diff --git a/src/__tests__/main/process-manager/utils/shellEscape.test.ts b/src/__tests__/main/process-manager/utils/shellEscape.test.ts
new file mode 100644
index 00000000..7ae1c54e
--- /dev/null
+++ b/src/__tests__/main/process-manager/utils/shellEscape.test.ts
@@ -0,0 +1,140 @@
+import { describe, it, expect } from 'vitest';
+import {
+	escapeCmdArg,
+	escapePowerShellArg,
+	escapeCmdArgs,
+	escapePowerShellArgs,
+	isPowerShellShell,
+	escapeArgsForShell,
+} from '../../../../main/process-manager/utils/shellEscape';
+
+describe('shellEscape', () => {
+	describe('escapeCmdArg', () => {
+		it('should not escape simple arguments', () => {
+			expect(escapeCmdArg('hello')).toBe('hello');
+			expect(escapeCmdArg('world123')).toBe('world123');
+			expect(escapeCmdArg('file.txt')).toBe('file.txt');
+		});
+
+		it('should escape arguments with spaces', () => {
+			expect(escapeCmdArg('hello world')).toBe('"hello world"');
+			expect(escapeCmdArg('path with spaces')).toBe('"path with spaces"');
+		});
+
+		it('should escape arguments with special characters', () => {
+			expect(escapeCmdArg('foo&bar')).toBe('"foo&bar"');
+			expect(escapeCmdArg('foo|bar')).toBe('"foo|bar"');
+			expect(escapeCmdArg('foo<bar')).toBe('"foo<bar"');
+			expect(escapeCmdArg('foo>bar')).toBe('"foo>bar"');
+		});
+
+		it('should escape double quotes by doubling them', () => {
+			expect(escapeCmdArg('say "hello"')).toBe('"say ""hello"""');
+		});
+
+		it('should escape carets by doubling them', () => {
+			expect(escapeCmdArg('foo^bar')).toBe('"foo^^bar"');
+		});
+
+		it('should escape arguments with newlines', () => {
+			expect(escapeCmdArg('line1\nline2')).toBe('"line1\nline2"');
+			expect(escapeCmdArg('line1\r\nline2')).toBe('"line1\r\nline2"');
+		});
+
+		it('should escape long arguments', () => {
+			const longArg = 'a'.repeat(150);
+			expect(escapeCmdArg(longArg)).toBe(`"${longArg}"`);
+		});
+	});
+
+	describe('escapePowerShellArg', () => {
+		it('should not escape simple arguments', () => {
+			expect(escapePowerShellArg('hello')).toBe('hello');
+			expect(escapePowerShellArg('world123')).toBe('world123');
+			expect(escapePowerShellArg('file.txt')).toBe('file.txt');
+		});
+
+		it('should escape arguments with spaces', () => {
+			expect(escapePowerShellArg('hello world')).toBe("'hello world'");
+		});
+
+		it('should escape arguments with special characters', () => {
+			expect(escapePowerShellArg('foo&bar')).toBe("'foo&bar'");
+			expect(escapePowerShellArg('foo$bar')).toBe("'foo$bar'");
+			expect(escapePowerShellArg('foo`bar')).toBe("'foo`bar'");
+		});
+
+		it('should escape single quotes by doubling them', () => {
+			expect(escapePowerShellArg("it's")).toBe("'it''s'");
+			expect(escapePowerShellArg("say 'hello'")).toBe("'say ''hello'''");
+		});
+
+		it('should escape arguments with PowerShell-specific characters', () => {
+			expect(escapePowerShellArg('foo@bar')).toBe("'foo@bar'");
+			expect(escapePowerShellArg('foo{bar}')).toBe("'foo{bar}'");
+			expect(escapePowerShellArg('foo[bar]')).toBe("'foo[bar]'");
+		});
+
+		it('should escape long arguments', () => {
+			const longArg = 'a'.repeat(150);
+			expect(escapePowerShellArg(longArg)).toBe(`'${longArg}'`);
+		});
+	});
+
+	describe('escapeCmdArgs', () => {
+		it('should escape multiple arguments', () => {
+			const result = escapeCmdArgs(['simple', 'with space', 'say "hi"']);
+			expect(result).toEqual(['simple', '"with space"', '"say ""hi"""']);
+		});
+	});
+
+	describe('escapePowerShellArgs', () => {
+		it('should escape multiple arguments', () => {
+			const result = escapePowerShellArgs(['simple', 'with space', "it's"]);
+			expect(result).toEqual(['simple', "'with space'", "'it''s'"]);
+		});
+	});
+
+	describe('isPowerShellShell', () => {
+		it('should detect Windows PowerShell', () => {
+			expect(isPowerShellShell('powershell.exe')).toBe(true);
+			expect(isPowerShellShell('C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe')).toBe(
+				true
+			);
+			expect(isPowerShellShell('PowerShell.exe')).toBe(true);
+		});
+
+		it('should detect PowerShell Core (pwsh)', () => {
+			expect(isPowerShellShell('pwsh')).toBe(true);
+			expect(isPowerShellShell('pwsh.exe')).toBe(true);
+			expect(isPowerShellShell('C:\\Program Files\\PowerShell\\7\\pwsh.exe')).toBe(true);
+		});
+
+		it('should not detect cmd.exe as PowerShell', () => {
+			expect(isPowerShellShell('cmd.exe')).toBe(false);
+			expect(isPowerShellShell('C:\\Windows\\System32\\cmd.exe')).toBe(false);
+		});
+
+		it('should handle undefined and empty strings', () => {
+			expect(isPowerShellShell(undefined)).toBe(false);
+			expect(isPowerShellShell('')).toBe(false);
+		});
+	});
+
+	describe('escapeArgsForShell', () => {
+		it('should use PowerShell escaping for PowerShell shells', () => {
+			const result = escapeArgsForShell(['with space', "it's"], 'powershell.exe');
+			expect(result).toEqual(["'with space'", "'it''s'"]);
+		});
+
+		it('should use cmd.exe escaping for cmd.exe shells', () => {
+			const result = escapeArgsForShell(['with space', 'say "hi"'], 'cmd.exe');
+			expect(result).toEqual(['"with space"', '"say ""hi"""']);
+		});
+
+		it('should default to cmd.exe escaping when no shell specified', () => {
+			const result = escapeArgsForShell(['with space', 'say "hi"']);
+			expect(result).toEqual(['"with space"', '"say ""hi"""']);
+		});
+	});
+});
diff --git a/src/cli/services/storage.ts b/src/cli/services/storage.ts
index 8e43bc54..739133b6 100644
--- a/src/cli/services/storage.ts
+++ b/src/cli/services/storage.ts
@@ -22,16 +22,16 @@ function getConfigDir(): string {
 	const home = os.homedir();
 
