Mortgage Document Types

Mortgage Document Types

Purpose

Work with document classification in the mortgage underwriting system.

Document Type Constants

Located in internal/​model/​document.go:

Income Documents

Asset Documents

Credit Documents

Collateral Documents

Type Inference Logic

Located in internal/​document/​store.go:

// Files are classified by checking if filename contains pattern
lower := strings.ToLower(filepath.Base(path))
for pattern, docType := range patterns {
    if strings.Contains(lower, pattern) {
        return docType
    }
}

Adding a New Document Type

Step 1: Add constant to internal/​model/​document.go

const (
    // ... existing types ...
    DocTypeNewType DocumentType = "new_type"
)

Step 2: Add pattern to internal/​document/​store.go

patterns := map[string]model.DocumentType{
    // ... existing patterns ...
    "new_pattern": model.DocTypeNewType,
}

Step 3: Add to agent's document lists

In the relevant agent (e.g., internal/​agent/​income/​income.go):

func (a *Agent) RequiredDocuments() []model.DocumentType {
    return []model.DocumentType{
        model.DocTypeW2,
        model.DocTypeNewType,  // Add here
    }
}

Step 4: Update prompts

Update the agent's prompt to describe how to handle the new document type.

Document Structure

type Document struct {
    ID            string            // Hash-based unique ID
    ApplicationID string            // Loan application ID
    Type          DocumentType      // One of the DocType* constants
    FileName      string            // Original filename
    MimeType      string            // application/​pdf, image/​png, etc.
    FilePath      string            // Local filesystem path
    GeminiURI     string            // Cached Gemini File API URI
    UploadedAt    time.Time
    BorrowerID    string
    Year          int               // Tax year for tax docs
    Period        string            // Pay period for paystubs
    Metadata      map[string]string // Additional metadata
}

Supported MIME Types

From internal/​document/​store.go:MimeTypeFromExtension:

• .pdf -> application/​pdf
• .png -> image/​png
• .jpg, .jpeg -> image/​jpeg
• .gif -> image/​gif
• .webp -> image/​webp

Related Files

• internal/​model/​document.go - Type definitions
• internal/​document/​store.go - Loading and type inference
• cmd/​underwriter/​main.go - CLI type inference