diff --git a/edi_party_data_oca/components/common.py b/edi_party_data_oca/components/common.py
index bb2dec005..ad088a690 100644
--- a/edi_party_data_oca/components/common.py
+++ b/edi_party_data_oca/components/common.py
@@ -40,14 +40,15 @@ def _party_from_partner(self, **kw):
         party = DotDict(
             name=self._get_name(),
             identifiers=self._get_identifiers(),
-            # TODO: is this only for UBL?
             endpoint=self._get_endpoint(),
+            lang=self._get_lang(),
+            partner=self.partner,
         )
         party.update(kw)
         return party
 
     def _get_name(self):
-        name_field = getattr(self.work, "party_data_name_field", "display_name")
+        name_field = getattr(self.work, "party_data_name_field", "name")
         return self.partner[name_field]
 
     def _get_endpoint(self):
@@ -71,3 +72,12 @@ def _get_indentity(self, id_number):
             },
             value=id_number.name,
         )
+
+    def _get_lang(self):
+        lang_code = getattr(self.work, "lang", False) or self.partner.lang
+        if not lang_code:
+            return False
+        lang = self.env["res.lang"]._get_data(code=lang_code)
+        if not lang:
+            return False
+        return {"name": lang.name, "code": lang.code, "short": lang.code.split("_")[0]}
diff --git a/edi_party_data_oca/tests/test_party_data.py b/edi_party_data_oca/tests/test_party_data.py
index 08a766b50..7d1484cd5 100644
--- a/edi_party_data_oca/tests/test_party_data.py
+++ b/edi_party_data_oca/tests/test_party_data.py
@@ -57,8 +57,16 @@ def setUpClass(cls):
     def _get_provider(self, partner, **kw):
         return get_party_data_component(self.exc_record, partner, **kw)
 
+    def _expected_lang(self, partner):
+        if not partner.lang:
+            return False
+        lang = self.env["res.lang"]._get_data(code=partner.lang)
+        if not lang:
+            return False
+        return {"name": lang.name, "code": lang.code, "short": lang.code.split("_")[0]}
+
     def _make_expected_data(
-        self, partner, number, allowed_codes=None, name_field="display_name", **kw
+        self, partner, number, allowed_codes=None, name_field="name", **kw
     ):
         data = {
             "name": partner[name_field],
@@ -68,6 +76,8 @@ def _make_expected_data(
                 {"attrs": {"schemeID": "cat3"}, "value": f"cat3-p{number}"},
             ],
             "endpoint": {},
+            "lang": self._expected_lang(partner),
+            "partner": partner,
         }
         data.update(kw)
         if allowed_codes:
@@ -102,32 +112,62 @@ def test_data(self):
             res = provider.get_party()
             self.assertEqual(res, expected_data)
 
-    def test_data_no_fullname(self):
+    def test_data_fullname_override(self):
+        # `name` is the default `party_data_name_field` since it doesn't embed
+        # multi-company/disambiguation suffixes the way `display_name` does;
+        # `display_name` is still available by explicit override.
         expected = (
             (
                 self.partner1,
-                self._make_expected_data(self.partner1, 1, name_field="name"),
+                self._make_expected_data(self.partner1, 1, name_field="display_name"),
             ),
             (
                 self.partner2,
                 self._make_expected_data(
-                    self.partner2, 2, allowed_codes=["cat2", "cat3"], name_field="name"
+                    self.partner2,
+                    2,
+                    allowed_codes=["cat2", "cat3"],
+                    name_field="display_name",
                 ),
             ),
             (
                 self.partner3,
                 self._make_expected_data(
-                    self.partner3, 3, allowed_codes=["cat3"], name_field="name"
+                    self.partner3, 3, allowed_codes=["cat3"], name_field="display_name"
                 ),
             ),
         )
         for partner, expected_data in expected:
             provider = self._get_provider(
-                partner, work_ctx={"party_data_name_field": "name"}
+                partner, work_ctx={"party_data_name_field": "display_name"}
             )
             res = provider.get_party()
             self.assertEqual(res, expected_data)
 
