June 2026 monthly summary for facebookresearch/momentum. Key feature delivered: introduced an immutable builder for the Character class to set metadata for FBX exports via Character.with_metadata(metadata: str). This enables attaching arbitrary data to characters and improves the flexibility of character geometry bindings, aligning with existing builder patterns (with_locators, with_parameter_limits, with_skinned_locators) and preserving immutability by returning a new Character instance. API modernization also included regeneration of geometry.pyi to reflect the new builder. No documented major bug fixes this month; the focus was on delivering the feature and ensuring API consistency. Overall impact: enhances export fidelity and data-rich character representations, supporting downstream tooling and data pipelines that rely on character metadata. Demonstrated technologies/skills: Python API design for immutable objects, builder pattern adherence, code generation/regeneration (geometry.pyi), review and collaboration on a GitHub PR, and changelog/documentation alignment. Commit reference included in the work: db73044ae5e48942002ce636513bf0b7dcac34c2; PR 1469; Differential Revision: D106872137; code review by cstollmeta.