diff --git a/internal/cli/check.go b/internal/cli/check.go
index b629a93..534f57b 100644
--- a/internal/cli/check.go
+++ b/internal/cli/check.go
@@ -108,7 +108,7 @@ func (mfa *CLIApp) fetchManifestToTemp(
 	if tmpErr != nil {
 		_ = rc.Close()
 
-		return "", fmt.Errorf("failed to create temp file: %w", tmpErr)
+		return "", tmpErr
 	}
 
 	tmpPath := tmpFile.Name()
@@ -126,7 +126,7 @@ func (mfa *CLIApp) fetchManifestToTemp(
 	if cpErr != nil {
 		_ = mfa.Fs.Remove(tmpPath)
 
-		return "", fmt.Errorf("failed to download manifest: %w", cpErr)
+		return "", fmt.Errorf("download manifest: %w", cpErr)
 	}
 
 	return tmpPath, nil
@@ -142,7 +142,7 @@ func verifyRequiredSigner(chk *mfer.Checker, requiredSigner string) error {
 
 	_, err := hex.DecodeString(requiredSigner)
 	if err != nil {
-		return fmt.Errorf("invalid fingerprint: must be valid hex: %w", err)
+		return fmt.Errorf("invalid fingerprint: %w", err)
 	}
 
 	if !chk.IsSigned() {
@@ -232,7 +232,7 @@ func findExtraFiles(
 
 	err := chk.FindExtraFiles(ctx, extraResults)
 	if err != nil {
-		return fmt.Errorf("failed to check for extra files: %w", err)
+		return fmt.Errorf("find extra files: %w", err)
 	}
 
 	<-extraDone
@@ -275,7 +275,7 @@ func runCheck(
 	progressWg.Wait()
 
 	if err != nil {
-		return 0, fmt.Errorf("check failed: %w", err)
+		return 0, fmt.Errorf("check files: %w", err)
 	}
 
 	// Wait for results processing to complete
@@ -296,14 +296,14 @@ func (mfa *CLIApp) checkManifestOperation(
 
 	manifestPath, err := mfa.resolveManifestArg(cmd)
 	if err != nil {
-		return fmt.Errorf("check: %w", err)
+		return err
 	}
 
 	// URL manifests need to be downloaded to a temp file for the checker
 	if isHTTPURL(manifestPath) {
 		tmpPath, tmpErr := mfa.fetchManifestToTemp(ctx, manifestPath)
 		if tmpErr != nil {
-			return fmt.Errorf("check: %w", tmpErr)
+			return tmpErr
 		}
 
 		defer func() { _ = mfa.Fs.Remove(tmpPath) }()
@@ -324,7 +324,7 @@ func (mfa *CLIApp) checkManifestOperation(
 		Fs:           mfa.Fs,
 	})
 	if err != nil {
-		return fmt.Errorf("failed to load manifest: %w", err)
+		return fmt.Errorf("load manifest: %w", err)
 	}
 
 	// Check signature requirement
diff --git a/internal/cli/entry_test.go b/internal/cli/entry_test.go
index dabfb17..d12a1c6 100644
--- a/internal/cli/entry_test.go
+++ b/internal/cli/entry_test.go
@@ -382,7 +382,7 @@ func TestGenerateRefusesTwoFilesAtOnePath(t *testing.T) {
 			}, fs)
 			assert.Equal(t, 1, runCLI(opts))
 			assert.Contains(t, testStderr(t, opts),
-				`generate: failed to enumerate paths: duplicate path "a.txt": `+
+				`enumerate files: duplicate path "a.txt": `+
 					tc.first+"/a.txt and "+tc.second+"/a.txt")
 
 			exists, err := afero.Exists(fs, testOutput)
@@ -674,7 +674,7 @@ func TestCheckRequireSignatureRefusesOtherSigningKey(t *testing.T) {
 	}, fs)
 	assert.Equal(t, 1, runCLI(opts))
 	assert.Contains(t, testStderr(t, opts),
-		"failed to load manifest: signature verification failed: "+
+		"load manifest: "+
 			"embedded public key block must hold exactly one key, found 2")
 }
 
diff --git a/internal/cli/errmsg_test.go b/internal/cli/errmsg_test.go
index 9b65ecf..ac5fb5f 100644
--- a/internal/cli/errmsg_test.go
+++ b/internal/cli/errmsg_test.go
@@ -303,7 +303,7 @@ func TestManifestLoaderHTTPStatusMessage(t *testing.T) {
 	_, err := mfa.openManifestReader(context.Background(), server.URL+"/foo.mf")
 	require.ErrorIs(t, err, errHTTPStatus)
 	assert.EqualError(t, err,
-		"failed to fetch "+server.URL+"/foo.mf: HTTP 404")
+		"download manifest "+server.URL+"/foo.mf: unexpected HTTP status 404")
 }
 
 func TestFetchManifestHTTPStatusMessage(t *testing.T) {
@@ -325,7 +325,7 @@ func TestFetchManifestHTTPStatusMessage(t *testing.T) {
 		return cmd.Run(context.Background(), []string{cmdFetch, server.URL})
 	})
 	require.ErrorIs(t, err, errHTTPStatus)
-	assert.EqualError(t, err, "failed to fetch manifest: HTTP 404")
+	assert.EqualError(t, err, "download manifest: unexpected HTTP status 404")
 }
 
