fix(tui): deferred command output during streaming

- Queued transcript command panels until the active agent turn ends.

- Added regression coverage for slash-command output mounting exactly once.

Fixes #4806

packages/coding-agent/CHANGELOG.md

@@ -6,6 +6,10 @@
 
 - Memoized non-message token totals (system prompt, tool schemas, skills) so the per-turn compaction and context-threshold paths recompute them at most once per input change instead of on every call. `getContextBreakdown` and `#estimateStoredContextTokens` previously re-tokenized the system prompt and every tool's wire schema (per-tool `JSON.stringify`) several times per turn over inputs that change at most once per turn.
 
+### Fixed
+
+- Fixed `/mcp`, `/mcp list`, and `/tools` output duplicating in terminal scrollback when invoked during agent streaming by deferring command panels until the active turn ends ([#4806](https://github.com/can1357/oh-my-pi/issues/4806)).
+
 ## [16.3.11] - 2026-07-06
 
 ### Changed

packages/coding-agent/src/modes/controllers/command-controller-shared.ts

@@ -105,5 +105,5 @@ export function showCommandMessage(ctx: InteractiveModeContext, text: string): v
 	block.addChild(new DynamicBorder());
 	block.addChild(new Text(text, 1, 1));
 	block.addChild(new DynamicBorder());
-	ctx.present(block);
+	ctx.presentCommandOutput(block);
 }

packages/coding-agent/src/modes/controllers/command-controller.ts

@@ -59,7 +59,7 @@ function showMarkdownPanel(ctx: InteractiveModeContext, title: string, markdown:
 	block.addChild(new Spacer(1));
 	block.addChild(new Markdown(markdown.trim(), 1, 1, getMarkdownTheme()));
 	block.addChild(new DynamicBorder());
-	ctx.present(block);
+	ctx.presentCommandOutput(block);
 }
 
 export class CommandController {

packages/coding-agent/src/modes/controllers/event-controller.ts

@@ -1116,6 +1116,7 @@ export class EventController {
 		// final history — seal it instead of letting its spinner tick while idle.
 		this.#resolveDisplaceablePoll();
 		this.#resolveDisplaceableTodo();
+		this.ctx.flushPendingCommandOutput();
 		this.#lastAssistantComponent = undefined;
 		this.ctx.ui.requestRender();
 		this.#scheduleIdleCompaction();

packages/coding-agent/src/modes/interactive-mode.ts

@@ -515,6 +515,7 @@ export class InteractiveMode implements InteractiveModeContext {
 	collabHost?: CollabHost;
 	collabGuest?: CollabGuestLink;
 
+	#pendingCommandOutput: Component[] = [];
 	#pendingSlashCommands: SlashCommand[] = [];
 	#cleanupUnsubscribe?: () => void;
 	#signalTeardown?: SessionTeardown;
@@ -3490,6 +3491,24 @@ export class InteractiveMode implements InteractiveModeContext {
 		this.ui.requestRender();
 	}
 
+	/** Defer transcript command panels until the active turn can no longer grow above them. */
+	presentCommandOutput(content: Component | readonly Component[]): void {
+		if (!this.session.isStreaming) {
+			this.present(content);
+			return;
+		}
+		const items = Array.isArray(content) ? content : [content as Component];
+		this.#pendingCommandOutput.push(...items);
+	}
+
+	/** Mount every command panel queued while the agent was streaming. */
+	flushPendingCommandOutput(): void {
+		if (this.#pendingCommandOutput.length === 0) return;
+		const pending = this.#pendingCommandOutput;
+		this.#pendingCommandOutput = [];
+		this.present(pending);
+	}
+
 	#mountChatChild(item: Component): void {
 		this.chatContainer.addChild(item);
 		if (item instanceof ChatBlock) item.mount(this.#chatHost);

packages/coding-agent/src/modes/types.ts

@@ -231,6 +231,14 @@ export interface InteractiveModeContext {
 	 * runs) so their timers/subscriptions start.
 	 */
 	present(content: Component | readonly Component[]): void;
+	/**
+	 * Mount command output immediately while idle, or defer it until the active
+	 * agent turn ends so a growing live block cannot push duplicate rows into
+	 * native scrollback.
+	 */
+	presentCommandOutput(content: Component | readonly Component[]): void;
+	/** Mount command output deferred by {@link presentCommandOutput}. */
+	flushPendingCommandOutput(): void;
 	/**
 	 * Dispose every live block in the transcript (stopping timers/subscriptions)
 	 * and clear it. Used before a full rebuild so animated/streaming blocks do not

