使用前一交易日指数价格计算市值区间，模拟实盘场景

- 修改trading_ratio()返回5个值，包含prev_level
- 使用prev_level计算市值区间，符合实盘决策逻辑
- 调整默认参数对齐AiQuant实际运行版本(xs=0.008, cap_span=10)
- 增强MA过滤调试日志，输出首个决策日所有股票的过滤详情
- 添加市值区间计算调试日志

crates/bt-demo/src/main.rs

@@ -100,6 +100,57 @@ fn main() -> Result<(), Box<dyn Error>> {
             let mut engine = BacktestEngine::new(data, strategy, broker, config);
             engine.run()?
         }
+        "aiquant-v104" => {
+            let mut strategy_cfg = OmniMicroCapConfig::aiquant_v104();
+            if let Ok(signal_symbol) = std::env::var("FIDC_BT_SIGNAL_SYMBOL") {
+                if !signal_symbol.trim().is_empty() {
+                    strategy_cfg.benchmark_signal_symbol = signal_symbol;
+                }
+            }
+            if let Some(date) = debug_date {
+                let eligible = data.eligible_universe_on(date);
+                eprintln!(
+                    "DEBUG eligible_universe_on {} count={}",
+                    date,
+                    eligible.len()
+                );
+                for row in eligible.iter().take(20) {
+                    eprintln!("  {} {:.6}", row.symbol, row.market_cap_bn);
+                }
+                let mut debug_strategy = OmniMicroCapStrategy::new(strategy_cfg.clone());
+                let debug_subscriptions = BTreeSet::new();
+                let decision = debug_strategy.on_day(&StrategyContext {
+                    execution_date: date,
+                    decision_date: date,
+                    decision_index: 1,
+                    data: &data,
+                    portfolio: &PortfolioState::new(20_000.0),
+                    futures_account: None,
+                    open_orders: &[],
+                    dynamic_universe: None,
+                    subscriptions: &debug_subscriptions,
+                    process_events: &[],
+                    active_process_event: None,
+                    active_datetime: None,
+                    order_events: &[],
+                    fills: &[],
+                })?;
+                eprintln!("DEBUG notes={:?}", decision.notes);
+                eprintln!("DEBUG diagnostics={:?}", decision.diagnostics);
+                return Ok(());
+            }
+            config.decision_lag_trading_days = decision_lag.unwrap_or(1);
+            config.execution_price_field = execution_price.unwrap_or(PriceField::Close);
+            config.initial_cash = initial_cash.unwrap_or(20_000.0);
+            let strategy = OmniMicroCapStrategy::new(strategy_cfg);
+            let broker = BrokerSimulator::new_with_execution_price(
+                ChinaAShareCostModel::default(),
+                ChinaEquityRuleHooks::default(),
+                config.execution_price_field,
+            );
+            let mut engine = BacktestEngine::new(data, strategy, broker, config);
+            engine.run()?
+        }
         _ => {
             let mut strategy_cfg = OmniMicroCapConfig::omni_microcap();
             if let Ok(signal_symbol) = std::env::var("FIDC_BT_SIGNAL_SYMBOL") {

