Suppress the startup banner under --json (closes #106)

Entry writes the banner to stdout before cobra parses anything, and the
scan that decides whether to write it knew --quiet, -q and --cron but
not --json. Every --json document therefore arrived behind two lines of
prose and a blank line, and `vaultik snapshot list --json | jq` failed.
Passing opts.JSON as extraQuiet could not help: that reaches UI.SetQuiet
through an fx OnStart hook, long after the banner is already written.
With the logger moved to stderr in #82, this was the last writer that
could put something on stdout the caller did not ask for.

The design question the issue raised is answered in favour of extending
the raw-argv scan rather than moving the banner after parsing. The
banner is printed first deliberately, so that it still appears when
cobra rejects the arguments and on --help; after parsing there is no
single place that covers those paths, so "after parsing" means either
reimplementing the banner in several handlers or losing it exactly where
a human most wants to know which build just ran. The objection to the
scan is that --json is a subcommand flag matched anywhere in the vector,
but --cron is already in the list and is also a subcommand flag: it
exists only on `snapshot create`. So this adds another instance of an
imprecision the code already accepts, not a new kind of one. The two
error directions are not symmetric either — a false positive loses a
decorative banner, a false negative corrupts a document — so the scan
errs toward suppression, and --json=false suppresses it exactly as
--quiet=false already does.

Three tests at the CLI layer, where internal/vaultik's existing guard
cannot reach. TestEntryJSONStdoutIsExactlyOneDocument runs Entry itself
over the process's real stdout descriptor, through cobra and the fx
graph to the document, and asserts the capture decodes as one JSON value
with nothing after it; it is hermetic because file:// storage needs no
credentials and `snapshot list` treats a destination store with no
metadata/ as an empty list rather than a failure. A second covers the
argument vectors of all five --json commands plus the pre-subcommand and
--json=true forms. A third asserts the banner is still printed without a
suppressing flag, so the first cannot be satisfied by deleting it.

AGENTS.md policy 9 still keyed the structured-log format on stdout's
TTY-ness after #82 moved that decision to stderr; it now names the log
stream. A rules file that misdescribes the code misleads exactly the
readers who trust it most.

Two smaller findings from the same review. bytesAttrKey's human-readable
byte formatting stopped applying under an open group, because the key
reaching the comparison is group-qualified: "bytes" logged under a group
arrives as "transfer.bytes" and fell back to a bare number. The match is
now made on the final dot-separated segment, tested both grouped and
ungrouped. And listEnv.stderr in snapshot_list_test.go, assigned but
never read since those tests began capturing the process's stderr, is
removed. Vaultik.Stderr is kept — nothing writes to it today, which its
comment now says outright rather than leaving the next reader to hunt
for a writer that does not exist.

`prune --json` still does not survive jq, for an unrelated reason found
while verifying this: pruneLocalSnapshots writes three lines of prose to
stdout with no --json awareness, on main and after this change alike,
and -q never suppressed them either. Filed as #108 rather than fixed
here, being a different writer on a different code path.

AGENTS.md

@@ -83,8 +83,8 @@ Version: 2025-06-08
    possible to mock or stub these side-effects in tests.
 
 9. Always use structured logging.  Log any relevant state/context with the
-   messages (but do not log secrets).  If stdout is not a terminal, output
-   the structured logs in jsonl format.
+   messages (but do not log secrets).  If the log stream is not a terminal,
+   output the structured logs in jsonl format.
 
 10. Avoid using bare strings or numbers in code, especially if they appear
     anywhere more than once.  Always define a constant (usually at the top

README.md

@@ -139,6 +139,11 @@ Format follows the stream: when stderr is a terminal the records are
 colorized one-liners, and when it is redirected or piped they are
 JSON, one object per line.
 
+The startup banner is the other thing that writes to stdout, and
+`--json` suppresses it, as `--quiet` and `--cron` do. So
+`vaultik snapshot list --json | jq .` works on its own, with no
+additional flag to quiet the banner first.
+
 ### environment variables
 
 * `VAULTIK_AGE_SECRET_KEY`: Age private key for decryption (required for `snapshot restore` and `snapshot verify --deep`)

