diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 79961cc5..d284bba4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -58,8 +58,12 @@ jobs:
       - if: matrix.project == 'js'
         run: npm install
 
+      # sblas links -lcblas; OpenBLAS exports the cblas_* symbols but ships no libcblas.so, so alias it
       - if: matrix.project == 'native'
-        run: sudo apt-get install -y libatlas-base-dev
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libopenblas-dev
+          sudo ln -sf "$(realpath /usr/lib/x86_64-linux-gnu/libopenblas.so)" /usr/lib/x86_64-linux-gnu/libcblas.so
 
       - name: scalaJSLink
         if: matrix.project == 'js'
diff --git a/.github/workflows/copilot-setup-steps.yml b/.github/workflows/copilot-setup-steps.yml
index a99e2984..b473a208 100644
--- a/.github/workflows/copilot-setup-steps.yml
+++ b/.github/workflows/copilot-setup-steps.yml
@@ -36,8 +36,12 @@ jobs:
           node-version: 22
           cache: npm
 
+      # sblas links -lcblas; OpenBLAS exports the cblas_* symbols but ships no libcblas.so, so alias it
       - name: prepare native
-        run: sudo apt-get install -y libatlas-base-dev
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libopenblas-dev
+          sudo ln -sf "$(realpath /usr/lib/x86_64-linux-gnu/libopenblas.so)" /usr/lib/x86_64-linux-gnu/libcblas.so
 
       - name: Setup Java 21
         uses: actions/setup-java@v4
diff --git a/build.mill b/build.mill
index 8ef5d489..4e993889 100644
--- a/build.mill
+++ b/build.mill
@@ -1,4 +1,4 @@
-//| mill-version: 1.3.0-M1
+//| mill-version: 1.3.0
 //| mill-jvm-version: 25
 //| mill-jvm-opts: [ "--add-modules", "jdk.incubator.vector", -XX:TrimNativeHeapInterval=60000]
 //| mvnDeps:
@@ -50,6 +50,7 @@ object V:
   val nativeBSP = false
   val jvmBSP = true
   val oslib = mvn"com.lihaoyi::os-lib::0.11.8"
+  val jsoniterVersion = "2.41.5"
 end V
 
 trait VecxtPublishModule extends PublishModule, ScalaModule, ScalafixModule:
diff --git a/vecxt_re/package.mill b/vecxt_re/package.mill
index 2f2956b3..4158c881 100644
--- a/vecxt_re/package.mill
+++ b/vecxt_re/package.mill
@@ -6,7 +6,12 @@ import mill.api.Task.Simple
 
 object `package` extends Module:
   trait VexctReModule extends PlatformScalaModule with build.VecxtPublishModule with build.ShareCompileResources:
-    def mvnDeps = super.mvnDeps() ++ Seq()
+    def mvnDeps = super.mvnDeps() ++ Seq(
+      mvn"com.github.plokhotnyuk.jsoniter-scala::jsoniter-scala-core::${build.V.jsoniterVersion}"
+    )
+    def compileMvnDeps = super.compileMvnDeps() ++ Seq(
+      mvn"com.github.plokhotnyuk.jsoniter-scala::jsoniter-scala-macros::${build.V.jsoniterVersion}"
+    )
 
