From 28669ea4c330ef0d6c442651a0db1fd4de587cb8 Mon Sep 17 00:00:00 2001
From: Daniel Rosel <daniel@alves.world>
Date: Fri, 23 Jan 2026 17:16:32 +0100
Subject: [PATCH] win: refomulated and re-inspired from library

---
 lab/case/thesis/simplified.py     | 288 +++++++++++++++++++++++++
 lab/case/thesis/simplified_env.py | 338 ++++++++++++++++++++++++++++++
 2 files changed, 626 insertions(+)
 create mode 100644 lab/case/thesis/simplified.py
 create mode 100644 lab/case/thesis/simplified_env.py

diff --git a/lab/case/thesis/simplified.py b/lab/case/thesis/simplified.py
new file mode 100644
index 0000000..3b3838e
--- /dev/null
+++ b/lab/case/thesis/simplified.py
@@ -0,0 +1,288 @@
+"""Minimal implementation of thesis pricing system.
+
+Implements the core loop: prices -> sessions -> demand -> prices
+with behavioral separability and robust pricing objective (Eq 23).
+
+Objects:
+- Session trajectories τ_s from mixture of H/A behavioral profiles
+- Demand proxy q̂ via weighted action aggregation (Eq 2)
+- COI leakage penalty for agent reconnaissance
+- Limbo: alternating price/demand history for trajectory analysis
+"""
+from __future__ import annotations
+from dataclasses import dataclass, field
+from typing import Dict, List, Tuple
+import numpy as np
+
+ACTION_WEIGHTS = {"add_to_cart": 0.8, "checkout": 0.9, "purchase": 1.0, "view": 0.15, "detail": 0.25, "hover": 0.3, "start": 0.05, "end": 0.0}
+TRANS_H = {"start": {"view": 0.85, "end": 0.15}, "view": {"detail": 0.4, "cart": 0.3, "view": 0.2, "end": 0.1},
+           "detail": {"cart": 0.5, "view": 0.3, "end": 0.2}, "cart": {"purchase": 0.6, "view": 0.25, "end": 0.15}, "purchase": {"end": 1.0}}
+TRANS_A = {"start": {"view": 0.95, "end": 0.05}, "view": {"detail": 0.6, "view": 0.25, "cart": 0.1, "end": 0.05},
+           "detail": {"view": 0.5, "cart": 0.15, "detail": 0.3, "end": 0.05}, "cart": {"view": 0.4, "purchase": 0.2, "end": 0.4}, "purchase": {"end": 1.0}}
+
+
+@dataclass
+class Event:
+    action: str
+    product_idx: int
+    price_seen: float
+    ts: float
+
+
+@dataclass
+class Session:
+    sid: str
+    events: List[Event]
+    actor: str  # H or A (ground truth label)
+    theta: Dict[str, float] = field(default_factory=dict)
+
+
+def compute_demand(session: Session) -> float:
+    """Compute demand proxy q̂ = Σ_k ω(a_k) for session (Eq 2)."""
+    return sum(ACTION_WEIGHTS.get(e.action, 0.1) for e in session.events)
+
+
+def kl_div(p: Dict[str, float], q: Dict[str, float]) -> float:
+    """KL divergence D_KL(p || q) for transition kernels."""
+    eps = 1e-10
+    keys = set(p.keys()) | set(q.keys())
+    return sum(p.get(k, eps) * np.log((p.get(k, eps) + eps) / (q.get(k, eps) + eps)) for k in keys)
+
+
+def build_kernel(events: List[Event]) -> Dict[str, Dict[str, float]]:
+    """Build empirical transition kernel from trajectory."""
+    trans: Dict[str, Dict[str, int]] = {}
+    prev = "start"
+    for e in events:
+        curr = e.action
+        trans.setdefault(prev, {})
+        trans[prev][curr] = trans[prev].get(curr, 0) + 1
+        prev = curr
+    kernel = {}
+    for s, dsts in trans.items():
+        total = sum(dsts.values())
+        kernel[s] = {d: c / total for d, c in dsts.items()} if total > 0 else {}
+    return kernel
+
+
+def compute_divergence(session: Session) -> Tuple[float, float]:
+    """Compute Δ_H, Δ_A divergence signals (Eq 20-21)."""
