Prevent Stale Charts and Filename Collisions

Use a separate output name for each active chart and session. Include a session-specific directory or another controlled unique identifier when your application assigns filenames. Clear the display field or retain an explicit error state after a failed render so a previous successful PNG cannot appear to represent new data.

For repeated renders, verify that the new image contains the new values, not merely that a file exists. Record creation time and a checksum during testing. Two concurrent sessions must not overwrite one another's files or remove files still used by the other session.