feat: support elide 1.6.0-rc.2 and make it the default

.github/workflows/benchmarks.yml

@@ -96,8 +96,10 @@ jobs:
         run: |
           set -euo pipefail
           ver="$(awk -F'"' '/^DEFAULT_VERSION = /{print $2}' elide/private/versions.bzl)"
-          echo "Elide version: $ver"
-          base="https://github.com/elide-dev/elide/releases/download/$ver"
+          tag="$(awk -F'"' -v v="$ver" '$2 == v && $4 != "" {print $4}' elide/private/versions.bzl)"
+          tag="${tag:-$ver}"
+          echo "Elide version: $ver (tag $tag)"
+          base="https://github.com/elide-dev/elide/releases/download/$tag"
           curl -fsSL -o elide.tgz "$base/elide.linux-amd64.tgz"
           curl -fsSL -o elide.tgz.sha256 "$base/elide.linux-amd64.tgz.sha256"
           echo "$(awk '{print $1}' elide.tgz.sha256)  elide.tgz" | sha256sum -c -

docs/extensions.md

@@ -26,7 +26,7 @@ elide.use(<a href="#elide.use-channel">channel</a>, <a href="#elide.use-integrit
 | <a id="elide.install-channel"></a>channel |  Release channel: nightly, preview, or release.   | String | optional |  `"nightly"`  |
 | <a id="elide.install-repo_prefix"></a>repo_prefix |  Prefix used to name per-platform download repos.   | String | optional |  `"elide"`  |
 | <a id="elide.install-url_template"></a>url_template |  Override release URL template. Tokens: {channel}, {version}, {os}, {cpu}, {ext}.   | String | optional |  `""`  |
-| <a id="elide.install-version"></a>version |  Elide release version tag, e.g. `1.2.0+20260602`. Must match an entry in elide/private/versions.bzl. Defaults to the most-recently verified release.   | String | optional |  `"1.3.6+20260628"`  |
+| <a id="elide.install-version"></a>version |  Elide release version, e.g. `1.6.0-rc.2` or `1.3.6+20260628`. Must match an entry in elide/private/versions.bzl. Defaults to the most-recently verified release.   | String | optional |  `"1.6.0-rc.2"`  |
 
 <a id="elide.use"></a>
 

elide/extensions.bzl

@@ -60,7 +60,7 @@ _install = tag_class(
         ),
         "version": attr.string(
             default = DEFAULT_VERSION,
-            doc = "Elide release version tag, e.g. `1.2.0+20260602`. " +
+            doc = "Elide release version, e.g. `1.6.0-rc.2` or `1.3.6+20260628`. " +
                   "Must match an entry in elide/private/versions.bzl. " +
                   "Defaults to the most-recently verified release.",
         ),

elide/kotlin/builder/Fallback.kt

@@ -12,18 +12,27 @@ object Fallback {
     // launch flag (no env var, no `Picked up …` notice). See WHIPLASH#1131.
     //
     // The option only exists on JDK 23+; passing it to an older `java` launcher is
-    // a fatal "Unrecognized option", so gate on the running feature version (the
-    // shim and the fallback builder share the toolchain JDK).
+    // a fatal "Unrecognized option", so gate on the JDK the fallback builder runs
+    // on: the launcher's JAVA_HOME. The shim itself runs on `elide java`, whose
+    // version says nothing about that JDK.
     private const val UNSAFE_SILENCER =
         "--wrapper_script_flag=--jvm_flag=--sun-misc-unsafe-memory-access=allow"
 
     internal fun unsafeSilencer(jdkFeature: Int): List<String> =
         if (jdkFeature >= 23) listOf(UNSAFE_SILENCER) else emptyList()
 
