Support Uint8Array / Buffer in api.stream* endpoints

[lilWolf011]

🚀 Feature Request: Binary support in streaming APIs

Hi Encore team 👋,

I’m a happy Encore user working with the api.streamInOut and related streaming functionality. Currently, these APIs only support JSON-compatible types (string, number, boolean, object), which limits binary use cases.

For example, this is not supported:

interface StreamIn {
  data: Uint8Array; // ❌ not currently allowed
}
interface StreamOut {
  data: Uint8Array;
}

🧩 Problem

Because Uint8Array or Buffer aren't supported, we have to base64-encode binary payloads to stream data between client and server.

This results in:

📦 ~33% payload overhead due to base64

🧮 Additional CPU usage from base64 encode/decode

🔁 Increased complexity on both ends

✅ Proposed Solution
Support Uint8Array (or Buffer) directly in streamed API definitions:

interface StreamIn {
  data: Uint8Array;
}
interface StreamOut {
  data: Uint8Array;
}

This would allow zero-copy, efficient binary streaming using msgpack, Protobuf, or similar.

🎯 Benefits

Improved performance: smaller payloads, less CPU work

Cleaner code: no need for manual base64 encoding/decoding
Better developer experience: closer to native WebSocket / streaming behavior
Future-friendly: enables higher throughput real-time use cases

🙏 Summary

Problem: Streaming endpoints only allow JSON-serializable types
Impact: Workarounds required for binary data, leading to inefficiency
Request: Add support for Uint8Array or Buffer in streaming APIs

Would love to see this in the roadmap — I’d be happy to help test or prototype if needed. Thanks for your amazing work on Encore!

[tom-groves]

+1 please, this would be amazing!

[prodemy-prosigmaka]

+1