# What changed in mockserver-client

> 183 changes in mockserver-client 9 from its official release notes, upgrade guides and advisories: 75 breaking, 2 deprecations, 5 security, 38 new APIs and options. Each one cited. Sources checked 2026-10-19. HTML: https://unstale.sh/npm/mockserver-client/

To see which of these apply to a repository, run `npx @unstale/cli init` in it.

## mockserver-client 9

### Breaking changes

- Forwarded and proxied requests now carry the client's Accept-Encoding filtered to supported decompression formats; the Java client no longer adds gzip,deflate by default. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Bodies without Content-Type that are not valid UTF-8 are now preserved as exact binary bytes; callbacks, templates, WASM, logs, and HAR expose them as base64. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A message is now everything read in one pass, up to 256 KiB, rather than one network read. Back-to-back data may therefore match as one message, and forwarded messages can be larger. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Binary expectation response delays are now applied in order without holding a thread; empty response data means no reply. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Binary proxying now applies backpressure instead of buffering unlimited replies when clients do not read; writes stall without dropping data. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The binary proxy listener is called as soon as each message is read, on its own thread; its response is the first upstream bytes after that message or null. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client's callback and breakpoint WebSockets now use the same trust and client-certificate settings as its HTTP requests. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Clearing with a DNS or binary matcher now clears only matching expectations; an empty request matcher clears all expectations and, for log/all types, matched DNS and binary log entries too. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client trusts only the configured CA chain for MockServer's certificate; include MockServer's CA if it signs the server certificate. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- With control-plane mTLS, Java clients trust only this chain for MockServer's certificate, and MockServer accepts only client certificates signed by this chain. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Rust struct literals for Delay now need to set newly added fields, or callers can use the provided constructors or builders. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Five distroless image variants move from Java 17 to Java 25, while -clustered moves to Java 21. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- MockServer now refuses to start when DNS mocking is enabled but its DNS port cannot be used. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The setting and its Java methods are removed; configured values are ignored, and per-message forwarding cannot be restored. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Undecodable upstream responses now produce a 502 naming the cause and close the bad connection instead of relaying partial data or reusing it. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Go client moves to the /v9 module path; update go get commands and imports from the /v7 or unsuffixed paths. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Go client module moves to the /v9 path; update go get commands and imports to use it. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTP/2 and HTTP/3 HEAD responses no longer carry a body, including forwarded responses; tunnelled responses preserve the headers a direct connection sends. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTP/3 startup now refuses a UDP port already held by another application on macOS. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Setting the HTTP/3 port without the required native, or when the UDP port cannot be used, now prevents startup instead of silently degrading. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Rust struct literals for HttpTemplate now need to set newly added fields, or callers can use the provided constructors or builders. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Idle client connections now close after five minutes by default; set the timeout to 0 to restore the previous behavior. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- When expectations in an initialization file repeat an id, the last one is kept in the first occurrence's position, matching PUT /mockserver/expectation behavior. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The container heap cap drops from 75% to 45% of the memory limit. A 256 MiB limit is no longer supported unless a small explicit heap is set. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- DNS and HTTP/3 ports now bind to localBoundIP as well; clients must send those requests to that address when it is set. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Binary expectations now match messages on proxied binary connections by default; set the option to false to always forward, as in 8.0.0. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The setting now limits HTTP/2 and HTTP/3 request headers and upstream response headers as well as HTTP/1.1 headers. Its default is 256 KB; set it to 8192 to retain the old HTTP/2 and HTTP/3 limit. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The default changed from unlimited to 256 KB, applying uniformly across protocols. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- This setting caps per-expectation mismatch log entries per request, defaulting to 50; set it to -1 to log every comparison. Matching and closest-match results are unchanged. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Oversized request bodies now receive 413 instead of a reset; HTTP/3 compressed bodies are limited by decompressed size. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The metric now has a reason label with values ring_full and in_flight_bytes; scripts and PromQL queries that assumed an unlabelled metric may need adjustment. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The metric now counts evicted entries rather than eviction episodes, so values are much larger and alerts need retuning. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node client now has an exports map that permits named package paths and blocks unlisted deep paths with ERR_PACKAGE_PATH_NOT_EXPORTED. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The package now has an exports map, so imports of unlisted internal paths fail to resolve. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The deep-import TypeScript typings no longer declare a default export; import from mockserver-client itself, use a namespace or require import, or enable esModuleInterop. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Its TypeScript typings now describe a plain object of named exports rather than a default export; the .default property is no longer typed. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The package now publishes its TypeScript typings, which use Node's types and therefore require @types/node. