Probe target
  repo: https://github.com/bloxbean/cardano-client-lib
  git HEAD: 4f1ea9c9117d7744851f382314386cfb7b4f5939
  project version: 0.8.0-pre5 (gradle.properties)
  method: bundled README plus shallow upstream API inspection

Inspected API
  function/.../TxBuilder.java
    @FunctionalInterface
    void apply(TxBuilderContext context, Transaction txn)
    default TxBuilder andThen(TxBuilder after)
  function/.../FeeCalculators.java
    feeCalculator(int noOfSigners, UpdateOutputFunction callback)
    UpdateOutputFunction.accept(BigInteger fee, List<TransactionOutput> outputs)
  function/.../BalanceTxBuilders.java
    balanceTx(...) composes fee calculation and change adjustment.

Conclusion
  balanceTx provides ordinary balancing. The fee/output callback directly
  supports fee-dependent outputs. Any custom TxBuilder sees and may transform
  the assembled Transaction and can be composed before/after balancing, giving
  a genuine observation hook. A final-output-dependent redeemer is expressible
  with effort by composing a custom transformer and an explicitly bounded
  rebalance loop; no dedicated convergence abstraction was found.