diff --git a/WORK_LOG.md b/WORK_LOG.md
index ba0e1d0..bb06d31 100644
--- a/WORK_LOG.md
+++ b/WORK_LOG.md
@@ -40,6 +40,7 @@ The routing method selection logic was updated so perpendicular port-angle cases
 mxpic_router/mxpic_router/builder.py
 mxpic_router/tests/test_eda_router_contract.py
 
+
 ## 2026-06-04
 
 ### Scope
@@ -207,3 +208,37 @@ Contract tests were added to verify electrical-family PCB routing and left-to-ri
 
 mxpic_router/mxpic_router/builder.py
 mxpic_router/tests/test_eda_router_contract.py
+
+
+## 2026-06-15
+
+### Scope
+
+Backend automatic route spacing extension for U-bend and mixed S-bend/U-bend bundles in `mxpic_router`.
+
+### Summary
+
+Recent work focused on extending the existing S-bend `Lstart` spacing strategy to U-bend routes and improving collision avoidance when both route types appear in the same bundle.
+
+### Completed Work
+
+#### 1. U-Bend Spacing Support
+
+Automatic `ubend_p2p` routes now receive width-aware `length` offsets within compatible route groups.
+
+The U-bend ordering logic was refined so inner routes use shorter lengths and outer routes use longer lengths, including reversed port-order cases.
+
+#### 2. Mixed Route-Type Coordination
+
+Mixed S-bend/U-bend groups now share coordinated spacing.
+
+U-bend routes are assigned the shorter length range first, while S-bend routes receive larger `Lstart` values after accounting for the U-bend group envelope, including route width, spacing, and bend radius.
+
+#### 3. Test Coverage Update
+
+Contract tests were added and updated for U-bend spacing, reversed port-order U-bend routing, and mixed S-bend/U-bend bundle spacing.
+
+### Modified Files
+
+mxpic_router/mxpic_router/builder.py
+mxpic_router/tests/test_eda_router_contract.py
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