+    kernel = build_kernel(session.events)
+    delta_h = sum(kl_div(kernel.get(s, {}), TRANS_H.get(s, {})) for s in kernel) / max(len(kernel), 1)
+    delta_a = sum(kl_div(kernel.get(s, {}), TRANS_A.get(s, {})) for s in kernel) / max(len(kernel), 1)
+    return delta_h, delta_a
+
+
+def estimate_alpha(session: Session, beta: float = 2.0) -> float:
+    """Per-session contamination estimate α̂(τ') = σ(β(Δ_H - Δ_A))."""
+    dh, da = compute_divergence(session)
+    return 1.0 / (1.0 + np.exp(-beta * (dh - da))) if (dh + da) > 0 else 0.5
+
+
+def sample_trajectory(rng: np.random.Generator, trans: Dict, prices: np.ndarray, is_agent: bool) -> Tuple[List[Event], int]:
+    """Sample session trajectory from behavioral kernel."""
+    state, t, pidx = "start", 0.0, int(rng.integers(0, len(prices)))
+    events = []
+    while state != "end" and len(events) < 30:
+        if state != "start":
+            events.append(Event(action=state, product_idx=pidx, price_seen=float(prices[pidx]), ts=t))
+        probs = trans.get(state, {"end": 1.0})
+        state = rng.choice(list(probs.keys()), p=list(probs.values()))
+        t += max(0.2, rng.gamma(1.5, 0.8) if is_agent else rng.gamma(2.0, 1.2))
+    return events, pidx
+
+
+def put_prices_to_market(prices: np.ndarray, alpha: float = 0.2, n_sessions: int = 50,
+                         seed: int | None = None) -> Tuple[Dict[str, float], Dict[str, str]]:
+    """Generate sessions from mixture model Q(p) = (1-α)E[d_H] + αE[d_A] (Eq 3).
+
+    Returns:
+        demand_mapping: session_id -> demand proxy q̂
+        hidden_labels: session_id -> actor class (H or A)
+    """
+    rng = np.random.default_rng(seed)
+    demand_mapping, hidden_labels = {}, {}
+
+    for i in range(n_sessions):
+        sid = f"s{i:04d}"
+        is_agent = rng.random() < alpha
+        trans = TRANS_A if is_agent else TRANS_H
+        theta = {"price_sens": rng.uniform(0.05, 0.2), "base_conv": 0.01} if is_agent else {"price_sens": rng.uniform(1.5, 4.0), "base_conv": rng.uniform(0.2, 0.5)}
+        events, _ = sample_trajectory(rng, trans, prices, is_agent)
+        session = Session(sid=sid, events=events, actor="A" if is_agent else "H", theta=theta)
+        demand_mapping[sid] = compute_demand(session)
+        hidden_labels[sid] = session.actor
+
+    return demand_mapping, hidden_labels
+
+
+@dataclass
+class LimboUpdate:
+    utype: str  # "prices" or "demand"
+    data: np.ndarray | Dict[str, float]
+    t: int
+
+
+class Limbo:
+    """Historical trajectory of alternating price/demand observations."""
+
+    def __init__(self):
+        self.history: List[LimboUpdate] = []
+        self._t = 0
+
+    def add_update(self, utype: str, data: np.ndarray | Dict[str, float]) -> Dict:
+        self.history.append(LimboUpdate(utype=utype, data=data, t=self._t))
+        self._t += 1
+        return self.on_update(utype)
+
+    def on_update(self, utype: str) -> Dict:
+        """React to update: after prices -> return observed demand; after demand -> signal price update needed."""
+        if utype == "prices":
+            return {"action": "observe_demand", "msg": "awaiting market response"}
+        return {"action": "set_prices", "msg": "demand observed, update prices"}
+
+    def get_prices_history(self) -> List[np.ndarray]:
+        return [u.data for u in self.history if u.utype == "prices"]
+
+    def get_demand_history(self) -> List[Dict[str, float]]:
+        return [u.data for u in self.history if u.utype == "demand"]
+
+
+class System:
+    """Main pricing system implementing robust Stackelberg objective.
