diff --git a/src/cmd/go/internal/base/goflags.go b/src/cmd/go/internal/base/goflags.go
index eced2c5d582268..3d5a76d54b758d 100644
--- a/src/cmd/go/internal/base/goflags.go
+++ b/src/cmd/go/internal/base/goflags.go
@@ -88,7 +88,7 @@ type boolFlag interface {
 }
 
 // SetFromGOFLAGS sets the flags in the given flag set using settings in $GOFLAGS.
-func SetFromGOFLAGS(flags *flag.FlagSet) {
+func SetFromGOFLAGS(flags *flag.FlagSet, ignoreErrors bool) {
 	InitGOFLAGS()
 
 	// This loop is similar to flag.Parse except that it ignores
@@ -121,22 +121,22 @@ func SetFromGOFLAGS(flags *flag.FlagSet) {
 
 		if fb, ok := f.Value.(boolFlag); ok && fb.IsBoolFlag() {
 			if hasValue {
-				if err := flags.Set(f.Name, value); err != nil {
+				if err := flags.Set(f.Name, value); err != nil && !ignoreErrors {
 					fmt.Fprintf(flags.Output(), "go: invalid boolean value %q for flag %s (from %s): %v\n", value, name, where, err)
 					flags.Usage()
 				}
 			} else {
-				if err := flags.Set(f.Name, "true"); err != nil {
+				if err := flags.Set(f.Name, "true"); err != nil && !ignoreErrors {
 					fmt.Fprintf(flags.Output(), "go: invalid boolean flag %s (from %s): %v\n", name, where, err)
 					flags.Usage()
 				}
 			}
 		} else {
-			if !hasValue {
+			if !hasValue && !ignoreErrors {
 				fmt.Fprintf(flags.Output(), "go: flag needs an argument: %s (from %s)\n", name, where)
 				flags.Usage()
 			}
-			if err := flags.Set(f.Name, value); err != nil {
+			if err := flags.Set(f.Name, value); err != nil && !ignoreErrors {
 				fmt.Fprintf(flags.Output(), "go: invalid value %q for flag %s (from %s): %v\n", value, name, where, err)
 				flags.Usage()
 			}
diff --git a/src/cmd/go/internal/modfetch/fetch.go b/src/cmd/go/internal/modfetch/fetch.go
index eeab6da62a2dad..b3c77dfbc21786 100644
--- a/src/cmd/go/internal/modfetch/fetch.go
+++ b/src/cmd/go/internal/modfetch/fetch.go
@@ -525,7 +525,7 @@ func readGoSum(dst map[module.Version][]string, file string, data []byte) {
 				// ignore malformed line so that go mod tidy can fix go.sum
 				continue
 			} else {
-				base.Fatalf("malformed go.sum:\n%s:%d: wrong number of fields %v\n", file, lineno, len(f))
+				base.Fatalf("go: malformed go.sum:\n%s:%d: wrong number of fields %v\n", file, lineno, len(f))
 			}
 		}
 		if f[2] == emptyGoModHash {
@@ -574,32 +574,32 @@ func checkMod(ctx context.Context, mod module.Version) {
 	// Do the file I/O before acquiring the go.sum lock.
 	ziphash, err := CachePath(ctx, mod, "ziphash")
 	if err != nil {
-		base.Fatalf("verifying %v", module.VersionError(mod, err))
+		base.Fatalf("go: verifying %v", module.VersionError(mod, err))
 	}
 	data, err := lockedfile.Read(ziphash)
 	if err != nil {
-		base.Fatalf("verifying %v", module.VersionError(mod, err))
+		base.Fatalf("go: verifying %v", module.VersionError(mod, err))
 	}
 	data = bytes.TrimSpace(data)
 	if !isValidSum(data) {
 		// Recreate ziphash file from zip file and use that to check the mod sum.
 		zip, err := CachePath(ctx, mod, "zip")
 		if err != nil {
-			base.Fatalf("verifying %v", module.VersionError(mod, err))
+			base.Fatalf("go: verifying %v", module.VersionError(mod, err))
 		}
 		err = hashZip(mod, zip, ziphash)
 		if err != nil {
-			base.Fatalf("verifying %v", module.VersionError(mod, err))
+			base.Fatalf("go: verifying %v", module.VersionError(mod, err))
 		}
 		return
 	}
 	h := string(data)
 	if !strings.HasPrefix(h, "h1:") {
-		base.Fatalf("verifying %v", module.VersionError(mod, fmt.Errorf("unexpected ziphash: %q", h)))
+		base.Fatalf("go: verifying %v", module.VersionError(mod, fmt.Errorf("unexpected ziphash: %q", h)))
 	}
 
 	if err := checkModSum(mod, h); err != nil {
-		base.Fatalf("%s", err)
+		base.Fatal(err)
 	}
 }
 
