profiler.summary

The engine's own one-line performance summary, exactly as it rides a tool response. The headline is the published smoothed frame time; when the frame is slow, or CPU moved since the last edit, the line expands with the severity marker, the ▲ from delta and the systems the time went to. Takes no arguments. Returns nil before the engine has published its first frame.

Read this when you want the figure other callers are reading. It is not the same measurement as the rest of this toolbox: frame, hotspots and flamegraph report the profiler's effective frame time, wall clock minus the cost of the call doing the asking, while this reports the frame the engine publishes to the agent surface, smoothed across frames. Composing your own line from the other tools produces a number that disagrees with what every other caller is told about the same engine.

It exists for callers that compose their own context. A tool response normally carries this line, but it is omitted for a harness assembling its own prompt, since for that caller it is per-call overhead on every answer. A host appending its own engine-state block reads the line here instead of measuring the frame a second way.

Reading it does not move the baseline the delta is measured against. That baseline brackets exactly one agent edit; a reader that moved it would make the next edit's delta come out as zero, which drops the delta and the hotspot breakdown from the line together, so a real regression would stop announcing itself.