diff --git a/tests/unit/test_deployment_config.py b/tests/unit/test_deployment_config.py
new file mode 100644
index 0000000..090cf86
--- /dev/null
+++ b/tests/unit/test_deployment_config.py
@@ -0,0 +1,96 @@
+import os
+import pytest
+from tools.deployment_config import (
+    get_deployment_mode,
+    is_dev_mode,
+    is_prod_mode,
+    get_data_path,
+    get_db_path,
+    should_preserve_dev_data,
+    log_api_key_warning,
+    get_deployment_mode_dict
+)
+
+
+def test_get_deployment_mode_default():
+    """Test default deployment mode is PROD"""
+    # Clear env to test default
+    os.environ.pop("DEPLOYMENT_MODE", None)
+    assert get_deployment_mode() == "PROD"
+
+
+def test_get_deployment_mode_dev():
+    """Test DEV mode detection"""
+    os.environ["DEPLOYMENT_MODE"] = "DEV"
+    assert get_deployment_mode() == "DEV"
+    assert is_dev_mode() == True
+    assert is_prod_mode() == False
+
+
+def test_get_deployment_mode_prod():
+    """Test PROD mode detection"""
+    os.environ["DEPLOYMENT_MODE"] = "PROD"
+    assert get_deployment_mode() == "PROD"
+    assert is_dev_mode() == False
+    assert is_prod_mode() == True
+
+
+def test_get_data_path_prod():
+    """Test production data path"""
+    os.environ["DEPLOYMENT_MODE"] = "PROD"
+    assert get_data_path("./data/agent_data") == "./data/agent_data"
+
+
+def test_get_data_path_dev():
+    """Test dev data path substitution"""
+    os.environ["DEPLOYMENT_MODE"] = "DEV"
+    assert get_data_path("./data/agent_data") == "./data/dev_agent_data"
+
+
+def test_get_db_path_prod():
+    """Test production database path"""
+    os.environ["DEPLOYMENT_MODE"] = "PROD"
+    assert get_db_path("data/trading.db") == "data/trading.db"
+
+
+def test_get_db_path_dev():
+    """Test dev database path substitution"""
+    os.environ["DEPLOYMENT_MODE"] = "DEV"
+    assert get_db_path("data/trading.db") == "data/trading_dev.db"
+    assert get_db_path("data/jobs.db") == "data/jobs_dev.db"
+
+
+def test_should_preserve_dev_data_default():
+    """Test default preserve flag is False"""
+    os.environ.pop("PRESERVE_DEV_DATA", None)
+    assert should_preserve_dev_data() == False
+
+
+def test_should_preserve_dev_data_true():
+    """Test preserve flag can be enabled"""
+    os.environ["PRESERVE_DEV_DATA"] = "true"
+    assert should_preserve_dev_data() == True
+
+
+def test_log_api_key_warning_in_dev(capsys):
+    """Test warning logged when API keys present in DEV mode"""
+    os.environ["DEPLOYMENT_MODE"] = "DEV"
+    os.environ["OPENAI_API_KEY"] = "sk-test123"
+
+    log_api_key_warning()
+
+    captured = capsys.readouterr()
+    assert "⚠️  WARNING: Production API keys detected in DEV mode" in captured.out
+    assert "OPENAI_API_KEY" in captured.out
+
+
+def test_get_deployment_mode_dict():
+    """Test deployment mode dictionary generation"""
+    os.environ["DEPLOYMENT_MODE"] = "DEV"
+    os.environ["PRESERVE_DEV_DATA"] = "true"
+
+    result = get_deployment_mode_dict()
+
+    assert result["deployment_mode"] == "DEV"
+    assert result["is_dev_mode"] == True
+    assert result["preserve_dev_data"] == True
diff --git a/tools/deployment_config.py b/tools/deployment_config.py
new file mode 100644
index 0000000..9e0297e
--- /dev/null
+++ b/tools/deployment_config.py
@@ -0,0 +1,133 @@
+"""
+Deployment mode configuration utilities
+
+Handles PROD vs DEV mode differentiation including:
+- Data path isolation
+- Database path isolation
+- API key validation warnings
+- Deployment mode detection
