Merge pull request #1390 from RooVetGit/cte/terminal-middle-out

Terminal "middle-out": smart truncation for terminal output

src/core/Cline.ts

@@ -25,7 +25,6 @@ import {
 	addLineNumbers,
 	stripLineNumbers,
 	everyLineHasLineNumbers,
-	truncateOutput,
 } from "../integrations/misc/extract-text"
 import { TerminalManager, ExitCodeDetails } from "../integrations/terminal/TerminalManager"
 import { UrlContentFetcher } from "../services/browser/UrlContentFetcher"
@@ -55,11 +54,12 @@ import { HistoryItem } from "../shared/HistoryItem"
 import { ClineAskResponse } from "../shared/WebviewMessage"
 import { GlobalFileNames } from "../shared/globalFileNames"
 import { defaultModeSlug, getModeBySlug, getFullModeDetails } from "../shared/modes"
+import { EXPERIMENT_IDS, experiments as Experiments, ExperimentId } from "../shared/experiments"
 import { calculateApiCost } from "../utils/cost"
 import { fileExistsAtPath } from "../utils/fs"
 import { arePathsEqual, getReadablePath } from "../utils/path"
 import { parseMentions } from "./mentions"
-import { RooIgnoreController, LOCK_TEXT_SYMBOL } from "./ignore/RooIgnoreController"
+import { RooIgnoreController } from "./ignore/RooIgnoreController"
 import { AssistantMessageContent, parseAssistantMessage, ToolParamName, ToolUseName } from "./assistant-message"
 import { formatResponse } from "./prompts/responses"
 import { SYSTEM_PROMPT } from "./prompts/system"
@@ -70,7 +70,7 @@ import { BrowserSession } from "../services/browser/BrowserSession"
 import { McpHub } from "../services/mcp/McpHub"
 import crypto from "crypto"
 import { insertGroups } from "./diff/insert-groups"
-import { EXPERIMENT_IDS, experiments as Experiments, ExperimentId } from "../shared/experiments"
+import { OutputBuilder } from "../integrations/terminal/OutputBuilder"
 
 const cwd =
 	vscode.workspace.workspaceFolders?.map((folder) => folder.uri.fsPath).at(0) ?? path.join(os.homedir(), "Desktop") // may or may not exist but fs checking existence would immediately ask for permission which would be bad UX, need to come up with a better solution
@@ -912,30 +912,43 @@ export class Cline {
 	// Tools
 
 	async executeCommandTool(command: string): Promise<[boolean, ToolResponse]> {
+		const { terminalOutputLimit } = (await this.providerRef.deref()?.getState()) ?? {}
+
 		const terminalInfo = await this.terminalManager.getOrCreateTerminal(cwd)
-		terminalInfo.terminal.show() // weird visual bug when creating new terminals (even manually) where there's an empty space at the top.
-		const process = this.terminalManager.runCommand(terminalInfo, command)
+		// Weird visual bug when creating new terminals (even manually) where
+		// there's an empty space at the top.
+		terminalInfo.terminal.show()
+		const process = this.terminalManager.runCommand(terminalInfo, command, terminalOutputLimit)
 
 		let userFeedback: { text?: string; images?: string[] } | undefined
 		let didContinue = false
-		const sendCommandOutput = async (line: string): Promise<void> => {
+
+		const sendCommandOutput = async (line: string) => {
 			try {
 				const { response, text, images } = await this.ask("command_output", line)
+
 				if (response === "yesButtonClicked") {
-					// proceed while running
+					// Proceed while running.
 				} else {
 					userFeedback = { text, images }
 				}
+
 				didContinue = true
-				process.continue() // continue past the await
+				process.continue() // Continue past the await.
 			} catch {
-				// This can only happen if this ask promise was ignored, so ignore this error
+				// This can only happen if this ask promise was ignored, so ignore this error.
 			}
 		}
 
-		let lines: string[] = []
+		let completed = false
+		let exitDetails: ExitCodeDetails | undefined
+
+		let builder = new OutputBuilder({ maxSize: terminalOutputLimit })
+		let output: string | undefined = undefined
+
 		process.on("line", (line) => {
-			lines.push(line)
+			builder.append(line)
+
 			if (!didContinue) {
 				sendCommandOutput(line)
 			} else {
@@ -943,13 +956,8 @@ export class Cline {
 			}
 		})
 
-		let completed = false
-		let exitDetails: ExitCodeDetails | undefined
-		process.once("completed", (output?: string) => {
-			// Use provided output if available, otherwise keep existing result.
-			if (output) {
-				lines = output.split("\n")
-			}
+		process.once("completed", (buffer?: string) => {
+			output = buffer
 			completed = true
 		})
 
@@ -965,19 +973,17 @@ export class Cline {
 
 		await process
 
-		// Wait for a short delay to ensure all messages are sent to the webview
+		// Wait for a short delay to ensure all messages are sent to the webview.
 		// This delay allows time for non-awaited promises to be created and
 		// for their associated messages to be sent to the webview, maintaining
 		// the correct order of messages (although the webview is smart about
-		// grouping command_output messages despite any gaps anyways)
+		// grouping command_output messages despite any gaps anyways).
 		await delay(50)
-
-		const { terminalOutputLineLimit } = (await this.providerRef.deref()?.getState()) ?? {}
-		const output = truncateOutput(lines.join("\n"), terminalOutputLineLimit)
-		const result = output.trim()
+		const result = output || builder.content
 
 		if (userFeedback) {
 			await this.say("user_feedback", userFeedback.text, userFeedback.images)
+
 			return [
 				true,
 				formatResponse.toolResult(
@@ -991,9 +997,11 @@ export class Cline {
 
 		if (completed) {
 			let exitStatus = "No exit code available"
+
 			if (exitDetails !== undefined) {
 				if (exitDetails.signal) {
 					exitStatus = `Process terminated by signal ${exitDetails.signal} (${exitDetails.signalName})`
+
 					if (exitDetails.coreDumpPossible) {
 						exitStatus += " - core dump possible"
 					}
@@ -1001,15 +1009,16 @@ export class Cline {
 					exitStatus = `Exit code: ${exitDetails.exitCode}`
 				}
 			}
+
 			return [false, `Command executed. ${exitStatus}${result.length > 0 ? `\nOutput:\n${result}` : ""}`]
-		} else {
-			return [
-				false,
-				`Command is still running in the user's terminal.${
-					result.length > 0 ? `\nHere's the output so far:\n${result}` : ""
-				}\n\nYou will be updated on the terminal status and new output in the future.`,
-			]
 		}
+
+		return [
+			false,
+			`Command is still running in the user's terminal.${
+				result.length > 0 ? `\nHere's the output so far:\n${result}` : ""
+			}\n\nYou will be updated on the terminal status and new output in the future.`,
+		]
 	}
 
 	async *attemptApiRequest(previousApiReqIndex: number, retryAttempt: number = 0): ApiStream {
@@ -3495,7 +3504,7 @@ export class Cline {
 			terminalDetails += "\n\n# Actively Running Terminals"
 			for (const busyTerminal of busyTerminals) {
 				terminalDetails += `\n## Original command: \`${busyTerminal.lastCommand}\``
-				const newOutput = this.terminalManager.getUnretrievedOutput(busyTerminal.id)
+				const newOutput = this.terminalManager.readLine(busyTerminal.id)
 				if (newOutput) {
 					terminalDetails += `\n### New Output\n${newOutput}`
 				} else {
@@ -3507,7 +3516,7 @@ export class Cline {
 		if (inactiveTerminals.length > 0) {
 			const inactiveTerminalOutputs = new Map<number, string>()
 			for (const inactiveTerminal of inactiveTerminals) {
-				const newOutput = this.terminalManager.getUnretrievedOutput(inactiveTerminal.id)
+				const newOutput = this.terminalManager.readLine(inactiveTerminal.id)
 				if (newOutput) {
 					inactiveTerminalOutputs.set(inactiveTerminal.id, newOutput)
 				}

src/core/mentions/index.ts

@@ -2,13 +2,13 @@ import * as vscode from "vscode"
 import * as path from "path"
 import { openFile } from "../../integrations/misc/open-file"
 import { UrlContentFetcher } from "../../services/browser/UrlContentFetcher"
-import { mentionRegexGlobal, formatGitSuggestion, type MentionSuggestion } from "../../shared/context-mentions"
+import { mentionRegexGlobal } from "../../shared/context-mentions"
 import fs from "fs/promises"
 import { extractTextFromFile } from "../../integrations/misc/extract-text"
 import { isBinaryFile } from "isbinaryfile"
 import { diagnosticsToProblemsString } from "../../integrations/diagnostics"
 import { getCommitInfo, getWorkingState } from "../../utils/git"
-import { getLatestTerminalOutput } from "../../integrations/terminal/get-latest-output"
+import { getLatestTerminalOutput } from "../../integrations/terminal/getLatestTerminalOutput"
 
