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OpenAI: GPT-5.3-Codex

GPT-5.3-Codex is OpenAI’s most advanced agentic coding model, combining the frontier software engineering performance of GPT-5.2-Codex with the broader reasoning and professional knowledge capabilities of GPT-5.2. It achieves state-of-the-art results...

Provider
OpenRouter
Availability
Available
Model ID
openai/gpt-5.3-codex
Snapshot
2026-10-07
Evaluation Verdict

OpenAI GPT-5.3 Codex Spark provides ultra-responsive code generation (75.0% SWE-bench Verified, 1438 Coding Elo), blending speed with frontier reasoning for real-time agent pair programming.

OpenAI: GPT-5.3-Codex Benchmarks & Agentic Accuracy

Verified primary research & developer preference metrics

Primary Sources Verified
SWE-bench Verified
75%
Fast Autonomous ModeCodex Technical Report ↗
LiveCodeBench
78.6%
ThinkingLiveCodeBench ↗
LMSYS Coding Elo
1438Elo
Coding ArenaLMSYS Arena ↗
AIME 2024 / 2025
94.2%
ThinkingCodex Technical Report ↗
Pricing ($ / 1M tokens)
$2.5/ $10
$0.45 cached readStandard API Pricing

What This Means in Real Software Development

  • 75.0% on SWE-bench Verified with rapid execution.
  • Optimized for real-time terminal interactions, shell command generation, and fast build troubleshooting.
  • Near-zero first-token latency (<300ms TTFT) makes it feel instantaneous in the Swarm TUI.
  • Highly stable for automated test repair loops and continuous integration pipelines.

Swarm Multi-Agent Topology

Tier 1: High-Speed Frontier CoderRole: Coder Subagent

Best Paired With: Claude 3.7 Sonnet as Lead Planner

High throughput and elite coding logic make it ideal for rapid iterative development cycles.

Git Worktree Isolation Advantage:

Executes rapid code edits and commits to isolated Git worktrees without blocking the user.

What Developers & Practitioners Are Saying

Real-world field observations, production strengths, and developer consensus

Field Consensus

"Ultra-responsive Codex variant tailored for instant completions and rapid subagent triage."

Verified Real-World Strengths

  • High throughput
  • Instant start-up time for fast terminal command validation
  • Affordable token economics

Production Caveats & Gaps

  • Less suitable for deep architectural system planning
Benchmark Reality Check

What the benchmark tests: Evaluates rapid code completion and localized error patching.

Production caveat: Best assigned as a Coder or Validator subagent under a primary planner.

Primary Sources & Methodology Citations

OpenAI: GPT-5.3-Codex model overview

OpenAI: GPT-5.3-Codex is listed in the public Swarm catalog through OpenRouter. This page summarizes the verified catalog fields used by Swarm without claiming real-time access for every provider account.

Provider
OpenRouter
Family
OpenRouter
Context window
400K tokens
Thinking support
off · low · medium · high · xhigh
Availability status
Available
Catalog ID
openrouter/openai/gpt-5.3-codex
  • File input
  • Image input
  • Text input
  • Text output
  • Reasoning
  • Tools
  • Structured output
  • JSON

Run OpenAI: GPT-5.3-Codex in Swarm

Verified CLI workflow & multi-agent architecture

Quickstart Guide →
bash — swarm run
$swarm ctl model set --provider openrouter --model openrouter/openai/gpt-5.3-codex

# Or switch interactively inside the terminal TUI:

>/models

Subagent Role Matrix

Assign OpenAI: GPT-5.3-Codex to specialized system roles in ~/.swarm/config.json:

  • Primary / Planner: Orchestrates full task DAGs and multi-stage pipelines.
  • Coder Subagent: Generates code and unit tests inside private Git worktrees.
  • Finder Subagent: Performs read-only code search, symbol discovery, and mapping.
System Agent Roles →Why Swarm Architecture →
← All OpenRouter models

Public catalog snapshot. Catalog availability is not a real-time provider status or an access guarantee.