0009. Renderer-freeze exception for canvas allocation and indicator loading

• Status: Accepted
• Date: 2026-10-10
• Deciders: tseka (founder-authorized)
• Amends: ADR 0005, ADR 0008

Context

The 2026-10-10 runtime audit found two costs inside the frozen renderer area.

1. Canvas memory. Each chart allocated every canvas layer up front:

   • a drawing layer on every pane;
   • a left-axis pair even when no left axis is shown, sized to the full plot when the host had no left-axis layer;
   • a full-plot crosshair canvas.

   The landing hero held 9 canvases (38.6 MiB at DPR 2).

2. Indicator loading. createChartController loaded every indicator module before mounting. The workbench made 81 JS requests on first load.

Decision

The founder authorizes changes to the frozen paths (engine/**, controllers/**), limited to two areas.

Canvas allocation and sizing. This covers:

• when a pane, axis, drawing or crosshair surface is created or released;
• the size of its backing store, which is the drawn area times DPR;
• where the surface sits in the DOM, without changing stacking order.

Indicator loading. This covers:

• the build-time static catalog;
• on-demand loading of indicator modules;
• adding newly loaded definitions to the calculation runtimes;
• the async boundaries for adding an indicator, restoring a layout and running Agent tools.

The layout-autosave scheduling change (coalescing viewport-driven checks) is also covered, because it lives in the same controllers path.

These stay frozen:

• drawing algorithms (engine/renderers/** paint code);
• engine/scale/**;
• foundation/tokens/fonts.ts;
• any change to what a frame draws.

Before and after builds must produce pixel-identical output.

Consequences

• PR 363045841/KLineChartQuant#309 ships the change.
• Screenshots of the hero and workbench harnesses are byte-identical before and after.
• Synchronous indicator methods accept only loaded definitions. Hosts call loadIndicators first, or opt into indicatorLoading: 'all'.
• Any other renderer change still needs its own ADR.