GPT-5.4 Across Platforms: ChatGPT, API, Codex Get Reasoning Upgrade
The new model rollout includes a Codex agent capable of filing personal taxes more accurately than humans.
OpenAI has rolled out GPT-5.4, a reasoning-focused upgrade, across its core platforms: ChatGPT, the developer API, and Codex. The most striking application highlighted is Codex's new capability to file personal taxes. By being granted access to a user's personal financial details, the AI can make superior assumptions about tax treatment, providing immediate feedback and reportedly achieving accuracy that surpasses that of a human accountant. This positions Codex not just as a coding assistant but as a potential agent for complex, high-stakes personal finance tasks.
This launch occurs within a highly competitive landscape. In early March 2026, Anthropic's Claude Opus 4.6 made waves by solving a complex open graph theory problem involving Hamiltonian cycles in a 3D directed graph—a problem that had stumped computer science pioneer Donald Knuth for weeks. Knuth called the achievement a "dramatic advance in automatic deduction." Meanwhile, former OpenAI CTO Mira Murati's startup, Thinking Machines Labs, secured a massive multiyear deal with Nvidia for at least a gigawatt of next-gen Vera Rubin compute, signaling her intent to build frontier models despite recent employee departures. The industry is also seeing consolidation, with Meta acquiring Moltbook, a Reddit-like network for AI agents built on the OpenClaw framework.
- GPT-5.4 delivers a reasoning upgrade across OpenAI's ChatGPT, API, and Codex platforms.
- Codex can now file personal taxes with high accuracy by accessing user details for better tax assumptions.
- The release follows Claude Opus 4.6's landmark solve of a complex graph theory problem that stumped Donald Knuth.
Why It Matters
AI is moving beyond chat and coding into high-stakes, expert domains like tax preparation, demanding new levels of accuracy and trust.