@@ -684,7 +684,7 @@ func haveModSumLocked(mod module.Version, h string) bool {
 			return true
 		}
 		if strings.HasPrefix(vh, "h1:") {
-			base.Fatalf("verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, sumFileName, vh)
+			base.Fatalf("go: verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, sumFileName, vh)
 		}
 	}
 	// Also check workspace sums.
@@ -696,7 +696,7 @@ func haveModSumLocked(mod module.Version, h string) bool {
 			if h == vh {
 				foundMatch = true
 			} else if strings.HasPrefix(vh, "h1:") {
-				base.Fatalf("verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, goSumFile, vh)
+				base.Fatalf("go: verifying %s@%s: checksum mismatch\n\tdownloaded: %v\n\t%s:     %v"+goSumMismatch, mod.Path, mod.Version, h, goSumFile, vh)
 			}
 		}
 	}
@@ -895,7 +895,7 @@ func TrimGoSum(keep map[module.Version]bool) {
 	defer goSum.mu.Unlock()
 	inited, err := initGoSum()
 	if err != nil {
-		base.Fatalf("%s", err)
+		base.Fatal(err)
 	}
 	if !inited {
 		return
diff --git a/src/cmd/go/internal/test/testflag.go b/src/cmd/go/internal/test/testflag.go
index 425378889d9af0..22c3ab13021628 100644
--- a/src/cmd/go/internal/test/testflag.go
+++ b/src/cmd/go/internal/test/testflag.go
@@ -222,7 +222,7 @@ func (f *shuffleFlag) Set(value string) error {
 //	go test fmt -custom-flag-for-fmt-test
 //	go test -x math
 func testFlags(args []string) (packageNames, passToTest []string) {
-	base.SetFromGOFLAGS(&CmdTest.Flag)
+	base.SetFromGOFLAGS(&CmdTest.Flag, false)
 	addFromGOFLAGS := map[string]bool{}
 	CmdTest.Flag.Visit(func(f *flag.Flag) {
 		if short := strings.TrimPrefix(f.Name, "test."); passFlagToTest[short] {
diff --git a/src/cmd/go/internal/toolchain/exec.go b/src/cmd/go/internal/toolchain/exec.go
index 820fe93e87c377..acfb9e943ca77a 100644
--- a/src/cmd/go/internal/toolchain/exec.go
+++ b/src/cmd/go/internal/toolchain/exec.go
@@ -44,12 +44,12 @@ func execGoToolchain(gotoolchain, dir, exe string) {
 				if e.ProcessState.Exited() {
 					os.Exit(e.ProcessState.ExitCode())
 				}
-				base.Fatalf("exec %s: %s", gotoolchain, e.ProcessState)
+				base.Fatalf("go: exec %s: %s", gotoolchain, e.ProcessState)
 			}
-			base.Fatalf("exec %s: %s", exe, err)
+			base.Fatalf("go: exec %s: %s", exe, err)
 		}
 		os.Exit(0)
 	}
 	err := syscall.Exec(exe, os.Args, os.Environ())
-	base.Fatalf("exec %s: %v", gotoolchain, err)
+	base.Fatalf("go: exec %s: %v", gotoolchain, err)
 }
diff --git a/src/cmd/go/internal/toolchain/select.go b/src/cmd/go/internal/toolchain/select.go
index 9fd1549a61bbc1..84fa7f685c97b7 100644
--- a/src/cmd/go/internal/toolchain/select.go
+++ b/src/cmd/go/internal/toolchain/select.go
@@ -8,10 +8,10 @@ package toolchain
 import (
 	"context"
 	"errors"
+	"flag"
 	"fmt"
 	"go/build"
 	"io/fs"
-	"log"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -20,10 +20,12 @@ import (
 
 	"cmd/go/internal/base"
 	"cmd/go/internal/cfg"
+	"cmd/go/internal/cmdflag"
 	"cmd/go/internal/gover"
 	"cmd/go/internal/modfetch"
 	"cmd/go/internal/modload"
 	"cmd/go/internal/run"
+	"cmd/go/internal/work"
 