+    /** Feature version of the JDK at [javaHome], from its `release` file; 0 when unknown. */
+    fun jdkFeature(javaHome: String?): Int {
+        if (javaHome.isNullOrEmpty()) return 0
+        val release = File(javaHome, "release").takeIf { it.isFile } ?: return 0
+        val line = release.readLines().firstOrNull { it.startsWith("JAVA_VERSION=") } ?: return 0
+        return line.substringAfter('=').trim('"').takeWhile { it.isDigit() }.toIntOrNull() ?: 0
+    }
+
     fun command(
         stockBuilder: String,
         flagfile: String,
-        jdkFeature: Int = Runtime.version().feature(),
+        jdkFeature: Int = jdkFeature(System.getenv("JAVA_HOME")),
     ): List<String> =
         listOf(stockBuilder) + unsafeSilencer(jdkFeature) + "--flagfile=$flagfile"
 

elide/private/download.bzl

@@ -2,7 +2,7 @@
 
 """Repository rule that downloads one elide release artifact for one platform."""
 
-load(":versions.bzl", "DEFAULT_CHANNEL", "DEFAULT_URL_TEMPLATE", "archive_ext", "binary_ext")
+load(":versions.bzl", "DEFAULT_CHANNEL", "DEFAULT_URL_TEMPLATE", "archive_ext", "binary_ext", "release_tag")
 
 visibility(["//elide/...", "//tests/..."])
 
@@ -60,7 +60,7 @@ def _elide_download_impl(ctx):
     cpu = ctx.attr.cpu
     url = (ctx.attr.url_template or DEFAULT_URL_TEMPLATE).format(
         channel = ctx.attr.channel or DEFAULT_CHANNEL,
-        version = ctx.attr.version,
+        version = release_tag(ctx.attr.version),
         os = os,
         cpu = cpu,
         ext = archive_ext(os),
@@ -94,6 +94,10 @@ def _elide_download_impl(ctx):
             ctx.execute(["chmod", "+x", "bin/" + name])
         for name in ["native-image", "native-image-configure"]:
             ctx.execute(["chmod", "+x", "lib/svm/bin/" + name])
+
+        # The JDK's process launcher helper also lacks it; without it every
+        # subprocess started from `elide java` fails with posix_spawn EACCES.
+        ctx.execute(["chmod", "+x", "lib/jspawnhelper"])
     bin_ext = binary_ext(os)
     binary_path = ctx.attr.binary_path or ("bin/elide" + bin_ext)
     ctx.file("BUILD.bazel", _BUILD_TEMPLATE.format(

elide/private/versions.bzl

@@ -51,6 +51,7 @@ DEFAULT_CHANNEL = "nightly"
 # Hashes verified 2026-06-22 against GitHub release tag 1.3.4+20260622.
 # Hashes verified 2026-06-23 against GitHub release tag 1.3.4+20260623.
 # Hashes verified 2026-06-28 against GitHub release tag 1.3.6+20260628.
+# Hashes verified 2026-10-12 against GitHub release tag v1.6.0-rc.2.
 ELIDE_VERSIONS = {
     "1.2.0+20260602": {
         ("linux", "amd64"): "sha256-yIQZwU4nM0SN19Zj2rdikdWBpj9d+fVlJK0d10p3DRA=",
@@ -106,11 +107,35 @@ ELIDE_VERSIONS = {
         ("macos", "arm64"): "sha256-IPUIc9kYzc1mxpva0PX88yGA7UsWS+dneXTfhJxUxRA=",
         ("windows", "amd64"): "sha256-mKvMV80P8OFl0Qw1fTjH33qRw239sIPqJ0m18VAhlt8=",
     },
+    "1.6.0-rc.2": {
+        ("linux", "amd64"): "sha256-hlwps26EHnSj+mZtqTGylHzACQAKcUrZIPWW3Q8OV5c=",
+        ("linux", "arm64"): "sha256-rVHHv97BWesWwT2s9eMW/BNYYtjivxps8xiZOeKJSSw=",
+        ("macos", "arm64"): "sha256-eWiPIObRBd6ZxAtCpSR1gtAb2S9IRufTP7KxddFrOug=",
+        ("windows", "amd64"): "sha256-KGilECOjaOLFVMy1jhiHx2dcWUbXVW9n9Hp1kOF06uw=",
+    },
+}
+
+# Versions whose GitHub release tag differs from the version string. Nightly tags
+# (`1.3.6+20260628`) are the version itself; release candidates and releases are
+# tagged with a leading `v`.
+RELEASE_TAGS = {
+    "1.6.0-rc.2": "v1.6.0-rc.2",
 }
 
