diff --git a/webview-ui/src/utils/__tests__/command-validation.spec.ts b/webview-ui/src/utils/__tests__/command-validation.spec.ts
index acea548e14..2f7b3ba4f7 100644
--- a/webview-ui/src/utils/__tests__/command-validation.spec.ts
+++ b/webview-ui/src/utils/__tests__/command-validation.spec.ts
@@ -41,6 +41,9 @@ describe("Command Validation", () => {
 			expect(parseCommand("npm test $(echo test)")).toEqual(["npm test", "echo test"])
 			expect(parseCommand("npm test `echo test`")).toEqual(["npm test", "echo test"])
 			expect(parseCommand("diff <(sort f1) <(sort f2)")).toEqual(["diff", "sort f1", "sort f2"])
+			// fish-style command substitution using parentheses
+			expect(parseCommand("echo (whoami)")).toEqual(["echo", "whoami"])
+			expect(parseCommand("echo (echo test)")).toEqual(["echo", "echo test"])
 		})
 
 		it("handles nested backticks with escaped inner backticks", () => {
@@ -1097,6 +1100,14 @@ describe("Unified Command Decision Functions", () => {
 			expect(getCommandDecision("echo `echo \\`whoami\\``", ["echo"], [])).toBe("ask_user")
 			// And should be auto-denied when inner command is on the denylist
 			expect(getCommandDecision("echo `echo \\`whoami\\``", ["echo"], ["whoami"])).toBe("auto_deny")
+
+			// Fish-style substitutions behave like subshells
+			expect(getCommandDecision("npm install (echo test)", allowedCommands, deniedCommands)).toBe("auto_approve")
+			expect(getCommandDecision("npm install (npm test)", allowedCommands, deniedCommands)).toBe("auto_deny")
+
+			// Ensure hidden subshell commands are validated even if outer command is allowed
+			expect(getCommandDecision("echo (whoami)", ["echo", "ls"], [])).toBe("ask_user")
+			expect(getCommandDecision("echo (whoami)", ["echo", "ls"], ["whoami"])).toBe("auto_deny")
 		})
 
 		it("properly validates subshell commands when no denylist is present", () => {
diff --git a/webview-ui/src/utils/command-validation.ts b/webview-ui/src/utils/command-validation.ts
index 9b4f93dad9..f309722991 100644
--- a/webview-ui/src/utils/command-validation.ts
+++ b/webview-ui/src/utils/command-validation.ts
@@ -273,6 +273,21 @@ function parseCommandLine(command: string): string[] {
 			return `__SUBSH_${subshells.length - 1}__`
 		})
 
+	// Handle fish-style command substitutions and POSIX subshell grouping: ( ... )
+	// At this point we've already replaced $(), <() and >() earlier, so any remaining (...) are either
+	// fish command substitutions or subshell groupings. We treat them as subshells to validate inner commands.
+	processedCommand = processedCommand.replace(/\(([^()]*)\)/g, (full, inner: string, offset: number, str: string) => {
+		// If this was actually a pattern preceded by $, < or > it would have been handled earlier.
+		// Guard anyway: if the preceding character indicates a different construct, keep original.
+		const prevChar = offset > 0 ? str[offset - 1] : ""
+		if (prevChar === "$" || prevChar === "<" || prevChar === ">") {
+			return full
+		}
+		const content = (inner || "").trim()
+		if (!content) return full
+		subshells.push(content)
+		return `__SUBSH_${subshells.length - 1}__`
+	})
 	// Then handle quoted strings
 	processedCommand = processedCommand.replace(/"[^"]*"/g, (match) => {
 		quotes.push(match)