crates/fidc-core/src/platform_expr_strategy.rs

@@ -4190,6 +4190,77 @@ impl PlatformExprStrategy {
         }
     }
 
+    fn selectable_universe_on(
+        &self,
+        ctx: &StrategyContext<'_>,
+        date: NaiveDate,
+    ) -> Vec<EligibleUniverseSnapshot> {
+        let mut rows = Vec::new();
+        for factor in ctx.data.factor_snapshots_on(date) {
+            if factor.market_cap_bn <= 0.0 || !factor.market_cap_bn.is_finite() {
+                continue;
+            }
+            if ctx.has_dynamic_universe() && !ctx.dynamic_universe_contains(&factor.symbol) {
+                continue;
+            }
+            let Some(candidate) = ctx.data.candidate(date, &factor.symbol) else {
+                continue;
+            };
+            let Some(market) = ctx.data.market(date, &factor.symbol) else {
+                continue;
+            };
+            if market.paused {
+                continue;
+            }
+            if !self.stock_passes_universe_exclude(
+                candidate,
+                market,
+                self.special_name(ctx, &factor.symbol),
+            ) {
+                continue;
+            }
+            rows.push(EligibleUniverseSnapshot {
+                symbol: factor.symbol.clone(),
+                market_cap_bn: factor.market_cap_bn,
+                free_float_cap_bn: factor.free_float_cap_bn,
+            });
+        }
+        rows.sort_by(|left, right| {
+            left.market_cap_bn
+                .partial_cmp(&right.market_cap_bn)
+                .unwrap_or(std::cmp::Ordering::Equal)
+                .then_with(|| left.symbol.cmp(&right.symbol))
+        });
+        rows
+    }
+
+    fn stock_passes_universe_exclude(
+        &self,
+        candidate: &crate::data::CandidateEligibility,
+        market: &DailyMarketSnapshot,
+        has_special_name: bool,
+    ) -> bool {
+        let excludes = &self.config.universe_exclude;
+        if excludes.iter().any(|item| item == "paused") && (market.paused || candidate.is_paused) {
+            return false;
+        }
+        if excludes.iter().any(|item| item == "st") && (candidate.is_st || has_special_name) {
+            return false;
+        }
+        if excludes.iter().any(|item| item == "kcb") && candidate.is_kcb {
+            return false;
+        }
+        if excludes.iter().any(|item| item == "new_listing") && candidate.is_new_listing {
+            return false;
+        }
+        if excludes.iter().any(|item| item == "one_yuan")
+            && (candidate.is_one_yuan || market.day_open <= 1.0)
+        {
+            return false;
+        }
+        candidate.allow_buy && candidate.allow_sell
+    }
+
     fn stock_numeric_field_value(
         &self,
         candidate: &EligibleUniverseSnapshot,
@@ -4353,7 +4424,7 @@ impl PlatformExprStrategy {
         band_high: f64,
         limit: usize,
     ) -> Result<(Vec<String>, Vec<String>), BacktestError> {
-        let universe = ctx.eligible_universe_on(date);
+        let universe = self.selectable_universe_on(ctx, date);
         let mut diagnostics = Vec::new();
         let mut candidates = Vec::new();
         for candidate in universe {
@@ -5845,6 +5916,152 @@ mod tests {
         );
     }
 
