Method handleSiUiResource

server/src/mcp-tools.ts:2076–2131

* Handle SI UI resource request - serves MCP Apps shell with A2UI surface

(uri: string, sessionId: string)

   * Handle SI UI resource request - serves MCP Apps shell with A2UI surface
   */
  private async handleSiUiResource(uri: string, sessionId: string): Promise<{
    contents: Array<{ uri: string; mimeType: string; text: string }>;
  }> {
    // Get the session to retrieve the latest A2UI surface
    const session = await siDb.getSession(sessionId);
    if (!session) {
      throw new Error(`SI session not found: ${sessionId}`);
    }

    // Get the most recent message with a surface
    const messages = await siDb.getSessionMessages(sessionId, 1);
    const latestMessage = messages[0];

    // Build a surface from ui_elements if we don't have a native surface yet
    // This provides backwards compatibility during migration
    let surface = latestMessage?.ui_elements
      ? {
          surfaceId: `si-session-${sessionId}`,
          catalogId: "si-standard",
          components: (latestMessage.ui_elements as Array<{ type: string; data: Record<string, unknown> }>).map((el, idx) => ({
            id: `elem-${idx}`,
            component: { [el.type]: el.data },
          })),
        }
      : {
          surfaceId: `si-session-${sessionId}`,
          catalogId: "si-standard",
          components: [],
        };

    // Read the shell template
    const shellPath = join(__dirname, "../public/si-apps/shell.html");
    let shellHtml: string;
    try {
      shellHtml = await readFile(shellPath, "utf-8");
    } catch {
      throw new Error("SI Apps shell template not found");
    }

    // Inject the surface data into the shell
    const surfaceScript = `window.__SI_SURFACE__ = ${JSON.stringify(surface)};`;
    const injectedHtml = shellHtml.replace(
      /\/\/ This will be replaced by server-side injection[\s\S]*?\/\/ window\.__SI_SURFACE__ = .*$/m,
      surfaceScript
    );

    return {
      contents: [
        {
          uri,
          mimeType: "text/html",
          text: injectedHtml,
        },
      ],
    };
  }
}