 	"golang.org/x/mod/module"
 )
@@ -85,9 +87,6 @@ func FilterEnv(env []string) []string {
 // It must be called early in startup.
 // See https://go.dev/doc/toolchain#select.
 func Select() {
-	log.SetPrefix("go: ")
-	defer log.SetPrefix("")
-
 	if !modload.WillBeEnabled() {
 		return
 	}
@@ -133,15 +132,15 @@ func Select() {
 			v := gover.FromToolchain(min)
 			if v == "" {
 				if plus {
-					base.Fatalf("invalid GOTOOLCHAIN %q: invalid minimum toolchain %q", gotoolchain, min)
+					base.Fatalf("go: invalid GOTOOLCHAIN %q: invalid minimum toolchain %q", gotoolchain, min)
 				}
-				base.Fatalf("invalid GOTOOLCHAIN %q", gotoolchain)
+				base.Fatalf("go: invalid GOTOOLCHAIN %q", gotoolchain)
 			}
 			minToolchain = min
 			minVers = v
 		}
 		if plus && suffix != "auto" && suffix != "path" {
-			base.Fatalf("invalid GOTOOLCHAIN %q: only version suffixes are +auto and +path", gotoolchain)
+			base.Fatalf("go: invalid GOTOOLCHAIN %q: only version suffixes are +auto and +path", gotoolchain)
 		}
 		mode = suffix
 	}
@@ -172,7 +171,7 @@ func Select() {
 				// has a suffix like "go1.21.1-foo" and toolchain is "go1.21.1".)
 				toolVers := gover.FromToolchain(toolchain)
 				if toolVers == "" || (!strings.HasPrefix(toolchain, "go") && !strings.Contains(toolchain, "-go")) {
-					base.Fatalf("invalid toolchain %q in %s", toolchain, base.ShortPath(file))
+					base.Fatalf("go: invalid toolchain %q in %s", toolchain, base.ShortPath(file))
 				}
 				if gover.Compare(toolVers, minVers) > 0 {
 					gotoolchain = toolchain
@@ -194,7 +193,7 @@ func Select() {
 	// so that we have initialized gover.Startup for use in error messages.
 	if target := os.Getenv(targetEnv); target != "" && TestVersionSwitch != "loop" {
 		if gover.LocalToolchain() != target {
-			base.Fatalf("toolchain %v invoked to provide %v", gover.LocalToolchain(), target)
+			base.Fatalf("go: toolchain %v invoked to provide %v", gover.LocalToolchain(), target)
 		}
 		os.Unsetenv(targetEnv)
 
@@ -225,7 +224,7 @@ func Select() {
 	// We want to disallow mistakes / bad ideas like GOTOOLCHAIN=bash,
 	// since we will find that in the path lookup.
 	if !strings.HasPrefix(gotoolchain, "go1") && !strings.Contains(gotoolchain, "-go1") {
-		base.Fatalf("invalid GOTOOLCHAIN %q", gotoolchain)
+		base.Fatalf("go: invalid GOTOOLCHAIN %q", gotoolchain)
 	}
 
 	Exec(gotoolchain)
@@ -244,8 +243,6 @@ var TestVersionSwitch string
 // as a source of Go toolchains. Otherwise Exec tries the PATH but then downloads
 // a toolchain if necessary.
 func Exec(gotoolchain string) {
-	log.SetPrefix("go: ")
-
 	writeBits = sysWriteBits()
 
 	count, _ := strconv.Atoi(os.Getenv(countEnv))
@@ -253,7 +250,7 @@ func Exec(gotoolchain string) {
 		fmt.Fprintf(os.Stderr, "go: switching from go%v to %v [depth %d]\n", gover.Local(), gotoolchain, count)
 	}
 	if count >= maxSwitch {
-		base.Fatalf("too many toolchain switches")
+		base.Fatalf("go: too many toolchain switches")
 	}
 	os.Setenv(countEnv, fmt.Sprint(count+1))
 
@@ -276,7 +273,7 @@ func Exec(gotoolchain string) {
 	case "loop", "mismatch":
 		exe, err := os.Executable()
 		if err != nil {
-			base.Fatalf("%v", err)
+			base.Fatal(err)
 		}
 		execGoToolchain(gotoolchain, os.Getenv("GOROOT"), exe)
 	}
@@ -291,7 +288,7 @@ func Exec(gotoolchain string) {
 	// GOTOOLCHAIN=auto looks in PATH and then falls back to download.
 	// GOTOOLCHAIN=path only looks in PATH.
 	if pathOnly {
-		base.Fatalf("cannot find %q in PATH", gotoolchain)
+		base.Fatalf("go: cannot find %q in PATH", gotoolchain)
 	}
 
