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April 2026 Platform Updates

🚨 2026 Critical Updates 15 min 400 BASE XP

What's New in April 2026

Codex Agent

OpenAI expanded Codex from a code-generation model into a full autonomous coding agent. Available in ChatGPT, it can work with files, terminals, and apps via "background computer use" — operating alongside the user on macOS.

GPT-5.4 Family GA

The GPT-5.4 family is now the recommended default for all API usage:

  • gpt-5.4 — Balanced flagship (replaces GPT-4o)
  • gpt-5.4-mini — Cost-effective (replaces GPT-4o-mini)
  • gpt-5.4-nano — Ultra-lightweight edge model

Agents SDK v0.14+

April 2026 updates introduced native sandbox execution, harness/compute separation, and standardized MCP integration into the Agents SDK.

Model Deprecation Timeline

ModelStatusAction Required
GPT-4o⚠️ Maintenance modeMigrate to gpt-5.4
GPT-4o-mini⚠️ Maintenance modeMigrate to gpt-5.4-mini
o1, o3-mini⚠️ LegacyMigrate to gpt-5.4 with reasoning
Assistants API⚠️ No new featuresMigrate to Responses API
DALL-E 3⚠️ LegacyMigrate to GPT Image 2
🚨 Action Required: If you're using GPT-4o, o1, or the Assistants API, plan your migration now. These APIs will enter deprecation cycles as GPT-5.4 and Responses API become the standard.
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What has Codex evolved into in April 2026?
A code completion tool
A full autonomous coding agent that works with files, terminals, and apps
A database
A testing framework
Watch: 139x Rust Speedup
April 2026 Platform Updates | 2026 Critical Updates — OpenAI Academy