agent loop detected: re-running failed dbt tests with no changes

TL;DR

dbt tests are deterministic: same data, same test, same result. Re-running a failing test without changing the data or the test cannot pass. Stop the loop, read the failure, fix the data or the expectation, then run once. Test re-runs are for verifying fixes, not for wishing.

agent loop detected: re-running failed dbt tests with no changes

Use this when

• An agent re-runs failing dbt tests with no intervening change.
• The failures are identical across runs.
• The agent's plan is stuck on make the tests pass by repetition.

Not for this skill when

• The data or test changed between runs. That is iteration, not a loop.
• Tests are flaky. That is a different problem.

Steps

1. Confirm nothing changed between runs: same code, same data, same command. Note the sameness. Verify: the loop is proven pointless
2. Stop re-running. Note the halt. Verify: the loop breaks
3. Read the test failure output: which rows violate which expectation. Note the violation. Verify: the failure is understood
4. Fix the data upstream or correct the test expectation. Note the change. Verify: something actually changes
5. Run the tests once and confirm they pass. Note the green run. Verify: the fix is verified with one run

Variant phrasings

agent rerunning dbt tests loop

The paraphrase.

dbt test deterministic failure

The concept phrasing.

Compatibility: dbt Core test execution. Determinism holds for tests on stable data; streaming sources need care.

Why it happens

Tests encode expectations about data, and neither the data nor the expectation changes between identical runs. Re-running is magical thinking with a compute bill. Agents fall into it because re-run is the available action and diagnosis feels harder, but the failure output already contains the diagnosis: the violating rows are listed. The loop breaks the moment the agent reads instead of reruns.

Edge cases / pitfalls

• Tests on streaming or frequently-updated sources can legitimately change between runs. Verify the data is stable before calling it a loop.
• A test that fails on timing (freshness) rather than content can pass on re-run honestly. Distinguish content failures from timing failures.
• Re-running the full test suite to verify one fix is fine. Re-running the same failing test with no fix is the loop.
• If the agent cannot fix the data or the test, escalate with the violation listed. Do not loop while waiting for permission.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst5syRXNEgN7wk9m8LKKHbg