Refactor agent architecture and add session storage

Major architectural improvements:
- Renamed AgentSession → Agent (state/ → agent/)
- Removed id field from AgentState
- Fixed transport abstraction to pass messages directly instead of using callbacks
- Eliminated circular dependencies in transport creation

Transport changes:
- Changed signature: run(messages, userMessage, config, signal)
- Removed getMessages callback from ProviderTransport and AppTransport
- Transports now filter attachments internally

Session storage:
- Added SessionRepository with IndexedDB backend
- Auto-save sessions after first exchange
- Auto-generate titles from first user message
- Session list dialog with search and delete
- Persistent storage permission dialog
- Browser extension now auto-loads last session

UI improvements:
- ChatPanel creates single AgentInterface instance in setAgent()
- Added drag & drop file upload to MessageEditor
- Fixed artifacts panel auto-opening on session load
- Added "Drop files here" i18n strings
- Changed "Continue Without Saving" → "Continue Anyway"

Web example:
- Complete rewrite of main.ts with clean architecture
- Added check script to package.json
- Session management with URL state
- Editable session titles

Browser extension:
- Added full session storage support
- History and new session buttons
- Auto-load most recent session on open
- Session titles in header

packages/web-ui/src/agent/transports/AppTransport.ts

@@ -0,0 +1,370 @@
+import type {
+	AgentContext,
+	Api,
+	AssistantMessage,
+	AssistantMessageEvent,
+	Context,
+	Message,
+	Model,
+	PromptConfig,
+	SimpleStreamOptions,
+	ToolCall,
+	UserMessage,
+} from "@mariozechner/pi-ai";
+import { agentLoop } from "@mariozechner/pi-ai";
+import { AssistantMessageEventStream } from "@mariozechner/pi-ai/dist/utils/event-stream.js";
+import { parseStreamingJson } from "@mariozechner/pi-ai/dist/utils/json-parse.js";
+import { clearAuthToken, getAuthToken } from "../../utils/auth-token.js";
+import { i18n } from "../../utils/i18n.js";
+import type { ProxyAssistantMessageEvent } from "./proxy-types.js";
+import type { AgentRunConfig, AgentTransport } from "./types.js";
+
+/**
+ * Stream function that proxies through a server instead of calling providers directly.
+ * The server strips the partial field from delta events to reduce bandwidth.
+ * We reconstruct the partial message client-side.
+ */
+function streamSimpleProxy(
+	model: Model<any>,
+	context: Context,
+	options: SimpleStreamOptions & { authToken: string },
+	proxyUrl: string,
+): AssistantMessageEventStream {
+	const stream = new AssistantMessageEventStream();
+
+	(async () => {
+		// Initialize the partial message that we'll build up from events
+		const partial: AssistantMessage = {
+			role: "assistant",
+			stopReason: "stop",
+			content: [],
+			api: model.api,
+			provider: model.provider,
+			model: model.id,
+			usage: {
+				input: 0,
+				output: 0,
+				cacheRead: 0,
+				cacheWrite: 0,
+				cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+			},
+		};
+
+		let reader: ReadableStreamDefaultReader<Uint8Array> | undefined;
+
+		// Set up abort handler to cancel the reader
+		const abortHandler = () => {
+			if (reader) {
+				reader.cancel("Request aborted by user").catch(() => {});
+			}
+		};
+
+		if (options.signal) {
+			options.signal.addEventListener("abort", abortHandler);
+		}
+
+		try {
+			const response = await fetch(`${proxyUrl}/api/stream`, {
+				method: "POST",
+				headers: {
+					Authorization: `Bearer ${options.authToken}`,
+					"Content-Type": "application/json",
+				},
+				body: JSON.stringify({
+					model,
+					context,
+					options: {
+						temperature: options.temperature,
+						maxTokens: options.maxTokens,
+						reasoning: options.reasoning,
+						// Don't send apiKey or signal - those are added server-side
+					},
+				}),
+				signal: options.signal,
+			});
+
+			if (!response.ok) {
+				let errorMessage = `Proxy error: ${response.status} ${response.statusText}`;
+				try {
+					const errorData = await response.json();
+					if (errorData.error) {
+						errorMessage = `Proxy error: ${errorData.error}`;
+					}
+				} catch {
+					// Couldn't parse error response, use default message
+				}