 export async function openMention(mention?: string): Promise<void> {
 	if (!mention) {

src/core/webview/ClineProvider.ts

@@ -10,17 +10,17 @@ import simpleGit from "simple-git"
 import { setPanel } from "../../activate/registerCommands"
 
 import { ApiConfiguration, ApiProvider, ModelInfo, API_CONFIG_KEYS } from "../../shared/api"
-import { CheckpointStorage } from "../../shared/checkpoints"
 import { findLast } from "../../shared/array"
-import { CustomSupportPrompts, supportPrompt } from "../../shared/support-prompt"
+import { supportPrompt } from "../../shared/support-prompt"
 import { GlobalFileNames } from "../../shared/globalFileNames"
 import { SecretKey, GlobalStateKey, SECRET_KEYS, GLOBAL_STATE_KEYS } from "../../shared/globalState"
 import { HistoryItem } from "../../shared/HistoryItem"
 import { ApiConfigMeta, ExtensionMessage } from "../../shared/ExtensionMessage"
 import { checkoutDiffPayloadSchema, checkoutRestorePayloadSchema, WebviewMessage } from "../../shared/WebviewMessage"
-import { Mode, CustomModePrompts, PromptComponent, defaultModeSlug, ModeConfig } from "../../shared/modes"
+import { Mode, PromptComponent, defaultModeSlug, ModeConfig } from "../../shared/modes"
 import { checkExistKey } from "../../shared/checkExistApiConfig"
 import { EXPERIMENT_IDS, experiments as Experiments, experimentDefault, ExperimentId } from "../../shared/experiments"
+import { TERMINAL_OUTPUT_LIMIT } from "../../shared/terminal"
 import { downloadTask } from "../../integrations/misc/export-markdown"
 import { openFile, openImage } from "../../integrations/misc/open-file"
 import { selectImages } from "../../integrations/misc/process-images"
@@ -1215,7 +1215,6 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 						await this.postStateToWebview()
 						break
 					case "checkpointStorage":
-						console.log(`[ClineProvider] checkpointStorage: ${message.text}`)
 						const checkpointStorage = message.text ?? "task"
 						await this.updateGlobalState("checkpointStorage", checkpointStorage)
 						await this.postStateToWebview()
@@ -1249,8 +1248,8 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 						await this.updateGlobalState("writeDelayMs", message.value)
 						await this.postStateToWebview()
 						break
-					case "terminalOutputLineLimit":
-						await this.updateGlobalState("terminalOutputLineLimit", message.value)
+					case "terminalOutputLimit":
+						await this.updateGlobalState("terminalOutputLimit", message.value)
 						await this.postStateToWebview()
 						break
 					case "mode":
@@ -2134,7 +2133,7 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 			screenshotQuality,
 			preferredLanguage,
 			writeDelayMs,
-			terminalOutputLineLimit,
+			terminalOutputLimit,
 			fuzzyMatchThreshold,
 			mcpEnabled,
 			enableMcpServerCreation,
@@ -2186,7 +2185,7 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 			screenshotQuality: screenshotQuality ?? 75,
 			preferredLanguage: preferredLanguage ?? "English",
 			writeDelayMs: writeDelayMs ?? 1000,
-			terminalOutputLineLimit: terminalOutputLineLimit ?? 500,
+			terminalOutputLimit: terminalOutputLimit ?? TERMINAL_OUTPUT_LIMIT,
 			fuzzyMatchThreshold: fuzzyMatchThreshold ?? 1.0,
 			mcpEnabled: mcpEnabled ?? true,
 			enableMcpServerCreation: enableMcpServerCreation ?? true,
@@ -2334,7 +2333,7 @@ export class ClineProvider implements vscode.WebviewViewProvider {
 			screenshotQuality: stateValues.screenshotQuality ?? 75,
 			fuzzyMatchThreshold: stateValues.fuzzyMatchThreshold ?? 1.0,
 			writeDelayMs: stateValues.writeDelayMs ?? 1000,
-			terminalOutputLineLimit: stateValues.terminalOutputLineLimit ?? 500,
+			terminalOutputLimit: stateValues.terminalOutputLimit ?? TERMINAL_OUTPUT_LIMIT,
 			mode: stateValues.mode ?? defaultModeSlug,
 			preferredLanguage:
 				stateValues.preferredLanguage ??

src/integrations/misc/__tests__/extract-text.test.ts

@@ -1,4 +1,4 @@
-import { addLineNumbers, everyLineHasLineNumbers, stripLineNumbers, truncateOutput } from "../extract-text"
+import { addLineNumbers, everyLineHasLineNumbers, stripLineNumbers } from "../extract-text"
 
 describe("addLineNumbers", () => {
 	it("should add line numbers starting from 1 by default", () => {
@@ -101,67 +101,3 @@ describe("stripLineNumbers", () => {
 		expect(stripLineNumbers(input)).toBe(expected)
 	})
 })
-
-describe("truncateOutput", () => {
-	it("returns original content when no line limit provided", () => {
-		const content = "line1\nline2\nline3"
-		expect(truncateOutput(content)).toBe(content)
-	})
-
-	it("returns original content when lines are under limit", () => {
-		const content = "line1\nline2\nline3"
-		expect(truncateOutput(content, 5)).toBe(content)
-	})
-
-	it("truncates content with 20/80 split when over limit", () => {
-		// Create 25 lines of content
-		const lines = Array.from({ length: 25 }, (_, i) => `line${i + 1}`)
-		const content = lines.join("\n")
-
-		// Set limit to 10 lines
-		const result = truncateOutput(content, 10)
-
-		// Should keep:
-		// - First 2 lines (20% of 10)
-		// - Last 8 lines (80% of 10)
-		// - Omission indicator in between
-		const expectedLines = [
-			"line1",
-			"line2",
-			"",
-			"[...15 lines omitted...]",
-			"",
-			"line18",
-			"line19",
-			"line20",
-			"line21",
-			"line22",
-			"line23",
-			"line24",
-			"line25",
-		]
-		expect(result).toBe(expectedLines.join("\n"))
-	})
-
-	it("handles empty content", () => {
-		expect(truncateOutput("", 10)).toBe("")
-	})
-
-	it("handles single line content", () => {
-		expect(truncateOutput("single line", 10)).toBe("single line")
-	})
-
-	it("handles windows-style line endings", () => {
-		// Create content with windows line endings
-		const lines = Array.from({ length: 15 }, (_, i) => `line${i + 1}`)
-		const content = lines.join("\r\n")
-
-		const result = truncateOutput(content, 5)
-
-		// Should keep first line (20% of 5 = 1) and last 4 lines (80% of 5 = 4)
-		// Split result by either \r\n or \n to normalize line endings
-		const resultLines = result.split(/\r?\n/)
-		const expectedLines = ["line1", "", "[...10 lines omitted...]", "", "line12", "line13", "line14", "line15"]
-		expect(resultLines).toEqual(expectedLines)
-	})
-})

src/integrations/misc/extract-text.ts

@@ -89,37 +89,3 @@ export function stripLineNumbers(content: string): string {
 	const lineEnding = content.includes("\r\n") ? "\r\n" : "\n"
 	return processedLines.join(lineEnding)
 }
-
-/**
- * Truncates multi-line output while preserving context from both the beginning and end.
- * When truncation is needed, it keeps 20% of the lines from the start and 80% from the end,
- * with a clear indicator of how many lines were omitted in between.
- *
- * @param content The multi-line string to truncate
- * @param lineLimit Optional maximum number of lines to keep. If not provided or 0, returns the original content
- * @returns The truncated string with an indicator of omitted lines, or the original content if no truncation needed
- *
- * @example
- * // With 10 line limit on 25 lines of content:
- * // - Keeps first 2 lines (20% of 10)
- * // - Keeps last 8 lines (80% of 10)
- * // - Adds "[...15 lines omitted...]" in between
- */
-export function truncateOutput(content: string, lineLimit?: number): string {
-	if (!lineLimit) {
-		return content
-	}
-
-	const lines = content.split("\n")
-	if (lines.length <= lineLimit) {
-		return content
-	}
-
-	const beforeLimit = Math.floor(lineLimit * 0.2) // 20% of lines before
-	const afterLimit = lineLimit - beforeLimit // remaining 80% after
-	return [
-		...lines.slice(0, beforeLimit),
-		`\n[...${lines.length - lineLimit} lines omitted...]\n`,
-		...lines.slice(-afterLimit),
-	].join("\n")
-}

