diff --git a/money-machine/src-python/tests/test_trading_signal_amount.py b/money-machine/src-python/tests/test_trading_signal_amount.py
new file mode 100644
index 0000000..fc23882
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+++ b/money-machine/src-python/tests/test_trading_signal_amount.py
@@ -0,0 +1,271 @@
+"""
+Tests for changes introduced in the 'harden desktop security' PR:
+
+  1. TradingSignal.amount field — added to engine/strategies/base.py.
+  2. signal_generator.py — TradingSignal is now imported from
+     engine.strategies.base (the local duplicate was removed), and
+     _parse_json_response maps 'amount_pct' from the AI response to
+     the signal's `amount` field.
+
+Scope is limited to the code that was modified in this PR. The
+surrounding Strategy / SignalGenerator behaviour is pre-existing and
+tested elsewhere.
+"""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+from typing import List
+
+import pytest
+
+SRC_PYTHON = Path(__file__).resolve().parent.parent
+if str(SRC_PYTHON) not in sys.path:
+    sys.path.insert(0, str(SRC_PYTHON))
+
+from engine.strategies.base import TradingSignal  # noqa: E402
+from engine.signal_generator import SignalGenerator  # noqa: E402
+
+
+
+# ---------------------------------------------------------------------------
+# TradingSignal.amount field
+# ---------------------------------------------------------------------------
+
+
+def test_trading_signal_amount_defaults_to_none() -> None:
+    """The new `amount` field must be Optional and default to None so that
+    existing code that does not pass an amount continues to work."""
+    signal = TradingSignal(symbol="BTC/USDT", action="HOLD", confidence=0.0)
+    assert signal.amount is None
+
+
+def test_trading_signal_amount_can_be_set() -> None:
+    """Callers that explicitly pass amount= must be able to read it back."""
+    signal = TradingSignal(
+        symbol="BTC/USDT",
+        action="BUY",
+        confidence=0.75,
+        amount=0.02,
+    )
+    assert signal.amount == pytest.approx(0.02)
+
+
+def test_trading_signal_amount_zero_is_allowed() -> None:
+    """Zero is a valid explicit amount (signals a 0-size order intent)."""
+    signal = TradingSignal(
+        symbol="ETH/USDT",
+        action="SELL",
+        confidence=0.5,
+        amount=0.0,
+    )
+    assert signal.amount == 0.0
+
+
+def test_trading_signal_to_dict_includes_amount() -> None:
+    """to_dict() must serialise the amount field so IPC consumers receive it."""
+    signal = TradingSignal(
+        symbol="BTC/USDT",
+        action="BUY",
+        confidence=0.8,
+        amount=0.015,
+    )
+    d = signal.to_dict()
+    assert "amount" in d
+    assert d["amount"] == pytest.approx(0.015)
+
+
+def test_trading_signal_to_dict_amount_none_when_not_set() -> None:
+    """When amount is not provided, to_dict() must include the key with None."""
+    signal = TradingSignal(symbol="BTC/USDT", action="HOLD", confidence=0.0)
+    d = signal.to_dict()
+    assert "amount" in d
+    assert d["amount"] is None
+
+
+def test_trading_signal_amount_position_in_field_order() -> None:
+    """Verify that amount sits between take_profit and reasoning as specified."""
+    signal = TradingSignal(
+        symbol="BTC/USDT",
+        action="BUY",
+        confidence=0.7,
+        entry_price=50_000.0,
+        stop_loss=49_000.0,
+        take_profit=52_000.0,
+        amount=0.01,
+        reasoning="test",
+    )
+    assert signal.take_profit == pytest.approx(52_000.0)
+    assert signal.amount == pytest.approx(0.01)
+    assert signal.reasoning == "test"
+
+
+# ---------------------------------------------------------------------------
+# TradingSignal import in signal_generator.py
+# ---------------------------------------------------------------------------
+
+
+def test_signal_generator_imports_trading_signal_from_base() -> None:
+    """signal_generator.py must import TradingSignal from
+    engine.strategies.base, not define its own copy."""
+    import engine.signal_generator as sg_module
+
+    # The module must not define TradingSignal itself.
+    assert not hasattr(sg_module, "TradingSignal") or (
+        sg_module.TradingSignal is TradingSignal
+    ), (
+        "signal_generator defines its own TradingSignal instead of "
+        "importing from engine.strategies.base"
+    )
+
+
+def test_signal_generator_trading_signal_is_same_class() -> None:
+    """The TradingSignal used by the generator must be the canonical one
+    from engine.strategies.base so that downstream consumers (risk shield,
+    pipeline) receive the right type."""
+    import engine.signal_generator as sg_module
+    import importlib
+
+    # Reload to get a fresh reference, unaffected by other test ordering.
+    importlib.reload(sg_module)
+    from engine.signal_generator import SignalGenerator as SG
+    from engine.strategies.base import TradingSignal as TS
+
+    gen = SG(api_key="")
+    # Verify that the fallback rule-based path returns the canonical type.
