diff --git a/CHANGELOG.md b/CHANGELOG.md
index b329316..ebe2874 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@ All notable changes to the tp library are documented here.
 - `tp-runtime-manifest`, advertising `tp-transaction-protocol-v1+v2` without removing the v1 participant route.
 - Supported `tp-transaction-execution-route` kill switch with `structured` as
   the default live authority and `v1` as the complete legacy rollback route.
+- Public `tp-transaction-participate-v2` registration for cross-package
+  structured participants, with the v1 call-shape adapter retained unchanged.
 - Native property policies and contribution composition with explicit nil/absence, normalization, validation, equality, merge, projection, named direct styles, and explicit `tp-computed` value sources.
 - `tp-propertize`, `tp-apply`, and `tp-watch` as the one-shot string, one-shot buffer-range, and reactive existing-text conveniences over the same direct property/surface core.
 - Retained logical objects with `tp-object-retain` and `tp-object-attach-fragment`, allowing one object to own multiple disjoint physical fragments without placing handles or positions in plans.
diff --git a/README.md b/README.md
index fefcd13..fb99678 100644
--- a/README.md
+++ b/README.md
@@ -187,7 +187,7 @@ cycles instead of spinning.
 | Core inspection and debug | `tp-debug-*`, `tp-intervals`, `tp-intervals-map`, `tp-plist`, `tp-text-snapshot`, `tp-empty-p` |
 | Property policy and declarations | `tp-define-property-policy`, `tp-register-text-property`, `tp-text-declarations`, `tp-computed`, `tp-resolve-value`, `tp-merge-declarations`, `tp-define-style`, `tp-style-declarations` |
 | Static recipes | `define-tp`/`tp-define-layer`, `define-tps`/`define-tp-group`/`tp-define-group`, layer/group queries, undefine/reset/describe |
-| Signals and bindings | signal create/read/peek/set/dispose, binding install/read/dispose, `tp-variable-signal`, `tp-with-transaction`, `tp-transaction-participate`, read-only `tp-transaction-active-p`, `tp-runtime-manifest`, counters/reset |
+| Signals and bindings | signal create/read/peek/set/dispose, binding install/read/dispose, `tp-variable-signal`, `tp-with-transaction`, `tp-transaction-participate`, `tp-transaction-participate-v2`, read-only `tp-transaction-active-p`, `tp-runtime-manifest`, counters/reset |
 | Objects and plans | plan/result constructors, `tp-object-ensure`, retain/reuse, fragment/content-range attachment, resolve, mounted/mounts |
 | Host ranges | `tp-range-anchor-create`, `tp-range-anchor-live-p`, `tp-object-attach-range`, `tp-range-rebase` |
 | Surfaces | mount/update/scoped update, materialize, live/revision/client-state, at-point, report/report-summary/inspect, unmount |
diff --git a/README_CN.md b/README_CN.md
index a5d8261..8415628 100644
--- a/README_CN.md
+++ b/README_CN.md
@@ -182,7 +182,7 @@ effect 的 input/version tuple，重复或超过图规模上限时停止循环
 | Core inspection 与 debug | `tp-debug-*`、`tp-intervals`、`tp-intervals-map`、`tp-plist`、`tp-text-snapshot`、`tp-empty-p` |
 | Property policy 与 declaration | `tp-define-property-policy`、`tp-register-text-property`、`tp-text-declarations`、`tp-computed`、`tp-resolve-value`、`tp-merge-declarations`、`tp-define-style`、`tp-style-declarations` |
 | 静态 recipe | `define-tp`/`tp-define-layer`、`define-tps`/`define-tp-group`/`tp-define-group`、layer/group 查询、undefine/reset/describe |
-| Signal 与 binding | signal create/read/peek/set/dispose、binding install/read/dispose、`tp-variable-signal`、`tp-with-transaction`、`tp-transaction-participate`、只读 `tp-transaction-active-p`、`tp-runtime-manifest`、counter/reset |
+| Signal 与 binding | signal create/read/peek/set/dispose、binding install/read/dispose、`tp-variable-signal`、`tp-with-transaction`、`tp-transaction-participate`、`tp-transaction-participate-v2`、只读 `tp-transaction-active-p`、`tp-runtime-manifest`、counter/reset |
 | Object 与 plan | plan/result constructor、`tp-object-ensure`、retain/reuse、fragment/content-range attach、resolve、mounted/mounts |
 | Host range | `tp-range-anchor-create`、`tp-range-anchor-live-p`、`tp-object-attach-range`、`tp-range-rebase` |
 | Surface | mount/update/scoped update、materialize、live/revision/client-state、at-point、report/report-summary/inspect、unmount |
diff --git a/docs/API-REFERENCE.md b/docs/API-REFERENCE.md
index 51b355b..83b6355 100644
--- a/docs/API-REFERENCE.md
+++ b/docs/API-REFERENCE.md
@@ -231,6 +231,11 @@ tp-binding-dispose 释放单个 binding。
  (lambda () (my-publish))
  (lambda () (my-rollback)))
 
