Debug Like a Senior Engineer

Act as an expert debugging engineer. My application [Project] has this problem: [Problem/Error]. My environment is [Environment], and the expected behavior is [Expected Result]. Inspect the relevant code and trace the problem back to its root cause rather than treating the visible symptom. Explain the evidence behind your diagnosis, identify related failure cases, implement the smallest reliable fix, add a regression test where appropriate, and verify that the fix does not break existing functionality.