Claude Opus 4.5 vs GPT-5.1-Codex-Max vs Gemini 3 Pro: 2025 AI Coding Showdown

Introduction

November 2025 will be remembered as a landmark month for AI coding tools. Within a single week, the three leading AI companies released their most powerful coding models:

• November 18: Google launches Gemini 3 Pro
• November 19: OpenAI debuts GPT-5.1-Codex-Max
• November 24: Anthropic releases Claude Opus 4.5

Each model brings unique strengths to the table. This comprehensive comparison breaks down the benchmarks, pricing, features, and use cases to help you decide which model fits your workflow.

Quick Comparison

| Feature | Claude Opus 4.5 | GPT-5.1-Codex-Max | Gemini 3 Pro | |---------|-----------------|-------------------|--------------| | Release Date | Nov 24, 2025 | Nov 19, 2025 | Nov 18, 2025 | | Company | Anthropic | OpenAI | Google | | SWE-bench Verified | Leader | 77.9% | 76.2% | | Context Window | 200K+ | Multi-context via compaction | 1M input | | Input Price | $5/M tokens | $1.25/M* | TBD | | Output Price | $25/M tokens | $10/M* | TBD | | Key Feature | Effort parameter | 24-hour tasks | Vibe coding | | Best For | Complex coding | Ultra-long tasks | Multimodal |

*GPT-5 base pricing; Codex-Max API pricing not yet announced

Model Deep Dives

Claude Opus 4.5

Released: November 24, 2025 Model ID: claude-opus-4-5-20251101

Anthropic's flagship model focuses on code quality and developer control. The standout features are:

Effort Parameter: Unlike other models, Opus 4.5 lets developers explicitly control the tradeoff between speed and capability. Low effort for quick tasks, high effort for complex debugging.

Context Compaction: Proprietary technology that summarizes and compresses context during long sessions, enabling 30-minute autonomous coding sessions without degradation.

Safety Leadership: Anthropic claims Opus 4.5 is their "most robustly aligned model," with industry-leading resistance to prompt injection and reduced concerning behaviors in agentic scenarios.

Token Efficiency: At medium effort, matches Sonnet 4.5 performance while using 76% fewer output tokens. At high effort, exceeds Sonnet 4.5 by 4.3 percentage points while using 48% fewer tokens.

GPT-5.1-Codex-Max

Released: November 19, 2025 Model ID: Not yet public

OpenAI's Codex-Max is built specifically for extended autonomous coding. Its defining characteristics:

24-Hour Task Capability: In internal evaluations, OpenAI observed Codex-Max working on tasks for more than 24 hours, persistently iterating, fixing test failures, and delivering successful results.

Multi-Context Compaction: The first OpenAI model natively trained to operate across multiple context windows through compaction, enabling project-scale refactors and multi-hour agent loops.

Reasoning Tiers: Ships with "Medium" (daily driver) and "xHigh" (deep focus) reasoning modes for different task complexities.

Windows Native: First OpenAI model trained specifically for Windows environments, improving developer experience on non-Unix systems.

Codex Integration: Tight integration with OpenAI's Codex CLI, IDE extension, and cloud services.

Gemini 3 Pro

Released: November 18, 2025 Model ID: gemini-3-pro

Google's entry emphasizes multimodal capabilities and massive context. Key features:

1 Million Token Context: Accepts 1M input tokens with 64K output - the largest context window of the three models.

"Vibe Coding": Natural language is the only syntax you need. Gemini 3 Pro is designed for describing what you want in plain English and getting working code.

Google Antigravity: A new agentic development platform (IDE) where AI agents plan, write, and debug code across editor, terminal, and browser simultaneously.

Multimodal Architecture: Unified transformer that processes text, image, audio, video, and code together, enabling cross-modal reasoning (e.g., sketch to code).

Wide Availability: Available in Cursor, GitHub, JetBrains, Manus, Replit, and Google's own platforms (AI Studio, Vertex AI, Gemini CLI).

Benchmark Comparison

SWE-bench Verified

The industry's most respected coding benchmark tests real-world software engineering tasks.

| Model | Score | Notes | |-------|-------|-------| | Claude Opus 4.5 | Leader | "Outperforms all frontier models" | | GPT-5.1-Codex-Max | 77.9% | At xHigh reasoning effort | | Gemini 3 Pro | 76.2% | Solid performance |

Winner: Claude Opus 4.5

Anthropic hasn't disclosed exact numbers, but their claim of "leading all frontier models" puts them above Codex-Max's 77.9%. All three models show strong SWE-bench performance, with the gap between them relatively small.

