We propose a model of collaborative work in pairs. Each potential partner draws an idea from a distribution that depends on their unobserved ability. The partners then choose to combine their ideas, or work separately. These decisions are based on the intrinsic value of their projects, but also on signaling payoffs, which depend on the public’s assessment of individual contributions to joint work. In equilibrium, collaboration strategies both justify and are justified by public assessments. When partners are symmetric, equilibria with symmetric collaborative strategies are often fragile, in a sense made precise in the paper. In such cases, asymmetric equilibria exist: upon observing a collaborative outcome, the public ascribes higher credit to one of the partners based on payoff-irrelevant ``identities.” Such favored identities do receive a higher payoff relative to their disfavored counterparts conditional on collaborating, but may receive lower overall expected payoff. Finally, we study a policy that sometimes (but not always) clarifies the ordinal ranking of partners’ contributions, and find that such disclosures can be Pareto-improving and reduce the scope for discrimination across payoff-irrelevant identities.