Fix stderr display corruption in TUI

package.json

@@ -34,7 +34,7 @@
 	"engines": {
 		"node": ">=20.0.0"
 	},
-	"version": "2.19.0",
+	"version": "2.19.1",
 	"dependencies": {
 		"@mariozechner/jiti": "^2.6.5",
 		"@dreb/coding-agent": "*",

packages/agent/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@dreb/agent-core",
-	"version": "2.19.0",
+	"version": "2.19.1",
 	"description": "General-purpose agent with transport abstraction, state management, and attachment support",
 	"type": "module",
 	"main": "./dist/index.js",

packages/ai/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@dreb/ai",
-	"version": "2.19.0",
+	"version": "2.19.1",
 	"description": "Unified LLM API with automatic model discovery and provider configuration",
 	"type": "module",
 	"main": "./dist/index.js",

packages/coding-agent/README.md

@@ -674,6 +674,7 @@ dreb --thinking high "Solve this complex problem"
 | `DREB_SEARXNG_URL` | Base URL for SearXNG backend (default: `http://localhost:8888`) |
 | `DREB_BRAVE_API_KEY` | API key for Brave search backend |
 | `DREB_WEB_SEARCH_RATE_LIMIT_MS` | Minimum delay between web searches in milliseconds (default: `10000`) |
+| `DREB_DEBUG` | Show debug-level messages in the TUI chat feed (default: suppressed) |
 | `VISUAL`, `EDITOR` | External editor for Ctrl+G |
 
 ---

packages/coding-agent/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@dreb/coding-agent",
-	"version": "2.19.0",
+	"version": "2.19.1",
 	"description": "Coding agent CLI with read, bash, edit, write tools and session management",
 	"type": "module",
 	"drebConfig": {

packages/coding-agent/src/cli/args.ts

@@ -5,6 +5,7 @@
 import type { ThinkingLevel } from "@dreb/agent-core";
 import chalk from "chalk";
 import { APP_NAME, CONFIG_DIR_NAME, ENV_AGENT_DIR } from "../config.js";
+import { log } from "../core/logger.js";
 import { allTools, type ToolName } from "../core/tools/index.js";
 
 export type Mode = "text" | "json" | "rpc";
@@ -109,7 +110,7 @@ export function parseArgs(args: string[], extensionFlags?: Map<string, { type: "
 				if (name in allTools) {
 					validTools.push(name as ToolName);
 				} else {
-					console.error(
+					log.warn(
 						chalk.yellow(`Warning: Unknown tool "${name}". Valid tools: ${Object.keys(allTools).join(", ")}`),
 					);
 				}
@@ -120,7 +121,7 @@ export function parseArgs(args: string[], extensionFlags?: Map<string, { type: "
 			if (isValidThinkingLevel(level)) {
 				result.thinking = level;
 			} else {
-				console.error(
+				log.warn(
 					chalk.yellow(
 						`Warning: Invalid thinking level "${level}". Valid values: ${VALID_THINKING_LEVELS.join(", ")}`,
 					),

packages/coding-agent/src/cli/file-processor.ts

@@ -6,6 +6,7 @@ import { access, readFile, stat } from "node:fs/promises";
 import type { ImageContent } from "@dreb/ai";
 import chalk from "chalk";
 import { resolve } from "path";
+import { log } from "../core/logger.js";
 import { resolveReadPath } from "../core/tools/path-utils.js";
 import { formatDimensionNote, resizeImage } from "../utils/image-resize.js";
 import { detectSupportedImageMimeTypeFromFile } from "../utils/mime.js";
@@ -35,7 +36,7 @@ export async function processFileArguments(fileArgs: string[], options?: Process
 			await access(absolutePath);
 		} catch {
 			// File does not exist — print a user-friendly error and exit
-			console.error(chalk.red(`Error: File not found: ${absolutePath}`));
+			log.error(chalk.red(`Error: File not found: ${absolutePath}`));
 			process.exit(1);
 		}
 
@@ -91,7 +92,7 @@ export async function processFileArguments(fileArgs: string[], options?: Process
 				text += `<file name="${absolutePath}">\n${content}\n</file>\n`;
 			} catch (error: unknown) {
 				const message = error instanceof Error ? error.message : String(error);
-				console.error(chalk.red(`Error: Could not read file ${absolutePath}: ${message}`));
+				log.error(chalk.red(`Error: Could not read file ${absolutePath}: ${message}`));
 				process.exit(1);
 			}
 		}

