Add extension mode context

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Added
+
+- Added `ctx.mode` to extension contexts so extensions can distinguish TUI, RPC, JSON, and print mode.
+
 ### Fixed
 
 - Fixed opening and listing very large JSONL session files by reading session entries line-by-line instead of materializing the full file as one string ([#5231](https://github.com/earendil-works/pi/issues/5231)).

packages/coding-agent/docs/extensions.md

@@ -860,9 +860,13 @@ All handlers receive `ctx: ExtensionContext`.
 
 UI methods for user interaction. See [Custom UI](#custom-ui) for full details.
 
+### ctx.mode
+
+Current run mode: `"tui"`, `"rpc"`, `"json"`, or `"print"`. Use `ctx.mode === "tui"` to guard terminal-only features such as `custom()`, component factories, terminal input, and direct TUI rendering.
+
 ### ctx.hasUI
 
-`false` in print mode (`-p`) and JSON mode. `true` in interactive and RPC mode. In RPC mode, dialog methods (`select`, `confirm`, `input`, `editor`) work via the extension UI sub-protocol, and fire-and-forget methods (`notify`, `setStatus`, `setWidget`, `setTitle`, `setEditorText`) emit requests to the client. Some TUI-specific methods are no-ops or return defaults (see [rpc.md](rpc.md#extension-ui-protocol)).
+`true` in TUI and RPC modes. `false` in print mode (`-p`) and JSON mode. Use this to guard dialog methods (`select`, `confirm`, `input`, `editor`) and fire-and-forget methods (`notify`, `setStatus`, `setWidget`, `setTitle`, `setEditorText`) that work in both TUI and RPC modes. In RPC mode, some TUI-specific methods are no-ops or return defaults (see [rpc.md](rpc.md#extension-ui-protocol)).
 
 ### ctx.cwd
 
@@ -2516,14 +2520,14 @@ const highlighted = highlightCode(code, lang, theme);
 
 ## Mode Behavior
 
-| Mode | UI Methods | Notes |
-|------|-----------|-------|
-| Interactive | Full TUI | Normal operation |
-| RPC (`--mode rpc`) | JSON protocol | Host handles UI, see [rpc.md](rpc.md) |
-| JSON (`--mode json`) | No-op | Event stream to stdout, see [json.md](json.md) |
-| Print (`-p`) | No-op | Extensions run but can't prompt |
+| Mode | `ctx.mode` | `ctx.hasUI` | Notes |
+|------|------------|-------------|-------|
+| Interactive | `"tui"` | `true` | Full TUI with terminal rendering |
+| RPC (`--mode rpc`) | `"rpc"` | `true` | Dialogs and notifications via JSON protocol; `custom()` returns `undefined`. See [rpc.md](rpc.md) |
+| JSON (`--mode json`) | `"json"` | `false` | Event stream to stdout; UI methods are no-ops |
+| Print (`-p`) | `"print"` | `false` | Extensions run but can't prompt |
 
-In non-interactive modes, check `ctx.hasUI` before using UI methods.
+Use `ctx.mode === "tui"` before TUI-specific features (`custom()`, component factories, terminal input). Use `ctx.hasUI` before dialog and notification methods that work in both TUI and RPC modes.
 
 ## Examples Reference
 

packages/coding-agent/docs/rpc.md

@@ -1003,7 +1003,7 @@ Some `ExtensionUIContext` methods are not supported or degraded in RPC mode beca
 - `getTheme()` returns `undefined`
 - `setTheme()` returns `{ success: false, error: "..." }`
 
-Note: `ctx.hasUI` is `true` in RPC mode because the dialog and fire-and-forget methods are functional via the extension UI sub-protocol.
+Note: `ctx.mode` is `"rpc"` and `ctx.hasUI` is `true` in RPC mode because the dialog and fire-and-forget methods are functional via the extension UI sub-protocol. Use `ctx.mode === "tui"` to guard TUI-specific features like `custom()` that require a real terminal.
 
