[v26.1.x] rpk/connect: don't cap version segments at two digits

src/go/rpk/pkg/cli/connect/BUILD

@@ -1,4 +1,4 @@
-load("@rules_go//go:def.bzl", "go_library")
+load("@rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "connect",
@@ -24,3 +24,10 @@ go_library(
         "@org_uber_go_zap//:zap",
     ],
 )
+
+go_test(
+    name = "connect_test",
+    srcs = ["install_test.go"],
+    embed = [":connect"],
+    deps = ["@com_github_stretchr_testify//require"],
+)

src/go/rpk/pkg/cli/connect/install.go

@@ -132,12 +132,15 @@ func downloadAndInstallConnect(ctx context.Context, fs afero.Fs, installPath, do
 // validateVersion validates that the provided version in the flag is either
 // 'latest' or it's a full semantic version.
 func validateVersion(version string) error {
-	// This simple regexp just matches that a semver is in the string, it may
-	// be prefixed with 'v' and contain anything after. Nothing to capture.
+	// The version may be prefixed with 'v' and carry a prerelease or build
+	// suffix (e.g. '4.102.0-rc1'), which is forwarded to the manifest for
+	// lookup; the manifest is the source of truth for what is published.
+	// Segments are unbounded in width: Connect minor versions passed 99 in
+	// 4.100.0.
 	if version == "latest" {
 		return nil
 	}
-	vMatch := regexp.MustCompile(`^v?\d{1,2}\.\d{1,2}\.\d{1,2}`).MatchString(version)
+	vMatch := regexp.MustCompile(`^v?\d+\.\d+\.\d+(?:[-+][0-9A-Za-z.-]+)?$`).MatchString(version)
 	if !vMatch {
 		return fmt.Errorf("provided version %q is not valid. Ensure is either 'latest' or it follows the format MAJOR.MINOR.PATCH (e.g., 2.1.3)", version)
 	}

src/go/rpk/pkg/cli/connect/install_test.go

@@ -0,0 +1,27 @@
+// Copyright 2026 Redpanda Data, Inc.
+//
+// Use of this software is governed by the Business Source License
+// included in the file licenses/BSL.md
+//
+// As of the Change Date specified in that file, in accordance with
+// the Business Source License, use of this software will be governed
+// by the Apache License, Version 2.0
+
+package connect
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestValidateVersion(t *testing.T) {
+	// Connect minor versions passed 99 in 4.100.0, so segments must not be
+	// capped in width.
+	for _, ok := range []string{"latest", "4.99.0", "4.102.0", "v4.102.0", "4.102.0-rc1", "4.102.100"} {
+		require.NoError(t, validateVersion(ok), ok)
+	}
+	for _, bad := range []string{"", "abc", "4", "4.102", "garbage", "4.102.0garbage", "4.102.0 "} {
+		require.Error(t, validateVersion(bad), bad)
+	}
+}