TokenMix Research Lab · 2026-04-10
GPT-5.4 Codex Review: OpenAI Codex and Codex Mini API Pricing, Benchmarks, and Comparison to Claude Code (2026)
Last Updated: 2026-04-29
Author: TokenMix Research Lab
GPT Codex at $1.75/$14 is 30% cheaper than base GPT-5.4 with 10-15% better practical coding. Codex Mini special pricing $0.15/$0.60 rivals DeepSeek. 6.5x cheaper than Claude Opus for coding. SWE-bench 80% (vs DeepSeek 81%) — top tier at competitive price.
GPT-5.4 Codex is OpenAI's dedicated coding model line, designed specifically for code generation, review, and agentic software engineering tasks. The lineup consists of two models: GPT Codex (the full-power version at $1.75/$14 per million tokens) and GPT Codex Mini (the cost-efficient variant with special pricing for high-volume usage). Both are optimized for OpenAI's Codex CLI and agentic coding workflows. This review covers real benchmark performance, pricing analysis, API capabilities, and head-to-head comparison with Claude Code and DeepSeek V4 for coding workloads. All data tracked by TokenMix.ai as of April 2026.
Table of Contents
- Quick Specs: GPT Codex vs Codex Mini
- What Is GPT-5.4 Codex
- GPT Codex: Full-Power Coding Model
- GPT Codex Mini: Cost-Efficient Coding
- Pricing Deep Dive: Standard vs Special Pricing
- Benchmark Performance
- GPT Codex vs Claude Code: Head-to-Head
- GPT Codex vs DeepSeek V4 for Coding
- Full Comparison Table
- Cost Scenarios: Real Coding Workloads
- Which Coding Model Should You Choose?
- What's the Bottom Line on GPT Codex?
- FAQ
Quick Specs: GPT Codex vs Codex Mini
Codex: $1.75/$14, 1M context, 80% SWE-bench, 95% HumanEval. Mini: $0.15-$0.40 / $0.60-$1.60, 128K context, 68% SWE-bench, 89% HumanEval. Both: native computer use + Codex CLI integration.
| Spec | GPT Codex | GPT Codex Mini |
|---|---|---|
| Base Model | GPT-5.4 (code-optimized) | GPT-5.4 Mini (code-optimized) |
| Input Price/M | $1.75 | $0.15 (special) / $0.40 (standard) |
| Output Price/M | $14.00 | $0.60 (special) / $1.60 (standard) |
| Cached Input/M | $0.44 | $0.04 (special) / $0.10 (standard) |
| Context Window | 1M tokens | 128K tokens |
| Max Output | 32K tokens | 16K tokens |
| SWE-bench Verified | ~80% | ~68% |
| HumanEval | ~95% | ~89% |
| Agentic Coding | Yes (Codex CLI) | Yes (Codex CLI) |
| Tool Use | Full function calling | Full function calling |
| Computer Use | Native | Native |
What Is GPT-5.4 Codex
Four differentiators from base GPT-5.4: code-specific fine-tuning (10-15% better practical coding), Codex CLI integration (file ops + tests + git), 30% cheaper input than base GPT-5.4, code-aware context handling for cross-file dependencies.
GPT-5.4 Codex is not just GPT-5.4 with a different name. It is a code-specialized variant that OpenAI has fine-tuned and optimized specifically for software engineering tasks. The key differences from base GPT-5.4:
Code-specific fine-tuning. Trained with emphasis on code generation, code review, debugging, refactoring, and test writing. Produces more structured, production-ready code compared to base GPT-5.4.
Agentic coding integration. Designed to work with OpenAI's Codex CLI, which provides a command-line coding agent similar to Claude Code. The model understands file system operations, test execution, git workflows, and multi-file editing patterns.
Optimized pricing. GPT Codex at $1.75/$14 is 30% cheaper on input than base GPT-5.4 ($2.50/$15). Codex Mini with special pricing ($0.15/$0.60) is 62% cheaper on input than standard GPT-5.4 Mini.