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A Node callback is no longer re-registered with its full times limit after MockServer removes its expectation; reconnects occur only while the expectation remains. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The launcher runs the bundled Java runtime directly without a shell and passes arguments separately; MOCKSERVER_JAVA_OPTS is split on whitespace with quoted text kept together, and spawnOptions.shell is ignored. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node browser transport now rejects 4xx and 5xx responses as the Node transport does. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- withStyle and withSchemaType now return a new instance instead of mutating the existing instance; callers must use the returned value to observe the change. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- withStyle and withSchemaType now return a new instance instead of mutating the existing instance; callers must use the returned value to observe the change. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Verification now counts only requests for the matched OpenAPI operation; verifySequence behavior is unchanged. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Now rejects instead of hanging when MockServer answers with an error. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- withStyle now returns a new instance instead of mutating the existing instance; callers must use the returned value to observe the change. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The PHP launcher builds a quoted cmd.exe command line on Windows and throws BinaryInstallException for unsafe arguments or more than one percent sign across the path and arguments. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The MCP server now rejects calls missing required arguments with JSON-RPC error -32602 and names the missing arguments in data.missingArguments; null counts as missing. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Unknown fields now produce a 400 instead of silently checking at least one message; count constraints belong inside count. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- On Windows, the launcher invokes cmd.exe with quoted arguments and raises ValueError for unsafe characters or more than one percent sign across the path and extra arguments. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Bodies whose bytes are already materialized are replayed verbatim instead of being decoded with replacement characters and re-encoded when the declared charset does not match the bytes. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Response verification now applies body matchers in verify and verifySequence instead of silently replacing them with an empty-object match. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A client that stops reading a response is now disconnected or reset after one minute by default; set this to 0 to disable the timeout. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Python client now returns a DnsRequestDefinition or dict for DNS requests instead of an empty HttpRequest. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Python client now returns a DnsRequestDefinition or dict for DNS requests instead of an empty HttpRequest. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client now throws for control-plane errors instead of returning the error's text. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client now raises for status codes of 400 or greater instead of returning the error text as its result. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- An unfiltered listing includes expectations whose request matcher is not(...); DNS/binary filters return only matching expectations. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client now throws for control-plane errors instead of returning the error's text. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client now raises for status codes of 400 or greater instead of returning the error text as its result. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node client's TypeScript return type changes to Promise<RequestDefinition[]>; narrow each result to HttpRequest before reading HTTP-specific fields. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node client's return type is now Promise<RequestDefinition[]> rather than Promise<HttpResponse[]>; narrow results before using HTTP-specific fields. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node client's TypeScript return type changes to Promise<RequestDefinition[]>; narrow each result to HttpRequest before reading HTTP-specific fields. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node client's return type is now Promise<RequestDefinition[]> rather than Promise<HttpResponse[]>; narrow results before using HTTP-specific fields. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Enums are now non-exhaustive and server-sent unknown values map to Unknown; Unknown cannot be serialized back to the server. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Public enums are now non-exhaustive, requiring wildcard match arms; server-sent enums gain an Unknown variant that cannot be sent back. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Mutating the set returned by this method is no longer observed; change Subject Alternative Name lists through Configuration methods. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Mutating the set returned by this method is no longer observed; change Subject Alternative Name lists through Configuration methods. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Start failures now reject with an Error when Java cannot run or exits before readiness; failed starts clean up the launched process, and polling has a timeout. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Response status codes outside 100–999 are now rejected; invalid entries in initialization or persisted expectations are skipped with a warning. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Stop failures and timeouts now reject and stop the launched process; refusal or server errors no longer resolve as if MockServer stopped. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- TCP chaos latency and bandwidth now behave like a slow link: inbound data stays ordered, bandwidth is shared per connection, and latency plus bandwidth settings add together. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The option is now on by default, so a failing or invalid response or forward template returns 500 rather than 404 or 502. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A verification with an upper bound now fails rather than passing when the event log is truncated. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Verification sequences now check DNS/binary steps and match requests as received when redaction is enabled; verification kinds that cannot count DNS/binary traffic are rejected with 400. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- No longer passes when the server rejected the call or could not be reached. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### Security