     trait VexctReTest extends ScalaTests, TestModule.Munit:
       def mvnDeps = super.mvnDeps() ++ Seq(
diff --git a/vecxt_re/src/AmountUnit.scala b/vecxt_re/src/AmountUnit.scala
new file mode 100644
index 00000000..268f016d
--- /dev/null
+++ b/vecxt_re/src/AmountUnit.scala
@@ -0,0 +1,9 @@
+package vecxt_re
+
+/** The scale a monetary amount is quoted in. `multiplier` is the number of major currency units in one of this unit. */
+enum AmountUnit(val multiplier: Long):
+  case One extends AmountUnit(1L)
+  case K extends AmountUnit(1_000L)
+  case Mn extends AmountUnit(1_000_000L)
+  case Bn extends AmountUnit(1_000_000_000L)
+end AmountUnit
diff --git a/vecxt_re/src/Ccy.scala b/vecxt_re/src/Ccy.scala
new file mode 100644
index 00000000..0318a2ae
--- /dev/null
+++ b/vecxt_re/src/Ccy.scala
@@ -0,0 +1,43 @@
+package vecxt_re
+
+import com.github.plokhotnyuk.jsoniter_scala.core.*
+
+/** An ISO 4217 currency code, e.g. `Ccy.USD` or `Ccy("SEK")`. Open, so callers may use currencies not listed here. */
+opaque type Ccy = String
+object Ccy:
+  def apply(code: String): Ccy =
+    require(code.length == 3 && code.forall(c => c >= 'A' && c <= 'Z'), s"Not an ISO 4217 currency code: '$code'")
+    code
+  end apply
+
+  val USD: Ccy = "USD"
+  val EUR: Ccy = "EUR"
+  val GBP: Ccy = "GBP"
+  val CHF: Ccy = "CHF"
+  val JPY: Ccy = "JPY"
+  val AUD: Ccy = "AUD"
+  val CAD: Ccy = "CAD"
+  val NZD: Ccy = "NZD"
+
+  /** The currencies predefined above. */
+  val majorCurrencies: IArray[Ccy] = IArray(USD, EUR, GBP, CHF, JPY, AUD, CAD, NZD)
+
+  extension (c: Ccy) def code: String = c
+  end extension
+
+  given CanEqual[Ccy, Ccy] = CanEqual.derived
+
+  /** Encodes as the bare code, e.g. `"USD"`. Decoding validates the code as [[apply]] does. */
+  given JsonValueCodec[Ccy] with
+    def decodeValue(in: JsonReader, default: Ccy): Ccy =
+      val code = in.readString(null)
+      if code == null then in.decodeError("expected a currency code, got null")
+      else
+        try Ccy(code)
+        catch case e: IllegalArgumentException => in.decodeError(e.getMessage)
+      end if
+    end decodeValue
+    def encodeValue(x: Ccy, out: JsonWriter): Unit = out.writeVal(x)
+    def nullValue: Ccy = null.asInstanceOf[Ccy]
+  end given
+end Ccy
diff --git a/vecxt_re/src/CurrencyValue.scala b/vecxt_re/src/CurrencyAmount.scala
similarity index 85%
rename from vecxt_re/src/CurrencyValue.scala
rename to vecxt_re/src/CurrencyAmount.scala
index 7e47b652..d7596501 100644
--- a/vecxt_re/src/CurrencyValue.scala
+++ b/vecxt_re/src/CurrencyAmount.scala
@@ -1,16 +1,7 @@
 package vecxt_re
 
-enum Ccy derives CanEqual:
-  case USD, EUR, GBP, CHF, JPY, AUD, CAD, NZD
-end Ccy
-
-/** The scale a monetary amount is quoted in. `multiplier` is the number of major currency units in one of this unit. */
-enum AmountUnit(val multiplier: Long):
-  case One extends AmountUnit(1L)
-  case K extends AmountUnit(1_000L)
-  case Mn extends AmountUnit(1_000_000L)
-  case Bn extends AmountUnit(1_000_000_000L)
-end AmountUnit
+import com.github.plokhotnyuk.jsoniter_scala.core.*
+import com.github.plokhotnyuk.jsoniter_scala.macros.*
 
 /** This should _NOT_ be used for actual cash values. We use double here because this intended for financial simulation
   * where errors of <0.01 are meaningless. An absolute monetary quantity denominated in a single currency, e.g. a
@@ -72,4 +63,7 @@ object CurrencyAmount:
       java.lang.Double.compare(a.amount, b.amount)
     end compare
   end given
+
+  /** In major currency units, e.g. `{"amount":2500000.0,"ccy":"USD"}` */
+  given JsonValueCodec[CurrencyAmount] = JsonCodecMaker.make
 end CurrencyAmount
diff --git a/vecxt_re/src/CurrencyRate.scala b/vecxt_re/src/CurrencyRate.scala
new file mode 100644
index 00000000..9c89f1de
--- /dev/null
+++ b/vecxt_re/src/CurrencyRate.scala
@@ -0,0 +1,13 @@
+package vecxt_re
+
+import java.time.LocalDate
+
+import com.github.plokhotnyuk.jsoniter_scala.core.*
+import com.github.plokhotnyuk.jsoniter_scala.macros.*
+
+case class CurrencyRate(date: LocalDate, base: Ccy, quote: Ccy, rate: Double)
+
+object CurrencyRate:
+  /** e.g. `{"date":"2026-10-27","base":"EUR","quote":"USD","rate":1.08}` */
+  given JsonValueCodec[CurrencyRate] = JsonCodecMaker.make
+end CurrencyRate
diff --git a/vecxt_re/test/src/currencyAmount.test.scala b/vecxt_re/test/src/currencyAmount.test.scala
index d664b71f..4cc709ac 100644
--- a/vecxt_re/test/src/currencyAmount.test.scala
+++ b/vecxt_re/test/src/currencyAmount.test.scala
@@ -1,5 +1,7 @@
 package vecxt_re
 