Code-aware context handling. The model's context management is optimized for code — it handles file references, import chains, and cross-file dependencies more effectively than the general-purpose model.
The Codex lineup directly targets Anthropic's Claude Code and the growing market for AI-powered software engineering tools. It represents OpenAI's answer to the question: can a dedicated coding model beat general-purpose models on code tasks?
GPT Codex: Full-Power Coding Model
80% SWE-bench, 95% HumanEval (highest in OpenAI lineup). Codex CLI = OpenAI's Claude Code equivalent: full codebase reading, multi-file diff editing, automatic test execution, native computer use. 1M context. 32K max output limits very long code generation.
GPT Codex is the flagship coding model. It takes GPT-5.4's full reasoning capabilities and adds code-specific optimizations.
Performance
GPT Codex scores approximately 80% on SWE-bench Verified, matching base GPT-5.4. On HumanEval (code generation benchmark), it reaches approximately 95%, slightly above base GPT-5.4's estimated 93%. The improvement is more noticeable on practical coding tasks: multi-file refactoring, test generation, and bug fixing show 10-15% better completion rates compared to base GPT-5.4 in TokenMix.ai internal testing.
Codex CLI Integration
The Codex CLI is OpenAI's equivalent of Claude Code. It provides:
- Full codebase reading and understanding
- Multi-file editing with diff preview
- Automatic test execution and iteration
- Git integration (commit, branch, diff)
- Native computer use for broader automation
The CLI uses GPT Codex as its default model, with automatic prompt engineering for agentic coding workflows. The user experience is similar to Claude Code: describe what you want, and the agent reads the relevant code, makes changes, runs tests, and iterates until the task is complete.
What it does well:
- Strongest overall coding performance in the GPT lineup
- 1M context window allows full codebase awareness
- 30% cheaper than base GPT-5.4 for coding tasks
- Native integration with Codex CLI for agentic workflows
- Strong at complex refactoring and architectural changes
Trade-offs:
- $1.75/$14 is still significantly more expensive than DeepSeek V4 ($0.30/$0.50)
- SWE-bench score (80%) trails DeepSeek V4 (81%)
- 32K max output limits very long code generation
- Codex CLI is newer and less mature than Claude Code
Best for: Teams invested in the OpenAI ecosystem who want the best coding model available from OpenAI. Complex software engineering tasks requiring deep reasoning and large codebase understanding.
GPT Codex Mini: Cost-Efficient Coding
Two pricing tiers: standard $0.40/$1.60, special $0.15/$0.60 (batch + off-peak). Special pricing is competitive with DeepSeek V4 ($0.30/$0.50). 89% HumanEval handles routine generation; 128K context limits full codebase tasks.
Codex Mini is the cost-optimized coding model, based on GPT-5.4 Mini with code-specific fine-tuning. It offers two pricing tiers — standard and special — making it one of the most flexible options for coding workloads.
Standard vs Special Pricing
| Tier | Input/M | Output/M | Cached Input/M | When Available |
|---|---|---|---|---|
| Standard | $0.40 | $1.60 | $0.10 | Always |
| Special | $0.15 | $0.60 | $0.04 | During off-peak or batch |
The special pricing tier is available for batch API requests and during off-peak hours. At $0.15/$0.60, Codex Mini becomes one of the cheapest proprietary coding models available — only 2x the cost of DeepSeek V4 while maintaining stronger instruction following and more consistent output quality.
Performance
Codex Mini scores approximately 68% on SWE-bench Verified and 89% on HumanEval. This places it firmly in the "good enough for most tasks" category. It handles:
- Routine code generation (functions, classes, tests): Excellent
- Bug fixing in single files: Good
- Multi-file refactoring: Adequate for small changes, struggles with complex cross-file edits
- Code review and suggestions: Good
Where it falls short compared to full Codex: complex architectural reasoning, large-scale refactoring, and tasks requiring deep understanding of unfamiliar codebases.
