/**
 * MemPalace ↔ pi bridge.
 *
 * Registers every MemPalace MCP tool as a pi tool that proxies to `tools/call`.
 * Two interchangeable transports, selected at load time:
 *
 *   - LOCAL (default): spawn the `mempalace-mcp` stdio server as a subprocess
 *     (StdioMcpClient) — hardened with per-request timeouts + generation-tracked
 *     respawn/self-heal for slow cold-opens (see below).
 *   - EXTERNAL: connect to a shared MemPalace over HTTP (RemoteMcpClient) when
 *     $MEMPALACE_REMOTE_URL is set — e.g. one palace serving pi + opencode +
 *     native. Optional bearer auth via $MEMPALACE_REMOTE_TOKEN. No local
 *     `mempalace-mcp` process is spawned in this mode.
 *
 * Either way the client performs the MCP `initialize` handshake, lists tools,
 * and the extension body below is transport-agnostic (depends only on the
 * IMcpClient interface).
 *
 * Lifecycle automation (per ~/.agents/skills/mempalace/SKILL.md):
 *   - Wake-up (auto): on first user prompt of a fresh session, inject
 *     `mempalace_status` + `mempalace_diary_read` output as context so the
 *     agent orients itself the way the mempalace skill describes. Skipped
 *     on resume/fork (palace context is already in the thread).
 *   - Feeding (auto): stage + mine this container's pi transcripts into the
 *     palace on `session_shutdown` and on a debounced `agent_settled`. Needs
 *     no LLM turn (pi transcripts are JSONL on disk), which is why it CAN be
 *     automatic where the diary cannot. The file-side work is delegated to
 *     `mempalace-pi-session --prepare` (export + threshold + staging, plus the
 *     rsync to the palace host when the palace is remote); the mine itself
 *     must run through THIS client, because the palace is single-writer and
 *     this process is the holder — a CLI `mempalace mine` during a live
 *     session dies with "palace ... is held by PID <ours>". Going through the
 *     client also means it automatically targets whichever palace this bridge
 *     is pointed at (local stdio or a shared remote one).
 *       - MEMPALACE_FEED=0                 disable feeding entirely
 *       - MEMPALACE_FEED_BIN               helper to run (default mempalace-pi-session)
 *       - MEMPALACE_FEED_WING              target wing (default wing_conversations)
 *       - MEMPALACE_FEED_DEBOUNCE_MS       min gap between mid-session feeds (default 600000)
 *   - Mailbox (auto): read the RFC 003 coordination log and surface the asks
 *     this device actually OWES a reply to — at wake-up, and again on a
 *     debounced `agent_settled` so events arriving mid-session are seen this
 *     session rather than the next one. Owed-ness is DERIVED (see deriveOwed);
 *     it is not the `status="open"` filter, because `status` is written once
 *     into an append-only log and an answered ask keeps matching forever.
 *     Inert unless BOTH $MEMPALACE_PI_DEVICE and $MEMPALACE_REMOTE_URL are set:
 *     on one shared palace `to_agent` carries the entire distinction between
 *     machines, so an unstamped client has no address to be reached at.
 *       - MEMPALACE_MAILBOX=0              disable mailbox reads entirely
 *       - MEMPALACE_MAILBOX_POLL_MS        min gap between mid-session polls (default 300000)
 *       - MEMPALACE_MAILBOX_RESURFACE_MS   re-announce a still-owed ask after (default 3600000)
 *   - Wind-down (manual): `/mempalace-diary` command prompts the LLM to
 *     write an AAAK-formatted diary entry. Not fully auto because pi
 *     sessions are typically short/tactical and session_shutdown is too
 *     late to drive an LLM turn.
 *
 * Identity: `agent_name` for diary calls comes from $MEMPALACE_AGENT_NAME,
 * defaulting to "pi". First diary write creates `wing_pi`.
 *
 * Fail-soft: if the MCP subprocess can't start, pi keeps working without
 * palace tools (warning on stderr only).
 *
 * Stall protection: every JSON-RPC request carries a timeout. If
 * `mempalace-mcp` wedges (e.g. OrbStack virtiofs cold-open of a large
 * chroma.sqlite3 / HNSW load), the awaiting promise would otherwise hang
 * forever and freeze the pi TUI (ESC cancels the LLM stream, not a pending
 * tool execution). On timeout we reject the request AND kill the wedged
 * child, so pi gets an error instead of hanging and later calls fail fast.
 * This is a per-REQUEST timeout, not a process-lifetime one — the
 * long-lived server is only killed when a request genuinely stalls.
 *   - MEMPALACE_MCP_TIMEOUT_MS       tool-call/request timeout (default 60000)
 *   - MEMPALACE_MCP_INIT_TIMEOUT_MS  initialize+tools/list timeout (default 300000)
 *   Set either to 0 to disable (legacy unbounded behavior).
 *
 * Self-heal (respawn): a stall-kill (or any crash) is no longer a permanent
 * latch. The next tool call transparently respawns `mempalace-mcp` and
 * retries, with capped exponential backoff so a persistently-broken server
 * can't hot-loop. The respawn budget resets on ANY successful JSON-RPC
 * response (proof the server is actually live), so a recovered server
 * regains full patience. The two timeouts above are deliberately split:
 * the long INIT timeout lets a genuine first cold-open finish without being
 * killed (the original incident), while the short per-call timeout still
 * aggressively kills a stuck query. After a server has opened the palace
 * once, the OS page cache is warm, so respawn cold-opens are fast — which
 * is exactly why a generous INIT timeout + bounded respawn compose well
 * instead of overlapping.
 *   - MEMPALACE_MCP_MAX_RESPAWNS       respawn attempts before giving up (default 2; 0 disables self-heal)
 *   - MEMPALACE_MCP_RESPAWN_BACKOFF_MS base backoff, doubled per attempt (default 1000)
 *
 * Debug: set MEMPALACE_EXT_DEBUG=1 to surface mempalace-mcp stderr.
 */

import { type ChildProcessWithoutNullStreams, spawn } from "node:child_process";
import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
import { Type } from "typebox";

// Minimal MCP stdio JSON-RPC client. MCP uses newline-delimited JSON.
interface McpTool {
	name: string;
	description?: string;
	inputSchema?: unknown;
}

interface Pending {
	resolve: (v: any) => void;
	reject: (e: Error) => void;
	timer: ReturnType<typeof setTimeout> | null;
}

// Transport-agnostic client contract. The extension body depends only on this,
// so LOCAL (StdioMcpClient) and EXTERNAL (RemoteMcpClient) are drop-in swaps.
// Each implementation owns its own reliability model — stdio uses timeout +
// kill + respawn; http uses fetch + AbortController timeout (+ 404 re-init if
// a future streamable-HTTP server issues sessions).
interface IMcpClient {
	tools: McpTool[];
	readonly alive: boolean;
	onExit: (() => void) | null;
	start(): Promise<void>;
	callTool(name: string, args: Record<string, unknown>): Promise<any>;
	ensureAlive(): Promise<boolean>;
	stop(): void | Promise<void>;
}

const num = (envVal: string | undefined, fallback: number): number => {
	const n = envVal !== undefined ? Number(envVal) : Number.NaN;
	return Number.isFinite(n) && n >= 0 ? n : fallback;
};

// One event as returned by `mempalace_event_list`. Every field is optional on
// purpose: this is parsed from a tool's JSON text, so it is untrusted input and
// a missing/renamed field must degrade to "not owed" rather than throw.
type LogEvent = {
	id?: string;
	seq?: number;
	hlc?: string;
	type?: string;
	status?: string;
	from_agent?: string;
	to_agent?: string;
	correlation_id?: string | null;
	created_at?: string;
	body?: string;
	metadata?: Record<string, unknown> | null;
};

const sleep = (ms: number): Promise<void> =>
	new Promise((res) => {
		const t = setTimeout(res, ms);
		if (typeof t.unref === "function") t.unref();
	});

class StdioMcpClient implements IMcpClient {
	private proc: ChildProcessWithoutNullStreams | null = null;
	private nextId = 1;
	private pending = new Map<number, Pending>();
	private stdoutBuf = "";
	private ready: Promise<void> | null = null;
	public tools: McpTool[] = [];

