claude-code/src/components/Messages.tsx

import { feature } from 'bun:bundle'
import chalk from 'chalk'
import type { UUID } from 'crypto'
import type { RefObject } from 'react'
import * as React from 'react'
import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
import { every } from 'src/utils/set.js'
import { getIsRemoteMode } from '../bootstrap/state.js'
import type { Command } from '../commands.js'
import { BLACK_CIRCLE } from '../constants/figures.js'
import { useTerminalSize } from '../hooks/useTerminalSize.js'
import type { ScrollBoxHandle } from '@anthropic/ink'
import { useTerminalNotification } from '@anthropic/ink'
import { Box, Text } from '@anthropic/ink'
import { useShortcutDisplay } from '../keybindings/useShortcutDisplay.js'
import type { Screen } from '../screens/REPL.js'
import type { Tools } from '../Tool.js'
import { findToolByName } from '../Tool.js'
import type { AgentDefinitionsResult } from '@claude-code-best/builtin-tools/tools/AgentTool/loadAgentsDir.js'
import type {
  Message as MessageType,
  NormalizedMessage,
  ProgressMessage as ProgressMessageType,
  RenderableMessage,
} from '../types/message.js'
import { type AdvisorBlock, isAdvisorBlock } from '../utils/advisor.js'
import { collapseBackgroundBashNotifications } from '../utils/collapseBackgroundBashNotifications.js'
import { collapseHookSummaries } from '../utils/collapseHookSummaries.js'
import { collapseReadSearchGroups } from '../utils/collapseReadSearch.js'
import { collapseTeammateShutdowns } from '../utils/collapseTeammateShutdowns.js'
import { getGlobalConfig } from '../utils/config.js'
import { isEnvTruthy } from '../utils/envUtils.js'
import { isFullscreenEnvEnabled } from '../utils/fullscreen.js'
import { applyGrouping } from '../utils/groupToolUses.js'
import {
  buildMessageLookups,
  createAssistantMessage,
  deriveUUID,
  getMessagesAfterCompactBoundary,
  getToolUseID,
  getToolUseIDs,
  hasUnresolvedHooksFromLookup,
  isNotEmptyMessage,
  normalizeMessages,
  reorderMessagesInUI,
  type StreamingThinking,
  type StreamingToolUse,
  shouldShowUserMessage,
} from '../utils/messages.js'
import { plural } from '../utils/stringUtils.js'
import { renderableSearchText } from '../utils/transcriptSearch.js'
import { Divider } from '@anthropic/ink'
import type { UnseenDivider } from './FullscreenLayout.js'
import { LogoV2 } from './LogoV2/LogoV2.js'
import { StreamingMarkdown } from './Markdown.js'
import { hasContentAfterIndex, MessageRow } from './MessageRow.js'
import {
  InVirtualListContext,
  type MessageActionsNav,
  MessageActionsSelectedContext,
  type MessageActionsState,
} from './messageActions.js'
import { AssistantThinkingMessage } from './messages/AssistantThinkingMessage.js'
import { isNullRenderingAttachment } from './messages/nullRenderingAttachments.js'
import { OffscreenFreeze } from './OffscreenFreeze.js'
import type { ToolUseConfirm } from './permissions/PermissionRequest.js'
import { StatusNotices } from './StatusNotices.js'
import type { JumpHandle } from './VirtualMessageList.js'

// Memoed logo header: this box is the FIRST sibling before all MessageRows
// in main-screen mode. If it becomes dirty on every Messages re-render,
// renderChildren's seenDirtyChild cascade disables prevScreen (blit) for
// ALL subsequent siblings — every MessageRow re-writes from scratch instead
// of blitting. In long sessions (~2800 messages) this is 150K+ writes/frame
// and pegs CPU at 100%. Memo on agentDefinitions so a new messages array
// doesn't invalidate the logo subtree. LogoV2/StatusNotices internally
// subscribe to useAppState/useSettings for their own updates.
const LogoHeader = React.memo(function LogoHeader({
  agentDefinitions,
}: {
  agentDefinitions: AgentDefinitionsResult | undefined
}): React.ReactNode {
  // LogoV2 has its own internal OffscreenFreeze (catches its useAppState
  // re-renders). This outer freeze catches agentDefinitions changes and any
  // future StatusNotices subscriptions while the header is in scrollback.
  return (
    <OffscreenFreeze>
      <Box flexDirection="column" gap={1}>
        <LogoV2 />
        <React.Suspense fallback={null}>
          <StatusNotices agentDefinitions={agentDefinitions} />
        </React.Suspense>
      </Box>
    </OffscreenFreeze>
  )
})

// Dead code elimination: conditional import for proactive mode
/* eslint-disable @typescript-eslint/no-require-imports */
const proactiveModule =
  feature('PROACTIVE') || feature('KAIROS')
    ? require('../proactive/index.js')
    : null
const BRIEF_TOOL_NAME: string | null =
  feature('KAIROS') || feature('KAIROS_BRIEF')
    ? (
        require('@claude-code-best/builtin-tools/tools/BriefTool/prompt.js') as typeof import('@claude-code-best/builtin-tools/tools/BriefTool/prompt.js')
      ).BRIEF_TOOL_NAME
    : null
const SEND_USER_FILE_TOOL_NAME: string | null = feature('KAIROS')
  ? (
      require('@claude-code-best/builtin-tools/tools/SendUserFileTool/prompt.js') as typeof import('@claude-code-best/builtin-tools/tools/SendUserFileTool/prompt.js')
    ).SEND_USER_FILE_TOOL_NAME
  : null

/* eslint-enable @typescript-eslint/no-require-imports */
import { VirtualMessageList } from './VirtualMessageList.js'

