fix: add character limit to prevent terminal output context explosion (#5777)

* fix: add character limit to prevent terminal output context explosion

- Enhanced truncateOutput function to accept character limits alongside line limits
- Character limits take priority over line limits to prevent context window explosion
- Added terminalOutputCharacterLimit setting (default: 100,000 characters)
- Updated all terminal output processing to use both limits
- Added comprehensive tests for character limit functionality

Fixes #5775

* feat: add terminal output character limit setting to UI

- Add character limit slider to Terminal Settings UI (default: 50,000)
- Update ExtensionStateContext to manage character limit state
- Add validation for positive character limit values
- Add English translation and translations for all 17 supported languages
- Connect UI to backend through proper message handling
- Character limit takes precedence over line limit to prevent memory issues

* fix: update test expectations for character limit edge cases

- Fix multi-byte character test to account for JavaScript's string length behavior
- Fix newline content test to match actual slice behavior
- Tests now correctly validate the truncateOutput function's character limit handling

---------

Co-authored-by: Roo Code <[email protected]>
Co-authored-by: Daniel Riccio <[email protected]>

Author: 3 people

packages/types/src/global-settings.ts

@@ -22,6 +22,13 @@ import { languagesSchema } from "./vscode.js"
  */
 export const DEFAULT_WRITE_DELAY_MS = 1000
 
+/**
+ * Default terminal output character limit constant.
+ * This provides a reasonable default that aligns with typical terminal usage
+ * while preventing context window explosions from extremely long lines.
+ */
+export const DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT = 50_000
+
 /**
  * GlobalSettings
  */
@@ -85,6 +92,7 @@ export const globalSettingsSchema = z.object({
 	maxReadFileLine: z.number().optional(),
 
 	terminalOutputLineLimit: z.number().optional(),
+	terminalOutputCharacterLimit: z.number().optional(),
 	terminalShellIntegrationTimeout: z.number().optional(),
 	terminalShellIntegrationDisabled: z.boolean().optional(),
 	terminalCommandDelay: z.number().optional(),
@@ -228,6 +236,7 @@ export const EVALS_SETTINGS: RooCodeSettings = {
 	soundVolume: 0.5,
 
 	terminalOutputLineLimit: 500,
+	terminalOutputCharacterLimit: DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
 	terminalShellIntegrationTimeout: 30000,
 	terminalCommandDelay: 0,
 	terminalPowershellCounter: false,

src/core/environment/getEnvironmentDetails.ts

@@ -6,6 +6,7 @@ import pWaitFor from "p-wait-for"
 import delay from "delay"
 
 import type { ExperimentId } from "@roo-code/types"
+import { DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT } from "@roo-code/types"
 
 import { EXPERIMENT_IDS, experiments as Experiments } from "../../shared/experiments"
 import { formatLanguage } from "../../shared/language"
@@ -25,7 +26,11 @@ export async function getEnvironmentDetails(cline: Task, includeFileDetails: boo
 
 	const clineProvider = cline.providerRef.deref()
 	const state = await clineProvider?.getState()
-	const { terminalOutputLineLimit = 500, maxWorkspaceFiles = 200 } = state ?? {}
+	const {
+		terminalOutputLineLimit = 500,
+		terminalOutputCharacterLimit = DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
+		maxWorkspaceFiles = 200,
+	} = state ?? {}
 
 	// It could be useful for cline to know if the user went from one or no
 	// file to another between messages, so we always include this context.
@@ -111,7 +116,11 @@ export async function getEnvironmentDetails(cline: Task, includeFileDetails: boo
 			let newOutput = TerminalRegistry.getUnretrievedOutput(busyTerminal.id)
 
 			if (newOutput) {
-				newOutput = Terminal.compressTerminalOutput(newOutput, terminalOutputLineLimit)
+				newOutput = Terminal.compressTerminalOutput(
+					newOutput,
+					terminalOutputLineLimit,
+					terminalOutputCharacterLimit,
+				)
 				terminalDetails += `\n### New Output\n${newOutput}`
 			}
 		}
@@ -139,7 +148,11 @@ export async function getEnvironmentDetails(cline: Task, includeFileDetails: boo
 				let output = process.getUnretrievedOutput()
 
 				if (output) {
-					output = Terminal.compressTerminalOutput(output, terminalOutputLineLimit)
+					output = Terminal.compressTerminalOutput(
+						output,
+						terminalOutputLineLimit,
+						terminalOutputCharacterLimit,
+					)
 					terminalOutputs.push(`Command: \`${process.command}\`\n${output}`)
 				}
 			}

src/core/tools/executeCommandTool.ts

@@ -4,7 +4,7 @@ import * as vscode from "vscode"
 
 import delay from "delay"
 
-import { CommandExecutionStatus } from "@roo-code/types"
+import { CommandExecutionStatus, DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT } from "@roo-code/types"
 import { TelemetryService } from "@roo-code/telemetry"
 
 import { Task } from "../task/Task"
@@ -63,7 +63,11 @@ export async function executeCommandTool(
 			const executionId = cline.lastMessageTs?.toString() ?? Date.now().toString()
 			const clineProvider = await cline.providerRef.deref()
 			const clineProviderState = await clineProvider?.getState()
-			const { terminalOutputLineLimit = 500, terminalShellIntegrationDisabled = false } = clineProviderState ?? {}
+			const {
+				terminalOutputLineLimit = 500,
+				terminalOutputCharacterLimit = DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
+				terminalShellIntegrationDisabled = false,
+			} = clineProviderState ?? {}
 
 			// Get command execution timeout from VSCode configuration (in seconds)
 			const commandExecutionTimeoutSeconds = vscode.workspace
@@ -87,6 +91,7 @@ export async function executeCommandTool(
 				customCwd,
 				terminalShellIntegrationDisabled,
 				terminalOutputLineLimit,
+				terminalOutputCharacterLimit,
 				commandExecutionTimeout,
 			}
 