	// Per-request timeouts (ms). 0 = disabled (unbounded, legacy behavior).
	private requestTimeoutMs = num(process.env.MEMPALACE_MCP_TIMEOUT_MS, 60_000);
	private initTimeoutMs = num(process.env.MEMPALACE_MCP_INIT_TIMEOUT_MS, 300_000);
	// Self-heal (respawn) controls.
	private maxRespawns = num(process.env.MEMPALACE_MCP_MAX_RESPAWNS, 2);
	private respawnBackoffMs = num(process.env.MEMPALACE_MCP_RESPAWN_BACKOFF_MS, 1_000);
	private respawns = 0; // consecutive respawn attempts; reset on any success
	private reviving: Promise<boolean> | null = null;
	// Liveness: true only between a completed init and the matching death.
	// Inferring from `proc` is racy (non-null during the SIGTERM→exit window).
	private healthy = false;
	// Spawn generation. Each (re)spawn bumps it; death handlers carry the gen
	// they were attached for and no-op if a newer server has since taken over
	// (prevents a stale OLD-proc 'exit' from clobbering a freshly respawned one).
	private gen = 0;
	// Spawn args remembered so a respawn can reuse them (set via constructor).
	private command: string;
	private args: string[];
	// Fired when the child process dies (exit or stall-kill). Lets the
	// extension flip `available` so later tool calls fail fast.
	public onExit: (() => void) | null = null;

	constructor(command = "mempalace-mcp", args: string[] = []) {
		this.command = command;
		this.args = args;
	}

	/** True only when a server has completed init and not since died. */
	get alive(): boolean {
		return this.healthy;
	}

	async start(): Promise<void> {
		if (this.ready) return this.ready;
		this.ready = (async () => {
			const myGen = ++this.gen;
			const child = spawn(this.command, this.args, { stdio: ["pipe", "pipe", "pipe"] });
			this.proc = child;
			child.on("error", (err) => this.handleDeath(myGen, err));
			child.on("exit", (code) =>
				this.handleDeath(myGen, new Error(`mempalace-mcp exited (code=${code})`)),
			);
			this.proc.stdout.setEncoding("utf8");
			this.proc.stdout.on("data", (chunk: string) => this.onStdout(chunk));
			// Drain stderr silently. Re-enable by setting MEMPALACE_EXT_DEBUG=1.
			this.proc.stderr.setEncoding("utf8");
			if (process.env.MEMPALACE_EXT_DEBUG) {
				this.proc.stderr.on("data", (chunk: string) => {
					process.stderr.write(`[mempalace-mcp stderr] ${chunk}`);
				});
			} else {
				this.proc.stderr.resume(); // drain without logging
			}

			// MCP initialize handshake. Cold-open over virtiofs can be slow, so
			// use the (longer) init timeout here rather than the per-call one.
			await this.request(
				"initialize",
				{
					protocolVersion: "2024-11-05",
					capabilities: {},
					clientInfo: { name: "pi-mempalace-ext", version: "0.1.0" },
				},
				this.initTimeoutMs,
			);
			this.notify("notifications/initialized", {});

			const listed = await this.request("tools/list", {}, this.initTimeoutMs);
			this.tools = (listed?.tools as McpTool[]) ?? [];
			// Init complete and the process is still ours — mark live so ensureAlive()
			// reports true. Guard against a death that raced in during init.
			if (myGen === this.gen) this.healthy = true;
		})();
		return this.ready;
	}

	private onStdout(chunk: string) {
		this.stdoutBuf += chunk;
		let nl: number;
		while ((nl = this.stdoutBuf.indexOf("\n")) !== -1) {
			const line = this.stdoutBuf.slice(0, nl).trim();
			this.stdoutBuf = this.stdoutBuf.slice(nl + 1);
			if (!line) continue;
			let msg: any;
			try {
				msg = JSON.parse(line);
			} catch {
				continue;
			}
			if (typeof msg.id === "number" && this.pending.has(msg.id)) {
				const p = this.pending.get(msg.id)!;
				this.settle(msg.id);
				if (msg.error) p.reject(new Error(msg.error.message ?? "MCP error"));
				else {
					// A successful response proves the server is live — restore the
					// full respawn budget for any future (unrelated) stall.
					this.respawns = 0;
					p.resolve(msg.result);
				}
			}
			// notifications (no id) ignored for now.
		}
	}

	/** Remove a pending request and clear its timeout timer. */
	private settle(id: number) {
		const p = this.pending.get(id);
		if (p?.timer) clearTimeout(p.timer);
		this.pending.delete(id);
	}

	private failAll(err: Error) {
		for (const id of [...this.pending.keys()]) {
			const p = this.pending.get(id)!;
			this.settle(id);
			p.reject(err);
		}
	}

	/**
	 * Child died (exit, spawn error, or stall-kill): reject everything.
	 * Ignored if a newer generation has already taken over — a late 'exit'
	 * from a killed old process must not tear down a fresh respawn.
	 */
	private handleDeath(gen: number, err: Error) {
		if (gen !== this.gen) return; // stale handler from a superseded process
		this.proc = null;
		this.healthy = false;
		// Clear the memoized start() promise so a subsequent start()/ensureAlive()
		// spawns a fresh server instead of returning the dead one's promise.
		this.ready = null;
		this.failAll(err);
		try {
			this.onExit?.();
		} catch {}
	}

	/**
	 * Ensure a live, initialized server — respawning a dead one with capped
	 * exponential backoff. Returns whether the server is alive afterwards.
	 * Concurrent callers share a single in-flight revive. The attempt counter
	 * is reset by `onStdout` on any successful response, so a server that comes
	 * back and works regains its full budget; a server that keeps dying hits
	 * `maxRespawns` and stays down (restart pi) rather than hot-looping.
	 */
	async ensureAlive(): Promise<boolean> {
		if (this.alive) return true;
		if (this.reviving) return this.reviving;
		this.reviving = (async () => {
			while (!this.alive && this.respawns < this.maxRespawns) {
				this.respawns++;
				await sleep(this.respawnBackoffMs * 2 ** (this.respawns - 1));
				// Force a fresh spawn: drop any settled (rejected/dead) start()
				// promise so start() doesn't short-circuit on a stale memo. Safe
				// because ensureAlive is serialized (single `reviving`) and only
				// runs while not healthy — no useful in-flight start() can exist.
				this.ready = null;
				try {
					await this.start();
				} catch {
					// start() rejected (e.g. respawn cold-open also stalled and was
					// killed). Loop until the budget is exhausted.
				}
			}
			return this.alive;
		})();
		try {
			return await this.reviving;
		} finally {
			this.reviving = null;
		}
	}

	private write(obj: unknown) {
		if (!this.proc) throw new Error("MCP process not started");
		this.proc.stdin.write(`${JSON.stringify(obj)}\n`);
	}

	private notify(method: string, params: unknown) {
		this.write({ jsonrpc: "2.0", method, params });
	}

	request(method: string, params: unknown, timeoutMs = this.requestTimeoutMs): Promise<any> {
		const id = this.nextId++;
		return new Promise((resolve, reject) => {
			let timer: ReturnType<typeof setTimeout> | null = null;
			if (timeoutMs > 0) {
				timer = setTimeout(() => {
					if (!this.pending.has(id)) return;
					this.settle(id);
					reject(
						new Error(
							`mempalace-mcp request '${method}' timed out after ${timeoutMs}ms ` +
								`(server wedged — likely cold storage open). Terminating the ` +
								`stalled server; it will be respawned on the next call.`,
						),
					);
					// Kill the wedged child so subsequent calls fail fast instead of
					// stacking up behind a dead server. The 'exit' handler
					// (handleDeath) rejects any other pending requests.
					this.kill();
				}, timeoutMs);
				// Don't let a pending MCP timer keep the event loop alive.
				if (typeof timer.unref === "function") timer.unref();
			}
			this.pending.set(id, { resolve, reject, timer });
			try {
				this.write({ jsonrpc: "2.0", id, method, params });
			} catch (err) {
				this.settle(id);
				reject(err as Error);
			}
		});
	}

	async callTool(name: string, args: Record<string, unknown>): Promise<any> {
		return this.request("tools/call", { name, arguments: args });
	}

	/** SIGTERM then SIGKILL grace, for stall recovery. */
	private kill() {
		const proc = this.proc;
		if (!proc) return;
		try {
			proc.kill("SIGTERM");
		} catch {}
		const t = setTimeout(() => {
			try {
				proc.kill("SIGKILL");
			} catch {}
		}, 2_000);
		if (typeof t.unref === "function") t.unref();
	}

	stop() {
		if (this.proc) {
			try {
				this.proc.kill("SIGTERM");
			} catch {}
			this.proc = null;
		}
	}
}

