Proofreader API separate from Prompt?

[Colin Mummery]

I've read the Proofreader API description and I'm just trying to plan the user interface for integrating this into my HTML/JS book authoring app. I've already successfully integrated the Prompt and Rewriter APIs for a variety of uses but am I right in thinking that the Proofreader API is using a completely different model install that requires it's own separate download into the browser so that if the ProofReader API is ready to use, this doesn't mean the Prompt/Rewriter API is ready to use or vice-versa? And should I assume that the context window for Proofreader will be the same limited size that Prompt has?

[Thomas Steiner]

Hi Colin,

On Sun, Jul 5, 2026 at 7:54 AM Colin Mummery <colin....@gmail.com> wrote:

I've read the Proofreader API description and I'm just trying to plan the user interface for integrating this into my HTML/JS book authoring app.

Fantastic!

 

I've already successfully integrated the Prompt and Rewriter APIs for a variety of uses but am I right in thinking that the Proofreader API is using a completely different model install that requires it's own separate download into the browser so that if the ProofReader API is ready to use, this doesn't mean the Prompt/Rewriter API is ready to use or vice-versa?

That's correct, we're experimenting with a separate smaller model for Summarizer with the `preference` option set to `'speed'` and the Proofreader API. Kenji announced it in this message. You can observe this on the page `chrome://on-device-internals` on the "Broker State" tab. I just simulated a fresh install:

After the installation, you should see that the model weighs about 117.32 MiB. 

 

And should I assume that the context window for Proofreader will be the same limited size that Prompt has?

 The Proofreader API currently has an assumed infinite context window, as it will internally deal with the chunking of really long input itself. See this section of the draft spec.

Cheers,

Tom

  

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