Coding
Directional only- GPT-5.3 Codex
- 67.2
- Grok Code Fast 1
- 70.8
- Weighted basis
- 3 vs 1 rows
- Reading
- Directional only
GPT-5.3 Codex vs Grok Code Fast 1
Updated September 3, 2026. Public scores include evidence status and uncertainty. They are not guarantees for a specific workload.
Decision reading
GPT-5.3 Codex has the higher public score, 65.52 versus 37.81, and the 90% score intervals do not overlap.
1 results are shared. Category rows based on different benchmark sets are marked directional and do not name a winner.
Which one for your work
Recommendations appear only when a shared evidence basis or an explicit operating constraint supports the call. Secondary and unsupported use cases stay disclosed below the initial list.
Long documents
Prompts that approach the documented context limit
GPT-5.3 Codex
GPT-5.3 Codex has the larger documented context window.
Confidence: documented
Chat turn cost
1K fresh input + 500 output tokens
Grok Code Fast 1
Grok Code Fast 1 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.
Confidence: listed-rates
Cache-heavy agent loop cost
200K cached + 20K fresh input + 10K output tokens
Grok Code Fast 1
Grok Code Fast 1 has the lower estimated token cost for this stated workload. GPT-5.3 Codex has no published cached-input rate, so cached tokens use its listed input rate. Grok Code Fast 1 has no published cached-input rate, so cached tokens use its listed input rate.
Confidence: rate-fallback
Show secondary and unsupported calls
Repository review cost
50K fresh input + 3K output tokens
Grok Code Fast 1
Grok Code Fast 1 has the lower estimated token cost for this stated workload. Costs use the listed standard API rates.
Confidence: listed-rates
Coding work
Code generation, repair, and software-engineering tasks
Not enough matched evidence
The category averages use different weighted benchmark sets, so they are directional rather than like-for-like.
Confidence: limited
Agentic work
Tool use, computer use, and multi-step task completion
Not enough matched evidence
No shared weighted benchmark basis supports a winner.
Confidence: limited
What is actually comparable
Shared results can support a head-to-head reading. Results present for only one model describe coverage, not superiority.
7 GPT-5.3 Codex only
1 Shared
- Shared results
- 1
- GPT-5.3 Codex only
- 7
- Grok Code Fast 1 only
- 0
- Like-for-like categories
- 0 / 8
1 category uses different evidence sets. Those rows remain visible for coverage context but do not name a winner.
Category results, on a stated basis
Each row states whether both averages use the same weighted benchmark set. Directional and not-comparable rows remain visible, but they never receive a winner in this template.
Agentic
Not comparable- GPT-5.3 Codex
- 71.4
- Grok Code Fast 1
- Not measured
- Weighted basis
- 2 vs 0 rows
- Reading
- Not comparable
Reasoning
Not comparable- GPT-5.3 Codex
- Not measured
- Grok Code Fast 1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Knowledge
Not comparable- GPT-5.3 Codex
- Not measured
- Grok Code Fast 1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Math
Not comparable- GPT-5.3 Codex
- Not measured
- Grok Code Fast 1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Multilingual
Not comparable- GPT-5.3 Codex
- Not measured
- Grok Code Fast 1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Multimodal
Not comparable- GPT-5.3 Codex
- Not measured
- Grok Code Fast 1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
Instruction following
Not comparable- GPT-5.3 Codex
- Not measured
- Grok Code Fast 1
- Not measured
- Weighted basis
- 0 vs 0 rows
- Reading
- Not comparable
| Category | GPT-5.3 Codex | Grok Code Fast 1 | Weighted basis | Reading |
|---|---|---|---|---|
| Coding | 67.2 | 70.8 | Directional only3 vs 1 rows | Directional only |
| Agentic | 71.4 | Not measured | Not comparable2 vs 0 rows | Not comparable |
| Reasoning | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Knowledge | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Math | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Multilingual | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Multimodal | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
| Instruction following | Not measured | Not measured | Not comparable0 vs 0 rows | Not comparable |
Shape of the matched evidence
Only shared public evidence is shown. Sparse evidence stays a ruled list rather than being closed into a radar shape.
Too few matched category axes support a radar. The ruled list below shows only shared benchmark results; positions use each benchmark’s normalized display scale when available.
SWE-bench Verified
Coding
GPT-5.3 Codex: 85%Grok Code Fast 1: 70.8%Normalized gap 14.2GPT-5.3 Codex source Grok Code Fast 1 source
What each workload costs
Three fixed token mixes turn per-token rates into comparable decisions. Each scenario states context fit and whether cached input had to fall back to the published list-input rate.
Chat turn
1K fresh input + 500 output tokens
- GPT-5.3 Codex
- $0.00875
- Fits in one request
- Grok Code Fast 1
- $0.00095
- Fits in one request
Grok Code Fast 1 has the lower modeled cost
Costs use the listed standard API rates.
Repository review
50K fresh input + 3K output tokens
- GPT-5.3 Codex
- $0.1295
- Fits in one request
- Grok Code Fast 1
- $0.0145
- Fits in one request
Grok Code Fast 1 has the lower modeled cost
Costs use the listed standard API rates.
