refactor(leantui): decompose the model into cohesive subsystems#3455
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The model struct and update.go had accumulated several distinct concerns. This splits them into cohesive units without changing behavior: - Extract per-session usage aggregation into a usageTracker (usage.go), replacing four model fields (usageBySession, rootSessionID, latestUsageSessionID, sessionStack) with one. - Extract in-flight tool-call state into a toolTracker (toolstate.go), replacing the tools map and toolOrder slice; finish() returns an immutable snapshot for the model to commit. - Move runtime event handling out of update.go into events.go, leaving update.go focused on input and command dispatch (761 -> 418 lines). - Deduplicate run-lifecycle boilerplate via beginRun(). - Deduplicate thinking-level guard/error handling via thinkingLevelChangeable() and reportThinkingLevelError(). No functional change; existing tests updated for the new field names.
Group the scrollable conversation content — finalized blocks, the in-progress streamed block, and in-flight tool calls — into a single transcript type that owns its rendering (the former conversationLines). - model loses blocks, pending, and toolz (3 fields -> 1 transcript), dropping from 21 to 18 fields. - block, pendingBlock, blockKind, spinnerFrames and the spinner/pending rendering move into transcript.go alongside the type. - conversationLines becomes transcript.lines(width, spinnerFrame, busy, sessionState); the busy flag is now an explicit render input. - resetConversation's manual pending/tool reset becomes transcript.clearActive(), which keeps committed scrollback intact. No functional change; tests updated for the new field paths.
aheritier
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rumpl
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Sayt-0
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Jul 3, 2026
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What
Progressively decomposes
pkg/leantui's largemodelstruct andupdate.gointo cohesive, independently-testable subsystems. No functional change — purely structural. Done as a series of behavior-preserving commits.Commits
1. Extract usage/tool trackers and split
update.gousageTracker(usage.go): per-session token/cost aggregation — the session stack, root/latest bookkeeping, and "active session" resolution. Replaces four model fields (usageBySession,rootSessionID,latestUsageSessionID,sessionStack) with one.toolTracker(toolstate.go): in-flight tool-call state (toolsmap +toolOrder);finish()returns an immutable snapshot for the model to commit.events.go, leavingupdate.gofocused on input and command dispatch.beginRun) and thinking-level guard/error handling.2. Extract the
transcripttypetranscripttype that owns its rendering (the formerconversationLines, nowtranscript.lines).resetConversation's manual pending/tool reset becomestranscript.clearActive(), which keeps committed scrollback intact.Net effect
The
modelstruct drops from ~30 fields to 18, andupdate.gofrom 761 to ~417 lines. The three most self-contained concerns (usage, conversation content, tool state) are now typed components with their behavior exercisable in isolation.Validation
go build ./...— passesgo test ./pkg/leantui/...— passes (tests touched only for renamed field paths; no assertions changed)golangci-lint run ./pkg/leantui/...(v2.12.2, repo config) — 0 issuesDeliberately left alone
The differential
renderer, theeditor, and thekeysparser are already cohesive single-responsibility units. ArunStateextraction (busy/runCancel/queue) was considered but held back — it is borderline because the actualapp.Runcalls must stay on the model; the run-lifecycle fields are grouped together to make that a clean follow-up if desired.