# Verification record — `flutter_rust_bridge_hello`

## Result

PASS. The PoC exit criterion (from
`docs/architecture/proof-of-concept-plan.md` §2: "Flutter can call Rust
and receive event stream data") is met.

## Environment

| Field | Value |
|---|---|
| Date | 2026-05-13 |
| Host OS | Linux (Arch, kernel 7.0.5-arch1-1, x86_64) |
| Flutter | 3.41.9 stable (Dart 3.11.5) |
| Rust toolchain | stable 1.95.0 |
| `flutter_rust_bridge` (Rust + Dart) | 2.12.0 |
| `flutter_rust_bridge_codegen` | 2.12.0 |
| Target | linux desktop (x86_64-unknown-linux-gnu) |

## Reproduction

```bash
# 1. Generate Dart bindings + Rust glue from rust/src/api.
flutter_rust_bridge_codegen generate

# 2. Build the Linux desktop bundle (this builds the cdylib too, via cargokit).
flutter build linux --debug

# 3. Run the headless verification test. The cdylib lives in the build bundle,
#    so we point dart:ffi at it via LD_LIBRARY_PATH.
LD_LIBRARY_PATH="$PWD/build/linux/x64/debug/bundle/lib:$LD_LIBRARY_PATH" \
    flutter test test/poc_verification_test.dart
```

## Observed result

```
00:00 +0: loading /home/.../test/poc_verification_test.dart
00:00 +0: (setUpAll)
00:00 +0: Chanora FRB hello PoC greet() returns typed result for valid input
00:00 +1: Chanora FRB hello PoC greet() surfaces typed error for empty input
00:00 +2: Chanora FRB hello PoC counterStream() delivers the expected event sequence
00:00 +3: (tearDownAll)
00:00 +3: All tests passed!
```

## What the verification proves

| Exit-criterion sub-claim | Evidence |
|---|---|
| Dart can call Rust | `greet(name: 'Chanora')` returns a `GreetResult` whose `message` field originated in Rust. |
| Typed result DTO crosses the boundary | `GreetResult.elapsedMicros` is a typed `BigInt` (Rust `u64`) deserialised correctly on the Dart side. |
| Typed error DTO crosses the boundary | `greet(name: '   ')` throws a `GreetError` instance on the Dart side (`isA<GreetError>()`); the Rust `Err(...)` arm is reached and reified as a Dart exception. |
| Dart can receive a Rust event stream | `counterStream(count: 4, intervalMs: 50)` yields exactly 4 ordered `CounterTick` events with `seq = 0..3` and matching `note` payloads. |
| Streams close cleanly | The `await for` loop terminates on its own without timeout. |

## Scope honestly NOT validated by this spike

- Performance characteristics of the bridge under load.
- Android, iOS, macOS, Windows targets.
- Lifecycle behaviour across Flutter hot-restart or Dart isolate boundaries.
- Cancellation semantics (Dart listener disconnect while Rust still produces).
- Behaviour with large/complex DTO graphs.
- Backpressure on the event stream.
- The full Chanora bridge DTO catalogue (owned by `chanora_bridge`).
- The "schema-controlled" half of DEC-014 — this PoC uses macro-driven
  generation only.
