Diagnostic Director API

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Blueprint: Diagnostic Probe

Add Diagnostic Probe from Diagnostic Director > Probes. Connect execution through the node and connect any supported Blueprint value to its wildcard Value pin. The node formats common scalar, enum, object, text, name, and struct values through Unreal property formatting. It observes the value without changing it and passes execution through.

Set Probe Label to a readable name such as Health or Current Weapon. Labels may repeat; the Blueprint asset, graph, and node identity keep probe instances distinct. Internal identities are not shown in the Inspector or emitted to logs.

Include in Logs defaults to false. When enabled, every hit writes one event to LogDiagnosticDirectorProbe at the selected non-fatal verbosity: VeryVerbose, Verbose, Log, Display, Warning, or Error. Log is the default. Fatal is not available.

C++: Diagnostic Probe

Call the exported helper with a stable key, display label, formatted value, and type name:

UDD_ProbeLibrary::RecordProbe(this, TEXT("WeaponAmmo"), TEXT("Ammo Remaining"),
    LexToString(Ammo), TEXT("int32"), false);

The remaining parameters are EDD_ProbeVerbosity (default Log when logging is enabled) and a friendly source name (default C++). The C++ helper does not require callers to construct internal probe records or identities.

Existing APIs

Log Diagnostic emits an event to Unreal logging at Verbose, Information, Warning, or Error priority. Optional on-screen output is independent. This event-oriented API may remain in production code.

Assert reports a failed development assertion and invokes Unreal’s non-fatal ensure diagnostic. Ensure reports a failed condition and returns the condition for branching.

Try Enter Reentry Guard claims a guard identified by world, scope object, and key. It returns false for a repeated active claim. Release Reentry Guard releases the corresponding guard. These remain runtime gameplay/control-flow APIs, not Editor controls.