diff --git a/crates/ml/examples/precompute_features.rs b/crates/ml/examples/precompute_features.rs
index 03010ec43..6d8032e00 100644
--- a/crates/ml/examples/precompute_features.rs
+++ b/crates/ml/examples/precompute_features.rs
@@ -161,6 +161,12 @@ struct Opts {
     #[arg(long, default_value_t = 0.1)]
     imbalance_bar_ewma_alpha: f64,
 
+    /// Volume bar size: contracts of one-sided volume per bar. Used when
+    /// `data_source != "mbp10"`. Default 100 matches `DEFAULT_VOLUME_BAR_SIZE`.
+    /// MUST match the trainer's value for cache HIT.
+    #[arg(long, default_value_t = 100)]
+    volume_bar_size: u64,
+
     /// Skip confirmation prompt
     #[arg(long)]
     yes: bool,
@@ -278,6 +284,7 @@ async fn main() -> Result<()> {
         &opts.data_source,
         opts.imbalance_bar_threshold,
         opts.imbalance_bar_ewma_alpha,
+        opts.volume_bar_size,
     ).context("Failed to compute cache key")?;
     let early_check_path = output_dir.join(format!("{hex_key_early}.fxcache"));
     if early_check_path.exists() {
@@ -387,9 +394,9 @@ async fn main() -> Result<()> {
         );
         bars
     } else {
-        let bars = ml::features::build_volume_bars(&all_front_month_trades, ml::features::DEFAULT_VOLUME_BAR_SIZE);
+        let bars = ml::features::build_volume_bars(&all_front_month_trades, opts.volume_bar_size);
         info!("Volume bars built: {} bars ({} contracts/bar) in {:.1}s",
-            bars.len(), ml::features::DEFAULT_VOLUME_BAR_SIZE, t1.elapsed().as_secs_f64());
+            bars.len(), opts.volume_bar_size, t1.elapsed().as_secs_f64());
         bars
     };
 
@@ -528,7 +535,17 @@ async fn main() -> Result<()> {
             all_snapshots.sort_by_key(|s| s.timestamp);
             info!("Loaded {} MBP-10 snapshots in {:.1}s", all_snapshots.len(), t2.elapsed().as_secs_f64());
 
-            // Load trades (parallel)
+            // Load trades (parallel) and filter front-month per-file.
+            //
+            // Pre-2026-05-09: this branch loaded trades unfiltered, leaking
+            // off-contract trade activity into the per-bar OFI/VPIN/Kyle's
+            // Lambda computations during contract rollover windows. Volume
+            // bar formation already filters front-month at line 354 of this
+            // file; the OFI side did not. Audit confirmed the latent bug
+            // affected every prior MBP-10+trades production run.
+            //
+            // Fix: mirror the per-file `filter_front_month` call from the
+            // volume bar path so OFI windows only see in-month trades.
             let all_trades = if let Some(ref tdir) = trades_dir {
                 let mut trade_files = collect_dbn_files_recursive(tdir);
                 trade_files.sort();
@@ -536,7 +553,13 @@ async fn main() -> Result<()> {
                     use rayon::prelude::*;
                     trade_files.par_iter().filter_map(|path| {
                         match load_trades_sync(path) {
-                            Ok(t) => { info!("  {} trades from {:?}", t.len(), path.file_name()); Some(t) }
+                            Ok(t) => {
+                                let raw_count = t.len();
+                                let filtered = ml::features::filter_front_month(&t);
+                                info!("  {} trades from {:?} ({} front-month)",
+                                    raw_count, path.file_name(), filtered.len());
+                                Some(filtered)
+                            }
                             Err(e) => { tracing::warn!("  Failed {:?}: {e}", path.file_name()); None }
                         }
                     }).collect()
@@ -771,6 +794,7 @@ async fn main() -> Result<()> {
         &opts.data_source,
         opts.imbalance_bar_threshold,
         opts.imbalance_bar_ewma_alpha,
+        opts.volume_bar_size,
     ).context("Failed to compute cache key")?;
     let cache_key: [u8; 32] = hex::decode(&hex_key)
         .context("Invalid hex key")?
diff --git a/crates/ml/examples/train_baseline_rl.rs b/crates/ml/examples/train_baseline_rl.rs
index 801ed3a9b..affd958ca 100644
--- a/crates/ml/examples/train_baseline_rl.rs
+++ b/crates/ml/examples/train_baseline_rl.rs
@@ -252,6 +252,12 @@ struct Args {
     #[arg(long, default_value_t = 0.1)]
     imbalance_bar_ewma_alpha: f64,
 
