Short answer: As of November 9, 2026, neither model is a strong default for a new production integration: OpenAI marks GPT-5 deprecated, and Anthropic marks Claude Sonnet 4.5 deprecated and says it retires on November 30, 2026. Anthropic recommends Sonnet 5.5; for GPT-5, check OpenAI’s current migration guidance rather than assuming a replacement. If you need to compare these models for an existing system or short-term evaluation, GPT-5 has lower listed standard token rates and larger listed context and output limits. Those advantages do not remove the lifecycle risk. (OpenAI GPT-5 API documentation; Anthropic Claude Sonnet 4.5 documentation)
At a glance
| API factor | GPT-5 | Claude Sonnet 4.5 |
|---|---|---|
| API model name | gpt-5 (snapshot: gpt-5-2025-08-07) |
claude-sonnet-4-5 (snapshot: claude-sonnet-4-5-20250929) |
| Status | Deprecated; consult OpenAI’s current migration guidance | Deprecated; retires November 30, 2026; Anthropic recommends Sonnet 5.5 |
| Context window | 400,000 tokens | 200,000 tokens |
| Maximum output | 128,000 tokens | 64,000 tokens |
| Standard input price | $1.25 per million tokens | $3 per million tokens |
| Standard output price | $10 per million tokens | $15 per million tokens |
| Practical takeaway | Lower listed token rates and larger listed limits, but deprecated | Higher listed rates and smaller limits, with a stated retirement date approaching |
Prices are in USD per million tokens. These are listed API rates; caching and other billing conditions can affect actual charges. Check the providers’ current documentation before deploying. (OpenAI GPT-5 API documentation; Anthropic Claude Sonnet 4.5 documentation)
Which model fits which workload?
For an existing GPT-5 integration
On the listed standard, uncached token rates, GPT-5 costs less per input and output token than Claude Sonnet 4.5. Its listed context and maximum-output limits are also larger. But GPT-5 is deprecated, so weigh those differences against migration effort and future availability before expanding a GPT-5-dependent system. (OpenAI GPT-5 API documentation)
For an existing Claude Sonnet 4.5 integration
Anthropic says Sonnet 4.5 remains functional but is deprecated, is no longer recommended, and is scheduled to retire on November 30, 2026. Anthropic recommends Sonnet 5.5. If evaluating Sonnet 4.5 for a new deployment, account for the stated retirement date and test the recommended replacement as well. (Anthropic Claude Sonnet 4.5 documentation)
What a coding comparison actually shows
A third-party author reports testing Claude Sonnet 4.5 and GPT-5 Codex on two observability-platform tasks: anomaly detection and distributed alert deduplication. The author says GPT-5 Codex delivered integrated code in both tasks, while Claude’s implementations were not integrated; the author also praised Claude’s alert-deduplication architecture and reported defects in its anomaly-detection implementation. The author’s reported combined run costs were $0.95 for GPT-5 Codex and $1.68 for Claude. (Composio’s coding comparison)
Treat this as a narrow, author-reported result—not a general API-model ranking. It covers two tasks in one codebase and IDE setup, and names GPT-5 Codex, which should not be silently treated as identical to every GPT-5 API offering. The evaluation does not establish which model is better for writing, general reasoning, or your production environment. Use it as a reminder to assess correctness, integration, and defects in your own tests, not as a substitute for them.
API cost: a like-for-like example
At the listed standard rates, GPT-5 costs less per million input and output tokens than Claude Sonnet 4.5. For a simple uncached request using 10,000 input tokens and 1,000 output tokens:
- GPT-5: (0.01 × $1.25) + (0.001 × $10) = $0.0225
- Claude Sonnet 4.5: (0.01 × $3) + (0.001 × $15) = $0.045
This token-only example uses USD, assumes the same input and output token counts for each model, and excludes cached tokens and other charges. The request volumes are below both models’ listed context and maximum-output limits. It is not a forecast of your application’s bill: prompt and response lengths, caching, and workload behavior can change actual usage. The listed rates alone are not a reason to adopt a deprecated model. (OpenAI GPT-5 API documentation; Anthropic Claude Sonnet 4.5 documentation)
Production API considerations
The provider documentation lists the model IDs, lifecycle status, context and output limits, and token prices above. The available comparison evidence does not establish that one model’s API is universally easier to integrate, more reliable, or cheaper for every application. Verify any workload-specific API requirements in current provider documentation, then test them in your own stack.
A practical evaluation should:
- Confirm the exact model ID and lifecycle. Don’t conflate GPT-5 with GPT-5 Codex, GPT-5.1, or GPT-5.2—or Sonnet 4.5 with later Sonnet models.
- Use representative inputs and tools. Include typical requests, edge cases, long prompts, and the tool behavior your application depends on.
- Score the outcomes that matter. Measure correctness, integration success, failure rate, latency, and human review or repair time—not just whether a response looks convincing.
- Record actual token usage and cost. Compare the same workload and billing assumptions, including retries or follow-up repair where relevant.
- Test migration candidates before committing. Both models in this comparison are deprecated; account for migration and retirement risk in the selection.
Bottom line: For an existing-system or short-term comparison, GPT-5 has lower listed standard API rates and larger listed token limits. For a new production system, the more consequential finding is that both models are deprecated—and Claude Sonnet 4.5 has a stated retirement date of November 30, 2026. Check current provider migration guidance and evaluate suitable candidates against your own workload before choosing a long-term deployment.
Sources
Claude Sonnet 4.5 — Claude Platform Docs
GPT-5 Codex vs. Claude Sonnet 4.5: Agentic coding test — Composio