Since 2005, Switzerland’s federal Integration policy has structured the social inclusion of (im)migrants in the country; legal settlement, access to social aid, and naturalization itself are contingent on discretionary judgments as to whether a migrant is linguistically and culturally “integrated” into Swiss society. While public and policy discourse frame the concept of “integration” as a more inclusive departure from Switzerland’s historically “assimilationist” migration policy, discussion has too often overlooked how the shifting and productively vague notion of “integration” constitutes a terrain of social practice—one where the tense, mutually constitutive relationship between reception and regulation, ethics and politics, is negotiated by a host of mobility mediators. Positioned in between migrant and citizen, these persons, often humanitarian volunteers (bénévoles) and “migrants” themselves, teach and broker the cultural-linguistic competences of integration while bridging, too, the ethical and economic dimensions of cross-border mobility. This dissertation draws on 14 months of ethnographic research, conducted in the aftermath of the 2008 financial crisis, among volunteer workers, French language teachers, and undocumented persons distributed across a network of migrant aid agencies, NGOs, and centers of migrant-education in Geneva. The dissertation asks: How is the concept of “integration” in Geneva constructed and practiced? How does its practice enable or foreclose migrant legality? How do situated mediators broker migrants’ economic and social mobility through acts of teaching and linguistic-cultural socialization? What forms of hospitality or solidarity do these envisage? And, in particular, what semiotic processes render the differences—the categories of mobility, person, and (in)hospitable practice—by which integration is imagined and performed? In analyzing everyday practices of migrant socialization, this dissertation advances the concept of "welcome work"—the forms of ethically-charged interstitial brokerage and mediation that aim to articulate migrant with state and citizen. Exploring the ironies and ambivalences of Swiss Integration policy, the dissertation chapters track varied scales and terrains of (in)hospitality: the social and policy distinctions between various types of national strangers/guests (and their relationship to the state’s integration criteria); the moral-economic imagination of the French language in night classes for precarious migrant job-seekers; the cultivation of migrants’ aesthetic sensibilities via pedagogies of “culture”; and practices of legal mediation by which migrant legality, presence, and Swiss jurisdiction itself are brokered and made. By examining the work of intermediaries on the integration front-line, this dissertation contributes to scholarship on mobility and migration by attending to the interstitial spaces of reception—the space between migrant and state that allows for their articulation to become conceivable in terms of “guest” and “host.” In this space, “welcome work” becomes a salient terrain where mediators and migrants alike attempt to reconcile hospitable aspirations and ethics with a national politics of crisis management and border closure.