[API (us-east-1.api.x.ai)] grok-4-fast-reasoning and grok-4-fast-non-reasoning context size limitation

Status: ACTIVE

Severity: disruption

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Updates:

Mon, 02 Feb 2026 17:37:35 GMT

Investigating

We are currently seeing issues on requests where context length is over 120k tokens. Currently investigating root cause.

via xAI System Status