// ───────────────────────────────────────────────────────────────────────
// RemoteMcpClient — EXTERNAL transport (streamable-HTTP / sessionless JSON-RPC).
//
// VENDORED from pi-extensions/extensions/mcp-loader.ts (class RemoteMcpClient).
// Kept as a copy rather than a shared import because the two repos ship
// independently; the canonical implementation lives in mcp-loader.ts. Port
// protocol fixes in both directions.
//
// MCP-STREAMABLE-HTTP-CLIENT-SYNC: v1
// This token must match the canonical block's. Bump it in BOTH files whenever
// the streamable-HTTP protocol handling changes; scripts/check-mcp-client-sync.sh
// fails when they diverge (skips gracefully if pi-extensions isn't checked out).
//
// Deltas from the canonical copy:
//   • protocolVersion pinned to "2024-11-05" to match mempalace-mcp's stdio
//     handshake (the server echoes whatever it is sent, so cosmetic today,
//     but keeps both transports consistent).
//   • per-request AbortController timeout honouring MEMPALACE_MCP_TIMEOUT_MS /
//     MEMPALACE_MCP_INIT_TIMEOUT_MS, mirroring StdioMcpClient's timeout ethos.
//   • alive / ensureAlive / onExit to satisfy IMcpClient.
//
// NOTE: mempalace-mcp --transport http is a SESSIONLESS, stateless JSON-RPC
// server (no Mcp-Session-Id, always application/json, Connection: close), so
// the session-id / SSE / 404-reinit branches below are never exercised against
// it today. They are retained so this client also works unchanged if mempalace
// later moves to a full streamable-HTTP (FastMCP) transport.
// ───────────────────────────────────────────────────────────────────────
const REMOTE_PROTOCOL_VERSION = "2024-11-05";
const REMOTE_CLIENT_INFO = { name: "pi-mempalace-ext", version: "0.1.0" };

class RemoteMcpClient implements IMcpClient {
	private url: string;
	private extraHeaders: Record<string, string>;
	private sessionId: string | null = null;
	private nextId = 1;
	public tools: McpTool[] = [];
	// Unused for HTTP (no child process to die) — present to satisfy IMcpClient.
	public onExit: (() => void) | null = null;

	private requestTimeoutMs = num(process.env.MEMPALACE_MCP_TIMEOUT_MS, 60_000);
	private initTimeoutMs = num(process.env.MEMPALACE_MCP_INIT_TIMEOUT_MS, 300_000);
	private healthy = false;
	private reviving: Promise<boolean> | null = null;

	constructor(url: string, headers?: Record<string, string>) {
		this.url = url;
		this.extraHeaders = headers ?? {};
	}

	get alive(): boolean {
		return this.healthy;
	}

	async start(): Promise<void> {
		await this.request(
			"initialize",
			{ protocolVersion: REMOTE_PROTOCOL_VERSION, capabilities: {}, clientInfo: REMOTE_CLIENT_INFO },
			{ timeoutMs: this.initTimeoutMs },
		);
		await this.notify("notifications/initialized", {});
		const listed = await this.request("tools/list", {}, { timeoutMs: this.initTimeoutMs });
		this.tools = (listed?.tools as McpTool[]) ?? [];
		this.healthy = true;
	}

	async callTool(name: string, args: Record<string, unknown>): Promise<any> {
		return this.request("tools/call", { name, arguments: args });
	}

	/**
	 * Re-establish connectivity (and re-list tools) after a fetch failure.
	 * For the stateless server this is just a fresh initialize+tools/list;
	 * concurrent callers share one in-flight attempt.
	 */
	async ensureAlive(): Promise<boolean> {
		if (this.healthy) return true;
		if (this.reviving) return this.reviving;
		this.reviving = (async () => {
			try {
				this.sessionId = null;
				await this.start();
			} catch {
				// stays unhealthy
			}
			return this.healthy;
		})();
		try {
			return await this.reviving;
		} finally {
			this.reviving = null;
		}
	}

	async stop(): Promise<void> {
		this.healthy = false;
		if (!this.sessionId) return;
		try {
			await fetch(this.url, { method: "DELETE", headers: this.buildHeaders() });
		} catch {}
	}

	private buildHeaders(): Record<string, string> {
		const h: Record<string, string> = {
			"Content-Type": "application/json",
			Accept: "application/json, text/event-stream",
			"MCP-Protocol-Version": REMOTE_PROTOCOL_VERSION,
			...this.extraHeaders,
		};
		if (this.sessionId) h["Mcp-Session-Id"] = this.sessionId;
		return h;
	}

	private signalFor(timeoutMs: number): AbortSignal | undefined {
		return timeoutMs > 0 ? AbortSignal.timeout(timeoutMs) : undefined;
	}

	private async reinitialize(): Promise<void> {
		await this.request(
			"initialize",
			{ protocolVersion: REMOTE_PROTOCOL_VERSION, capabilities: {}, clientInfo: REMOTE_CLIENT_INFO },
			{ timeoutMs: this.initTimeoutMs, allowReinitOn404: false },
		);
		await this.notify("notifications/initialized", {});
	}

	private async request(
		method: string,
		params: unknown,
		opts: { timeoutMs?: number; allowReinitOn404?: boolean } = {},
	): Promise<any> {
		const timeoutMs = opts.timeoutMs ?? this.requestTimeoutMs;
		const allowReinitOn404 = opts.allowReinitOn404 ?? true;
		const id = this.nextId++;
		const body = JSON.stringify({ jsonrpc: "2.0", id, method, params });
		const sessionAtStart = this.sessionId;
		let res: Response;
		try {
			res = await fetch(this.url, {
				method: "POST",
				headers: this.buildHeaders(),
				body,
				signal: this.signalFor(timeoutMs),
			});
		} catch (err) {
			// Network failure / timeout (AbortError) — mark unreachable so the next
			// tool call triggers ensureAlive().
			this.healthy = false;
			const e = err as Error;
			const reason =
				e.name === "AbortError" || e.name === "TimeoutError"
					? `timed out after ${timeoutMs}ms`
					: e.message;
			throw new Error(`mempalace remote request '${method}' failed: ${reason}`);
		}

		const sid = res.headers.get("Mcp-Session-Id") ?? res.headers.get("mcp-session-id");
		if (sid) this.sessionId = sid;

		// 404 + we sent a session id → server forgot us. Drop id, re-init, retry once.
		if (res.status === 404 && sessionAtStart && allowReinitOn404) {
			try {
				await res.arrayBuffer();
			} catch {}
			this.sessionId = null;
			await this.reinitialize();
			return this.request(method, params, { timeoutMs, allowReinitOn404: false });
		}

		if (!res.ok) {
			let detail = "";
			try {
				detail = (await res.text()).slice(0, 200);
			} catch {}
			throw new Error(`mempalace remote: HTTP ${res.status} on ${method}${detail ? `: ${detail}` : ""}`);
		}

		const ct = (res.headers.get("content-type") ?? "").toLowerCase();
		if (ct.includes("text/event-stream")) {
			return await this.readSseForResponse(res, id);
		}
		if (ct.includes("application/json")) {
			const json: any = await res.json();
			if (json.error) throw new Error(json.error.message ?? "MCP error");
			return json.result;
		}
		if (res.status === 202) return undefined;
		throw new Error(`mempalace remote: unexpected content-type "${ct}" on ${method}`);
	}

	private async notify(method: string, params: unknown): Promise<void> {
		const body = JSON.stringify({ jsonrpc: "2.0", method, params });
		let res: Response;
		try {
			res = await fetch(this.url, {
				method: "POST",
				headers: this.buildHeaders(),
				body,
				signal: this.signalFor(this.requestTimeoutMs),
			});
		} catch (err) {
			throw new Error(`mempalace remote: fetch failed on notify ${method}: ${(err as Error).message}`);
		}
		try {
			await res.arrayBuffer();
		} catch {}
		if (!res.ok && res.status !== 202) {
			throw new Error(`mempalace remote: HTTP ${res.status} on notify ${method}`);
		}
	}

	private async readSseForResponse(res: Response, expectedId: number): Promise<any> {
		if (!res.body) throw new Error("mempalace remote: SSE response had no body");
		const reader = res.body.getReader();
		const decoder = new TextDecoder();
		let buf = "";
		let dataLines: string[] = [];

		const tryDispatch = (): { matched: boolean; result?: any } => {
			if (dataLines.length === 0) return { matched: false };
			const data = dataLines.join("\n");
			dataLines = [];
			let msg: any;
			try {
				msg = JSON.parse(data);
			} catch {
				return { matched: false };
			}
			if (typeof msg.id === "number" && msg.id === expectedId) {
				if (msg.error) throw new Error(msg.error.message ?? "MCP error");
				return { matched: true, result: msg.result };
			}
			return { matched: false };
		};

		try {
			while (true) {
				const { done, value } = await reader.read();
				if (done) break;
				buf += decoder.decode(value, { stream: true });
				let nl: number;
				while ((nl = buf.indexOf("\n")) !== -1) {
					const rawLine = buf.slice(0, nl);
					buf = buf.slice(nl + 1);
					const line = rawLine.endsWith("\r") ? rawLine.slice(0, -1) : rawLine;
					if (line === "") {
						const out = tryDispatch();
						if (out.matched) return out.result;
					} else if (line.startsWith(":")) {
						// SSE comment / keepalive — ignore
					} else if (line.startsWith("data:")) {
						dataLines.push(line.slice(5).replace(/^ /, ""));
					}
				}
			}
			const out = tryDispatch();
			if (out.matched) return out.result;
		} finally {
			try {
				reader.cancel();
			} catch {}
		}
		throw new Error(`mempalace remote: SSE stream closed without response for id=${expectedId}`);
	}
}

