diff --git a/.github/workflows/test_branch.yml b/.github/workflows/test_branch.yml
index 48838a79..23a299e7 100644
--- a/.github/workflows/test_branch.yml
+++ b/.github/workflows/test_branch.yml
@@ -47,18 +47,19 @@ jobs:
           sbt test
 
       ### Update & build
-#      - name: Integration test
-#        run: |
-#          git clone https://github.com/fluencelabs/aqua-playground.git
-#          cd aqua-playground
-#          npm i
-#          cd ..
-#          sbt "cli/run -i aqua-playground/aqua/examples -o aqua-playground/src/compiled/examples -m aqua-playground/node_modules -c \"uniqueConst = 1\" -c \"anotherConst = \\\"ab\\\"\""
-#          cd aqua-playground
-#          npm run examples
-#          cd ..
-#          sbt "cliJS/fastOptJS"
-#          rm -rf aqua-playground/src/compiled/examples/*
-#          node cli/.js/target/scala-3.0.1/cli-fastopt.js -i aqua-playground/aqua/examples -o aqua-playground/src/compiled/examples -m aqua-playground/node_modules -c "uniqueConst = 1" -c "anotherConst = \"ab\""
-#          cd aqua-playground
-#          npm run examples
+      - name: Integration test
+        run: |
+          git clone https://github.com/fluencelabs/aqua-playground.git
+          cd aqua-playground
+          rm -rf src/compiled/examples/*
+          npm i
+          cd ..
+          sbt "cli/run -i aqua-playground/aqua/examples -o aqua-playground/src/compiled/examples -m aqua-playground/node_modules -c \"UNIQUE_CONST = 1\" -c \"ANOTHER_CONST = \\\"ab\\\"\""
+          cd aqua-playground
+          npm run examples
+          cd ..
+          sbt "cliJS/fastOptJS"
+          rm -rf aqua-playground/src/compiled/examples/*
+          node cli/.js/target/scala-3.0.1/cli-fastopt.js -i aqua-playground/aqua/examples -o aqua-playground/src/compiled/examples -m aqua-playground/node_modules -c "UNIQUE_CONST = 1" -c "ANOTHER_CONST = \"ab\""
+          cd aqua-playground
+          npm run examples
diff --git a/.jvmopts b/.jvmopts
index 1321950e..5de9cbcb 100644
--- a/.jvmopts
+++ b/.jvmopts
@@ -1,6 +1,6 @@
 -Dfile.encoding=UTF8
 -Xms1G
--Xmx5G
+-Xmx6G
 -XX:ReservedCodeCacheSize=500M
 -XX:+TieredCompilation
 -XX:+UseParallelGC
\ No newline at end of file
diff --git a/aqua-src/export.aqua b/aqua-src/export.aqua
index 24ef4491..67d492c5 100644
--- a/aqua-src/export.aqua
+++ b/aqua-src/export.aqua
@@ -1,4 +1,6 @@
-module Export.Test declares foobar, foo, bar
+module Export.Test declares foobar, foo, bar, ExpSrv, FA
+
+const FA = "constant"
 
 func bar() -> string:
     <- " I am MyFooBar bar"
@@ -12,5 +14,6 @@ func foobar() -> []string:
     res <- bar()
     <- res
 
-service ExpSrv:
-   baz()
\ No newline at end of file
+service ExpSrv("exp-srv"):
+   baz()
+   log: string -> ()
\ No newline at end of file
diff --git a/aqua-src/import.aqua b/aqua-src/import.aqua
index 7a2219f2..937308c9 100644
--- a/aqua-src/import.aqua
+++ b/aqua-src/import.aqua
@@ -1,8 +1,9 @@
 -- import.aqua
 module Import.Test
-import foobar from "export.aqua"
+import foobar, FA as C, ExpSrv from "export.aqua"
 
-use foo as f from "export.aqua" as Exp
+use foo as f, FA as U from "export.aqua" as Exp
+use foo as f, FA from "export.aqua" as Exp1
 
 use "export.aqua"
 
@@ -10,7 +11,13 @@ import "gen/OneMore.aqua"
 
 import OneMore as OM from "gen/OneMore.aqua"
 
