http4k Files

Distribution notice - from 1 October 2026, Maven Central receives http4k releases approximately quarterly. maven.http4k.org continues on the normal 1-2 week cadence. Both channels are supported. Background and current status: DISTRIBUTION.md (www.http4k.org)

Changelog:

• http4k-*: Upgrade versions & Gradle
• http4k-ai-core: [Break] toCompletionSequence is replaced by toSseSequence and toJsonLinesSequence.
• http4k-web-htmx: [Break] Upgrade to HTMX 4.0.0 so webjars will have changed URL and version we are shipping. If you're not on HTMX 4 then expect breaks.
• http4k-connect-ai-anthropic-*: [Break] The Messages API model is much more complete, so a few things move. In rough order of how likely you are to hit them:
  • Handling response content: Content has many more arms plus an Unknown.
  • Setting a system prompt: system is a List<Content.Text> rather than a SystemPrompt.
  • Using tools: Tool(name, description, schema) becomes Tool.User(name, schema, description), and ToolResult.content is a List<Content> rather than Any.
  • Sending images: Source(data, mediaType) becomes Source.Base64(data, mediaType).
  • Streaming: MessageGenerationEvent gains StopMessage at the end of the stream and an Unknown arm, and Error carries ErrorDetail(type, message).
• http4k-postbox: [New module!] Reliable asynchronous processing of HTTP requests using http4k's uniform transactional outbox/inbox pattern
• http4k-connect-amazon-cognitoidentity-fake: [New module!] Amazon Cognito Identity fake, backed by a Storage<StoredIdentity>. One identity per pool and set of logins, as the real service does. H/T @torfinnberset
• http4k-connect-amazon-xray: [New module!] AWS X-Ray read APIs, covering GetTraceSummaries and BatchGetTraces. Segment documents are returned as the raw JSON X-Ray stores; the root-cause structures of a trace summary are not modelled. H/T @torfinnberset
• http4k-connect-amazon-xray-fake: [New module!] AWS X-Ray fake, backed by a Storage<StoredTrace>. It evaluates annotation.<key> = "<value>" filter expressions and refuses any other, rather than answering with every trace in the window. H/T @torfinnberset
• http4k-format-kotlinx-serialization: [Fix [#1609]] Parse rejects top-level arrays, silently dropping OpenAPI examples for list bodies. H/T @cies
• http4k-format-jackson-csv: [Fix] CSV deserialization column ordering and unknown columns handling H/T @aharin
• http4k-connect-amazon-dynamodb-fake: [Fix] failed TransactWriteItems now returns the same TransactionCanceledException error as DynamoDB, with a reason for each item. H/T @torfinnberset
• http4k-connect-ai-anthropic-*: [Fix] temperature, top_k and top_p only sent when set. Opus 4.7+, preventing request failure.
• http4k-ai-llm-anthropic: [Fix] Claude 5 models return a Thinking block by default, which the chat shim rejected.
• http4k-connect-ai-anthropic-fake: [Fix] Streamed responses emit a complete event sequence.
• http4k-connect-amazon-iot: DescribeCertificate, which reads a certificate's status, owner, mode and validity window from its id. H/T @torfinnberset
• http4k-connect-amazon-iot-fake: DescribeCertificate, backed by a Storage<StoredCertificate>. H/T @torfinnberset
• http4k-connect-amazon-sqs: ChangeMessageVisibility, which returns a received message to the queue early (timeout 0) or extends the time a consumer holds it. H/T @torfinnberset
• http4k-connect-amazon-sqs-fake: ChangeMessageVisibility. Received messages stay visible in the fake, so the call only checks that the queue exists. H/T @torfinnberset
• http4k-core: [Deprecation] Align ResponseLens/ResponseKet lenses with Request equivalents. H/T @aharin