Collections API seems to be broken in Eleventy 3.1.0 or later

[sentience]

Operating system

macOS Tahoe 26.1

Eleventy

3.1.2

Describe the bug

I use the Collections API in my Eleventy config to create a primaryNav collection that contains all pages of my site with the primary tag set:

  // Sort nav bar collections
  console.log("Adding collection 'primaryNav' for tag 'primary'");
  eleventyConfig.addCollection("primaryNav", (collectionsApi) =>
    collectionsApi
      .getFilteredByTag("primary")
      .sort((pageA, pageB) => pageA.data.order - pageB.data.order);
  );

This works fine up to Eleventy 3.0.0, but in 3.1.x collectionsApi.getFilteredByTag("primary") always returns an empty array. In my debugging, I have also confirmed that collectionsApi.getAll() likewise always returns an empty array.

Reproduction Source Code URL

https://github.com/sentience/eleventy-collections-api-issue

Contains this version of the code with debug output (see below):

  // Sort nav bar collections
  console.log("Adding collection 'primaryNav' for tag 'primary'");
  eleventyConfig.addCollection("primaryNav", (collectionsApi) => {
    console.log(
      "DEBUG collectionsApi.getAll().length: ",
      collectionsApi.getAll().length,
    );
    return collectionsApi
      .getFilteredByTag("primary")
      .sort((pageA, pageB) => pageA.data.order - pageB.data.order);
  });

Screenshots

Build output with Eleventy 3.0.0:

Adding collection 'primaryNav' for tag 'primary'
DEBUG collectionsApi.getAll().length:  0
DEBUG collectionsApi.getAll().length:  2
[11ty] Writing ./_site/index.html from ./index.liquid
[11ty] Writing ./_site/about/index.html from ./about.liquid
[11ty] Copied 11 Wrote 2 files in 0.10 seconds (v3.0.0)

Build output with Eleventy 3.1.2:

Adding collection 'primaryNav' for tag 'primary'
DEBUG collectionsApi.getAll().length:  0
[11ty] Writing ./_site/about/index.html from ./about.liquid
[11ty] Writing ./_site/index.html from ./index.liquid
[11ty] Copied 11 Wrote 2 files in 0.11 seconds (v3.1.2)