diff --git a/src/components/settings/settings-panel.tsx b/src/components/settings/settings-panel.tsx
index 4782b5cb..8def206f 100644
--- a/src/components/settings/settings-panel.tsx
+++ b/src/components/settings/settings-panel.tsx
@@ -8,6 +8,7 @@ import { McpTab } from './tabs/mcp-tab'
 import { BoardTab } from './tabs/board-tab'
 import { VoiceTab } from './tabs/voice-tab'
 import { AdvancedTab } from './tabs/advanced-tab'
+import { SystemTab } from './tabs/system-tab'
 import { GitTab } from './tabs/git-tab'
 import { GithubTab } from './tabs/github-tab'
 import { DiscordTab } from './tabs/discord-tab'
@@ -81,6 +82,7 @@ type TabId =
   | 'github'
   | 'discord'
   | 'batches'
+  | 'runtime'
   | 'updates'
   | 'advanced'
 
@@ -128,6 +130,7 @@ const TAB_GROUPS: TabGroup[] = [
     id: 'system',
     label: 'System',
     tabs: [
+      { id: 'runtime', label: 'Runtime', hint: 'Global defaults, sessions, GC, limits' },
       { id: 'advanced', label: 'Advanced', hint: 'Terminal, panels, performance, git, shortcuts' },
       { id: 'updates', label: 'Updates', hint: 'Check for app updates' },
     ],
@@ -208,6 +211,8 @@ export function SettingsPanel() {
         return <DiscordTab />
       case 'batches':
         return <BatchesTab />
+      case 'runtime':
+        return <SystemTab />
       case 'updates':
         return <UpdatesTab />
       case 'advanced':
diff --git a/src/components/settings/tabs/system-tab.tsx b/src/components/settings/tabs/system-tab.tsx
new file mode 100644
index 00000000..1a313541
--- /dev/null
+++ b/src/components/settings/tabs/system-tab.tsx
@@ -0,0 +1,183 @@
+import { useEffect, useState } from 'react'
+import { SettingSection, SettingRow } from '@/components/shared/setting-components'
+import { getAppSettings, updateAppSettings, type AppSettings } from '@/lib/ipc/settings'
+
+/**
+ * Global backend settings (`~/.kaitencode/settings.json` via get/update_app_settings).
+ * These were previously only editable by hand-editing the JSON. See the settings
+ * audit — this tab closes the "no UI" gap for AppSettings.
+ */
+export function SystemTab() {
+  const [s, setS] = useState<AppSettings | null>(null)
+  const [error, setError] = useState<string | null>(null)
+
+  useEffect(() => {
+    getAppSettings()
+      .then(setS)
+      .catch((e: unknown) => { setError(e instanceof Error ? e.message : String(e)) })
+  }, [])
+
+  const commit = (patch: Partial<AppSettings>) => {
+    setS((prev) => (prev ? { ...prev, ...patch } : prev))
+    void updateAppSettings(patch).catch((e: unknown) => {
+      setError(e instanceof Error ? e.message : String(e))
+    })
+  }
+
+  if (!s) {
+    return <div className="text-sm text-text-secondary">{error ?? 'Loading…'}</div>
+  }
+
+  return (
+    <div className="space-y-6">
+      {error && <div className="rounded-md bg-error/10 px-3 py-2 text-xs text-error">{error}</div>}
+
+      <SettingSection
+        title="Global defaults"
+        description="Fallbacks when a workspace, column, or task doesn't specify its own. Per-workspace overrides (Workspace tab) win over these."
+      >
+        <SettingRow label="Default agent CLI" description="Which AI CLI new agents use by default.">
+          <Select
+            value={s.default_agent_cli}
+            onChange={(v) => { commit({ default_agent_cli: v }) }}
+            options={[{ value: 'claude', label: 'Claude' }, { value: 'codex', label: 'Codex' }]}
+          />
+        </SettingRow>
+        <SettingRow label="Default model" description="Empty = use the CLI's own default.">
+          <Text value={s.default_model} placeholder="(CLI default)" onCommit={(v) => { commit({ default_model: v }) }} mono />
+        </SettingRow>
+        <SettingRow label="Session strategy" description="Reuse a task's existing agent session, or start fresh each run.">
+          <Select
+            value={s.default_session_strategy}
+            onChange={(v) => { commit({ default_session_strategy: v }) }}
+            options={[{ value: 'fresh', label: 'Fresh' }, { value: 'reuse', label: 'Reuse' }]}
+          />
+        </SettingRow>
+        <SettingRow label="Advance mode" description="Whether tasks auto-advance through columns or wait for you.">
+          <Select
+            value={s.default_advance_mode}
+            onChange={(v) => { commit({ default_advance_mode: v }) }}
+            options={[{ value: 'auto', label: 'Auto' }, { value: 'manual', label: 'Manual' }]}
+          />
+        </SettingRow>
+      </SettingSection>
+
+      <SettingSection
+        title="Sessions & cleanup"
+        description="Lifecycle of agent tmux sessions and archived tasks."
+        border
+      >
+        <SettingRow label="Max agent sessions" description="Global ceiling on live agent tmux sessions.">
