Pick GPT-5.1 for adaptive reasoning that scales compute to task difficulty or general-purpose reasoning, coding and tool use. Pick Grok 4 for 256k context with native tool use or real-time data via x integration. On a tight budget at scale, GPT-5.1 is the value pick.
GPT-5.1 (OpenAI) and Grok 4 (xAI) are two of the models people most often weigh against each other in 2026. GPT-5.1 is openAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Grok 4 is xAI's 2M-context model with live data access and strong reasoning chops. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences
Price: GPT-5.1 is about 2.4× cheaper on input ($1.25/$10 per 1M tokens vs $3/$15 per 1M tokens) — meaningful once you are processing millions of tokens a month.
Context window: GPT-5.1 holds 1.6× more — 400K (~600 pages) vs 256K (~384 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
Recency: GPT-5.1 is the newer model by about 4 months (released November 13, 2025), usually meaning fresher training data and capabilities.
Specifications
Spec
GPT-5.1
Grok 4
Provider
OpenAI (US)
xAI (US)
Released
November 13, 2025
July 9, 2025
Context window
400K (~600 pages)
256K (~384 pages)
Price (in/out)
$1.25/$10 per 1M tokens
$3/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Adaptive reasoning that scales compute to task difficulty: GPT-5.1 — At $1.25/$10 per 1M tokens it undercuts Grok 4 ($3/$15 per 1M tokens), and that gap compounds at volume.
General-purpose reasoning, coding and tool use: GPT-5.1 — OpenAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line — and it runs cheaper at $1.25/$10 per 1M tokens.
A large ~400K context for long documents and sessions: GPT-5.1 — Its 400K window holds about 1.6× more than Grok 4's 256K in a single prompt.
256K context with native tool use: Grok 4 — GPT-5.1 is comparatively weak here — exact context window unconfirmed (400K vs 410K across trackers)
Real-time data via X integration: Grok 4 — Grok 4 lists real-time data via X integration among its strengths; GPT-5.1 does not.
Strong academic reasoning: Grok 4 — Grok 4 lists strong academic reasoning among its strengths; GPT-5.1 does not.
Lowest cost at scale: GPT-5.1 — At $1.25/$10 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input: GPT-5.1 — Its 400K window is about 1.6× larger than Grok 4's 256K, fitting roughly 600 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume: GPT-5.1 — At $1.25/$10 per 1M tokens it undercuts Grok 4, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases: GPT-5.1 — Larger 400K window fits more in one prompt.
Anyone whose priority is adaptive reasoning that scales compute to task difficulty: GPT-5.1 — It is specifically built for that.
Anyone whose priority is 256k context with native tool use: Grok 4 — That is its strongest area.
GPT-5.1: where it fits
OpenAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Released November 13, 2025 by OpenAI, it is built for adaptive reasoning that scales compute to task difficulty, general-purpose reasoning, coding and tool use, a large ~400K context for long documents and sessions, and text and image input.
Its trade-offs are real: superseded by GPT-5.2 through GPT-5.6 — kept for compatibility rather than being current, no reliably published SWE-Bench Verified figure, exact context window unconfirmed (400K vs 410K across trackers), and premium output price at $10/1M for a now-older model. At $1.25 in / $10 out per million tokens, it sits in the mid price band.
Grok 4: where it fits
XAI's 2M-context model with live data access and strong reasoning chops. Released July 9, 2025 by xAI, it is built for 256K context with native tool use, real-time data via X integration, strong academic reasoning, and no long-context surcharge.
Its trade-offs: smaller ecosystem than OpenAI/Google, and less independent benchmark coverage. At $3 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
GPT-5.1 and Grok 4 overlap enough that the right pick depends on your specific job. GPT-5.1 costs less per token; GPT-5.1 holds the larger context; and each leads in its own area — GPT-5.1 for adaptive reasoning that scales compute to task difficulty, Grok 4 for 256k context with native tool use. Rather than crowning one, run the same hard task through both once and let the results decide.
Frequently asked questions
Is GPT-5.1 or Grok 4 better for coding?
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.1 leans toward adaptive reasoning that scales compute to task difficulty while Grok 4 leans toward 256k context with native tool use, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.1 or Grok 4?
GPT-5.1 is cheaper — $1.25/$10 per 1M tokens vs $3/$15 per 1M tokens, roughly 2.4× apart on input.
Which has the bigger context window?
GPT-5.1 — 400K vs 256K, about 1.6× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both GPT-5.1 and Grok 4 together?
Yes — a multi-model platform like LumiChats gives you GPT-5.1, Grok 4 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, GPT-5.1 or Grok 4?
GPT-5.1 — released November 13, 2025, about 4 months after Grok 4.
GPT-5.1 vs Grok 4
OpenAI · US | xAI · US · Updated June 2026
Quick verdict
Pick GPT-5.1 for adaptive reasoning that scales compute to task difficulty or general-purpose reasoning, coding and tool use. Pick Grok 4 for 256k context with native tool use or real-time data via x integration. On a tight budget at scale, GPT-5.1 is the value pick.
GPT-5.1 (OpenAI) and Grok 4 (xAI) are two of the models people most often weigh against each other in 2026. GPT-5.1 is openAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Grok 4 is xAI's 2M-context model with live data access and strong reasoning chops. They diverge most on price and context window — each quantified below from the models' real specs.
Key differences at a glance
▸Price: GPT-5.1 is about 2.4× cheaper on input ($1.25/$10 per 1M tokens vs $3/$15 per 1M tokens) — meaningful once you are processing millions of tokens a month.
