Variable: stripStaleChartsProcessor

const stripStaleChartsProcessor: InputProcessor

Mastra input processor that strips chartId fields from every tool-invocation result in prior assistant messages before they reach the model.

Why: chartIds are turn-scoped from the model’s point of view - each prepare_chart / render_data call mints a fresh id and the host UI binds it to that turn’s reply. Mastra Memory replays prior tool results into the prompt; if old chartIds leak through, the model is tempted to copy them verbatim into the new turn’s [chart:<id>] markers and the host UI ends up rendering an unrelated chart from the chart cache (or a 404 once the 1h TTL elapsed). This processor removes the temptation by deleting chartId keys from every assistant message’s tool results before the prompt is built. The current turn’s tool results don’t exist yet at processInput time, so they pass through unmodified.

The strip is recursive - any nested chartId field is removed, regardless of which tool produced the result. This covers prepare_chart / render_data top-level chartIds and any legacy datasets[].chartId payloads uniformly without coupling to specific tool ids.

Wired onto every agent by default via buildAgents; opt out with MastraPluginConfig.stripStaleCharts: false.