diff --git a/cardano_node_tests/utils/logfiles.py b/cardano_node_tests/utils/logfiles.py
index 96f994a63..4723c5d5b 100644
--- a/cardano_node_tests/utils/logfiles.py
+++ b/cardano_node_tests/utils/logfiles.py
@@ -93,19 +93,33 @@ def _warn_once(message: str) -> None:
 # * Workaround for node issue https://github.com/IntersectMBO/cardano-node/issues/4369
 #   "MAIN THREAD FAILED"
 
-if (os.environ.get("GITHUB_ACTIONS") or "").lower() == "true":
-    # We sometimes see this error on CI. It seems time is not synced properly on GitHub runners.
-    ERRORS_IGNORED.append("TraceBlockFromFuture")
-
-if cluster_nodes.get_cluster_type().type == cluster_nodes.ClusterType.TESTNET:
-    ERRORS_IGNORED.extend(
-        (
-            # We can get this error when some clients are old, or are using wrong
-            # network magic.
-            "TrHandshakeClientError",
-            "TracePromoteWarmBigLedgerPeerAborted",
+
+def _get_ignored_error_regexes() -> list[str]:
+    """Return regexes of errors that are ignored in all log files.
+
+    The environment-specific regexes are added lazily, so the cluster type is
+    determined on first use rather than at import time, and the module doesn't
+    mutate `ERRORS_IGNORED` on import.
+    """
+    errors_ignored = list(ERRORS_IGNORED)
+
+    if (os.environ.get("GITHUB_ACTIONS") or "").lower() == "true":
+        # We sometimes see this error on CI. It seems time is not synced properly
+        # on GitHub runners.
+        errors_ignored.append("TraceBlockFromFuture")
+
+    if cluster_nodes.get_cluster_type().type == cluster_nodes.ClusterType.TESTNET:
+        errors_ignored.extend(
+            (
+                # We can get this error when some clients are old, or are using wrong
+                # network magic.
+                "TrHandshakeClientError",
+                "TracePromoteWarmBigLedgerPeerAborted",
+            )
         )
-    )
+
+    return errors_ignored
+
 
 # Errors that are ignored if there are expected messages in the log file before the error
 ERRORS_LOOK_BACK_LINES = 10
@@ -1029,6 +1043,8 @@ def _search(
             look_back_map=ERRORS_LOOK_BACK_MAP,
         )
 
+    ignored_error_regexes = _get_ignored_error_regexes()
+
     with locking.FileLockIfXdist(lock_file):
         errors = []
         for logfile in cluster_env.state_dir.glob("*.std*"):
@@ -1045,7 +1061,7 @@ def _search(
             # the whole file is going to be searched and the rules apply to all of it.
             ignore_rules = _get_ignore_rules(cluster_env=cluster_env, timestamp=timestamp)
             errors_ignored = _get_ignore_regex(
-                ignore_rules=ignore_rules, regexes=ERRORS_IGNORED, logfile=logfile
+                ignore_rules=ignore_rules, regexes=ignored_error_regexes, logfile=logfile
             )
 
             # Search for errors in the log file
diff --git a/framework_tests/test_logfiles.py b/framework_tests/test_logfiles.py
index 62bea5270..85a78a25e 100644
--- a/framework_tests/test_logfiles.py
+++ b/framework_tests/test_logfiles.py
@@ -1036,3 +1036,53 @@ def test_rotated_logs_mtime_tiebreak(tmp_path: pl.Path):
 
     records = logfiles._get_rotated_logs(logfile=logfile, seek=0, timestamp=0.0, inode=None)
     assert [r.logfile for r in records] == [older, newer, logfile]
+
+
+@pytest.mark.parametrize(
+    ("github_actions", "cluster_type", "extra_regexes"),
+    (
+        pytest.param("", "local", [], id="local"),
+        pytest.param("true", "local", ["TraceBlockFromFuture"], id="github_actions"),
+        pytest.param(
+            "",
+            "testnet",
+            ["TrHandshakeClientError", "TracePromoteWarmBigLedgerPeerAborted"],
+            id="testnet",
+        ),
+        pytest.param(
+            "true",
+            "testnet",
+            [
+                "TraceBlockFromFuture",
+                "TrHandshakeClientError",
+                "TracePromoteWarmBigLedgerPeerAborted",
+            ],
+            id="github_actions_testnet",
+        ),
+    ),
+)
+def test_get_ignored_error_regexes(
+    monkeypatch: pytest.MonkeyPatch,
+    github_actions: str,
+    cluster_type: str,
+    extra_regexes: list[str],
+):
+    """Check that the ignored error regexes reflect the runtime environment.
+
+    The environment-specific regexes are added lazily based on the current environment,
+    not based on the environment seen when the module was imported.
+    """
+    monkeypatch.setenv("GITHUB_ACTIONS", github_actions)
+    cluster_type_obj = (
+        cluster_nodes.TestnetCluster()
+        if cluster_type == "testnet"
+        else cluster_nodes.LocalCluster()
+    )
+    monkeypatch.setattr(cluster_nodes, "get_cluster_type", lambda: cluster_type_obj)
+
+    regexes = logfiles._get_ignored_error_regexes()
+
+    assert set(logfiles.ERRORS_IGNORED).issubset(regexes)
+    for extra in extra_regexes:
+        assert extra in regexes
+    assert len(regexes) == len(logfiles.ERRORS_IGNORED) + len(extra_regexes)