feat: add full derivatives analytics layer (options + futures)

Implements all phases of the derivatives expansion plan:

Rust core (crates/ferro_ta_core/src/options/, src/futures/):
- BSM and Black-76 pricing (scalar + vectorized batch)
- Greeks: delta, gamma, vega, theta, rho
- Implied volatility solver (Newton + bisection fallback)
- Smile/skew metrics: ATM IV, 25-delta RR/BF, skew slope, convexity
- Chain helpers: moneyness labels, strike selection by offset or delta
- Synthetic forwards, basis, annualized basis, implied carry, carry spread
- Continuous contract stitching: weighted, back-adjusted, ratio-adjusted
- Curve analytics: calendar spreads, slope, contango/backwardation summary

PyO3 bindings (src/options/, src/futures/):
- All Rust functions registered and exposed via _ferro_ta extension

Python API (python/ferro_ta/analysis/):
- options.py: pricing, greeks, IV, smile, chain, legacy iv_rank/percentile/zscore
- futures.py: basis, carry, curve, roll, synthetic, continuous contracts
- options_strategy.py: typed strategy schemas (expiry/strike selectors, leg presets, risk controls, simulation limits)
- derivatives_payoff.py: multi-leg payoff aggregation and Greeks aggregation

Bug fix: wrap _to_f64 calls in iv_rank/iv_percentile/iv_zscore to raise
FerroTAInputError (not plain ValueError) for 2D array input.

Docs: derivatives.rst, derivatives-analytics.md, options-volatility.md,
quickstart.rst, index.rst, api/analysis.rst all updated.

Tests: 2053 pass, 12 skipped. All CI checks pass locally.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

crates/ferro_ta_core/src/futures/basis.rs

@@ -0,0 +1,55 @@
+//! Basis and carry analytics.
+
+/// Futures basis: futures - spot.
+pub fn basis(spot: f64, future: f64) -> f64 {
+    if !spot.is_finite() || !future.is_finite() {
+        f64::NAN
+    } else {
+        future - spot
+    }
+}
+
+/// Annualized simple basis return.
+pub fn annualized_basis(spot: f64, future: f64, time_to_expiry: f64) -> f64 {
+    if !spot.is_finite()
+        || !future.is_finite()
+        || !time_to_expiry.is_finite()
+        || spot <= 0.0
+        || time_to_expiry <= 0.0
+    {
+        return f64::NAN;
+    }
+    (future / spot - 1.0) / time_to_expiry
+}
+
+/// Implied continuously compounded carry rate.
+pub fn implied_carry_rate(spot: f64, future: f64, time_to_expiry: f64) -> f64 {
+    if !spot.is_finite()
+        || !future.is_finite()
+        || !time_to_expiry.is_finite()
+        || spot <= 0.0
+        || future <= 0.0
+        || time_to_expiry <= 0.0
+    {
+        return f64::NAN;
+    }
+    (future / spot).ln() / time_to_expiry
+}
+
+/// Carry spread relative to the risk-free rate.
+pub fn carry_spread(spot: f64, future: f64, rate: f64, time_to_expiry: f64) -> f64 {
+    implied_carry_rate(spot, future, time_to_expiry) - rate
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{annualized_basis, basis, carry_spread, implied_carry_rate};
+
+    #[test]
+    fn basis_helpers_work() {
+        assert_eq!(basis(100.0, 103.0), 3.0);
+        assert!(annualized_basis(100.0, 103.0, 0.25) > 0.0);
+        assert!(implied_carry_rate(100.0, 103.0, 0.25) > 0.0);
+        assert!(carry_spread(100.0, 103.0, 0.02, 0.25).is_finite());
+    }
+}

crates/ferro_ta_core/src/futures/curve.rs

@@ -0,0 +1,83 @@
+//! Futures curve and term-structure analytics.
+
+use super::basis;
+
+/// Curve summary metrics.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct CurveSummary {
+    pub front_basis: f64,
+    pub average_basis: f64,
+    pub slope: f64,
+    pub is_contango: bool,
+}
+
+fn regression_slope(xs: &[f64], ys: &[f64]) -> f64 {
+    if xs.len() != ys.len() || xs.len() < 2 {
+        return f64::NAN;
+    }
+    let n = xs.len() as f64;
+    let mean_x = xs.iter().sum::<f64>() / n;
+    let mean_y = ys.iter().sum::<f64>() / n;
+    let mut cov = 0.0;
+    let mut var = 0.0;
+    for (&x, &y) in xs.iter().zip(ys.iter()) {
+        cov += (x - mean_x) * (y - mean_y);
+        var += (x - mean_x) * (x - mean_x);
+    }
+    if var == 0.0 {
+        f64::NAN
+    } else {
+        cov / var
+    }
+}
+
+/// Calendar spreads between adjacent contracts.
+pub fn calendar_spreads(futures_prices: &[f64]) -> Vec<f64> {
+    futures_prices.windows(2).map(|w| w[1] - w[0]).collect()
+}
+
+/// Curve slope across tenor buckets.
+pub fn curve_slope(tenors: &[f64], futures_prices: &[f64]) -> f64 {
+    regression_slope(tenors, futures_prices)
+}
+
+/// Summary statistics for a forward curve.
+pub fn curve_summary(spot: f64, tenors: &[f64], futures_prices: &[f64]) -> CurveSummary {
+    if futures_prices.is_empty() || tenors.len() != futures_prices.len() {
+        return CurveSummary {
+            front_basis: f64::NAN,
+            average_basis: f64::NAN,
+            slope: f64::NAN,
+            is_contango: false,
+        };
+    }
+    let bases: Vec<f64> = futures_prices
+        .iter()
+        .map(|&price| basis::basis(spot, price))
+        .collect();
+    let average_basis = bases.iter().sum::<f64>() / bases.len() as f64;
+    let is_contango = futures_prices.windows(2).all(|w| w[1] >= w[0]);
+    CurveSummary {
+        front_basis: basis::basis(spot, futures_prices[0]),
+        average_basis,
+        slope: curve_slope(tenors, futures_prices),
+        is_contango,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{calendar_spreads, curve_slope, curve_summary};
+
+    #[test]
+    fn calendar_spreads_are_correct() {
+        assert_eq!(calendar_spreads(&[100.0, 101.0, 103.0]), vec![1.0, 2.0]);
+    }
+
+    #[test]
+    fn curve_summary_detects_contango() {
+        let summary = curve_summary(100.0, &[0.1, 0.5, 1.0], &[101.0, 102.0, 104.0]);
+        assert!(summary.is_contango);
+        assert!(curve_slope(&[0.1, 0.5, 1.0], &[101.0, 102.0, 104.0]) > 0.0);
+    }
+}