 ### Extension UI Requests (stdout)
 

packages/coding-agent/examples/extensions/custom-header.ts

@@ -47,7 +47,7 @@ function getPiMascot(theme: Theme): string[] {
 export default function (pi: ExtensionAPI) {
 	// Set custom header immediately on load (if UI is available)
 	pi.on("session_start", async (_event, ctx) => {
-		if (ctx.hasUI) {
+		if (ctx.mode === "tui") {
 			ctx.ui.setHeader((_tui, theme) => {
 				return {
 					render(_width: number): string[] {

packages/coding-agent/examples/extensions/doom-overlay/index.ts

@@ -23,7 +23,7 @@ export default function (pi: ExtensionAPI) {
 		description: "Play DOOM as an overlay. Q to pause and exit.",
 
 		handler: async (args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("DOOM requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/handoff.ts

@@ -81,7 +81,7 @@ export default function (pi: ExtensionAPI) {
 	pi.registerCommand("handoff", {
 		description: "Transfer context to a new focused session",
 		handler: async (args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("handoff requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/interactive-shell.ts

@@ -146,7 +146,7 @@ export default function (pi: ExtensionAPI) {
 		}
 
 		// No UI available (print mode, RPC, etc.)
-		if (!ctx.hasUI) {
+		if (ctx.mode !== "tui") {
 			return {
 				result: { output: "(interactive commands require TUI)", exitCode: 1, cancelled: false, truncated: false },
 			};

packages/coding-agent/examples/extensions/qna.ts

@@ -31,7 +31,7 @@ export default function (pi: ExtensionAPI) {
 	pi.registerCommand("qna", {
 		description: "Extract questions from last assistant message into editor",
 		handler: async (_args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("qna requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/question.ts

@@ -41,7 +41,7 @@ export default function question(pi: ExtensionAPI) {
 		parameters: QuestionParams,
 
 		async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				return {
 					content: [{ type: "text", text: "Error: UI not available (running in non-interactive mode)" }],
 					details: {

packages/coding-agent/examples/extensions/questionnaire.ts

@@ -82,7 +82,7 @@ export default function questionnaire(pi: ExtensionAPI) {
 		parameters: QuestionnaireParams,
 
 		async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				return errorResult("Error: UI not available (running in non-interactive mode)");
 			}
 			if (params.questions.length === 0) {

packages/coding-agent/examples/extensions/snake.ts

@@ -311,7 +311,7 @@ export default function (pi: ExtensionAPI) {
 		description: "Play Snake!",
 
 		handler: async (_args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("Snake requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/space-invaders.ts

@@ -529,7 +529,7 @@ export default function (pi: ExtensionAPI) {
 		description: "Play Space Invaders!",
 
 		handler: async (_args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("Space Invaders requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/summarize.ts

@@ -115,7 +115,7 @@ const buildSummaryPrompt = (conversationText: string): string =>
 	].join("\n");
 
 const showSummaryUi = async (summary: string, ctx: ExtensionCommandContext) => {
-	if (!ctx.hasUI) {
+	if (ctx.mode !== "tui") {
 		return;
 	}
 

packages/coding-agent/examples/extensions/tic-tac-toe.ts

@@ -779,7 +779,7 @@ Decide the target cell first, then dump every action for the turn in one go.
 		description: "Play tic-tac-toe against the agent",
 
 		handler: async (_args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("Tic-tac-toe requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/todo.ts

@@ -284,7 +284,7 @@ export default function (pi: ExtensionAPI) {
 	pi.registerCommand("todos", {
 		description: "Show all todos on the current branch",
 		handler: async (_args, ctx) => {
-			if (!ctx.hasUI) {
+			if (ctx.mode !== "tui") {
 				ctx.ui.notify("/todos requires interactive mode", "error");
 				return;
 			}

packages/coding-agent/examples/extensions/tools.ts

@@ -67,6 +67,11 @@ export default function toolsExtension(pi: ExtensionAPI) {
 	pi.registerCommand("tools", {
 		description: "Enable/disable tools",
 		handler: async (_args, ctx) => {
+			if (ctx.mode !== "tui") {
+				ctx.ui.notify("/tools requires TUI mode", "error");
+				return;
+			}
+
 			// Refresh tool list
 			allTools = pi.getAllTools();
 

