Context CompactionMarker

CompactionMarker

One quiet line in the assistant turn where a compaction was applied, was running, or failed. It opens the Context pane through onView.

import 'package:agent_kit/agent_kit.dart';

Demo

Done: the context was compacted. The gallery passes episodesSummarized: 3, tokensBefore: 41000, tokensAfter: 9000 and an onView, so the line reads "3 episodes summarized · 41k → 9k" and shows View.

Running: compaction in progress. The gallery passes state: running and detail: 'summarizing episode 4 · 24k'. No lead glyph and no View button; the line is a StatusMark with the running status.

Failed: compaction failed. The gallery passes state: failed and detail: 'the previous context is unchanged'. Red X glyph, red title, and View (the gallery passes onView).

Parameters

Parameter	Type	Notes
item	CompactionItem (required, positional)	The state, episodesSummarized, tokensBefore, tokensAfter and detail of the event.
onView	VoidCallback?	Opens the Context pane on Now. Without it the View button is left out. The button is also hidden while the state is running.

Theme roles

ink (done title), muted (detail text), typeScale.uiSmall, colors.iconSecondary (done glyph), colors.borderSubtle (hairline), statusStyle(ChatStatus.failed).ink (failed glyph and title).

Size classes

The widget reads sizeClassOf(context).isCompact:

• Compact: "N episodes summarized" is left out, the hairline is replaced by a spacer, and the line may wrap to two lines. The sizes text (41k → 9k) stays.
• Otherwise: one line, with the hairline between the text and the View button.

sizeClassOf returns the nearest SizeClassBuilder's class, or expanded when there is none (transcript_support.dart).

Accessibility

• The whole line is one Semantics node labelled with the title and the parts joined by commas. Its children are excluded.
• A running line is a live region (liveRegion: running).
• The View button is a KitTextButton with the label "View".
• No reduced-motion handling in the code.

Gallery and tests

• Gallery scene: Components (GalleryScene.components). Specimen: ContextSpecimens in apps/gallery/lib/components/context.dart, the "Compaction marker: done, running, failed" entries.
• Golden: apps/gallery/test/component_shots_test.dart writes compaction_marker_light.png and _dark.png (shot indices 0 to 2). The whole sheet is in apps/gallery/test/goldens/components_1000_<theme>.png.
• Other tests:
  • packages/agent_kit/test/context/context_marker_test.dart: "done: title, figures and View", "running: no View, shows the detail", "failed: says so and that nothing changed", "the marker's View opens the Context pane".
  • packages/agent_kit/test/context/context_golden_test.dart (tag golden): packages/agent_kit/test/goldens/context_marker_390_<theme>.png and context_marker_1000_<theme>.png.

---

Generated from docs/components/context/CompactionMarker.md. Edit the file there; changes made on the wiki are overwritten.