-export foo_wrapper as wrap, foobar as barfoo
+export consts as main--, foobar as barfoo
+
+func consts():
+   ExpSrv.log(C)
+   ExpSrv.log(Exp.U)
+   ExpSrv.log(Exp1.FA)
+   ExpSrv.log(Export.Test.FA)
 
 func foo_wrapper() -> string:
     z <- Exp.f()
@@ -20,4 +27,6 @@ func foo_wrapper() -> string:
     OM "ohmygod"
     OM.more_call()
     OM.consume(q)
+    ExpSrv.log(C)
+    ExpSrv.log(Exp.U)
     <- z
\ No newline at end of file
diff --git a/aqua-src/ret.aqua b/aqua-src/ret.aqua
index 13acd12d..e80862bd 100644
--- a/aqua-src/ret.aqua
+++ b/aqua-src/ret.aqua
@@ -3,7 +3,7 @@ module Ret
 import Service from "service.aqua"
 
 use "error.aqua"
-export GetStr, tupleFunc, Service as S
+export GetStr, multiReturnFunc, Service as S
 
 service GetStr("multiret-test"):
     retStr: string -> string
@@ -11,18 +11,21 @@ service GetStr("multiret-test"):
 service GetNum("multiret-num"):
     retNum: -> u8
 
-const someNum = 5
-const someStr = "some-str"
+const SOME_NUM = 5
+const SOME_STR = "some-str"
 
 func tupleFunc() -> string, u8:
-    str <- GetStr.retStr(someStr)
+    str <- GetStr.retStr(SOME_STR)
     n <- GetNum.retNum()
     Err.Peer.is_connected("Connected?")
     <- str, n
 
 func multiReturnFunc(somethingToReturn: []u8, smthOption: ?string) -> []string, u8, string, []u8, ?string, u8:
     res: *string
-    res <- GetStr.retStr(someStr)
-    res <- GetStr.retStr("random-str")
+    res <- GetStr.retStr(SOME_STR)
+    try:
+        res <- GetStr.retStr("random-str")
+    catch e:
+        GetStr.retStr(e.msg)
     res, tNum <- tupleFunc()
-    <- res, 5, someStr, somethingToReturn, smthOption, tNum
+    <- res, 5, SOME_STR, somethingToReturn, smthOption, tNum
diff --git a/backend/air/src/main/scala/aqua/backend/air/AirGen.scala b/backend/air/src/main/scala/aqua/backend/air/AirGen.scala
index 524a4859..dc86df09 100644
--- a/backend/air/src/main/scala/aqua/backend/air/AirGen.scala
+++ b/backend/air/src/main/scala/aqua/backend/air/AirGen.scala
@@ -29,10 +29,10 @@ object AirGen extends Logging {
   def valueToData(vm: ValueModel): DataView = vm match {
     case LiteralModel(value, _) => DataView.StringScalar(value)
     case VarModel(name, t, lambda) =>
-      val n = t match {
+      val n = (t match {
         case _: StreamType => "$" + name
         case _ => name
-      }
+      }).replace('.', '_')
       if (lambda.isEmpty) DataView.Variable(n)
       else DataView.VarLens(n, lambdaToString(lambda.toList))
   }
@@ -43,10 +43,10 @@ object AirGen extends Logging {
     case list => list.reduceLeft(SeqGen(_, _))
   }
 
-  def exportToString(exportTo: Call.Export): String = exportTo match {
+  def exportToString(exportTo: Call.Export): String = (exportTo match {
     case Call.Export(name, _: StreamType) => "$" + name
     case Call.Export(name, _) => name
-  }
+  }).replace('.', '_')
 
   private def folder(op: ResolvedOp, ops: Chain[AirGen]): Eval[AirGen] =
     op match {
diff --git a/build.sbt b/build.sbt
index 99182168..29c27c89 100644
--- a/build.sbt
+++ b/build.sbt
@@ -17,7 +17,7 @@ val declineV = "2.1.0"
 name := "aqua-hll"
 
 val commons = Seq(
-  baseAquaVersion := "0.2.2",
+  baseAquaVersion := "0.3.0",
   version         := baseAquaVersion.value + "-" + sys.env.getOrElse("BUILD_NUMBER", "SNAPSHOT"),
   scalaVersion    := dottyVersion,
   libraryDependencies ++= Seq(
diff --git a/cli/.jvm/src/main/scala/aqua/Test.scala b/cli/.jvm/src/main/scala/aqua/Test.scala
index 949abb6d..72ddea77 100644
--- a/cli/.jvm/src/main/scala/aqua/Test.scala
+++ b/cli/.jvm/src/main/scala/aqua/Test.scala
@@ -16,7 +16,7 @@ object Test extends IOApp.Simple {
       start <- IO(System.currentTimeMillis())
       _ <- AquaPathCompiler
         .compileFilesTo[IO](
-          Path("./aqua-src"),
+          Path("./aqua-src/import.aqua"),
           List(Path("./aqua")),
           Path("./target"),
           TypeScriptBackend,
diff --git a/cli/src/main/scala/aqua/AppOps.scala b/cli/src/main/scala/aqua/AppOps.scala
index 7c220f95..feb992bd 100644
--- a/cli/src/main/scala/aqua/AppOps.scala
+++ b/cli/src/main/scala/aqua/AppOps.scala
@@ -97,12 +97,12 @@ object AppOps {
 