 func TestFetchFileHTTPStatusMessage(t *testing.T) {
@@ -343,7 +343,108 @@ func TestFetchFileHTTPStatusMessage(t *testing.T) {
 			&mfer.MFFilePath{}, nil)
 	})
 	require.ErrorIs(t, err, errHTTPStatus)
-	assert.EqualError(t, err, "HTTP 500")
+	assert.EqualError(t, err, "unexpected HTTP status 500")
+}
+
+// TestCheckCorruptManifestMessage runs check on a file that is not a
+// manifest.
+func TestCheckCorruptManifestMessage(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewMemMapFs()
+	require.NoError(t, afero.WriteFile(fs, "/bad.mf", []byte("not a manifest"), 0o644))
+
+	mfa := &CLIApp{Fs: fs}
+	cmd := mfa.checkCommand()
+	cmd.Action = mfa.checkManifestOperation
+
+	// checkManifestOperation logs to the process-global logger.
+	err := runLocked(func() error {
+		return cmd.Run(context.Background(), []string{cmdCheck, "/bad.mf"})
+	})
+	assert.EqualError(t, err, "load manifest: invalid file format")
+}
+
+// TestListMissingManifestMessage runs list on a manifest file that does not
+// exist.
+func TestListMissingManifestMessage(t *testing.T) {
+	t.Parallel()
+
+	mfa := &CLIApp{Fs: afero.NewMemMapFs()}
+	cmd := mfa.listCommand()
+
+	// listManifestOperation sets the process-global log level.
+	err := runLocked(func() error {
+		return cmd.Run(context.Background(), []string{cmdList, "/nope.mf"})
+	})
+	require.ErrorIs(t, err, os.ErrNotExist)
+	assert.EqualError(t, err, "open /nope.mf: file does not exist")
+}
+
+// TestFetchHashMismatchMessage runs fetch against a server that sends a
+// listed file with other content of the same size.
+func TestFetchHashMismatchMessage(t *testing.T) {
+	t.Parallel()
+
+	manifest := builtManifest(t, map[string][]byte{testFileTxt: []byte("listed")})
+
+	server := httptest.NewServer(fetchTestHandler(manifest,
+		map[string][]byte{testFileTxt: []byte("served")}))
+	defer server.Close()
+
+	mfa := &CLIApp{Fs: afero.NewMemMapFs(), maxManifestSize: mfer.MaxManifestSize}
+	cmd := mfa.fetchCommand()
+	cmd.Action = mfa.fetchManifestOperation
+
+	// fetchManifestOperation logs to the process-global logger.
+	err := runLocked(func() error {
+		return cmd.Run(context.Background(),
+			[]string{cmdFetch, "--" + flagDest, t.TempDir(), server.URL})
+	})
+	require.ErrorIs(t, err, errHashMismatch)
+	assert.EqualError(t, err, "download "+testFileTxt+": hash mismatch")
+}
+
+// TestFreshenBackslashPathMessage runs freshen on a tree that has gained a
+// file whose name holds a backslash, which a manifest path may not contain.
+func TestFreshenBackslashPathMessage(t *testing.T) {
+	t.Parallel()
+
+	fs := afero.NewOsFs()
+	root, manifestPath := setupFreshenDir(t, fs,
+		map[string]string{testFileTxt: "content"})
+	writeTestFile(t, fs, filepath.Join(root, `a\b.txt`), "new")
+
+	mfa := &CLIApp{Fs: fs}
+	cmd := mfa.freshenCommand()
+	cmd.Action = mfa.freshenManifestOperation
+
+	// freshenManifestOperation logs to the process-global logger.
+	err := runLocked(func() error {
+		return cmd.Run(context.Background(),
+			[]string{cmdFreshen, testFlagBase, root, manifestPath})
+	})
+	assert.EqualError(t, err,
+		`path "a\\b.txt" contains backslash; use forward slashes only`)
+}
+
+// TestFreshenReadErrorMessage has freshen hash a directory as though it
+// were a file, so reading it fails.
+func TestFreshenReadErrorMessage(t *testing.T) {
+	t.Parallel()
+
+	root := t.TempDir()
+	require.NoError(t, os.Mkdir(filepath.Join(root, "sub"), 0o750))
+
+	hasher := &freshenHasher{
+		fs:      afero.NewOsFs(),
+		absBase: root,
+		builder: mfer.NewBuilder(),
+	}
+
+	err := hasher.processEntry(&freshenEntry{path: "sub", needsHash: true})
+	assert.EqualError(t, err,
+		"read "+filepath.Join(root, "sub")+": is a directory")
 }
 
 func TestURLRequiredMessage(t *testing.T) {
diff --git a/internal/cli/export.go b/internal/cli/export.go
index 8f9d2c0..d537039 100644
--- a/internal/cli/export.go
+++ b/internal/cli/export.go
@@ -26,12 +26,12 @@ func (mfa *CLIApp) exportManifestOperation(
 ) error {
 	pathOrURL, err := mfa.resolveManifestArg(cmd)
 	if err != nil {
-		return fmt.Errorf("export: %w", err)
+		return err
 	}
 
 	rc, err := mfa.openManifestReader(ctx, pathOrURL)
 	if err != nil {
-		return fmt.Errorf("export: %w", err)
+		return err
 	}
 
 	defer func() { _ = rc.Close() }()
@@ -39,7 +39,7 @@ func (mfa *CLIApp) exportManifestOperation(
 	//nolint:contextcheck // mfer loads a manifest without a context
 	manifest, err := mfer.NewManifestFromReader(rc)
 	if err != nil {
-		return fmt.Errorf("export: failed to parse manifest: %w", err)
+		return fmt.Errorf("parse manifest: %w", err)
 	}
 
 	files := manifest.Files()
@@ -76,7 +76,7 @@ func (mfa *CLIApp) exportManifestOperation(
 
 	err = enc.Encode(entries)
 	if err != nil {
-		return fmt.Errorf("export: failed to encode JSON: %w", err)
+		return fmt.Errorf("encode JSON: %w", err)
 	}
 
 	return nil
diff --git a/internal/cli/fetch.go b/internal/cli/fetch.go
index 0244d67..8b0f569 100644
--- a/internal/cli/fetch.go
+++ b/internal/cli/fetch.go
@@ -239,7 +239,7 @@ func reportDownloadProgress(progress <-chan DownloadProgress, done chan<- struct
 func manifestBaseURL(manifestURL string) (*url.URL, error) {
 	parsed, err := url.Parse(manifestURL)
 	if err != nil {
-		return nil, fmt.Errorf("fetch: invalid manifest URL: %w", err)
+		return nil, fmt.Errorf("invalid manifest URL: %w", err)
 	}
 
 	// JoinPath cleans the path it builds, so ".." drops the manifest's
@@ -268,7 +268,7 @@ func downloadManifestFiles(
 		// Sanitize the path to prevent path traversal attacks
 		localPath, err := sanitizePath(f.GetPath())
 		if err != nil {
-			return 0, 0, fmt.Errorf("invalid path in manifest: %w", err)
+			return 0, 0, fmt.Errorf("invalid file entry: %w", err)
 		}
 
 		if alreadyPresent(dest, localPath, f) {
@@ -284,7 +284,7 @@ func downloadManifestFiles(
 
 		err = downloadFile(ctx, client, fileURL, dest, localPath, f, progress)
 		if err != nil {
-			return 0, 0, fmt.Errorf("failed to download %s: %w", f.GetPath(), err)
+			return 0, 0, fmt.Errorf("download %s: %w", f.GetPath(), err)
 		}
 
 		downloaded++
@@ -376,7 +376,7 @@ func (mfa *CLIApp) fetchManifestOperation(
 
 	err = os.MkdirAll(dest, dirPerms)
 	if err != nil {
-		return fmt.Errorf("failed to create destination directory %s: %w", dest, err)
+		return err
 	}
 
 	// Create progress channel and start progress reporter goroutine
@@ -403,7 +403,7 @@ func (mfa *CLIApp) fetchManifestOperation(
 	// "mfer check" can verify the tree later.
 	err = saveManifest(dest, manifestData)
 	if err != nil {
-		return fmt.Errorf("failed to save manifest: %w", err)
+		return fmt.Errorf("save manifest: %w", err)
 	}
 
 	// Print summary
@@ -446,11 +446,11 @@ func (mfa *CLIApp) fetchManifest(
 		return readErr
 	})
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to fetch manifest: %w", err)
+		return nil, nil, fmt.Errorf("download manifest: %w", err)
 	}
 
 	if int64(len(manifestData)) > mfa.maxManifestSize {
-		return nil, nil, fmt.Errorf("failed to fetch manifest: %w of %d bytes",
+		return nil, nil, fmt.Errorf("download manifest: %w of %d bytes",
 			errManifestTooLarge, mfa.maxManifestSize)
 	}
 
