Enable sequential mcp call

Author: Nifury

packages/opencode/src/config/config.ts

@@ -258,6 +258,9 @@ export const Info = Schema.Struct({
         description:
           "Enable Anthropic's native tools (web_search_20260209, web_fetch_20260209) for Anthropic models",
       }),
+      sequential_mcp_tools: Schema.optional(Schema.Boolean).annotate({
+        description: "Execute MCP tool calls sequentially instead of in parallel",
+      }),
     }),
   ),
 })

packages/opencode/src/session/prompt.ts

@@ -455,15 +455,19 @@ NOTE: At any point in time through this workflow you should feel free to ask the
         })
       }
 
+      const cfg = yield* config.get()
+      const sequential = cfg.experimental?.sequential_mcp_tools ?? false
+      let mcpQueue = Promise.resolve<unknown>(undefined)
+
       for (const [key, item] of Object.entries(yield* mcp.tools())) {
         const execute = item.execute
         if (!execute) continue
 
         const schema = yield* Effect.promise(() => Promise.resolve(asSchema(item.inputSchema).jsonSchema))
         const transformed = ProviderTransform.schema(input.model, schema)
         item.inputSchema = jsonSchema(transformed)
-        item.execute = (args, opts) =>
-          run.promise(
+        item.execute = (args, opts) => {
+          const work = () => run.promise(
             Effect.gen(function* () {
               const ctx = context(args, opts)
               yield* plugin.trigger(
@@ -530,6 +534,13 @@ NOTE: At any point in time through this workflow you should feel free to ask the
               return output
             }),
           )
+          if (sequential) {
+            const next = mcpQueue.then(() => work(), () => work())
+            mcpQueue = next.then(() => {}, () => {})
+            return next
+          }
+          return work()
+        }
         tools[key] = item
       }