crates/ferro_ta_core/src/futures/mod.rs

@@ -0,0 +1,6 @@
+//! Futures analytics core.
+
+pub mod basis;
+pub mod curve;
+pub mod roll;
+pub mod synthetic;

crates/ferro_ta_core/src/futures/roll.rs

@@ -0,0 +1,109 @@
+//! Continuous futures roll helpers.
+
+/// Weighted stitching using next-contract weights in [0, 1].
+pub fn weighted_continuous(front: &[f64], next: &[f64], next_weights: &[f64]) -> Vec<f64> {
+    if front.len() != next.len() || front.len() != next_weights.len() {
+        return Vec::new();
+    }
+    front
+        .iter()
+        .zip(next.iter())
+        .zip(next_weights.iter())
+        .map(|((&f, &n), &w)| f * (1.0 - w) + n * w)
+        .collect()
+}
+
+fn roll_index(weights: &[f64]) -> Option<usize> {
+    if weights.is_empty() {
+        return None;
+    }
+    weights
+        .iter()
+        .enumerate()
+        .find(|(_, w)| **w >= 0.5)
+        .map(|(idx, _)| idx)
+        .or_else(|| weights.iter().position(|w| *w > 0.0))
+        .or(Some(weights.len() - 1))
+}
+
+/// Back-adjusted continuous series using the roll date implied by the weights.
+pub fn back_adjusted_continuous(front: &[f64], next: &[f64], next_weights: &[f64]) -> Vec<f64> {
+    if front.len() != next.len() || front.len() != next_weights.len() || front.is_empty() {
+        return Vec::new();
+    }
+    let idx = roll_index(next_weights).unwrap_or(front.len() - 1);
+    let gap = next[idx] - front[idx];
+    front
+        .iter()
+        .enumerate()
+        .map(|(i, &value)| if i < idx { value + gap } else { next[i] })
+        .collect()
+}
+
+/// Ratio-adjusted continuous series using the roll date implied by the weights.
+pub fn ratio_adjusted_continuous(front: &[f64], next: &[f64], next_weights: &[f64]) -> Vec<f64> {
+    if front.len() != next.len() || front.len() != next_weights.len() || front.is_empty() {
+        return Vec::new();
+    }
+    let idx = roll_index(next_weights).unwrap_or(front.len() - 1);
+    let ratio = if front[idx] == 0.0 {
+        1.0
+    } else {
+        next[idx] / front[idx]
+    };
+    front
+        .iter()
+        .enumerate()
+        .map(|(i, &value)| if i < idx { value * ratio } else { next[i] })
+        .collect()
+}
+
+/// Annualized roll yield from front and next prices.
+pub fn roll_yield(front_price: f64, next_price: f64, time_to_expiry: f64) -> f64 {
+    if !front_price.is_finite()
+        || !next_price.is_finite()
+        || !time_to_expiry.is_finite()
+        || front_price <= 0.0
+        || time_to_expiry <= 0.0
+    {
+        return f64::NAN;
+    }
+    (next_price / front_price - 1.0) / time_to_expiry
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        back_adjusted_continuous, ratio_adjusted_continuous, roll_yield, weighted_continuous,
+    };
+
+    #[test]
+    fn weighted_roll_blends_contracts() {
+        let out = weighted_continuous(&[100.0, 101.0], &[102.0, 103.0], &[0.0, 1.0]);
+        assert_eq!(out, vec![100.0, 103.0]);
+    }
+
+    #[test]
+    fn adjusted_rolls_return_full_series() {
+        let weights = [0.0, 0.25, 0.75, 1.0];
+        assert_eq!(
+            back_adjusted_continuous(
+                &[100.0, 101.0, 102.0, 103.0],
+                &[101.0, 102.0, 103.0, 104.0],
+                &weights
+            )
+            .len(),
+            4
+        );
+        assert_eq!(
+            ratio_adjusted_continuous(
+                &[100.0, 101.0, 102.0, 103.0],
+                &[101.0, 102.0, 103.0, 104.0],
+                &weights
+            )
+            .len(),
+            4
+        );
+        assert!(roll_yield(100.0, 102.0, 30.0 / 365.0).is_finite());
+    }
+}

crates/ferro_ta_core/src/futures/synthetic.rs

@@ -0,0 +1,78 @@
+//! Synthetic futures helpers built from put-call parity.
+
+/// Synthetic forward price from call/put parity.
+pub fn synthetic_forward(
+    call_price: f64,
+    put_price: f64,
+    strike: f64,
+    rate: f64,
+    time_to_expiry: f64,
+) -> f64 {
+    if !call_price.is_finite()
+        || !put_price.is_finite()
+        || !strike.is_finite()
+        || !rate.is_finite()
+        || !time_to_expiry.is_finite()
+        || strike <= 0.0
+        || time_to_expiry < 0.0
+    {
+        return f64::NAN;
+    }
+    (call_price - put_price) * (rate * time_to_expiry).exp() + strike
+}
+
+/// Synthetic spot price implied by call/put parity with continuous carry.
+pub fn synthetic_spot(
+    call_price: f64,
+    put_price: f64,
+    strike: f64,
+    rate: f64,
+    carry: f64,
+    time_to_expiry: f64,
+) -> f64 {
+    if !call_price.is_finite()
+        || !put_price.is_finite()
+        || !strike.is_finite()
+        || !rate.is_finite()
+        || !carry.is_finite()
+        || !time_to_expiry.is_finite()
+        || strike <= 0.0
+        || time_to_expiry < 0.0
+    {
+        return f64::NAN;
+    }
+    (call_price - put_price + strike * (-rate * time_to_expiry).exp())
+        * (carry * time_to_expiry).exp()
+}
+
+/// Put-call parity residual. Zero means the inputs are parity-consistent.
+pub fn parity_gap(
+    call_price: f64,
+    put_price: f64,
+    spot: f64,
+    strike: f64,
+    rate: f64,
+    carry: f64,
+    time_to_expiry: f64,
+) -> f64 {
+    call_price
+        - put_price
+        - (spot * (-carry * time_to_expiry).exp() - strike * (-rate * time_to_expiry).exp())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{parity_gap, synthetic_forward};
+
+    #[test]
+    fn synthetic_forward_is_consistent() {
+        let forward = synthetic_forward(8.0, 5.0, 100.0, 0.02, 0.5);
+        assert!(forward > 100.0);
+    }
+
+    #[test]
+    fn parity_gap_zero_when_consistent() {
+        let gap = parity_gap(10.45, 5.57, 100.0, 100.0, 0.05, 0.0, 1.0);
+        assert!(gap.abs() < 0.05);
+    }
+}