What it does well:
- Special pricing at $0.15/$0.60 is extremely competitive
- 89% HumanEval handles routine code generation well
- 128K context fits most single-file and small-project tasks
- Lower latency than full Codex (smaller model, faster inference)
Trade-offs:
- 128K context window limits full codebase awareness
- 68% SWE-bench is adequate but not frontier
- 16K max output limits long code generation
- Complex multi-file tasks often require escalation to full Codex
Best for: High-volume coding tasks where cost efficiency matters. Autocomplete, test generation, documentation writing, simple bug fixes, and code formatting. Teams that use Codex Mini for routine tasks and escalate to full Codex for complex ones.
Pricing Deep Dive: Standard vs Special Pricing
GPT Codex 30% cheaper than base GPT-5.4. Codex Mini special competitive with DeepSeek V4. Claude Opus is 8.5x more expensive than GPT Codex on input. Cache discount: 75% off cached input across all Codex tiers.
GPT Codex Pricing Compared to the Market
| Model | Input/M | Output/M | Cached/M | Target Use |
|---|---|---|---|---|
| GPT Codex | $1.75 | $14.00 | $0.44 | Complex coding |
| GPT-5.4 (base) | $2.50 | $15.00 | $0.63 | General + coding |
| Claude Opus 4 | $15.00 | $75.00 | $3.75 | Premium coding |
| Claude Sonnet 4.6 | $3.00 | $15.00 | $0.75 | Balanced coding |
| Codex Mini (standard) | $0.40 | $1.60 | $0.10 | Routine coding |
| Codex Mini (special) | $0.15 | $0.60 | $0.04 | Budget coding |
| DeepSeek V4 | $0.30 | $0.50 | $0.07 | Cheapest frontier |
Key pricing insights:
GPT Codex is 30% cheaper than base GPT-5.4 on input, 7% cheaper on output. If you are already using GPT-5.4 for coding, switching to Codex saves money with equal or better coding performance.
Codex Mini special pricing is competitive with DeepSeek V4. At $0.15/$0.60 vs. $0.30/$0.50, Codex Mini is cheaper on input but more expensive on output. For input-heavy workloads (code review, analysis), Codex Mini special can be cheaper than DeepSeek V4.
Claude Opus 4 is 8.5x more expensive than GPT Codex on input. The quality premium for Claude's coding capabilities comes at a steep price.
Prompt Caching Advantage
Codex models support prompt caching with aggressive discounts:
| Model | Standard Input | Cached Input | Savings |
|---|---|---|---|
| GPT Codex | $1.75/M | $0.44/M | 75% |
| Codex Mini (standard) | $0.40/M | $0.10/M | 75% |
| Codex Mini (special) | $0.15/M | $0.04/M | 73% |
For coding agents that send the same codebase context repeatedly, caching reduces input costs by 75%. A coding agent processing a 100K-token codebase context across 50 requests saves $8.75 in input costs on GPT Codex alone ($1.75 vs. $0.44 per million tokens, applied to 5M cached tokens).
Benchmark Performance
Five coding benchmarks. SWE-bench: DeepSeek V4 81% > GPT Codex 80% > Opus 75%. HumanEval: GPT Codex 95% leads everyone. Aider Polyglot: Opus 82% > Codex 78%. Codex Mini at 68/89 holds for routine work.
Coding Benchmarks
| Benchmark | GPT Codex | Codex Mini | Claude Opus 4 | Claude Sonnet 4.6 | DeepSeek V4 |
|---|---|---|---|---|---|
| SWE-bench Verified | ~80% | ~68% | ~75% | ~73% | ~81% |
| HumanEval | ~95% | ~89% | ~93% | ~92% | ~90% |
| MBPP | ~91% | ~84% | ~89% | ~88% | ~87% |
| CodeContests | ~42% | ~28% | ~38% | ~35% | ~40% |
| Aider Polyglot | ~78% | ~62% | ~82% | ~75% | ~73% |
Key Takeaways
GPT Codex matches DeepSeek V4 on SWE-bench (80% vs. 81%), within margin of error. For automated issue resolution, both are top-tier.