+          <Num value={s.max_agent_sessions} min={1} onCommit={(v) => { commit({ max_agent_sessions: v }) }} />
+        </SettingRow>
+        <SettingRow label="GC interval (minutes)" description="How often the garbage collector sweeps stale sessions.">
+          <Num value={s.gc_interval_minutes} min={1} onCommit={(v) => { commit({ gc_interval_minutes: v }) }} />
+        </SettingRow>
+        <SettingRow label="Idle sleep (minutes)" description="Detach a session after this long idle.">
+          <Num value={s.idle_sleep_minutes} min={1} onCommit={(v) => { commit({ idle_sleep_minutes: v }) }} />
+        </SettingRow>
+        <SettingRow label="Idle kill (hours)" description="Kill a session after this long idle.">
+          <Num value={s.idle_kill_hours} min={1} onCommit={(v) => { commit({ idle_kill_hours: v }) }} />
+        </SettingRow>
+        <SettingRow label="Archive purge (days)" description="Permanently delete archived tasks after this many days.">
+          <Num value={s.archive_purge_days} min={1} onCommit={(v) => { commit({ archive_purge_days: v }) }} />
+        </SettingRow>
+      </SettingSection>
+
+      <SettingSection title="Limits" description="Guard-rails and version checks." border>
+        <SettingRow
+          label="MCP recursion depth"
+          description="Max depth of an agent-spawned task chain (human → agent → agent…). Raise if you hit 'recursion depth exceeded'."
+        >
+          <Num value={s.mcp_max_recursion_depth} min={0} onCommit={(v) => { commit({ mcp_max_recursion_depth: v }) }} />
+        </SettingRow>
+        <SettingRow label="Claude min version" description="Warn at startup if installed Claude is older. Empty = accept any.">
+          <Text value={s.claude_min_version ?? ''} placeholder="(any)" onCommit={(v) => { commit({ claude_min_version: v }) }} mono />
+        </SettingRow>
+        <SettingRow label="Codex min version" description="Warn at startup if installed Codex is older. Empty = accept any.">
+          <Text value={s.codex_min_version ?? ''} placeholder="(any)" onCommit={(v) => { commit({ codex_min_version: v }) }} mono />
+        </SettingRow>
+      </SettingSection>
+    </div>
+  )
+}
+
+// ─── Local field controls ─────────────────────────────────────────────────
+
+function Select({
+  value,
+  onChange,
+  options,
+}: {
+  value: string
+  onChange: (v: string) => void
+  options: { value: string; label: string }[]
+}) {
+  return (
+    <select
+      value={value}
+      onChange={(e) => { onChange(e.target.value) }}
+      className="rounded-md border border-border-default bg-bg px-2.5 py-1.5 text-sm text-text-primary focus:border-accent focus:outline-none"
+    >
+      {options.map((o) => (
+        <option key={o.value} value={o.value}>{o.label}</option>
+      ))}
+    </select>
+  )
+}
+
+/** Commits on blur / Enter so we don't write settings.json on every keystroke. */
+function Text({
+  value,
+  placeholder,
+  onCommit,
+  mono = false,
+}: {
+  value: string
+  placeholder?: string
+  onCommit: (v: string) => void
+  mono?: boolean
+}) {
+  const [local, setLocal] = useState(value)
+  useEffect(() => { setLocal(value) }, [value])
+  return (
+    <input
+      type="text"
+      value={local}
+      placeholder={placeholder}
+      onChange={(e) => { setLocal(e.target.value) }}
+      onBlur={() => { if (local !== value) onCommit(local.trim()) }}
+      onKeyDown={(e) => { if (e.key === 'Enter') (e.target as HTMLInputElement).blur() }}
+      className={`w-40 rounded-md border border-border-default bg-bg px-2.5 py-1.5 text-sm text-text-primary placeholder:text-text-secondary/50 focus:border-accent focus:outline-none ${mono ? 'font-mono' : ''}`}
+    />
+  )
+}
+
+function Num({
+  value,
+  min,
+  onCommit,
+}: {
+  value: number
+  min: number
+  onCommit: (v: number) => void
+}) {
+  const [local, setLocal] = useState(String(value))
+  useEffect(() => { setLocal(String(value)) }, [value])
+  return (
+    <input
+      type="number"
+      min={min}
+      step={1}
+      value={local}
+      onChange={(e) => { setLocal(e.target.value) }}
+      onBlur={() => {
+        const n = Number.parseInt(local, 10)
+        if (Number.isFinite(n) && n >= min && n !== value) onCommit(n)
+        else setLocal(String(value))
+      }}
+      onKeyDown={(e) => { if (e.key === 'Enter') (e.target as HTMLInputElement).blur() }}
+      className="w-28 rounded-md border border-border-default bg-bg px-2.5 py-1.5 text-sm text-text-primary focus:border-accent focus:outline-none"
+    />
+  )
+}
diff --git a/src/hooks/use-settings-sync.ts b/src/hooks/use-settings-sync.ts
index 5db5b572..e0b4d528 100644
--- a/src/hooks/use-settings-sync.ts
+++ b/src/hooks/use-settings-sync.ts
@@ -54,25 +54,34 @@ export function useSettingsSync() {
     void loadSettings()
   }, [activeWorkspaceId, loadWorkspaceSettings])
 
