foxhunt/crates/ml/examples/train_baseline_rl.rs

#![allow(
    clippy::assertions_on_constants,
    clippy::assertions_on_result_states,
    clippy::clone_on_copy,
    clippy::decimal_literal_representation,
    clippy::doc_markdown,
    clippy::empty_line_after_doc_comments,
    clippy::field_reassign_with_default,
    clippy::get_unwrap,
    clippy::identity_op,
    clippy::inconsistent_digit_grouping,
    clippy::indexing_slicing,
    clippy::integer_division,
    clippy::len_zero,
    clippy::let_underscore_must_use,
    clippy::manual_div_ceil,
    clippy::manual_let_else,
    clippy::manual_range_contains,
    clippy::modulo_arithmetic,
    clippy::needless_range_loop,
    clippy::non_ascii_literal,
    clippy::redundant_clone,
    clippy::shadow_reuse,
    clippy::shadow_same,
    clippy::shadow_unrelated,
    clippy::single_match_else,
    clippy::str_to_string,
    clippy::string_slice,
    clippy::tests_outside_test_module,
    clippy::too_many_lines,
    clippy::unnecessary_wraps,
    clippy::unseparated_literal_suffix,
    clippy::use_debug,
    clippy::useless_vec,
    clippy::wildcard_enum_match_arm,
    clippy::else_if_without_else,
    clippy::expect_used,
    clippy::missing_const_for_fn,
    clippy::similar_names,
    clippy::type_complexity,
    clippy::collapsible_else_if,
    clippy::doc_lazy_continuation,
    clippy::items_after_test_module,
    clippy::map_clone,
    clippy::multiple_unsafe_ops_per_block,
    clippy::unwrap_or_default,
    clippy::assign_op_pattern,
    clippy::needless_borrow,
    clippy::println_empty_string,
    clippy::unnecessary_cast,
    clippy::used_underscore_binding,
    clippy::create_dir,
    clippy::implicit_saturating_sub,
    clippy::exit,
    clippy::expect_fun_call,
    clippy::too_many_arguments,
    clippy::unnecessary_map_or,
    clippy::unwrap_used,
    dead_code,
    unused_imports,
    unused_variables,
    clippy::cloned_ref_to_slice_refs,
    clippy::neg_multiply,
    clippy::while_let_loop,
    clippy::bool_assert_comparison,
    clippy::excessive_precision,
    clippy::trivially_copy_pass_by_ref,
    clippy::op_ref,
    clippy::redundant_closure,
    clippy::unnecessary_lazy_evaluations,
    clippy::if_then_some_else_none,
    clippy::unnecessary_to_owned,
    clippy::single_component_path_imports,
)]
//! Walk-forward RL training binary for DQN and PPO models.
//!
//! Trains models using expanding walk-forward windows on real OHLCV data loaded
//! from Databento DBN files. Supports early stopping, checkpoint saving, and
//! normalization statistics export for reproducible evaluation.
//!
//! # Usage
//!
//! ```bash
//! SQLX_OFFLINE=true cargo run -p ml --example train_baseline -- \
//!     --model both --epochs 50 \
//!     --data-dir test_data/futures-baseline \
//!     --output-dir ml/trained_models
//! ```

#![allow(unused_crate_dependencies)]
#![deny(
    clippy::unwrap_used,
    clippy::expect_used,
    clippy::panic,
    clippy::indexing_slicing
)]

use std::path::{Path, PathBuf};

use anyhow::{Context, Result};
use clap::Parser;
use serde_json::Value;
use tracing::{error, info, warn};

use ml::trainers::dqn::{DQNHyperparameters, DQNTrainer};
use ml::trainers::ppo::{PpoHyperparameters, PpoTrainer, PpoTrainingMetrics};

#[allow(unreachable_pub)]
mod baseline_common;
use baseline_common::completion::{write_failure_marker, write_success_marker, CompletionMetrics};
use baseline_common::{load_all_bars, spread_cost_bps};
use common::metrics::{server as metrics_server, training_metrics as metrics};
use ml::features::extraction::{extract_ml_features, FeatureVector};
use ml_core::gpu::profile::GpuProfile;
use ml::types::OHLCVBar;
use ml::walk_forward::{
    generate_walk_forward_indices_from_timestamps,
    WalkForwardConfig,
};

// ---------------------------------------------------------------------------
// CLI Arguments
// ---------------------------------------------------------------------------

/// Walk-forward training binary for DQN and PPO baseline models.
#[derive(Parser, Debug)]
#[command(name = "train_baseline_rl", about = "Train DQN/PPO with walk-forward RL windows")]
struct Args {
    /// Which model(s) to train: "dqn", "ppo", or "both"
    #[arg(long, default_value = "both")]
    model: String,

    /// Maximum training epochs per fold
    #[arg(long, default_value_t = 50)]
    epochs: usize,

    // batch_size always auto-scaled from VRAM (no CLI override).

    /// Path to directory containing .dbn.zst files (env: FOXHUNT_DATA_DIR)
    #[arg(long, env = "FOXHUNT_DATA_DIR")]
    data_dir: PathBuf,

    /// Output directory for trained model checkpoints
    #[arg(long, default_value = "ml/trained_models")]
    output_dir: PathBuf,

    /// Optional path to hyperopt results JSON -- overrides matching config fields
    #[arg(long)]
    hyperopt_params: Option<PathBuf>,

    /// Feature dimension (42 market + 3 portfolio = 45, or 53 with OFI; must match trainer `state_dim`)
    #[arg(long, default_value_t = 43)]
    feature_dim: usize,

    /// Early stopping patience (epochs without improvement)
    #[arg(long, default_value_t = 10)]
    patience: usize,

    /// Number of actions (5 exposure levels for DQN, pass --num-actions 45 for PPO)
    #[arg(long, default_value_t = 5)]
    num_actions: usize,

    /// Walk-forward: initial training window in months
    #[arg(long, default_value_t = 12)]
    train_months: u32,

    /// Walk-forward: validation window in months
    #[arg(long, default_value_t = 3)]
    val_months: u32,

    /// Walk-forward: test window in months
    #[arg(long, default_value_t = 3)]
    test_months: u32,

    /// Walk-forward: step size in months between folds
    #[arg(long, default_value_t = 3)]
    step_months: u32,

    /// Cap the number of walk-forward folds trained. 0 = no cap (use all
    /// generated folds). Used by the multi_fold_convergence smoke test to run
    /// a 3-fold subset locally instead of the full 6-fold L40S gate.
    #[arg(long, default_value_t = 0)]
    max_folds: usize,