 	// Set up modules without an explicit go.mod, to download distribution.
@@ -310,9 +307,9 @@ func Exec(gotoolchain string) {
 	dir, err := modfetch.Download(context.Background(), m)
 	if err != nil {
 		if errors.Is(err, fs.ErrNotExist) {
-			base.Fatalf("download %s for %s/%s: toolchain not available", gotoolchain, runtime.GOOS, runtime.GOARCH)
+			base.Fatalf("go: download %s for %s/%s: toolchain not available", gotoolchain, runtime.GOOS, runtime.GOARCH)
 		}
-		base.Fatalf("download %s: %v", gotoolchain, err)
+		base.Fatalf("go: download %s: %v", gotoolchain, err)
 	}
 
 	// On first use after download, set the execute bits on the commands
@@ -321,7 +318,7 @@ func Exec(gotoolchain string) {
 	if runtime.GOOS != "windows" {
 		info, err := os.Stat(filepath.Join(dir, "bin/go"))
 		if err != nil {
-			base.Fatalf("download %s: %v", gotoolchain, err)
+			base.Fatalf("go: download %s: %v", gotoolchain, err)
 		}
 		if info.Mode()&0111 == 0 {
 			// allowExec sets the exec permission bits on all files found in dir.
@@ -342,7 +339,7 @@ func Exec(gotoolchain string) {
 					return nil
 				})
 				if err != nil {
-					base.Fatalf("download %s: %v", gotoolchain, err)
+					base.Fatalf("go: download %s: %v", gotoolchain, err)
 				}
 			}
 
@@ -384,7 +381,7 @@ func Exec(gotoolchain string) {
 			err = raceSafeCopy(srcUGoMod, srcGoMod)
 		}
 		if err != nil {
-			base.Fatalf("download %s: %v", gotoolchain, err)
+			base.Fatalf("go: download %s: %v", gotoolchain, err)
 		}
 	}
 
@@ -475,7 +472,7 @@ func modGoToolchain() (file, goVers, toolchain string) {
 
 	data, err := os.ReadFile(file)
 	if err != nil {
-		base.Fatalf("%v", err)
+		base.Fatal(err)
 	}
 	return file, gover.GoModLookup(data, "go"), gover.GoModLookup(data, "toolchain")
 }
@@ -492,6 +489,7 @@ func goInstallVersion() bool {
 
 	// Check for pkg@version.
 	var arg string
+	var cmdFlags *flag.FlagSet
 	switch os.Args[1] {
 	default:
 		return false
@@ -500,6 +498,7 @@ func goInstallVersion() bool {
 		// across a toolchain switch. To make that work, assume the pkg@version
 		// is the last argument and skip the flag parsing.
 		arg = os.Args[len(os.Args)-1]
+		cmdFlags = &work.CmdInstall.Flag
 	case "run":
 		// For run, the pkg@version can be anywhere on the command line,
 		// because it is preceded by run flags and followed by arguments to the
@@ -507,6 +506,7 @@ func goInstallVersion() bool {
 		// flags a little bit, to know whether each flag takes an optional argument.
 		// We can still allow unknown flags as long as they have an explicit =value.
 		args := os.Args[2:]
+		cmdFlags = &run.CmdRun.Flag
 		for i := 0; i < len(args); i++ {
 			a := args[i]
 			if !strings.HasPrefix(a, "-") {
@@ -554,6 +554,20 @@ func goInstallVersion() bool {
 		return false
 	}
 
+	// Make a best effort to parse flags so that module flags like -modcacherw
+	// will take effect (see https://go.dev/issue/64282).
+	args := os.Args[2:]
+	for len(args) > 0 {
+		var err error
+		_, args, err = cmdflag.ParseOne(cmdFlags, args)
+		if errors.Is(err, cmdflag.ErrFlagTerminator) {
+			break
+		}
+		// Ignore all other errors: they may be new flags — or updated syntax for
+		// existing flags — intended for a newer Go toolchain.
+	}
+	base.SetFromGOFLAGS(cmdFlags, true)
+
 	// It would be correct to simply return true here, bypassing use
 	// of the current go.mod or go.work, and let "go run" or "go install"
 	// do the rest, including a toolchain switch.
diff --git a/src/cmd/go/internal/vet/vetflag.go b/src/cmd/go/internal/vet/vetflag.go
index eb7af6508d00be..601ae9aa64ba16 100644
--- a/src/cmd/go/internal/vet/vetflag.go
+++ b/src/cmd/go/internal/vet/vetflag.go
@@ -116,7 +116,7 @@ func vetFlags(args []string) (passToVet, packageNames []string) {
 
