GPT-5.3-Codex-Spark vs Llama 3.1 405B Instruct
GPT-5.3-Codex-Spark (2026) and Llama 3.1 405B Instruct (2024) are agentic coding models from OpenAI and AI at Meta. GPT-5.3-Codex-Spark ships a 131K-token context window, while Llama 3.1 405B Instruct ships a 128K-token context window. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit. It focuses on practical selection signals rather than broad model-family marketing. The goal is to make the tradeoff clear before deeper testing.
GPT-5.3-Codex-Spark is safer overall; choose Llama 3.1 405B Instruct when provider fit matters.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-02-12 | 2024-07-23 |
| Context window | 131K | 128K |
| Parameters | — | 405B |
| Architecture | decoder only | decoder only |
| License | Proprietary | Open Source |
| Knowledge cutoff | - | - |
Pricing and availability
| Pricing attribute | GPT-5.3-Codex-Spark | Llama 3.1 405B Instruct |
|---|---|---|
| Input price | - | $2.4/1M tokens |
| Output price | - | $2.4/1M tokens |
| Providers |
Capabilities
| Capability | GPT-5.3-Codex-Spark | Llama 3.1 405B Instruct |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | No |
| Function calling | Yes | No |
| Tool use | Yes | No |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on function calling: GPT-5.3-Codex-Spark, tool use: GPT-5.3-Codex-Spark, and code execution: GPT-5.3-Codex-Spark. Both models share structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
Pricing coverage is uneven: GPT-5.3-Codex-Spark has no token price sourced yet and Llama 3.1 405B Instruct has $2.4/1M input tokens. Provider availability is 1 tracked routes versus 11. Treat unknown pricing as an integration gap, then verify the route you will actually call before estimating production spend.
Choose GPT-5.3-Codex-Spark when coding workflow support and larger context windows are central to the workload. Choose Llama 3.1 405B Instruct when provider fit and broader provider choice are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions. It also helps separate model capability from provider packaging, which can change cost and latency. For teams standardizing a stack, that distinction is often the difference between a benchmark win and a reliable deployment.
FAQ
Which has a larger context window, GPT-5.3-Codex-Spark or Llama 3.1 405B Instruct?
GPT-5.3-Codex-Spark supports 131K tokens, while Llama 3.1 405B Instruct supports 128K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Is GPT-5.3-Codex-Spark or Llama 3.1 405B Instruct open source?
GPT-5.3-Codex-Spark is listed under Proprietary. Llama 3.1 405B Instruct is listed under Open Source. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for function calling, GPT-5.3-Codex-Spark or Llama 3.1 405B Instruct?
GPT-5.3-Codex-Spark has the clearer documented function calling signal in this comparison. If function calling is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for tool use, GPT-5.3-Codex-Spark or Llama 3.1 405B Instruct?
GPT-5.3-Codex-Spark has the clearer documented tool use signal in this comparison. If tool use is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for structured outputs, GPT-5.3-Codex-Spark or Llama 3.1 405B Instruct?
Both GPT-5.3-Codex-Spark and Llama 3.1 405B Instruct expose structured outputs. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run GPT-5.3-Codex-Spark and Llama 3.1 405B Instruct?
GPT-5.3-Codex-Spark is available on OpenAI API. Llama 3.1 405B Instruct is available on OctoAI API (Deprecated), Together AI, Fireworks AI, IBM watsonx, and Scale AI GenAI Platform. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.