@@ -458,7 +458,7 @@ func (mfa *CLIApp) fetchManifest(
 	//nolint:contextcheck // mfer loads a manifest without a context
 	manifest, err := mfer.NewManifestFromReader(bytes.NewReader(manifestData))
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to parse manifest: %w", err)
+		return nil, nil, fmt.Errorf("parse manifest: %w", err)
 	}
 
 	requiredSigner := cmd.String(flagRequireSignature)
@@ -561,7 +561,7 @@ func verifyFetchedSigner(manifestData []byte, requiredSigner string) error {
 		Fs:           memFs,
 	})
 	if err != nil {
-		return fmt.Errorf("failed to load manifest: %w", err)
+		return fmt.Errorf("load manifest: %w", err)
 	}
 
 	return verifyRequiredSigner(chk, requiredSigner)
@@ -653,7 +653,7 @@ func checkNoSymlinks(dest, p string) error {
 		}
 
 		if err != nil {
-			return fmt.Errorf("failed to check %s for a symlink: %w", current, err)
+			return err
 		}
 
 		if info.Mode()&os.ModeSymlink != 0 {
@@ -770,7 +770,7 @@ func tempPathFor(localPath string) string {
 func verifyDownloadedHash(digest []byte, entry *mfer.MFFilePath) error {
 	computed, err := multihash.Encode(digest, multihash.SHA2_256)
 	if err != nil {
-		return fmt.Errorf("failed to encode hash: %w", err)
+		return fmt.Errorf("encode hash: %w", err)
 	}
 
 	for _, hash := range entry.GetHashes() {
@@ -797,7 +797,7 @@ func downloadFile(
 	// so every entry point to downloadFile gets the same treatment.
 	localPath, err := sanitizePath(localPath)
 	if err != nil {
-		return fmt.Errorf("invalid path: %w", err)
+		return fmt.Errorf("invalid file entry: %w", err)
 	}
 
 	// Create parent directories if needed
@@ -812,7 +812,7 @@ func downloadFile(
 
 		err = os.MkdirAll(dir, dirPerms)
 		if err != nil {
-			return fmt.Errorf("failed to create directory %s: %w", dir, err)
+			return err
 		}
 	}
 
@@ -846,7 +846,7 @@ func createTempFile(dest, tmpPath string) (*os.File, error) {
 	out, err := os.OpenFile( //nolint:gosec // G304: see comment above
 		path, os.O_RDWR|os.O_CREATE|os.O_EXCL, filePerms)
 	if err != nil {
-		return nil, fmt.Errorf("failed to create temp file: %w", err)
+		return nil, err
 	}
 
 	return out, nil
@@ -859,12 +859,7 @@ func moveIntoPlace(dest, tmpPath, localPath string) error {
 		return err
 	}
 
-	err = os.Rename(filepath.Join(dest, tmpPath), filepath.Join(dest, localPath))
-	if err != nil {
-		return fmt.Errorf("failed to rename temp file: %w", err)
-	}
-
-	return nil
+	return os.Rename(filepath.Join(dest, tmpPath), filepath.Join(dest, localPath))
 }
 
 // saveResponse writes resp's body to tmpPath, verifies it against entry,
@@ -899,7 +894,7 @@ func saveResponse(
 			_ = out.Close()
 			_ = os.Remove(filepath.Join(dest, tmpPath))
 
-			return fmt.Errorf("failed to set mode: %w", err)
+			return err
 		}
 	}
 
diff --git a/internal/cli/fetch_test.go b/internal/cli/fetch_test.go
index bb79298..8d61b20 100644
--- a/internal/cli/fetch_test.go
+++ b/internal/cli/fetch_test.go
@@ -502,8 +502,9 @@ func TestManifestDownloadStopsAtLimit(t *testing.T) {
 				[]string{cmd.Name, server.URL + "/index.mf"})
 		})
 		require.ErrorIs(t, err, errManifestTooLarge, cmd.Name)
-		require.ErrorContains(t, err,
-			"maximum allowed size of 65536 bytes", cmd.Name)
+		require.EqualError(t, err,
+			"download manifest: file exceeds maximum allowed size of 65536 bytes",
+			cmd.Name)
 	}
 
 	leftover, err := os.ReadDir(tmpDir)
@@ -605,27 +606,27 @@ func TestFetchRefusesSymlinks(t *testing.T) {
 	}{
 		{
 			"parent directory", "sub/deeper/file.txt", "sub", ".",
-			"failed to download sub/deeper/file.txt",
+			"download sub/deeper/file.txt",
 		},
 		{
 			"directory inside a plain directory", "docs/data/passwd", "docs/data", ".",
-			"failed to download docs/data/passwd",
+			"download docs/data/passwd",
 		},
 		{
 			"temp file", testFileTxt, ".file.txt.tmp", newFile,
-			"failed to download " + testFileTxt,
+			"download " + testFileTxt,
 		},
 		{
 			"file", testFileTxt, testFileTxt, newFile,
-			"failed to download " + testFileTxt,
+			"download " + testFileTxt,
 		},
 		{
 			"manifest temp file", testFileTxt, tempPathFor(defaultManifestName), newFile,
-			"failed to save manifest",
+			"save manifest",
 		},
 		{
 			"manifest", testFileTxt, defaultManifestName, newFile,
-			"failed to save manifest",
+			"save manifest",
 		},
 	}
 
@@ -692,7 +693,7 @@ func TestFetchDoesNotSkipThroughSymlink(t *testing.T) {
 	}, afero.NewOsFs())
 	assert.Equal(t, 1, runCLI(opts))
 	assert.Contains(t, testStderr(t, opts),
-		"failed to download sub/"+testFileTxt+": symlink in path not allowed: "+link)
+		"download sub/"+testFileTxt+": symlink in path not allowed: "+link)
 	assert.Equal(t, map[string][]byte{testFileTxt: content}, filesUnder(t, outside))
 }
 
@@ -762,7 +763,8 @@ func TestGetRetriesTransientStatusesOnly(t *testing.T) {
 
 			err := getNothing(testClient(), server.URL, 10*time.Second)
 			require.ErrorIs(t, err, errHTTPStatus)
-			require.EqualError(t, err, fmt.Sprintf("HTTP %d", tt.status))
+			require.EqualError(t, err,
+				fmt.Sprintf("unexpected HTTP status %d", tt.status))
 			assert.Equal(t, tt.requests, requests.Load())
 		})
 	}
@@ -1228,7 +1230,7 @@ func TestFetchRequireSignature(t *testing.T) {
 		manifest, required := manifestSignedByAnotherKey(t, files)
 
 		assertFetchRefused(t, manifest, files,
-			"failed to parse manifest: signature verification failed: "+
+			"parse manifest: "+
 				"embedded public key block must hold exactly one key, found 2",
 			"--"+flagRequireSignature, required)
 	})
diff --git a/internal/cli/freshen.go b/internal/cli/freshen.go
index e39fbb5..8a1e0a7 100644
--- a/internal/cli/freshen.go
+++ b/internal/cli/freshen.go
@@ -165,8 +165,7 @@ func (s *freshenScanner) walk(path string, info fs.FileInfo, walkErr error) erro
 	// Get relative path
 	relPath, err := filepath.Rel(s.absBase, path)
 	if err != nil {
-		return fmt.Errorf(
-			"freshen: failed to compute relative path for %s: %w", path, err)
+		return err
 	}
 
