refactor(tui): /clean pass on per-section visibility plumbing

- domain/details: extract `norm()`, fold parseDetailsMode + resolveSections
  into terser functional form, reject array values for resolveSections
- slash /details: destructure tokens, factor reset/mode into one dispatch,
  drop DETAIL_MODES set + DetailsMode/SectionName imports (parseDetailsMode
  + isSectionName narrow + return), centralize usage strings
- ToolTrail: collapse 4 separate xxxSection vars into one memoized
  `visible` map; effect deps stabilize on the memo identity instead of
  4 primitives

ui-tui/src/app/slash/commands/core.ts

@@ -10,7 +10,7 @@ import type {
 } from '../../../gatewayTypes.js'
 import { writeOsc52Clipboard } from '../../../lib/osc52.js'
 import { configureDetectedTerminalKeybindings, configureTerminalKeybindings } from '../../../lib/terminalSetup.js'
-import type { DetailsMode, Msg, PanelSection, SectionName } from '../../../types.js'
+import type { Msg, PanelSection } from '../../../types.js'
 import type { StatusBarMode } from '../../interfaces.js'
 import { patchOverlayState } from '../../overlayStore.js'
 import { patchUiState } from '../../uiStore.js'
@@ -38,7 +38,11 @@ const flagFromArg = (arg: string, current: boolean): boolean | null => {
   return null
 }
 
-const DETAIL_MODES = new Set(['collapsed', 'cycle', 'expanded', 'hidden', 'toggle'])
+const RESET_WORDS = new Set(['reset', 'clear', 'default'])
+const CYCLE_WORDS = new Set(['cycle', 'toggle'])
+const DETAILS_USAGE =
+  'usage: /details [hidden|collapsed|expanded|cycle]  or  /details <section> [hidden|collapsed|expanded|reset]'
+const DETAILS_SECTION_USAGE = 'usage: /details <section> [hidden|collapsed|expanded|reset]'
 
 export const coreCommands: SlashCommand[] = [
   {
@@ -150,9 +154,7 @@ export const coreCommands: SlashCommand[] = [
         gateway
           .rpc<ConfigGetValueResponse>('config.get', { key: 'details_mode' })
           .then(r => {
-            if (ctx.stale()) {
-              return
-            }
+            if (ctx.stale()) return
 
             const mode = parseDetailsMode(r?.value) ?? ui.detailsMode
             patchUiState({ detailsMode: mode })
@@ -164,59 +166,38 @@ export const coreCommands: SlashCommand[] = [
 
             transcript.sys(`details: ${mode}${overrides ? `  (${overrides})` : ''}`)
           })
-          .catch(() => {
-            if (!ctx.stale()) {
-              transcript.sys(`details: ${ui.detailsMode}`)
-            }
-          })
+          .catch(() => !ctx.stale() && transcript.sys(`details: ${ui.detailsMode}`))
 
         return
       }
 
-      const tokens = arg.trim().toLowerCase().split(/\s+/)
+      const [first, second] = arg.trim().toLowerCase().split(/\s+/)
 
-      // Per-section override: `/details <section> <mode>`
-      if (tokens.length >= 2 && isSectionName(tokens[0])) {
-        const section = tokens[0] as SectionName
-        const action = tokens[1] ?? ''
+      if (second && isSectionName(first)) {
+        const reset = RESET_WORDS.has(second)
+        const mode = reset ? null : parseDetailsMode(second)
 
-        if (action === 'reset' || action === 'clear' || action === 'default') {
-          const { [section]: _drop, ...rest } = ui.sections
-          patchUiState({ sections: rest })
-          gateway
-            .rpc<ConfigSetResponse>('config.set', { key: `details_mode.${section}`, value: '' })
-            .catch(() => {})
-          transcript.sys(`details ${section}: reset`)
-
-          return
+        if (!reset && !mode) {
+          return transcript.sys(DETAILS_SECTION_USAGE)
         }
 