+    minimal_data = [[i * 1000, 50000 + i, 50100 + i, 49900 + i, 50050 + i, 100] for i in range(25)]
+    import asyncio
+    signal = asyncio.run(
+        gen.generate_signal("BTC/USDT", minimal_data, portfolio_balance=10_000.0)
+    )
+    assert isinstance(signal, TS)
+
+
+# ---------------------------------------------------------------------------
+# SignalGenerator._parse_json_response — amount_pct mapping
+# ---------------------------------------------------------------------------
+
+
+def _make_market_data(n: int = 5, price: float = 50_000.0) -> List[List]:
+    """Return minimal OHLCV rows for parse tests."""
+    return [[i * 1_000, price, price + 100, price - 100, price, 100] for i in range(n)]
+
+
+def test_parse_json_response_maps_amount_pct_to_amount() -> None:
+    """_parse_json_response must read 'amount_pct' from the AI JSON and
+    store it in TradingSignal.amount so position sizers can use it."""
+    gen = SignalGenerator(api_key="")
+    market_data = _make_market_data()
+
+    response_json = json.dumps(
+        {
+            "action": "BUY",
+            "confidence": 0.8,
+            "entry_price": 50_000.0,
+            "stop_loss": 49_000.0,
+            "take_profit": 52_000.0,
+            "amount_pct": 0.015,
+            "reasoning": "strong momentum",
+        }
+    )
+
+    signal = gen._parse_json_response("BTC/USDT", response_json, market_data)
+
+    assert signal.action == "BUY"
+    assert signal.confidence == pytest.approx(0.8)
+    assert signal.amount == pytest.approx(0.015)
+
+
+def test_parse_json_response_amount_is_none_when_key_absent() -> None:
+    """If 'amount_pct' is absent from the AI response, signal.amount must
+    be None (not crash or default to a hard-coded value)."""
+    gen = SignalGenerator(api_key="")
+    market_data = _make_market_data()
+
+    response_json = json.dumps(
+        {
+            "action": "SELL",
+            "confidence": 0.6,
+            "reasoning": "overbought",
+        }
+    )
+
+    signal = gen._parse_json_response("BTC/USDT", response_json, market_data)
+
+    assert signal.action == "SELL"
+    assert signal.amount is None
+
+
+def test_parse_json_response_amount_pct_null_maps_to_none() -> None:
+    """An explicit null/None in the AI response must also yield amount=None."""
+    gen = SignalGenerator(api_key="")
+    market_data = _make_market_data()
+
+    response_json = json.dumps(
+        {
+            "action": "HOLD",
+            "confidence": 0.3,
+            "amount_pct": None,
+            "reasoning": "unclear",
+        }
+    )
+
+    signal = gen._parse_json_response("BTC/USDT", response_json, market_data)
+    assert signal.amount is None
+
+
+def test_parse_json_response_falls_back_on_invalid_json() -> None:
+    """If the AI returns garbage, _parse_json_response must return a HOLD
+    signal rather than raising."""
+    gen = SignalGenerator(api_key="")
+    market_data = _make_market_data()
+
+    signal = gen._parse_json_response("BTC/USDT", "this is not json {{{{", market_data)
+
+    assert signal.action == "HOLD"
+    assert isinstance(signal, TradingSignal)
+
+
+def test_parse_json_response_invalid_action_falls_back_to_hold() -> None:
+    """An unrecognised action string in the AI response must not crash
+    _parse_json_response; a HOLD fallback should be returned instead."""
+    gen = SignalGenerator(api_key="")
+    market_data = _make_market_data()
+
+    response_json = json.dumps(
+        {
+            "action": "YOLO",
+            "confidence": 0.9,
+            "amount_pct": 0.02,
+            "reasoning": "moon",
+        }
+    )
+
+    # TradingSignal.__post_init__ raises ValueError for invalid actions,
+    # so _parse_json_response must catch that and return a HOLD.
+    signal = gen._parse_json_response("BTC/USDT", response_json, market_data)
+    assert signal.action == "HOLD"
+
+
+# ---------------------------------------------------------------------------
+# Regression: amount field round-trips through to_dict / constructor
+# ---------------------------------------------------------------------------
+
+
+def test_trading_signal_round_trip_with_amount() -> None:
+    """A signal reconstructed from to_dict() must preserve the amount."""
+    original = TradingSignal(
+        symbol="ETH/USDT",
+        action="BUY",
+        confidence=0.65,
+        entry_price=3_000.0,
+        amount=0.02,
+        reasoning="round-trip test",
+    )
+    d = original.to_dict()
+    reconstructed = TradingSignal(**d)
+    assert reconstructed.amount == pytest.approx(0.02)
+    assert reconstructed.symbol == "ETH/USDT"
+    assert reconstructed.reasoning == "round-trip test"