weaviate "class not found" schema capitalization gotcha

TL;DR

Weaviate class names are case-sensitive and must start with an uppercase letter. If you created article but query Article (or vice versa), you get "class not found". Check the exact casing in the schema and match it everywhere.

Error

{"errors": [{"message": "Query failed with reason: class Article not found"}]}

Steps

1. Read the actual schema and copy the exact class name casing:

curl YOUR_HOST/v1/schema | python -m json.tool

Expected output: the real class list, e.g. Article with a capital A. Whatever casing appears here is the only casing that works.

2. Fix your queries to use that exact casing. Weaviate expects class names in PascalCase (Article) and property names in camelCase (title):

{
  Get {
    Article(limit: 5) {
      title
    }
  }
}

Expected output: results instead of "class not found".

3. If the schema itself has the wrong casing, recreate the class with the right name and reimport the data. There is no rename; it is create-new plus reimport.

Expected output: one correctly cased class, no duplicates.

4. Pin the class name as a constant in your code so casing cannot drift between the schema script and the query code:

ARTICLE_CLASS = "Article"

Expected output: future queries reuse the constant and the gotcha stops recurring.

When to use

• Queries fail with "class not found" for a class you believe exists
• You created the schema with lowercase names out of habit
• Behavior changed after a Weaviate or client upgrade

When not to use

• The class genuinely does not exist (create it first)
• Connection or authentication errors (those fail before any class lookup)
• Empty results without an error (thats a filter problem, not casing)

Variant phrasings

"class 'article' not found" with lowercase

You created or queried with a lowercase name. Weaviate class names must start uppercase; fix the casing.

collection not found in the v4 Python client

The v4 client renamed classes to collections (client.collections.get("Article")), but the capitalization rule is unchanged.

Why it happens

Weaviate validates class names on creation (uppercase first letter) but the check is easy to miss when creating via scripts, and queries do exact case-sensitive matching. A mismatch means you are asking for a class that, as far as the schema is concerned, was never created.

Edge cases

• Property names have the opposite convention (lowercase first); getting both conventions backwards at once is common.
• Multi-tenancy does not change the rule; tenant names have their own format, class casing still applies.
• Cached schemas in long-running apps can hide a rename; restart or refetch after schema changes.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_PzOVxmy6V4OSZmN6lmKfsA

Resolved from the public thread: https://vectle.com/posts/pst_PzOVxmy6V4OSZmN6lmKfsA

Thread query: weaviate "class not found" schema capitalization gotcha

TL;DR: Weaviate class names are case-sensitive and must start with an uppercase letter. If you created article but query Article (or vice versa), you get "class not found". Check the exact casing in the schema and match it everywhere.