Fabric 1.20.1: server features (commands, LuckPerms, Placeholder API, economy API, client link) and client mod (HUD, editor, shop and market windows); Paper client link; docs and examples

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DjMbLQujBHunCCu5GpsHaT

docs/fabric.md

@@ -0,0 +1,56 @@
+# Fabric: server mod features and the client mod
+
+Two jars, both for **Fabric 1.20.1**:
+
+| Jar | Install on | Needs |
+|---|---|---|
+| `scopenet-fabric-1.20.1.jar` (server mod) | the server (and a single-player world if you want the commands there) | Fabric API. Optional: LuckPerms, Placeholder API |
+| `scopenet-client-fabric-1.20.1.jar` (client mod) | players who want the HUD, claim borders and shop/market windows | Fabric API |
+
+The client mod is optional and display-only. The server stays in charge of claims, money and permissions; every button in the client is an ordinary command. A player without it loses nothing. You can install both jars on the same machine (for example a single-player world), because the client mod shares no code with the server mod.
+
+Other Minecraft versions keep the original behaviour (sign-in, stats, claims, Live Map) and do not get the commands yet.
+
+## Build
+
+```sh
+gradle -p integrations -Ploader=fabric -PmcVersion=1.20.1 :fabric:build        # server mod
+gradle -p integrations -Ploader=fabric-client :fabric-client:build              # client mod
+```
+
+The core logic (`integrations/common`, package `net.scopenet.core`) is platform-neutral and unit-tested with `gradle -p integrations :common:test`. The Fabric classes are thin adapters over it.
+
+## What the server mod adds (same behaviour as the Paper plugin)
+
+* **Essentials:** `/spawn /home /sethome /delhome /back /tpa /tpaccept /tpdeny /rtp /warp /playtime` (homes and warps saved in `config/scopenet/essentials.json`). `/back` remembers where you were before SCOPENET teleports and where you died.
+* **Economy:** `/balance /pay /baltop /shop /sell hand /market (sell|buy) /orders /transactions`. Selling and buying go through an escrow file (`economy-pending.json`) so a crash or a panel outage never loses an item or a payment.
+* **Guilds:** `/guild` (info, create, leave, claim, unclaim, map, chat, sethome, home, members, bank, pay, sell, market), `/claim`, `/unclaim`. Claim checks use the same local index as the rest of the mod.
+* **Admin:** `/scopenet help | status | reload` (alias `/sn`).
+* **Permissions:** the same `scopenet.command.*` nodes as Paper. With the LuckPerms mod installed its answer wins; otherwise `permissions.default_level` decides, and admin nodes need operator level 2. `scopenet.claims.bypass` lets staff build in other guilds' claims.
+* **Placeholder API:** `%scopenet:level%`, `%scopenet:guild%`, `%scopenet:balance%`, `%scopenet:playtime%`, `%scopenet:quest_progress%` and the rest of the Paper list (see `Placeholders.KEYS`).
+* **Economy for other mods:** `net.scopenet.fabric.api.ScopenetEconomy` (Fabric's stand-in for Vault): `balance`, `deposit`, `withdraw`, all asynchronous and safe to retry.
+
+Not on Fabric yet: `/trade` (needs a chest window), item sorting of homes/warps into a menu (they are listed in chat), and teleports by other mods are not remembered for `/back`.
+
+### Economy mods
+
+SCOPENET keeps the ledger in the panel, so its money is one number per player across your network. Other Fabric mods can use it through `ScopenetEconomy`. Adapters that register SCOPENET as a provider inside third-party economy mods (Impactor, Common Economy API and similar) are **not included**: their APIs change between versions and I could not build against them, so shipping guesses would risk silent money bugs. They are small to add once the exact versions are chosen; the extension point is `ScopenetEconomy`.
+
+## The client mod
+
+* **HUD widgets:** Level (with XP bar and server level), Balance, Guild, Claim (who owns the chunk you are in) and Quests. Each can be on, compact or off.
+* **Claim borders:** green boxes around your guild's land and red around other guilds', within 4 chunks.
+* **Windows:** press **K** for the menu, then **Shop** (every price, your held item and what it is worth, one-click sell), **Market** (browse, one-click buy, list your held item) or **Settings**.
+* **HUD layout editor:** Settings → *Edit HUD layout*. Drag widgets, right-click to hide or show, scroll to resize. Positions snap to screen anchors, so they hold on any window size.
+* **Toasts:** level-ups, achievements and guild changes, each switchable.
+* **Keys:** *Open SCOPENET menu* (K) and *Show or hide SCOPENET HUD* (unbound) in Controls → SCOPENET.
+
+Settings are saved to `config/scopenet-client.json` (see `examples/fabric-client/`).
+
+### How it talks to the server
+
+Two plugin-message channels, `scopenet:s2c` and `scopenet:c2s`, carrying JSON in a Minecraft UTF string (`net.scopenet.core.Wire`). The client says hello; the server then sends its state, the claims around the player, and answers market and shop requests. The same channels work on the Paper plugin (`clientlink.enabled` in `config.yml`), so the client mod works on both. Turn the link off with `clientlink.enabled=false`.
+
+## Status
+
+The shared core, the escrow flow, the client-link protocol and the placeholders are covered by unit tests that run in CI (`CommandsTest`, `LinkTest`, `EssentialsServiceTest`). **The Fabric server mod, the client mod and the Paper additions have not been compiled or run**, because the build environment they were written in cannot download Minecraft, Fabric or Paper. Build them, then report any compile errors.

docs/server-integration.md

@@ -8,7 +8,7 @@ Use **online-mode=true**. The server's authlib-injector agent redirects Minecraf
 2. Create a server under **Servers**, choose **Members** or **Groups** for a private community, and copy its `sn_…` token. Give each server its own token.
 3. Install one server integration from Releases:
    - Paper/Purpur/Spigot: `scopenet-paper-VERSION.jar` in `plugins/`. Built against the Bukkit 1.20.1 API; intended for 1.20.1, 1.21.1 and 26.x. No NMS dependency. Folia is not supported.
-   - Fabric: `scopenet-fabric-MC-VERSION.jar` in `mods/`. No Fabric API or client mod required.
+   - Fabric: `scopenet-fabric-MC-VERSION.jar` in `mods/`. Sign-in, stats, claims and the Live Map need no Fabric API or client mod. The 1.20.1 build adds commands, permissions, placeholders and the client link, and needs Fabric API; see [fabric.md](fabric.md).
    - Forge: `scopenet-forge-MC-VERSION.jar` in `mods/`. Server-only installation; clients do not need SCOPENET.
    - Mod builds are **exact-version** artifacts for **1.20.1, 1.21.1, 26.1.2, 26.2 and 26.3**. Do not install one on a different Minecraft version. Future 26.x releases need their own verified builds.
 4. Configure Paper at `plugins/SCOPENET/config.yml`:
@@ -71,6 +71,6 @@ gradle -p integrations -Ploader=forge -PmcVersion=1.21.1 :forge:build
 gradle -p integrations -Ploader=fabric -PmcVersion=26.3 :fabric:build
 ```
 
-Substitute `fabric`/`forge` and the exact version as required. JARs are in the selected module's `build/libs/`. `-PreleaseVersion=X.Y.Z` stamps the artifact and metadata. The locally built 0.4.0 matrix for 1.20.1, 1.21.1, and 26.3 plus Paper is in [`release-artifacts/0.4.0`](../release-artifacts/0.4.0/README.md), with SHA-256 checksums. The **Server integrations** workflow can rebuild the matrix when Actions usage is available again.
+The optional Fabric client mod builds with `-Ploader=fabric-client :fabric-client:build`. Substitute `fabric`/`forge` and the exact version as required. JARs are in the selected module's `build/libs/`. `-PreleaseVersion=X.Y.Z` stamps the artifact and metadata. The locally built 0.4.0 matrix for 1.20.1, 1.21.1, and 26.3 plus Paper is in [`release-artifacts/0.4.0`](../release-artifacts/0.4.0/README.md), with SHA-256 checksums. The **Server integrations** workflow can rebuild the matrix when Actions usage is available again.
 
 Before production, test a valid login, wrong password, disabled account, denied group, missing launcher launch, panel outage, name-change/reconnect with the same inventory, chat count, heartbeat retry, and restart on a copy of your server world. Build/API tests do not replace a live Minecraft client/server compatibility check with your modpack.

examples/fabric-client/scopenet-client.json

@@ -1,27 +1,24 @@
 {
-  "_about": "SCOPENET client mod (Fabric 1.20.1) -> config/scopenet-client.json. The in-game config screen edits this file; you rarely need to change it by hand. The mod is in development and this format may grow.",
   "enabled": true,
   "hud": {
     "scale": 1.0,
     "opacity": 0.85,
-    "widgets": {
-      "balance":      { "enabled": true,  "anchor": "top_right",    "x": -8, "y": 8,   "compact": false },
-      "level":        { "enabled": true,  "anchor": "top_left",     "x": 8,  "y": 8,   "showXpBar": true },
-      "guild":        { "enabled": true,  "anchor": "bottom_left",  "x": 8,  "y": -8,  "showClaimOwner": true },
-      "quests":       { "enabled": false, "anchor": "middle_right", "x": -8, "y": 0,   "maxShown": 3 },
-      "claimBorders": { "enabled": true,  "showOnlyWhenSneaking": false }
-    },
     "hideInF3": true,
-    "hideWhileChatOpen": false
+    "hideWhileChatOpen": false,
+    "claimBorders": true,
+    "claimBordersOnlyWhenSneaking": false,
+    "widgets": {
+      "level":   { "enabled": true,  "anchor": "top_left",     "x": 8,  "y": 8,   "compact": false },
+      "balance": { "enabled": true,  "anchor": "top_right",    "x": -8, "y": 8,   "compact": false },
+      "guild":   { "enabled": true,  "anchor": "bottom_left",  "x": 8,  "y": -40, "compact": false },
+      "claim":   { "enabled": true,  "anchor": "top_center",   "x": 0,  "y": 8,   "compact": false },
+      "quests":  { "enabled": false, "anchor": "middle_right", "x": -8, "y": 0,   "compact": false }
+    }
   },
   "notifications": {
     "levelUp": true,
     "achievements": true,
-    "friendRequests": true,
+    "guild": true,
-    "gameInvites": true
+    "errors": true
-  },
-  "keybinds": {
-    "openMenu": "key.keyboard.k",
-    "toggleHud": "key.keyboard.h"
   }
 }

examples/fabric-server/scopenet.properties

@@ -1,6 +1,7 @@
 # SCOPENET for Fabric (server side)  ->  config/scopenet.properties
-# Works with the same panel as the Paper plugin. Keys marked [planned] are read once the Fabric
+# Same panel as the Paper plugin. Sign-in, stats, claims and the Live Map work on every supported Fabric version.
-# feature-parity work lands; unknown keys are ignored, so it is safe to keep them here.
+# Commands, permissions, placeholders and the client link need Fabric API and are in the Fabric 1.20.1 build.
+# Extra files the mod creates: config/scopenet/essentials.json (homes, warps), guild-homes.json, economy-pending.json.
 
 # --- Connection (required) ---------------------------------------------------
 # Your panel address and the token from Servers -> this server in the panel.
@@ -24,29 +25,30 @@ economy.enabled=true
 # (also needs Live Map switched on for this server in the panel).
 livemap.enabled=true
 
-# --- Essentials [planned] ----------------------------------------------------
+# --- Essentials (1.20.1) -----------------------------------------------------
-# Homes, warps, /back, /tpa and /rtp. Same defaults as Paper.
+# /spawn /home /sethome /delhome /back /tpa /tpaccept /tpdeny /rtp /warp /playtime
 essentials.max_homes=5
 essentials.rtp_radius=2500
 essentials.tpa_timeout_seconds=60
 
-# --- Permissions [planned] ---------------------------------------------------
+# --- Economy (1.20.1) --------------------------------------------------------
-# Uses the LuckPerms mod when it is installed (nodes are scopenet.command.*, same as Paper).
+# Shown next to amounts.
-# Without it, these defaults apply: "all" lets every player use the command, "op" limits to operators.
-permissions.default_level=all
-permissions.admin_commands=op
-
-# --- Economy mods [planned] --------------------------------------------------
-# auto   : use the first supported economy mod found (Impactor, Common Economy API), else SCOPENET's own balances
-# scopenet: always use SCOPENET balances (other mods can still read them through the SCOPENET API)
-economy.provider=auto
 economy.currency_symbol=$
 
-# --- Placeholder API [planned] -----------------------------------------------
+# --- Permissions (1.20.1) ----------------------------------------------------
-# Registers %scopenet:level%, %scopenet:guild%, %scopenet:balance%, %scopenet:playtime%,
+# With the LuckPerms mod installed, its answer wins. Use the same nodes as the Paper plugin
-# %scopenet:quest_progress% when Placeholder API (Fabric) is installed.
+# (scopenet.command.home, scopenet.command.guild.bank.withdraw, scopenet.claims.bypass ...).
+# Without LuckPerms, or when LuckPerms has no setting for a node:
+#   all : every player may use ordinary commands
+#   op  : only operators may
+# Admin nodes (/scopenet status and reload, scopenet.claims.bypass) always need operator level 2 by default.
+permissions.default_level=all
+
+# --- Placeholder API (1.20.1) ------------------------------------------------
+# With Placeholder API installed, registers %scopenet:level%, %scopenet:guild%, %scopenet:balance%,
+# %scopenet:playtime%, %scopenet:quest_progress% and the rest of the Paper placeholder list.
 placeholders.enabled=true
 
-# --- Client mod link [planned] -----------------------------------------------
+# --- Client mod link (1.20.1) ------------------------------------------------
-# Send balance, level and guild info to players who have the SCOPENET client mod.
+# Send balance, level, guild and claim info to players who have the SCOPENET client mod.
 clientlink.enabled=true

examples/paper/config.yml

@@ -114,6 +114,15 @@ integrations:
     enabled: true
     report-interval-seconds: 30
 
+# ==============================================================================
+# Client mod link
+# Sends balance, level, guild and claim info to players who have the optional SCOPENET
+# client mod (HUD widgets, claim overlay, shop and market windows). Players without it
+# are unaffected. Display only: everything the client does is an ordinary command.
+# ==============================================================================
+clientlink:
+  enabled: true
+
 # ==============================================================================
 # Permissions (set these in LuckPerms, not here)
 #   scopenet.command.<command>             e.g. scopenet.command.home

integrations/common/src/main/java/net/scopenet/core/ClientLink.java

@@ -194,6 +194,36 @@ public final class ClientLink {
         send(p, m);
     }
 
+    /**
+     * Events the panel queued for this server (level-ups, achievements, guild changes). Safe to call from any thread:
+     * each becomes a toast on the player's client and forces a fresh state.