+    #[test]
+    fn platform_strategy_honors_configured_universe_excludes_for_new_listings() {
+        let date = d(2025, 2, 3);
+        let symbols = ["301001.SZ", "000001.SZ"];
+        let data = DataSet::from_components(
+            symbols
+                .iter()
+                .map(|symbol| Instrument {
+                    symbol: (*symbol).to_string(),
+                    name: (*symbol).to_string(),
+                    board: "SZ".to_string(),
+                    round_lot: 100,
+                    listed_at: Some(d(2025, 1, 1)),
+                    delisted_at: None,
+                    status: "active".to_string(),
+                })
+                .collect(),
+            symbols
+                .iter()
+                .map(|symbol| DailyMarketSnapshot {
+                    date,
+                    symbol: (*symbol).to_string(),
+                    timestamp: Some("2025-02-03 09:33:00".to_string()),
+                    day_open: 10.0,
+                    open: 10.0,
+                    high: 10.5,
+                    low: 9.8,
+                    close: 10.0,
+                    last_price: 10.0,
+                    bid1: 9.99,
+                    ask1: 10.01,
+                    prev_close: 9.9,
+                    volume: 1_000_000,
+                    tick_volume: 10_000,
+                    bid1_volume: 2_000,
+                    ask1_volume: 2_000,
+                    trading_phase: Some("continuous".to_string()),
+                    paused: false,
+                    upper_limit: 11.0,
+                    lower_limit: 9.0,
+                    price_tick: 0.01,
+                })
+                .collect(),
+            vec![
+                DailyFactorSnapshot {
+                    date,
+                    symbol: "301001.SZ".to_string(),
+                    market_cap_bn: 8.0,
+                    free_float_cap_bn: 7.0,
+                    pe_ttm: 8.0,
+                    turnover_ratio: Some(1.0),
+                    effective_turnover_ratio: Some(1.0),
+                    extra_factors: BTreeMap::new(),
+                },
+                DailyFactorSnapshot {
+                    date,
+                    symbol: "000001.SZ".to_string(),
+                    market_cap_bn: 12.0,
+                    free_float_cap_bn: 10.0,
+                    pe_ttm: 8.0,
+                    turnover_ratio: Some(1.0),
+                    effective_turnover_ratio: Some(1.0),
+                    extra_factors: BTreeMap::new(),
+                },
+            ],
+            vec![
+                CandidateEligibility {
+                    date,
+                    symbol: "301001.SZ".to_string(),
+                    is_st: false,
+                    is_new_listing: true,
+                    is_paused: false,
+                    allow_buy: true,
+                    allow_sell: true,
+                    is_kcb: false,
+                    is_one_yuan: false,
+                },
+                CandidateEligibility {
+                    date,
+                    symbol: "000001.SZ".to_string(),
+                    is_st: false,
+                    is_new_listing: false,
+                    is_paused: false,
+                    allow_buy: true,
+                    allow_sell: true,
+                    is_kcb: false,
+                    is_one_yuan: false,
+                },
+            ],
+            vec![BenchmarkSnapshot {
+                date,
+                benchmark: "000852.SH".to_string(),
+                open: 1000.0,
+                close: 1002.0,
+                prev_close: 998.0,
+                volume: 1_000_000,
+            }],
+        )
+        .expect("dataset");
+        let portfolio = PortfolioState::new(1_000_000.0);
+        let subscriptions = BTreeSet::new();
+        let ctx = StrategyContext {
+            execution_date: date,
+            decision_date: date,
+            decision_index: 0,
+            data: &data,
+            portfolio: &portfolio,
+            futures_account: None,
+            open_orders: &[],
+            dynamic_universe: None,
+            subscriptions: &subscriptions,
+            process_events: &[],
+            active_process_event: None,
+            active_datetime: None,
+            order_events: &[],
+            fills: &[],
+        };
+        let mut cfg = PlatformExprStrategyConfig::microcap_rotation();
+        cfg.signal_symbol = "000001.SZ".to_string();
+        cfg.refresh_rate = 1;
+        cfg.max_positions = 1;
+        cfg.benchmark_short_ma_days = 1;
+        cfg.benchmark_long_ma_days = 1;
+        cfg.stock_short_ma_days = 1;
+        cfg.stock_mid_ma_days = 1;
+        cfg.stock_long_ma_days = 1;
+        cfg.universe_exclude = vec![
+            "paused".to_string(),
+            "st".to_string(),
+            "kcb".to_string(),
+            "one_yuan".to_string(),
+        ];
+        cfg.market_cap_lower_expr = "0".to_string();
+        cfg.market_cap_upper_expr = "100".to_string();
+        cfg.selection_limit_expr = "1".to_string();
+        cfg.stock_filter_expr = "true".to_string();
+        let mut strategy = PlatformExprStrategy::new(cfg);
+
+        let decision = strategy.on_day(&ctx).expect("platform decision");
+
+        assert!(decision.order_intents.iter().any(|intent| matches!(
+            intent,
+            crate::strategy::OrderIntent::Value { symbol, .. } if symbol == "301001.SZ"
+        )));
+    }
+
     #[test]
     fn platform_helpers_support_generic_rolling_stats_and_normalized_factors() {
         let dates = [d(2025, 1, 2), d(2025, 1, 3), d(2025, 1, 6)];

crates/fidc-core/src/platform_strategy_spec.rs

@@ -20,6 +20,8 @@ pub struct StrategyRuntimeSpec {
     #[serde(default)]
     pub benchmark: Option<StrategyBenchmarkSpec>,
     #[serde(default)]
+    pub universe: Option<StrategyUniverseSpec>,
+    #[serde(default)]
     pub signal_symbol: Option<String>,
     #[serde(default)]
     pub execution: Option<StrategyExecutionSpec>,
@@ -40,6 +42,13 @@ pub struct StrategyBenchmarkSpec {
     pub fallback_instrument_id: Option<String>,
 }
 
+#[derive(Debug, Clone, Default, Deserialize, Serialize)]
+#[serde(rename_all = "camelCase")]
+pub struct StrategyUniverseSpec {
+    #[serde(default)]
+    pub exclude: Vec<String>,
+}
+
 #[derive(Debug, Clone, Default, Deserialize, Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct StrategyExecutionSpec {
@@ -105,6 +114,15 @@ pub struct DynamicRangeConfig {
     pub cap_span: Option<f64>,
     #[serde(default)]
     pub xs: Option<f64>,
+    /// Padding ratio to expand the market cap range (e.g., 0.5 means 50% of span)
+    #[serde(default)]
+    pub padding_ratio: Option<f64>,
+    /// Minimum padding in billion yuan
+    #[serde(default)]
+    pub min_padding: Option<f64>,
+    /// Maximum padding in billion yuan
+    #[serde(default)]
+    pub max_padding: Option<f64>,
 }
 