-        const sectionMode = parseDetailsMode(action)
+        const { [first]: _drop, ...rest } = ui.sections
 
-        if (!sectionMode) {
-          return transcript.sys('usage: /details <section> [hidden|collapsed|expanded|reset]')
-        }
-
-        patchUiState({ sections: { ...ui.sections, [section]: sectionMode } })
+        patchUiState({ sections: mode ? { ...rest, [first]: mode } : rest })
         gateway
-          .rpc<ConfigSetResponse>('config.set', { key: `details_mode.${section}`, value: sectionMode })
+          .rpc<ConfigSetResponse>('config.set', { key: `details_mode.${first}`, value: mode ?? '' })
           .catch(() => {})
-        transcript.sys(`details ${section}: ${sectionMode}`)
+        transcript.sys(`details ${first}: ${mode ?? 'reset'}`)
 
         return
       }
 
-      // Global mode (existing behavior).
-      const mode = tokens[0] ?? ''
+      const next = CYCLE_WORDS.has(first ?? '') ? nextDetailsMode(ui.detailsMode) : parseDetailsMode(first)
 
-      if (!DETAIL_MODES.has(mode)) {
-        return transcript.sys(
-          'usage: /details [hidden|collapsed|expanded|cycle]  or  /details <section> [hidden|collapsed|expanded|reset]'
-        )
+      if (!next) {
+        return transcript.sys(DETAILS_USAGE)
       }
 
-      const next = mode === 'cycle' || mode === 'toggle' ? nextDetailsMode(ui.detailsMode) : (mode as DetailsMode)
-
       patchUiState({ detailsMode: next })
       gateway.rpc<ConfigSetResponse>('config.set', { key: 'details_mode', value: next }).catch(() => {})
       transcript.sys(`details: ${next}`)

ui-tui/src/components/thinking.tsx

@@ -707,34 +707,39 @@ export const ToolTrail = memo(function ToolTrail({
   trail?: string[]
   activity?: ActivityItem[]
 }) {
-  const thinkingSection = sectionMode('thinking', detailsMode, sections)
-  const toolsSection = sectionMode('tools', detailsMode, sections)
-  const subagentsSection = sectionMode('subagents', detailsMode, sections)
-  const activitySection = sectionMode('activity', detailsMode, sections)
+  const visible = useMemo(
+    () => ({
+      thinking: sectionMode('thinking', detailsMode, sections),
+      tools: sectionMode('tools', detailsMode, sections),
+      subagents: sectionMode('subagents', detailsMode, sections),
+      activity: sectionMode('activity', detailsMode, sections)
+    }),
+    [detailsMode, sections]
+  )
 
   const [now, setNow] = useState(() => Date.now())
-  const [openThinking, setOpenThinking] = useState(thinkingSection === 'expanded')
-  const [openTools, setOpenTools] = useState(toolsSection === 'expanded')
-  const [openSubagents, setOpenSubagents] = useState(subagentsSection === 'expanded')
-  const [deepSubagents, setDeepSubagents] = useState(subagentsSection === 'expanded')
-  const [openMeta, setOpenMeta] = useState(activitySection === 'expanded')
+  const [openThinking, setOpenThinking] = useState(visible.thinking === 'expanded')
+  const [openTools, setOpenTools] = useState(visible.tools === 'expanded')
+  const [openSubagents, setOpenSubagents] = useState(visible.subagents === 'expanded')
+  const [deepSubagents, setDeepSubagents] = useState(visible.subagents === 'expanded')
+  const [openMeta, setOpenMeta] = useState(visible.activity === 'expanded')
 
   useEffect(() => {
-    if (!tools.length || (toolsSection !== 'expanded' && !openTools)) {
+    if (!tools.length || (visible.tools !== 'expanded' && !openTools)) {
       return
     }
 
