fix(session): catch plugin defects and normalize static MCP headers

Aleksandr Lossenko · claude · Aleksandr Lossenko · commit fe9889d4e58f · 2026-05-18T22:49:58.000+02:00
Co-Authored-By: Claude Sonnet 4.6 &lt;noreply@anthropic.com&gt;
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
@@ -407,16 +407,17 @@ export const layer = Layer.effect(
                 { tool: key, sessionID: ctx.sessionID, callID: opts.toolCallId },
                 { args },
               )
-              // === BEGIN ADDITIONS ===
               const meta = (item as { __mcp?: { server: string; tool: string } }).__mcp
               let mcpHeaders: Record<string, string> | undefined
               if (meta) {
                 const cfg = yield* config.get()
                 const serverCfg = cfg.mcp?.[meta.server]
-                const staticHeaders =
-                  serverCfg && "headers" in serverCfg && serverCfg.headers
-                    ? { ...serverCfg.headers }
-                    : {}
+                const staticHeaders: Record<string, string> = {}
+                if (serverCfg && "headers" in serverCfg && serverCfg.headers) {
+                  for (const [k, v] of Object.entries(serverCfg.headers)) {
+                    staticHeaders[k.toLowerCase()] = v
+                  }
+                }
                 const output = { headers: staticHeaders }
                 yield* plugin
                   .trigger(
@@ -430,31 +431,28 @@ export const layer = Layer.effect(
                     output,
                   )
                   .pipe(
-                    Effect.catch((_err) => {
-                      const err = _err as unknown
+                    Effect.catchCause((cause) => {
                       log.warn("mcp.call.before plugin failed", {
                         server: meta.server,
                         tool: meta.tool,
                         sessionID: ctx.sessionID,
                         callID: opts.toolCallId,
-                        error: err instanceof Error ? err.message : String(err),
+                        error: Cause.pretty(cause),
                       })
-                      return Effect.succeed(output)
+                      return Effect.void
                     }),
                   )
                 mcpHeaders = output.headers
               }
-              // === END ADDITIONS ===
 
               const result: Awaited<ReturnType<NonNullable<typeof execute>>> = yield* Effect.gen(function* () {
                 yield* ctx.ask({ permission: key, metadata: {}, patterns: ["*"], always: ["*"] })
-                // === BEGIN MODIFICATION ===
                 return yield* Effect.promise(() => {
-                  if (meta && mcpHeaders) {
+                  if (mcpHeaders) {
                     return MCP.McpCallContext.run(
                       {
-                        server: meta.server,
-                        tool: meta.tool,
+                        server: meta!.server,
+                        tool: meta!.tool,
                         sessionID: ctx.sessionID,
                         callID: opts.toolCallId,
                         headers: mcpHeaders,
@@ -464,7 +462,6 @@ export const layer = Layer.effect(
                   }
                   return execute(args, opts)
                 })
-                // === END MODIFICATION ===
               }).pipe(
                 Effect.withSpan("Tool.execute", {
                   attributes: {