/**
 * Pick the transport from the environment: MEMPALACE_REMOTE_URL selects the
 * EXTERNAL (HTTP) client; unset falls back to the LOCAL stdio server.
 */
function createClient(): IMcpClient {
	const remoteUrl = process.env.MEMPALACE_REMOTE_URL?.trim();
	if (remoteUrl) {
		return new RemoteMcpClient(remoteUrl, authHeaders());
	}
	return new StdioMcpClient("mempalace-mcp");
}

/** Bearer auth header for the remote transport, if MEMPALACE_REMOTE_TOKEN is set. */
function authHeaders(): Record<string, string> | undefined {
	const token = process.env.MEMPALACE_REMOTE_TOKEN?.trim();
	return token ? { Authorization: `Bearer ${token}` } : undefined;
}

export default async function mempalaceExtension(pi: ExtensionAPI) {
	const client = createClient();
	let available = false;
	const agentName = process.env.MEMPALACE_AGENT_NAME ?? "pi";

	// --- Edge provenance (RFC 001 §7.3.2, Phase 2) -------------------------
	// Provenance belongs to the sync boundary, not to the agent. §7.3.2 ranks
	// "agent via skill" as the ❌ worst possible stamper — per-call boilerplate,
	// forgettable, improvisable — and the client/edge as the ⚠️ acceptable
	// interim until per-device tokens let the primary stamp authoritatively
	// (Phase 4). So the bridge stamps, uniformly, from host-supplied env, and no
	// skill instruction or LLM discipline is involved. Being self-asserted it is
	// ADVISORY: a hint, never load-bearing for authz or destructive scoping.
	//
	// R1 (solitary operation stays unchanged) is why this is doubly gated: it is
	// inert unless the host both labels the device AND points this client at a
	// shared palace. A solitary devbox is single-origin by definition (§7.3.3),
	// so it stamps nothing and loses nothing.
	const device = process.env.MEMPALACE_PI_DEVICE?.trim();
	const shared = Boolean(process.env.MEMPALACE_REMOTE_URL?.trim());
	const stampProvenance = device && shared;

	// Which parameter carries "who wrote this", per tool. An ALLOWLIST, never a
	// blanket default: mempalace 3.8.0's dispatcher rejects undeclared arguments
	// with -32602 (mcp_server.py:6440 — it used to drop them silently), so
	// injecting into a tool that has no such property would break every call.
	// diary_write and kg_add have no writer slot at all and are handled below.
	const WRITER_PARAM: Record<string, string> = {
		mempalace_add_drawer: "added_by",
		mempalace_checkpoint: "added_by",
		mempalace_mine: "agent",
		mempalace_event_append: "from_agent",
		mempalace_artifact_put: "created_by",
	};
	// `mine` produces bulk machine-extracted content, not agent-authored memory.
	// Labelling its harness segment `miner` keeps the existing pi/opencode/miner
	// taxonomy honest while still recording which box did the mining.
	const MINER_TOOLS = new Set(["mempalace_mine"]);
	const identity = (toolName: string) =>
		`${MINER_TOOLS.has(toolName) ? "miner" : agentName}@${device}`;

	// diary_write has NO usable writer parameter (§7.3.1: "none usable") and the
	// device must never go in agent_name — `wing = f"wing_{agent_name}"`, so that
	// splinters the diary into one wing per host and hides entries from
	// diary_read. The entry TEXT is the only channel left, and it is also the
	// only one a *reader* ever sees: search results project a fixed key set and
	// diary_read returns content, so neither ever shows metadata. A metadata-only
	// fix would not have prevented the 2026-08-25 cross-host misattribution.
	// Prefixing (not appending) keeps the marker in chunk 0 and in the reader's
	// first line. AAAK is pipe-separated, so `HOST:x|SESSION:…` stays in-dialect.
	const HOST_MARKER = /(^|\|)\s*HOST:/;
	const markEntry = (v: unknown): unknown =>
		typeof v === "string" && v.trim() !== "" && !HOST_MARKER.test(v)
			? `HOST:${device}|${v}`
			: v;

	/** Stamp origin into a tool's arguments in place. Never overwrites a value
	 *  the caller set explicitly — an explicit argument wins, so a deliberate
	 *  re-file on behalf of another device stays possible. */
	const applyProvenance = (toolName: string, args: Record<string, unknown>) => {
		const param = WRITER_PARAM[toolName];
		if (param) {
			const current = args[param];
			if (typeof current !== "string" || current.trim() === "") {
				args[param] = identity(toolName);
			}
		}
		if (toolName === "mempalace_diary_write") {
			if ("entry" in args) args.entry = markEntry(args.entry);
			if ("content" in args) args.content = markEntry(args.content);
		}
		// checkpoint files drawers AND writes one diary entry through the same
		// server path, so its nested diary entry needs the marker too.
		if (toolName === "mempalace_checkpoint" && args.diary && typeof args.diary === "object") {
			const diary = args.diary as Record<string, unknown>;
			if ("entry" in diary) diary.entry = markEntry(diary.entry);
		}
	};

	// Gate: inject wake-up context only on the first before_agent_start of a
	// fresh session. Set true on resume/fork (context already in thread).
	let wokeUp = false;

	try {
		client.onExit = () => {
			// Child died (stall-kill or crash): mark unavailable. The next tool
			// call will attempt a bounded respawn via client.ensureAlive().
			available = false;
		};
		await client.start();
		available = true;
	} catch (err) {
		// First cold-open stalled/crashed. Give the bounded self-heal a chance
		// before giving up entirely — a respawn often succeeds against a now-warm
		// page cache. Only fail-soft if even that is exhausted.
		process.stderr.write(
			`[mempalace ext] mempalace-mcp start failed: ${(err as Error).message} — attempting respawn\n`,
		);
		available = await client.ensureAlive();
		if (!available) {
			process.stderr.write(
				"[mempalace ext] mempalace-mcp unavailable after retries; continuing without palace tools\n",
			);
			return; // fail-soft: pi keeps working without palace tools
		}
	}

	// Register MCP tools as pi tools. Pass the MCP `inputSchema` through as
	// the pi `parameters` schema so the LLM sees the real parameter names
	// (e.g. `agent_name`, not guessed `agent`). TypeBox schemas are plain
	// JSON Schema at runtime, so `Type.Unsafe` is sufficient to wrap an
	// externally-sourced JSON Schema — no conversion needed.
	for (const tool of client.tools) {
		const schema =
			tool.inputSchema && typeof tool.inputSchema === "object"
				? (Type.Unsafe<Record<string, unknown>>(tool.inputSchema as object) as unknown as ReturnType<typeof Type.Object>)
				: Type.Object({}, { additionalProperties: true });
		pi.registerTool({
			name: tool.name,
			label: tool.name,
			description: tool.description ?? `MemPalace tool: ${tool.name}`,
			parameters: schema,
			async execute(_toolCallId, params) {
				if (!available) {
					// Stall-kill/crash is not a permanent latch: try a bounded respawn.
					available = await client.ensureAlive();
				}
				if (!available) {
					return {
						content: [
							{
								type: "text",
								text: "mempalace-mcp not available (respawn budget exhausted) — restart pi to retry palace tools",
							},
						],
						details: {},
						isError: true,
					};
				}
				try {
					const args = { ...((params ?? {}) as Record<string, unknown>) };
					if (stampProvenance) applyProvenance(tool.name, args);
					const result = await client.callTool(tool.name, args);
					// MCP tool results use { content: [...], isError?: boolean }
					return {
						content: result?.content ?? [{ type: "text", text: JSON.stringify(result) }],
						details: { raw: result },
						isError: result?.isError === true,
					};
				} catch (err) {
					return {
						content: [{ type: "text", text: `MCP call failed: ${(err as Error).message}` }],
						details: {},
						isError: true,
					};
				}
			},
		});
	}

