diff --git a/nisse-dev/src/nisse_dev/config.py b/nisse-dev/src/nisse_dev/config.py
index e4d414c..a5c7919 100644
--- a/nisse-dev/src/nisse_dev/config.py
+++ b/nisse-dev/src/nisse_dev/config.py
@@ -233,12 +233,14 @@ class AgentConfig:
     workspace: Path
     project: str
     llm_base_url: str
-    llm_token: str
+    # Credentials never appear in a repr: a failing test or a log line
+    # would print them.
+    llm_token: str = field(repr=False)
     roles: RoleMap
     matrix: MatrixConfig
     operators: frozenset[str]
     gitea_url: str
-    gitea_token: str
+    gitea_token: str = field(repr=False)
     gitea_repo: str
     gitea_operators: frozenset[str]
     build_host: BuildHost
@@ -248,7 +250,7 @@ class AgentConfig:
     # (push_user, push_token), or the path to a deploy key (push_key).
     push_key: Path | None = None
     push_user: str | None = None
-    push_token: str | None = None
+    push_token: str | None = field(default=None, repr=False)
     max_output_tokens: int = DEFAULT_MAX_OUTPUT_TOKENS
     request_timeout_s: float = DEFAULT_REQUEST_TIMEOUT_S
     tuning: Tuning = field(default_factory=Tuning)
diff --git a/nisse-dev/src/nisse_dev/git.py b/nisse-dev/src/nisse_dev/git.py
index 56f5596..8b0203b 100644
--- a/nisse-dev/src/nisse_dev/git.py
+++ b/nisse-dev/src/nisse_dev/git.py
@@ -18,7 +18,7 @@ Pull requests are opened from the agent's own host with its Gitea API token
 """
 
 import shlex
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from pathlib import Path
 
 from nisse_dev.execution import HostUnavailable, SSHHost
@@ -67,14 +67,15 @@ class HTTPSToken:
     """A push-only account's token, for HTTPS remotes (D4)."""
 
     username: str
-    token: str
+    # Never in a repr: a failing test or a log line would print it.
+    token: str = field(repr=False)
 
 
 @dataclass(frozen=True)
 class SSHKey:
     """A deploy key's private half, for SSH remotes (D4)."""
 
-    private_key: str
+    private_key: str = field(repr=False)
 
 
 PushCredential = HTTPSToken | SSHKey
diff --git a/nisse-dev/src/nisse_dev/matrix.py b/nisse-dev/src/nisse_dev/matrix.py
index ca94ce9..76ee235 100644
--- a/nisse-dev/src/nisse_dev/matrix.py
+++ b/nisse-dev/src/nisse_dev/matrix.py
@@ -16,7 +16,7 @@ import re
 import threading
 import uuid
 from collections.abc import Callable
-from dataclasses import dataclass
+from dataclasses import dataclass, field
 from urllib.parse import unquote
 
 import httpx
@@ -40,7 +40,7 @@ class TransportError(RuntimeError):
 class MatrixConfig:
     homeserver: str
     user_id: str
-    token: str
+    token: str = field(repr=False)  # never in a repr or a log line
     room_id: str
 
 
diff --git a/nisse-dev/tests/test_config.py b/nisse-dev/tests/test_config.py
index 4b3943f..596d5e2 100644
--- a/nisse-dev/tests/test_config.py
+++ b/nisse-dev/tests/test_config.py
@@ -360,3 +360,10 @@ def test_a_push_token_needs_its_user_and_excludes_a_key() -> None:
         build(gitea__push_user="pusher")
     with pytest.raises(ConfigError, match="not both"):
         build(gitea__push_user="p", gitea__push_token="t", gitea__push_key="~/k")
+
+
+def test_no_credential_appears_in_the_config_repr() -> None:
+    config = build(gitea__push_user="pusher", gitea__push_token="${TEST_GITEA_TOKEN}")
+    text = repr(config)
+    for secret in SECRETS.values():
+        assert secret not in text
diff --git a/nisse-dev/tests/test_git.py b/nisse-dev/tests/test_git.py
index 369b23a..1a81524 100644
--- a/nisse-dev/tests/test_git.py
+++ b/nisse-dev/tests/test_git.py
@@ -135,10 +135,25 @@ def test_a_failed_push_still_kills_its_agent(
 
 
 def _agents() -> set[str]:
+    """Live ssh-agents. A killed one lingers as a zombie in a CI container,
+    where nothing reaps orphans, so zombies don't count."""
     out = subprocess.run(
         ["pgrep", "-x", "ssh-agent"], capture_output=True, text=True, check=False
     ).stdout
-    return set(out.split())
+    live = set()
+    for pid in out.split():
+        try:
+            stat = Path(f"/proc/{pid}/stat").read_text()
+        except FileNotFoundError:
+            continue
+        if stat.rsplit(")", 1)[1].split()[0] != "Z":
+            live.add(pid)
+    return live
+
+
+def test_credentials_never_appear_in_a_repr() -> None:
+    assert "s3cr3t" not in repr(HTTPSToken("pusher", "s3cr3t"))
+    assert "PRIVATE" not in repr(SSHKey("-----BEGIN OPENSSH PRIVATE KEY-----"))
 
 
 def test_a_remote_url_is_quoted_not_interpreted(repo: GitRepo, tmp_path: Path) -> None: