Architecture

Stendar pairs a production DeFi execution engine with public policy contracts, provider adapters, wallet adapters, notifications, CLI tooling, and AI adapter packages. Private product harness and hosted surfaces live under internal/.

Layered model

1. Public interfaces: SDK, CLI, notifications, LangChain, and Vercel AI adapter packages.
2. Policy v2 shared decision contract: Shared fail-closed schemas for approvals, limits, and execution constraints.
3. Runtime policy enforcement: PolicyEngine checks on DeFi execution flows and compatibility adapters.
4. DeFi execution engine: Deterministic runtime flows through DeFiRuntime.
5. Providers, chains, and wallets: The concrete on-chain adapters and signing infrastructure.

Component graph

graph TD
  SDK[SDK / Client surface] --> PolicyEngine[PolicyEngine runtime checks]
  AI[LangChain / Vercel AI adapters] --> SDK
  CLI[CLI] --> SDK
  PolicyV2[Policy v2 decision contract] -. fail-closed semantics via adapters .-> PolicyEngine
  PolicyEngine --> Runtime[DeFiRuntime execution engine]

  Runtime --> Providers[Protocol providers]
  Providers --> Chains[Chain adapters]
  Runtime --> Wallets[Wallet adapters]
  Runtime --> Events[TypedEmitter RuntimeEvents]
  Events --> Notifiers[@stendar/notifications]

Runtime lifecycle (conceptual)

This sequence models the public runtime lifecycle and uses conceptual participants, not concrete class names. Runtime execution uses PolicyEngine, while Policy v2 defines the shared structured decision contract for fail-closed adapters.

sequenceDiagram
  participant Interface as SDK / AI / CLI surface
  participant Policy as Policy decision contract (Policy v2)
  participant Runtime as DeFiRuntime
  participant Provider as Provider
  participant Wallet as WalletAdapter
  participant Chain as ChainAdapter

  Interface->>Policy: evaluate(intent, context)
  Policy-->>Interface: allow | deny | review_required | approval_required | blocked_until_evidence
  alt denied or approval required
    Interface-->>Interface: block or require approval handling
  else allowed
    Interface->>Runtime: execute(intent)
    Runtime->>Provider: getQuote/buildTransaction
    Runtime->>Chain: simulateTransaction()
    alt dryRun
      Runtime-->>Interface: simulated result
    else live
      Runtime->>Wallet: signTransaction()
      Runtime->>Chain: sendTransaction()
      Runtime->>Chain: waitForConfirmation()
      Runtime-->>Interface: confirmed/failed result
    end
  end

Why this shape

• PolicyEngine remains the active execution path today for lower-level access.
• Policy v2 schemas provide the shared decision contract now, while compatibility adapters preserve raw runtime evidence and behavior during convergence.
• The DeFi execution engine stays focused on deterministic execution across pluggable chains, providers, and wallets.
• Event emission keeps observability and notification routing first-class.

Continue with Runtime lifecycle and Best execution.