/**
 * In brief-only mode, filter messages to show ONLY Brief tool_use blocks,
 * their tool_results, and real user input. All assistant text is dropped —
 * if the model forgets to call Brief, the user sees nothing for that turn.
 * That's on the model to get right; the filter does not second-guess it.
 */
export function filterForBriefTool<
  T extends {
    type: string
    subtype?: string
    isMeta?: boolean
    isApiErrorMessage?: boolean
    message?: {
      content: Array<{
        type: string
        name?: string
        tool_use_id?: string
      }>
    }
    attachment?: {
      type: string
      isMeta?: boolean
      origin?: unknown
      commandMode?: string
    }
  },
>(messages: T[], briefToolNames: string[]): T[] {
  const nameSet = new Set(briefToolNames)
  // tool_use always precedes its tool_result in the array, so we can collect
  // IDs and match against them in a single pass.
  const briefToolUseIDs = new Set<string>()
  return messages.filter(msg => {
    // System messages (attach confirmation, remote errors, compact boundaries)
    // must stay visible — dropping them leaves the viewer with no feedback.
    // Exception: api_metrics is per-turn debug noise (TTFT, config writes,
    // hook timing) that defeats the point of brief mode. Still visible in
    // transcript mode (ctrl+o) which bypasses this filter.
    if (msg.type === 'system') return msg.subtype !== 'api_metrics'
    const block = msg.message?.content[0]
    if (msg.type === 'assistant') {
      // API error messages (auth failures, rate limits, etc.) must stay visible
      if (msg.isApiErrorMessage) return true
      // Keep Brief tool_use blocks (renders with standard tool call chrome,
      // and must be in the list so buildMessageLookups can resolve tool results)
      if (block?.type === 'tool_use' && block.name && nameSet.has(block.name)) {
        if ('id' in block) {
          briefToolUseIDs.add((block as { id: string }).id)
        }
        return true
      }
      return false
    }
    if (msg.type === 'user') {
      if (block?.type === 'tool_result') {
        return (
          block.tool_use_id !== undefined &&
          briefToolUseIDs.has(block.tool_use_id)
        )
      }
      // Real user input only — drop meta/tick messages.
      return !msg.isMeta
    }
    if (msg.type === 'attachment') {
      // Human input drained mid-turn arrives as a queued_command attachment
      // (query.ts mid-chain drain → getQueuedCommandAttachments). Keep it —
      // it's what the user typed. commandMode === 'prompt' positively
      // identifies human-typed input; task-notification callers set
      // mode: 'task-notification' but not origin/isMeta, so the positive
      // commandMode check is required to exclude them.
      const att = msg.attachment
      return (
        att?.type === 'queued_command' &&
        att.commandMode === 'prompt' &&
        !att.isMeta &&
        att.origin === undefined
      )
    }
    return false
  })
}

/**
 * Full-transcript companion to filterForBriefTool. When the Brief tool is
 * in use, the model's text output is redundant with the SendUserMessage
 * content it wrote right after — drop the text so only the SendUserMessage
 * block shows. Tool calls and their results stay visible.
 *
 * Per-turn: only drops text in turns that actually called Brief. If the
 * model forgets, text still shows — otherwise the user would see nothing.
 */
export function dropTextInBriefTurns<
  T extends {
    type: string
    isMeta?: boolean
    message?: { content: Array<{ type: string; name?: string }> }
  },
>(messages: T[], briefToolNames: string[]): T[] {
  const nameSet = new Set(briefToolNames)
  // First pass: find which turns (bounded by non-meta user messages) contain
  // a Brief tool_use. Tag each assistant text block with its turn index.
  const turnsWithBrief = new Set<number>()
  const textIndexToTurn: number[] = []
  let turn = 0
  for (let i = 0; i < messages.length; i++) {
    const msg = messages[i]!
    const block = msg.message?.content[0]
    if (msg.type === 'user' && block?.type !== 'tool_result' && !msg.isMeta) {
      turn++
      continue
    }
    if (msg.type === 'assistant') {
      if (block?.type === 'text') {
        textIndexToTurn[i] = turn
      } else if (
        block?.type === 'tool_use' &&
        block.name &&
        nameSet.has(block.name)
      ) {
        turnsWithBrief.add(turn)
      }
    }
  }
  if (turnsWithBrief.size === 0) return messages
  // Second pass: drop text blocks whose turn called Brief.
  return messages.filter((_, i) => {
    const t = textIndexToTurn[i]
    return t === undefined || !turnsWithBrief.has(t)
  })
}