crates/ferro_ta_core/src/lib.rs

@@ -26,8 +26,10 @@ assert!((sma[2] - 2.0).abs() < 1e-10);
 ```
 */
 
+pub mod futures;
 pub mod math;
 pub mod momentum;
+pub mod options;
 pub mod overlap;
 pub mod statistic;
 pub mod volatility;

crates/ferro_ta_core/src/options/chain.rs

@@ -0,0 +1,162 @@
+//! Option chain analytics helpers.
+
+use super::greeks::model_greeks;
+use super::{ChainGreeksContext, OptionContract, OptionEvaluation, OptionKind};
+
+/// Return the index of the strike closest to the reference price.
+pub fn atm_index(strikes: &[f64], reference_price: f64) -> Option<usize> {
+    if strikes.is_empty() || !reference_price.is_finite() {
+        return None;
+    }
+    strikes
+        .iter()
+        .enumerate()
+        .filter(|(_, strike)| strike.is_finite())
+        .min_by(|(_, a), (_, b)| {
+            (*a - reference_price)
+                .abs()
+                .partial_cmp(&(*b - reference_price).abs())
+                .unwrap_or(std::cmp::Ordering::Equal)
+        })
+        .map(|(idx, _)| idx)
+}
+
+/// Label strikes as ITM (1), ATM (0), or OTM (-1).
+pub fn label_moneyness(strikes: &[f64], reference_price: f64, kind: OptionKind) -> Vec<i8> {
+    let mut labels = Vec::with_capacity(strikes.len());
+    let atm_idx = atm_index(strikes, reference_price);
+    for (idx, &strike) in strikes.iter().enumerate() {
+        if Some(idx) == atm_idx {
+            labels.push(0);
+            continue;
+        }
+        let label = match kind {
+            OptionKind::Call => {
+                if strike < reference_price {
+                    1
+                } else {
+                    -1
+                }
+            }
+            OptionKind::Put => {
+                if strike > reference_price {
+                    1
+                } else {
+                    -1
+                }
+            }
+        };
+        labels.push(label);
+    }
+    labels
+}
+
+/// Select a strike relative to the ATM strike by offset steps.
+pub fn select_strike_by_offset(
+    strikes: &[f64],
+    reference_price: f64,
+    offset: isize,
+) -> Option<f64> {
+    let idx = atm_index(strikes, reference_price)? as isize + offset;
+    if idx < 0 || idx >= strikes.len() as isize {
+        None
+    } else {
+        Some(strikes[idx as usize])
+    }
+}
+
+/// Select the strike whose delta is closest to the requested target.
+pub fn select_strike_by_delta(
+    strikes: &[f64],
+    vols: &[f64],
+    context: ChainGreeksContext,
+    target_delta: f64,
+) -> Option<f64> {
+    if strikes.len() != vols.len() || strikes.is_empty() {
+        return None;
+    }
+    strikes
+        .iter()
+        .zip(vols.iter())
+        .filter(|(strike, vol)| strike.is_finite() && vol.is_finite())
+        .min_by(|(strike_a, vol_a), (strike_b, vol_b)| {
+            let delta_a = model_greeks(OptionEvaluation {
+                contract: OptionContract {
+                    model: context.model,
+                    underlying: context.reference_price,
+                    strike: **strike_a,
+                    rate: context.rate,
+                    carry: context.carry,
+                    time_to_expiry: context.time_to_expiry,
+                    kind: context.kind,
+                },
+                volatility: **vol_a,
+            })
+            .delta;
+            let delta_b = model_greeks(OptionEvaluation {
+                contract: OptionContract {
+                    model: context.model,
+                    underlying: context.reference_price,
+                    strike: **strike_b,
+                    rate: context.rate,
+                    carry: context.carry,
+                    time_to_expiry: context.time_to_expiry,
+                    kind: context.kind,
+                },
+                volatility: **vol_b,
+            })
+            .delta;
+            (delta_a - target_delta)
+                .abs()
+                .partial_cmp(&(delta_b - target_delta).abs())
+                .unwrap_or(std::cmp::Ordering::Equal)
+        })
+        .map(|(strike, _)| *strike)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{atm_index, label_moneyness, select_strike_by_delta, select_strike_by_offset};
+    use crate::options::{ChainGreeksContext, OptionKind, PricingModel};
+
+    #[test]
+    fn atm_index_finds_nearest() {
+        let strikes = [90.0, 100.0, 110.0];
+        assert_eq!(atm_index(&strikes, 103.0), Some(1));
+    }
+
+    #[test]
+    fn moneyness_labels_calls() {
+        let strikes = [90.0, 100.0, 110.0];
+        assert_eq!(
+            label_moneyness(&strikes, 100.0, OptionKind::Call),
+            vec![1, 0, -1]
+        );
+    }
+
+    #[test]
+    fn offset_selects_expected_strike() {
+        let strikes = [90.0, 100.0, 110.0];
+        assert_eq!(select_strike_by_offset(&strikes, 101.0, 1), Some(110.0));
+    }
+
+    #[test]
+    fn delta_selection_returns_a_strike() {
+        let strikes = [80.0, 90.0, 100.0, 110.0, 120.0];
+        let vols = [0.28, 0.24, 0.20, 0.22, 0.26];
+        let strike = select_strike_by_delta(
+            &strikes,
+            &vols,
+            ChainGreeksContext {
+                model: PricingModel::BlackScholes,
+                reference_price: 100.0,
+                rate: 0.01,
+                carry: 0.0,
+                time_to_expiry: 0.5,
+                kind: OptionKind::Call,
+            },
+            0.25,
+        );
+        assert!(strike.is_some());
+    }
+}

crates/ferro_ta_core/src/options/greeks.rs

@@ -0,0 +1,230 @@
+//! Option Greeks.
+
+use super::normal::{cdf, pdf};
+use super::pricing::{black_76_price, black_scholes_price};
+use super::{Greeks, OptionEvaluation, OptionKind, PricingModel};
+
+fn bs_inputs_valid(
+    underlying: f64,
+    strike: f64,
+    rate: f64,
+    carry: f64,
+    time_to_expiry: f64,
+    volatility: f64,
+) -> bool {
+    underlying.is_finite()
+        && strike.is_finite()
+        && rate.is_finite()
+        && carry.is_finite()
+        && time_to_expiry.is_finite()
+        && volatility.is_finite()