TODO.md

@@ -25,6 +25,44 @@ release" is exactly the contradiction
 
 # Completed Steps
 
+- 2026-08-09: Stopped the startup banner from contaminating `--json`
+  documents ([issue #106](https://git.eeqj.de/sneak/vaultik/issues/106)).
+  `Entry` writes the banner to stdout before cobra parses anything, and
+  the flag scan that suppresses it knew `--quiet`, `-q` and `--cron` but
+  not `--json`, so every `--json` document arrived behind two lines of
+  prose and a blank line, and `vaultik snapshot list --json | jq` failed.
+  With the logger already on stderr from
+  [issue #82](https://git.eeqj.de/sneak/vaultik/issues/82), this was the
+  last writer that could put something on stdout that the caller did not
+  ask for. The design question the issue raised — extend the raw-argv
+  scan, or move the banner after parsing — is answered in favour of the
+  scan: the banner is printed first deliberately, so that it still
+  appears when cobra rejects the arguments and on `--help`, and after
+  parsing there is no single place that covers those paths. The stated
+  cost of the scan, that `--json` is a subcommand flag matched anywhere
+  in the vector, is a cost `--cron` already carries — it exists only on
+  `snapshot create` — so this adds an instance of an accepted
+  imprecision rather than a new kind, and the two error directions are
+  not symmetric: a false positive loses a decorative banner, a false
+  negative corrupts a document. Regression tests at the CLI layer, where
+  `internal/vaultik`'s existing guard cannot reach: one runs `Entry`
+  itself over the process's real stdout descriptor, through cobra and fx
+  to the document, made hermetic by `file://` storage; a second covers
+  the argument vectors of all five `--json` commands; a third asserts the
+  banner is still printed without a suppressing flag, so the first
+  cannot be satisfied by deleting the banner. Also corrected `AGENTS.md`
+  policy 9, which still keyed the structured-log format on stdout's
+  TTY-ness after #82 moved that decision to stderr — a rules file that
+  misdescribes the code misleads exactly the readers who trust it most.
+  Two smaller findings from the same review: `bytesAttrKey`'s
+  human-readable byte formatting silently stopped applying under an open
+  group, because the key reaching the comparison is group-qualified
+  (`transfer.bytes`), now matched on its final segment and tested both
+  ways; and `listEnv.stderr` in `snapshot_list_test.go`, assigned but
+  never read since those tests began capturing the process's stderr, is
+  removed. `Vaultik.Stderr` is kept — nothing writes to it today, which
+  its comment now says outright.
+
 - 2026-08-09: Moved the logger to stderr and fixed `TTYHandler`'s
   discarded attributes
   ([issue #82](https://git.eeqj.de/sneak/vaultik/issues/82),

internal/cli/entry.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"io"
 	"os"
 	"strings"
 	"time"
@@ -14,18 +15,12 @@ import (
 const shortCommitLen = 12
 
 // Entry is the main entry point for the CLI application.
-// It prints the startup banner (unless a quiet flag is present in os.Args),
-// executes the root cobra command, and routes any returned error through
-// the ui.Writer so the user sees a properly formatted "🛑 ERROR:" line.
+// It prints the startup banner to stdout (unless a banner-suppressing
+// flag is present in os.Args — see bannerSuppressedInArgs), executes the
+// root cobra command, and routes any returned error through the
+// ui.Writer so the user sees a properly formatted "🛑 ERROR:" line.
 func Entry() {
-	if !bannerSuppressedInArgs(os.Args[1:]) {
-		short := globals.Commit
-		if len(short) > shortCommitLen {
-			short = short[:shortCommitLen]
-		}
-
-		writeStartupBanner(ui.New(os.Stdout), time.Now().UTC(), short)
-	}
+	emitStartupBanner(os.Args[1:], os.Stdout)
 
 	rootCmd := NewRootCommand()
 	rootCmd.SilenceErrors = true
@@ -37,6 +32,24 @@ func Entry() {
 	}
 }
 
+// emitStartupBanner writes the startup banner to w unless args (the
+// argument vector with the program name already stripped) contains a
+// flag that suppresses it. Split out of Entry so that the decision — the
+// only thing standing between a --json invocation and a parseable
+// stdout — is reachable from a test without running the whole CLI.
+func emitStartupBanner(args []string, w io.Writer) {
+	if bannerSuppressedInArgs(args) {
+		return
+	}
+
+	short := globals.Commit
+	if len(short) > shortCommitLen {
+		short = short[:shortCommitLen]
+	}
+
+	writeStartupBanner(ui.New(w), time.Now().UTC(), short)
+}
+
 // ReportErrorf emits a user-facing error to stderr in the standard
 // 🛑 ERROR: format. Use it from goroutine error paths (where returning
 // an error to cobra isn't an option) and anywhere else a CLI command
@@ -46,9 +59,20 @@ func ReportErrorf(format string, args ...any) {
 }
 
