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Get started freeGPT-5.5 vs GPT-5 Codex
Compare GPT-5.5 and GPT-5 Codex. Build AI products powered by either model on Appaca.
Model Comparison
| Feature | GPT-5.5 | GPT-5 Codex |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Model Type | text | text |
| Context Window | 1,000,000 tokens | 400,000 tokens |
| Input Cost | $5.00/ 1M tokens | $1.25/ 1M tokens |
| Output Cost | $30.00/ 1M tokens | $10.00/ 1M tokens |
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With Appaca you don't have to pick — build apps that are powered by GPT-5.5, GPT-5 Codex, for your specific use case.
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New appStrengths & Best Use Cases
GPT-5.5
OpenAI1. Strongest Agentic Coding Model
- State-of-the-art on Terminal-Bench 2.0 (82.7%), Expert-SWE (73.1%), and SWE-Bench Pro (58.6%), outperforming GPT-5.4 on complex coding tasks.
- Holds context across large systems, reasons through ambiguous failures, and carries changes through surrounding codebases with fewer tokens.
2. Higher Intelligence at GPT-5.4 Latency
- Co-designed, trained, and served on NVIDIA GB200/GB300 NVL72 systems to match GPT-5.4 per-token latency while performing at a significantly higher level.
- Uses fewer tokens to complete the same tasks, making it more efficient as well as more capable.
3. Powerful for Knowledge Work & Computer Use
- Scores 84.9% on GDPval (44 occupations) and 78.7% on OSWorld-Verified for autonomous computer operation.
- Excels at generating documents, spreadsheets, and reports; naturally moves across finding information, using tools, and checking output.
4. Scientific Research Co-Scientist
- Leading performance on GeneBench, BixBench, and FrontierMath; helped discover a new proof about Ramsey numbers verified in Lean.
- Strong enough to meaningfully accelerate progress at the frontiers of biomedical and mathematical research.
GPT-5 Codex
OpenAI1. Purpose-Built for Agentic Coding
- Optimized specifically for scenarios where the model must act as an autonomous or semi-autonomous coding agent.
- Tailored for Codex workflows such as planning, editing, debugging, and multi-step tool-driven code tasks.
2. Advanced Coding Reasoning
- Extends GPT-5's higher reasoning mode to better handle complex software logic and multi-file dependencies.
- Produces more accurate, structured, and maintainable code across modern programming languages.
3. Strong Tool Use in Developer-Like Environments
- Designed for Codex's agent environment, enabling the model to:
- Read and modify files
- Follow function signatures and API contracts
- Navigate codebases with awareness of context and structure
4. Large Context Window for Full-Project Understanding
- 400,000-token context allows ingestion of:
- Entire repositories
- Multiple files at once
- Architectural descriptions
- Enables long-range reasoning across codebases rather than isolated snippets.
5. Multimodal Capability for Development Tasks
- Accepts text and image as input (great for screenshots of error logs, UI mocks, whiteboards).
- Outputs text only, focusing its output precision on code, reasoning, and documentation.
6. Continuous Snapshot Updates
- The underlying model version is regularly upgraded behind the scenes.
- Ensures developers always use the best coding-enhanced GPT-5 variant without changing model names.
7. Reliable Instruction Following
- Very strong adherence to constraints like:
- File/folder structure requirements
- Framework conventions
- Naming patterns
- Linting rules
- Makes it suitable for production coding agents.
8. Broad API Integration
- Available only in the Responses API, giving you:
- Streaming
- Structured outputs
- Function calling
- Allows creation of interactive coding tools and agent workflows with tight model control.
Prompts to Get Started
Use these prompts to power AI products you build on Appaca. Each works great with the models above.
Best for GPT-5.5
textSocial Proof Compilation Post
Write a social post that compiles customer testimonials and results.
Cold Outreach Email Generator
Generate high-converting cold emails for sales, networking, or partnerships.
Competitor Analysis Framework
Analyse a competitor's marketing strategy across key dimensions.
Best for GPT-5 Codex
textNetworking Follow-Up Email
Write a follow-up email after a networking event or meeting. Keeps the conversation going and solidifies the connection.
Monitoring & Alerting Plan
Define a monitoring and alerting strategy for a service or application.
Instagram Product Caption
Write an engaging Instagram caption to promote a product with a call to action.