- The Ruby launcher builds a quoted cmd.exe command line on Windows and raises MockServer::Error for unsafe arguments; it no longer uses a shell on Linux or macOS. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The launcher builds a quoted cmd.exe command line on Windows and refuses launcher paths containing a double quote, line break, NUL, or more than one percent sign. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The launcher builds a quoted cmd.exe command line on Windows and refuses launcher paths containing a double quote, line break, NUL, or more than one percent sign. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The launcher builds a quoted cmd.exe command line on Windows and refuses launcher paths containing a double quote, line break, NUL, or more than one percent sign. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Internal x-http2 headers are no longer leaked into recorded, matched, or forwarded requests and responses. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### Deprecations

- http_request remains supported as a deprecated alias of request_override. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- http_response remains supported as a deprecated alias of response_override. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### New APIs and options

- Helm adds a pre-stop sleep setting, defaulting to 0 and requiring Kubernetes 1.30 or newer. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Helm adds a termination grace period setting, defaulting to 45 seconds, for graceful draining. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Binary responses can select whether to answer only, answer and forward while dropping the server reply, or forward and replace the server reply. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Bounds how long a callback waits for its client id; callback and breakpoint registration rejects if the id does not arrive within the configured timeout. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Go, .NET and Rust add a typed `CHECK_FAILURE_RATE` threshold metric for load scenarios. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Closes callback and breakpoint WebSockets without resetting MockServer. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The selected DNS port can be read from `ClientAndServer`, including the instance injected by the JUnit 5 extension. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Python and Ruby clients gained a conditional-matcher type. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Go adds conditional request matcher fields and a `ConditionalRequest(...)` helper. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Python can build and read conditional if/then/else request matchers using `if_request`, `then_request`, `else_request` and `not_condition`. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Typed client calls compare a described request with every active expectation, field by field. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Typed client calls explain which expectation would serve a recorded request, why earlier expectations were passed over, which lower-priority expectations it hides, and how the request was handled. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Typed client calls list the closest expectations for recent unmatched requests, optionally with a suggested JSON patch for each. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Forward loops back to MockServer stop after 10 hops with 508 Loop Detected; setting the limit to 0 disables the forwarding header. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The dashboard uses this authenticated, redacted endpoint to load full bodies for entries whose displayed bodies are truncated. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Rust and PHP add a helper for building conditional request matchers. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- .NET adds `If`, `Then` and `Else` fields and the `RequestIf(...)` helper for conditional request matchers. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client sends and exposes the primary flag, allowing a primary response action to be combined with a second action. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Configures the maximum input length for deterministicFromInput embedding mocks, which now default to a 1,048,576-character limit. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Python, Go, .NET, Rust and PHP load-scenario steps can specify per-step checks and a `checks` list. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Rust load steps gain `name(...)` and `label(key, value)` methods, and load scenarios gain `label(key, value)`. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Rust client's LoadThresholdMetric enum gains the CheckFailureRate variant. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The enum gains a CheckFailureRate variant for the new per-step load check threshold. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The event log is now bounded by size as well as count. The setting is enabled by default, using a heap-based limit; set it to 0 to restore count-only bounding. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Delayed responses are capped to bound resource use; requests within the limit are unaffected. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Queued template actions are capped to bound resource use; requests within the limit are unaffected. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A new metric is provided for pending delayed tasks. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A new metric counts response write stalls, labelled by protocol and scope. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A new metric counts WebSocket read pauses. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Builder types now live in this module, which can be augmented instead of mockserver-client/llm. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Set this property to false to opt out of the dev-mode defaults used by the JUnit rule and extension. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Spring listener exposes the selected DNS port through the `${mockServerDnsPort}` placeholder. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The new `@MockServerDnsPort` annotation exposes the selected DNS port. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The selected DNS port can be read from `MockServerRule`. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- `@MockServerTest` now accepts `mockserver.dnsEnabled` and `mockserver.dnsPort`. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Python and Ruby clients now support per-step load checks. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Java client adds a method to retrieve recorded request definitions, including DNS queries and binary messages. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- TurnBuilder is now declared alongside the other builder constructors. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### Performance

