Read the architecture at run time instead of a Buildarch ldflag (closes #259)

The Makefile no longer passes the architecture to the linker. The
Buildarch variable in main and the field and setter in globals are
gone; the startup log line reports runtime.GOARCH as `arch`.
CONVENTIONS.md drops Buildarch from its main, globals, logger and
Makefile examples, as the sneak/prompts conventions do.

Model: opus-5-5

CONVENTIONS.md

@@ -117,13 +117,11 @@ import (
 var (
     Appname string = "CHANGEME"
     Version string
-    Buildarch string
 )
 
 func main() {
     globals.Appname = Appname
     globals.Version = Version
-    globals.Buildarch = Buildarch
 
     fx.New(
         fx.Provide(
@@ -823,7 +821,7 @@ func (l *Logger) Identify() {
     l.log.Info("starting",
         "appname", l.params.Globals.Appname,
         "version", l.params.Globals.Version,
-        "buildarch", l.params.Globals.Buildarch,
+        "arch", runtime.GOARCH,
     )
 }
 ```
@@ -945,20 +943,17 @@ import "go.uber.org/fx"
 var (
     Appname string
     Version string
-    Buildarch string
 )
 
 // Struct for DI
 type Globals struct {
     Appname string
     Version string
-    Buildarch string
 }
 
 func New(lc fx.Lifecycle) (*Globals, error) {
     n := &Globals{
         Appname: Appname,
-        Buildarch: Buildarch,
         Version: Version,
     }
     return n, nil
@@ -972,13 +967,11 @@ func New(lc fx.Lifecycle) (*Globals, error) {
 var (
     Appname string = "CHANGEME"  // Default, overridden by build
     Version string               // Set at build time
-    Buildarch string               // Set at build time
 )
 
 func main() {
     globals.Appname = Appname
     globals.Version = Version
-    globals.Buildarch = Buildarch
     // ...
 }
 ```
@@ -989,10 +982,9 @@ Use ldflags to inject version information at build time:
 
 ```makefile
 VERSION := $(shell git describe --tags --always)
-BUILDARCH := $(shell go env GOARCH)
 
 build:
-    go build -ldflags "-X main.Version=$(VERSION) -X main.Buildarch=$(BUILDARCH)" ./cmd/httpd
+    go build -ldflags "-X main.Version=$(VERSION)" ./cmd/httpd
 ```
 
 ---

Makefile

@@ -2,8 +2,7 @@
 
 BINARY := upaasd
 VERSION := $(shell git describe --tags --always --dirty 2>/dev/null || echo "dev")
-BUILDARCH := $(shell go env GOARCH)
+LDFLAGS := -X main.Version=$(VERSION)
-LDFLAGS := -X main.Version=$(VERSION) -X main.Buildarch=$(BUILDARCH)
 
 all: check build
 

TODO.md

@@ -20,6 +20,11 @@ regress.
 
 # Completed Steps
 
+- 2026-10-02: The build no longer passes the CPU architecture in: upaas reads it
+  from Go's `runtime.GOARCH` when it runs, and the startup log line reports it
+  as `arch`. `CONVENTIONS.md` follows the updated conventions in `sneak/prompts`
+  (#259).
+
 - 2026-10-01: Built images are tagged `upaas-<app>:<short hash>`, git's short
   form of the commit built, instead of the deployment number. A redeploy of a
   commit gives its tag to the new image; the old one is kept while the app runs

cmd/upaasd/main.go

@@ -27,13 +27,11 @@ import (
 var (
 	Appname = "upaas" //nolint:gochecknoglobals // build-time variable
 	Version string    //nolint:gochecknoglobals // build-time variable
-	Buildarch string    //nolint:gochecknoglobals // build-time variable
 )
 
 func main() {
 	globals.SetAppname(Appname)
 	globals.SetVersion(Version)
-	globals.SetBuildarch(Buildarch)
 
 	fx.New(
 		fx.Provide(

internal/globals/globals.go

@@ -15,14 +15,12 @@ var (
 	mu      sync.RWMutex
 	appname string
 	version string
-	buildarch string
 )
 
 // Globals holds build-time variables for dependency injection.
 type Globals struct {
 	Appname string
 	Version string
-	Buildarch string
 }
 
 // New creates a new Globals instance from package-level variables.
@@ -33,7 +31,6 @@ func New(_ fx.Lifecycle) (*Globals, error) {
 	return &Globals{
 		Appname: appname,
 		Version: version,
-		Buildarch: buildarch,
 	}, nil
 }
 
@@ -52,11 +49,3 @@ func SetVersion(ver string) {
 
 	version = ver
 }
-
-// SetBuildarch sets the build architecture (used for testing and main init).
-func SetBuildarch(arch string) {
-	mu.Lock()
-	defer mu.Unlock()
-
-	buildarch = arch
-}

internal/logger/logger.go

@@ -4,6 +4,7 @@ package logger
 import (
 	"log/slog"
 	"os"
+	"runtime"
 
 	"go.uber.org/fx"
 
@@ -81,6 +82,6 @@ func (l *Logger) Identify() {
 	l.log.Info("starting",
 		"appname", l.params.Globals.Appname,
 		"version", l.params.Globals.Version,
-		"buildarch", l.params.Globals.Buildarch,
+		"arch", runtime.GOARCH,
 	)
 }

internal/logger/logger_test.go

@@ -0,0 +1,34 @@
+package logger //nolint:testpackage // sets the unexported log and params fields
+
+import (
+	"bytes"
+	"encoding/json"
+	"log/slog"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"sneak.berlin/go/upaas/internal/globals"
+)
+
+func TestIdentifyLogsArchitectureFromRuntime(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+
+	l := &Logger{
+		log: slog.New(slog.NewJSONHandler(&buf, nil)),
+		params: Params{
+			Globals: &globals.Globals{Appname: "upaas-test", Version: "test"},
+		},
+	}
+
+	l.Identify()
+
+	var line map[string]any
+
+	require.NoError(t, json.Unmarshal(buf.Bytes(), &line))
+	assert.Equal(t, runtime.GOARCH, line["arch"])
+}