+				throw new Error(errorMessage);
+			}
+
+			// Parse SSE stream
+			reader = response.body!.getReader();
+			const decoder = new TextDecoder();
+			let buffer = "";
+
+			while (true) {
+				const { done, value } = await reader.read();
+				if (done) break;
+
+				// Check if aborted after reading
+				if (options.signal?.aborted) {
+					throw new Error("Request aborted by user");
+				}
+
+				buffer += decoder.decode(value, { stream: true });
+				const lines = buffer.split("\n");
+				buffer = lines.pop() || "";
+
+				for (const line of lines) {
+					if (line.startsWith("data: ")) {
+						const data = line.slice(6).trim();
+						if (data) {
+							const proxyEvent = JSON.parse(data) as ProxyAssistantMessageEvent;
+							let event: AssistantMessageEvent | undefined;
+
+							// Handle different event types
+							// Server sends events with partial for non-delta events,
+							// and without partial for delta events
+							switch (proxyEvent.type) {
+								case "start":
+									event = { type: "start", partial };
+									break;
+
+								case "text_start":
+									partial.content[proxyEvent.contentIndex] = {
+										type: "text",
+										text: "",
+									};
+									event = { type: "text_start", contentIndex: proxyEvent.contentIndex, partial };
+									break;
+
+								case "text_delta": {
+									const content = partial.content[proxyEvent.contentIndex];
+									if (content?.type === "text") {
+										content.text += proxyEvent.delta;
+										event = {
+											type: "text_delta",
+											contentIndex: proxyEvent.contentIndex,
+											delta: proxyEvent.delta,
+											partial,
+										};
+									} else {
+										throw new Error("Received text_delta for non-text content");
+									}
+									break;
+								}
+								case "text_end": {
+									const content = partial.content[proxyEvent.contentIndex];
+									if (content?.type === "text") {
+										content.textSignature = proxyEvent.contentSignature;
+										event = {
+											type: "text_end",
+											contentIndex: proxyEvent.contentIndex,
+											content: content.text,
+											partial,
+										};
+									} else {
+										throw new Error("Received text_end for non-text content");
+									}
+									break;
+								}
+
+								case "thinking_start":
+									partial.content[proxyEvent.contentIndex] = {
+										type: "thinking",
+										thinking: "",
+									};
+									event = { type: "thinking_start", contentIndex: proxyEvent.contentIndex, partial };
+									break;
+
+								case "thinking_delta": {
+									const content = partial.content[proxyEvent.contentIndex];
+									if (content?.type === "thinking") {
+										content.thinking += proxyEvent.delta;
+										event = {
+											type: "thinking_delta",
+											contentIndex: proxyEvent.contentIndex,
+											delta: proxyEvent.delta,
+											partial,
+										};
+									} else {
+										throw new Error("Received thinking_delta for non-thinking content");
+									}
+									break;
+								}
+
+								case "thinking_end": {
+									const content = partial.content[proxyEvent.contentIndex];
+									if (content?.type === "thinking") {
+										content.thinkingSignature = proxyEvent.contentSignature;
+										event = {
+											type: "thinking_end",
+											contentIndex: proxyEvent.contentIndex,
+											content: content.thinking,
+											partial,
+										};
+									} else {
+										throw new Error("Received thinking_end for non-thinking content");
+									}
+									break;
+								}
+
+								case "toolcall_start":
+									partial.content[proxyEvent.contentIndex] = {
+										type: "toolCall",
+										id: proxyEvent.id,
+										name: proxyEvent.toolName,
+										arguments: {},
+										partialJson: "",
+									} satisfies ToolCall & { partialJson: string } as ToolCall;
+									event = { type: "toolcall_start", contentIndex: proxyEvent.contentIndex, partial };
+									break;
+
+								case "toolcall_delta": {
+									const content = partial.content[proxyEvent.contentIndex];
+									if (content?.type === "toolCall") {
+										(content as any).partialJson += proxyEvent.delta;
