fix(terminal): read host IDE shell from CLINE_TERMINAL_SHELL_PATH instead of COMSPEC/SHELL

Host integrations (the JetBrains plugin) forwarded the user's IDE terminal
shell by overriding COMSPEC on Windows. COMSPEC is an OS-level contract that
must keep pointing at cmd.exe: cross-spawn, Node's shell:true, and npm .cmd
shims all pass cmd-style /d /s /c arguments to whatever it references.
With IntelliJ's default terminal shell (PowerShell) forwarded as COMSPEC,
every .cmd-shimmed child process spawned by cline-core broke - e.g. the
Claude Code provider failed with:
  /d : The term '/d' is not recognized ...

Introduce a dedicated CLINE_TERMINAL_SHELL_PATH env var that hosts can set
safely. It takes precedence in getShell(), in the standalone terminal's
default-shell pick, and in the system-prompt shell report for background
exec mode, while COMSPEC/SHELL keep their OS semantics.

Fixes #11290

apps/vscode/src/core/prompts/system-prompt/components/system_info.ts

@@ -1,5 +1,5 @@
 import osModule from "node:os"
-import { getShell } from "@utils/shell"
+import { getHostProvidedShell, getShell } from "@utils/shell"
 import osName from "os-name"
 import { getWorkspacePaths } from "@/hosts/vscode/hostbridge/workspace/getWorkspacePaths"
 import { SystemPromptSection } from "../templates/placeholders"
@@ -21,7 +21,13 @@ Home Directory: {{homeDir}}
  */
 function getEffectiveShell(context: SystemPromptContext): string {
 	if (context.terminalExecutionMode === "backgroundExec") {
-		// Background exec uses the system default shell, not VS Code config
+		// Background exec uses the host-forwarded shell if present (mirrors
+		// StandaloneTerminalProcess.getDefaultShell), otherwise the system
+		// default shell, not the VS Code config.
+		const hostShell = getHostProvidedShell()
+		if (hostShell) {
+			return hostShell
+		}
 		if (process.platform === "win32") {
 			return process.env.COMSPEC || "cmd.exe"
 		} else {

apps/vscode/src/integrations/terminal/standalone/StandaloneTerminalProcess.ts

@@ -9,6 +9,7 @@
  */
 
 import { telemetryService } from "@services/telemetry"
+import { getHostProvidedShell } from "@utils/shell"
 import { ChildProcess, spawn } from "child_process"
 import { EventEmitter } from "events"
 import { terminateProcessTree } from "@/utils/process-termination"
@@ -308,6 +309,12 @@ export class StandaloneTerminalProcess extends EventEmitter<TerminalProcessEvent
 	 * @returns The default shell path
 	 */
 	private getDefaultShell(): string {
+		// A shell explicitly forwarded by the host IDE (e.g. the JetBrains
+		// terminal profile) takes precedence over the OS defaults.
+		const hostShell = getHostProvidedShell()
+		if (hostShell) {
+			return hostShell
+		}
 		if (process.platform === "win32") {
 			return process.env.COMSPEC || "cmd.exe"
 		}

apps/vscode/src/test/shell.test.ts

@@ -1,4 +1,4 @@
-import { getShell } from "@utils/shell"
+import { getShell, HOST_SHELL_ENV_VAR } from "@utils/shell"
 import { expect } from "chai"
 import { afterEach, beforeEach, describe, it } from "mocha"
 import { userInfo } from "os"
@@ -36,6 +36,7 @@ describe("Shell Detection Tests", () => {
 		// Clear environment variables for a clean test
 		delete process.env.SHELL
 		delete process.env.COMSPEC
+		delete process.env[HOST_SHELL_ENV_VAR]
 
 		// Default userInfo() mock
 		;(userInfo as any) = () => ({ shell: null })
@@ -49,6 +50,42 @@ describe("Shell Detection Tests", () => {
 		;(userInfo as any) = originalUserInfo
 	})
 
