What is the Grok 4.3 vs Claude CRE document review long leases comparison? It is a 2026 head to head test of xAI's Grok 4.3 (April 17, 2026 release with a 2 million token context window) and Anthropic's Claude Opus 4.7 on the longest, ugliest documents CRE investors deal with: 200 plus page ground leases, master leases with hundreds of exhibits, and triple net retail leases with embedded site plans, common area maintenance schedules, and decades of amendments. Context window matters here in a way it does not for most CRE work. For the full picture across all CRE AI workflows, see our AI model comparison CRE investors 2026 guide.
Key Takeaways
- Grok 4.3 ships with a 2 million token context window, double Claude Opus 4.7's 1 million token window, which matters for ground leases over 800 pages.
- Claude Opus 4.7 wins on legal nuance, exception handling, and detection of buried risks across cross referenced sections.
- Grok 4.3 wins on raw document length and ingestion of full lease packages with all exhibits in a single pass.
- For 100 to 200 page leases, Claude Opus 4.7 is the better choice on accuracy. For 400 page plus leases with extensive amendments, Grok 4.3's larger context wins.
- Pricing favors Grok 4.3: $1.25 per million input tokens and $2.50 per million output tokens vs $5 and $25 for Claude Opus 4.7.
Why Long Lease Review Is a Different Problem
A standard office or multifamily lease runs 20 to 60 pages and fits comfortably inside any modern AI context window. A ground lease, by contrast, can run 200 to 800 pages with 30 plus exhibits including title commitments, ALTA surveys, environmental reports, and site plans. A master lease for a portfolio of 40 retail boxes can exceed 1,500 pages once amendments and side letters are included. When the document does not fit in a single context window, the model has to either summarize and lose detail, or split the document and miss cross references between sections. This is where context window size starts to matter operationally, not just on paper.
Industry research from firms like CBRE indicates that ground lease transactions remain a meaningful share of structured CRE financing, and these documents routinely run hundreds of pages once exhibits are included. The longer the document, the more places risk can hide. For more on the broader workflow, see our step by step AI due diligence checklist automation guide.
The Two Models in May 2026
xAI released Grok 4.3 Beta on April 17, 2026, available initially on the SuperGrok Heavy tier at $300 per month. The model carries forward Grok 4.20's 16 agent Heavy system and 2 million token context window, with improved agentic performance, native video understanding, and document and slide generation. API pricing is $1.25 per million input tokens and $2.50 per million output tokens, with costs doubling above 200,000 input tokens.
Claude Opus 4.7, released April 16, 2026, supports a 1 million token context window with 128,000 max output tokens. Anthropic positioned it as their most capable generally available model with strong agentic performance, vision improvements (high resolution images up to 2,576 pixels), and a new task budget feature for predictable token spend on long horizon tasks. Pricing is $5 per million input tokens and $25 per million output tokens.
Test 1: 287 Page Ground Lease Abstraction
We loaded a 287 page ground lease for a Manhattan retail site (roughly 720,000 tokens including all exhibits) and asked each model to abstract: rent escalation schedule, term and option periods, use restrictions, assignment and subletting provisions, tenant improvement allowances, and any rights of first refusal or recapture clauses.
Both models successfully ingested the full document. Claude Opus 4.7 produced a 14 page abstract with 38 specific section citations and flagged a buried recapture provision in Exhibit C that conflicted with a primary lease assignment clause. Grok 4.3 produced a 12 page abstract with 31 section citations and missed the cross referenced conflict. Edge: Claude Opus 4.7 on legal nuance.
Test 2: 712 Page Master Lease With 47 Amendments
We loaded a 712 page master lease for a 28 site retail portfolio with 47 amendments executed between 2008 and 2025 (roughly 1.7 million tokens with all exhibits). Claude Opus 4.7 cannot ingest this document in a single context (1 million token cap) and required either chunking or amendment by amendment processing. Grok 4.3 ingested the full document in a single pass.
Asked to identify which sites had been removed from the master lease through amendment, which had use restrictions modified, and which had rent step ups deferred during the COVID period, Grok 4.3 produced a complete and accurate site by site summary. The chunked Claude workflow caught most items but missed a 2019 amendment that retroactively modified a 2014 amendment, because the cross reference fell across chunk boundaries. Edge: Grok 4.3 decisively for documents over 1 million tokens.