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

@@ -56,6 +56,7 @@ import {
 	type ContextUsage,
 	type ExtensionCommandContextActions,
 	type ExtensionErrorListener,
+	type ExtensionMode,
 	ExtensionRunner,
 	type ExtensionUIContext,
 	type InputSource,
@@ -187,6 +188,7 @@ export interface AgentSessionConfig {
 
 export interface ExtensionBindings {
 	uiContext?: ExtensionUIContext;
+	mode?: ExtensionMode;
 	commandContextActions?: ExtensionCommandContextActions;
 	abortHandler?: () => void;
 	shutdownHandler?: ShutdownHandler;
@@ -300,6 +302,7 @@ export class AgentSession {
 	private _baseToolsOverride?: Record<string, AgentTool>;
 	private _sessionStartEvent: SessionStartEvent;
 	private _extensionUIContext?: ExtensionUIContext;
+	private _extensionMode: ExtensionMode = "print";
 	private _extensionCommandContextActions?: ExtensionCommandContextActions;
 	private _extensionAbortHandler?: () => void;
 	private _extensionShutdownHandler?: ShutdownHandler;
@@ -2064,6 +2067,9 @@ export class AgentSession {
 		if (bindings.uiContext !== undefined) {
 			this._extensionUIContext = bindings.uiContext;
 		}
+		if (bindings.mode !== undefined) {
+			this._extensionMode = bindings.mode;
+		}
 		if (bindings.commandContextActions !== undefined) {
 			this._extensionCommandContextActions = bindings.commandContextActions;
 		}
@@ -2136,7 +2142,7 @@ export class AgentSession {
 	}
 
 	private _applyExtensionBindings(runner: ExtensionRunner): void {
-		runner.setUIContext(this._extensionUIContext);
+		runner.setUIContext(this._extensionUIContext, this._extensionMode);
 		runner.bindCommandContext(this._extensionCommandContextActions);
 
 		this._extensionErrorUnsubscriber?.();

packages/coding-agent/src/core/extensions/index.ts

@@ -66,6 +66,7 @@ export type {
 	ExtensionFactory,
 	ExtensionFlag,
 	ExtensionHandler,
+	ExtensionMode,
 	// Runtime
 	ExtensionRuntime,
 	ExtensionShortcut,

packages/coding-agent/src/core/extensions/runner.ts

@@ -28,6 +28,7 @@ import type {
 	ExtensionError,
 	ExtensionEvent,
 	ExtensionFlag,
+	ExtensionMode,
 	ExtensionRuntime,
 	ExtensionShortcut,
 	ExtensionUIContext,
@@ -225,6 +226,7 @@ export class ExtensionRunner {
 	private extensions: Extension[];
 	private runtime: ExtensionRuntime;
 	private uiContext: ExtensionUIContext;
+	private mode: ExtensionMode = "print";
 	private cwd: string;
 	private sessionManager: SessionManager;
 	private modelRegistry: ModelRegistry;
@@ -354,8 +356,9 @@ export class ExtensionRunner {
 		this.reloadHandler = async () => {};
 	}
 
-	setUIContext(uiContext?: ExtensionUIContext): void {
+	setUIContext(uiContext?: ExtensionUIContext, mode: ExtensionMode = "print"): void {
 		this.uiContext = uiContext ?? noOpUIContext;
+		this.mode = mode;
 	}
 
 	getUIContext(): ExtensionUIContext {
@@ -578,6 +581,10 @@ export class ExtensionRunner {
 				runner.assertActive();
 				return runner.uiContext;
 			},
+			get mode() {
+				runner.assertActive();
+				return runner.mode;
+			},
 			get hasUI() {
 				runner.assertActive();
 				return runner.hasUI();

packages/coding-agent/src/core/extensions/types.ts

@@ -295,10 +295,14 @@ export interface CompactOptions {
 /**
  * Context passed to extension event handlers.
  */
+export type ExtensionMode = "tui" | "rpc" | "json" | "print";
+
 export interface ExtensionContext {
 	/** UI methods for user interaction */
 	ui: ExtensionUIContext;
-	/** Whether UI is available (false in print/RPC mode) */
+	/** Current run mode. Use "tui" to guard terminal-only UI such as custom components. */
+	mode: ExtensionMode;
+	/** Whether dialog-capable UI is available (true in TUI and RPC modes) */
 	hasUI: boolean;
 	/** Current working directory */
 	cwd: string;

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

@@ -1508,6 +1508,7 @@ export class InteractiveMode {
 		const uiContext = this.createExtensionUIContext();
 		await this.session.bindExtensions({
 			uiContext,
+			mode: "tui",
 			abortHandler: () => {
 				this.restoreQueuedMessagesToEditor({ abort: true });
 			},
@@ -1654,6 +1655,7 @@ export class InteractiveMode {
 		// Create a context for shortcut handlers
 		const createContext = (): ExtensionContext => ({
 			ui: this.createExtensionUIContext(),
+			mode: "tui",
 			hasUI: true,
 			cwd: this.sessionManager.getCwd(),
 			sessionManager: this.sessionManager,

