Add custom header to mcp

Author: Nifury

packages/opencode/src/mcp/context.ts

@@ -0,0 +1,21 @@
+import { Context } from "../util/context"
+
+interface McpCallContext {
+  metadata?: Record<string, string>
+}
+
+const context = Context.create<McpCallContext>("mcp-call")
+
+export const McpCallContext = {
+  provide<R>(value: McpCallContext, fn: () => R): R {
+    return context.provide(value, fn)
+  },
+
+  get current(): McpCallContext | undefined {
+    try {
+      return context.use()
+    } catch {
+      return undefined
+    }
+  },
+}

packages/opencode/src/mcp/index.ts

@@ -23,6 +23,24 @@ import { BusEvent } from "../bus/bus-event"
 import { Bus } from "@/bus"
 import { TuiEvent } from "@/cli/cmd/tui/event"
 import open from "open"
+import { McpCallContext } from "./context"
+
+function createContextAwareFetch(baseFetch?: typeof globalThis.fetch): typeof globalThis.fetch {
+  const fetchFn = baseFetch ?? globalThis.fetch
+  return (input, init) => {
+    const ctx = McpCallContext.current
+    if (ctx) {
+      const headers = new Headers(init?.headers)
+      if (ctx.metadata) {
+        for (const [key, value] of Object.entries(ctx.metadata)) {
+          headers.set(key, value)
+        }
+      }
+      return fetchFn(input, { ...init, headers })
+    }
+    return fetchFn(input, init)
+  }
+}
 
 export namespace MCP {
   const log = Log.create({ service: "mcp" })
@@ -362,19 +380,22 @@ export namespace MCP {
         )
       }
 
+      const contextFetch = createContextAwareFetch()
       const transports: Array<{ name: string; transport: TransportWithAuth }> = [
         {
           name: "StreamableHTTP",
           transport: new StreamableHTTPClientTransport(new URL(mcp.url), {
             authProvider,
             requestInit: mcp.headers ? { headers: mcp.headers } : undefined,
+            fetch: contextFetch,
           }),
         },
         {
           name: "SSE",
           transport: new SSEClientTransport(new URL(mcp.url), {
             authProvider,
             requestInit: mcp.headers ? { headers: mcp.headers } : undefined,
+            fetch: contextFetch,
           }),
         },
       ]

packages/opencode/src/session/prompt.ts

@@ -25,6 +25,7 @@ import MAX_STEPS from "../session/prompt/max-steps.txt"
 import { defer } from "../util/defer"
 import { ToolRegistry } from "../tool/registry"
 import { MCP } from "../mcp"
+import { McpCallContext } from "../mcp/context"
 import { LSP } from "../lsp"
 import { ReadTool } from "../tool/read"
 import { FileTime } from "../file/time"
@@ -111,6 +112,7 @@ export namespace SessionPrompt {
     format: MessageV2.Format.optional(),
     system: z.string().optional(),
     variant: z.string().optional(),
+    metadata: z.record(z.string(), z.string()).optional(),
     parts: z.array(
       z.discriminatedUnion("type", [
         MessageV2.TextPart.omit({
@@ -184,7 +186,7 @@ export namespace SessionPrompt {
       return message
     }
 
-    return loop({ sessionID: input.sessionID })
+    return loop({ sessionID: input.sessionID, metadata: input.metadata })
   })
 
   export async function resolvePromptParts(template: string): Promise<PromptInput["parts"]> {
@@ -273,6 +275,7 @@ export namespace SessionPrompt {
   export const LoopInput = z.object({
     sessionID: SessionID.zod,
     resume_existing: z.boolean().optional(),
+    metadata: z.record(z.string(), z.string()).optional(),
   })
   export const loop = fn(LoopInput, async (input) => {
     const { sessionID, resume_existing } = input
@@ -611,6 +614,7 @@ export namespace SessionPrompt {
         processor,
         bypassAgentCheck,
         messages: msgs,
+        metadata: input.metadata,
       })
 
       // Inject StructuredOutput tool if JSON schema mode enabled
@@ -749,6 +753,7 @@ export namespace SessionPrompt {
     processor: SessionProcessor.Info
     bypassAgentCheck: boolean
     messages: MessageV2.WithParts[]
+    metadata?: Record<string, string>
   }) {
     using _ = log.time("resolveTools")
     const tools: Record<string, AITool> = {}
@@ -864,7 +869,12 @@ export namespace SessionPrompt {
           always: ["*"],
         })
 
-        const result = await execute(args, opts)
+        const result = await McpCallContext.provide(
+          {
+            metadata: input.metadata,
+          },
+          () => execute(args, opts),
+        )
 
         await Plugin.trigger(
           "tool.execute.after",