type Props = {
  messages: MessageType[]
  tools: Tools
  commands: Command[]
  verbose: boolean
  toolJSX: {
    jsx: React.ReactNode | null
    shouldHidePromptInput: boolean
    shouldContinueAnimation?: true
  } | null
  toolUseConfirmQueue: ToolUseConfirm[]
  inProgressToolUseIDs: Set<string>
  isMessageSelectorVisible: boolean
  conversationId: string
  screen: Screen
  streamingToolUses: StreamingToolUse[]
  showAllInTranscript?: boolean
  agentDefinitions?: AgentDefinitionsResult
  onOpenRateLimitOptions?: () => void
  /** Hide the logo/header - used for subagent zoom view */
  hideLogo?: boolean
  isLoading: boolean
  /** In transcript mode, hide all thinking blocks except the last one */
  hidePastThinking?: boolean
  /** Streaming thinking content (live updates, not frozen) */
  streamingThinking?: StreamingThinking | null
  /** Streaming text preview (rendered as last item so transition to final message is positionally seamless) */
  streamingText?: string | null
  /** When true, only show Brief tool output (hide everything else) */
  isBriefOnly?: boolean
  /** Fullscreen-mode "─── N new ───" divider. Renders before the first
   *  renderableMessage derived from firstUnseenUuid (matched by the 24-char
   *  prefix that deriveUUID preserves). */
  unseenDivider?: UnseenDivider
  /** Fullscreen-mode ScrollBox handle. Enables React-level virtualization when present. */
  scrollRef?: RefObject<ScrollBoxHandle | null>
  /** Fullscreen-mode: enable sticky-prompt tracking (writes via ScrollChromeContext). */
  trackStickyPrompt?: boolean
  /** Transcript search: jump-to-index + setSearchQuery/nextMatch/prevMatch. */
  jumpRef?: RefObject<JumpHandle | null>
  /** Transcript search: fires when match count/position changes. */
  onSearchMatchesChange?: (count: number, current: number) => void
  /** Paint an existing DOM subtree to fresh Screen, scan. Element comes
   *  from the main tree (all real providers). Message-relative positions. */
  scanElement?: (
    el: import('@anthropic/ink').DOMElement,
  ) => import('@anthropic/ink').MatchPosition[]
  /** Position-based CURRENT highlight. positions stable (msg-relative),
   *  rowOffset tracks scroll. null clears. */
  setPositions?: (
    state: {
      positions: import('@anthropic/ink').MatchPosition[]
      rowOffset: number
      currentIdx: number
    } | null,
  ) => void
  /** Bypass MAX_MESSAGES_WITHOUT_VIRTUALIZATION. For one-shot headless renders
   *  (e.g. /export via renderToString) where the memory concern doesn't apply
   *  and the "already in scrollback" justification doesn't hold. */
  disableRenderCap?: boolean
  /** In-transcript cursor; expanded overrides verbose for selected message. */
  cursor?: MessageActionsState | null
  setCursor?: (cursor: MessageActionsState | null) => void
  /** Passed through to VirtualMessageList (heightCache owns visibility). */
  cursorNavRef?: React.Ref<MessageActionsNav>
  /** Render only collapsed.slice(start, end). For chunked headless export
   *  (streamRenderedMessages in exportRenderer.tsx): prep runs on the FULL
   *  messages array so grouping/lookups are correct, but only this slice
   *  chunk instead of the full session. The logo renders only for chunk 0
   *  (start === 0); later chunks are mid-stream continuations.
   *  Measured Mar 2026: 538-msg session, 20 slices → −55% plateau RSS. */
  renderRange?: readonly [start: number, end: number]
}

const MAX_MESSAGES_TO_SHOW_IN_TRANSCRIPT_MODE = 30

// Safety cap for the non-virtualized render path (fullscreen off or
// explicitly disabled). Ink mounts a full fiber tree per message (~250 KB
// RSS each); yoga layout height grows unbounded; the screen buffer is sized
// to fit every line. At ~2000 messages this is ~3000-line screens, ~500 MB
// of fibers, and per-frame write costs that push the process into a GC
// death spiral (observed: 59 GB RSS, 14k mmap/munmap/sec). Content dropped
// from this slice has already been printed to terminal scrollback — users
// can still scroll up natively. VirtualMessageList (the default ant path)
// bypasses this cap entirely. Headless one-shot renders (e.g. /export)
// pass disableRenderCap to opt out — they have no scrollback and the
// memory concern doesn't apply to renderToString.
//
// The slice boundary is tracked as a UUID anchor, not a count-derived
// index. Count-based slicing (slice(-200)) drops one message from the
// front on every append, shifting scrollback content and forcing a full
// terminal reset per turn (CC-941). Quantizing to 50-message steps
// (CC-1154) helped but still shifted on compaction and collapse regrouping
// since those change collapsed.length without adding messages. The UUID
// anchor only advances when rendered count genuinely exceeds CAP+STEP —
// immune to length churn from grouping/compaction (CC-1174).
//
// The anchor stores BOTH uuid and index. Some uuids are unstable between
// renders: collapseHookSummaries derives the merged uuid from the first
// summary in a group, but reorderMessagesInUI reshuffles hook adjacency
// as tool results stream in, changing which summary is first. When the
// uuid vanishes, falling back to the stored index (clamped) keeps the
// slice roughly where it was instead of resetting to 0 — which would
// jump from ~200 rendered messages to the full history, orphaning
// in-progress badge snapshots in scrollback.
const MAX_MESSAGES_WITHOUT_VIRTUALIZATION = 200
const MESSAGE_CAP_STEP = 50

export type SliceAnchor = { uuid: string; idx: number } | null

/** Exported for testing. Mutates anchorRef when the window needs to advance. */
export function computeSliceStart(
  collapsed: ReadonlyArray<{ uuid: string }>,
  anchorRef: { current: SliceAnchor },
  cap = MAX_MESSAGES_WITHOUT_VIRTUALIZATION,
  step = MESSAGE_CAP_STEP,
): number {
  const anchor = anchorRef.current
  const anchorIdx = anchor
    ? collapsed.findIndex(m => m.uuid === anchor.uuid)
    : -1
  // Anchor found → use it. Anchor lost → fall back to stored index
  // (clamped) so collapse-regrouping uuid churn doesn't reset to 0.
  let start =
    anchorIdx >= 0
      ? anchorIdx
      : anchor
        ? Math.min(anchor.idx, Math.max(0, collapsed.length - cap))
        : 0
  if (collapsed.length - start > cap + step) {
    start = collapsed.length - cap
  }
  // Refresh anchor from whatever lives at the current start — heals a
  // stale uuid after fallback and captures a new one after advancement.
  const msgAtStart = collapsed[start]
  if (
    msgAtStart &&
    (anchor?.uuid !== msgAtStart.uuid || anchor.idx !== start)
  ) {
    anchorRef.current = { uuid: msgAtStart.uuid, idx: start }
  } else if (!msgAtStart && anchor) {
    anchorRef.current = null
  }
  return start
}

