GPT-5.3-Codex

vgpt-5-3-codex-2026-02-05

OpenAI

Modelcodingagenticcodexspecialist

Strong

About This Model

OpenAI's agentic coding specialist: ~80% SWE-bench Verified, 77.3% Terminal-Bench, SOTA on SWE-Bench Pro at release, ~25% faster than GPT-5.2-Codex. The 5.3 generation was Codex-only — there is no general-purpose GPT-5.3.

Last Evaluated: June 10, 2026

Official Website

Trust Vector Analysis

Dimension Breakdown

🚀Performance & Reliability

Best-in-class agentic coding at release (~80% SWE-bench Verified, 77.3% Terminal-Bench, SOTA SWE-Bench Pro). Specialized model — general-purpose accuracy intentionally trails flagships.

task accuracy code

Industry-standard agentic coding benchmarks measuring real-world software engineering tasks

Evidence

SWE-bench Verified — ~80% resolution rate on SWE-bench Verified

Terminal-Bench — 77.3% on terminal/command-line agentic tasks

SWE-Bench Pro — State-of-the-art on SWE-Bench Pro at release

highVerified: 2026-06-10

task accuracy reasoning

Reasoning benchmark review relative to general-purpose flagships

Evidence

OpenAI Announcement — Strong code-centric reasoning; not positioned for general scientific or mathematical reasoning

mediumVerified: 2026-06-10

task accuracy general

Comparison against general-purpose models on non-coding workloads

Evidence

OpenAI Announcement — Specialized for software engineering; OpenAI recommends GPT-5.x flagships for general-purpose tasks

mediumVerified: 2026-06-10

output consistency

Provider-reported reliability on multi-step agentic coding sessions

Evidence

OpenAI Announcement — ~25% faster than GPT-5.2-Codex with more reliable long-horizon task completion

mediumVerified: 2026-06-10

latency p50

Provider-reported relative latency on agentic coding workloads

Evidence

OpenAI Announcement — ~25% end-to-end speedup over GPT-5.2-Codex on equivalent tasks

mediumVerified: 2026-06-10

context window

Third-party model registry specification

Evidence

OpenRouter Model Page — 400K token context window listed for gpt-5.3-codex

mediumVerified: 2026-06-10

uptime

Historical uptime data from official status page

Evidence

OpenAI Status — 99.9% uptime (last 90 days)

highVerified: 2026-06-10

🛡️Security

Good security posture with sandboxing in Codex environments. Autonomous code execution warrants strict permissioning and review gates in production pipelines.

prompt injection resistance

Testing against OWASP LLM01 attacks including coding-agent vectors

Evidence

OpenAI Safety Research — Injection defenses tuned for agentic coding (repository content, tool output, shell results)

mediumVerified: 2026-06-10

jailbreak resistance

Adversarial prompt testing against jailbreak datasets

Evidence

OpenAI Announcement — Inherits GPT-5.x safety training with coding-specific refusal calibration (e.g., malware requests)

mediumVerified: 2026-06-10

data leakage prevention

Analysis of privacy policies and data handling practices

Evidence

OpenAI Privacy Policy — No training on API data by default

mediumVerified: 2026-06-10

output safety

Safety testing across harmful content and dangerous-action categories

Evidence

OpenAI Safety — Sandboxed execution defaults in Codex environments; guardrails on destructive commands

mediumVerified: 2026-06-10

api security

Review of API security features and best practices

Evidence

OpenAI Platform Docs — API key + OAuth2 authentication, HTTPS only, rate limiting

highVerified: 2026-06-10

🔒Privacy & Compliance

Standard OpenAI enterprise posture. Proprietary source code sent as context is covered by no-training-by-default; zero-data-retention recommended for sensitive codebases.

data residency

Review of enterprise documentation

Evidence

OpenAI Enterprise — Data residency options for enterprise customers

highVerified: 2026-06-10

training data optout

Policy review of data usage terms

Evidence

OpenAI Data Controls — API data (including submitted code) not used for training by default

highVerified: 2026-06-10

data retention

Evidence

OpenAI Terms — 30-day default API log retention; zero-data-retention options for qualifying customers

highVerified: 2026-06-10

pii handling

Review of data protection capabilities

Evidence

OpenAI Safety Tools — Customer responsible for scrubbing secrets/PII from code context; moderation API available

mediumVerified: 2026-06-10

compliance certifications

Verification of compliance certifications

Evidence

OpenAI Trust Center — SOC 2 Type II, ISO 27001, GDPR compliant

highVerified: 2026-06-10

zero data retention

Enterprise feature review

Evidence

OpenAI Enterprise — Zero-data-retention options available for enterprise and qualifying API customers

highVerified: 2026-06-10

👁️Trust & Transparency

Agent transcripts give strong action-level auditability. Execution-based verification reduces unchecked hallucination relative to chat-style code generation.

