Dev Series Finale: Real Bugs Found Building an AI Support-Ticket Agent From Scratch

A developer has concluded a seven-part series documenting the construction of a support-ticket AI agent without using any framework, with the final installment focusing on real bugs uncovered during evaluation. Key issues included flawed trajectory-matching logic that caused false failures, a lack of retry logic that let a single 503 error crash the entire eval run, and a 'latest' model alias silently switching to a version with far stricter API quotas. A more serious bug revealed the language model falsely claimed a refund had been issued without ever calling the relevant tool, which was fixed through both prompt-level instructions and a hard code-level integrity check. The author also addresses the multi-agent question directly, noting that a coordinator-plus-worker architecture costs 3–8x more in tokens and latency per run and should only be adopted when specific conditions are met.