	// --- Automatic transcript feeding ---
	//
	// Split deliberately: `mempalace-pi-session --prepare` does the palace-free
	// file work (export + quality threshold + staging, plus the rsync to the
	// palace host in remote mode) and prints the path to mine; we then mine it
	// through this client. See the header note on single-writer contention.
	const feedEnabled = (process.env.MEMPALACE_FEED ?? "1") !== "0";
	const feedBin = process.env.MEMPALACE_FEED_BIN || "mempalace-pi-session";
	const feedWing = process.env.MEMPALACE_FEED_WING ?? "wing_conversations";
	const feedDebounceMs = num(process.env.MEMPALACE_FEED_DEBOUNCE_MS, 600_000);
	const feedPrepareTimeoutMs = num(process.env.MEMPALACE_FEED_PREPARE_TIMEOUT_MS, 120_000);
	const feedMineTimeoutMs = num(process.env.MEMPALACE_FEED_MINE_TIMEOUT_MS, 30_000);
	let lastFeedAt = 0; // 0 => the first settled turn also acts as a catch-up
	let feedInFlight: Promise<void> | null = null;

	/** Run `mempalace-feed --prepare`; resolve the path to mine, or null. */
	function prepareFeed(reason: string): Promise<string | null> {
		return new Promise((resolve) => {
			// A missing helper surfaces as an async 'error' event (ENOENT), not a
			// throw, so the handler below is the fail-soft path.
			const child = spawn(feedBin, ["--prepare", "--reason", reason, "--wing", feedWing], {
				stdio: ["ignore", "pipe", "pipe"],
			});
			let out = "";
			let settled = false;
			const finish = (value: string | null) => {
				if (settled) return;
				settled = true;
				clearTimeout(timer);
				resolve(value);
			};
			const timer = setTimeout(() => {
				try {
					child.kill("SIGKILL");
				} catch {
					/* already gone */
				}
				finish(null);
			}, feedPrepareTimeoutMs);
			child.stdout.on("data", (chunk) => {
				out += String(chunk);
			});
			child.stderr.on("data", () => {
				/* the script keeps its own log */
			});
			child.on("error", () => finish(null));
			child.on("exit", (code) => {
				if (code !== 0) return finish(null);
				const match = out.match(/^MINE_SOURCE=(.+)$/m);
				finish(match ? match[1].trim() : null);
			});
		});
	}

	/**
	 * Stage + mine this container's transcripts. Never throws, and coalesces:
	 * an overlapping trigger joins the in-flight run instead of racing it.
	 */
	function feedPalace(reason: string): Promise<void> {
		if (!feedEnabled || !available) return Promise.resolve();
		if (feedInFlight) return feedInFlight;
		const run = (async () => {
			try {
				const source = await prepareFeed(reason);
				if (!source) return;
				await Promise.race([
					client.callTool("mempalace_mine", {
						source,
						mode: "convos",
						wing: feedWing,
						// Internal call: it does not pass through the registered tool's
						// execute(), so it stamps itself. These ARE this harness's own
						// transcripts from this device, so the harness segment is the
						// agent (not `miner`) even though the tool is `mine`.
						agent: stampProvenance ? `${agentName}@${device}` : agentName,
					}),
					new Promise((_resolve, reject) =>
						setTimeout(
							() => reject(new Error(`mine timed out after ${feedMineTimeoutMs}ms`)),
							feedMineTimeoutMs,
						),
					),
				]);
				lastFeedAt = Date.now();
			} catch (err) {
				process.stderr.write(
					`[mempalace ext] feed (${reason}) failed: ${(err as Error).message}\n`,
				);
			}
		})();
		feedInFlight = run.finally(() => {
			feedInFlight = null;
		});
		return feedInFlight;
	}

	// Mid-session feed. A hard container kill runs no handler at all, so this is
	// what bounds crash loss to one debounce window instead of a whole session.
	// Re-mining a grown transcript purges and refiles that source_file, so
	// repeated ticks refresh a session's drawers rather than duplicating them.
	pi.on("agent_settled", async () => {
		if (Date.now() - lastFeedAt < feedDebounceMs) return;
		void feedPalace("tick"); // deliberately not awaited: never stall a turn
	});

	pi.on("session_shutdown", async () => {
		// Feed before stopping the client: we are the palace holder, so nothing
		// else can mine while we live. pi awaits this handler, so the mine really
		// does complete; feedMineTimeoutMs keeps a wedged palace from hanging exit.
		await feedPalace("shutdown");
		client.stop();
	});

	pi.on("session_start", async (event, ctx) => {
		// On resume/fork, the previous session's palace context is already in
		// the thread — skip the wake-up injection.
		if (event.reason === "resume" || event.reason === "fork") {
			wokeUp = true;
		}
		ctx.ui.notify(
			`mempalace bridge: ${client.tools.length} tools registered (agent=${agentName})`,
			"info",
		);
	});

	// --- Automatic mailbox delivery (RFC 003 coordination log) -------------
	//
	// Doubly gated, exactly like the stamper above: a device label AND a shared
	// palace. On one shared palace every client reports the same origin_replica,
	// so `to_agent` carries the whole distinction between machines and an
	// unstamped client has no address to be reached at — there is nothing to read.
	const mailboxEnabled = Boolean(stampProvenance) && process.env.MEMPALACE_MAILBOX !== "0";
	const mailboxPollMs = num(process.env.MEMPALACE_MAILBOX_POLL_MS, 300_000);
	const mailboxResurfaceMs = num(process.env.MEMPALACE_MAILBOX_RESURFACE_MS, 3_600_000);
	// The address is the NON-miner identity: `mine` is the only tool that stamps
	// itself `miner@device`, and nobody addresses a mailbox to the miner.
	const mailboxAddress = `${agentName}@${device}`;
	// Only these close an obligation. `claimed` and `ready` are deliberately NOT
	// terminal — that is what expresses "taken, but not finished", so picked-up
	// work keeps resurfacing until it is actually closed out.
	const TERMINAL_STATUS = new Set(["applied", "superseded", "failed", "blocked"]);
	let lastMailboxPollAt = 0;
	// event id -> when we last surfaced it. In-memory ON PURPOSE. After a restart
	// this forgets, so an ask already seen can be shown again; that is the SAFE
	// failure direction. A spuriously resurfacing item is visible noise a human
	// corrects in one turn, whereas a suppressed unanswered ask is silent and
	// permanent. Never "fix" the noise by persisting this into a decision that
	// can hide an obligation.
	const surfaced = new Map<string, number>();

	/** Parse an `event_list` result into a plain array. Never throws. */
	const parseEvents = (raw: unknown): LogEvent[] => {
		try {
			const text = extractText(raw);
			if (!text) return [];
			const parsed = JSON.parse(text);
			const list = Array.isArray(parsed) ? parsed : parsed?.events;
			return Array.isArray(list) ? (list as LogEvent[]) : [];
		} catch {
			// Malformed or non-JSON payload: report nothing owed rather than guessing.
			return [];
		}
	};

	/**
	 * Is `later` strictly after `earlier` in the fleet's ordering?
	 *
	 * Prefer `hlc` — a hybrid logical clock rendered fixed-width
	 * (`<unix_ms:13 digits>-<counter:6 hex>-<replica_id>`), so a plain string
	 * comparison IS the causal comparison, and it stays correct once a second
	 * replica exists. `seq` is the arrival rowid of THIS database, so on a mesh
	 * the same event carries a different `seq` per replica and a reply can land
	 * before the ask it answers.
	 *
	 * Fall back to `seq` only when either side lacks an `hlc` (a server predating
	 * the field, or a row whose backfill did not run). On a single replica the two
	 * agree, so the fallback is not a downgrade today — it is the single-replica
	 * case still being handled after the mesh case became primary.
	 *
	 * NEVER compare `created_at`: it is server-generated at second precision, so
	 * ties are routine, and a tie or a skew there can suppress an UNANSWERED ask
	 * outright. Every failure mode here is deliberately kept on the
	 * noisy-but-visible side — an answered item resurfacing is annoying, an
	 * unanswered ask going silent defeats the mailbox.
	 */
	const isStrictlyAfter = (later: LogEvent, earlier: LogEvent): boolean => {
		if (
			typeof later.hlc === "string" &&
			typeof earlier.hlc === "string" &&
			later.hlc !== "" &&
			earlier.hlc !== ""
		) {
			return later.hlc > earlier.hlc;
		}
		if (typeof later.seq !== "number" || typeof earlier.seq !== "number") return false;
		return later.seq > earlier.seq;
	};