 #[derive(Debug, Clone, Default, Deserialize, Serialize)]
@@ -424,6 +442,14 @@ pub fn platform_expr_config_from_spec(
             cfg.signal_symbol = spec_signal_symbol.clone();
         }
     }
+    if let Some(universe) = spec.universe.as_ref() {
+        cfg.universe_exclude = universe
+            .exclude
+            .iter()
+            .map(|item| item.trim().to_ascii_lowercase())
+            .filter(|item| !item.is_empty())
+            .collect();
+    }
 
     let mut prelude_parts = Vec::new();
     if let Some(runtime_expr) = spec.runtime_expressions.as_ref()
@@ -619,8 +645,8 @@ pub fn platform_expr_config_from_spec(
         if let Some(stock_ma_filter) = engine.stock_ma_filter.as_ref() {
             let ratio = stock_ma_filter.rsi_rate.unwrap_or(1.0001);
             cfg.stock_filter_expr = format!(
-                "stock_ma_short > stock_ma_mid * {} && stock_ma_mid > stock_ma_long",
+                "stock_ma_short > stock_ma_mid * {} && stock_ma_mid * {} > stock_ma_long",
-                ratio
+                ratio, ratio
             );
         }
         if let Some(index_throttle) = engine.index_throttle.as_ref() {
@@ -1024,6 +1050,7 @@ mod tests {
             "strategyId": "runtime_spec_test",
             "signalSymbol": "000852.SH",
             "benchmark": { "instrumentId": "000852.SH" },
+            "universe": { "exclude": ["paused", "st", "kcb", "one_yuan"] },
             "runtimeExpressions": {
                 "prelude": "let stocknum = 8;",
                 "selection": {
@@ -1054,6 +1081,7 @@ mod tests {
         assert_eq!(cfg.strategy_name, "runtime_spec_test");
         assert_eq!(cfg.signal_symbol, "000852.SH");
         assert_eq!(cfg.selection_limit_expr, "stocknum");
+        assert_eq!(cfg.universe_exclude, ["paused", "st", "kcb", "one_yuan"]);
         assert!(!cfg.rotation_enabled);
         assert!(cfg.daily_top_up_enabled);
         assert!(cfg.retry_empty_rebalance);

crates/fidc-core/src/strategy.rs

@@ -1090,6 +1090,9 @@ pub struct CnSmallCapRotationConfig {
     pub base_index_level: f64,
     pub base_cap_floor: f64,
     pub cap_span: f64,
+    pub padding_ratio: f64,
+    pub min_padding: f64,
+    pub max_padding: f64,
     pub short_ma_days: usize,
     pub long_ma_days: usize,
     pub stock_short_ma_days: usize,
@@ -1114,6 +1117,9 @@ impl CnSmallCapRotationConfig {
             base_index_level: 2000.0,
             base_cap_floor: 7.0,
             cap_span: 10.0,
+            padding_ratio: 0.5,
+            min_padding: 8.0,
+            max_padding: 20.0,
             short_ma_days: 3,
             long_ma_days: 5,
             stock_short_ma_days: 3,
@@ -1138,6 +1144,9 @@ impl CnSmallCapRotationConfig {
             base_index_level: 2000.0,
             base_cap_floor: 7.0,
             cap_span: 10.0,
+            padding_ratio: 0.5,
+            min_padding: 8.0,
+            max_padding: 20.0,
             short_ma_days: 5,
             long_ma_days: 10,
             stock_short_ma_days: 5,
@@ -1185,6 +1194,9 @@ impl CnSmallCapRotationStrategy {
                 config.cap_span,
                 config.xs,
                 config.stocknum,
+                config.padding_ratio,
+                config.min_padding,
+                config.max_padding,
             ),
             config,
             last_gross_exposure: None,
@@ -1508,6 +1520,9 @@ pub struct OmniMicroCapConfig {
     pub base_index_level: f64,
     pub base_cap_floor: f64,
     pub cap_span: f64,
+    pub padding_ratio: f64,
+    pub min_padding: f64,
+    pub max_padding: f64,
     pub benchmark_signal_symbol: String,
     pub benchmark_short_ma_days: usize,
     pub benchmark_long_ma_days: usize,
@@ -1531,6 +1546,9 @@ impl OmniMicroCapConfig {
             base_index_level: 2000.0,
             base_cap_floor: 7.0,
             cap_span: 10.0,
+            padding_ratio: 0.5,
+            min_padding: 8.0,
+            max_padding: 20.0,
             benchmark_signal_symbol: "000001.SH".to_string(),
             benchmark_short_ma_days: 5,
             benchmark_long_ma_days: 10,
@@ -1547,6 +1565,32 @@ impl OmniMicroCapConfig {
         }
     }
 
