Mortgage Document Types

Purpose

Work with document classification in the mortgage underwriting system.

Document Type Constants

Located in internal/model/document.go:

Income Documents

| Constant | Description | Filename Patterns | |----------|-------------|-------------------| | DocTypeW2 | W-2 wage statements | *w2*, *w-2* | | DocType1099 | 1099 contractor income | *1099* | | DocTypePaystub | Pay stubs/earnings | *paystub*, *pay_stub*, *pay-stub*, *earnings* | | DocTypeTaxReturn | Tax returns (1040) | *tax*, *1040* | | DocTypeProfitLoss | P&L statements | *profit*, *p&l*, *pnl* | | DocTypeEmploymentLetter | Employment verification | *employment*, *verification* |

Asset Documents

| Constant | Description | Filename Patterns | |----------|-------------|-------------------| | DocTypeBankStatement | Bank statements | *bank* | | DocTypeAssetStatement | General assets | *asset* | | DocTypeRetirementStmt | 401k/IRA statements | *retirement*, *401k*, *ira* | | DocTypeGiftLetter | Gift fund letters | *gift* |

Credit Documents

| Constant | Description | Filename Patterns | |----------|-------------|-------------------| | DocTypeCreditReport | Credit bureau reports | *credit* | | DocTypeDebtPayoff | Debt payoff letters | *payoff*, *debt* |

Collateral Documents

| Constant | Description | Filename Patterns | |----------|-------------|-------------------| | DocTypeAppraisal | Property appraisals | *appraisal* | | DocTypePurchaseContract | Purchase agreements | *purchase*, *contract* | | DocTypeTitleReport | Title reports | *title* | | DocTypePropertyInsurance | Hazard insurance | *insurance*, *hazard*, *homeowner* |

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