flowchart LR
    subgraph before["Before: command-buffer stamp"]
        direction TB
        A1["dispatch / draw encoders"] --> S1["cb.writeTimestampIntoHeap"]
        S1 --> B1["next encoders"]
        S1 -. "another process loads the GPU:<br/>written at the end of the command buffer" .-> E1["stamp after later work"]
    end
    subgraph after["After: a compute encoder of its own"]
        direction TB
        A2["dispatch / draw encoders"] --> S2["barrier after all stages<br/>precise timestamp<br/>4-byte copy (zeros onto zeros)"]
        S2 --> B2["next encoders"]
    end