Atlas / xAI / Grok 4 Fast (Reasoning)

Grok 4 Fast (Reasoning)

Fast reasoning variant of Grok 4. Optimized for speed while maintaining reasoning capabilities.

Active Reasoning Tools

Current pricing

Input

$0.20

Output

$0.50

per 1M tokens Source ↗

Specifications

Context window

131.1K tokens

Max output

16.4K tokens

Knowledge cutoff

Jul 2025

Capabilities

✓ Function calling / Tools

✗ Image understanding

✓ Extended thinking / Reasoning

✗ Audio input/output

TierUnitInputCached inputOutputEffectiveSource

Standard Per 1M tokens $0.20 — $0.50 March 12, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 11, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 10, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 9, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 8, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 7, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 6, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 March 1, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Feb. 22, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Feb. 15, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Feb. 8, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Feb. 1, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Jan. 25, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Jan. 11, 2026 Source

Standard Per 1M tokens $0.20 — $0.50 Jan. 10, 2026 Source