+    /// Volume bar size: contracts of one-sided volume per bar. Used when
+    /// `data_source != "mbp10"`. Default 100. MUST match precompute's value
+    /// for cache HIT.
+    #[arg(long, default_value_t = 100)]
+    volume_bar_size: u64,
+
     /// Enable offline RL mode: train exclusively from a pre-collected dataset,
     /// skipping online experience collection. Requires --dataset-path.
     #[arg(long, default_value_t = false)]
@@ -619,6 +625,7 @@ fn run_training(args: &Args) -> Result<Vec<RlTrainingResult>> {
         "mbp10",
         args.imbalance_bar_threshold,
         args.imbalance_bar_ewma_alpha,
+        args.volume_bar_size,
         cache_dir_override.as_deref(),
     );
 
diff --git a/crates/ml/src/feature_cache.rs b/crates/ml/src/feature_cache.rs
index 201735a87..fd6834ffa 100644
--- a/crates/ml/src/feature_cache.rs
+++ b/crates/ml/src/feature_cache.rs
@@ -15,23 +15,24 @@ use std::path::{Path, PathBuf};
 /// (add / remove / modify) produces a different key.
 ///
 /// Production defaults for the bar-formation params (matches `dqn-production.toml`):
-/// `imbalance_bar_threshold = 0.5`, `imbalance_bar_ewma_alpha = 0.1`.
+/// `imbalance_bar_threshold = 0.5`, `imbalance_bar_ewma_alpha = 0.1`,
+/// `volume_bar_size = 100` (matches `DEFAULT_VOLUME_BAR_SIZE`).
 pub fn calculate_dbn_cache_key(data_dir: &Path) -> Result<String> {
-    calculate_dbn_cache_key_full(data_dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1)
+    calculate_dbn_cache_key_full(data_dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100)
 }
 
 /// Extended cache key that includes MBP-10 and trades directories AND bar
 /// formation parameters. The cache is invalidated when ANY data source
 /// changes — OHLCV, MBP-10, trades — OR when bar-formation params change.
 ///
-/// Bar-formation params (`imbalance_bar_threshold`, `imbalance_bar_ewma_alpha`)
-/// are hashed in regardless of `data_source` because: (a) they uniquely identify
-/// the bar stream the cache contains, (b) downstream features (e.g. log-returns,
-/// targets) depend on bar boundaries, and (c) without this, two runs configured
-/// with different thresholds will silently share the same cache file (canonical
-/// 2026-05-09 audit: 14 prior production runs all collided on `a3f933aa...` /
-/// `c07c960a...` keys regardless of TOML threshold value because the bar params
-/// were not in the hash).
+/// Bar-formation params (`imbalance_bar_threshold`, `imbalance_bar_ewma_alpha`,
+/// `volume_bar_size`) are hashed in regardless of `data_source` because:
+/// (a) they uniquely identify the bar stream the cache contains, (b) downstream
+/// features (e.g. log-returns, targets) depend on bar boundaries, and
+/// (c) without this, two runs configured with different params will silently
+/// share the same cache file (canonical 2026-05-09 audit: 14 prior production
+/// runs all collided on `a3f933aa...` / `c07c960a...` keys regardless of TOML
+/// threshold value because the bar params were not in the hash).
 pub fn calculate_dbn_cache_key_full(
     data_dir: &Path,
     mbp10_dir: Option<&Path>,
@@ -40,6 +41,7 @@ pub fn calculate_dbn_cache_key_full(
     data_source: &str,
     imbalance_bar_threshold: f64,
     imbalance_bar_ewma_alpha: f64,
+    volume_bar_size: u64,
 ) -> Result<String> {
     let mut hasher = Sha256::new();
 
@@ -54,6 +56,8 @@ pub fn calculate_dbn_cache_key_full(
     hasher.update(b"|");
     hasher.update(&imbalance_bar_ewma_alpha.to_le_bytes());
     hasher.update(b"|");
+    hasher.update(&volume_bar_size.to_le_bytes());
+    hasher.update(b"|");
 
