The original user context can disappear unless the delegation chain is preserved explicitly. Once a gateway intermediates access, the backend needs a way to know who initiated the action, what was delegated, and which scope was passed through. Without that, auditability and accountability weaken.
Why This Matters for Security Teams
An MCP gateway changes the trust boundary. Once requests are brokered between a user-facing client and backend servers, the backend can no longer assume the original caller is still visible in the session or token. That breaks a core security expectation: the ability to answer who asked for what, under which authority, and with what delegated scope. This is not just an audit problem. It affects authorization, incident response, and policy enforcement.
When delegation is implicit, backend services may see only the gateway identity, a generic service token, or a flattened context that hides the original user intent. In practice, that creates room for overbroad access, weak accountability, and failed repudiation checks. Current guidance suggests treating the delegation chain as first-class security data, not metadata that can be dropped for convenience. The risk is especially visible in autonomous and agentic workflows, where tool calls can branch quickly and permissions are exercised at machine speed. NHI Management Group’s research on agentic risk and mcp security shows how quickly gaps in context and access scoping become operational blind spots, especially when platforms expose secrets or tool permissions too broadly. See AI Agents: The New Attack Surface report and The State of MCP Server Security 2025 for the underlying exposure patterns.
In practice, many security teams notice the failure only after a backend action cannot be tied back to the initiating user, rather than through intentional delegation design.
How It Works in Practice
The fix is not to remove the gateway. It is to make delegation explicit, cryptographically verifiable, and preserved end to end. An MCP gateway should pass identity context, scope, and request intent in a way the backend can validate at request time. That usually means a combination of workload identity, short-lived credentials, and policy evaluation that happens with full context rather than a static role lookup.
For user-mediated flows, the gateway should attach a delegation artifact that states who initiated the request, what the gateway is allowed to do on their behalf, and the expiration of that delegation. For service-to-service paths, the backend should trust the gateway only if the gateway can prove its own workload identity and if the original subject remains intact. Emerging practice favours tokens or assertions with explicit claims over opaque pass-through sessions. The operational goal is simple: the backend must be able to distinguish “gateway acted” from “gateway acted for this user, for this purpose, within this scope.”
- Preserve the original subject, not just the gateway service account.
- Bind delegated scope to a short TTL so authority expires automatically.
- Log the full chain: user, gateway, backend, tool, and requested action.
- Evaluate authorization at runtime using policy-as-code, not static RBAC alone.
This aligns with the direction described in the OWASP Top 10 for Agentic Applications 2026 and the NIST guidance in NIST SP 800-53 Rev 5 Security and Privacy Controls, both of which support strong identity, auditability, and least privilege. NHI Management Group’s OWASP Agentic Applications Top 10 and Analysis of Claude Code Security both reinforce the same practical point: agentic systems need runtime control, not just perimeter control.
These controls tend to break down when the gateway normalizes all requests into a single backend principal, because the original actor, scope, and purpose are no longer recoverable downstream.
Common Variations and Edge Cases
Tighter delegation controls often increase implementation overhead, requiring organisations to balance stronger accountability against lower friction for developers and operators. That tradeoff becomes visible in mixed environments where some backend services understand delegated identity while others still expect a single service token.
There is no universal standard for this yet. Some teams propagate user context in headers, others use signed claims, and some rely on token exchange or workload identity frameworks. The best practice is evolving toward preserving provenance in a way that is machine-verifiable and resistant to header spoofing or token replay. For multi-hop chains, each hop should either preserve the original subject or explicitly record a constrained sub-delegation, so the audit trail does not collapse into a single anonymous gateway identity. This matters even more when MCP gateways front autonomous agents, because agents can chain tools, change objectives mid-run, or trigger actions that the initiating user did not foresee.
Edge cases also appear in cross-tenant systems, partner integrations, and legacy backends. If a backend cannot parse delegation claims, then the safer option is to deny privileged actions rather than silently degrade to gateway-only authorization. That is especially important when organizations are trying to contain the kind of broad access and blind spots highlighted in the AI Agents: The New Attack Surface report. In gateway-heavy architectures, the common failure is not broken transport. It is broken provenance.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
OWASP Agentic AI Top 10, CSA MAESTRO and OWASP Non-Human Identity Top 10 address the attack and risk surface, while NIST AI RMF and NIST CSF 2.0 set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| OWASP Agentic AI Top 10 | A2 | Covers broken delegation and tool abuse in agentic request paths. |
| CSA MAESTRO | GOV-03 | Addresses governance of autonomous actions across mediated service chains. |
| NIST AI RMF | GOVERN | Supports accountability, traceability, and risk management for AI-mediated actions. |
| OWASP Non-Human Identity Top 10 | NHI-01 | Relevant to preserving identity context and limiting over-privileged non-human access. |
| NIST CSF 2.0 | PR.AC-4 | Least-privilege access and identity verification apply directly to gateway mediation. |
Use short-lived delegated identity and keep the original subject intact end to end.
Related resources from NHI Mgmt Group
Deepen Your Knowledge
Reviewed and updated by the NHIMG editorial team on August 2, 2026.
NHI Mgmt Group — the #1 independent authority on Non-Human Identity, IAM, and Agentic AI security. nhimg.org
