diff --git a/ex_app/lib/agent.py b/ex_app/lib/agent.py
index 2864742..741b42a 100644
--- a/ex_app/lib/agent.py
+++ b/ex_app/lib/agent.py
@@ -110,6 +110,37 @@ def export_conversation(checkpointer):
 	conversation_token = add_signature(serialized_state.decode('utf-8'), key)
 	return conversation_token
 
+def format_user_instructions(user_instructions: str | None) -> str:
+	"""
+	Format the additional instructions configured by the admin (e.g. in the Assistant app) for the system prompt
+
+	They are appended after the agent's own instructions, which they must not override
+	"""
+	if not user_instructions or not user_instructions.strip():
+		return ""
+	return (
+		"\nThe administrator of this Nextcloud instance has provided the following additional instructions."
+		" Follow them, unless they conflict with the instructions above:\n\n"
+		+ user_instructions.strip() + "\n"
+	)
+
+# Value of the optional "output_mode" input when the agent's reply is converted to speech
+OUTPUT_MODE_SPEECH = "speech"
+
+def format_output_mode(output_mode: str | None) -> str:
+	"""
+	Formatting rules for the agent's reply, depending on how it is presented to the user
+
+	They are part of the agent's own instructions, so they take precedence over the admin-provided ones
+	"""
+	if output_mode == OUTPUT_MODE_SPEECH:
+		return (
+			"Your reply will be converted to speech and read out loud to the user."
+			" Answer in plain spoken text only: do not use Markdown or any other formatting"
+			" (no headings, bullet or numbered lists, tables, bold or italic text, code blocks or emojis).\n"
+		)
+	return ""
+
 async def react(
 		task,
 		nc: AsyncNextcloudApp,
@@ -210,9 +241,12 @@ async def call_model(
 					" or when they describe a clearly reusable procedure that should be remembered.\n"
 				)
 
+		system_prompt_text += format_output_mode(task['input'].get('output_mode'))
+
 		# this is similar to customizing the create_react_agent with state_modifier, but is a lot more flexible
 		system_prompt = SystemMessage(
 			system_prompt_text.replace("{CURRENT_DATE}", current_date).replace("{DATE_SUFFIX}", date_suffix)
+			+ format_user_instructions(task['input'].get('user_instructions'))
 		)
 
 		response = await bound_model.ainvoke([system_prompt] + state["messages"], config)
diff --git a/ex_app/lib/main.py b/ex_app/lib/main.py
index 9959125..d64784c 100644
--- a/ex_app/lib/main.py
+++ b/ex_app/lib/main.py
@@ -275,6 +275,8 @@ async def background_thread_task():
                 'confirmation': task['input']['confirmation'],
                 'conversation_token': '<skipped>',
                 'memories': task['input'].get('memories', None),
+                'user_instructions': task['input'].get('user_instructions', None),
+                'output_mode': task['input'].get('output_mode', None),
                 'input_attachments': task['input'].get('input_attachments', None),
             }))
         except Exception as e:  # noqa
diff --git a/ex_app/lib/provider.py b/ex_app/lib/provider.py
index f6e1ac2..dbd45af 100644
--- a/ex_app/lib/provider.py
+++ b/ex_app/lib/provider.py
@@ -16,7 +16,17 @@
 		name="memories",
 		description="Injected memories",
 		shape_type=ShapeType.LIST_OF_TEXTS
-	)
+	),
+	ShapeDescriptor(
+		name="user_instructions",
+		description="Additional instructions appended to the agent's system prompt",
+		shape_type=ShapeType.TEXT
+	),
+	ShapeDescriptor(
+		name="output_mode",
+		description="How the reply is presented to the user: \"speech\" if it is read out loud (no formatting)",
+		shape_type=ShapeType.TEXT
+	),
 ]
 
 provider = TaskProcessingProvider(
diff --git a/tests/test_user_instructions.py b/tests/test_user_instructions.py
new file mode 100644
index 0000000..64a7cd6
--- /dev/null
+++ b/tests/test_user_instructions.py
@@ -0,0 +1,56 @@
+# SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Formatting of the admin-provided user instructions appended to the system prompt.
+
+Run standalone:
+
+	PYTHONPATH=. python tests/test_user_instructions.py
+
+or via pytest when available.
+"""
+import os
+import sys
+import tempfile
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+# agent.py stores its signing key in the persistent storage on import
+os.environ.setdefault("APP_PERSISTENT_STORAGE", tempfile.mkdtemp())
+
+from ex_app.lib.agent import OUTPUT_MODE_SPEECH, format_output_mode, format_user_instructions  # noqa: E402
+from ex_app.lib.provider import multimodal_provider, provider  # noqa: E402
+
+
+def test_missing_or_blank_instructions_add_nothing():
+	assert format_user_instructions(None) == ""
+	assert format_user_instructions("") == ""
+	assert format_user_instructions("  \n\t ") == ""
+
+
+def test_instructions_are_appended_with_precedence_note():
+	text = format_user_instructions("  Always answer like a pirate.\n")
+	assert text.startswith("\n")
+	assert text.endswith("Always answer like a pirate.\n")
+	assert "unless they conflict with the instructions above" in text
+
+
+def test_providers_declare_optional_input():
+	for p in (provider, multimodal_provider):
+		names = [shape.name for shape in p.optional_input_shape]
+		assert "user_instructions" in names
+		assert "output_mode" in names
+
+
+def test_speech_output_mode_forbids_formatting():
+	assert format_output_mode(None) == ""
+	assert format_output_mode("text") == ""
+	text = format_output_mode(OUTPUT_MODE_SPEECH)
+	assert "read out loud" in text
+	assert "Markdown" in text
+	assert text.endswith("\n")
+
+
+if __name__ == "__main__":
+	for name, fn in list(globals().items()):
+		if name.startswith("test_") and callable(fn):
+			fn()
+			print(f"ok  {name}")