fix(server): inject OpenCode MCP servers once

docs/providers.md

@@ -26,6 +26,8 @@ Pi import discovery reads Pi's persisted JSONL session files because Pi RPC does
 
 Pi RPC extension UI dialog requests (`select`, `input`, `editor`, `confirm`) are bridged into Paseo question permissions and answered with `extension_ui_response`. Fire-and-forget extension UI requests such as notifications are intentionally ignored by the provider adapter unless Paseo grows first-class UI for them.
 
+OpenCode MCP injection is dynamic and session-scoped. Call OpenCode's `mcp.add` endpoint with the MCP server config and do not follow it with `mcp.connect`; `connect` only toggles MCP servers already present in OpenCode's own config. New OpenCode versions return `McpServerNotFoundError`/404 for `connect` after a dynamic add because the server is not config-backed, while older versions silently swallowed the same missing-config path.
+
 Draft metadata lookups should avoid creating provider sessions when the upstream provider has top-level APIs for that metadata. Prefer `AgentClient.listModels`, `listModes`, `listCommands`, or `listFeatures` over creating a scratch `AgentSession`; scratch sessions can show up as empty native sessions in provider import/history UIs.
 
 ---

packages/server/src/server/agent/providers/opencode-agent.test.ts

@@ -585,6 +585,46 @@ describe("OpenCode adapter context-window normalization", () => {
 });
 
 describe("OpenCode adapter startTurn error handling", () => {
+  test("dynamically adds injected MCP servers without config-backed connect", async () => {
+    const runtime = new TestOpenCodeRuntime();
+    const openCodeClient = new TestOpenCodeClient();
+    runtime.enqueueClient(openCodeClient);
+    const cwd = tmpCwd();
+    const client = new OpenCodeAgentClient(createTestLogger(), undefined, { runtime });
+
+    try {
+      const session = await client.createSession({
+        provider: "opencode",
+        cwd,
+        mcpServers: {
+          paseo: {
+            type: "http",
+            url: "http://127.0.0.1:6767/mcp/agents?callerAgentId=test-agent",
+          },
+        },
+      });
+
+      await collectTurnEvents(streamSession(session, "hello"));
+
+      expect(openCodeClient.calls.mcpAdd).toEqual([
+        {
+          directory: cwd,
+          name: "paseo",
+          config: {
+            type: "remote",
+            url: "http://127.0.0.1:6767/mcp/agents?callerAgentId=test-agent",
+            enabled: true,
+          },
+        },
+      ]);
+      expect(openCodeClient.calls.mcpConnect).toEqual([]);
+
+      await session.close();
+    } finally {
+      rmSync(cwd, { recursive: true, force: true });
+    }
+  });
+
   test("emits turn_started before live OpenCode timeline items", async () => {
     const eventsGate = createTestDeferred<void>();
     const globalEvents = [

packages/server/src/server/agent/providers/opencode-agent.ts

@@ -3170,16 +3170,10 @@ class OpenCodeAgentSession implements AgentSession {
         config,
       }),
     );
-    await this.runMcpOperation("connect", name, () =>
-      this.client.mcp.connect({
-        directory: this.config.cwd,
-        name,
-      }),
-    );
   }
 
   private async runMcpOperation(
-    operation: "add" | "connect",
+    operation: "add",
     name: string,
     run: () => Promise<{ error?: unknown }>,
   ): Promise<void> {

packages/server/src/server/agent/providers/opencode/test-utils/test-opencode-runtime.ts

@@ -56,6 +56,8 @@ export class TestOpenCodeClient {
     eventSubscribe: [] as unknown[],
     experimentalSessionList: [] as unknown[],
     globalEvent: [] as unknown[],
+    mcpAdd: [] as unknown[],
+    mcpConnect: [] as unknown[],
     permissionReply: [] as unknown[],
     providerList: [] as unknown[],
     questionReject: [] as unknown[],
@@ -74,6 +76,8 @@ export class TestOpenCodeClient {
   commandListResponse: OpenCodeResponse = { data: [] };
   eventStream: AsyncIterable<unknown>;
   experimentalSessionListResponse: OpenCodeResponse = { data: [] };
+  mcpAddResponse: OpenCodeResponse = {};
+  mcpConnectResponse: OpenCodeResponse = {};
   permissionReplyResponse: OpenCodeResponse = {};
   providerListResponse: OpenCodeResponse = { data: { connected: [], all: [] } };
   providerListImplementation: (() => Promise<OpenCodeResponse>) | null = null;
@@ -135,8 +139,14 @@ export class TestOpenCodeClient {
         },
       },
       mcp: {
-        add: async () => ({}),
-        connect: async () => ({}),
+        add: async (parameters: unknown) => {
+          this.calls.mcpAdd.push(parameters);
+          return this.mcpAddResponse;
+        },
+        connect: async (parameters: unknown) => {
+          this.calls.mcpConnect.push(parameters);
+          return this.mcpConnectResponse;
+        },
       },
       permission: {
         reply: async (parameters: unknown) => {