diff --git a/lib/content/block-path.sx b/lib/content/block-path.sx
new file mode 100644
index 00000000..7eef08a9
--- /dev/null
+++ b/lib/content/block-path.sx
@@ -0,0 +1,45 @@
+;; content-on-sx — locate a block in the tree (ancestor section path).
+;;
+;; The read-side companion to doc-find-deep (which returns the block) and the
+;; move/reparent ops (which relocate it): content/block-path returns the list of
+;; ancestor section ids, root-first, leading to a block id — i.e. where the
+;; block sits in the tree. A top-level block has an empty path; a block one
+;; section deep has a one-element path; a missing id returns nil (distinct from
+;; the empty-list path of a present top-level block). content/block-depth is the
+;; path length (0 = top level, -1 = absent). Useful for breadcrumbs and for
+;; scoping an edit to a block's enclosing section. Pure traversal; descends into
+;; any block carrying a children list, like the rest of the tree helpers.
+;;
+;; Requires (loaded by harness): block.sx, doc.sx.
+
+(define
+  bp-in-blocks
+  (fn
+    (blocks id trail)
+    (if
+      (= (len blocks) 0)
+      nil
+      (let
+        ((b (first blocks)))
+        (if
+          (= (blk-id b) id)
+          trail
+          (let
+            ((ch (st-iv-get b "children")))
+            (let
+              ((found (if (list? ch) (bp-in-blocks ch id (append trail (list (blk-id b)))) nil)))
+              (if (= found nil) (bp-in-blocks (rest blocks) id trail) found))))))))
+
+;; ancestor section ids (root-first) for `id`, or nil if the block is absent.
+(define
+  content/block-path
+  (fn (doc id) (bp-in-blocks (doc-blocks doc) id (list))))
+
+;; depth of `id`: 0 at top level, n nested n sections deep, -1 if absent.
+(define
+  content/block-depth
+  (fn
+    (doc id)
+    (let
+      ((p (content/block-path doc id)))
+      (if (= p nil) -1 (len p)))))
diff --git a/lib/content/conformance.sh b/lib/content/conformance.sh
index f248ba4c..6de638b0 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 move clone query toc anchor outline flatten transform normalize find-replace stats summary index table callout media data wire validate sanitize store snapshot crdt crdt-tree crdt-blocks crdt-store sync md-import md-doc fed)
+SUITES=(block doc render api meta page page-full markdown text section compose tree-edit move block-path clone query toc anchor outline flatten transform normalize find-replace stats summary index table callout media data wire validate sanitize store snapshot crdt crdt-tree crdt-blocks crdt-store sync md-import md-doc fed)
 
