API: Simba 1.6 retired at version 2026-09-21, switched off 2026-11-21

API: Simba 1.6 retired at version `2026-09-21`, switched off 2026-11-21

simba-english and simba-multilingual - the Simba 1.6 pair - are being withdrawn in two steps:

From API version 2026-09-21 they are no longer selectable. Naming either returns 400 with the error code model_retired.
On 2026-11-21 both models are switched off. From that date they are unreachable on every API version, including a workspace pinned below the retirement.

If you use either model, you have until 2026-11-21 to migrate, and for most integrations that is a one-line model change. Pinning your workspace’s API version to a date before 2026-09-21 keeps things working in the meantime with no code change at all - but it is a migration window, not an exemption, and it ends on the same day for everyone.

Why the shorter notice. Our usual sunset window is 12 months. Simba 1.6 is a previous-generation family: it cannot serve /v1/audio/stream/with-timestamps at all and runs at roughly 2.5x the time-to-first-byte of the streaming-native models. Consolidating onto the Simba 3 fleet is what lets us keep improving latency and quality for everyone, and we did not want to spend a year running two stacks to do it.

Where to go.

From	To	Notes
`simba-english`	`simba-3.2`	English. Lower time-to-first-byte, richer expressivity, streaming-native. Serves a curated stock roster plus your own cloned voices.
`simba-english`	`simba-3.0`	English, if you need a voice outside the `simba-3.2` roster. Accepts every catalog voice.
`simba-multilingual`	`simba-3.0`	English, `de-DE`, `es-ES`, `es-MX`, `fr-FR`, `it-IT`, `pt-BR`. Streaming-native, and a cloned voice speaks all of them from one voice ID.

An omitted model is unaffected: it already resolves to simba-3.0.

If you synthesize outside Simba 3.0’s seven locales, simba-3.0 on its own is not a like-for-like replacement - and we are not asking you to drop those languages. Broader multilingual coverage on the current model generation is planned to be available before this date, and we will confirm the model and the timing directly rather than leave you to read it off a changelog. Talk to us so we can line your migration up with it.

If that coverage is not in your hands by 2026-11-21, we move the shutdown date rather than cut the languages off. That is the commitment; the date is not.

What changed at this version. POST /v1/audio/speech and both /v1/audio/stream routes reject the two ids. GET /v1/audio/models returns only the models you can actually call, and each voice’s models array in GET /v1/voices does the same - so a picker driven off either endpoint stays correct without special-casing.

Read the dates off the API. While your workspace is pinned below 2026-09-21, both models still appear in GET /v1/audio/models carrying retired_at: "2026-09-21" and sunset_at: "2026-11-21". Surface sunset_at in your own tooling if you have a deadline to track.

See the API Versioning guide for how to read and set your workspace’s pinned version.