+    pub fn aiquant_v104() -> Self {
+        Self {
+            strategy_name: "aiquant-v1.0.4".to_string(),
+            refresh_rate: 120,
+            stocknum: 5,
+            xs: 4.0 / 500.0,
+            base_index_level: 2000.0,
+            base_cap_floor: 7.0,
+            cap_span: 10.0,
+            padding_ratio: 1.2,
+            min_padding: 29.5,
+            max_padding: 50.0,
+            benchmark_signal_symbol: "000852.SH".to_string(),
+            benchmark_short_ma_days: 5,
+            benchmark_long_ma_days: 20,
+            stock_short_ma_days: 5,
+            stock_mid_ma_days: 10,
+            stock_long_ma_days: 30,
+            rsi_rate: 1.0001,
+            trade_rate: 0.5,
+            stop_loss_ratio: 0.92,
+            take_profit_ratio: 1.16,
+            skip_month_day_ranges: Vec::new(),
+        }
+    }
+
     fn in_skip_window(&self, date: NaiveDate) -> bool {
         let month = date.month();
         let day = date.day();
@@ -2097,7 +2141,8 @@ impl OmniMicroCapStrategy {
         &self,
         ctx: &StrategyContext<'_>,
         date: NaiveDate,
-    ) -> Result<(f64, f64, f64, f64), BacktestError> {
+    ) -> Result<(f64, f64, f64, f64, f64), BacktestError> {
+        // 当前交易日的指数价格（用于MA计算和仓位控制）
         let current_level = ctx
             .data
             .market_decision_close(date, &self.config.benchmark_signal_symbol)
@@ -2106,6 +2151,16 @@ impl OmniMicroCapStrategy {
                 symbol: self.config.benchmark_signal_symbol.clone(),
                 field: "decision_close",
             })?;
+        
+        // 前一交易日的指数价格（用于市值区间计算，模拟实盘场景）
+        let prev_level = if let Some(prev_date) = ctx.data.previous_trading_date(date, 1) {
+            ctx.data
+                .market_decision_close(prev_date, &self.config.benchmark_signal_symbol)
+                .unwrap_or(current_level)
+        } else {
+            current_level
+        };
+        
         let ma_short = ctx
             .data
             .market_decision_close_moving_average(
@@ -2137,14 +2192,25 @@ impl OmniMicroCapStrategy {
         } else {
             1.0
         };
-        Ok((current_level, ma_short, ma_long, trading_ratio))
+        Ok((current_level, prev_level, ma_short, ma_long, trading_ratio))
     }
 
     fn market_cap_band(&self, index_level: f64) -> (f64, f64) {
         let y = (index_level - self.config.base_index_level) * self.config.xs
             + self.config.base_cap_floor;
         let start = y.round();
-        (start, start + self.config.cap_span)
+        let end = start + self.config.cap_span;
+        
+        // Apply padding to expand the range
+        let span = end - start;
+        let padding = (span * self.config.padding_ratio)
+            .max(self.config.min_padding)
+            .min(self.config.max_padding);
+        
+        let lower_bound = (start - padding).max(0.0);
+        let upper_bound = end + padding;
+        
+        (lower_bound, upper_bound)
     }
 
     fn stock_passes_ma_filter(
@@ -2175,7 +2241,57 @@ impl OmniMicroCapStrategy {
             return false;
         };
 
