What changed in late 2025: the "frontier model" decision got harder
In a short period, three major vendors shipped notable upgrades: OpenAI released GPT-5.2 on December 11, 2025 with variants positioned for different levels of difficulty and trustworthiness.[1] Anthropic launched Claude Opus 4.5 in November 2025 and emphasized long-horizon performance, token efficiency, and safety robustness including improved prompt injection resistance.[2] Google introduced Gemini 3 Pro in preview in November 2025 as part of the Gemini 3 launch and expanded access across products and the Gemini API.[3][4]
For law firms, "which model is best" is the wrong first question. The right first question is: "Which model is best for this specific workflow, risk tier, and data classification?" ABA guidance makes clear that lawyers must understand the benefits and risks of the technologies used to deliver legal services and must protect confidentiality and supervise outputs.[5]
High-level comparison table (legal workflow lens)
| Category | GPT-5.2 | Claude Opus 4.5 | Gemini 3 Pro |
|---|---|---|---|
| Release timing | Dec 11, 2025 release notes for GPT-5.2 tiers (Instant, Thinking, Pro).[1] | Nov 24, 2025 launch noted in Anthropic release notes and blog.[6][2] | Nov 2025 Gemini 3 Pro preview; API changelog notes Gemini 3 Pro preview model.[3][4] |
| Best-fit legal use cases | Drafting acceleration, structured matter plans, summarization, tool-based workflows, internal ops.[1] | Long-document consistency, long-horizon drafting, robustness focus, document engineering workflows.[2] | Workspace-adjacent productivity, multimodal ingestion, planning and synthesis workflows.[3] |
| Primary risk themes | Hallucinations, overreliance, tool misreporting, confidentiality without governance; system card documents scenario-dependent failure modes.[7] | Confidentiality and verification; prompt injection reduced but not eliminated; still requires access controls.[2] | Confidentiality + agentic action risk if connected to files/email; provenance and verification still essential.[3] |
| Ethics baseline for all three | Competence, confidentiality, communication, and reasonable fees plus review obligations under ABA guidance apply regardless of vendor.[5] | ||
How to choose: match model to matter-risk, not hype
Step 1: Classify the workflow
Example segmentation:
- Low-risk: internal SOPs, marketing, training docs, public summaries.
- Medium-risk: contract first drafts using templates, de-identified memos, client emails with review.
- High-risk: legal conclusions, filings, privileged strategy, discovery strategy, anything going to court or regulators.
Step 2: Pick your "default" and your "specialists"
Many firms will benefit from a default model for general drafting and planning, plus specialists: one that excels at long-horizon consistency checking, and one that integrates smoothly with the firm's productivity environment. GPT-5.2's tiering (Instant vs Thinking vs Pro) can support internal routing by task difficulty and required quality.[1] Opus 4.5's emphasis on long-horizon efficiency and safety robustness is attractive for document engineering and controlled environments.[2] Gemini 3 Pro's positioning inside Google's ecosystem can reduce adoption friction for firms already standardized on Google tools.[3]
Step 3: Standardize verification and provenance
Your policy should never depend on a vendor claim that a model is "more trustworthy." Treat every model output as a draft that must be verified. OpenAI's system card explicitly discusses deception and hallucination behavior varying by scenario and constraints, reinforcing the need for structured review and cautious prompt design.[7]
Non-negotiables: governance every firm needs
- Confidentiality controls consistent with ABA Model Rule 1.6 duties described in ABA guidance.[5]
- Competence and training so attorneys understand failure modes and proper supervision.[5]
- Review gates: nothing external leaves without attorney review and cite-check.
- Auditability: keep prompt/output records for high-risk work.
- Client communication policy: when and how AI use is disclosed, consistent with communication duties highlighted in ABA guidance.[5]
Bottom line
GPT-5.2, Opus 4.5, and Gemini 3 Pro are all credible productivity multipliers for law firms, but each shines in different workflow shapes: GPT-5.2 for broad professional task execution and tiered quality routing,[1] Opus 4.5 for long-horizon work and safety robustness framing,[2] and Gemini 3 Pro for multimodal, ecosystem-integrated workflows.[3][4] The decisive factor is not the model. It is the surrounding system: confidentiality, verification, training, and supervision aligned with ABA duties.[5]
References
- OpenAI Help Center, "ChatGPT — Release Notes: December 11, 2025 (GPT-5.2)" (Dec 2025).
- Anthropic, "Introducing Claude Opus 4.5" (Nov 2025).
- Google, "A new era of intelligence with Gemini 3" (Nov 2025).
- Google AI for Developers, "Gemini API changelog: Gemini 3 Pro preview" (Nov 18, 2025).
- American Bar Association, "ABA issues first ethics guidance on a lawyer's use of AI tools" (Jul 29, 2024).
- Anthropic Support, "Release Notes: Claude Opus 4.5 launch" (Nov 24, 2025).
- OpenAI, "Update to GPT-5 System Card: GPT-5.2" (PDF, Dec 2025).