GPT-5.1 Codex vs GPT-4o Audio
Compare pricing, context windows, and strengths for GPT-5.1 Codex by OpenAI and GPT-4o Audio by OpenAI - and see how to put either to work in Appaca.
GPT-5.1 Codex
Version of GPT-5.1 optimized for agentic coding inside Codex and similar environments, with strong reasoning and multimodal support.
View GPT-5.1 CodexGPT-4o Audio
Preview multimodal model that accepts and outputs audio, optimized for natural voice interactions and real-time conversational experiences.
View GPT-4o AudioGPT-5.1 Codex vs GPT-4o Audio at a glance
Specs and pricing side by side, from the Appaca AI models directory.
| Spec | GPT-5.1 Codex | GPT-4o Audio |
|---|---|---|
| Provider | OpenAI | OpenAI |
| Model type | Text | Audio |
| Context window | 400K tokens | 128K tokens |
| Input price | $1.25 / 1M tokens | $2.5 / 1M tokens |
| Output price | $10 / 1M tokens | $10 / 1M tokens |
| Audio input price | - | $40 / 1M tokens |
| Audio output price | - | $80 / 1M tokens |
| Status | Superseded by GPT-5.2 Codex | Current |
How GPT-5.1 Codex and GPT-4o Audio differ
What the numbers mean in practice when choosing between GPT-5.1 Codex and GPT-4o Audio.
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GPT-5.1 Codex is 50% cheaper on input tokens ($1.25 vs $2.5 per million), which adds up quickly in document-heavy workloads.
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GPT-5.1 Codex's 400K tokens context window is roughly 3.1x larger than GPT-4o Audio's 128K tokens, so it can work across bigger codebases, contracts, or archives in one pass.
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These are different kinds of model: GPT-5.1 Codex is a text model while GPT-4o Audio is an audio model, so they often complement each other in a workflow rather than compete.
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GPT-5.1 Codex has been superseded by GPT-5.2 Codex - for new builds, consider the newer model first.
Strengths side by side
Where each model shines, according to benchmarks and provider positioning.
GPT-5.1 Codex
1. Purpose-Built for Agentic Coding
- Designed specifically for environments where the model acts as an autonomous or semi-autonomous coding agent.
- Optimized for multi-step reasoning in code tasks such as planning, refactoring, debugging, file generation, and tool coordination.
2. Enhanced Coding Intelligence
- Extends GPT-5.1's advanced reasoning capabilities to handle complex software architecture decisions.
- Better accuracy in code generation across languages (JavaScript, Python, TypeScript, Go, Rust, etc.).
- Produces cleaner, more idiomatic code aligned with modern frameworks and best practices.
3. Superior Tool Use & Code Navigation
- Excels at reading, understanding, and transforming multi-file codebases.
- Works well with Codex workflows that simulate real developer tooling.
- Strong at following function signatures, constraints, and code patterns within an existing project.
4. Long-Range Context Awareness
- 400,000-token context window enables the model to ingest large repositories or multiple files simultaneously.
- Supports deep analysis of project structures, dependencies, and cross-file logic.
5. Multi-Modal Development Capabilities
- Accepts text + image input and output - suitable for tasks like:
- Reading UI mockups or screenshots to generate code
- Understanding architectural diagrams
- Reviewing images of whiteboard sessions
6. Agentic Workflow Optimization
- Built to manage longer chains of thought and execution typically required in:
- Automated code repair
- Project bootstrapping
- Linting and migration tasks
- Long-running coding agents using planning + execution loops
7. Continually Updated Model Snapshot
- Codex-specific version receives regular upgrades behind the scenes.
- Ensures the latest coding improvements without requiring developers to update model names.
8. Reliable Instruction Following
- Highly consistent in honoring explicit constraints:
- Code styles
- Folder structures
- API contracts
- Framework conventions
9. Broad API Support
- Works across Chat Completions, Responses API, Realtime, Assistants, and more.
- Ideal for apps that need live, reasoning-heavy coding agents or generative dev environments.
GPT-4o Audio
1. True multimodal audio model
- Accepts raw audio as input and produces audio or text as output.
- Enables hands-free, voice-first app experiences.
2. Natural real-time speech interaction
- Low-latency audio generation suitable for conversational agents.
- Great for voice assistants, phone bots, and interactive voice UI.
3. Large 128K context window
- Supports long conversations, call transcripts, instructions, or multi-part interactions.
- Ideal for building persistent voice agents or phone workflows.
4. High-output capacity
- Up to 16,384 max output tokens for extended responses or long explanations.
- Suitable for complex reasoning tasks in voice format.
5. Hybrid text + audio workloads
- Combine audio input/output with text prompts, instructions, or structured control.
- Useful for customer support bots, spoken form systems, IVR replacements, etc.
6. Compatible with the latest APIs
- Works with Chat Completions, Responses API, Realtime API, and Assistants.
- Supports streaming, function calling, and advanced developer tooling.
7. Strong performance for a preview model
- High reasoning and expression abilities relative to most audio-capable models.
- Designed for production-style experimentation prior to full release.
8. Ideal for next-gen voice applications
- Build lifelike AI agents, interview bots, tutoring systems, and spoken knowledge tools.
- Perfect for startups building audio-first user experiences.
Use GPT-5.1 Codex or GPT-4o Audio - or both
Appaca is the AI workspace for operators. Build internal tools and AI co-workers powered by GPT-5.1 Codex or GPT-4o Audio - connected to your real data and ready for your whole team. No code, no deployment.
Describe it, and it's built
Tell the Appaca agent the internal tool you need and it builds a working app powered by GPT-5.1 Codex or GPT-4o Audio. No code, no API keys, no deployment.
Switch models without rebuilding
Start on GPT-5.1 Codex, test the same tool on GPT-4o Audio, and keep whichever performs better - the rest of your app stays exactly as it is.
Automated for the whole team
Schedule tools to run on autopilot - daily digests, weekly reports, real-time triggers - and share them with your whole team from one workspace.
Describe it, and it's built
Tell the Appaca agent what your team needs and it builds a working app powered by GPT-5.1 Codex or GPT-4o Audio - connected to the tools you already use.
Related comparisons
See how GPT-5.1 Codex and GPT-4o Audio stack up against other models in the directory.
FAQs
GPT-5.1 Codex is generally cheaper: $1.25 input / $10 output per million tokens, versus $2.5 / $10 for GPT-4o Audio. Actual cost depends on how many tokens your workload reads and writes.
GPT-5.1 Codex has the larger context window at 400K tokens, compared to 128K tokens for GPT-4o Audio. A larger window means the model can consider more text at once - useful for long contracts, codebases, or months of records.
It depends on the job. Compare the pricing, context window, and strengths above against your workload - and remember the choice isn't permanent. In Appaca you can build a tool on GPT-5.1 Codex, test the same tool on GPT-4o Audio, and switch at any time without rebuilding anything.
Yes. Appaca is a no-code AI workspace: describe the internal tool your team needs and the Appaca agent builds it as a working app powered by GPT-5.1 Codex, GPT-4o Audio, or any other model in the directory - with a built-in database, team access, and integrations. No API keys to wire up and nothing to deploy.
Build AI tools with GPT-5.1 Codex or GPT-4o Audio
Describe the tool your team needs and get a working app powered by the model you choose - with a built-in database, team access, and integrations. No code, no deployment.