Validate the selected http client profile and keep a list

clicommand/agent_start.go

@@ -26,6 +26,7 @@ import (
 	"github.com/buildkite/agent/v3/api"
 	"github.com/buildkite/agent/v3/core"
 	"github.com/buildkite/agent/v3/internal/agentapi"
+	"github.com/buildkite/agent/v3/internal/agenthttp"
 	"github.com/buildkite/agent/v3/internal/awslib"
 	awssigner "github.com/buildkite/agent/v3/internal/cryptosigner/aws"
 	"github.com/buildkite/agent/v3/internal/experiments"
@@ -1122,6 +1123,10 @@ var AgentStartCommand = cli.Command{
 
 		l.Info("Using http client profile: %s", cfg.HTTPClientProfile)
 
+		if !slices.Contains(agenthttp.ValidHTTPClientProfiles, cfg.HTTPClientProfile) {
+			l.Fatal("HTTP client profile %s is not in list of valid profiles: %v", cfg.HTTPClientProfile, agenthttp.ValidHTTPClientProfiles)
+		}
+
 		if len(cfg.AllowedRepositories) > 0 {
 			agentConf.AllowedRepositories = make([]*regexp.Regexp, 0, len(cfg.AllowedRepositories))
 			for _, v := range cfg.AllowedRepositories {

clicommand/global.go

@@ -45,8 +45,8 @@ var (
 
 	HTTPClientProfileFlag = cli.StringFlag{
 		Name:   "http-client-profile",
-		Usage:  "Enable a http client profile, either standard, gcp or stdlib",
-		Value:  "standard",
+		Usage:  "Enable a http client profile, either default or stdlib",
+		Value:  "default",
 		EnvVar: "BUILDKITE_AGENT_HTTP_CLIENT_PROFILE",
 	}
 

internal/agenthttp/client.go

@@ -11,6 +11,10 @@ import (
 	"golang.org/x/net/http2"
 )
 
+var (
+	ValidHTTPClientProfiles = []string{"stdlib", "default"}
+)
+
 // NewClient creates a HTTP client. Note that the default timeout is 60 seconds;
 // for some use cases (e.g. artifact operations) use [WithNoTimeout].
 func NewClient(opts ...ClientOption) *http.Client {
@@ -47,6 +51,8 @@ func NewClient(opts ...ClientOption) *http.Client {
 		}
 	}
 
+	// fall back to the default http client profile
+
 	cacheKey := transportCacheKey{
 		AllowHTTP2: conf.AllowHTTP2,
 		TLSConfig:  conf.TLSConfig,