     // Hash only file contents (size + mtime), not paths.
     // This makes the key independent of CWD, relative/absolute paths,
@@ -101,8 +105,8 @@ mod tests {
     fn test_cache_key_includes_symbol() {
         let dir = Path::new("test_data/futures-baseline");
         if !dir.exists() { return; }
-        let key_es = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1).unwrap();
-        let key_nq = calculate_dbn_cache_key_full(dir, None, None, "NQ.FUT", "mbp10", 0.5, 0.1).unwrap();
+        let key_es = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
+        let key_nq = calculate_dbn_cache_key_full(dir, None, None, "NQ.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
         assert_ne!(key_es, key_nq, "Different symbols must produce different cache keys");
     }
 
@@ -110,8 +114,8 @@ mod tests {
     fn test_cache_key_includes_data_source() {
         let dir = Path::new("test_data/futures-baseline");
         if !dir.exists() { return; }
-        let key_ohlcv = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "ohlcv", 0.5, 0.1).unwrap();
-        let key_mbp10 = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1).unwrap();
+        let key_ohlcv = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "ohlcv", 0.5, 0.1, 100).unwrap();
+        let key_mbp10 = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
         assert_ne!(key_ohlcv, key_mbp10, "Different data sources must produce different cache keys");
     }
 
@@ -119,8 +123,8 @@ mod tests {
     fn test_cache_key_includes_bar_threshold() {
         let dir = Path::new("test_data/futures-baseline");
         if !dir.exists() { return; }
-        let key_a = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1).unwrap();
-        let key_b = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 2.5, 0.1).unwrap();
+        let key_a = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
+        let key_b = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 2.5, 0.1, 100).unwrap();
         assert_ne!(key_a, key_b, "Different imbalance_bar_threshold must produce different cache keys");
     }
 
@@ -128,17 +132,26 @@ mod tests {
     fn test_cache_key_includes_bar_alpha() {
         let dir = Path::new("test_data/futures-baseline");
         if !dir.exists() { return; }
-        let key_a = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1).unwrap();
-        let key_b = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 1.0).unwrap();
+        let key_a = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
+        let key_b = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 1.0, 100).unwrap();
         assert_ne!(key_a, key_b, "Different imbalance_bar_ewma_alpha must produce different cache keys");
     }
 
+    #[test]
+    fn test_cache_key_includes_volume_bar_size() {
+        let dir = Path::new("test_data/futures-baseline");
+        if !dir.exists() { return; }
+        let key_a = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "ohlcv", 0.5, 0.1, 100).unwrap();
+        let key_b = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "ohlcv", 0.5, 0.1, 500).unwrap();
+        assert_ne!(key_a, key_b, "Different volume_bar_size must produce different cache keys");
+    }
+
     #[test]
     fn test_cache_key_stable() {
         let dir = Path::new("test_data/futures-baseline");
         if !dir.exists() { return; }
-        let key1 = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1).unwrap();
-        let key2 = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1).unwrap();
+        let key1 = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
+        let key2 = calculate_dbn_cache_key_full(dir, None, None, "ES.FUT", "mbp10", 0.5, 0.1, 100).unwrap();
         assert_eq!(key1, key2, "Same inputs must produce same key");
     }
 }
diff --git a/crates/ml/src/fxcache.rs b/crates/ml/src/fxcache.rs
index 561430397..9ecda0e4a 100644
--- a/crates/ml/src/fxcache.rs
+++ b/crates/ml/src/fxcache.rs
@@ -690,8 +690,9 @@ pub fn norm_stats_path_for_key(
 /// * `mbp10_dir` — Optional MBP-10 order book data directory
 /// * `trades_dir` — Optional trades data directory
 /// * `data_source` — Data source mode (`"mbp10"` or `"ohlcv"`)
-/// * `imbalance_bar_threshold` — Bar formation threshold (must match producer's value)
-/// * `imbalance_bar_ewma_alpha` — Bar formation EWMA alpha (must match producer's value)
+/// * `imbalance_bar_threshold` — Imbalance bar formation threshold (must match producer's value)
+/// * `imbalance_bar_ewma_alpha` — Imbalance bar EWMA alpha (must match producer's value)
+/// * `volume_bar_size` — Volume bar contracts/bar (must match producer's value)
 /// * `cache_dir_override` — Explicit cache directory (from CLI `--feature-cache-dir`)
 pub fn discover_and_load(
     data_dir: &Path,
@@ -701,6 +702,7 @@ pub fn discover_and_load(
     data_source: &str,
     imbalance_bar_threshold: f64,
     imbalance_bar_ewma_alpha: f64,
+    volume_bar_size: u64,
     cache_dir_override: Option<&Path>,
 ) -> Option<FxCacheData> {
     // 1. Resolve cache directory
@@ -709,7 +711,7 @@ pub fn discover_and_load(
     // 2. Compute cache key (includes symbol + data_source + bar params)
     let key_hex = crate::feature_cache::calculate_dbn_cache_key_full(
         data_dir, mbp10_dir, trades_dir, symbol, data_source,
-        imbalance_bar_threshold, imbalance_bar_ewma_alpha,
+        imbalance_bar_threshold, imbalance_bar_ewma_alpha, volume_bar_size,
     )
     .ok()?;
     let key: [u8; 32] = hex::decode(&key_hex).ok()?.try_into().ok()?;
@@ -749,6 +751,7 @@ mod discover_tests {
             "mbp10",
             0.5,
             0.1,
+            100,
             None,
         );
         assert!(result.is_none());
@@ -780,6 +783,7 @@ mod discover_tests {
             "mbp10",
             0.5,
             0.1,
+            100,
             Some(&cache_dir),
         );
         // Strict match only — no "most recent" fallback
diff --git a/crates/ml/src/trainers/dqn/config.rs b/crates/ml/src/trainers/dqn/config.rs
index ac0cfba09..840e6514b 100644
--- a/crates/ml/src/trainers/dqn/config.rs
+++ b/crates/ml/src/trainers/dqn/config.rs
@@ -994,6 +994,13 @@ pub struct DQNHyperparameters {
     /// Only used when `data_source = "mbp10"`.
     pub imbalance_bar_ewma_alpha: f32,
 
