Long Context demo

The Long-Context Synthesis Cabinet

Give Claude a large transcript or document bundle and ask for a structured synthesis with decision logs, contradictions, and missing evidence.

Cast: Fable 5.1 or Opus 5Executives, researchers, program leads, editorsIntermediate20-45 minutes

"working memory"

Casting: which model to run

Claude Fable 5.1, Opus 5, and Sonnet 5 all carry a 1M-token context window with 128K max output, so the capacity is not the differentiator. Cast Fable 5.1 when the synthesis has to hold contradictions across the whole bundle; Opus 5 is enough for a single readable pass. Haiku 4.5 tops out at 200K and is the wrong cast here.

See the casting page for the full current lineup and API IDs. MagicClaude does not score models; Claude Reports covers benchmark comparisons and pricing analysis.

Setup: what the audience sees

The reveal is continuity: Claude can connect distant details, track contradictions, and produce a decision-ready map from material no one wants to reread end to end.

The setup matters because Claude demos fail when the prompt hides the goal, mixes private data into a public reveal, or asks for a finished answer without giving the model a way to expose assumptions.

  • Use a transcript, meeting bundle, or report set you have permission to process.
  • Tell Claude what decisions the synthesis should support.
  • Use sectioned XML-style prompt blocks so source material is not confused with instructions.

What this does not prove

It does not prove perfect recall. Anthropic warns that large context is working memory, not a guarantee that more text always improves accuracy.

Copyable promptPlain text
<objective>
Synthesize this long transcript bundle into a decision memo for the project lead.
</objective>
<source_material>
Paste transcript chunks, notes, or file summaries here.
</source_material>
<output>
1. One-paragraph executive readout
2. Decisions already made, with supporting evidence
3. Open disagreements or contradictions
4. Risks mentioned by multiple people
5. Missing evidence needed before the next milestone
6. A 10-item action list with owner placeholders
</output>
<rules>
- Quote sparingly.
- Say "not found in provided context" when evidence is missing.
- Keep assumptions separate from source-backed statements.
</rules>

The reveal: what should happen

  • The memo should find relationships across distant parts of the material.
  • Contradictions and missing evidence are the real magic, because they prevent false closure.
  • The output becomes a scaffold for a second pass, not a one-and-done answer.

Verification steps

A demo becomes useful when the audience can inspect it. Use the steps below to turn the reveal from theater into a repeatable workflow.

  1. Spot-check one decision, one risk, and one contradiction against the source material.
  2. Ask Claude to produce a compact source map for the highest-impact claims.
  3. If the output is used operationally, require a human owner to approve each action item.

Guardrails

  • Chunk or summarize private material according to your data policy.
  • Do not rely on long context alone for regulated decisions.
  • Use explicit "not found" instructions to reduce pressure toward invented evidence.

Variations

  • Board meeting packet synthesis.
  • Research interview synthesis.
  • Incident postmortem timeline and action register.

FAQ

Does a 1M-token context mean perfect recall?

No. Treat it as capacity for working context, then use source maps and spot checks for important claims.

Which model should I pick?

Claude Opus 5 is the default for a single synthesis pass, and Claude Fable 5.1 is the stronger cast when the material contains contradictions that have to be tracked across the whole bundle. Claude Sonnet 5 also has a 1M-token window if latency matters more than depth. Claude Haiku 4.5 is limited to 200K tokens.

Keep the act moving

Related demos and tools

Documents

PDF Evidence Table

Upload a PDF and ask Claude to separate claims, supporting pages, uncertainty, and follow-up checks into a reusable evidence table.

Agentic

Long-Horizon Agent

Give Claude Fable 5.1 a task too long for one turn and ask it to plan, execute, checkpoint its own progress, and report what it verified.

Tool

Demo Gallery Tool

Find more exact prompts by format, audience, and difficulty.

Tool

Prompt Remixer

Turn this prompt pattern into a themed copy-paste variant.

Primary Sources

These demos cite official Anthropic docs or help-center pages for capability claims. They do not claim identical output across accounts, plans, models, or dates.

Claude Platform Docs

Context windows

The context window is the text a model can reference for a response, and long contexts require deliberate management.

Claude Platform Docs

Claude Fable 5.1 overview

Claude Fable 5.1 (`claude-fable-5-1`) has a 1M-token context window, 128K max output, always-on adaptive thinking, and a default effort level of high in Claude Code and medium on Claude.ai and Cowork.

Claude Platform Docs

Claude Opus 5 overview

Claude Opus 5 (`claude-opus-5`) launched July 24, 2026 with a 1M-token context window, 128K max output, adaptive thinking, and an optional fast mode.

Claude Platform Docs

What's new in Claude Sonnet 5

Claude Sonnet 5 (`claude-sonnet-5`) supports a 1M-token context window by default and 128K max output tokens.

Claude Platform Docs

Increase output consistency

When exact JSON conformance matters, Anthropic recommends structured outputs rather than prompt-only formatting.