Centralize Go validation and build environments

build.go

@@ -54,10 +54,11 @@ type BuildResult struct {
 }
 
 // Build compiles the selected targets with Version injected through buildinfo.
-// It uses the prepared local Go environment, regenerates selected output files while preserving unrelated files,
+// It uses the available compatible local Go toolchain, applies ReleaseKit's
-// and verifies the version command on the native host before succeeding. An
+// readonly offline build settings, preserves effective cache and tool settings,
-// empty target set records source identity without running the Go toolchain.
+// and verifies the version command on the Go host before succeeding. An empty
-// Errors return partial build facts in the result.
+// target set records source identity without running the Go toolchain. Errors
+// return partial build facts in the result.
 func Build(ctx context.Context, request BuildRequest) (BuildResult, error) {
 	result, err := internalbuild.Build(ctx, internalbuild.Request{
 		RepositoryDir: request.RepositoryDir,

build_test.go

@@ -131,6 +131,95 @@ func main() {
 	}
 }
 
+func TestBuildIgnoresAmbientAndPersistentArchitectureTuning(t *testing.T) {
+	repository := newBuildConsumer(t, `package main
+import (
+	"fmt"
+	"os"
+	"gitea.maximumdirect.net/eric/ReleaseKit/buildinfo"
+)
+func main() { if len(os.Args) == 2 && os.Args[1] == "version" { fmt.Printf("fixture %s\n", buildinfo.Version()) } }
+`)
+
+	for _, source := range []string{"process environment", "Go environment file"} {
+		t.Run(source, func(t *testing.T) {
+			unsetBuildEnv(t, "GOAMD64")
+			unsetBuildEnv(t, "GOEXPERIMENT")
+			unsetBuildEnv(t, "GOFLAGS")
+			cache := filepath.Join(t.TempDir(), "configured-cache")
+			goEnv := filepath.Join(t.TempDir(), "go-env")
+			if source == "Go environment file" {
+				contents := fmt.Sprintf("GOAMD64=v2\nGOEXPERIMENT=loopvar\nGOFLAGS=-run=^$\nGOCACHE=%s\n", cache)
+				if err := os.WriteFile(goEnv, []byte(contents), 0o600); err != nil {
+					t.Fatal(err)
+				}
+			} else {
+				if err := os.WriteFile(goEnv, nil, 0o600); err != nil {
+					t.Fatal(err)
+				}
+				t.Setenv("GOAMD64", "v2")
+				t.Setenv("GOEXPERIMENT", "loopvar")
+				t.Setenv("GOFLAGS", "-run=^$")
+			}
+			t.Setenv("GOENV", goEnv)
+
+			result, err := releasekit.Build(context.Background(), releasekit.BuildRequest{
+				RepositoryDir: repository,
+				Version:       "v2.3.4",
+				Spec: releasekit.BuildSpec{
+					MainPackage: "./cmd/app",
+					BinaryName:  "fixture",
+					Targets:     []releasekit.Target{{OS: "linux", Arch: "amd64"}},
+				},
+				OutputDir: filepath.Join(t.TempDir(), "artifacts"),
+			})
+			if err != nil {
+				t.Fatalf("Build() error = %v; partial result = %#v", err, result)
+			}
+			metadata := goBuildMetadata(t, result.Artifacts[0].Path)
+			if !strings.Contains(metadata, "GOAMD64=v1") || strings.Contains(metadata, "GOAMD64=v2") || strings.Contains(metadata, "GOEXPERIMENT=loopvar") {
+				t.Fatalf("build metadata includes ambient tuning:\n%s", metadata)
+			}
+			if source == "Go environment file" {
+				entries, err := os.ReadDir(cache)
+				if err != nil || len(entries) == 0 {
+					t.Fatalf("configured persistent cache was not used: entries=%d error=%v", len(entries), err)
+				}
+			}
+		})
+	}
+}
+
+func goBuildMetadata(t *testing.T, binary string) string {
+	t.Helper()
+	t.Setenv("GOENV", "off")
+	t.Setenv("GOFLAGS", "")
+	t.Setenv("GOEXPERIMENT", "")
+	t.Setenv("GOAMD64", "")
+	t.Setenv("GOOS", "")
+	t.Setenv("GOARCH", "")
+	output, err := exec.Command("go", "version", "-m", binary).CombinedOutput()
+	if err != nil {
+		t.Fatalf("go version -m: %v\n%s", err, output)
+	}
+	return string(output)
+}
+
+func unsetBuildEnv(t *testing.T, key string) {
+	t.Helper()
+	value, exists := os.LookupEnv(key)
+	if err := os.Unsetenv(key); err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() {
+		if exists {
+			_ = os.Setenv(key, value)
+		} else {
+			_ = os.Unsetenv(key)
+		}
+	})
+}
+
 func TestBuildWithNoTargetsDoesNotInvokeCompiler(t *testing.T) {
 	repository := newBuildConsumer(t, `package main
 func main() {}

check.go

@@ -34,7 +34,8 @@ type ReleaseRequest struct {
 
 // Check validates one local, committed release candidate. It requires a clean
 // worktree and index on main, a committed note matching Product and Version,
-// and an unused local tag. If Validate is nil, the offline Go test suite runs.
+// and an unused local tag. If Validate is nil, the offline Go test suite runs
+// with the available compatible local Go toolchain and the Go host target.
 // If Build selects targets, Check builds them after validation in temporary
 // storage outside the worktree, then rechecks branch, HEAD, worktree, index,
 // and local tag state. Success establishes local candidate evidence only; it

docs/consumers/build.md

@@ -50,13 +50,18 @@ resolved from the repository. Selected artifact filenames are regenerated. Other
 directory are left in place. A failed later build or native version check returns the binaries already
 generated in `BuildResult.Artifacts`.
 