 	// Handle dotfiles
@@ -280,13 +279,8 @@ func (h *freshenHasher) reportProgress(n int64) {
 // processEntry hashes the entry if needed and adds it to the builder.
 func (h *freshenHasher) processEntry(e *freshenEntry) error {
 	if !e.needsHash {
-		// Use existing entry
-		err := addExistingToBuilder(h.builder, e.existing)
-		if err != nil {
-			return fmt.Errorf("failed to add %s: %w", e.path, err)
-		}
-
-		return nil
+		// Use existing entry; the error names the entry
+		return addExistingToBuilder(h.builder, e.existing)
 	}
 
 	// Need to read and hash the file
@@ -294,26 +288,21 @@ func (h *freshenHasher) processEntry(e *freshenEntry) error {
 
 	f, err := h.fs.Open(absPath)
 	if err != nil {
-		return fmt.Errorf("failed to open %s: %w", e.path, err)
+		return err
 	}
 
 	hash, bytesRead, err := hashFile(f, h.reportProgress)
 	_ = f.Close()
 
 	if err != nil {
-		return fmt.Errorf("failed to hash %s: %w", e.path, err)
+		return err
 	}
 
 	h.hashedBytes += bytesRead
 	h.hashedFiles++
 
-	// Add to builder with computed hash
-	err = addFileToBuilder(h.builder, e.path, e.size, e.mtime, e.mode, hash)
-	if err != nil {
-		return fmt.Errorf("failed to add %s: %w", e.path, err)
-	}
-
-	return nil
+	// Add to builder with computed hash; a refused path is named in the error
+	return addFileToBuilder(h.builder, e.path, e.size, e.mtime, e.mode, hash)
 }
 
 // writeFreshenedManifest writes the manifest atomically (write to a
@@ -325,7 +314,7 @@ func writeFreshenedManifest(
 
 	outFile, err := afs.Create(tmpPath)
 	if err != nil {
-		return fmt.Errorf("failed to create temp file: %w", err)
+		return err
 	}
 
 	err = builder.Build(ctx, outFile)
@@ -334,7 +323,7 @@ func writeFreshenedManifest(
 	if err != nil {
 		_ = afs.Remove(tmpPath)
 
-		return fmt.Errorf("failed to write manifest: %w", err)
+		return fmt.Errorf("build manifest: %w", err)
 	}
 
 	// Rename temp to final
@@ -342,7 +331,7 @@ func writeFreshenedManifest(
 	if err != nil {
 		_ = afs.Remove(tmpPath)
 
-		return fmt.Errorf("failed to rename manifest: %w", err)
+		return err
 	}
 
 	return nil
@@ -408,7 +397,7 @@ func (mfa *CLIApp) freshenScan(
 	}
 
 	if err != nil {
-		return nil, 0, fmt.Errorf("failed to scan filesystem: %w", err)
+		return nil, 0, fmt.Errorf("scan filesystem: %w", err)
 	}
 
 	// Remaining entries in existingByPath are removed files
@@ -477,7 +466,7 @@ func (mfa *CLIApp) loadExistingEntries(
 		Fs:   mfa.Fs,
 	})
 	if err != nil {
-		return nil, fmt.Errorf("failed to load manifest: %w", err)
+		return nil, fmt.Errorf("load manifest: %w", err)
 	}
 
 	existingFiles := manifest.Files()
@@ -503,7 +492,7 @@ func (mfa *CLIApp) freshenManifestOperation(
 	// Find manifest file
 	manifestPath, err := mfa.resolveFreshenManifestPath(cmd)
 	if err != nil {
-		return fmt.Errorf("freshen: %w", err)
+		return err
 	}
 
 	//nolint:contextcheck // mfer loads a manifest without a context
@@ -514,7 +503,7 @@ func (mfa *CLIApp) freshenManifestOperation(
 
 	absBase, err := filepath.Abs(basePath)
 	if err != nil {
-		return fmt.Errorf("freshen: invalid base path: %w", err)
+		return fmt.Errorf("invalid base path: %w", err)
 	}
 
 	// Phase 1: Scan filesystem
@@ -606,9 +595,7 @@ func hashFile(r io.Reader, progress func(int64)) ([]byte, int64, error) {
 			break
 		}
 
-		// Returned unwrapped: the caller renders this as
-		// "failed to hash <path>: <err>" and adding a second layer here
-		// would change that message.
+		// Returned unwrapped: a read error already names the file.
 		if err != nil {
 			return nil, total, err
 		}
diff --git a/internal/cli/gen.go b/internal/cli/gen.go
index 16ac69c..b32170f 100644
--- a/internal/cli/gen.go
+++ b/internal/cli/gen.go
@@ -74,7 +74,7 @@ func (mfa *CLIApp) collectInputPaths(args cli.Args) ([]string, error) {
 
 		ap, err := filepath.Abs(inputPath)
 		if err != nil {
-			return nil, fmt.Errorf("generate: invalid path %q: %w", inputPath, err)
+			return nil, fmt.Errorf("invalid path %q: %w", inputPath, err)
 		}
 		// Validate path exists before adding to list
 		if exists, _ := afero.Exists(mfa.Fs, ap); !exists {
@@ -129,8 +129,7 @@ func (mfa *CLIApp) enumerateInputs(
 		// Default to current directory
 		err := s.EnumeratePath(".", enumProgress)
 		if err != nil {
-			return fmt.Errorf(
-				"generate: failed to enumerate current directory: %w", err)
+			return fmt.Errorf("enumerate current directory: %w", err)
 		}
 
 		return nil
@@ -144,7 +143,7 @@ func (mfa *CLIApp) enumerateInputs(
 
 	err = s.EnumeratePaths(enumProgress, paths...)
 	if err != nil {
-		return fmt.Errorf("generate: failed to enumerate paths: %w", err)
+		return fmt.Errorf("enumerate files: %w", err)
 	}
 
 	return nil
@@ -229,7 +228,7 @@ func (mfa *CLIApp) generateManifestOperation(
 
 	outFile, err := mfa.Fs.Create(tmpPath)
 	if err != nil {
-		return fmt.Errorf("failed to create temp file: %w", err)
+		return err
 	}
 
 	// Set up signal handler to clean up temp file on Ctrl-C
@@ -268,19 +267,19 @@ func (mfa *CLIApp) generateManifestOperation(
 	scanWg.Wait()
 
 	if err != nil {
-		return fmt.Errorf("failed to generate manifest: %w", err)
+		return fmt.Errorf("generate manifest: %w", err)
 	}
 
 	// Close file before rename to ensure all data is flushed
 	err = outFile.Close()
 	if err != nil {
-		return fmt.Errorf("failed to close temp file: %w", err)
+		return err
 	}
 
