fix: sanitize .env before loading to prevent token duplication (#8908)

When .env files become corrupted (e.g. concatenated KEY=VALUE pairs on
a single line due to concurrent writes or encoding issues), both
python-dotenv and load_env() would parse the entire concatenated string
as a single value. This caused bot tokens to appear duplicated up to 8×,
triggering InvalidToken errors from the Telegram API.

Root cause: _sanitize_env_lines() — which correctly splits concatenated
lines — was only called during save_env_value() writes, not during reads.

Fix:
- load_env() now calls _sanitize_env_lines() before parsing
- env_loader.load_hermes_dotenv() sanitizes the .env file on disk
  before python-dotenv reads it, so os.getenv() also returns clean values
- Added tests reproducing the exact corruption pattern from #8908

Closes #8908

tests/test_env_sanitize_on_load.py

@@ -0,0 +1,94 @@
+"""Tests for .env sanitization during load to prevent token duplication (#8908)."""
+
+import os
+import tempfile
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+
+def test_load_env_sanitizes_concatenated_lines():
+    """Verify load_env() splits concatenated KEY=VALUE pairs.
+
+    Reproduces the scenario from #8908 where a corrupted .env file
+    contained multiple tokens on a single line, causing the bot token
+    to be duplicated 8 times.
+    """
+    from hermes_cli.config import load_env
+
+    token = "8356550917:AAGGEkzg06Hrc3Hjb3Sa1jkGVDOdU_lYy2Q"
+    # Simulate concatenated line: TOKEN=xxx followed immediately by another key
+    corrupted = f"TELEGRAM_BOT_TOKEN={token}ANTHROPIC_API_KEY=sk-ant-test123\n"
+
+    with tempfile.NamedTemporaryFile(
+        mode="w", suffix=".env", delete=False, encoding="utf-8"
+    ) as f:
+        f.write(corrupted)
+        env_path = Path(f.name)
+
+    try:
+        with patch("hermes_cli.config.get_env_path", return_value=env_path):
+            result = load_env()
+        assert result.get("TELEGRAM_BOT_TOKEN") == token, (
+            f"Token should be exactly '{token}', got '{result.get('TELEGRAM_BOT_TOKEN')}'"
+        )
+        assert result.get("ANTHROPIC_API_KEY") == "sk-ant-test123"
+    finally:
+        env_path.unlink(missing_ok=True)
+
+
+def test_load_env_normal_file_unchanged():
+    """A well-formed .env file should be parsed identically."""
+    from hermes_cli.config import load_env
+
+    content = (
+        "TELEGRAM_BOT_TOKEN=mytoken123\n"
+        "ANTHROPIC_API_KEY=sk-ant-key\n"
+        "# comment\n"
+        "\n"
+        "OPENAI_API_KEY=sk-openai\n"
+    )
+
+    with tempfile.NamedTemporaryFile(
+        mode="w", suffix=".env", delete=False, encoding="utf-8"
+    ) as f:
+        f.write(content)
+        env_path = Path(f.name)
+
+    try:
+        with patch("hermes_cli.config.get_env_path", return_value=env_path):
+            result = load_env()
+        assert result["TELEGRAM_BOT_TOKEN"] == "mytoken123"
+        assert result["ANTHROPIC_API_KEY"] == "sk-ant-key"
+        assert result["OPENAI_API_KEY"] == "sk-openai"
+    finally:
+        env_path.unlink(missing_ok=True)
+
+
+def test_env_loader_sanitizes_before_dotenv():
+    """Verify env_loader._sanitize_env_file_if_needed fixes corrupted files."""
+    from hermes_cli.env_loader import _sanitize_env_file_if_needed
+
+    token = "8356550917:AAGGEkzg06Hrc3Hjb3Sa1jkGVDOdU_lYy2Q"
+    corrupted = f"TELEGRAM_BOT_TOKEN={token}ANTHROPIC_API_KEY=sk-ant-test\n"
+
+    with tempfile.NamedTemporaryFile(
+        mode="w", suffix=".env", delete=False, encoding="utf-8"
+    ) as f:
+        f.write(corrupted)
+        env_path = Path(f.name)
+
+    try:
+        _sanitize_env_file_if_needed(env_path)
+        with open(env_path, encoding="utf-8") as f:
+            lines = f.readlines()
+        # Should be split into two separate lines
+        assert len(lines) == 2, f"Expected 2 lines, got {len(lines)}: {lines}"
+        assert lines[0].startswith("TELEGRAM_BOT_TOKEN=")
+        assert lines[1].startswith("ANTHROPIC_API_KEY=")
+        # Token should not contain the second key
+        parsed_token = lines[0].strip().split("=", 1)[1]
+        assert parsed_token == token
+    finally:
+        env_path.unlink(missing_ok=True)