   def constantOpts[F[_]: LiftParser: Comonad]: Opts[List[TransformConfig.Const]] =
     Opts
-      .options[String]("const", "Constant that will be used in an aqua code", "c")
+      .options[String]("const", "Constant that will be used in an aqua code. Constant name must be upper cased.", "c")
       .mapValidated { strs =>
         val parsed = strs.map(s => ConstantExpr.onlyLiteral.parseAll(s))
 
-        val errors = parsed.collect { case Left(er) =>
-          er
+        val errors = parsed.zip(strs).collect { case (Left(er), str) =>
+          str
         }
 
         NonEmptyList
@@ -113,7 +113,8 @@ object AppOps {
                 TransformConfig.Const(v._1.value, LiteralModel(v._2.value, v._2.ts))
             })
           ) { errors =>
-            Validated.invalid(errors.map(_.toString))
+            val errorMsgs = errors.map (str => s"Invalid constant definition '$str'.")
+            Validated.invalid(errorMsgs)
           }
       }
       .withDefault(List.empty)
diff --git a/model/src/main/scala/aqua/model/AquaContext.scala b/model/src/main/scala/aqua/model/AquaContext.scala
index 845fa017..fa7a4e19 100644
--- a/model/src/main/scala/aqua/model/AquaContext.scala
+++ b/model/src/main/scala/aqua/model/AquaContext.scala
@@ -27,6 +27,9 @@ case class AquaContext(
   private def prefixFirst[T](prefix: String, pair: (String, T)): (String, T) =
     (prefix + pair._1, pair._2)
 
+  def isEmpty: Boolean = this == AquaContext.blank
+  def nonEmpty: Boolean = !isEmpty
+
   def pick(
     name: String,
     rename: Option[String],
@@ -45,7 +48,19 @@ case class AquaContext(
           services = getter(_.services)
         )
       }
-      .filter(_.`type`(name).nonEmpty)
+      .filter(_.nonEmpty)
+
+  def pickHeader: AquaContext =
+    AquaContext.blank.copy(module = module, declares = declares, exports = exports)
+
+  def pickDeclared(implicit semi: Semigroup[AquaContext]): AquaContext =
+    if (module.isEmpty) this
+    else
+      declares
+        .flatMap(pick(_, None))
+        .foldLeft(pickHeader)(
+          _ |+| _
+        )
 
   def allTypes(prefix: String = ""): Map[String, Type] =
     abilities
@@ -83,6 +98,7 @@ case class AquaContext(
             types ++
             values.view.mapValues(_.lastType) ++
             services.view.mapValues(_.`type`) ++
+            // TODO do we need to pass abilities as type?
             abilities.flatMap { case (n, c) =>
               c.`type`(n).map(n -> _)
             }
diff --git a/model/src/main/scala/aqua/model/ValueModel.scala b/model/src/main/scala/aqua/model/ValueModel.scala
index 761489ae..ce222a20 100644
--- a/model/src/main/scala/aqua/model/ValueModel.scala
+++ b/model/src/main/scala/aqua/model/ValueModel.scala
@@ -100,6 +100,8 @@ case class VarModel(name: String, `type`: Type, lambda: Chain[LambdaModel] = Cha
       case Some(vv) => vv // TODO check that lambda is empty, otherwise error
       case None => this // Should not happen
     }
+
+  override def toString(): String = s"var{$name: " + `type` + s"}.${lambda.toList.mkString(".")}"
 }
 
 object VarModel {
diff --git a/model/transform/src/main/scala/aqua/model/transform/TransformConfig.scala b/model/transform/src/main/scala/aqua/model/transform/TransformConfig.scala
index 601fc034..b4cb2808 100644
--- a/model/transform/src/main/scala/aqua/model/transform/TransformConfig.scala
+++ b/model/transform/src/main/scala/aqua/model/transform/TransformConfig.scala
@@ -24,21 +24,39 @@ case class TransformConfig(
   // or relay's variable otherwise
   val hostPeerId: TransformConfig.Const =
     TransformConfig.Const(
-      "host_peer_id",
+      "HOST_PEER_ID",
       relayVarName.fold[ValueModel](LiteralModel.initPeerId)(r => VarModel(r, ScalarType.string))
     )
 