+(tp-transaction-participate-v2
+ :key 'my-structured-state
+ :stage (lambda () (my-stage))
+ :rollback (lambda () (my-rollback)))
+
 (tp-transaction-active-p)
 
 (setq tp-transaction-execution-route 'structured) ; structured 或 v1
@@ -247,7 +252,9 @@ tp-binding-dispose 释放单个 binding。
 tp-with-transaction 将 signal、binding、surface 和注册的 transaction
 participant 一起原子处理。participant 必须在 active transaction 内注册；
 publish 在 surface publication 后、source commit 前运行，失败时按逆序
-rollback。tp-variable-signal 用 Emacs variable watcher 适配全局或指定
+rollback。跨包 structured consumer 使用 `tp-transaction-participate-v2`；它
+返回 key，不暴露内部 participant 对象。tp-variable-signal 用 Emacs variable
+watcher 适配全局或指定
 Buffer 的变量，不是旧的 $variable API。
 
 tp-transaction-active-p 是只读边界查询：只在当前 dynamic extent 已进入
@@ -268,7 +275,9 @@ tp-runtime-manifest 返回防御性 capability snapshot；本版本的
 `:execution-routes` 为 `(structured v1)`、`:route-option` 为
 `tp-transaction-execution-route`，兼容字段 `:execution-route` 与
 `:batch-execution` 也均为 `structured`，`:batch-execute` 为 non-nil。公开
-`tp-transaction-participate` 仍是 v1 adapter，manifest 以 `:v1-adapter` 和
+structured registration 由 `:structured-participant-api` 指向
+`tp-transaction-participate-v2`；`tp-transaction-participate` 仍是 v1 adapter，
+manifest 以 `:v1-adapter` 和
 `:v1-rollback-route` 明确声明 adapter 与完整旧 route 均保留；
 `:single-live-writer` 明确声明 route 不会双写；
 `:batch-artifacts` 与 `:shadow-proof` 也保持 non-nil。
diff --git a/docs/API-SEMANTICS.md b/docs/API-SEMANTICS.md
index 5db443d..dea442e 100644
--- a/docs/API-SEMANTICS.md
+++ b/docs/API-SEMANTICS.md
@@ -211,6 +211,11 @@ TP 为每个 interval 保存：
 
 `tp-transaction-participate` 允许 client side state 在 surfaces 发布后、source commit 前加入同一 rollback boundary。它保留公共 v1 调用形状，但在默认 structured route 中适配成同一个 participant record 的 `stage` capability，只执行一次。participant key 在一个 outer transaction 中必须唯一。它不是 observer；失败会回滚 transaction。Observer failure 只记录，不回滚已提交结果。
 
+跨包 consumer 使用公开 `tp-transaction-participate-v2` 直接注册 structured
+`stage`/`rollback` pair；返回值仍是 key，内部 participant identity、state 与
+journal 不暴露。完整 v1 execution route 也能执行该同一 v2 participant object，
+因此 Ebox 可以独立 cutover，而不要求同步改变 TP live route。
+
 publication batch、structured participant、final marker 与 tagged outcome 共享
 现有 journal/change-group，不复制第二份 live state。默认 `structured` route 是
 唯一 live writer：surface 从 candidate entries 执行，participant 从 candidate
diff --git a/tests/tp-transaction-tests.el b/tests/tp-transaction-tests.el
index fc7519c..d02ee7e 100644
--- a/tests/tp-transaction-tests.el
+++ b/tests/tp-transaction-tests.el
@@ -17,6 +17,7 @@
 (require 'tp-surface)
 
