# Binary Hub Protocol (wire) — Known Issues

For planned/actionable work see `SIGNALR_BINARY_PROTOCOL_TODO.md`.
For higher-level SignalR abstractions see `SIGNALR_ISSUES.md`.

## ISSUE-01: AsyncSegment send-path unsupported on WebAssembly

**Severity:** Major (on WASM) · **Status:** Workaround-in-place · **Area:** `AsyncPipeWriterOutput` / WASM runtime

### Description
`AsyncPipeWriterOutput.SyncAwaitFlush` uses `Task.Wait(timeout)` — deadlocks the single-threaded WASM UI thread. Therefore, WASM clients cannot SEND with `AsyncSegment` mode.

### Known workaround (multi-layer)
1. **`AcBinaryHubProtocolOptions.Validate()`** throws `PlatformNotSupportedException` if WASM + AsyncSegment combination is requested → prevents deadlock
2. **Consumer code-level safety-net** downgrades `AsyncSegment → Segment` on WASM (see `FruitBankHybrid.Web.Client/Program.cs` Configure lambda)
3. **Receive-path** on WASM is fully supported — `SegmentBufferReaderInput` with synchronous fallback at `CHUNK_END` means WASM clients CAN receive AsyncSegment-chunked data from a non-WASM sender, they just cannot send AsyncSegment themselves

### Related TODO
None — architectural constraint of browser WASM threading model.

## ISSUE-02: StaticWebAssets SDK "Illegal characters" noise (consumer build)

**Severity:** Cosmetic (non-blocking) · **Status:** Upstream SDK limitation · **Area:** SDK, not our code

### Description
Consumer projects using `Microsoft.NET.Sdk.BlazorWebAssembly` may see "Illegal characters in path" errors in the VS design-time error list. Originates from the SDK's `DefineStaticWebAssets` task calling legacy `FileIOPermission.EmulateFileIOPermissionChecks`, which is stricter than NTFS (e.g., double spaces or certain path patterns in any wwwroot asset trigger it).

Build succeeds, app runs — the "error" is error-list-only.

### Known workaround
Ignore the error-list entry. If it becomes truly blocking, inspect wwwroot (including transitive from RCL projects) for problematic filenames (double spaces, control chars, reserved chars).

### Related TODO
None — upstream SDK fix required.