ForceFlush never flushes the LoggerProvider, so GenAI audit records are silently dropped when the Actor checkpoints

[Rachael-Graham]

Disclosure: this issue was written by an AI agent (Claude) while verifying kagent's
audit-logging documentation, and reviewed by a human before filing.

Summary

ForceFlush flushes the TracerProvider only. The LoggerProvider's batch processor is never
flushed, so GenAI audit log records can be lost when Substrate checkpoints the Actor as the
response closes. The loss is silent — no error, no retry, and the records are dropped rather
than deferred to the next resume.

For a feature whose audience is security and compliance review, silent loss is a
correctness problem rather than a caveat.

The code

// go/adk/pkg/telemetry/tracing.go:50-61
func ForceFlush(ctx context.Context) {
	type flusher interface{ ForceFlush(context.Context) error }
	fp, ok := otel.GetTracerProvider().(flusher)     // <-- TracerProvider only
	if !ok {
		return
	}
	flushCtx, cancel := context.WithTimeout(context.WithoutCancel(ctx), flushTimeout())
	defer cancel()
	if err := fp.ForceFlush(flushCtx); err != nil {
		otel.Handle(err)
	}
}

newLoggerProvider wraps its exporter in sdklog.NewBatchProcessor, so log records sit in
a batch queue with the same hazard the ForceFlush doc comment describes for spans.
grep -rn 'GetLoggerProvider' go returns zero hits in the repository.

Spans have an opt-in pre-response flush and logs have no equivalent:

• go/core/internal/translator/kagent/compiler.go:75 sets KAGENT_PRE_RESPONSE_TRACE_FLUSH=true
• go/adk/pkg/a2a/server/server.go:110 honours it
• grep -rn 'PRE_RESPONSE' go shows no logging counterpart

Observed

On a kind cluster with logging enabled via Harness.spec.env, two identical single-turn
invokes of the same AgentInstance with the same prompt produced 0 GenAI log records and
then 3. A second invoke did not release the first turn's missing records, so they were
dropped rather than deferred.

Later in the same session, with a 3-replica WorkerPool, delivery was reliable across four
consecutive invokes. So the loss is load- and timing-dependent rather than constant, which
is consistent with a batch-interval race.

Expected

ForceFlush also flushes the LoggerProvider, or a KAGENT_PRE_RESPONSE_LOG_FLUSH-style
opt-in exists that matches the trace behaviour, so a record emitted during a turn is
exported before the Actor is checkpointed.

Suggested fix

Cast otel.GetLoggerProvider() alongside the tracer provider in ForceFlush and flush
both, reusing the existing timeout.