JuliusBrussee/caveman · warning

filter ${key} must be a boolean

Error message

filter ${key} must be a boolean

What it means

The boolean filters has_error and compressed must be actual JSON booleans when present. Strings ("true"), 0/1, or null throw with the key named. Omitting the key is valid.

Source

Thrown at packages/cli/src/agent-mcp.ts:486

  for (const key of stringListKeys) {
    const value = filters[key];
    if (value === undefined) continue;
    if (!Array.isArray(value) || value.length === 0 || value.some((entry) => typeof entry !== "string" || entry.trim() === "")) {
      throw new Error(`filter ${key} must be a non-empty array of non-empty strings`);
    }
    if (key === "status_class" && value.some((entry) => !["2xx", "4xx", "5xx"].includes(entry as string))) {
      throw new Error("filter status_class values must be 2xx, 4xx, or 5xx");
    }
  }
  for (const key of ["min_cost_usd", "max_cost_usd", "min_total_tokens", "max_total_tokens", "min_latency_ms", "max_latency_ms"]) {
    const value = filters[key];
    if (value !== undefined && (typeof value !== "number" || !Number.isFinite(value))) {
      throw new Error(`filter ${key} must be a finite number`);
    }
  }
  for (const key of ["has_error", "compressed"]) {
    const value = filters[key];
    if (value !== undefined && typeof value !== "boolean") throw new Error(`filter ${key} must be a boolean`);
  }
  const monitor = filters.monitor;
  if (monitor !== undefined) {
    if (!monitor || typeof monitor !== "object" || Array.isArray(monitor)) throw new Error("filter monitor must be an object");
    const monitorUnknown = Object.keys(monitor).filter((key) => key !== "id" && key !== "verdict");
    if (monitorUnknown.length > 0) throw new Error(`filter monitor has unknown key(s): ${monitorUnknown.sort().join(", ")}`);
    if (typeof monitor.id !== "string" || monitor.id.trim() === "") throw new Error("filter monitor.id is required");
    if (typeof monitor.verdict !== "string" || !["pass", "fail", "error"].includes(monitor.verdict)) {
      throw new Error("filter monitor.verdict must be pass, fail, or error");
    }
  }
}

function optionalEnum(args: JSONObject, key: string, values: string[]): void {
  const value = args[key];
  if (value !== undefined && (typeof value !== "string" || !values.includes(value))) {
    throw new Error(`${key} must be one of ${values.join(", ")}`);
  }

View on GitHub (pinned to 27d5a3981a)

Solutions

1. Convert before calling: value === "true" / Boolean(value) as appropriate for the source.
2. Send real JSON true/false literals.
3. Omit the key when the filter is not wanted.

Example fix

// before
{ filters: { has_error: process.env.HAS_ERROR } } // string "true"/undefined

// after
{ filters: { has_error: process.env.HAS_ERROR === "1" } }

for (const k of ["has_error", "compressed"]) {
  if (filters[k] !== undefined && typeof filters[k] !== "boolean") {
    throw new Error(`${k} must be boolean`);
  }
}

function isBoolean(v: unknown): v is boolean { return typeof v === "boolean"; }

When it happens

Trigger: has_error: "true" (string from env var or query param); has_error: 1; compressed: "false" which would otherwise be truthy and silently wrong.

Common situations: Reading flags from process.env or URL query strings and passing them through unconverted; LLM tool calls quoting booleans.

Related errors

• filters must be an object
• unknown trace filter(s): ${unknown.sort().join(", ")}
• filter ${key} must be a non-empty array of non-empty strings
• filter status_class values must be 2xx, 4xx, or 5xx
• filter ${key} must be a finite number

AI-assisted analysis of JuliusBrussee/caveman@27d5a3981a (2026-08-15). Data as JSON: /api/errors/059e1192b251cc1e. Report an issue: GitHub.