+    def test_lang(self):
+        # No lang set on the partner -> no `lang` key rendered.
+        self.partner1.lang = False
+        provider = self._get_provider(self.partner1)
+        self.assertFalse(provider.get_party()["lang"])
+        # Partner's own lang is used by default.
+        self.partner1.lang = "en_US"
+        provider = self._get_provider(self.partner1)
+        self.assertEqual(
+            provider.get_party()["lang"],
+            {"name": "English (US)", "code": "en_US", "short": "en"},
+        )
+        # `work_ctx["lang"]` takes precedence over the partner's own lang.
+        self.partner2.lang = False
+        provider = self._get_provider(self.partner2, work_ctx={"lang": "en_US"})
+        self.assertEqual(
+            provider.get_party()["lang"],
+            {"name": "English (US)", "code": "en_US", "short": "en"},
+        )
+
+    def test_partner_in_party_data(self):
+        provider = self._get_provider(self.partner1)
+        self.assertEqual(provider.get_party()["partner"], self.partner1)
+
     def test_data_limited_1(self):
         self.exc_type.id_category_ids = self.category1
         expected = (
diff --git a/edi_sale_ubl_output_oca/tests/test_order_response_out.py b/edi_sale_ubl_output_oca/tests/test_order_response_out.py
index 1ecb08fb9..5b538f179 100644
--- a/edi_sale_ubl_output_oca/tests/test_order_response_out.py
+++ b/edi_sale_ubl_output_oca/tests/test_order_response_out.py
@@ -52,16 +52,33 @@ def test_get_template(self):
 
     def test_render_values(self):
         # TODO: test w/ some identifiers
+        def make_lang(record):
+            if not record.lang:
+                return False
+            lang = self.env["res.lang"]._get_data(code=record.lang)
+            if not lang:
+                return False
+            return {
+                "name": lang.name,
+                "code": lang.code,
+                "short": lang.code.split("_")[0],
+            }
+
         def make_party(record):
             return dict(
                 name=record.name,
                 identifiers=[],
                 endpoint={},
+                lang=make_lang(record),
+                partner=record,
             )
 
         values = self.exc_tmpl._get_render_values(self.record)
         expected = [
-            ("seller_party", make_party(self.order.company_id)),
+            # Match what the code_snippet actually passes to `get_party_data`:
+            # `record.company_id.partner_id` (a res.partner), not the
+            # res.company itself (which has no `lang` field).
+            ("seller_party", make_party(self.order.company_id.partner_id)),
             ("buyer_party", make_party(self.order.partner_id)),
         ]
         for k, v in expected:
diff --git a/edi_ubl_output_base_oca/templates/qweb_tmpl_party.xml b/edi_ubl_output_base_oca/templates/qweb_tmpl_party.xml
index d1683fc88..bbb9d3516 100644
--- a/edi_ubl_output_base_oca/templates/qweb_tmpl_party.xml
+++ b/edi_ubl_output_base_oca/templates/qweb_tmpl_party.xml
@@ -5,6 +5,7 @@
             xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2"
             xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2"
         >
+            <t t-set="partner" t-value="partner or party.partner" />
             <cac:Party>
                 <t t-if="party.endpoint">
                     <cbc:EndpointID
@@ -23,6 +24,34 @@
                 <cac:PartyName t-if="party.name">
                     <cbc:Name t-esc="party.name">Moderna Produkter AB</cbc:Name>
                 </cac:PartyName>
+                <cac:Language t-if="party.lang">
+                    <cbc:ID t-esc="party.lang.short">de</cbc:ID>
+                    <cbc:Name t-esc="party.lang.name">Schweiz / Deutsch</cbc:Name>
+                    <cbc:LocaleCode t-esc="party.lang.code">de_CH</cbc:LocaleCode>
+                </cac:Language>
+
+                <cac:PostalAddress t-if="show_full_address">
+                    <t t-call="edi_ubl_output_base_oca.qweb_tmpl_ubl_address" />
+                </cac:PostalAddress>
+                <cac:PartyTaxScheme t-if="show_tax_scheme and partner.vat">
+                    <cbc:CompanyID t-esc="partner.vat" />
+                    <cac:TaxScheme>
+                        <cbc:ID>VAT</cbc:ID>
+                    </cac:TaxScheme>
+                </cac:PartyTaxScheme>
+                <cac:PartyLegalEntity t-if="show_legal_entity">
+                    <cbc:RegistrationName
+                        t-esc="partner.name"
+                    >ACME</cbc:RegistrationName>
+                    <cac:RegistrationAddress>
+                        <t t-call="edi_ubl_output_base_oca.qweb_tmpl_ubl_address" />
+                    </cac:RegistrationAddress>
+                </cac:PartyLegalEntity>
+                <cac:Contact t-if="show_contact">
+                    <cbc:Name t-if="partner.name" t-esc="partner.name" />
+                    <cbc:Telephone t-if="partner.phone" t-esc="partner.phone" />
+                    <cbc:ElectronicMail t-if="partner.email" t-esc="partner.email" />
+                </cac:Contact>
             </cac:Party>
         </t>
     </template>
diff --git a/edi_ubl_output_base_oca/tests/test_templates.py b/edi_ubl_output_base_oca/tests/test_templates.py
index e47832c07..9812f3513 100644
--- a/edi_ubl_output_base_oca/tests/test_templates.py
+++ b/edi_ubl_output_base_oca/tests/test_templates.py
@@ -62,6 +62,88 @@ def test_party_with_endpoint_and_identifiers(self):
         identification = root.find(".//cac:PartyIdentification/cbc:ID", NS)
         self.assertEqual(identification.text, "8591234567894")
 