packages/coding-agent/src/core/agent-session.ts

@@ -64,6 +64,7 @@ import {
 } from "./extensions/index.js";
 import { checkScriptContent, extractScriptPaths, isForbiddenCommand } from "./forbidden-commands.js";
 import { type GitRepoState, getGitRepoState } from "./git-repo-state.js";
+import { log } from "./logger.js";
 import type { BashExecutionMessage, CustomMessage } from "./messages.js";
 import type { ModelRegistry } from "./model-registry.js";
 import { PerformanceTracker } from "./performance-tracker.js";
@@ -646,7 +647,7 @@ export class AgentSession {
 				this._emit({ type: "message_start", message });
 				this._emit({ type: "message_end", message });
 			} catch (err) {
-				console.error(
+				log.warn(
 					`[subagent] Failed to deliver cancellation message for agent ${agentId}: ${err instanceof Error ? err.message : String(err)}`,
 				);
 			}
@@ -662,13 +663,13 @@ export class AgentSession {
 			} else {
 				// Fallback: if streaming started between the isStreaming check and this call, deliver as follow-up
 				this.agent.prompt(message).catch((promptErr) => {
-					console.error(
+					log.warn(
 						`[subagent] prompt() failed for background agent ${agentId}: ${promptErr instanceof Error ? promptErr.message : String(promptErr)}`,
 					);
 					try {
 						this.agent.followUp(message);
 					} catch (followUpErr) {
-						console.error(
+						log.error(
 							`[subagent] followUp() also failed for background agent ${agentId}: ${followUpErr instanceof Error ? followUpErr.message : String(followUpErr)}. Background result lost.`,
 						);
 					}
@@ -684,7 +685,7 @@ export class AgentSession {
 				success: result.exitCode === 0,
 			});
 		} catch (emitErr) {
-			console.error(
+			log.warn(
 				`[subagent] background_agent_end emit failed: ${emitErr instanceof Error ? emitErr.message : String(emitErr)}`,
 			);
 		}
@@ -1484,7 +1485,7 @@ export class AgentSession {
 
 		const skill = this.resourceLoader.getSkills().skills.find((s) => s.name === skillName);
 		if (!skill) {
-			console.error(`Unknown skill "${skillName}" — no skill found with that name`);
+			log.warn(`Unknown skill "${skillName}" — no skill found with that name`);
 			return text;
 		}
 

packages/coding-agent/src/core/buddy/buddy-controller.ts

@@ -13,6 +13,7 @@
  * and Telegram (activity gating + reaction budget) can use different strategies.
  */
 
+import { log } from "../logger.js";
 import { type BuddyManager, checkOllama } from "./buddy-manager.js";
 import type { BuddyState } from "./buddy-types.js";
 
@@ -212,7 +213,7 @@ export class BuddyController {
 		} catch (err) {
 			if (!thinkingEnded) this.callbacks.onThinkingEnd();
 			this.removeContextEntry(marker);
-			console.error("[buddy] triggerReaction failed:", err instanceof Error ? err.message : err);
+			log.debug(`[buddy] triggerReaction failed: ${err instanceof Error ? err.message : String(err)}`);
 		}
 	}
 
@@ -247,7 +248,7 @@ export class BuddyController {
 		} catch (err) {
 			if (!thinkingEnded) this.callbacks.onThinkingEnd();
 			this.removeContextEntry(marker);
-			console.error("[buddy] handleNameCall failed:", err instanceof Error ? err.message : err);
+			log.debug(`[buddy] handleNameCall failed: ${err instanceof Error ? err.message : String(err)}`);
 		}
 	}
 

packages/coding-agent/src/core/event-bus.ts

@@ -1,4 +1,5 @@
 import { EventEmitter } from "node:events";
+import { log } from "./logger.js";
 
 export interface EventBus {
 	emit(channel: string, data: unknown): void;
@@ -20,7 +21,7 @@ export function createEventBus(): EventBusController {
 				try {
 					await handler(data);
 				} catch (err) {
-					console.error(`Event handler error (${channel}):`, err);
+					log.warn(`Event handler error (${channel}): ${err instanceof Error ? err.message : String(err)}`);
 				}
 			};
 			emitter.on(channel, safeHandler);