	/**
	 * Has one of MY events closed this candidate?
	 *
	 * Owed-ness cannot be read off `status`: event_ack APPENDS and never mutates,
	 * and `status` is written once, so a directed "open" keeps matching the
	 * mailbox query forever — answered or not. It has to be derived by joining
	 * the candidate to my own replies.
	 */
	const isAnswered = (candidate: LogEvent, mine: LogEvent[]): boolean =>
		mine.some((m) => {
			// (c) terminal status only.
			if (!TERMINAL_STATUS.has(String(m.status))) return false;
			// (a) LOAD-BEARING ordering test, and the reason it must exist: without
			// it one terminal reply suppresses every LATER ask on the same
			// correlation_id forever — silently, permanently, and worst on exactly
			// the long-running threads the correlation join is for.
			// See isStrictlyAfter for why the key is `hlc` and not `seq`/`created_at`.
			if (!isStrictlyAfter(m, candidate)) return false;
			// (b) join on the exact ack (written for us by event_ack), else on a
			// shared correlation_id — which is why correlation_id is mandatory on a
			// directed open: without it there is no key to join a reply back to.
			const ackOf = m.metadata?.ack_of;
			if (typeof ackOf === "string" && candidate.id && ackOf === candidate.id) return true;
			return Boolean(m.correlation_id && m.correlation_id === candidate.correlation_id);
		});

	/**
	 * Has the ORIGINAL REQUESTER explicitly withdrawn this candidate?
	 *
	 * RFC 003 §3.3 clause 3 clears an ask only on "no event **of yours**", and the
	 * skill states the consequence outright: "there is nothing anyone can do about
	 * it from the other end". That asymmetry is deliberate and mostly right — owed
	 * ness is a statement about the RECIPIENT's accountability, and a requester
	 * must not be able to delete an obligation the recipient genuinely has.
	 *
	 * It is wrong in exactly one case: the requester withdrawing its OWN ask.
	 *
	 * MEASURED COST, 2026-09-08/09. pi@mbp-m1-2020 withdrew a v1.8.13 rollout ask
	 * to pi@tor-ms22 (evt seq 119: terminal `superseded`, same correlation_id,
	 * `metadata.closes` naming it, body "DO NOT SPEND A MINUTE ON v1.8.13") and
	 * recorded the withdrawal as done. It had no effect: seq 119's `from_agent` is
	 * mbp, so it could never satisfy a join that only looks at tor-ms22's own
	 * events. tor-ms22's next wake-up — 8h later, on the first boot of the image
	 * shipping this very derivation — still listed the ask as owed, 41h old, for a
	 * release that had been superseded and never installed there. It had to spend a
	 * write closing an ask nobody wanted answered. The asymmetry is also INVISIBLE
	 * from the sender's side: mbp did everything a sender is told to do and got a
	 * result indistinguishable from success.
	 *
	 * WHY AN EXPLICIT MARKER AND NOT "ANY TERMINAL EVENT FROM THE REQUESTER".
	 * This file's standing rule is that every failure mode stays on the
	 * noisy-but-visible side, because a spuriously resurfacing item is one turn of
	 * human correction whereas a suppressed unanswered ask is silent and permanent.
	 * Inferring release from any terminal event would breach that: a requester
	 * appending `applied` for its own bookkeeping — on the correlation, addressed
	 * to me, before I ever replied — would silently delete a real obligation.
	 * So release must be STATED, not inferred. `withdraws` is the canonical key;
	 * `closes` is honoured because it is already this fleet's de-facto marker (mbp
	 * seq 119, emb seq 117/118 all use it), and either must name this exact ask —
	 * its `correlation_id` or its event `id`. Prose does not count.
	 *
	 * WHY THIS DOES NOT BREAK THE FIXED POINT IN RFC 003 §9.2. §9.2 rejects letting
	 * terminal directed events into the owed set, because then every closure mints a
	 * fresh obligation and the loop never terminates. That argument is about
	 * CANDIDATES. This adds a CLEARER. A withdrawal carries a terminal status, so it
	 * can never be a candidate, and nothing new becomes owed. The asserting shape
	 * (`open`) and the clearing shape (terminal) stay disjoint. A reader who reaches
	 * for §9.2 to object is answering a different question.
	 */
	const isWithdrawn = (candidate: LogEvent, inbound: LogEvent[]): boolean => {
		const requester = candidate.from_agent;
		if (!requester) return false;
		// Names THIS ask specifically: its correlation or its id. A marker naming
		// something else, or carrying prose, is not a withdrawal of this ask.
		const names = (v: unknown): boolean =>
			typeof v === "string" &&
			v.length > 0 &&
			((Boolean(candidate.correlation_id) && v === candidate.correlation_id) ||
				(Boolean(candidate.id) && v === candidate.id));
		return inbound.some((e) => {
			// Only the party that ASKED may retract. A third party writing a terminal
			// event on a shared correlation must never clear my obligation.
			if (e.from_agent !== requester) return false;
			// Addressed to the party being released. `to_agent=<me>` also matches '*'
			// at the SQL level (RFC 003 §7.4), and a broadcast must not be able to
			// quietly empty every machine's mailbox at once.
			if (e.to_agent !== mailboxAddress) return false;
			if (!TERMINAL_STATUS.has((e.status ?? "").toLowerCase())) return false;
			// Same ordering guard, same reason as isAnswered: a withdrawal must not
			// retire an ask the requester sent LATER on the same correlation.
			if (!isStrictlyAfter(e, candidate)) return false;
			const ackOf = e.metadata?.ack_of;
			const joins =
				(typeof ackOf === "string" && Boolean(candidate.id) && ackOf === candidate.id) ||
				Boolean(e.correlation_id && e.correlation_id === candidate.correlation_id);
			if (!joins) return false;
			return names(e.metadata?.withdraws) || names(e.metadata?.closes);
		});
	};

	/**
	 * Directed asks addressed to this device with no terminal reply from it, and
	 * not explicitly withdrawn by whoever sent them (see isWithdrawn).
	 */
	async function deriveOwed(): Promise<LogEvent[]> {
		if (!mailboxEnabled || !available) return [];
		try {
			const [candidatesRaw, mineRaw, inboundRaw] = await Promise.all([
				client.callTool("mempalace_event_list", {
					to_agent: mailboxAddress,
					status: "open",
					limit: 50,
				}),
				// `order: "desc"` is a fix, not a flourish. event_list defaults to `asc`
				// (append order), so this asked for the OLDEST 100 events this device
				// ever wrote — meaning that once a device passes 100 authored events its
				// most RECENT replies fall out of the join window and every ask it just
				// answered resurfaces as owed. Latent rather than theoretical: tor-ms22
				// was at ~20 authored events when this was written. The window has to be
				// anchored at the newest end for the same reason the join uses `hlc`.
				client.callTool("mempalace_event_list", {
					from_agent: mailboxAddress,
					limit: 100,
					order: "desc",
				}),
				// Inbound with NO status filter, deliberately: a withdrawal carries a
				// TERMINAL status and is therefore structurally invisible to the
				// `status: "open"` candidate query above — the same omission deriveClosed
				// is built on. No amount of polling the open set could ever see one.
				client.callTool("mempalace_event_list", {
					to_agent: mailboxAddress,
					limit: 100,
					order: "desc",
				}),
			]);
			const candidates = parseEvents(candidatesRaw).filter((c) => {
				// `to_agent: <me>` ALSO matches `*` broadcasts, per the tool contract.
				// The protocol says a broadcast owes nobody a reply, so a broadcast
				// written with status="open" must not enter anyone's owed set --
				// otherwise this code contradicts the skill that documents it, and
				// every machine would think it personally owed the same answer.
				// This also gives the "don't broadcast an ask" anti-pattern teeth:
				// broadcasting one now demonstrably reaches no owed set at all.
				if (c.to_agent === "*") return false;
				// You cannot owe yourself.
				return c.from_agent !== mailboxAddress;
			});
			if (candidates.length === 0) return [];
			const mine = parseEvents(mineRaw);
			const inbound = parseEvents(inboundRaw);
			return candidates.filter((c) => !isAnswered(c, mine) && !isWithdrawn(c, inbound));
		} catch {
			// Fail silent and open: a mailbox read must never break a session.
			return [];
		}
	}

