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name: work-on-milestone description: | Use this skill when asked to work on a milestone. You are not required to complete the milestone when this skill is invoked.

Working Through a Milestone

Before Starting

1. Review the last commit: git show HEAD
2. Run tests to see current state: mise test
3. Read relevant test files in testcases/ to understand expected behavior
4. CRITICAL: Assess host interface sufficiency
   • Review src/tclc.h (TclHostOps) to understand available primitives
   • Determine if the feature can be implemented using existing ops
   • If TclHostOps needs to be extended: STOP IMMEDIATELY and inform the user
   • Do not proceed until you have received explicit approval and direction

Implementation Loop

For each failing test:

1. Identify what's missing - parse test output to understand the gap
2. C interpreter changes (in src/):
   • Create new builtin_*.c file if adding a command
   • Add declarations to internal.h
   • Register command in interp.c builtins table
   • Implement using TclHostOps primitives only
3. Go host changes (in interp/):
   • Implement callbacks in callbacks.go
   • Add state to Interp struct in tclc.go if needed
   • Follow shimmering rules in interp/CLAUDE.md
4. Run tests: mise test
5. Iterate until tests pass

Key Patterns

• List operations mutate: Use ops->list.from() to copy before iterating
• String lengths: Count carefully, don't include null terminator
• Shimmering: Use Get*() methods in Go for type conversion, never access Object fields directly
• Error messages: Match TCL's exact format (check test expectations)

After All Tests Pass

1. Run tests multiple times to verify stability
2. Commit with detailed message explaining:
   • What was implemented
   • Key implementation details
   • Important learnings for future work
3. Use the format from CLAUDE.md (heredoc, co-author line)

File Checklist for New Commands

• src/builtin_<cmd>.c - implementation
• src/internal.h - declaration
• src/interp.c - registration
• interp/callbacks.go - host callbacks (if new ops needed)
• interp/tclc.go - state/structs (if needed)