     const id = setInterval(() => setNow(Date.now()), 500)
 
     return () => clearInterval(id)
-  }, [toolsSection, openTools, tools.length])
+  }, [openTools, tools.length, visible.tools])
 
   useEffect(() => {
-    setOpenThinking(thinkingSection === 'expanded')
-    setOpenTools(toolsSection === 'expanded')
-    setOpenSubagents(subagentsSection === 'expanded')
-    setOpenMeta(activitySection === 'expanded')
-  }, [thinkingSection, toolsSection, subagentsSection, activitySection])
+    setOpenThinking(visible.thinking === 'expanded')
+    setOpenTools(visible.tools === 'expanded')
+    setOpenSubagents(visible.subagents === 'expanded')
+    setOpenMeta(visible.activity === 'expanded')
+  }, [visible])
 
   const cot = useMemo(() => thinkingPreview(reasoning, 'full', THINKING_COT_MAX), [reasoning])
 
@@ -877,7 +882,7 @@ export const ToolTrail = memo(function ToolTrail({
   // override means "I don't want to see meta at all", so respect it.
 
   if (detailsMode === 'hidden') {
-    if (activitySection === 'hidden') {
+    if (visible.activity === 'hidden') {
       return null
     }
 
@@ -900,13 +905,13 @@ export const ToolTrail = memo(function ToolTrail({
   // hidden sections stay hidden so the override is honoured.
 
   const expandAll = () => {
-    if (thinkingSection !== 'hidden') setOpenThinking(true)
-    if (toolsSection !== 'hidden') setOpenTools(true)
-    if (subagentsSection !== 'hidden') {
+    if (visible.thinking !== 'hidden') setOpenThinking(true)
+    if (visible.tools !== 'hidden') setOpenTools(true)
+    if (visible.subagents !== 'hidden') {
       setOpenSubagents(true)
       setDeepSubagents(true)
     }
-    if (activitySection !== 'hidden') setOpenMeta(true)
+    if (visible.activity !== 'hidden') setOpenMeta(true)
   }
 
   const metaTone: 'dim' | 'error' | 'warn' = activity.some(i => i.tone === 'error')
@@ -920,7 +925,7 @@ export const ToolTrail = memo(function ToolTrail({
       {spawnTree.map((node, index) => (
         <SubagentAccordion
           branch={index === spawnTree.length - 1 ? 'last' : 'mid'}
-          expanded={subagentsSection === 'expanded' || deepSubagents}
+          expanded={visible.subagents === 'expanded' || deepSubagents}
           key={node.item.id}
           node={node}
           peak={spawnPeak}
@@ -938,7 +943,7 @@ export const ToolTrail = memo(function ToolTrail({
     render: (rails: boolean[]) => ReactNode
   }[] = []
 
-  if (hasThinking && thinkingSection !== 'hidden') {
+  if (hasThinking && visible.thinking !== 'hidden') {
     panels.push({
       header: (
         <Box
@@ -951,7 +956,7 @@ export const ToolTrail = memo(function ToolTrail({
           }}
         >
           <Text color={t.color.dim} dim={!thinkingLive}>
-            <Text color={t.color.amber}>{thinkingSection === 'expanded' || openThinking ? '▾ ' : '▸ '}</Text>
+            <Text color={t.color.amber}>{visible.thinking === 'expanded' || openThinking ? '▾ ' : '▸ '}</Text>
             {thinkingLive ? (
               <Text bold color={t.color.cornsilk}>
                 Thinking
@@ -971,7 +976,7 @@ export const ToolTrail = memo(function ToolTrail({
         </Box>
       ),
       key: 'thinking',
-      open: thinkingSection === 'expanded' || openThinking,
+      open: visible.thinking === 'expanded' || openThinking,
       render: rails => (
         <Thinking
           active={reasoningActive}
@@ -986,7 +991,7 @@ export const ToolTrail = memo(function ToolTrail({
     })
   }
 