packages/coding-agent/src/core/logger.ts

@@ -0,0 +1,57 @@
+/**
+ * Structured logger that routes messages appropriately based on mode.
+ *
+ * In interactive TUI mode (when stderr is taken over):
+ * - debug: suppressed unless DREB_DEBUG=1
+ * - warn/error: routed through writeIntercepted with level info → displayed in TUI feed
+ *
+ * In non-interactive modes (JSON, RPC, print, or before TUI starts):
+ * - All levels write to real stderr (the diagnostic side-channel)
+ */
+
+import { isStderrTakenOver, writeIntercepted, writeRawStderr } from "./stderr-guard.js";
+
+export type LogLevel = "debug" | "warn" | "error";
+
+const isDebugEnabled = (): boolean => process.env.DREB_DEBUG === "1";
+
+export const log = {
+	/**
+	 * Debug-level message. Suppressed in interactive mode unless DREB_DEBUG=1.
+	 * Always writes to stderr in non-interactive modes.
+	 */
+	debug(message: string): void {
+		if (isStderrTakenOver()) {
+			if (isDebugEnabled()) {
+				writeIntercepted(message, "debug");
+			}
+			// Otherwise silently suppressed
+		} else {
+			writeRawStderr(`${message}\n`);
+		}
+	},
+
+	/**
+	 * Warning-level message. Always displayed to the user.
+	 * In TUI: shown in chat feed as warning. In non-interactive: written to stderr.
+	 */
+	warn(message: string): void {
+		if (isStderrTakenOver()) {
+			writeIntercepted(message, "warn");
+		} else {
+			writeRawStderr(`${message}\n`);
+		}
+	},
+
+	/**
+	 * Error-level message. Always displayed to the user.
+	 * In TUI: shown in chat feed as error. In non-interactive: written to stderr.
+	 */
+	error(message: string): void {
+		if (isStderrTakenOver()) {
+			writeIntercepted(message, "error");
+		} else {
+			writeRawStderr(`${message}\n`);
+		}
+	},
+};

packages/coding-agent/src/core/model-resolver.ts

@@ -8,6 +8,7 @@ import chalk from "chalk";
 import { minimatch } from "minimatch";
 import { isValidThinkingLevel } from "../cli/args.js";
 import { DEFAULT_THINKING_LEVEL } from "./defaults.js";
+import { log } from "./logger.js";
 import type { ModelRegistry } from "./model-registry.js";
 
 /** Default model IDs for each known provider */
@@ -483,7 +484,7 @@ export async function findInitialModel(options: {
 			modelRegistry,
 		});
 		if (resolved.error) {
-			console.error(chalk.red(resolved.error));
+			log.error(chalk.red(resolved.error));
 			process.exit(1);
 		}
 		if (resolved.model) {
@@ -559,7 +560,7 @@ export async function restoreModelFromSession(
 	const reason = !restoredModel ? "model no longer exists" : "no API key available";
 
 	if (shouldPrintMessages) {
-		console.error(chalk.yellow(`Warning: Could not restore model ${savedProvider}/${savedModelId} (${reason}).`));
+		log.warn(chalk.yellow(`Warning: Could not restore model ${savedProvider}/${savedModelId} (${reason}).`));
 	}
 
 	// If we already have a model, use it as fallback

packages/coding-agent/src/core/package-manager.ts

@@ -7,8 +7,10 @@ import ignore from "ignore";
 import { minimatch } from "minimatch";
 import { CONFIG_DIR_NAME } from "../config.js";
 import { type GitSource, parseGitUrl } from "../utils/git.js";
+import { log } from "./logger.js";
 import { isStdoutTakenOver } from "./output-guard.js";
 import type { PackageSource, SettingsManager } from "./settings-manager.js";
+import { isStderrTakenOver } from "./stderr-guard.js";
 
 const NETWORK_TIMEOUT_MS = 10000;
 const UPDATE_CHECK_CONCURRENCY = 4;
@@ -2157,13 +2159,34 @@ export class DefaultPackageManager implements PackageManager {
 
 	private runCommand(command: string, args: string[], options?: { cwd?: string }): Promise<void> {
 		return new Promise((resolvePromise, reject) => {
+			const stderrTaken = isStderrTakenOver();
+			const stdoutTaken = isStdoutTakenOver();
+			// When TUI owns the terminal, pipe stdout/stderr to avoid corrupting the display.
+			// When stdout is taken over (non-interactive pipe mode), route to fd 2 (stderr) as before.
+			// Otherwise inherit for normal terminal output.
+			const stdio: import("node:child_process").StdioOptions = stderrTaken
+				? ["ignore", "pipe", "pipe"]
+				: stdoutTaken
+					? ["ignore", 2, 2]
+					: "inherit";
 			const child = spawn(command, args, {
 				cwd: options?.cwd,
-				stdio: isStdoutTakenOver() ? ["ignore", 2, 2] : "inherit",
+				stdio,
 				shell: process.platform === "win32",
 			});
+			if (stderrTaken) {
+				child.stdout?.on("data", (chunk: Buffer) => {
+					log.debug(chunk.toString());
+				});
+				child.stderr?.on("data", (chunk: Buffer) => {
+					log.warn(chunk.toString());
+				});
+			}
 			child.on("error", reject);
-			child.on("exit", (code) => {
+			// Use "close" instead of "exit" to ensure all piped stdio data
+			// has been delivered before we resolve/reject. "exit" can fire while
+			// buffered data events are still pending in the pipe.
+			child.on("close", (code) => {
 				if (code === 0) {
 					resolvePromise();
 				} else {