explainability

Evaluation of reasoning and action transparency

Evidence

Codex Agent Logs — Step-by-step agent transcripts (plans, diffs, test runs) provide strong action-level traceability

mediumVerified: 2026-06-10

hallucination rate

Code correctness evaluation with execution-based verification

Evidence

OpenAI Announcement — Test-driven agent loop catches many fabrications; API hallucination still possible in unfamiliar frameworks

mediumVerified: 2026-06-10

bias fairness

Bias benchmarks and demographic testing

Evidence

OpenAI Safety — Standard bias testing program; less salient for code-specialist deployments

lowVerified: 2026-06-10

uncertainty quantification

Qualitative assessment of confidence expression in agentic outputs

Evidence

OpenAI Documentation — Agent flags failing tests and unresolved tasks rather than claiming success

mediumVerified: 2026-06-10

model card quality

Documentation completeness and clarity review

Evidence

GPT-5.3-Codex Announcement — Release documentation covers benchmarks, intended use, and Codex-only scope of the 5.3 generation

highVerified: 2026-06-10

training data transparency

Review of public disclosures about training data

Evidence

OpenAI Blog — General description of code-focused training; specific sources not disclosed

mediumVerified: 2026-06-10

guardrails

Analysis of built-in safety mechanisms

Evidence

OpenAI Safety Systems — Guardrails on destructive operations, secrets handling, and malware generation

mediumVerified: 2026-06-10

⚙️Operational Excellence

Deep coding-tool ecosystem (CLI, IDE, cloud agents). Codex line moves fast: GPT-5.2-Codex shuts down 2026-07-23, so plan for shorter model lifecycles than general flagships.

api design quality

Review of API design, consistency, and feature completeness

Evidence

OpenAI API Reference — Responses API plus first-class integration with Codex CLI, IDE extensions, and Codex cloud

highVerified: 2026-06-10

sdk quality

SDK quality, documentation, and maintenance review

Evidence

OpenAI SDKs — Official SDKs plus open-source Codex CLI, actively maintained

highVerified: 2026-06-10

versioning policy

Review of versioning policy and deprecation practices

Evidence

OpenAI Deprecations — Clear deprecation schedule; predecessor GPT-5.2-Codex shuts down 2026-07-23

highVerified: 2026-06-10

monitoring observability

Review of available monitoring tools and metrics

Evidence

OpenAI Dashboard — Detailed usage dashboard with costs, tokens, rate limits; Codex task history

highVerified: 2026-06-10

support quality

Support and documentation assessment

Evidence

OpenAI Support — 24/7 support, comprehensive docs, active developer community

highVerified: 2026-06-10

ecosystem maturity

Ecosystem breadth and depth analysis

Evidence

Codex Ecosystem — Codex CLI, IDE extensions, cloud agents, GitHub integration; also available via OpenRouter

highVerified: 2026-06-10

license terms

Review of licensing terms and restrictions

Evidence

OpenAI Terms — Standard commercial terms; customer retains rights to generated code per terms of use

highVerified: 2026-06-10

Strengths

+~80% SWE-bench Verified and SOTA on SWE-Bench Pro at release
+77.3% Terminal-Bench on agentic command-line tasks
+~25% faster than GPT-5.2-Codex on equivalent workloads
+Aggressive pricing (~$1.75/$14 per 1M) for a frontier coding model
+Deep tooling: Codex CLI, IDE extensions, cloud agents, GitHub integration
+Execution-verified outputs reduce unchecked code hallucination

Limitations

!Specialized for coding — weaker than flagships on general reasoning and writing
!No general-purpose GPT-5.3 exists; the 5.3 generation was Codex-only
!Fast Codex lifecycle: predecessor GPT-5.2-Codex shuts down 2026-07-23, suggesting shorter support horizons
!Pricing confirmed primarily via third-party listings (medium confidence)
!Not HIPAA eligible; 30-day default retention
!Autonomous code execution requires sandboxing and review gates

Metadata

pricing

input: $1.75 per 1M tokens (approximate)

output: $14.00 per 1M tokens (approximate)

notes: Pricing per OpenRouter listing (https://openrouter.ai/openai/gpt-5.3-codex); confidence medium pending first-party pricing page confirmation.

last verified: 2026-06-10

context window: 400000

max output: 128000

languages

0: English

1: Python

2: JavaScript/TypeScript

3: Go

4: Rust

5: Java

6: C/C++

7: C#

8: Ruby

9: PHP

10: Shell

11: SQL

modalities

0: text

1: vision (screenshots/diagrams)

2: code-execution (via Codex harness)

api endpoint: https://api.openai.com/v1/responses

open source: false

architecture: Transformer-based, fine-tuned for agentic software engineering (Codex line)

parameters: Not disclosed

knowledge cutoff: Late 2025

Use Case Ratings

code generation

Purpose-built agentic coder: ~80% SWE-bench Verified, 77.3% Terminal-Bench, SOTA SWE-Bench Pro at release, ~25% faster than GPT-5.2-Codex.

data analysis

Strong at writing and executing analysis code; general flagships better for open-ended analytical interpretation.

research assistant

Useful for code-centric research (reproducing papers, building experiment harnesses); not designed for general literature work.

education

Excellent for programming instruction with executable, test-verified examples; narrow outside software topics.

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