[Manishram-ai]

Description

The code block download button looks up the file extension with language in languageExtensionMap, which is case-sensitive and also matches keys on Object.prototype. The highlighter lowercases the language, so ```Python is highlighted fine but downloads as file.txt, and ```constructor downloads as file.function Object() { [native code] }.

This lowercases the language before the lookup and uses Object.hasOwn, like markdown.ts already does.

Type of Change

• Bug fix (non-breaking change which fixes an issue)

Changes Made

• download-button.tsx: lowercase the language and check own keys only
• tests for Python, JSON and TypeScript, and for constructor, toString and __proto__ falling back to .txt
• patch changeset

Testing

• All existing tests pass
• Added new tests for the changes

The 6 new tests fail on main and pass with this change. The full streamdown suite passes (1,316 tests), and Biome is clean on the changed files.

Checklist

• My code follows the project's code style
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have created a changeset (pnpm changeset)
• All my commits are signed

Changeset

• I have created a changeset for these changes

[vercel]

@Manishram-ai is attempting to deploy a commit to the Vercel Team on Vercel.

A member of the Team first needs to authorize it.

[farnabaz]

LGTM, Thanks