+    def test_party_full_blocks(self):
+        self.partner.write({"vat": "CHE-000.000.000 MWST", "phone": "+41 123434343"})
+        party = DotDict(
+            name="ACME Vendor",
+            identifiers=[],
+            endpoint={},
+            partner=self.partner,
+            lang={"name": "Schweiz / Deutsch", "code": "de_CH", "short": "de"},
+        )
+        xml = self._render(
+            "edi_ubl_output_base_oca.qweb_tmpl_ubl_party",
+            {
+                "party": party,
+                "show_full_address": True,
+                "show_tax_scheme": True,
+                "show_legal_entity": True,
+                "show_contact": True,
+            },
+        )
+        root = etree.fromstring(
+            f"<root xmlns:cac='{NS['cac']}' xmlns:cbc='{NS['cbc']}'>{xml}</root>"
+        )
+        lang_node = root.find(".//cac:Language", NS)
+        self.assertEqual(lang_node.find("cbc:ID", NS).text, "de")
+        self.assertEqual(lang_node.find("cbc:Name", NS).text, "Schweiz / Deutsch")
+        self.assertEqual(lang_node.find("cbc:LocaleCode", NS).text, "de_CH")
+        self.assertEqual(
+            root.find("cac:Party/cac:PostalAddress/cbc:StreetName", NS).text,
+            "Foo street 1",
+        )
+        self.assertEqual(
+            root.find(".//cac:PartyTaxScheme/cbc:CompanyID", NS).text,
+            "CHE-000.000.000 MWST",
+        )
+        legal_entity = root.find(".//cac:PartyLegalEntity", NS)
+        self.assertEqual(
+            legal_entity.find("cbc:RegistrationName", NS).text, "ACME Vendor"
+        )
+        self.assertEqual(
+            legal_entity.find("cac:RegistrationAddress/cbc:StreetName", NS).text,
+            "Foo street 1",
+        )
+        contact = root.find(".//cac:Contact", NS)
+        self.assertEqual(contact.find("cbc:Name", NS).text, "ACME Vendor")
+        self.assertEqual(contact.find("cbc:Telephone", NS).text, "+41 123434343")
+
+    def test_party_show_flags_default_off(self):
+        # Without explicitly passing the `show_*` flags, none of the optional
+        # blocks render, even when `party.partner` carries data for them.
+        self.partner.write({"vat": "CHE-000.000.000 MWST"})
+        party = DotDict(
+            name="ACME Vendor", identifiers=[], endpoint={}, partner=self.partner
+        )
+        xml = self._render(
+            "edi_ubl_output_base_oca.qweb_tmpl_ubl_party", {"party": party}
+        )
+        root = etree.fromstring(
+            f"<root xmlns:cac='{NS['cac']}' xmlns:cbc='{NS['cbc']}'>{xml}</root>"
+        )
+        self.assertIsNone(root.find(".//cac:PostalAddress", NS))
+        self.assertIsNone(root.find(".//cac:PartyTaxScheme", NS))
+        self.assertIsNone(root.find(".//cac:PartyLegalEntity", NS))
+        self.assertIsNone(root.find(".//cac:Contact", NS))
+
+    def test_party_explicit_partner_overrides_party_partner(self):
+        other_partner = self.env["res.partner"].create(
+            {"name": "Other Partner", "street": "Other street"}
+        )
+        party = DotDict(
+            name="ACME Vendor", identifiers=[], endpoint={}, partner=self.partner
+        )
+        xml = self._render(
+            "edi_ubl_output_base_oca.qweb_tmpl_ubl_party",
+            {"party": party, "partner": other_partner, "show_full_address": True},
+        )
+        root = etree.fromstring(
+            f"<root xmlns:cac='{NS['cac']}' xmlns:cbc='{NS['cbc']}'>{xml}</root>"
+        )
+        self.assertEqual(
+            root.find(".//cac:PostalAddress/cbc:StreetName", NS).text, "Other street"
+        )
+
     def test_address(self):
         xml = self._render(
             "edi_ubl_output_base_oca.qweb_tmpl_ubl_address", {"partner": self.partner}