Nautilus

India Macro-Regime - 5-state Gaussian HMM

Nautilus is a state-space modeling framework that applies a 5-state Gaussian Hidden Markov Model to infer latent market regimes from price, volatility, and macro data. These regimes drive a rule-based execution layer with gated exposure and adaptive sizing, enabling robust, forward-consistent strategy behavior.

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Use Cases

Regime-Aware Strategy Development

Fit a 5-state HMM to Nifty 50 and apply the resulting Hard Gate to any base signal. The gate zeros positions in Stress and Panic regimes while preserving full exposure in Bull states.

from nautilus.etl.loader import load_index
from nautilus.etl.macro import build_macro_features
from nautilus.strategies.regime import fit_hmm, REGIMES
from nautilus.strategies.momentum import compute_price_above_ma
from nautilus.backtests.engine import run_backtest

nifty      = load_index(start="2018-01-01")
price      = nifty["Close"]
macro_raw  = build_macro_features(price, raw=True)   # unshifted — for HMM input

result     = fit_hmm(price, macro_df=macro_raw, n_states=5, n_iter=200)
gate       = result.soft_kelly                        # continuous [0, 1] multiplier

ma_signal  = compute_price_above_ma(price, window=45) # pre-shifted +1D
gated_sig  = (ma_signal * gate.reindex(price.index).ffill()).clip(0, 1)

bt = run_backtest(price, gated_sig, cost_bps=10, name="MA(45) + HMM Gate")
print(bt.metrics["Sharpe"], bt.metrics["CAGR"], bt.metrics["Max DD"])

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Current Regime Snapshot

Read the live regime, confidence, and Kelly multiplier in three lines.

result   = fit_hmm(price, macro_df=macro_raw)
state    = int(result.states[-1])
conf     = float(result.posteriors[-1].max())
kelly    = float(result.soft_kelly[-1])

print(f"{REGIMES[state]['name']}  {conf:.0%} conf  {kelly:.2f}x Kelly")
# Bull Quiet  94% conf  1.00x Kelly

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Forward Regime Probability Forecast

Project the Markov chain N days forward from the current posterior to get a probability distribution over regimes at any future horizon.

from nautilus.strategies.regime import markov_forecast, REGIME_NAMES

paths = markov_forecast(result.trans_matrix, result.posteriors[-1], horizon=20)
print("Regime probabilities at t+20:")
for name, prob in zip(REGIME_NAMES, paths[-1]):
    print(f"  {name:<16} {prob:.1%}")

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Portfolio Risk Overlay

Scale a multi-asset portfolio's positions by the regime gate in one vectorised step.

import pandas as pd

# portfolio_returns: DataFrame with one column per asset
gate_series = (
    pd.Series(result.soft_kelly, index=result.dates)
    .reindex(portfolio_returns.index).ffill().fillna(0)
)
portfolio_gated = portfolio_returns.mul(gate_series, axis=0)

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Cross-Sectional Regime Factory

Fit independent HMMs across an entire universe and build a regime dashboard for every stock in one loop.

from nautilus.etl.loader import load_index
from nautilus.strategies.regime import fit_hmm, REGIMES

universe = ["RELIANCE.NS", "TCS.NS", "HDFCBANK.NS", "INFY.NS", "ICICIBANK.NS"]
snapshot = {}

for ticker in universe:
    df  = load_index(ticker=ticker, start="2021-01-01")
    res = fit_hmm(df["Close"], n_states=5, n_iter=100)
    if res is None:
        continue
    cur = int(res.states[-1])
    snapshot[ticker] = {
        "regime":  REGIMES[cur]["name"],
        "kelly":   round(float(res.soft_kelly[-1]), 3),
        "conf":    round(float(res.posteriors[-1].max()), 3),
    }

import pandas as pd
print(pd.DataFrame(snapshot).T.sort_values("kelly", ascending=False))

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Walk-Forward Out-of-Sample Validation

from sklearn.preprocessing import RobustScaler

TRAIN_YEARS, OOS_DAYS = 3, 126
results = []

for oos_start in pd.date_range(price.index[int(TRAIN_YEARS*252)], price.index[-OOS_DAYS-1], freq="126D"):
    train = price.loc[:oos_start]
    oos   = price.loc[oos_start: oos_start + pd.Timedelta(days=200)]
    if len(train) < 300 or len(oos) < 30:
        continue

    from nautilus.strategies.regime import build_hmm_features
    res     = fit_hmm(train, n_states=5, n_iter=100)
    feat    = build_hmm_features(oos)
    scaler  = RobustScaler().fit(build_hmm_features(train).values)
    _, post = res.model.score_samples(scaler.transform(feat.values))
    from nautilus.strategies.regime import MULT_VEC
    results.append({"oos_start": oos_start.date(), "mean_kelly": float((post @ MULT_VEC).mean())})

print(pd.DataFrame(results))

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Regime Attribution + Event Study

Decompose Nifty returns by HMM regime and study return windows around RBI policy dates.

import numpy as np

log_ret   = np.log(price / price.shift(1))
state_aln = pd.Series(result.states, index=result.dates).reindex(price.index).ffill()

attribution = (
    pd.DataFrame({"return": log_ret, "regime": state_aln})
    .dropna()
    .groupby("regime")["return"]
    .agg(["mean", "std", "count"])
)
attribution["ann_sharpe"] = attribution["mean"] / attribution["std"] * np.sqrt(252)
attribution.index = [REGIMES[i]["name"] for i in attribution.index]
print(attribution.round(4))

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FastAPI / Lambda Deployment

Wrap the regime engine in a REST endpoint or serverless handler.