 // bannerSuppressedInArgs reports whether any of args is a flag that
-// should suppress the startup banner (--quiet/-q/--cron). Stops at the
-// "--" argument terminator. Recognizes both long forms and short -q,
-// including combined short flags like "-qv".
+// should suppress the startup banner (--quiet/-q/--cron/--json). Stops
+// at the "--" argument terminator. Recognizes both long forms and short
+// -q, including combined short flags like "-qv".
+//
+// This scans the raw argument vector because the banner is printed
+// before cobra parses anything — deliberately, so that it still appears
+// when cobra rejects the arguments and on --help. The consequence is
+// that a flag is matched wherever it occurs in the vector, including
+// positions where the command it belongs to would not accept it.
+// --json is a subcommand flag rather than a persistent one, but so is
+// --cron (it exists only on `snapshot create`), so this adds no new
+// class of imprecision. The only cost of a false positive is a missing
+// decorative banner; the cost of a false negative is a corrupt document
+// on stdout, so the scan errs deliberately in that direction.
 func bannerSuppressedInArgs(args []string) bool {
 	for _, a := range args {
 		if a == "--" {
@@ -56,11 +80,13 @@ func bannerSuppressedInArgs(args []string) bool {
 		}
 
 		switch a {
-		case "--quiet", "-q", "--cron":
+		case "--quiet", "-q", "--cron", "--json":
 			return true
 		}
 
-		if strings.HasPrefix(a, "--quiet=") || strings.HasPrefix(a, "--cron=") {
+		if strings.HasPrefix(a, "--quiet=") ||
+			strings.HasPrefix(a, "--cron=") ||
+			strings.HasPrefix(a, "--json=") {
 			return true
 		}
 		// Combined short flags like -qv or -vq.