    /// Optional cap on total bars loaded from fxcache. When set, truncates the
    /// fxcache data to the first N bars after load but before GPU upload.
    /// Used by smoke tests to keep VRAM usage predictable (full ES.FUT is 697k
    /// bars ≈ 290 MB on GPU with OFI; a ~500k cap reserves ~60 MB headroom
    /// on 4 GB GPUs). 0 = unlimited (default; matches pre-change behaviour).
    /// OFI + features + targets + timestamps truncate in lockstep per the
    /// data_loading.rs precedent (commit 2ac956298 OFI/bars desync fix).
    #[arg(long, default_value_t = 0)]
    max_bars: usize,

    /// Learning rate for optimizer
    #[arg(long, default_value_t = 1e-4)]
    learning_rate: f64,

    /// Symbol subdirectory to load (e.g. "ES.FUT", "NQ.FUT")
    #[arg(long, default_value = "ES.FUT")]
    symbol: String,

    /// Maximum absolute per-bar return; larger moves are clamped (contract roll filter)
    #[arg(long, default_value_t = 0.01)]
    max_bar_return: f64,

    /// Round-trip commission cost in basis points (1 bps = 0.01%)
    /// Applied to BUY/SELL rewards; HOLD is free.
    /// Default 1.0 bps covers ~$4 exchange+broker for ES e-mini.
    #[arg(long, default_value_t = 1.0)]
    tx_cost_bps: f64,

    /// Instrument tick size in price units (ES=0.25, NQ=0.25, ZN=1/64)
    #[arg(long, default_value_t = 0.25)]
    tick_size: f64,

    /// Typical bid-ask spread in ticks (ES=1.0, ZN=1.0, 6E=2.0)
    /// Half-spread slippage is added to `tx_cost_bps` per trade.
    #[arg(long, default_value_t = 1.0)]
    spread_ticks: f64,

    /// Number of top hyperopt configs to train as ensemble (default 1 = best only).
    /// When > 1, loads `top_k_params` from the hyperopt JSON and trains a separate
    /// model for each param set, saving as `dqn_ensemble_{k}_fold_{fold}.safetensors`.
    #[arg(long, default_value_t = 1)]
    ensemble_top_k: usize,

    /// Optional path to MBP-10 order book data directory for OFI features.
    /// When set, enables 8 OFI features (OFI L1/L5, depth imbalance, VPIN, etc.)
    /// expanding state dimension from 43 to 51.
    #[arg(long)]
    mbp10_data_dir: Option<PathBuf>,

    /// Optional path to trade data directory (.dbn.zst files with Schema::Trades).
    /// When set, real trade buy/sell classification feeds VPIN and Kyle's Lambda
    /// instead of the tick-rule proxy. Requires --mbp10-data-dir to take effect.
    #[arg(long)]
    trades_data_dir: Option<PathBuf>,

    /// Enable offline RL mode: train exclusively from a pre-collected dataset,
    /// skipping online experience collection. Requires --dataset-path.
    #[arg(long, default_value_t = false)]
    offline: bool,

    /// Path to a pre-collected experience dataset (bincode format).
    /// Used with --offline to load a fixed dataset into the replay buffer.
    #[arg(long)]
    dataset_path: Option<PathBuf>,

    /// Collect and save a dataset from the current policy, then exit.
    /// Use this to generate datasets for offline training.
    #[arg(long)]
    collect_dataset: Option<PathBuf>,

    /// Disable Branching DQN (3-head: exposure, order, urgency). Enabled by default.
    #[arg(long)]
    no_branching: bool,

    /// Initial trading capital in dollars. Lower capital teaches conservative
    /// position sizing. Must match hyperopt --initial-capital for consistency.
    #[arg(long, default_value_t = 35_000.0)]
    initial_capital: f64,

    /// Named training profile to load from config/training/<profile>.toml.
    /// Profile values are applied after hyperopt JSON but before explicit CLI args.
    /// Known profiles: dqn-production, dqn-smoketest, dqn-hyperopt.
    #[arg(long, default_value = "dqn-production")]
    training_profile: String,

    /// Feature cache directory (overrides FOXHUNT_FEATURE_CACHE_DIR and auto-discovery)
    #[arg(long)]
    feature_cache_dir: Option<String>,

    /// Per-run RNG seed (Plan 5 Task 5 Phase B). Default 42 — historic implicit
    /// value; changing produces a different but still deterministic trajectory.
    /// Exported to children via `FOXHUNT_SEED` so every CUDA module that
    /// previously used a fixed seed (Xavier init, action selector, PPO replay
    /// seeds, regime dropout) mixes this value through `cuda_pipeline::mix_seed`
    /// (SplitMix64 avalanche). Used by `argo-train.sh --multi-seed N` to fan
    /// out N independent training trajectories on identical data + folds.
    #[arg(long, default_value_t = 42)]
    seed: u64,
}

// ---------------------------------------------------------------------------
// Hyperopt parameter loading
// ---------------------------------------------------------------------------

/// Load `best_params` from a hyperopt results JSON file.
///
/// Expected format: `{ "model_key": { "best_params": { ... }, ... } }`
/// Returns `None` if the file doesn't exist or can't be parsed.
#[allow(clippy::cognitive_complexity)]
fn load_hyperopt_params(hp_path: &Option<PathBuf>, model_key: &str) -> Option<Value> {
    let file_path = hp_path.as_ref()?;
    if !file_path.exists() {
        info!("Hyperopt params file not found: {}, using defaults", file_path.display());
        return None;
    }
    let contents = match std::fs::read_to_string(file_path) {
        Ok(c) => c,
        Err(e) => {
            warn!("Failed to read hyperopt params {}: {}", file_path.display(), e);
            return None;
        }
    };
    let json: Value = match serde_json::from_str(&contents) {
        Ok(v) => v,
        Err(e) => {
            warn!("Failed to parse hyperopt params JSON: {}", e);
            return None;
        }
    };
    let params = json.get(model_key)
        .and_then(|m| m.get("best_params"))
        .cloned();
    if params.is_some() {
        info!("Loaded hyperopt params for '{}' from {}", model_key, file_path.display());
    } else {
        warn!("No best_params found for '{}' in {}", model_key, file_path.display());
    }
    params
}