# FastAPI
from fastapi import FastAPI
app = FastAPI()

@app.get("/regime")
def get_regime():
    nifty  = load_index(start="2018-01-01")
    result = fit_hmm(nifty["Close"], n_states=5, n_iter=200)
    state  = int(result.states[-1])
    return {
        "regime":     REGIMES[state]["name"],
        "confidence": round(float(result.posteriors[-1].max()), 4),
        "soft_kelly": round(float(result.soft_kelly[-1]), 4),
        "gate_open":  state < 4,
    }

# AWS Lambda
def lambda_handler(event, context):
    import json
    return {"statusCode": 200, "body": json.dumps(get_regime())}

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Automated Daily Report

forecast = markov_forecast(result.trans_matrix, result.posteriors[-1], horizon=20)
top_t20  = int(forecast[-1].argmax())

report = (
    f"=== NAUTILUS DAILY REPORT — {pd.Timestamp.today().date()} ===\n"
    f"Regime   : {REGIMES[state]['name']}  ({conf:.0%} conf)\n"
    f"Soft Kelly: {kelly:.2f}x  |  Gate: {'OPEN' if state < 4 else 'CLOSED'}\n"
    f"Nifty 50 : {float(price.iloc[-1]):,.0f}  |  1D: {float(price.pct_change().iloc[-1]*100):+.2f}%\n"
    f"T+20 view: {REGIMES[top_t20]['name']}  ({forecast[-1].max():.0%})"
)
print(report)
# pipe to telegram.send(report) / email / Slack

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Dashboard

nautilus
# or
streamlit run src/nautilus/dashboard/regime_dashboard.py

Opens at http://localhost:8501. The dashboard includes:

• Nifty 50 price chart with regime shading and Soft Kelly overlay
• 5-state probability stack + 20-day Markov forecast
• Regime-filtered backtest vs plain MA with 18-metric comparison table
• RBI repo rate, India 10Y G-Sec yield, and yield spread panel
• US macro monitor — S&P 500, 10Y−3M Treasury spread, Fed Funds Rate
• BRICS FX normalised to 100, US–India trade flows, Global EPU index
• Regime attribution table and transition matrix heatmap
• Monthly returns heatmap and full CSV export

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Model architecture

position(t) = base_signal(t) × hard_gate(t−1)

hard_gate(t) = f( argmax P(state | data₁..ₜ) )
  Bull Quiet    → 1.00×   (full exposure)
  Bull Volatile → 0.85×   (mild haircut)
  Neutral       → 0.75×   (moderate reduction)
  Stress        → 0.00×   (flat — no longs)
  Panic         → 0.00×   (cash)

HMM input features: vol_21d, ret_21d, vol_ratio (21/63), vol_of_vol, ret_5d, drawdown, bond_yield_chg_21d, yield_spread, repo_easing, dma_200_ratio.

All signals are pre-shifted +1D before entering the backtest engine. No look-ahead.

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Data sources

Series	Source	Cadence
Nifty 50	^NSEI via yfinance + Parquet cache	Daily
India 10Y G-Sec	Bundled india_10y_yield.csv	Bundled (2018–present)
RBI Repo Rate	Bundled rbi_repo_rate.csv + optional live scrape	Bundled
US 10Y Treasury	^TNX via yfinance	Daily
US 3M T-Bill	^IRX via yfinance	Daily
S&P 500	^GSPC via yfinance	Daily
Fed Funds Rate	Hardcoded policy anchors	Per FOMC

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Backtest metrics

18 metrics across four groups: Returns (Total Return, CAGR, Ann. Vol), Risk-Adjusted (Sharpe, Sortino, Calmar, Profit Factor), Drawdown (Max DD, Max DD Days, Longest DD Days, Avg DD, DD Episodes, Recovery Days, Current DD), Trade (Win Rate, Avg Win, Avg Loss).

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Project layout

src/nautilus/
├── config.py                # paths, tickers, model defaults
├── cli.py                   # nautilus command entry point
├── data/                    # bundled CSVs (shipped with wheel)
│   ├── india_10y_yield.csv
│   └── rbi_repo_rate.csv
├── etl/
│   ├── loader.py            # yfinance download + Parquet cache
│   └── macro.py             # macro pipeline (raw= flag for HMM)
├── strategies/
│   ├── momentum.py          # MA signal, price-above-MA regime
│   └── regime.py            # HMM fitting, Markov forecast
├── backtests/
│   └── engine.py            # vectorised engine + 18-metric suite
└── dashboard/
    └── regime_dashboard.py  # Streamlit app

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Honest limitations

• In-sample only. The HMM is fit and evaluated on the same history. Reported Sharpe and CAGR are descriptive, not predictive. Use walk-forward validation before drawing conclusions.
• State identity can shift. Regime labels are assigned post-hoc by sorting on vol − return. State identities can change between re-fits; anchoring logic is not yet implemented.
• Sparse macro features. The repo rate changes ~4–6 times per year. Forward-filling creates ~250 identical rows between decisions.
• Hard gate multipliers are hand-tuned. They are not derived from a risk model.
• No statistical significance. With ~2,700 days the standard error on annualised Sharpe is ≈ 0.35. A 0.3 improvement is within noise.
• Research tool, not a trading system. No order routing, position reconciliation, or risk limit enforcement.

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License

MIT - see LICENSE.