Compare Two Contracts in 15 Minutes With One Opus 4.8 Prompt

With Fable 5 pulled this week, here is the long-document workflow that still runs on Opus 4.8, narrowed to the highest-value version: reconciling two agreements and citing the exact clause behind every difference.

What You Will Learn

• Why the million-token diligence move stops working this week, and what replaces it
• The one prompt that reconciles two long agreements on Opus 4.8 in about 15 minutes
• How a forced citation on every claim turns the output into something you can check
• Where the same workflow pays off again: renewals, leases, policy updates, and MSAs

Last week's diligence trick relied on Fable 5 and its 1M-token context window: paste an entire data room, ask one question, get one answer. As of this week that move is unavailable. A US export-control order has suspended Fable 5, so the read-everything-at-once approach is off the table until the suspension lifts.

The work itself has not gone anywhere. You still need to know what changed between the old contract and the new one, and you still need to know it before you sign. Opus 4.8 remains available and handles two long agreements at once without strain. The shift is one of scope: instead of one model swallowing a whole data room, you point Opus 4.8 at a focused comparison and make it cite every clause it leans on.

This is a PromptHacker Premium deep dive.

The full prompt, the two-stage workflow, and the four reuse cases are below for Premium members.

Why This Still Works Without Fable 5

Two contracts, even long ones, are a small fraction of what a 1M-token window was built to hold. Opus 4.8 keeps both agreements in view comfortably, which means the comparison you actually need does not depend on the model that got suspended. What changes is how you frame the task. A whole data room invites a broad question. Two documents reward a narrow one.

The trick is scope plus citations. Scope keeps the model on the one question that matters this week: where does the newer agreement differ from the older one. Citations keep the output honest. When you require a section reference and a direct quote for every difference, you can verify each line against the source in seconds instead of trusting a summary you cannot trace.

The Prompt

Paste both agreements into a single Opus 4.8 conversation, then send the prompt below as your instruction.

The Prompt

You are my contracts analyst. I am pasting two related agreements. Work in two stages and stop after stage one. STAGE ONE: Plan only. Tell me what each document is, the sections you will compare, and anything missing or unusual. Do not analyze yet. Wait for my approval. STAGE TWO (after I say "approved"): Produce a one-page memo: (1) every place the two documents conflict or where the newer one changes the older, each citing the exact section and quoting the language, ranked by how much it matters; (2) new obligations, fees, or deadlines, with citations; (3) the three things I should renegotiate or clarify before signing; (4) a two-sentence plain-language bottom line. Cite a section for every claim. If something is ambiguous, say so. Do not pad.

How to run it: Read the stage-one plan first. If the model misnamed a document or skipped a section you care about, correct it before you reply. Once the plan looks right, send "approved" and let it produce the memo. Start to finish, the review runs about 15 minutes and saves the 2 to 3 hours a manual side-by-side normally takes.

Why It Works

The citation requirement is what makes the memo usable. Every difference, every new fee, and every deadline arrives tied to a section number and a direct quote, so you can open the contract and confirm it yourself. A claim you cannot trace is a claim you cannot defend in a negotiation, and the forced citation removes that gap.

The two-stage pause does the second job. By stopping after the plan, the model shows you its reading of each document before it commits to conclusions. If it labeled the amendment as the master agreement or skipped the indemnity section, you catch the misread in the plan, where it costs you one correction, rather than in the memo, where it would have shaped the whole analysis.

Where to Reuse It

The same two-document comparison fits any review where a new version has to be checked against an old one. Vendor renewals are the obvious case: drop in last year's contract and this year's proposed terms, and the memo surfaces the price changes and the quietly added clauses. Lease comparisons work the same way, whether you are weighing two sites or comparing a renewal against the prior term.

Policy updates benefit too: run the current policy against the proposed revision and see exactly which obligations shifted. The reconciliation that pays off most often is an MSA against its amendments, where the changes are scattered across documents and easy to lose track of by hand. In each case, the scope stays narrow and the citations stay mandatory.

Action Steps Summary

• Pick the pair. Choose the two related agreements you need reconciled, such as a current contract and its renewal, and open a single Opus 4.8 conversation.
• Paste both, then the prompt. Drop the full text of both documents in, then send the two-stage prompt above as your instruction.
• Check the plan. Read the stage-one plan and correct any mislabeled document or skipped section before you go further.
• Approve and read the memo. Reply "approved," then review the one-page memo of ranked differences, new obligations, and the three items to renegotiate.
• Verify the citations. Spot-check the section references against the source contracts before you act on anything, then take the three flagged items into your negotiation.