feat(coding-agent): add user_bash event and theme API extensions

- user_bash event for intercepting ! and !! commands (#528)
- Extensions can return { operations } or { result } to redirect/replace
- executeBashWithOperations() for custom BashOperations execution
- session.recordBashResult() for extensions handling bash themselves
- Theme API: getAllThemes(), getTheme(), setTheme() on ctx.ui
- mac-system-theme.ts example: sync with macOS dark/light mode
- Updated ssh.ts to use user_bash event

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

@@ -103,6 +103,9 @@ export type {
 	TreePreparation,
 	TurnEndEvent,
 	TurnStartEvent,
+	// Events - User Bash
+	UserBashEvent,
+	UserBashEventResult,
 	WriteToolResultEvent,
 } from "./types.js";
 // Type guards

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

@@ -5,7 +5,7 @@
 import type { AgentMessage } from "@mariozechner/pi-agent-core";
 import type { ImageContent, Model } from "@mariozechner/pi-ai";
 import type { KeyId } from "@mariozechner/pi-tui";
-import { theme } from "../../modes/interactive/theme/theme.js";
+import { type Theme, theme } from "../../modes/interactive/theme/theme.js";
 import type { ModelRegistry } from "../model-registry.js";
 import type { SessionManager } from "../session-manager.js";
 import type {
@@ -33,6 +33,8 @@ import type {
 	ToolCallEvent,
 	ToolCallEventResult,
 	ToolResultEventResult,
+	UserBashEvent,
+	UserBashEventResult,
 } from "./types.js";
 
 /** Combined result from all before_agent_start handlers */
@@ -89,6 +91,9 @@ const noOpUIContext: ExtensionUIContext = {
 	get theme() {
 		return theme;
 	},
+	getAllThemes: () => [],
+	getTheme: () => undefined,
+	setTheme: (_theme: string | Theme) => ({ success: false, error: "UI not available" }),
 };
 
 export class ExtensionRunner {
@@ -399,6 +404,35 @@ export class ExtensionRunner {
 		return result;
 	}
 
+	async emitUserBash(event: UserBashEvent): Promise<UserBashEventResult | undefined> {
+		const ctx = this.createContext();
+
+		for (const ext of this.extensions) {
+			const handlers = ext.handlers.get("user_bash");
+			if (!handlers || handlers.length === 0) continue;
+
+			for (const handler of handlers) {
+				try {
+					const handlerResult = await handler(event, ctx);
+					if (handlerResult) {
+						return handlerResult as UserBashEventResult;
+					}
+				} catch (err) {
+					const message = err instanceof Error ? err.message : String(err);
+					const stack = err instanceof Error ? err.stack : undefined;
+					this.emitError({
+						extensionPath: ext.path,
+						event: "user_bash",
+						error: message,
+						stack,
+					});
+				}
+			}
+		}
+
+		return undefined;
+	}
+
 	async emitContext(messages: AgentMessage[]): Promise<AgentMessage[]> {
 		const ctx = this.createContext();
 		let currentMessages = structuredClone(messages);

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

@@ -18,6 +18,7 @@ import type { ImageContent, Model, TextContent, ToolResultMessage } from "@mario
 import type { Component, EditorComponent, EditorTheme, KeyId, TUI } from "@mariozechner/pi-tui";
 import type { Static, TSchema } from "@sinclair/typebox";
 import type { Theme } from "../../modes/interactive/theme/theme.js";
+import type { BashResult } from "../bash-executor.js";
 import type { CompactionPreparation, CompactionResult } from "../compaction/index.js";
 import type { EventBus } from "../event-bus.js";
 import type { ExecOptions, ExecResult } from "../exec.js";
@@ -31,6 +32,7 @@ import type {
 	SessionEntry,
 	SessionManager,
 } from "../session-manager.js";
+import type { BashOperations } from "../tools/bash.js";
 import type { EditToolDetails } from "../tools/edit.js";
 import type {
 	BashToolDetails,
@@ -147,6 +149,15 @@ export interface ExtensionUIContext {
 
 	/** Get the current theme for styling. */
 	readonly theme: Theme;
+
+	/** Get all available themes with their names and file paths. */
+	getAllThemes(): { name: string; path: string | undefined }[];
+
+	/** Load a theme by name without switching to it. Returns undefined if not found. */
+	getTheme(name: string): Theme | undefined;
+
+	/** Set the current theme by name or Theme object. */
+	setTheme(theme: string | Theme): { success: boolean; error?: string };
 }
 
 // ============================================================================
@@ -378,6 +389,21 @@ export interface TurnEndEvent {
 	toolResults: ToolResultMessage[];
 }
 
+// ============================================================================
+// User Bash Events
+// ============================================================================
+
+/** Fired when user executes a bash command via ! or !! prefix */
+export interface UserBashEvent {
+	type: "user_bash";
+	/** The command to execute */
+	command: string;
+	/** True if !! prefix was used (excluded from LLM context) */
+	excludeFromContext: boolean;
+	/** Current working directory */
+	cwd: string;
+}
+
 // ============================================================================
 // Tool Events
 // ============================================================================
@@ -481,6 +507,7 @@ export type ExtensionEvent =
 	| AgentEndEvent
 	| TurnStartEvent
 	| TurnEndEvent
+	| UserBashEvent
 	| ToolCallEvent
 	| ToolResultEvent;
 
@@ -497,6 +524,14 @@ export interface ToolCallEventResult {
 	reason?: string;
 }
 
+/** Result from user_bash event handler */
+export interface UserBashEventResult {
+	/** Custom operations to use for execution */
+	operations?: BashOperations;
+	/** Full replacement: extension handled execution, use this result */
+	result?: BashResult;
+}
+
 export interface ToolResultEventResult {
 	content?: (TextContent | ImageContent)[];
 	details?: unknown;
@@ -598,6 +633,7 @@ export interface ExtensionAPI {
 	on(event: "turn_end", handler: ExtensionHandler<TurnEndEvent>): void;
 	on(event: "tool_call", handler: ExtensionHandler<ToolCallEvent, ToolCallEventResult>): void;
 	on(event: "tool_result", handler: ExtensionHandler<ToolResultEvent, ToolResultEventResult>): void;
+	on(event: "user_bash", handler: ExtensionHandler<UserBashEvent, UserBashEventResult>): void;
 
 	// =========================================================================
 	// Tool Registration