AI agents in 2026 operate CRMs, trigger workflows, and deploy code. The shift from reading to writing data has exposed a fundamental problem: authentication wasn't designed for autonomous systems that act across dozens of tools on behalf of multiple users.
The pattern is familiar to any CTO running agents at scale. API keys proliferate. Service accounts accumulate permissions. Token refresh logic spreads across services. Six months in, nobody can definitively answer what an agent can access or why.
Four platforms emerged in 2026 to address this: Composio handles OAuth lifecycles across 500+ integrations without exposing credentials to agent code. Arcade implements just-in-time verification, requiring explicit approval for high-risk actions. Merge Agent Handler uses Tool Packs to enforce scoped access with audit trails. Nango focuses on OAuth and token management for teams with existing agent stacks.
The authentication tax
The trade-offs are clear. Composio centralizes auth and reliability but adds another dependency. Arcade's approval gates slow execution but prevent the "oops" moments that make headlines. Merge delivers enterprise governance at the cost of flexibility. Nango keeps things lightweight but leaves more auth logic in your code.
Hyperscalers offer alternatives: Google Vertex AI, AWS Bedrock, and Azure integrate auth in agent builders for cloud-native stacks. The bet there is that tighter platform integration outweighs third-party flexibility.
What this means in practice
The real question isn't which platform is "best." It's where you want complexity to live. Teams choosing Composio are saying: "We'd rather not own OAuth refresh logic for 50 SaaS tools." Teams choosing Merge are saying: "Audit trails matter more than velocity."
History suggests the winners will be platforms that make credential rotation boring and permission reviews automatic. The losers will be teams still managing API keys in spreadsheets when the first security incident hits.
Notably absent from vendor pitches: specific funding figures or market size data. The enterprise deals are happening quietly, led by proven players like Kore.ai (400+ Fortune 2000 clients, 250+ connectors) rather than startups chasing hype.
Worth watching: How hyperscaler auth integrations mature over the next 12 months. If AWS Bedrock makes agent authentication truly seamless, the third-party platforms will need sharper differentiation than "we have more integrations."