+    /// Volume bar size: contracts of one-sided volume per bar. Higher =
+    /// fewer/longer bars. Used when `data_source != "mbp10"`. Default: 100
+    /// (matches `DEFAULT_VOLUME_BAR_SIZE` for backwards compatibility with
+    /// pre-2026-05-09 caches). Must match between `precompute_features` and
+    /// trainer for fxcache HIT (cache key includes this value).
+    pub volume_bar_size: u64,
+
     // Offline RL mode (CQL/IQL on fixed datasets)
     /// Offline RL mode: skip online experience collection, train from a fixed dataset.
     /// Requires `dataset_path` to point to a pre-collected experience dataset.
@@ -1587,6 +1594,7 @@ impl DQNHyperparameters {
             max_bars: 0, // 0 = unlimited
             imbalance_bar_threshold: 100.0,
             imbalance_bar_ewma_alpha: 0.1,
+            volume_bar_size: 100,
 
             // Offline RL: disabled by default (online training with experience collection)
             offline_mode: false,
diff --git a/crates/ml/src/trainers/dqn/data_loading.rs b/crates/ml/src/trainers/dqn/data_loading.rs
index 26413837d..10a230c4f 100644
--- a/crates/ml/src/trainers/dqn/data_loading.rs
+++ b/crates/ml/src/trainers/dqn/data_loading.rs
@@ -151,6 +151,7 @@ impl DQNTrainer {
             &self.hyperparams.data_source,
             f64::from(self.hyperparams.imbalance_bar_threshold),
             f64::from(self.hyperparams.imbalance_bar_ewma_alpha),
+            self.hyperparams.volume_bar_size,
             cache_dir_override,
         ) {
             // OFI is unconditional — the model requires order flow data.
@@ -276,10 +277,11 @@ impl DQNTrainer {
                 all_front_month.sort_by_key(|t| t.timestamp);
 
                 let bars = crate::features::build_volume_bars(
-                    &all_front_month, crate::features::DEFAULT_VOLUME_BAR_SIZE,
+                    &all_front_month, self.hyperparams.volume_bar_size,
                 );
-                info!("Volume bars: {} bars from {} trades ({} front-month)",
-                    bars.len(), total_raw, all_front_month.len());
+                info!("Volume bars: {} bars from {} trades ({} front-month, size={})",
+                    bars.len(), total_raw, all_front_month.len(),
+                    self.hyperparams.volume_bar_size);
 
                 if bars.is_empty() {
                     return Err(anyhow::anyhow!(
diff --git a/crates/ml/src/training_profile.rs b/crates/ml/src/training_profile.rs
index b5987afd0..eda064098 100644
--- a/crates/ml/src/training_profile.rs
+++ b/crates/ml/src/training_profile.rs
@@ -95,6 +95,10 @@ pub struct TrainingSection {
     /// EWMA alpha for adaptive imbalance threshold. Default: 0.1.
     pub imbalance_bar_ewma_alpha: Option<f64>,
 