 	if (platform === 'darwin') {
-		return path.posix.join(home, 'Library', 'Application Support', 'Maestro');
+		return path.join(home, 'Library', 'Application Support', 'Maestro');
 	} else if (platform === 'win32') {
-		return path.posix.join(
-			process.env.APPDATA || path.posix.join(home, 'AppData', 'Roaming'),
+		return path.join(
+			process.env.APPDATA || path.join(home, 'AppData', 'Roaming'),
 			'Maestro'
 		);
 	} else {
 		// Linux and others
-		return path.posix.join(
-			process.env.XDG_CONFIG_HOME || path.posix.join(home, '.config'),
+		return path.join(
+			process.env.XDG_CONFIG_HOME || path.join(home, '.config'),
 			'Maestro'
 		);
 	}
@@ -42,7 +42,7 @@ function getConfigDir(): string {
  * Returns undefined if file doesn't exist
  */
 function readStoreFile<T>(filename: string): T | undefined {
-	const filePath = path.posix.join(getConfigDir(), filename);
+	const filePath = path.join(getConfigDir(), filename);
 
 	try {
 		const content = fs.readFileSync(filePath, 'utf-8');
@@ -101,7 +101,7 @@ export function readGroups(): Group[] {
  * Check if migration to per-session history format has been completed
  */
 function hasMigrated(): boolean {
-	const markerPath = path.posix.join(getConfigDir(), 'history-migrated.json');
+	const markerPath = path.join(getConfigDir(), 'history-migrated.json');
 	return fs.existsSync(markerPath);
 }
 
@@ -109,7 +109,7 @@ function hasMigrated(): boolean {
  * Get the history directory path
  */
 function getHistoryDir(): string {
-	return path.posix.join(getConfigDir(), 'history');
+	return path.join(getConfigDir(), 'history');
 }
 
