diff --git a/docs/index.rst b/docs/index.rst
index 46cf69f..358790a 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -489,6 +489,21 @@ One can use `docxtpl` module directly on command line to generate a docx from a
 
 See tests/module_execute.py for an example.
 
+JSON context may include typed objects via a ``__docxtpl__`` envelope so the CLI can
+build ``RichText`` and ``Subdoc`` values before render:
+
+* RichText (use with ``{{r var }}``)::
+
+     {"__docxtpl__": "richtext", "runs": [{"text": "Hello ", "bold": false}, {"text": "world", "bold": true}]}
+
+* Subdoc (use with ``{{p var }}``, alone on its paragraph). Provide either
+  ``docx_base64`` or ``path`` (mutually exclusive). Subdoc envelopes require
+  ``docxcompose`` (``pip install "docxtpl[subdoc]"``)::
+
+     {"__docxtpl__": "subdoc", "path": "fragment.docx"}
+
+See tests/envelope_execute.py for a full CLI example.
+
 Examples
 --------
 
diff --git a/docxtpl/__init__.py b/docxtpl/__init__.py
index 5559d4f..bb3a0dc 100644
--- a/docxtpl/__init__.py
+++ b/docxtpl/__init__.py
@@ -8,6 +8,7 @@
 __version__ = "0.20.2"
 
 # flake8: noqa
+from .envelope import expand_context
 from .inline_image import InlineImage
 from .listing import Listing
 from .richtext import RichText, R, RichTextParagraph, RP
diff --git a/docxtpl/__main__.py b/docxtpl/__main__.py
index 59cf049..0923f97 100644
--- a/docxtpl/__main__.py
+++ b/docxtpl/__main__.py
@@ -2,6 +2,7 @@
 import json
 import os
 
+from .envelope import expand_context
 from .template import DocxTemplate, TemplateError
 
 TEMPLATE_ARG = "template_path"
@@ -130,6 +131,7 @@ def make_docxtemplate(template_path):
 