+     */
+    public void onPanelEvents(JsonArray events) {
+        for (JsonElement element : events) {
+            if (!element.isJsonObject()) continue;
+            JsonObject n = element.getAsJsonObject();
+            String kind = PlayerCache.str(n, "kind", "");
+            String uuidText = PlayerCache.str(n, "uuid", "");
+            JsonObject d = PlayerCache.obj(n, "data");
+            UUID uuid;
+            try { uuid = UUID.fromString(uuidText); } catch (IllegalArgumentException e) { continue; }
+            String title, text;
+            switch (kind) {
+                case "level_up" -> { title = "Level up!"; text = ("server".equals(PlayerCache.str(d, "scope", "")) ? "Server level " : "Level ") + (long) PlayerCache.num(d, "level", 0); }
+                case "achievement" -> { title = "Achievement unlocked"; text = PlayerCache.str(d, "title", ""); }
+                case "guild_join" -> { title = "Guild"; text = "Joined " + PlayerCache.str(d, "guild", "a guild"); }
+                case "guild_leave" -> { title = "Guild"; text = "Left " + PlayerCache.str(d, "guild", "your guild"); }
+                default -> { continue; }
+            }
+            final String t = title, x = text, k = kind;
+            env.platform.runMain(() -> env.platform.player(uuid).ifPresent(p -> {
+                notify(p, k, t, x);
+                lastState.remove(uuid);
+                cache.refresh(p, info -> pushState(p));
+            }));
+        }
+    }
+
     /** About once a second: new chunk, new claims, or new state for every client. */
     public void tick() {
         for (UUID id : new ArrayList<>(clients)) {

integrations/common/src/test/java/net/scopenet/core/LinkTest.java

@@ -114,6 +114,17 @@ class LinkTest {
         assertEquals(35.0, shop.getAsJsonObject("held").get("unit").getAsDouble());
     }
 
+    @Test void panelEventsBecomeToasts() {
+        link.receive(alex, msg("{\"t\":\"hello\"}"));
+        link.onPanelEvents(JsonParser.parseString("[{\"kind\":\"level_up\",\"uuid\":\"" + alex.id + "\",\"data\":{\"scope\":\"global\",\"level\":13}},"
+                + "{\"kind\":\"achievement\",\"uuid\":\"" + alex.id + "\",\"data\":{\"title\":\"Deep Diver\"}},"
+                + "{\"kind\":\"unknown\",\"uuid\":\"" + alex.id + "\",\"data\":{}},{\"kind\":\"level_up\",\"uuid\":\"nope\"}]").getAsJsonArray());
+        List<JsonObject> toasts = sent.stream().filter(m -> m.get("t").getAsString().equals("notify")).toList();
+        assertEquals(2, toasts.size());
+        assertEquals("Level 13", toasts.get(0).get("text").getAsString());
+        assertEquals("Deep Diver", toasts.get(1).get("text").getAsString());
+    }
+
     @Test void disabledClientLinkIsSilent() {
         kit.env.features = new Features(true, true, true, true, true, false, "$");
         link.receive(alex, msg("{\"t\":\"hello\"}"));

integrations/fabric-client/build.gradle

@@ -0,0 +1,16 @@
+plugins { id 'fabric-loom' version '1.8.13' }
+// Client-only companion to the SCOPENET plugin / Fabric server mod. Fabric 1.20.1.
+// It needs nothing from `common`: the messages are plain JSON inside a Minecraft UTF string.
+java.sourceCompatibility = JavaVersion.VERSION_17
+java.targetCompatibility = JavaVersion.VERSION_17
+dependencies {
+    minecraft 'com.mojang:minecraft:1.20.1'
+    mappings loom.officialMojangMappings()
+    modImplementation 'net.fabricmc:fabric-loader:0.16.10'
+    modImplementation 'net.fabricmc.fabric-api:fabric-api:0.92.2+1.20.1'
+}
+processResources {
+    inputs.property 'version', project.version
+    filesMatching('fabric.mod.json') { expand(version: project.version) }
+}
+base.archivesName = 'scopenet-client-fabric-1.20.1'

integrations/fabric-client/src/main/java/net/scopenet/client/ClientConfig.java

@@ -0,0 +1,105 @@
+package net.scopenet.client;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import net.fabricmc.loader.api.FabricLoader;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.Writer;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/** config/scopenet-client.json: what to show and where. Edited in game (K, then Settings) or by hand. */
+public final class ClientConfig {
+    private static final Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+    private static final Path FILE = FabricLoader.getInstance().getConfigDir().resolve("scopenet-client.json");
+
+    /** Where a widget sits. {@code x}/{@code y} are offsets from the chosen screen anchor. */
+    public static final class WidgetConfig {
+        public boolean enabled = true;
+        public String anchor = "top_left";
+        public int x = 8;
+        public int y = 8;
+        public boolean compact = false;
+
+        WidgetConfig(boolean enabled, String anchor, int x, int y) { this.enabled = enabled; this.anchor = anchor; this.x = x; this.y = y; }
+        public WidgetConfig() { }
+    }
+
+    public static final class Hud {
+        public float scale = 1.0f;
+        public float opacity = 0.85f;
+        public boolean hideInF3 = true;
+        public boolean hideWhileChatOpen = false;
+        public boolean claimBorders = true;
+        public boolean claimBordersOnlyWhenSneaking = false;
+        public Map<String, WidgetConfig> widgets = defaults();
+    }
+
+    public static final class Notifications {
+        public boolean levelUp = true;
+        public boolean achievements = true;
+        public boolean guild = true;
+        public boolean errors = true;
+    }
+
+    public boolean enabled = true;
+    public Hud hud = new Hud();
+    public Notifications notifications = new Notifications();
+
+    public static Map<String, WidgetConfig> defaults() {
+        Map<String, WidgetConfig> m = new LinkedHashMap<>();
+        m.put("level", new WidgetConfig(true, "top_left", 8, 8));
+        m.put("balance", new WidgetConfig(true, "top_right", -8, 8));
+        m.put("guild", new WidgetConfig(true, "bottom_left", 8, -40));
+        m.put("claim", new WidgetConfig(true, "top_center", 0, 8));
+        m.put("quests", new WidgetConfig(false, "middle_right", -8, 0));
+        return m;
+    }
+
+    public WidgetConfig widget(String id) { return hud.widgets.computeIfAbsent(id, k -> defaults().getOrDefault(k, new WidgetConfig())); }
+
+    public static ClientConfig load() {
+        ClientConfig config = new ClientConfig();
+        if (Files.exists(FILE)) {
+            try (Reader in = Files.newBufferedReader(FILE)) {
+                JsonObject root = JsonParser.parseReader(in).getAsJsonObject();
+                ClientConfig read = GSON.fromJson(root, ClientConfig.class);
+                if (read != null) config = read;
+            } catch (IOException | RuntimeException e) {
+                System.err.println("[SCOPENET] Could not read " + FILE + ", using defaults: " + e.getMessage());
+            }
+        }
+        // Keep every widget present, and values sane.
+        Map<String, WidgetConfig> merged = defaults();
+        if (config.hud == null) config.hud = new Hud();
+        if (config.hud.widgets != null) merged.putAll(config.hud.widgets);
+        config.hud.widgets = merged;
+        if (config.notifications == null) config.notifications = new Notifications();
+        config.hud.scale = Math.max(0.5f, Math.min(2.0f, config.hud.scale));
+        config.hud.opacity = Math.max(0.1f, Math.min(1.0f, config.hud.opacity));
+        return config;
+    }
+
+    public void save() {
+        try {
+            Path tmp = FILE.resolveSibling(FILE.getFileName() + ".tmp");
+            try (Writer w = Files.newBufferedWriter(tmp)) { GSON.toJson(this, w); }
+            Files.move(tmp, FILE, StandardCopyOption.REPLACE_EXISTING);
+        } catch (IOException e) {
+            System.err.println("[SCOPENET] Could not save " + FILE + ": " + e.getMessage());
+        }
+    }
+
+    public void resetHud() {
+        hud.widgets = defaults();
+        hud.scale = 1.0f;
+        hud.opacity = 0.85f;
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/ClientState.java

@@ -0,0 +1,124 @@
+package net.scopenet.client;
+
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** What the server last told this client. Everything is optional: before the first message the HUD shows nothing. */
+public final class ClientState {
+    public record Quest(int done, int total) {}
+    public record Guild(String name, String tag, String role, long claims) {}
+    public record Owner(String name, String tag, boolean mine) {}
+    public record Listing(long id, String seller, String guildTag, String itemId, String itemName, int amount, double price) {}
+    public record ShopItem(String id, String name, double price) {}
+    public record Held(String id, String name, int count, double unit) {}
+
+    public volatile boolean connected;
+    public volatile String server = "";
+    public volatile String currency = "$";
+    public volatile boolean featEconomy, featGuilds, featClaims, featEssentials;
+
+    public volatile boolean hasState;
+    public volatile String name = "";
+    public volatile long level = 1, xp, xpNow, xpNext, serverLevel = 1;
+    public volatile double xpPct, serverXpPct, balance;
+    public volatile String title = "", rank = "";
+    public volatile Guild guild;
+    public volatile Quest daily = new Quest(0, 0), weekly = new Quest(0, 0);
+    public volatile long playtime, kills, deaths;
+
+    public volatile String claimDim = "";
+    public volatile int claimCx, claimCz, claimRadius;
+    public volatile String claimCells = "";
+    public volatile Owner claimOwner;
+
+    public volatile List<Listing> market = List.of();
+    public volatile List<ShopItem> shop = List.of();
+    public volatile Held held;
+    public volatile long marketAt, shopAt;
+
+    /** Called on the client thread with a server message; returns a toast (kind, title, text) or null. */
+    public String[] handle(String json) {
+        JsonObject m;
+        try { m = JsonParser.parseString(json).getAsJsonObject(); } catch (RuntimeException e) { return null; }
+        switch (str(m, "t")) {
+            case "hello" -> {
+                connected = true;
+                server = str(m, "server");
+                currency = m.has("currency") ? str(m, "currency") : "$";
+                JsonObject f = obj(m, "features");
+                featEconomy = bool(f, "economy"); featGuilds = bool(f, "guilds"); featClaims = bool(f, "claims"); featEssentials = bool(f, "essentials");
+            }
+            case "state" -> {
+                name = str(m, "name");
+                level = lng(m, "level", 1); xp = lng(m, "xp", 0); xpNow = lng(m, "xpNow", 0); xpNext = lng(m, "xpNext", 0);
+                xpPct = num(m, "xpPct"); title = str(m, "title"); serverLevel = lng(m, "serverLevel", 1); serverXpPct = num(m, "serverXpPct");
+                balance = num(m, "balance"); playtime = lng(m, "playtime", 0); kills = lng(m, "kills", 0); deaths = lng(m, "deaths", 0);
+                rank = str(m, "rank");
+                JsonObject g = obj(m, "guild");
+                guild = g == null ? null : new Guild(str(g, "name"), str(g, "tag"), str(g, "role"), lng(g, "claims", 0));
+                daily = quest(obj(m, "daily"));
+                weekly = quest(obj(m, "weekly"));
+                hasState = true;
+            }
+            case "claims" -> {
+                claimDim = str(m, "dim"); claimCx = (int) lng(m, "cx", 0); claimCz = (int) lng(m, "cz", 0);
+                claimRadius = (int) lng(m, "r", 0); claimCells = str(m, "cells");
+                JsonObject o = obj(m, "owner");
+                claimOwner = o == null ? null : new Owner(str(o, "name"), str(o, "tag"), bool(o, "mine"));
+            }
+            case "market" -> {
+                List<Listing> list = new ArrayList<>();
+                for (JsonElement e : arr(m, "listings")) {
+                    JsonObject l = e.getAsJsonObject();
+                    list.add(new Listing(lng(l, "id", 0), str(l, "seller_name"), l.has("seller_guild") && l.get("seller_guild").isJsonPrimitive() ? str(l, "seller_guild") : null,
+                            str(l, "item_id"), str(l, "item_name"), (int) lng(l, "amount", 1), num(l, "price")));
+                }
+                market = list;
+                if (m.has("balance")) balance = num(m, "balance");
+                marketAt = System.currentTimeMillis();
+            }
+            case "shop" -> {
+                List<ShopItem> list = new ArrayList<>();
+                for (JsonElement e : arr(m, "items")) {
+                    JsonObject i = e.getAsJsonObject();
+                    list.add(new ShopItem(str(i, "id"), str(i, "name"), num(i, "price")));
+                }
+                shop = list;
+                JsonObject h = obj(m, "held");
+                held = h == null ? null : new Held(str(h, "id"), str(h, "name"), (int) lng(h, "count", 0), h.has("unit") ? num(h, "unit") : -1);
+                shopAt = System.currentTimeMillis();
+            }
+            case "notify" -> { return new String[]{str(m, "kind"), str(m, "title"), str(m, "text")}; }
+            default -> { }
+        }
+        return null;
+    }
+
+    /** Sample values so the layout editor can show every widget even with no server data. */
+    public static ClientState preview() {
+        ClientState s = new ClientState();
+        s.connected = true; s.hasState = true; s.featEconomy = true; s.featGuilds = true; s.featClaims = true; s.featEssentials = true;
+        s.level = 27; s.xpPct = 62; s.title = "Miner"; s.serverLevel = 9; s.balance = 12840.5;
+        s.guild = new Guild("Iron Wolves", "IRON", "officer", 14);
+        s.daily = new Quest(2, 3); s.weekly = new Quest(1, 4);
+        s.claimCells = "x"; s.claimOwner = new Owner("Iron Wolves", "IRON", true);
+        return s;
+    }
+
+    public void reset() {
+        connected = false; hasState = false; guild = null; claimOwner = null; claimCells = ""; market = List.of(); shop = List.of(); held = null;
+    }
+
+    private static Quest quest(JsonObject o) { return o == null ? new Quest(0, 0) : new Quest((int) lng(o, "done", 0), (int) lng(o, "total", 0)); }
+    private static String str(JsonObject o, String k) { JsonElement e = o == null ? null : o.get(k); return e != null && e.isJsonPrimitive() ? e.getAsString() : ""; }
+    private static double num(JsonObject o, String k) { JsonElement e = o == null ? null : o.get(k); return e != null && e.isJsonPrimitive() && e.getAsJsonPrimitive().isNumber() ? e.getAsDouble() : 0; }
+    private static long lng(JsonObject o, String k, long d) { JsonElement e = o == null ? null : o.get(k); return e != null && e.isJsonPrimitive() && e.getAsJsonPrimitive().isNumber() ? e.getAsLong() : d; }
+    private static boolean bool(JsonObject o, String k) { JsonElement e = o == null ? null : o.get(k); return e != null && e.isJsonPrimitive() && e.getAsBoolean(); }
+    private static JsonObject obj(JsonObject o, String k) { JsonElement e = o == null ? null : o.get(k); return e != null && e.isJsonObject() ? e.getAsJsonObject() : null; }
+    private static JsonArray arr(JsonObject o, String k) { JsonElement e = o == null ? null : o.get(k); return e != null && e.isJsonArray() ? e.getAsJsonArray() : new JsonArray(); }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/Link.java

@@ -0,0 +1,59 @@
+package net.scopenet.client;
+
+import com.google.gson.JsonObject;
+import net.fabricmc.fabric.api.client.networking.v1.ClientPlayConnectionEvents;
+import net.fabricmc.fabric.api.client.networking.v1.ClientPlayNetworking;
+import net.fabricmc.fabric.api.networking.v1.PacketByteBufs;
+import net.minecraft.client.Minecraft;
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.network.chat.Component;
+import net.minecraft.client.gui.components.toasts.SystemToast;
+import net.minecraft.resources.ResourceLocation;
+
+/** The channel to the SCOPENET server mod or plugin. Messages are JSON in a Minecraft UTF string. */
+public final class Link {
+    private static final ResourceLocation TO_CLIENT = new ResourceLocation("scopenet", "s2c");
+    private static final ResourceLocation TO_SERVER = new ResourceLocation("scopenet", "c2s");
+
+    private final ClientState state;
+    private final ClientConfig config;
+
+    Link(ClientState state, ClientConfig config) { this.state = state; this.config = config; }
+
+    void register() {
+        ClientPlayNetworking.registerGlobalReceiver(TO_CLIENT, (client, handler, buf, sender) -> {
+            String json = buf.readUtf(32767 * 3);
+            client.execute(() -> toast(state.handle(json)));
+        });
+        ClientPlayConnectionEvents.JOIN.register((handler, sender, client) -> send("hello"));
+        ClientPlayConnectionEvents.DISCONNECT.register((handler, client) -> state.reset());
+    }
+
+    public void send(String type) {
+        JsonObject m = new JsonObject();
+        m.addProperty("t", type);
+        if (type.equals("hello")) m.addProperty("mod", "0.1.0");
+        FriendlyByteBuf buf = PacketByteBufs.create();
+        buf.writeUtf(m.toString(), 32767 * 3);
+        try { ClientPlayNetworking.send(TO_SERVER, buf); } catch (RuntimeException ignored) { /* not in a world */ }
+    }
+
+    /** Run a server command as the player, exactly as if typed. */
+    public static void command(String command) {
+        Minecraft mc = Minecraft.getInstance();
+        if (mc.player != null) mc.player.connection.sendCommand(command.startsWith("/") ? command.substring(1) : command);
+    }
+
+    private void toast(String[] t) {
+        if (t == null) return;
+        boolean wanted = switch (t[0]) {
+            case "level_up" -> config.notifications.levelUp;
+            case "achievement" -> config.notifications.achievements;
+            case "guild_join", "guild_leave" -> config.notifications.guild;
+            case "error" -> config.notifications.errors;
+            default -> true;
+        };
+        if (!wanted || !config.enabled) return;
+        SystemToast.add(Minecraft.getInstance().getToasts(), SystemToast.SystemToastIds.PERIODIC_NOTIFICATION, Component.literal(t[1]), Component.literal(t[2]));
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/ScopenetClient.java

@@ -0,0 +1,47 @@
+package net.scopenet.client;
+
+import com.mojang.blaze3d.platform.InputConstants;
+import net.fabricmc.api.ClientModInitializer;
+import net.fabricmc.fabric.api.client.event.lifecycle.v1.ClientTickEvents;
+import net.fabricmc.fabric.api.client.keybinding.v1.KeyBindingHelper;
+import net.fabricmc.fabric.api.client.rendering.v1.HudRenderCallback;
+import net.fabricmc.fabric.api.client.rendering.v1.WorldRenderEvents;
+import net.minecraft.client.KeyMapping;
+import net.scopenet.client.hud.ClaimBorders;
+import net.scopenet.client.hud.Hud;
+import net.scopenet.client.screen.MenuScreen;
+import org.lwjgl.glfw.GLFW;
+
+/**
+ * SCOPENET client: HUD widgets, claim borders, and the shop and market windows. Everything it shows comes from the
+ * server over the {@code scopenet:s2c} channel, and everything it does is an ordinary command, so the server stays
+ * in charge. If the server has no SCOPENET, this does nothing.