packages/coding-agent/test/issue-4806-command-output.test.ts

@@ -0,0 +1,81 @@
+import { afterEach, beforeAll, beforeEach, describe, expect, it, vi } from "bun:test";
+import * as path from "node:path";
+import { Agent } from "@oh-my-pi/pi-agent-core";
+import { ModelRegistry } from "@oh-my-pi/pi-coding-agent/config/model-registry";
+import { resetSettingsForTest, Settings } from "@oh-my-pi/pi-coding-agent/config/settings";
+import { InteractiveMode } from "@oh-my-pi/pi-coding-agent/modes/interactive-mode";
+import { initTheme } from "@oh-my-pi/pi-coding-agent/modes/theme/theme";
+import type { AgentSessionEvent } from "@oh-my-pi/pi-coding-agent/session/agent-session";
+import { AgentSession } from "@oh-my-pi/pi-coding-agent/session/agent-session";
+import { AuthStorage } from "@oh-my-pi/pi-coding-agent/session/auth-storage";
+import { HistoryStorage } from "@oh-my-pi/pi-coding-agent/session/history-storage";
+import { SessionManager } from "@oh-my-pi/pi-coding-agent/session/session-manager";
+import { Text } from "@oh-my-pi/pi-tui";
+import { TempDir } from "@oh-my-pi/pi-utils";
+
+describe("issue #4806 command output during streaming", () => {
+	let authStorage: AuthStorage;
+	let mode: InteractiveMode;
+	let session: AgentSession;
+	let streaming = true;
+	let tempDir: TempDir;
+
+	beforeAll(() => {
+		initTheme();
+	});
+
+	beforeEach(async () => {
+		vi.spyOn(process.stdout, "write").mockReturnValue(true);
+		vi.spyOn(process.stdin, "resume").mockReturnValue(process.stdin);
+		vi.spyOn(process.stdin, "pause").mockReturnValue(process.stdin);
+		vi.spyOn(process.stdin, "setEncoding").mockReturnValue(process.stdin);
+		if (typeof process.stdin.setRawMode === "function") {
+			vi.spyOn(process.stdin, "setRawMode").mockReturnValue(process.stdin);
+		}
+
+		resetSettingsForTest();
+		tempDir = TempDir.createSync("@pi-issue-4806-");
+		await Settings.init({ inMemory: true, cwd: tempDir.path() });
+		authStorage = await AuthStorage.create(path.join(tempDir.path(), "testauth.db"));
+		const modelRegistry = new ModelRegistry(authStorage);
+		const model = modelRegistry.find("anthropic", "claude-sonnet-4-5");
+		if (!model) throw new Error("Expected claude-sonnet-4-5 test model");
+		session = new AgentSession({
+			agent: new Agent({ initialState: { model, systemPrompt: ["Test"], tools: [], messages: [] } }),
+			sessionManager: SessionManager.create(tempDir.path(), tempDir.path()),
+			settings: Settings.isolated(),
+			modelRegistry,
+		});
+		streaming = true;
+		Object.defineProperty(session, "isStreaming", { configurable: true, get: () => streaming });
+		mode = new InteractiveMode(session, "test");
+		mode.isInitialized = true;
+		mode.ui.requestRender = vi.fn();
+	});
+
+	afterEach(async () => {
+		mode?.stop();
+		HistoryStorage.resetInstance();
+		vi.restoreAllMocks();
+		await session?.dispose();
+		authStorage?.close();
+		tempDir?.removeSync();
+		resetSettingsForTest();
+	});
+
+	it("mounts slash-command output once after the active turn ends", async () => {
+		const streamedReply = new Text("agent is streaming", 0, 0);
+		mode.chatContainer.addChild(streamedReply);
+
+		mode.handleToolsCommand();
+
+		expect(mode.chatContainer.children).toEqual([streamedReply]);
+
+		streaming = false;
+		await mode.eventController.handleEvent({ type: "agent_end", messages: [] } as AgentSessionEvent);
+
+		expect(mode.chatContainer.children).toHaveLength(2);
+		const transcript = mode.chatContainer.render(80).join("\n");
+		expect(transcript.match(/Available Tools/g)).toHaveLength(1);
+	});
+});

packages/coding-agent/test/issue-956-repro.test.ts

@@ -84,6 +84,10 @@ describe("issue #956: interactive /mcp test", () => {
 				for (const item of Array.isArray(content) ? content : [content]) addChild(item);
 				requestRender();
 			},
+			presentCommandOutput: (content: unknown) => {
+				for (const item of Array.isArray(content) ? content : [content]) addChild(item);
+				requestRender();
+			},
 			ui: { requestRender },
 			editor: {},
 			showError,

packages/coding-agent/test/mcp-command-reauth.test.ts

@@ -59,6 +59,7 @@ function createController(authStorage: AuthStorage, mcpManagerOverrides: Record<
 	const controller = new MCPCommandController({
 		chatContainer: { addChild: vi.fn() },
 		present,
+		presentCommandOutput: present,
 		ui: { requestRender: vi.fn() },
 		editor,
 		showError,

packages/coding-agent/test/mcp-command-toggle.test.ts

@@ -53,6 +53,7 @@ function createController() {
 	const controller = new MCPCommandController({
 		chatContainer: { addChild: vi.fn() },
 		present: vi.fn(),
+		presentCommandOutput: vi.fn(),
 		ui: { requestRender: vi.fn() },
 		editor: {},
 		showError: vi.fn(),