+def release_tag(version):
+    """Returns the GitHub release tag that publishes `version`.
+
+    Args:
+        version: str. An Elide version, e.g. `1.6.0-rc.2` or `1.3.6+20260628`.
+
+    Returns:
+        str. The release tag, which the `{version}` URL token expands to.
+    """
+    return RELEASE_TAGS.get(version, version)
+
 # Default version used when consumers call elide.install() without a version.
 # Points at the most-recently verified entry in ELIDE_VERSIONS above.
-DEFAULT_VERSION = "1.3.6+20260628"
+DEFAULT_VERSION = "1.6.0-rc.2"
 
 # GitHub releases serve each tag as an immutable artifact. The {channel} token
 # is accepted but unused here; it remains available for consumers who override

tests/kotlin_builder/FallbackTest.kt

@@ -1,5 +1,6 @@
 package elide.kotlin.builder
 
+import java.nio.file.Files
 import kotlin.test.Test
 import kotlin.test.assertEquals
 
@@ -24,4 +25,18 @@ class FallbackTest {
             Fallback.command(stockBuilder = "/bin/stock", flagfile = "/tmp/f", jdkFeature = 23),
         )
     }
+
+    @Test fun readsFeatureVersionFromJavaHome() {
+        val home = Files.createTempDirectory("jdk").toFile()
+        try {
+            assertEquals(0, Fallback.jdkFeature(home.path))
+            home.resolve("release").writeText("IMPLEMENTOR=\"x\"\nJAVA_VERSION=\"21.0.5\"\n")
+            assertEquals(21, Fallback.jdkFeature(home.path))
+            home.resolve("release").writeText("JAVA_VERSION=\"25\"\n")
+            assertEquals(25, Fallback.jdkFeature(home.path))
+            assertEquals(0, Fallback.jdkFeature(null))
+        } finally {
+            home.deleteRecursively()
+        }
+    }
 }

tests/versions_test.bzl

@@ -5,7 +5,7 @@
 load("@bazel_skylib//lib:unittest.bzl", "asserts", "unittest")
 
 # buildifier: disable=bzl-visibility
-load("//elide/private:versions.bzl", "PLATFORMS", "archive_ext", "binary_ext")
+load("//elide/private:versions.bzl", "DEFAULT_VERSION", "ELIDE_VERSIONS", "PLATFORMS", "archive_ext", "binary_ext", "release_tag")
 
 def _archive_ext_test_impl(ctx):
     env = unittest.begin(ctx)
@@ -36,6 +36,15 @@ def _platforms_complete_test_impl(ctx):
 
 _platforms_complete_test = unittest.make(_platforms_complete_test_impl)
 
+def _release_tag_test_impl(ctx):
+    env = unittest.begin(ctx)
+    asserts.equals(env, "1.3.6+20260628", release_tag("1.3.6+20260628"))
+    asserts.equals(env, "v1.6.0-rc.2", release_tag("1.6.0-rc.2"))
+    asserts.true(env, DEFAULT_VERSION in ELIDE_VERSIONS, "DEFAULT_VERSION has no integrity row")
+    return unittest.end(env)
+
+_release_tag_test = unittest.make(_release_tag_test_impl)
+
 def versions_test_suite(name):
     """Wires unit tests for versions.bzl helpers.
 
@@ -45,11 +54,13 @@ def versions_test_suite(name):
     _archive_ext_test(name = "archive_ext_test")
     _binary_ext_test(name = "binary_ext_test")
     _platforms_complete_test(name = "platforms_complete_test")
+    _release_tag_test(name = "release_tag_test")
     native.test_suite(
         name = name,
         tests = [
             ":archive_ext_test",
             ":binary_ext_test",
             ":platforms_complete_test",
+            ":release_tag_test",
         ],
     )