+ */
+public final class ScopenetClient implements ClientModInitializer {
+    private static ClientConfig config;
+    private static ClientState state;
+    private static Link link;
+
+    public static ClientConfig config() { return config; }
+    public static ClientState state() { return state; }
+    public static Link link() { return link; }
+
+    @Override public void onInitializeClient() {
+        config = ClientConfig.load();
+        state = new ClientState();
+        link = new Link(state, config);
+        link.register();
+
+        Hud hud = new Hud(state, config);
+        HudRenderCallback.EVENT.register((graphics, tickDelta) -> hud.render(graphics, tickDelta));
+        ClaimBorders borders = new ClaimBorders(state, config);
+        WorldRenderEvents.LAST.register(borders::render);
+
+        KeyMapping menu = KeyBindingHelper.registerKeyBinding(new KeyMapping("key.scopenet.menu", InputConstants.Type.KEYSYM, GLFW.GLFW_KEY_K, "key.categories.scopenet"));
+        KeyMapping toggle = KeyBindingHelper.registerKeyBinding(new KeyMapping("key.scopenet.toggle_hud", InputConstants.Type.KEYSYM, GLFW.GLFW_KEY_UNKNOWN, "key.categories.scopenet"));
+        ClientTickEvents.END_CLIENT_TICK.register(client -> {
+            while (menu.consumeClick()) if (client.screen == null && client.player != null) client.setScreen(new MenuScreen());
+            while (toggle.consumeClick()) { config.enabled = !config.enabled; config.save(); }
+        });
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/Ui.java

@@ -0,0 +1,58 @@
+package net.scopenet.client;
+
+import net.minecraft.client.gui.Font;
+import net.minecraft.client.gui.GuiGraphics;
+
+import java.util.Locale;
+
+/** Shared look: the SCOPENET palette and a few drawing helpers, so every widget and window feels like one app. */
+public final class Ui {
+    public static final int ACCENT = 0xFF8B6CFF, CYAN = 0xFF22D3EE, GOLD = 0xFFFBBF24, GREEN = 0xFF34D399, RED = 0xFFFB7185;
+    public static final int TEXT = 0xFFE6E8EE, MUTED = 0xFF9AA0AE, PANEL = 0x0E1014, PANEL_2 = 0x1A1D25, LINE = 0xFF2B2F3A;
+
+    private Ui() {}
+
+    public static int alpha(int rgb, float opacity) {
+        return (Math.max(0, Math.min(255, (int) (opacity * 255))) << 24) | (rgb & 0xFFFFFF);
+    }
+
+    public static String money(String symbol, double value) { return symbol + String.format(Locale.US, "%,.2f", value); }
+
+    /** A card: dark rounded-looking panel with a coloured edge on the left. */
+    public static void card(GuiGraphics g, int x, int y, int w, int h, int accent, float opacity) {
+        g.fill(x + 1, y, x + w - 1, y + h, alpha(PANEL, opacity));
+        g.fill(x, y + 1, x + w, y + h - 1, alpha(PANEL, opacity));
+        g.fill(x, y + 1, x + 2, y + h - 1, accent);
+    }
+
+    /** A flat panel with a 1px border, for windows. */
+    public static void window(GuiGraphics g, int x, int y, int w, int h) {
+        g.fill(x - 1, y - 1, x + w + 1, y + h + 1, LINE);
+        g.fill(x, y, x + w, y + h, 0xF0101319);
+    }
+
+    public static void bar(GuiGraphics g, int x, int y, int w, int h, double pct, int colour, float opacity) {
+        g.fill(x, y, x + w, y + h, alpha(0x2B2F3A, Math.max(opacity, 0.6f)));
+        int filled = (int) Math.round(w * Math.max(0, Math.min(100, pct)) / 100.0);
+        if (filled > 0) g.fill(x, y, x + filled, y + h, colour);
+    }
+
+    /** The item for a panel id ("DIAMOND" or "modid:item"); barrier if the client doesn't know it. */
+    public static net.minecraft.world.item.ItemStack stackFor(String panelId, int count) {
+        String registry = panelId.contains(":") ? panelId : "minecraft:" + panelId.toLowerCase(Locale.ROOT);
+        net.minecraft.resources.ResourceLocation id = net.minecraft.resources.ResourceLocation.tryParse(registry);
+        net.minecraft.world.item.Item item = id == null ? net.minecraft.world.item.Items.AIR : net.minecraft.core.registries.BuiltInRegistries.ITEM.get(id);
+        if (item == net.minecraft.world.item.Items.AIR) item = net.minecraft.world.item.Items.BARRIER;
+        return new net.minecraft.world.item.ItemStack(item, Math.max(1, count));
+    }
+
+    public static boolean inside(double mx, double my, int x, int y, int w, int h) { return mx >= x && mx < x + w && my >= y && my < y + h; }
+
+    public static String clip(Font font, String text, int maxWidth) {
+        if (font.width(text) <= maxWidth) return text;
+        String ellipsis = "…";
+        int end = text.length();
+        while (end > 0 && font.width(text.substring(0, end) + ellipsis) > maxWidth) end--;
+        return text.substring(0, end) + ellipsis;
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/hud/ClaimBorders.java

@@ -0,0 +1,49 @@
+package net.scopenet.client.hud;
+
+import net.fabricmc.fabric.api.client.rendering.v1.WorldRenderContext;
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.blaze3d.vertex.VertexConsumer;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.LevelRenderer;
+import net.minecraft.client.renderer.RenderType;
+import net.minecraft.world.phys.Vec3;
+import net.scopenet.client.ClientConfig;
+import net.scopenet.client.ClientState;
+
+/** Draws the borders of claimed chunks around you in the world: green for your guild's land, red for anyone else's. */
+public final class ClaimBorders {
+    private final ClientState state;
+    private final ClientConfig config;
+
+    public ClaimBorders(ClientState state, ClientConfig config) { this.state = state; this.config = config; }
+
+    public void render(WorldRenderContext context) {
+        Minecraft mc = Minecraft.getInstance();
+        if (!config.enabled || !config.hud.claimBorders || !state.connected || !state.featClaims || state.claimCells.isEmpty() || mc.player == null) return;
+        if (config.hud.claimBordersOnlyWhenSneaking && !mc.player.isShiftKeyDown()) return;
+        if (context.consumers() == null) return;
+        // Only the world the server sent the map for.
+        String dim = mc.level == null ? "" : mc.level.dimension().location().toString();
+        if (!dim.equals(state.claimDim)) return;
+
+        int r = state.claimRadius, side = r * 2 + 1;
+        String cells = state.claimCells;
+        if (cells.length() != side * side) return;
+        Vec3 cam = context.camera().getPosition();
+        PoseStack pose = context.matrixStack();
+        VertexConsumer lines = context.consumers().getBuffer(RenderType.lines());
+        double y0 = Math.floor(mc.player.getY()) - 6, y1 = y0 + 14;
+        pose.pushPose();
+        pose.translate(-cam.x, -cam.y, -cam.z);
+        for (int dz = -r; dz <= r; dz++) {
+            for (int dx = -r; dx <= r; dx++) {
+                char cell = cells.charAt((dz + r) * side + (dx + r));
+                if (cell == '0') continue;
+                float cr = cell == '1' ? 0.2f : 0.98f, cg = cell == '1' ? 0.85f : 0.35f, cb = cell == '1' ? 0.55f : 0.45f;
+                double x0 = (state.claimCx + dx) * 16.0, z0 = (state.claimCz + dz) * 16.0;
+                LevelRenderer.renderLineBox(pose, lines, x0 + 0.02, y0, z0 + 0.02, x0 + 15.98, y1, z0 + 15.98, cr, cg, cb, 0.9f);
+            }
+        }
+        pose.popPose();
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/hud/Hud.java

@@ -0,0 +1,60 @@
+package net.scopenet.client.hud;
+
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.gui.Font;
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.screens.ChatScreen;
+import net.scopenet.client.ClientConfig;
+import net.scopenet.client.ClientConfig.WidgetConfig;
+import net.scopenet.client.ClientState;
+
+/** Lays out and draws the widgets. The editor uses the same maths, so what you place is what you get. */
+public final class Hud {
+    public static final String[] ANCHORS = {"top_left", "top_center", "top_right", "middle_left", "middle_center", "middle_right", "bottom_left", "bottom_center", "bottom_right"};
+
+    private final ClientState state;
+    private final ClientConfig config;
+
+    public Hud(ClientState state, ClientConfig config) { this.state = state; this.config = config; }
+
+    /** Top-left corner for a widget of size (w, h) on a screen of (sw, sh) (in HUD units, i.e. already divided by the scale). */
+    public static int[] place(WidgetConfig c, int sw, int sh, int w, int h) {
+        String a = c.anchor == null ? "top_left" : c.anchor;
+        int x = a.endsWith("right") ? sw - w : a.endsWith("center") ? (sw - w) / 2 : 0;
+        int y = a.startsWith("bottom") ? sh - h : a.startsWith("middle") ? (sh - h) / 2 : 0;
+        return new int[]{x + c.x, y + c.y};
+    }
+
+    /** The anchor nearest to a spot, and the offsets from it, so dragged widgets keep their place on any window size. */
+    public static void anchorTo(WidgetConfig c, int sw, int sh, int w, int h, int left, int top) {
+        double cx = left + w / 2.0, cy = top + h / 2.0;
+        String col = cx < sw / 3.0 ? "left" : cx > sw * 2 / 3.0 ? "right" : "center";
+        String row = cy < sh / 3.0 ? "top" : cy > sh * 2 / 3.0 ? "bottom" : "middle";
+        String anchor = row + "_" + col;
+        c.anchor = anchor;
+        int bx = anchor.endsWith("right") ? sw - w : anchor.endsWith("center") ? (sw - w) / 2 : 0;
+        int by = anchor.startsWith("bottom") ? sh - h : anchor.startsWith("middle") ? (sh - h) / 2 : 0;
+        c.x = left - bx;
+        c.y = top - by;
+    }
+
+    public void render(GuiGraphics g, float tickDelta) {
+        Minecraft mc = Minecraft.getInstance();
+        if (!config.enabled || !state.connected || mc.options.hideGui || mc.player == null) return;
+        if (config.hud.hideInF3 && mc.options.renderDebug) return;
+        if (config.hud.hideWhileChatOpen && mc.screen instanceof ChatScreen) return;
+        Font font = mc.font;
+        float scale = config.hud.scale;
+        int sw = (int) (g.guiWidth() / scale), sh = (int) (g.guiHeight() / scale);
+        g.pose().pushPose();
+        g.pose().scale(scale, scale, 1f);
+        for (HudWidget widget : Widgets.ALL) {
+            WidgetConfig c = config.widget(widget.id);
+            if (!c.enabled || !widget.available(state)) continue;
+            int w = widget.width(font, state, c), h = widget.height(font, state, c);
+            int[] at = place(c, sw, sh, w, h);
+            widget.draw(g, font, state, c, at[0], at[1], config.hud.opacity);
+        }
+        g.pose().popPose();
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/hud/HudWidget.java

@@ -0,0 +1,24 @@
+package net.scopenet.client.hud;
+
+import net.minecraft.client.gui.Font;
+import net.minecraft.client.gui.GuiGraphics;
+import net.scopenet.client.ClientConfig;
+import net.scopenet.client.ClientState;
+
+/** One draggable piece of the HUD. */
+public abstract class HudWidget {
+    public final String id;
+    public final String label;
+
+    protected HudWidget(String id, String label) { this.id = id; this.label = label; }
+
+    /** False when the server says this system is off, or there's nothing to show. The editor ignores this. */
+    public abstract boolean available(ClientState s);
+
+    public abstract int width(Font font, ClientState s, ClientConfig.WidgetConfig c);
+
+    public abstract int height(Font font, ClientState s, ClientConfig.WidgetConfig c);
+
+    /** Draw with the top-left corner at (x, y). */
+    public abstract void draw(GuiGraphics g, Font font, ClientState s, ClientConfig.WidgetConfig c, int x, int y, float opacity);
+}

integrations/fabric-client/src/main/java/net/scopenet/client/hud/Widgets.java

@@ -0,0 +1,109 @@
+package net.scopenet.client.hud;
+
+import net.minecraft.client.gui.Font;
+import net.minecraft.client.gui.GuiGraphics;
+import net.scopenet.client.ClientConfig.WidgetConfig;
+import net.scopenet.client.ClientState;
+import net.scopenet.client.Ui;
+
+import java.util.List;
+
+/** The built-in HUD widgets: level, balance, guild, claim and quests. */
+public final class Widgets {
+    private Widgets() {}
+
+    public static final List<HudWidget> ALL = List.of(new Level(), new Balance(), new Guild(), new Claim(), new Quests());
+
+    static final class Level extends HudWidget {
+        Level() { super("level", "Level"); }
+        @Override public boolean available(ClientState s) { return s.hasState; }
+        @Override public int width(Font f, ClientState s, WidgetConfig c) { return c.compact ? 64 : 118; }
+        @Override public int height(Font f, ClientState s, WidgetConfig c) { return c.compact ? 22 : 34; }
+        @Override public void draw(GuiGraphics g, Font f, ClientState s, WidgetConfig c, int x, int y, float o) {
+            int w = width(f, s, c), h = height(f, s, c);
+            Ui.card(g, x, y, w, h, Ui.ACCENT, o);
+            g.drawString(f, "Lv " + s.level, x + 7, y + 5, Ui.TEXT, true);
+            if (!c.compact) {
+                String title = s.title.isEmpty() ? "" : Ui.clip(f, s.title, w - 52);
+                g.drawString(f, title, x + w - 6 - f.width(title), y + 5, Ui.MUTED, true);
+                Ui.bar(g, x + 7, y + 18, w - 14, 5, s.xpPct, Ui.ACCENT, o);
+                String text = Math.round(s.xpPct) + "%  ·  SMP Lv " + s.serverLevel;
+                g.drawString(f, text, x + 7, y + 25, Ui.MUTED, false);
+            } else {
+                Ui.bar(g, x + 7, y + 15, w - 14, 4, s.xpPct, Ui.ACCENT, o);
+            }
+        }
+    }
+
+    static final class Balance extends HudWidget {
+        Balance() { super("balance", "Balance"); }
+        @Override public boolean available(ClientState s) { return s.hasState && s.featEconomy; }
+        private String text(ClientState s) { return Ui.money(s.currency, s.balance); }
+        @Override public int width(Font f, ClientState s, WidgetConfig c) { return Math.max(c.compact ? 50 : 76, f.width(text(s)) + 18); }
+        @Override public int height(Font font, ClientState s, WidgetConfig c) { return c.compact ? 18 : 28; }
+        @Override public void draw(GuiGraphics g, Font f, ClientState s, WidgetConfig c, int x, int y, float o) {
+            int w = width(f, s, c), h = height(f, s, c);
+            Ui.card(g, x, y, w, h, Ui.GOLD, o);
+            if (!c.compact) {
+                g.drawString(f, "BALANCE", x + 7, y + 4, Ui.MUTED, false);
+                g.drawString(f, text(s), x + 7, y + 15, Ui.GOLD, true);
+            } else {
+                g.drawString(f, text(s), x + 7, y + 5, Ui.GOLD, true);
+            }
+        }
+    }
+
+    static final class Guild extends HudWidget {
+        Guild() { super("guild", "Guild"); }
+        @Override public boolean available(ClientState s) { return s.hasState && s.featGuilds && s.guild != null; }
+        @Override public int width(Font f, ClientState s, WidgetConfig c) { return c.compact ? 86 : 124; }
+        @Override public int height(Font f, ClientState s, WidgetConfig c) { return c.compact ? 18 : 30; }
+        @Override public void draw(GuiGraphics g, Font f, ClientState s, WidgetConfig c, int x, int y, float o) {