@@ -133,6 +138,7 @@ export type ExecuteCommandOptions = {
 	customCwd?: string
 	terminalShellIntegrationDisabled?: boolean
 	terminalOutputLineLimit?: number
+	terminalOutputCharacterLimit?: number
 	commandExecutionTimeout?: number
 }
 
@@ -144,6 +150,7 @@ export async function executeCommand(
 		customCwd,
 		terminalShellIntegrationDisabled = false,
 		terminalOutputLineLimit = 500,
+		terminalOutputCharacterLimit = DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
 		commandExecutionTimeout = 0,
 	}: ExecuteCommandOptions,
 ): Promise<[boolean, ToolResponse]> {
@@ -179,7 +186,11 @@ export async function executeCommand(
 	const callbacks: RooTerminalCallbacks = {
 		onLine: async (lines: string, process: RooTerminalProcess) => {
 			accumulatedOutput += lines
-			const compressedOutput = Terminal.compressTerminalOutput(accumulatedOutput, terminalOutputLineLimit)
+			const compressedOutput = Terminal.compressTerminalOutput(
+				accumulatedOutput,
+				terminalOutputLineLimit,
+				terminalOutputCharacterLimit,
+			)
 			const status: CommandExecutionStatus = { executionId, status: "output", output: compressedOutput }
 			clineProvider?.postMessageToWebview({ type: "commandExecutionStatus", text: JSON.stringify(status) })
 
@@ -198,7 +209,11 @@ export async function executeCommand(
 			} catch (_error) {}
 		},
 		onCompleted: (output: string | undefined) => {
-			result = Terminal.compressTerminalOutput(output ?? "", terminalOutputLineLimit)
+			result = Terminal.compressTerminalOutput(
+				output ?? "",
+				terminalOutputLineLimit,
+				terminalOutputCharacterLimit,
+			)
 			cline.say("command_output", result)
 			completed = true
 		},

src/core/webview/ClineProvider.ts

@@ -28,6 +28,7 @@ import {
 	openRouterDefaultModelId,
 	glamaDefaultModelId,
 	ORGANIZATION_ALLOW_ALL,
+	DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
 } from "@roo-code/types"
 import { TelemetryService } from "@roo-code/telemetry"
 import { CloudService, getRooCodeApiUrl } from "@roo-code/cloud"
@@ -1393,6 +1394,7 @@ export class ClineProvider
 			cachedChromeHostUrl,
 			writeDelayMs,
 			terminalOutputLineLimit,
+			terminalOutputCharacterLimit,
 			terminalShellIntegrationTimeout,
 			terminalShellIntegrationDisabled,
 			terminalCommandDelay,
@@ -1493,6 +1495,7 @@ export class ClineProvider
 			cachedChromeHostUrl: cachedChromeHostUrl,
 			writeDelayMs: writeDelayMs ?? DEFAULT_WRITE_DELAY_MS,
 			terminalOutputLineLimit: terminalOutputLineLimit ?? 500,
+			terminalOutputCharacterLimit: terminalOutputCharacterLimit ?? DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
 			terminalShellIntegrationTimeout: terminalShellIntegrationTimeout ?? Terminal.defaultShellIntegrationTimeout,
 			terminalShellIntegrationDisabled: terminalShellIntegrationDisabled ?? false,
 			terminalCommandDelay: terminalCommandDelay ?? 0,
@@ -1662,6 +1665,8 @@ export class ClineProvider
 			fuzzyMatchThreshold: stateValues.fuzzyMatchThreshold ?? 1.0,
 			writeDelayMs: stateValues.writeDelayMs ?? DEFAULT_WRITE_DELAY_MS,
 			terminalOutputLineLimit: stateValues.terminalOutputLineLimit ?? 500,
+			terminalOutputCharacterLimit:
+				stateValues.terminalOutputCharacterLimit ?? DEFAULT_TERMINAL_OUTPUT_CHARACTER_LIMIT,
 			terminalShellIntegrationTimeout:
 				stateValues.terminalShellIntegrationTimeout ?? Terminal.defaultShellIntegrationTimeout,
 			terminalShellIntegrationDisabled: stateValues.terminalShellIntegrationDisabled ?? false,

src/core/webview/webviewMessageHandler.ts

@@ -1049,8 +1049,29 @@ export const webviewMessageHandler = async (
 			await provider.postStateToWebview()
 			break
 		case "terminalOutputLineLimit":
-			await updateGlobalState("terminalOutputLineLimit", message.value)
-			await provider.postStateToWebview()
+			// Validate that the line limit is a positive number
+			const lineLimit = message.value
+			if (typeof lineLimit === "number" && lineLimit > 0) {
+				await updateGlobalState("terminalOutputLineLimit", lineLimit)
+				await provider.postStateToWebview()
+			} else {
+				vscode.window.showErrorMessage(
+					t("common:errors.invalid_line_limit") || "Terminal output line limit must be a positive number",
+				)
+			}
+			break
+		case "terminalOutputCharacterLimit":
+			// Validate that the character limit is a positive number
+			const charLimit = message.value
+			if (typeof charLimit === "number" && charLimit > 0) {
+				await updateGlobalState("terminalOutputCharacterLimit", charLimit)
+				await provider.postStateToWebview()
+			} else {
+				vscode.window.showErrorMessage(
+					t("common:errors.invalid_character_limit") ||
+						"Terminal output character limit must be a positive number",
+				)
+			}
 			break
 		case "terminalShellIntegrationTimeout":
 			await updateGlobalState("terminalShellIntegrationTimeout", message.value)