Claude Opus 4.8 vs GPT-5.3-Codex
Claude Opus 4.8 and GPT-5.3-Codex are the direct 2026 API-model choice for agentic software engineering. Opus is the stronger high-autonomy pick: it leads on SWE-bench Pro, SWE-bench Verified, OSWorld computer use, provider breadth, and 1M-token context. GPT-5.3-Codex is the lower-cost OpenAI-native option, with a narrow Terminal-Bench 2.0 edge and first-class fit for teams already standardized on Codex CLI and OpenAI API workflows.
Pick Claude Opus 4.8 for autonomous repo work, complex multi-file engineering, computer-use agents, and long-context sessions: it leads GPT-5.3-Codex by 12.4 points on SWE-bench Pro and 18.7 points on OSWorld, with 1M context versus 400K. Pick GPT-5.3-Codex for cost-sensitive coding pipelines, OpenAI-native Codex workflows, and terminal automation where its $1.75/M input price and 77.3% Terminal-Bench 2.0 score matter more than the harder agent benchmarks.
Decision scorecard
Local evidence first| Signal | Claude Opus 4.8 | GPT-5.3-Codex |
|---|---|---|
| Product type | Standalone API model | Coding-specialized model |
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | custom coding agents, code generation, and tool loops |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 1m | 400k |
| Cheapest output | $25/1M tokens | $14/1M tokens |
| Provider routes | 6 tracked | 3 tracked |
| Shared benchmarks | SWE-bench Verified leader | 2 shared |
Decision tradeoffs
- Claude Opus 4.8 holds a shared-benchmark lead on SWE-bench Verified, ahead by 3.6 points.
- Claude Opus 4.8 has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Claude Opus 4.8 has broader tracked provider coverage for fallback and procurement flexibility.
- Claude Opus 4.8 uniquely exposes Multimodal and Parallel agents in local model data.
- Local decision data tags Claude Opus 4.8 for Coding, RAG, and Agents.
- GPT-5.3-Codex has the lower cheapest tracked output price at $14/1M tokens.
- Local decision data tags GPT-5.3-Codex for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Claude Opus 4.8
$10,250
Cheapest tracked route/tier: Anthropic
GPT-5.3-Codex
$4,900
Cheapest tracked route/tier: OpenRouter
Estimated monthly gap: $5,350. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- GPT-5.3-Codex is $11/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Multimodal and Parallel agents before moving production traffic.
- Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
- Claude Opus 4.8 is $11/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Opus 4.8 adds Multimodal and Parallel agents in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-05-28 | 2026-02-05 |
| Context window | 1m | 400k |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Not released | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2026-01 | 2025-08 |
Pricing and availability
| Pricing attribute | Claude Opus 4.8 | GPT-5.3-Codex |
|---|---|---|
| Input price | $5/1M tokens | $1.75/1M tokens |
| Output price | $25/1M tokens | $14/1M tokens |
| Providers |
Capabilities
| Capability | Claude Opus 4.8 | GPT-5.3-Codex |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | No |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | Yes | Yes |
| Parallel agents | Yes | No |
Benchmarks
| Benchmark | Claude Opus 4.8 | GPT-5.3-Codex |
|---|---|---|
| SWE-bench Verified | 88.6 | 85.0 |
| SWE-bench Pro | 69.2 | 56.8 |
Deep dive
The cleanest coding-agent signal favors Opus. Claude Opus 4.8 scores 69.2% on SWE-bench Pro versus 56.8% for GPT-5.3-Codex, and 88.6% on SWE-bench Verified versus 85.0%. Treat SWE-bench Pro as the more important row for production decisions because it is the harder, more contamination-resistant benchmark in the DAT-5924 handoff.
Computer-use and long-context work also favor Opus. Opus has an 83.4% OSWorld-Verified row, API-level computer-use tooling, dynamic multi-agent workflows through Claude Code, and a 1M-token context window. GPT-5.3-Codex now has the computer-use flag because its OSWorld score is sourced at 64.7%, but its documented context ceiling is 400K and its computer-use surface is oriented around Codex agent loops rather than a comparable API tool parameter.
GPT-5.3-Codex still has two practical wins. First, it is materially cheaper on standard OpenAI pricing at $1.75/M input and $14/M output, compared with Opus standard pricing at $5/M input and $25/M output. Second, it edges Opus on the same Terminal-Bench 2.0 leaderboard, 77.3% versus 74.6%, which matters for shell-heavy CI, local automation, and terminal agent loops.
The provider decision is not symmetrical. Opus is available across Anthropic API, AWS Bedrock, Google Vertex AI, Microsoft Foundry, OpenRouter, and Vercel AI Gateway, which helps enterprise procurement and multi-cloud routing. GPT-5.3-Codex is simpler for OpenAI-standardized teams because the same model ID works through the OpenAI API and Codex tooling, with OpenRouter and Vercel routes for aggregation.
FAQ
Which is better for autonomous coding agents?
Claude Opus 4.8 is the stronger default for autonomous coding agents. It leads GPT-5.3-Codex on SWE-bench Pro by 12.4 points and on SWE-bench Verified by 3.6 points, and it has the broader computer-use and long-context surface.
When should I choose GPT-5.3-Codex instead?
Choose GPT-5.3-Codex when token cost, OpenAI platform fit, Codex CLI workflows, or terminal automation are the deciding factors. Its standard input price is $1.75/M versus $5/M for Opus, and it narrowly leads on Terminal-Bench 2.0.
Are the Terminal-Bench scores directly comparable?
Use the Terminal-Bench 2.0 rows for a direct comparison: GPT-5.3-Codex scores 77.3% and Claude Opus 4.8 scores 74.6% on the same independent leaderboard. Do not compare GPT-5.3-Codex's 2.0 row against Opus 4.8's separate Terminal-Bench 2.1 launch row.
Which model is better for computer use?
Claude Opus 4.8 is better for computer use in the sourced data. It scores 83.4% on OSWorld-Verified versus 64.7% for GPT-5.3-Codex, and Anthropic exposes a more explicit computer-use API surface.
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.