fix: add v prefix to version in container build download URL

internal/container/build.go

@@ -229,18 +229,27 @@ func miseInstallBlock(langs []DetectedLang) string {
 func pluralDownloadBlock(version, arch string) string {
 	var b strings.Builder
 
+	var url string
 	if version == "" || version == "dev" {
 		// Use latest release URL pattern (no API call needed)
-		fmt.Fprintf(&b, "RUN curl -sfL \"https://github.com/zhubert/plural/releases/latest/download/plural_Linux_%s.tar.gz\" | tar -xz -C /tmp plural && \\\n", arch)
-		b.WriteString("    mv /tmp/plural /usr/local/bin/plural && \\\n")
-		b.WriteString("    chmod +x /usr/local/bin/plural\n\n")
+		url = fmt.Sprintf("https://github.com/zhubert/plural/releases/latest/download/plural_Linux_%s.tar.gz", arch)
 	} else {
-		// Exact version download
-		fmt.Fprintf(&b, "RUN curl -sfL \"https://github.com/zhubert/plural/releases/download/%s/plural_Linux_%s.tar.gz\" | tar -xz -C /tmp plural && \\\n", version, arch)
-		b.WriteString("    mv /tmp/plural /usr/local/bin/plural && \\\n")
-		b.WriteString("    chmod +x /usr/local/bin/plural\n\n")
+		// Exact version download — ensure "v" prefix for GitHub release tag
+		tag := version
+		if !strings.HasPrefix(tag, "v") {
+			tag = "v" + tag
+		}
+		url = fmt.Sprintf("https://github.com/zhubert/plural/releases/download/%s/plural_Linux_%s.tar.gz", tag, arch)
 	}
 
+	// Download to file first so curl failures surface clearly instead of
+	// producing misleading tar errors (e.g. "invalid magic" on a 404).
+	fmt.Fprintf(&b, "RUN curl -sfL -o /tmp/plural.tar.gz \"%s\" && \\\n", url)
+	b.WriteString("    tar -xz -C /tmp plural -f /tmp/plural.tar.gz && \\\n")
+	b.WriteString("    rm /tmp/plural.tar.gz && \\\n")
+	b.WriteString("    mv /tmp/plural /usr/local/bin/plural && \\\n")
+	b.WriteString("    chmod +x /usr/local/bin/plural\n\n")
+
 	return b.String()
 }
 

internal/container/build_test.go

@@ -416,6 +416,23 @@ func TestPluralDownloadBlock(t *testing.T) {
 			t.Error("release version should not use /latest/download/")
 		}
 	})
+
+	t.Run("version without v prefix gets v added", func(t *testing.T) {
+		block := pluralDownloadBlock("1.2.0", "arm64")
+		if !strings.Contains(block, "/download/v1.2.0/") {
+			t.Errorf("version without v prefix should get v added, got: %s", block)
+		}
+	})
+
+	t.Run("downloads to file before extracting", func(t *testing.T) {
+		block := pluralDownloadBlock("v1.0.0", "arm64")
+		if !strings.Contains(block, "-o /tmp/plural.tar.gz") {
+			t.Error("should download to file first")
+		}
+		if !strings.Contains(block, "-f /tmp/plural.tar.gz") {
+			t.Error("should extract from downloaded file")
+		}
+	})
 }
 
 func TestMiseInstallBlock_RubyAndPython(t *testing.T) {