Can AI compare two versions of a contract? Let software find every change. Let AI explain them. Let a lawyer decide.
Short answer. Yes, if you split the job. Finding every difference between two versions is mechanical work that a text-comparison tool does exactly, with no omissions: Word’s Compare feature, or a standard library such as Python’s difflib. Explaining what each change means for you is where a language model helps, by summarising edits and flagging changed obligations, dates and amounts. Asking a model alone to compare two long contracts is risky, because models can miss details in long inputs, and a 2024 study of AI legal research tools found hallucination rates of 17 to 33 per cent even with retrieval. Use AI for the explanation and a lawyer for the judgement. This is general information, not legal advice.
01
Two jobs, two tools
Job
Best tool
Why
Find every changed word, number and clause
A text diff: Word Compare, Python difflib, or a diff in your document system
It is exact. Python’s difflib computes the deltas between two texts and can produce HTML or unified diffs, so nothing is skipped.
Explain each change in plain language
A language model reading the diff with the surrounding clauses
It reads a short, specific input instead of two long documents, which is easier for a model.
Judge the risk and decide
A lawyer
Accountability sits with a person, and the effect of a change depends on the whole agreement and your position.
02
Where an AI-only comparison fails
Two long contracts are a long input. Lost in the Middle found that models often do worse when the relevant detail sits in the middle of a long input, and RULER found that only about half of the long-context models it tested kept satisfactory performance at 32K tokens, though all claimed that much or more. A changed number on page 40 is exactly what can slip.
Contract review is also hard in itself. The CUAD dataset, built with dozens of legal experts, holds more than 13,000 annotations of the clauses a reviewer would care about, and its authors described the models they tested as having nascent performance. Magesh and colleagues found in 2024 that retrieval-based legal research tools from LexisNexis and Thomson Reuters each hallucinated between 17% and 33% of the time.
03
What a lawyer must still read
Changed obligations: shall, may, must, and the conditions attached.
Numbers and dates: amounts, percentages, notice periods, cure periods and deadlines.
Definitions, and every clause that uses a changed definition.
Deleted protections, such as caps on liability, termination rights and indemnities.
Cross-references and numbering, which can break when a clause is added or removed.
Schedules, annexures and side letters, which a comparison of the main body does not cover.
Edits that look like formatting. A changed font or moved paragraph can hide a changed word, so rely on the diff, not on how the page looks.
04
How an office would set this up
Get both versions as editable files where you can. If one is a scan, run OCR and proofread the text first.
Accept or reject tracked changes so each file shows one clean version.
Run a text diff and save the report.
Give the model each change with the clauses around it and ask for a table: clause, old text, new text, effect and risk flag, quoting both versions exactly.
Have a lawyer read the table against the diff, then read the clauses flagged high-risk in full.
Keep the diff report, the table and the reviewer’s name with the matter file.
05
What ANVE does today
ANVE does not list contract comparison as a function. Its documents function answers questions over the office’s own documents and shows the source passage, which helps a reader check a clause in either version. Legal research and compliance check are agents that can be built with a paid pilot; they are not shipped products.
The documents function runs today in ANVE’s development build. No sealed unit exists yet.
06
Questions people ask
Is Word’s Compare feature enough?
It finds changes reliably but does not explain them. It is the right first step, and an AI summary of the diff can be the second.
Can I send a draft contract to a cloud AI service?
That is a confidentiality decision for you and your client. A local model avoids sending privileged drafts to a third party. This is general information, not legal advice.
How accurate are legal AI tools?
A 2024 preregistered study found that retrieval-based legal research tools hallucinated between 17% and 33% of the time, less than a general chatbot but far from zero. Supervision by a lawyer is still needed.
Does a lawyer still need to read the whole contract?
For anything that matters, yes. The comparison tells the lawyer where to look first; it does not replace reading.
07
What is not real yet
No sealed ANVE unit exists; every image of the appliance on this site is a labelled render. The software runs today on a development machine. No customers yet, no certifications, no delivery date, and the final price is not announced.
Reservations are ₹999 in India or US$12 elsewhere, refundable in full until you confirm an order in writing (terms). Offices that cannot use cloud AI can apply to be one of ten design partners.