-Builds use the prepared local Go toolchain, readonly module mode, disabled
+Builds use the available compatible Go toolchain selected locally; ReleaseKit
-module network access, `CGO_ENABLED=0`, `-trimpath`, and `-buildvcs=false`. Each
+does not download a different toolchain automatically. It disables workspace
-selected target is compiled explicitly. ReleaseKit then runs the `version`
+discovery and module network access, uses readonly module mode, sets
-command on a native binary and requires `<binary> <version>` followed by a
+`CGO_ENABLED=0`, and passes `-trimpath` and `-buildvcs=false`. Effective cache,
-newline. If no selected target matches the Go host, it builds a temporary
+module-cache, temporary-directory, and tool settings are retained, including
-native binary for this check and removes it afterward. Cross-compilation does
+values from Go's persistent environment file. Ambient experiment and CPU
-not promise that a binary runs on another platform.
+feature settings are cleared so the selected toolchain uses its baseline for
+each target. Each selected target is compiled explicitly. ReleaseKit then runs
+the `version` command on a native binary and requires `<binary> <version>`
+followed by a newline. If no selected target matches the Go host, it builds a
+temporary native binary for this check and removes it afterward.
+Cross-compilation does not promise that a binary runs on another platform.
 
 An empty target list records the source commit and returns without invoking Go,
 creating the output directory, or running a version check. It does not require a

docs/consumers/check.md

@@ -25,8 +25,14 @@ product name and exact version as complete title elements. No local tag with
 that version may already exist.
 
 The callback receives the captured repository, commit, and version. ReleaseKit
-calls it once. When omitted, ReleaseKit runs the offline Go test command. The
+calls it once. When omitted, ReleaseKit runs
-check revalidates the branch, commit, and cleanliness after validation.
+`go test -mod=readonly -count=1 ./...` with the available compatible local Go
+toolchain; it does not download a different toolchain automatically. The suite
+uses the Go host target, disables workspace and module network access, and
+ignores ambient `GOFLAGS`, experiment, and CPU feature overrides. Effective
+cache and native cgo/C-tool settings are preserved, including values from Go's
+persistent environment file. The check revalidates the branch, commit, and
+cleanliness after validation.
 
 A successful check is evidence about the local candidate only. It does not
 check whether a remote branch or tag is available and does not create a tag.

docs/internal/gotool.md

@@ -0,0 +1,42 @@
+# Go command environments
+
+`internal/gotool` resolves effective Go settings once for a validation or build
+operation and applies the shared environment to its Go commands. It uses
+`internal/process` for cancellation, the working directory, output, and wrapped
+errors.
+
+## Configuration discovery
+
+The owner asks the installed `go` command for `GOHOSTOS` and `GOHOSTARCH`, then
+queries effective operational settings with that host selected. Both queries
+use `GOTOOLCHAIN=local` and controlled `GOFLAGS`. Discovery sets
+`GOEXPERIMENT=none` and clears architecture feature variables so an invalid or
+nonbaseline tuning value cannot prevent settings from being read. The
+experiment override is discovery-only.
+
+The persistent Go environment remains active during discovery. The owner copies
+the effective cache and module-cache locations, Go root, temporary directory,
+and native cgo/C-tool configuration into its settings. This captures values
+supplied by either the process environment or the persistent Go environment
+file.
+
+## Command environments
+
+Every Go command receives `GOENV=off`, so removed persistent values cannot
+return. ReleaseKit owns `GOFLAGS=-mod=readonly`, `GOWORK=off`,
+`GOTOOLCHAIN=local`, `GOPROXY=off`, `GONOPROXY=none`, and `GOSUMDB=off`.
+Native commands use `GOHOSTOS` and `GOHOSTARCH` and retain the effective
+`CGO_ENABLED`, `CC`, `CXX`, `PKG_CONFIG`, and `CGO_CFLAGS`, `CGO_CPPFLAGS`,
+`CGO_CXXFLAGS`, and `CGO_LDFLAGS`. Static commands use the selected target and
+`CGO_ENABLED=0`.
+
+Both modes clear `GOEXPERIMENT` and the Go architecture feature variables
+`GOAMD64`, `GOARM`, `GOARM64`, `GO386`, `GOMIPS`, `GOMIPS64`, `GOPPC64`,
+`GORISCV64`, and `GOWASM`. The selected Go toolchain supplies its ordinary
+baseline values. Effective `GOCACHE`, `GOCACHEPROG`, `GOMODCACHE`, `GOPATH`,
+`GOROOT`, and `GOTMPDIR` values are retained. Other process variables remain
+available to child commands.
+
+Candidate validation uses native mode for the offline `go test` suite. Builds
+use static mode for selected-target compilation and the native version-check
+build. The native version executable itself runs as a normal child process.

