AI / Core OpenAI Codex Application Fundamentals Interview Questions
What are the current recommended models for OpenAI Codex and the API, and when do you choose each?
Model selection in the OpenAI / Codex ecosystem as of mid-2026 centres on the GPT-5.x family. The right choice depends on task complexity, latency requirements, and cost.
| Model | Best for | Context window | Key capability |
|---|---|---|---|
| gpt-5.5 | API-based code generation and general agentic tasks | Large | Strongest for complex coding, reasoning, and professional workflows |
| gpt-5.4 | Codex app/CLI default - most tasks | 1M (experimental) | Native computer use, complex tool use, long-horizon tasks |
| gpt-5.4-mini | Faster, lower-cost option for lighter tasks or subagents | Standard | Speed and cost efficiency |
| gpt-5.3-codex | Maximum agentic coding capability, complex real-world SE | Standard | 25% faster than predecessor; strongest coding + reasoning fusion |
| gpt-5.3-codex-spark | Near-instant coding iteration (research preview, Pro only) | 128k tokens | 1000+ tokens/second; text-only at launch; powered by Cerebras |
| codex-mini-latest | CLI optimised, low-latency code Q&A | Standard | Priced $1.50/1M input, $6/1M output via Responses API |
Key guidance:
- For API-based code generation: start with
gpt-5.5 - For Codex app/CLI most tasks:
gpt-5.4is the default - For maximum agentic coding power:
gpt-5.3-codex - For speed and lower cost:
gpt-5.4-miniorcodex-mini-latest
Note: gpt-5.2-codex and gpt-5.3-codex (when accessed via ChatGPT sign-in) are deprecated in the Codex surfaces - update references to current models.
Invest now in Acorns!!! 🚀
Join Acorns and get your $5 bonus!
Acorns is a micro-investing app that automatically invests your "spare change" from daily purchases into diversified, expert-built portfolios of ETFs. It is designed for beginners, allowing you to start investing with as little as $5. The service automates saving and investing. Disclosure: I may receive a referral bonus.
Invest now!!! Get Free equity stock (US, UK only)!
Use Robinhood app to invest in stocks. It is safe and secure. Use the Referral link to claim your free stock when you sign up!.
The Robinhood app makes it easy to trade stocks, crypto and more.
Webull! Receive free stock by signing up using the link: Webull signup.
More Related questions...
