Document the max_history setting for the magic commands

docs/source/users/index.md

@@ -785,6 +785,25 @@ A function that computes the lowest common multiples of two integers, and
 a function that runs 5 test cases of the lowest common multiple function
 ```
 
+### Configuring the amount of history to include in the context
+
+By default, two previous Human/AI message exchanges are included in the context of the new prompt.
+You can change this using the IPython `%config` magic, for example:
+
+```python
+%config AiMagics.max_history = 4
+```
+
+Note that old messages are still kept locally in memory,
+so they will be included in the context of the next prompt after raising the `max_history` value.
+
+You can configure the value for all notebooks
+by specifying `c.AiMagics.max_history` traitlet in `ipython_config.py`, for example:
+
+```python
+c.AiMagics.max_history = 4
+```
+
 ### Clearing the chat history
 
 You can run the `%ai reset` line magic command to clear the chat history. After you do this,