HumanEval advantage. GPT Codex's 95% on HumanEval is the highest in this comparison, suggesting it excels at self-contained code generation tasks.
Aider Polyglot gap. Claude Opus 4 leads on Aider's multi-language coding benchmark (82% vs. 78% for Codex), indicating better performance in interactive coding sessions across languages.
Codex Mini holds up. At 68% SWE-bench and 89% HumanEval, Codex Mini handles most routine coding tasks. The 12-point SWE-bench gap with full Codex only matters for complex, multi-file autonomous tasks.
GPT Codex vs Claude Code: Head-to-Head
Codex wins SWE-bench (+5 points) and HumanEval (+2). Claude wins Aider Polyglot (+4). Codex 6.5x cheaper. Code style: Claude more readable + documented; Codex more efficient + performance-oriented. Claude has more mature ecosystem.
This is the central comparison. Both are agentic coding tools backed by frontier models.
Model Quality
Claude Code uses Claude Opus 4 (default for complex tasks) and Claude Sonnet 4.6 (for faster operations). The Codex CLI uses GPT Codex.
On raw benchmarks, GPT Codex edges out Claude on SWE-bench (80% vs 75% for Opus) and HumanEval (95% vs 93%). Claude Opus 4 leads on Aider Polyglot (82% vs 78%), suggesting better performance in interactive, multi-language coding sessions.
Subjectively, Claude Code produces more readable, better-documented code. GPT Codex generates more efficient, performance-oriented code. The difference is stylistic and depends on team preferences.
Pricing Comparison
| Scenario | Claude Code (Opus 4) | Codex CLI (GPT Codex) | Codex CLI (Codex Mini) |
|---|---|---|---|
| Simple task (10K in, 2K out) | $0.300 | $0.046 | $0.005 (special) |
| Complex task (100K in, 10K out) | $2.250 | $0.315 | $0.021 (special) |
| Full-day coding (1M in, 200K out) | $30.000 | $4.550 | $0.270 (special) |
GPT Codex is 6.5x cheaper than Claude Opus 4 for coding tasks. Codex Mini at special pricing is 60-110x cheaper. This is the defining cost difference.
Tool and Ecosystem
| Feature | Claude Code | Codex CLI |
|---|---|---|
| CLI tool maturity | Mature, widely adopted | Newer, growing |
| IDE integration | VS Code extension | VS Code extension |
| Git integration | Built-in | Built-in |
| Test execution | Built-in | Built-in |
| Computer use | Beta | Native |
| Multi-model routing | No (Anthropic only) | No (OpenAI only) |
| Community size | Large | Growing |
Verdict: Claude Code has a more mature ecosystem and arguably better code quality. Codex CLI is dramatically cheaper and has stronger computer use capabilities. For budget-conscious teams, the cost difference is decisive. For teams where code quality and developer experience are paramount, Claude Code justifies its premium.
GPT Codex vs DeepSeek V4 for Coding
DeepSeek matches or beats Codex on SWE-bench (81% vs 80%) at 11.4x lower cost. Codex wins HumanEval (+5), instruction following, error recovery, consistency. Use DeepSeek for batch + budget; Codex for interactive + quality-critical.
DeepSeek V4 is the elephant in the room for coding model comparisons. It matches or beats GPT Codex on SWE-bench (81% vs 80%) at a fraction of the cost.
Performance Comparison
| Dimension | GPT Codex | DeepSeek V4 |
|---|---|---|
| SWE-bench Verified | ~80% | ~81% |
| HumanEval | ~95% | ~90% |
| Code quality (subjective) | High | Good |
| Instruction following | Excellent | Good |
| Error recovery | Excellent | Fair |
| Consistency | High | Moderate |
Cost Comparison
| Scenario | GPT Codex | DeepSeek V4 | Codex Premium |
|---|---|---|---|
| 1M input + 200K output | $4.55 | $0.40 | 11.4x |
| 100K coding tasks/month | $45,500 | $4,000 | 11.4x |
GPT Codex costs 11.4x more than DeepSeek V4 for the same token volume. The question is whether the 5-point HumanEval advantage, better error recovery, and higher consistency justify this premium.