+	// --------------------------------------------------------------------------
+	// Host-Provided Shell Override (CLINE_TERMINAL_SHELL_PATH)
+	// --------------------------------------------------------------------------
+	describe("Host-Provided Shell Override", () => {
+		it("wins over VS Code config, userInfo, and COMSPEC on Windows", () => {
+			Object.defineProperty(process, "platform", { value: "win32" })
+			mockVsCodeConfig("windows", "PowerShell", {
+				PowerShell: { path: "C:\\Program Files\\PowerShell\\7\\pwsh.exe" },
+			})
+			;(userInfo as any) = () => ({ shell: "C:\\Custom\\PowerShell.exe" })
+			process.env.COMSPEC = "C:\\Windows\\System32\\cmd.exe"
+			process.env[HOST_SHELL_ENV_VAR] = "C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe"
+
+			expect(getShell()).to.equal("C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe")
+		})
+
+		it("wins over userInfo and SHELL on POSIX", () => {
+			Object.defineProperty(process, "platform", { value: "darwin" })
+			vscode.workspace.getConfiguration = () => ({ get: () => undefined }) as any
+			;(userInfo as any) = () => ({ shell: "/bin/zsh" })
+			process.env.SHELL = "/bin/bash"
+			process.env[HOST_SHELL_ENV_VAR] = "/usr/local/bin/fish"
+
+			expect(getShell()).to.equal("/usr/local/bin/fish")
+		})
+
+		it("is ignored when blank", () => {
+			Object.defineProperty(process, "platform", { value: "darwin" })
+			vscode.workspace.getConfiguration = () => ({ get: () => undefined }) as any
+			;(userInfo as any) = () => ({ shell: "/bin/zsh" })
+			process.env[HOST_SHELL_ENV_VAR] = "   "
+
+			expect(getShell()).to.equal("/bin/zsh")
+		})
+	})
+
 	// --------------------------------------------------------------------------
 	// Windows Shell Detection
 	// --------------------------------------------------------------------------

apps/vscode/src/utils/shell.ts

@@ -43,6 +43,28 @@ interface LinuxTerminalProfile {
 
 type LinuxTerminalProfiles = Record<string, LinuxTerminalProfile>
 
+// -----------------------------------------------------
+// 0) Host-Provided Shell Override
+// -----------------------------------------------------
+
+/**
+ * Environment variable through which host integrations (e.g. the JetBrains
+ * plugin) forward the user's IDE terminal profile shell to cline-core.
+ *
+ * A dedicated variable is used instead of overriding COMSPEC/SHELL because
+ * COMSPEC is an OS-level contract that must keep pointing at cmd.exe:
+ * cross-spawn, Node's `shell: true`, and npm `.cmd` shims all pass cmd-style
+ * `/d /s /c` arguments to whatever COMSPEC references. Overriding it with
+ * PowerShell breaks every such child process (see cline/cline#11290).
+ */
+export const HOST_SHELL_ENV_VAR = "CLINE_TERMINAL_SHELL_PATH"
+
+/** Returns the shell explicitly forwarded by the host IDE, or null. */
+export function getHostProvidedShell(): string | null {
+	const shell = process.env[HOST_SHELL_ENV_VAR]?.trim()
+	return shell || null
+}
+
 // -----------------------------------------------------
 // 1) VS Code Terminal Configuration Helpers
 // -----------------------------------------------------
@@ -299,6 +321,12 @@ export function getShellForProfile(profileId: string): string {
 // -----------------------------------------------------
 
 export function getShell(): string {
+	// 0. A shell explicitly forwarded by the host IDE wins over detection.
+	const hostShell = getHostProvidedShell()
+	if (hostShell) {
+		return hostShell
+	}
+
 	// 1. Check VS Code config first.
 	if (process.platform === "win32") {
 		// Special logic for Windows