feat: add stdin support for ExecaTerminalProcess

- Add writeStdin method to RooTerminalProcess interface
- Add abstract writeStdin to BaseTerminalProcess
- Implement writeStdin in ExecaTerminalProcess using stdin pipe
- Implement writeStdin in TerminalProcess using terminal.sendText
- Change ExecaTerminalProcess from stdin: 'ignore' to stdin: 'pipe'
- Update WriteStdinTool to use unified process.writeStdin() method

This enables write_stdin tool to work with both VSCode terminals and
Execa terminals, providing consistent interactive terminal support.

src/core/tools/WriteStdinTool.ts

@@ -4,7 +4,6 @@ import { Task } from "../task/Task"
 import { ToolUse } from "../../shared/tools"
 import { formatResponse } from "../prompts/responses"
 import { ProcessManager } from "../../integrations/terminal/ProcessManager"
-import { Terminal } from "../../integrations/terminal/Terminal"
 import { t } from "../../i18n"
 
 import { BaseTool, ToolCallbacks } from "./BaseTool"
@@ -122,22 +121,16 @@ export class WriteStdinTool extends BaseTool<"write_stdin"> {
 			// Process escape sequences in input
 			const processedChars = this.processEscapeSequences(chars)
 
-			// Write to stdin
+			// Write to stdin using the unified writeStdin interface
 			const { terminal, process } = entry
 			let writeSuccess = false
 
 			try {
-				if (terminal instanceof Terminal) {
-					// VSCode terminal - use sendText
-					// Note: sendText automatically adds a newline by default, so we pass false
-					// to prevent double newlines when the input already ends with \n
-					terminal.terminal.sendText(processedChars, false)
-					writeSuccess = true
-				} else {
-					// Execa terminal - would need stdin pipe support
-					// For now, we'll indicate this isn't supported for execa
-					// TODO: Implement stdin support for ExecaTerminalProcess
-					const errorMsg = `Session ${session_id} is using a non-interactive terminal. Interactive stdin is only supported for VSCode terminals.`
+				// Use the process writeStdin method which works for both VSCode and Execa terminals
+				writeSuccess = process.writeStdin(processedChars)
+
+				if (!writeSuccess) {
+					const errorMsg = `Failed to write to session ${session_id}: stdin is not available`
 					await task.say("error", errorMsg)
 					pushToolResult(`Error: ${errorMsg}`)
 					return

src/integrations/terminal/BaseTerminalProcess.ts

@@ -137,6 +137,13 @@ export abstract class BaseTerminalProcess extends EventEmitter<RooTerminalProces
 	 */
 	abstract getUnretrievedOutput(): string
 
+	/**
+	 * Write characters to stdin.
+	 * @param chars The characters to write
+	 * @returns true if write was successful, false if stdin is not available
+	 */
+	abstract writeStdin(chars: string): boolean
+
 	/**
 	 * Clears the internal output buffer when all content has been retrieved.
 	 *

src/integrations/terminal/ExecaTerminalProcess.ts

@@ -42,8 +42,8 @@ export class ExecaTerminalProcess extends BaseTerminalProcess {
 				shell: true,
 				cwd: this.terminal.getCurrentWorkingDirectory(),
 				all: true,
-				// Ignore stdin to ensure non-interactive mode and prevent hanging
-				stdin: "ignore",
+				// Use pipe for stdin to allow interactive input via writeStdin
+				stdin: "pipe",
 				env: {
 					...process.env,
 					// Ensure UTF-8 encoding for Ruby, CocoaPods, etc.
@@ -241,6 +241,26 @@ export class ExecaTerminalProcess extends BaseTerminalProcess {
 		return output.slice(0, index)
 	}
 
+	/**
+	 * Write characters to stdin of the running process.
+	 * @param chars The characters to write
+	 * @returns true if write was successful
+	 */
+	public override writeStdin(chars: string): boolean {
+		if (!this.subprocess?.stdin) {
+			console.warn("[ExecaTerminalProcess#writeStdin] No stdin available")
+			return false
+		}
+
+		try {
+			this.subprocess.stdin.write(chars)
+			return true
+		} catch (error) {
+			console.error("[ExecaTerminalProcess#writeStdin] Failed to write:", error)
+			return false
+		}
+	}
+
 	private emitRemainingBufferIfListening() {
 		if (!this.isListening) {
 			return

src/integrations/terminal/TerminalProcess.ts

@@ -314,6 +314,28 @@ export class TerminalProcess extends BaseTerminalProcess {
 		return this.removeEscapeSequences(outputToProcess)
 	}
 
+	/**
+	 * Write characters to stdin of the running process.
+	 * For VSCode terminals, this uses sendText which sends to the terminal.
+	 * @param chars The characters to write
+	 * @returns true if write was successful
+	 */
+	public override writeStdin(chars: string): boolean {
+		try {
+			const vsceTerminal = this.terminal.terminal
+			if (!vsceTerminal) {
+				console.warn("[TerminalProcess#writeStdin] No VSCode terminal available")
+				return false
+			}
+			// sendText with addNewline=false to avoid double newlines
+			vsceTerminal.sendText(chars, false)
+			return true
+		} catch (error) {
+			console.error("[TerminalProcess#writeStdin] Failed to write:", error)
+			return false
+		}
+	}
+
 	private emitRemainingBufferIfListening() {
 		if (this.isListening) {
 			const remainingBuffer = this.getUnretrievedOutput()

src/integrations/terminal/types.ts

@@ -37,6 +37,11 @@ export interface RooTerminalProcess extends EventEmitter<RooTerminalProcessEvent
 	hasUnretrievedOutput: () => boolean
 	getUnretrievedOutput: () => string
 	trimRetrievedOutput: () => void
+	/**
+	 * Write characters to stdin. Returns true if write was successful.
+	 * May return false if stdin is not available (e.g., stdin: "ignore").
+	 */
+	writeStdin: (chars: string) => boolean
 }
 
 export type RooTerminalProcessResultPromise = RooTerminalProcess & Promise<void>