+            ClientState.Guild guild = s.guild;
+            int w = width(f, s, c), h = height(f, s, c);
+            Ui.card(g, x, y, w, h, Ui.CYAN, o);
+            String head = "[" + guild.tag() + "] " + guild.name();
+            g.drawString(f, Ui.clip(f, head, w - 14), x + 7, y + 4, Ui.TEXT, true);
+            if (!c.compact) g.drawString(f, guild.role() + "  ·  " + guild.claims() + " chunks", x + 7, y + 17, Ui.MUTED, false);
+        }
+    }
+
+    static final class Claim extends HudWidget {
+        Claim() { super("claim", "Claim"); }
+        @Override public boolean available(ClientState s) { return s.featClaims && !s.claimCells.isEmpty(); }
+        private String text(ClientState s) {
+            ClientState.Owner o = s.claimOwner;
+            if (o == null) return "Wilderness";
+            String name = o.tag().isEmpty() ? o.name() : "[" + o.tag() + "] " + o.name();
+            return (o.mine() ? "Your land: " : "Claimed: ") + name;
+        }
+        @Override public int width(Font f, ClientState s, WidgetConfig c) { return f.width(text(s)) + 18; }
+        @Override public int height(Font f, ClientState s, WidgetConfig c) { return 18; }
+        @Override public void draw(GuiGraphics g, Font f, ClientState s, WidgetConfig c, int x, int y, float o) {
+            int w = width(f, s, c);
+            ClientState.Owner owner = s.claimOwner;
+            int colour = owner == null ? Ui.MUTED : owner.mine() ? Ui.GREEN : Ui.RED;
+            Ui.card(g, x, y, w, 18, colour, o);
+            g.drawString(f, text(s), x + 9, y + 5, colour == Ui.MUTED ? Ui.TEXT : colour, true);
+        }
+    }
+
+    static final class Quests extends HudWidget {
+        Quests() { super("quests", "Quests"); }
+        @Override public boolean available(ClientState s) { return s.hasState && (s.daily.total() + s.weekly.total()) > 0; }
+        @Override public int width(Font f, ClientState s, WidgetConfig c) { return 96; }
+        @Override public int height(Font f, ClientState s, WidgetConfig c) { return 38; }
+        @Override public void draw(GuiGraphics g, Font f, ClientState s, WidgetConfig c, int x, int y, float o) {
+            int w = width(f, s, c);
+            Ui.card(g, x, y, w, 38, Ui.GREEN, o);
+            row(g, f, "Daily", s.daily, x + 7, y + 4, w - 14);
+            row(g, f, "Weekly", s.weekly, x + 7, y + 21, w - 14);
+        }
+        private void row(GuiGraphics g, Font f, String label, ClientState.Quest q, int x, int y, int w) {
+            g.drawString(f, label, x, y, Ui.MUTED, false);
+            String n = q.done() + "/" + q.total();
+            g.drawString(f, n, x + w - f.width(n), y, Ui.TEXT, true);
+            Ui.bar(g, x, y + 10, w, 3, q.total() == 0 ? 0 : 100.0 * q.done() / q.total(), Ui.GREEN, 1f);
+        }
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/screen/HudEditorScreen.java

@@ -0,0 +1,120 @@
+package net.scopenet.client.screen;
+
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.network.chat.Component;
+import net.scopenet.client.ClientConfig;
+import net.scopenet.client.ClientConfig.WidgetConfig;
+import net.scopenet.client.ClientState;
+import net.scopenet.client.ScopenetClient;
+import net.scopenet.client.Ui;
+import net.scopenet.client.hud.Hud;
+import net.scopenet.client.hud.HudWidget;
+import net.scopenet.client.hud.Widgets;
+
+/**
+ * Drag the widgets where you want them. Right-click a widget to hide or show it, scroll to resize everything.
+ * Positions snap to the nearest screen anchor, so the layout holds on any window size.
+ */
+public final class HudEditorScreen extends Screen {
+    private final Screen parent;
+    private final ClientConfig config = ScopenetClient.config();
+    private final ClientState preview = ClientState.preview();
+    private HudWidget dragging;
+    private double grabDx, grabDy;
+
+    public HudEditorScreen(Screen parent) { super(Component.literal("HUD layout")); this.parent = parent; }
+
+    private float scale() { return config.hud.scale; }
+    private int sw() { return (int) (width / scale()); }
+    private int sh() { return (int) (height / scale()); }
+
+    private int[] size(HudWidget w) {
+        WidgetConfig c = config.widget(w.id);
+        return new int[]{w.width(font, preview, c), w.height(font, preview, c)};
+    }
+
+    private int[] origin(HudWidget w) {
+        int[] s = size(w);
+        return Hud.place(config.widget(w.id), sw(), sh(), s[0], s[1]);
+    }
+
+    @Override protected void init() {
+        addRenderableWidget(Button.builder(Component.literal("Reset"), b -> { config.resetHud(); }).bounds(width / 2 - 104, height - 28, 100, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Done"), b -> onClose()).bounds(width / 2 + 4, height - 28, 100, 20).build());
+    }
+
+    @Override public void render(GuiGraphics g, int mouseX, int mouseY, float delta) {
+        g.fill(0, 0, width, height, 0x99000000);
+        // Faint guides at the thirds, showing where anchors switch.
+        for (int i = 1; i <= 2; i++) {
+            g.fill(width * i / 3, 0, width * i / 3 + 1, height, 0x22FFFFFF);
+            g.fill(0, height * i / 3, width, height * i / 3 + 1, 0x22FFFFFF);
+        }
+        g.drawCenteredString(font, "Drag to move  ·  Right-click to show or hide  ·  Scroll to resize", width / 2, 8, Ui.TEXT);
+        g.pose().pushPose();
+        g.pose().scale(scale(), scale(), 1f);
+        for (HudWidget w : Widgets.ALL) {
+            WidgetConfig c = config.widget(w.id);
+            int[] s = size(w), at = origin(w);
+            float opacity = c.enabled ? config.hud.opacity : 0.25f;
+            w.draw(g, font, preview, c, at[0], at[1], opacity);
+            boolean hover = Ui.inside(mouseX / scale(), mouseY / scale(), at[0], at[1], s[0], s[1]);
+            int outline = w == dragging ? Ui.ACCENT : hover ? Ui.TEXT : Ui.alpha(0xFFFFFF, 0.3f);
+            g.renderOutline(at[0] - 1, at[1] - 1, s[0] + 2, s[1] + 2, outline);
+            if (!c.enabled) g.drawString(font, "hidden", at[0] + 4, at[1] + s[1] + 2, Ui.RED, false);
+        }
+        g.pose().popPose();
+        super.render(g, mouseX, mouseY, delta);
+    }
+
+    private HudWidget at(double mx, double my) {
+        HudWidget found = null;
+        for (HudWidget w : Widgets.ALL) {
+            int[] s = size(w), o = origin(w);
+            if (Ui.inside(mx / scale(), my / scale(), o[0], o[1], s[0], s[1])) found = w; // later ones draw on top
+        }
+        return found;
+    }
+
+    @Override public boolean mouseClicked(double mx, double my, int button) {
+        if (super.mouseClicked(mx, my, button)) return true;
+        HudWidget w = at(mx, my);
+        if (w == null) return false;
+        if (button == 1) { WidgetConfig c = config.widget(w.id); c.enabled = !c.enabled; return true; }
+        if (button == 0) {
+            int[] o = origin(w);
+            dragging = w;
+            grabDx = mx / scale() - o[0];
+            grabDy = my / scale() - o[1];
+            return true;
+        }
+        return false;
+    }
+
+    @Override public boolean mouseDragged(double mx, double my, int button, double dx, double dy) {
+        if (dragging == null || button != 0) return super.mouseDragged(mx, my, button, dx, dy);
+        int[] s = size(dragging);
+        int left = (int) Math.round(mx / scale() - grabDx), top = (int) Math.round(my / scale() - grabDy);
+        left = Math.max(0, Math.min(sw() - s[0], left));
+        top = Math.max(0, Math.min(sh() - s[1], top));
+        Hud.anchorTo(config.widget(dragging.id), sw(), sh(), s[0], s[1], left, top);
+        return true;
+    }
+
+    @Override public boolean mouseReleased(double mx, double my, int button) {
+        dragging = null;
+        return super.mouseReleased(mx, my, button);
+    }
+
+    @Override public boolean mouseScrolled(double mx, double my, double delta) {
+        config.hud.scale = Math.max(0.5f, Math.min(2.0f, config.hud.scale + (float) delta * 0.05f));
+        return true;
+    }
+
+    @Override public void onClose() {
+        config.save();
+        minecraft.setScreen(parent);
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/screen/MarketScreen.java

@@ -0,0 +1,118 @@
+package net.scopenet.client.screen;
+
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.network.chat.Component;
+import net.scopenet.client.ClientState;
+import net.scopenet.client.Link;
+import net.scopenet.client.ScopenetClient;
+import net.scopenet.client.Ui;
+
+import java.util.List;
+
+/** The player market: browse what people are selling, buy with one click, and list the item in your hand. */
+public final class MarketScreen extends Screen {
+    private static final int W = 300, ROW = 30, LIST_TOP = 44;
+    private final ClientState state = ScopenetClient.state();
+    private int scroll;
+    private int age;
+    private int refreshIn = -1;
+    private EditBox price;
+    private Button list;
+    private String notice = "";
+
+    public MarketScreen() { super(Component.literal("Market")); }
+
+    private int left() { return (width - W) / 2; }
+    private int top() { return 12; }
+    private int listHeight() { return Math.max(ROW * 3, height - 24 - LIST_TOP - 64); }
+
+    @Override protected void init() {
+        ScopenetClient.link().send("market");
+        int y = top() + LIST_TOP + listHeight() + 12;
+        price = new EditBox(font, left() + 10, y, 70, 18, Component.literal("Price"));
+        price.setMaxLength(12);
+        price.setHint(Component.literal("Price"));
+        price.setFilter(s -> s.matches("[0-9]{0,9}(\\.[0-9]{0,2})?"));
+        addRenderableWidget(price);
+        list = Button.builder(Component.literal("List held item"), b -> listHeld()).bounds(left() + 86, y - 1, 100, 20).build();
+        addRenderableWidget(list);
+        addRenderableWidget(Button.builder(Component.literal("Refresh"), b -> { ScopenetClient.link().send("market"); notice = ""; }).bounds(left() + W - 70, y - 1, 60, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Back"), b -> minecraft.setScreen(new MenuScreen())).bounds(left() + 10, y + 26, 60, 18).build());
+    }
+
+    private void listHeld() {
+        String text = price.getValue();
+        if (text.isEmpty() || text.equals(".")) { notice = "Type a price first."; return; }
+        Link.command("market sell " + text);
+        price.setValue("");
+        notice = "Listing sent…";
+        refreshIn = 30;
+    }
+
+    @Override public void tick() {
+        if (++age >= 200) { age = 0; ScopenetClient.link().send("market"); }
+        if (refreshIn >= 0 && --refreshIn < 0) ScopenetClient.link().send("market");
+    }
+
+    @Override public boolean mouseScrolled(double mx, double my, double delta) {
+        int max = Math.max(0, state.market.size() * ROW - listHeight());
+        scroll = (int) Math.max(0, Math.min(max, scroll - delta * ROW / 2));
+        return true;
+    }
+
+    @Override public boolean mouseClicked(double mx, double my, int button) {
+        int left = left(), top = top(), lh = listHeight();
+        if (button == 0 && Ui.inside(mx, my, left, top + LIST_TOP, W, lh)) {
+            List<ClientState.Listing> items = state.market;
+            for (int i = 0; i < items.size(); i++) {
+                int y = top + LIST_TOP + i * ROW - scroll;
+                if (Ui.inside(mx, my, left + W - 60, y + 4, 48, ROW - 10)) {
+                    ClientState.Listing l = items.get(i);
+                    Link.command("market buy " + l.id());
+                    notice = "Buying #" + l.id() + "…";
+                    refreshIn = 30;
+                    return true;
+                }
+            }
+        }
+        return super.mouseClicked(mx, my, button);
+    }
+
+    @Override public void render(GuiGraphics g, int mouseX, int mouseY, float delta) {
+        renderBackground(g);
+        int left = left(), top = top(), lh = listHeight();
+        Ui.window(g, left, top, W, LIST_TOP + lh + 76);
+        g.fill(left, top, left + W, top + 3, Ui.CYAN);
+        g.drawString(font, "Player Market", left + 10, top + 10, Ui.CYAN, true);
+        String bal = "Balance " + Ui.money(state.currency, state.balance);
+        g.drawString(font, bal, left + W - 10 - font.width(bal), top + 10, Ui.GOLD, true);
+        g.drawString(font, state.market.size() + " listing" + (state.market.size() == 1 ? "" : "s"), left + 10, top + 26, Ui.MUTED, false);
+
+        List<ClientState.Listing> items = state.market;
+        g.enableScissor(left + 1, top + LIST_TOP, left + W - 1, top + LIST_TOP + lh);
+        for (int i = 0; i < items.size(); i++) {
+            int y = top + LIST_TOP + i * ROW - scroll;
+            if (y + ROW < top + LIST_TOP || y > top + LIST_TOP + lh) continue;
+            ClientState.Listing l = items.get(i);
+            boolean affordable = state.balance >= l.price() || l.guildTag() != null;
+            g.fill(left + 6, y, left + W - 6, y + ROW - 2, Ui.alpha(Ui.PANEL_2, 0.9f));
+            g.renderItem(Ui.stackFor(l.itemId(), l.amount()), left + 10, y + 5);
+            g.renderItemDecorations(font, Ui.stackFor(l.itemId(), l.amount()), left + 10, y + 5);
+            g.drawString(font, Ui.clip(font, l.itemName() + " x" + l.amount(), 150), left + 32, y + 4, Ui.TEXT, true);
+            String seller = l.guildTag() != null ? "[" + l.guildTag() + "] guild" : l.seller();
+            g.drawString(font, Ui.clip(font, seller + "  ·  #" + l.id(), 150), left + 32, y + 15, Ui.MUTED, false);
+            String p = Ui.money(state.currency, l.price());
+            g.drawString(font, p, left + W - 68 - font.width(p), y + 9, Ui.GREEN, true);
+            boolean hover = Ui.inside(mouseX, mouseY, left + W - 60, y + 4, 48, ROW - 10);
+            g.fill(left + W - 60, y + 4, left + W - 12, y + ROW - 6, affordable ? (hover ? Ui.alpha(Ui.ACCENT, 1f) : Ui.alpha(Ui.ACCENT, 0.75f)) : Ui.alpha(Ui.RED, 0.35f));
+            g.drawCenteredString(font, "Buy", left + W - 36, y + 10, Ui.TEXT);
+        }
+        g.disableScissor();
+        if (items.isEmpty()) g.drawCenteredString(font, state.marketAt == 0 ? "Loading listings…" : "No listings. Be the first to sell something!", left + W / 2, top + LIST_TOP + 24, Ui.MUTED);
+        if (!notice.isEmpty()) g.drawString(font, notice, left + 10, top + LIST_TOP + lh + 2, Ui.MUTED, false);
+        super.render(g, mouseX, mouseY, delta);
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/screen/MenuScreen.java

@@ -0,0 +1,55 @@
+package net.scopenet.client.screen;
+
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.network.chat.Component;
+import net.scopenet.client.ClientState;
+import net.scopenet.client.ScopenetClient;
+import net.scopenet.client.Ui;
+
+/** The hub (press K): who you are on this server, and the way into the shop, market and settings. */
+public final class MenuScreen extends Screen {
+    private static final int W = 236, H = 176;
+    private final ClientState state = ScopenetClient.state();
