When are we going to get proper error messages?

[Die4Ever2005]

These

UnknownError: Other generic failures occurred.

Are so annoying to try to debug

[Thomas Steiner]

Hi there,

This error can occur when JSON Schema constraints are invalid. We have an internal bug open to improve this. Here's an example:

const session = await LanguageModel.create();
const schema = { "type": "answer" };
await session.prompt(`Is red a color?`, { responseConstraint: schema });
> Uncaught UnknownError: Other generic failures occurred.

Another source of this error is if the GPU runs into an "out of memory" situation. In such cases, often (but not always) the "bypass performance requirements" flag is set, but we'd still appreciate a new bug report with attached GPU logs and crash logs (see the troubleshooting guide for how to obtain those).

Thanks,

Tom 

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[Die4Ever2005]

It seems like this is the regex causing the issue

let m = await LanguageModel.create(); await m.prompt('hello', {responseConstraint: /^[^\n><]{1,800}$/});

It fails every time. Works fine if I remove the responseConstraint.

Version 145.0.7632.18 (Official Build) beta (64-bit)
Foundational model state: Ready
Model Name: v3Nano
Version: 2025.06.30.1229
Backend Type: GPU (highest quality)
File path: /home/ray/.config/google-chrome-beta/OptGuideOnDeviceModel/2025.8.8.1141
Folder size: 4,088.14 MiB

[Die4Ever2005]

This also fails with a simple regex

let m = await LanguageModel.create();

await m.prompt('hello', {responseConstraint: /^.*$/});

Uncaught UnknownError: Other generic failures occurred.

[Die4Ever2005]

Same issue on
Version 145.0.7632.26 (Official Build) beta (64-bit)

[Felipe Marcos de abreu Aquino]

I’ve been following this thread and can confirm that I'm seeing similar behavior. The generic UnknownError is indeed a major roadblock for debugging, especially when working with complex responseConstraint implementations.

Regarding the Regex issue mentioned:

It seems the current parser for responseConstraint might be struggling with specific engine-level validations before even hitting the model. Even a catch-all regex like /^.*$/ failing suggests that the validation layer itself might be crashing or timing out before the GPU backend can process the prompt.

To help the team, I’ll perform a few more tests on my end with:

Different backend types (switching between GPU and CPU if possible).

Testing if the same failure occurs with very short prompts vs longer ones.

@Tom, as a developer with long-term experience in complex system architectures, I'd suggest that even if the root cause is a GPU memory/timeout issue, the API should ideally catch these specific failure modes and map them to more descriptive error codes (e.g., REGEXP_VALIDATION_FAILED or INSUFFICIENT_GPU_RESOURCES) rather than the catch-all UnknownError.

I'll collect my logs and attach them to a new bug report as suggested.

Best regards,

Felipe Aquino

Senior Software Developer

To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/chrome-ai-dev-preview-discuss/ebde2c01-41cf-4ff7-a867-6163dea8cf04n%40chromium.org.

[Thomas Steiner]

Thank you all for confirming the source of these errors. We'd appreciate quick bug reports with just these minimal reproductive cases at https://new.crbug.com. Thank you very much! There's work happening on making the error messages more useful, but specific pain points definitely help the team focus their attention on the most confusing ones.

Cheers,

Tom 

[Sumeet Singh]

Hi Tom,

Thank you for the update. I will submit a bug report with these reproduction cases at https://new.crbug.com (https://new.crbug.com) as requested.

Best regards,

Sumeet Singh

To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/chrome-ai-dev-preview-discuss/CALgRrLm71B%3DH2GyNO-Rtz5pTquwcBP6222C86ubTuSDW6-xGwQ%40mail.gmail.com.

[Die4Ever2005]

I filed the bug, but I couldn't find the right component to file it under

https://issues.chromium.org/issues/479676595

[Sumeet Singh]

Hi Tom,

I have filed a bug report for the issues discussed in this thread: https://issues.chromium.org/issues/479676595 (https://issues.chromium.org/issues/479676595).

Like Die4Ever2005, I was unsure which component to file it under, so please let us know if it needs to be updated or moved to a different category.

Best regards,

Sumeet Singh

[Thomas Steiner]

Thanks, both! Blink > AI > Prompt is the right component! Perfect!