+										content.arguments = parseStreamingJson((content as any).partialJson) || {};
+										event = {
+											type: "toolcall_delta",
+											contentIndex: proxyEvent.contentIndex,
+											delta: proxyEvent.delta,
+											partial,
+										};
+										partial.content[proxyEvent.contentIndex] = { ...content }; // Trigger reactivity
+									} else {
+										throw new Error("Received toolcall_delta for non-toolCall content");
+									}
+									break;
+								}
+
+								case "toolcall_end": {
+									const content = partial.content[proxyEvent.contentIndex];
+									if (content?.type === "toolCall") {
+										delete (content as any).partialJson;
+										event = {
+											type: "toolcall_end",
+											contentIndex: proxyEvent.contentIndex,
+											toolCall: content,
+											partial,
+										};
+									}
+									break;
+								}
+
+								case "done":
+									partial.stopReason = proxyEvent.reason;
+									partial.usage = proxyEvent.usage;
+									event = { type: "done", reason: proxyEvent.reason, message: partial };
+									break;
+
+								case "error":
+									partial.stopReason = proxyEvent.reason;
+									partial.errorMessage = proxyEvent.errorMessage;
+									partial.usage = proxyEvent.usage;
+									event = { type: "error", reason: proxyEvent.reason, error: partial };
+									break;
+
+								default: {
+									// Exhaustive check
+									const _exhaustiveCheck: never = proxyEvent;
+									console.warn(`Unhandled event type: ${(proxyEvent as any).type}`);
+									break;
+								}
+							}
+
+							// Push the event to stream
+							if (event) {
+								stream.push(event);
+							} else {
+								throw new Error("Failed to create event from proxy event");
+							}
+						}
+					}
+				}
+			}
+
+			// Check if aborted after reading
+			if (options.signal?.aborted) {
+				throw new Error("Request aborted by user");
+			}
+
+			stream.end();
+		} catch (error) {
+			const errorMessage = error instanceof Error ? error.message : String(error);
+			if (errorMessage.toLowerCase().includes("proxy") && errorMessage.includes("Unauthorized")) {
+				clearAuthToken();
+			}
+			partial.stopReason = options.signal?.aborted ? "aborted" : "error";
+			partial.errorMessage = errorMessage;
+			stream.push({
+				type: "error",
+				reason: partial.stopReason,
+				error: partial,
+			} satisfies AssistantMessageEvent);
+			stream.end();
+		} finally {
+			// Clean up abort handler
+			if (options.signal) {
+				options.signal.removeEventListener("abort", abortHandler);
+			}
+		}
+	})();
+
+	return stream;
+}
+
+// Proxy transport executes the turn using a remote proxy server
+/**
+ * Transport that uses an app server with user authentication tokens.
+ * The server manages user accounts and proxies requests to LLM providers.
+ */
+export class AppTransport implements AgentTransport {
+	// Hardcoded proxy URL for now - will be made configurable later
+	private readonly proxyUrl = "https://genai.mariozechner.at";
+
+	async *run(messages: Message[], userMessage: Message, cfg: AgentRunConfig, signal?: AbortSignal) {
+		const authToken = await getAuthToken();
+		if (!authToken) {
+			throw new Error(i18n("Auth token is required for proxy transport"));
+		}
+
+		// Use proxy - no local API key needed
+		const streamFn = <TApi extends Api>(model: Model<TApi>, context: Context, options?: SimpleStreamOptions) => {
+			return streamSimpleProxy(
+				model,
+				context,
+				{
+					...options,
+					authToken,
+				},
+				this.proxyUrl,
+			);
+		};
+
+		// Filter out attachments from messages
+		const filteredMessages = messages.map((m) => {
+			if (m.role === "user") {
+				const { attachments, ...rest } = m as any;
+				return rest;
+			}
+			return m;
+		});
+
+		const context: AgentContext = {
+			systemPrompt: cfg.systemPrompt,
+			messages: filteredMessages,
+			tools: cfg.tools,
+		};
+
+		const pc: PromptConfig = {
+			model: cfg.model,
+			reasoning: cfg.reasoning,
+		};
+
+		// Yield events from the upstream agentLoop iterator
+		// Pass streamFn as the 5th parameter to use proxy
+		for await (const ev of agentLoop(userMessage as unknown as UserMessage, context, pc, signal, streamFn as any)) {
+			yield ev;
+		}
+	}
+}

