diff --git a/client/src/components/Level.tsx b/client/src/components/Level.tsx
index 0159d28..90dd3ef 100644
--- a/client/src/components/Level.tsx
+++ b/client/src/components/Level.tsx
@@ -22,9 +22,9 @@ import './level.css'
 import { Button } from './Button'
 import { ConnectionContext, useLeanClient } from '../connection';
 import { useGetGameInfoQuery, useLoadLevelQuery } from '../state/api';
-import { codeEdited, selectCode } from '../state/progress';
-import { useAppDispatch } from '../hooks';
-import { useSelector } from 'react-redux';
+import { codeEdited, selectCode, progressSlice } from '../state/progress';
+import { useAppDispatch, useAppSelector } from '../hooks';
+import { useStore } from 'react-redux';
 
 import { EditorContext, ConfigContext, ProgressContext, VersionContext } from '../../../node_modules/lean4-infoview/src/infoview/contexts';
 import { EditorConnection, EditorEvents } from '../../../node_modules/lean4-infoview/src/infoview/editorConnection';
@@ -63,7 +63,7 @@ function Level() {
   const codeviewRef = useRef<HTMLDivElement>(null)
   const introductionPanelRef = useRef<HTMLDivElement>(null)
 
-  const initialCode = useSelector(selectCode(worldId, levelId))
+  const initialCode = useAppSelector(selectCode(worldId, levelId))
 
   const [commandLineMode, setCommandLineMode] = useState(true)
   const [commandLineInput, setCommandLineInput] = useState("")
@@ -114,6 +114,8 @@ function Level() {
 
   const gameInfo = useGetGameInfoQuery()
 
+  useLoadWorldFiles(worldId)
+
   const level = useLoadLevelQuery({world: worldId, level: levelId})
 
   const dispatch = useAppDispatch()
@@ -277,8 +279,8 @@ function useLevelEditor(worldId: string, levelId: number, codeviewRef, initialCo
       let model = monaco.editor.getModel(uri)
       if (!model) {
         model = monaco.editor.createModel(initialCode, 'lean4', uri)
-        model.onDidChangeContent(() => onDidChangeContent(model.getValue()))
       }
+      model.onDidChangeContent(() => onDidChangeContent(model.getValue()))
       editor.setModel(model)
       editor.setPosition(model.getFullModelRange().getEndPosition())
 
@@ -288,9 +290,32 @@ function useLevelEditor(worldId: string, levelId: number, codeviewRef, initialCo
       const taskGutter = new LeanTaskGutter(infoProvider.client, editor)
       const abbrevRewriter = new AbbreviationRewriter(new AbbreviationProvider(), model, editor)
 
-      return () => { abbrevRewriter.dispose(); taskGutter.dispose(); model.dispose() }
+      return () => { abbrevRewriter.dispose(); taskGutter.dispose(); }
     }
   }, [editor, levelId, connection, leanClientStarted])
 