/// Load top-K param sets from a hyperopt results JSON file.
///
/// Expected format: `{ "model_key": { "top_k_params": [{ "params": {...}, ... }, ...], "best_params": {...} } }`
/// Falls back to `best_params` as a single entry when `top_k_params` is absent.
/// Returns a vec of length `k` (or fewer if not enough entries), each entry `Some(params)` or `None`.
fn load_top_k_params(hp_path: &Option<PathBuf>, model_key: &str, k: usize) -> Vec<Option<Value>> {
    let file_path = match hp_path.as_ref() {
        Some(p) if p.exists() => p,
        _ => return vec![None; k],
    };
    let Ok(contents) = std::fs::read_to_string(file_path) else {
        return vec![None; k];
    };
    let Ok(json): Result<Value, _> = serde_json::from_str(&contents) else {
        return vec![None; k];
    };
    let top_k = json
        .get(model_key)
        .and_then(|m| m.get("top_k_params"))
        .and_then(|v| v.as_array());
    if let Some(arr) = top_k {
        arr.iter()
            .take(k)
            .map(|entry| entry.get("params").cloned())
            .collect()
    } else {
        // Fallback: just use best_params as the single entry
        let best = json
            .get(model_key)
            .and_then(|m| m.get("best_params"))
            .cloned();
        vec![best]
    }
}

fn hp_f64(params: &Option<Value>, key: &str) -> Option<f64> {
    params.as_ref()?.get(key)?.as_f64()
}

/// JSON-born values are always f64 (JSON has no float32 type), but most
/// DQNHyperparameters kernel-facing fields are f32 (post f64→f32 ABI refactor
/// in commit d64adc14f). This helper narrows f64→f32 at the ingest boundary
/// so call sites don't repeat `as f32` casts.
fn hp_f32(params: &Option<Value>, key: &str) -> Option<f32> {
    params.as_ref()?.get(key)?.as_f64().map(|v| v as f32)
}

fn hp_usize(params: &Option<Value>, key: &str) -> Option<usize> {
    params.as_ref()?.get(key)?.as_u64().map(|v| v as usize)
}

fn hp_bool(params: &Option<Value>, key: &str) -> Option<bool> {
    params.as_ref()?.get(key)?.as_bool()
}

// ---------------------------------------------------------------------------
// Fold data helpers
// ---------------------------------------------------------------------------

// ---------------------------------------------------------------------------
// DQN Training
// ---------------------------------------------------------------------------

/// Build DQN hyperparameters from args, hyperopt JSON, and GPU profile.
///
/// Extracted from the old `train_dqn_fold` so it can be called ONCE before the fold
/// loop. The returned hyperparams are ready for `DQNTrainer::new`.
#[allow(clippy::cognitive_complexity)]
fn build_dqn_hyperparams(
    args: &Args,
    hp: &Option<Value>,
    total_cost_bps: f64,
) -> DQNHyperparameters {
    let gpu_profile = GpuProfile::load();

    let hp_hidden_base = hp_usize(hp, "hidden_dim_base");
    let dqn_hidden_base = hp_hidden_base.or_else(|| {
        info!("  [DQN] hidden_dim_base: {} (from GPU profile)", gpu_profile.training.hidden_dim_base);
        Some(gpu_profile.training.hidden_dim_base)
    });

    let epsilon_start = hp_f32(hp, "epsilon_start").unwrap_or(0.05);

    let mut hyperparams = DQNHyperparameters {
        learning_rate: hp_f64(hp, "learning_rate").unwrap_or(args.learning_rate),
        batch_size: gpu_profile.training.batch_size,
        gamma: hp_f32(hp, "gamma").unwrap_or(0.95),
        epsilon_start,
        epsilon_end: hp_f32(hp, "epsilon_end").unwrap_or(0.01),
        epsilon_decay: hp_f32(hp, "epsilon_decay").unwrap_or(0.995),
        buffer_size: hp_usize(hp, "buffer_size").unwrap_or(gpu_profile.training.buffer_size),
        min_replay_size: hp_usize(hp, "min_replay_size").unwrap_or(1000),
        epochs: args.epochs,
        checkpoint_frequency: 10,
        hidden_dim_base: dqn_hidden_base,
        warmup_steps: 0,
        early_stopping_enabled: true,
        transaction_cost_multiplier: total_cost_bps as f32,
        per_alpha: hp_f32(hp, "per_alpha").unwrap_or(0.6),
        per_beta_start: hp_f32(hp, "per_beta_start").unwrap_or(0.4),
        dueling_hidden_dim: hp_usize(hp, "dueling_hidden_dim").unwrap_or(128),
        n_steps: hp_usize(hp, "n_steps").unwrap_or(3),
        tau: hp_f32(hp, "tau").unwrap_or(0.005),
        num_atoms: hp_usize(hp, "num_atoms")
            .unwrap_or(gpu_profile.training.num_atoms),
        v_min: hp_f32(hp, "v_min").unwrap_or_else(|| {
            let gamma = hp_f64(hp, "gamma").unwrap_or(0.95);
            -(10.0_f64 / (1.0 - gamma) * 1.2).clamp(20.0, 300.0) as f32
        }),
        v_max: hp_f32(hp, "v_max").unwrap_or_else(|| {
            let gamma = hp_f64(hp, "gamma").unwrap_or(0.95);
            (10.0_f64 / (1.0 - gamma) * 1.2).clamp(20.0, 300.0) as f32
        }),
        noisy_sigma_init: hp_f32(hp, "noisy_sigma_init").unwrap_or(0.5),
        num_quantiles: hp_usize(hp, "num_quantiles").unwrap_or(32),
        noisy_epsilon_floor: Some(hp_f32(hp, "noisy_epsilon_floor").unwrap_or(0.05)),
        hold_penalty_weight: hp_f32(hp, "hold_penalty_weight").unwrap_or(0.01),
        max_position_absolute: hp_f32(hp, "max_position_absolute").unwrap_or(2.0),
        max_leverage: hp_f32(hp, "max_leverage").unwrap_or(5.0),
        huber_delta: hp_f32(hp, "huber_delta").unwrap_or(10.0),
        entropy_coefficient: hp_f64(hp, "entropy_coefficient").unwrap_or(0.01),
        curiosity_weight: hp_f32(hp, "curiosity_weight").unwrap_or(0.1),
        // SP4 Layer B: `weight_decay` removed from DQNHyperparameters; per-group
        // rates are sourced from ISV[WD_RATE[group]] at runtime.
        kelly_fractional: hp_f32(hp, "kelly_fractional").unwrap_or(0.5),
        kelly_max_fraction: hp_f32(hp, "kelly_max_fraction").unwrap_or(0.25),
        mbp10_data_dir: args.mbp10_data_dir.as_ref().map(|p| p.to_string_lossy().into_owned()).unwrap_or_else(|| "test_data/futures-baseline-mbp10".to_string()),
        trades_data_dir: args.trades_data_dir.as_ref().map(|p| p.to_string_lossy().into_owned()).unwrap_or_else(|| "test_data/futures-baseline-trades".to_string()),
        offline_mode: args.offline,
        dataset_path: args.dataset_path.as_ref().map(|p| p.to_string_lossy().into_owned()),
        replay_buffer_vram_fraction: gpu_profile.training.replay_buffer_vram_fraction as f32,
        gpu_timesteps_per_episode: gpu_profile.experience.gpu_timesteps_per_episode,
        gpu_n_episodes: gpu_profile.experience.gpu_n_episodes.unwrap_or(256),
        ..DQNHyperparameters::default()
    };