src/integrations/terminal/OutputBuilder.ts

@@ -0,0 +1,183 @@
+import { TERMINAL_OUTPUT_LIMIT } from "../../shared/terminal"
+
+interface OutputBuilderOptions {
+	maxSize?: number // Max size of the buffer.
+	preserveStartPercent?: number // % of `maxSize` to preserve at start.
+	preserveEndPercent?: number // % of `maxSize` to preserve at end
+	truncationMessage?: string
+}
+
+/**
+ * OutputBuilder manages terminal output with intelligent middle truncation.
+ *
+ * When output exceeds a specified size limit, this class truncates content
+ * primarily from the middle, preserving both the beginning (command context)
+ * and the end (recent output) of the buffer for better diagnostic context.
+ */
+export class OutputBuilder {
+	public readonly preserveStartSize: number
+	public readonly preserveEndSize: number
+	public readonly truncationMessage: string
+
+	private startBuffer = ""
+	private endBuffer = ""
+	private _bytesProcessed = 0
+	private _bytesRemoved = 0
+	private _cursor = 0
+
+	constructor({
+		maxSize = TERMINAL_OUTPUT_LIMIT, // 100KB
+		preserveStartPercent = 50, // 50% of `maxSize`
+		preserveEndPercent = 50, // 50% of `maxSize`
+		truncationMessage = "\n[... OUTPUT TRUNCATED ...]\n",
+	}: OutputBuilderOptions = {}) {
+		this.preserveStartSize = Math.floor((preserveStartPercent / 100) * maxSize)
+		this.preserveEndSize = Math.floor((preserveEndPercent / 100) * maxSize)
+
+		if (this.preserveStartSize + this.preserveEndSize > maxSize) {
+			throw new Error("Invalid configuration: preserve sizes exceed maxSize")
+		}
+
+		this.truncationMessage = truncationMessage
+	}
+
+	append(content: string): this {
+		if (content.length === 0) {
+			return this
+		}
+
+		this._bytesProcessed += content.length
+
+		if (!this.isTruncated) {
+			this.startBuffer += content
+
+			const excessBytes = this.startBuffer.length - (this.preserveStartSize + this.preserveEndSize)
+
+			if (excessBytes <= 0) {
+				return this
+			}
+
+			this.endBuffer = this.startBuffer.slice(-this.preserveEndSize)
+			this.startBuffer = this.startBuffer.slice(0, this.preserveStartSize)
+			this._bytesRemoved += excessBytes
+		} else {
+			// Already in truncation mode; append to `endBuffer`.
+			this.endBuffer += content
+
+			// If `endBuffer` gets too large, trim it.
+			if (this.endBuffer.length > this.preserveEndSize) {
+				const excessBytes = this.endBuffer.length - this.preserveEndSize
+				this.endBuffer = this.endBuffer.slice(excessBytes)
+				this._bytesRemoved += excessBytes
+			}
+		}
+
+		return this
+	}
+
+	/**
+	 * Reads unprocessed content from the current cursor position, handling both
+	 * truncated and non-truncated states.
+	 *
+	 * The algorithm handles three cases:
+	 * 1. Non-truncated buffer:
+	 *    - Simply returns remaining content from cursor position.
+	 *
+	 * 2. Truncated buffer, cursor in start portion:
+	 *    - Returns remaining start content plus all end content.
+	 *    - This ensures we don't miss the transition between buffers.
+	 *
+	 * 3. Truncated buffer, cursor in end portion:
+	 *    - Adjusts cursor position by subtracting removed bytes and start buffer length.
+	 *    - Uses Math.max to prevent negative indices if cursor adjustment overshoots.
+	 *    - Returns remaining content from adjusted position in end buffer.
+	 *
+	 * This approach ensures continuous reading even across truncation
+	 * boundaries, while properly tracking position in both start and end
+	 * portions of truncated content.
+	 */
+	read() {
+		let output
+
+		if (!this.isTruncated) {
+			output = this.startBuffer.slice(this.cursor)
+		} else if (this.cursor < this.startBuffer.length) {
+			output = this.startBuffer.slice(this.cursor) + this.endBuffer
+		} else {
+			output = this.endBuffer.slice(Math.max(this.cursor - this.bytesRemoved - this.startBuffer.length, 0))
+		}
+
+		this._cursor = this.bytesProcessed
+		return output
+	}
+
+	/**
+	 * Same as above, but read only line at a time.
+	 */
+	readLine() {
+		let output
+		let index = -1
+
+		if (!this.isTruncated) {
+			output = this.startBuffer.slice(this.cursor)
+			index = output.indexOf("\n")
+		} else if (this.cursor < this.startBuffer.length) {
+			output = this.startBuffer.slice(this.cursor)
+			index = output.indexOf("\n")
+
+			if (index === -1) {
+				output = output + this.endBuffer
+				index = output.indexOf("\n")
+			}
+		} else {
+			output = this.endBuffer.slice(Math.max(this.cursor - this.bytesRemoved - this.startBuffer.length, 0))
+			index = output.indexOf("\n")
+		}
+
+		if (index >= 0) {
+			this._cursor = this.bytesProcessed - (output.length - index) + 1
+			return output.slice(0, index + 1)
+		}
+
+		this._cursor = this.bytesProcessed
+		return output
+	}
+
+	public reset(content?: string) {
+		this.startBuffer = ""
+		this.endBuffer = ""
+		this._bytesProcessed = 0
+		this._bytesRemoved = 0
+		this._cursor = 0
+
+		if (content) {
+			this.append(content)
+		}
+	}
+
+	public get content() {
+		return this.isTruncated ? this.startBuffer + this.truncationMessage + this.endBuffer : this.startBuffer
+	}
+
+	public get size() {
+		return this.isTruncated
+			? this.startBuffer.length + this.truncationMessage.length + this.endBuffer.length
+			: this.startBuffer.length
+	}
+
+	public get isTruncated() {
+		return this._bytesRemoved > 0
+	}
+
+	public get bytesProcessed() {
+		return this._bytesProcessed
+	}
+
+	public get bytesRemoved() {
+		return this._bytesRemoved
+	}
+
+	public get cursor() {
+		return this._cursor
+	}
+}

src/integrations/terminal/TerminalManager.ts

@@ -1,8 +1,11 @@
 import pWaitFor from "p-wait-for"
 import * as vscode from "vscode"
+
+import { TERMINAL_OUTPUT_LIMIT } from "../../shared/terminal"
 import { arePathsEqual } from "../../utils/path"
-import { mergePromise, TerminalProcess, TerminalProcessResultPromise } from "./TerminalProcess"
+import { TerminalProcess } from "./TerminalProcess"
 import { TerminalInfo, TerminalRegistry } from "./TerminalRegistry"
+import { mergePromise, TerminalProcessResultPromise } from "./mergePromise"
 
 /*
 TerminalManager:
@@ -15,8 +18,6 @@ TerminalProcess extends EventEmitter and implements Promise:
 - process.continue() resolves promise and stops event emission
 - Allows real-time output handling or background execution
 
-getUnretrievedOutput() fetches latest output for ongoing commands
-
 Enables flexible command execution:
 - Await for completion
 - Listen to real-time events
@@ -30,7 +31,6 @@ Supported shells:
 Linux/macOS: bash, fish, pwsh, zsh
 Windows: pwsh
 
-
 Example:
 
 const terminalManager = new TerminalManager(context);
@@ -49,7 +49,7 @@ await process;
 process.continue();
 
 // Later, if you need to get the unretrieved output:
-const unretrievedOutput = terminalManager.getUnretrievedOutput(terminalId);
+const unretrievedOutput = terminalManager.readLine(terminalId);
 console.log('Unretrieved output:', unretrievedOutput);
 
 Resources:
@@ -259,10 +259,14 @@ export class TerminalManager {
 		}
 	}
 
-	runCommand(terminalInfo: TerminalInfo, command: string): TerminalProcessResultPromise {
+	runCommand(
+		terminalInfo: TerminalInfo,
+		command: string,
+		terminalOutputLimit = TERMINAL_OUTPUT_LIMIT,
+	): TerminalProcessResultPromise {
 		terminalInfo.busy = true
 		terminalInfo.lastCommand = command
-		const process = new TerminalProcess()
+		const process = new TerminalProcess(terminalOutputLimit)
 		this.processes.set(terminalInfo.id, process)
 
 		process.once("completed", () => {
@@ -347,12 +351,13 @@ export class TerminalManager {
 			.map((t) => ({ id: t.id, lastCommand: t.lastCommand }))
 	}
 