const MessagesImpl = ({
  messages,
  tools,
  commands,
  verbose,
  toolJSX,
  toolUseConfirmQueue,
  inProgressToolUseIDs,
  isMessageSelectorVisible,
  conversationId,
  screen,
  streamingToolUses,
  showAllInTranscript = false,
  agentDefinitions,
  onOpenRateLimitOptions,
  hideLogo = false,
  isLoading,
  hidePastThinking = false,
  streamingThinking,
  streamingText,
  isBriefOnly = false,
  unseenDivider,
  scrollRef,
  trackStickyPrompt,
  jumpRef,
  onSearchMatchesChange,
  scanElement,
  setPositions,
  disableRenderCap = false,
  cursor = null,
  setCursor,
  cursorNavRef,
  renderRange,
}: Props): React.ReactNode => {
  const { columns } = useTerminalSize()
  const toggleShowAllShortcut = useShortcutDisplay(
    'transcript:toggleShowAll',
    'Transcript',
    'Ctrl+E',
  )

  const normalizedMessages = useMemo(
    () => normalizeMessages(messages).filter(isNotEmptyMessage),
    [messages],
  )

  // Check if streaming thinking should be visible (streaming or within 30s timeout)
  const isStreamingThinkingVisible = useMemo(() => {
    if (!streamingThinking) return false
    if (streamingThinking.isStreaming) return true
    if (streamingThinking.streamingEndedAt) {
      return Date.now() - streamingThinking.streamingEndedAt < 30000
    }
    return false
  }, [streamingThinking])

  // Find the last thinking block (message UUID + content index) for hiding past thinking in transcript mode
  // When streaming thinking is visible, use a special ID that won't match any completed thinking block
  // With adaptive thinking, only consider thinking blocks from the current turn and stop searching once we
  // hit the last user message.
  const lastThinkingBlockId = useMemo(() => {
    if (!hidePastThinking) return null
    // If streaming thinking is visible, hide all completed thinking blocks by using a non-matching ID
    if (isStreamingThinkingVisible) return 'streaming'
    // Iterate backwards to find the last message with a thinking block
    for (let i = normalizedMessages.length - 1; i >= 0; i--) {
      const msg = normalizedMessages[i]
      if (msg?.type === 'assistant') {
        const content = msg.message!.content as Array<{ type: string }>
        // Find the last thinking block in this message
        for (let j = content.length - 1; j >= 0; j--) {
          if (content[j]?.type === 'thinking') {
            return `${msg.uuid}:${j}`
          }
        }
      } else if (msg?.type === 'user') {
        const content = msg.message!.content as Array<{ type: string }>
        const hasToolResult = content.some(
          block => block.type === 'tool_result',
        )
        if (!hasToolResult) {
          // Reached a previous user turn so don't show stale thinking from before
          return 'no-thinking'
        }
      }
    }
    return null
  }, [normalizedMessages, hidePastThinking, isStreamingThinkingVisible])

  // Find the latest user bash output message (from ! commands)
  // This allows us to show full output for the most recent bash command
  const latestBashOutputUUID = useMemo(() => {
    // Iterate backwards to find the last user message with bash output
    for (let i = normalizedMessages.length - 1; i >= 0; i--) {
      const msg = normalizedMessages[i]
      if (msg?.type === 'user') {
        const content = msg.message!.content as Array<{ type: string; text?: string }>
        // Check if any text content is bash output
        for (const block of content) {
          if (block.type === 'text') {
            const text = block.text ?? ''
            if (
              text.startsWith('<bash-stdout') ||
              text.startsWith('<bash-stderr')
            ) {
              return msg.uuid
            }
          }
        }
      }
    }
    return null
  }, [normalizedMessages])

  // streamingToolUses updates on every input_json_delta while normalizedMessages
  // stays stable — precompute the Set so the filter is O(k) not O(n×k) per chunk.
  const normalizedToolUseIDs = useMemo(
    () => getToolUseIDs(normalizedMessages),
    [normalizedMessages],
  )

  const streamingToolUsesWithoutInProgress = useMemo(
    () =>
      streamingToolUses.filter(
        stu =>
          !inProgressToolUseIDs.has(stu.contentBlock.id) &&
          !normalizedToolUseIDs.has(stu.contentBlock.id),
      ),
    [streamingToolUses, inProgressToolUseIDs, normalizedToolUseIDs],
  )

  const syntheticStreamingToolUseMessages = useMemo(
    () =>
      streamingToolUsesWithoutInProgress.flatMap(streamingToolUse => {
        const msg = createAssistantMessage({
          content: [streamingToolUse.contentBlock],
        })
        // Override randomUUID with deterministic value derived from content
        // block ID to prevent React key changes on every memo recomputation.
        // Same class of bug fixed in normalizeMessages (commit 383326e613):
        // fresh randomUUID → unstable React keys → component remounts →
        // Ink rendering corruption (overlapping text from stale DOM nodes).
        msg.uuid = deriveUUID(streamingToolUse.contentBlock.id as UUID, 0)
        return normalizeMessages([msg])
      }),
    [streamingToolUsesWithoutInProgress],
  )

  const isTranscriptMode = screen === 'transcript'
  // Hoisted to mount-time — this component re-renders on every scroll.
  const disableVirtualScroll = useMemo(
    () => isEnvTruthy(process.env.CLAUDE_CODE_DISABLE_VIRTUAL_SCROLL),
    [],
  )
  // Virtual scroll replaces the transcript cap: everything is scrollable and
  // memory is bounded by the mounted-item count, not the total. scrollRef is
  // only passed when isFullscreenEnvEnabled() is true (REPL.tsx gates it),
  // so scrollRef's presence is the signal.
  const virtualScrollRuntimeGate = scrollRef != null && !disableVirtualScroll
  const shouldTruncate =
    isTranscriptMode && !showAllInTranscript && !virtualScrollRuntimeGate