docs/internal/overview.md

@@ -39,8 +39,9 @@ these implemented packages:
 | `internal/delivery` | Tagged-checkout verification, artifact inventory/hash validation, manifest assembly, and coordination of hosted delivery results. |
 | `internal/git` | Git command boundary, push-destination resolution, exact ref inspection, and tag operations, including captured-endpoint verification during recovery. |
 | `internal/gitea` | Gitea API transport, hosted release pages, asset inspection, manifests, and uploads. |
+| `internal/gotool` | Effective Go configuration discovery and shared native-validation and static-build environments; see [Go command environments](gotool.md). |
 | `internal/tempdir` | Disposable system temporary storage outside source worktrees. |
-| `internal/process` | Cancellable child-process execution with per-command environment overlays. |
+| `internal/process` | Cancellable child-process execution with per-command environment overlays and removals. |
 | `internal/publish` | Publication guards, one validation run, annotated tag creation, push, and recovery state. |
 | `internal/runtimeinfo` | Private version lookup used by the runtime facade. |
 | `internal/versioncontract` | Shared stable-version rules and linker-symbol identity. |
@@ -62,6 +63,7 @@ not a separate release matrix:
 | --- | --- | --- |
 | Runtime version lookup and injected application version | `buildinfo`, `internal/runtimeinfo`, `internal/versioncontract`, `internal/build` | `TestVersionInConsumerExecutable`, `TestVersion` |
 | Candidate capture, committed note, one validation, and rechecks | `releasekit.Check`, `internal/candidate`, `cmd/releasekit/internal/cli` | `TestCheckCapturesCandidateAndCallsValidationOnce`, `TestCheckRechecksHeadAndWorktreeAfterCallback`, `TestCheckCommandBindsConfiguredChecksToCapturedCandidate` |
+| Shared Go settings for validation and builds | `internal/gotool`, `internal/process`, `internal/candidate`, `internal/build` | `TestDefaultValidationDoesNotInheritGOFLAGSRunFilter`, `TestNativeAndStaticCommandsUseOwnedBaseline`, `TestPersistentSettingsPreserveCachesAndNativeCTools`, `TestBuildIgnoresAmbientAndPersistentArchitectureTuning` |
 | Authoritative endpoint and exact annotated tag publication | `releasekit.Publish`, `internal/publish`, `internal/git` | `TestPublishPushesOnlyTheCapturedAnnotatedTag`, `TestResolveUsesPushURLAndQueriesWithoutMutation` |
 | Publication partial and uncertain recovery | `internal/publish`, `internal/git` | `TestPublishRejectedPushKeepsLocalTagAndReportsNotPublished`, `TestPublishLostAcknowledgmentConfirmsExactRemoteObject`, `TestPublishLostAcknowledgmentWithChangedEndpointRemainsUnknown`, `TestPublishUnavailableReconciliationRemainsUnknownAndPreservesPushError` |
 | Cross-builds, version smoke checks, empty target sets, and partial outputs | `releasekit.Build`, `internal/build`, `buildinfo` | `TestBuildCreatesSelectedTargetsAndInjectsVersion`, `TestBuildWithNoTargetsDoesNotInvokeCompiler`, `TestBuildReturnsPartialArtifactsAfterTargetFailure` |

docs/roadmap/implementation.md

@@ -1,6 +1,6 @@
 # ReleaseKit audit implementation plan
 
-Status: Stage 1 complete; Stage 2 not started.
+Status: Stages 1 and 2 complete; Stage 3 not started.
 Baseline: `e4be7fa` (2026-10-06). The [audit](audit.md) records the evidence,
 product goals, and selected direction. This document owns implementation order
 and completion criteria for that work.
@@ -160,6 +160,14 @@ survive. Preserve existing version injection, empty-target, cancellation, and
 partial-build behavior. Fixtures use temporary Go configuration and never edit
 the developer's persistent settings.
 
+**Completed:** Shared Go configuration now drives default validation,
+toolchain/host queries, target builds, and the native smoke build. Failing
+validation fixtures prove process and persistent `GOFLAGS` cannot suppress a
+real test and that cross-target settings still run tests on the host. Build
+metadata confirms ambient and persistent tuning are cleared, and a temporary
+persistent cache is used. Focused tests, the full offline suite, API boundary
+checks, and documentation whitespace checks pass.
+
 ## Stage 3 — Make product checks additive
 
 **Covers:** F4 and ReleaseKit's own F1 exposure. **Primary owners:** `check.go`,

internal/build/build.go

@@ -11,10 +11,10 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"sort"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/ReleaseKit/internal/candidate"
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/gotool"
 	"gitea.maximumdirect.net/eric/ReleaseKit/internal/versioncontract"
 )
 
@@ -115,15 +115,17 @@ func Build(ctx context.Context, request Request) (Result, error) {
 		return result, fmt.Errorf("create build output directory %q: %w", result.OutputDir, err)
 	}
 
-	compiler, err := runGo(ctx, repositoryDir, nil, "version")
+	goTool, err := gotool.New(ctx, repositoryDir)
+	if err != nil {
+		return result, fmt.Errorf("prepare Go toolchain: %w", err)
+	}
+	compiler, err := goTool.Run(ctx, repositoryDir, gotool.Native, gotool.Target{}, nil, "version")
 	if err != nil {
 		return result, fmt.Errorf("identify Go compiler: %w", err)
 	}
 	result.Compiler = strings.TrimSpace(string(compiler))
-	host, err := hostTarget(ctx, repositoryDir)
+	goHost := goTool.HostTarget()
-	if err != nil {
+	host := Target{OS: goHost.OS, Arch: goHost.Arch}
-		return result, fmt.Errorf("identify Go host: %w", err)
-	}
 