 def render_docx(doc, json_data):
     try:
+        json_data = expand_context(doc, json_data)
         doc.render(json_data)
         return doc
     except TemplateError:
diff --git a/docxtpl/envelope.py b/docxtpl/envelope.py
new file mode 100644
index 0000000..8231c93
--- /dev/null
+++ b/docxtpl/envelope.py
@@ -0,0 +1,95 @@
+# -*- coding: utf-8 -*-
+"""JSON-serializable envelopes for Subdoc and RichText in CLI / embedders."""
+from __future__ import annotations
+
+import base64
+import io
+from typing import Any, Optional
+
+from .richtext import RichText
+
+DOCXTPL_KEY = "__docxtpl__"
+
+
+def is_envelope(value: Any) -> bool:
+    return isinstance(value, dict) and DOCXTPL_KEY in value
+
+
+def _expand_subdoc(tpl, envelope: dict):
+    try:
+        from .subdoc import Subdoc  # noqa: F401
+    except ImportError as e:
+        raise RuntimeError(
+            'Subdoc envelopes require docxcompose. Install with: pip install "docxtpl[subdoc]"'
+        ) from e
+
+    has_b64 = "docx_base64" in envelope and envelope["docx_base64"] is not None
+    has_path = "path" in envelope and envelope["path"]
+    if has_b64 and has_path:
+        raise RuntimeError("Subdoc envelope must not set both docx_base64 and path")
+    if not has_b64 and not has_path:
+        raise RuntimeError("Subdoc envelope requires docx_base64 or path")
+
+    if has_path:
+        return tpl.new_subdoc(envelope["path"])
+    try:
+        raw = base64.b64decode(envelope["docx_base64"])
+    except Exception as e:
+        raise RuntimeError("Invalid docx_base64 in subdoc envelope") from e
+    return tpl.new_subdoc(io.BytesIO(raw))
+
+
+def _expand_richtext(tpl, envelope: dict) -> RichText:
+    runs = envelope.get("runs")
+    if runs is None:
+        raise RuntimeError("RichText envelope requires a runs array")
+    if not isinstance(runs, list):
+        raise RuntimeError("RichText envelope runs must be a list")
+
+    rt = RichText()
+    for i, run in enumerate(runs):
+        if not isinstance(run, dict):
+            raise RuntimeError("RichText run #%s must be an object" % i)
+        if "text" not in run:
+            raise RuntimeError("RichText run #%s requires text" % i)
+        kwargs = {}
+        for key in (
+            "bold",
+            "italic",
+            "underline",
+            "strike",
+            "subscript",
+            "superscript",
+            "color",
+            "size",
+            "font",
+            "style",
+        ):
+            if key in run and run[key] is not None:
+                kwargs[key] = run[key]
+        url = run.get("url")
+        if url:
+            kwargs["url_id"] = tpl.build_url_id(url)
+        rt.add(run["text"], **kwargs)
+    return rt
+
+
+def expand_value(tpl, value: Any) -> Any:
+    if is_envelope(value):
+        kind = value.get(DOCXTPL_KEY)
+        if kind == "subdoc":
+            return _expand_subdoc(tpl, value)
+        if kind == "richtext":
+            return _expand_richtext(tpl, value)
+        raise RuntimeError("Unknown __docxtpl__ envelope type: %r" % kind)
+
+    if isinstance(value, list):
+        return [expand_value(tpl, item) for item in value]
+    if isinstance(value, dict):
+        return {k: expand_value(tpl, v) for k, v in value.items()}
+    return value
+
+
+def expand_context(tpl, context: Any) -> Any:
+    """Expand __docxtpl__ envelopes in a JSON-loaded context before render()."""
+    return expand_value(tpl, context)
diff --git a/tests/envelope_cli.py b/tests/envelope_cli.py
new file mode 100644
index 0000000..32bae4c
--- /dev/null
+++ b/tests/envelope_cli.py
@@ -0,0 +1,214 @@
+# -*- coding: utf-8 -*-
+"""Tests for JSON CLI envelopes (subdoc + richtext)."""
+import base64
+import io
+import json
+import os
+import subprocess
+import sys
+import tempfile
+import unittest
+import zipfile
+
+from docx import Document
+
+from docxtpl import DocxTemplate, RichText, expand_context
+
+os.chdir(os.path.dirname(__file__))
+os.makedirs("output", exist_ok=True)
+
+
+def _docx_bytes_with_paragraph(text):
+    doc = Document()
+    doc.add_paragraph(text)
+    buf = io.BytesIO()
+    doc.save(buf)
+    return buf.getvalue()
+
+
+def _template_with_p_placeholder(varname):
+    """Build a minimal .docx whose body is a single {{p varname }} paragraph."""
+    doc = Document()
+    p = doc.add_paragraph()
+    p.add_run("{{p %s }}" % varname)
+    buf = io.BytesIO()
+    doc.save(buf)
+    buf.seek(0)
+    return buf
+
+
+def _template_with_r_placeholder(varname, prefix="Label: "):
+    doc = Document()
+    p = doc.add_paragraph()
+    p.add_run(prefix)
+    p.add_run("{{r %s }}" % varname)
+    buf = io.BytesIO()
+    doc.save(buf)
+    buf.seek(0)
+    return buf
+
+
+class EnvelopeTests(unittest.TestCase):
+    def test_expand_richtext_envelope(self):
+        tpl = DocxTemplate(_template_with_r_placeholder("body"))
+        ctx = expand_context(
+            tpl,
+            {
+                "body": {
+                    "__docxtpl__": "richtext",
+                    "runs": [
+                        {"text": "Hello ", "bold": False},
+                        {"text": "world", "bold": True},
+                    ],
+                }
+            },
+        )
+        self.assertIsInstance(ctx["body"], RichText)
+        tpl.render(ctx)
+        out = "output/envelope_richtext.docx"
+        tpl.save(out)
+        self.assertTrue(os.path.isfile(out))
+
+    def test_expand_subdoc_envelope(self):
+        mini = _docx_bytes_with_paragraph("Inserted block")
+        tpl = DocxTemplate(_template_with_p_placeholder("body"))
+        ctx = expand_context(
+            tpl,
+            {
+                "body": {
+                    "__docxtpl__": "subdoc",
+                    "docx_base64": base64.b64encode(mini).decode("ascii"),
+                }
+            },
+        )
+        from docxtpl.subdoc import Subdoc
+
+        self.assertIsInstance(ctx["body"], Subdoc)
+        tpl.render(ctx)
+        out = "output/envelope_subdoc.docx"
