fix: avoid login flag for csh shells

core/tools/implementations/runTerminalCommand.ts

@@ -22,7 +22,10 @@ function getDecodedOutput(data: Buffer): string {
     return data.toString();
   }
 } // Simple helper function to use login shell on Unix/macOS and PowerShell on Windows
-function getShellCommand(command: string): { shell: string; args: string[] } {
+export function getShellCommand(command: string): {
+  shell: string;
+  args: string[];
+} {
   if (process.platform === "win32") {
     // Windows: Use PowerShell
     return {
@@ -32,10 +35,20 @@ function getShellCommand(command: string): { shell: string; args: string[] } {
   } else {
     // Unix/macOS: Use login shell to source .bashrc/.zshrc etc.
     const userShell = process.env.SHELL || "/bin/bash";
-    return { shell: userShell, args: ["-l", "-c", command] };
+    return {
+      shell: userShell,
+      args: shellSupportsLoginFlag(userShell)
+        ? ["-l", "-c", command]
+        : ["-c", command],
+    };
   }
 }
 
+function shellSupportsLoginFlag(shell: string): boolean {
+  const shellName = shell.split(/[\\/]/).pop()?.toLowerCase();
+  return shellName !== "csh" && shellName !== "tcsh";
+}
+
 import { fileURLToPath } from "node:url";
 import { ToolImpl } from ".";
 import {

core/tools/implementations/runTerminalCommand.vitest.ts

@@ -15,7 +15,7 @@ import {
 import { IDE, ToolExtras } from "../..";
 import * as processTerminalStates from "../../util/processTerminalStates";
 import { runTerminalCommandTool } from "../definitions/runTerminalCommand";
-import { runTerminalCommandImpl } from "./runTerminalCommand";
+import { getShellCommand, runTerminalCommandImpl } from "./runTerminalCommand";
 
 // We're using real child processes, so ensure these aren't mocked
 vi.unmock("node:child_process");
@@ -857,4 +857,16 @@ describe("runTerminalCommandTool.evaluateToolCallPolicy", () => {
 
     expect(result).toBe("allowedWithPermission");
   });
+
+  it("does not pass login-shell flag to csh-family shells", () => {
+    const previousShell = process.env.SHELL;
+    process.env.SHELL = "/bin/tcsh";
+    try {
+      const { shell, args } = getShellCommand("pwd");
+      expect(shell).toBe("/bin/tcsh");
+      expect(args).toEqual(["-c", "pwd"]);
+    } finally {
+      process.env.SHELL = previousShell;
+    }
+  });
 });

extensions/cli/src/tools/runTerminalCommand.test.ts

@@ -1,4 +1,5 @@
 import {
+  getShellCommand,
   isRunningInWsl,
   runTerminalCommandTool,
 } from "./runTerminalCommand.js";
@@ -70,7 +71,7 @@
   });
 
   describe("basic error handling", () => {
     it("should handle non-existent commands", async () => {
       const command = "definitely-not-a-real-command-xyz123";
 
       await expect(runTerminalCommandTool.run({ command })).rejects.toMatch(
@@ -121,4 +122,18 @@
       });
     }
   });
+
+  describe("shell selection", () => {
+    it("does not pass login-shell flag to csh-family shells", () => {
+      const previousShell = process.env.SHELL;
+      process.env.SHELL = "/bin/tcsh";
+      try {
+        const { shell, args } = getShellCommand("pwd");
+        expect(shell).toBe("/bin/tcsh");
+        expect(args).toEqual(["-c", "pwd"]);
+      } finally {
+        process.env.SHELL = previousShell;
+      }
+    });
+  });
 });

extensions/cli/src/tools/runTerminalCommand.ts

@@ -63,7 +63,10 @@ function getBashMaxLines(): number {
 }
 
 // Helper function to use login shell on Unix/macOS and PowerShell on Windows and available shell in WSL
-function getShellCommand(command: string): { shell: string; args: string[] } {
+export function getShellCommand(command: string): {
+  shell: string;
+  args: string[];
+} {
   if (process.platform === "win32") {
     // Windows: Use PowerShell
     return {
@@ -77,13 +80,25 @@ function getShellCommand(command: string): { shell: string; args: string[] } {
     const wslShell = process.env.SHELL || "/bin/bash";
     return {
       shell: wslShell,
-      args: ["-l", "-c", command],
+      args: shellSupportsLoginFlag(wslShell)
+        ? ["-l", "-c", command]
+        : ["-c", command],
     };
   }
 
   // Unix/macOS: Use login shell to source .bashrc/.zshrc etc.
   const userShell = process.env.SHELL || "/bin/bash";
-  return { shell: userShell, args: ["-l", "-c", command] };
+  return {
+    shell: userShell,
+    args: shellSupportsLoginFlag(userShell)
+      ? ["-l", "-c", command]
+      : ["-c", command],
+  };
+}
+
+function shellSupportsLoginFlag(shell: string): boolean {
+  const shellName = shell.split(/[\\/]/).pop()?.toLowerCase();
+  return shellName !== "csh" && shellName !== "tcsh";
 }
 
 export function runCommandInBackground(command: string): {