+        && underlying > 0.0
+        && strike > 0.0
+        && time_to_expiry > 0.0
+        && volatility > 0.0
+}
+
+fn numerical_theta<F>(time_to_expiry: f64, price_fn: F) -> f64
+where
+    F: Fn(f64) -> f64,
+{
+    if time_to_expiry <= 0.0 {
+        return 0.0;
+    }
+    let h = time_to_expiry.clamp(1e-6, 1.0 / 365.0);
+    let t_minus = (time_to_expiry - h).max(1e-8);
+    let t_plus = time_to_expiry + h;
+    let price_minus = price_fn(t_minus);
+    let price_plus = price_fn(t_plus);
+    (price_minus - price_plus) / (t_plus - t_minus)
+}
+
+/// Black-Scholes-Merton Greeks.
+pub fn black_scholes_greeks(
+    spot: f64,
+    strike: f64,
+    rate: f64,
+    dividend_yield: f64,
+    time_to_expiry: f64,
+    volatility: f64,
+    kind: OptionKind,
+) -> Greeks {
+    if !bs_inputs_valid(
+        spot,
+        strike,
+        rate,
+        dividend_yield,
+        time_to_expiry,
+        volatility,
+    ) {
+        return Greeks {
+            delta: f64::NAN,
+            gamma: f64::NAN,
+            vega: f64::NAN,
+            theta: f64::NAN,
+            rho: f64::NAN,
+        };
+    }
+
+    let sqrt_t = time_to_expiry.sqrt();
+    let sigma_sqrt_t = volatility * sqrt_t;
+    let discount = (-rate * time_to_expiry).exp();
+    let carry_discount = (-dividend_yield * time_to_expiry).exp();
+    let d1 = ((spot / strike).ln()
+        + (rate - dividend_yield + 0.5 * volatility * volatility) * time_to_expiry)
+        / sigma_sqrt_t;
+    let d2 = d1 - sigma_sqrt_t;
+    let pdf_d1 = pdf(d1);
+
+    let delta = match kind {
+        OptionKind::Call => carry_discount * cdf(d1),
+        OptionKind::Put => carry_discount * (cdf(d1) - 1.0),
+    };
+    let gamma = carry_discount * pdf_d1 / (spot * sigma_sqrt_t);
+    let vega = spot * carry_discount * pdf_d1 * sqrt_t;
+    let theta = match kind {
+        OptionKind::Call => {
+            -(spot * carry_discount * pdf_d1 * volatility) / (2.0 * sqrt_t)
+                - rate * strike * discount * cdf(d2)
+                + dividend_yield * spot * carry_discount * cdf(d1)
+        }
+        OptionKind::Put => {
+            -(spot * carry_discount * pdf_d1 * volatility) / (2.0 * sqrt_t)
+                + rate * strike * discount * cdf(-d2)
+                - dividend_yield * spot * carry_discount * cdf(-d1)
+        }
+    };
+    let rho = match kind {
+        OptionKind::Call => strike * time_to_expiry * discount * cdf(d2),
+        OptionKind::Put => -strike * time_to_expiry * discount * cdf(-d2),
+    };
+
+    Greeks {
+        delta,
+        gamma,
+        vega,
+        theta,
+        rho,
+    }
+}
+
+/// Black-76 Greeks with respect to the forward.
+pub fn black_76_greeks(
+    forward: f64,
+    strike: f64,
+    rate: f64,
+    time_to_expiry: f64,
+    volatility: f64,
+    kind: OptionKind,
+) -> Greeks {
+    if !bs_inputs_valid(forward, strike, rate, 0.0, time_to_expiry, volatility) {
+        return Greeks {
+            delta: f64::NAN,
+            gamma: f64::NAN,
+            vega: f64::NAN,
+            theta: f64::NAN,
+            rho: f64::NAN,
+        };
+    }
+
+    let sqrt_t = time_to_expiry.sqrt();
+    let sigma_sqrt_t = volatility * sqrt_t;
+    let discount = (-rate * time_to_expiry).exp();
+    let d1 =
+        ((forward / strike).ln() + 0.5 * volatility * volatility * time_to_expiry) / sigma_sqrt_t;
+    let pdf_d1 = pdf(d1);
+
+    let delta = match kind {
+        OptionKind::Call => discount * cdf(d1),
+        OptionKind::Put => -discount * cdf(-d1),
+    };
+    let gamma = discount * pdf_d1 / (forward * sigma_sqrt_t);
+    let vega = discount * forward * pdf_d1 * sqrt_t;
+    let theta = numerical_theta(time_to_expiry, |t| {
+        black_76_price(forward, strike, rate, t, volatility, kind)
+    });
+    let rho =
+        -time_to_expiry * black_76_price(forward, strike, rate, time_to_expiry, volatility, kind);
+
+    Greeks {
+        delta,
+        gamma,
+        vega,
+        theta,
+        rho,
+    }
+}
+
+/// Model-dispatched Greeks.
+pub fn model_greeks(input: OptionEvaluation) -> Greeks {
+    let contract = input.contract;
+    match contract.model {
+        PricingModel::BlackScholes => black_scholes_greeks(
+            contract.underlying,
+            contract.strike,
+            contract.rate,
+            contract.carry,
+            contract.time_to_expiry,
+            input.volatility,
+            contract.kind,
+        ),
+        PricingModel::Black76 => black_76_greeks(
+            contract.underlying,
+            contract.strike,
+            contract.rate,
+            contract.time_to_expiry,
+            input.volatility,
+            contract.kind,
+        ),
+    }
+}
+
+/// Price derivative with respect to calendar time using the selected model.
+pub fn model_theta(input: OptionEvaluation) -> f64 {
+    let contract = input.contract;
+    numerical_theta(contract.time_to_expiry, |t| match contract.model {
+        PricingModel::BlackScholes => black_scholes_price(
+            contract.underlying,
+            contract.strike,
+            contract.rate,
+            contract.carry,
+            t,
+            input.volatility,
+            contract.kind,
+        ),
+        PricingModel::Black76 => black_76_price(
+            contract.underlying,
+            contract.strike,
+            contract.rate,
+            t,
+            input.volatility,
+            contract.kind,
+        ),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{black_76_greeks, black_scholes_greeks};
+    use crate::options::OptionKind;
+
+    #[test]
+    fn bsm_greeks_are_finite() {
+        let g = black_scholes_greeks(100.0, 100.0, 0.05, 0.0, 1.0, 0.2, OptionKind::Call);
+        assert!(g.delta.is_finite());
+        assert!(g.gamma.is_finite());
+        assert!(g.vega.is_finite());
+        assert!(g.theta.is_finite());
+        assert!(g.rho.is_finite());
+    }
+
+    #[test]
+    fn black_76_greeks_are_finite() {
+        let g = black_76_greeks(100.0, 100.0, 0.03, 1.0, 0.2, OptionKind::Put);
+        assert!(g.delta.is_finite());