  // Anchor for the first rendered message in the non-virtualized cap slice.
  // Monotonic advance only — mutation during render is idempotent (safe
  // under StrictMode double-render). See MAX_MESSAGES_WITHOUT_VIRTUALIZATION
  // comment above for why this replaced count-based slicing.
  const sliceAnchorRef = useRef<SliceAnchor>(null)

  // Expensive message transforms — filter, reorder, group, collapse, lookups.
  // All O(n) over 27k messages. Split from the renderRange slice so scrolling
  // (which only changes renderRange) doesn't re-run these. Previously this
  // useMemo included renderRange → every scroll rebuilt 6 Maps over 27k
  // messages + 4 filter/map passes = ~50ms alloc per scroll → GC pressure →
  // 100-173ms stop-the-world pauses on the 1GB heap.
  const { collapsed, lookups, hasTruncatedMessages, hiddenMessageCount } =
    useMemo(() => {
      // In fullscreen mode the alt buffer has no native scrollback, so the
      // compact-boundary filter just hides history the ScrollBox could
      // otherwise scroll to. Main-screen mode keeps the filter — pre-compact
      // rows live above the viewport in native scrollback there, and
      // re-rendering them triggers full resets.
      // includeSnipped: UI rendering keeps snipped messages for scrollback
      // (this PR's core goal — full history in UI, filter only for the model).
      // Also avoids a UUID mismatch: normalizeMessages derives new UUIDs, so
      // projectSnippedView's check against original removedUuids would fail.
      const compactAwareMessages =
        verbose || isFullscreenEnvEnabled()
          ? normalizedMessages
          : getMessagesAfterCompactBoundary(normalizedMessages, {
              includeSnipped: true,
            })

      const messagesToShowNotTruncated = reorderMessagesInUI(
        compactAwareMessages
          .filter(
            (msg): msg is Exclude<NormalizedMessage, ProgressMessageType> =>
              msg.type !== 'progress',
          )
          // CC-724: drop attachment messages that AttachmentMessage renders as
          // null (hook_success, hook_additional_context, hook_cancelled, etc.)
          // BEFORE counting/slicing so they don't inflate the "N messages"
          // count in ctrl-o or consume slots in the 200-message render cap.
          .filter(msg => !isNullRenderingAttachment(msg))
          .filter(_ => shouldShowUserMessage(_, isTranscriptMode)) as Parameters<typeof reorderMessagesInUI>[0],
        syntheticStreamingToolUseMessages,
      )
      // Three-tier filtering. Transcript mode (ctrl+o screen) is truly unfiltered.
      // Brief-only: SendUserMessage + user input only. Default: drop redundant
      // assistant text in turns where SendUserMessage was called (the model's
      // text is working-notes that duplicate the SendUserMessage content).
      const briefToolNames = [BRIEF_TOOL_NAME, SEND_USER_FILE_TOOL_NAME].filter(
        (n): n is string => n !== null,
      )
      // dropTextInBriefTurns should only trigger on SendUserMessage turns —
      // SendUserFile delivers a file without replacement text, so dropping
      // assistant text for file-only turns would leave the user with no context.
      const dropTextToolNames = [BRIEF_TOOL_NAME].filter(
        (n): n is string => n !== null,
      )
      const briefFiltered =
        briefToolNames.length > 0 && !isTranscriptMode
          ? isBriefOnly
            ? filterForBriefTool(messagesToShowNotTruncated as Parameters<typeof filterForBriefTool>[0], briefToolNames)
            : dropTextToolNames.length > 0
              ? dropTextInBriefTurns(
                  messagesToShowNotTruncated as Parameters<typeof dropTextInBriefTurns>[0],
                  dropTextToolNames,
                )
              : messagesToShowNotTruncated
          : messagesToShowNotTruncated

      const messagesToShow = shouldTruncate
        ? briefFiltered.slice(-MAX_MESSAGES_TO_SHOW_IN_TRANSCRIPT_MODE)
        : briefFiltered

      const hasTruncatedMessages =
        shouldTruncate &&
        briefFiltered.length > MAX_MESSAGES_TO_SHOW_IN_TRANSCRIPT_MODE

      const { messages: groupedMessages } = applyGrouping(
        messagesToShow as MessageType[],
        tools,
        verbose,
      )

      const collapsed = collapseBackgroundBashNotifications(
        collapseHookSummaries(
          collapseTeammateShutdowns(
            collapseReadSearchGroups(groupedMessages, tools),
          ),
        ),
        verbose,
      )

      const lookups = buildMessageLookups(normalizedMessages, messagesToShow as MessageType[])

      const hiddenMessageCount =
        messagesToShowNotTruncated.length -
        MAX_MESSAGES_TO_SHOW_IN_TRANSCRIPT_MODE

      return {
        collapsed,
        lookups,
        hasTruncatedMessages,
        hiddenMessageCount,
      }
    }, [
      verbose,
      normalizedMessages,
      isTranscriptMode,
      syntheticStreamingToolUseMessages,
      shouldTruncate,
      tools,
      isBriefOnly,
    ])

  // Cheap slice — only runs when scroll range or slice config changes.
  const renderableMessages = useMemo(() => {
    // Safety cap for the non-virtualized render path. Applied here (not at
    // the JSX site) so renderMessageRow's index-based lookups and
    // dividerBeforeIndex compute on the same array. VirtualMessageList
    // never sees this slice — virtualScrollRuntimeGate is constant for the
    // component's lifetime (scrollRef is either always passed or never).
    // renderRange is first: the chunked export path slices the
    // post-grouping array so each chunk gets correct tool-call grouping.
    const capApplies = !virtualScrollRuntimeGate && !disableRenderCap
    const sliceStart = capApplies
      ? computeSliceStart(collapsed, sliceAnchorRef)
      : 0
    return renderRange
      ? collapsed.slice(renderRange[0], renderRange[1])
      : sliceStart > 0
        ? collapsed.slice(sliceStart)
        : collapsed
  }, [collapsed, renderRange, virtualScrollRuntimeGate, disableRenderCap])

  const streamingToolUseIDs = useMemo(
    () => new Set(streamingToolUses.map(_ => _.contentBlock.id)),
    [streamingToolUses],
  )