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

@@ -71,6 +71,7 @@ export async function runPrintMode(runtimeHost: AgentSessionRuntime, options: Pr
 	const rebindSession = async (): Promise<void> => {
 		session = runtimeHost.session;
 		await session.bindExtensions({
+			mode: mode === "json" ? "json" : "print",
 			commandContextActions: {
 				waitForIdle: () => session.agent.waitForIdle(),
 				newSession: async (newSessionOptions) => runtimeHost.newSession(newSessionOptions),

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

@@ -317,6 +317,7 @@ export async function runRpcMode(runtimeHost: AgentSessionRuntime): Promise<neve
 		session = runtimeHost.session;
 		await session.bindExtensions({
 			uiContext: createExtensionUIContext(),
+			mode: "rpc",
 			commandContextActions: {
 				waitForIdle: () => session.agent.waitForIdle(),
 				newSession: async (options) => runtimeHost.newSession(options),

packages/coding-agent/test/extensions-runner.test.ts

@@ -9,7 +9,12 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { AuthStorage } from "../src/core/auth-storage.ts";
 import { createExtensionRuntime, discoverAndLoadExtensions } from "../src/core/extensions/loader.ts";
 import { ExtensionRunner } from "../src/core/extensions/runner.ts";
-import type { ExtensionActions, ExtensionContextActions, ProviderConfig } from "../src/core/extensions/types.ts";
+import type {
+	ExtensionActions,
+	ExtensionContextActions,
+	ExtensionUIContext,
+	ProviderConfig,
+} from "../src/core/extensions/types.ts";
 import { KeybindingsManager, type KeyId } from "../src/core/keybindings.ts";
 import { ModelRegistry } from "../src/core/model-registry.ts";
 import { SessionManager } from "../src/core/session-manager.ts";
@@ -441,6 +446,38 @@ describe("ExtensionRunner", () => {
 			controller.abort();
 			expect(ctx.signal?.aborted).toBe(true);
 		});
+
+		it("exposes print mode and hasUI false by default", async () => {
+			const result = await discoverAndLoadExtensions([], tempDir, tempDir);
+			const runner = new ExtensionRunner(result.extensions, result.runtime, tempDir, sessionManager, modelRegistry);
+			runner.bindCore(extensionActions, extensionContextActions);
+
+			const ctx = runner.createContext();
+			expect(ctx.mode).toBe("print");
+			expect(ctx.hasUI).toBe(false);
+		});
+
+		it("exposes rpc mode with hasUI true when an RPC UI context is provided", async () => {
+			const result = await discoverAndLoadExtensions([], tempDir, tempDir);
+			const runner = new ExtensionRunner(result.extensions, result.runtime, tempDir, sessionManager, modelRegistry);
+			runner.bindCore(extensionActions, extensionContextActions);
+			runner.setUIContext({} as ExtensionUIContext, "rpc");
+
+			const ctx = runner.createContext();
+			expect(ctx.mode).toBe("rpc");
+			expect(ctx.hasUI).toBe(true);
+		});
+
+		it("exposes tui mode with hasUI true when a TUI UI context is provided", async () => {
+			const result = await discoverAndLoadExtensions([], tempDir, tempDir);
+			const runner = new ExtensionRunner(result.extensions, result.runtime, tempDir, sessionManager, modelRegistry);
+			runner.bindCore(extensionActions, extensionContextActions);
+			runner.setUIContext({} as ExtensionUIContext, "tui");
+
+			const ctx = runner.createContext();
+			expect(ctx.mode).toBe("tui");
+			expect(ctx.hasUI).toBe(true);
+		});
 	});
 
 	describe("error handling", () => {

packages/coding-agent/test/trigger-compact-extension.test.ts

@@ -4,6 +4,7 @@ import type { ExtensionAPI, ExtensionCommandContext, ExtensionContext } from "..
 
 function createContext(tokens: number | null, compact = vi.fn()): ExtensionContext {
 	return {
+		mode: "print",
 		hasUI: false,
 		ui: {} as ExtensionContext["ui"],
 		cwd: process.cwd(),