[starc007]

What

On touch screens, chart inspection marks now follow the finger directly instead of gliding behind it.

• Line Chart: the crosshair, dots, axis pill and the dimming past the crosshair, plus the tooltip, which trailed on a deliberately softer spring.
• Bar Chart: the category band.
• Sparkline: the interactive readout dot.
• Composition Chart: the crosshair.

Mouse and keyboard keep the glide, and data-change springs are untouched.

Why

Every inspection mark moved to the inspected sample on a spring. With a mouse that reads as smooth, but under a finger any glide reads as lag. This was reported on mobile for the line chart.

How

• The shared xy inspector reports when a touch drag starts and ends (onTouchChange), and useInspection holds a touching flag.
• While it's set, the line, bar and sparkline marks use an instant transition.
• Composition Chart tracks the same flag locally in its plot.

Other charts checked

• Price Target Fan: its scrub crosshair uses the stiff, critically damped handle spring (about 0.1s), commented as intentional for continuous scrubbing, so it's left as is.
• Candlestick: the crosshair isn't animated.
• The rest only fade or scale on inspect, or already follow the pointer.

Verification

• bun run check passes, and bun test passes 190 accessibility tests.
• Browser, 375px mobile emulation with simulated touch drags:
  • The line chart crosshair and tooltip sat at their final positions 40ms after each move.
  • The composition crosshair went straight from one column to the next with no in-between frames.
• Desktop mouse still glides: 16 distinct crosshair positions over 400ms on Composition.
• Not tested on a physical phone.
• Composition Chart is already released, so its updatedAt is bumped and it has a changelog line. Line, Bar and Sparkline are still this week's new entries.