+
+    public MenuScreen() { super(Component.literal("SCOPENET")); }
+
+    @Override protected void init() {
+        int left = (width - W) / 2, top = (height - H) / 2;
+        int bw = 104, gap = 8, x1 = left + 10, x2 = left + W - 10 - bw;
+        boolean eco = state.connected && state.featEconomy;
+        Button shop = Button.builder(Component.literal("Shop"), b -> minecraft.setScreen(new ShopScreen())).bounds(x1, top + 86, bw, 20).build();
+        Button market = Button.builder(Component.literal("Market"), b -> minecraft.setScreen(new MarketScreen())).bounds(x2, top + 86, bw, 20).build();
+        shop.active = eco;
+        market.active = eco;
+        addRenderableWidget(shop);
+        addRenderableWidget(market);
+        addRenderableWidget(Button.builder(Component.literal("HUD layout"), b -> minecraft.setScreen(new HudEditorScreen(this))).bounds(x1, top + 86 + 20 + gap, bw, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Settings"), b -> minecraft.setScreen(new SettingsScreen(this))).bounds(x2, top + 86 + 20 + gap, bw, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Close"), b -> onClose()).bounds(left + (W - 80) / 2, top + H - 26, 80, 18).build());
+    }
+
+    @Override public void render(GuiGraphics g, int mouseX, int mouseY, float delta) {
+        renderBackground(g);
+        int left = (width - W) / 2, top = (height - H) / 2;
+        Ui.window(g, left, top, W, H);
+        g.fill(left, top, left + W, top + 3, Ui.ACCENT);
+        g.drawString(font, "SCOPENET", left + 10, top + 10, Ui.ACCENT, true);
+        if (!state.connected) {
+            g.drawCenteredString(font, "This server isn't running SCOPENET", left + W / 2, top + 50, Ui.TEXT);
+            g.drawCenteredString(font, "or its client link is turned off.", left + W / 2, top + 62, Ui.MUTED);
+        } else {
+            g.drawString(font, state.server.isEmpty() ? "Connected" : state.server, left + W - 10 - font.width(state.server), top + 10, Ui.MUTED, false);
+            g.drawString(font, state.name + (state.title.isEmpty() ? "" : "  ·  " + state.title), left + 10, top + 28, Ui.TEXT, true);
+            g.drawString(font, "Level " + state.level, left + 10, top + 42, Ui.MUTED, false);
+            Ui.bar(g, left + 10, top + 54, W - 20, 5, state.xpPct, Ui.ACCENT, 1f);
+            if (state.featEconomy) g.drawString(font, Ui.money(state.currency, state.balance), left + 10, top + 66, Ui.GOLD, true);
+            if (state.guild != null) {
+                String guild = "[" + state.guild.tag() + "] " + state.guild.name();
+                g.drawString(font, guild, left + W - 10 - font.width(guild), top + 66, Ui.CYAN, true);
+            }
+        }
+        super.render(g, mouseX, mouseY, delta);
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/screen/SettingsScreen.java

@@ -0,0 +1,110 @@
+package net.scopenet.client.screen;
+
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.components.AbstractSliderButton;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.network.chat.Component;
+import net.scopenet.client.ClientConfig;
+import net.scopenet.client.ScopenetClient;
+import net.scopenet.client.Ui;
+import net.scopenet.client.hud.Widgets;
+
+import java.util.function.BooleanSupplier;
+import java.util.function.Consumer;
+
+/** Every client option in one place. Changes apply immediately and are saved when you leave. */
+public final class SettingsScreen extends Screen {
+    private final Screen parent;
+    private final ClientConfig config = ScopenetClient.config();
+
+    public SettingsScreen(Screen parent) { super(Component.literal("SCOPENET settings")); this.parent = parent; }
+
+    private static Component onOff(boolean on) { return Component.literal(on ? "§aOn" : "§cOff"); }
+
+    private Button toggle(int x, int y, int w, String label, BooleanSupplier get, Consumer<Boolean> set) {
+        return Button.builder(Component.literal(label + ": ").append(onOff(get.getAsBoolean())), b -> {
+            set.accept(!get.getAsBoolean());
+            b.setMessage(Component.literal(label + ": ").append(onOff(get.getAsBoolean())));
+        }).bounds(x, y, w, 20).build();
+    }
+
+    private static final class Slider extends AbstractSliderButton {
+        private final String label;
+        private final double min, max;
+        private final Consumer<Double> apply;
+        private final boolean percent;
+
+        Slider(int x, int y, int w, String label, double min, double max, double value, boolean percent, Consumer<Double> apply) {
+            super(x, y, w, 20, Component.empty(), (value - min) / (max - min));
+            this.label = label; this.min = min; this.max = max; this.apply = apply; this.percent = percent;
+            updateMessage();
+        }
+
+        private double current() { return min + (max - min) * this.value; }
+
+        @Override protected void updateMessage() {
+            setMessage(Component.literal(label + ": " + (percent ? Math.round(current() * 100) + "%" : String.format("%.2f", current()))));
+        }
+
+        @Override protected void applyValue() { apply.accept(current()); }
+    }
+
+    @Override protected void init() {
+        int colW = 150, gap = 8;
+        int x1 = width / 2 - colW - gap / 2, x2 = width / 2 + gap / 2;
+        int y = 34, step = 22;
+
+        addRenderableWidget(toggle(x1, y, colW, "HUD", () -> config.enabled, v -> config.enabled = v));
+        addRenderableWidget(toggle(x2, y, colW, "Hide with F3", () -> config.hud.hideInF3, v -> config.hud.hideInF3 = v));
+        y += step;
+        addRenderableWidget(new Slider(x1, y, colW, "Opacity", 0.1, 1.0, config.hud.opacity, true, v -> config.hud.opacity = v.floatValue()));
+        addRenderableWidget(new Slider(x2, y, colW, "Size", 0.5, 2.0, config.hud.scale, true, v -> config.hud.scale = v.floatValue()));
+        y += step;
+        addRenderableWidget(toggle(x1, y, colW, "Claim borders", () -> config.hud.claimBorders, v -> config.hud.claimBorders = v));
+        addRenderableWidget(toggle(x2, y, colW, "Only when sneaking", () -> config.hud.claimBordersOnlyWhenSneaking, v -> config.hud.claimBordersOnlyWhenSneaking = v));
+        y += step + 8;
+
+        // One button per widget: On -> Compact -> Off.
+        int i = 0;
+        for (var widget : Widgets.ALL) {
+            ClientConfig.WidgetConfig c = config.widget(widget.id);
+            int x = i % 2 == 0 ? x1 : x2;
+            addRenderableWidget(Button.builder(widgetLabel(widget.label, c), b -> {
+                if (!c.enabled) { c.enabled = true; c.compact = false; }
+                else if (!c.compact) c.compact = true;
+                else { c.enabled = false; c.compact = false; }
+                b.setMessage(widgetLabel(widget.label, c));
+            }).bounds(x, y, colW, 20).build());
+            if (i % 2 == 1) y += step;
+            i++;
+        }
+        if (i % 2 == 1) y += step;
+        y += 8;
+
+        addRenderableWidget(toggle(x1, y, colW, "Level-up toasts", () -> config.notifications.levelUp, v -> config.notifications.levelUp = v));
+        addRenderableWidget(toggle(x2, y, colW, "Achievement toasts", () -> config.notifications.achievements, v -> config.notifications.achievements = v));
+        y += step;
+        addRenderableWidget(toggle(x1, y, colW, "Guild toasts", () -> config.notifications.guild, v -> config.notifications.guild = v));
+        addRenderableWidget(toggle(x2, y, colW, "Error toasts", () -> config.notifications.errors, v -> config.notifications.errors = v));
+        y += step + 8;
+
+        addRenderableWidget(Button.builder(Component.literal("Edit HUD layout…"), b -> minecraft.setScreen(new HudEditorScreen(this))).bounds(x1, y, colW, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Done"), b -> onClose()).bounds(x2, y, colW, 20).build());
+    }
+
+    private static Component widgetLabel(String label, ClientConfig.WidgetConfig c) {
+        return Component.literal(label + ": ").append(Component.literal(!c.enabled ? "§cOff" : c.compact ? "§eCompact" : "§aOn"));
+    }
+
+    @Override public void render(GuiGraphics g, int mouseX, int mouseY, float delta) {
+        renderBackground(g);
+        g.drawCenteredString(font, "SCOPENET settings", width / 2, 14, Ui.ACCENT);
+        super.render(g, mouseX, mouseY, delta);
+    }
+
+    @Override public void onClose() {
+        config.save();
+        minecraft.setScreen(parent);
+    }
+}

integrations/fabric-client/src/main/java/net/scopenet/client/screen/ShopScreen.java

@@ -0,0 +1,92 @@
+package net.scopenet.client.screen;
+
+import net.minecraft.client.gui.GuiGraphics;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.network.chat.Component;
+import net.scopenet.client.ClientState;
+import net.scopenet.client.Link;
+import net.scopenet.client.ScopenetClient;
+import net.scopenet.client.Ui;
+
+import java.util.List;
+
+/** The server shop: what each item sells for, and a button to sell what's in your hand. */
+public final class ShopScreen extends Screen {
+    private static final int W = 280, ROW = 24, LIST_TOP = 44;
+    private final ClientState state = ScopenetClient.state();
+    private int scroll;
+    private int age;
+    private Button sell;
+
+    public ShopScreen() { super(Component.literal("Shop")); }
+
+    private int left() { return (width - W) / 2; }
+    private int top() { return 12; }
+    private int listHeight() { return Math.max(ROW * 3, height - 24 - LIST_TOP - 54); }
+
+    @Override protected void init() {
+        ScopenetClient.link().send("shop");
+        sell = Button.builder(Component.literal("Sell held item"), b -> { Link.command("sell hand"); age = -30; })
+                .bounds(left() + W - 130, top() + LIST_TOP + listHeight() + 10, 120, 20).build();
+        addRenderableWidget(sell);
+        addRenderableWidget(Button.builder(Component.literal("Back"), b -> minecraft.setScreen(new MenuScreen())).bounds(left() + 10, top() + LIST_TOP + listHeight() + 34, 60, 18).build());
+    }
+
+    @Override public void tick() {
+        if (++age >= 40) { age = 0; ScopenetClient.link().send("shop"); }
+        ClientState.Held held = state.held;
+        sell.active = held != null && held.unit() > 0;
+    }
+
+    @Override public boolean mouseScrolled(double mx, double my, double delta) {
+        int max = Math.max(0, state.shop.size() * ROW - listHeight());
+        scroll = (int) Math.max(0, Math.min(max, scroll - delta * ROW));
+        return true;
+    }
+
+    @Override public void render(GuiGraphics g, int mouseX, int mouseY, float delta) {
+        renderBackground(g);
+        int left = left(), top = top(), lh = listHeight();
+        Ui.window(g, left, top, W, LIST_TOP + lh + 62);
+        g.fill(left, top, left + W, top + 3, Ui.GOLD);
+        g.drawString(font, "Server Shop", left + 10, top + 10, Ui.GOLD, true);
+        String bal = Ui.money(state.currency, state.balance);
+        g.drawString(font, bal, left + W - 10 - font.width(bal), top + 10, Ui.TEXT, true);
+        g.drawString(font, "Hold items and press Sell. Prices are per item.", left + 10, top + 26, Ui.MUTED, false);
+
+        List<ClientState.ShopItem> items = state.shop;
+        ClientState.Held held = state.held;
+        g.enableScissor(left + 1, top + LIST_TOP, left + W - 1, top + LIST_TOP + lh);
+        for (int i = 0; i < items.size(); i++) {
+            int y = top + LIST_TOP + i * ROW - scroll;
+            if (y + ROW < top + LIST_TOP || y > top + LIST_TOP + lh) continue;
+            ClientState.ShopItem item = items.get(i);
+            boolean hover = Ui.inside(mouseX, mouseY, left + 6, y, W - 12, ROW - 2);
+            boolean match = held != null && held.id().equalsIgnoreCase(item.id());
+            g.fill(left + 6, y, left + W - 6, y + ROW - 2, match ? Ui.alpha(Ui.GOLD, 0.18f) : hover ? Ui.alpha(0xFFFFFF, 0.06f) : Ui.alpha(Ui.PANEL_2, 0.9f));
+            g.renderItem(Ui.stackFor(item.id(), 1), left + 10, y + 3);
+            g.drawString(font, Ui.clip(font, title(item.name()), 130), left + 32, y + 8, Ui.TEXT, true);
+            String price = Ui.money(state.currency, item.price());
+            g.drawString(font, price, left + W - 12 - font.width(price), y + 8, Ui.GREEN, true);
+        }
+        g.disableScissor();
+        if (items.isEmpty()) g.drawCenteredString(font, "Loading prices…", left + W / 2, top + LIST_TOP + 20, Ui.MUTED);
+
+        int infoY = top + LIST_TOP + lh + 14;
+        if (held == null) g.drawString(font, "Your hand is empty", left + 10, infoY, Ui.MUTED, false);
+        else {
+            g.renderItem(Ui.stackFor(held.id(), held.count()), left + 10, infoY - 4);
+            g.drawString(font, Ui.clip(font, held.name() + " x" + held.count(), 100), left + 30, infoY - 2, Ui.TEXT, true);
+            g.drawString(font, held.unit() > 0 ? "worth " + Ui.money(state.currency, held.unit() * held.count()) : "can't be sold here", left + 30, infoY + 9, held.unit() > 0 ? Ui.GREEN : Ui.RED, false);
+        }
+        super.render(g, mouseX, mouseY, delta);
+    }
+
+    private static String title(String name) {
+        if (name.isEmpty()) return name;
+        StringBuilder out = new StringBuilder();
+        for (String part : name.split(" ")) out.append(part.isEmpty() ? "" : Character.toUpperCase(part.charAt(0)) + part.substring(1)).append(' ');
+        return out.toString().trim();
+    }
+}

integrations/fabric-client/src/main/resources/assets/scopenet-client/lang/en_us.json

@@ -0,0 +1,5 @@
+{
+  "key.categories.scopenet": "SCOPENET",
+  "key.scopenet.menu": "Open SCOPENET menu",
+  "key.scopenet.toggle_hud": "Show or hide SCOPENET HUD"
+}

integrations/fabric-client/src/main/resources/fabric.mod.json

@@ -0,0 +1,10 @@
+{
+  "schemaVersion": 1,
+  "id": "scopenet_client",
+  "version": "${version}",
+  "name": "SCOPENET Client",
+  "description": "HUD widgets, claim borders, and shop and market windows for SCOPENET servers. Display only: the server stays in charge of money, claims and permissions.",
+  "environment": "client",
+  "entrypoints": { "client": ["net.scopenet.client.ScopenetClient"] },
+  "depends": { "fabricloader": ">=0.16.10", "minecraft": "1.20.1", "java": ">=17", "fabric-api": "*" }
+}

integrations/fabric/build.gradle

@@ -8,12 +8,19 @@ if (providers.gradleProperty('verifyMixins').isPresent()) {
 }
 java.sourceCompatibility = JavaVersion.toVersion(targetJava)
 java.targetCompatibility = JavaVersion.toVersion(targetJava)
+def features = mc == '1.20.1'   // commands, permissions, economy, client link: Fabric API based, 1.20.1 only for now
 dependencies {
     minecraft "com.mojang:minecraft:${mc}"
     mappings loom.officialMojangMappings()
     modImplementation 'net.fabricmc:fabric-loader:0.16.10'
     implementation project(':common')
+    if (features) {
+        modImplementation 'net.fabricmc.fabric-api:fabric-api:0.92.2+1.20.1'
+        // Optional at runtime: present only when the LuckPerms mod is installed.
