AG-UI Kotlin 0.5.0 aligns with 1.0 through interrupts, activities, multimodality, and strict state boundaries
AG-UI released Kotlin core, client, and tools 0.5.0 on November 5. The SDK now targets AG-UI 1.0 with REASONING events, interrupt/resume outcomes, ACTIVITY snapshots and deltas, tool errors, and multimodal user messages, while adding browser Wasm and macOS Arm64 targets and tightening event, input, and RFC 6902 state validation.
Why it matters
Kotlin moves from basic event transport to 1.0 semantics for pausing, resuming, agent activities, and multimodal history across Android, JVM, browser Wasm, and Apple Silicon. Strict state-delta handling also turns potential silent divergence into an observable failure boundary.
A closer look
Core adds Interrupt, ResumeStatus, ResumeEntry, ActivityMessage, Role.ACTIVITY, ToolMessage.error, and multimodal UserMessage, and fixes stack overflow on long JSON Pointer inputs. The client no longer echoes Activity messages back to the agent, preserves multimodal tool content, metadata, and subagent attribution, and applies patches without recursion. A malformed STATE_DELTA is fatal; an inapplicable delta is reported through onStateError. Maximum JSON depth drops from 512 to 128, and a successful outcome serializes to a type-only object.
Who this is for
Teams maintaining Android, JVM, Kotlin Multiplatform, Wasm, or macOS AG-UI clients and cross-SDK interoperability layers.
Original sources
Revisions & corrections (1)
— The official release is a dated, evidence-complete protocol-alignment event with explicit additions, breaking changes and failure semantics.