# Section 03 Code Review: suggest_scale Reference Mode

## Summary

The implementation faithfully follows the plan. The core logic is correct and code quality is consistent with the existing codebase.

## Issues

### 1. [MEDIUM] `_reference_mode` drops `session` parameter from plan spec

Plan specifies `session` as first param; implementation omits it since it's unused. This is defensible and cleaner — the code is self-consistent.

### 2. [HIGH] Potential `intended_use=None` crash

FastMCP doesn't enforce type constraints — a client could send `null` for `intended_use`. If `model=None` and `intended_use=None`, the guard catches it (`not None` is `True`). But adding a type guard `if intended_use is None: intended_use = ""` at the top of `_build_suggest_scale` would be safer.

### 3. [LOW] No test for reference mode with nonexistent scene

The code handles it correctly (scene-not-found guard runs before reference mode branch), but it's untested.

### 4. [LOW] Sprint docstring in test file is stale

Test file header references "Sprint 3c" but this is Sprint 3e.

## What Looks Good

1. All 4 plan-specified tests present and correct
2. Guard ordering is correct: both-empty → scene resolution → reference mode → model path
3. `mode: "model"` added to existing result dict
4. MCP tool signature updated correctly
5. Median-per-axis calculation reuses same approach as model path
6. Matching logic correctly implements case-insensitive substring matching
7. Zero-match output matches plan spec exactly
8. `scale_range` dict included for non-zero matches