Cache-heavy agent loop
200K cached + 20K fresh input + 10K output tokens
- GPT-5.3 Codex
- $0.525
- Fits in one request
- Cached input priced at the published list-input rate
- Grok Code Fast 1
- $0.059
- Fits in one request
- Cached input priced at the published list-input rate
Grok Code Fast 1 has the lower modeled cost
GPT-5.3 Codex has no published cached-input rate, so cached tokens use its listed input rate. Grok Code Fast 1 has no published cached-input rate, so cached tokens use its listed input rate.
Specification differences
Sourced differences are shown directly. Missing facts stay explicit instead of being inferred from a model name or family.
SpecificationGPT-5.3 CodexGrok Code Fast 1
Context window
Maximum documented context; output-token limits may be lower.
GPT-5.3 Codex
Grok Code Fast 1
256K
API model ID
GPT-5.3 Codex
gpt-5.3-codex
OpenAI GPT-5.3 Codex model documentationGrok Code Fast 1
Not sourced
Cached-input rate
A missing cached-input rate falls back to the listed input rate only in the stated workload estimate.
GPT-5.3 Codex
Not published
Grok Code Fast 1
Not published
Documented inputs
GPT-5.3 Codex
text, image
OpenAI model catalogGrok Code Fast 1
Not sourced
Documented outputs
GPT-5.3 Codex
Grok Code Fast 1
Not sourced
Provider availability
GPT-5.3 Codex
Generally Available · OpenAI Responses API
OpenAI model catalogGrok Code Fast 1
Not sourced
Reasoning profile
GPT-5.3 Codex
Reasoning
Grok Code Fast 1
Non-Reasoning
Weight access
GPT-5.3 Codex
Proprietary
Grok Code Fast 1
Proprietary
License
GPT-5.3 Codex
Proprietary
Grok Code Fast 1
Proprietary
Release date
GPT-5.3 Codex
2026-02-05
Grok Code Fast 1
2025-08-28
If you already use one of these models
- Deployment change
- The models list different providers, so authentication, endpoint behavior, limits, and feature support may change.
- Quality signal
- GPT-5.3 Codex has the higher public score, 65.52 versus 37.81, and the 90% score intervals do not overlap.
- Workload cost
- Repository review: $0.1295 vs $0.0145. Cache-heavy agent loop: $0.525 vs $0.059.
- Context tradeoff
- GPT-5.3 Codex has the larger documented window (400K).
Run the same representative tasks against both endpoints before changing production traffic.
Benchmark evidence
The full public result ledger is available for audit without forcing a wide desktop table onto a phone.
Browse raw public benchmark evidence8 rows
Agentic
Terminal-Bench 2.0
GPT-5.3 Codex77.3%SourceGrok Code Fast 1—Not directly comparable
OSWorld-Verified
GPT-5.3 Codex64.7%SourceGrok Code Fast 1—Not directly comparable
Gert Labs
GPT-5.3 Codex57.47%SourceGrok Code Fast 1—Not directly comparable
JobBench
GPT-5.3 Codex33.7%SourceGrok Code Fast 1—Not directly comparable
Coding
SWE-bench Verified
GPT-5.3 Codex85%SourceGrok Code Fast 170.8%SourceGPT-5.3 Codex leads this result
SWE-bench Pro
GPT-5.3 Codex56.8%SourceGrok Code Fast 1—Not directly comparable
SWE-Rebench
GPT-5.3 Codex58.2%SourceGrok Code Fast 1—Not directly comparable
Vibe Code Bench
GPT-5.3 Codex61.77%SourceGrok Code Fast 1—Not directly comparable
Frequently asked questions
Which is better, GPT-5.3 Codex or Grok Code Fast 1?
GPT-5.3 Codex has the higher public score, 65.52 versus 37.81, and the 90% score intervals do not overlap. That is the clearest overall quality signal in the current public data.
Which is better for coding, GPT-5.3 Codex or Grok Code Fast 1?
The current coding averages use different weighted benchmark sets, so BenchLM does not name a winner from them. Read the shared benchmark rows directly and test the models on the same task set.
Which is better for agentic tasks, GPT-5.3 Codex or Grok Code Fast 1?
The published evidence does not provide a shared weighted agentic tasks basis for both models, so BenchLM does not name a agentic tasks winner.
Which costs less, GPT-5.3 Codex or Grok Code Fast 1?
For the stated presets, chat costs $0.00875 on GPT-5.3 Codex and $0.00095 on Grok Code Fast 1; repository review costs $0.1295 and $0.0145; the cache-heavy agent loop costs $0.525 and $0.059. GPT-5.3 Codex has no published cached-input rate, so cached tokens use its listed input rate. Grok Code Fast 1 has no published cached-input rate, so cached tokens use its listed input rate.
Which has the larger context window, GPT-5.3 Codex or Grok Code Fast 1?
GPT-5.3 Codex has the larger documented context window: 400K, compared with 256K.
Related comparisons
Last updated September 3, 2026
Watch GPT-5.3 Codex vs Grok Code Fast 1
One weekly email when material rank, price, or benchmark evidence changes make this matchup worth revisiting.
Read a sample issueJoin 2,000+ readers.