# Wave 9 Agent 9: Files Requiring Updates (If Needed)

**Status**: ✅ **NO UPDATES NEEDED** - All callers already use `mut` extractor

---

## Caller Analysis

### Files That Call extract_current_features()

#### 1. ml/src/features/extraction.rs (Line 98)
**Status**: ✅ No change needed
**Reason**: Extractor already declared as `mut` on line 89

```rust
// Line 89
let mut extractor = FeatureExtractor::new();

// Line 98
let features = extractor.extract_current_features()?;  // ✓ Works with &mut self
```

#### 2. ml/src/trainers/dqn.rs (Line 925)
**Status**: ✅ No change needed
**Reason**: Extractor already declared as `mut` on line 915

```rust
// Line 915
let mut extractor = FeatureExtractor::new();

// Line 925
let features_225 = extractor.extract_current_features()?;  // ✓ Works with &mut self
```

---

## Potential Future Callers

If new code calls `extract_current_features()`, it must:

1. Declare the extractor as mutable:
   ```rust
   let mut extractor = FeatureExtractor::new();  // Must be mut
   ```

2. Ensure mutable borrow is available:
   ```rust
   let features = extractor.extract_current_features()?;  // Requires &mut
   ```

### Common Pattern
```rust
use ml::features::extraction::{extract_ml_features, FeatureExtractor};

// Option 1: Use the public API (recommended)
let features = extract_ml_features(&bars)?;

// Option 2: Custom extraction (advanced)
let mut extractor = FeatureExtractor::new();  // ← Must be mut
for bar in bars.iter() {
    extractor.update(bar)?;
    let features = extractor.extract_current_features()?;  // ← Needs &mut
}
```

---

## Compilation Verification

### Command
```bash
cargo check --workspace
```

### Result
```
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.52s
```

✅ **0 errors** related to signature change

---

## Why No Updates Were Needed

The signature change from `&self` to `&mut self` is **fully backward compatible** because:

1. All existing callers already declare `let mut extractor`
2. Rust allows mutable references where immutable references were previously used
3. The change makes the API more flexible (supports both mutable and stateful operations)

---

## Agent 10 Recommendation

No additional caller updates are needed. Agent 10 can proceed directly to wiring `extract_wave_d_features()` into the pipeline.