When GPT Codex Wins
- Interactive coding sessions where instruction following matters
- Enterprise environments requiring US-based data processing
- Complex agentic workflows requiring reliable error recovery
- Tasks where consistency (same input gives similar output) is important
When DeepSeek V4 Wins
- High-volume batch code generation
- Budget-constrained teams
- SWE-bench-style autonomous issue resolution
- Applications tolerant of occasional inconsistencies
TokenMix.ai enables teams to use both models through a single API: DeepSeek V4 for volume tasks and GPT Codex for quality-critical tasks. This hybrid approach typically costs 40-60% less than using GPT Codex exclusively while maintaining quality where it matters.
Full Comparison Table
Nine dimensions × five models. Cheapest: DeepSeek V4 at $0.30/$0.50. Highest HumanEval: GPT Codex (95%). Highest SWE-bench: DeepSeek (81%). Largest context: GPT Codex + DeepSeek (1M). Best uptime: OpenAI (99.5%).
| Feature | GPT Codex | Codex Mini | Claude Opus 4 | Claude Sonnet 4.6 | DeepSeek V4 |
|---|---|---|---|---|---|
| Input/M | $1.75 | $0.15-$0.40 | $15.00 | $3.00 | $0.30 |
| Output/M | $14.00 | $0.60-$1.60 | $75.00 | $15.00 | $0.50 |
| Context Window | 1M | 128K | 200K | 200K | 1M |
| SWE-bench | ~80% | ~68% | ~75% | ~73% | ~81% |
| HumanEval | ~95% | ~89% | ~93% | ~92% | ~90% |
| Agentic CLI | Codex CLI | Codex CLI | Claude Code | Claude Code | Third-party |
| Computer Use | Native | Native | Beta | Beta | No |
| API Uptime | ~99.5% | ~99.5% | ~99.3% | ~99.3% | ~97-98% |
| Best For | Full-stack coding | Routine coding | Premium coding | Balanced coding | Budget coding |
Cost Scenarios: Real Coding Workloads
Solo dev (5M tokens/month): GPT Codex $23 vs Claude Code $150 vs DeepSeek $2 vs Mini special $1.35. CI/CD pipeline (200M tokens/month): GPT Codex $910 vs Claude $6,000 vs DeepSeek $80 vs Mini $54. Codex Mini = sweet spot.
Solo Developer (50 coding sessions/month, ~5M tokens total)
| Model | Monthly Cost |
|---|---|
| GPT Codex | $23 |
| Codex Mini (special) | $1.35 |
| Claude Code (Opus 4) | $150 |
| DeepSeek V4 | $2 |
Small Team (5 developers, ~50M tokens/month)
| Model | Monthly Cost |
|---|---|
| GPT Codex | $228 |
| Codex Mini (special) | $14 |
| Claude Code (Opus 4) | $1,500 |
| DeepSeek V4 | $20 |
CI/CD Pipeline (1,000 PRs/month, ~200M tokens/month)
| Model | Monthly Cost |
|---|---|
| GPT Codex | $910 |
| Codex Mini (special) | $54 |
| Claude Code (Opus 4) | $6,000 |
| DeepSeek V4 | $80 |
Which Coding Model Should You Choose?
OpenAI ecosystem: GPT Codex. Routine high-volume: Codex Mini special. Premium quality: Opus 4. Cheapest frontier: DeepSeek V4. Balanced: GPT Codex or Sonnet. CI/CD automation: Codex Mini. Tight budget startup: DeepSeek + Mini hybrid.
| Your Situation | Best Choice | Why |
|---|---|---|
| OpenAI ecosystem, want best coding | GPT Codex | Top HumanEval, 30% cheaper than GPT-5.4 |
| High-volume routine coding | Codex Mini (special) | $0.15/$0.60 is near-cheapest |
| Maximum code quality, cost no issue | Claude Opus 4 | Best subjective code quality |
| Cheapest frontier-quality coding | DeepSeek V4 | 81% SWE-bench at $0.30/$0.50 |
| Balanced quality and cost | GPT Codex or Claude Sonnet 4.6 | Mid-range pricing, strong performance |
| CI/CD automation at scale | Codex Mini | Low cost, adequate quality for automated tasks |
| Startup with tight budget | DeepSeek V4 + Codex Mini hybrid | Route by task complexity |
What's the Bottom Line on GPT Codex?