+        assert!(g.gamma.is_finite());
+        assert!(g.vega.is_finite());
+        assert!(g.theta.is_finite());
+        assert!(g.rho.is_finite());
+    }
+}

crates/ferro_ta_core/src/options/iv.rs

@@ -0,0 +1,241 @@
+//! Implied volatility inversion and IV-series helpers.
+
+use super::greeks::model_greeks;
+use super::pricing::{model_price, price_lower_bound, price_upper_bound};
+use super::{IvSolverConfig, OptionContract, OptionEvaluation};
+
+/// Solve implied volatility with guarded Newton iterations and bisection fallback.
+pub fn implied_volatility(
+    contract: OptionContract,
+    target_price: f64,
+    config: IvSolverConfig,
+) -> f64 {
+    if !target_price.is_finite()
+        || !contract.underlying.is_finite()
+        || !contract.strike.is_finite()
+        || !contract.rate.is_finite()
+        || !contract.carry.is_finite()
+        || !contract.time_to_expiry.is_finite()
+        || target_price < 0.0
+        || contract.underlying <= 0.0
+        || contract.strike <= 0.0
+        || contract.time_to_expiry < 0.0
+    {
+        return f64::NAN;
+    }
+    if contract.time_to_expiry == 0.0 {
+        return 0.0;
+    }
+
+    let lower = price_lower_bound(contract);
+    let upper = price_upper_bound(contract);
+    if target_price < lower - config.tolerance || target_price > upper + config.tolerance {
+        return f64::NAN;
+    }
+    if (target_price - lower).abs() <= config.tolerance {
+        return 0.0;
+    }
+
+    let mut low_vol = 1e-9;
+    let mut high_vol = config.initial_guess.max(0.25).max(low_vol * 10.0);
+    let mut high_price = model_price(OptionEvaluation {
+        contract,
+        volatility: high_vol,
+    });
+    while high_price < target_price && high_vol < 10.0 {
+        high_vol *= 2.0;
+        high_price = model_price(OptionEvaluation {
+            contract,
+            volatility: high_vol,
+        });
+    }
+    if high_price < target_price {
+        return f64::NAN;
+    }
+
+    let mut vol = config.initial_guess.clamp(low_vol, high_vol).max(1e-4);
+    for _ in 0..config.max_iterations.max(1) {
+        let price = model_price(OptionEvaluation {
+            contract,
+            volatility: vol,
+        });
+        let diff = price - target_price;
+        if diff.abs() <= config.tolerance {
+            return vol;
+        }
+
+        if diff > 0.0 {
+            high_vol = high_vol.min(vol);
+        } else {
+            low_vol = low_vol.max(vol);
+        }
+
+        let vega = model_greeks(OptionEvaluation {
+            contract,
+            volatility: vol,
+        })
+        .vega;
+
+        let next = if vega.is_finite() && vega.abs() > 1e-10 {
+            let candidate = vol - diff / vega;
+            if candidate > low_vol && candidate < high_vol {
+                candidate
+            } else {
+                0.5 * (low_vol + high_vol)
+            }
+        } else {
+            0.5 * (low_vol + high_vol)
+        };
+        vol = next;
+    }
+
+    let final_price = model_price(OptionEvaluation {
+        contract,
+        volatility: vol,
+    });
+    if (final_price - target_price).abs() <= config.tolerance * 10.0 {
+        vol
+    } else {
+        f64::NAN
+    }
+}
+
+fn validate_window(window: usize) -> bool {
+    window >= 1
+}
+
+/// Rolling IV rank.
+pub fn iv_rank(iv_series: &[f64], window: usize) -> Vec<f64> {
+    let n = iv_series.len();
+    let mut out = vec![f64::NAN; n];
+    if !validate_window(window) || n < window {
+        return out;
+    }
+
+    for end in (window - 1)..n {
+        let start = end + 1 - window;
+        let mut min_v = f64::INFINITY;
+        let mut max_v = f64::NEG_INFINITY;
+        for &v in &iv_series[start..=end] {
+            if v.is_finite() {
+                min_v = min_v.min(v);
+                max_v = max_v.max(v);
+            }
+        }
+        let current = iv_series[end];
+        if !current.is_finite() || !min_v.is_finite() || !max_v.is_finite() {
+            out[end] = f64::NAN;
+            continue;
+        }
+        let spread = max_v - min_v;
+        out[end] = if spread == 0.0 {
+            0.0
+        } else {
+            (current - min_v) / spread
+        };
+    }
+    out
+}
+
+/// Rolling IV percentile.
+pub fn iv_percentile(iv_series: &[f64], window: usize) -> Vec<f64> {
+    let n = iv_series.len();
+    let mut out = vec![f64::NAN; n];
+    if !validate_window(window) || n < window {
+        return out;
+    }
+
+    for end in (window - 1)..n {
+        let start = end + 1 - window;
+        let current = iv_series[end];
+        let count = iv_series[start..=end]
+            .iter()
+            .filter(|&&v| v <= current)
+            .count();
+        out[end] = count as f64 / window as f64;
+    }
+    out
+}
+
+/// Rolling IV z-score.
+pub fn iv_zscore(iv_series: &[f64], window: usize) -> Vec<f64> {
+    let n = iv_series.len();
+    let mut out = vec![f64::NAN; n];
+    if !validate_window(window) || n < window {
+        return out;
+    }
+
+    for end in (window - 1)..n {
+        let start = end + 1 - window;
+        let mut count = 0usize;
+        let mut sum = 0.0;
+        for &v in &iv_series[start..=end] {
+            if v.is_finite() {
+                count += 1;
+                sum += v;
+            }
+        }
+        if count == 0 {
+            out[end] = f64::NAN;
+            continue;
+        }
+        let mean = sum / count as f64;
+        let mut var = 0.0;
+        for &v in &iv_series[start..=end] {
+            if v.is_finite() {
+                let d = v - mean;
+                var += d * d;
+            }
+        }
+        let std = (var / count as f64).sqrt();
+        let current = iv_series[end];
+        out[end] = if !current.is_finite() || std == 0.0 {
+            f64::NAN
+        } else {
+            (current - mean) / std
+        };
+    }
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{implied_volatility, iv_percentile, iv_rank, iv_zscore};
+    use crate::options::pricing::black_scholes_price;