+
+    Manages the alternating loop:
+    1. Set prices p_t
+    2. Observe demand response Q̂(p_t)
+    3. Estimate contamination α from behavioral signals
+    4. Compute next prices via robust objective (Eq 23)
+    """
+
+    def __init__(self, n_products: int = 10, costs: np.ndarray | None = None, lambda_coi: float = 0.5, seed: int | None = 42):
+        self.n = n_products
+        self.rng = np.random.default_rng(seed)
+        self.costs = costs if costs is not None else self.rng.uniform(10, 50, n_products)
+        self.refs = self.costs * (1 + self.rng.uniform(0.2, 0.5, n_products))  # base prices with margin
+        self.lambda_coi = lambda_coi
+        self.limbo = Limbo()
+        self._alpha_est = 0.2  # current contamination estimate
+        self._sessions: List[Session] = []
+
+    @property
+    def alpha(self) -> float:
+        return self._alpha_est
+
+    def _estimate_alpha_from_sessions(self) -> float:
+        """Aggregate per-session α̂ estimates."""
+        if not self._sessions:
+            return self._alpha_est
+        alphas = [estimate_alpha(s) for s in self._sessions[-50:]]  # use recent sessions
+        return float(np.mean(alphas))
+
+    def _revenue_under_demand(self, prices: np.ndarray, demand: Dict[str, float]) -> float:
+        """Compute expected revenue R(p, d) from demand proxy."""
+        agg_demand = np.zeros(self.n)
+        for sid, q in demand.items():
+            if self._sessions:
+                sess = next((s for s in self._sessions if s.sid == sid), None)
+                if sess and sess.events:
+                    pidx = sess.events[0].product_idx
+                    agg_demand[pidx] += q
+        return float(np.dot(prices, agg_demand))
+
+    def _coi_leakage(self, prices: np.ndarray) -> float:
+        """COI_leak = α · InfoValue (query-tax surrogate)."""
+        return self._alpha_est * 1.0
+
+    def _objective(self, prices: np.ndarray, demand: Dict[str, float]) -> float:
+        """Robust objective: R(p,d) - λ·COI_leak (Eq 23 simplified)."""
+        revenue = self._revenue_under_demand(prices, demand)
+        cost = float(np.sum(self.costs))  # fixed cost approximation
+        profit = revenue - cost
+        coi_penalty = self.lambda_coi * self._coi_leakage(prices) * float(np.mean(prices - self.costs))
+        return profit - coi_penalty
+
+    def compute_prices(self, demand: Dict[str, float] | None = None) -> np.ndarray:
+        """Compute next prices via simple gradient-like update on robust objective.
+
+        In a full implementation this would be replaced by DR-RL policy output.
+        Here we use a heuristic: adjust margins based on α estimate.
+        """
+        self._alpha_est = self._estimate_alpha_from_sessions()
+
+        # base margin adjustment: higher α -> lower margins (defensive pricing)
+        margin_scale = 1.0 - 0.5 * self._alpha_est  # reduce margins under high contamination
+        margins = (self.refs - self.costs) * margin_scale
+
+        # add small noise for exploration
+        noise = self.rng.normal(0, 0.02, self.n) * self.costs
+        prices = np.clip(self.costs + margins + noise, self.costs * 1.02, self.refs * 1.3)
+
+        self.limbo.add_update("prices", prices)
+        return prices
+
+    def observe_demand(self, prices: np.ndarray, alpha_true: float = 0.2, n_sessions: int = 50) -> Dict[str, float]:
+        """Observe market response to prices."""
+        demand_map, labels = put_prices_to_market(prices, alpha=alpha_true, n_sessions=n_sessions, seed=int(self.rng.integers(0, 10000)))
+
+        # reconstruct sessions for α estimation
+        for sid, actor in labels.items():
+            events, _ = sample_trajectory(self.rng, TRANS_A if actor == "A" else TRANS_H, prices, actor == "A")
+            self._sessions.append(Session(sid=sid, events=events, actor=actor))
+
+        self.limbo.add_update("demand", demand_map)
+        return demand_map
+
+    def step(self, alpha_true: float = 0.2, n_sessions: int = 50) -> Tuple[np.ndarray, Dict[str, float], float]:
+        """Single simulation step: prices -> demand -> reward."""
+        demand_hist = self.limbo.get_demand_history()
+        prices = self.compute_prices(demand_hist[-1] if demand_hist else None)
+        demand = self.observe_demand(prices, alpha_true, n_sessions)
+        reward = self._objective(prices, demand)
+        return prices, demand, reward
+
+    def run(self, n_steps: int = 100, alpha_true: float = 0.2) -> Dict:
+        """Run simulation for n_steps, return trajectory."""
