Live-Stream Penetration Decline / Trend Root-Cause Diagnosis (Universal Edition)

Preflight: Environment & Execution Gate (MUST)

Before Part 0, verify the execution environment in order:

1. ae-cli config current succeeds and the intended account/session is active.
2. python3, scripts/ae_query.sh, and scripts/dim_analyzer.py are available.
3. The confirmed project_id is accessible to the current session.
4. Bash shell required — scripts use bash syntax (heredoc, set -uo pipefail); Windows users need WSL or Git Bash.

【MUST·analysis-meta event list bug fallback】 On ae-cli ≥6.0.47, analysis-meta event list may fail with INVALID_CAPABILITY_INPUT. Fallback: ae-cli capability run metadata.event.list --input '{"project_id":<pid>,"queries":[...],"limit":200}'. Same for metadata.event.get (--input '{"project_id":<pid>,"event_name":"<name>"}', returns data.event with event_props). Do NOT abort event discovery on the CLI bug.

If CLI/login/permission/query execution fails at any point:

• Report the exact failed capability and the available error text to the user.
• Ask the user to restore access or provide the missing input.
• Do NOT infer, fabricate, or reuse data-backed conclusions for the failed window.
• Stop at the failed gate; continue only after the failure is resolved.