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Very Long Text Summarization

Processes texts too large for a single context window using hierarchical multi-pass extraction with armies of cheap models. Produces structured knowledge maps, indexed summaries, and skill drafts — not just prose compression.

When to Use​

✅ Use for:

  • Professional handbooks and textbooks (100-1000+ pages)
  • Career biographies and memoirs (extracting expertise patterns)
  • Large codebases (architecture-level understanding)
  • Research paper collections (synthesizing findings across papers)
  • Any text exceeding a single context window (~100K tokens)

❌ NOT for:

  • Short documents (<10 pages) — just read them directly
  • Real-time conversation summarization (use auto-compact patterns)
  • Code documentation generation (use technical-writer)
  • Simple TL;DR requests (not worth the multi-pass overhead)

Architecture: Three-Pass Hierarchical Extraction​

flowchart TD
  D[Document] --> C[Chunk into segments]
  C --> P1["Pass 1: Haiku army\n(parallel extraction)"]
  P1 --> I[Intermediate summaries]
  I --> P2["Pass 2: Sonnet synthesis\n(merge + structure)"]
  P2 --> S[Structured knowledge map]
  S --> P3["Pass 3: Opus refinement\n(optional, for skill drafts)"]
  P3 --> O[Final output]

Pass 1: Chunked Extraction (Haiku Army)​

Split the document into overlapping chunks (~4K tokens each, 500 token overlap). Deploy one Haiku call per chunk in parallel. Each extracts:

extraction_template:
  summary: "2-3 sentence summary of this section"
  key_claims: ["list of factual claims or assertions"]
  processes: ["any step-by-step procedures described"]
  decisions: ["any decision points or heuristics mentioned"]
  failures: ["any failures, mistakes, or anti-patterns described"]
  aha_moments: ["any insights, realizations, or conceptual breakthroughs"]
  metaphors: ["any metaphors or mental models used"]
  temporal: ["any 'things changed when...' or 'before X, after Y' patterns"]
  quotes: ["notable direct quotes worth preserving"]
  references: ["any citations, links, or cross-references"]

Cost: ~$0.001 per chunk. A 300-page book (~150K tokens) = ~38 chunks = ~$0.04 total for Pass 1.

Parallelism: All chunks run simultaneously. A 300-page book completes Pass 1 in ~3 seconds (wall clock), not 3 minutes.

Pass 2: Synthesis (Sonnet)​

Feed all Pass 1 extractions into one or more Sonnet calls. Sonnet merges, deduplicates, and structures the knowledge.

synthesis_template:
  document_summary: "1-2 paragraph executive summary"
  
  knowledge_map:
    core_concepts:
      - concept: "name"
        definition: "what it means in this domain"
        relationships: ["connects to concept X because..."]
    
    processes:
      - name: "process name"
        steps: ["ordered steps"]
        decision_points: ["where choices are made"]
        common_mistakes: ["what goes wrong"]
    
    expertise_patterns:
      - pattern: "what experts do differently"
        novice_mistake: "what novices do instead"
        aha_moment: "the insight that bridges the gap"
    
    temporal_evolution:
      - period: "date range"
        paradigm: "what was believed/practiced"
        change_trigger: "what caused the shift"
    
    key_metaphors:
      - metaphor: "how practitioners think about X"
        maps_to: "the underlying structure it represents"
  
  index:
    - topic: "topic name"
      chunk_ids: [3, 7, 12]  # Which original chunks cover this
      summary: "1 sentence"

Cost: ~$0.02-0.05 depending on extraction volume. The index preserves traceability back to specific book sections.

Pass 3: Refinement (Opus, Optional)​

For skill-draft output mode: Opus takes the knowledge map and produces a SKILL.md following the skill-architect template. This is the "crystallize skill from handbook" pipeline.

Cost: ~$0.10. Only run when the output is a skill draft.

Chunking Strategy​

Semantic Chunking (Preferred)​

Split on document structure — chapter boundaries, section headings, paragraph breaks. Preserves semantic coherence within each chunk.

def semantic_chunk(text: str, max_tokens: int = 4000, overlap: int = 500) -> list[str]:
    """Split text on structural boundaries with overlap."""
    # Split on headings, then merge short sections
    sections = split_on_headings(text)  # ##, ###, etc.
    
    chunks = []
    current = ""
    
    for section in sections:
        if count_tokens(current + section) > max_tokens:
            chunks.append(current)
            # Overlap: keep the last ~500 tokens
            current = get_last_n_tokens(current, overlap) + section
        else:
            current += section
    
    if current:
        chunks.append(current)
    
    return chunks

Fixed-Size Chunking (Fallback)​

For unstructured text without headings. Split on paragraph boundaries, targeting ~4K tokens with 500-token overlap.

Why Overlap?​

Concepts that span chunk boundaries need to appear in both chunks to be extracted. Without overlap, you lose cross-boundary knowledge.

Output Modes​

Mode 1: Summary​

Produces a structured summary with executive overview, key concepts, and index.

Use for: Quick understanding of a long document. Reading a handbook before a meeting.

Mode 2: Knowledge Map​

Produces the full knowledge map: concepts, processes, expertise patterns, temporal evolution, metaphors. Machine-readable (YAML/JSON) for downstream processing.

Use for: Feeding into skill creation, domain meta-skill development, or cross-document analysis.

Mode 3: Skill Draft​

Produces a SKILL.md following the skill-architect template, with the handbook's expertise encoded as decision trees, anti-patterns, and shibboleths.

Use for: Converting professional handbooks into Claude skills. The KE pipeline.

Cost Model​

Document SizePagesChunksPass 1 (Haiku)Pass 2 (Sonnet)Pass 3 (Opus)Total
Article104$0.004$0.01—$0.014
Chapter3010$0.01$0.02—$0.03
Handbook30038$0.04$0.05$0.10$0.19
Textbook800100$0.10$0.10$0.10$0.30
Encyclopedia2000+250+$0.25$0.20$0.10$0.55

Processing time is dominated by the longest single Haiku call (~2-3s). With full parallelism, even a 2000-page text completes Pass 1 in under 5 seconds.

Anti-Patterns​

Single-Pass Summarization​

Wrong: Feed the entire document into one Opus call. Why: Exceeds context window, or attention dilution produces weak extraction on such long input. Right: Hierarchical multi-pass. Cheap parallel extraction → expensive synthesis.

Summarization Without Structure​

Wrong: Produce a 2-paragraph prose summary of a 300-page handbook. Why: The structure IS the knowledge. A flat summary loses the decision trees, failure patterns, and temporal evolution that make skills valuable. Right: Structured knowledge map with indexed access back to source sections.

Skipping Overlap​

Wrong: Chunk on hard boundaries with no overlap. Why: Cross-boundary concepts get split and lost. Right: 500-token overlap between chunks. Each chunk includes the tail of the previous chunk.

Ignoring Source Traceability​

Wrong: Produce extractions without tracking which chunk they came from. Why: When a claim seems wrong, you need to verify it against the source. Without traceability, you can't. Right: Every extraction carries a chunk_id linking back to the original text segment.