+    use crate::options::{IvSolverConfig, OptionContract, OptionKind, PricingModel};
+
+    #[test]
+    fn solver_recovers_input_vol() {
+        let price = black_scholes_price(100.0, 100.0, 0.05, 0.0, 1.0, 0.2, OptionKind::Call);
+        let iv = implied_volatility(
+            OptionContract {
+                model: PricingModel::BlackScholes,
+                underlying: 100.0,
+                strike: 100.0,
+                rate: 0.05,
+                carry: 0.0,
+                time_to_expiry: 1.0,
+                kind: OptionKind::Call,
+            },
+            price,
+            IvSolverConfig {
+                initial_guess: 0.3,
+                tolerance: 1e-8,
+                max_iterations: 100,
+            },
+        );
+        assert!((iv - 0.2).abs() < 1e-6);
+    }
+
+    #[test]
+    fn iv_helpers_match_expected_values() {
+        let iv = [10.0, 20.0, 30.0, 15.0, 22.0];
+        let rank = iv_rank(&iv, 3);
+        let pct = iv_percentile(&iv, 3);
+        let z = iv_zscore(&iv, 3);
+        assert!(rank[0].is_nan() && rank[1].is_nan());
+        assert!((rank[2] - 1.0).abs() < 1e-12);
+        assert!((pct[3] - (1.0 / 3.0)).abs() < 1e-12);
+        assert!((z[2] - 1.224_744_871).abs() < 1e-6);
+    }
+}

crates/ferro_ta_core/src/options/mod.rs

@@ -0,0 +1,88 @@
+//! Options analytics core.
+//!
+//! This module contains pricing, Greeks, implied volatility inversion,
+//! IV-series helpers, and smile/chain utilities. The public API is scalar-first
+//! and is used by the PyO3 bridge to build vectorized batch functions.
+
+pub mod chain;
+pub mod greeks;
+pub mod iv;
+pub mod normal;
+pub mod pricing;
+pub mod surface;
+
+/// Option side.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum OptionKind {
+    /// Call option.
+    Call,
+    /// Put option.
+    Put,
+}
+
+impl OptionKind {
+    /// Returns +1 for calls and -1 for puts.
+    pub fn sign(self) -> f64 {
+        match self {
+            Self::Call => 1.0,
+            Self::Put => -1.0,
+        }
+    }
+}
+
+/// Supported pricing models.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum PricingModel {
+    /// Black-Scholes-Merton with continuous carry/dividend yield.
+    BlackScholes,
+    /// Black-76 using the forward price as the underlying input.
+    Black76,
+}
+
+/// Primary first-order Greeks returned by the pricing engine.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Greeks {
+    pub delta: f64,
+    pub gamma: f64,
+    pub vega: f64,
+    pub theta: f64,
+    pub rho: f64,
+}
+
+/// Shared contract fields for model-based option analytics.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct OptionContract {
+    pub model: PricingModel,
+    pub underlying: f64,
+    pub strike: f64,
+    pub rate: f64,
+    pub carry: f64,
+    pub time_to_expiry: f64,
+    pub kind: OptionKind,
+}
+
+/// Contract plus volatility for pricing and Greeks.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct OptionEvaluation {
+    pub contract: OptionContract,
+    pub volatility: f64,
+}
+
+/// Solver configuration for implied volatility inversion.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct IvSolverConfig {
+    pub initial_guess: f64,
+    pub tolerance: f64,
+    pub max_iterations: usize,
+}
+
+/// Shared context for strike selection and smile analytics.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct ChainGreeksContext {
+    pub model: PricingModel,
+    pub reference_price: f64,
+    pub rate: f64,
+    pub carry: f64,
+    pub time_to_expiry: f64,
+    pub kind: OptionKind,
+}

crates/ferro_ta_core/src/options/normal.rs

@@ -0,0 +1,44 @@
+//! Normal distribution helpers.
+
+const INV_SQRT_2PI: f64 = 0.398_942_280_401_432_7;
+
+/// Standard normal probability density function.
+pub fn pdf(x: f64) -> f64 {
+    INV_SQRT_2PI * (-0.5 * x * x).exp()
+}
+
+/// Standard normal cumulative distribution function.
+///
+/// Uses a common Abramowitz-Stegun style approximation that is fast and
+/// sufficiently accurate for option pricing work.
+pub fn cdf(x: f64) -> f64 {
+    let ax = x.abs();
+    let t = 1.0 / (1.0 + 0.231_641_9 * ax);
+    let poly = (((((1.330_274_429 * t - 1.821_255_978) * t) + 1.781_477_937) * t - 0.356_563_782)
+        * t
+        + 0.319_381_530)
+        * t;
+    let approx = 1.0 - pdf(ax) * poly;
+    if x >= 0.0 {
+        approx
+    } else {
+        1.0 - approx
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{cdf, pdf};
+
+    #[test]
+    fn cdf_is_reasonable() {
+        assert!((cdf(0.0) - 0.5).abs() < 1e-7);
+        assert!((cdf(1.0) - 0.841_344_746).abs() < 5e-5);
+        assert!((cdf(-1.0) - 0.158_655_254).abs() < 5e-5);
+    }
+
+    #[test]
+    fn pdf_is_reasonable() {
+        assert!((pdf(0.0) - 0.398_942_280_4).abs() < 1e-10);
+    }
+}

crates/ferro_ta_core/src/options/pricing.rs

@@ -0,0 +1,187 @@
+//! Option pricing models.
+
+use super::normal::cdf;
+use super::{OptionContract, OptionEvaluation, OptionKind, PricingModel};
+
+fn invalid_inputs(underlying: f64, strike: f64, time_to_expiry: f64, volatility: f64) -> bool {
+    !underlying.is_finite()
+        || !strike.is_finite()
+        || !time_to_expiry.is_finite()
+        || !volatility.is_finite()
+        || underlying <= 0.0
+        || strike <= 0.0
+        || time_to_expiry < 0.0
+        || volatility < 0.0
+}
+
+/// Black-Scholes-Merton price with continuous carry/dividend yield.
+pub fn black_scholes_price(
+    spot: f64,
+    strike: f64,
+    rate: f64,
+    dividend_yield: f64,
+    time_to_expiry: f64,
+    volatility: f64,
+    kind: OptionKind,
+) -> f64 {
+    if invalid_inputs(spot, strike, time_to_expiry, volatility) || !rate.is_finite() {
+        return f64::NAN;
+    }
+    if time_to_expiry == 0.0 {
+        return match kind {
+            OptionKind::Call => (spot - strike).max(0.0),
+            OptionKind::Put => (strike - spot).max(0.0),
+        };
+    }
+
+    let discount = (-rate * time_to_expiry).exp();
+    let carry_discount = (-dividend_yield * time_to_expiry).exp();
+    if volatility == 0.0 {
