Option D treats prompts as production configuration and executable application behavior rather than informal text. A prompt modification can change output format, tool-selection behavior, policy enforcement, downstream compatibility, token usage, or model quality just as materially as an ordinary source-code change. Consequently, prompt changes need traceability, review, testing, and rollback.

A single source of truth prevents different application paths from silently using inconsistent prompt versions. Version control provides an immutable history showing who changed the prompt, what changed, and which application release used it. Pull-request review enables peer assessment and automated evaluation before deployment. The same configuration-as-code principle appears throughout Claude Code’s project configuration model, where shared project configuration is designed to live with version-controlled project artifacts.

A removes governance and creates an uncontrolled external state. B increases hidden runtime behavior and bypasses normal review. C solves fragmentation but leaves the exact governance failure described in the scenario—the ability to ship prompt changes without review.

Therefore, D provides reproducibility and controlled change management. Relevant Study Guide topics: prompt versioning, configuration management, source control, change review, reproducibility, regression testing, and rollback.

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