   return {editor, infoProvider, editorConnection}
 }
+
+/** Open all files in this world on the server so that they will load faster when accessed */
+function useLoadWorldFiles(worldId) {
+  const gameInfo = useGetGameInfoQuery()
+  const store = useStore()
+
+  useEffect(() => {
+    if (gameInfo.data) {
+      const models = []
+      for (let levelId = 1; levelId <= gameInfo.data.worldSize[worldId]; levelId++) {
+        const uri = monaco.Uri.parse(`file:///${worldId}/${levelId}`)
+        let model = monaco.editor.getModel(uri)
+        if (model) {
+          models.push(model)
+        } else {
+          const code = selectCode(worldId, levelId)(store.getState())
+          models.push(monaco.editor.createModel(code, 'lean4', uri))
+        }
+      }
+      return () => { for (let model of models) { model.dispose() } }
+    }
+  }, [gameInfo.data, worldId])
+}
diff --git a/package-lock.json b/package-lock.json
index e4f50b9..26c2ec9 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -21,7 +21,7 @@
         "cytoscape-klay": "^3.1.4",
         "debounce": "^1.2.1",
         "express": "^4.18.2",
-        "lean4-infoview": "https://gitpkg.now.sh/leanprover/vscode-lean4/lean4-infoview?master",
+        "lean4-infoview": "https://gitpkg.now.sh/leanprover/vscode-lean4/lean4-infoview?de0062c",
         "lean4web": "github:hhu-adam/lean4web",
         "path-browserify": "^1.0.1",
         "react": "^18.2.0",
@@ -6048,8 +6048,8 @@
     "node_modules/lean4-infoview": {
       "name": "@leanprover/infoview",
       "version": "0.4.2",
-      "resolved": "https://gitpkg.now.sh/leanprover/vscode-lean4/lean4-infoview?master",
-      "integrity": "sha512-XthMPhgRGoP/3lClX5LEQNXQYmzEcIQQBuK6AZ4RC5NKcTU7XUpA0qtZTQcWkPeZbOqz02FX5Dg8f4P1CDMuGw==",
+      "resolved": "https://gitpkg.now.sh/leanprover/vscode-lean4/lean4-infoview?de0062c",
+      "integrity": "sha512-xrKjl6/+Myn0UeBmEgkba6LStBfjb4iIC7fSJ3tAJxG0CrsKBmBCeU/sfjah3RNw7ieetLeFGd6YvxtoI4nPhQ==",
       "license": "Apache-2.0",
       "dependencies": {
         "@leanprover/infoview-api": "~0.2.1",
diff --git a/package.json b/package.json
index 18ca722..9a7bd2f 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
     "cytoscape-klay": "^3.1.4",
     "debounce": "^1.2.1",
     "express": "^4.18.2",
-    "lean4-infoview": "https://gitpkg.now.sh/leanprover/vscode-lean4/lean4-infoview?master",
+    "lean4-infoview": "https://gitpkg.now.sh/leanprover/vscode-lean4/lean4-infoview?de0062c",
     "lean4web": "github:hhu-adam/lean4web",
     "path-browserify": "^1.0.1",
     "react": "^18.2.0",
diff --git a/server/index.mjs b/server/index.mjs
index 30a91de..9c0c394 100644
--- a/server/index.mjs
+++ b/server/index.mjs
@@ -1,7 +1,7 @@
 import { WebSocketServer } from 'ws';
 import express from 'express'
 import path from 'path'
-import { spawn } from 'child_process';
+import * as cp from 'child_process';
 import * as url from 'url';
 import * as rpc from 'vscode-ws-jsonrpc';
 import * as jsonrpcserver from 'vscode-ws-jsonrpc/server';
@@ -34,7 +34,34 @@ if (isDevelopment) {
     cwd = "."
 }
 
+/** We keep a queue of started Lean Server processes to be ready when a user arrives */
+const queue = []
+const queueLength = 5
+
+/** start Lean Server processes to refill the queue */
+function fillQueue() {
+    while (queue.length < queueLength) {
+        const serverProcess = cp.spawn(cmd, cmdArgs, { cwd })
+        serverProcess.on('error', error =>
+            console.error(`Launching Lean Server failed: ${error}`)
+        );
+        if (serverProcess.stderr !== null) {
+            serverProcess.stderr.on('data', data =>
+                console.error(`Lean Server: ${data}`)
+            );
+        }
+
+        queue.push(serverProcess)
+    }
+}
+
+fillQueue()
+
 wss.addListener("connection", function(ws) {
+
+    const ps = queue.shift() // Pick the first Lean process; it's likely to be ready immediately
+    fillQueue()
+
     const socket = {
         onMessage: (cb) => { ws.on("message", cb) },
         onError: (cb) => { ws.on("error", cb) },
@@ -44,7 +71,7 @@ wss.addListener("connection", function(ws) {
     const reader = new rpc.WebSocketMessageReader(socket);
     const writer = new rpc.WebSocketMessageWriter(socket);
     const socketConnection = jsonrpcserver.createConnection(reader, writer, () => ws.close())
-    const serverConnection = jsonrpcserver.createServerProcess('Lean Server', cmd, cmdArgs, { cwd });
+    const serverConnection = jsonrpcserver.createProcessStreamConnection(ps);
     socketConnection.forward(serverConnection, message => {
         console.log(`CLIENT: ${JSON.stringify(message)}`)
         return message;
diff --git a/server/leanserver/GameServer/Commands.lean b/server/leanserver/GameServer/Commands.lean
index 9068e41..8ca11b4 100644
--- a/server/leanserver/GameServer/Commands.lean
+++ b/server/leanserver/GameServer/Commands.lean
@@ -79,9 +79,12 @@ elab "Statement" statementName:ident ? descr:str sig:declSig val:declVal : comma
   -- | none => `(lemma $(mkIdent "XX") $sig $val) -- TODO: Make it into an `example`
   -- | some name => `(lemma $name $sig $val)
 