+    /// Volume bar size (contracts/bar). Used when `data_source != "mbp10"`.
+    /// Default: 100. Must match between precompute and trainer for cache HIT.
+    pub volume_bar_size: Option<u64>,
+
     /// Maximum bars to load for training. 0 = unlimited (load all data).
     /// Useful for fast smoketests on large datasets.
     pub max_bars: Option<usize>,
@@ -811,6 +815,9 @@ impl DqnTrainingProfile {
             if let Some(v) = t.imbalance_bar_ewma_alpha {
                 hp.imbalance_bar_ewma_alpha = v as f32;
             }
+            if let Some(v) = t.volume_bar_size {
+                hp.volume_bar_size = v;
+            }
         }
 
         // [exploration]
diff --git a/docs/dqn-wire-up-audit.md b/docs/dqn-wire-up-audit.md
index 753b70300..721a87464 100644
--- a/docs/dqn-wire-up-audit.md
+++ b/docs/dqn-wire-up-audit.md
@@ -2,6 +2,56 @@
 
 **Status:** Populated during Plan 1 Task 6 (A.5 orphan audit). Updated on every commit per Invariant 7.
 
+## 2026-05-09 — volume_bar_size in cache key + OFI front-month filter fix
+
+`crates/ml/src/trainers/dqn/data_loading.rs` updated in two places:
+1. Line 146: `discover_and_load` call now passes
+   `self.hyperparams.volume_bar_size` as the new bar-formation cache-key param
+   (8 → 9 args).
+2. Line 279: `build_volume_bars` now uses `self.hyperparams.volume_bar_size`
+   instead of the `DEFAULT_VOLUME_BAR_SIZE` constant. Tuning this knob via
+   TOML now actually changes bar density (was previously a no-op via the
+   same fossilization pattern as `imbalance_bar_threshold` pre-fix).
+
+### New CLI / TOML / Argo plumbing
+
+- `Hyperparams.volume_bar_size: u64` field added (default 100, matches
+  `DEFAULT_VOLUME_BAR_SIZE`). TrainingProfile loader reads `volume_bar_size`
+  TOML key.
+- `--volume-bar-size` CLI arg on `precompute_features` and
+  `train_baseline_rl` (default 100). Wired into Argo workflow params
+  `volume-bar-size` (default `"100"`) on both `train-template.yaml` and
+  `train-multi-seed-template.yaml`. `scripts/argo-train.sh` exposes
+  `--volume-bar-size <n>` for ad-hoc overrides.
+- New Argo workflow param `data-source` (default `"mbp10"`) threaded
+  through to `precompute_features --data-source`. Exposed as
+  `--data-source <s>` on `argo-train.sh`. Lets experiments toggle volume
+  vs imbalance bar mode without TOML edits.
+
+### Cache key
+
+`calculate_dbn_cache_key_full` signature: 7 args → 8 args (added
+`volume_bar_size: u64`). Hashed via `to_le_bytes()` after the imbalance
+params. New unit test `test_cache_key_includes_volume_bar_size` pins the
+contract; passes alongside the 5 existing tests.
+
+### Latent OFI bug fix (atomic with this commit)
+
+`crates/ml/examples/precompute_features.rs:539-557` (the OFI/VPIN/Kyle's
+Lambda computation branch) was loading trades unfiltered for per-bar
+microstructure feature computation. Pre-fix: the volume bar formation
+path filtered front-month per-file (line 354), but the OFI path did not,
+leaking off-contract trade activity into per-bar microstructure features
+during contract rollover windows.
+
+Fix: mirror the per-file `filter_front_month` call from the volume bar
+path. Volume bar formation and OFI computation now both see the same
+in-month trade tape. Severity in production: small (front-month dominates
+ES.FUT trade volume by 10-100×, contamination ≪ 1%) but real and present
+in every prior MBP-10+trades production run. Filed alongside the
+volume_bar_size cache-key fix because both are architectural cleanups
+the wgdc8 experiment surfaced.
+
 ## 2026-05-09 — fxcache key includes bar formation params + precompute_features actually USES data_source
 