 	// Record the set of vet tool flags set by GOFLAGS. We want to pass them to
 	// the vet tool, but only if they aren't overridden by an explicit argument.
-	base.SetFromGOFLAGS(&CmdVet.Flag)
+	base.SetFromGOFLAGS(&CmdVet.Flag, false)
 	addFromGOFLAGS := map[string]bool{}
 	CmdVet.Flag.Visit(func(f *flag.Flag) {
 		if isVetFlag[f.Name] {
diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
index d380aae489436f..b309cb867ab264 100644
--- a/src/cmd/go/main.go
+++ b/src/cmd/go/main.go
@@ -234,7 +234,7 @@ func invoke(cmd *base.Command, args []string) {
 	if cmd.CustomFlags {
 		args = args[1:]
 	} else {
-		base.SetFromGOFLAGS(&cmd.Flag)
+		base.SetFromGOFLAGS(&cmd.Flag, false)
 		cmd.Flag.Parse(args[1:])
 		args = cmd.Flag.Args()
 	}
diff --git a/src/cmd/go/testdata/script/install_modcacherw_issue64282.txt b/src/cmd/go/testdata/script/install_modcacherw_issue64282.txt
new file mode 100644
index 00000000000000..ea644f789ea2f2
--- /dev/null
+++ b/src/cmd/go/testdata/script/install_modcacherw_issue64282.txt
@@ -0,0 +1,32 @@
+# Regression test for https://go.dev/issue/64282:
+# 'go install' and 'go run' with pkg@version arguments should make
+# a best effort to parse flags before they download modules to
+# identify which toolchain version to use, because those flags
+# may affect the downloaded contents.
+
+# However, the best-effort flag parsing should not interfere with
+# actual flag parsing if we don't switch toolchains. In particular,
+# unrecognized flags should still be diagnosed after the module for
+# the requested package has been downloaded and checked for toolchain
+# upgrades.
+
+! go install -cake=delicious -modcacherw example.com/printversion@v0.1.0
+stderr '^flag provided but not defined: -cake$'
+
+[!short] go install -modcacherw example.com/printversion@v0.1.0
+	# Because the -modcacherw flag was set, we should be able to modify the contents
+	# of a directory within the module cache.
+cp $WORK/extraneous.txt $GOPATH/pkg/mod/example.com/printversion@v0.1.0/extraneous_file.go
+
+
+# We should also apply flags from GOFLAGS at this step.
+
+go clean -modcache
+env GOFLAGS=-modcacherw
+! go install -cake=delicious example.com/printversion@v0.1.0
+stderr '^flag provided but not defined: -cake$'
+cp $WORK/extraneous.txt $GOPATH/pkg/mod/example.com/printversion@v0.1.0/extraneous_file.go
+
+
+-- $WORK/extraneous.txt --
+This is not a Go source file.
diff --git a/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt b/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt
index 23c41beae90ae3..35fad2919326f3 100644
--- a/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt
+++ b/src/cmd/go/testdata/script/malformed_gosum_issue62345.txt
@@ -1,5 +1,5 @@
 ! go mod download
-stderr '^malformed go.sum:\n.*go.sum:3: wrong number of fields 5\n$'
+stderr '^go: malformed go.sum:\n.*go.sum:3: wrong number of fields 5\n$'
 
 go mod tidy
 cmp go.sum go.sum.after-tidy
diff --git a/src/cmd/go/testdata/script/work_sum_mismatch.txt b/src/cmd/go/testdata/script/work_sum_mismatch.txt
index ca5d71dc5e73c7..d4997aa37246e0 100644
--- a/src/cmd/go/testdata/script/work_sum_mismatch.txt
+++ b/src/cmd/go/testdata/script/work_sum_mismatch.txt
@@ -4,7 +4,7 @@
 cmpenv stderr want-error
 
 -- want-error --
-verifying rsc.io/sampler@v1.3.0/go.mod: checksum mismatch
+go: verifying rsc.io/sampler@v1.3.0/go.mod: checksum mismatch
 	downloaded: h1:T1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
 	$WORK${/}gopath${/}src${/}a${/}go.sum:     h1:U1hPZKmBbMNahiBKFy5HrXp6adAjACjK9JXDnKaTXpA=
 
@@ -58,4 +58,4 @@ import (
 
 func main() {
 	fmt.Println(quote.Hello())
-}
\ No newline at end of file
+}