TerminalBench 2.0

Tests command-line proficiency and system operations.

| Model | Score | |-------|-------| | GPT-5.1-Codex-Max | 58.1% | | Gemini 3 Pro | 54.2% | | Claude Opus 4.5 | Not disclosed |

Winner: GPT-5.1-Codex-Max

OpenAI's focus on system-level operations shows here. The Windows-specific training likely contributes to Codex-Max's terminal proficiency.

LMArena

Crowdsourced human preference rankings.

| Model | Score | |-------|-------| | Gemini 3 Pro | 1501 | | Previous leader (Gemini 2.5 Pro) | 1451 |

Winner: Gemini 3 Pro

Google's model took the top spot on LMArena at launch, though Claude and OpenAI models may not have been fully evaluated yet.

Multi-Language Coding (Aider Polyglot)

Tests proficiency across multiple programming languages.

| Model | Performance | |-------|-------------| | Claude Opus 4.5 | 10.6% improvement over Sonnet 4.5, leads 7/8 languages | | GPT-5.1-Codex-Max | Strong multi-language support | | Gemini 3 Pro | Good across languages |

Winner: Claude Opus 4.5

Anthropic's explicit focus on multi-language performance gives Opus 4.5 the edge for polyglot developers.

Extended/Agentic Tasks

| Model | Capability | |-------|------------| | GPT-5.1-Codex-Max | 24+ hour autonomous tasks | | Claude Opus 4.5 | 30-minute sessions, 65% fewer tokens | | Gemini 3 Pro | 1M context, multi-agent orchestration |

Winner: GPT-5.1-Codex-Max (for duration), Claude Opus 4.5 (for efficiency)

For sheer duration, Codex-Max wins with day-long task capability. For efficiency within sessions, Opus 4.5's context compaction uses significantly fewer tokens.

Pricing Comparison

API Costs

| Model | Input (per 1M tokens) | Output (per 1M tokens) | |-------|----------------------|------------------------| | Claude Opus 4.5 | $5 | $25 | | GPT-5 (base) | $1.25 | $10 | | GPT-5.1-Codex-Max | TBD (API coming soon) | TBD | | Gemini 3 Pro | TBD | TBD |

Subscription Plans

OpenAI:

• Plus ($20/month): 30-150 local tasks every 5 hours
• Pro ($200/month): Unlimited workweek access, 300-1500 local tasks every 5 hours

Anthropic:

• API pay-as-you-go
• Claude Pro subscription for app access
• Claude Max for heavy users

Google:

• Free tier available
• Pro subscription for advanced features
• Student: Free 1-year Gemini Pro (includes 2TB Drive storage)

Cost Analysis

For high-volume API usage, GPT-5's base pricing ($1.25/$10) is most economical - but Codex-Max API pricing isn't announced yet.

For heavy individual use, Claude's token efficiency (65% fewer tokens for long tasks) can offset higher per-token costs.

For students, Gemini 3 Pro's free year is unbeatable.

Feature Comparison

Context Handling

| Feature | Opus 4.5 | Codex-Max | Gemini 3 Pro | |---------|----------|-----------|--------------| | Max context | 200K+ | Multi-window | 1M | | Context compaction | Yes | Yes | No | | Long-task duration | 30 min | 24+ hours | Session-based |

Developer Control

| Feature | Opus 4.5 | Codex-Max | Gemini 3 Pro | |---------|----------|-----------|--------------| | Effort/reasoning tiers | Yes (3 levels) | Yes (2 levels) | No | | Custom system prompts | Yes | Yes | Yes | | Fine-tuning | No | Enterprise | Vertex AI |

Platform Availability

| Platform | Opus 4.5 | Codex-Max | Gemini 3 Pro | |----------|----------|-----------|--------------| | Direct API | Yes | Coming soon | Yes | | VS Code | Via extensions | Native extension | Via extensions | | CLI | Claude Code | Codex CLI | Gemini CLI | | AWS Bedrock | Yes | No | No | | Google Cloud | Vertex AI | No | Vertex AI | | Azure | Yes | Yes | No |

Safety & Alignment

| Feature | Opus 4.5 | Codex-Max | Gemini 3 Pro | |---------|----------|-----------|--------------| | Prompt injection resistance | Industry-leading | Standard | Standard | | Alignment claims | "Most robust" | Standard | Standard | | Enterprise compliance | SOC 2, HIPAA, GDPR | SOC 2 | SOC 2 |

Use Case Recommendations

Best for Complex Debugging: Claude Opus 4.5

Why: The effort parameter lets you dial up reasoning power for difficult bugs. Combined with strong multi-file understanding and safety features, Opus 4.5 is ideal for production debugging.