    // Load training profile (TOML) and apply to hyperparams.
    let profile = ml::training_profile::DqnTrainingProfile::load(&args.training_profile);
    profile.apply_to(&mut hyperparams);
    // CLI args override profile
    hyperparams.epochs = args.epochs;
    hyperparams.learning_rate = hp_f64(hp, "learning_rate").unwrap_or(args.learning_rate);
    hyperparams.initial_capital = args.initial_capital as f32;

    hyperparams
}

/// Train a single DQN fold on a pre-initialized trainer.
///
/// The trainer already has GPU data uploaded (via `init_from_fxcache`).
/// This function sets per-fold ranges, resets state, and runs training.
///
/// Returns the best validation loss achieved.
#[allow(clippy::cognitive_complexity, clippy::too_many_arguments)]
fn train_dqn_fold(
    rt: &tokio::runtime::Runtime,
    trainer: &mut DQNTrainer,
    fold: usize,
    train_features: &[[f64; 42]],
    val_features: &[[f64; 42]],
    train_targets: &[[f64; 6]],
    val_targets: &[[f64; 6]],
    range: &ml::walk_forward::FoldRange,
    output_dir: &Path,
    checkpoint_prefix: &str,
) -> Result<f64> {
    info!("  [DQN] Fold {} -- {} train, {} val features", fold, train_features.len(), val_features.len());

    // Set fold range + val data + reset
    trainer.set_training_range(range.train_start, range.train_end, range.val_start, range.val_end);
    trainer.set_val_data_from_slices(val_features, val_targets, range.val_start);
    rt.block_on(trainer.reset_for_fold())
        .context("reset_for_fold failed")?;

    // Checkpoint callback: save best model to output directory
    let output_dir_owned = output_dir.to_path_buf();
    let prefix_owned = checkpoint_prefix.to_owned();
    let checkpoint_callback = move |epoch: usize, data: Vec<u8>, is_best: bool| -> Result<String> {
        let suffix = if is_best { "best" } else { &format!("epoch{}", epoch) };
        let ckpt_path = output_dir_owned.join(format!("{}_fold{}_{}.safetensors", prefix_owned, fold, suffix));
        let tmp_path = ckpt_path.with_extension("safetensors.tmp");
        std::fs::write(&tmp_path, &data)
            .with_context(|| format!("Failed to write checkpoint tmp: {}", tmp_path.display()))?;
        if let Err(e) = std::fs::rename(&tmp_path, &ckpt_path) {
            drop(std::fs::remove_file(&tmp_path));
            return Err(e).with_context(|| format!("Failed to rename checkpoint: {} -> {}", tmp_path.display(), ckpt_path.display()));
        }
        info!("  [DQN] Fold {} saved checkpoint: {} (prefix: {})", fold, ckpt_path.display(), prefix_owned);
        Ok(ckpt_path.to_string_lossy().into_owned())
    };

    let metrics = rt.block_on(
        trainer.train_fold_from_slices(train_features, train_targets, checkpoint_callback)
    ).map_err(|e| {
        error!("  [DQN] Fold {} training error chain: {:#}", fold, e);
        e
    }).context("DQNTrainer training failed")?;

    info!(
        "  [DQN] Fold {} complete -- loss={:.6} epochs_trained={} converged={}",
        fold, metrics.loss, metrics.epochs_trained, metrics.convergence_achieved
    );

    Ok(metrics.loss)
}

// ---------------------------------------------------------------------------
// Training orchestration
// ---------------------------------------------------------------------------

/// Container for per-model RL results collected during training.
struct RlTrainingResult {
    model_name: String,
    fold_results: Vec<(usize, f64)>,
    total_epochs: usize,
}

/// Run the full walk-forward RL training pipeline.
///
/// Returns per-model results so `main()` can write completion markers.
#[allow(clippy::cognitive_complexity, clippy::too_many_lines)]
fn run_training(args: &Args) -> Result<Vec<RlTrainingResult>> {
    let train_dqn = args.model == "dqn" || args.model == "both";
    let train_ppo = args.model == "ppo" || args.model == "both";

    info!("=== Walk-Forward Baseline Training ===");
    info!("  Model(s): {}", args.model);
    info!("  Symbol: {}", args.symbol);
    info!("  Epochs: {}", args.epochs);
    info!("  Batch size: auto (from VRAM)");
    info!("  Data dir: {}", args.data_dir.display());
    info!("  Output dir: {}", args.output_dir.display());
    info!("  Feature dim: {}", args.feature_dim);
    info!("  Num actions: {}", args.num_actions);
    info!("  Learning rate: {:.1e}", args.learning_rate);
    info!("  Tx cost: {:.1} bps commission + {:.1} tick spread (tick_size={:.4})",
        args.tx_cost_bps, args.spread_ticks, args.tick_size);
    info!("  Patience: {}", args.patience);
    if let Some(ref hp_path) = args.hyperopt_params {
        info!("  Hyperopt params: {}", hp_path.display());
    }
    if args.ensemble_top_k > 1 {
        info!("  Ensemble top-K: {} (training multiple models per fold)", args.ensemble_top_k);
    }

    // 1. Try fxcache first, fall back to DBN loading + feature extraction
    info!("Step 1/5: Loading data...");
    let data_load_start = std::time::Instant::now();

    let cache_dir_override = args.feature_cache_dir.as_ref().map(|s| std::path::PathBuf::from(s));
    let mbp10 = args.mbp10_data_dir.as_ref().filter(|p| p.exists());
    let trades = args.trades_data_dir.as_ref().filter(|p| p.exists());

