feat: increase batch size limits to 15 and add testing_batch_size setting

Batch size configuration:
- Increase coding agent batch size limit from 1-3 to 1-15
- Increase testing agent batch size limit from 1-5 to 1-15
- Add separate `testing_batch_size` setting (previously only CLI-configurable)
- Pass testing_batch_size through full stack: schema → settings router →
  agent router → process manager → CLI flag

UI changes:
- Replace 3-button batch size selector with range slider (1-15)
- Add new Slider component (ui/src/components/ui/slider.tsx)
- Add "Features per Testing Agent" slider in settings panel
- Add custom slider CSS styling for webkit and mozilla

Updated across: CLAUDE.md, autonomous_agent_demo.py, parallel_orchestrator.py,
server/{schemas,routers,services}, and UI types/hooks/components.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/SettingsModal.tsx

@@ -10,6 +10,7 @@ import {
   DialogTitle,
 } from '@/components/ui/dialog'
 import { Switch } from '@/components/ui/switch'
+import { Slider } from '@/components/ui/slider'
 import { Label } from '@/components/ui/label'
 import { Alert, AlertDescription } from '@/components/ui/alert'
 import { Button } from '@/components/ui/button'
@@ -63,6 +64,12 @@ export function SettingsModal({ isOpen, onClose }: SettingsModalProps) {
     }
   }
 
+  const handleTestingBatchSizeChange = (size: number) => {
+    if (!updateSettings.isPending) {
+      updateSettings.mutate({ testing_batch_size: size })
+    }
+  }
+
   const handleProviderChange = (providerId: string) => {
     if (!updateSettings.isPending) {
       updateSettings.mutate({ api_provider: providerId })
@@ -432,28 +439,34 @@ export function SettingsModal({ isOpen, onClose }: SettingsModalProps) {
               </div>
             </div>
 
-            {/* Features per Agent */}
+            {/* Features per Coding Agent */}
             <div className="space-y-2">
-              <Label className="font-medium">Features per Agent</Label>
+              <Label className="font-medium">Features per Coding Agent</Label>
               <p className="text-sm text-muted-foreground">
-                Number of features assigned to each coding agent
+                Number of features assigned to each coding agent session
               </p>
-              <div className="flex rounded-lg border overflow-hidden">
-                {[1, 2, 3].map((size) => (
-                  <button
-                    key={size}
-                    onClick={() => handleBatchSizeChange(size)}
-                    disabled={isSaving}
-                    className={`flex-1 py-2 px-3 text-sm font-medium transition-colors ${
-                      (settings.batch_size ?? 1) === size
-                        ? 'bg-primary text-primary-foreground'
-                        : 'bg-background text-foreground hover:bg-muted'
-                    } ${isSaving ? 'opacity-50 cursor-not-allowed' : ''}`}
-                  >
-                    {size}
-                  </button>
-                ))}
-              </div>
+              <Slider
+                min={1}
+                max={15}
+                value={settings.batch_size ?? 3}
+                onChange={handleBatchSizeChange}
+                disabled={isSaving}
+              />
+            </div>
+
+            {/* Features per Testing Agent */}
+            <div className="space-y-2">
+              <Label className="font-medium">Features per Testing Agent</Label>
+              <p className="text-sm text-muted-foreground">
+                Number of features assigned to each testing agent session
+              </p>
+              <Slider
+                min={1}
+                max={15}
+                value={settings.testing_batch_size ?? 3}
+                onChange={handleTestingBatchSizeChange}
+                disabled={isSaving}
+              />
             </div>
 
             {/* Update Error */}

ui/src/components/ui/slider.tsx

@@ -0,0 +1,44 @@
+import * as React from "react"
+import { cn } from "@/lib/utils"
+
+interface SliderProps extends Omit<React.InputHTMLAttributes<HTMLInputElement>, 'onChange'> {
+  min: number
+  max: number
+  value: number
+  onChange: (value: number) => void
+  label?: string
+}
+
+function Slider({
+  className,
+  min,
+  max,
+  value,
+  onChange,
+  disabled,
+  ...props
+}: SliderProps) {
+  return (
+    <div className={cn("flex items-center gap-3", className)}>
+      <input
+        type="range"
+        min={min}
+        max={max}
+        value={value}
+        onChange={(e) => onChange(Number(e.target.value))}
+        disabled={disabled}
+        className={cn(
+          "slider-input h-2 w-full cursor-pointer appearance-none rounded-full bg-input transition-colors",
+          "focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring",
+          disabled && "cursor-not-allowed opacity-50"
+        )}
+        {...props}
+      />
+      <span className="min-w-[2ch] text-center text-sm font-semibold tabular-nums">
+        {value}
+      </span>
+    </div>
+  )
+}
+
+export { Slider }

ui/src/hooks/useProjects.ts

@@ -302,6 +302,7 @@ const DEFAULT_SETTINGS: Settings = {
   testing_agent_ratio: 1,
   playwright_headless: true,
   batch_size: 3,
+  testing_batch_size: 3,
   api_provider: 'claude',
   api_base_url: null,
   api_has_auth_token: false,

ui/src/lib/types.ts

@@ -579,7 +579,8 @@ export interface Settings {
   ollama_mode: boolean
   testing_agent_ratio: number  // Regression testing agents (0-3)
   playwright_headless: boolean
-  batch_size: number  // Features per coding agent batch (1-3)
+  batch_size: number  // Features per coding agent batch (1-15)
+  testing_batch_size: number  // Features per testing agent batch (1-15)
   api_provider: string
   api_base_url: string | null
   api_has_auth_token: boolean
@@ -592,6 +593,7 @@ export interface SettingsUpdate {
   testing_agent_ratio?: number
   playwright_headless?: boolean
   batch_size?: number
+  testing_batch_size?: number
   api_provider?: string
   api_base_url?: string
   api_auth_token?: string

ui/src/styles/globals.css

@@ -1472,3 +1472,53 @@
 ::-webkit-scrollbar-thumb:hover {
   background: var(--muted-foreground);
 }
+
+/* ============================================================================
+   Slider (range input) styling
+   ============================================================================ */
+
+.slider-input::-webkit-slider-thumb {
+  -webkit-appearance: none;
+  appearance: none;
+  width: 16px;
+  height: 16px;
+  border-radius: 50%;
+  background: var(--primary);
+  border: 2px solid var(--primary-foreground);
+  box-shadow: var(--shadow-sm);
+  cursor: pointer;
+  transition: transform 150ms, box-shadow 150ms;
+}
+
+.slider-input::-webkit-slider-thumb:hover {
+  transform: scale(1.15);
+  box-shadow: var(--shadow);
+}
+
+.slider-input::-moz-range-thumb {
+  width: 16px;
+  height: 16px;
+  border-radius: 50%;
+  background: var(--primary);
+  border: 2px solid var(--primary-foreground);
+  box-shadow: var(--shadow-sm);
+  cursor: pointer;
+  transition: transform 150ms, box-shadow 150ms;
+}
+
+.slider-input::-moz-range-thumb:hover {
+  transform: scale(1.15);
+  box-shadow: var(--shadow);
+}
+
+.slider-input::-webkit-slider-runnable-track {
+  height: 8px;
+  border-radius: 9999px;
+  background: var(--input);
+}
+
+.slider-input::-moz-range-track {
+  height: 8px;
+  border-radius: 9999px;
+  background: var(--input);
+}