VAPI•5mo ago

Voice formatting for gpt-5-mini

I'm using gpt-5-mini and it's doing weird things like explicitly saying "equals sign" and "slash" when referring to numbers. Eg.. instead of 150 grams of protein per day it'll say 150 "g" protein "slash" day. Any ideas what's happening here? There's nothing in my system prompt that should be causing this..

When dealing with gpt-4o-* it didn't do this so it would appear something changed with the updated model? Is this a temperature thing? Anything we can fix? How do i change the voice formatting setting?

Any help would be appreciated

spontaneous-moccasin•8/19/25, 9:55 PM

Use chatgpt 5o
Also enable voice formatting if disabled

sacred-roseOP•8/20/25, 1:06 AM

It is enabled by default and i didnt disabled voice formatting. Are you saying use gpt-5 vs gpt-5-mini? I mean ya that'd be good but it's also 4x more expensive.

The concern i have is 4o-mini does not do this at all.

KyleAPP•8/21/25, 2:41 PM

Hi franny,

For applying voice formatting to text output with GPT-5-mini, you can control how text is transformed for natural-sounding speech through Vapi's voice formatting plan. Voice formatting is enabled by default and includes steps like expanding numbers, abbreviations, and handling email formats.

To customize or disable formatting:

**Disable Formatting:** Set `voice.chunkPlan.enabled = false` or `voice.chunkPlan.formatPlan.enabled = false` to use raw output.
**Customize Formatting:**
- Use formattersEnabledformattersEnabled in assistant.voice.chunkPlan.formatPlanassistant.voice.chunkPlan.formatPlan to control specific transformations.
- Add custom replacements by using:

    { "type": "exact", "key": "hello", "value": "hi" }

    { "type": "exact", "key": "hello", "value": "hi" }

or regex-based:

    { "type": "regex", "regex": "\\b[a-zA-Z]{5}\\b", "value": "hi" }

    { "type": "regex", "regex": "\\b[a-zA-Z]{5}\\b", "value": "hi" }

You can find more details in the voice formatting plan documentation.

sacred-roseOP•8/24/25, 7:24 PM

so since htis is enabled by default why is it not working ?

KyleAPP•8/27/25, 7:04 AM

It seems like there might be a misunderstanding about the default settings. Can you provide more details about what specifically isn't working? This will help me assist you better.

Voice formatting for gpt-5-mini

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