fix(mcp): auto-reconnect MCP servers after transient listTools failure

When tools() encounters a listTools() failure, fork a background
reconnection fiber via createAndStore() instead of permanently
removing the server. The current turn gets no tools from that server,
but the background fiber re-establishes the connection so tools are
available on the next turn.

Previously, a single transient error (network blip, server restart)
would permanently delete the MCP server from the session with no
recovery path.

packages/opencode/src/mcp/index.ts

@@ -24,7 +24,7 @@ import { BusEvent } from "../bus/bus-event"
 import { Bus } from "@/bus"
 import { TuiEvent } from "@/cli/cmd/tui/event"
 import open from "open"
-import { Effect, Layer, ServiceMap, Stream } from "effect"
+import { Effect, Layer, Scope, ServiceMap, Stream } from "effect"
 import { InstanceState } from "@/effect/instance-state"
 import { makeRunPromise } from "@/effect/run-service"
 import { ChildProcess, ChildProcessSpawner } from "effect/unstable/process"
@@ -464,6 +464,7 @@ export namespace MCP {
   export const layer = Layer.effect(
     Service,
     Effect.gen(function* () {
+      const scope = yield* Scope.Scope
       const spawner = yield* ChildProcessSpawner.ChildProcessSpawner
       const auth = yield* McpAuth.Service
 
@@ -658,7 +659,18 @@ export namespace MCP {
                   return e
                 },
               }).pipe(Effect.option)
-              if (toolsResult._tag === "None") return
+
+              if (toolsResult._tag === "None") {
+                // Fork background reconnection — tools come back next turn
+                const mcpConfig = config[clientName]
+                if (mcpConfig && isMcpConfigured(mcpConfig)) {
+                  yield* createAndStore(clientName, mcpConfig).pipe(
+                    Effect.catch(() => Effect.void),
+                    Effect.forkIn(scope),
+                  )
+                }
+                return
+              }
 
               const mcpConfig = config[clientName]
               const entry = isMcpConfigured(mcpConfig) ? mcpConfig : undefined

packages/opencode/test/mcp/lifecycle.test.ts

@@ -185,7 +185,7 @@ function withInstance(
 // Bug #1: tools() silently deletes clients on transient listTools() failure
 // ========================================================================
 
-test.todo(
+test(
   "tools() removes client from state when listTools fails",
   withInstance(
     {
@@ -216,9 +216,10 @@ test.todo(
       serverState.listToolsShouldFail = true
       await MCP.tools()
 
-      // After the transient error clears, tools should recover
-      // automatically — the server shouldn't be permanently removed.
+      // After the transient error clears, the background reconnection
+      // fiber should restore the server. Give it a tick to complete.
       serverState.listToolsShouldFail = false
+      await new Promise((r) => setTimeout(r, 100))
 
       const toolsRecovered = await MCP.tools()
       expect(Object.keys(toolsRecovered).length).toBeGreaterThan(0)
@@ -230,7 +231,7 @@ test.todo(
 // Bug #2: status() shows stale data after tools() deletes a client
 // ========================================================================
 
-test.todo(
+test(
   "status shows 'failed' after tools() encounters a transient error",
   withInstance(
     {
@@ -256,7 +257,9 @@ test.todo(
       await MCP.tools()
       serverState.listToolsShouldFail = false
 
-      // After the error clears, status should recover automatically
+      // Give background reconnection fiber time to complete
+      await new Promise((r) => setTimeout(r, 100))
+
       await MCP.tools()
       const statusAfter = await MCP.status()
       expect(statusAfter["status-server"]?.status).toBe("connected")