diff --git a/.github/workflows/api-spec.yml b/.github/workflows/api-spec.yml
index 2ee1d8b..8204cf2 100644
--- a/.github/workflows/api-spec.yml
+++ b/.github/workflows/api-spec.yml
@@ -98,6 +98,11 @@ jobs:
           base: .api-spec-tmp/base.yaml
           revision: .api-spec-tmp/revision.yaml
           fail-on: ERR
+          # Upload to oasdiff.com to get a side-by-side review link (exposed as
+          # the review_url output), but suppress the action's own comment with an
+          # empty token — we post a single combined comment below.
+          review: true
+          github-token: ""
 
       - name: Generate changelog
         id: changelog
@@ -108,6 +113,9 @@ jobs:
           revision: .api-spec-tmp/revision.yaml
           format: markdown
           output-to-file: changelog.md
+          # As above: keep the upload/review_url output, suppress the auto-comment.
+          review: true
+          github-token: ""
 
       - name: Determine whether the spec changed
         id: changes
@@ -135,12 +143,20 @@ jobs:
         env:
           GH_TOKEN: ${{ github.token }}
           PREV_ID: ${{ steps.prev-comment.outputs.id }}
+          REVIEW_URL: ${{ steps.changelog.outputs.review_url }}
         run: |
           {
             echo "<!-- api-spec-workflow -->"
             echo "## ⚠️ API specification — non-breaking changes"
             echo ""
+            echo "<details><summary>API changes</summary>"
+            echo ""
             cat changelog.md
+            echo ""
+            echo "</details>"
+            if [ -n "$REVIEW_URL" ]; then
+              printf '\n🔍 [View the full side-by-side review](%s)\n' "$REVIEW_URL"
+            fi
           } > comment.md
           if [ -n "$PREV_ID" ]; then
             jq -Rs '{body: .}' < comment.md \
@@ -154,16 +170,24 @@ jobs:
         env:
           GH_TOKEN: ${{ github.token }}
           PREV_ID: ${{ steps.prev-comment.outputs.id }}
+          REVIEW_URL: ${{ steps.breaking.outputs.review_url }}
         run: |
           {
             echo "<!-- api-spec-workflow -->"
             echo "## 🛑 API specification — breaking changes detected"
             echo ""
             if [ -s changelog.md ]; then
+              echo "<details><summary>API changes</summary>"
+              echo ""
               cat changelog.md
+              echo ""
+              echo "</details>"
             else
               echo "The breaking-changes check flagged incompatible changes. Review the workflow logs for details."
             fi
+            if [ -n "$REVIEW_URL" ]; then
+              printf '\n🔍 [View the full side-by-side review](%s)\n' "$REVIEW_URL"
+            fi
           } > comment.md
           if [ -n "$PREV_ID" ]; then
             jq -Rs '{body: .}' < comment.md \
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c6233cd..24eaa0d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@ See [keep a changelog] for information about writing changes to this log.
 
 ## [Unreleased]
 
+- [PR-51](https://github.com/itk-dev/event-database-api/pull/51)
+  Show the API-spec diff summary inline in the PR comment (collapsed) alongside the oasdiff review link
 - [PR-49](https://github.com/itk-dev/event-database-api/pull/49)
   Bump oasdiff-action to v0.1.5 in the API-spec workflow
 - [PR-48](https://github.com/itk-dev/event-database-api/pull/48)