 `crates/ml/src/trainers/dqn/data_loading.rs:146` — `discover_and_load`
diff --git a/infra/k8s/argo/train-multi-seed-template.yaml b/infra/k8s/argo/train-multi-seed-template.yaml
index e2c1c5c49..934cc2cad 100644
--- a/infra/k8s/argo/train-multi-seed-template.yaml
+++ b/infra/k8s/argo/train-multi-seed-template.yaml
@@ -100,6 +100,15 @@ spec:
         value: "0.5"
       - name: imbalance-bar-ewma-alpha
         value: "0.1"
+      # Volume bar size (contracts/bar). Used when data-source != "mbp10".
+      # Default 100 matches DEFAULT_VOLUME_BAR_SIZE. Cache key includes this.
+      - name: volume-bar-size
+        value: "100"
+      # Data source mode: "mbp10" (imbalance bars from MBP-10) or "ohlcv"
+      # (volume bars from trades). Threaded into both precompute_features and
+      # the trainer so cache keys align.
+      - name: data-source
+        value: "mbp10"
 
   volumes:
     - name: git-ssh-key
@@ -353,8 +362,10 @@ spec:
               --trades-data-dir /data/futures-baseline-trades \
               --output-dir /feature-cache \
               --symbol {{workflow.parameters.symbol}} \
+              --data-source {{workflow.parameters.data-source}} \
               --imbalance-bar-threshold {{workflow.parameters.imbalance-bar-threshold}} \
               --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}} \
+              --volume-bar-size {{workflow.parameters.volume-bar-size}} \
               --yes; then
               echo "=== Feature cache ready ==="
             else
@@ -370,8 +381,10 @@ spec:
                 --trades-data-dir /data/futures-baseline-trades \
                 --output-dir /feature-cache \
                 --symbol {{workflow.parameters.symbol}} \
+                --data-source {{workflow.parameters.data-source}} \
                 --imbalance-bar-threshold {{workflow.parameters.imbalance-bar-threshold}} \
                 --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}} \
+                --volume-bar-size {{workflow.parameters.volume-bar-size}} \
                 --yes
             fi
 
@@ -501,7 +514,8 @@ spec:
               --seed "$SEED" \
               --max-folds {{workflow.parameters.folds}} \
               --imbalance-bar-threshold {{workflow.parameters.imbalance-bar-threshold}} \
-              --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}}
+              --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}} \
+              --volume-bar-size {{workflow.parameters.volume-bar-size}}
 
             echo "=== Training complete: seed=$SEED folds={{workflow.parameters.folds}} ==="
 
diff --git a/infra/k8s/argo/train-template.yaml b/infra/k8s/argo/train-template.yaml
index 394165b96..c1ca49a3a 100644
--- a/infra/k8s/argo/train-template.yaml
+++ b/infra/k8s/argo/train-template.yaml
@@ -73,6 +73,10 @@ spec:
         value: "0.5"
       - name: imbalance-bar-ewma-alpha
         value: "0.1"
+      - name: volume-bar-size
+        value: "100"
+      - name: data-source
+        value: "mbp10"
 
   volumes:
     - name: git-ssh-key
@@ -373,8 +377,10 @@ spec:
               --trades-data-dir /data/futures-baseline-trades \
               --output-dir /feature-cache \
               --symbol {{workflow.parameters.symbol}} \
+              --data-source {{workflow.parameters.data-source}} \
               --imbalance-bar-threshold {{workflow.parameters.imbalance-bar-threshold}} \
               --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}} \
+              --volume-bar-size {{workflow.parameters.volume-bar-size}} \
               --yes; then
               echo "=== Feature cache ready ==="
             else
@@ -388,8 +394,10 @@ spec:
                 --trades-data-dir /data/futures-baseline-trades \
                 --output-dir /feature-cache \
                 --symbol {{workflow.parameters.symbol}} \
+                --data-source {{workflow.parameters.data-source}} \
                 --imbalance-bar-threshold {{workflow.parameters.imbalance-bar-threshold}} \
                 --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}} \
+                --volume-bar-size {{workflow.parameters.volume-bar-size}} \
                 --yes
               echo "=== Feature cache regenerated ==="
             fi
@@ -616,6 +624,7 @@ spec:
               --epochs {{workflow.parameters.train-epochs}} \
               --imbalance-bar-threshold {{workflow.parameters.imbalance-bar-threshold}} \
               --imbalance-bar-ewma-alpha {{workflow.parameters.imbalance-bar-ewma-alpha}} \
+              --volume-bar-size {{workflow.parameters.volume-bar-size}} \
               $HYPEROPT_FLAG
 