+  val initPeerId: TransformConfig.Const =
+    TransformConfig.Const(
+      "INIT_PEER_ID",
+      LiteralModel.initPeerId
+    )
+
+  val nil: TransformConfig.Const =
+    TransformConfig.Const(
+      "nil", // TODO: shouldn't it be NIL?
+      LiteralModel.nil
+    )
+
+  val lastError: TransformConfig.Const =
+    TransformConfig.Const(
+      "LAST_ERROR",
+      VarModel.lastError
+    )
+
+  val constantsMap =
+    (hostPeerId :: initPeerId :: nil :: lastError :: constants)
+      .map(c => c.name -> c.value)
+      .toMap
+
   implicit val aquaContextMonoid: Monoid[AquaContext] = {
-    val constantsMap = (hostPeerId :: constants).map(c => c.name -> c.value).toMap
+
     AquaContext
       .implicits(
         AquaContext.blank
-          .copy(values =
-            Map(
-              VarModel.lastError.name -> VarModel.lastError,
-              "nil" -> LiteralModel.nil
-            ) ++ constantsMap
-          )
+          .copy(values = constantsMap)
       )
       .aquaContextMonoid
   }
diff --git a/parser/src/main/scala/aqua/parser/expr/ConstantExpr.scala b/parser/src/main/scala/aqua/parser/expr/ConstantExpr.scala
index dc1ed97b..797a8a22 100644
--- a/parser/src/main/scala/aqua/parser/expr/ConstantExpr.scala
+++ b/parser/src/main/scala/aqua/parser/expr/ConstantExpr.scala
@@ -22,14 +22,14 @@ object ConstantExpr extends Expr.Leaf {
 
   override def p[F[_]: LiftParser: Comonad]: P[ConstantExpr[F]] =
     ((((`const` *> ` ` *> Name
-      .p[F] <* ` `) ~ `?`.?).with1 <* `=` <* ` `) ~ Value.`value`).map {
+      .upper[F] <* ` `) ~ `?`.?).with1 <* `=` <* ` `) ~ Value.`value`).map {
       case ((name, mark), value) =>
         ConstantExpr(name, value, mark.nonEmpty)
     }
 
   def onlyLiteral[F[_]: LiftParser: Comonad]: P[(Name[F], Literal[F])] =
     ((((Name
-      .p[F] <* ` `) ~ `?`.?).with1 <* `=` <* ` `) ~ Value.literal).map { case ((name, _), value) =>
+      .upper[F] <* ` `) ~ `?`.?).with1 <* `=` <* ` `) ~ Value.literal).map { case ((name, _), value) =>
       (name, value)
     }
 }
diff --git a/parser/src/main/scala/aqua/parser/head/FromExpr.scala b/parser/src/main/scala/aqua/parser/head/FromExpr.scala
index a1ec63b2..fa6a7200 100644
--- a/parser/src/main/scala/aqua/parser/head/FromExpr.scala
+++ b/parser/src/main/scala/aqua/parser/head/FromExpr.scala
@@ -27,4 +27,10 @@ object FromExpr {
 
   def importFrom[F[_]: LiftParser: Comonad]: P[NonEmptyList[NameOrAbAs[F]]] =
       comma[NameOrAbAs[F]](nameOrAbAs[F]) <* ` ` <* `from`
+
+  def show[F[_]](ne: NonEmptyList[NameOrAbAs[F]]): String =
+    ne.toList.map(_.fold(
+      non => non._1.value + non._2.map(_.value).fold("")(" as "+_),
+      non => non._1.value + non._2.map(_.value).fold("")(" as "+_)
+    )).mkString(", ")
 }
\ No newline at end of file
diff --git a/parser/src/main/scala/aqua/parser/head/ImportExpr.scala b/parser/src/main/scala/aqua/parser/head/ImportExpr.scala
index 1c00aa47..be54ddf8 100644
--- a/parser/src/main/scala/aqua/parser/head/ImportExpr.scala
+++ b/parser/src/main/scala/aqua/parser/head/ImportExpr.scala
@@ -8,8 +8,11 @@ import cats.parse.Parser
 import cats.~>
 
