JetBrains/koog 0.7.3 on GitHub

Published 26 March 2026

New Features

Bedrock prompt caching: Added CacheControl property on Assistant, User, and System messages within the Prompt and integrated explicit cache blocks in the Bedrock Converse API (#1583)

Agent deadlock fix: Fixed deadlock when agent.run() is called from within executor.submit — when the agent was invoked from a worker thread of the configured ExecutorService, runBlocking(context) would dispatch the coroutine back onto that executor and park the calling thread (KG-750, #1716)
AIAgentTool for simple agents: Fixed AIAgentTool to support simple agents that accept primitives as input by introducing AIAgentToolInput wrapper (#1729)
MCP custom transport: Fixed runtime crash when using non-default custom MCP transports in MCPToolRegistryProvider (#1740)
Anthropic tool error reporting: Added is_error flag for failed tool calls in the Anthropic client so the model is properly informed of tool execution failures (#1700)
DeepSeek reasoning with tool calls: Ensured reasoningContent is preserved and merged with tool calls to satisfy DeepSeek API requirements (#1614)

ToolRegistry.Builder removed: Unified everything under expect/actual ToolRegistryBuilder. Removed tools(Any) overload that was interfering with tools(List) and causing unexpected bugs (#1746)

Removed stale coreLibrariesVersion override: The convention plugins were setting coreLibrariesVersion = "2.1.21" which made published POMs declare kotlin-stdlib 2.1.21, mismatching the actual 2.3.x compiler version. Removed the override so the POM picks up the real compiler version (#1697, #1722)

Updated serialization documentation with Java snippets (#1732)
Added Java implementation for custom subgraphs documentation (KG-770, #1730)
Added Java implementation for OpenTelemetry, Langfuse, and Weave integration documentation (KG-760, #1696)
Moved "Chat agent with memory" tutorial under "Chat memory" feature section (#1686)