diff --git a/lib/content/conformance.sh b/lib/content/conformance.sh
index 67fea63a..482edf4d 100755
--- a/lib/content/conformance.sh
+++ b/lib/content/conformance.sh
@@ -15,7 +15,7 @@ if [ ! -x "$SX_SERVER" ]; then
   fi
 fi
 
-SUITES=(block doc render api meta page page-full markdown text section compose tree-edit clone query toc anchor outline flatten transform normalize find-replace stats table callout data wire validate store snapshot crdt crdt-store sync md-import md-doc fed)
+SUITES=(block doc render api meta page page-full markdown text section compose tree-edit move clone query toc anchor outline flatten transform normalize find-replace stats table callout data wire validate store snapshot crdt crdt-store sync md-import md-doc fed)
 
 OUT_JSON="lib/content/scoreboard.json"
 OUT_MD="lib/content/scoreboard.md"
@@ -47,6 +47,7 @@ run_suite() {
 (load "lib/content/section.sx")
 (load "lib/content/compose.sx")
 (load "lib/content/tree-edit.sx")
+(load "lib/content/move.sx")
 (load "lib/content/clone.sx")
 (load "lib/content/query.sx")
 (load "lib/content/toc.sx")
diff --git a/lib/content/move.sx b/lib/content/move.sx
new file mode 100644
index 00000000..374c6288
--- /dev/null
+++ b/lib/content/move.sx
@@ -0,0 +1,69 @@
+;; content-on-sx — relative block reorder.
+;;
+;; Move a top-level block to just before / after another block by id — more
+;; ergonomic than the index-based doc-move. No-op if either id is missing.
+;; Immutable; composes the doc.sx list helpers.
+;;
+;; Requires (loaded by harness): doc.sx.
+
+(define
+  content/move-before
+  (fn
+    (doc id target)
+    (let
+      ((blk (doc-find doc id)))
+      (if
+        (= blk nil)
+        doc
+        (let
+          ((without (ct-remove-id (doc-blocks doc) id)))
+          (let
+            ((idx (ct-index-of without target)))
+            (if
+              (= idx -1)
+              doc
+              (doc-with-blocks doc (ct-insert-at without idx blk)))))))))
+
+(define
+  content/move-after
+  (fn
+    (doc id target)
+    (let
+      ((blk (doc-find doc id)))
+      (if
+        (= blk nil)
+        doc
+        (let
+          ((without (ct-remove-id (doc-blocks doc) id)))
+          (let
+            ((idx (ct-index-of without target)))
+            (if
+              (= idx -1)
+              doc
+              (doc-with-blocks
+                doc
+                (ct-insert-at without (+ idx 1) blk)))))))))
+
+(define
+  content/move-to-front
+  (fn
+    (doc id)
+    (let
+      ((blk (doc-find doc id)))
+      (if
+        (= blk nil)
+        doc
+        (doc-with-blocks doc (cons blk (ct-remove-id (doc-blocks doc) id)))))))
+
+(define
+  content/move-to-back
+  (fn
+    (doc id)
+    (let
+      ((blk (doc-find doc id)))
+      (if
+        (= blk nil)
+        doc
+        (doc-with-blocks
+          doc
+          (append (ct-remove-id (doc-blocks doc) id) (list blk)))))))
diff --git a/lib/content/scoreboard.json b/lib/content/scoreboard.json
index 9db0743e..b0fd1304 100644
--- a/lib/content/scoreboard.json
+++ b/lib/content/scoreboard.json
@@ -12,6 +12,7 @@
     "section": {"pass": 25, "fail": 0},
     "compose": {"pass": 17, "fail": 0},
     "tree-edit": {"pass": 17, "fail": 0},
+    "move": {"pass": 11, "fail": 0},
     "clone": {"pass": 10, "fail": 0},
     "query": {"pass": 13, "fail": 0},
     "toc": {"pass": 8, "fail": 0},
@@ -36,7 +37,7 @@
     "md-doc": {"pass": 12, "fail": 0},
     "fed": {"pass": 20, "fail": 0}
   },
-  "total_pass": 657,
+  "total_pass": 668,
   "total_fail": 0,
-  "total": 657
+  "total": 668
 }
diff --git a/lib/content/scoreboard.md b/lib/content/scoreboard.md
index 31b5f85f..d70fa4c2 100644
--- a/lib/content/scoreboard.md
+++ b/lib/content/scoreboard.md
@@ -16,6 +16,7 @@ _Generated by `lib/content/conformance.sh`_
 | section | 25 | 0 | 25 |
 | compose | 17 | 0 | 17 |
 | tree-edit | 17 | 0 | 17 |
+| move | 11 | 0 | 11 |
 | clone | 10 | 0 | 10 |
 | query | 13 | 0 | 13 |
 | toc | 8 | 0 | 8 |
@@ -39,4 +40,4 @@ _Generated by `lib/content/conformance.sh`_
 | md-import | 38 | 0 | 38 |
 | md-doc | 12 | 0 | 12 |
 | fed | 20 | 0 | 20 |
-| **Total** | **657** | **0** | **657** |
+| **Total** | **668** | **0** | **668** |
diff --git a/lib/content/tests/move.sx b/lib/content/tests/move.sx
new file mode 100644
index 00000000..31595762
--- /dev/null
+++ b/lib/content/tests/move.sx
@@ -0,0 +1,63 @@
+;; Extension — relative block reorder.
+
+(st-bootstrap-classes!)
+(content/bootstrap!)
+
+(define
+  d
+  (doc-append
+    (doc-append
+      (doc-append (doc-empty "d") (mk-text "a" "A"))
+      (mk-text "b" "B"))
+    (mk-text "c" "C")))
+
+;; ── move-before ──
+(content-test
+  "move-before"
+  (doc-ids (content/move-before d "c" "a"))
+  (list "c" "a" "b"))
+(content-test
+  "move-before mid"
+  (doc-ids (content/move-before d "c" "b"))
+  (list "a" "c" "b"))
+(content-test "move-before immutable" (doc-ids d) (list "a" "b" "c"))
+
+;; ── move-after ──
+(content-test
+  "move-after"
+  (doc-ids (content/move-after d "a" "b"))
+  (list "b" "a" "c"))
+(content-test
+  "move-after last"
+  (doc-ids (content/move-after d "a" "c"))
+  (list "b" "c" "a"))
+
+;; ── move-to-front / back ──
+(content-test
+  "move-to-front"
+  (doc-ids (content/move-to-front d "c"))
+  (list "c" "a" "b"))
+(content-test
+  "move-to-back"
+  (doc-ids (content/move-to-back d "a"))
+  (list "b" "c" "a"))
+(content-test
+  "front already first"
+  (doc-ids (content/move-to-front d "a"))
+  (list "a" "b" "c"))
+
+;; ── no-ops ──
+(content-test
+  "missing id no-op"
+  (doc-ids (content/move-before d "zzz" "a"))
+  (list "a" "b" "c"))
+(content-test
+  "missing target no-op"
+  (doc-ids (content/move-before d "a" "zzz"))
+  (list "a" "b" "c"))
+
+;; ── render after move ──
+(content-test
+  "render after move"
+  (asHTML (content/move-after d "a" "c"))
+  "<p>B</p><p>C</p><p>A</p>")
diff --git a/plans/content-on-sx.md b/plans/content-on-sx.md
index 2223679f..79440e4e 100644
--- a/plans/content-on-sx.md
+++ b/plans/content-on-sx.md
@@ -19,7 +19,7 @@ injected adapter, not core.
 