+        return match kind {
+            OptionKind::Call => (spot * carry_discount - strike * discount).max(0.0),
+            OptionKind::Put => (strike * discount - spot * carry_discount).max(0.0),
+        };
+    }
+
+    let sqrt_t = time_to_expiry.sqrt();
+    let sigma_sqrt_t = volatility * sqrt_t;
+    let d1 = ((spot / strike).ln()
+        + (rate - dividend_yield + 0.5 * volatility * volatility) * time_to_expiry)
+        / sigma_sqrt_t;
+    let d2 = d1 - sigma_sqrt_t;
+
+    match kind {
+        OptionKind::Call => spot * carry_discount * cdf(d1) - strike * discount * cdf(d2),
+        OptionKind::Put => strike * discount * cdf(-d2) - spot * carry_discount * cdf(-d1),
+    }
+}
+
+/// Black-76 price using the forward price as the underlying input.
+pub fn black_76_price(
+    forward: f64,
+    strike: f64,
+    rate: f64,
+    time_to_expiry: f64,
+    volatility: f64,
+    kind: OptionKind,
+) -> f64 {
+    if invalid_inputs(forward, strike, time_to_expiry, volatility) || !rate.is_finite() {
+        return f64::NAN;
+    }
+    let discount = (-rate * time_to_expiry).exp();
+    if time_to_expiry == 0.0 {
+        return discount
+            * match kind {
+                OptionKind::Call => (forward - strike).max(0.0),
+                OptionKind::Put => (strike - forward).max(0.0),
+            };
+    }
+    if volatility == 0.0 {
+        return discount
+            * match kind {
+                OptionKind::Call => (forward - strike).max(0.0),
+                OptionKind::Put => (strike - forward).max(0.0),
+            };
+    }
+
+    let sqrt_t = time_to_expiry.sqrt();
+    let sigma_sqrt_t = volatility * sqrt_t;
+    let d1 =
+        ((forward / strike).ln() + 0.5 * volatility * volatility * time_to_expiry) / sigma_sqrt_t;
+    let d2 = d1 - sigma_sqrt_t;
+
+    let signed = kind.sign();
+    discount * signed * (forward * cdf(signed * d1) - strike * cdf(signed * d2))
+}
+
+/// Model-dispatched option price.
+pub fn model_price(input: OptionEvaluation) -> f64 {
+    let contract = input.contract;
+    match contract.model {
+        PricingModel::BlackScholes => black_scholes_price(
+            contract.underlying,
+            contract.strike,
+            contract.rate,
+            contract.carry,
+            contract.time_to_expiry,
+            input.volatility,
+            contract.kind,
+        ),
+        PricingModel::Black76 => black_76_price(
+            contract.underlying,
+            contract.strike,
+            contract.rate,
+            contract.time_to_expiry,
+            input.volatility,
+            contract.kind,
+        ),
+    }
+}
+
+/// Lower no-arbitrage bound for the option price.
+pub fn price_lower_bound(contract: OptionContract) -> f64 {
+    match contract.model {
+        PricingModel::BlackScholes => {
+            let discount = (-contract.rate * contract.time_to_expiry).exp();
+            let carry_discount = (-contract.carry * contract.time_to_expiry).exp();
+            match contract.kind {
+                OptionKind::Call => {
+                    (contract.underlying * carry_discount - contract.strike * discount).max(0.0)
+                }
+                OptionKind::Put => {
+                    (contract.strike * discount - contract.underlying * carry_discount).max(0.0)
+                }
+            }
+        }
+        PricingModel::Black76 => {
+            let discount = (-contract.rate * contract.time_to_expiry).exp();
+            discount
+                * match contract.kind {
+                    OptionKind::Call => (contract.underlying - contract.strike).max(0.0),
+                    OptionKind::Put => (contract.strike - contract.underlying).max(0.0),
+                }
+        }
+    }
+}
+
+/// Upper no-arbitrage bound for the option price.
+pub fn price_upper_bound(contract: OptionContract) -> f64 {
+    match contract.model {
+        PricingModel::BlackScholes => match contract.kind {
+            OptionKind::Call => {
+                contract.underlying * (-contract.carry * contract.time_to_expiry).exp()
+            }
+            OptionKind::Put => contract.strike * (-contract.rate * contract.time_to_expiry).exp(),
+        },
+        PricingModel::Black76 => {
+            let discount = (-contract.rate * contract.time_to_expiry).exp();
+            discount
+                * match contract.kind {
+                    OptionKind::Call => contract.underlying,
+                    OptionKind::Put => contract.strike,
+                }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{black_76_price, black_scholes_price};
+    use crate::options::OptionKind;
+
+    #[test]
+    fn black_scholes_prices_are_reasonable() {
+        let call = black_scholes_price(100.0, 100.0, 0.05, 0.0, 1.0, 0.2, OptionKind::Call);
+        let put = black_scholes_price(100.0, 100.0, 0.05, 0.0, 1.0, 0.2, OptionKind::Put);
+        assert!((call - 10.4506).abs() < 1e-3);
+        assert!((put - 5.5735).abs() < 1e-3);
+    }
+
+    #[test]
+    fn black_76_prices_are_reasonable() {
+        let call = black_76_price(100.0, 100.0, 0.03, 1.0, 0.2, OptionKind::Call);
+        let put = black_76_price(100.0, 100.0, 0.03, 1.0, 0.2, OptionKind::Put);
+        assert!((call - 7.730_148).abs() < 1e-3);
+        assert!((put - 7.730_148).abs() < 1e-3);
+    }
+}

crates/ferro_ta_core/src/options/surface.rs

@@ -0,0 +1,240 @@
+//! Smile and surface analytics helpers.
+
+use super::chain::atm_index;
+use super::greeks::model_greeks;
+use super::{ChainGreeksContext, OptionContract, OptionEvaluation, OptionKind, PricingModel};
+
+/// Smile summary metrics.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct SmileMetrics {
+    pub atm_iv: f64,
+    pub risk_reversal_25d: f64,
+    pub butterfly_25d: f64,
+    pub skew_slope: f64,
+    pub convexity: f64,
+}
+
+/// Linear interpolation helper.
+pub fn linear_interpolate(xs: &[f64], ys: &[f64], target: f64) -> f64 {
+    if xs.len() != ys.len() || xs.is_empty() {
+        return f64::NAN;
+    }
+    if target <= xs[0] {
+        return ys[0];
+    }