 case class ImportExpr[F[_]](filename: Literal[F]) extends FilenameExpr[F] {
+
   override def mapK[K[_]: Comonad](fk: F ~> K): ImportExpr[K] =
     copy(filename.mapK(fk))
+
+  override def toString: String = s"import ${filename.value}"
 }
 
 object ImportExpr extends HeaderExpr.Leaf {
diff --git a/parser/src/main/scala/aqua/parser/head/ImportFromExpr.scala b/parser/src/main/scala/aqua/parser/head/ImportFromExpr.scala
index a0e84987..4f226caa 100644
--- a/parser/src/main/scala/aqua/parser/head/ImportFromExpr.scala
+++ b/parser/src/main/scala/aqua/parser/head/ImportFromExpr.scala
@@ -12,8 +12,11 @@ case class ImportFromExpr[F[_]](
   imports: NonEmptyList[FromExpr.NameOrAbAs[F]],
   filename: Literal[F]
 ) extends FilenameExpr[F] with FromExpr[F] {
+
   override def mapK[K[_]: Comonad](fk: F ~> K): ImportFromExpr[K] =
     copy(FromExpr.mapK(imports)(fk), filename.mapK(fk))
+
+  override def toString: String = s"import ${FromExpr.show(imports)} from ${filename.value}"
 }
 
 object ImportFromExpr extends HeaderExpr.Leaf {
diff --git a/parser/src/main/scala/aqua/parser/head/UseExpr.scala b/parser/src/main/scala/aqua/parser/head/UseExpr.scala
index a7f44aaf..80871ca6 100644
--- a/parser/src/main/scala/aqua/parser/head/UseExpr.scala
+++ b/parser/src/main/scala/aqua/parser/head/UseExpr.scala
@@ -11,8 +11,12 @@ case class UseExpr[F[_]](
   filename: Literal[F],
   asModule: Option[Ability[F]]
 ) extends FilenameExpr[F] {
+
   override def mapK[K[_]: Comonad](fk: F ~> K): UseExpr[K] =
     copy(filename.mapK(fk), asModule.map(_.mapK(fk)))
+
+  override def toString(): String =
+    s"use ${filename.value}${asModule.map(_.value).fold("")(" as " + _)}"
 }
 
 object UseExpr extends HeaderExpr.Leaf {
diff --git a/parser/src/main/scala/aqua/parser/head/UseFromExpr.scala b/parser/src/main/scala/aqua/parser/head/UseFromExpr.scala
index fa8a1db0..a70edabf 100644
--- a/parser/src/main/scala/aqua/parser/head/UseFromExpr.scala
+++ b/parser/src/main/scala/aqua/parser/head/UseFromExpr.scala
@@ -16,6 +16,9 @@ case class UseFromExpr[F[_]](
 
   override def mapK[K[_]: Comonad](fk: F ~> K): UseFromExpr[K] =
     copy(FromExpr.mapK(imports)(fk), filename.mapK(fk), asModule.mapK(fk))
+
+  override def toString(): String =
+    s"use ${FromExpr.show(imports)} from ${filename.value} as ${asModule.value}"
 }
 
 object UseFromExpr extends HeaderExpr.Leaf {
diff --git a/parser/src/main/scala/aqua/parser/lexer/Name.scala b/parser/src/main/scala/aqua/parser/lexer/Name.scala
index b12bd851..4b7f25ff 100644
--- a/parser/src/main/scala/aqua/parser/lexer/Name.scala
+++ b/parser/src/main/scala/aqua/parser/lexer/Name.scala
@@ -24,8 +24,11 @@ object Name {
   def p[F[_]: LiftParser: Comonad]: P[Name[F]] =
     `name`.lift.map(Name(_))
 
+  def upper[F[_]: LiftParser: Comonad]: P[Name[F]] =
+    NAME.lift.map(Name(_))
+
   def dotted[F[_]: LiftParser: Comonad]: P[Name[F]] =
-    ((`Class`.repSep(`.`).map(_.toList.mkString(".")) ~ `.`).?.with1 ~ `name`).string.lift
+    ((`Class` ~ `.`).backtrack.rep0.?.with1 ~ P.oneOf(`name` :: NAME :: Nil)).string.lift
       .map(Name(_))
 