+        trajectory = {"prices": [], "demand": [], "rewards": [], "alpha_est": [], "alpha_true": alpha_true}
+        for _ in range(n_steps):
+            p, d, r = self.step(alpha_true)
+            trajectory["prices"].append(p)
+            trajectory["demand"].append(d)
+            trajectory["rewards"].append(r)
+            trajectory["alpha_est"].append(self._alpha_est)
+        return trajectory
+
+
+def coi_erosion(n_agents: int, price_std: float) -> float:
+    """COI erosion from Theorem 1: as N->inf, min(p_1..p_N)->p_min."""
+    if n_agents <= 1:
+        return 0.0
+    log_n = np.log(n_agents)
+    shift = price_std * (np.sqrt(2 * log_n) - (np.log(log_n) + np.log(4 * np.pi)) / (2 * np.sqrt(2 * log_n) + 1e-6))
+    return float(min(shift / (price_std * 2 + 1e-6), 1.0))
+
+
+if __name__ == "__main__":
+    # quick demo
+    sys = System(n_products=5, seed=42)
+    traj = sys.run(n_steps=20, alpha_true=0.25)
+    print(f"avg reward: {np.mean(traj['rewards']):.2f}, final α̂: {traj['alpha_est'][-1]:.3f}")
+
+    prices = np.array([20.0, 35.0, 50.0, 25.0, 40.0])
+    demand, labels = put_prices_to_market(prices, alpha=0.3, n_sessions=20, seed=123)
+    print(f'sessions: {len(demand)}, agents: {sum(1 for l in labels.values() if l=="A")}')
+
+    for n in [1, 5, 10, 50, 100]:
+        ero = coi_erosion(n, price_std=5.0)
+        print(f'N={n:3d} agents -> COI erosion: {ero:.3f}')
+
+    # test separability
+    events = [Event('view', 0, 20.0, 0.1), Event('detail', 0, 20.0, 0.5), Event('cart', 0, 20.0, 1.0),
+    Event('purchase', 0, 20.0, 2.0)]
+    sess_h = Session(sid='test', events=events, actor='H')
+    print(f'human-like session α̂: {estimate_alpha(sess_h):.3f}')
+
+    events_a = [Event('view', 0, 20.0, 0.1), Event('detail', 0, 20.0, 0.2), Event('view', 0, 20.0, 0.3),
+    Event('detail', 0, 20.0, 0.4)]
+    sess_a = Session(sid='test2', events=events_a, actor='A')
+    print(f'agent-like session α̂: {estimate_alpha(sess_a):.3f}')
diff --git a/lab/case/thesis/simplified_env.py b/lab/case/thesis/simplified_env.py
new file mode 100644
index 0000000..e18454b
--- /dev/null
+++ b/lab/case/thesis/simplified_env.py
@@ -0,0 +1,338 @@
+"""Gymnasium-compatible RL environment for thesis pricing system.
+
+Wraps simplified.System with standard Gym interface for training pricing policies.
+Supports multiple reward modes and contamination scenarios.
+
+Action: price multipliers [0.5, 1.5] applied to reference prices
+Observation: [prices, demand_agg, alpha_est, margins, position_proxy]
+Reward: configurable objective (revenue, profit, robust, coi-aware)
+"""
+from __future__ import annotations
+from dataclasses import dataclass
+from typing import Any, Dict, Tuple
+import numpy as np
+
+try:
+    import gymnasium as gym
+    from gymnasium import spaces
+    HAS_GYM = True
+except ImportError:
+    HAS_GYM = False
+
+from .simplified import (System, Session, Event, Limbo, put_prices_to_market,
+                         compute_demand, estimate_alpha, coi_erosion, TRANS_H, TRANS_A)
+
+
+@dataclass
+class EnvConfig:
+    """Configuration for pricing environment."""
+    n_products: int = 5
+    max_steps: int = 200
+    sessions_per_step: int = 30
+    alpha_true: float = 0.2           # true contamination level
+    alpha_drift: float = 0.0          # per-step drift in α
+    alpha_bounds: Tuple[float, float] = (0.0, 0.6)
+    lambda_coi: float = 0.5           # COI penalty weight
+    lambda_vol: float = 0.1           # volatility penalty weight
+    reward_mode: str = "robust"       # revenue | profit | robust | coi_aware
+    normalize_reward: bool = True
+    seed: int | None = 42
+
+
+class PricingEnv:
+    """RL environment for dynamic pricing under agent contamination.
