What is OpenAI Codex?

OpenAI Codex is a cloud-based autonomous coding agent that runs in a sandboxed environment. Built on GPT-5.3-Codex, it can read codebases, write and edit code across multiple files, run tests, and submit pull requests from natural language task descriptions. Codex operates asynchronously, handling tasks in parallel while developers focus on other work.

The product is available through ChatGPT subscriptions (Plus at $20/month, Pro at $200/month) and via the API using codex-mini-latest at $1.50/1M input tokens and $6.00/1M output tokens. Codex supports both cloud sandbox and local terminal execution modes.

OpenAI was founded in 2015 and is headquartered in San Francisco. The company is valued at approximately $500-730B and is preparing for an IPO that could value it at up to $1 trillion.

Pros & Cons

Pros

+Runs tasks autonomously in parallel in sandboxed environments
+Strong multi-file editing and codebase-level reasoning
+Vision capabilities for interpreting screenshots and UI mocks
+Available via ChatGPT subscription and API
+GPT-5.3-Codex is the most capable agentic coding model

Cons

-Still fails 43% of professional-level tasks
-Cannot access the internet for dependency resolution
-Requires 3-5 iterations on average for error-free output
-Desktop app limited to macOS with usage caps

OpenAI Codex Pricing

Free trial available

ChatGPT Plus$20/month

✓30-150 Codex tasks per 5 hours
✓Cloud sandbox execution
✓PR creation and code review

ChatGPT Pro$200/month

✓300-1,500 tasks per 5 hours
✓Higher rate limits
✓Priority access

API (codex-mini-latest)$1.50/1M input, $6.00/1M output

✓75% prompt caching discount
✓Responses API access
✓Programmatic integration

EnterpriseCustom

✓SCIM, EKM, user analytics
✓Custom data retention
✓No training on business data

View official pricing page

Using OpenAI Codex with Respan

Respan provides observability for AI-generated code workflows powered by OpenAI Codex. Teams can monitor code quality, track task completion rates, and evaluate the accuracy of Codex-generated changes before they reach production.