  // Divider insertion point: first renderableMessage whose uuid shares the
  // 24-char prefix with firstUnseenUuid (deriveUUID keeps the first 24
  // chars of the source message uuid, so this matches any block from it).
  const dividerBeforeIndex = useMemo(() => {
    if (!unseenDivider) return -1
    const prefix = unseenDivider.firstUnseenUuid.slice(0, 24)
    return renderableMessages.findIndex(m => m.uuid.slice(0, 24) === prefix)
  }, [unseenDivider, renderableMessages])

  const selectedIdx = useMemo(() => {
    if (!cursor) return -1
    return renderableMessages.findIndex(m => m.uuid === cursor.uuid)
  }, [cursor, renderableMessages])

  // Fullscreen: click a message to toggle verbose rendering for it. Keyed by
  // tool_use_id where available so a tool_use and its tool_result (separate
  // rows) expand together; falls back to uuid for groups/thinking. Stale keys
  // are harmless — they never match anything in renderableMessages.
  const [expandedKeys, setExpandedKeys] = useState<ReadonlySet<string>>(
    () => new Set(),
  )
  const onItemClick = useCallback((msg: RenderableMessage) => {
    const k = expandKey(msg)
    setExpandedKeys(prev => {
      const next = new Set(prev)
      if (next.has(k)) next.delete(k)
      else next.add(k)
      return next
    })
  }, [])
  const isItemExpanded = useCallback(
    (msg: RenderableMessage) =>
      expandedKeys.size > 0 && expandedKeys.has(expandKey(msg)),
    [expandedKeys],
  )
  // Only hover/click messages where the verbose toggle reveals more:
  // collapsed read/search groups, or tool results that self-report truncation
  // via isResultTruncated. Callback must be stable across message updates: if
  // its identity (or return value) flips during streaming, onMouseEnter
  // attaches after the mouse is already inside → hover never fires. tools is
  // session-stable; lookups is read via ref so the callback doesn't churn on
  // every new message.
  const lookupsRef = useRef(lookups)
  lookupsRef.current = lookups
  const isItemClickable = useCallback(
    (msg: RenderableMessage): boolean => {
      if (msg.type === 'collapsed_read_search') return true
      if (msg.type === 'assistant') {
        const content = msg.message!.content
        const b = (Array.isArray(content) ? content[0] : undefined) as unknown as AdvisorBlock | undefined
        return (
          b != null &&
          isAdvisorBlock(b) &&
          b.type === 'advisor_tool_result' &&
          b.content.type === 'advisor_result'
        )
      }
      if (msg.type !== 'user') return false
      const b = (msg.message!.content as Array<{ type: string; tool_use_id?: string; is_error?: boolean; [key: string]: unknown }>)[0]
      if (b?.type !== 'tool_result' || b.is_error || !msg.toolUseResult)
        return false
      const name = lookupsRef.current.toolUseByToolUseID.get(
        b.tool_use_id ?? '',
      )?.name
      const tool = name ? findToolByName(tools, name) : undefined
      return tool?.isResultTruncated?.(msg.toolUseResult as never) ?? false
    },
    [tools],
  )

  const canAnimate =
    (!toolJSX || !!toolJSX.shouldContinueAnimation) &&
    !toolUseConfirmQueue.length &&
    !isMessageSelectorVisible

  const hasToolsInProgress = inProgressToolUseIDs.size > 0

  // Report progress to terminal (for terminals that support OSC 9;4)
  const { progress } = useTerminalNotification()
  const prevProgressState = useRef<string | null>(null)
  const progressEnabled =
    getGlobalConfig().terminalProgressBarEnabled &&
    !getIsRemoteMode() &&
    !(proactiveModule?.isProactiveActive() ?? false)
  useEffect(() => {
    const state = progressEnabled
      ? hasToolsInProgress
        ? 'indeterminate'
        : 'completed'
      : null
    if (prevProgressState.current === state) return
    prevProgressState.current = state
    progress(state)
  }, [progress, progressEnabled, hasToolsInProgress])
  useEffect(() => {
    return () => progress(null)
  }, [progress])

  const messageKey = useCallback(
    (msg: RenderableMessage) => `${msg.uuid}-${conversationId}`,
    [conversationId],
  )

  const renderMessageRow = (msg: RenderableMessage, index: number) => {
    const prevType = index > 0 ? renderableMessages[index - 1]?.type : undefined
    const isUserContinuation = msg.type === 'user' && prevType === 'user'
    // hasContentAfter is only consumed for collapsed_read_search groups;
    // skip the scan for everything else. streamingText is rendered as a
    // sibling after this map, so it's never in renderableMessages — OR it
    // in explicitly so the group flips to past tense as soon as text starts
    // streaming instead of waiting for the block to finalize.
    const hasContentAfter =
      msg.type === 'collapsed_read_search' &&
      (!!streamingText ||
        hasContentAfterIndex(
          renderableMessages,
          index,
          tools,
          streamingToolUseIDs,
        ))

