I want to know why breadcrumb values look truncated in Sentry and how to keep more of that data.

Breadcrumb strings are truncated when they hit the SDK or server per-value size limit. Data that’s already been truncated in Sentry can’t be restored.

You can raise the client limit up to 8192 characters.

For Python:

sentry_sdk.init(dsn="...", max_value_length=8192)

For JavaScript:

Sentry.init({ dsn: "...", maxValueLength: 8192 });

Don’t set this higher than needed. Oversized events can hit the payload size limit and be dropped.

If you still need more data, put it on the scope as context / extras instead of using a giant breadcrumb. See How can I retrieve truncated data in Sentry?.

If the UI shows Invalid JSON data: Data too long, see that article