+        compileOnly 'net.luckperms:api:5.4'
+    }
 }
+if (features) sourceSets.main.java.srcDirs += ['src/mc1.20.1/java']
 sourceSets.main.java.srcDirs += ['../minecraft/src/main/java', "../minecraft/src/${mc}/java"]
 sourceSets.main.resources.srcDirs += ['../minecraft/src/main/resources']
 apply from: '../minecraft/build-info.gradle'

integrations/fabric/src/main/java/net/scopenet/fabric/ScopenetFabric.java

@@ -1,11 +1,22 @@
 package net.scopenet.fabric;
 
 import net.fabricmc.api.DedicatedServerModInitializer;
+import net.fabricmc.loader.api.FabricLoader;
 
-/** Server-only; lifecycle and admission hooks are shared mixins. */
+/** Server-only; lifecycle and admission hooks are shared mixins. Commands and extras need Fabric API (1.20.1 build). */
 public final class ScopenetFabric implements DedicatedServerModInitializer {
     @Override public void onInitializeServer() {
         if (Boolean.getBoolean("scopenet.verifyMixins"))
             org.spongepowered.asm.mixin.MixinEnvironment.getCurrentEnvironment().audit();
+        if (!FabricLoader.getInstance().isModLoaded("fabric-api")) return;
+        try {
+            Class<?> features = Class.forName("net.scopenet.fabric.features.FabricFeatures");
+            ((Runnable) features.getDeclaredConstructor().newInstance()).run();
+        } catch (ClassNotFoundException e) {
+            // This build (another Minecraft version) only has the core integration.
+        } catch (Throwable t) {
+            System.err.println("[SCOPENET] Commands and extras could not start: " + t);
+            t.printStackTrace();
+        }
     }
 }

integrations/fabric/src/main/resources/fabric.mod.json

@@ -6,5 +6,6 @@
   "environment": "server",
   "entrypoints": { "server": ["net.scopenet.fabric.ScopenetFabric"] },
   "mixins": ["scopenet.mixins.json"],
-  "depends": { "fabricloader": ">=0.16.10", "minecraft": "${mc}", "java": ">=${java}" }
+  "depends": { "fabricloader": ">=0.16.10", "minecraft": "${mc}", "java": ">=${java}" },
+  "suggests": { "fabric-api": "*", "luckperms": "*", "placeholder-api": "*" }
 }

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/api/ScopenetEconomy.java

@@ -0,0 +1,60 @@
+package net.scopenet.fabric.api;
+
+import com.google.gson.JsonObject;
+import net.scopenet.core.Panel;
+
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicReference;
+
+/**
+ * SCOPENET's economy for other mods (the Fabric stand-in for Vault). Balances live in the panel, so every call is
+ * asynchronous. Every change carries an operation id, so a retried call never pays twice.
+ *
+ * <pre>{@code
+ * ScopenetEconomy.get().ifPresent(eco -> eco.balance(uuid).thenAccept(b -> ...));
+ * }</pre>
+ */
+public final class ScopenetEconomy {
+    private static final AtomicReference<ScopenetEconomy> INSTANCE = new AtomicReference<>();
+
+    private final Panel panel;
+    private final java.util.concurrent.Executor io;
+
+    public ScopenetEconomy(Panel panel, java.util.concurrent.Executor io) { this.panel = panel; this.io = io; }
+
+    /** Empty until the server has started and SCOPENET economy is enabled. */
+    public static java.util.Optional<ScopenetEconomy> get() { return java.util.Optional.ofNullable(INSTANCE.get()); }
+
+    public static void install(ScopenetEconomy economy) { INSTANCE.set(economy); }
+
+    public static void uninstall() { INSTANCE.set(null); }
+
+    public CompletableFuture<Double> balance(UUID player, String name) {
+        JsonObject body = new JsonObject();
+        body.addProperty("uuid", player.toString());
+        body.addProperty("username", name);
+        return CompletableFuture.supplyAsync(() -> {
+            try { return panel.call("economy/balance", body).getAsJsonObject().get("balance").getAsDouble(); }
+            catch (Exception e) { throw new java.util.concurrent.CompletionException(e); }
+        }, io);
+    }
+
+    /** Add (positive) or remove (negative) money. Fails, without changing anything, if the player can't afford it. Returns the new balance. */
+    public CompletableFuture<Double> change(UUID player, String name, double delta, String reason) {
+        JsonObject body = new JsonObject();
+        body.addProperty("operation_id", UUID.randomUUID().toString());
+        body.addProperty("uuid", player.toString());
+        body.addProperty("username", name);
+        body.addProperty("delta", delta);
+        body.addProperty("description", reason == null || reason.isBlank() ? "Other mod" : reason);
+        return CompletableFuture.supplyAsync(() -> {
+            try { return panel.call("economy/adjust", body).getAsJsonObject().get("balance").getAsDouble(); }
+            catch (Exception e) { throw new java.util.concurrent.CompletionException(e); }
+        }, io);
+    }
+
+    public CompletableFuture<Double> deposit(UUID player, String name, double amount, String reason) { return change(player, name, Math.abs(amount), reason); }
+
+    public CompletableFuture<Double> withdraw(UUID player, String name, double amount, String reason) { return change(player, name, -Math.abs(amount), reason); }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/FabricConfig.java

@@ -0,0 +1,47 @@
+package net.scopenet.fabric.features;
+
+import net.scopenet.core.EssentialsConfig;
+import net.scopenet.core.Features;
+import net.scopenet.integration.Settings;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Properties;
+
+/** The Fabric-only keys in config/scopenet.properties (the shared keys are read by {@link Settings}). */
+final class FabricConfig {
+    static final Path FILE = Path.of("config", "scopenet.properties");
+    private final Properties p = new Properties();
+
+    static FabricConfig load() {
+        FabricConfig c = new FabricConfig();
+        if (Files.exists(FILE)) {
+            try (Reader in = Files.newBufferedReader(FILE, StandardCharsets.UTF_8)) { c.p.load(in); }
+            catch (IOException e) { System.err.println("[SCOPENET] Could not read " + FILE + ": " + e.getMessage()); }
+        }
+        return c;
+    }
+
+    private int integer(String key, int fallback) {
+        try { return Integer.parseInt(p.getProperty(key, String.valueOf(fallback)).trim()); } catch (NumberFormatException e) { return fallback; }
+    }
+
+    boolean bool(String key, boolean fallback) { return Boolean.parseBoolean(p.getProperty(key, String.valueOf(fallback)).trim()); }
+    String text(String key, String fallback) { return p.getProperty(key, fallback).trim(); }
+
+    EssentialsConfig essentials() {
+        return new EssentialsConfig(Math.max(0, integer("essentials.max_homes", 5)), Math.max(10, integer("essentials.rtp_radius", 2500)),
+                Math.max(5, integer("essentials.tpa_timeout_seconds", 60)) * 1000L, 15);
+    }
+
+    Features features(Settings s) {
+        return new Features(s.essentialsEnabled(), s.economyEnabled(), s.guildsEnabled(), s.socialEnabled(), s.landClaimingEnabled(),
+                bool("clientlink.enabled", true), text("economy.currency_symbol", "$"));
+    }
+
+    /** {@code permissions.default_level}: "all" lets everyone use commands unless LuckPerms says otherwise, "op" limits them to operators. */
+    boolean everyoneByDefault() { return !text("permissions.default_level", "all").equalsIgnoreCase("op"); }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/FabricFeatures.java

@@ -0,0 +1,214 @@
+package net.scopenet.fabric.features;
+
+import com.google.gson.JsonArray;
+import com.mojang.brigadier.CommandDispatcher;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.builder.LiteralArgumentBuilder;
+import com.mojang.brigadier.context.CommandContext;
+import com.mojang.brigadier.suggestion.Suggestions;
+import com.mojang.brigadier.suggestion.SuggestionsBuilder;
+import net.fabricmc.fabric.api.entity.event.v1.ServerLivingEntityEvents;
+import net.fabricmc.fabric.api.event.lifecycle.v1.ServerLifecycleEvents;
+import net.fabricmc.fabric.api.event.lifecycle.v1.ServerTickEvents;
+import net.fabricmc.fabric.api.networking.v1.PacketByteBufs;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayConnectionEvents;
+import net.fabricmc.fabric.api.networking.v1.ServerPlayNetworking;
+import net.minecraft.commands.CommandSourceStack;
+import net.minecraft.commands.Commands;
+import net.minecraft.network.FriendlyByteBuf;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import net.scopenet.core.*;
+import net.scopenet.fabric.api.ScopenetEconomy;
+import net.scopenet.integration.Integration;
+import net.scopenet.integration.Settings;
+import net.scopenet.minecraft.Bridge;
+
+import java.nio.file.Path;
+import java.util.*;
+import java.util.concurrent.CompletableFuture;
+import java.util.logging.Logger;
+
+/**
+ * Everything beyond sign-in on Fabric 1.20.1: the shared commands (homes, warps, TPA, RTP, economy, guilds…), LuckPerms
+ * permissions, Placeholder API, the economy API for other mods, and the link to the optional client mod.
+ * Runs when Fabric API is installed; all behaviour comes from {@code net.scopenet.core}.
+ */
+public final class FabricFeatures implements Runnable {
+    private static final Logger LOG = Logger.getLogger("SCOPENET");
+    private static final ResourceLocation TO_CLIENT = new ResourceLocation(Wire.S2C);
+    private static final ResourceLocation FROM_CLIENT = new ResourceLocation(Wire.C2S);
+
+    private MinecraftServer server;
+    private FabricPlatform platform;
+    private Env env;
+    private CommandSet commands;
+    private PlayerCache cache;
+    private ClientLink link;
+    private Perms perms;
+    private FabricConfig config;
+    private int ticks;
+    private String placeholderStatus = "off";
+
+    CommandSet commandSet() { return commands; }
+
+    @Override public void run() {
+        ServerLifecycleEvents.SERVER_STARTED.register(this::started);
+        ServerLifecycleEvents.SERVER_STOPPING.register(s -> stopping());
+        ServerTickEvents.END_SERVER_TICK.register(s -> tick());
+        ServerPlayConnectionEvents.DISCONNECT.register((handler, s) -> { if (link != null) link.disconnected(handler.getPlayer().getUUID()); });
+        // /back also returns you to where you died.
