The extension spec's CORS section requires
'Access-Control-Allow-Headers: Content-Type, If-None-Match' and
'Access-Control-Expose-Headers: ETag' on hosted card and catalog
endpoints; the served responses allowed only Content-Type and exposed
nothing, which would stop a browser-based client from reading the ETag
or sending If-None-Match for a cross-origin 304 revalidation. Both the
explicit discovery_response headers and the CORSMiddleware preflight
config now emit the full set, with tests asserting the headers on the
card response and on a browser preflight requesting If-None-Match.
Claude
5e4acb59ab