BA-00P · LESSON 04

Handle a slow payment

KEY DEFINITIONS

Terms used in this lesson

RBF: Replace-by-fee: a policy for replacing an unconfirmed transaction with a conflicting one that pays more.
CPFP: Child Pays for Parent: a high-fee child transaction raises the combined fee rate of an unconfirmed package.
Transaction ID: The identifier produced by hashing a Bitcoin transaction’s non-witness serialization.

Diagnose low fees, distinguish replace-by-fee from child-pays-for-parent, and decide when waiting is safer than changing the transaction.

65 min Difficulty 1/5 Not started

VISUAL MODEL

See the whole mechanism before going step by step

Use the diagrams to orient yourself. Then the guided explanation below teaches every part in depth.

4 explanatory views

CONCEPT-SPECIFIC MAP · state machineOne valid action transforms a known stateSelect any state to inspect its exact role.

RELATIONSHIP MAPOrdered mechanism flow

01
BEFOREKnown state
Identify the facts and objects that exist before the action.
02
ACTIONHandle a slow payment
The Handle a slow payment lesson isolates the event that proposes a change.
03
RULEDeterministic check
The enforcing rule accepts or rejects the proposed transition.
04
AFTERSuccessor state
Accepted work creates a new state without silently changing the prior facts.
05
FAILUREState unchanged
A failed condition must not produce a partially accepted successor.

Rule shown: A valid transition names the prior state, action, enforcing rule, and successor state.

STAGE 1 OF 5BEFORE: Known state

Identify the facts and objects that exist before the action.

Governing relationship: A valid transition names the prior state, action, enforcing rule, and successor state. Complete path: 1. BEFORE, Known state. Identify the facts and objects that exist before the action. 2. ACTION, Handle a slow payment. The Handle a slow payment lesson isolates the event that proposes a change. 3. RULE, Deterministic check. The enforcing rule accepts or rejects the proposed transition. 4. AFTER, Successor state. Accepted work creates a new state without silently changing the prior facts. 5. FAILURE, State unchanged. A failed condition must not produce a partially accepted successor.

1. State transitionWhat exists, what changes, and what results

BEFORE

A 200 vB parent pays 200 sats. Its 120 vB child can pay 4,600 sats.

MECHANISM

Find the txid, confirmation count, fee rate, size, replacement signal, and whether your node or wallet still has the transaction.

AFTER

Diagnose the exact unconfirmed state before choosing a fee-bumping method, then reason about the whole valid transaction set.

Text equivalent: Starting from A 200 vB parent pays 200 sats. Its 120 vB child can pay 4,600 sats. The mechanism begins when Find the txid, confirmation count, fee rate, size, replacement signal, and whether your node or wallet still has the transaction. The resulting lesson is Diagnose the exact unconfirmed state before choosing a fee-bumping method, then reason about the whole valid transaction set.

2. Mechanism pathSelect a stage to inspect its job

STAGE 1 OF 5

Inspect current state

Find the txid, confirmation count, fee rate, size, replacement signal, and whether your node or wallet still has the transaction.

Complete path: 1. Inspect current state: Find the txid, confirmation count, fee rate, size, replacement signal, and whether your node or wallet still has the transaction. 2. Compare with current demand: A fee rate is a bid for scarce block space, not a guarantee. Recent blocks and mempool estimates provide evidence, but demand can change. 3. Choose wait, RBF, or CPFP: Waiting changes nothing. RBF creates a higher-fee conflict spending an original input. CPFP spends an unconfirmed output with a child whose fee improves the package economics. 4. Preserve payment intent: A replacement should keep the intended recipient and amount unless the user explicitly changes them. Fee increases usually reduce change or add input value. 5. Verify the new package: Check the replacement or parent-child package as a complete transaction set, then monitor whether one valid history confirms.

3. Rule and failure boundaryWhat accepts the result and where it can stop

ACCEPTED PATH

The replacement or child must be valid, policies must accept it, and the relevant fee comparison must use the whole replacement or ancestor package.

CHANGED CONDITION

Paying a large child fee cannot help when the child is invalid, spends the wrong output, or cannot reach miners that evaluate the package.

Important distinction: Pressing speed up edits a transaction already on Bitcoin. A wallet creates a new replacement or child transaction. Nodes and miners apply their policies to the new candidate or package.

Text equivalent: The accepted path is enforced by The replacement or child must be valid, policies must accept it, and the relevant fee comparison must use the whole replacement or ancestor package. If the required condition changes, Paying a large child fee cannot help when the child is invalid, spends the wrong output, or cannot reach miners that evaluate the package.

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Learn the idea

A slow payment is usually a fee-market or relay problem, not evidence that Bitcoin has lost it. First identify whether the transaction is in mempools, replaceable, has a spendable change or recipient output, or has already confirmed. Then choose among waiting, replacing the sender's transaction, or attaching a fee-paying child.

GUIDED EXPLANATION1/5 ideas inspected

Inspect current state

Find the txid, confirmation count, fee rate, size, replacement signal, and whether your node or wallet still has the transaction.

The worked example follows the explanation

Inspect every idea above to open it.

Important distinction“Pressing speed up edits a transaction already on Bitcoin.”

A wallet creates a new replacement or child transaction. Nodes and miners apply their policies to the new candidate or package.

FINISH LEARNING FIRST

The questions unlock after every required learning activity

Inspect every guided idea, open the worked example, rebuild its mechanism, and complete the deterministic lesson tool. Your progress is saved automatically.