- The event-log thread now batches wake-ups while traffic flows, reducing CPU use; log entries may reach the console, disk capture, and dashboard up to 10 ms later. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The receive buffer is sized up to reduce stalls with curl's OpenSSL QUIC stack; raise the host's net.core.rmem_max for the full 4 MiB buffer. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The GraalVM engine is shared process-wide and parsed scripts are cached; template rendering uses a dedicated bounded pool so saturated renders do not block unrelated event-loop work. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Shutdown is effectively instant after removing a redundant fixed Netty quiet-period wait. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Disk capture is cheaper and batches writes. Output lines may differ byte-for-byte while parsing to the same JSON; a hard kill can lose up to 8 KB of recent lines. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Three forwarding and proxy-pass paths no longer block a pool thread for the full upstream round trip, increasing proxy concurrency with a small thread pool. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### Behavior and default changes

- Binary proxying now keeps one upstream connection for the client's whole connection, relays TLS on that connection, and tunnels through configured upstream proxies. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Closest-match comparisons now stop after the first 1,000 expectations in serving order; the hint indicates when it was truncated. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Unexpected internal failures now return a 500 with a generic message and correlation id; invalid requests remain 400 responses. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTP/2 tunnels now answer 100 Continue themselves and pass the request and full body once; unsupported expectations receive 417 and oversized bodies receive 413. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Forwarded-request metrics now label at most 500 distinct upstream hosts; additional hosts are grouped under _other. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTPS and SOCKS upstream proxies now resolve destination host names themselves instead of requiring MockServer to resolve them. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Invalid forwarding keys or certificates and undecodable upstream responses do not trigger retries; idempotent requests are retried once on a fresh connection after a pooled connection closes on reuse. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Uploads abandoned by the client are logged once at INFO rather than ERROR with a stack trace; nothing is logged at WARN or ERROR. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- An HTTP/2 upstream connection may now open only one stream of its own at a time, with the same per-stream body-piece limit. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Docker images now use ZGC by default; -aot retains G1. Overriding JAVA_TOOL_OPTIONS replaces the default options, so include -XX:+UseZGC to retain ZGC. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The JUnit 5 extension now defaults to dev mode, using maxLogEntries=1000 and maxExpectations=1000 instead of heap-derived sizes; set mockserver.devMode=false or raise the caps if deeper history is needed. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The JUnit 4 rule now defaults to dev mode, using maxLogEntries=1000 and maxExpectations=1000 instead of heap-derived sizes; set mockserver.devMode=false or raise the caps if deeper history is needed. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Log entries now include each request or response body once; message, arguments, and proxied-exchange expectation bodies use short forms instead of repeating full bodies. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Peer-closed or reset connections are logged at cause-appropriate levels in MockServer's own log; set DEBUG to see the quieter entries. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The default cap rises from 100,000 to 250,000 on large heaps; the effective default also scales with the reduced container heap cap. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The default is now 50 instead of -1, limiting logged expectation mismatch entries per request without changing matching or verification behavior. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A new metric counts drift analyses skipped when the backlog fills, rather than allowing the backlog to grow without limit. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- CommonJS-style imports work with or without esModuleInterop; default imports require esModuleInterop. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- When MockServer runs as its own process, Netty off-heap buffer memory is capped by default at a quarter of max heap, with a 64 MiB minimum and a cap no greater than heap; reaching the cap closes the connection that… (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- With transparentProxyEnabled, PROXY-prefixed connections are parsed and matched or recorded as HTTP, and remote-address callbacks and templates see the real client address. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Calls filtered by request now also return error log entries associated with that request. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Calls filtered by request now also return error log entries associated with that request. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Inbound and outbound TLS handshakes now use this timeout, with a 20-second default, instead of a hard-coded 10-second limit. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Verifying by the id of a DNS or binary expectation now counts the DNS queries or binary messages that expectation answered. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### Tooling