-  if (hasTools && toolsSection !== 'hidden') {
+  if (hasTools && visible.tools !== 'hidden') {
     panels.push({
       header: (
         <Chevron
@@ -998,14 +1003,14 @@ export const ToolTrail = memo(function ToolTrail({
               setOpenTools(v => !v)
             }
           }}
-          open={toolsSection === 'expanded' || openTools}
+          open={visible.tools === 'expanded' || openTools}
           suffix={toolTokensLabel}
           t={t}
           title="Tool calls"
         />
       ),
       key: 'tools',
-      open: toolsSection === 'expanded' || openTools,
+      open: visible.tools === 'expanded' || openTools,
       render: rails => (
         <Box flexDirection="column">
           {groups.map((group, index) => {
@@ -1045,7 +1050,7 @@ export const ToolTrail = memo(function ToolTrail({
     })
   }
 
-  if (hasSubagents && !inlineDelegateKey && subagentsSection !== 'hidden') {
+  if (hasSubagents && !inlineDelegateKey && visible.subagents !== 'hidden') {
     // Spark + summary give a one-line read on the branch shape before
     // opening the subtree.  `/agents` opens the full-screen audit overlay.
     const suffix = spawnSpark ? `${spawnSummaryLabel}  ${spawnSpark}  (/agents)` : `${spawnSummaryLabel}  (/agents)`
@@ -1063,19 +1068,19 @@ export const ToolTrail = memo(function ToolTrail({
               setDeepSubagents(false)
             }
           }}
-          open={subagentsSection === 'expanded' || openSubagents}
+          open={visible.subagents === 'expanded' || openSubagents}
           suffix={suffix}
           t={t}
           title="Spawn tree"
         />
       ),
       key: 'subagents',
-      open: subagentsSection === 'expanded' || openSubagents,
+      open: visible.subagents === 'expanded' || openSubagents,
       render: renderSubagentList
     })
   }
 
-  if (hasMeta && activitySection !== 'hidden') {
+  if (hasMeta && visible.activity !== 'hidden') {
     panels.push({
       header: (
         <Chevron
@@ -1087,14 +1092,14 @@ export const ToolTrail = memo(function ToolTrail({
               setOpenMeta(v => !v)
             }
           }}
-          open={activitySection === 'expanded' || openMeta}
+          open={visible.activity === 'expanded' || openMeta}
           t={t}
           title="Activity"
           tone={metaTone}
         />
       ),
       key: 'meta',
-      open: activitySection === 'expanded' || openMeta,
+      open: visible.activity === 'expanded' || openMeta,
       render: rails => (
         <Box flexDirection="column">
           {meta.map((row, index) => (

ui-tui/src/domain/details.ts

@@ -1,7 +1,15 @@
 import type { DetailsMode, SectionName, SectionVisibility } from '../types.js'
 
 const MODES = ['hidden', 'collapsed', 'expanded'] as const
-export const SECTION_NAMES: readonly SectionName[] = ['thinking', 'tools', 'subagents', 'activity']
+
+export const SECTION_NAMES = ['thinking', 'tools', 'subagents', 'activity'] as const
+
+// Activity panel = ambient meta (gateway hints, terminal-parity nudges,
+// background-process notifications).  Hidden out of the box because tool
+// failures already render inline on the failing tool row — the panel itself
+// is noise for typical use.  Opt back in via `display.sections.activity` or
+// `/details activity collapsed`.
+const SECTION_DEFAULTS: SectionVisibility = { activity: 'hidden' }
 
 const THINKING_FALLBACK: Record<string, DetailsMode> = {
   collapsed: 'collapsed',
@@ -9,66 +17,36 @@ const THINKING_FALLBACK: Record<string, DetailsMode> = {
   truncated: 'collapsed'
 }
 