 (declare-function tp--transaction-participate-v2 "tp-reactive" (&rest args))
+(declare-function tp-transaction-participate-v2 "tp-reactive" (&rest args))
 (declare-function tp--transaction-participant-protocol "tp-reactive" (value))
 (declare-function tp--transaction-participant-state "tp-reactive" (value))
 (declare-function tp--transaction-participant-journal "tp-reactive" (value))
@@ -388,6 +389,32 @@
                    '(:owner old-state)))
     (should (eq (tp--transaction-participant-state participant) 'committed))))
 
+(ert-deftest tp-transaction-test-public-v2-participant-api-spans-both-routes ()
+  "The public v2 API registers one v2 object under structured and v1 writers."
+  (dolist (route '(structured v1))
+    (let ((tp-transaction-execution-route route)
+          (tp-transaction-test--trace nil)
+          participant)
+      (should
+       (eq
+        (tp-with-transaction
+          (should
+           (eq
+            (tp-transaction-participate-v2
+             :key 'public-v2
+             :stage (lambda () (push 'stage tp-transaction-test--trace))
+             :rollback (lambda () (push 'rollback tp-transaction-test--trace))
+             :journal '(:owner public))
+            'public-v2))
+          (setq participant (car tp--transaction-participants))
+          'body-result)
+        'body-result))
+      (should (equal tp-transaction-test--trace '(stage)))
+      (should (eq (tp--transaction-participant-protocol participant) 'v2))
+      (should (equal (tp--transaction-participant-journal participant)
+                     '(:owner public)))
+      (should (eq (tp--transaction-participant-state participant) 'committed)))))
+
 (ert-deftest tp-transaction-test-v2-participant-stage-fault-rolls-back-prior-only ()
   "A structured stage fault reverses only participants that entered staged."
   (let ((tp-transaction-test--trace nil)
@@ -1604,6 +1631,8 @@
                 'tp-transaction-execution-route))
     (should (eq (plist-get manifest :batch-execution) 'structured))
     (should (plist-get manifest :batch-execute))
+    (should (eq (plist-get manifest :structured-participant-api)
+                'tp-transaction-participate-v2))
     (should (plist-get manifest :v1-adapter))
     (should (plist-get manifest :v1-rollback-route))
     (should (plist-get manifest :single-live-writer))
diff --git a/tp-reactive.el b/tp-reactive.el
index 6127ee5..4b56c99 100644
--- a/tp-reactive.el
+++ b/tp-reactive.el
@@ -744,6 +744,19 @@ participant's opaque owner-local state."
    (tp--transaction-make-participant
     key stage rollback 'v2 precommit after-commit journal)))
 
+;;;###autoload
+(cl-defun tp-transaction-participate-v2
+    (&key key stage rollback precommit after-commit journal)
+  "Register a structured rollback-capable participant under KEY.
+STAGE and ROLLBACK are required no-argument functions.  PRECOMMIT may be one
+declared package-owned validator; AFTER-COMMIT is contained work queued only
+after final accept.  JOURNAL is opaque owner-local rollback state.  Return KEY
+without exposing TP's internal participant object."
+  (tp--transaction-participate-v2
+   :key key :stage stage :rollback rollback :precommit precommit
+   :after-commit after-commit :journal journal)
+  key)
+
 (defun tp--transaction-participants-in-registration-order ()
   "Return the authoritative participants in deterministic declaration order."
   (reverse tp--transaction-participants))
diff --git a/tp.el b/tp.el
index 3885f15..1d0a9aa 100644
--- a/tp.el
+++ b/tp.el
@@ -75,6 +75,7 @@
     :route-option tp-transaction-execution-route
     :batch-execution structured
     :batch-execute t
+    :structured-participant-api tp-transaction-participate-v2
     :v1-adapter t
     :v1-rollback-route t
     :single-live-writer t