    // Collapse diffs for messages beyond the latest N messages.
    // verbose (ctrl+o) overrides and always shows full diffs.
    const DIFF_COLLAPSE_DISTANCE = 0
    const shouldCollapseDiffs =
      renderableMessages.length - 1 - index > DIFF_COLLAPSE_DISTANCE

    const k = messageKey(msg)
    const row = (
      <MessageRow
        key={k}
        message={msg}
        isUserContinuation={isUserContinuation}
        hasContentAfter={hasContentAfter}
        tools={tools}
        commands={commands}
        verbose={
          verbose ||
          isItemExpanded(msg) ||
          (cursor?.expanded === true && index === selectedIdx)
        }
        inProgressToolUseIDs={inProgressToolUseIDs}
        streamingToolUseIDs={streamingToolUseIDs}
        screen={screen}
        canAnimate={canAnimate}
        onOpenRateLimitOptions={onOpenRateLimitOptions}
        lastThinkingBlockId={lastThinkingBlockId}
        latestBashOutputUUID={latestBashOutputUUID}
        columns={columns}
        isLoading={isLoading}
        lookups={lookups}
        shouldCollapseDiffs={shouldCollapseDiffs}
      />
    )

    // Per-row Provider — only 2 rows re-render on selection change.
    // Wrapped BEFORE divider branch so both return paths get it.
    const wrapped = (
      <MessageActionsSelectedContext.Provider
        key={k}
        value={index === selectedIdx}
      >
        {row}
      </MessageActionsSelectedContext.Provider>
    )

    if (unseenDivider && index === dividerBeforeIndex) {
      return [
        <Box key="unseen-divider" marginTop={1}>
          <Divider
            title={`${unseenDivider.count} new ${plural(unseenDivider.count, 'message')}`}
            width={columns}
            color="inactive"
          />
        </Box>,
        wrapped,
      ]
    }
    return wrapped
  }

  // Search indexing: for tool_result messages, look up the Tool and use
  // its extractSearchText — tool-owned, precise, matches what
  // renderToolResultMessage shows. Falls back to renderableSearchText
  // (duck-types toolUseResult) for tools that haven't implemented it,
  // and for all non-tool-result message types. The drift-catcher test
  // (toolSearchText.test.tsx) renders + compares to keep these in sync.
  //
  // A second-React-root reconcile approach was tried and ruled out
  // (measured 3.1ms/msg, growing — flushSyncWork processes all roots;
  // component hooks mutate shared state → main root accumulates updates).
  const searchTextCache = useRef(new WeakMap<RenderableMessage, string>())
  const extractSearchText = useCallback(
    (msg: RenderableMessage): string => {
      const cached = searchTextCache.current.get(msg)
      if (cached !== undefined) return cached
      let text = renderableSearchText(msg)
      // If this is a tool_result message and the tool implements
      // extractSearchText, prefer that — it's precise (tool-owned)
      // vs renderableSearchText's field-name heuristic.
      if (
        msg.type === 'user' &&
        msg.toolUseResult &&
        Array.isArray(msg.message.content)
      ) {
        const tr = msg.message.content.find(b => b.type === 'tool_result')
        if (tr && 'tool_use_id' in tr) {
          const tu = lookups.toolUseByToolUseID.get(tr.tool_use_id)
          const tool = tu && findToolByName(tools, tu.name)
          const extracted = tool?.extractSearchText?.(
            msg.toolUseResult as never,
          )
          // undefined = tool didn't implement → keep heuristic. Empty
          // string = tool says "nothing to index" → respect that.
          if (extracted !== undefined) text = extracted
        }
      }
      // Cache LOWERED: setSearchQuery's hot loop indexOfs per keystroke.
      // Lowering here (once, at warm) vs there (every keystroke) trades
      // ~same steady-state memory for zero per-keystroke alloc. Cache
      // GC's with messages on transcript exit. Tool methods return raw;
      // renderableSearchText already lowercases (redundant but cheap).
      const lowered = text.toLowerCase()
      searchTextCache.current.set(msg, lowered)
      return lowered
    },
    [tools, lookups],
  )

  return (
    <>
      {/* Logo */}
      {!hideLogo && !(renderRange && renderRange[0] > 0) && (
        <LogoHeader agentDefinitions={agentDefinitions} />
      )}

      {/* Truncation indicator */}
      {hasTruncatedMessages && (
        <Divider
          title={`${toggleShowAllShortcut} to show ${chalk.bold(hiddenMessageCount)} previous messages`}
          width={columns}
        />
      )}

      {/* Show all indicator */}
      {isTranscriptMode &&
        showAllInTranscript &&
        hiddenMessageCount > 0 &&
        // disableRenderCap (e.g. [ dump-to-scrollback) means we're uncapped
        // as a one-shot escape hatch, not a toggle — ctrl+e is dead and
        // nothing is actually "hidden" to restore.
        !disableRenderCap && (
          <Divider
            title={`${toggleShowAllShortcut} to hide ${chalk.bold(hiddenMessageCount)} previous messages`}
            width={columns}
          />
        )}

      {/* Messages - rendered as memoized MessageRow components.
          flatMap inserts the unseen-divider as a separate keyed sibling so
          (a) non-fullscreen renders pay no per-message Fragment wrap, and
          (b) divider toggle in fullscreen preserves all MessageRows by key.
          Pre-compute derived values instead of passing renderableMessages to
          each row - React Compiler pins props in the fiber's memoCache, so
          passing the array would accumulate every historical version
          (~1-2MB over a 7-turn session). */}
      {virtualScrollRuntimeGate ? (
        <InVirtualListContext.Provider value={true}>
          <VirtualMessageList
            messages={renderableMessages}
            scrollRef={scrollRef}
            columns={columns}
            itemKey={messageKey}
            renderItem={renderMessageRow}
            onItemClick={onItemClick}
            isItemClickable={isItemClickable}
            isItemExpanded={isItemExpanded}
            trackStickyPrompt={trackStickyPrompt}
            selectedIndex={selectedIdx >= 0 ? selectedIdx : undefined}
            cursorNavRef={cursorNavRef}
            setCursor={setCursor}
            jumpRef={jumpRef}
            onSearchMatchesChange={onSearchMatchesChange}
            scanElement={scanElement}
            setPositions={setPositions}
            extractSearchText={extractSearchText}
          />
        </InVirtualListContext.Provider>
      ) : (
        renderableMessages.flatMap(renderMessageRow)
      )}