 /**
@@ -117,7 +117,7 @@ function getHistoryDir(): string {
  */
 function getSessionHistoryPath(sessionId: string): string {
 	const safeId = sanitizeSessionId(sessionId);
-	return path.posix.join(getHistoryDir(), `${safeId}.json`);
+	return path.join(getHistoryDir(), `${safeId}.json`);
 }
 
 /**
diff --git a/src/main/process-manager/spawners/ChildProcessSpawner.ts b/src/main/process-manager/spawners/ChildProcessSpawner.ts
index f5c857d5..c9550c8c 100644
--- a/src/main/process-manager/spawners/ChildProcessSpawner.ts
+++ b/src/main/process-manager/spawners/ChildProcessSpawner.ts
@@ -14,6 +14,7 @@ import { ExitHandler } from '../handlers/ExitHandler';
 import { buildChildProcessEnv } from '../utils/envBuilder';
 import { saveImageToTempFile } from '../utils/imageUtils';
 import { buildStreamJsonMessage } from '../utils/streamJsonBuilder';
+import { escapeArgsForShell, isPowerShellShell } from '../utils/shellEscape';
 
 /**
  * Handles spawning of child processes (non-PTY).
@@ -178,46 +179,18 @@ export class ChildProcessSpawner {
 					{ command: spawnCommand }
 				);
 
-				// Check if we're using PowerShell (for SSH commands to avoid cmd.exe 8191 char limit)
-				const isPowerShell =
-					typeof config.shell === 'string' && config.shell.toLowerCase().includes('powershell');
+				// Use the shell escape utility for proper argument escaping
+				const shellPath = typeof config.shell === 'string' ? config.shell : undefined;
+				spawnArgs = escapeArgsForShell(finalArgs, shellPath);
 
-				if (isPowerShell) {
-					// Escape arguments for PowerShell (supports longer command lines than cmd.exe)
-					spawnArgs = finalArgs.map((arg) => {
-						const needsQuoting = /[ &|<>^%!()"\n\r#?*`$]/.test(arg) || arg.length > 100;
-						if (needsQuoting) {
-							// PowerShell escaping: wrap in single quotes, escape single quotes by doubling
-							const escaped = arg.replace(/'/g, "''");
-							return `'${escaped}'`;
-						}
-						return arg;
-					});
-					logger.info('[ProcessManager] Escaped args for PowerShell', 'ProcessManager', {
-						originalArgsCount: finalArgs.length,
-						escapedArgsCount: spawnArgs.length,
-						escapedPromptArgLength: spawnArgs[spawnArgs.length - 1]?.length,
-						escapedPromptArgPreview: spawnArgs[spawnArgs.length - 1]?.substring(0, 200),
-						argsModified: finalArgs.some((arg, i) => arg !== spawnArgs[i]),
-					});
-				} else {
-					// Escape arguments for cmd.exe when using shell
-					spawnArgs = finalArgs.map((arg) => {
-						const needsQuoting = /[ &|<>^%!()"\n\r#?*]/.test(arg) || arg.length > 100;
-						if (needsQuoting) {
-							const escaped = arg.replace(/"/g, '""').replace(/\^/g, '^^');
-							return `"${escaped}"`;
-						}
-						return arg;
-					});
-					logger.info('[ProcessManager] Escaped args for Windows shell', 'ProcessManager', {
-						originalArgsCount: finalArgs.length,
-						escapedArgsCount: spawnArgs.length,
-						escapedPromptArgLength: spawnArgs[spawnArgs.length - 1]?.length,
-						escapedPromptArgPreview: spawnArgs[spawnArgs.length - 1]?.substring(0, 200),
-						argsModified: finalArgs.some((arg, i) => arg !== spawnArgs[i]),
-					});
-				}
+				const shellType = isPowerShellShell(shellPath) ? 'PowerShell' : 'cmd.exe';
+				logger.info(`[ProcessManager] Escaped args for ${shellType}`, 'ProcessManager', {
+					originalArgsCount: finalArgs.length,
+					escapedArgsCount: spawnArgs.length,
+					escapedPromptArgLength: spawnArgs[spawnArgs.length - 1]?.length,
+					escapedPromptArgPreview: spawnArgs[spawnArgs.length - 1]?.substring(0, 200),
+					argsModified: finalArgs.some((arg, i) => arg !== spawnArgs[i]),
+				});
 			}
 