   def nameAs[F[_]: LiftParser: Comonad]: P[As[F]] =
diff --git a/parser/src/main/scala/aqua/parser/lexer/Token.scala b/parser/src/main/scala/aqua/parser/lexer/Token.scala
index 26ba235e..9a349395 100644
--- a/parser/src/main/scala/aqua/parser/lexer/Token.scala
+++ b/parser/src/main/scala/aqua/parser/lexer/Token.scala
@@ -19,8 +19,10 @@ object Token {
   private val AZ = ('A' to 'Z').toSet
   private val f09 = ('0' to '9').toSet
   private val anum = az ++ AZ ++ f09
+  private val upperAnum = AZ ++ f09
   private val f_ = Set('_')
   private val anum_ = anum ++ f_
+  private val upperAnum_ = upperAnum ++ f_
   private val nl = Set('\n', '\r')
 
   val ` *` : P0[String] = P.charsWhile0(fSpaces)
@@ -59,9 +61,10 @@ object Token {
   val ` : ` : P[Unit] = P.char(':').surroundedBy(` `.?)
   val `anum_*` : P[Unit] = P.charsWhile(anum_).void
 
+  val NAME: P[String] = P.charsWhile(upperAnum_).string
   val `name`: P[String] = (P.charIn(az) ~ P.charsWhile(anum_).?).string
 
-  val `Class`: P[String] = (P.charIn(AZ) ~ P.charsWhile(anum_).?).map { case (c, s) ⇒
+  val `Class`: P[String] = (P.charIn(AZ) ~ P.charsWhile(anum_).backtrack.?).map { case (c, s) ⇒
     c.toString ++ s.getOrElse("")
   }
   val `\n` : P[Unit] = P.string("\n\r") | P.char('\n') | P.string("\r\n")
diff --git a/parser/src/test/scala/aqua/parser/AssignmentExprSpec.scala b/parser/src/test/scala/aqua/parser/AssignmentExprSpec.scala
index f089ff54..8050f195 100644
--- a/parser/src/test/scala/aqua/parser/AssignmentExprSpec.scala
+++ b/parser/src/test/scala/aqua/parser/AssignmentExprSpec.scala
@@ -18,16 +18,16 @@ class AssignmentExprSpec extends AnyFlatSpec with Matchers with AquaSpec {
       AssignmentExpr[Id]("a", toVar("b"))
     )
 
-    parseConstant("const a = b") should be(
-      ConstantExpr[Id]("a", toVar("b"), skipIfAlreadyDefined = false)
+    parseConstant("const A = B") should be(
+      ConstantExpr[Id]("A", toVar("B"), skipIfAlreadyDefined = false)
     )
 
-    parseConstant("const a = 1") should be(
-      ConstantExpr[Id]("a", toNumber(1), skipIfAlreadyDefined = false)
+    parseConstant("const A = 1") should be(
+      ConstantExpr[Id]("A", toNumber(1), skipIfAlreadyDefined = false)
     )
 
-    parseConstant("const a ?= 1") should be(
-      ConstantExpr[Id]("a", toNumber(1), skipIfAlreadyDefined = true)
+    parseConstant("const A ?= 1") should be(
+      ConstantExpr[Id]("A", toNumber(1), skipIfAlreadyDefined = true)
     )
   }
 }
diff --git a/parser/src/test/scala/aqua/parser/head/FromSpec.scala b/parser/src/test/scala/aqua/parser/head/FromSpec.scala
index d70db83a..5060576b 100644
--- a/parser/src/test/scala/aqua/parser/head/FromSpec.scala
+++ b/parser/src/test/scala/aqua/parser/head/FromSpec.scala
@@ -14,6 +14,12 @@ class FromSpec extends AnyFlatSpec with Matchers with AquaSpec {
 