	/**
	 * Terminal replies to asks THIS device sent. NOT work — news.
	 *
	 * Why this is a second query rather than a widened deriveOwed(): deriveOwed()
	 * asks the log for `status: "open"`, and a reply that CLOSES an ask is by
	 * definition not open, so it is structurally invisible to that filter — no
	 * amount of polling or waiting could ever have surfaced it.
	 *
	 * Measured 2026-09-07: emb-7kj4vr4g closed a v1.8.13 rollout ask with a
	 * task.reply at status=applied, and the operator reasonably expected to be
	 * told. The mailbox stayed silent and was CORRECT to — "owed" means "you must
	 * reply", and nothing was owed. But the single most useful thing a fleet can
	 * tell a human is "the thing you asked for is done" (here: done, AND your
	 * premise was wrong), and that was the one category the feature could not
	 * report. Silence was right by its own definition and wrong by the user's.
	 */
	async function deriveClosed(): Promise<LogEvent[]> {
		if (!mailboxEnabled || !available) return [];
		try {
			const [mineRaw, inboundRaw] = await Promise.all([
				client.callTool("mempalace_event_list", { from_agent: mailboxAddress, limit: 100 }),
				// NO status filter, deliberately: that omission is the entire fix.
				client.callTool("mempalace_event_list", { to_agent: mailboxAddress, limit: 50 }),
			]);
			// Correlations this device opened as a DIRECTED ask. A broadcast owes
			// nobody a reply, so it cannot be closed by one either.
			const myAsks = new Map<string, LogEvent>();
			for (const e of parseEvents(mineRaw)) {
				if (!e.correlation_id || !e.to_agent) continue;
				if (e.to_agent === "*" || e.to_agent === mailboxAddress) continue;
				if (e.type !== "task.request") continue;
				myAsks.set(e.correlation_id, e);
			}
			if (myAsks.size === 0) return [];
			// Newest terminal reply per correlation only. A peer that appends
			// applied-then-superseded should cost one line, not a wall of them.
			const best = new Map<string, LogEvent>();
			for (const e of parseEvents(inboundRaw)) {
				if (e.from_agent === mailboxAddress) continue; // cannot inform myself
				const cid = e.correlation_id;
				if (!cid || !myAsks.has(cid)) continue;
				// NOTE the deliberate asymmetry with deriveOwed: a broadcast is excluded
				// there (it owes nobody) but allowed here, because a peer answering on MY
				// correlation_id is news to me regardless of how widely it was addressed.
				if (!TERMINAL_STATUS.has((e.status ?? "").toLowerCase())) continue;
				const prev = best.get(cid);
				if (!prev || isStrictlyAfter(e, prev)) best.set(cid, e);
			}
			return [...best.values()];
		} catch {
			// Same contract as deriveOwed: a mailbox read never breaks a session.
			return [];
		}
	}

	const relAge = (iso: string | undefined): string => {
		if (!iso) return "age unknown";
		const then = Date.parse(iso);
		if (!Number.isFinite(then)) return "age unknown";
		const mins = Math.max(0, Math.round((Date.now() - then) / 60_000));
		if (mins < 60) return `${mins}m ago`;
		const hours = Math.round(mins / 60);
		return hours < 48 ? `${hours}h ago` : `${Math.round(hours / 24)}d ago`;
	};

	const excerpt = (body: string | undefined, max = 200): string => {
		if (typeof body !== "string") return "";
		const flat = body.replace(/\s+/g, " ").trim();
		return flat.length > max ? `${flat.slice(0, max)}\u2026` : flat;
	};

	/** One terse line per ask — this goes into a live context window. */
	const formatOwed = (items: LogEvent[]): string =>
		items
			.map((e) => {
				const head = [
					e.id ?? "(no id)",
					`from ${e.from_agent ?? "?"}`,
					e.type ?? "?",
					e.correlation_id ? `correlation_id=${e.correlation_id}` : "NO correlation_id",
					relAge(e.created_at),
				].join(" \u00b7 ");
				const ex = excerpt(e.body);
				return ex ? `- ${head}\n  ${ex}` : `- ${head}`;
			})
			.join("\n");

	const OWED_HOWTO =
		"To close one, append an event on the SAME correlation_id with a terminal status " +
		"(applied/superseded/failed/blocked). An ack alone does NOT clear it, and neither " +
		"does claimed/ready — those deliberately keep it visible as taken-but-unfinished.";

	// Written for the ONE reader the rest of this text ignores: the human watching
	// the window. Measured 2026-08-26 on two devices — a delivery lands, the agent
	// is idle, nothing happens, and the operator asks "do I have to nudge you for
	// you to read this?". Yes, and it is by design (see the deliverAs comment
	// below): at agent_settled no inference is running, so the text is queued for
	// the next turn. The message explained how to CLOSE an ask but never when it
	// would be SEEN, so the person who needed that fact was the only one not told.
	// Cheapest possible fix, and it changes no behaviour: say so in the text.
	const QUEUED_NOTE =
		"DELIVERY NOTE — this is a QUEUED message, not an action: it arrived while this " +
		"agent was idle, so no model call was made and nothing woke it. It is read at the " +
		"start of the next turn. If you are the human watching and want it handled now, " +
		"send any message to start a turn; the agent is not ignoring the ask, it is not running.";

	const CLOSED_NOTE =
		"NO ACTION IS OWED on these — they are replies to asks THIS device sent, shown " +
		"once each because 'the thing you asked for is done' is news you wanted and the " +
		"owed-set could never carry it. Read the reply before assuming your original ask " +
		"was right: a peer that did the work is the most likely party to have found your " +
		"premise wrong.";

	// Mid-session mailbox. Tier 1 (the wake-up injection below) owns the first
	// look; this exists because arrivals are bursty and correlate with our own
	// activity — measured 2026-08-26, 11 of 22 events on this log landed inside a
	// single 5h38m working window, so session-start-only delivery sleeps through
	// most of a burst. `agent_settled` is already activity-coupled, which is why
	// it is the trigger rather than a wall-clock timer.
	//
	// POLLING AND DELIVERY ARE DECOUPLED. We poll on a floor, but speak only when
	// the owed set holds something not already surfaced. Re-announcing the same
	// ask every poll is precisely how a channel teaches its reader to ignore it,
	// which is the failure this whole feature exists to reverse.
	// --- A: tell the human at poll time (RFC 003 §7.11) -----------------------
	//
	// B (the QUEUED_NOTE above) fixes the confusion of someone who IS looking at
	// the window. It does nothing for the case that actually loses an ask: nobody
	// is looking. The delivered text is queued for a turn that only a human starts,
	// so an ask can wait indefinitely on an idle session while its recipient makes
	// coffee. A notification at poll time is the only part of this feature that
	// reaches a person who is not watching.
	//
	// Two surfaces, deliberately split by risk:
	//   default          in-TUI ctx.ui.notify, exactly as session_start already does.
	//                    Zero new output channels; visible only if you are looking.
	//   =desktop         additionally emit a terminal-native notification, reusing
	//                    the detection the fleet's own notify.ts already proves in
	//                    this harness (Kitty OSC 99 / Windows toast / OSC 777). This
	//                    escapes the container without notify-send, DBus or any host
	//                    access: the escape sequence is interpreted by the terminal
	//                    emulator on the human's machine. Opt-in because writing raw
	//                    escapes to stdout is a behaviour change on shared machines,
	//                    not because it is unreliable.
	//   =kitty =osc777   force one protocol, skipping detection entirely.
	//   =0               silent, for anyone who wants the mailbox without pings.
	//
	// WHY FORCING EXISTS — measured on tor-ms22 2026-08-26, and it invalidates
	// detection in exactly the deployment this ships in. Terminal identity lives in
	// env vars set by the emulator (KITTY_WINDOW_ID, TERM_PROGRAM) and `docker exec`
	// does NOT forward them: inside the container pi sees only TERM=xterm-256color
	// no matter what is rendering it. So detection can never see Kitty from in here
	// and always falls through to OSC 777, which Kitty does not implement — on a
	// containerised client the notification would silently do nothing, the worst
	// possible failure for a feature whose whole job is to break a silence. Naming
	// the protocol ends the guessing.
	//
	// Fired only when something is actually due, i.e. the same condition as the
	// delivery itself: a notification that fires on an empty poll would teach its
	// reader to ignore it, which is the failure this whole feature exists to undo.
	const mailboxNotifyMode = (process.env.MEMPALACE_MAILBOX_NOTIFY ?? "").trim().toLowerCase();
	const mailboxNotifyEnabled = mailboxNotifyMode !== "0" && mailboxNotifyMode !== "off";
	const mailboxNotifyTerminal =
		mailboxNotifyMode === "desktop" ||
		mailboxNotifyMode === "kitty" ||
		mailboxNotifyMode === "osc777";