 ## Status (rolling)
 
-`bash lib/content/conformance.sh` → **657/657** (Phases 1–4 COMPLETE + ~29 extensions: HTML/SX escaping, Markdown render + import/export incl. tables & frontmatter (full round-trip), CRDT replication, tree-aware validation, snapshot cache, doc metadata, plain-text render, nested block trees + deep editing + flatten, doc stats, table + callout blocks, HTML page wrapper + SEO page, doc composition + id-remap, portable data + wire serialization, block query + transforms + find/replace, TOC + anchored headings + outline, normalization)
+`bash lib/content/conformance.sh` → **668/668** (Phases 1–4 COMPLETE + ~30 extensions: HTML/SX escaping, Markdown render + import/export incl. tables & frontmatter (full round-trip), CRDT replication, tree-aware validation, snapshot cache, doc metadata, plain-text render, nested block trees + deep editing + flatten + relative reorder, doc stats, table + callout blocks, HTML page wrapper + SEO page, doc composition + id-remap, portable data + wire serialization, block query + transforms + find/replace, TOC + anchored headings + outline, normalization)
 
 ## Ground rules
 
@@ -101,6 +101,7 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 - [x] anchored-heading render (`anchor.sx`: content/html-anchored, functional TOC links)
 - [x] document outline (`outline.sx`: content/outline, nested heading tree)
 - [x] document flatten (`flatten.sx`: content/flatten, un-nest sections; inverse of wrap-section)
+- [x] relative reorder (`move.sx`: content/move-before/after/to-front/to-back by id)
 - [x] document normalization (`normalize.sx`: content/normalize, drop empty blocks/sections)
 - [x] global find/replace (`find-replace.sx`: content/find-replace across text-bearing blocks)
 - [x] portable data serialization (`data.sx`: content/to-data + from-data, round-trips tree)
@@ -108,6 +109,11 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 
 ## Progress log
 
+- 2026-06-07 — Extension: relative block reorder (`move.sx`).
+  `content/move-before` / `content/move-after` move a top-level block to just
+  before/after another by id; `content/move-to-front` / `move-to-back` too. More
+  ergonomic than index-based doc-move; no-op on missing ids; immutable. 11 tests;
+  suite 668/668.
 - 2026-06-07 — Extension: callout/admonition block (`callout.sx`). `CtCallout`
   holds kind (note/warning/tip) + text; answers asHTML (`<aside class="callout
   callout-KIND">`, escaped), asSx, asText, asMarkdown: (`> **kind:** text`).