-	getUnretrievedOutput(terminalId: number): string {
+	readLine(terminalId: number): string {
 		if (!this.terminalIds.has(terminalId)) {
 			return ""
 		}
+
 		const process = this.processes.get(terminalId)
-		return process ? process.getUnretrievedOutput() : ""
+		return process ? process.readLine() : ""
 	}
 
 	isProcessHot(terminalId: number): boolean {

src/integrations/terminal/TerminalProcess.ts

@@ -5,6 +5,34 @@ import { inspect } from "util"
 
 import { ExitCodeDetails } from "./TerminalManager"
 import { TerminalInfo, TerminalRegistry } from "./TerminalRegistry"
+import { OutputBuilder } from "./OutputBuilder"
+
+// How long to wait after a process outputs anything before we consider it
+// "cool" again
+const PROCESS_HOT_TIMEOUT_NORMAL = 2_000
+const PROCESS_HOT_TIMEOUT_COMPILING = 15_000
+
+// These markers indicate the command is some kind of local dev server
+// recompiling the app, which we want to wait for output of before sending
+// request to Roo.
+const COMPILE_MARKERS = ["compiling", "building", "bundling", "transpiling", "generating", "starting"]
+
+const COMPILE_MARKER_NULLIFIERS = [
+	"compiled",
+	"success",
+	"finish",
+	"complete",
+	"succeed",
+	"done",
+	"end",
+	"stop",
+	"exit",
+	"terminate",
+	"error",
+	"fail",
+]
+
+const EMIT_INTERVAL = 250
 
 export interface TerminalProcessEvents {
 	line: [line: string]
@@ -21,20 +49,28 @@ export interface TerminalProcessEvents {
 	stream_available: [id: number, stream: AsyncIterable<string>]
 }
 
-// how long to wait after a process outputs anything before we consider it "cool" again
-const PROCESS_HOT_TIMEOUT_NORMAL = 2_000
-const PROCESS_HOT_TIMEOUT_COMPILING = 15_000
-
 export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
-	waitForShellIntegration: boolean = true
-	private isListening: boolean = true
+	public waitForShellIntegration = true
+	private _isHot = false
+
+	private isListening = true
 	private terminalInfo: TerminalInfo | undefined
-	private lastEmitTime_ms: number = 0
-	private fullOutput: string = ""
-	private lastRetrievedIndex: number = 0
-	isHot: boolean = false
+	private lastEmitTime_ms = 0
+	private outputBuilder?: OutputBuilder
 	private hotTimer: NodeJS.Timeout | null = null
 
+	public get isHot() {
+		return this._isHot
+	}
+
+	private set isHot(value: boolean) {
+		this._isHot = value
+	}
+
+	constructor(private readonly terminalOutputLimit: number) {
+		super()
+	}
+
 	async run(terminal: vscode.Terminal, command: string) {
 		if (terminal.shellIntegration && terminal.shellIntegration.executeCommand) {
 			// Get terminal info to access stream
@@ -66,7 +102,7 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 				})
 			})
 
-			// getUnretrievedOutput needs to know if streamClosed, so store this for later
+			// readLine needs to know if streamClosed, so store this for later
 			this.terminalInfo = terminalInfo
 
 			// Execute command
@@ -89,61 +125,58 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 			 * - OSC 633 ; E ; <commandline> [; <nonce>] ST - Explicitly set command line with optional nonce
 			 */
 
-			// Process stream data
+			this.outputBuilder = new OutputBuilder({ maxSize: this.terminalOutputLimit })
+
+			/**
+			 * Some commands won't result in output flushing until the command
+			 * completes. This locks the UI. Should we set a timer to prompt
+			 * the user to continue?
+			 */
+
 			for await (let data of stream) {
-				// Check for command output start marker
+				// Check for command output start marker.
 				if (!commandOutputStarted) {
 					preOutput += data
 					const match = this.matchAfterVsceStartMarkers(data)
+
 					if (match !== undefined) {
 						commandOutputStarted = true
 						data = match
-						this.fullOutput = "" // Reset fullOutput when command actually starts
+						this.outputBuilder.reset() // Reset output when command actually starts.
 					} else {
 						continue
 					}
 				}
 
 				// Command output started, accumulate data without filtering.
-				// notice to future programmers: do not add escape sequence
-				// filtering here: fullOutput cannot change in length (see getUnretrievedOutput),
+				// Notice to future programmers: do not add escape sequence
+				// filtering here: output cannot change in length (see `readLine`),
 				// and chunks may not be complete so you cannot rely on detecting or removing escape sequences mid-stream.
-				this.fullOutput += data
+				this.outputBuilder.append(data)
 
 				// For non-immediately returning commands we want to show loading spinner
-				// right away but this wouldnt happen until it emits a line break, so
-				// as soon as we get any output we emit to let webview know to show spinner
+				// right away but this wouldn't happen until it emits a line break, so
+				// as soon as we get any output we emit to let webview know to show spinner.
 				const now = Date.now()
-				if (this.isListening && (now - this.lastEmitTime_ms > 100 || this.lastEmitTime_ms === 0)) {
-					this.emitRemainingBufferIfListening()
+				const timeSinceLastEmit = now - this.lastEmitTime_ms
+
+				if (this.isListening && timeSinceLastEmit > EMIT_INTERVAL) {
+					this.flushLine()
 					this.lastEmitTime_ms = now
 				}
 
-				// 2. Set isHot depending on the command.
+				// Set isHot depending on the command.
 				// This stalls API requests until terminal is cool again.
 				this.isHot = true
+
 				if (this.hotTimer) {
 					clearTimeout(this.hotTimer)
 				}
-				// these markers indicate the command is some kind of local dev server recompiling the app, which we want to wait for output of before sending request to cline
-				const compilingMarkers = ["compiling", "building", "bundling", "transpiling", "generating", "starting"]
-				const markerNullifiers = [
-					"compiled",
-					"success",
-					"finish",
-					"complete",
-					"succeed",
-					"done",
-					"end",
-					"stop",
-					"exit",
-					"terminate",
-					"error",
-					"fail",
-				]
+
 				const isCompiling =
-					compilingMarkers.some((marker) => data.toLowerCase().includes(marker.toLowerCase())) &&
-					!markerNullifiers.some((nullifier) => data.toLowerCase().includes(nullifier.toLowerCase()))
+					COMPILE_MARKERS.some((marker) => data.toLowerCase().includes(marker.toLowerCase())) &&
+					!COMPILE_MARKER_NULLIFIERS.some((nullifier) => data.toLowerCase().includes(nullifier.toLowerCase()))
+
 				this.hotTimer = setTimeout(
 					() => {
 						this.isHot = false
@@ -152,18 +185,18 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 				)
 			}
 
-			// Set streamClosed immediately after stream ends
+			// Set streamClosed immediately after stream ends.
 			if (this.terminalInfo) {
 				this.terminalInfo.streamClosed = true
 			}
 
-			// Wait for shell execution to complete and handle exit details
-			const exitDetails = await shellExecutionComplete
+			// Wait for shell execution to complete and handle exit details.
+			await shellExecutionComplete
 			this.isHot = false
 
 			if (commandOutputStarted) {
-				// Emit any remaining output before completing
-				this.emitRemainingBufferIfListening()
+				// Emit any remaining output before completing.
+				this.flushAll()
 			} else {
 				console.error(
 					"[Terminal Process] VSCE output start escape sequence (]633;C or ]133;C) not received! VSCE Bug? preOutput: " +
@@ -171,62 +204,77 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 				)
 			}
 
-			// console.debug("[Terminal Process] raw output: " + inspect(output, { colors: false, breakLength: Infinity }))
-
-			// fullOutput begins after C marker so we only need to trim off D marker
+			// Output begins after C marker so we only need to trim off D marker
 			// (if D exists, see VSCode bug# 237208):
-			const match = this.matchBeforeVsceEndMarkers(this.fullOutput)
+			const match = this.matchBeforeVsceEndMarkers(this.outputBuilder.content)
+
 			if (match !== undefined) {
-				this.fullOutput = match
+				this.outputBuilder.reset(match)
 			}
 