+        ServerLivingEntityEvents.ALLOW_DEATH.register((entity, source, amount) -> {
+            if (entity instanceof ServerPlayer p && commands != null) commands.essentials.remember(p.getUUID(), platform.wrap(p).pos());
+            return true;
+        });
+        ServerPlayNetworking.registerGlobalReceiver(FROM_CLIENT, (s, player, handler, buf, sender) -> {
+            byte[] data = new byte[buf.readableBytes()];
+            buf.readBytes(data);
+            s.execute(() -> { if (link != null) link.receive(platform.wrap(player), data); });
+        });
+    }
+
+    // ---- lifecycle -------------------------------------------------------------------------
+
+    private void started(MinecraftServer s) {
+        Integration integration = Bridge.integration();
+        if (integration == null) { LOG.warning("SCOPENET is not connected to a panel; commands are off."); return; }
+        server = s;
+        config = FabricConfig.load();
+        perms = new Perms(config.everyoneByDefault());
+        platform = new FabricPlatform(s, perms);
+        Path dir = Path.of("config", "scopenet");
+        env = new Env(platform, new PanelAdapter(integration), config.features(integration.settings()), dir, System::currentTimeMillis, new Random(), LOG);
+        commands = new CommandSet(env, config.essentials());
+        cache = new PlayerCache(env);
+        link = new ClientLink(env, cache, s.getMotd(), (player, bytes) -> {
+            FriendlyByteBuf buf = PacketByteBufs.create();
+            buf.writeBytes(bytes);
+            ServerPlayer target = s.getPlayerList().getPlayer(player.uuid());
+            if (target != null && ServerPlayNetworking.canSend(target, TO_CLIENT)) ServerPlayNetworking.send(target, TO_CLIENT, buf);
+        });
+        integration.onNotifications(events -> link.onPanelEvents(events));
+        Bridge.claimBypass = p -> perms.has(p, "scopenet.claims.bypass");
+
+        registerCommands(s.getCommands().getDispatcher());
+        registerPlaceholders();
+        ScopenetEconomy.install(new ScopenetEconomy(env.panel, r -> platform.runAsync(r)));
+        LOG.info("SCOPENET commands ready (" + commands.all().size() + " commands, "
+                + (Perms.luckPermsPresent() ? "LuckPerms" : "default permissions") + ").");
+    }
+
+    private void stopping() {
+        ScopenetEconomy.uninstall();
+        Bridge.claimBypass = p -> false;
+        if (platform != null) platform.shutdown();
+        commands = null;
+    }
+
+    private void registerPlaceholders() {
+        if (!config.bool("placeholders.enabled", true)) { placeholderStatus = "off (config)"; return; }
+        if (!net.fabricmc.loader.api.FabricLoader.getInstance().isModLoaded("placeholder-api")) { placeholderStatus = "Placeholder API not installed"; return; }
+        try {
+            int n = PlaceholderApiModule.register(new Placeholders(env, cache));
+            placeholderStatus = "active (" + n + ")";
+        } catch (Throwable t) {
+            placeholderStatus = "failed: " + t;
+            LOG.warning("Placeholder API could not be used: " + t);
+        }
+    }
+
+    private void tick() {
+        if (commands == null) return;
+        ticks++;
+        if (ticks % 20 == 0) {
+            cache.tick(p -> link.pushState(p));
+            link.tick();
+        }
+        if (ticks % 40 == 0) commands.tick();
+    }
+
+    // ---- commands --------------------------------------------------------------------------
+
+    private void registerCommands(CommandDispatcher<CommandSourceStack> dispatcher) {
+        List<CoreCommand> all = new ArrayList<>(commands.all());
+        all.add(new ScopenetCommand(this));
+        for (CoreCommand command : all) {
+            List<String> names = new ArrayList<>();
+            names.add(command.name());
+            names.addAll(command.aliases());
+            for (String name : names) {
+                LiteralArgumentBuilder<CommandSourceStack> root = Commands.literal(name)
+                        .executes(ctx -> execute(ctx, command, ""))
+                        .then(Commands.argument("args", StringArgumentType.greedyString())
+                                .suggests((ctx, builder) -> suggest(ctx, command, builder))
+                                .executes(ctx -> execute(ctx, command, StringArgumentType.getString(ctx, "args"))));
+                dispatcher.register(root);
+            }
+        }
+    }
+
+    private int execute(CommandContext<CommandSourceStack> ctx, CoreCommand command, String argText) {
+        ServerPlayer sp = ctx.getSource().getPlayer();
+        if (sp == null) { ctx.getSource().sendFailure(Component.literal("Only players can use this command.")); return 0; }
+        String[] args = argText.isBlank() ? new String[0] : argText.trim().split("\\s+");
+        CorePlayer player = platform.wrap(sp);
+        try {
+            command.run(player, args);
+        } catch (RuntimeException e) {
+            LOG.warning("/" + command.name() + " failed: " + e);
+            player.send(Format.RED + "Something went wrong running that command.");
+            return 0;
+        }
+        return 1;
+    }
+
+    private CompletableFuture<Suggestions> suggest(CommandContext<CommandSourceStack> ctx, CoreCommand command, SuggestionsBuilder builder) {
+        ServerPlayer sp = ctx.getSource().getPlayer();
+        if (sp != null) {
+            String before = builder.getInput().substring(0, builder.getStart()).stripLeading();
+            if (before.startsWith("/")) before = before.substring(1);
+            String[] tokens = before.isBlank() ? new String[0] : before.split(" ");
+            List<String> typed = new ArrayList<>(Arrays.asList(tokens).subList(Math.min(1, tokens.length), tokens.length));
+            typed.add(builder.getRemaining());
+            String partial = builder.getRemaining().toLowerCase(Locale.ROOT);
+            for (String candidate : command.complete(platform.wrap(sp), typed.toArray(new String[0]))) {
+                if (candidate.toLowerCase(Locale.ROOT).startsWith(partial)) builder.suggest(candidate);
+            }
+        }
+        return builder.buildFuture();
+    }
+
+    // ---- /scopenet -------------------------------------------------------------------------
+
+    void sendStatus(CorePlayer p) {
+        Integration integration = Bridge.integration();
+        Settings s = integration.settings();
+        p.send(Format.GOLD + "=== SCOPENET Status ===");
+        p.send(Format.GRAY + "Panel: " + Format.WHITE + s.panel() + Format.GRAY + "   Token: " + (s.token().isEmpty() ? Format.RED + "missing" : Format.GREEN + "set"));
+        Features f = env.features;
+        p.send(Format.GRAY + "Essentials: " + flag(f.essentials()) + Format.GRAY + "  Economy: " + flag(f.economy()) + Format.GRAY + "  Guilds: " + flag(f.guilds())
+                + Format.GRAY + "  Claims: " + flag(f.landClaiming()) + Format.GRAY + "  Client link: " + flag(f.clientLink()));
+        p.send(Format.GRAY + "Claim index: " + (integration.client().claims().loaded() ? Format.GREEN + integration.client().claims().claimCount() + " claims" : Format.YELLOW + "loading"));
+        p.send(Format.GRAY + "Permissions: " + Format.WHITE + (Perms.luckPermsPresent() ? "LuckPerms" : "defaults (" + (config.everyoneByDefault() ? "everyone" : "operators") + ")"));
+        p.send(Format.GRAY + "Placeholder API: " + Format.WHITE + placeholderStatus);
+        p.send(Format.GRAY + "Pending transactions: " + Format.WHITE + commands.jobs.pending());
+    }
+
+    private static String flag(boolean on) { return on ? Format.GREEN + "on" : Format.RED + "off"; }
+
+    void reload(CorePlayer p) {
+        try {
+            Settings next = Settings.load(FabricConfig.FILE);
+            Bridge.integration().reload(next);
+            config = FabricConfig.load();
+            perms = new Perms(config.everyoneByDefault());
+            env.features = config.features(next);
+            commands.essentials.configure(config.essentials());
+            p.send(Format.GREEN + "SCOPENET config reloaded.");
+        } catch (Exception e) {
+            p.send(Format.RED + "Reload failed: " + e.getMessage());
+        }
+    }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/FabricItems.java

@@ -0,0 +1,34 @@
+package net.scopenet.fabric.features;
+
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.nbt.TagParser;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.world.item.ItemStack;
+import net.scopenet.core.Item;
+
+/** ItemStack <-> the shared {@link Item}. The exact stack (enchantments, names, NBT) travels as SNBT in {@code data}. */
+final class FabricItems {
+    private FabricItems() {}
+
+    static Item toCore(ItemStack stack) {
+        String registryId = BuiltInRegistries.ITEM.getKey(stack.getItem()).toString();
+        return new Item(Item.panelId(registryId), stack.getHoverName().getString(), stack.getCount(), stack.save(new CompoundTag()).toString());
+    }
+
+    /** The stack for an item, restoring the exact NBT when it came from this platform; otherwise rebuilt from id and count. */
+    static ItemStack fromCore(Item item) {
+        if (!item.data().isEmpty()) {
+            try {
+                ItemStack stack = ItemStack.of(TagParser.parseTag(item.data()));
+                if (!stack.isEmpty()) return stack;
+            } catch (Exception ignored) {
+                // Another platform's serialisation: fall through to id and count.
+            }
+        }
+        ResourceLocation id = ResourceLocation.tryParse(Item.registryId(item.id()));
+        net.minecraft.world.item.Item type = id == null ? null : BuiltInRegistries.ITEM.get(id);
+        if (type == null || type == net.minecraft.world.item.Items.AIR) return ItemStack.EMPTY;
+        return new ItemStack(type, Math.max(1, item.count()));
+    }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/FabricPlatform.java

@@ -0,0 +1,75 @@
+package net.scopenet.fabric.features;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.scopenet.core.CorePlayer;
+import net.scopenet.core.Platform;
+import net.scopenet.core.Pos;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Optional;
+import java.util.UUID;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+/** The shared logic's view of a running Fabric server. */
+final class FabricPlatform implements Platform {
+    private final MinecraftServer server;
+    private final Perms perms;
+    private final ExecutorService io = Executors.newFixedThreadPool(4, r -> {
+        Thread t = new Thread(r, "scopenet-io");
+        t.setDaemon(true);
+        return t;
+    });
+
+    FabricPlatform(MinecraftServer server, Perms perms) { this.server = server; this.perms = perms; }
+
+    void shutdown() { io.shutdownNow(); }
+
+    CorePlayer wrap(ServerPlayer p) { return new FabricPlayer(p, this, perms); }
+
+    ServerLevel level(String id) {
+        ResourceLocation location = ResourceLocation.tryParse(id);
+        return location == null ? null : server.getLevel(ResourceKey.create(Registries.DIMENSION, location));
+    }
+
+    @Override public Optional<CorePlayer> player(UUID uuid) { return Optional.ofNullable(server.getPlayerList().getPlayer(uuid)).map(this::wrap); }
+
+    @Override public Optional<CorePlayer> playerByName(String name) { return Optional.ofNullable(server.getPlayerList().getPlayerByName(name)).map(this::wrap); }
+
+    @Override public Collection<? extends CorePlayer> online() {
+        List<CorePlayer> out = new ArrayList<>();
+        for (ServerPlayer p : server.getPlayerList().getPlayers()) out.add(wrap(p));
+        return out;
+    }
+
+    @Override public Optional<Pos> safeSurface(String world, int x, int z) {
+        ServerLevel level = level(world);
+        if (level == null || level.dimensionType().hasCeiling()) return Optional.empty(); // the Nether roof is bedrock
+        int y = level.getHeight(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, x, z);
+        if (y <= level.getMinBuildHeight() + 1) return Optional.empty();
+        BlockState ground = level.getBlockState(new BlockPos(x, y - 1, z));
+        if (!ground.blocksMotion() || !ground.getFluidState().isEmpty()) return Optional.empty();
+        return Optional.of(new Pos(world, x + 0.5, y, z + 0.5, 0, 0));
+    }
+
+    @Override public Pos worldSpawn(String world) {
+        ServerLevel level = level(world);
+        if (level == null) level = server.overworld();
+        BlockPos spawn = level.getSharedSpawnPos();
+        return new Pos(level.dimension().location().toString(), spawn.getX(), spawn.getY(), spawn.getZ(), 0, 0);
+    }
+
+    @Override public void runMain(Runnable task) { server.execute(task); }
+
+    @Override public void runAsync(Runnable task) { io.execute(task); }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/FabricPlayer.java

@@ -0,0 +1,63 @@
+package net.scopenet.fabric.features;
+
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.stats.Stats;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+import net.scopenet.core.CorePlayer;
+import net.scopenet.core.Item;
+import net.scopenet.core.Pos;
+
+import java.util.Optional;
+import java.util.UUID;
+
+/** A {@link CorePlayer} over a Fabric ServerPlayer. */
+final class FabricPlayer implements CorePlayer {
+    private final ServerPlayer player;
+    private final FabricPlatform platform;
+    private final Perms perms;
+
+    FabricPlayer(ServerPlayer player, FabricPlatform platform, Perms perms) {
+        this.player = player; this.platform = platform; this.perms = perms;
+    }
+
+    ServerPlayer handle() { return player; }
+
+    @Override public UUID uuid() { return player.getUUID(); }
+    @Override public String name() { return player.getGameProfile().getName(); }
+
+    @Override public Pos pos() {
+        ServerLevel level = player.serverLevel();
+        return new Pos(level.dimension().location().toString(), player.getX(), player.getY(), player.getZ(), player.getYRot(), player.getXRot());
+    }
+
+    @Override public void send(String message) { player.sendSystemMessage(Component.literal(message)); }
+
+    @Override public void teleport(Pos destination) {
+        ServerLevel level = platform.level(destination.world());
+        if (level == null) { send("§cThat dimension is not loaded."); return; }
+        player.teleportTo(level, destination.x(), destination.y(), destination.z(), destination.yaw(), destination.pitch());
+    }
+
+    @Override public boolean hasPermission(String node) { return perms.has(player, node); }
+
+    @Override public long playtimeSeconds() {
+        return player.getStats().getValue(Stats.CUSTOM.get(Stats.PLAY_TIME)) / 20L;
+    }
+
+    @Override public Optional<Item> heldItem() {
+        ItemStack stack = player.getMainHandItem();
+        return stack.isEmpty() ? Optional.empty() : Optional.of(FabricItems.toCore(stack));
+    }
+
+    @Override public void clearHeld() { player.setItemInHand(InteractionHand.MAIN_HAND, ItemStack.EMPTY); }
+
+    @Override public void give(Item item) {
+        ItemStack stack = FabricItems.fromCore(item);
+        if (stack.isEmpty()) { send("§cCould not deliver " + item.id() + " x" + item.count() + ". Ask an admin."); return; }
+        player.getInventory().add(stack);
+        if (!stack.isEmpty()) player.drop(stack, false);
+    }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/LuckPermsLookup.java

@@ -0,0 +1,21 @@
+package net.scopenet.fabric.features;
+
+import net.luckperms.api.LuckPerms;
+import net.luckperms.api.LuckPermsProvider;
+import net.luckperms.api.model.user.User;
+import net.luckperms.api.util.Tristate;
+import net.minecraft.server.level.ServerPlayer;
+
+/** Only loaded when the LuckPerms mod is present (see {@link Perms}). */
+final class LuckPermsLookup {
+    private LuckPermsLookup() {}
+
+    /** True or false when LuckPerms has the node set for this player, null when it has no opinion. */
+    static Boolean check(ServerPlayer player, String node) {
+        LuckPerms api = LuckPermsProvider.get();
+        User user = api.getUserManager().getUser(player.getUUID());
+        if (user == null) return null;
+        Tristate result = user.getCachedData().getPermissionData().checkPermission(node);
+        return result == Tristate.UNDEFINED ? null : result.asBoolean();
+    }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/Perms.java

@@ -0,0 +1,36 @@
+package net.scopenet.fabric.features;
+
+import net.fabricmc.loader.api.FabricLoader;
+import net.minecraft.server.level.ServerPlayer;
+
+/**
+ * Permission checks. With the LuckPerms mod installed its answer wins whenever the node is set; otherwise (or when
+ * LuckPerms has no opinion) the defaults apply: ordinary commands follow {@code permissions.default_level}, and
+ * admin nodes need operator level 2. Same node names as the Paper plugin, so one LuckPerms setup serves both.
+ */
+final class Perms {
+    private static final boolean LUCKPERMS = FabricLoader.getInstance().isModLoaded("luckperms");
+    private final boolean everyoneByDefault;
+
+    Perms(boolean everyoneByDefault) { this.everyoneByDefault = everyoneByDefault; }
+
+    static boolean luckPermsPresent() { return LUCKPERMS; }
+
+    static boolean isAdminNode(String node) {
+        return node.equals("scopenet.claims.bypass") || node.startsWith("scopenet.admin")
+                || node.equals("scopenet.command.scopenet.status") || node.equals("scopenet.command.scopenet.reload");
+    }
+
+    boolean has(ServerPlayer player, String node) {
+        if (LUCKPERMS) {
+            try {
+                Boolean answer = LuckPermsLookup.check(player, node);
+                if (answer != null) return answer;
+            } catch (Throwable t) {
+                // LuckPerms not ready yet or an API change: fall back to the defaults below.
+            }
+        }
+        if (isAdminNode(node)) return player.hasPermissions(2);
+        return everyoneByDefault || player.hasPermissions(2);
+    }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/PlaceholderApiModule.java

@@ -0,0 +1,43 @@
+package net.scopenet.fabric.features;
+
+import net.minecraft.resources.ResourceLocation;
+import net.minecraft.server.level.ServerPlayer;
+import net.scopenet.core.Placeholders;
+
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+import java.util.Optional;
+
+/**
+ * Registers %scopenet:level%, %scopenet:balance%… with Placeholder API (Fabric) when it is installed. Done through
+ * reflection so SCOPENET builds and runs without it and tolerates small API differences; any problem just leaves
+ * the placeholders off and is reported in /scopenet status.