+import com.github.plokhotnyuk.jsoniter_scala.core.*
+
 import AmountUnit.*
 import Ccy.*
 
@@ -107,4 +109,33 @@ class CurrencyAmountSuite extends munit.FunSuite:
     assertEquals(CurrencyAmount(2.5, Mn, USD).toString, "2500000.00 USD")
     assertEquals(CurrencyAmount(-1.234, K, EUR).toString, "-1234.00 EUR")
 
+  test("currencies not predefined can be created from their code"):
+    val sek = Ccy("SEK")
+    assertEquals(sek.code, "SEK")
+    assertEquals(sek, Ccy("SEK"))
+    assertEquals(Ccy("USD"), USD)
+    assertEquals(CurrencyAmount(1, K, sek).toString, "1000.00 SEK")
+    intercept[IllegalArgumentException](CurrencyAmount(1, K, sek) + CurrencyAmount(1, K, USD))
+
+  test("invalid currency codes are rejected"):
+    intercept[IllegalArgumentException](Ccy("usd"))
+    intercept[IllegalArgumentException](Ccy("US"))
+    intercept[IllegalArgumentException](Ccy("USDX"))
+    intercept[IllegalArgumentException](Ccy(""))
+
+  test("json is in major units with the currency code"):
+    val x = CurrencyAmount(2.5, Mn, USD)
+    val json = """{"amount":2500000.0,"ccy":"USD"}"""
+    assertEquals(writeToString(x), json)
+    assertEquals(readFromString[CurrencyAmount](json), x)
+
+  test("json round trips a currency not predefined"):
+    val x = CurrencyAmount(-1.234, K, Ccy("SEK"))
+    assertEquals(readFromString[CurrencyAmount](writeToString(x)), x)
+
+  test("json with a missing field or invalid currency is rejected"):
+    intercept[JsonReaderException](readFromString[CurrencyAmount]("""{"amount":1.0}"""))
+    intercept[JsonReaderException](readFromString[CurrencyAmount]("""{"ccy":"USD"}"""))
+    intercept[JsonReaderException](readFromString[CurrencyAmount]("""{"amount":1.0,"ccy":"usd"}"""))
+
 end CurrencyAmountSuite
diff --git a/vecxt_re/test/src/currencyRate.test.scala b/vecxt_re/test/src/currencyRate.test.scala
new file mode 100644
index 00000000..41c087b9
--- /dev/null
+++ b/vecxt_re/test/src/currencyRate.test.scala
@@ -0,0 +1,34 @@
+package vecxt_re
+
+import java.time.LocalDate
+
+import com.github.plokhotnyuk.jsoniter_scala.core.*
+
+class CurrencyRateSuite extends munit.FunSuite:
+
+  private val eurUsd = CurrencyRate(LocalDate.of(2026, 10, 27), Ccy.EUR, Ccy.USD, 1.08)
+  private val eurUsdJson = """{"date":"2026-10-27","base":"EUR","quote":"USD","rate":1.08}"""
+
+  test("rate encodes to json"):
+    assertEquals(writeToString(eurUsd), eurUsdJson)
+
+  test("rate decodes from json"):
+    assertEquals(readFromString[CurrencyRate](eurUsdJson), eurUsd)
+
+  test("currencies not predefined round trip"):
+    val r = CurrencyRate(LocalDate.of(2026, 1, 2), Ccy("SEK"), Ccy.CHF, 0.083)
+    assertEquals(readFromString[CurrencyRate](writeToString(r)), r)
+
+  test("ccy encodes as its bare code"):
+    assertEquals(writeToString(Ccy.GBP), "\"GBP\"")
+    assertEquals(readFromString[Ccy]("\"NOK\""), Ccy("NOK"))
+
+  test("invalid currency codes are rejected when decoding"):
+    intercept[JsonReaderException](readFromString[CurrencyRate](eurUsdJson.replace("\"EUR\"", "\"eur\"")))
+    intercept[JsonReaderException](readFromString[CurrencyRate](eurUsdJson.replace("\"USD\"", "\"USDX\"")))
+    intercept[JsonReaderException](readFromString[CurrencyRate](eurUsdJson.replace("\"USD\"", "null")))
+
+  test("missing fields are rejected"):
+    intercept[JsonReaderException](readFromString[CurrencyRate]("""{"date":"2026-10-27","base":"EUR","rate":1.08}"""))
+
+end CurrencyRateSuite