diff --git a/README.md b/README.md
index eb9ba02..6718a7d 100644
--- a/README.md
+++ b/README.md
@@ -220,8 +220,8 @@ export default defineConfig({
 | `-e,` `--env-file` `<path|false>` | Env file path, or "false" to disable env file loading |
 | `--config` `<path>` | Config file path (default: auto-detect) |
 | `-p,` `--prefix` | Prefixed output mode (no TUI, for CI/scripts) |
-| `--only` `<a,b,...>` | Only run these processes (+ their dependencies) |
-| `--exclude` `<a,b,...>` | Exclude these processes |
+| `-o,` `--only` `<a,b,...>` | Only run these processes (+ their dependencies) |
+| `-x,` `--exclude` `<a,b,...>` | Exclude these processes |
 | `--kill-others` | Kill all processes when any exits (regardless of exit code) |
 | `--kill-others-on-fail` | Kill all processes when any exits with non-zero code |
 | `--max-restarts` `<n>` | Max auto-restarts for crashed processes |
diff --git a/src/cli-flags.ts b/src/cli-flags.ts
index 8c06f0b..cba3d13 100644
--- a/src/cli-flags.ts
+++ b/src/cli-flags.ts
@@ -138,6 +138,7 @@ export const FLAGS: FlagDef[] = [
 	{
 		type: 'value',
 		long: '--only',
+		short: '-o',
 		key: 'only',
 		description: 'Only run these processes (+ their dependencies)',
 		valueName: '<a,b,...>',
@@ -147,6 +148,7 @@ export const FLAGS: FlagDef[] = [
 	{
 		type: 'value',
 		long: '--exclude',
+		short: '-x',
 		key: 'exclude',
 		description: 'Exclude these processes',
 		valueName: '<a,b,...>',
diff --git a/src/cli.test.ts b/src/cli.test.ts
index 2ea1df3..35f33f6 100644
--- a/src/cli.test.ts
+++ b/src/cli.test.ts
@@ -175,12 +175,48 @@ describe('parseArgs', () => {
 		expect(result.exclude).toEqual(['migrate'])
 	})
 
+	test('-o is short for --only', () => {
+		const result = parseArgs(argv('-o', 'api,web'))
+		expect(result.only).toEqual(['api', 'web'])
+	})
+
+	test('-x is short for --exclude', () => {
+		const result = parseArgs(argv('-x', 'migrate'))
+		expect(result.exclude).toEqual(['migrate'])
+	})
+
+	test('repeated --only merges values', () => {
+		const result = parseArgs(argv('--only', 'api', '--only', 'web'))
+		expect(result.only).toEqual(['api', 'web'])
+	})
+
+	test('repeated -o merges comma-separated values', () => {
+		const result = parseArgs(argv('-o', 'api,db', '-o', 'web'))
+		expect(result.only).toEqual(['api', 'db', 'web'])
+	})
+
+	test('repeated --exclude merges values', () => {
+		const result = parseArgs(argv('--exclude', 'db', '-x', 'migrate'))
+		expect(result.exclude).toEqual(['db', 'migrate'])
+	})
+
+	test('mixed short and long flags merge', () => {
+		const result = parseArgs(argv('-o', 'api', '--only', 'web'))
+		expect(result.only).toEqual(['api', 'web'])
+	})
+
 	test('--only and --exclude can coexist', () => {
 		const result = parseArgs(argv('--only', 'api,web,db', '--exclude', 'db'))
 		expect(result.only).toEqual(['api', 'web', 'db'])
 		expect(result.exclude).toEqual(['db'])
 	})
 
+	test('-o and -x can coexist', () => {
+		const result = parseArgs(argv('-o', 'api,web', '-x', 'web'))
+		expect(result.only).toEqual(['api', 'web'])
+		expect(result.exclude).toEqual(['web'])
+	})
+
 	test('init sets init flag', () => {
 		expect(parseArgs(argv('init')).init).toBe(true)
 	})
diff --git a/src/cli.ts b/src/cli.ts
index 3063ac4..7b2f496 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -93,7 +93,8 @@ export function parseArgs(argv: string[]): ParsedArgs {
 				const value = flag.parse ? flag.parse(next, arg) : next
 				const current = (result as any)[flag.key]
 				if (Array.isArray(current)) {
-					current.push(value)
+					if (Array.isArray(value)) current.push(...value)
+					else current.push(value)
 				} else {
 					;(result as any)[flag.key] = value
 				}
diff --git a/src/ui/prefix.test.ts b/src/ui/prefix.test.ts
index fd679d9..5775965 100644
--- a/src/ui/prefix.test.ts
+++ b/src/ui/prefix.test.ts
@@ -292,6 +292,42 @@ describe('PrefixDisplay (integration)', () => {
 		expect(exitCode).toBe(1)
 	}, 10000)
 
+	test('-o filters to named process and its deps', async () => {
+		const config = writeConfig(
+			'only-filter.json',
+			JSON.stringify({
+				processes: {
+					db: { command: "echo 'db ready'" },
+					api: { command: "echo 'api ready'", dependsOn: ['db'] },
+					web: { command: "echo 'web ready'" }
+				}
+			})
+		)
+		const { stdout, exitCode } = await runPrefix(config, ['-o', 'api'])
+		expect(stdout).toContain('[api]')
+		expect(stdout).toContain('[db]')
+		expect(stdout).not.toContain('[web]')
+		expect(exitCode).toBe(0)
+	}, 10000)
+
+	test('repeated -o merges filters', async () => {
+		const config = writeConfig(
+			'only-repeated.json',
+			JSON.stringify({
+				processes: {
+					a: { command: "echo 'a'" },
+					b: { command: "echo 'b'" },
+					c: { command: "echo 'c'" }
+				}
+			})
+		)
+		const { stdout, exitCode } = await runPrefix(config, ['-o', 'a', '-o', 'b'])
+		expect(stdout).toContain('[a]')
+		expect(stdout).toContain('[b]')
+		expect(stdout).not.toContain('[c]')
+		expect(exitCode).toBe(0)
+	}, 10000)
+
 	test('cursor-up sequences are stripped to preserve prefix', async () => {
 		// Use bun -e to emit real escape bytes — avoids printf portability issues
 		const config = writeConfig(