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Favicon for sesame

Sesame: CSM 1B

sesame/csm-1b

BenchmarksCompare

CSM 1B is a conversational speech model from Sesame. It accepts text input and produces English speech output, with voice options spanning conversational and read-speech styles. At 1B parameters, it is suited for dialogue-oriented applications such as voice assistants and interactive agents.

Modalities
Price
$7/M characters
Context
4K
Released
Apr 23, 2026
BenchmarksCompare
PlaygroundBenchmarksProvidersPerformanceUptimeAppsActivityFAQExplore

Playground

Benchmarks

Scores on standardized evaluations and this model’s own outputs on shared benchmark prompts. Higher percentages are better — and each rank shows where this model lands among the models evaluated on that source.

Providers

This model is hosted by one provider. OpenRouter forwards every request to it directly — no routing decisions to make.

Performance

Throughput is how fast the model writes (tokens per second — higher is better). Latency is total round-trip time (lower is better). TTFT is time-to-first-token — how long before you see anything appear (lower is better).

Uptime

Uptime is the percentage of the past 3 days that at least one provider was responding to requests. Availability is the percentage of time that inference was successfully served. OpenRouter continuously monitors and uses the next-best provider when one returns an error.

Apps

Public apps that send the most traffic to this model. Good signal for what real production workloads look like — and a hint at which use cases this model is best suited for.

Activity

Token volume and request traffic to this model over time.

API

Drop-in code to call this model. OpenRouter's API is OpenAI-compatible — most SDKs work by just swapping the base URL. The only thing that changes between models is the model slug below.

Explore more models

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$7.00--
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Uptime (3d)The model was reachable. Request routed to a provider.
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Availability (3d)The model returned inference from any provider. Errors and empty responses count against it.
100.00%

Availability over the last 3 days

Last 72 hours
Availability 100.00%
3 Days Ago2 Days AgoYesterdayNow

Not enough uptime data to display yet.

When an error occurs in an upstream provider, we can recover by routing to another healthy provider, if your request filters allow it. You can access per-provider uptime data programmatically through the Endpoints API. Learn more about our load balancing and provider routing options.

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4.
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Frequently asked questions

CSM 1B is a conversational speech model from Sesame. It accepts text input and produces English speech output, with voice options spanning conversational and read-speech styles. At 1B parameters, it is suited for dialogue-oriented applications such as voice assistants and interactive agents.

CSM 1B costs $7.00/M characters.

CSM 1B ships 7 voices. Pass a voice ID in the voice field of a text-to-speech request; the IDs this endpoint accepts are listed with the model in the models API.

CSM 1B accepts text as input and returns generated speech audio.

CSM 1B was released on April 23, 2026.