-			// console.debug(`[Terminal Process] processed output via ${matchSource}: ` + inspect(output, { colors: false, breakLength: Infinity }))
-
-			// for now we don't want this delaying requests since we don't send diagnostics automatically anymore (previous: "even though the command is finished, we still want to consider it 'hot' in case so that api request stalls to let diagnostics catch up")
+			// For now we don't want this delaying requests since we don't send
+			// diagnostics automatically anymore (previous: "even though the
+			// command is finished, we still want to consider it 'hot' in case
+			// so that api request stalls to let diagnostics catch up").
 			if (this.hotTimer) {
 				clearTimeout(this.hotTimer)
 			}
+
 			this.isHot = false
 
-			this.emit("completed", this.removeEscapeSequences(this.fullOutput))
+			this.emit("completed", this.removeEscapeSequences(this.outputBuilder.content))
 			this.emit("continue")
 		} else {
 			terminal.sendText(command, true)
-			// For terminals without shell integration, we can't know when the command completes
-			// So we'll just emit the continue event after a delay
+			// For terminals without shell integration, we can't know when the command completes.
+			// So we'll just emit the continue event.
 			this.emit("completed")
 			this.emit("continue")
 			this.emit("no_shell_integration")
-			// setTimeout(() => {
-			// 	console.log(`Emitting continue after delay for terminal`)
-			// 	// can't emit completed since we don't if the command actually completed, it could still be running server
-			// }, 500) // Adjust this delay as needed
 		}
 	}
 
-	private emitRemainingBufferIfListening() {
-		if (this.isListening) {
-			const remainingBuffer = this.getUnretrievedOutput()
-			if (remainingBuffer !== "") {
-				this.emit("line", remainingBuffer)
-			}
-		}
+	public readLine() {
+		return this.processOutput(this.outputBuilder?.readLine() || "")
 	}
 
-	continue() {
-		this.emitRemainingBufferIfListening()
+	public read() {
+		return this.processOutput(this.outputBuilder?.read() || "")
+	}
+
+	public continue() {
+		this.flushAll()
 		this.isListening = false
 		this.removeAllListeners("line")
 		this.emit("continue")
 	}
 
-	// Returns complete lines with their carriage returns.
-	// The final line may lack a carriage return if the program didn't send one.
-	getUnretrievedOutput(): string {
-		// Get raw unretrieved output
-		let outputToProcess = this.fullOutput.slice(this.lastRetrievedIndex)
+	private flushLine() {
+		if (!this.isListening) {
+			return
+		}
 
-		// Check for VSCE command end markers
+		const line = this.readLine()
+
+		if (line) {
+			this.emit("line", line)
+		}
+	}
+
+	private flushAll() {
+		if (!this.isListening) {
+			return
+		}
+
+		const buffer = this.read()
+
+		if (buffer) {
+			this.emit("line", buffer)
+		}
+	}
+
+	private processOutput(outputToProcess: string) {
+		// Check for VSCE command end markers.
 		const index633 = outputToProcess.indexOf("\x1b]633;D")
 		const index133 = outputToProcess.indexOf("\x1b]133;D")
 		let endIndex = -1
@@ -239,32 +287,7 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 			endIndex = index133
 		}
 
-		// If no end markers were found yet (possibly due to VSCode bug#237208):
-		//   For active streams: return only complete lines (up to last \n).
-		//   For closed streams: return all remaining content.
-		if (endIndex === -1) {
-			if (!this.terminalInfo?.streamClosed) {
-				// Stream still running - only process complete lines
-				endIndex = outputToProcess.lastIndexOf("\n")
-				if (endIndex === -1) {
-					// No complete lines
-					return ""
-				}
-
-				// Include carriage return
-				endIndex++
-			} else {
-				// Stream closed - process all remaining output
-				endIndex = outputToProcess.length
-			}
-		}
-
-		// Update index and slice output
-		this.lastRetrievedIndex += endIndex
-		outputToProcess = outputToProcess.slice(0, endIndex)
-
-		// Clean and return output
-		return this.removeEscapeSequences(outputToProcess)
+		return this.removeEscapeSequences(endIndex >= 0 ? outputToProcess.slice(0, endIndex) : outputToProcess)
 	}
 
 	private stringIndexMatch(
@@ -282,18 +305,20 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 			prefixLength = 0
 		} else {
 			startIndex = data.indexOf(prefix)
+
 			if (startIndex === -1) {
 				return undefined
 			}
+
 			if (bell.length > 0) {
 				// Find the bell character after the prefix
 				const bellIndex = data.indexOf(bell, startIndex + prefix.length)
+
 				if (bellIndex === -1) {
 					return undefined
 				}
 
 				const distanceToBell = bellIndex - startIndex
-
 				prefixLength = distanceToBell + bell.length
 			} else {
 				prefixLength = prefix.length
@@ -307,6 +332,7 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 			endIndex = data.length
 		} else {
 			endIndex = data.indexOf(suffix, contentStart)
+
 			if (endIndex === -1) {
 				return undefined
 			}
@@ -323,7 +349,7 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 	// This method could be extended to handle other escape sequences, but any additions
 	// should be carefully considered to ensure they only remove control codes and don't
 	// alter the actual content or behavior of the output stream.
-	private removeEscapeSequences(str: string): string {
+	private removeEscapeSequences(str: string) {
 		return stripAnsi(str.replace(/\x1b\]633;[^\x07]+\x07/gs, "").replace(/\x1b\]133;[^\x07]+\x07/gs, ""))
 	}
 
@@ -396,20 +422,3 @@ export class TerminalProcess extends EventEmitter<TerminalProcessEvents> {
 		return match133 !== undefined ? match133 : match633
 	}
 }
-
-export type TerminalProcessResultPromise = TerminalProcess & Promise<void>
-
-// Similar to execa's ResultPromise, this lets us create a mixin of both a TerminalProcess and a Promise: https://github.com/sindresorhus/execa/blob/main/lib/methods/promise.js
-export function mergePromise(process: TerminalProcess, promise: Promise<void>): TerminalProcessResultPromise {
-	const nativePromisePrototype = (async () => {})().constructor.prototype
-	const descriptors = ["then", "catch", "finally"].map(
-		(property) => [property, Reflect.getOwnPropertyDescriptor(nativePromisePrototype, property)] as const,
-	)
-	for (const [property, descriptor] of descriptors) {
-		if (descriptor) {
-			const value = descriptor.value.bind(promise)
-			Reflect.defineProperty(process, property, { ...descriptor, value })
-		}
-	}
-	return process as TerminalProcessResultPromise
-}

