Compositions AgentContextPane

AgentContextPane

The Context pane of one chat, which loads the chat's context structure from the backend and shows it with ContextPane as the Context tab of the workspace that AgentWorkbench opens.

import 'package:agent_kit/agent_kit.dart';

Demo

Phone (scene F at 390 px): the Context pane as the Context tab of the full-screen workspace sheet, which covers the chat. The shot shows the meter (48.6k of 128k tokens, 38%), the Now, History and Compactions tabs, and the Now rows: fixed, compacted memory and live messages. The gallery builds it through AgentWorkbench with the Context workspace controller.

Parameters

Parameter	Type	Notes
backend	AgentBackend	required. Supplies loadContext, loadHistoryRange and loadSummary. Without the context capability the pane shows a quiet line instead.
chatId	String	required. The chat whose context is loaded. A change of chat or backend reloads the structure.
view	ContextView?	required, and may be null. The serving view (ChatSnapshot.context). Each change reloads the structure. Null shows "This chat has no context data yet."
controller	ContextPaneController?	Passed to ContextPane. AgentWorkbench calls its showNow() when the header meter or the compaction marker opens the pane.
now	DateTime?	Replaces the wall clock for ages. Passed to ContextPane.
renderer	MarkdownRenderer	Default LeanMarkdownRenderer(). Passed to ContextPane.

Theme roles

BbTheme roles read in agent_context_pane.dart:

• surface: the background of the quiet line (:88).
• faint and typeScale.ui: the text of the quiet line (:95).

Size classes

The pane does not read SizeClass. It fills the area it is given. The ContextPane it builds lays out by its own width: from KitLayout.contextSplit (680 px) the summary detail sits beside the list (context/context_pane.dart:319; context/README.md:25). The 680 px value comes from bb-ui's KitLayout.

Accessibility

None in the code. This file has no Semantics, labels or key handling. The ContextPane it builds reads BbTheme.reducedMotion (context/context_pane.dart:193).

Gallery and tests

• Gallery scene: F (Context) at 1600 px and 390 px. buildScene in apps/gallery/lib/src/scenes.dart:127-151 builds the workbench with controller.contextWorkspaceController as its workspace (:136-139). AgentWorkbench._paneBuilder (packages/agent_kit/lib/src/compositions/agent_workbench.dart:305) builds this pane for the Context tab.
• Golden: the shot is a copy of apps/gallery/test/goldens/f_context_390_light.png (and _dark.png). apps/gallery/test/scenes_golden_test.dart writes it (scene context at 390 × 844), not component_shots_test.dart. The copies are byte-identical to the scene goldens.
• Other tests:
  • No test mounts AgentContextPane directly. Grep for AgentContextPane under packages/agent_kit/test/ finds nothing.
  • packages/agent_kit/test/context/context_marker_test.dart (group AgentWorkbench): the compaction marker's View and the header meter open the Context pane through the workbench.
  • packages/agent_kit/test/context/context_pane_test.dart tests ContextPane, the widget this pane builds.
• No package golden covers this pane.

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