name: unison-development description: Write, test, and update Unison code using the Unison MCP tool. Use when working with Unison language files (.u extension), UCM operations, or Unison projects. An extension to the XP skill.

Unison Development

• Uses xp skill.
• Use the Unison MCP server commands for all operations.

Core Principles

1. ALWAYS work in branches - create one with an appropriate name
2. NEVER run UCM commands on the command line — use MCP tools only (exception: branch creation)
3. NEVER use scratch.u files — use MCP tools directly
4. Code is stored by the UCM, NOT Git — NEVER suggest git commits for code changes
5. NEVER use commit-helper agent — Unison code is managed by UCM
6. Always use fully qualified names when writing code
7. Use the MCP tools to explore the codebase before writing code

Branch Creation (MANDATORY FIRST STEP)

Before making any code changes, create a branch with the MCP server tool. Use descriptive branch names like extract-domain-service or fix-login-bug.

Workflow

1. Explore: Use view-definitions, search-definitions-by-name, list-project-definitions to understand existing code
2. Typecheck: Use mcp__unison__typecheck-code to validate code before updating
3. Update: Use mcp__unison__update-definitions to apply changes directly to the codebase
4. Test: Use mcp__unison__run-tests to verify changes

Handling Typecheck Errors During Update

When update-definitions returns affected definitions that no longer typecheck:

-- The definitions below no longer typecheck with the changes above.
-- Please fix the errors and try `update` again.

CRITICAL:

• The MCP server creates a temporary branch with affected code in sourceCodeUpdates
• Fix ALL affected definitions and include them in the next update-definitions call
• DO NOT omit functions — they will be removed from codebase
• Include all fixes in a single update-definitions call

Modifying Abilities

When modifying abilities, include all affected dependents in the same update:

1. View the ability and its default handler
2. Use list-definition-dependents to find all callers
3. Update the ability AND all dependents together in one update-definitions call

Success Criteria

• All code typechecks successfully via MCP tools
• Tests pass via mcp__unison__run-tests
• Fully qualified names used throughout