20  Complete Example: Document Processor

This chapter is a full example focused on file I/O and robust data processing, with an agent in the loop where it adds real value.

20.1 This Chapter Will Cover

• Reading and writing files safely
• Iterating over documents/data with durable progress tracking
• Extracting structured data from messy inputs
• Error handling patterns that survive retries and restarts
• Specs + mocks for deterministic tests, plus evals for extraction quality