GPT-5.3 Codex
Most capable agentic coding model to date, optimized for long-horizon software engineering tasks with configurable reasoning and multimodal input.
GPT-5.3 Codex at a glance
Context window
400K tokens
Input price
$1.75
per 1M tokens
Output price
$14
per 1M tokens
Why use GPT-5.3 Codex
Strengths, benchmarks, and where GPT-5.3 Codex fits in your team's workflow.
1. Strongest Codex Model for Agentic Engineering
- OpenAI positions GPT-5.3 Codex as its most capable agentic coding model to date.
- Built for long-horizon software engineering tasks that require planning, iteration, and reliable code transformation across files.
2. Configurable Reasoning + Multimodal Input
- Supports configurable reasoning effort from low to xhigh so teams can trade off depth against latency.
- Accepts both text and image inputs while producing text output.
3. Large Context for Real Codebases
- 400 k token context window helps it work across larger repositories, implementation plans, and supporting documentation.
- Allows up to 128 k output tokens for longer code generations, patches, and technical write-ups.
4. Current Knowledge for Modern Dev Workflows
- Knowledge cut-off of Aug 31 2025 keeps it aligned with newer frameworks, libraries, and tooling.
- Supports streaming, function calling, and structured outputs for agent-style coding workflows.
Power your team with GPT-5.3 Codex
Appaca is the AI workspace for operators. Build internal tools and AI co-workers powered by GPT-5.3 Codex - connected to your real data and ready for your whole team. No code, no deployment.
Build internal AI tools
Describe what you need and the Appaca agent builds it - lead scorers, report generators, email drafters - with GPT-5.3 Codex as the engine. No code, no deployment.
Give GPT-5.3 Codex your real data
Connect the tools your team already uses - Slack, Notion, Google Sheets, Airtable, and more - so GPT-5.3 Codex works with real context, not generic answers.
Automate recurring tasks
Schedule GPT-5.3 Codex to run on autopilot - daily digests, weekly summaries, or real-time triggers - all managed inside your Appaca workspace.
Describe it, and it's built
Tell the Appaca agent what your team needs and it builds a working app powered by GPT-5.3 Codex - connected to the tools you already use.
Where teams use GPT-5.3 Codex
See how teams put GPT-5.3 Codex to work inside Appaca - internal tools and AI agents that work around you.
Sales
Score leads, draft follow-ups, and summarise deals with GPT-5.3 Codex doing the heavy lifting.
Explore Appaca for SalesMarketing
Draft, repurpose, and report on campaigns in your brand voice - powered by GPT-5.3 Codex.
Explore Appaca for MarketingOperations
Automate reporting, vendor tracking, and process docs with AI built around your workflow.
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Build internal AI tools with GPT-5.3 Codex
Describe the tool your team needs and get a working app powered by GPT-5.3 Codex - with a built-in database, team access, and integrations. No code, no deployment.