src/integrations/terminal/__tests__/OutputBuilder.test.ts

@@ -0,0 +1,272 @@
+// npx jest src/integrations/terminal/__tests__/OutputBuilder.test.ts
+
+import { OutputBuilder } from "../OutputBuilder"
+
+describe("OutputBuilder", () => {
+	describe("basic functionality", () => {
+		it("should create instance with default settings", () => {
+			const builder = new OutputBuilder()
+			expect(builder).toBeInstanceOf(OutputBuilder)
+			expect(builder.content).toBe("")
+			expect(builder.isTruncated).toBe(false)
+			expect(builder.size).toBe(0)
+		})
+
+		it("should append and retrieve content", () => {
+			const builder = new OutputBuilder()
+			builder.append("Hello, ")
+			builder.append("world!")
+
+			expect(builder.content).toBe("Hello, world!")
+			expect(builder.isTruncated).toBe(false)
+			expect(builder.size).toBe(13)
+		})
+
+		it("should reset content properly", () => {
+			const builder = new OutputBuilder()
+			builder.append("Hello, world!")
+			builder.reset()
+
+			expect(builder.content).toBe("")
+			expect(builder.isTruncated).toBe(false)
+			expect(builder.size).toBe(0)
+		})
+	})
+
+	describe("truncation behavior", () => {
+		it("should not truncate content below max size", () => {
+			// Create with 100 byte limit.
+			const builder = new OutputBuilder({
+				maxSize: 100,
+				preserveStartPercent: 20,
+				preserveEndPercent: 80,
+			})
+
+			// Add 50 bytes of content.
+			builder.append("a".repeat(50))
+
+			expect(builder.content).toBe("a".repeat(50))
+			expect(builder.isTruncated).toBe(false)
+			expect(builder.size).toBe(50)
+		})
+
+		it("should truncate content correctly when exceeding max size", () => {
+			// Small buffer for testing
+			const maxSize = 100
+			const truncationMessage = "[...TRUNCATED...]"
+			const builder = new OutputBuilder({
+				maxSize,
+				preserveStartPercent: 20,
+				preserveEndPercent: 80,
+				truncationMessage,
+			})
+
+			// Calculate preserve sizes.
+			const preserveStartSize = Math.floor(0.2 * maxSize) // 20 bytes
+			const preserveEndSize = Math.floor(0.8 * maxSize) // 80 bytes
+
+			// Add content that exceeds the 100 byte limit.
+			builder.append("a".repeat(120))
+
+			// Check truncation happened.
+			expect(builder.isTruncated).toBe(true)
+
+			// Verify content structure.
+			const content = builder.content
+
+			// Should have this structure:
+			// [start 20 chars] + [truncation message] + [end 80 chars]
+			expect(content).toBe("a".repeat(preserveStartSize) + truncationMessage + "a".repeat(preserveEndSize))
+
+			// Size should be: startSize + truncationMessage.length + endSize
+			expect(builder.size).toBe(preserveStartSize + truncationMessage.length + preserveEndSize)
+		})
+
+		it("should preserve start and end with different percentages", () => {
+			// Small buffer with 50/50 split.
+			const builder = new OutputBuilder({
+				maxSize: 100,
+				preserveStartPercent: 50,
+				preserveEndPercent: 50,
+				truncationMessage: "[...]",
+			})
+
+			// Add 200 bytes.
+			builder.append("a".repeat(200))
+
+			// Should preserve 50 at start, 50 at end.
+			expect(builder.content).toBe("a".repeat(50) + "[...]" + "a".repeat(50))
+			expect(builder.isTruncated).toBe(true)
+		})
+
+		it("should handle multiple content additions after truncation", () => {
+			const builder = new OutputBuilder({
+				maxSize: 100,
+				preserveStartPercent: 30,
+				preserveEndPercent: 70,
+				truncationMessage: "[...]",
+			})
+
+			// Initial content that triggers truncation.
+			builder.append("a".repeat(120))
+			expect(builder.isTruncated).toBe(true)
+
+			// Add more content - should update end portion.
+			builder.append("b".repeat(20))
+
+			// Should contain start (a's), truncation message, and end with both a's and b's.
+			const content = builder.content
+			expect(content.startsWith("a".repeat(30))).toBe(true)
+			expect(content.indexOf("[...]")).toBe(30)
+			expect(content.endsWith("b".repeat(20))).toBe(true)
+		})
+	})
+
+	describe("edge cases", () => {
+		it("should handle empty string appends", () => {
+			const builder = new OutputBuilder({ maxSize: 100 })
+			builder.append("")
+			expect(builder.content).toBe("")
+			expect(builder.size).toBe(0)
+		})
+
+		it("should handle content exactly at size limit", () => {
+			const builder = new OutputBuilder({ maxSize: 100 })
+			builder.append("a".repeat(100))
+
+			// Should not trigger truncation at exactly the limit.
+			expect(builder.isTruncated).toBe(false)
+			expect(builder.size).toBe(100)
+		})
+
+		it("should handle very small max sizes", () => {
+			// 10 byte max with 3 byte start, 7 byte end.
+			const builder = new OutputBuilder({
+				maxSize: 10,
+				preserveStartPercent: 30,
+				preserveEndPercent: 70,
+				truncationMessage: "...",
+			})
+
+			builder.append("1234567890abc")
+
+			// Get result and validate structure (start + message + end).
+			const result = builder.content
+			expect(result.startsWith("123")).toBe(true)
+			expect(result.indexOf("...")).toBe(3)
+
+			// For small buffers, there might be differences in exact content
+			// based on implementation details.
+			// But the combined length should be correct:
+			// startSize(3) + message(3) + endSize(7) = 13
+			expect(result.length).toBe(13)
+		})
+
+		it("should throw error for invalid configuration", () => {
+			// Preserve percentages that add up to more than 100%.
+			expect(() => {
+				new OutputBuilder({
+					maxSize: 100,
+					preserveStartPercent: 60,
+					preserveEndPercent: 60,
+				})
+			}).toThrow()
+		})
+
+		it("should handle continuous appending beyond multiple truncations", () => {
+			// Small buffer for testing multiple truncations.
+			const builder = new OutputBuilder({
+				maxSize: 20,
+				preserveStartPercent: 25, // 5 bytes
+				preserveEndPercent: 75, // 15 bytes
+				truncationMessage: "...",
+			})
+
+			// First append - triggers truncation.
+			builder.append("a".repeat(30))
+			expect(builder.isTruncated).toBe(true)
+			expect(builder.content).toBe("a".repeat(5) + "..." + "a".repeat(15))
+
+			// Second append with different character.
+			builder.append("b".repeat(10))
+
+			// Should maintain start buffer, but end buffer should now have some b's.
+			const expectedEndBuffer = "a".repeat(5) + "b".repeat(10)
+			expect(builder.content).toBe("a".repeat(5) + "..." + expectedEndBuffer)
+
+			// Third append with another character.
+			builder.append("c".repeat(5))
+
+			// End buffer should shift again.
+			const finalEndBuffer = "a".repeat(0) + "b".repeat(10) + "c".repeat(5)
+			expect(builder.content).toBe("a".repeat(5) + "..." + finalEndBuffer)
+		})
+	})
+
+	describe("read", () => {
+		it("handles truncated output", () => {
+			const builder = new OutputBuilder({
+				maxSize: 60,
+				preserveStartPercent: 40,
+				preserveEndPercent: 60,
+				truncationMessage: " ... ",
+			})
+
+			builder.append("Beginning content that will partially remain. ")
+			expect(builder.content).toBe("Beginning content that will partially remain. ")
+			expect(builder.bytesProcessed).toBe(46)
+			expect(builder.bytesRemoved).toBe(0)
+			expect(builder.read()).toBe("Beginning content that will partially remain. ")
+			expect(builder.cursor).toBe(46)
+
+			builder.append("Ending content that will remain until another append. ")
+			expect(builder.content).toBe("Beginning content that w ... t will remain until another append. ")
+			expect(builder.bytesProcessed).toBe(100)
+			expect(builder.bytesRemoved).toBe(40)
+			expect(builder.read()).toBe("t will remain until another append. ")
+			expect(builder.cursor).toBe(100)
+
+			builder.append("Fin. ")
+			expect(builder.content).toBe("Beginning content that w ... l remain until another append. Fin. ")
+			expect(builder.bytesProcessed).toBe(105)
+			expect(builder.bytesRemoved).toBe(45)
+			expect(builder.read()).toBe("Fin. ")
+			expect(builder.cursor).toBe(105)
+
+			builder.append("Foo bar baz. ")
+			expect(builder.content).toBe("Beginning content that w ... l another append. Fin. Foo bar baz. ")
+			expect(builder.bytesProcessed).toBe(118)
+			expect(builder.bytesRemoved).toBe(58)
+			expect(builder.read()).toBe("Foo bar baz. ")
+			expect(builder.cursor).toBe(118)
+
+			builder.append("Lorem ipsum dolor sit amet, libris convenire vix ei, ea cum aperiam liberavisse. ")
+			expect(builder.content).toBe("Beginning content that w ... vix ei, ea cum aperiam liberavisse. ")
+			expect(builder.bytesProcessed).toBe(199)
+			expect(builder.bytesRemoved).toBe(139)
+			expect(builder.read()).toBe("vix ei, ea cum aperiam liberavisse. ")
+			expect(builder.cursor).toBe(199)
+		})
+	})
+
+	describe("readLine", () => {
+		it("handles truncated output", () => {
+			const builder = new OutputBuilder({
+				maxSize: 60,
+				preserveStartPercent: 40,
+				preserveEndPercent: 60,
+				truncationMessage: " ... ",
+			})
+
+			builder.append("Lorem ipsum dolor sit amet.\nLibris convenire vix ei.")
+			expect(builder.content).toBe("Lorem ipsum dolor sit amet.\nLibris convenire vix ei.")
+			expect(builder.readLine()).toBe("Lorem ipsum dolor sit amet.\n")
+			expect(builder.readLine()).toBe("Libris convenire vix ei.")
+
+			builder.append("Est aliqua quis aliqua.\nAliquip culpa id cillum enim.")
+			expect(builder.content).toBe("Lorem ipsum dolor sit am ... liqua.\nAliquip culpa id cillum enim.")
+			expect(builder.readLine()).toBe("liqua.\n")
+			expect(builder.readLine()).toBe("Aliquip culpa id cillum enim.")
+		})
+	})
+})

src/integrations/terminal/__tests__/TerminalProcess.test.ts

@@ -2,7 +2,7 @@
 
 import * as vscode from "vscode"
 