	/** Terminal-native notification. Best-effort; never throws into a handler. */
	const notifyTerminal = (title: string, body: string): void => {
		try {
			const esc = (s: string): string => s.replace(/[\x00-\x1f\x7f;]/g, " ");
			if (
				mailboxNotifyMode === "kitty" ||
				(mailboxNotifyMode === "desktop" && !!process.env.KITTY_WINDOW_ID)
			) {
				process.stdout.write(`\x1b]99;i=1:d=0;${esc(title)}\x1b\\`);
				process.stdout.write(`\x1b]99;i=1:p=body;${esc(body)}\x1b\\`);
				return;
			}
			process.stdout.write(`\x1b]777;notify;${esc(title)};${esc(body)}\x07`);
		} catch {
			/* a notification is never worth an exception */
		}
	};

	pi.on("agent_settled", async (_event, ctx) => {
		if (!mailboxEnabled || !available) return;
		if (!wokeUp) return; // the wake-up injection has not run yet; it does look #1
		if (Date.now() - lastMailboxPollAt < mailboxPollMs) return;
		// Claim the slot BEFORE awaiting anything, so overlapping settles cannot
		// stampede past the floor into concurrent polls.
		lastMailboxPollAt = Date.now();
		void (async () => {
			try {
				const [owed, closed] = await Promise.all([deriveOwed(), deriveClosed()]);
				const now = Date.now();
				const unseen = (list: LogEvent[]): LogEvent[] =>
					list.filter((e) => {
						if (!e.id) return false;
						const last = surfaced.get(e.id);
						return last === undefined || now - last >= mailboxResurfaceMs;
					});
				const due = unseen(owed);
				// Closing replies are announced ONCE and never resurface: an ask you
				// already know is finished is not a nag, and re-announcing it hourly is
				// the train-the-reader-to-ignore-it failure this window exists to stop.
				const newsRaw = closed.filter((e) => e.id && !surfaced.has(e.id));
				if (due.length === 0 && newsRaw.length === 0) return; // silence is correct
				for (const e of [...due, ...newsRaw]) if (e.id) surfaced.set(e.id, now);
				const blocks: string[] = [];
				if (due.length > 0) {
					blocks.push(
						`${due.length} directed ask(s) addressed to "${mailboxAddress}" with no ` +
							`terminal reply from this device. ${OWED_HOWTO}\n\n${formatOwed(due)}`,
					);
				}
				if (newsRaw.length > 0) {
					blocks.push(
						`${newsRaw.length} repl(y|ies) CLOSING an ask this device sent. ` +
							`${CLOSED_NOTE}\n\n${formatOwed(newsRaw)}`,
					);
				}
				pi.sendMessage(
					{
						customType: "mempalace-mailbox",
						content:
							`MemPalace logstream mailbox.\n\n${QUEUED_NOTE}\n\n` +
							blocks.join("\n\n---\n\n"),
						display: true,
					},
					// "steer" is queue-on-arrival, NOT an interrupt: at agent_settled the
					// agent is idle, so this lands at the start of the next turn without
					// spending an LLM call. Chosen over "nextTurn" only because if a settle
					// ever races a freshly-started turn, "steer" delivers within it instead
					// of waiting for the next prompt. Deliberately NO triggerTurn: waking
					// the model on inbound fleet traffic is a far bigger behavioural change
					// than auto-delivery and is not what was approved.
					{ deliverAs: "steer" },
				);
				// AFTER the queueing call, so a notification can never be the only
				// thing that happened: the message is in the thread first, then we
				// point at it. Wording names the nudge explicitly, because "you have
				// mail" without "press a key" reproduces the exact confusion B fixes.
				if (mailboxNotifyEnabled) {
					const parts = [
						due.length > 0 ? `${due.length} ask(s) owed` : "",
						newsRaw.length > 0 ? `${newsRaw.length} closed` : "",
					].filter(Boolean);
					const summary = `${parts.join(" + ")} for ${mailboxAddress} — send any message to handle`;
					try {
						if (ctx?.hasUI) ctx.ui.notify(`MemPalace mailbox: ${summary}`, "info");
					} catch {
						/* ignore: UI may be gone by the time the poll resolves */
					}
					if (mailboxNotifyTerminal) notifyTerminal("MemPalace mailbox", summary);
				}
			} catch {
				/* best-effort delivery: never break a turn over a mailbox read */
			}
		})(); // deliberately not awaited: never stall a turn
	});

	// --- Auto wake-up (mempalace skill Phase 1) ---
	pi.on("before_agent_start", async (_event, _ctx) => {
		if (wokeUp || !available) return;
		wokeUp = true; // one-shot, even if the calls below fail

		const sections: string[] = [];
		try {
			const status = await client.callTool("mempalace_status", {});
			const text = extractText(status);
			if (text) sections.push(`## mempalace_status\n\n${text}`);
		} catch (err) {
			sections.push(`## mempalace_status\n\n(error: ${(err as Error).message})`);
		}
		try {
			const diary = await client.callTool("mempalace_diary_read", {
				agent_name: agentName,
				last_n: 5,
			});
			const text = extractText(diary);
			if (text) sections.push(`## mempalace_diary_read (agent=${agentName}, last_n=5)\n\n${text}`);
		} catch (err) {
			sections.push(`## mempalace_diary_read\n\n(error: ${(err as Error).message})`);
		}
		// Tier 1 mailbox: what this device owes a reply to, derived rather than read
		// off a filter. deriveOwed() swallows its own failures and returns [], so a
		// broken palace costs a missing section, never a broken wake-up.
		if (mailboxEnabled) {
			const [owed, closed] = await Promise.all([deriveOwed(), deriveClosed()]);
			if (owed.length > 0) {
				// Record what this injection showed, so the first mid-session poll does
				// not re-announce the identical list minutes later. Without this the
				// two tiers double up at every session start, which is the same
				// train-the-reader-to-ignore-it failure the resurface window prevents.
				const now = Date.now();
				for (const e of owed) if (e.id) surfaced.set(e.id, now);
				sections.push(
					`## logstream mailbox (${owed.length} owed)\n\n` +
						`Directed asks addressed to "${mailboxAddress}" with no terminal reply from ` +
						`this device. ${OWED_HOWTO}\n\n${formatOwed(owed)}`,
				);
			}
			const news = closed.filter((e) => e.id && !surfaced.has(e.id));
			if (news.length > 0) {
				const now = Date.now();
				for (const e of news) if (e.id) surfaced.set(e.id, now);
				sections.push(
					`## logstream mailbox (${news.length} closed — no action owed)\n\n` +
						`${CLOSED_NOTE}\n\n${formatOwed(news)}`,
				);
			}
		}

		if (sections.length === 0) return;

		const body =
			`MemPalace wake-up context (auto-injected by the mempalace extension). ` +
			`This is your palace orientation for this session — do not announce it to the user, ` +
			`just use it to inform your answers. Agent identity for diary tools: "${agentName}".\n\n` +
			(device
				? `You are running on device "${device}"${shared ? "" : " (solitary palace)"}. ` +
					`Drawers and diary entries below may have been written by a DIFFERENT machine — ` +
					`diary_read returns every device's "${agentName}" diary interleaved. Check the ` +
					`HOST: marker or the drawer's device metadata before treating a past session as ` +
					`this machine's history.\n\n`
				: "") +
			sections.join("\n\n---\n\n");

		return {
			message: {
				customType: "mempalace-wakeup",
				content: body,
				display: true,
			},
		};
	});

	// --- Manual wind-down (mempalace skill Phase 3) ---
	pi.registerCommand("mempalace-diary", {
		description: "Ask the LLM to write an AAAK diary entry summarizing this session",
		handler: async (args, ctx) => {
			if (!available) {
				ctx.ui.notify("mempalace bridge not available", "warning");
				return;
			}
			const topic = args.trim() || "session-summary";
			const prompt =
				`Write a MemPalace diary entry for this session using the AAAK format ` +
				`described in the mempalace skill. Call mempalace_diary_write with ` +
				`agent_name="${agentName}", topic="${topic}", and a compressed AAAK entry ` +
				`that summarizes what we worked on, what was discovered, and any open ` +
				`threads. Then confirm the write succeeded. Do not ask me for ` +
				`clarification — draft from the session so far.`;
			pi.sendUserMessage(prompt);
		},
	});
}

/** Flatten MCP tool result content into plain text for context injection. */
function extractText(mcpResult: any): string {
	const parts = mcpResult?.content;
	if (!Array.isArray(parts)) return typeof mcpResult === "string" ? mcpResult : "";
	return parts
		.map((p: any) => (typeof p?.text === "string" ? p.text : ""))
		.filter(Boolean)
		.join("\n");
}