 	for index, target := range result.Targets {
 		if err := ctx.Err(); err != nil {
@@ -134,7 +136,7 @@ func Build(ctx context.Context, request Request) (Result, error) {
 		if request.Output != nil {
 			fmt.Fprintf(request.Output, "building %s/%s as %s\n", target.OS, target.Arch, filename)
 		}
-		if err := buildTarget(ctx, repositoryDir, request.Spec.MainPackage, path, request.Version, target); err != nil {
+		if err := buildTarget(ctx, goTool, repositoryDir, request.Spec.MainPackage, path, request.Version, target); err != nil {
 			return result, fmt.Errorf("build target %s/%s: %w", target.OS, target.Arch, err)
 		}
 		artifact := Artifact{Path: path, Filename: filename, Target: target}
@@ -164,7 +166,7 @@ func Build(ctx context.Context, request Request) (Result, error) {
 		if request.Output != nil {
 			fmt.Fprintf(request.Output, "building temporary version check for %s/%s\n", host.OS, host.Arch)
 		}
-		if err := buildTarget(ctx, repositoryDir, request.Spec.MainPackage, smokePath, request.Version, host); err != nil {
+		if err := buildTarget(ctx, goTool, repositoryDir, request.Spec.MainPackage, smokePath, request.Version, host); err != nil {
 			return result, fmt.Errorf("build native version check: %w", err)
 		}
 	}
@@ -236,76 +238,13 @@ func gitCommit(ctx context.Context, repositoryDir string) (string, error) {
 	return strings.TrimSpace(string(output)), nil
 }
 
-func hostTarget(ctx context.Context, repositoryDir string) (Target, error) {
+func buildTarget(ctx context.Context, goTool *gotool.Tool, repositoryDir, mainPackage, outputPath, version string, target Target) error {
-	output, err := runGo(ctx, repositoryDir, nil, "env", "GOHOSTOS", "GOHOSTARCH")
-	if err != nil {
-		return Target{}, err
-	}
-	parts := strings.Fields(string(output))
-	if len(parts) != 2 {
-		return Target{}, fmt.Errorf("unexpected Go host response %q", output)
-	}
-	return Target{OS: parts[0], Arch: parts[1]}, nil
-}
-
-func buildTarget(ctx context.Context, repositoryDir, mainPackage, outputPath, version string, target Target) error {
 	ldflags := "-s -w -X " + versioncontract.InjectedVersionLinkerSymbol + "=" + version
-	_, err := runGo(ctx, repositoryDir, map[string]string{"GOOS": target.OS, "GOARCH": target.Arch},
+	_, err := goTool.Run(ctx, repositoryDir, gotool.Static, gotool.Target{OS: target.OS, Arch: target.Arch}, nil,
 		"build", "-o", outputPath, "-mod=readonly", "-trimpath", "-buildvcs=false", "-ldflags", ldflags, mainPackage)
 	return err
 }
 
-func runGo(ctx context.Context, directory string, target map[string]string, args ...string) ([]byte, error) {
-	commandArgs := append([]string(nil), args...)
-	command := exec.CommandContext(ctx, "go", commandArgs...)
-	command.Dir = directory
-	command.Env = goEnvironment(target)
-	output, err := command.CombinedOutput()
-	if err == nil {
-		return output, nil
-	}
-	if ctx.Err() != nil {
-		err = fmt.Errorf("%w: %v", ctx.Err(), err)
-	}
-	if len(output) != 0 {
-		return output, fmt.Errorf("go %s: %w: %s", strings.Join(commandArgs, " "), err, strings.TrimSpace(string(output)))
-	}
-	return output, fmt.Errorf("go %s: %w", strings.Join(commandArgs, " "), err)
-}
-
-func goEnvironment(target map[string]string) []string {
-	controlled := map[string]bool{
-		"GOWORK": true, "GOPROXY": true, "GONOPROXY": true, "GOSUMDB": true,
-		"GOTOOLCHAIN": true, "GOFLAGS": true, "CGO_ENABLED": true, "GOOS": true, "GOARCH": true,
-	}
-	for key := range target {
-		controlled[key] = true
-	}
-	environment := make([]string, 0, len(os.Environ())+len(controlled))
-	for _, entry := range os.Environ() {
-		key, _, ok := strings.Cut(entry, "=")
-		if !ok || !controlled[key] {
-			environment = append(environment, entry)
-		}
-	}
-	values := map[string]string{
-		"GOWORK": "off", "GOPROXY": "off", "GONOPROXY": "none", "GOSUMDB": "off",
-		"GOTOOLCHAIN": "local", "GOFLAGS": "-mod=readonly", "CGO_ENABLED": "0",
-	}
-	for key, value := range target {
-		values[key] = value
-	}
-	keys := make([]string, 0, len(values))
-	for key := range values {
-		keys = append(keys, key)
-	}
-	sort.Strings(keys)
-	for _, key := range keys {
-		environment = append(environment, key+"="+values[key])
-	}
-	return environment
-}
-
 func hashArtifact(artifact *Artifact) error {
 	file, err := os.Open(artifact.Path)
 	if err != nil {
@@ -322,7 +261,6 @@ func hashArtifact(artifact *Artifact) error {
 
 func checkVersion(ctx context.Context, binaryPath, binaryName, version string) error {
 	command := exec.CommandContext(ctx, binaryPath, "version")
-	command.Env = goEnvironment(nil)
 	output, err := command.CombinedOutput()
 	if err != nil {
 		if ctx.Err() != nil {

internal/candidate/check.go

@@ -10,8 +10,8 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
-	"sync"
 