▸Context window: GPT-5.1 holds 1.6× more — 400K (~600 pages) vs 256K (~384 pages). But effective recall usually fades long before the advertised ceiling, so the bigger number only helps if the model reasons over it.
▸Recency: GPT-5.1 is the newer model by about 4 months (released November 13, 2025), usually meaning fresher training data and capabilities.
Side-by-side specs
Spec
GPT-5.1
Grok 4
Provider
OpenAI (US)
xAI (US)
Released
November 13, 2025
July 9, 2025
Context window
400K (~600 pages)
256K (~384 pages)
Price (in/out)
$1.25/$10 per 1M tokens
$3/$15 per 1M tokens
Open weight?
No — API only
No — API only
Modalities
text, image, code
text, image, code
SWE-Bench Verified
Not published
Not published
MRCR v2 @ 1M
Not published
Not published
Who wins what
Adaptive reasoning that scales compute to task difficulty
GPT-5.1
At $1.25/$10 per 1M tokens it undercuts Grok 4 ($3/$15 per 1M tokens), and that gap compounds at volume.
General-purpose reasoning, coding and tool use
GPT-5.1
OpenAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line — and it runs cheaper at $1.25/$10 per 1M tokens.
A large ~400K context for long documents and sessions
GPT-5.1
Its 400K window holds about 1.6× more than Grok 4's 256K in a single prompt.
256K context with native tool use
Grok 4
GPT-5.1 is comparatively weak here — exact context window unconfirmed (400K vs 410K across trackers)
Real-time data via X integration
Grok 4
Grok 4 lists real-time data via X integration among its strengths; GPT-5.1 does not.
Strong academic reasoning
Grok 4
Grok 4 lists strong academic reasoning among its strengths; GPT-5.1 does not.
Lowest cost at scale
GPT-5.1
At $1.25/$10 per 1M tokens, it is the cheaper of the two — the gap dominates the bill on high-volume workloads.
Largest single-prompt input
GPT-5.1
Its 400K window is about 1.6× larger than Grok 4's 256K, fitting roughly 600 pages in one prompt.
Which should you pick?
A cost-sensitive startup shipping high volume
→ GPT-5.1
At $1.25/$10 per 1M tokens it undercuts Grok 4, and on millions of tokens that margin decides the monthly bill.
Someone analysing very long documents or codebases
→ GPT-5.1
Larger 400K window fits more in one prompt.
Anyone whose priority is adaptive reasoning that scales compute to task difficulty
→ GPT-5.1
It is specifically built for that.
Anyone whose priority is 256k context with native tool use
→ Grok 4
That is its strongest area.
GPT-5.1: where it fits
OpenAI's late-2025 GPT-5.1 at $1.25/$10 — a capable general model since surpassed by the GPT-5.2–5.6 line. Released November 13, 2025 by OpenAI, it is built for adaptive reasoning that scales compute to task difficulty, general-purpose reasoning, coding and tool use, a large ~400K context for long documents and sessions, and text and image input.
Its trade-offs are real: superseded by GPT-5.2 through GPT-5.6 — kept for compatibility rather than being current, no reliably published SWE-Bench Verified figure, exact context window unconfirmed (400K vs 410K across trackers), and premium output price at $10/1M for a now-older model. At $1.25 in / $10 out per million tokens, it sits in the mid price band.
Grok 4: where it fits
XAI's 2M-context model with live data access and strong reasoning chops. Released July 9, 2025 by xAI, it is built for 256K context with native tool use, real-time data via X integration, strong academic reasoning, and no long-context surcharge.
Its trade-offs: smaller ecosystem than OpenAI/Google, and less independent benchmark coverage. At $3 in / $15 out per million tokens, it sits in the mid price band.
The bottom line for this matchup
GPT-5.1 and Grok 4 overlap enough that the right pick depends on your specific job. GPT-5.1 costs less per token; GPT-5.1 holds the larger context; and each leads in its own area — GPT-5.1 for adaptive reasoning that scales compute to task difficulty, Grok 4 for 256k context with native tool use. Rather than crowning one, run the same hard task through both once and let the results decide.
Want both GPT-5.1 and Grok 4 without two subscriptions? LumiChats gives you these plus 40+ models under one ₹69/day pass (about $1/day) — draft with one, cross-check with the other.
Public SWE-Bench figures are not available for either model, so the honest test is your own repository — run an identical real bug through both. By design, GPT-5.1 leans toward adaptive reasoning that scales compute to task difficulty while Grok 4 leans toward 256k context with native tool use, and that positioning usually predicts which feels better on your codebase.
Which is cheaper, GPT-5.1 or Grok 4?
GPT-5.1 is cheaper — $1.25/$10 per 1M tokens vs $3/$15 per 1M tokens, roughly 2.4× apart on input.
Which has the bigger context window?
GPT-5.1 — 400K vs 256K, about 1.6× larger. Useful only if the model actually reasons over the full window, which not all do.
Can I use both GPT-5.1 and Grok 4 together?
Yes — a multi-model platform like LumiChats gives you GPT-5.1, Grok 4 and 40+ others under one ₹69/day pass (about $1/day), so you can draft with one and cross-check with the other instead of buying two subscriptions.
Which is newer, GPT-5.1 or Grok 4?
GPT-5.1 — released November 13, 2025, about 4 months after Grok 4.
Specifications and benchmarks reflect publicly reported figures as of June 2026 and may change as providers release updates. Always verify on your own workload.