(False, "noncallable", id="getgid-noncallable"),
+    ],
+)
+def test_docker_argv_omits_user_when_uid_gid_unavailable(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+    break_uid: bool | str,
+    break_gid: bool | str,
+) -> None:
+    """Regression for #582: omit --user unless both getuid and getgid are callable."""
+    repo = tmp_path / "repo"
+    repo.mkdir()
+
+    def _break(attr: str, how: bool | str) -> None:
+        if how is False:
+            return
+        if how == "noncallable":
+            monkeypatch.setattr(sandbox.os, attr, object(), raising=False)
+        else:
+            monkeypatch.delattr(sandbox.os, attr, raising=False)
+
+    _break("getuid", break_uid)
+    _break("getgid", break_gid)
+
+    fr = FakeRunner()
+    runner = sandbox.DockerAgentRunner(
+        repo_root=repo, runner=fr, image="agent-img", host_home=tmp_path,
+    )
+    try:
+        runner.run(["claude", "-p", "hi"], cwd=str(repo))
+        argv = fr.calls[0]
+        assert argv[:3] == ["docker", "run", "--rm"]
+        assert "--user" not in argv
+        assert "agent-img" in argv
+    finally:
+        runner.close()
+
+
 def test_require_docker_sandbox_reports_missing_image(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(sandbox.shutil, "which", lambda name: "/usr/bin/docker")
     fr = FakeRunner(ap.RunResult(1, "", "no such image"))
diff --git a/tests/test_session_transcript.py b/tests/test_session_transcript.py
index 19c0a6d9..5af1a244 100644
--- a/tests/test_session_transcript.py
+++ b/tests/test_session_transcript.py
@@ -196,9 +196,17 @@ def test_handler_bad_agent_is_invalid_request() -> None:
     assert resp["error"]["code"] == "invalid_request"
 
 
-def test_handler_returns_degraded_when_absent() -> None:
+def test_handler_returns_degraded_when_absent(
+    store: KBStore, monkeypatch: pytest.MonkeyPatch
+) -> None:
     from vouch.jsonl_server import handle_request
 
+    # handle_request discovers the KB via cwd; point both agent search roots
+    # at empty dirs so the locator misses and returns the degraded payload.
+    monkeypatch.chdir(store.root)
+    monkeypatch.setenv("VOUCH_CLAUDE_PROJECTS_DIR", str(store.kb_dir / "no-claude"))
+    monkeypatch.setenv("CODEX_HOME", str(store.kb_dir / "no-codex"))
+
     resp = handle_request({
         "id": "3", "method": "kb.session_transcript",
         "params": {"session_id": "11111111-1111-1111-1111-111111111111"},