diff --git a/packages/testing/src/execution_testing/cli/pytest_commands/plugins/execute/execute_flags/execute_flags.py b/packages/testing/src/execution_testing/cli/pytest_commands/plugins/execute/execute_flags/execute_flags.py
index cb1e2a26fba..a20f22d460d 100644
--- a/packages/testing/src/execution_testing/cli/pytest_commands/plugins/execute/execute_flags/execute_flags.py
+++ b/packages/testing/src/execution_testing/cli/pytest_commands/plugins/execute/execute_flags/execute_flags.py
@@ -75,5 +75,17 @@ def pytest_configure(config: pytest.Config) -> None:
             "flags or the CHAIN_ID/RPC_CHAIN_ID environment variables."
         )
 
+    setattr(  # noqa: B010
+        config, "_original_chain_id_default", ChainConfigDefaults.chain_id
+    )
+
     # write to config
     ChainConfigDefaults.chain_id = chain_id
+
+
+def pytest_unconfigure(config: pytest.Config) -> None:
+    """Restore the previous chain-id default after the session ends."""
+    if hasattr(config, "_original_chain_id_default"):
+        ChainConfigDefaults.chain_id = getattr(  # noqa: B009
+            config, "_original_chain_id_default"
+        )
diff --git a/packages/testing/src/execution_testing/cli/tests/test_pytest_execute_command.py b/packages/testing/src/execution_testing/cli/tests/test_pytest_execute_command.py
index c24b4734469..61036140b5f 100644
--- a/packages/testing/src/execution_testing/cli/tests/test_pytest_execute_command.py
+++ b/packages/testing/src/execution_testing/cli/tests/test_pytest_execute_command.py
@@ -1,8 +1,16 @@
 """Tests for execute command click CLI."""
 
+from pathlib import Path
+from unittest.mock import patch
+
 import pytest
 from click.testing import CliRunner
 
+from ...test_types.chain_config_types import (
+    DEFAULT_CHAIN_ID,
+    ChainConfigDefaults,
+)
+from ...test_types.transaction_types import Transaction
 from ..pytest_commands.execute import execute
 
 
@@ -108,3 +116,50 @@ def test_all_execute_subcommands_help_no_conflicts(runner: CliRunner) -> None:
             f"execute {subcommand} --help has conflicting option string\n"
             f"Output: {result.output}"
         )
+
+
+def test_execute_remote_leaks_chain_id_into_later_defaults(
+    runner: CliRunner, tmp_path: Path
+) -> None:
+    """Demonstrate that an in-process execute session leaks chain ID."""
+    inner_test = tmp_path / "test_inner.py"
+    inner_test.write_text(
+        "\n".join(
+            [
+                "from execution_testing import (",
+                "    Account,",
+                "    Environment,",
+                "    TestAddress,",
+                "    Transaction,",
+                ")",
+                "",
+                "def test_noop(state_test) -> None:",
+                "    state_test(",
+                "        env=Environment(),",
+                "        pre={TestAddress: Account(balance=1_000_000)},",
+                "        post={},",
+                "        tx=Transaction(),",
+                "    )",
+            ]
+        )
+    )
+
+    ChainConfigDefaults.chain_id = DEFAULT_CHAIN_ID
+    with patch(
+        "execution_testing.cli.pytest_commands.plugins.execute.rpc.remote.EthRPC"
+    ) as mock_eth_rpc:
+        mock_eth_rpc.return_value.chain_id.return_value = 12345
+        result = runner.invoke(
+            execute,
+            [
+                "remote",
+                "--rpc-endpoint=http://localhost:12345",
+                "--chain-id=12345",
+                "--collect-only",
+                "-q",
+                str(inner_test),
+            ],
+        )
+
+    assert result.exit_code == 0, result.output
+    assert Transaction().chain_id == DEFAULT_CHAIN_ID