What is flash v2.5 | ElevenLabs | Page 1

chrome archBOT Mar 30, 2026, 10:55 AM

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AI-generated Answer for kishore_vb

ElevenLabs Flash v2.5 is the company’s ultra‑low‑latency text‑to‑speech model optimized for real‑time use (e.g., voice agents/interactive apps). (elevenlabs.io)

Key facts

Typical time‑to‑first‑audio ≈75 ms (excludes app/network). (elevenlabs.io)
Supports 32 languages. (elevenlabs.io)
40,000‑character limit per request. (elevenlabs.io)
Model ID: eleven_flash_v2_5. (elevenlabs.io)
Faster and 50% lower price per character than alternatives in its class; intended for Agents Platform and interactive applications. (elevenlabs.io)
Compared with Turbo, Flash v2.5 trades some quality/emotional depth for significantly lower latency. (help.elevenlabs.io)

fossil oak Mar 30, 2026, 10:58 AM

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Does it support english?

chrome archBOT Mar 30, 2026, 10:58 AM

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AI-generated Answer for kishore_vb

Yes—Flash v2.5 supports English (US, UK, Australia, Canada) as part of its 32 supported languages. (elevenlabs.io)

Sources:
Models | ElevenLabs Documentation

fossil oak Mar 30, 2026, 10:59 AM

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when we set the agent's primary language to en, the API rejects it with:

"Invalid conversation config: Value error, English Agents must use turbo or flash v2."

Why is that?

chrome archBOT Mar 30, 2026, 10:59 AM

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AI-generated Answer for kishore_vb

Because ElevenAgents enforces a model rule by language: when an agent’s primary language is English, it must use the English‑only, low‑latency v2 models (Flash v2 or Turbo v2). The platform automatically uses the v2.5 multilingual models only when you add non‑English languages—“English will always use the v2 model.” If you try to pair primaryLanguage=en with a v2.5 model, the validator throws that error. (elevenlabs.io)

To resolve it, select Flash v2 or Turbo v2 for the agent’s TTS (e.g., model IDs eleven_flash_v2 or eleven_turbo_v2), or leave the default (Flash v2) for English. (elevenlabs.io)

Sources:
Language | ElevenLabs Documentation
Models | ElevenLabs Documentation

fossil oak Mar 30, 2026, 11:01 AM

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But we want to use Flash v2.5 because we have 4 different secondary language which we use via overrides

chrome archBOT Mar 30, 2026, 11:01 AM

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AI-generated Answer for kishore_vb

Short answer: In ElevenAgents you can’t set English to use Flash v2.5. When an agent’s output language is English, the platform forces the v2 model; additional languages automatically use the v2.5 multilingual model. That’s why the API rejects “en” with Flash v2.5. (elevenlabs.io)

What to do

Keep primary language = English. Add your four languages under Additional Languages; those languages will route to Flash v2.5 automatically, while English stays on Flash v2. Configure per-language voice/first-message overrides as needed. (elevenlabs.io)
If you want automatic switching, enable the Language Detection system tool so the agent flips to the user’s detected language at runtime. (elevenlabs.io)

Note: Flash v2.5 itself supports 32 languages (including English) via the standalone TTS API using model_id eleven_flash_v2_5—but Agents still keep English on v2 by design. (elevenlabs.io)

Sources:
Language | ElevenLabs Documentation
Language | ElevenLabs Documentation
Language detection | ElevenLabs Documentation
ElevenLabs — Meet Flash

fossil oak Mar 30, 2026, 11:03 AM

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How are you sure that it will use flash v2.5 for other languages rather than multilingual model?

chrome archBOT Mar 30, 2026, 11:03 AM

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AI-generated Answer for kishore_vb

Short answer: because the Agents “Language” guide explicitly says so.

In ElevenAgents, adding “Additional languages” switches the agent’s TTS to “the v2.5 Multilingual model,” while English “will always use the v2 model.” That is the platform default routing: EN → Flash v2; non‑EN → Flash v2.5. (elevenlabs.io)
“Flash v2.5” is the multilingual Flash model (low‑latency across 32 languages), distinct from the separate “Multilingual v2” family used for long‑form/high‑quality. (elevenlabs.io)
If you ever want to force a different family per language/voice, Multi‑voice settings let you override the agent’s default to Flash, Turbo, or Multilingual; otherwise the default behavior above applies. (elevenlabs.io)

So, when your primary language is English and you add secondary languages, Agents will use Flash v2.5 for those other languages by default, not the Multilingual v2 model. (elevenlabs.io)

Sources:
Language | ElevenLabs Documentation
ElevenLabs — Meet Flash
Multi-voice support | ElevenLabs Documentation
Language | ElevenLabs Documentation

fossil oak Mar 30, 2026, 11:22 AM

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What happens if the user switches the language mid call?

#What is flash v2.5