             echo "=== Training complete ==="
diff --git a/scripts/argo-train.sh b/scripts/argo-train.sh
index 852996e13..e257bb456 100755
--- a/scripts/argo-train.sh
+++ b/scripts/argo-train.sh
@@ -33,6 +33,8 @@ TAG=""
 PROFILE=false
 IMBALANCE_BAR_THRESHOLD=""
 IMBALANCE_BAR_EWMA_ALPHA=""
+VOLUME_BAR_SIZE=""
+DATA_SOURCE=""
 
 usage() {
   cat <<EOF
@@ -61,6 +63,10 @@ Options:
   --imbalance-bar-ewma-alpha <f>  Override imbalance bar EWMA alpha (default: 0.1).
                                   α=1.0 disables adaptation (this codebase's reversed
                                   convention). MUST match between precompute and trainer.
+  --volume-bar-size <n>           Override volume bar size in contracts (default: 100).
+                                  Used when --data-source != "mbp10". Cache key includes.
+  --data-source <s>               Data source mode: "mbp10" or "ohlcv" (default: "mbp10").
+                                  Threaded into both precompute and trainer.
   --profile            Wrap training under nsys (NVIDIA Nsight Systems) and
                        upload .nsys-rep artefacts to MinIO bucket
                        foxhunt-training-artifacts/profiles/<sha>/. Forces the
@@ -100,6 +106,8 @@ while [[ $# -gt 0 ]]; do
     --profile)     PROFILE=true; shift ;;
     --imbalance-bar-threshold)  IMBALANCE_BAR_THRESHOLD="$2"; shift 2 ;;
     --imbalance-bar-ewma-alpha) IMBALANCE_BAR_EWMA_ALPHA="$2"; shift 2 ;;
+    --volume-bar-size)          VOLUME_BAR_SIZE="$2"; shift 2 ;;
+    --data-source)              DATA_SOURCE="$2"; shift 2 ;;
     --dry-run)     DRY_RUN=true; shift ;;
     -h|--help)     usage ;;
     *)             echo "Unknown option: $1"; usage ;;
@@ -158,6 +166,8 @@ if [[ "$USE_MULTI_SEED" == "false" ]]; then
   [[ "$SANITIZER" != "none" ]] && CMD="$CMD -p sanitizer=$SANITIZER"
   [[ -n "$IMBALANCE_BAR_THRESHOLD" ]]  && CMD="$CMD -p imbalance-bar-threshold=$IMBALANCE_BAR_THRESHOLD"
   [[ -n "$IMBALANCE_BAR_EWMA_ALPHA" ]] && CMD="$CMD -p imbalance-bar-ewma-alpha=$IMBALANCE_BAR_EWMA_ALPHA"
+  [[ -n "$VOLUME_BAR_SIZE" ]]          && CMD="$CMD -p volume-bar-size=$VOLUME_BAR_SIZE"
+  [[ -n "$DATA_SOURCE" ]]              && CMD="$CMD -p data-source=$DATA_SOURCE"
 
   $BASELINE && CMD="$CMD -p hyperopt-trials=0"
   $WATCH    && CMD="$CMD --watch"
@@ -291,6 +301,8 @@ CMD="$CMD -p profile=$PROFILE"
 [[ -n "$TAG" ]]      && CMD="$CMD --labels foxhunt-tag=$TAG"
 [[ -n "$IMBALANCE_BAR_THRESHOLD" ]]  && CMD="$CMD -p imbalance-bar-threshold=$IMBALANCE_BAR_THRESHOLD"
 [[ -n "$IMBALANCE_BAR_EWMA_ALPHA" ]] && CMD="$CMD -p imbalance-bar-ewma-alpha=$IMBALANCE_BAR_EWMA_ALPHA"
+[[ -n "$VOLUME_BAR_SIZE" ]]          && CMD="$CMD -p volume-bar-size=$VOLUME_BAR_SIZE"
+[[ -n "$DATA_SOURCE" ]]              && CMD="$CMD -p data-source=$DATA_SOURCE"
 [[ "$SANITIZER" != "none" ]] && CMD="$CMD -p sanitizer=$SANITIZER"
 
 $BASELINE && CMD="$CMD -p hyperopt-trials=0"