Extraction Pipeline Patterns

Kreuzberg's format detection -> extraction -> fallback orchestration for 75+ file formats

Core Pipeline Architecture

The extraction pipeline (crates/kreuzberg/src/core/pipeline.rs, crates/kreuzberg/src/extraction/) orchestrates:

1. Format Detection - MIME type inference + extension validation -> select appropriate extractor
2. Intelligent Extraction - Route to format-specific extractors (PDF, DOCX, Excel, HTML, images, archives, etc.)
3. Fallback Strategies - Password-protected PDFs, OCR for images, nested archive handling, corrupted file recovery
4. Post-Processing Pipeline - Validators, quality processing, chunking, custom hooks (see core/pipeline.rs)

Format Detection Strategy

Location: crates/kreuzberg/src/core/mime.rs, crates/kreuzberg/src/core/formats.rs

Pattern: detect via magic bytes, validate extension alignment (prevent spoofing), route to extractor. Multiple extractors for same format -> choose highest confidence/specificity.

// Pseudocode: core/mime.rs
match (magic_bytes(content), extension) {
    (Some(fmt), Some(ext)) if aligned -> Ok(fmt),
    (Some(fmt), Some(ext)) if misaligned -> Err(FormatMismatch),
    (Some(fmt), None) -> Ok(fmt),  // magic bytes only
    (None, Some(ext)) -> Ok(from_extension(ext)),
    _ -> Err(UnknownFormat),
}

Extraction Modules (75 Formats)

Extraction Dispatcher

// Pseudocode: extraction/mod.rs
let format = detect_format(source.bytes, source.extension);
let result = match format {
    Pdf -> extract_pdf(source, config),
    Docx -> extract_docx(source, config),
    Image -> extract_image_with_ocr_fallback(source, config),
    Archive -> extract_archive_recursive(source, config),
    _ -> extract_with_plugin(format, source, config),
};
run_pipeline(result, config)  // post-processing always runs

Fallback Strategies

• Password-Protected PDFs: Try primary password -> secondary password list -> return is_encrypted=true in metadata on failure
• OCR Fallback: If image text extraction confidence < threshold, trigger OCR backend; return both results with scores
• Nested Archives: Recursive extraction with configurable depth limit; flatten or preserve hierarchy
• Corrupted File Recovery: Stream-based parsing, emit content up to error point, include error location in metadata

Configuration Integration

Location: crates/kreuzberg/src/core/config.rs, crates/kreuzberg/src/core/config_validation.rs

ExtractionConfig holds format-specific configs (pdf, image, html, office), fallback orchestration (fallback), and post-processing (postprocessor, chunking, keywords). See struct definition in config.rs.

Plugin System Integration

Location: crates/kreuzberg/src/plugins/

• CustomExtractor: Override built-in format extractors
• PostProcessor: Modify results after extraction (Early/Middle/Late stages)
• Validator: Fail-fast validation (e.g., minimum text length)
• OCRBackend: Swap OCR engine

Plugin registry loaded at startup, cached for zero-cost lookup.

Feature Flag Strategy

Location: Cargo.toml (workspace), crates/kreuzberg/Cargo.toml, FEATURE_MATRIX.md

20+ features across 9 language bindings. Key feature groups:

Conditional compilation: modules gated with #[cfg(feature = "...")]. Runtime validate_config() warns if requested feature not compiled in.

Feature Flag Critical Rules

1. Never mix conflicting features - e.g., ocr-minimal + tesseract should error at compile time
2. Always provide feature diagnostics - Config validation must warn if feature unavailable
3. Default to maximum feature set - Unless embedded/minimal specifically requested
4. Test all feature combinations - Matrix testing in CI catches regressions
5. WASM incompatible with embeddings, keywords, OCR

Critical Rules

1. Always use format detection before routing to extractors (prevent confusion attacks)
2. Stream-based parsing for PDFs/archives to handle multi-GB files
3. Post-pipeline is mandatory: All extraction results flow through run_pipeline() for validators/hooks
4. Plugin overrides are order-dependent: Plugins registered first take priority
5. Fallback timeouts: Set reasonable OCR/archive extraction timeouts (config-driven)
6. Metadata preservation: Include format detection confidence, extraction method used, any fallbacks applied

Related Skills

• ocr-backend-management - OCR engine selection and image preprocessing
• chunking-embeddings - Post-extraction text splitting with FastEmbed
• api-server-mcp - Axum endpoint for extraction pipeline exposure and MCP server