What's broken

create-story reads planning artifacts (epics, architecture, UX spec) but never reads the existing source files it marks as UPDATE in dev notes. When a story modifies an existing file, the dev agent has no knowledge of its current state, so it improvises design decisions at implementation time.

Steps to reproduce

1. Run create-story for any story that modifies an existing file (e.g., a screen that adds auth to an existing layout)
2. The generated dev notes describe what to create but not what to preserve in the file being modified
3. The dev agent implements the story without understanding the file's existing behaviors
4. Code review catches regressions that should have been prevented at the story level

Expected behavior

For every file marked UPDATE (not NEW) in the architecture directory structure, create-story should:

• Read the file completely
• Document its current state in dev notes (state machine, API calls, data shapes, existing behaviors)
• Specify what the story changes and what must be preserved

Why this matters

A story implementation must leave the system working end-to-end — not just satisfy its stated ACs. If an interaction with existing code is required for the feature to work, it is a requirement whether or not it is explicitly written in the story.

Environment

• BMad Method latest
• Affects: bmad-create-story/workflow.md Step 3