 	// Atomic rename
 	err = mfa.Fs.Rename(tmpPath, outputPath)
 	if err != nil {
-		return fmt.Errorf("failed to rename temp file: %w", err)
+		return err
 	}
 
 	success = true
diff --git a/internal/cli/list.go b/internal/cli/list.go
index adc9e37..ed0fff9 100644
--- a/internal/cli/list.go
+++ b/internal/cli/list.go
@@ -19,12 +19,12 @@ func (mfa *CLIApp) listManifestOperation(ctx context.Context, cmd *cli.Command)
 
 	pathOrURL, err := mfa.resolveManifestArg(cmd)
 	if err != nil {
-		return fmt.Errorf("list: %w", err)
+		return err
 	}
 
 	rc, err := mfa.openManifestReader(ctx, pathOrURL)
 	if err != nil {
-		return fmt.Errorf("list: %w", err)
+		return err
 	}
 
 	defer func() { _ = rc.Close() }()
@@ -32,7 +32,7 @@ func (mfa *CLIApp) listManifestOperation(ctx context.Context, cmd *cli.Command)
 	//nolint:contextcheck // mfer loads a manifest without a context
 	manifest, err := mfer.NewManifestFromReader(rc)
 	if err != nil {
-		return fmt.Errorf("list: failed to parse manifest: %w", err)
+		return fmt.Errorf("parse manifest: %w", err)
 	}
 
 	files := manifest.Files()
diff --git a/internal/cli/manifest_loader.go b/internal/cli/manifest_loader.go
index ca3e64b..d661f7b 100644
--- a/internal/cli/manifest_loader.go
+++ b/internal/cli/manifest_loader.go
@@ -15,17 +15,13 @@ import (
 // manifestFetchTimeout bounds HTTP requests made to fetch a manifest.
 const manifestFetchTimeout = 30 * time.Second
 
-// errHTTPStatus indicates an HTTP response with a non-OK status code.
-//
-// Its text is the literal "HTTP" prefix of the rendered "HTTP <code>"
-// message that mfer has always printed, so that wrapping it does not
-// change any user-visible output. Match it with errors.Is; do not read
-// its message.
-var errHTTPStatus = errors.New("HTTP")
+// errHTTPStatus indicates an HTTP response with a non-OK status code. It is
+// followed by the code, as in "unexpected HTTP status 404".
+var errHTTPStatus = errors.New("unexpected HTTP status")
 
 // errManifestTooLarge indicates a manifest download that passed
 // CLIApp.maxManifestSize.
-var errManifestTooLarge = errors.New("manifest exceeds maximum allowed size")
+var errManifestTooLarge = errors.New("file exceeds maximum allowed size")
 
 // isHTTPURL returns true if the string starts with http:// or https://.
 func isHTTPURL(s string) bool {
@@ -40,20 +36,22 @@ func (mfa *CLIApp) openManifestReader(
 	if isHTTPURL(pathOrURL) {
 		client := &http.Client{Timeout: manifestFetchTimeout}
 
+		// The *url.Error that NewRequestWithContext and Do return names
+		// the URL.
 		req, err := http.NewRequestWithContext(ctx, http.MethodGet, pathOrURL, nil)
 		if err != nil {
-			return nil, fmt.Errorf("failed to fetch %s: %w", pathOrURL, err)
+			return nil, fmt.Errorf("download manifest: %w", err)
 		}
 
 		resp, err := client.Do(req)
 		if err != nil {
-			return nil, fmt.Errorf("failed to fetch %s: %w", pathOrURL, err)
+			return nil, fmt.Errorf("download manifest: %w", err)
 		}
 
 		if resp.StatusCode != http.StatusOK {
 			_ = resp.Body.Close()
 
-			return nil, fmt.Errorf("failed to fetch %s: %w %d",
+			return nil, fmt.Errorf("download manifest %s: %w %d",
 				pathOrURL, errHTTPStatus, resp.StatusCode)
 		}
 
diff --git a/mfer/builder.go b/mfer/builder.go
index 470e2ee..ddc98c6 100644
--- a/mfer/builder.go
+++ b/mfer/builder.go
@@ -246,7 +246,7 @@ func (b *Builder) AddFileWithHash(
 ) error {
 	err := ValidatePath(string(path))
 	if err != nil {
-		return fmt.Errorf("add file: %w", err)
+		return err
 	}
 
 	if size < 0 {
@@ -329,22 +329,19 @@ func (b *Builder) Build(ctx context.Context, w io.Writer) error {
 	// Generate outer wrapper
 	err := m.generateOuter(ctx)
 	if err != nil {
-		return fmt.Errorf("build: generate outer: %w", err)
+		return err
 	}
 
 	// Generate final output
 	err = m.generate(ctx)
 	if err != nil {
-		return fmt.Errorf("build: generate: %w", err)
+		return err
 	}
 
 	// Write to output
 	_, err = w.Write(m.output.Bytes())
-	if err != nil {
-		return fmt.Errorf("build: write output: %w", err)
-	}
 
-	return nil
+	return err
 }
 
 // addEntry adds entry to the manifest unless an entry with its path is
diff --git a/mfer/deserialize.go b/mfer/deserialize.go
index bfd019c..ddbaffd 100644
--- a/mfer/deserialize.go
+++ b/mfer/deserialize.go
@@ -24,13 +24,12 @@ var (
 	errCompressedHashWrong  = errors.New("compressed data hash mismatch")
 	errSignatureNoPubKey    = errors.New("signature present but no public key")
 	errDecompressedTooLarge = errors.New("decompressed data exceeds maximum allowed size")
-	errManifestTooLarge     = errors.New("manifest exceeds maximum allowed size")
+	errManifestTooLarge     = errors.New("file exceeds maximum allowed size")
 	errUUIDMismatch         = errors.New("outer and inner UUID mismatch")
 	errInvalidFileFormat    = errors.New("invalid file format")
-	errInvalidManifestPath  = errors.New("manifest contains invalid path")
-	errDecodedTooLarge      = errors.New(
-		"manifest would take too much memory to decode")
-	errSignerNotSigningKey = errors.New(
+	errInvalidManifestPath  = errors.New("invalid file entry")
+	errDecodedTooLarge      = errors.New("too much memory needed")
+	errSignerNotSigningKey  = errors.New(
 		"signer is not the fingerprint of the key that made the signature")
 )
 
@@ -58,7 +57,7 @@ func (m *manifest) validateOuterHeader() error {
 	// Validate outer UUID before any decompression
 	err := validateUUID(m.pbOuter.GetUuid())
 	if err != nil {
-		return fmt.Errorf("outer UUID invalid: %w", err)
+		return fmt.Errorf("outer message: %w", err)
 	}
 
 	return nil
@@ -73,7 +72,7 @@ func (m *manifest) verifyOuterIntegrity() error {
 
 	_, err := h.Write(m.pbOuter.GetInnerMessage())
 	if err != nil {
-		return fmt.Errorf("deserialize: hash write: %w", err)
+		return fmt.Errorf("hash inner message: %w", err)
 	}
 
 	sha256Hash := h.Sum(nil)
@@ -91,9 +90,7 @@ func (m *manifest) verifyOuterIntegrity() error {
 
 	sigString, err := m.signatureString()
 	if err != nil {
-		return fmt.Errorf(
-			"failed to generate signature string for verification: %w", err,
-		)
+		return fmt.Errorf("build signature string: %w", err)
 	}
 