-export const parseDetailsMode = (v: unknown): DetailsMode | null => {
-  const s = typeof v === 'string' ? v.trim().toLowerCase() : ''
+const norm = (v: unknown) => String(v ?? '').trim().toLowerCase()
 
-  return MODES.find(m => m === s) ?? null
-}
+export const parseDetailsMode = (v: unknown): DetailsMode | null =>
+  MODES.find(m => m === norm(v)) ?? null
 
 export const isSectionName = (v: unknown): v is SectionName =>
   typeof v === 'string' && (SECTION_NAMES as readonly string[]).includes(v)
 
 export const resolveDetailsMode = (d?: { details_mode?: unknown; thinking_mode?: unknown } | null): DetailsMode =>
-  parseDetailsMode(d?.details_mode) ??
-  THINKING_FALLBACK[
-    String(d?.thinking_mode ?? '')
-      .trim()
-      .toLowerCase()
-  ] ??
-  'collapsed'
+  parseDetailsMode(d?.details_mode) ?? THINKING_FALLBACK[norm(d?.thinking_mode)] ?? 'collapsed'
 
-// Build a SectionVisibility from a free-form `display.sections` config blob.
-// Skips keys that aren't recognized section names or don't parse to a valid
-// mode — partial overrides are intentional, missing keys fall through to the
-// global details_mode at render time.
-export const resolveSections = (raw: unknown): SectionVisibility => {
-  const out: SectionVisibility = {}
+// Build SectionVisibility from a free-form blob.  Unknown section names and
+// invalid modes are dropped silently — partial overrides are intentional, so
+// missing keys fall through to SECTION_DEFAULTS / global at lookup time.
+export const resolveSections = (raw: unknown): SectionVisibility =>
+  raw && typeof raw === 'object' && !Array.isArray(raw)
+    ? (Object.fromEntries(
+        Object.entries(raw as Record<string, unknown>)
+          .map(([k, v]) => [k, parseDetailsMode(v)] as const)
+          .filter(([k, m]) => !!m && isSectionName(k))
+      ) as SectionVisibility)
+    : {}
 
-  if (!raw || typeof raw !== 'object') {
-    return out
-  }
-
-  for (const [k, v] of Object.entries(raw as Record<string, unknown>)) {
-    const mode = parseDetailsMode(v)
-
-    if (mode && isSectionName(k)) {
-      out[k] = mode
-    }
-  }
-
-  return out
-}
-
-// Built-in per-section defaults applied when the user has no explicit
-// override.  The activity panel (gateway hints, terminal-parity nudges,
-// background-process notifications) is hidden out of the box — it's noise
-// for the typical day-to-day user, who only cares about thinking + tools +
-// streamed content.  Tool failures still surface inline on the failing tool
-// row; this default only suppresses the ambient meta feed.
-//
-// Opt back in with `display.sections.activity: collapsed` (under chevron)
-// or `expanded` (always open) in `~/.hermes/config.yaml`, or live with
-// `/details activity collapsed`.
-const SECTION_DEFAULTS: SectionVisibility = { activity: 'hidden' }
-
-// Resolve the effective mode for one section: explicit override wins,
-// then the SECTION_DEFAULTS fallback, then the global details_mode.
-// Single source of truth — every render site that needs to know "is this
-// section open by default" calls this.
+// Effective mode for one section: explicit override → SECTION_DEFAULTS → global.
+// Single source of truth for "is this section open by default / rendered at all".
 export const sectionMode = (
   name: SectionName,
   global: DetailsMode,
   sections?: SectionVisibility
 ): DetailsMode => sections?.[name] ?? SECTION_DEFAULTS[name] ?? global
 
-export const nextDetailsMode = (m: DetailsMode): DetailsMode => MODES[(MODES.indexOf(m) + 1) % MODES.length]!
+export const nextDetailsMode = (m: DetailsMode): DetailsMode =>
+  MODES[(MODES.indexOf(m) + 1) % MODES.length]!