Example use case: Finding a race condition that only appears under load in a distributed system.

Best for Extended Autonomous Tasks: GPT-5.1-Codex-Max

Why: 24-hour task capability and multi-context compaction enable project-scale refactoring that runs overnight.

Example use case: Migrating a large codebase from one framework to another while you sleep.

Best for Multimodal Development: Gemini 3 Pro

Why: Unified processing of text, images, and code enables unique workflows like sketch-to-code and video analysis.

Example use case: Converting wireframe images directly into React components.

Best for Maximum Context: Gemini 3 Pro

Why: 1M token context window fits entire codebases without truncation.

Example use case: Analyzing a legacy codebase with hundreds of files simultaneously.

Best for Token Efficiency: Claude Opus 4.5

Why: 65% fewer tokens for long tasks and 76% fewer at medium effort dramatically reduce costs for high-volume use.

Example use case: Continuous integration code review that runs on every PR.

Best for Windows Development: GPT-5.1-Codex-Max

Why: First major model trained specifically for Windows environments.

Example use case: .NET development, PowerShell scripting, Windows system administration.

Best for Students: Gemini 3 Pro

Why: Free 1-year access makes it accessible for learning.

Example use case: Learning to code, completing coursework, building portfolio projects.

Real-World Performance

Enterprise Reports

Claude Opus 4.5:

• 50-75% reduction in tool-calling errors
• Successful multi-codebase refactoring
• Self-improving autonomous agents

GPT-5.1-Codex-Max:

• Completed 24-hour internal tasks
• Project-scale changes across multiple repos
• Strong Windows/enterprise adoption

Gemini 3 Pro:

• 100% on AIME 2025 (with code execution)
• Strong multimodal reasoning scores
• Popular in educational settings

Developer Sentiment

Based on community feedback:

• Opus 4.5: Praised for code quality, criticized for pricing
• Codex-Max: Praised for long tasks, not yet widely available
• Gemini 3 Pro: Praised for context size, "vibe coding" polarizing

Which Should You Choose?

Choose Claude Opus 4.5 if:

• Code quality is your top priority
• You need fine-grained control over reasoning effort
• You work with multiple programming languages
• Enterprise security/compliance matters
• You want predictable, efficient token usage

Choose GPT-5.1-Codex-Max if:

• You need ultra-long autonomous task execution
• Windows development is important
• You're already in the OpenAI ecosystem
• You want Codex CLI/IDE integration
• You have tasks that run for hours

Choose Gemini 3 Pro if:

• Maximum context window is critical
• You do multimodal development (images, video, audio)
• You're a student or cost-conscious
• You prefer "vibe coding" style interaction
• You need Google Cloud integration

The Hybrid Approach

Many teams are finding success using multiple models:

1. Gemini 3 Pro for initial codebase analysis (massive context)
2. Claude Opus 4.5 for complex debugging and code review (quality)
3. GPT-5.1-Codex-Max for overnight refactoring jobs (duration)

This multi-model strategy optimizes for each tool's strengths.

Conclusion

November 2025's three-way release gives developers unprecedented options for AI-assisted coding:

• Claude Opus 4.5 leads on benchmarks and offers unique developer control
• GPT-5.1-Codex-Max enables previously impossible long-duration tasks
• Gemini 3 Pro brings massive context and multimodal capabilities

There's no single "best" model - the right choice depends on your specific needs, budget, and workflow. The good news: competition between these titans is driving rapid improvement and better pricing for everyone.

For most developers, we recommend starting with Claude Opus 4.5 for its benchmark leadership, token efficiency, and effort parameter flexibility. But keep Codex-Max and Gemini 3 Pro in your toolkit for the tasks where they excel.

Ready to try them?

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