+    for i in 1..xs.len() {
+        if target <= xs[i] {
+            let x0 = xs[i - 1];
+            let x1 = xs[i];
+            let y0 = ys[i - 1];
+            let y1 = ys[i];
+            let w = if x1 == x0 {
+                0.0
+            } else {
+                (target - x0) / (x1 - x0)
+            };
+            return y0 + w * (y1 - y0);
+        }
+    }
+    ys[ys.len() - 1]
+}
+
+/// ATM implied volatility by nearest strike.
+pub fn atm_iv(strikes: &[f64], vols: &[f64], reference_price: f64) -> f64 {
+    if strikes.len() != vols.len() || strikes.is_empty() || !reference_price.is_finite() {
+        return f64::NAN;
+    }
+    atm_index(strikes, reference_price)
+        .and_then(|idx| vols.get(idx).copied())
+        .unwrap_or(f64::NAN)
+}
+
+fn regression_slope(xs: &[f64], ys: &[f64]) -> f64 {
+    if xs.len() != ys.len() || xs.len() < 2 {
+        return f64::NAN;
+    }
+    let n = xs.len() as f64;
+    let mean_x = xs.iter().sum::<f64>() / n;
+    let mean_y = ys.iter().sum::<f64>() / n;
+    let mut cov = 0.0;
+    let mut var = 0.0;
+    for (&x, &y) in xs.iter().zip(ys.iter()) {
+        cov += (x - mean_x) * (y - mean_y);
+        var += (x - mean_x) * (x - mean_x);
+    }
+    if var == 0.0 {
+        f64::NAN
+    } else {
+        cov / var
+    }
+}
+
+fn closest_delta_iv(
+    strikes: &[f64],
+    vols: &[f64],
+    context: ChainGreeksContext,
+    target_delta: f64,
+) -> f64 {
+    let mut best_iv = f64::NAN;
+    let mut best_distance = f64::INFINITY;
+    for (&strike, &vol) in strikes.iter().zip(vols.iter()) {
+        if !strike.is_finite() || !vol.is_finite() {
+            continue;
+        }
+        let delta = model_greeks(OptionEvaluation {
+            contract: OptionContract {
+                model: context.model,
+                underlying: context.reference_price,
+                strike,
+                rate: context.rate,
+                carry: context.carry,
+                time_to_expiry: context.time_to_expiry,
+                kind: context.kind,
+            },
+            volatility: vol,
+        })
+        .delta;
+        if !delta.is_finite() {
+            continue;
+        }
+        let distance = (delta - target_delta).abs();
+        if distance < best_distance {
+            best_distance = distance;
+            best_iv = vol;
+        }
+    }
+    best_iv
+}
+
+/// Smile metrics from a single expiry slice.
+pub fn smile_metrics(
+    strikes: &[f64],
+    vols: &[f64],
+    reference_price: f64,
+    rate: f64,
+    carry: f64,
+    time_to_expiry: f64,
+    model: PricingModel,
+) -> SmileMetrics {
+    if strikes.len() != vols.len() || strikes.len() < 3 || reference_price <= 0.0 {
+        return SmileMetrics {
+            atm_iv: f64::NAN,
+            risk_reversal_25d: f64::NAN,
+            butterfly_25d: f64::NAN,
+            skew_slope: f64::NAN,
+            convexity: f64::NAN,
+        };
+    }
+
+    let atm_idx = match atm_index(strikes, reference_price) {
+        Some(idx) => idx,
+        None => {
+            return SmileMetrics {
+                atm_iv: f64::NAN,
+                risk_reversal_25d: f64::NAN,
+                butterfly_25d: f64::NAN,
+                skew_slope: f64::NAN,
+                convexity: f64::NAN,
+            }
+        }
+    };
+    let atm_iv = vols[atm_idx];
+
+    let call_25 = closest_delta_iv(
+        strikes,
+        vols,
+        ChainGreeksContext {
+            model,
+            reference_price,
+            rate,
+            carry,
+            time_to_expiry,
+            kind: OptionKind::Call,
+        },
+        0.25,
+    );
+    let put_25 = closest_delta_iv(
+        strikes,
+        vols,
+        ChainGreeksContext {
+            model,
+            reference_price,
+            rate,
+            carry,
+            time_to_expiry,
+            kind: OptionKind::Put,
+        },
+        -0.25,
+    );
+    let risk_reversal_25d = call_25 - put_25;
+    let butterfly_25d = 0.5 * (call_25 + put_25) - atm_iv;
+
+    let log_moneyness: Vec<f64> = strikes
+        .iter()
+        .map(|&k| (k / reference_price).ln())
+        .collect();
+    let skew_slope = regression_slope(&log_moneyness, vols);
+    let convexity = if atm_idx > 0 && atm_idx + 1 < strikes.len() {
+        let x0 = log_moneyness[atm_idx - 1];
+        let x1 = log_moneyness[atm_idx];
+        let x2 = log_moneyness[atm_idx + 1];
+        let y0 = vols[atm_idx - 1];
+        let y1 = vols[atm_idx];
+        let y2 = vols[atm_idx + 1];
+        let left = if x1 == x0 { 0.0 } else { (y1 - y0) / (x1 - x0) };
+        let right = if x2 == x1 { 0.0 } else { (y2 - y1) / (x2 - x1) };
+        right - left
+    } else {
+        f64::NAN
+    };
+
+    SmileMetrics {
+        atm_iv,
+        risk_reversal_25d,
+        butterfly_25d,
+        skew_slope,
+        convexity,
+    }
+}
+
+/// Term-structure slope from (tenor, atm_iv) points.
+pub fn term_structure_slope(tenors: &[f64], atm_ivs: &[f64]) -> f64 {
+    regression_slope(tenors, atm_ivs)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{atm_iv, smile_metrics, term_structure_slope};
+    use crate::options::PricingModel;
+
+    #[test]
+    fn atm_selection_works() {
+        let strikes = [90.0, 100.0, 110.0];
+        let vols = [0.24, 0.20, 0.22];
+        assert!((atm_iv(&strikes, &vols, 102.0) - 0.20).abs() < 1e-12);
+    }
+
+    #[test]
+    fn smile_metrics_are_finite() {
+        let strikes = [80.0, 90.0, 100.0, 110.0, 120.0];
+        let vols = [0.30, 0.25, 0.20, 0.22, 0.27];
+        let metrics = smile_metrics(
+            &strikes,
+            &vols,
+            100.0,
+            0.02,
+            0.0,
+            0.5,
+            PricingModel::BlackScholes,
+        );
+        assert!(metrics.atm_iv.is_finite());
+        assert!(metrics.skew_slope.is_finite());
+    }
+
+    #[test]
+    fn term_slope_is_reasonable() {
+        let tenors = [0.1, 0.5, 1.0];
+        let vols = [0.18, 0.20, 0.22];
+        assert!(term_structure_slope(&tenors, &vols) > 0.0);
+    }
+}