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/gotool"
 	"gitea.maximumdirect.net/eric/ReleaseKit/internal/process"
 	"gitea.maximumdirect.net/eric/ReleaseKit/internal/versioncontract"
 )
@@ -216,35 +216,13 @@ func hasLocalTag(ctx context.Context, repositoryDir, version string) (bool, erro
 }
 
 func runDefaultValidation(ctx context.Context, repositoryDir string, output io.Writer) error {
-	environment := map[string]string{
+	tool, err := gotool.New(ctx, repositoryDir)
-		"GOWORK":      "off",
+	if err != nil {
-		"GOPROXY":     "off",
+		return fmt.Errorf("prepare Go toolchain: %w", err)
-		"GONOPROXY":   "none",
-		"GOSUMDB":     "off",
-		"GOTOOLCHAIN": "local",
 	}
-	var writer io.Writer = output
+	_, err = tool.Run(ctx, repositoryDir, gotool.Native, gotool.Target{}, output,
-	if output != nil {
+		"test", "-mod=readonly", "-count=1", "./...")
-		writer = &synchronizedWriter{writer: output}
+	return err
-	}
-	return process.Run(ctx, process.Invocation{
-		Args:   []string{"go", "test", "-mod=readonly", "-count=1", "./..."},
-		Dir:    repositoryDir,
-		Env:    environment,
-		Stdout: writer,
-		Stderr: writer,
-	})
-}
-
-type synchronizedWriter struct {
-	mu     sync.Mutex
-	writer io.Writer
-}
-
-func (w *synchronizedWriter) Write(p []byte) (int, error) {
-	w.mu.Lock()
-	defer w.mu.Unlock()
-	return w.writer.Write(p)
 }
 
 func validStableVersion(version string) bool {

internal/candidate/check_test.go

@@ -90,6 +90,60 @@ func TestCheckRunsDefaultOfflineGoValidation(t *testing.T) {
 	}
 }
 
+func TestDefaultValidationDoesNotInheritGOFLAGSRunFilter(t *testing.T) {
+	repository := newRepository(t, "# Example Product v1.2.3\n\nRelease note.\n")
+	writeTestFile(t, repository, "failure_test.go", "package candidate\nimport \"testing\"\nfunc TestExpectedFailure(t *testing.T) { t.Fatal(\"expected fixture failure\") }\n")
+	gitRun(t, repository, "add", "failure_test.go")
+	gitRun(t, repository, "commit", "-m", "add failing validation fixture")
+
+	for _, source := range []string{"process environment", "Go environment file"} {
+		t.Run(source, func(t *testing.T) {
+			unsetCandidateEnv(t, "GOFLAGS", "GOOS", "GOARCH")
+			goEnv := filepath.Join(t.TempDir(), "go-env")
+			if source == "Go environment file" {
+				if err := os.WriteFile(goEnv, []byte("GOFLAGS=-run=^$\nGOOS=windows\nGOARCH=arm64\n"), 0o600); err != nil {
+					t.Fatal(err)
+				}
+			} else {
+				if err := os.WriteFile(goEnv, nil, 0o600); err != nil {
+					t.Fatal(err)
+				}
+				t.Setenv("GOFLAGS", "-run=^$")
+				t.Setenv("GOOS", "windows")
+				t.Setenv("GOARCH", "arm64")
+			}
+			t.Setenv("GOENV", goEnv)
+			var output bytes.Buffer
+			_, err := Check(context.Background(), Request{
+				RepositoryDir: repository,
+				Product:       "Example Product",
+				Version:       testVersion,
+				Output:        &output,
+			})
+			if err == nil || !strings.Contains(output.String(), "TestExpectedFailure") {
+				t.Fatalf("Check() error = %v, output = %q; wanted the failing standard test to run", err, output.String())
+			}
+		})
+	}
+}
+
+func unsetCandidateEnv(t *testing.T, keys ...string) {
+	t.Helper()
+	for _, key := range keys {
+		value, exists := os.LookupEnv(key)
+		if err := os.Unsetenv(key); err != nil {
+			t.Fatal(err)
+		}
+		t.Cleanup(func() {
+			if exists {
+				_ = os.Setenv(key, value)
+			} else {
+				_ = os.Unsetenv(key)
+			}
+		})
+	}
+}
+
 func TestCheckRejectsInvalidVersionsBeforeGitAccess(t *testing.T) {
 	for _, version := range []string{"v01.2.3", "v1.2.3-alpha", "1.2.3"} {
 		t.Run(version, func(t *testing.T) {