 	// Loading a manifest takes no context; gpgTimeout still bounds gpg.
@@ -104,7 +101,7 @@ func (m *manifest) verifyOuterIntegrity() error {
 		m.pbOuter.GetSigningPubKey(),
 	)
 	if err != nil {
-		return fmt.Errorf("signature verification failed: %w", err)
+		return err
 	}
 
 	if !strings.EqualFold(string(m.pbOuter.GetSigner()), signingKey) {
@@ -135,7 +132,7 @@ func (m *manifest) decompressInner() ([]byte, error) {
 		zstd.WithDecodeBuffersBelow(0),
 		zstd.WithDecoderMaxWindow(zstdWindowSize))
 	if err != nil {
-		return nil, fmt.Errorf("deserialize: zstd reader: %w", err)
+		return nil, fmt.Errorf("create decompressor: %w", err)
 	}
 	defer zr.Close()
 
@@ -150,7 +147,7 @@ func (m *manifest) decompressInner() ([]byte, error) {
 
 	dat, err := io.ReadAll(limitedReader)
 	if err != nil {
-		return nil, fmt.Errorf("deserialize: decompress: %w", err)
+		return nil, fmt.Errorf("decompress inner message: %w", err)
 	}
 
 	if int64(len(dat)) >= MaxDecompressedSize {
@@ -266,7 +263,7 @@ func (m *manifest) deserializeInner() error {
 
 	err = checkDecodedSize(dat)
 	if err != nil {
-		return fmt.Errorf("deserialize: unmarshal inner: %w", err)
+		return fmt.Errorf("unmarshal inner message: %w", err)
 	}
 
 	// Deserialize inner message
@@ -275,7 +272,7 @@ func (m *manifest) deserializeInner() error {
 	// Unknown fields would cost memory; mfer never writes a loaded manifest out.
 	err = proto.UnmarshalOptions{DiscardUnknown: true}.Unmarshal(dat, m.pbInner)
 	if err != nil {
-		return fmt.Errorf("deserialize: unmarshal inner: %w", err)
+		return fmt.Errorf("unmarshal inner message: %w", err)
 	}
 
 	if m.pbInner.GetVersion() != MFFile_VERSION_ONE {
@@ -285,7 +282,7 @@ func (m *manifest) deserializeInner() error {
 	// Validate inner UUID
 	err = validateUUID(m.pbInner.GetUuid())
 	if err != nil {
-		return fmt.Errorf("inner UUID invalid: %w", err)
+		return fmt.Errorf("inner message: %w", err)
 	}
 
 	// Verify UUIDs match
diff --git a/mfer/deserialize_test.go b/mfer/deserialize_test.go
index 878a6a8..a8b53d6 100644
--- a/mfer/deserialize_test.go
+++ b/mfer/deserialize_test.go
@@ -49,6 +49,6 @@ func TestReadAtMost(t *testing.T) {
 	_, err = readAtMost(input, maxSize)
 	require.ErrorIs(t, err, errManifestTooLarge)
 	require.EqualError(t, err,
-		"manifest exceeds maximum allowed size of 65536 bytes")
+		"file exceeds maximum allowed size of 65536 bytes")
 	assert.Equal(t, maxSize-1, input.Len(), "bytes left unread")
 }
diff --git a/mfer/errmsg_test.go b/mfer/errmsg_test.go
index d2dc32c..1f2d3c9 100644
--- a/mfer/errmsg_test.go
+++ b/mfer/errmsg_test.go
@@ -74,14 +74,18 @@ func TestValidatePathMessagesVerbatim(t *testing.T) {
 	}
 }
 
-// TestSerializeInternalErrorMessagesVerbatim pins the two distinct
-// "internal error" messages, which differ between generate and
-// generateOuter and have always done so.
-func TestSerializeInternalErrorMessagesVerbatim(t *testing.T) {
+// TestSerializeInnerNotSetMessagesVerbatim pins the messages generate and
+// generateOuter return when the inner message is missing.
+func TestSerializeInnerNotSetMessagesVerbatim(t *testing.T) {
 	t.Parallel()
 
 	m := &manifest{}
-	require.EqualError(t, m.generate(context.Background()),
-		"internal error: pbInner not set")
-	require.EqualError(t, m.generateOuter(context.Background()), "internal error")
+
+	err := m.generate(context.Background())
+	require.ErrorIs(t, err, errInnerNotSet)
+	require.EqualError(t, err, "inner message not set")
+
+	err = m.generateOuter(context.Background())
+	require.ErrorIs(t, err, errInternal)
+	require.EqualError(t, err, "inner message not set")
 }
diff --git a/mfer/gpg.go b/mfer/gpg.go
index f2c095e..21b89c3 100644
--- a/mfer/gpg.go
+++ b/mfer/gpg.go
@@ -53,7 +53,7 @@ const (
 )
 
 var (
-	errGPGKeyNotFound      = errors.New("gpg key not found")
+	errGPGKeyNotFound      = errors.New("GPG key not found")
 	errFingerprintNotFound = errors.New("fingerprint not found for key")
 	errSigningKeyCount     = errors.New(
 		"embedded public key block must hold exactly one key")
@@ -88,8 +88,9 @@ func gpgArgs(opts []string, positional ...string) []string {
 }
 
 // runGPG runs the gpg binary in batch mode with the given arguments and
-// optional stdin, returning captured stdout and stderr. gpg is killed when
-// ctx ends or gpgTimeout passes, whichever comes first.
+// optional stdin, returning captured stdout and stderr. If gpg fails, the
+// error ends with what gpg wrote to stderr. gpg is killed when ctx ends or
+// gpgTimeout passes, whichever comes first.
 func runGPG(
 	ctx context.Context, stdin io.Reader, args ...string,
 ) (*bytes.Buffer, *bytes.Buffer, error) {
@@ -125,13 +126,28 @@ func runGPG(
 		// "signal: killed"; return the reason instead.
 		err = ctx.Err()
 		if errors.Is(err, context.DeadlineExceeded) {
-			err = fmt.Errorf("gpg timed out: %w", err)
+			err = fmt.Errorf("timed out: %w", err)
 		}
 	}
 
+	if err != nil {
+		err = withStderr(err, &stderr)
+	}
+
 	return &stdout, &stderr, err
 }
 
