Updated documentation for Grammar Backend

[shuaills]

Motivation

Improve documentation clarity around grammar backends.

#2505

Modifications

Updated documentation to clarify Xgrammar's JSON support and regex limitation.

Checklist

• Format your code according to the Contributor Guide.
• Add unit tests as outlined in the Contributor Guide.
• Update documentation as needed, including docstrings or example tutorials.

[zhaochenyang20]

You can define a JSON schema or regular expression to constrain the model's output, which depends on the grammar backend.

SGlang has two backends: outlines (default) and Xgrammar. Xgrammar enhances JSON decoding performance but does not support regular expressions. To use Xgrammar, add --grammar-backend xgrammar when launching the server:

[shuaills]

Updated and verified the functionality with Xgrammar backend.

[zhaochenyang20]

This is just to update the current document, so a tiny modification is good enough. However, for the constraint decoding tutorial, please truly launch the server to check its correctness. Also, what's the status of the tutorial? @shuaills

[shuaills]

This is just to update the current document, so a tiny modification is good enough. However, for the constraint decoding tutorial, please truly launch the server to check its correctness. Also, what's the status of the tutorial? @shuaills

I'm working on it. Should it be in Jupyter Notebook format? And where should I put the tutorial?

[zhaochenyang20]

This is just to update the current document, so a tiny modification is good enough. However, for the constraint decoding tutorial, please truly launch the server to check its correctness. Also, what's the status of the tutorial? @shuaills

I'm working on it. Should it be in Jupyter Notebook format? And where should I put the tutorial?

It should be a Notebook. Put it under docs/backend

[zhaochenyang20]

Just tiny modification. Then we can merge it.