vllm-project/vllm · error · ValueError

-O is missing its value

Error message

-O is missing its value

What it means

The bare '-O' flag is the last token of argv: the parser expects its value as the next token (i + 1) but i + 1 is past the end of the list, so optimization-level cannot be set and parsing aborts with ValueError('-O is missing its value').

Source

Thrown at tools/recipes/recipe_json_to_vllm_config.py:488

        raise ValueError(f"Expected model after 'vllm serve', got {model!r}")

    config: dict[str, Any] = {"model": model}

    i = 3
    while i < len(argv):
        token = argv[i]

        # -O3 / -O=3
        if token.startswith("-O") and token != "-O":
            value = token[3:] if token.startswith("-O=") else token[2:]
            merge_value(config, ["optimization-level"], coerce(value))
            i += 1
            continue

        # -O 3
        if token == "-O":
            if i + 1 >= len(argv):
                raise ValueError("-O is missing its value")
            merge_value(config, ["optimization-level"], coerce(argv[i + 1]))
            i += 2
            continue

        # Selected common short aliases.
        if token in SHORT_ALIASES:
            if i + 1 >= len(argv):
                raise ValueError(f"{token} is missing its value")
            merge_value(
                config,
                [SHORT_ALIASES[token]],
                coerce(argv[i + 1]),
            )
            i += 2
            continue

        if not token.startswith("--"):
            raise ValueError(

View on GitHub (pinned to c794754062)

Solutions

1. jq '.argv' recipe.json and check the last tokens
2. Append the missing value ('-O 3') or switch to the attached forms '-O3' / '-O=3' which cannot dangle
3. Re-fetch the recipe if the value was lost in rendering/report the malformed recipe

Example fix

# before
"argv": ["vllm", "serve", "m", "-O"]
# after
"argv": ["vllm", "serve", "m", "-O3"]

argv = [str(x) for x in recipe["argv"]]
for i, tok in enumerate(argv):
    if tok in ("-O", "-tp", "-pp", "-dp") and i + 1 >= len(argv):
        raise SystemExit(f"{tok} dangles at end of argv without a value")

When it happens

Trigger: Recipe argv ending in exactly '-O', e.g. ['vllm','serve','m','-O']; a renderer bug dropping the optimization level value; truncation of the argv array.

Common situations: Recipes API emitting '-O' with a value that got filtered out (e.g. null dropped during JSON rendering); manual editing that removed the trailing value.

Related errors

• Cannot merge nested option {'.'.join(path)!r}: {part!r} is a
• Expected recipe argv to start with: ['vllm', 'serve', MODEL,
• Expected model after 'vllm serve', got {model!r}
• {token} is missing its value
• Unexpected positional/short argument {token!r}. The converte

AI-assisted analysis of vllm-project/vllm@c794754062 (2026-08-14). Data as JSON: /api/errors/acbdcffa20e6f33e. Report an issue: GitHub.