internal/gotool/gotool.go

@@ -0,0 +1,203 @@
+// Package gotool owns Go configuration discovery and ReleaseKit's Go command
+// environments.
+package gotool
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"strings"
+	"sync"
+
+	"gitea.maximumdirect.net/eric/ReleaseKit/internal/process"
+)
+
+// Mode selects the target environment for a Go command.
+type Mode uint8
+
+const (
+	// Native runs Go for the toolchain host and keeps its effective cgo settings.
+	Native Mode = iota
+	// Static runs Go for the selected target with cgo disabled.
+	Static
+)
+
+// Target selects a Go operating system and architecture.
+type Target struct {
+	OS   string
+	Arch string
+}
+
+// Tool holds the host target and effective operational settings resolved from
+// the process environment and Go's persistent environment file.
+type Tool struct {
+	host     Target
+	settings map[string]string
+}
+
+var operationalSettings = []string{
+	"CC", "CXX", "CGO_CFLAGS", "CGO_CPPFLAGS", "CGO_CXXFLAGS", "CGO_ENABLED", "CGO_LDFLAGS",
+	"GOCACHE", "GOCACHEPROG", "GOMODCACHE", "GOPATH", "GOROOT", "GOTMPDIR", "PKG_CONFIG",
+}
+
+var architectureFeatures = []string{
+	"GOAMD64", "GOARM", "GOARM64", "GO386", "GOMIPS", "GOMIPS64", "GOPPC64", "GORISCV64", "GOWASM",
+}
+
+// New discovers the Go toolchain host and its effective cache, tool, and cgo
+// settings. Discovery uses the selected local Go command and neutralizes
+// ambient flags, experiments, and architecture tuning so they cannot prevent
+// configuration from being read.
+func New(ctx context.Context, directory string) (*Tool, error) {
+	var host struct {
+		OS   string `json:"GOHOSTOS"`
+		Arch string `json:"GOHOSTARCH"`
+	}
+	output, err := discover(ctx, directory, discoveryEnvironment(), "go", "env", "-json", "GOHOSTOS", "GOHOSTARCH")
+	if err != nil {
+		return nil, fmt.Errorf("identify Go host: %w", err)
+	}
+	if err := json.Unmarshal(output, &host); err != nil {
+		return nil, fmt.Errorf("decode Go host settings: %w", err)
+	}
+	if host.OS == "" || host.Arch == "" {
+		return nil, fmt.Errorf("Go returned an incomplete host target: %s", strings.TrimSpace(string(output)))
+	}
+	tool := &Tool{host: Target{OS: host.OS, Arch: host.Arch}}
+
+	environment := discoveryEnvironment()
+	environment["GOOS"] = tool.host.OS
+	environment["GOARCH"] = tool.host.Arch
+	args := append([]string{"go", "env", "-json"}, operationalSettings...)
+	output, err = discover(ctx, directory, environment, args...)
+	if err != nil {
+		return nil, fmt.Errorf("resolve effective Go settings: %w", err)
+	}
+	var settings map[string]string
+	if err := json.Unmarshal(output, &settings); err != nil {
+		return nil, fmt.Errorf("decode effective Go settings: %w", err)
+	}
+	for _, key := range operationalSettings {
+		if _, ok := settings[key]; !ok {
+			return nil, fmt.Errorf("Go did not report effective setting %s", key)
+		}
+	}
+	tool.settings = settings
+	return tool, nil
+}
+
+// HostTarget reports the Go command's host operating system and architecture.
+func (tool *Tool) HostTarget() Target {
+	return tool.host
+}
+
+// Run executes a Go command with ReleaseKit's shared offline baseline. Native
+// commands use the host target and effective cgo configuration. Static commands
+// use target and disable cgo. Output, when supplied, receives stdout and stderr
+// as the command runs; the returned bytes retain both streams for diagnostics.
+func (tool *Tool) Run(ctx context.Context, directory string, mode Mode, target Target, output io.Writer, args ...string) ([]byte, error) {
+	if len(args) == 0 {
+		return nil, errors.New("Go command requires arguments")
+	}
+	environment := tool.environment(mode, target)
+	captured := &combinedWriter{output: output}
+	commandArgs := append([]string{"go"}, args...)
+	err := process.Run(ctx, process.Invocation{
+		Args:   commandArgs,
+		Dir:    directory,
+		Env:    environment,
+		Stdout: captured,
+		Stderr: captured,
+	})
+	contents := captured.Bytes()
+	if err != nil {
+		if len(contents) != 0 {
+			return contents, fmt.Errorf("go %s: %w: %s", strings.Join(args, " "), err, strings.TrimSpace(string(contents)))
+		}
+		return contents, fmt.Errorf("go %s: %w", strings.Join(args, " "), err)
+	}
+	return contents, nil
+}
+
+func (tool *Tool) environment(mode Mode, target Target) map[string]string {
+	if mode == Native || target.OS == "" || target.Arch == "" {
+		target = tool.host
+	}
+	values := make(map[string]string, len(tool.settings)+len(architectureFeatures)+12)
+	for key, value := range tool.settings {
+		values[key] = value
+	}
+	values["GOENV"] = "off"
+	values["GOFLAGS"] = "-mod=readonly"
+	values["GOWORK"] = "off"
+	values["GOTOOLCHAIN"] = "local"
+	values["GOPROXY"] = "off"
+	values["GONOPROXY"] = "none"
+	values["GOSUMDB"] = "off"
+	values["GOOS"] = target.OS
+	values["GOARCH"] = target.Arch
+	values["GOEXPERIMENT"] = ""
+	for _, key := range architectureFeatures {
+		values[key] = ""
+	}
+	if mode == Static {
+		values["CGO_ENABLED"] = "0"
+	}
+	return values
+}
+
+func discoveryEnvironment() map[string]string {
+	environment := map[string]string{
+		"GOFLAGS":      "-mod=readonly",
+		"GOTOOLCHAIN":  "local",
+		"GOWORK":       "off",
+		"GOEXPERIMENT": "none",
+	}
+	for _, key := range architectureFeatures {
+		environment[key] = ""
+	}
+	return environment
+}
+
+func discover(ctx context.Context, directory string, environment map[string]string, args ...string) ([]byte, error) {
+	captured := &combinedWriter{}
+	err := process.Run(ctx, process.Invocation{
+		Args:   args,
+		Dir:    directory,
+		Env:    environment,
+		Stdout: captured,
+		Stderr: captured,
+	})
+	contents := captured.Bytes()
+	if err != nil {
+		if len(contents) != 0 {
+			return contents, fmt.Errorf("%s: %w: %s", strings.Join(args, " "), err, strings.TrimSpace(string(contents)))
+		}
+		return contents, fmt.Errorf("%s: %w", strings.Join(args, " "), err)
+	}
+	return contents, nil
+}
+
+type combinedWriter struct {
+	mu     sync.Mutex
+	output io.Writer
+	buffer bytes.Buffer
+}
+
+func (writer *combinedWriter) Write(contents []byte) (int, error) {
+	writer.mu.Lock()
+	defer writer.mu.Unlock()
+	if writer.output == nil {
+		return writer.buffer.Write(contents)
+	}
+	return io.MultiWriter(&writer.buffer, writer.output).Write(contents)
+}
+
+func (writer *combinedWriter) Bytes() []byte {
+	writer.mu.Lock()
+	defer writer.mu.Unlock()
+	return append([]byte(nil), writer.buffer.Bytes()...)
+}

