RPC Server

Source file: pkg/rpc/server.go

The JSON-RPC dispatcher routes tachyon_* methods to the engine. It is used by both the HTTP API (POST /rpc) and the MCP server (tools/call).

Design decisions

Method-per-verb mapping

Each JSON-RPC method maps 1:1 to an engine verb:

Method	Engine call	Request type
`tachyon_compile`	`eng.Compile`	`types.CompileRequest`
`tachyon_test`	`eng.Test`	`types.TestRequest`
`tachyon_simulate`	`eng.Simulate`	`types.SimulateRequest`
`tachyon_deploy`	`eng.Deploy`	`types.DeployRequest`
`tachyon_call`	`eng.Call`	`types.CallRequest`
`tachyon_chain_list`	`eng.ChainList`	(none)
`tachyon_chain_register`	`eng.ChainRegister`	`types.ChainRegisterRequest`
`tachyon_chain_use`	`eng.ChainUse`	`types.ChainUseRequest`
`tachyon_artifact_get`	`eng.ArtifactGet`	`types.ArtifactGetRequest`
`tachyon_registry_lookup`	`eng.RegistryLookup`	`types.RegistryLookupRequest`
`tachyon_health`	`eng.Health`	(none)

Envelope passthrough

The engine returns types.Envelope[T]. The JSON-RPC layer passes this through as the result field. This means JSON-RPC responses have the same shape as REST responses:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "ok": true,
    "data": { ... }
  }
}

Standard JSON-RPC error codes

-32700 — Parse error (malformed JSON)
-32602 — Invalid params (type mismatch, missing field)
-32601 — Method not found

Engine errors are not JSON-RPC errors. They are returned in the envelope's error field with ok: false. This preserves the engine's structured error taxonomy across all transports.

Context propagation

The JSON-RPC dispatcher accepts a context.Context and passes it to engine methods. This enables request cancellation and timeout propagation from the HTTP server or MCP caller.

Modifying the RPC server

What to change	Where
Add JSON-RPC method	`pkg/rpc/server.go` — add case in `Dispatch`
Change error codes	`pkg/rpc/server.go` — `rpcError` struct
Add batch support	`pkg/rpc/server.go` — parse array requests