-import { TerminalProcess, mergePromise } from "../TerminalProcess"
+import { TerminalProcess } from "../TerminalProcess"
 import { TerminalInfo, TerminalRegistry } from "../TerminalRegistry"
 
 // Mock vscode.window.createTerminal
@@ -34,7 +34,7 @@ describe("TerminalProcess", () => {
 	let mockStream: AsyncIterableIterator<string>
 
 	beforeEach(() => {
-		terminalProcess = new TerminalProcess()
+		terminalProcess = new TerminalProcess(100 * 1024)
 
 		// Create properly typed mock terminal
 		mockTerminal = {
@@ -173,32 +173,4 @@ describe("TerminalProcess", () => {
 			expect(terminalProcess["isListening"]).toBe(false)
 		})
 	})
-
-	describe("getUnretrievedOutput", () => {
-		it("returns and clears unretrieved output", () => {
-			terminalProcess["fullOutput"] = `\x1b]633;C\x07previous\nnew output\x1b]633;D\x07`
-			terminalProcess["lastRetrievedIndex"] = 17 // After "previous\n"
-
-			const unretrieved = terminalProcess.getUnretrievedOutput()
-			expect(unretrieved).toBe("new output")
-
-			expect(terminalProcess["lastRetrievedIndex"]).toBe(terminalProcess["fullOutput"].length - "previous".length)
-		})
-	})
-
-	describe("mergePromise", () => {
-		it("merges promise methods with terminal process", async () => {
-			const process = new TerminalProcess()
-			const promise = Promise.resolve()
-
-			const merged = mergePromise(process, promise)
-
-			expect(merged).toHaveProperty("then")
-			expect(merged).toHaveProperty("catch")
-			expect(merged).toHaveProperty("finally")
-			expect(merged instanceof TerminalProcess).toBe(true)
-
-			await expect(merged).resolves.toBeUndefined()
-		})
-	})
 })

src/integrations/terminal/__tests__/mergePromise.test.ts

@@ -0,0 +1,20 @@
+// npx jest src/integrations/terminal/__tests__/mergePromise.test.ts
+
+import { TerminalProcess } from "../TerminalProcess"
+import { mergePromise } from "../mergePromise"
+
+describe("mergePromise", () => {
+	it("merges promise methods with terminal process", async () => {
+		const process = new TerminalProcess(100 * 1024)
+		const promise = Promise.resolve()
+
+		const merged = mergePromise(process, promise)
+
+		expect(merged).toHaveProperty("then")
+		expect(merged).toHaveProperty("catch")
+		expect(merged).toHaveProperty("finally")
+		expect(merged instanceof TerminalProcess).toBe(true)
+
+		await expect(merged).resolves.toBeUndefined()
+	})
+})

src/integrations/terminal/mergePromise.ts

@@ -0,0 +1,23 @@
+import { TerminalProcess } from "./TerminalProcess"
+
+export type TerminalProcessResultPromise = TerminalProcess & Promise<void>
+
+// Similar to execa's ResultPromise, this lets us create a mixin of both a
+// TerminalProcess and a Promise:
+// https://github.com/sindresorhus/execa/blob/main/lib/methods/promise.js
+export function mergePromise(process: TerminalProcess, promise: Promise<void>): TerminalProcessResultPromise {
+	const nativePromisePrototype = (async () => {})().constructor.prototype
+
+	const descriptors = ["then", "catch", "finally"].map(
+		(property) => [property, Reflect.getOwnPropertyDescriptor(nativePromisePrototype, property)] as const,
+	)
+
+	for (const [property, descriptor] of descriptors) {
+		if (descriptor) {
+			const value = descriptor.value.bind(promise)
+			Reflect.defineProperty(process, property, { ...descriptor, value })
+		}
+	}
+
+	return process as TerminalProcessResultPromise
+}

src/shared/ExtensionMessage.ts

@@ -124,7 +124,7 @@ export interface ExtensionState {
 	fuzzyMatchThreshold?: number
 	preferredLanguage: string
 	writeDelayMs: number
-	terminalOutputLineLimit?: number
+	terminalOutputLimit?: number
 	mcpEnabled: boolean
 	enableMcpServerCreation: boolean
 	mode: Mode

src/shared/WebviewMessage.ts

@@ -68,7 +68,7 @@ export interface WebviewMessage {
 		| "enhancedPrompt"
 		| "draggedImages"
 		| "deleteMessage"
-		| "terminalOutputLineLimit"
+		| "terminalOutputLimit"
 		| "mcpEnabled"
 		| "enableMcpServerCreation"
 		| "searchCommits"

src/shared/globalState.ts

@@ -66,7 +66,7 @@ export const GLOBAL_STATE_KEYS = [
 	"fuzzyMatchThreshold",
 	"preferredLanguage", // Language setting for Cline's communication
 	"writeDelayMs",
-	"terminalOutputLineLimit",
+	"terminalOutputLimit",
 	"mcpEnabled",
 	"enableMcpServerCreation",
 	"alwaysApproveResubmit",

src/shared/terminal.ts

@@ -0,0 +1 @@
+export const TERMINAL_OUTPUT_LIMIT = 100 * 1024

src/utils/git.ts

@@ -1,9 +1,9 @@
 import { exec } from "child_process"
 import { promisify } from "util"
-import { truncateOutput } from "../integrations/misc/extract-text"
+
+import { OutputBuilder } from "../integrations/terminal/OutputBuilder"
 
 const execAsync = promisify(exec)
-const GIT_OUTPUT_LINE_LIMIT = 500
 
 export interface GitCommit {
 	hash: string
@@ -122,8 +122,9 @@ export async function getCommitInfo(hash: string, cwd: string): Promise<string>
 			"\nFull Changes:",
 		].join("\n")
 
-		const output = summary + "\n\n" + diff.trim()
-		return truncateOutput(output, GIT_OUTPUT_LINE_LIMIT)
+		const builder = new OutputBuilder()
+		builder.append(summary + "\n\n" + diff.trim())
+		return builder.content
 	} catch (error) {
 		console.error("Error getting commit info:", error)
 		return `Failed to get commit info: ${error instanceof Error ? error.message : String(error)}`
@@ -150,9 +151,10 @@ export async function getWorkingState(cwd: string): Promise<string> {
 
 		// Get all changes (both staged and unstaged) compared to HEAD
 		const { stdout: diff } = await execAsync("git diff HEAD", { cwd })
-		const lineLimit = GIT_OUTPUT_LINE_LIMIT
-		const output = `Working directory changes:\n\n${status}\n\n${diff}`.trim()
-		return truncateOutput(output, lineLimit)
+
+		const builder = new OutputBuilder()
+		builder.append(`Working directory changes:\n\n${status}\n\n${diff}`.trim())
+		return builder.content
 	} catch (error) {
 		console.error("Error getting working state:", error)
 		return `Failed to get working state: ${error instanceof Error ? error.message : String(error)}`

webview-ui/src/components/settings/AdvancedSettings.tsx

@@ -3,6 +3,7 @@ import { VSCodeCheckbox } from "@vscode/webview-ui-toolkit/react"
 import { Cog } from "lucide-react"
 
 import { EXPERIMENT_IDS, ExperimentId } from "../../../../src/shared/experiments"
+import { TERMINAL_OUTPUT_LIMIT } from "../../../../src/shared/terminal"
 
 import { cn } from "@/lib/utils"
 