packages/web-ui/src/agent/transports/ProviderTransport.ts

@@ -0,0 +1,56 @@
+import { type AgentContext, agentLoop, type Message, type PromptConfig, type UserMessage } from "@mariozechner/pi-ai";
+import { getAppStorage } from "../../storage/app-storage.js";
+import type { AgentRunConfig, AgentTransport } from "./types.js";
+
+/**
+ * Transport that calls LLM providers directly.
+ * Optionally routes calls through a CORS proxy if enabled in settings.
+ */
+export class ProviderTransport implements AgentTransport {
+	async *run(messages: Message[], userMessage: Message, cfg: AgentRunConfig, signal?: AbortSignal) {
+		// Get API key from storage
+		const apiKey = await getAppStorage().providerKeys.getKey(cfg.model.provider);
+		if (!apiKey) {
+			throw new Error("no-api-key");
+		}
+
+		// Check if CORS proxy is enabled
+		const proxyEnabled = await getAppStorage().settings.get<boolean>("proxy.enabled");
+		const proxyUrl = await getAppStorage().settings.get<string>("proxy.url");
+
+		// Clone model and modify baseUrl if proxy is enabled
+		let model = cfg.model;
+		if (proxyEnabled && proxyUrl && cfg.model.baseUrl) {
+			model = {
+				...cfg.model,
+				baseUrl: `${proxyUrl}/?url=${encodeURIComponent(cfg.model.baseUrl)}`,
+			};
+		}
+
+		// Filter out attachments from messages
+		const filteredMessages = messages.map((m) => {
+			if (m.role === "user") {
+				const { attachments, ...rest } = m as any;
+				return rest;
+			}
+			return m;
+		});
+
+		const context: AgentContext = {
+			systemPrompt: cfg.systemPrompt,
+			messages: filteredMessages,
+			tools: cfg.tools,
+		};
+
+		const pc: PromptConfig = {
+			model,
+			reasoning: cfg.reasoning,
+			apiKey,
+		};
+
+		// Yield events from agentLoop
+		for await (const ev of agentLoop(userMessage as unknown as UserMessage, context, pc, signal)) {
+			yield ev;
+		}
+	}
+}

packages/web-ui/src/agent/transports/index.ts

@@ -0,0 +1,3 @@
+export * from "./AppTransport.js";
+export * from "./ProviderTransport.js";
+export * from "./types.js";

packages/web-ui/src/agent/transports/proxy-types.ts

@@ -0,0 +1,15 @@
+import type { StopReason, Usage } from "@mariozechner/pi-ai";
+
+export type ProxyAssistantMessageEvent =
+	| { type: "start" }
+	| { type: "text_start"; contentIndex: number }
+	| { type: "text_delta"; contentIndex: number; delta: string }
+	| { type: "text_end"; contentIndex: number; contentSignature?: string }
+	| { type: "thinking_start"; contentIndex: number }
+	| { type: "thinking_delta"; contentIndex: number; delta: string }
+	| { type: "thinking_end"; contentIndex: number; contentSignature?: string }
+	| { type: "toolcall_start"; contentIndex: number; id: string; toolName: string }
+	| { type: "toolcall_delta"; contentIndex: number; delta: string }
+	| { type: "toolcall_end"; contentIndex: number }
+	| { type: "done"; reason: Extract<StopReason, "stop" | "length" | "toolUse">; usage: Usage }
+	| { type: "error"; reason: Extract<StopReason, "aborted" | "error">; errorMessage: string; usage: Usage };

packages/web-ui/src/agent/transports/types.ts

@@ -0,0 +1,21 @@
+import type { AgentEvent, AgentTool, Message, Model } from "@mariozechner/pi-ai";
+
+// The minimal configuration needed to run a turn.
+export interface AgentRunConfig {
+	systemPrompt: string;
+	tools: AgentTool<any>[];
+	model: Model<any>;
+	reasoning?: "low" | "medium" | "high";
+}
+
+// Events yielded by transports must match the @mariozechner/pi-ai prompt() events.
+// We re-export the Message type above; consumers should use the upstream AgentEvent type.
+
+export interface AgentTransport {
+	run(
+		messages: Message[],
+		userMessage: Message,
+		config: AgentRunConfig,
+		signal?: AbortSignal,
+	): AsyncIterable<AgentEvent>; // passthrough of AgentEvent from upstream
+}