internal/cli/entry_banner_test.go

@@ -0,0 +1,295 @@
+package cli //nolint:testpackage // needs access to unexported emitStartupBanner
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/adrg/xdg"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+// Command words and flags used to build argument vectors below. They are
+// constants rather than repeated literals so that a rename shows up as a
+// compile error in one place.
+const (
+	cmdSnapshot = "snapshot"
+	cmdList     = "list"
+	cmdCreate   = "create"
+	cmdVerify   = "verify"
+	cmdRemove   = "remove"
+	cmdPrune    = "prune"
+	cmdRemote   = "remote"
+	cmdInfo     = "info"
+
+	flagJSON  = "--json"
+	flagQuiet = "--quiet"
+
+	// someSnapshotID is any snapshot identifier: these tests never run
+	// the command, so it only has to occupy the positional argument.
+	someSnapshotID = "host_2026-01-01T00:00:00Z"
+)
+
+// placeholderJSONDocument stands in for whatever document a --json
+// command writes to stdout. `snapshot list --json` with no snapshots
+// prints exactly this; the other --json commands print an object rather
+// than an array, but this test is not about their shape. It is about
+// what is on stdout *before* them, which is the same for all of them
+// because Entry prints the banner before cobra has parsed anything and
+// therefore before it can know which command is running.
+const placeholderJSONDocument = "[]\n"
+
+// jsonArgumentVectors are the argument vectors of every --json
+// invocation the CLI accepts, with the program name stripped exactly as
+// Entry strips it. Each one must leave stdout untouched by the banner.
+//
+//nolint:gochecknoglobals // read-only test fixture shared by two tests
+var jsonArgumentVectors = map[string][]string{
+	"snapshot list":   {cmdSnapshot, cmdList, flagJSON},
+	"snapshot verify": {cmdSnapshot, cmdVerify, someSnapshotID, flagJSON},
+	"snapshot remove": {cmdSnapshot, cmdRemove, someSnapshotID, flagJSON},
+	"prune":           {cmdPrune, flagJSON},
+	"remote info":     {cmdRemote, cmdInfo, flagJSON},
+
+	// --json before the subcommand, and with an explicit value: the
+	// scan is positional, so both forms have to be recognized.
+	"json first":      {flagJSON, cmdSnapshot, cmdList},
+	"json with value": {cmdSnapshot, cmdList, flagJSON + "=true"},
+
+	// A --json invocation that also carries a flag with a value, so the
+	// scan cannot be fooled by an argument that consumes the next one.
+	"json with config": {
+		"--config", "/nonexistent/vaultik.yml", cmdSnapshot, cmdList, flagJSON,
+	},
+}
+
+// TestJSONInvocationStdoutIsExactlyOneDocument is the CLI-layer
+// regression guard for issue #106: `vaultik snapshot list --json | jq`
+// must work with no other flags.
+//
+// internal/vaultik's TestListSnapshots_JSONStdoutIsOnlyTheDocument
+// guards the same contract one layer down, but it calls the library
+// function directly and so cannot see Entry, which is where the
+// contamination was: the startup banner is written to stdout before
+// cobra parses anything, and the suppression scan did not know about
+// --json. The two banner lines and the blank line landed ahead of the
+// document and `jq` refused the result.
+//
+// The document is a constant here because this test is about the
+// argument vectors, one per --json command; the one that runs a real
+// command end to end is TestEntryJSONStdoutIsExactlyOneDocument below.
+func TestJSONInvocationStdoutIsExactlyOneDocument(t *testing.T) {
+	t.Parallel()
+
+	for name, argv := range jsonArgumentVectors {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			var stdout bytes.Buffer
+
+			emitStartupBanner(argv, &stdout)
+
+			require.Empty(t, stdout.String(),
+				"nothing may reach stdout ahead of a --json document")
+
+			_, err := stdout.WriteString(placeholderJSONDocument)
+			require.NoError(t, err)
+
+			requireExactlyOneJSONDocument(t, stdout.String())
+		})
+	}
+}
+
+// TestBannerStillPrintedWithoutSuppressingFlag pins the other half of
+// the contract. Without it, deleting the banner outright would satisfy
+// the test above, and the banner is wanted on interactive invocations.
+func TestBannerStillPrintedWithoutSuppressingFlag(t *testing.T) {
+	t.Parallel()
+
+	for name, argv := range map[string][]string{
+		"no flags": {cmdSnapshot, cmdList},
+		"verbose":  {cmdSnapshot, cmdList, "--verbose"},
+		"after the terminator": {
+			cmdSnapshot, "restore", "--", flagJSON,
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			var stdout bytes.Buffer
+
+			emitStartupBanner(argv, &stdout)
+
+			assert.Contains(t, stdout.String(), "starting up at",
+				"the banner belongs on invocations that did not opt out")
+		})
+	}
+}
+
+// TestBannerSuppressedInArgs covers the suppression scan directly,
+// including the flags that suppressed the banner before --json joined
+// them, so that adding --json cannot regress them.