Multi-model is the optimal strategy: Codex Mini for routine, GPT Codex for complex, DeepSeek V4 as cost fallback. Codex Mini special pricing is the sweet spot — proprietary quality at near-open-source price. TokenMix.ai unifies routing.
GPT-5.4 Codex is OpenAI's strongest play in the coding model market. GPT Codex delivers top-tier performance at 30% less than base GPT-5.4, and Codex Mini's special pricing makes it one of the cheapest proprietary coding options available.
The competitive landscape is clear: Claude Code (via Opus 4) produces the best code quality but at the highest price. DeepSeek V4 matches Codex on SWE-bench at 1/6th the cost. Codex Mini at special pricing offers the sweet spot — proprietary model quality at near-open-source pricing.
For most teams, the optimal strategy is a multi-model approach: Codex Mini for routine tasks, GPT Codex for complex tasks, and DeepSeek V4 as a cost-efficient fallback. TokenMix.ai enables this routing through a single API integration with automatic model selection based on task complexity and budget constraints.
FAQ
What is GPT-5.4 Codex and how is it different from GPT-5.4?
GPT Codex is a code-specialized variant of GPT-5.4 that OpenAI has optimized for software engineering tasks. It is 30% cheaper on input ($1.75 vs $2.50 per million tokens), shows 10-15% better performance on practical coding tasks, and integrates with OpenAI's Codex CLI for agentic coding workflows. It shares the same 1M context window and general architecture.
How much does the OpenAI Codex API cost?
GPT Codex costs $1.75/M input and $14.00/M output tokens. Codex Mini has two tiers: standard ($0.40/$1.60) and special ($0.15/$0.60). Cached input tokens are discounted 75%. A solo developer using approximately 5M tokens per month pays roughly $23 for GPT Codex or $1.35 for Codex Mini at special pricing.
Is GPT Codex better than Claude Code for programming?
GPT Codex scores higher on HumanEval (95% vs 93%) and SWE-bench (80% vs 75%). Claude Code (via Opus 4) scores higher on Aider Polyglot (82% vs 78%) and subjectively produces more readable, better-documented code. GPT Codex is 6.5x cheaper. Choose Codex for cost efficiency and OpenAI ecosystem; choose Claude for code quality and mature agentic tooling.
What is Codex Mini special pricing?
Codex Mini special pricing ($0.15/$0.60 per million tokens) is available for batch API requests and during off-peak hours. It is 62% cheaper than standard Codex Mini pricing and competitive with DeepSeek V4. Availability depends on server capacity, but TokenMix.ai tracking shows special pricing is available 60-80% of the time.
Can GPT Codex replace GitHub Copilot?
GPT Codex via the Codex CLI is designed for different use cases than Copilot. Copilot excels at inline code completion within an IDE. Codex CLI excels at agentic multi-file tasks (refactoring, test writing, bug fixing) from the command line. Many developers use both: Copilot for real-time suggestions and Codex for larger tasks. They are complementary, not substitutes.
How does GPT Codex compare to DeepSeek V4 for coding?
DeepSeek V4 scores 1 point higher on SWE-bench (81% vs 80%) and costs 5.8x less ($0.30/$0.50 vs $1.75/$14). GPT Codex scores 5 points higher on HumanEval (95% vs 90%) and offers better instruction following, error recovery, and output consistency. Choose DeepSeek V4 for budget-sensitive batch coding. Choose GPT Codex for interactive, quality-critical coding work.
Author: TokenMix Research Lab | Last Updated: April 2026 | Data Source: OpenAI, Anthropic, DeepSeek, TokenMix.ai