      {streamingText && !isBriefOnly && (
        <Box
          alignItems="flex-start"
          flexDirection="row"
          marginTop={1}
          width="100%"
        >
          <Box flexDirection="row">
            <Box minWidth={2}>
              <Text color="text">{BLACK_CIRCLE}</Text>
            </Box>
            <Box flexDirection="column">
              <StreamingMarkdown>{streamingText}</StreamingMarkdown>
            </Box>
          </Box>
        </Box>
      )}

      {isStreamingThinkingVisible && streamingThinking && !isBriefOnly && (
        <Box marginTop={1}>
          <AssistantThinkingMessage
            param={{
              type: 'thinking',
              thinking: streamingThinking.thinking,
            }}
            addMargin={false}
            isTranscriptMode={true}
            verbose={verbose}
            hideInTranscript={false}
          />
        </Box>
      )}
    </>
  )
}

/** Key for click-to-expand: tool_use_id where available (so tool_use + its
 *  tool_result expand together), else uuid for groups/thinking. */
function expandKey(msg: RenderableMessage): string {
  return (
    (msg.type === 'assistant' || msg.type === 'user'
      ? getToolUseID(msg)
      : null) ?? msg.uuid
  )
}

// Custom comparator to prevent unnecessary re-renders during streaming.
// Default React.memo does shallow comparison which fails when:
// 1. onOpenRateLimitOptions callback is recreated (doesn't affect render output)
// 2. streamingToolUses array is recreated on every delta, but only contentBlock matters for rendering
// 3. streamingThinking changes on every delta - we DO want to re-render for this
function setsEqual<T>(a: Set<T>, b: Set<T>): boolean {
  if (a.size !== b.size) return false
  for (const item of a) {
    if (!b.has(item)) return false
  }
  return true
}

export const Messages = React.memo(MessagesImpl, (prev, next) => {
  const keys = Object.keys(prev) as (keyof typeof prev)[]
  for (const key of keys) {
    if (
      key === 'onOpenRateLimitOptions' ||
      key === 'scrollRef' ||
      key === 'trackStickyPrompt' ||
      key === 'setCursor' ||
      key === 'cursorNavRef' ||
      key === 'jumpRef' ||
      key === 'onSearchMatchesChange' ||
      key === 'scanElement' ||
      key === 'setPositions'
    )
      continue
    if (prev[key] !== next[key]) {
      if (key === 'streamingToolUses') {
        const p = prev.streamingToolUses
        const n = next.streamingToolUses
        if (
          p.length === n.length &&
          p.every((item, i) => item.contentBlock === n[i]?.contentBlock)
        ) {
          continue
        }
      }
      if (key === 'inProgressToolUseIDs') {
        if (setsEqual(prev.inProgressToolUseIDs, next.inProgressToolUseIDs)) {
          continue
        }
      }
      if (key === 'unseenDivider') {
        const p = prev.unseenDivider
        const n = next.unseenDivider
        if (
          p?.firstUnseenUuid === n?.firstUnseenUuid &&
          p?.count === n?.count
        ) {
          continue
        }
      }
      if (key === 'tools') {
        const p = prev.tools
        const n = next.tools
        if (
          p.length === n.length &&
          p.every((tool, i) => tool.name === n[i]?.name)
        ) {
          continue
        }
      }
      // streamingThinking changes frequently - always re-render when it changes
      // (no special handling needed, default behavior is correct)
      return false
    }
  }
  return true
})

export function shouldRenderStatically(
  message: RenderableMessage,
  streamingToolUseIDs: Set<string>,
  inProgressToolUseIDs: Set<string>,
  siblingToolUseIDs: ReadonlySet<string>,
  screen: Screen,
  lookups: ReturnType<typeof buildMessageLookups>,
): boolean {
  if (screen === 'transcript') {
    return true
  }
  switch (message.type) {
    case 'attachment':
    case 'user':
    case 'assistant': {
      if (message.type === 'assistant') {
        const block = (message.message!.content as Array<{ type: string; id?: string }>)[0]
        if (block?.type === 'server_tool_use') {
          return lookups.resolvedToolUseIDs.has(block.id!)
        }
      }
      const toolUseID = getToolUseID(message)
      if (!toolUseID) {
        return true
      }
      if (streamingToolUseIDs.has(toolUseID)) {
        return false
      }
      if (inProgressToolUseIDs.has(toolUseID)) {
        return false
      }

      // Check if there are any unresolved PostToolUse hooks for this tool use
      // If so, keep the message transient so the HookProgressMessage can update
      if (hasUnresolvedHooksFromLookup(toolUseID, 'PostToolUse', lookups)) {
        return false
      }

      return every(siblingToolUseIDs, lookups.resolvedToolUseIDs)
    }
    case 'system': {
      // api errors always render dynamically, since we hide
      // them as soon as we see another non-error message.
      return message.subtype !== 'api_error'
    }
    case 'grouped_tool_use': {
      const allResolved = message.messages.every(msg => {
        const content = (msg.message!.content as Array<{ type: string; id?: string }>)[0]
        return (
          content?.type === 'tool_use' &&
          lookups.resolvedToolUseIDs.has(content.id!)
        )
      })
      return allResolved
    }
    case 'collapsed_read_search': {
      // In prompt mode, never mark as static to prevent flicker between API turns
      // (In transcript mode, we already returned true at the top of this function)
      return false
    }
    default:
      return true
  }
}