# Code Review: FRE-327 - Checkpoint & Resume

## Verdict: APPROVED with suggestions

Reviewed all 4 files in `src/checkpoint/`:
- `__init__.py` (13 lines)
- `checkpoint_schema.py` (218 lines)
- `state_manager.py` (326 lines)
- `resume_handler.py` (303 lines)

## Strengths
✅ Well-designed checkpoint schema with proper versioning
✅ Atomic file writes to prevent corruption
✅ Book hash validation to detect input changes
✅ Good progress tracking per stage
✅ Graceful interrupt handling with checkpoint saving
✅ Clear separation between StateManager and ResumeHandler

## Suggestions (non-blocking)

### 1. resume_handler.py:121-122 - Dead code
```python
if self._checkpoint is None and self.should_resume():
    pass
```
This does nothing and should be removed.

### 2. resume_handler.py:207-208 - Dead code
```python
if self._checkpoint is None and self.should_resume():
    pass
```
Another dead code block that should be removed.

### 3. checkpoint_schema.py:154 - Potential KeyError
```python
return CheckpointStage[self.current_stage.upper()]
```
Could raise KeyError if `current_stage` is set to an invalid value. Consider using `.get()` instead.

### 4. state_manager.py:155-156, 188, 210 - Import inside function
```python
from src.checkpoint.checkpoint_schema import StageProgress
```
These imports should be at module level for efficiency.

### 5. state_manager.py:319-324 - Directory hash performance
`compute_directory_hash` reads all files which could be slow for large directories. Consider caching or using mtime-based approach.

## Overall Assessment
Solid checkpoint and resume implementation. The issues identified are minor and do not block functionality.