September 29, 2026
Codex can use third-party models: GLM-5.3 Flash and Kimi K3 for enterprise teams
On Sep 29, enterprise teams gained access to GLM-5.3 Flash and Kimi K3 in Codex. Their usage can count toward commitments to OpenAI. Codex is an AI coding agent, not a model or IDE.
Gergely Orosz
@gergelyorosz
It is precisely moves like these that make it feel as if OpenAI is pulling ahead of Anthropic. Anthropic has closed everything off: Claude Code is closed, you cannot use other models with Claude Code, and so on. OpenAI is the opposite: Codex is open source, and you can use other models. They have also made GLM-5.3 as simple as possible:
Philip Kiely @philipkiely
Enterprise teams can now use open models like GLM-5.3 Flash and Kimi K3 natively in Codex and count spend against their OpenAI commit.
· 2.1K views
Claude Code is closed to third-party models, in Gergely Orosz's assessment. In Codex, enterprise teams can connect GLM-5.3 Flash and Kimi K3 natively.
Codex is not open source: its CLI is proprietary.
Cost of entry. Codex has no free tier. As of Sep 26, Pro starts at $17 per month, Max: $100–200, Team: from $20 per seat.
As of Sep 26, Codex was available in 14 places: five surfaces and nine integrations.
