configure 'lowerCaseResponseHeaders' is deprecated; 'match…

Error message

configure 'lowerCaseResponseHeaders' is deprecated; 'match header X' is already case-insensitive and 'karate.lowerCase(responseHeaders)' covers direct map access

What it means

Karate v2 removed the `configure lowerCaseResponseHeaders` option. Header matching is already case-insensitive and `karate.lowerCase(responseHeaders)` covers direct map access, so the option is a no-op that logs this deprecation warning explaining the built-in replacements.

Solutions

Delete `configure lowerCaseResponseHeaders` from the feature/config (no replacement needed for match header)
If direct map access needs lowercase keys, wrap with karate.lowerCase(responseHeaders)
Update assertions that depended on lowercase keys to use case-insensitive match or karate.lowerCase
Grep for lowerCaseResponseHeaders across karate-config.js and *.feature and remove all occurrences

Example fix

// before
* configure lowerCaseResponseHeaders = true
* def h = responseHeaders
// after
* def h = karate.lowerCase(responseHeaders)

Defensive patterns

Strategy: validation

Validate before calling

grep -rn 'lowerCaseResponseHeaders' karate-config.js features/ && echo 'deprecated configure key found'

Prevention

Rely on case-insensitive `match header` instead of lowercasing maps
Use karate.lowerCase(responseHeaders) only where direct map access needs lowercase keys
Write header assertions that don't depend on key casing
Sweep configs for removed v1 keys as part of upgrade checklists

When it happens

Trigger: A feature or JS config containing `configure lowerCaseResponseHeaders = true`, typically copied from a Karate v1 project that needed lowercased response header maps.

Common situations: v1→v2 migration of karate-config.js; tests asserting exact header map keys that relied on the old lowercasing; copied snippets from older codebases.

Understand the failure class

Background: "is deprecated and will be removed" — deprecation warnings for old API names, keywords, and options, and how to migrate before the removal release — this error's family across 29 libraries.

Related errors

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/17c61dd496ab74f8. Report an issue: GitHub.

Appendix: source

Thrown at karate-core/src/main/java/io/karatelabs/core/KarateConfig.java:446

                this.onStepFailure = value;
            }

            // Driver configuration
            case "driver" -> {
                this.driverConfig = value;
            }

            // Deprecated v1 options - no-op with one-line migration hint
            case "logPrettyRequest", "logPrettyResponse" -> {
                logger.warn("configure '{}' is deprecated; use 'configure logging = {{ pretty: true|false }}'", key);
            }
            case "printEnabled" -> {
                logger.warn("configure 'printEnabled' is deprecated; print/karate.log go to the 'karate.scenario' "
                        + "SLF4J category - set its level to WARN in logback.xml to keep them off the console, "
                        + "or 'configure logging = {{ console: \"warn\" }}' to quiet all karate console output");
            }
            case "lowerCaseResponseHeaders" -> {
                logger.warn("configure 'lowerCaseResponseHeaders' is deprecated; "
                        + "'match header X' is already case-insensitive and 'karate.lowerCase(responseHeaders)' "
                        + "covers direct map access");
            }
            case "logModifier" -> {
                logger.warn("configure 'logModifier' is removed; "
                        + "use the declarative form: 'configure logging = {{ mask: {{ headers: [...], jsonPaths: [...], patterns: [...] }} }}'");
            }

            // No channel-type cases: channels (grpc, kafka, …) are configured via their rich
            // JS object — karate.channel('kafka') / the boot.ext('kafka') object — not via global
            // 'configure <type>'. 'configure' stays strict so key typos fail loudly.
            default -> throw new RuntimeException("unexpected 'configure' key: '" + key + "'");
        }
    }

    private void configureSsl(Object value) {
        if (value == null) {
            this.ssl.clear();

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