+  let scope ← getScope
+
   elabCommand thmStatement
   modifyCurLevel fun level => pure {level with
     goal := sig,
+    scope := scope,
     descrText := descr.getString,
     descrFormat := match statementName with
     | none => "example " ++ (toString <| reprint sig.raw) ++ " := by"
@@ -187,17 +190,28 @@ elab "TacticDoc" name:ident content:str : command =>
 instance : Quote TacticDocEntry `term :=
 ⟨λ entry => Syntax.mkCApp ``TacticDocEntry.mk #[quote entry.name, quote entry.content]⟩
 
+/-- Throw an error if tactic doc does not exist -/
+def checkTacticDoc (name : Name) : CommandElabM Unit := do
+  let some _ := (tacticDocExt.getState (← getEnv)).find? (·.name = name)
+    | throwError "Missing Tactic Documentation: {name}"
+
 /-- Declare tactics that are introduced by this level. -/
 elab "NewTactics" args:ident* : command => do
-  modifyCurLevel fun level => pure {level with newTactics := args.map (·.getId)}
+  let names := args.map (·.getId)
+  for name in names do checkTacticDoc name
+  modifyCurLevel fun level => pure {level with newTactics := names}
 
 /-- Declare tactics that are temporarily disabled in this level -/
 elab "DisabledTactics" args:ident* : command => do
-  modifyCurLevel fun level => pure {level with disabledTactics := args.map (·.getId)}
+  let names := args.map (·.getId)
+  for name in names do checkTacticDoc name
+  modifyCurLevel fun level => pure {level with disabledTactics := names}
 
 /-- Temporarily disable all tactics except the ones declared here -/
 elab "OnlyTactics" args:ident* : command => do
-  modifyCurLevel fun level => pure {level with onlyTactics := args.map (·.getId)}
+  let names := args.map (·.getId)
+  for name in names do checkTacticDoc name
+  modifyCurLevel fun level => pure {level with onlyTactics := names}
 
 /-! ## Lemmas -/
 
diff --git a/server/leanserver/GameServer/EnvExtensions.lean b/server/leanserver/GameServer/EnvExtensions.lean
index 9c1f13d..7c5f57f 100644
--- a/server/leanserver/GameServer/EnvExtensions.lean
+++ b/server/leanserver/GameServer/EnvExtensions.lean
@@ -161,9 +161,10 @@ deriving ToJson, FromJson, Repr
 def getCurLevelId [MonadError m] : m LevelId := do
   return { game := ← getCurGameId, world := ← getCurWorldId, level := ← getCurLevelIdx}
 
-/--
-
+/-- Instance to make GameLevel Repr work -/
+instance : Repr Elab.Command.Scope := ⟨fun s _ => repr s.currNamespace⟩
 
+/--
 Fields:
 - TODO
 - introduction: Theory block shown all the time.
@@ -195,6 +196,7 @@ structure GameLevel where
   lemmas: Array Availability := default
   hints: Array GoalHintEntry := default
   goal : TSyntax `Lean.Parser.Command.declSig := default
+  scope : Elab.Command.Scope := default
   descrText: String := default
   descrFormat : String := default
   deriving Inhabited, Repr
diff --git a/server/leanserver/GameServer/FileWorker.lean b/server/leanserver/GameServer/FileWorker.lean
index 75e5166..a82ea56 100644
--- a/server/leanserver/GameServer/FileWorker.lean
+++ b/server/leanserver/GameServer/FileWorker.lean
@@ -77,13 +77,24 @@ partial def findForbiddenTactics (inputCtx : Parser.InputContext) (level : GameL
   | .atom info val =>
     -- ignore syntax elements that do not start with a letter
     -- and ignore "with" keyword
-    if 0 < val.length ∧ val.data[0]!.isAlpha ∧ val != "with" then
+    if 0 < val.length ∧ val.data[0]!.isAlpha ∧ val != "with" ∧ val != "at" then
       if ¬ ((level.tactics.map (·.name.toString))).contains val then
         addErrorMessage info s!"You have not unlocked the tactic '{val}' yet!"
       else if level.disabledTactics.contains val
         ∨ (¬ level.onlyTactics.isEmpty ∧ ¬ level.onlyTactics.contains val)then
         addErrorMessage info s!"The tactic '{val}' is disabled in this level!"
-  | .ident info rawVal val preresolved => return ()
+  | .ident info rawVal val preresolved =>
+      let ns ←
+        try resolveGlobalConst (mkIdent val)
+        catch | _ => pure [] -- catch "unknown constant" error
+      for n in ns do
+        let some (.thmInfo ..) := (← getEnv).find? n
+          | return () -- not a theroem -> ignore
+        if ¬ ((level.lemmas.map (·.name))).contains n then
+          addErrorMessage info s!"You have not unlocked the lemma '{n}' yet!"
+        else if level.disabledLemmas.contains n
+          ∨ (¬ level.onlyLemmas.isEmpty ∧ ¬ level.onlyLemmas.contains n)then
+          addErrorMessage info s!"The lemma '{n}' is disabled in this level!"
 where addErrorMessage (info : SourceInfo) (s : MessageData) :=
   modify fun st => { st with
     messages := st.messages.add {
@@ -139,10 +150,10 @@ def compileProof (inputCtx : Parser.InputContext) (snap : Snapshot) (hasWidgets
           let tacticStx := (#[skip] ++ tacticStx.getArgs ++ #[done]).map (⟨.⟩)
           let tacticStx := ← `(Lean.Parser.Tactic.tacticSeq| $[$(tacticStx)]*)
 