 			// Determine shell option to pass to child_process.spawn.
diff --git a/src/main/process-manager/utils/shellEscape.ts b/src/main/process-manager/utils/shellEscape.ts
new file mode 100644
index 00000000..ba3f6214
--- /dev/null
+++ b/src/main/process-manager/utils/shellEscape.ts
@@ -0,0 +1,121 @@
+/**
+ * Shell argument escaping utilities for Windows cmd.exe and PowerShell.
+ *
+ * These functions handle escaping command line arguments to prevent injection
+ * and ensure proper argument passing when spawning processes via shell.
+ *
+ * References:
+ * - cmd.exe escaping: https://docs.microsoft.com/en-us/windows-server/administration/windows-commands/cmd
+ * - PowerShell escaping: https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_quoting_rules
+ *
+ * For production use, consider using the 'shescape' npm package which provides
+ * more comprehensive cross-platform shell escaping with extensive testing.
+ */
+
+/**
+ * Characters that require quoting in cmd.exe.
+ * Based on cmd.exe special characters: https://ss64.com/nt/syntax-esc.html
+ */
+const CMD_SPECIAL_CHARS = /[ &|<>^%!()"\n\r#?*]/;
+
+/**
+ * Characters that require quoting in PowerShell.
+ * Based on PowerShell special characters: https://ss64.com/ps/syntax-esc.html
+ */
+const POWERSHELL_SPECIAL_CHARS = /[ &|<>^%!()"\n\r#?*`$@{}[\]';,]/;
+
+/**
+ * Escape a single argument for use in cmd.exe.
+ *
+ * Strategy:
+ * 1. If the argument contains special characters or is long, wrap in double quotes
+ * 2. Escape existing double quotes by doubling them
+ * 3. Escape carets (^) as they're the escape character in cmd.exe
+ *
+ * @param arg - The argument to escape
+ * @returns The escaped argument safe for cmd.exe
+ */
+export function escapeCmdArg(arg: string): string {
+	// If no special characters and not too long, return as-is
+	if (!CMD_SPECIAL_CHARS.test(arg) && arg.length <= 100) {
+		return arg;
+	}
+
+	// Escape double quotes by doubling them, and carets by doubling
+	const escaped = arg.replace(/"/g, '""').replace(/\^/g, '^^');
+
+	// Wrap in double quotes
+	return `"${escaped}"`;
+}
+
+/**
+ * Escape a single argument for use in PowerShell.
+ *
+ * Strategy:
+ * 1. If the argument contains special characters or is long, wrap in single quotes
+ * 2. Escape existing single quotes by doubling them (PowerShell's single-quote escape)
+ *
+ * Single quotes in PowerShell treat the content as a literal string, which is
+ * safer than double quotes (which allow variable expansion).
+ *
+ * @param arg - The argument to escape
+ * @returns The escaped argument safe for PowerShell
+ */
+export function escapePowerShellArg(arg: string): string {
+	// If no special characters and not too long, return as-is
+	if (!POWERSHELL_SPECIAL_CHARS.test(arg) && arg.length <= 100) {
+		return arg;
+	}
+
+	// Escape single quotes by doubling them (PowerShell's escape mechanism)
+	const escaped = arg.replace(/'/g, "''");
+
+	// Wrap in single quotes (prevents variable expansion)
+	return `'${escaped}'`;
+}
+
+/**
+ * Escape an array of arguments for use in cmd.exe.
+ *
+ * @param args - The arguments to escape
+ * @returns The escaped arguments safe for cmd.exe
+ */
+export function escapeCmdArgs(args: string[]): string[] {
+	return args.map(escapeCmdArg);
+}
+
+/**
+ * Escape an array of arguments for use in PowerShell.
+ *
+ * @param args - The arguments to escape
+ * @returns The escaped arguments safe for PowerShell
+ */
+export function escapePowerShellArgs(args: string[]): string[] {
+	return args.map(escapePowerShellArg);
+}
+
+/**
+ * Detect if a shell path refers to PowerShell.
+ *
+ * @param shellPath - The shell path to check
+ * @returns True if the shell is PowerShell (either Windows PowerShell or PowerShell Core)
+ */
+export function isPowerShellShell(shellPath: string | undefined): boolean {
+	if (!shellPath) return false;
+	const lower = shellPath.toLowerCase();
+	return lower.includes('powershell') || lower.includes('pwsh');
+}
+
+/**
+ * Escape arguments based on the target shell.
+ *
+ * @param args - The arguments to escape
+ * @param shell - The shell path or name (optional, defaults to cmd.exe behavior)
+ * @returns The escaped arguments
+ */
+export function escapeArgsForShell(args: string[], shell?: string): string[] {
+	if (isPowerShellShell(shell)) {
+		return escapePowerShellArgs(args);
+	}
+	return escapeCmdArgs(args);
+}
diff --git a/src/main/process-manager/utils/streamJsonBuilder.ts b/src/main/process-manager/utils/streamJsonBuilder.ts
index 60c6e80b..57454d74 100644
--- a/src/main/process-manager/utils/streamJsonBuilder.ts
+++ b/src/main/process-manager/utils/streamJsonBuilder.ts
@@ -17,20 +17,19 @@ interface TextContent {
 type MessageContent = ImageContent | TextContent;
 