+
+    Implements the thesis formulation where:
+    - Platform sets prices p_t
+    - Market responds with mixture demand Q(p) = (1-α)D_H + αD_A
+    - Agent estimates contamination α̂ from behavioral signals
+    - Reward balances profit vs COI leakage
+
+    Observation space (normalized):
+        [0:n]     - current prices / ref_prices
+        [n:2n]    - aggregated demand per product
+        [2n]      - estimated contamination α̂
+        [2n+1]    - true contamination α (if observable, else 0)
+        [2n+2:3n+2] - current margins (prices - costs) / costs
+        [3n+2]    - step / max_steps
+
+    Action space:
+        price multipliers in [0.5, 1.5] applied to reference prices
+    """
+
+    metadata = {"render_modes": ["human", "ansi"]}
+
+    def __init__(self, cfg: EnvConfig | None = None):
+        if not HAS_GYM:
+            raise ImportError("gymnasium required")
+        self.cfg = cfg or EnvConfig()
+        self.n = self.cfg.n_products
+        self._sys: System | None = None
+        self._t = 0
+        self._alpha = self.cfg.alpha_true
+        self._last_prices: np.ndarray | None = None
+        self._last_demand: Dict[str, float] | None = None
+        self._episode_rewards: list[float] = []
+        self._demand_agg = np.zeros(self.n)
+
+        # gymnasium spaces
+        self.action_space = spaces.Box(low=0.5, high=1.5, shape=(self.n,), dtype=np.float32)
+        obs_dim = self.n + self.n + 1 + 1 + self.n + 1  # prices + demand + α̂ + α + margins + t
+        self.observation_space = spaces.Box(low=-np.inf, high=np.inf, shape=(obs_dim,), dtype=np.float32)
+
+    def _build_obs(self) -> np.ndarray:
+        """Construct observation vector."""
+        if self._sys is None:
+            return np.zeros(self.observation_space.shape[0], dtype=np.float32)
+
+        prices = self._last_prices if self._last_prices is not None else self._sys.refs
+        price_ratio = prices / (self._sys.refs + 1e-6)
+        demand_norm = self._demand_agg / (np.sum(self._demand_agg) + 1e-6)
+        margins = (prices - self._sys.costs) / (self._sys.costs + 1e-6)
+        t_norm = self._t / self.cfg.max_steps
+
+        obs = np.concatenate([
+            price_ratio,                          # [0:n]
+            demand_norm,                          # [n:2n]
+            [self._sys.alpha],                    # [2n] estimated α̂
+            [self._alpha],                        # [2n+1] true α
+            margins,                              # [2n+2:3n+2]
+            [t_norm],                             # [3n+2]
+        ])
+        return obs.astype(np.float32)
+
+    def _compute_reward(self, prices: np.ndarray, demand: Dict[str, float]) -> float:
+        """Compute reward based on configured mode."""
+        cfg, sys = self.cfg, self._sys
+        if sys is None:
+            return 0.0
+
+        # aggregate demand per product
+        agg = np.zeros(self.n)
+        for sid, q in demand.items():
+            sess = next((s for s in sys._sessions if s.sid == sid), None)
+            if sess and sess.events:
+                pidx = sess.events[0].product_idx
+                agg[pidx] += q
+        self._demand_agg = agg
+
+        revenue = float(np.dot(prices, agg))
+        cost = float(np.dot(sys.costs, np.clip(agg, 0, 1)))  # simplified cost model
+        profit = revenue - cost
+
+        # volatility penalty (price changes)
+        vol_penalty = 0.0
+        if self._last_prices is not None:
+            price_change = np.abs(prices - self._last_prices) / (sys.refs + 1e-6)
+            vol_penalty = cfg.lambda_vol * float(np.mean(price_change))
+
+        # COI leakage penalty
+        avg_margin = float(np.mean(prices - sys.costs))
+        coi_leak = sys.alpha * avg_margin
+
+        if cfg.reward_mode == "revenue":
+            r = revenue
+        elif cfg.reward_mode == "profit":
+            r = profit
+        elif cfg.reward_mode == "robust":
+            # robust objective: profit - λ_coi * COI_leak - λ_vol * volatility
+            r = profit - cfg.lambda_coi * coi_leak - vol_penalty
+        elif cfg.reward_mode == "coi_aware":
+            # adaptive: heavier penalty at high contamination
+            adaptive_lambda = cfg.lambda_coi * (1 + 2 * sys.alpha)
+            r = profit - adaptive_lambda * coi_leak - vol_penalty
+        else:
+            r = profit
+
+        if cfg.normalize_reward:
+            r = r / (float(np.sum(sys.refs)) + 1e-6)  # normalize by potential revenue
+
+        return float(r)
+
+    def reset(self, seed: int | None = None, options: dict | None = None) -> Tuple[np.ndarray, dict]:
+        """Reset environment to initial state."""
