Pacific Island countries are frequently positioned as recipients of development assistance or locations of strategic competition. Such representations obscure how regional institutions articulate the purposes that external cooperation should serve. This article examines how Pacific diplomatic texts define legitimate partnership and how those definitions appear in selected Chinese and United States cooperation documents. A qualitative documentary analysis compares seven official texts published between 2017 and 2025, distinguishing regional agenda articulation, textual accommodation by partners, and implementation outcomes. The analysis identifies three connected practices: prioritizing climate security, constructing an oceanic regional subject, and specifying obligations through regional strategies and maritime claims. References to Pacific priorities in joint declarations indicate selective textual accommodation, while the continued presence of external strategic objectives demonstrates its limits. Neither rhetorical convergence nor endorsement establishes that Pacific actors controlled negotiations or secured implementation. The article contributes an evidence-sensitive account of discursive agency in sustainability diplomacy: authority can be exercised through the criteria used to evaluate partnerships, even where material inequalities persist. It also identifies the conditions under which recognition could become accountable cooperation, including traceable links between declared priorities, decision procedures, and implementation evidence.