    // Cache key data_source MUST match what `precompute_features` writes with
    // (default: "mbp10"). Mismatch produces silent cache MISS → DBN fallback,
    // which uploaded RAW (un-normalised) features pre-fix and caused
    // label_scale=5443 (raw-price magnitude) on Argo deploys. The DBN fallback
    // below now applies NormStats::normalize_batch as defence-in-depth so even
    // a future data_source drift cannot reintroduce raw values into training.
    let fxcache_data = ml::fxcache::discover_and_load(
        &args.data_dir,
        &args.symbol,
        mbp10.map(|p| p.as_path()),
        trades.map(|p| p.as_path()),
        "mbp10",
        cache_dir_override.as_deref(),
    );

    // Load data into fxcache-compatible arrays: features, targets, timestamps, ofi
    let fxcache = if let Some(cached) = fxcache_data {
        info!("  Loaded {} bars + features from fxcache in {:.1}s",
            cached.bar_count, data_load_start.elapsed().as_secs_f64());
        cached
    } else {
        // Fall back to DBN loading — this is SLOW (148GB MBP-10 parsing).
        //
        // Defence-in-depth: apply NormStats::normalize_batch here too. The
        // fxcache fast path is z-normalised at write time
        // (precompute_features.rs:625-631). If the cache lookup misses for ANY
        // reason (data_source mismatch, schema-hash drift, missing file) and
        // the loader falls into this branch, raw features would have flowed
        // unchanged into the GPU state buffer — exactly the bug observed on
        // Argo train-h5gxb (epoch-0 Sharpe=141 from raw-price labels). Always
        // normalise here so the consumer (`init_from_fxcache`) sees the same
        // unit-scale features regardless of which path produced them.
        info!("  Loading OHLCV bars from DBN files...");
        let bars = load_all_bars(&args.data_dir, &args.symbol)?;
        if bars.is_empty() {
            anyhow::bail!("No bars loaded from {}", args.data_dir.display());
        }
        info!("  Loaded {} bars ({} to {})",
            bars.len(),
            bars.first().map(|b| b.timestamp.to_string()).unwrap_or_default(),
            bars.last().map(|b| b.timestamp.to_string()).unwrap_or_default(),
        );

        info!("  Extracting {}-dimensional features...", args.feature_dim);
        let all_features_raw = extract_ml_features(&bars)
            .context("Feature extraction failed")?;
        let warmup_offset = bars.len().saturating_sub(all_features_raw.len());
        info!("  Extracted {} feature vectors (warmup period consumed {} bars)",
            all_features_raw.len(), warmup_offset);

        // Apply z-score normalisation — same op `precompute_features.rs:629`
        // applies on the canonical fxcache path. Without this, feature[0]
        // carries raw log-returns and downstream GPU consumers (aux head,
        // vol_normalizer) see scale-mismatched values.
        let norm_stats = ml::walk_forward::NormStats::from_features(&all_features_raw);
        let all_features = norm_stats.normalize_batch(&all_features_raw);
        info!("  Features z-score normalised (DBN-fallback path; {} bars × 42 dims)",
            all_features.len());

        // Build FxCacheData from DBN results (features are already warmup-trimmed)
        let aligned_bars = &bars[warmup_offset..];
        let n = all_features.len();
        let timestamps: Vec<i64> = aligned_bars.iter()
            .map(|b| b.timestamp.timestamp_nanos_opt().unwrap_or(0))
            .collect();
        let targets: Vec<[f64; 6]> = aligned_bars.iter()
            .map(|b| [b.close, b.close, b.close, b.close, b.open, b.open])
            .collect();
        let ofi = vec![[0.0_f64; ml_core::state_layout::OFI_DIM]; n];

        ml::fxcache::FxCacheData {
            timestamps,
            features: all_features,
            targets,
            ofi,
            cache_key: [0u8; 32],
            bar_count: n,
            has_ofi: false,
        }
    };

    // Apply --max-bars cap. 0 = unlimited (default behaviour unchanged).
    // OFI + features + targets + timestamps truncate in lockstep per the
    // data_loading.rs precedent (commit 2ac956298 OFI/bars desync fix).
    let fxcache = if args.max_bars > 0 && fxcache.bar_count > args.max_bars {
        let n = args.max_bars;
        let full = fxcache.bar_count;
        info!(
            "  max-bars={}: truncating fxcache {} → {} bars (incl. OFI)",
            n, full, n
        );
        let mut features = fxcache.features;
        let mut targets = fxcache.targets;
        let mut ofi = fxcache.ofi;
        let mut timestamps = fxcache.timestamps;
        features.truncate(n);
        targets.truncate(n);
        ofi.truncate(n);
        timestamps.truncate(n);
        debug_assert_eq!(features.len(), n);
        debug_assert_eq!(targets.len(), n);
        debug_assert_eq!(ofi.len(), n);
        debug_assert_eq!(timestamps.len(), n);
        ml::fxcache::FxCacheData {
            timestamps,
            features,
            targets,
            ofi,
            cache_key: fxcache.cache_key,
            bar_count: n,
            has_ofi: fxcache.has_ofi,
        }
    } else {
        fxcache
    };

    // 2. Generate walk-forward fold ranges from timestamps (zero-copy)
    info!("Step 2/5: Generating walk-forward fold ranges...");
    let wf_config = WalkForwardConfig {
        initial_train_months: args.train_months,
        val_months: args.val_months,
        test_months: args.test_months,
        step_months: args.step_months,
    };
    let mut fold_ranges = generate_walk_forward_indices_from_timestamps(&fxcache.timestamps, &wf_config);
    if fold_ranges.is_empty() {
        anyhow::bail!(
            "No walk-forward folds generated. Need at least {} months of data.",
            wf_config.initial_train_months + wf_config.val_months + wf_config.test_months
        );
    }
    // --max-folds cap (smoke-test support). 0 = no cap. Truncates from the end,
    // keeping chronological ordering so the first N folds train.
    if args.max_folds > 0 && fold_ranges.len() > args.max_folds {
        let full_count = fold_ranges.len();
        fold_ranges.truncate(args.max_folds);
        info!(
            "  --max-folds={} capped {} folds down to {}",
            args.max_folds, full_count, fold_ranges.len()
        );
    }
    info!("  Generated {} walk-forward folds (zero-copy index ranges)", fold_ranges.len());

    // Record data loading + feature extraction time
    if train_dqn {
        metrics::record_data_load("dqn", data_load_start.elapsed().as_secs_f64());
    }
    if train_ppo {
        metrics::record_data_load("ppo", data_load_start.elapsed().as_secs_f64());
    }