internal/gotool/gotool_test.go

@@ -0,0 +1,138 @@
+package gotool
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"testing"
+)
+
+func TestNativeAndStaticCommandsUseOwnedBaseline(t *testing.T) {
+	clearGoSettings(t)
+	t.Setenv("GOENV", "off")
+	t.Setenv("GOFLAGS", "-run=^$")
+	t.Setenv("GOOS", "windows")
+	t.Setenv("GOARCH", "arm64")
+	t.Setenv("GOAMD64", "v2")
+	t.Setenv("GOEXPERIMENT", "loopvar")
+
+	tool, err := New(context.Background(), t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tool.HostTarget() != (Target{OS: runtime.GOOS, Arch: runtime.GOARCH}) {
+		t.Fatalf("Go host = %#v, want runtime host %s/%s", tool.HostTarget(), runtime.GOOS, runtime.GOARCH)
+	}
+
+	native := readSettings(t, tool, Native, Target{}, "GOENV", "GOOS", "GOARCH", "GOFLAGS", "GOAMD64", "GOEXPERIMENT", "CGO_ENABLED")
+	if native["GOENV"] != "" || native["GOOS"] != runtime.GOOS || native["GOARCH"] != runtime.GOARCH {
+		t.Fatalf("native environment = %#v", native)
+	}
+	if native["GOFLAGS"] != "-mod=readonly" || native["GOAMD64"] == "v2" || native["GOEXPERIMENT"] != "" {
+		t.Fatalf("native Go settings = %#v", native)
+	}
+	if native["CGO_ENABLED"] == "" {
+		t.Fatalf("native cgo setting was not resolved: %#v", native)
+	}
+
+	static := readSettings(t, tool, Static, Target{OS: "linux", Arch: "amd64"}, "GOOS", "GOARCH", "GOFLAGS", "CGO_ENABLED", "GOAMD64", "GOEXPERIMENT")
+	if static["GOOS"] != "linux" || static["GOARCH"] != "amd64" || static["CGO_ENABLED"] != "0" {
+		t.Fatalf("static environment = %#v", static)
+	}
+	if static["GOFLAGS"] != "-mod=readonly" || static["GOAMD64"] != "v1" || static["GOEXPERIMENT"] != "" {
+		t.Fatalf("static baseline settings = %#v", static)
+	}
+}
+
+func TestPersistentSettingsPreserveCachesAndNativeCTools(t *testing.T) {
+	clearGoSettings(t)
+	cache := filepath.Join(t.TempDir(), "configured-cache")
+	moduleCache := filepath.Join(t.TempDir(), "configured-module-cache")
+	temporary := filepath.Join(t.TempDir(), "configured-temporary")
+	if err := os.Mkdir(temporary, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	goEnv := filepath.Join(t.TempDir(), "go-env")
+	contents := strings.Join([]string{
+		"GOFLAGS=-run=^$",
+		"GOOS=windows",
+		"GOARCH=arm64",
+		"GOAMD64=v2",
+		"GOEXPERIMENT=loopvar",
+		"GOCACHE=" + cache,
+		"GOMODCACHE=" + moduleCache,
+		"GOTMPDIR=" + temporary,
+		"CGO_ENABLED=1",
+		"CC=releasekit-test-cc",
+		"CXX=releasekit-test-cxx",
+		"CGO_CFLAGS=-O0 -g",
+		"PKG_CONFIG=releasekit-test-pkg-config",
+	}, "\n") + "\n"
+	if err := os.WriteFile(goEnv, []byte(contents), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("GOENV", goEnv)
+
+	tool, err := New(context.Background(), t.TempDir())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if tool.HostTarget() != (Target{OS: runtime.GOOS, Arch: runtime.GOARCH}) {
+		t.Fatalf("Go host = %#v, want runtime host %s/%s", tool.HostTarget(), runtime.GOOS, runtime.GOARCH)
+	}
+	native := readSettings(t, tool, Native, Target{}, "GOENV", "GOOS", "GOARCH", "GOFLAGS", "GOAMD64", "GOEXPERIMENT", "CGO_ENABLED", "CC", "CXX", "CGO_CFLAGS", "GOCACHE", "GOMODCACHE", "GOTMPDIR", "PKG_CONFIG")
+	if native["GOENV"] != "" || native["GOOS"] != runtime.GOOS || native["GOARCH"] != runtime.GOARCH {
+		t.Fatalf("native environment = %#v", native)
+	}
+	if native["GOFLAGS"] != "-mod=readonly" || native["GOAMD64"] == "v2" || native["GOEXPERIMENT"] != "" {
+		t.Fatalf("persisted overrides were not cleared: %#v", native)
+	}
+	if native["CGO_ENABLED"] != "1" || native["CC"] != "releasekit-test-cc" || native["CXX"] != "releasekit-test-cxx" || native["CGO_CFLAGS"] != "-O0 -g" || native["PKG_CONFIG"] != "releasekit-test-pkg-config" {
+		t.Fatalf("persistent native C settings = %#v", native)
+	}
+	if native["GOCACHE"] != cache || native["GOMODCACHE"] != moduleCache || native["GOTMPDIR"] != temporary {
+		t.Fatalf("persistent cache settings = %#v", native)
+	}
+	static := readSettings(t, tool, Static, Target{OS: "linux", Arch: "amd64"}, "GOENV", "GOOS", "GOARCH", "GOFLAGS", "CGO_ENABLED", "GOAMD64", "GOEXPERIMENT", "GOCACHE")
+	if static["GOENV"] != "" || static["GOOS"] != "linux" || static["GOARCH"] != "amd64" || static["CGO_ENABLED"] != "0" || static["GOAMD64"] != "v1" || static["GOEXPERIMENT"] != "" || static["GOCACHE"] != cache {
+		t.Fatalf("persistent static environment = %#v", static)
+	}
+}
+
+func readSettings(t *testing.T, tool *Tool, mode Mode, target Target, names ...string) map[string]string {
+	t.Helper()
+	args := append([]string{"env", "-json"}, names...)
+	output, err := tool.Run(context.Background(), t.TempDir(), mode, target, nil, args...)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var settings map[string]string
+	if err := json.Unmarshal(output, &settings); err != nil {
+		t.Fatalf("decode Go environment %q: %v", output, err)
+	}
+	return settings
+}
+
+func clearGoSettings(t *testing.T) {
+	t.Helper()
+	for _, key := range []string{
+		"GOENV", "GOFLAGS", "GOWORK", "GOTOOLCHAIN", "GOPROXY", "GONOPROXY", "GOSUMDB",
+		"GOOS", "GOARCH", "GOEXPERIMENT", "GOAMD64", "GOARM", "GOARM64", "GO386", "GOMIPS", "GOMIPS64", "GOPPC64", "GORISCV64", "GOWASM",
+		"CGO_ENABLED", "CC", "CXX", "CGO_CFLAGS", "CGO_CPPFLAGS", "CGO_CXXFLAGS", "CGO_LDFLAGS", "GOCACHE", "GOCACHEPROG", "GOMODCACHE", "GOPATH", "GOROOT", "GOTMPDIR", "PKG_CONFIG",
+	} {
+		value, exists := os.LookupEnv(key)
+		if err := os.Unsetenv(key); err != nil {
+			t.Fatal(err)
+		}
+		t.Cleanup(func() {
+			if exists {
+				_ = os.Setenv(key, value)
+			} else {
+				_ = os.Unsetenv(key)
+			}
+		})
+	}
+}

