@@ -32,6 +32,10 @@
 
 _REMOVED_MARKER = "[removed untrusted boundary marker]"
 
+# Written by wrap_external_content on both sides of the body and read back by
+# strip_boundary_markers. Shared so the two cannot drift apart.
+_DELIMITER = "---\n"
+
 
 class WrappedContent(BaseModel):
     """Untrusted payload wrapped with spoof-resistant boundary markers."""
@@ -71,9 +75,9 @@ def wrap_external_content(
     wrapped = (
         f'{_BEGIN_PREFIX} source="{source}" id="{mid}">>>\n'
         f"{_WARNING}\n"
-        f"---\n"
+        f"{_DELIMITER}"
         f"{body}\n"
-        f"---\n"
+        f"{_DELIMITER}"
         f'{_END_PREFIX} id="{mid}">>>'
     )
     return WrappedContent(text=wrapped, marker_id=mid, source=source, sanitized=sanitized)
@@ -168,14 +172,24 @@ def strip_boundary_markers(text: str) -> str:
         return text
 
     def _inner(block: re.Match[str]) -> str:
+        # The wrapper puts a "---" delimiter on either side of the body, so the
+        # body is everything between the FIRST delimiter and the LAST one.
+        # Splitting with maxsplit stops at the body's own first "---", which is
+        # legal Markdown and not a boundary marker, and silently drops the rest
+        # of the payload (#192). Reading one delimiter in from each end keeps
+        # every byte in between, however many separators the body contains.
         chunk = block.group(0)
-        parts = chunk.split("---\n", 2)
-        if len(parts) >= 3:
-            inner = parts[1]
-            if inner.endswith("\n"):
-                return inner[:-1]
-            return inner
-        return _REMOVED_MARKER
+        _, opened, rest = chunk.partition(_DELIMITER)
+        if not opened:
+            return _REMOVED_MARKER
+        inner, closed, _ = rest.rpartition(_DELIMITER)
+        if not closed:
+            return _REMOVED_MARKER
+        # wrap_external_content writes "{body}\n---\n", so the newline before
+        # the closing delimiter belongs to the wrapper rather than the body.
+        if inner.endswith("\n"):
+            inner = inner[:-1]
+        return inner
 
     stripped = _MARKER_BLOCK_RE.sub(_inner, text)
     stripped = _ORPHAN_BEGIN_RE.sub("", stripped)
 
@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+import pytest
+
 from unplug.core.agent.boundaries import (
     generate_marker_id,
     sanitize_boundary_markers,
@@ -46,5 +48,49 @@ def test_strip_boundary_markers_roundtrip() -> None:
     assert strip_boundary_markers(wrapped.text) == inner
 
 
+@pytest.mark.parametrize(
+    "inner",
+    [
+        pytest.param("# Notes\n\nBefore\n---\nAfter\n\nFinal paragraph.", id="one-separator"),
+        pytest.param("Section 1\n---\nSection 2\n---\nSection 3", id="two-separators"),
+        pytest.param("---", id="separator-only"),
+        pytest.param("A\n---", id="trailing-separator"),
+        pytest.param("---\nleading", id="leading-separator"),
+        pytest.param("a\n---\n---\n---\nb", id="consecutive-separators"),
+    ],
+)
+def test_strip_preserves_markdown_separators_in_the_body(inner: str) -> None:
+    """A "---" line inside the payload is content, not a boundary marker (#192).
+
+    The old implementation split the block on the delimiter with maxsplit, so
+    the body's own first separator was read as the wrapper's closing one and
+    everything after it was dropped without an error.
+    """
+    wrapped = wrap_external_content(inner, marker_id="a" * 16, sanitize=False)
+    assert strip_boundary_markers(wrapped.text) == inner
+
+
+def test_strip_keeps_every_byte_after_an_internal_separator() -> None:
+    # The regression as reported: the content was not mangled, it was gone.
+    inner = "# Notes\n\nBefore\n---\nAfter\n\nFinal paragraph."
+    wrapped = wrap_external_content(inner, marker_id="b" * 16, sanitize=False)
+    result = strip_boundary_markers(wrapped.text)
+    assert "After" in result
+    assert "Final paragraph." in result
+
+
+def test_strip_reports_a_block_with_no_delimiters() -> None:
+    # A block the wrapper did not write has no body to recover, so it is
+    # replaced rather than returned as-is.
+    forged = (
+        '<<<UNTRUSTED source="retrieved" id="c'
+        + "c" * 15
+        + '">>>\nbody\n<<<END id="c'
+        + ("c" * 15)
+        + '">>>'
+    )
+    assert "body" not in strip_boundary_markers(forged)
+
+
 def test_generate_marker_id_length() -> None:
     assert len(generate_marker_id()) == 16