Models · OpenAI · Out sinceReleased 24 Feb 2026

GPT-5.3-Codex

Available on OpenRouterOn OpenRouterAvailable nowGenerally availableClosed (can't be downloaded)Proprietary

GPT-5.3-Codex is made by OpenAI. We don't have enough test results yet to rank it. It's mid-priced to use.

Auto-created from OpenRouter catalog; verify details.

Writing & creativity: —
Research & analysis: —
Coding: —
Price: Mid-priced$1.75 / $14
Price per 1M (blended)Blended / 1M: $4.81
MemoryContext: 400K
Longest answerMax output: —
Test resultsResults: 8 (8 independent8 indep.)
Out sinceReleased: 24 Feb 2026
Made byVendor: OpenAI
UnderstandsInputs: —

Scores are out of 100 for each area, compared with every model we track; “#” is its rank. Context is how much text it can read at once (1M is roughly 700,000 words). Blended price mixes the cost of what you send and what it writes back.

Thinking levels

Reasoning settings

You can't choose how long this one thinks.

No adjustable reasoning setting listed.

Links

Using it through OpenRouter

On OpenRouter

OpenRouter is a service that gives access to many AI models in one place. This model is listed there as openai/gpt-5.3-codex.

Route it as openai/gpt-5.3-codex at $1.75 in / $14 out per 1M tokens, 400K context. Listed since 24 Feb 2026.

include_reasoningmax_completion_tokensmax_tokensreasoningreasoning_effortresponse_formatseedstructured_outputstool_choicetools

Every test result

Every result

All the numbers,with where they came from.

Every result we've found for this model, with who measured it and a link to where we read it.

All raw rows (vendor and independent kept separate), with setting label, source, date, harness and notes.

All results for this model
						NotesNotes
Epoch Capabilities Index	156.8	Default	Independent testIndependentEpoch AI ↗	1 Oct 2026	—	Epoch Capabilities Index; 90% CI 153.5-160.8; best of listed model versions
IOI (Vals)	53.8%	Extra highreasoning_effort=xhigh	Independent testIndependentVals.ai ↗	29 Sep 2026	—	±6.312 stderr; $2.681/test
LiveCodeBench	87.3%	Extra highreasoning_effort=xhigh	Independent testIndependentVals.ai ↗	1 Sep 2026	—	±0.968 stderr; $0.092/test
METR 50% time horizon	5.8 h	Default	Independent testIndependentMETR ↗	8 May 2026	METR react agent (Inspect)	50% time horizon, METR-Horizon-v1.1; 95% CI 195-816 min; 80% horizon 54.7 min; release 2026-02-05; raw data https://metr.org/assets/benchmark_results_1_1.yaml
SWE Atlas - Codebase QnA	32.6%	Extra highGPT 5.3 (Codex) xHigh	Independent testIndependentScale AI SEAL ↗	1 Oct 2026	Codex	rank 7 (Scale rank accounts for CI); ±4.9; entry added 2026-02-25
SWE Atlas - Refactoring	42.4%	Extra highGPT 5.3 (Codex) xHigh	Independent testIndependentScale AI SEAL ↗	1 Oct 2026	Codex	rank 9 (Scale rank accounts for CI); ±6.76; entry added 2026-05-06
SWE Atlas - Test Writing	39.0%	Extra highGPT 5.3 (Codex) xHigh	Independent testIndependentScale AI SEAL ↗	1 Oct 2026	Codex	rank 2 (Scale rank accounts for CI); ±6.12; entry added 2026-03-26
SWE-bench Verified	74.8%	Highgpt-5.3-codex_high	Independent testIndependentEpoch AI ↗	25 Feb 2026	—	Epoch-run SWE-bench Verified (Epoch scaffold); no runs after 2026-06; stderr 2.0pt; data https://epoch.ai/data/benchmark_data.zip (swe_bench_verified.csv)