    // Create output directory
    std::fs::create_dir_all(&args.output_dir)
        .with_context(|| format!("Failed to create output dir: {}", args.output_dir.display()))?;

    // Resolve the shared norm_stats.json sibling of the fxcache. precompute_features
    // writes one norm_stats per cache key — RL training uses the same stats for
    // every fold (unlike supervised which recomputes per-fold). evaluate_baseline
    // expects per-fold files, so we copy the shared file into output_dir once per
    // fold below. Falls back silently if the cache_key is zero (DBN-fallback load)
    // or the stats file doesn't exist — evaluate will warn rather than fail the
    // workflow.
    let shared_norm_stats_src = if fxcache.cache_key == [0u8; 32] {
        None
    } else {
        ml::fxcache::norm_stats_path_for_key(
            &args.data_dir,
            cache_dir_override.as_deref(),
            &fxcache.cache_key,
        )
        .filter(|p| p.exists())
    };

    // 3. Create tokio runtime ONCE, create DQN trainer ONCE, upload fxcache to GPU ONCE
    let rt = tokio::runtime::Builder::new_current_thread()
        .enable_all()
        .build()
        .context("Failed to create tokio runtime")?;

    // Compute average spread slippage in bps from the full dataset
    let avg_price = {
        let sum: f64 = fxcache.targets.iter().map(|t| t[2]).sum(); // raw_close
        if fxcache.bar_count > 0 { sum / fxcache.bar_count as f64 } else { 0.0 }
    };
    let avg_spread_bps = spread_cost_bps(avg_price, args.tick_size, args.spread_ticks);
    let total_cost_bps = args.tx_cost_bps + avg_spread_bps;
    info!("  Total tx cost: {:.2} bps (commission {:.1} + spread {:.2})",
        total_cost_bps, args.tx_cost_bps, avg_spread_bps);

    // Compute bars_per_day from actual timestamps — correct annualization for imbalance bars
    let bars_per_day = {
        let ts = &fxcache.timestamps;
        if ts.len() > 1 {
            let first_ns = ts[0];
            let last_ns = ts[ts.len() - 1];
            let span_days = (last_ns - first_ns) as f64 / (86_400.0 * 1e9);
            let trading_days = span_days * (252.0 / 365.0); // ~252/365 are trading days
            if trading_days > 1.0 { ts.len() as f64 / trading_days } else { 390.0 }
        } else {
            390.0
        }
    };
    info!("  Bars per day (from data): {:.0} ({} total bars)", bars_per_day, fxcache.bar_count);

    // Build DQN trainer ONCE (shared across folds)
    let mut dqn_trainer = if train_dqn {
        let hp = load_hyperopt_params(&args.hyperopt_params, "dqn");
        let mut hyperparams = build_dqn_hyperparams(args, &hp, total_cost_bps);
        hyperparams.bars_per_day = bars_per_day as f32;
        let mut trainer = DQNTrainer::new(hyperparams)
            .context("Failed to create DQNTrainer")?;

        // Upload full fxcache to GPU ONCE — all folds index into this data
        info!("  Uploading {} bars to GPU via init_from_fxcache...", fxcache.bar_count);
        rt.block_on(trainer.init_from_fxcache(
            &fxcache.features, &fxcache.targets, &fxcache.ofi,
        )).context("init_from_fxcache failed")?;
        info!("  GPU data uploaded — ready for fold loop");
        Some(trainer)
    } else {
        None
    };

    // Build ensemble trainers ONCE (shared across folds) — upload data once each.
    // Previously these were created inside the fold loop, re-uploading per fold.
    let mut ensemble_trainers: Vec<DQNTrainer> = Vec::new();
    if train_dqn && args.ensemble_top_k > 1 && args.hyperopt_params.is_some() {
        let param_sets = load_top_k_params(
            &args.hyperopt_params,
            "dqn",
            args.ensemble_top_k,
        );
        // k=0 is the primary trainer, so build trainers for k=1..
        for (k, hp) in param_sets.iter().enumerate().skip(1) {
            let ens_hyperparams = build_dqn_hyperparams(args, hp, total_cost_bps);
            match DQNTrainer::new(ens_hyperparams) {
                Ok(mut ens_trainer) => {
                    info!("  Uploading fxcache to ensemble trainer {}...", k);
                    if let Err(e) = rt.block_on(ens_trainer.init_from_fxcache(
                        &fxcache.features, &fxcache.targets, &fxcache.ofi,
                    )) {
                        error!("  [DQN] Ensemble trainer {} init_from_fxcache failed: {}", k, e);
                        continue;
                    }
                    ensemble_trainers.push(ens_trainer);
                }
                Err(e) => {
                    error!("  [DQN] Failed to create ensemble trainer {}: {}", k, e);
                }
            }
        }
        info!("  Created {} ensemble trainers (data uploaded once each)", ensemble_trainers.len());
    }

    // 4. Train each fold
    info!("Step 4/5: Training models on each fold...");
    let mut dqn_results: Vec<(usize, f64)> = Vec::new();
    let mut ppo_results: Vec<(usize, f64)> = Vec::new();

    for (fold_idx, range) in fold_ranges.iter().enumerate() {
        info!("--- Fold {} ---", range.fold);
        info!(
            "  Train: bars [{}..{}] ({} bars), Val: bars [{}..{}] ({} bars)",
            range.train_start, range.train_end,
            range.train_end - range.train_start,
            range.val_start, range.val_end,
            range.val_end - range.val_start,
        );

        // Persist per-fold norm_stats copy for evaluate_baseline. Source is the
        // single `.norm_stats.json` emitted by precompute_features; destination
        // path matches the supervised training convention so evaluate finds it
        // at `<output_dir>/norm_stats_fold{N}.json`.
        if let Some(src) = &shared_norm_stats_src {
            let dst = args.output_dir.join(format!("norm_stats_fold{}.json", range.fold));
            if let Err(e) = std::fs::copy(src, &dst) {
                warn!(
                    "  norm_stats_fold{} copy failed ({} -> {}): {}",
                    range.fold, src.display(), dst.display(), e
                );
            }
        }

        // Slice features/targets for this fold (zero-copy from fxcache arrays)
        let train_feat = &fxcache.features[range.train_start..range.train_end];
        let val_feat = &fxcache.features[range.val_start..range.val_end];
        let train_tgt = &fxcache.targets[range.train_start..range.train_end];
        let val_tgt = &fxcache.targets[range.val_start..range.val_end];

        if train_feat.is_empty() || val_feat.is_empty() {
            warn!("  Fold {} -- empty features, skipping", range.fold);
            continue;
        }