 OUT_JSON="lib/content/scoreboard.json"
 OUT_MD="lib/content/scoreboard.md"
@@ -48,6 +48,7 @@ run_suite() {
 (load "lib/content/compose.sx")
 (load "lib/content/tree-edit.sx")
 (load "lib/content/move.sx")
+(load "lib/content/block-path.sx")
 (load "lib/content/clone.sx")
 (load "lib/content/query.sx")
 (load "lib/content/toc.sx")
diff --git a/lib/content/scoreboard.json b/lib/content/scoreboard.json
index 4363092f..a09ac9b1 100644
--- a/lib/content/scoreboard.json
+++ b/lib/content/scoreboard.json
@@ -13,6 +13,7 @@
     "compose": {"pass": 17, "fail": 0},
     "tree-edit": {"pass": 17, "fail": 0},
     "move": {"pass": 24, "fail": 0},
+    "block-path": {"pass": 13, "fail": 0},
     "clone": {"pass": 10, "fail": 0},
     "query": {"pass": 20, "fail": 0},
     "toc": {"pass": 8, "fail": 0},
@@ -43,7 +44,7 @@
     "md-doc": {"pass": 12, "fail": 0},
     "fed": {"pass": 20, "fail": 0}
   },
-  "total_pass": 812,
+  "total_pass": 825,
   "total_fail": 0,
-  "total": 812
+  "total": 825
 }
diff --git a/lib/content/scoreboard.md b/lib/content/scoreboard.md
index 96e5ece7..d7db1c92 100644
--- a/lib/content/scoreboard.md
+++ b/lib/content/scoreboard.md
@@ -17,6 +17,7 @@ _Generated by `lib/content/conformance.sh`_
 | compose | 17 | 0 | 17 |
 | tree-edit | 17 | 0 | 17 |
 | move | 24 | 0 | 24 |
+| block-path | 13 | 0 | 13 |
 | clone | 10 | 0 | 10 |
 | query | 20 | 0 | 20 |
 | toc | 8 | 0 | 8 |
@@ -46,4 +47,4 @@ _Generated by `lib/content/conformance.sh`_
 | md-import | 38 | 0 | 38 |
 | md-doc | 12 | 0 | 12 |
 | fed | 20 | 0 | 20 |
-| **Total** | **812** | **0** | **812** |
+| **Total** | **825** | **0** | **825** |
diff --git a/lib/content/tests/block-path.sx b/lib/content/tests/block-path.sx
new file mode 100644
index 00000000..1cce954a
--- /dev/null
+++ b/lib/content/tests/block-path.sx
@@ -0,0 +1,59 @@
+;; Extension — locate a block in the tree (ancestor section path).
+
+(st-bootstrap-classes!)
+(content/bootstrap!)
+(content-bootstrap-section!)
+
+;; doc: top-level "a", section "s" containing "x" and nested section "i"
+;; containing "z".
+(define
+  d
+  (doc-append
+    (doc-append (doc-empty "d") (mk-text "a" "A"))
+    (mk-section
+      "s"
+      (list (mk-text "x" "X") (mk-section "i" (list (mk-text "z" "Z")))))))
+
+;; ── block-path ──
+(content-test
+  "top-level block has empty path"
+  (content/block-path d "a")
+  (list))
+(content-test "one-deep block path" (content/block-path d "x") (list "s"))
+(content-test
+  "two-deep block path"
+  (content/block-path d "z")
+  (list "s" "i"))
+(content-test "section's own path" (content/block-path d "i") (list "s"))
+(content-test "missing id path nil" (content/block-path d "zzz") nil)
+
+;; nil (absent) is distinct from () (present top-level)
+(content-test
+  "absent vs top-level distinguishable"
+  (if (= (content/block-path d "a") nil) "nil" "list")
+  "list")
+
+;; ── block-depth ──
+(content-test "depth top-level" (content/block-depth d "a") 0)
+(content-test "depth one" (content/block-depth d "x") 1)
+(content-test "depth two" (content/block-depth d "z") 2)
+(content-test "depth section" (content/block-depth d "i") 1)
+(content-test "depth absent" (content/block-depth d "zzz") -1)
+
+;; ── path tracks reparenting (composes with move.sx) ──
+;; (rebuild expectation directly; move tested elsewhere)
+(define
+  flat
+  (doc-append
+    (doc-append (doc-empty "d") (mk-section "sec" (list)))
+    (mk-text "p" "P")))
+(content-test
+  "before: p at top level"
+  (content/block-depth flat "p")
+  0)
+
+;; ── empty doc ──
+(content-test
+  "empty doc path nil"
+  (content/block-path (doc-empty "e") "x")
+  nil)
diff --git a/plans/content-on-sx.md b/plans/content-on-sx.md
index 587992e9..708b74e7 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` → **812/812** (Phases 1–4 COMPLETE + ~34 extensions, hardened: HTML/SX escaping, Markdown render + import/export incl. tables & frontmatter (full round-trip), CvRDT flat + nested-tree + durable replication, tree-aware validation, snapshot cache, doc metadata, plain-text render, nested block trees + deep editing + flatten + relative reorder, doc stats + summary + multi-doc index, table + callout + media 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` → **825/825** (Phases 1–4 COMPLETE + ~34 extensions, hardened: HTML/SX escaping, Markdown render + import/export incl. tables & frontmatter (full round-trip), CvRDT flat + nested-tree + durable replication, tree-aware validation, snapshot cache, doc metadata, plain-text render, nested block trees + deep editing + flatten + relative reorder, doc stats + summary + multi-doc index, table + callout + media 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
 
@@ -137,6 +137,18 @@ lib/content/api.sx ── (content/edit) (content/render) (content/history) ─
 
 ## Progress log
 
+- 2026-06-07 — Feature: `content/block-path` + `content/block-depth`
+  (block-path.sx, new suite). The read-side companion to doc-find-deep (locate
+  the block) and move-into/promote (relocate it): returns the ancestor-section
+  id chain (root-first) for a block id — where it sits in the tree — or nil if
+  absent (distinct from the `()` path of a present top-level block). block-depth
+  is the path length (0 top-level, -1 absent). For breadcrumbs and scoping an
+  edit to a block's enclosing section; distinct from toc/outline (which work on
+  headings). Pure traversal. Also ran an adversarial probe this pass: confirmed
+  clone/remap-ids + prefix-ids are tree-wide, and all 12 block types + CtDoc have
+  asMarkdown: methods (no missing-render-method bug). +13 tests. 825/825 (43
+  suites).
+
 - 2026-06-07 — Feature: tree reparent in move.sx. Until now insert/move were
   positional and top-level only, so a block could never be moved *into* a section
   or *out* of one — a real gap for editing nested documents. Added