- The Node client typings now declare this existing runtime method, with a typed Har document as its resolved value. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)

### Fixes and other changes

- .NET and Rust clients can now read a load scenario using the CHECK_FAILURE_RATE threshold. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Tunnel handling now preserves streamed responses, isolates request and stream failures, routes known destinations through MockServer matching, and avoids losing or duplicating requests in the described edge cases. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTP/3 request bodies with content encodings are decompressed for matching and forwarding, while original compressed bytes are retained. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- verify, verifyNever, and sequence verification now count DNS and binary requests matched by request or expectation id. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Python, Ruby, Rust, Go, .NET and PHP clients now support building and reading back previously missing expectation fields, including overrides, matchers, response settings, templates and action settings. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Expectation.from_dict no longer drops an OpenAPI request matcher. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTPS forward-proxying now pools HTTP/2 upstream connections, reducing local-port exhaustion under sustained load. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTP/2 gRPC streams, including server reflection, now end normally when the client ends its request with trailers instead of closing the connection and other streams. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- After-raw-response pipelined exchanges now preserve the next response on the same connection. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Mocked 1xx-only responses, or 1xx responses with a body or trailers, are sent as interim responses followed by a clean stream reset instead of hanging clients or breaking connections. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Unexpected upstream connection errors now fail pending forwards, send GOAWAY, close the connection, and prevent its reuse from the pool. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- HTTP/3 bodies without Content-Encoding retain the bytes received when forwarded; text without a charset still uses ISO-8859-1, while JSON and XML default to UTF-8. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The HTTP/3 UDP port is released when the server stops or fails to start, allowing immediate restart or another application to bind it. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Python's HttpOverrideForwardedRequest now supports request_override and response_override, sends overrides under accepted names alongside modifiers or response_template, and reads overrides back from MockServer. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Reading back a Java API header or query parameter added with an empty or null value list no longer throws NullPointerException. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Header sections exactly at the configured limit are accepted regardless of how network reads split the final header line. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The minimum is now 1 byte; zero or negative values no longer produce inconsistent body limits across protocols. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The minimum is now 1 byte; zero or negative values no longer produce inconsistent body limits across protocols. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- A Java client callback whose WebSocket registration fails no longer occupies a WebSocket expectation slot. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Named imports now work; previously only the default import worked. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Named ES-module imports in the Node client and launcher were fixed. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The bypass list now applies consistently to HTTP, HTTPS, and SOCKS upstream proxies; leading-dot suffixes and normalized IPv6 addresses are supported. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The PHP client now sends an empty request matcher as an object rather than an array. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Free-port helpers no longer return a port another application is listening on at 127.0.0.1 or ::1. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Python synchronous client now exposes respond_with_grpc_bidi, previously available only on its async sibling. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Proxied response headers, trailers, and cookies beginning with matcher marker characters are recorded literally rather than parsed as matcher syntax. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Retrieving log messages without a request matcher now includes messages about DNS and binary requests. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Rust clients can now parse load scenarios that omit abortOnFail, thresholds, stages, rows or captures, which previously failed to parse. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Node launcher now honors the configured startupRetries value instead of always reading it as 500. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- Verification.from_dict no longer drops an OpenAPI request matcher. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Python synchronous client now exposes with_chaos, previously available only on its async sibling. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)
- The Python synchronous client now exposes with_steps, previously available only on its async sibling. (9.0.0) — [release notes](https://github.com/mock-server/mockserver-monorepo/blob/30539acf3f11806d46e4aef46886c51a46e6e305/changelog.md#900---2026-10-15)