+        tpl.save(out)
+        self.assertTrue(os.path.isfile(out))
+        with zipfile.ZipFile(out) as zf:
+            xml = zf.read("word/document.xml").decode("utf-8")
+        self.assertIn("Inserted block", xml)
+
+    def test_expand_subdoc_path_envelope(self):
+        from docxtpl.subdoc import Subdoc
+
+        tpl = DocxTemplate(_template_with_p_placeholder("body"))
+        ctx = expand_context(
+            tpl,
+            {
+                "body": {
+                    "__docxtpl__": "subdoc",
+                    "path": "templates/envelope_cli_sub.docx",
+                }
+            },
+        )
+        self.assertIsInstance(ctx["body"], Subdoc)
+        tpl.render(ctx)
+        out = "output/envelope_subdoc_path.docx"
+        tpl.save(out)
+        with zipfile.ZipFile(out) as zf:
+            xml = zf.read("word/document.xml").decode("utf-8")
+        self.assertIn("Inserted via CLI", xml)
+
+    def test_cli_end_to_end_envelopes(self):
+        out = "output/envelope_cli_e2e.docx"
+        if os.path.exists(out):
+            os.unlink(out)
+        result = subprocess.run(
+            [
+                sys.executable,
+                "-m",
+                "docxtpl",
+                "templates/envelope_cli_tpl.docx",
+                "templates/envelope_cli.json",
+                out,
+                "-o",
+                "-q",
+            ],
+            capture_output=True,
+            text=True,
+        )
+        self.assertEqual(
+            result.returncode,
+            0,
+            "CLI failed: stdout=%r stderr=%r" % (result.stdout, result.stderr),
+        )
+        self.assertTrue(os.path.isfile(out))
+        with zipfile.ZipFile(out) as zf:
+            xml = zf.read("word/document.xml").decode("utf-8")
+        self.assertIn("Hello", xml)
+        self.assertIn("world", xml)
+        self.assertIn("Inserted via CLI", xml)
+
+    def test_cli_end_to_end_base64_subdoc(self):
+        mini = _docx_bytes_with_paragraph("Base64 block")
+        with tempfile.TemporaryDirectory() as tmp:
+            tpl_path = os.path.join(tmp, "tpl.docx")
+            json_path = os.path.join(tmp, "ctx.json")
+            out_path = os.path.join(tmp, "out.docx")
+            buf = _template_with_p_placeholder("body")
+            with open(tpl_path, "wb") as fh:
+                fh.write(buf.read())
+            with open(json_path, "w") as fh:
+                json.dump(
+                    {
+                        "body": {
+                            "__docxtpl__": "subdoc",
+                            "docx_base64": base64.b64encode(mini).decode("ascii"),
+                        }
+                    },
+                    fh,
+                )
+            result = subprocess.run(
+                [
+                    sys.executable,
+                    "-m",
+                    "docxtpl",
+                    tpl_path,
+                    json_path,
+                    out_path,
+                    "-o",
+                    "-q",
+                ],
+                capture_output=True,
+                text=True,
+            )
+            self.assertEqual(
+                result.returncode,
+                0,
+                "CLI failed: stdout=%r stderr=%r" % (result.stdout, result.stderr),
+            )
+            with zipfile.ZipFile(out_path) as zf:
+                xml = zf.read("word/document.xml").decode("utf-8")
+            self.assertIn("Base64 block", xml)
+
+    def test_unknown_envelope_type(self):
+        tpl = DocxTemplate(_template_with_r_placeholder("body"))
+        with self.assertRaises(RuntimeError):
+            expand_context(
+                tpl, {"body": {"__docxtpl__": "nope", "runs": []}}
+            )
+
+    def test_nested_list_expansion(self):
+        tpl = DocxTemplate(_template_with_r_placeholder("body"))
+        ctx = expand_context(
+            tpl,
+            {
+                "rows": [
+                    {
+                        "body": {
+                            "__docxtpl__": "richtext",
+                            "runs": [{"text": "row1", "bold": True}],
+                        }
+                    }
+                ]
+            },
+        )
+        self.assertIsInstance(ctx["rows"][0]["body"], RichText)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tests/envelope_execute.py b/tests/envelope_execute.py
new file mode 100644
index 0000000..a5570af
--- /dev/null
+++ b/tests/envelope_execute.py
@@ -0,0 +1,29 @@
+import os
+import sys
+
+TEMPLATE_PATH = "templates/envelope_cli_tpl.docx"
+JSON_PATH = "templates/envelope_cli.json"
+OUTPUT_FILENAME = "output/envelope_cli.docx"
+OVERWRITE = "-o"
+QUIET = "-q"
+
+
+os.chdir(os.path.dirname(__file__))
+os.makedirs("output", exist_ok=True)
+
+if os.path.exists(OUTPUT_FILENAME):
+    os.unlink(OUTPUT_FILENAME)
+
+cmd = "%s -m docxtpl %s %s %s %s %s" % (
+    sys.executable,
+    TEMPLATE_PATH,
+    JSON_PATH,
+    OUTPUT_FILENAME,
+    OVERWRITE,
+    QUIET,
+)
+print('Executing "%s" ...' % cmd)
+os.system(cmd)
+
+if os.path.exists(OUTPUT_FILENAME):
+    print("    --> File %s has been generated." % OUTPUT_FILENAME)
diff --git a/tests/templates/envelope_cli.json b/tests/templates/envelope_cli.json
new file mode 100644
index 0000000..27d34e7
--- /dev/null
+++ b/tests/templates/envelope_cli.json
@@ -0,0 +1,13 @@
+{
+  "highlight": {
+    "__docxtpl__": "richtext",
+    "runs": [
+      {"text": "Hello ", "bold": false},
+      {"text": "world", "bold": true}
+    ]
+  },
+  "block": {
+    "__docxtpl__": "subdoc",
+    "path": "templates/envelope_cli_sub.docx"
+  }
+}
diff --git a/tests/templates/envelope_cli_sub.docx b/tests/templates/envelope_cli_sub.docx
new file mode 100644
index 0000000..28de051
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diff --git a/tests/templates/envelope_cli_tpl.docx b/tests/templates/envelope_cli_tpl.docx
new file mode 100644
index 0000000..a544aed
Binary files /dev/null and b/tests/templates/envelope_cli_tpl.docx differ