+// withStderr returns err followed by what gpg wrote to stderr, or err alone
+// when gpg wrote nothing.
+func withStderr(err error, stderr *bytes.Buffer) error {
+	messages := strings.TrimSpace(stderr.String())
+	if messages == "" {
+		return err
+	}
+
+	return fmt.Errorf("%w: %s", err, messages)
+}
+
 // parseFingerprint extracts the first fingerprint from gpg --with-colons
 // output, or returns ok=false if none is present.
 func parseFingerprint(colonOutput string) (string, bool) {
@@ -174,7 +190,7 @@ func gpgSign(
 ) ([]byte, string, error) {
 	tmpDir, err := os.MkdirTemp("", "mfer-gpg-sign-*")
 	if err != nil {
-		return nil, "", fmt.Errorf("failed to create temp dir: %w", err)
+		return nil, "", err
 	}
 
 	defer func() { _ = os.RemoveAll(tmpDir) }()
@@ -191,19 +207,19 @@ func gpgSign(
 		"--local-user", string(keyID),
 	)
 	if err != nil {
-		return nil, "", fmt.Errorf("gpg sign failed: %w: %s", err, stderr.String())
+		return nil, "", fmt.Errorf("gpg sign: %w", err)
 	}
 
 	// The last argument of SIG_CREATED is the fingerprint of the key that
 	// made the signature.
 	created, ok := parseStatusLine(stdout.String(), "SIG_CREATED")
 	if !ok {
-		return nil, "", fmt.Errorf("%w: %s", errSigningKeyNotReported, stderr.String())
+		return nil, "", withStderr(errSigningKeyNotReported, stderr)
 	}
 
 	sig, err := os.ReadFile(sigFile) //nolint:gosec // G304: inside tmpDir, made above
 	if err != nil {
-		return nil, "", fmt.Errorf("failed to read signature: %w", err)
+		return nil, "", err
 	}
 
 	return sig, created[len(created)-1], nil
@@ -212,11 +228,11 @@ func gpgSign(
 // gpgExportPublicKey exports the public key for the specified key ID.
 // Returns the armored public key.
 func gpgExportPublicKey(ctx context.Context, keyID GPGKeyID) ([]byte, error) {
-	stdout, stderr, err := runGPG(ctx, nil,
+	stdout, _, err := runGPG(ctx, nil,
 		gpgArgs([]string{"--export", gpgOptArmor}, string(keyID))...,
 	)
 	if err != nil {
-		return nil, fmt.Errorf("gpg export failed: %w: %s", err, stderr.String())
+		return nil, fmt.Errorf("gpg export: %w", err)
 	}
 
 	if stdout.Len() == 0 {
@@ -228,13 +244,11 @@ func gpgExportPublicKey(ctx context.Context, keyID GPGKeyID) ([]byte, error) {
 
 // gpgGetKeyFingerprint gets the full fingerprint for a key ID.
 func gpgGetKeyFingerprint(ctx context.Context, keyID GPGKeyID) ([]byte, error) {
-	stdout, stderr, err := runGPG(ctx, nil,
+	stdout, _, err := runGPG(ctx, nil,
 		gpgArgs([]string{"--with-colons", "--fingerprint"}, string(keyID))...,
 	)
 	if err != nil {
-		return nil, fmt.Errorf(
-			"gpg fingerprint lookup failed: %w: %s", err, stderr.String(),
-		)
+		return nil, fmt.Errorf("gpg fingerprint lookup: %w", err)
 	}
 
 	fpr, ok := parseFingerprint(stdout.String())
@@ -250,14 +264,12 @@ func gpgGetKeyFingerprint(ctx context.Context, keyID GPGKeyID) ([]byte, error) {
 func gpgImportOneKey(ctx context.Context, gpgHome, pubKeyFile string) error {
 	// --status-fd 1 sends gpg's status lines to stdout, which importing
 	// otherwise leaves empty; its messages go to stderr.
-	importStdout, importStderr, err := runGPG(ctx, nil,
+	importStdout, _, err := runGPG(ctx, nil,
 		gpgArgs([]string{gpgOptHomedir, gpgHome, gpgOptStatusFD, "1", "--import"},
 			pubKeyFile)...,
 	)
 	if err != nil {
-		return fmt.Errorf(
-			"failed to import public key: %w: %s", err, importStderr.String(),
-		)
+		return fmt.Errorf("gpg import: %w", err)
 	}
 
 	// The first argument of IMPORT_RES counts the primary keys gpg read
@@ -284,7 +296,7 @@ func gpgVerify(ctx context.Context, data, signature, pubKey []byte) (string, err
 	// Create temporary directory for GPG operations
 	tmpDir, err := os.MkdirTemp("", "mfer-gpg-verify-*")
 	if err != nil {
-		return "", fmt.Errorf("failed to create temp dir: %w", err)
+		return "", err
 	}
 
 	defer func() { _ = os.RemoveAll(tmpDir) }()
@@ -292,7 +304,7 @@ func gpgVerify(ctx context.Context, data, signature, pubKey []byte) (string, err
 	// Set restrictive permissions
 	err = os.Chmod(tmpDir, privateDirPerms)
 	if err != nil {
-		return "", fmt.Errorf("failed to set temp dir permissions: %w", err)
+		return "", err
 	}
 
 	// Write public key to temp file
@@ -300,7 +312,7 @@ func gpgVerify(ctx context.Context, data, signature, pubKey []byte) (string, err
 
 	err = os.WriteFile(pubKeyFile, pubKey, privateFilePerms)
 	if err != nil {
-		return "", fmt.Errorf("failed to write public key: %w", err)
+		return "", err
 	}
 
 	// Write signature to temp file
@@ -308,7 +320,7 @@ func gpgVerify(ctx context.Context, data, signature, pubKey []byte) (string, err
 
 	err = os.WriteFile(sigFile, signature, privateFilePerms)
 	if err != nil {
-		return "", fmt.Errorf("failed to write signature: %w", err)
+		return "", err
 	}
 
 	// Write data to temp file
@@ -316,7 +328,7 @@ func gpgVerify(ctx context.Context, data, signature, pubKey []byte) (string, err
 
 	err = os.WriteFile(dataFile, data, privateFilePerms)
 	if err != nil {
-		return "", fmt.Errorf("failed to write data: %w", err)
+		return "", err
 	}
 
 	err = gpgImportOneKey(ctx, tmpDir, pubKeyFile)
@@ -326,14 +338,12 @@ func gpgVerify(ctx context.Context, data, signature, pubKey []byte) (string, err
 
 	// --status-fd 1 sends gpg's status lines to stdout, which verifying a
 	// detached signature otherwise leaves empty; its messages go to stderr.
-	verifyStdout, verifyStderr, err := runGPG(ctx, nil,
+	verifyStdout, _, err := runGPG(ctx, nil,
 		gpgArgs([]string{gpgOptHomedir, tmpDir, gpgOptStatusFD, "1", gpgOptVerify},
 			sigFile, dataFile)...,
 	)
 	if err != nil {
-		return "", fmt.Errorf(
-			"signature verification failed: %w: %s", err, verifyStderr.String(),
-		)
+		return "", fmt.Errorf("gpg verify: %w", err)
 	}
 
 	// gpg writes a VALIDSIG line for each good signature. Its first
diff --git a/mfer/gpg_test.go b/mfer/gpg_test.go
index 495b4fb..91eb13d 100644
--- a/mfer/gpg_test.go
+++ b/mfer/gpg_test.go
@@ -603,7 +603,8 @@ func fakeGPGPath(t *testing.T, script string) string {
 
