diff --git a/work/link-taxonomy-migration/README.md b/work/link-taxonomy-migration/README.md
index 4782aca..d4c8bc6 100644
--- a/work/link-taxonomy-migration/README.md
+++ b/work/link-taxonomy-migration/README.md
@@ -70,7 +70,11 @@ Every unit in `plan.md` is published, and:
       alongside a bare wikilink during prose cleanup, caught by `migrate verify`'s `cite-refs`
       diff and restored. Published as commit `a35c94e`. See `glossary.md` for the
       add-is-safe/remove-is-risky mechanism note this unit established.
-- [ ] u4 `kb/sources/`
+- [x] u4 `kb/sources/` - zero page edits needed. `types/source.md` declares no `related:` field
+      (only `entities:`/`concepts:`, same structural gap as comparisons), and all 27 source pages
+      already had those fields correctly populated via `xref link-source` at ingest time - there
+      was never an unlabelled edge here to fix. `migrate verify --from 177c7e9 --path kb/sources`:
+      0 findings. No commit, no session id spent beyond the check itself. See `glossary.md`.
 - [ ] u5 close-out - `migrate done`, version bump, `CHANGES.md`, workshop close
 
 ## Measured after u0
diff --git a/work/link-taxonomy-migration/glossary.md b/work/link-taxonomy-migration/glossary.md
index d56ebea..83b74f7 100644
--- a/work/link-taxonomy-migration/glossary.md
+++ b/work/link-taxonomy-migration/glossary.md
@@ -87,6 +87,14 @@ Deferred edges for later units, discovered while processing systems:
   entity-to-concept for authorship. Resolved as `see-also` in every such case on Karpathy's,
   Gupta's and Bush's own pages, checked against every register first - not a stretch, a genuine
   gap. Worth proposing a label (`originates`/`authored-by`?) if this recurs in u3/u4.
+- **`kb/sources/` pages carry no `related:` field either, same as comparisons.**
+  `types/source.md` declares only `page_ref_fields: [entities, concepts]` - `xref add` refuses
+  there with the identical "type does not declare a related: field" error. Unlike comparisons,
+  though, there is nothing left to migrate by hand: every one of the 27 source pages already had
+  `entities:`/`concepts:` correctly populated via `xref link-source` at ingest time, and their
+  prose "Verwandte Entities"/"Verwandte Concepts" sections already just mirror those fields -
+  there was never a labelled-vs-unlabelled distinction to fix here. `migrate verify --from
+  177c7e9 --path kb/sources` returns 0 findings against baseline. u4 closes with zero page edits.
 - **comparisons pages carry no `related:` field at all.** `types/comparison.md` declares only
   `entities` (`page_ref_fields: [entities]`) - unlabelled by the schema, like `sources:`. `xref
   add`/`xref remove` refuse on this type ("type does not declare a related: field"). The