dbt Fusion --sample emitted nanosecond timestamps BigQuery rejects

TL;DR

Upgrade to a release carrying the fix. If a dbt Fusion --sample run fails on BigQuery with a timestamp coercion error, look at the compiled filter: 9-digit fractional seconds are the fingerprint.

Steps

1. If a dbt Fusion --sample run fails on BigQuery with a timestamp coercion error, look at the compiled filter: 9-digit fractional seconds are the fingerprint. Upgrade to a release carrying the fix. Agents generating dbt sample windows should never hand-format timestamps at nanosecond precision for BigQuery; cap at 6 fractional digits to match what the warehouse accepts.

When to use

You are seeing this: '2026-06-05T03:50:56.538507786+00:00'. Use this skill when you run into "dbt Fusion --sample emitted nanosecond timestamps BigQuery rejects".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Source: GitHub issue dbt-labs/dbt#15242 (closed): on dbt Fusion with BigQuery, the --sample flag injected an event-time filter whose timestamp literals carried 9 fractional-second digits (nanosecond precision), e.g. '2026-06-05T03:50:56.538507786+00:00'. BigQuery TIMESTAMP and DATETIME support only 6 digits, so the implicit string-to-timestamp coercion failed and the run errored. Manually trimming the literal to 6 digits made the query valid. Fun root cause from the fix thread: the bug never showed for timestamps whose last three digits were 000, because Rust's AutoSi formatting trimmed them to microseconds. Fix merged.

Verified resolution: If a dbt Fusion --sample run fails on BigQuery with a timestamp coercion error, look at the compiled filter: 9-digit fractional seconds are the fingerprint. Upgrade to a release carrying the fix. Agents generating dbt sample windows should never hand-format timestamps at nanosecond precision for BigQuery; cap at 6 fractional digits to match what the warehouse accepts.

Source URL: https://github.com/dbt-labs/dbt/issues/15242