nodejs/node · error

quality already set\n

Error message

quality already set\n

What it means

`-Z` is a shortcut that pins compression quality to 11 (the maximum). The parser latches quality via `quality_set`, shared with `-q`, `--best`, and another `-Z`. Supplying `-Z` after any quality-affecting option triggers this message and returns COMMAND_INVALID.

Source

Thrown at deps/brotli/c/tools/brotli.c:424

            fprintf(stderr, "argument --verbose / -v already set\n");
            return COMMAND_INVALID;
          }
          params->verbosity = 1;
          continue;
        } else if (c == 'K') {
          if (concatenated_set) {
            fprintf(stderr, "argument -K / --concatenated already set\n");
            return COMMAND_INVALID;
          }
          concatenated_set = BROTLI_TRUE;
          params->allow_concatenated = BROTLI_TRUE;
          continue;
        } else if (c == 'V') {
          /* Don't parse further. */
          return COMMAND_VERSION;
        } else if (c == 'Z') {
          if (quality_set) {
            fprintf(stderr, "quality already set\n");
            return COMMAND_INVALID;
          }
          quality_set = BROTLI_TRUE;
          params->quality = 11;
          continue;
        }
        /* o/q/w/C/D/S with parameter is expected */
        if (c != 'o' && c != 'q' && c != 'w' && c != 'C' && c != 'D' &&
            c != 'S') {
          fprintf(stderr, "invalid argument -%c\n", c);
          return COMMAND_INVALID;
        }
        if (j + 1 != arg_len) {
          fprintf(stderr, "expected parameter for argument -%c\n", c);
          return COMMAND_INVALID;
        }
        i++;
        if (i == argc || !argv[i] || argv[i][0] == 0) {

View on GitHub (pinned to 1b2de5e052)

Solutions

1. Drop one quality setter: keep either `-Z`/`--best`/`-q 11` or an explicit `-q N`, not several.
2. Audit build scripts that hard-code a quality flag and parameterize it instead.

Example fix

# before
brotli -Z -q 9 in.txt
# after
brotli -q 11 in.txt

# bash: count quality setters (-Z, --best, -q, --quality)
q=$(printf '%s\n' "$@" | grep -cE '^(-Z|--best|-q|--quality.*)$')
if [ "$q" -gt 1 ]; then echo "multiple quality flags" >&2; exit 2; fi
brotli "$@"

# bash
if ! brotli "$@"; then rc=$?; echo "brotli exit $rc" >&2; exit "$rc"; fi

When it happens

Trigger: Passing `-Z` together with another quality setter: `brotli -Z -q 9 f`, `brotli --best -Z f`, or `brotli -Z -Z f`.

Common situations: Preset wrappers that always add `-Z` while a user also passes `-q`; migrating from `gzip -9` habits and adding both `-Z` and an explicit quality.

Related errors

• argument -K / --concatenated already set\n
• write to standard output already set (-o)\n
• error parsing quality value [%s]\n
• lgwin parameter already set\n
• comment already set\n

AI-assisted analysis of nodejs/node@1b2de5e052 (2026-08-13). Data as JSON: /api/errors/a7e7b0947c0d9637. Report an issue: GitHub.