@@ -13,12 +14,12 @@ import { Section } from "./Section"
 
 type AdvancedSettingsProps = HTMLAttributes<HTMLDivElement> & {
 	rateLimitSeconds: number
-	terminalOutputLineLimit?: number
+	terminalOutputLimit?: number
 	maxOpenTabsContext: number
 	diffEnabled?: boolean
 	fuzzyMatchThreshold?: number
 	setCachedStateField: SetCachedStateField<
-		"rateLimitSeconds" | "terminalOutputLineLimit" | "maxOpenTabsContext" | "diffEnabled" | "fuzzyMatchThreshold"
+		"rateLimitSeconds" | "terminalOutputLimit" | "maxOpenTabsContext" | "diffEnabled" | "fuzzyMatchThreshold"
 	>
 	experiments: Record<ExperimentId, boolean>
 	setExperimentEnabled: SetExperimentEnabled
@@ -26,7 +27,7 @@ type AdvancedSettingsProps = HTMLAttributes<HTMLDivElement> & {
 
 export const AdvancedSettings = ({
 	rateLimitSeconds,
-	terminalOutputLineLimit,
+	terminalOutputLimit = TERMINAL_OUTPUT_LIMIT,
 	maxOpenTabsContext,
 	diffEnabled,
 	fuzzyMatchThreshold,
@@ -71,21 +72,20 @@ export const AdvancedSettings = ({
 						<div className="flex items-center gap-2">
 							<input
 								type="range"
-								min="100"
-								max="5000"
-								step="100"
-								value={terminalOutputLineLimit ?? 500}
-								onChange={(e) =>
-									setCachedStateField("terminalOutputLineLimit", parseInt(e.target.value))
-								}
+								min={1024}
+								max={1024 * 1024}
+								step={1024}
+								value={terminalOutputLimit}
+								onChange={(e) => setCachedStateField("terminalOutputLimit", parseInt(e.target.value))}
 								className="h-2 focus:outline-0 w-4/5 accent-vscode-button-background"
 							/>
-							<span style={{ ...sliderLabelStyle }}>{terminalOutputLineLimit ?? 500}</span>
+							<span style={{ ...sliderLabelStyle }}>{Math.floor(terminalOutputLimit / 1024)} KB</span>
 						</div>
 					</div>
 					<p className="text-vscode-descriptionForeground text-sm mt-0">
-						Maximum number of lines to include in terminal output when executing commands. When exceeded
-						lines will be removed from the middle, saving tokens.
+						Maximum amount of terminal output (in kilobytes) to send to the LLM when executing commands. If
+						the output exceeds this limit, it will be removed from the middle so that the start and end of
+						the output are preserved.
 					</p>
 				</div>
 

webview-ui/src/components/settings/ExperimentalSettings.tsx

@@ -12,7 +12,7 @@ import { ExperimentalFeature } from "./ExperimentalFeature"
 
 type ExperimentalSettingsProps = HTMLAttributes<HTMLDivElement> & {
 	setCachedStateField: SetCachedStateField<
-		"rateLimitSeconds" | "terminalOutputLineLimit" | "maxOpenTabsContext" | "diffEnabled" | "fuzzyMatchThreshold"
+		"rateLimitSeconds" | "terminalOutputLimit" | "maxOpenTabsContext" | "diffEnabled" | "fuzzyMatchThreshold"
 	>
 	experiments: Record<ExperimentId, boolean>
 	setExperimentEnabled: SetExperimentEnabled

webview-ui/src/components/settings/SettingsView.tsx

@@ -2,8 +2,9 @@ import { forwardRef, memo, useCallback, useEffect, useImperativeHandle, useMemo,
 import { Button as VSCodeButton } from "vscrui"
 import { CheckCheck, SquareMousePointer, Webhook, GitBranch, Bell, Cog, FlaskConical } from "lucide-react"
 
-import { ExperimentId } from "../../../../src/shared/experiments"
 import { ApiConfiguration } from "../../../../src/shared/api"
+import { ExperimentId } from "../../../../src/shared/experiments"
+import { TERMINAL_OUTPUT_LIMIT } from "../../../../src/shared/terminal"
 
 import { vscode } from "@/utils/vscode"
 import { ExtensionStateContextType, useExtensionState } from "@/context/ExtensionStateContext"
@@ -77,7 +78,7 @@ const SettingsView = forwardRef<SettingsViewRef, SettingsViewProps>(({ onDone },
 		screenshotQuality,
 		soundEnabled,
 		soundVolume,
-		terminalOutputLineLimit,
+		terminalOutputLimit,
 		writeDelayMs,
 	} = cachedState
 
@@ -157,7 +158,7 @@ const SettingsView = forwardRef<SettingsViewRef, SettingsViewProps>(({ onDone },
 			vscode.postMessage({ type: "fuzzyMatchThreshold", value: fuzzyMatchThreshold ?? 1.0 })
 			vscode.postMessage({ type: "writeDelayMs", value: writeDelayMs })
 			vscode.postMessage({ type: "screenshotQuality", value: screenshotQuality ?? 75 })
-			vscode.postMessage({ type: "terminalOutputLineLimit", value: terminalOutputLineLimit ?? 500 })
+			vscode.postMessage({ type: "terminalOutputLimit", value: terminalOutputLimit ?? TERMINAL_OUTPUT_LIMIT })
 			vscode.postMessage({ type: "mcpEnabled", bool: mcpEnabled })
 			vscode.postMessage({ type: "alwaysApproveResubmit", bool: alwaysApproveResubmit })
 			vscode.postMessage({ type: "requestDelaySeconds", value: requestDelaySeconds })
@@ -379,7 +380,7 @@ const SettingsView = forwardRef<SettingsViewRef, SettingsViewProps>(({ onDone },
 				<div ref={advancedRef}>
 					<AdvancedSettings
 						rateLimitSeconds={rateLimitSeconds}
-						terminalOutputLineLimit={terminalOutputLineLimit}
+						terminalOutputLimit={terminalOutputLimit}
 						maxOpenTabsContext={maxOpenTabsContext}
 						diffEnabled={diffEnabled}
 						fuzzyMatchThreshold={fuzzyMatchThreshold}

webview-ui/src/context/ExtensionStateContext.tsx

@@ -1,15 +1,18 @@
 import React, { createContext, useCallback, useContext, useEffect, useState } from "react"
 import { useEvent } from "react-use"
+
 import { ApiConfigMeta, ExtensionMessage, ExtensionState } from "../../../src/shared/ExtensionMessage"
 import { ApiConfiguration } from "../../../src/shared/api"
-import { vscode } from "../utils/vscode"
-import { convertTextMateToHljs } from "../utils/textMateToHljs"
 import { findLastIndex } from "../../../src/shared/array"
 import { McpServer } from "../../../src/shared/mcp"
 import { checkExistKey } from "../../../src/shared/checkExistApiConfig"
 import { Mode, CustomModePrompts, defaultModeSlug, defaultPrompts, ModeConfig } from "../../../src/shared/modes"
 import { CustomSupportPrompts } from "../../../src/shared/support-prompt"
 import { experimentDefault, ExperimentId } from "../../../src/shared/experiments"
+import { TERMINAL_OUTPUT_LIMIT } from "../../../src/shared/terminal"
+
+import { vscode } from "@/utils/vscode"
+import { convertTextMateToHljs } from "@/utils/textMateToHljs"
 
 export interface ExtensionStateContextType extends ExtensionState {
 	didHydrateState: boolean
@@ -41,8 +44,8 @@ export interface ExtensionStateContextType extends ExtensionState {
 	setWriteDelayMs: (value: number) => void
 	screenshotQuality?: number
 	setScreenshotQuality: (value: number) => void
-	terminalOutputLineLimit?: number
-	setTerminalOutputLineLimit: (value: number) => void
+	terminalOutputLimit?: number
+	setTerminalOutputLimit: (value: number) => void
 	mcpEnabled: boolean
 	setMcpEnabled: (value: boolean) => void
 	enableMcpServerCreation: boolean
@@ -113,7 +116,7 @@ export const ExtensionStateContextProvider: React.FC<{ children: React.ReactNode
 		writeDelayMs: 1000,
 		browserViewportSize: "900x600",
 		screenshotQuality: 75,
-		terminalOutputLineLimit: 500,
+		terminalOutputLimit: TERMINAL_OUTPUT_LIMIT,
 		mcpEnabled: true,
 		enableMcpServerCreation: true,
 		alwaysApproveResubmit: false,
@@ -250,8 +253,7 @@ export const ExtensionStateContextProvider: React.FC<{ children: React.ReactNode
 		setPreferredLanguage: (value) => setState((prevState) => ({ ...prevState, preferredLanguage: value })),
 		setWriteDelayMs: (value) => setState((prevState) => ({ ...prevState, writeDelayMs: value })),
 		setScreenshotQuality: (value) => setState((prevState) => ({ ...prevState, screenshotQuality: value })),
-		setTerminalOutputLineLimit: (value) =>
-			setState((prevState) => ({ ...prevState, terminalOutputLineLimit: value })),
+		setTerminalOutputLimit: (value) => setState((prevState) => ({ ...prevState, terminalOutputLimit: value })),
 		setMcpEnabled: (value) => setState((prevState) => ({ ...prevState, mcpEnabled: value })),
 		setEnableMcpServerCreation: (value) =>
 			setState((prevState) => ({ ...prevState, enableMcpServerCreation: value })),