send_signal: wait for the target flow to settle before start fires

Wire the SDK's shared readiness gate (WaitFlowReady) into the send_signal tool: on {send:true}/{start:true}, poll the flow's node statuses until settled (bounded, best-effort), then fire — and surface still-reconciling nodes and hard reconcile faults in the output. Closes the 'spans:1, errors:0 false clean' gap where a signal fired right after build_flow vanished downstream and the model re-fired blindly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: Tiny Systems

cmd/signal_tool.go

@@ -62,10 +62,32 @@ func (sendSignalTool) Execute(ctx context.Context, execCtx sdktools.ExecutionCon
 	if err != nil {
 		return sdktools.ToolResult{Success: false, Error: fmt.Sprintf("marshal data: %v", err)}
 	}
+
+	// Readiness gate for start fires ({send:true}/{start:true}): a signal
+	// fired into a half-reconciled flow reaches the trigger but downstream
+	// nodes aren't routing yet — the message vanishes and the trace shows a
+	// lone trigger span that reads as a clean run. Wait for the target flow's
+	// node statuses to settle (best-effort, bounded), then fire regardless,
+	// surfacing any nodes that are still pending or hard-failed so the model
+	// knows what a thin trace means. Same gate the platform playground uses.
+	out := map[string]interface{}{"sent": true, "node_id": nodeID, "port": port}
+	if sdktools.IsStartFire(data) {
+		els, waited := sdktools.WaitFlowReady(ctx, execCtx, nodeID)
+		if waited > 0 {
+			out["readiness_waited_ms"] = waited.Milliseconds()
+		}
+		var warnings []string
+		warnings = append(warnings, sdktools.NodeStatusFaults(els)...)
+		if pending := sdktools.NotReadyNodes(els); len(pending) > 0 {
+			warnings = append(warnings, fmt.Sprintf("nodes still reconciling (a signal may not reach them yet): %v — if the trace shows only the trigger span, re-fire after they settle", pending))
+		}
+		if len(warnings) > 0 {
+			out["warnings"] = warnings
+		}
+	}
+
 	if err := execCtx.SignalSender.SendSignal(ctx, execCtx.ProjectName, nodeID, port, payload, ""); err != nil {
 		return sdktools.ToolResult{Success: false, Error: err.Error()}
 	}
-	return sdktools.ToolResult{Success: true, Output: map[string]interface{}{
-		"sent": true, "node_id": nodeID, "port": port,
-	}}
+	return sdktools.ToolResult{Success: true, Output: out}
 }

go.mod

@@ -12,7 +12,7 @@ require (
 	github.com/rs/zerolog v1.34.0
 	github.com/spf13/cobra v1.10.2
 	github.com/tiny-systems/ajson v0.1.6
-	github.com/tiny-systems/module v0.13.38
+	github.com/tiny-systems/module v0.13.39
 	github.com/tiny-systems/platform-api v0.5.6
 	github.com/tiny-systems/platform-go v0.2.4
 	google.golang.org/grpc v1.81.1

go.sum

@@ -723,6 +723,8 @@ github.com/tiny-systems/module v0.13.37 h1:a4xsLJQbWhXGqo3CPNxnYmcLD+kmreBHFZk8A
 github.com/tiny-systems/module v0.13.37/go.mod h1:Fu40dAvHY301ZoXVa3NErAR+M24WmpGkg0tjK7RQP+E=
 github.com/tiny-systems/module v0.13.38 h1:3INHGYHGhtkVLIjC15l6AHwiNRQV603t5dRhjIWd2Fk=
 github.com/tiny-systems/module v0.13.38/go.mod h1:Fu40dAvHY301ZoXVa3NErAR+M24WmpGkg0tjK7RQP+E=
+github.com/tiny-systems/module v0.13.39 h1:tKQg7szqH2N4t938dNzc5ga5VJ0ZhT4N4bDCcW+zK/8=
+github.com/tiny-systems/module v0.13.39/go.mod h1:Fu40dAvHY301ZoXVa3NErAR+M24WmpGkg0tjK7RQP+E=
 github.com/tiny-systems/otel-collector v0.5.1 h1:tylLj7f7O7n5o9R383Lojd0fN7j5jgZ76zFshJ0SE6c=
 github.com/tiny-systems/otel-collector v0.5.1/go.mod h1:EGo1dQ3+5iG3ejGJ8y9kMgHhOGB6WyoasJDUHesKXEA=
 github.com/tiny-systems/platform-api v0.5.6 h1:IJPslzpV06cJcHaloZ9mm18pE8DCpCqLc/PD0NGFOUA=