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Each product composes features into a feature chain. The chain defines the complete event dispatch for that product.

Event dispatch matrix

The following table shows which events each product responds to, and which feature handles them. Features are dispatched left-to-right -- earlier features validate before later features execute.

Event Easy Access Fixed Term ISA Personal Loan Mortgage Overdraft
AccountOpened Lifecycle Lifecycle Lifecycle Lifecycle Lifecycle Lifecycle
DepositReceived Deposit Deposit ISA -> Deposit Deposit Deposit Deposit
WithdrawalRequested Withdrawal TermLock -> Withdrawal Withdrawal -- -- Overdraft
EndOfDay Interest TermLock -> Interest Interest Interest Interest Interest
EndOfMonth -- -- -- Repayment Repayment --
MaturityReached -- (derived) -- -- -- --
AccountClosed Lifecycle Lifecycle Lifecycle Lifecycle Lifecycle Lifecycle

Bold = feature that gates or modifies the event before the standard handler runs.

Key observations:

  • Lending products (Personal Loan, Mortgage) have no WithdrawalRequested handler -- repayment is the only way funds leave the account.
  • Overdraft uses OverdraftFacility instead of WithdrawalProcessing -- it allows negative balances.
  • ISA and Fixed Term add validation features before the standard handler in the dispatch chain.

Easy Access

Instant-access savings account. Deposits and withdrawals at any time with daily interest accrual.

Feature chain: StatusLifecycle -> DepositAcceptance -> WithdrawalProcessing -> InterestAccrual

Defaults: annual_rate: 0.015 (1.5% p.a.)

Golden goluca file: easy_access_30d

Given an Easy Access savings account opened 2026-01-01 And a deposit of £1,000.00 When 30 days elapse to 2026-01-30 Then daily interest accrues at 1.5% p.a. And the goluca export round-trips cleanly

2026-01-01 * Deposit
  Equity:Capital -> Liability:Savings:alice 1000 GBP

2026-01-01 * Daily interest for 2026-01-01
  Expense:Interest -> Liability:Savings:alice 0.04 GBP

2026-01-02 * Daily interest for 2026-01-02
  Expense:Interest -> Liability:Savings:alice 0.04 GBP

  ... (daily interest of 0.04 GBP continues through 2026-01-30) ...

2026-01-30 * Daily interest for 2026-01-30
  Expense:Interest -> Liability:Savings:alice 0.04 GBP

30 days at 1.5% on £1,000 = 30 x £0.04 = £1.20 total interest.

Fixed Term

Higher-rate savings locked until a maturity date.

Feature chain: StatusLifecycle -> DepositAcceptance -> TermLock -> WithdrawalProcessing -> InterestAccrual

Defaults: annual_rate: 0.040 (4.0% p.a.)

Parameters: maturity_date (format 2006-01-02) -- required at account opening.

TermLock runs before WithdrawalProcessing and rejects any withdrawal before the maturity date. On the maturity date, TermLock fires MaturityReached during EndOfDay processing.

Golden goluca file: fixed_term_maturity

Given a Fixed Term account with maturity 2026-04-01 And a deposit of £5,000.00 When time advances past maturity to 2026-04-02 And £5,000.00 is withdrawn Then interest at 4.0% has accrued over ~91 days And the withdrawal succeeds post-maturity

2026-01-01 * Deposit
  Equity:Capital -> Liability:Savings:fixed 5000 GBP

2026-01-01 * Daily interest for 2026-01-01
  Expense:Interest -> Liability:Savings:fixed 0.54 GBP

  ... (daily interest of 0.54 GBP through 2026-02-04) ...

2026-02-05 * Daily interest for 2026-02-05
  Expense:Interest -> Liability:Savings:fixed 0.55 GBP

  ... (daily interest of 0.55 GBP through 2026-04-02) ...

2026-04-02 * Withdrawal
  Liability:Savings:fixed -> Equity:Capital 5000 GBP

2026-04-02 * Daily interest for 2026-04-02
  Expense:Interest -> Liability:Savings:fixed 0.55 GBP

~91 days at 4.0% on £5,000. Daily interest rises from £0.54 to £0.55 as accrued interest compounds. Withdrawal of the original £5,000 succeeds only after the maturity date.

ISA

Tax-free savings with an annual deposit allowance.

Feature chain: StatusLifecycle -> ISAWrapper -> DepositAcceptance -> WithdrawalProcessing -> InterestAccrual

Defaults: annual_rate: 0.035 (3.5% p.a.), isa_allowance: 2000000 (£20,000)

ISAWrapper runs before DepositAcceptance and tracks a running total (isa_deposited). Deposits exceeding the allowance are rejected before reaching DepositAcceptance.