-  // Save workspace settings to backend (debounced)
+  // Save workspace settings to backend (debounced).
   const saveSettings = useCallback(async (workspaceId: string, settings: WorkspaceSettings) => {
-    // Filter to only workspace-specific settings
+    // Only the nested {agent,git,voice,model} slices are workspace-synced.
     const workspaceSpecificSettings: WorkspaceSettings = {}
-
     if (settings.agent) workspaceSpecificSettings.agent = { ...settings.agent, envVars: {} }
     if (settings.git) workspaceSpecificSettings.git = settings.git
     if (settings.voice) workspaceSpecificSettings.voice = settings.voice
     if (settings.model) workspaceSpecificSettings.model = settings.model
 
-    // Skip if nothing to save
     if (Object.keys(workspaceSpecificSettings).length === 0) return
 
-    const configJson = JSON.stringify(workspaceSpecificSettings)
-
-    // Skip if unchanged
-    if (configJson === lastSavedRef.current) return
-
     try {
+      // MERGE into the current config rather than replacing it. The Workspace
+      // tab writes flat keys (defaultModel, maxConcurrentAgents, autoAdvance, …)
+      // to the SAME config JSON; serializing only our nested slices used to
+      // overwrite the whole blob and wipe those flat keys (and vice-versa).
+      // Re-read right before write to minimise the clobber window.
+      const current = await getWorkspace(workspaceId)
+      const existing: Record<string, unknown> =
+        current.config && current.config !== '{}'
+          ? (JSON.parse(current.config) as Record<string, unknown>)
+          : {}
+      const merged = { ...existing, ...workspaceSpecificSettings }
+      const configJson = JSON.stringify(merged)
+
+      // Skip if our merge wouldn't change anything.
+      if (configJson === lastSavedRef.current) return
+
       await updateWorkspaceConfig(workspaceId, configJson)
       lastSavedRef.current = configJson
     } catch (error) {
diff --git a/src/lib/ipc/settings.ts b/src/lib/ipc/settings.ts
index 47b0964f..6124dd6e 100644
--- a/src/lib/ipc/settings.ts
+++ b/src/lib/ipc/settings.ts
@@ -19,6 +19,11 @@ export interface AppSettings {
   default_runtime_mode: string
   /** Opt-in gate for interactive runtime mode (Phase 3). */
   interactive_mode_enabled: boolean
+  /** Startup CLI-version warning floors. null/"" = accept any version. */
+  claude_min_version: string | null
+  codex_min_version: string | null
+  /** Max depth of an agent-spawned task chain (MCP recursion guard). */
+  mcp_max_recursion_depth: number
 }
 
 export async function getAppSettings(): Promise<AppSettings> {
diff --git a/src/types/settings.ts b/src/types/settings.ts
index 7d607252..8dbaf8b7 100644
--- a/src/types/settings.ts
+++ b/src/types/settings.ts
@@ -211,7 +211,9 @@ export const DEFAULT_SETTINGS: Settings = {
     pushToTalk: true,
   },
   git: {
-    branchPrefix: 'feat/',
+    // Match the backend DEFAULT_BRANCH_PREFIX ('kaitencode/') and
+    // workspaceDefaults.branchPrefix — these were three different defaults.
+    branchPrefix: 'kaitencode/',
     autoPr: false,
     prTemplate: '',
     mergeStrategy: 'squash',