 /**
- * Build a stream-json message for Claude Code with images and text
+ * Build a stream-json message for Claude Code with images and text.
+ *
+ * Claude Code expects this format:
+ * {"type":"user","message":{"role":"user","content":[...]}}
+ *
+ * Content array should have images first (Claude convention), then text.
  */
 export function buildStreamJsonMessage(prompt: string, images: string[]): string {
 	const content: MessageContent[] = [];
 
-	// Add text content first
-	content.push({
-		type: 'text',
-		text: prompt,
-	});
-
-	// Add image content for each image
-	for (const imageDataUrl of images) {
-		const parsed = parseDataUrl(imageDataUrl);
+	// Add images first (Claude convention: images before text)
+	for (const dataUrl of images) {
+		const parsed = parseDataUrl(dataUrl);
 		if (parsed) {
 			content.push({
 				type: 'image',
@@ -43,9 +42,18 @@ export function buildStreamJsonMessage(prompt: string, images: string[]): string
 		}
 	}
 
+	// Add text content
+	content.push({
+		type: 'text',
+		text: prompt,
+	});
+
 	const message = {
-		type: 'user_message',
-		content,
+		type: 'user',
+		message: {
+			role: 'user',
+			content,
+		},
 	};
 
 	return JSON.stringify(message);
diff --git a/src/renderer/components/NewInstanceModal.tsx b/src/renderer/components/NewInstanceModal.tsx
index 46d310e3..8173ccef 100644
--- a/src/renderer/components/NewInstanceModal.tsx
+++ b/src/renderer/components/NewInstanceModal.tsx
@@ -1136,7 +1136,10 @@ export function NewInstanceModal({
 							}
 							onSshRemoteConfigChange={(config) => {
 								setAgentSshRemoteConfigs((prev) => {
-									const newConfigs = { ...prev, _pending_: config };
+									const newConfigs: Record<string, AgentSshRemoteConfig> = {
+										...prev,
+										_pending_: config,
+									};
 									if (selectedAgent) {
 										newConfigs[selectedAgent] = config;
 									}
diff --git a/src/renderer/hooks/useInlineWizard.ts b/src/renderer/hooks/useInlineWizard.ts
index b189cba4..4de626c4 100644
--- a/src/renderer/hooks/useInlineWizard.ts
+++ b/src/renderer/hooks/useInlineWizard.ts
@@ -586,7 +586,7 @@ export function useInlineWizard(): UseInlineWizardReturn {
 
 				// Step 4: Initialize conversation session (only for 'new' or 'iterate' modes)
 				// Only allow wizard for agents that support structured output
-				const supportedWizardAgents: ToolType[] = ['claude', 'claude-code', 'codex'];
+				const supportedWizardAgents: ToolType[] = ['claude-code', 'codex'];
 				if (
 					(mode === 'new' || mode === 'iterate') &&
 					agentType &&
@@ -699,7 +699,7 @@ export function useInlineWizard(): UseInlineWizardReturn {
 	const sendMessage = useCallback(
 		async (content: string, callbacks?: ConversationCallbacks): Promise<void> => {
 			// Only allow wizard for agents that support structured output
-			const supportedWizardAgents: ToolType[] = ['claude', 'claude-code', 'codex'];
+			const supportedWizardAgents: ToolType[] = ['claude-code', 'codex'];
 
 			// Get the tab ID from the current state, ensure currentTabId is set for visibility
 			const tabId = currentTabId || 'default';