Architecture

Nexus sits on the path out. The agent proposes. The gate decides. The record is written.

If Nexus says no, the action does not happen.

Request flow

flowchart LR
  A[Agent] --> B[Nexus]
  B --> C{Check}
  C -->|Allow| D[Action leaves]
  C -->|Stop| E[Action does not leave]
  C -->|Person| F[Action waits]
  B --> G[Record]

How the gate is built

Three layers sit under check, person, and record.

flowchart TB
  subgraph AgentRuntime["Agent runtime"]
    LC[Your agent]
  end

  subgraph Nexus["Nexus"]
    SDK["SDK wrap"]
    IAM[Identity]
    GW[Gateway]
    POL[Policy]
    AUD[Record]
  end

  subgraph Backend["Your systems"]
    API[APIs]
    DB[(Data)]
  end

  LC --> SDK
  SDK --> IAM
  IAM --> GW
  GW --> POL
  POL -->|allow| API
  POL -->|allow| DB
  POL -->|stop| AUD
  POL -->|person| AUD
  GW --> AUD

Identity

Who is allowed to act. Credentials for agents and for a person on the path. See AgentIAM.

Gateway

Inspection of tool calls and writes before they leave. See MCP Gateway.

Record

Every decision appends to an append-only, hash-chained log you can export. See Immutable audit trail.

Design principles

• The gate is the path out. Prompt rules are not the gate.
• Fail closed. If the gate cannot decide, the action does not leave.
• Same input, same decision. Allow, stop, or a person.
• The record is for proof. You can export it.

Deployment

See Deployment.