feat(tui): add /context command with a categorized context-window breakdown#3458
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…akdown Add a /context slash command that opens a dialog (consistent with the /cost dialog) showing the estimated composition of the context window, broken down by category: system prompt, tool definitions, prompt files, conversation messages, tool results, and compaction summary. The breakdown is computed in pkg/runtime from Session.GetMessages output using the usage-calibrated compaction estimator, plus tool schema and add_prompt_files estimates. Percentages are relative to the resolved context limit (same source as the sidebar gauge); the dialog renders a stacked usage bar, per-category rows with item counts, free space, and an explicit estimates disclaimer. Numbers can be copied as plain text. The computation runs in a tea.Cmd goroutine so lazily-started toolsets never block the UI, and remote runtimes report the feature as unavailable via an optional capability interface. Closes #3432
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Jul 3, 2026
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Closes #3432
Summary
Adds a
/contextslash command that opens a dialog (consistent with the existing/costdialog) showing the estimated context-window composition, broken down by category, with a stacked usage bar, per-category rows, free space, and a copy-to-clipboard action.Bar segments and row markers use per-category theme colors; the free space remainder is muted.
Issue expectations
/contextcommandpkg/tui/commands/commands.go(session.context): palette, slash parser, completion; compatible with--disable-commandsmessages.ShowContextDialogMsginpkg/tui/messages/toggle.go, next to the siblingShow*DialogMsgtypes (the issue sketchedsession.go;toggle.gois where the existing dialog messages live)pkg/tui/dialog/context.go, modeled oncost.go: scrollview,ccopies a plain-text version,Esc/Enter/qclosespkg/runtimefromSession.GetMessagespkg/runtime/context_breakdown.go:ContextBreakdown/ContextCategorytypes,(*LocalRuntime).ContextBreakdown(ctx, sess)compaction.EstimateMessageTokens, labeled as suchcompaction.NewSliceEstimator(same estimator the proactive compaction trigger uses); explicit disclaimer line in the dialogcontextLimitForAgentModel(same source as the sidebar gauge, including compaction-model capping); "context limit unknown" fallback for harness agents and uncatalogued modelstoolcommon/tokencount.goFormatTokenCounthelperFlow
Design decisions
ContextBreakdownEvent". An on-demand method was implemented instead: the data is fresh at dialog-open time and there is a single consumer today. feat(tui): per-sub-agent context accounting in the TUI #3438 can callLocalRuntime.ContextBreakdowndirectly; an event can be layered on later if feat(runtime): cross-agent compaction orchestration (explicit, user-triggered) #3439 needs one.pkg/app(same pattern asagentConfigProvider): remote runtimes show an info toast ("Context breakdown is not supported with remote runtimes").tea.Cmdgoroutine (unlike/tools, which blocks the Update loop) because tool listing may lazily start MCP toolsets.session.SummaryMessageContent()andSession.LastSummary()helpers classify the summary message by exact content, so a user message that merely starts with "Session Summary: " stays in the conversation bucket (pinned by a test). The two former string literals insession.gonow share the same helper.Testing
pkg/runtime(8 tests)pkg/tui/dialog(9 tests)pkg/sessionLastSummary,SummaryMessageContent/GetMessagesexact-content contractpkg/tui/commands/contextparse testgo build ./...,golangci-lint run ./...(0 issues),go run ./lint .(no offenses), full test suite green except pre-existing environment-dependent SSRF/network tests that also fail on a clean checkout ofmain.