The morning brief feature (CLAUDE_CODE_ENABLE_MORNING_BRIEF, CLAUDE_CODE_MORNING_BRIEF_PROMPT) has been removed. The environment variables no longer have any effect. This was a limited-availability feature that has been deprecated.
Evidence
Removal of CLAUDE_CODE_ENABLE_MORNING_BRIEF and CLAUDE_CODE_MORNING_BRIEF_PROMPT from environment variable registry (confirmed absent in new version, confirmed present in old version via string diff).
Strings lifted out of the shipped bundle, so the claim above can be checked against them.