+"""
+
+import os
+from typing import Optional
+
+
+def get_deployment_mode() -> str:
+    """
+    Get current deployment mode
+
+    Returns:
+        "PROD" or "DEV" (defaults to PROD if not set)
+    """
+    mode = os.getenv("DEPLOYMENT_MODE", "PROD").upper()
+    if mode not in ["PROD", "DEV"]:
+        print(f"⚠️  Invalid DEPLOYMENT_MODE '{mode}', defaulting to PROD")
+        return "PROD"
+    return mode
+
+
+def is_dev_mode() -> bool:
+    """Check if running in DEV mode"""
+    return get_deployment_mode() == "DEV"
+
+
+def is_prod_mode() -> bool:
+    """Check if running in PROD mode"""
+    return get_deployment_mode() == "PROD"
+
+
+def get_data_path(base_path: str) -> str:
+    """
+    Get data path based on deployment mode
+
+    Args:
+        base_path: Base data path (e.g., "./data/agent_data")
+
+    Returns:
+        Modified path for DEV mode or original for PROD
+
+    Example:
+        PROD: "./data/agent_data" -> "./data/agent_data"
+        DEV:  "./data/agent_data" -> "./data/dev_agent_data"
+    """
+    if is_dev_mode():
+        # Replace agent_data with dev_agent_data
+        return base_path.replace("agent_data", "dev_agent_data")
+    return base_path
+
+
+def get_db_path(base_db_path: str) -> str:
+    """
+    Get database path based on deployment mode
+
+    Args:
+        base_db_path: Base database path (e.g., "data/trading.db")
+
+    Returns:
+        Modified path for DEV mode or original for PROD
+
+    Example:
+        PROD: "data/trading.db" -> "data/trading.db"
+        DEV:  "data/trading.db" -> "data/trading_dev.db"
+    """
+    if is_dev_mode():
+        # Insert _dev before .db extension
+        if base_db_path.endswith(".db"):
+            return base_db_path[:-3] + "_dev.db"
+        return base_db_path + "_dev"
+    return base_db_path
+
+
+def should_preserve_dev_data() -> bool:
+    """
+    Check if dev data should be preserved between runs
+
+    Returns:
+        True if PRESERVE_DEV_DATA=true, False otherwise
+    """
+    preserve = os.getenv("PRESERVE_DEV_DATA", "false").lower()
+    return preserve in ["true", "1", "yes"]
+
+
+def log_api_key_warning() -> None:
+    """
+    Log warning if production API keys are detected in DEV mode
+
+    Checks for common API key environment variables and warns if found.
+    """
+    if not is_dev_mode():
+        return
+
+    # List of API key environment variables to check
+    api_key_vars = [
+        "OPENAI_API_KEY",
+        "ANTHROPIC_API_KEY",
+        "ALPHAADVANTAGE_API_KEY",
+        "JINA_API_KEY"
+    ]
+
+    detected_keys = []
+    for var in api_key_vars:
+        value = os.getenv(var)
+        if value and value != "" and "your_" not in value.lower():
+            detected_keys.append(var)
+
+    if detected_keys:
+        print("⚠️  WARNING: Production API keys detected in DEV mode")
+        print(f"   Detected: {', '.join(detected_keys)}")
+        print("   These keys will NOT be used - mock AI responses will be returned")
+        print("   This is expected if you're testing dev mode with existing .env file")
+
+
+def get_deployment_mode_dict() -> dict:
+    """
+    Get deployment mode information as dictionary (for API responses)
+
+    Returns:
+        Dictionary with deployment mode metadata
+    """
+    return {
+        "deployment_mode": get_deployment_mode(),
+        "is_dev_mode": is_dev_mode(),
+        "preserve_dev_data": should_preserve_dev_data() if is_dev_mode() else None
+    }