Agent UI v0.2.0 Specification

The v0.2.0 specification snapshot is aligned with the current latest specification.

v0.2.0 changes

• Replaces the early draft model with a runtime-first projection architecture.
• Defines standard event classes for lifecycle, status, text, reasoning, tool, action, queue, artifact, evidence, state, messages, and completion.
• Defines standard surfaces for composer, message parts, runtime status, tools, tasks, HITL, artifacts, evidence, and sessions.
• Defines backend coordination layers: summary, snapshot, window detail, timeline page, artifact preview, artifact content, evidence job, and diagnostics.
• Defines performance metrics for submit-to-status, first text paint, stream queue pressure, history restore, and resource usage.
• Adds client implementation guidance for session hydration and queue/steer behavior.
• Adds acceptance scenarios as behavior-level validation.
• Removes the old document-entrypoint requirement from the current standard.

See the latest specification for the full runtime and surface rules.