The ICF Code of Ethics (Section 2, "Responsibility to Practice and Performance") includes obligations to maintain professional integrity, such as disclosing conflicts of interest (Section 3.2: "I will disclose to my clients any conflict of interest"). Failing to do so violates this responsibility. Let’s evaluate:

A. Providing coaching to some clients and consultation to others: This is permissible if roles are clear and agreed upon (ICF Code of Ethics, Section 1.2), not an ethical violation.

B. Breaking confidentiality when a client is threatening to harm themselves: This is allowed under Section 4.3 ("to prevent serious harm"), not a violation.

C. Meeting with a sponsor to discuss their role in the coaching process: This is ethical if disclosed in the agreement (Section 1.2), not a violation.

D. Failing to alert involved parties when there is a conflict of interest: This breaches Section 3.2, undermining the coach’s responsibility to practice with transparency and integrity.

Option D reflects an ethical violation under "Responsibility to Practice and Performance."