+        seed = seed if seed is not None else self.cfg.seed
+        self._sys = System(n_products=self.n, lambda_coi=self.cfg.lambda_coi, seed=seed)
+        self._t = 0
+        self._alpha = self.cfg.alpha_true
+        self._last_prices = None
+        self._last_demand = None
+        self._episode_rewards = []
+        self._demand_agg = np.zeros(self.n)
+
+        info = {"alpha_true": self._alpha, "alpha_est": self._sys.alpha,
+                "costs": self._sys.costs.copy(), "refs": self._sys.refs.copy()}
+        return self._build_obs(), info
+
+    def step(self, action: np.ndarray) -> Tuple[np.ndarray, float, bool, bool, dict]:
+        """Execute one environment step.
+
+        Args:
+            action: price multipliers in [0.5, 1.5]
+
+        Returns:
+            obs, reward, terminated, truncated, info
+        """
+        if self._sys is None:
+            raise RuntimeError("call reset() first")
+
+        # convert action to prices
+        action = np.clip(action, 0.5, 1.5)
+        prices = self._sys.refs * action.astype(np.float64)
+        prices = np.clip(prices, self._sys.costs * 1.01, self._sys.refs * 2.0)
+
+        # drift contamination
+        if self.cfg.alpha_drift != 0:
+            self._alpha = np.clip(
+                self._alpha + self.cfg.alpha_drift * self._sys.rng.normal(),
+                *self.cfg.alpha_bounds)
+
+        # observe demand
+        demand = self._sys.observe_demand(prices, alpha_true=self._alpha, n_sessions=self.cfg.sessions_per_step)
+        self._sys.limbo.add_update("prices", prices)
+
+        # update α estimate
+        self._sys._alpha_est = self._sys._estimate_alpha_from_sessions()
+
+        reward = self._compute_reward(prices, demand)
+        self._episode_rewards.append(reward)
+
+        self._last_prices = prices.copy()
+        self._last_demand = demand
+        self._t += 1
+
+        terminated = self._t >= self.cfg.max_steps
+        truncated = False
+
+        info = {
+            "alpha_true": self._alpha,
+            "alpha_est": self._sys.alpha,
+            "revenue": float(np.dot(prices, self._demand_agg)),
+            "avg_margin": float(np.mean((prices - self._sys.costs) / self._sys.costs)),
+            "n_sessions": len(demand),
+            "coi_erosion": coi_erosion(int(self._alpha * self.cfg.sessions_per_step), float(np.std(prices))),
+        }
+
+        return self._build_obs(), reward, terminated, truncated, info
+
+    def render(self, mode: str = "human") -> str | None:
+        """Render environment state."""
+        if self._sys is None or self._last_prices is None:
+            return None
+
+        lines = [
+            f"t={self._t}/{self.cfg.max_steps}",
+            f"α_true={self._alpha:.3f} α̂={self._sys.alpha:.3f}",
+            f"prices: {self._last_prices.round(1)}",
+            f"demand: {self._demand_agg.round(2)}",
+            f"reward: {self._episode_rewards[-1] if self._episode_rewards else 0:.3f}",
+        ]
+        out = " | ".join(lines)
+        if mode == "human":
+            print(out)
+        return out
+
+    def close(self) -> None:
+        pass
+
+
+class ContaminationSweepEnv(PricingEnv):
+    """Environment that sweeps through contamination levels during training.
