Function established_pending_through 

pub async fn established_pending_through(
    pool: &PgPool,
    tracking_table: &TrackingTable,
    files: &BTreeMap<(u64, bool), Vec<MigrationSection>>,
    established: &BTreeSet<String>,
    through_version: u64,
) -> Result<Vec<u64>>

Migration versions ≤ through_version whose base/established-module sections are NOT yet applied on the target — i.e. versions the established set still needs before it is caught up to through_version. An empty result means caught up.

Adopting a module from a baseline at version V writes a tracking row that claims coverage through V. That claim is only honest if the target’s other modules are actually at V, so adoption checks this first and refuses when it isn’t — rolling an established (possibly-destructive) module forward is an explicit apply, never a side effect of adopting a different module.

Migrations at or below a fully-completed baseline the target already holds are covered and excluded (the honest applied-baseline watermark, distinct from the crossing watermark — a crashed baseline, with a non-completed section, does not count).