   import AquaSpec.*
 
+  "from constants" should "be parsed" in {
+    FromExpr.nameOrAbAs[Id].parseAll("SOME_CONSTANT").value shouldBe Right((toAb("SOME_CONSTANT"), None))
+
+    FromExpr.nameOrAbAs[Id].parseAll("SOME_CONSTANT as SC").value shouldBe Right((toAb("SOME_CONSTANT"), Some(toAb("SC"))))
+  }
+
   "from expression" should "be parsed" in {
     FromExpr.nameOrAbAs[Id].parseAll("Ability").value should be(Right(toAb("Ability") -> None))
     FromExpr.nameOrAbAs[Id].parseAll("Ability as Ab").value should be(
diff --git a/parser/src/test/scala/aqua/parser/head/UseSpec.scala b/parser/src/test/scala/aqua/parser/head/UseSpec.scala
new file mode 100644
index 00000000..b4fc34d1
--- /dev/null
+++ b/parser/src/test/scala/aqua/parser/head/UseSpec.scala
@@ -0,0 +1,30 @@
+package aqua.parser.head
+
+import aqua.AquaSpec
+import aqua.parser.expr.AbilityIdExpr
+import aqua.parser.lexer.{Literal, Token}
+import aqua.parser.lift.LiftParser.Implicits.*
+import aqua.types.LiteralType
+import cats.Id
+import cats.data.NonEmptyList
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class UseSpec extends AnyFlatSpec with Matchers with AquaSpec {
+
+  import AquaSpec.*
+
+  "use" should "be parsed" in {
+    UseFromExpr.p[Id].parseAll("use DECLARE_CONST2 as DC2 from \"declare.aqua\" as Declare").value shouldBe
+      UseFromExpr(
+        NonEmptyList.one(Right((toAb("DECLARE_CONST2"), Some(toAb("DC2"))))),
+        toStr("declare.aqua"),
+        toAb("Declare"))
+
+    UseFromExpr.p[Id].parseAll("use DECLARE_CONST from \"declare.aqua\" as Declare").value shouldBe
+      UseFromExpr(
+        NonEmptyList.one(Right((toAb("DECLARE_CONST"), None))),
+        toStr("declare.aqua"),
+        toAb("Declare"))
+  }
+}
diff --git a/parser/src/test/scala/aqua/parser/lexer/TokenSpec.scala b/parser/src/test/scala/aqua/parser/lexer/TokenSpec.scala
index f52760c1..63811e0a 100644
--- a/parser/src/test/scala/aqua/parser/lexer/TokenSpec.scala
+++ b/parser/src/test/scala/aqua/parser/lexer/TokenSpec.scala
@@ -44,4 +44,12 @@ class TokenSpec extends AnyFlatSpec with Matchers with EitherValues {
                       |""".stripMargin).value should be(())
   }
 
+  "name token" should "parse" in {
+    `name`.parseAll("some_name").value should be("some_name")
+  }
+
+  "NAME token" should "parse" in {
+    NAME.parseAll("SOME_NAME").value should be("SOME_NAME")
+  }
+
 }
diff --git a/parser/src/test/scala/aqua/parser/lexer/VarLambdaSpec.scala b/parser/src/test/scala/aqua/parser/lexer/VarLambdaSpec.scala
new file mode 100644
index 00000000..14fbccaa
--- /dev/null
+++ b/parser/src/test/scala/aqua/parser/lexer/VarLambdaSpec.scala
@@ -0,0 +1,26 @@
+package aqua.parser.lexer
+
+import aqua.parser.lift.LiftParser.Implicits.idLiftParser
+import cats.Id
+import cats.data.NonEmptyList
+import org.scalatest.EitherValues
+import org.scalatest.flatspec.AnyFlatSpec
+import org.scalatest.matchers.should.Matchers
+
+class VarLambdaSpec extends AnyFlatSpec with Matchers with EitherValues {
+
+  "var lambda" should "parse" in {
+    val opsP = (s: String) => Name.dotted[Id].parseAll(s).value
+    
+    opsP("SomeClass.some_val") should be(Name[Id]("SomeClass.some_val"))
+    
+    opsP("some_val") should be(Name[Id]("some_val"))
+    
+    opsP("SOME_CONST") should be(Name[Id]("SOME_CONST"))
+    
+    opsP("SomeClass.SOME_CONST") should be(Name[Id]("SomeClass.SOME_CONST"))
+    
+
+  }
+
+}
diff --git a/semantics/src/main/scala/aqua/semantics/CompilerState.scala b/semantics/src/main/scala/aqua/semantics/CompilerState.scala
index 87bdcd88..77138d3f 100644
--- a/semantics/src/main/scala/aqua/semantics/CompilerState.scala
+++ b/semantics/src/main/scala/aqua/semantics/CompilerState.scala
@@ -18,15 +18,12 @@ case class CompilerState[F[_]](
 object CompilerState {
   type S[F[_]] = State[CompilerState[F], Model]
 