+
+    Useful for curriculum learning: start with low α, gradually increase.
+    """
+
+    def __init__(self, cfg: EnvConfig | None = None, alpha_schedule: list[float] | None = None):
+        super().__init__(cfg)
+        self._schedule = alpha_schedule or [0.1, 0.2, 0.3, 0.4, 0.5]
+        self._schedule_idx = 0
+
+    def reset(self, seed: int | None = None, options: dict | None = None) -> Tuple[np.ndarray, dict]:
+        # advance schedule on reset
+        if options and options.get("advance_schedule", False):
+            self._schedule_idx = (self._schedule_idx + 1) % len(self._schedule)
+        self.cfg.alpha_true = self._schedule[self._schedule_idx]
+        return super().reset(seed, options)
+
+
+class AdversarialEnv(PricingEnv):
+    """Environment with adversarial contamination dynamics.
+
+    The contamination level responds to pricing policy: if prices are too predictable,
+    agents learn to exploit and α increases.
+    """
+
+    def __init__(self, cfg: EnvConfig | None = None, exploitation_rate: float = 0.02):
+        super().__init__(cfg)
+        self._exploit_rate = exploitation_rate
+        self._price_history: list[np.ndarray] = []
+
+    def step(self, action: np.ndarray) -> Tuple[np.ndarray, float, bool, bool, dict]:
+        obs, reward, term, trunc, info = super().step(action)
+
+        # track price history for predictability
+        if self._last_prices is not None:
+            self._price_history.append(self._last_prices.copy())
+
+        # increase α if prices are predictable (low variance over recent history)
+        if len(self._price_history) > 10:
+            recent = np.array(self._price_history[-10:])
+            predictability = 1.0 / (float(np.std(recent)) + 0.1)
+            self._alpha = np.clip(
+                self._alpha + self._exploit_rate * predictability * self._sys.rng.random(),
+                *self.cfg.alpha_bounds)
+
+        info["predictability"] = predictability if len(self._price_history) > 10 else 0.0
+        return obs, reward, term, trunc, info
+
+    def reset(self, seed: int | None = None, options: dict | None = None) -> Tuple[np.ndarray, dict]:
+        self._price_history = []
+        return super().reset(seed, options)
+
+
+def make_env(cfg: EnvConfig | None = None, env_type: str = "standard") -> PricingEnv:
+    """Factory for creating pricing environments."""
+    if env_type == "sweep":
+        return ContaminationSweepEnv(cfg)
+    elif env_type == "adversarial":
+        return AdversarialEnv(cfg)
+    return PricingEnv(cfg)
+
+
+# simple baseline policies for benchmarking
+def fixed_price_policy(refs: np.ndarray, margin: float = 0.0) -> np.ndarray:
+    """Fixed markup policy: always return ref * (1 + margin)."""
+    return np.ones(len(refs), dtype=np.float32) * (1.0 + margin)
+
+
+def random_policy(n: int, rng: np.random.Generator | None = None) -> np.ndarray:
+    """Random policy for exploration baseline."""
+    rng = rng or np.random.default_rng()
+    return rng.uniform(0.7, 1.3, n).astype(np.float32)
+
+
+def adaptive_policy(obs: np.ndarray, n: int, base_margin: float = 0.1) -> np.ndarray:
+    """Simple adaptive policy: reduce margins when α̂ is high."""
+    alpha_est = obs[2 * n]  # α̂ is at position 2n in observation
+    margin_scale = 1.0 - 0.4 * alpha_est  # defensive when α̂ high
+    return np.ones(n, dtype=np.float32) * (1.0 + base_margin * margin_scale)
+
+
+if __name__ == "__main__":
+    # demo run
+    cfg = EnvConfig(n_products=100, max_steps=100, alpha_true=0.25, reward_mode="robust")
+    env = make_env(cfg)
+    obs, info = env.reset()
+    print(f"initial: α={info['alpha_true']:.2f}")
+
+    total_reward = 0.0
+    for t in range(cfg.max_steps):
+        action = adaptive_policy(obs, cfg.n_products)
+        obs, reward, done, _, info = env.step(action)
+        total_reward += reward
+        if t % 10 == 0:
+            env.render()
+        if done:
+            break
+
+    print(f"\ntotal reward: {total_reward:.2f}, final α̂: {info['alpha_est']:.3f}")