| 1 | // Package mcpinteraction carries server-initiated MCP elicitation requests |
| 2 | // from the plugin transport to whichever frontend is driving the call, and the |
| 3 | // user's decision back. It has no UI dependency: the plugin layer hands a |
| 4 | // Broker through the per-call context, the controller layer implements it. |
| 5 | package mcpinteraction |
| 6 | |
| 7 | import ( |
| 8 | "context" |
| 9 | "encoding/json" |
| 10 | ) |
| 11 | |
| 12 | // Elicitation modes defined by MCP 2026-07-28. |
| 13 | const ( |
| 14 | ModeForm = "form" |
| 15 | ModeURL = "url" |
| 16 | ) |
| 17 | |
| 18 | // User actions in answer to an elicitation request. |
| 19 | const ( |
| 20 | ActionAccept = "accept" |
| 21 | ActionDecline = "decline" |
| 22 | ActionCancel = "cancel" |
| 23 | ) |
| 24 | |
| 25 | // Request is one server-initiated elicitation: a typed form (flat primitive |
| 26 | // schema) or a URL the server asks the user to visit. |
| 27 | type Request struct { |
| 28 | // ID is the host-assigned stable identifier for the pending decision, |
| 29 | // echoed by the frontend in the resolve call. |
| 30 | ID string |
| 31 | // Server is the MCP server asking. Surfaced so the user can see who is |
| 32 | // requesting before answering. |
| 33 | Server string |
| 34 | // Mode is "form" or "url". |
| 35 | Mode string |
| 36 | // Message is the server's human-readable explanation. |
| 37 | Message string |
| 38 | // RequestedSchema is the raw JSON schema for form mode. Flat primitives |
| 39 | // only (string/number/integer/boolean/enum, defaults, required, bounds). |
| 40 | RequestedSchema json.RawMessage |
| 41 | // URL is the credential-free HTTP/HTTPS target for url mode. |
| 42 | URL string |
| 43 | // ElicitationID is the server-assigned id for url mode completion. |
| 44 | ElicitationID string |
| 45 | } |
| 46 | |
| 47 | // Result is the user's decision. Action is accept/decline/cancel; Content is |
| 48 | // the submitted form values, present only for accept in form mode. |
| 49 | type Result struct { |
| 50 | Action string |
| 51 | Content map[string]any |
| 52 | } |
| 53 | |
| 54 | // Broker delivers one elicitation to the user and blocks until they answer. |
| 55 | // Implementations must respect ctx cancellation. Privacy: brokers must keep |
| 56 | // form values, URL query strings, and free-text answers out of logs and |
| 57 | // telemetry; only the request kind, action, and error class may be recorded. |
| 58 | type Broker interface { |
| 59 | Interact(ctx context.Context, req Request) (Result, error) |
| 60 | } |
| 61 | |
| 62 | type brokerKey struct{} |
| 63 | |
| 64 | // WithBroker attaches b to ctx for the duration of one MCP call. The broker |
| 65 | // travels with the call context — never with the shared plugin.Host — so |
| 66 | // concurrent tabs and turns cannot cross wires. |
| 67 | func WithBroker(ctx context.Context, b Broker) context.Context { |
| 68 | return context.WithValue(ctx, brokerKey{}, b) |
| 69 | } |
| 70 | |
| 71 | // FromContext returns the call's broker, or nil when the entry point has no |
| 72 | // decision channel (headless/bot). A nil broker means the request must be |
| 73 | // answered cancel — the model never guesses. |
| 74 | func FromContext(ctx context.Context) Broker { |
| 75 | if ctx == nil { |
| 76 | return nil |
| 77 | } |
| 78 | b, _ := ctx.Value(brokerKey{}).(Broker) |
| 79 | return b |
| 80 | } |
| 81 | |
| 82 | // SanitizeURLMode validates a url-mode request target. Only credential-free |
| 83 | // HTTP(S) URLs are presentable; anything else is refused before any UI sees it. |
| 84 | func SanitizeURLMode(req Request) bool { |
| 85 | if req.Mode != ModeURL { |
| 86 | return true |
| 87 | } |
| 88 | return allowedURL(req.URL) |
| 89 | } |
| 90 |