Migrate retired Grok models before May 15 2026

Effective May 15, 2026 at 12:00 PM PT, these model slugs retire from the xAI API:

• grok-4-1-fast-reasoning
• grok-4-1-fast-non-reasoning
• grok-4-fast-reasoning
• grok-4-fast-non-reasoning
• grok-4-0709
• grok-code-fast-1
• grok-3
• grok-imagine-image-pro

After that timestamp, those slugs continue to resolve and redirect automatically. Billing follows the redirect target — for most text slugs that means grok-4.3 pricing ($1.25 / 1M input, $2.50 / 1M output). Change the "model" field explicitly before May 15 so you pick reasoning effort and cost on purpose. Effort levels for grok-4.3: none, low, medium, high — see Set reasoning effort for the Responses / SDK shapes (reasoning.effort / reasoning_effort).

Redirect map

Retired slug	After May 15
grok-4-1-fast-reasoning	grok-4.3 with low effort
grok-4-1-fast-non-reasoning	grok-4.3 with none effort
grok-4-fast-reasoning	grok-4.3 with low effort
grok-4-fast-non-reasoning	grok-4.3 with none effort
grok-4-0709	grok-4.3 with low effort
grok-code-fast-1	grok-build-0.1
grok-3	grok-4.3 with none effort
grok-imagine-image-pro	grok-imagine-image-quality

grok-imagine-image-quality itself retires November 2, 2026 in favor of grok-imagine-image-2.0 — see Migrate from grok-imagine-image-quality.

Recommended one-line swaps

Code workloads — move grok-code-fast-1 to grok-build-0.1:

"model": "grok-build-0.1"

Reasoning workloads — move to grok-4.3 and set effort yourself (low matches the redirect; use medium or high when the job needs deeper reasoning):

# Chat Completions / shorthand field (grok-4.3)
response = client.chat.completions.create(
    model="grok-4.3",
    messages=[{"role": "user", "content": "Plan the migration steps."}],
    reasoning_effort="medium",
)

Non-reasoning workloads — grok-4.3 with none:

"model": "grok-4.3",
"reasoning": {"effort": "none"}

Pitfalls

• Keeping old slugs after May 15 and getting billed at grok-4.3 rates without noticing.
• Accepting the redirect's default low / none effort when your workload needs a different level.
• Stopping at grok-imagine-image-quality for Imagine — plan the Nov 2 move to grok-imagine-image-2.0 in the same pass.