diff --git a/tests/unit/orb_trader/__init__.py b/tests/unit/orb_trader/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/unit/orb_trader/test_sizing.py b/tests/unit/orb_trader/test_sizing.py
new file mode 100644
index 0000000..6472cfd
--- /dev/null
+++ b/tests/unit/orb_trader/test_sizing.py
@@ -0,0 +1,184 @@
+"""Unit tests for ORBTradingEngine._compute_sizing_capital."""
+from __future__ import annotations
+
+from types import SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+
+from apps.orb_trader.engine import ORBTradingEngine
+
+
+def _make_engine(
+    *,
+    initial_equity: float = 10_000.0,
+    daily_budget_reset: bool = True,
+    drawdown_governor_threshold: float | None = None,
+    drawdown_governor_min_scale: float = 0.30,
+    streak_sizing_win_bonus: float | None = None,
+    streak_sizing_loss_penalty: float | None = None,
+    streak_sizing_max: float = 2.5,
+    streak_sizing_min: float = 0.5,
+    peak_equity: float | None = None,
+    trades: list[dict] | None = None,
+) -> ORBTradingEngine:
+    params = SimpleNamespace(
+        daily_budget_reset=daily_budget_reset,
+        drawdown_governor_threshold=drawdown_governor_threshold,
+        drawdown_governor_min_scale=drawdown_governor_min_scale,
+        streak_sizing_win_bonus=streak_sizing_win_bonus,
+        streak_sizing_loss_penalty=streak_sizing_loss_penalty,
+        streak_sizing_max=streak_sizing_max,
+        streak_sizing_min=streak_sizing_min,
+    )
+    session = SimpleNamespace(
+        session_id="test-session",
+        initial_equity=initial_equity,
+    )
+    state = MagicMock()
+    state.get_peak_equity.return_value = peak_equity if peak_equity is not None else initial_equity
+    state.list_trades.return_value = trades or []
+
+    engine = object.__new__(ORBTradingEngine)
+    engine._params = params
+    engine._session = session
+    engine._state = state
+    return engine
+
+
+# ── daily_budget_reset ────────────────────────────────────────────────────────
+
+class TestDailyBudgetReset:
+    def test_reset_true_uses_initial_equity(self):
+        eng = _make_engine(initial_equity=10_000, daily_budget_reset=True)
+        assert eng._compute_sizing_capital(15_000) == pytest.approx(10_000)
+
+    def test_reset_false_uses_current_equity(self):
+        eng = _make_engine(initial_equity=10_000, daily_budget_reset=False)
+        assert eng._compute_sizing_capital(15_000) == pytest.approx(15_000)
+
+
+# ── Drawdown governor ─────────────────────────────────────────────────────────
+
+class TestDrawdownGovernor:
+    def test_no_drawdown_no_scaling(self):
+        eng = _make_engine(
+            drawdown_governor_threshold=0.025,
+            drawdown_governor_min_scale=0.30,
+            peak_equity=10_000,
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000)
+
+    def test_drawdown_below_threshold_no_scaling(self):
+        # 2% DD, threshold 2.5% → no scaling
+        eng = _make_engine(
+            drawdown_governor_threshold=0.025,
+            peak_equity=10_000,
+        )
+        result = eng._compute_sizing_capital(9_800)
+        assert result == pytest.approx(10_000)
+
+    def test_drawdown_at_full_governor(self):
+        # DD = 5% = 2 * threshold(2.5%) → excess = 1x threshold → scale = min_scale
+        eng = _make_engine(
+            drawdown_governor_threshold=0.025,
+            drawdown_governor_min_scale=0.30,
+            peak_equity=10_000,
+        )
+        result = eng._compute_sizing_capital(9_500)
+        assert result == pytest.approx(10_000 * 0.30)
+
+    def test_drawdown_partial_governor(self):
+        # DD = 3.75% → excess = 1.25% = 0.5 * threshold(2.5%)
+        # scale = max(0.30, 1.0 - 0.70 * 0.5) = max(0.30, 0.65) = 0.65
+        eng = _make_engine(
+            drawdown_governor_threshold=0.025,
+            drawdown_governor_min_scale=0.30,
+            peak_equity=10_000,
+        )
+        result = eng._compute_sizing_capital(9_625)
+        expected_scale = max(0.30, 1.0 - 0.70 * 0.5)
+        assert result == pytest.approx(10_000 * expected_scale, rel=1e-4)
+
+
+# ── Streak sizing ─────────────────────────────────────────────────────────────
+
+class TestStreakSizing:
+    def _win(self, pnl=100.0) -> dict:
+        return {"pnl": pnl}
+
+    def _loss(self, pnl=-100.0) -> dict:
+        return {"pnl": pnl}
+
+    def test_no_trades_no_multiplier(self):
+        eng = _make_engine(streak_sizing_win_bonus=0.70, trades=[])
+        assert eng._compute_sizing_capital(10_000) == pytest.approx(10_000)
+
+    def test_single_win_streak_1(self):
+        # streak_len=1 win → mult = 1 + 1*0.70 = 1.70
+        eng = _make_engine(
+            streak_sizing_win_bonus=0.70,
+            trades=[self._win()],  # newest first
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 1.70)
+
+    def test_two_wins_streak_2(self):
+        # streak_len=2 → mult = 1 + 2*0.70 = 2.40
+        eng = _make_engine(
+            streak_sizing_win_bonus=0.70,
+            trades=[self._win(), self._win()],
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 2.40)
+
+    def test_win_streak_capped_at_max(self):
+        # streak_len=5 → mult = 1 + 5*0.70 = 4.50 → capped at streak_max=2.5
+        eng = _make_engine(
+            streak_sizing_win_bonus=0.70,
+            streak_sizing_max=2.5,
+            trades=[self._win()] * 5,
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 2.5)
+
+    def test_loss_streak_reduces_sizing(self):
+        # streak_len=2 loss, loss_penalty=0.20 → mult = 1 - 2*0.20 = 0.60
+        eng = _make_engine(
+            streak_sizing_loss_penalty=0.20,
+            streak_sizing_min=0.5,
+            trades=[self._loss(), self._loss()],
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 0.60)
+
+    def test_loss_streak_floored_at_min(self):
+        eng = _make_engine(
+            streak_sizing_loss_penalty=0.20,
+            streak_sizing_min=0.5,
+            trades=[self._loss()] * 10,
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 0.5)
+
+    def test_streak_direction_newest_first(self):
+        # trades list DESC (newest first): [win, loss, loss]
+        # The most recent is a win → streak_len=1 → mult=1.70
+        eng = _make_engine(
+            streak_sizing_win_bonus=0.70,
+            trades=[self._win(), self._loss(), self._loss()],
+        )
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 1.70)
+
+    def test_streak_direction_oldest_not_used(self):
+        # trades list DESC: [loss, win, win]
+        # Most recent = loss, streak_len=1 → no win_bonus applies (only loss_penalty)
+        eng = _make_engine(
+            streak_sizing_win_bonus=0.70,
+            trades=[self._loss(), self._win(), self._win()],
+        )
+        # No loss_penalty configured, so streak_mult = 1.0
+        result = eng._compute_sizing_capital(10_000)
+        assert result == pytest.approx(10_000 * 1.0)