activity_exception

activity_exception is the quietest widget in Odoo: on most rows it renders literally nothing. Its template starts with a condition on the field value, and only when the record carries an exception activity does the icon appear, floated to the end of the cell, colored by the value, with a fixed tooltip: This record has an exception activity.

It sits on activity_exception_decoration, a selection field from mail.activity.mixin whose two values are Bootstrap color names, warning and danger. The CSS class is assembled directly from them (text-warning, text-danger), and the glyph comes from the companion char field activity_exception_icon, which the widget declares as its one field dependency so it loads without a view element.

The descriptor registers with zero options and label: false, an unusual descriptor key that suppresses the column header. That is why the exception column in core lists is a slim, unlabeled strip.

Exception activities are Odoo's way of saying something changed behind this document's back. The classic producer: a confirmed sales order whose customer or delivery data is modified afterward, prompting Odoo to attach a warning activity so someone reviews the impact. Deliveries, manufacturing orders and maintenance requests do the same.

The widget is the surfacing half of that system. In a fifty-row picking list, the one delivery whose sale order was tampered with shows a red flag; everything else stays visually silent. Zero configuration, zero noise, exactly one meaning.

The management takeaway: if your team sees these icons often, the icons are not the problem. They are pointing at a process that changes confirmed documents, and the fix belongs there, not in hiding the column.

The standard slim column

<list>
    <field name="name"/>
    <field name="activity_exception_decoration" widget="activity_exception"/>
</list>

No options, no string attribute needed: the descriptor's label: false keeps the header empty. The icon field loads automatically.

Creating an exception activity in code

record.activity_schedule(
    "mail.mail_activity_data_warning",
    summary="Customer changed after confirmation",
    note="Review pricing and delivery address.",
)

The warning activity type carries the decoration and icon; the mixin's computed fields propagate them to the record and the icon appears in every list using the widget.

The entire rendering logic is one getter. When the decoration field has a value, the widget builds its class string as text- plus the value, plus fa, plus the icon field's value, producing for example text-warning fa fa-warning. When the field is empty the template's guard renders nothing, not even an empty span.

Both inputs are computed on mail.activity.mixin from the record's activities: the decoration is the most severe decoration among the record's exception activities, and the icon follows it. Which is why you never write these fields; you schedule or resolve activities and the fields follow.

Because the widget renders nothing for empty values, it costs almost nothing to keep in every list. The only weight is the two extra fields in the data fetch, one of which you already placed in the view as the widget's anchor.

Odoo 20 is expected at Odoo Experience in Brussels, 24 to 26 September 2026. The changes below are read from the public development branch and are not final until release.

The widget keeps zero options and its registration, but the rendering changes visibly: the FontAwesome classes are dropped for Odoo's own oi icon set. The class string becomes oi text- plus the decoration, and the glyph moves to a dedicated icon getter. Custom CSS targeting .fa inside this widget, or custom activity types declaring FontAwesome icon names, will need review. We re-verify after release.