+ */
+final class PlaceholderApiModule {
+    private PlaceholderApiModule() {}
+
+    /** Returns how many placeholders were registered; throws if the API isn't usable. */
+    static int register(Placeholders values) throws ReflectiveOperationException {
+        Class<?> placeholders = Class.forName("eu.pb4.placeholders.api.Placeholders");
+        Class<?> handlerType = Class.forName("eu.pb4.placeholders.api.PlaceholderHandler");
+        Class<?> resultType = Class.forName("eu.pb4.placeholders.api.PlaceholderResult");
+        Method register = placeholders.getMethod("register", ResourceLocation.class, handlerType);
+        Method value = resultType.getMethod("value", String.class);
+        Method invalid = resultType.getMethod("invalid", String.class);
+
+        int count = 0;
+        for (String key : Placeholders.KEYS) {
+            Object handler = Proxy.newProxyInstance(handlerType.getClassLoader(), new Class<?>[]{handlerType}, (proxy, method, args) -> {
+                if (method.getDeclaringClass() == Object.class) return method.invoke(new Object(), args);
+                Object context = args[0];
+                ServerPlayer player = (ServerPlayer) context.getClass().getMethod("player").invoke(context);
+                if (player == null) return invalid.invoke(null, "No player");
+                Optional<String> text = values.resolve(player.getUUID(), key);
+                return text.isPresent() ? value.invoke(null, text.get()) : invalid.invoke(null, "Unknown placeholder");
+            });
+            register.invoke(null, new ResourceLocation("scopenet", key), handler);
+            count++;
+        }
+        return count;
+    }
+}

integrations/fabric/src/mc1.20.1/java/net/scopenet/fabric/features/ScopenetCommand.java

@@ -0,0 +1,55 @@
+package net.scopenet.fabric.features;
+
+import net.scopenet.core.CommandSet;
+import net.scopenet.core.CoreCommand;
+import net.scopenet.core.CorePlayer;
+import net.scopenet.core.Format;
+
+import java.util.List;
+import java.util.Locale;
+
+/** /scopenet help | status | reload (alias /sn), with the same nodes as the Paper plugin. */
+final class ScopenetCommand implements CoreCommand {
+    private final FabricFeatures features;
+
+    ScopenetCommand(FabricFeatures features) { this.features = features; }
+
+    @Override public String name() { return "scopenet"; }
+    @Override public List<String> aliases() { return List.of("sn"); }
+    @Override public String permission() { return "scopenet.command.scopenet"; }
+
+    @Override public List<String> complete(CorePlayer player, String[] args) {
+        return args.length <= 1 ? List.of("help", "status", "reload") : List.of();
+    }
+
+    @Override public void run(CorePlayer p, String[] args) {
+        String sub = args.length == 0 ? "help" : args[0].toLowerCase(Locale.ROOT);
+        switch (sub) {
+            case "help" -> {
+                if (!p.hasPermission("scopenet.command.scopenet.help")) { p.send(Format.RED + "You do not have permission to view SCOPENET help."); return; }
+                help(p);
+            }
+            case "status" -> {
+                if (!p.hasPermission("scopenet.command.scopenet.status")) { p.send(Format.RED + "You do not have permission to use /scopenet status."); return; }
+                features.sendStatus(p);
+            }
+            case "reload" -> {
+                if (!p.hasPermission("scopenet.command.scopenet.reload")) { p.send(Format.RED + "You do not have permission to reload SCOPENET."); return; }
+                features.reload(p);
+            }
+            default -> p.send(Format.RED + "Unknown command. Use " + Format.YELLOW + "/scopenet help");
+        }
+    }
+
+    private void help(CorePlayer p) {
+        p.send(Format.GOLD + "=================== " + Format.YELLOW + "SCOPENET Commands" + Format.GOLD + " ===================");
+        CommandSet set = features.commandSet();
+        if (set == null) return;
+        for (CoreCommand c : set.all()) {
+            if (!p.hasPermission(c.permission())) continue;
+            String aliases = c.aliases().isEmpty() ? "" : Format.DARK_GRAY + " (" + String.join(", ", c.aliases().stream().map(a -> "/" + a).toList()) + ")";
+            p.send(Format.YELLOW + " /" + c.name() + aliases);
+        }
+        p.send(Format.GRAY + "Open the launcher's Command guide for what each one does.");
+    }
+}

integrations/minecraft/src/main/java/net/scopenet/minecraft/Bridge.java

@@ -16,6 +16,12 @@ public final class Bridge {
     private static int mapTicks;
     private Bridge() {}
 
+    /** The running integration, or null before the server has started. */
+    public static Integration integration() { return integration; }
+
+    /** Lets a permissions system (LuckPerms) say who may build in other guilds' claims. Default: nobody. */
+    public static volatile java.util.function.Predicate<ServerPlayer> claimBypass = player -> false;
+
     public static void start(MinecraftServer server) {
         try {
             integration = new Integration(Settings.load(Path.of("config/scopenet.properties")),
@@ -103,6 +109,7 @@ public final class Bridge {
         Integration current = integration;
         if (current == null) return false;
         if (!current.settings().guildsEnabled() || !current.settings().landClaimingEnabled()) return true;
+        if (claimBypass.test(player)) return true;
         String dimension = Compat.dimension(player);
         ChunkCheckResult check = current.checkChunk(dimension, pos.getX() >> 4, pos.getZ() >> 4, player.getUUID());
         if (check.allowed()) return true;

integrations/paper/src/main/java/net/scopenet/paper/ClientLinkBridge.java

@@ -0,0 +1,108 @@
+package net.scopenet.paper;
+
+import net.scopenet.core.*;
+import net.scopenet.integration.Integration;
+import org.bukkit.Bukkit;
+import org.bukkit.Material;
+import org.bukkit.entity.Player;
+import org.bukkit.inventory.ItemStack;
+import org.bukkit.plugin.messaging.PluginMessageListener;
+
+import java.nio.file.Path;
+import java.util.*;
+import java.util.logging.Logger;
+
+/**
+ * Talks to the optional SCOPENET client mod (HUD, claim overlay, shop and market windows) through plugin messaging,
+ * using the same shared logic the Fabric server mod uses. Display only: the client's actions are ordinary commands.
+ */
+final class ClientLinkBridge implements PluginMessageListener {
+    private final ScopenetPlugin plugin;
+    private final Env env;
+    private final PlayerCache cache;
+    private final ClientLink link;
+    private final Placeholders placeholders;
+
+    ClientLinkBridge(ScopenetPlugin plugin, Integration integration) {
+        this.plugin = plugin;
+        PaperPlatform platform = new PaperPlatform(plugin);
+        Features features = new Features(true, plugin.getConfig().getBoolean("economy.enabled", true), integration.settings().guildsEnabled(),
+                integration.settings().socialEnabled(), integration.settings().landClaimingEnabled(),
+                plugin.getConfig().getBoolean("clientlink.enabled", true), plugin.getConfig().getString("economy.currency-symbol", "$"));
+        Logger log = plugin.getLogger();
+        env = new Env(platform, new PanelAdapter(integration), features, Path.of(plugin.getDataFolder().getPath()), System::currentTimeMillis, new Random(), log);
+        cache = new PlayerCache(env);
+        placeholders = new Placeholders(env, cache);
+        link = new ClientLink(env, cache, Bukkit.getServer().getName(), (p, bytes) -> {
+            Player target = Bukkit.getPlayer(p.uuid());
+            if (target != null) target.sendPluginMessage(plugin, Wire.S2C, bytes);
+        });
+    }
+
+    ClientLink link() { return link; }
+
+    void start() {
+        Bukkit.getMessenger().registerOutgoingPluginChannel(plugin, Wire.S2C);
+        Bukkit.getMessenger().registerIncomingPluginChannel(plugin, Wire.C2S, this);
+        Bukkit.getScheduler().runTaskTimer(plugin, () -> {
+            cache.tick(p -> link.pushState(p));
+            link.tick();
+        }, 40, 20);
+    }
+
+    void stop() {
+        Bukkit.getMessenger().unregisterOutgoingPluginChannel(plugin, Wire.S2C);
+        Bukkit.getMessenger().unregisterIncomingPluginChannel(plugin, Wire.C2S, this);
+    }
+
+    void quit(Player player) { link.disconnected(player.getUniqueId()); }
+
+    @Override public void onPluginMessageReceived(String channel, Player player, byte[] message) {
+        if (!Wire.C2S.equals(channel)) return;
+        link.receive(new PaperPlatform.PaperPlayer(player), message);
+    }
+
+    /** Panel events (level-ups, achievements, guild changes) become toasts on clients. Any thread. */
+    void panelEvents(com.google.gson.JsonArray events) { link.onPanelEvents(events); }
+
+    /** Bukkit adapters for the shared logic. Only what the client link needs is real. */
+    static final class PaperPlatform implements Platform {
+        private final ScopenetPlugin plugin;
+        PaperPlatform(ScopenetPlugin plugin) { this.plugin = plugin; }
+
+        @Override public Optional<CorePlayer> player(UUID uuid) { return Optional.ofNullable(Bukkit.getPlayer(uuid)).map(PaperPlayer::new); }
+        @Override public Optional<CorePlayer> playerByName(String name) { return Optional.ofNullable(Bukkit.getPlayerExact(name)).map(PaperPlayer::new); }
+        @Override public Collection<? extends CorePlayer> online() {
+            List<CorePlayer> out = new ArrayList<>();
+            for (Player p : Bukkit.getOnlinePlayers()) out.add(new PaperPlayer(p));
+            return out;
+        }
+        @Override public Optional<Pos> safeSurface(String world, int x, int z) { return Optional.empty(); }
+        @Override public Pos worldSpawn(String world) { return new Pos(world, 0, 64, 0, 0, 0); }
+        @Override public void runMain(Runnable task) {
+            if (Bukkit.isPrimaryThread()) task.run(); else Bukkit.getScheduler().runTask(plugin, task);
+        }
+        @Override public void runAsync(Runnable task) { Bukkit.getScheduler().runTaskAsynchronously(plugin, task); }
+
+        record PaperPlayer(Player p) implements CorePlayer {
+            @Override public UUID uuid() { return p.getUniqueId(); }
+            @Override public String name() { return p.getName(); }
+            @Override public Pos pos() {
+                org.bukkit.Location l = p.getLocation();
+                return new Pos(ScopenetPlugin.dimension(l.getWorld()), l.getX(), l.getY(), l.getZ(), l.getYaw(), l.getPitch());
+            }
+            @Override public void send(String message) { p.sendMessage(message); }
+            @Override public void teleport(Pos destination) { }
+            @Override public boolean hasPermission(String node) { return p.hasPermission(node); }
+            @Override public long playtimeSeconds() { return p.getStatistic(org.bukkit.Statistic.PLAY_ONE_MINUTE) / 20L; }
+            @Override public Optional<Item> heldItem() {
+                ItemStack hand = p.getInventory().getItemInMainHand();
+                if (hand.getType() == Material.AIR) return Optional.empty();
+                String name = hand.hasItemMeta() && hand.getItemMeta().hasDisplayName() ? hand.getItemMeta().getDisplayName() : hand.getType().name().replace('_', ' ');
+                return Optional.of(new Item(hand.getType().name(), name, hand.getAmount(), ""));
+            }
+            @Override public void clearHeld() { }
+            @Override public void give(Item item) { }
+        }
+    }
+}

integrations/paper/src/main/java/net/scopenet/paper/ScopenetPlugin.java

@@ -24,6 +24,7 @@ public final class ScopenetPlugin extends JavaPlugin implements Listener {
     private EconomyHandler economy;
     private ScopenetApiImpl api;
     private CompatManager compat;
+    private ClientLinkBridge clientLink;
 
     @Override public void onEnable() {
         // Install the deny-by-default listener even if configuration is invalid.
@@ -58,7 +59,11 @@ public final class ScopenetPlugin extends JavaPlugin implements Listener {
             api = new ScopenetApiImpl(integration.client());
             ScopenetApiProvider.register(api);
             getServer().getServicesManager().register(ScopenetApi.class, api, this, org.bukkit.plugin.ServicePriority.Normal);
-            integration.onNotifications(new EventBridge(this, api, getLogger())::accept);
+            // Optional client mod (HUD, claim overlay, shop and market windows).
+            clientLink = new ClientLinkBridge(this, integration);
+            clientLink.start();
+            EventBridge events = new EventBridge(this, api, getLogger());
+            integration.onNotifications(list -> { events.accept(list); clientLink.panelEvents(list); });
             Bukkit.getScheduler().runTaskTimer(this, this::warmProfiles, 100, 20 * 20);
 
             // Optional integrations (LuckPerms, PlaceholderAPI, Vault, CoreProtect, WorldGuard, Spark) are found and
@@ -180,6 +185,7 @@ public final class ScopenetPlugin extends JavaPlugin implements Listener {
 
     @Override public void onDisable() {
         if (compat != null) compat.stop();
+        if (clientLink != null) clientLink.stop();
         if (api != null) {
             getServer().getServicesManager().unregister(ScopenetApi.class, api);
             ScopenetApiProvider.unregister(api);
@@ -213,6 +219,7 @@ public final class ScopenetPlugin extends JavaPlugin implements Listener {
     public void leave(PlayerQuitEvent event) {
         deniedAt.remove(event.getPlayer().getUniqueId());
         if (api != null) api.forget(event.getPlayer().getUniqueId());
+        if (clientLink != null) clientLink.quit(event.getPlayer());
         if (integration != null) integration.activity.leave(event.getPlayer().getUniqueId(), event.getPlayer().getName());
     }
 

integrations/paper/src/main/java/net/scopenet/paper/commands/EconomyHandler.java

@@ -269,17 +269,21 @@ public final class EconomyHandler implements CommandExecutor, Listener {
 
     /** {@code asGuild}: list on behalf of the player's guild, or buy with its bank (see /guild market). */
     void handleMarket(Player player, String[] args, boolean asGuild) {
-        if (asGuild && args.length >= 2 && args[0].equalsIgnoreCase("buy")) {
+        if (args.length >= 2 && args[0].equalsIgnoreCase("buy")) {
+            if (!asGuild && !player.hasPermission("scopenet.command.market.buy")) {
+                player.sendMessage(ChatColor.RED + "You do not have permission to buy from the market.");
+                return;
+            }
             long listing;
             try { listing = Long.parseLong(args[1].replace("#", "")); } catch (NumberFormatException e) {
-                player.sendMessage(ChatColor.RED + "Usage: /guild market buy <listing number> (shown as Listing #n in /market)");
+                player.sendMessage(ChatColor.RED + "Usage: /" + (asGuild ? "guild market" : "market") + " buy <listing number> (shown as Listing #n in /market)");
                 return;
             }
             JsonObject payload = new JsonObject();
             payload.addProperty("listing_id", listing);
             payload.addProperty("buyer_uuid", player.getUniqueId().toString());
             payload.addProperty("buyer_name", player.getName());
-            payload.addProperty("as_guild", true);
+            if (asGuild) payload.addProperty("as_guild", true);
             operations.enqueue(player, "economy/market/buy", payload, Collections.emptyList(), null);
             return;
         }

integrations/paper/src/main/resources/config.yml

@@ -93,3 +93,12 @@ integrations:
   spark:
     enabled: true
     report-interval-seconds: 30
+
+# ==============================================================================
+# Client mod link
+# Sends balance, level, guild and claim info to players who have the optional SCOPENET
+# client mod (HUD widgets, claim overlay, shop and market windows). Players without it
+# are unaffected. Display only: everything the client does is an ordinary command.
+# ==============================================================================
+clientlink:
+  enabled: true

integrations/settings.gradle

@@ -10,6 +10,8 @@ include 'common', 'api', 'paper'
 // Build loaders separately: Forge and Loom use different Gradle generations.
 if (providers.gradleProperty('loader').orNull == 'fabric') include 'fabric'
 if (providers.gradleProperty('loader').orNull == 'forge') include 'forge'
+// The optional client mod (HUD, claim overlay, shop and market windows). Fabric 1.20.1; build with -Ploader=fabric-client.
+if (providers.gradleProperty('loader').orNull == 'fabric-client') include 'fabric-client'
 def mcVer = (providers.gradleProperty('mcVersion').orNull ?: startParameter.projectProperties['mcVersion'] ?: '').toString()
 if (mcVer.startsWith('26.') || mcVer == '26.x') {
     if (findProject(':fabric') != null) project(':fabric').buildFileName = 'modern.gradle'