internal/process/process.go

@@ -9,16 +9,18 @@ import (
 	"os"
 	"os/exec"
 	"sort"
+	"strings"
 )
 
-// Invocation describes one child process. Environment values overlay the
+// Invocation describes one child process. UnsetEnv removes inherited values
-// current process environment for this child only.
+// before Env overlays values for this child only.
 type Invocation struct {
-	Args   []string
+	Args     []string
-	Dir    string
+	Dir      string
-	Env    map[string]string
+	Env      map[string]string
-	Stdout io.Writer
+	UnsetEnv []string
-	Stderr io.Writer
+	Stdout   io.Writer
+	Stderr   io.Writer
 }
 
 // Run starts the command in the requested directory and waits for it to exit.
@@ -30,8 +32,8 @@ func Run(ctx context.Context, invocation Invocation) error {
 
 	command := exec.CommandContext(ctx, invocation.Args[0], invocation.Args[1:]...)
 	command.Dir = invocation.Dir
-	if len(invocation.Env) != 0 {
+	if len(invocation.Env) != 0 || len(invocation.UnsetEnv) != 0 {
-		command.Env = append(os.Environ(), environmentEntries(invocation.Env)...)
+		command.Env = environmentEntries(invocation.Env, invocation.UnsetEnv)
 	}
 	command.Stdout = invocation.Stdout
 	command.Stderr = invocation.Stderr
@@ -45,7 +47,21 @@ func Run(ctx context.Context, invocation Invocation) error {
 	return nil
 }
 
-func environmentEntries(environment map[string]string) []string {
+func environmentEntries(overlay map[string]string, unset []string) []string {
+	environment := make(map[string]string, len(os.Environ())+len(overlay))
+	for _, entry := range os.Environ() {
+		key, value, ok := strings.Cut(entry, "=")
+		if ok {
+			environment[key] = value
+		}
+	}
+	for _, key := range unset {
+		delete(environment, key)
+	}
+	for key, value := range overlay {
+		environment[key] = value
+	}
+
 	keys := make([]string, 0, len(environment))
 	for key := range environment {
 		keys = append(keys, key)

internal/process/process_test.go

@@ -58,6 +58,24 @@ func TestRunPreservesExitError(t *testing.T) {
 	}
 }
 
+func TestRunCanRemoveInheritedEnvironment(t *testing.T) {
+	t.Setenv("RELEASEKIT_PROCESS_INHERITED", "inherited")
+	var stdout bytes.Buffer
+	err := Run(context.Background(), Invocation{
+		Args:     []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "argument", "success"},
+		Env:      map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
+		UnsetEnv: []string{"RELEASEKIT_PROCESS_INHERITED"},
+		Stdout:   &stdout,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := fmt.Sprintf("%s|argument||", mustGetwd(t))
+	if stdout.String() != want {
+		t.Fatalf("stdout = %q, want %q", stdout.String(), want)
+	}
+}
+
 func TestRunReportsMissingExecutable(t *testing.T) {
 	err := Run(context.Background(), Invocation{Args: []string{"releasekit-command-that-does-not-exist"}})
 	if err == nil || !strings.Contains(err.Error(), "releasekit-command-that-does-not-exist") {
@@ -143,3 +161,12 @@ func helperExecutable(t *testing.T) string {
 	}
 	return executable
 }
+
+func mustGetwd(t *testing.T) string {
+	t.Helper()
+	workdir, err := os.Getwd()
+	if err != nil {
+		t.Fatal(err)
+	}
+	return workdir
+}