Golden goluca file: isa_30d

Given an ISA account opened 2026-01-01 And a deposit of £10,000.00 (within £20k allowance) When 30 days elapse Then daily interest accrues at 3.5% p.a.

2026-01-01 * Deposit
  Equity:Capital -> Liability:Savings:isa 10000 GBP

2026-01-01 * Daily interest for 2026-01-01
  Expense:Interest -> Liability:Savings:isa 0.95 GBP

  ... (daily interest of 0.95 GBP through 2026-01-13) ...

2026-01-14 * Daily interest for 2026-01-14
  Expense:Interest -> Liability:Savings:isa 0.96 GBP

  ... (daily interest of 0.96 GBP through 2026-01-30) ...

30 days at 3.5% on £10,000. Daily interest rises from £0.95 to £0.96 as accrued interest compounds.

Personal Loan

Unsecured lending. Interest accrues on the outstanding balance; monthly repayments reduce it.

Feature chain: StatusLifecycle -> DepositAcceptance -> InterestAccrual -> RepaymentSchedule

Defaults: annual_rate: 0.069 (6.9% p.a.)

Parameters: monthly_repayment (amount in minor units), repayment_source (ledger account path).

The loan is disbursed as a Deposit into the asset account. No withdrawal handler -- funds leave only via scheduled repayments.

Golden goluca file: personal_loan_30d

Given a Personal Loan account opened 2026-01-01 And £5,000.00 disbursed When 30 days elapse Then daily interest accrues at 6.9% p.a.

2026-01-01 * Deposit
  Equity:Capital -> Asset:Loans:alice 5000 GBP

2026-01-01 * Daily interest for 2026-01-01
  Expense:Interest -> Asset:Loans:alice 0.94 GBP

  ... (daily interest of 0.94 GBP through 2026-01-27) ...

2026-01-28 * Daily interest for 2026-01-28
  Expense:Interest -> Asset:Loans:alice 0.95 GBP

  ... (daily interest of 0.95 GBP through 2026-01-30) ...

30 days at 6.9% on £5,000. Daily interest rises from £0.94 to £0.95 as accrued interest compounds.

Mortgage

Residential mortgage. Same mechanics as Personal Loan with a different default rate.

Feature chain: StatusLifecycle -> DepositAcceptance -> InterestAccrual -> RepaymentSchedule

Defaults: annual_rate: 0.045 (4.5% p.a.)

Parameters: Same as Personal Loan -- monthly_repayment, repayment_source.

Golden goluca file: mortgage_30d

Given a Mortgage account opened 2026-01-01 And £100,000.00 disbursed When 30 days elapse Then daily interest accrues at 4.5% p.a.

2026-01-01 * Deposit
  Equity:Capital -> Asset:Loans:mortgage 100000 GBP

2026-01-01 * Daily interest for 2026-01-01
  Expense:Interest -> Asset:Loans:mortgage 12.32 GBP

2026-01-02 * Daily interest for 2026-01-02
  Expense:Interest -> Asset:Loans:mortgage 12.33 GBP

  ... (daily interest rises gradually: 12.33 -> 12.34 -> 12.35 -> 12.36 -> 12.37) ...

2026-01-30 * Daily interest for 2026-01-30
  Expense:Interest -> Asset:Loans:mortgage 12.37 GBP

30 days at 4.5% on £100,000. Daily interest starts at £12.32 and rises to £12.37 as accrued interest compounds.

Overdraft

Arranged overdraft facility on a current account.

Feature chain: StatusLifecycle -> DepositAcceptance -> OverdraftFacility -> InterestAccrual

Defaults: annual_rate: 0.159 (15.9% p.a.), overdraft_limit: 100000 (£1,000)

OverdraftFacility replaces WithdrawalProcessing -- it permits the balance to go negative down to -overdraft_limit and records the movement itself.

Golden goluca file: overdraft_30d

Given an Overdraft facility account opened 2026-01-01 And £500.00 drawn (within £1,000 limit) When 30 days elapse Then daily interest accrues at 15.9% p.a. on negative balance

2026-01-01 * Withdrawal
  Liability:Current:alice -> Equity:Capital 500 GBP

2026-01-01 * Daily interest for 2026-01-01
  Liability:Current:alice -> Income:Interest 0.21 GBP

  ... (daily interest of 0.21 GBP through 2026-01-24) ...

2026-01-25 * Daily interest for 2026-01-25
  Liability:Current:alice -> Income:Interest 0.22 GBP

  ... (daily interest of 0.22 GBP through 2026-01-30) ...

30 days at 15.9% on -£500. Interest direction is reversed (debit to liability, credit to income) because the balance is negative. Daily interest rises from £0.21 to £0.22.