+func TestBannerSuppressedInArgs(t *testing.T) {
+	t.Parallel()
+
+	for name, testCase := range map[string]struct {
+		args       []string
+		suppressed bool
+	}{
+		"quiet long":     {[]string{cmdSnapshot, cmdCreate, flagQuiet}, true},
+		"quiet short":    {[]string{cmdSnapshot, cmdCreate, "-q"}, true},
+		"quiet combined": {[]string{cmdSnapshot, cmdCreate, "-qv"}, true},
+		"cron":           {[]string{cmdSnapshot, cmdCreate, "--cron"}, true},
+		"json":           {[]string{cmdSnapshot, cmdList, flagJSON}, true},
+		"nothing":        {[]string{cmdSnapshot, cmdList}, false},
+		"empty":          {nil, false},
+		"json after dashes": {
+			[]string{cmdSnapshot, cmdList, "--", flagJSON}, false,
+		},
+		"quiet after dashes": {
+			[]string{cmdSnapshot, cmdCreate, "--", "-q"}, false,
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			assert.Equal(t, testCase.suppressed,
+				bannerSuppressedInArgs(testCase.args))
+		})
+	}
+}
+
+// hermeticConfig is a complete, valid config that needs no network and
+// no credentials: file:// storage is exempt from the S3 credential
+// checks, and FileStorer over a directory that does not exist lists
+// zero objects without erroring. Chunk, blob and compression settings
+// are filled in by config.Load.
+const hermeticConfig = `age_recipients:
+  - age1278m9q7dp3chsh2dcy82qk27v047zywyvtxwnj4cvt0z65jw6a7q5dqhfj
+snapshots:
+  test:
+    paths:
+      - %s
+storage_url: file://%s
+index_path: %s
+hostname: test-host
+`
+
+// TestEntryJSONStdoutIsExactlyOneDocument runs the real thing: Entry,
+// with a real argument vector, over the process's real stdout file
+// descriptor, all the way through cobra and the fx graph to the
+// document. It is the assertion the issue asks for — `vaultik snapshot
+// list --json | jq .` with no other flags — with the pipe replaced by a
+// decoder.
+//
+// `snapshot list` is the command chosen because it is the only --json
+// command that reaches its document without a populated destination
+// store: it reads the local index, streams `metadata/` (empty here),
+// and treats a barren destination as an empty list rather than a
+// failure.
+//
+// Not parallel: it replaces os.Args, os.Stdout and the xdg globals.
+func TestEntryJSONStdoutIsExactlyOneDocument(t *testing.T) {
+	dir := t.TempDir()
+	configPath := filepath.Join(dir, "config.yml")
+
+	contents := fmt.Sprintf(hermeticConfig,
+		filepath.Join(dir, "source"),
+		filepath.Join(dir, "store"),
+		filepath.Join(dir, "index.sqlite"))
+
+	require.NoError(t,
+		os.WriteFile(configPath, []byte(contents), configFileMode))
+
+	// The PID lock lives under xdg.DataHome, which xdg resolves at
+	// package init; point it at the temp dir so the test neither
+	// touches nor collides with the real one.
+	t.Setenv("XDG_DATA_HOME", filepath.Join(dir, "data"))
+	xdg.Reload()
+	t.Cleanup(xdg.Reload)
+
+	previousArgs := os.Args
+
+	t.Cleanup(func() {
+		os.Args = previousArgs
+		rootFlags = RootFlags{}
+	})
+
+	os.Args = []string{
+		"vaultik", "--config", configPath, cmdSnapshot, cmdList, flagJSON,
+	}
+
+	stdout := captureProcessStdout(t, Entry)
+
+	requireExactlyOneJSONDocument(t, stdout)
+
+	var snapshots []any
+
+	require.NoError(t, json.Unmarshal([]byte(stdout), &snapshots))
+	assert.Empty(t, snapshots,
+		"a destination store with no snapshots lists none")
+}
+
+// captureProcessStdout redirects the process's own stdout to a pipe for
+// the duration of fn and returns what was written to it. The redirection
+// has to be at the file-descriptor level rather than through an injected
+// writer, because the banner and the JSON encoder reach os.Stdout
+// independently and the point of the test is that both land in the same
+// place.
+//
+// Not parallel-safe: os.Stdout is process-global.
+func captureProcessStdout(t *testing.T, fn func()) string {
+	t.Helper()
+
+	reader, writer, err := os.Pipe()
+	require.NoError(t, err)
+
+	previous := os.Stdout
+	os.Stdout = writer
+
+	captured := make(chan string, 1)
+
+	go func() {
+		var buf bytes.Buffer
+
+		_, _ = io.Copy(&buf, reader)
+		captured <- buf.String()
+	}()
+
+	fn()
+
+	os.Stdout = previous
+
+	require.NoError(t, writer.Close())
+
+	out := <-captured
+
+	require.NoError(t, reader.Close())
+
+	return out
+}
+
+// requireExactlyOneJSONDocument fails unless stdout decodes as a single
+// JSON value with nothing before or after it — the property that makes
+// `| jq` work.
+func requireExactlyOneJSONDocument(t *testing.T, stdout string) {
+	t.Helper()
+
+	decoder := json.NewDecoder(strings.NewReader(stdout))
+
+	var document any
+
+	err := decoder.Decode(&document)
+	require.NoError(t, err,
+		"stdout must parse as JSON, got:\n%s", stdout)
+
+	_, err = decoder.Token()
+	require.ErrorIs(t, err, io.EOF,
+		"stdout must hold exactly one JSON document, got:\n%s", stdout)
+}