-          let cmdStx ← `(command|
-            set_option tactic.hygienic false in
-            theorem the_theorem $(level.goal) := by {$(⟨tacticStx⟩)} )
-          Elab.Command.elabCommandTopLevel cmdStx)
+          let cmdStx ← `(command| theorem the_theorem $(level.goal) := by {$(⟨tacticStx⟩)} )
+
+          Elab.Command.withScope (fun _ => level.scope) do -- use open namespaces and options as in the file
+            Elab.Command.elabCommandTopLevel cmdStx)
         cmdCtx cmdStateRef
     let postNew := (← tacticCacheNew.get).post
     snap.tacticCache.modify fun _ => { pre := postNew, post := {} }
diff --git a/server/leanserver/GameServer/Watchdog.lean b/server/leanserver/GameServer/Watchdog.lean
index bc0e09d..8c6fa10 100644
--- a/server/leanserver/GameServer/Watchdog.lean
+++ b/server/leanserver/GameServer/Watchdog.lean
@@ -102,6 +102,7 @@ def initAndRunWatchdog (args : List String) (i o e : FS.Stream) : IO Unit := do
   let i ← maybeTee "wdIn.txt" false i
   let o ← maybeTee "wdOut.txt" true o
   let e ← maybeTee "wdErr.txt" true e
+  let state := {env := ← createEnv, game := `TestGame}
   let initRequest ← i.readLspRequestAs "initialize" InitializeParams
   o.writeLspResponse {
     id     := initRequest.id
@@ -114,7 +115,6 @@ def initAndRunWatchdog (args : List String) (i o e : FS.Stream) : IO Unit := do
       : InitializeResult
     }
   }
-  let state := {env := ← createEnv, game := `TestGame}
   let context : ServerContext := {
     hIn            := i
     hOut           := o
diff --git a/server/testgame/TestGame/Levels/Predicate/L02_Rewrite.lean b/server/testgame/TestGame/Levels/Predicate/L02_Rewrite.lean
index 9e8f068..defa2fa 100644
--- a/server/testgame/TestGame/Levels/Predicate/L02_Rewrite.lean
+++ b/server/testgame/TestGame/Levels/Predicate/L02_Rewrite.lean
@@ -54,7 +54,7 @@ HiddenHint (a : ℕ) (b : ℕ) (c : ℕ) (d : ℕ) (h₁ : c = d) (h₂ : a = b)
 "Auch eine Möglichkeit.. Kannst du das Goal so umschreiben, dass es mit einer Annahme übereinstimmt?"
 
 Hint (a : ℕ) (b : ℕ) (h : b = a) : a = b =>
-"Naja auch Umwege führen ans Ziel... Wenn du das Goal zu `a = A` umschreibst, kann man es mit
+"Naja auch Umwege führen ans Ziel... Wenn du das Goal zu `a = a` umschreibst, kann man es mit
 `rfl` beweisen (rsp. das passiert automatisch.)"
 
 Hint (a : ℕ) (b : ℕ) (c : ℕ) (d : ℕ) (h₁ : c = d) (h₂ : d = b) (h₃ : d = a) : b = c =>