 // TestGPGTimeoutKillsGPG puts a fake gpg that never finishes first on
 // PATH and checks that a run past its deadline is killed and reported as
-// a timeout of the named operation, instead of hanging.
+// a timeout of the named operation, instead of hanging. The fake gpg writes
+// nothing to stderr, so the message ends with the timeout.
 func TestGPGTimeoutKillsGPG(t *testing.T) {
 	t.Setenv("PATH", fakeGPGPath(t, "#!/bin/sh\nexec sleep 10\n"))
 
@@ -612,7 +613,21 @@ func TestGPGTimeoutKillsGPG(t *testing.T) {
 
 	_, _, err := gpgSign(ctx, []byte("data"), GPGKeyID("any"))
 	require.ErrorIs(t, err, context.DeadlineExceeded)
-	assert.Contains(t, err.Error(), "gpg sign failed: gpg timed out")
+	assert.EqualError(t, err, "gpg sign: timed out: context deadline exceeded")
+}
+
+// TestGPGSignKeyNotReportedKeepsStderr puts a fake gpg first on PATH that
+// exits cleanly without reporting the key that signed, and checks that what
+// it wrote to stderr is in the message.
+func TestGPGSignKeyNotReportedKeepsStderr(t *testing.T) {
+	t.Setenv("PATH", fakeGPGPath(t,
+		"#!/bin/sh\necho 'gpg: note from the fake gpg' >&2\n"))
+
+	_, _, err := gpgSign(context.Background(), []byte("data"), GPGKeyID("any"))
+	require.ErrorIs(t, err, errSigningKeyNotReported)
+	assert.EqualError(t, err,
+		"gpg did not report the key that made the signature: "+
+			"gpg: note from the fake gpg")
 }
 
 // TestGPGCancelWhenChildHoldsOutput uses a fake gpg that runs sleep as a
diff --git a/mfer/manifest.go b/mfer/manifest.go
index 7e847d1..b172a12 100644
--- a/mfer/manifest.go
+++ b/mfer/manifest.go
@@ -10,7 +10,7 @@ import (
 )
 
 var (
-	errOuterNotSet  = errors.New("pbOuter not set")
+	errOuterNotSet  = errors.New("outer message not set")
 	errUUIDNotSet   = errors.New("UUID not set")
 	errSHA256NotSet = errors.New("SHA256 hash not set")
 )
@@ -65,7 +65,7 @@ func (m *manifest) signatureString() (string, error) {
 
 	mh, err := multihash.Encode(m.pbOuter.GetSha256(), multihash.SHA2_256)
 	if err != nil {
-		return "", fmt.Errorf("failed to encode multihash: %w", err)
+		return "", fmt.Errorf("encode multihash: %w", err)
 	}
 
 	uuidStr := hex.EncodeToString(m.pbOuter.GetUuid())
diff --git a/mfer/serialize.go b/mfer/serialize.go
index f0945a7..6688ed9 100644
--- a/mfer/serialize.go
+++ b/mfer/serialize.go
@@ -20,11 +20,9 @@ const MAGIC string = "ZNAVSRFG"
 var (
 	// errInnerNotSet is returned by generate when the inner manifest is
 	// missing.
-	errInnerNotSet = errors.New("internal error: pbInner not set")
+	errInnerNotSet = errors.New("inner message not set")
 	// errInternal is returned by generateOuter for the same condition.
-	// The two messages differ, and both are load-bearing for callers that
-	// match on text, so they are kept distinct.
-	errInternal = errors.New("internal error")
+	errInternal = errors.New("inner message not set")
 )
 
 // nanosecondsInt32 converts t's nanosecond component to int32.
@@ -65,14 +63,14 @@ func (m *manifest) generate(ctx context.Context) error {
 
 	dat, err := proto.MarshalOptions{Deterministic: true}.Marshal(m.pbOuter)
 	if err != nil {
-		return fmt.Errorf("serialize: marshal outer: %w", err)
+		return fmt.Errorf("marshal outer message: %w", err)
 	}
 
 	m.output = bytes.NewBufferString(MAGIC)
 
 	_, err = m.output.Write(dat)
 	if err != nil {
-		return fmt.Errorf("serialize: write output: %w", err)
+		return fmt.Errorf("write outer message: %w", err)
 	}
 
 	return nil
@@ -95,7 +93,7 @@ func (m *manifest) generateOuter(ctx context.Context) error {
 
 	innerData, err := proto.MarshalOptions{Deterministic: true}.Marshal(m.pbInner)
 	if err != nil {
-		return fmt.Errorf("serialize: marshal inner: %w", err)
+		return fmt.Errorf("marshal inner message: %w", err)
 	}
 
 	// Compress the inner data
@@ -103,12 +101,12 @@ func (m *manifest) generateOuter(ctx context.Context) error {
 
 	zw, err := zstd.NewWriter(idc, zstd.WithEncoderLevel(zstd.SpeedBestCompression))
 	if err != nil {
-		return fmt.Errorf("serialize: create compressor: %w", err)
+		return fmt.Errorf("create compressor: %w", err)
 	}
 
 	_, err = zw.Write(innerData)
 	if err != nil {
-		return fmt.Errorf("serialize: compress: %w", err)
+		return fmt.Errorf("compress inner message: %w", err)
 	}
 
 	_ = zw.Close()
@@ -120,7 +118,7 @@ func (m *manifest) generateOuter(ctx context.Context) error {
 
 	_, err = h.Write(compressedData)
 	if err != nil {
-		return fmt.Errorf("serialize: hash write: %w", err)
+		return fmt.Errorf("hash inner message: %w", err)
 	}
 
 	sha256Hash := h.Sum(nil)
@@ -149,12 +147,12 @@ func (m *manifest) generateOuter(ctx context.Context) error {
 func (m *manifest) signOuter(ctx context.Context) error {
 	sigString, err := m.signatureString()
 	if err != nil {
-		return fmt.Errorf("failed to generate signature string: %w", err)
+		return fmt.Errorf("build signature string: %w", err)
 	}
 
 	sig, signingKey, err := gpgSign(ctx, []byte(sigString), m.signingOptions.KeyID)
 	if err != nil {
-		return fmt.Errorf("failed to sign manifest: %w", err)
+		return err
 	}
 
 	m.pbOuter.Signature = sig
@@ -163,14 +161,14 @@ func (m *manifest) signOuter(ctx context.Context) error {
 	// fingerprint first.
 	fingerprint, err := gpgGetKeyFingerprint(ctx, GPGKeyID(signingKey))
 	if err != nil {
-		return fmt.Errorf("failed to get key fingerprint: %w", err)
+		return err
 	}
 
 	m.pbOuter.Signer = fingerprint
 
 	pubKey, err := gpgExportPublicKey(ctx, GPGKeyID(fingerprint))
 	if err != nil {
-		return fmt.Errorf("failed to export public key: %w", err)
+		return err
 	}
 
 	m.pbOuter.SigningPubKey = pubKey