        // fxcache features are pre-normalized (z-score at precompute time).
        // NormStats saved alongside .fxcache file for inference denormalization.
        let train_norm = train_feat;
        let val_norm = val_feat;

        // Train DQN
        if let Some(ref mut trainer) = dqn_trainer {
            let fold_str = fold_idx.to_string();
            let fold_start = std::time::Instant::now();

            if args.ensemble_top_k > 1 && args.hyperopt_params.is_some() {
                // Ensemble mode: train one model per top-K hyperopt param set.
                // Trainers were created + data uploaded BEFORE the fold loop.
                // Here we just set_training_range + reset_for_fold on each.
                let total_members = 1 + ensemble_trainers.len(); // k=0 (primary) + secondaries

                // k=0: Primary ensemble member uses the shared trainer
                {
                    let k = 0;
                    info!(
                        "  [DQN] Training ensemble member {}/{} on fold {}",
                        k + 1, total_members, range.fold
                    );
                    let prefix = format!("dqn_ensemble_{}", k);
                    match train_dqn_fold(
                        &rt, trainer, range.fold,
                        &train_norm, &val_norm, train_tgt, val_tgt,
                        range, &args.output_dir, &prefix,
                    ) {
                        Ok(best_loss) => {
                            info!("  [DQN] Ensemble member {} fold {} best_loss={:.6}",
                                k, range.fold, best_loss);
                            let elapsed = fold_start.elapsed().as_secs_f64();
                            metrics::set_epoch("dqn", &fold_str, fold_idx as f64);
                            metrics::set_epoch_loss("dqn", &fold_str, best_loss);
                            metrics::set_validation_loss("dqn", &fold_str, best_loss);
                            metrics::set_iteration_seconds("dqn", &fold_str, elapsed);
                            dqn_results.push((range.fold, best_loss));
                        }
                        Err(e) => {
                            error!("  [DQN] Ensemble member {} fold {} failed: {}",
                                k, range.fold, e);
                        }
                    }
                }

                // k=1..: Secondary ensemble members reuse pre-created trainers
                for (ens_idx, ens_trainer) in ensemble_trainers.iter_mut().enumerate() {
                    let k = ens_idx + 1;
                    info!(
                        "  [DQN] Training ensemble member {}/{} on fold {}",
                        k + 1, total_members, range.fold
                    );
                    let prefix = format!("dqn_ensemble_{}", k);
                    match train_dqn_fold(
                        &rt, ens_trainer, range.fold,
                        &train_norm, &val_norm, train_tgt, val_tgt,
                        range, &args.output_dir, &prefix,
                    ) {
                        Ok(best_loss) => {
                            info!("  [DQN] Ensemble member {} fold {} best_loss={:.6}",
                                k, range.fold, best_loss);
                        }
                        Err(e) => {
                            error!("  [DQN] Ensemble member {} fold {} failed: {}",
                                k, range.fold, e);
                        }
                    }
                }
            } else {
                // Single-model mode (default)
                match train_dqn_fold(
                    &rt, trainer, range.fold,
                    &train_norm, &val_norm, train_tgt, val_tgt,
                    range, &args.output_dir, "dqn",
                ) {
                    Ok(best_loss) => {
                        let elapsed = fold_start.elapsed().as_secs_f64();
                        metrics::set_epoch("dqn", &fold_str, fold_idx as f64);
                        metrics::set_epoch_loss("dqn", &fold_str, best_loss);
                        metrics::set_validation_loss("dqn", &fold_str, best_loss);
                        metrics::set_iteration_seconds("dqn", &fold_str, elapsed);
                        dqn_results.push((range.fold, best_loss));
                    }
                    Err(e) => {
                        error!("  [DQN] Fold {} failed: {:#}", range.fold, e);
                    }
                }
            }
        }

        // Train PPO (zero-copy: pass fxcache feature slices directly)
        if train_ppo {
            let hp_ppo = load_hyperopt_params(&args.hyperopt_params, "ppo");
            let fold_str = fold_idx.to_string();
            let fold_start = std::time::Instant::now();

            // Compute per-fold tx cost from fxcache targets (raw close at index 2)
            let train_closes: Vec<f64> = fxcache.targets[range.train_start..range.train_end]
                .iter().map(|t| t[2]).collect();
            let avg_price = if train_closes.is_empty() {
                0.0
            } else {
                train_closes.iter().sum::<f64>() / train_closes.len() as f64
            };
            let avg_spread_bps_ppo = spread_cost_bps(avg_price, args.tick_size, args.spread_ticks);
            let total_cost_bps_ppo = args.tx_cost_bps + avg_spread_bps_ppo;

            // Build PpoHyperparameters inline (same as old train_ppo_fold)
            let hp_ppo_hidden_base = hp_usize(&hp_ppo, "hidden_dim_base");
            let ppo_hidden_base = hp_ppo_hidden_base.or_else(|| {
                let profile = ml_core::gpu::profile::GpuProfile::load();
                info!("  [PPO] hidden_dim_base: {} (from GPU profile)", profile.training.hidden_dim_base);
                Some(profile.training.hidden_dim_base)
            });
            let ppo_hp = PpoHyperparameters {
                learning_rate: hp_f64(&hp_ppo, "learning_rate").unwrap_or(args.learning_rate),
                actor_learning_rate: Some(hp_f64(&hp_ppo, "policy_learning_rate").unwrap_or(args.learning_rate)),
                critic_learning_rate: Some(hp_f64(&hp_ppo, "value_learning_rate").unwrap_or(args.learning_rate * 3.0)),
                batch_size: ml_core::gpu::profile::GpuProfile::load().training.batch_size,
                gamma: hp_f64(&hp_ppo, "gamma").unwrap_or(0.99),
                clip_epsilon: hp_f64(&hp_ppo, "clip_epsilon").unwrap_or(0.2) as f32,
                vf_coef: hp_f64(&hp_ppo, "value_loss_coeff").unwrap_or(0.5) as f32,
                ent_coef: hp_f64(&hp_ppo, "entropy_coeff").unwrap_or(0.01) as f32,
                gae_lambda: hp_f64(&hp_ppo, "gae_lambda").unwrap_or(0.95) as f32,
                rollout_steps: hp_usize(&hp_ppo, "rollout_steps").unwrap_or(2048),
                minibatch_size: hp_usize(&hp_ppo, "minibatch_size").unwrap_or(64),
                epochs: args.epochs,
                early_stopping_enabled: true,
                transaction_cost_bps: total_cost_bps_ppo / 100.0,
                hidden_dim_base: ppo_hidden_base,
                ..PpoHyperparameters::conservative()
            };