internal/log/tty_handler.go

@@ -16,9 +16,23 @@ import (
 const groupSeparator = "."
 
 // bytesAttrKey is the attribute key whose int64 value is rendered as a
-// human-readable byte count rather than a bare number.
+// human-readable byte count rather than a bare number. Keys reaching
+// writeAttr are group-qualified, so the match is made against the final
+// dot-separated segment: without that, a "bytes" attribute logged under
+// an open group would arrive as "transfer.bytes" and silently lose its
+// formatting.
 const bytesAttrKey = "bytes"
 
+// isBytesAttr reports whether a group-qualified attribute key names the
+// byte-count attribute, i.e. whether its last segment is bytesAttrKey.
+func isBytesAttr(key string) bool {
+	if idx := strings.LastIndex(key, groupSeparator); idx >= 0 {
+		key = key[idx+len(groupSeparator):]
+	}
+
+	return key == bytesAttrKey
+}
+
 // ANSI color codes
 const (
 	colorReset  = "\033[0m"
@@ -236,7 +250,7 @@ func (h *TTYHandler) writeAttr(a slog.Attr) {
 			value = formatDuration(d)
 		}
 	case slog.KindInt64:
-		if a.Key == bytesAttrKey {
+		if isBytesAttr(a.Key) {
 			value = formatBytes(a.Value.Int64())
 		}
 	case slog.KindAny, slog.KindBool, slog.KindFloat64, slog.KindString,

internal/log/tty_handler_test.go

@@ -190,6 +190,51 @@ func TestTTYHandlerWithGroupQualifiesKeys(t *testing.T) {
 	assert.NotContains(t, attrs, "rows")
 }
 
+// TestTTYHandlerByteFormattingSurvivesGrouping guards the interaction
+// between the two features. The human-readable rendering of a "bytes"
+// attribute is selected by comparing the key, and keys reaching that
+// comparison are group-qualified, so a "bytes" attribute logged under an
+// open group arrived as "transfer.bytes" and fell back to a bare number.
+// No caller groups a byte count today, which is exactly why this needs a
+// test rather than a bug report.
+func TestTTYHandlerByteFormattingSurvivesGrouping(t *testing.T) {
+	t.Parallel()
+
+	const oneAndAHalfKiB = 1536
+
+	for name, testCase := range map[string]struct {
+		derive func(*slog.Logger) *slog.Logger
+		key    string
+	}{
+		"ungrouped": {
+			derive: func(l *slog.Logger) *slog.Logger { return l },
+			key:    "bytes",
+		},
+		"grouped": {
+			derive: func(l *slog.Logger) *slog.Logger {
+				return l.WithGroup("transfer")
+			},
+			key: "transfer.bytes",
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			var buf bytes.Buffer
+
+			logger := slog.New(log.NewTTYHandler(&buf, debugHandlerOptions()))
+			testCase.derive(logger).Info("uploaded", "bytes", oneAndAHalfKiB)
+
+			line := ansiEscape.ReplaceAllString(buf.String(), "")
+
+			assert.Contains(t, line, testCase.key+"=1.5 KB",
+				"a byte count must be human-readable however it is qualified")
+			assert.NotContains(t, line, strconv.Itoa(oneAndAHalfKiB),
+				"the raw number must not survive the formatting")
+		})
+	}
+}
+
 // TestTTYHandlerMatchesJSONHandlerAttributes is the drift guard. The
 // handler is chosen by TTY-ness, so a difference between these two is
 // invisible in whichever environment the developer is not in — which is

internal/vaultik/snapshot_list_test.go

@@ -108,7 +108,6 @@ type listEnv struct {
 	v      *vaultik.Vaultik
 	store  *observingStorer
 	stdout *bytes.Buffer
-	stderr *bytes.Buffer
 }
 
 func newListEnv(t *testing.T) *listEnv {
@@ -122,7 +121,6 @@ func newListEnv(t *testing.T) *listEnv {
 
 	store := newObservingStorer()
 	stdout := &bytes.Buffer{}
-	stderr := &bytes.Buffer{}
 
 	v := &vaultik.Vaultik{
 		Config: &config.Config{
@@ -135,13 +133,13 @@ func newListEnv(t *testing.T) *listEnv {
 		Repositories: database.NewRepositories(db),
 		DB:           db,
 		Stdout:       stdout,
-		Stderr:       stderr,
+		Stderr:       &bytes.Buffer{},
 		Stdin:        &bytes.Buffer{},
 		UI:           ui.NewWithColor(stdout, false),
 	}
 	v.SetContext(ctx)
 
-	return &listEnv{v: v, store: store, stdout: stdout, stderr: stderr}
+	return &listEnv{v: v, store: store, stdout: stdout}
 }
 
 // addLocal inserts a completed snapshot into the local index.

internal/vaultik/vaultik.go

@@ -47,7 +47,11 @@ type Vaultik struct {
 	// so that `--json | jq` works. Stderr completes the standard triple
 	// for anything a command needs to write there directly; diagnostics
 	// are not that — they go through internal/log, which writes to the
-	// process's stderr.
+	// process's stderr. No production code writes to Stderr today, so
+	// searching for its writers turns up nothing; it is kept as the
+	// injection point a direct stderr write would otherwise have to
+	// invent, and removing it would make the triple asymmetric for no
+	// gain.
 	Stdout io.Writer
 	Stderr io.Writer
 	Stdin  io.Reader