feat: add /thinking slash command for toggling thinking level (#129)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/pi-coding-agent/src/core/slash-commands.ts

@@ -34,5 +34,6 @@ export const BUILTIN_SLASH_COMMANDS: ReadonlyArray<BuiltinSlashCommand> = [
 	{ name: "compact", description: "Manually compact the session context" },
 	{ name: "resume", description: "Resume a different session" },
 	{ name: "reload", description: "Reload extensions, skills, prompts, and themes" },
+	{ name: "thinking", description: "Set thinking level (off/minimal/low/medium/high/xhigh)" },
 	{ name: "quit", description: "Quit pi" },
 ];

packages/pi-coding-agent/src/modes/interactive/components/settings-selector.ts

@@ -13,7 +13,7 @@ import {
 import { getSelectListTheme, getSettingsListTheme, theme } from "../theme/theme.js";
 import { DynamicBorder } from "./dynamic-border.js";
 
-const THINKING_DESCRIPTIONS: Record<ThinkingLevel, string> = {
+export const THINKING_DESCRIPTIONS: Record<ThinkingLevel, string> = {
 	off: "No reasoning",
 	minimal: "Very brief reasoning (~1k tokens)",
 	low: "Light reasoning (~2k tokens)",
@@ -73,7 +73,7 @@ export interface SettingsCallbacks {
 /**
  * A submenu component for selecting from a list of options.
  */
-class SelectSubmenu extends Container {
+export class SelectSubmenu extends Container {
 	private selectList: SelectList;
 
 	constructor(

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

@@ -7,7 +7,7 @@ import * as crypto from "node:crypto";
 import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
-import type { AgentMessage } from "@gsd/pi-agent-core";
+import type { AgentMessage, ThinkingLevel } from "@gsd/pi-agent-core";
 import type { AssistantMessage, ImageContent, Message, Model, OAuthProviderId } from "@gsd/pi-ai";
 import type {
 	AutocompleteItem,
@@ -85,7 +85,7 @@ import { ModelSelectorComponent } from "./components/model-selector.js";
 import { OAuthSelectorComponent } from "./components/oauth-selector.js";
 import { ScopedModelsSelectorComponent } from "./components/scoped-models-selector.js";
 import { SessionSelectorComponent } from "./components/session-selector.js";
-import { SettingsSelectorComponent } from "./components/settings-selector.js";
+import { SelectSubmenu, SettingsSelectorComponent, THINKING_DESCRIPTIONS } from "./components/settings-selector.js";
 import { SkillInvocationMessageComponent } from "./components/skill-invocation-message.js";
 import { ToolExecutionComponent } from "./components/tool-execution.js";
 import { TreeSelectorComponent } from "./components/tree-selector.js";
@@ -2015,6 +2015,12 @@ export class InteractiveMode {
 				await this.handleReloadCommand();
 				return;
 			}
+			if (text === "/thinking" || text.startsWith("/thinking ")) {
+				const arg = text.startsWith("/thinking ") ? text.slice(10).trim() : undefined;
+				this.editor.setText("");
+				this.handleThinkingCommand(arg);
+				return;
+			}
 			if (text === "/debug") {
 				this.handleDebugCommand();
 				this.editor.setText("");
@@ -2745,6 +2751,56 @@ export class InteractiveMode {
 		}
 	}
 
+	private handleThinkingCommand(arg?: string): void {
+		const availableLevels = this.session.getAvailableThinkingLevels();
+		if (availableLevels.length === 0) {
+			this.showStatus("Current model does not support thinking");
+			return;
+		}
+
+		if (arg) {
+			const level = arg.toLowerCase() as ThinkingLevel;
+			if (!availableLevels.includes(level)) {
+				this.showStatus(`Invalid thinking level "${arg}". Available: ${availableLevels.join(", ")}`);
+				return;
+			}
+			this.session.setThinkingLevel(level);
+			this.footer.invalidate();
+			this.updateEditorBorderColor();
+			this.showStatus(`Thinking level: ${level}`);
+			return;
+		}
+
+		this.showThinkingSelector();
+	}
+
+	private showThinkingSelector(): void {
+		const availableLevels = this.session.getAvailableThinkingLevels();
+		this.showSelector((done) => {
+			const selector = new SelectSubmenu(
+				"Thinking Level",
+				"Select reasoning depth for thinking-capable models",
+				availableLevels.map((level) => ({
+					value: level,
+					label: level,
+					description: THINKING_DESCRIPTIONS[level],
+				})),
+				this.session.thinkingLevel,
+				(value) => {
+					this.session.setThinkingLevel(value as ThinkingLevel);
+					this.footer.invalidate();
+					this.updateEditorBorderColor();
+					done();
+					this.showStatus(`Thinking level: ${value}`);
+				},
+				() => {
+					done();
+				},
+			);
+			return { component: selector, focus: selector };
+		});
+	}
+
 	private async cycleModel(direction: "forward" | "backward"): Promise<void> {
 		try {
 			const result = await this.session.cycleModel(direction);