After updating Jenkins from 1.449 to 1.457, the remote API for the latest promoted build stopped returning the artifacts.

For example, for a promotion process named "internal_release", accessing http://hostname:8080/job/jobname/promotion/latest/internal_release/api/xml yields only this information:

<promotion>
<action/>
<action>
<cause>
<shortDescription>Legacy code started this job. No cause information is available</shortDescription>
</cause>
</action>
<action/>
<action/>
<action/>
<building>false</building>
<duration>5890</duration>
<fullDisplayName>jobname » promotion » internal_release #17</fullDisplayName>
<id>2012-02-21_16-44-04</id>
<keepLog>false</keepLog>
<number>17</number>
<result>SUCCESS</result>
<timestamp>1329860644000</timestamp>
<url>
http://hostname:8080/job/jobname/promotion//internal_release/17/
</url>
<builtOn/>
<changeSet/>
</promotion>

A workaround to access the artifacts list would be to find a link from the promotion number to the actual build number, but this information does not seem available through the API.