# Muse Spark 1.3 vs GPT-5 Codex

Canonical HTML page: [Muse Spark 1.3 vs GPT-5 Codex](<https://impossibl.com/compare/meta/muse-spark-1.3/openai/gpt-5-codex>)
Markdown alternative: [Muse Spark 1.3 vs GPT-5 Codex as Markdown](<https://impossibl.com/compare/meta/muse-spark-1.3/openai/gpt-5-codex.md>)

Compare API pricing, context windows, and capabilities side by side. Prices are published API usage rates in USD; check billing units and context tiers alongside each price.

## Specifications and pricing

| Specification | Muse Spark 1.3 | GPT-5 Codex |
| --- | --- | --- |
| API identifier | meta/muse-spark-1.3 | openai/gpt-5-codex |
| Creator | Meta | OpenAI |
| Model type | Text generation | Text generation |
| Inputs | text, image | text, image |
| Outputs | text | text |
| Base input price (USD) | $1.25 per million input tokens | $1.25 per million input tokens |
| Base output price (USD) | $4.25 per million output tokens | $10.00 per million output tokens |
| Cache read price (USD) | $0.15 per million cached input tokens | $0.125 per million cached input tokens |
| Cache write price (USD) | Not published | Not published |
| One-hour cache write price (USD) | Not published | Not published |
| Audio input token price (USD) | Not published | Not published |
| Context window | 1,048,576 tokens | 400,000 tokens |
| Tool calling | Not published | Not published |
| Endpoints | /v1/chat/completions | /v1/chat/completions |
| Context pricing tiers (USD per million tokens) | None published | None published |
| Retirement | Not announced in the public catalog | Not announced in the public catalog |

When total input, including cached input, strictly exceeds a context threshold, the highest qualifying tier applies to the whole request. Consult each model's complete Markdown for tier-specific cache rates; an unpublished tier cache price does not establish the base cache rate.

## Muse Spark 1.3 vs GPT-5 Codex: side-by-side summary

Muse Spark 1.3 and GPT-5 Codex are available through the Impossibl API.

They share the `/v1/chat/completions` endpoint. Set the model identifier to select the model for a supported request.

Muse Spark 1.3 is created by Meta. It has a 1,048,576-token context window. Base API pricing (USD): $1.25 per million input tokens; $4.25 per million output tokens.

GPT-5 Codex is created by OpenAI. It has a 400,000-token context window. Base API pricing (USD): $1.25 per million input tokens; $10.00 per million output tokens.

## Model details

- [Muse Spark 1.3: full model facts as Markdown](<https://impossibl.com/meta/muse-spark-1.3.md>); [HTML model page](<https://impossibl.com/meta/muse-spark-1.3>)
- [GPT-5 Codex: full model facts as Markdown](<https://impossibl.com/openai/gpt-5-codex.md>); [HTML model page](<https://impossibl.com/openai/gpt-5-codex>)

For compatible text or embedding models with token pricing, the HTML comparison page provides a shared workload calculator. It excludes cache creation, tool calls, taxes, balance-purchase fees, and workspace-specific adjustments.

## Sources and related links

Prices, capabilities, limits, and availability describe the public Impossibl API offering. An unpublished fact is unknown; a published zero price is zero. Compare matching billing units and check context tiers before estimating costs.

- [Public Impossibl model catalog](<https://api.impossibl.com/v1/models>)
- [Full model directory as JSON](<https://impossibl.com/models.json>)
- [Model directory as Markdown](<https://impossibl.com/models.md>)
- [API quickstart](<https://impossibl.com/docs/agent-quickstart>)
- [Model documentation](<https://impossibl.com/docs/models>)