Starting in release 4.5, Language Agents are automatically backward-compatible with any 4.4.1+ Controller, so you can upgrade your agent while retaining your 4.4.1+ Controller. See Agent and Controller Compatibility documentation.
Note: If your Controller is older than 4.4.1, you must upgrade your Controller before upgrading your Language Agent.
To ensure a successful correlation, upgrade order should begin with agents on downstream tiers, followed by those on upstream tiers.
If you are upgrading multiple agents in your monitored environment, be sure to upgrade last the agents for tiers on which business transactions originate. See the following documents for step-by-step instructions, as needed: