fix(server): OpenCode 2 threads keep T3's tools after an idle project is evicted

apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.test.ts

@@ -2722,6 +2722,58 @@ describe("OpenCode2 adapter", () => {
       }).pipe(Effect.scoped),
   );
 
+  it.effect("adds T3's MCP server again on every turn, in case OpenCode dropped it", () =>
+    Effect.gen(function* () {
+      McpProviderSession.setMcpProviderSession({
+        environmentId: EnvironmentId.make("environment:opencode2-adapter"),
+        threadId,
+        providerSessionId: "mcp:opencode2-adapter",
+        providerInstanceId: instanceId,
+        endpoint: "http://127.0.0.1:3773/mcp",
+        authorizationHeader: "Bearer thread-credential",
+        browserToolsAvailable: false,
+      });
+      yield* Effect.addFinalizer(() =>
+        Effect.sync(() => McpProviderSession.clearMcpProviderSession(threadId)),
+      );
+      const server = "t3-code-thread_opencode2-adapter";
+      const add = [
+        out("mcp.add", {
+          server,
+          "location[directory]": WORK,
+          config: {
+            type: "remote",
+            url: "http://127.0.0.1:3773/mcp",
+            headers: { Authorization: "Bearer thread-credential" },
+            oauth: false,
+          },
+        }),
+        reply("mcp.add", null),
+      ];
+      const turn = [
+        out("session.prompt", { sessionID: SESSION, text: "<any>" }),
+        promptAccepted,
+        event("session.execution.succeeded", { sessionID: SESSION }),
+      ];
+      // OpenCode keeps runtime-added servers with the Location and forgets them
+      // when it evicts an idle one, without a reconnect T3 could notice.
+      const { runtime, thread } = yield* resumed([
+        ...add,
+        ...turn,
+        ...add,
+        ...turn,
+        // Removed when the session closes.
+        out("mcp.remove", { server, "location[directory]": WORK }),
+        reply("mcp.remove", null),
+      ]);
+      for (let index = 0; index < 2; index++) {
+        const terminal = yield* terminalOf(runtime).pipe(Effect.forkScoped);
+        yield* runtime.startTurn(turnInput(thread));
+        assert.equal((yield* Fiber.join(terminal))?.status, "completed");
+      }
+    }).pipe(Effect.scoped),
+  );
+
   it.effect("registers a long thread id's MCP server under a name OpenCode accepts", () =>
     Effect.gen(function* () {
       // Spelled out, this delegated thread's server name would be 120 characters.

apps/server/src/orchestration-v2/Adapters/OpenCode2AdapterV2.ts

@@ -396,7 +396,7 @@ interface ThreadState {
    * inbox, where the next prompt would deliver them first, so it cancels them.
    */
   readonly strandedSteers: Set<string>;
-  /** T3's MCP server as registered for this thread, and the instructions entry sent with it. */
+  /** T3's MCP server as last registered for this thread, and the instructions entry sent with it. */
   mcp:
     | { readonly name: string; readonly directory: string; readonly credential: string }
     | undefined;
@@ -3260,9 +3260,12 @@ export const make = Effect.fn("OpenCode2Adapter.make")(function* (instanceId: Pr
         yield* removeMcp(state.mcp);
         state.mcp = undefined;
       }
-      // T3's tools are an addition: a server that cannot add them still runs the turn.
-      if (wanted !== undefined && state.mcp === undefined) {
-        const added = yield* client.mcp
+      // Added on every turn: OpenCode drops runtime-added servers when it evicts
+      // an idle Location, and leaves an unchanged one connected. T3's tools are
+      // an addition: a server that cannot add them still runs the turn.
+      let mcpAvailable = false;
+      if (wanted !== undefined) {
+        mcpAvailable = yield* client.mcp
           .add({
             server: name,
             location: { directory },
@@ -3282,11 +3285,11 @@ export const make = Effect.fn("OpenCode2Adapter.make")(function* (instanceId: Pr
               ),
             ),
           );
-        if (added) state.mcp = wanted;
+        if (mcpAvailable) state.mcp = wanted;
       }
       const instructions = [
         buildRuntimeInstructions({ harness: "OpenCode", model: turnInput.modelSelection.model }),
-        t3OrchestrationSystemPrompt(state.mcp !== undefined),
+        t3OrchestrationSystemPrompt(mcpAvailable),
       ]
         .filter((part) => part !== undefined && part.length > 0)
         .join("\n\n");