-  def init[F[_]](ctx: AquaContext): CompilerState[F] = {
-    // TODO: should go to Monoid[AquaContext].empty, along with overriden constants
-    val withLE = ctx.copy(values = ctx.values + ("%last_error%" -> VarModel.lastError))
+  def init[F[_]](ctx: AquaContext): CompilerState[F] =
     CompilerState(
-      names = NamesState.init[F](withLE),
-      abilities = AbilitiesState.init[F](withLE),
-      types = TypesState.init[F](withLE)
+      names = NamesState.init[F](ctx),
+      abilities = AbilitiesState.init[F](ctx),
+      types = TypesState.init[F](ctx)
     )
-  }
 
   implicit def compilerStateMonoid[F[_]]: Monoid[S[F]] = new Monoid[S[F]] {
     override def empty: S[F] = State.pure(EmptyModel("compiler state monoid empty"))
diff --git a/semantics/src/main/scala/aqua/semantics/header/HeaderSem.scala b/semantics/src/main/scala/aqua/semantics/header/HeaderSem.scala
index 20420bdf..53463b60 100644
--- a/semantics/src/main/scala/aqua/semantics/header/HeaderSem.scala
+++ b/semantics/src/main/scala/aqua/semantics/header/HeaderSem.scala
@@ -58,6 +58,7 @@ object HeaderSem {
     def resolve(f: FilenameExpr[S]): ResAC[S] =
       imports
         .get(f.fileValue)
+        .map(_.pickDeclared)
         .fold[ResAC[S]](
           error(f.token, "Cannot resolve the import")
         )(validNec)
@@ -91,7 +92,7 @@ object HeaderSem {
             }
           )
         )
-        .reduce
+        .foldLeft[ResAC[S]](validNec(ctx.pickHeader))(_ |+| _)
 
     // Convert an imported context into a module (ability)
     def toModule(ctx: AquaContext, tkn: Token[S], rename: Option[Ability[S]]): ResAC[S] =
@@ -103,7 +104,7 @@ object HeaderSem {
             tkn,
             s"Used module has no `module` header. Please add `module` header or use ... as ModuleName, or switch to import"
           )
-        )(modName => validNec(acm.empty.copy(abilities = Map(modName -> ctx))))
+        )(modName => validNec(AquaContext.blank.copy(abilities = Map(modName -> ctx))))
 
     // Handler for every header expression, will be combined later
     val onExpr: PartialFunction[HeaderExpr[S], Res[S]] = {
@@ -154,27 +155,33 @@ object HeaderSem {
         // Import, map declarations
         resolve(f)
           .andThen(getFrom(f, _))
-          .map(ctx => HeaderSem[S](ctx, (c, _) => validNec(c)))
+          .map { ctx =>
+            HeaderSem[S](ctx, (c, _) => validNec(c))
+          }
 
       case f @ UseExpr(_, asModule) =>
         // Import, move into a module scope
         resolve(f)
           .andThen(toModule(_, f.token, asModule))
-          .map(fc => HeaderSem[S](fc, (c, _) => validNec(c)))
+          .map { fc =>
+            HeaderSem[S](fc, (c, _) => validNec(c))
+          }
 
       case f @ UseFromExpr(_, _, asModule) =>
         // Import, cherry-pick declarations, move to a module scope
         resolve(f)
           .andThen(getFrom(f, _))
           .andThen(toModule(_, f.token, Some(asModule)))
-          .map(fc => HeaderSem[S](fc, (c, _) => validNec(c)))
+          .map { fc =>
+            HeaderSem[S](fc, (c, _) => validNec(c))
+          }
 
       case ExportExpr(pubs) =>
         // Save exports, finally handle them
         validNec(
           HeaderSem[S](
             // Nothing there
-            acm.empty,
+            AquaContext.blank,
             (ctx, initCtx) =>
               pubs
                 .map(
@@ -197,7 +204,7 @@ object HeaderSem {
                     }
                   )
                 )
-                .foldLeft[ResAC[S]](validNec(ctx.exports.getOrElse(acm.empty)))(_ |+| _)
+                .foldLeft[ResAC[S]](validNec(ctx.exports.getOrElse(AquaContext.blank)))(_ |+| _)
                 .map(expCtx => ctx.copy(exports = Some(expCtx)))
           )
         )
diff --git a/semantics/src/main/scala/aqua/semantics/rules/ValuesAlgebra.scala b/semantics/src/main/scala/aqua/semantics/rules/ValuesAlgebra.scala
index 40b3e987..fa103daa 100644
--- a/semantics/src/main/scala/aqua/semantics/rules/ValuesAlgebra.scala
+++ b/semantics/src/main/scala/aqua/semantics/rules/ValuesAlgebra.scala
@@ -39,7 +39,7 @@ class ValuesAlgebra[F[_], Alg[_]](implicit N: NamesAlgebra[F, Alg], T: TypesAlge
           case Some(t) =>
             T.resolveLambda(t, ops)
               .map(Chain.fromSeq)
-              .map(VarModel(name.value.replace('.', '_'), t, _))
+              .map(VarModel(name.value, t, _))
               .map(Some(_))
           case None =>
             Free.pure(None)