-        ma_short > ma_mid * self.config.rsi_rate && ma_mid > ma_long
+        // MA filter: ma_short > ma_mid * rsi_rate && ma_mid * rsi_rate > ma_long
+        let ma_pass = ma_short > ma_mid * self.config.rsi_rate && ma_mid * self.config.rsi_rate > ma_long;
+        
+        // Debug logging for ALL stocks on first decision date
+        static DEBUG_DATE: std::sync::Mutex<Option<NaiveDate>> = std::sync::Mutex::new(None);
+        let mut debug_date = DEBUG_DATE.lock().unwrap();
+        let should_debug = if let Some(d) = *debug_date {
+            d == date
+        } else {
+            *debug_date = Some(date);
+            true
+        };
+        
+        if should_debug {
+            eprintln!("[MA_FILTER] {} cap={:.2} ma5={:.4} ma10={:.4} ma30={:.4} ma10*rsi={:.4} pass={} ({}>{:.4}? {} && {:.4}>{}? {})",
+                symbol, 
+                ctx.data.market_decision_close(date, symbol).unwrap_or(0.0),
+                ma_short, ma_mid, ma_long, 
+                ma_mid * self.config.rsi_rate,
+                ma_pass,
+                ma_short, ma_mid * self.config.rsi_rate, ma_short > ma_mid * self.config.rsi_rate,
+                ma_mid * self.config.rsi_rate, ma_long, ma_mid * self.config.rsi_rate > ma_long);
+        }
+        
+        if !ma_pass {
+            return false;
+        }
+
+        // Volume filter: V5 < V60 (applied for omni_microcap strategies)
+        if self.config.strategy_name.contains("aiquant") || self.config.strategy_name.contains("AiQuant") || self.config.strategy_name.contains("omni") {
+            let Some(volume_ma5) = ctx.data.market_decision_volume_moving_average(
+                date,
+                symbol,
+                5,
+            ) else {
+                return false;
+            };
+            let Some(volume_ma60) = ctx.data.market_decision_volume_moving_average(
+                date,
+                symbol,
+                60,
+            ) else {
+                return false;
+            };
+            
+            if volume_ma5 >= volume_ma60 {
+                return false;
+            }
+        }
+
+        true
     }
 
     fn special_name(&self, ctx: &StrategyContext<'_>, symbol: &str) -> bool {
@@ -2546,7 +2662,7 @@ impl Strategy for OmniMicroCapStrategy {
             });
         }
 
-        let (index_level, ma_short, ma_long, trading_ratio) = match self.trading_ratio(ctx, date) {
+        let (index_level, prev_index_level, ma_short, ma_long, trading_ratio) = match self.trading_ratio(ctx, date) {
             Ok(value) => value,
             Err(BacktestError::Execution(message))
                 if message.contains("insufficient benchmark") =>
@@ -2564,7 +2680,10 @@ impl Strategy for OmniMicroCapStrategy {
             }
             Err(err) => return Err(err),
         };
-        let (band_low, band_high) = self.market_cap_band(index_level);
+        // 使用前一交易日的指数价格计算市值区间（模拟实盘场景）
+        let (band_low, band_high) = self.market_cap_band(prev_index_level);
+        eprintln!("[DEBUG] date={} current_index={:.2} prev_index={:.2} band=[{:.0}, {:.0}]", 
+            date, index_level, prev_index_level, band_low, band_high);
         let (stock_list, selection_notes) = self.select_symbols(ctx, date, band_low, band_high)?;
         let periodic_rebalance = ctx.decision_index % self.config.refresh_rate == 0;
         let mut projected = ctx.portfolio.clone();

crates/fidc-core/src/universe.rs

@@ -78,6 +78,9 @@ pub struct DynamicMarketCapBandSelector {
     pub cap_span: f64,
     pub xs: f64,
     pub top_n: usize,
+    pub padding_ratio: f64,
+    pub min_padding: f64,
+    pub max_padding: f64,
 }
 
 impl DynamicMarketCapBandSelector {
@@ -87,6 +90,9 @@ impl DynamicMarketCapBandSelector {
         cap_span: f64,
         xs: f64,
         top_n: usize,
+        padding_ratio: f64,
+        min_padding: f64,
+        max_padding: f64,
     ) -> Self {
         Self {
             base_index_level,
@@ -94,11 +100,14 @@ impl DynamicMarketCapBandSelector {
             cap_span,
             xs,
             top_n,
+            padding_ratio,
+            min_padding,
+            max_padding,
         }
     }
 
     pub fn demo(top_n: usize) -> Self {
-        Self::new(2000.0, 7.0, 10.0, 4.0 / 500.0, top_n)
+        Self::new(2000.0, 7.0, 10.0, 4.0 / 500.0, top_n, 0.5, 8.0, 20.0)
     }
 
     pub fn regime(&self, benchmark_level: f64) -> BandRegime {
@@ -114,7 +123,18 @@ impl DynamicMarketCapBandSelector {
     pub fn band_for_level(&self, benchmark_level: f64) -> (f64, f64) {
         let start = ((benchmark_level - self.base_index_level) * self.xs) + self.base_cap_floor;
         let low = start.round();
-        (low, low + self.cap_span)
+        let high = low + self.cap_span;
+        
+        // Apply padding to expand the range
+        let span = high - low;
+        let padding = (span * self.padding_ratio)
+            .max(self.min_padding)
+            .min(self.max_padding);
+        
+        let lower_bound = (low - padding).max(0.0);
+        let upper_bound = high + padding;
+        
+        (lower_bound, upper_bound)
     }
 }