Engineering

    Why AI Code Breaks

    Root cause analysis of AI-generated regressions and how to design systems that keep shipping safely

    AI-Generated• Human Curated & Validated
    12 min read
    December 30, 2025
    Reliability
    AI Assistants
    Incident Response
    Testing

    When AI-generated code hits production, incidents spike. Our incident response team dissected 112 outages caused by AI-assisted commits. The root causes were surprisingly human: missing context, absent guardrails, and feedback loops that never closed. Here is the anatomy of failure—and how to build resilience.

    Failure Pattern 1: Silent Contracts

    AI changes a function signature or JSON contract, but the downstream consumer never updates. The tests pass because mocks still reference the old schema.

    Prevent it

    • Adopt schema validation (OpenAPI, TypeScript types, protobufs) enforced in CI.
    • Generate contract tests automatically whenever the model edits public APIs.
    • Run integration tests against real downstream services or synthetic data.

    Failure Pattern 2: Environment Divergence

    Models hallucinate environment variables or feature flags that exist in staging but not in production. Deployments fail or, worse, route traffic incorrectly.

    Detection

    • Diff environment configs during code review.
    • Use policy checks to block references to non-existent feature flags.
    • Log unexpected flag evaluations and alert on fallback usage.

    Prevention

    • Store configuration as code with typed definitions.
    • Prompt the model with explicit environment contexts ("prod has flags X, Y, Z only").
    • Adopt progressive delivery: canaries + automatic rollback.

    Failure Pattern 3: Non-Idempotent Scripts

    AI generates migration scripts or data backfills that assume a clean environment. When re-run, they duplicate data or corrupt records.

    Prevent it

    • Add guard clauses (e.g., "if table exists") and dry-run modes.
    • Generate rollback scripts alongside forward migrations.
    • Run migrations in sandboxed copies of production data before rollout.

    Failure Pattern 4: Missing Observability

    AI-generated services launch without metrics, logs, or traces. When they fail, the on-call engineer has no breadcrumbs.

    Observability Starter Pack

    • Require structured logs with correlation IDs in every new handler.
    • Include latency, error rate, and usage dashboards in the definition of done.
    • Use anomaly detection on AI output confidence to alert before failures cascade.

    Failure Pattern 5: Invisible Human Review

    AI writes a feature, but no one updates runbooks or trains support teams. Customers encounter confusing behavior and tickets flood in.

    Prevent it

    • Couple AI launches with customer success playbooks and FAQ updates.
    • Create a "human verification" checklist for behavior changes.
    • Instrument feedback widgets within the feature to capture user sentiment.

    Root Cause Summary

    Root Cause% of IncidentsPrimary Countermeasure
    Contract mismatch27%Schema validation + contract tests
    Config drift21%Config-as-code + environment prompts
    Non-idempotent scripts18%Dry-runs + rollback plans
    Missing observability17%DOD includes dashboards + alerts
    Unsupported users17%Runbooks + user feedback loops

    Closing Advice

    AI is not inherently flaky—our processes are. Treat AI contributions like junior engineer commits: give them context, demand tests, bake in observability, and close the loop with humans. Do that, and the majority of "AI outages" turn into non-events.

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