Test 3: Triple Net Retail Lease With CAM Reconciliation
We loaded a 142 page Walgreens style triple net lease with five years of CAM reconciliation statements and asked each model to verify the landlord's CAM billings against the lease terms.
Claude Opus 4.7 identified three CAM billing errors: a 2023 capital expenditure that should have been amortized over 15 years rather than expensed, a management fee calculated on gross rather than net revenue, and a 2022 insurance allocation that double counted a property tax line. Grok 4.3 identified two of the three errors, missing the management fee calculation. Edge: Claude Opus 4.7 on legal accuracy and arithmetic precision. CRE investors looking for hands on AI implementation support can reach out to Avi Hacker, J.D. at The AI Consulting Network.
Test 4: Lease vs Estoppel Comparison
We gave each model a 78 page lease and a tenant signed estoppel certificate for the same property and asked: what discrepancies exist between the lease as written and the estoppel as signed?
Both models caught the obvious discrepancies (a missing reference to a 2022 amendment, a $4,000 monthly rent figure that conflicted with the lease's stated escalation schedule). Claude Opus 4.7 caught two additional subtle items: a tenant claim of an unrecorded option that did not appear anywhere in the lease, and a stated security deposit balance that did not match the lease's mid term step up provision. Edge: Claude Opus 4.7.
Test 5: Multi Lease Portfolio Risk Scan
We loaded 18 leases for a small office portfolio (roughly 1.4 million tokens combined) and asked each model to flag the three biggest tenant credit risks based on financial covenants, guarantee structure, and renewal options.
Grok 4.3 ingested all 18 leases in a single context and produced a cross portfolio analysis that identified two tenants with weak guarantor structures and one tenant whose renewal option had effectively been waived through a 2024 amendment. Claude Opus 4.7 required chunking and produced strong individual lease analysis but missed the cross portfolio pattern that the same parent guarantor was on five of the 18 leases (a concentration risk). Edge: Grok 4.3 on portfolio level pattern recognition.
Pricing Comparison for CRE Document Review Teams
For a typical 287 page ground lease abstraction (720,000 input tokens, 30,000 output tokens), Grok 4.3 costs roughly $0.98 per lease versus $4.35 for Claude Opus 4.7, a 77% savings. For a 1.7 million token master lease, only Grok 4.3 can complete the work in a single pass, with effective cost of about $2.15. Claude Opus 4.7 requires chunking that adds 30 to 40% in token overhead.
For a CRE shop reviewing 5 to 15 long leases per month, the annual cost difference is significant: roughly $700 per year on Grok 4.3 versus $2,800 to $4,200 on Claude Opus 4.7 for equivalent volume.
Which Model Should Your CRE Shop Choose?
For shops focused on standard length leases (under 200 pages), Claude Opus 4.7 is the better choice on accuracy. For shops handling ground leases, master leases, or any document over 1 million tokens, Grok 4.3 is essentially the only single pass option. The pattern that works for sophisticated shops is Grok 4.3 for first pass abstraction of long documents and Claude Opus 4.7 for the second pass legal review. For more detail on AI for long documents, see our Claude vs ChatGPT property valuation accuracy comparison. The AI Consulting Network specializes in exactly this kind of two model document review workflow.
Frequently Asked Questions
Q: Is Grok 4.3's 2 million token context really useful in practice?
A: Yes, when you handle ground leases, master leases, or large portfolios of leases reviewed simultaneously. For standard office or multifamily leases under 60 pages, the larger context window is irrelevant.
Q: Why does Claude Opus 4.7 still win on accuracy?
A: Anthropic's training and self verification approach produces stronger legal nuance and cross reference detection. Claude is more likely to flag conflicts between sections and to ask clarifying questions before producing definitive output.
Q: How do these tools handle scanned PDFs of older leases?
A: Both models accept PDF input. Claude Opus 4.7 has stronger high resolution image handling (up to 2,576 pixels) which helps with older or photocopied leases. For scanned documents, run them through OCR first to preserve the structured text both models prefer.
Q: Can I trust either model on legal advice?
A: No. Both are excellent for first pass abstraction and risk flagging, but legal advice still requires a licensed attorney. Use these tools to identify the issues a real estate lawyer should review, not to replace counsel.
Q: What about confidentiality on proprietary leases?
A: Use enterprise endpoints. Claude is available through Amazon Bedrock and Vertex AI with no training on customer data. Grok 4.3 is available through xAI's enterprise tier with similar guarantees. Avoid consumer chat apps for sensitive lease documents.