            let fold_ckpt_dir = args.output_dir.join(format!("ppo_fold{}", range.fold));
            let ppo_trainer = PpoTrainer::new(
                ppo_hp,
                args.feature_dim,
                &fold_ckpt_dir,
                true,
                None,
            );
            match ppo_trainer {
                Ok(trainer) => {
                    let fold_idx_cap = range.fold;
                    let epochs_cap = args.epochs;
                    let progress_cb = move |m: PpoTrainingMetrics| {
                        info!("[PPO] Fold {} Epoch {}/{} -- value_loss={:.6}", fold_idx_cap, m.epoch, epochs_cap, m.value_loss);
                    };
                    match rt.block_on(trainer.train_from_slices(&train_norm, progress_cb)) {
                        Ok(metrics) => {
                            let best_loss = metrics.value_loss as f64;
                            let elapsed = fold_start.elapsed().as_secs_f64();
                            metrics::set_epoch("ppo", &fold_str, fold_idx as f64);
                            metrics::set_epoch_loss("ppo", &fold_str, best_loss);
                            metrics::set_validation_loss("ppo", &fold_str, best_loss);
                            metrics::set_iteration_seconds("ppo", &fold_str, elapsed);
                            ppo_results.push((range.fold, best_loss));
                        }
                        Err(e) => error!("PPO fold {} failed: {:#}", range.fold, e),
                    }
                }
                Err(e) => error!("  [PPO] Fold {} trainer init failed: {:#}", range.fold, e),
            }
        }
    }

    // 5. Summary
    info!("Step 5/5: Training Summary");
    info!("  ===================================");

    let mut all_results = Vec::new();
    let num_folds = fold_ranges.len();

    if train_dqn {
        info!("  DQN Results ({} folds):", dqn_results.len());
        for (fold, loss) in &dqn_results {
            info!("    Fold {}: best_val_metric = {:.6}", fold, loss);
        }
        if !dqn_results.is_empty() {
            let avg: f64 = dqn_results.iter().map(|(_, l)| l).sum::<f64>()
                / dqn_results.len() as f64;
            info!("    Average: {:.6}", avg);
        }
        all_results.push(RlTrainingResult {
            model_name: "dqn".to_owned(),
            fold_results: dqn_results,
            total_epochs: num_folds * args.epochs,
        });
    }
    if train_ppo {
        info!("  PPO Results ({} folds):", ppo_results.len());
        for (fold, loss) in &ppo_results {
            info!("    Fold {}: best_val_metric = {:.6}", fold, loss);
        }
        if !ppo_results.is_empty() {
            let avg: f64 = ppo_results.iter().map(|(_, l)| l).sum::<f64>()
                / ppo_results.len() as f64;
            info!("    Average: {:.6}", avg);
        }
        all_results.push(RlTrainingResult {
            model_name: "ppo".to_owned(),
            fold_results: ppo_results,
            total_epochs: num_folds * args.epochs,
        });
    }
    info!("  Checkpoints saved to: {}", args.output_dir.display());
    info!("  ===================================");

    Ok(all_results)
}

// ---------------------------------------------------------------------------
// Main
// ---------------------------------------------------------------------------

fn main() -> Result<()> {
    // Initialize tracing with optional OTLP export to Tempo
    let otlp_endpoint = std::env::var("OTEL_EXPORTER_OTLP_ENDPOINT").ok();
    if let Err(e) = common::observability::init_observability(
        "train_baseline_rl",
        otlp_endpoint.as_deref(),
    ) {
        eprintln!("Observability init failed (non-fatal): {e}");
    }

    let args = Args::parse();

    // Pre-allocate CUBLAS workspace for deterministic + faster tensor core ops.
    // Enable TF32 for all FP32 matmuls — ~8x throughput on H100 tensor cores.
    // Plan 5 Task 5 Phase B: export FOXHUNT_SEED so every CUDA module that
    // previously used a fixed seed mixes the per-run seed through
    // `cuda_pipeline::mix_seed`. Must happen BEFORE any module spins up an
    // RNG (Xavier init in particular runs at trainer construction time).
    // SAFETY: called once at startup before any multi-threading or CUDA work begins.
    #[allow(unsafe_code)]
    unsafe {
        std::env::set_var("CUBLAS_WORKSPACE_CONFIG", ":4096:8");
        std::env::set_var("NVIDIA_TF32_OVERRIDE", "1");
        std::env::set_var("FOXHUNT_SEED", args.seed.to_string());
    }

    info!(
        "=== Training: {} seed={} max_folds={} (epochs={}) ===",
        args.model, args.seed, args.max_folds, args.epochs
    );

    metrics::init();
    metrics_server::start_metrics_server(9094);
    common::metrics::questdb_sink::init(None);
    metrics::set_active_workers(1.0);

    // Ensure output directory exists before training so markers can always be written.
    if let Err(e) = std::fs::create_dir_all(&args.output_dir) {
        error!("Failed to create output dir {}: {}", args.output_dir.display(), e);
    }

    let result = run_training(&args);
    metrics::set_active_workers(0.0);

    // Push final metrics to pushgateway so they persist after pod termination
    if let Err(e) = metrics_server::push_to_gateway(None, "train_baseline_rl") {
        tracing::warn!("Failed to push metrics to gateway (non-fatal): {e}");
    }
    common::metrics::questdb_sink::flush();

    match result {
        Ok(results) => {
            for training_result in &results {
                let best_val = training_result
                    .fold_results
                    .iter()
                    .map(|(_, loss)| *loss)
                    .fold(f64::MAX, f64::min);

                let metrics = CompletionMetrics {
                    model: training_result.model_name.clone(),
                    symbol: args.symbol.clone(),
                    best_val_loss: (best_val < f64::MAX).then_some(best_val),
                    sharpe_ratio: None,
                    epochs_completed: training_result.total_epochs,
                    folds_completed: training_result.fold_results.len(),
                };
                write_success_marker(&args.output_dir, &metrics);
            }
            Ok(())
        }
        Err(e) => {
            let msg = format!("{:#}", e);
            error!("Training failed: {}", msg);
            write_failure_marker(&args.output_dir, &msg);
            Err(e)
        }
    }
}