M8-R14: preserve zero DSMR sample interval

.env.example

@@ -14,6 +14,7 @@ AUTH_BOOTSTRAP_PASSWORD=change-me
 
 # Optional: runtime overrides.
 # Leave these commented out to use the application's built-in defaults.
+# TZ=Europe/Amsterdam
 # APP_DEBUG=
 # AUTH_SESSION_COOKIE_NAME=
 # AUTH_SESSION_TTL_HOURS=

app/integrations/meter_sources.py

@@ -98,8 +98,10 @@ def _validate_field_value(kind: str, field: SourceConfigField, value: Any) -> No
     _check_type(field, value)
     if field.name == "path" and not value.startswith("/dev/"):
         raise SourceProfileError("warmtelink_serial config path must start with '/dev/'.")
-    if field.name in {"broker_port", "sample_interval_s", "baudrate"} and value <= 0:
+    if field.name in {"broker_port", "baudrate"} and value <= 0:
         raise SourceProfileError(f"Config field {field.name!r} must be greater than zero.")
+    if field.name == "sample_interval_s" and value < 0:
+        raise SourceProfileError("Config field 'sample_interval_s' must not be negative.")
     if field.name == "data_bits" and value != 7:
         raise SourceProfileError("warmtelink_serial data_bits must be 7.")
     if field.name == "parity" and value != "N":

app/services/timezone.py

@@ -19,8 +19,8 @@ Priority for resolving the local timezone
 -----------------------------------------
 1. ``TZ`` environment variable — ``ZoneInfo(os.environ["TZ"])``.
    Set ``TZ=Europe/Amsterdam`` in the deployment env for correct NL handling.
-2. System local timezone fallback: ``datetime.now().astimezone().tzinfo``.
+2. The DST-aware ``Europe/Amsterdam`` business timezone.  This keeps local-day
-   This matches the behaviour callers already relied on implicitly.
+   calculations deterministic when a deployment does not set ``TZ``.
 """
 
 from __future__ import annotations
@@ -40,7 +40,7 @@ def local_tz() -> "tzinfo":
     Resolution order:
     1. ``TZ`` environment variable (``ZoneInfo(TZ)``).  Set
        ``TZ=Europe/Amsterdam`` in production for correct NL/DST handling.
-    2. System local timezone via ``datetime.now().astimezone().tzinfo``.
+    2. The DST-aware ``Europe/Amsterdam`` business timezone.
 
     **Monkeypatch this function in tests** to get deterministic timezone
     behaviour regardless of CI host configuration::
@@ -51,9 +51,7 @@ def local_tz() -> "tzinfo":
     tz_env = os.environ.get("TZ", "").strip()
     if tz_env:
         return ZoneInfo(tz_env)
-    # System fallback — identical to the .astimezone() pattern already used
+    return ZoneInfo("Europe/Amsterdam")
-    # in homeassistant_inbound.py and poo.py.
-    return datetime.now().astimezone().tzinfo  # type: ignore[return-value]
 
 
 def to_local(dt: datetime) -> datetime:

docker-compose.yml

@@ -6,6 +6,8 @@ services:
     restart: "no"
     init: true
     command: ["python", "-m", "scripts.run_migrations"]
+    environment:
+      TZ: "${TZ:-Europe/Amsterdam}"
     volumes:
       - ./data:/app/data
       - ./.env:/app/.env:ro
@@ -17,6 +19,8 @@ services:
     user: "1000:1000"
     restart: unless-stopped
     init: true
+    environment:
+      TZ: "${TZ:-Europe/Amsterdam}"
     depends_on:
       migration:
         condition: service_completed_successfully

frontend/src/energy/CostView.test.tsx

@@ -79,6 +79,23 @@ const THERMAL_SUMMARY = {
   period_count: 4, degraded_count: 2,
   fixed_breakdown: { heating_network: '0.1', metering: '0.1', delivery_set: '0', hot_water_network: '0.1', other: '0.2' },
 }
+const ROUNDED_THERMAL_SUMMARY = {
+  ...THERMAL_SUMMARY,
+  heating: '20.12344',
+  hot_water_heating: '8.20005',
+  hot_water: '1.99995',
+  hot_water_tax: '0.40000',
+  variable_subtotal: '7.0000',
+  fixed_subtotal: '0.00004',
+  all_in: '9.99995',
+  fixed_breakdown: {
+    heating_network: '100.000000000000000001',
+    metering: '0.0000',
+    delivery_set: '20.20000',
+    hot_water_network: '30.30004',
+    other: '40.40005',
+  },
+}
 const THERMAL_VALUES = {
   variable: {
     heating: '20.123456789123456789', hot_water_heating: '8.200000000000000001',
@@ -95,6 +112,12 @@ const THERMAL_ROW = {
   cost_breakdown: { heating: '0.123456789' }, pricing_snapshot: THERMAL_VALUES,
   quality: 'unverifiable', degraded: false, degraded_reason: null,
 }
+const ROUNDED_THERMAL_ROW = {
+  ...THERMAL_ROW,
+  quantity: '1.23456',
+  cost: '0.12344',
+  cost_breakdown: { heating: '0.12345', hot_water: '0.10000' },
+}
 const THERMAL_ROW_OTHER_VERSION = {
   ...THERMAL_ROW, commodity: 'hot_water', period_start: '2026-06-22T10:15:00Z', period_end: '2026-06-22T10:30:00Z',
   contract_version_id: 100, quantity: '2.3', cost: '4.339506172839506170',
@@ -233,6 +256,32 @@ describe('CostView', () => {
     })
   })
 
+  it('uses the same bottom-aligned toolbar structure in both scopes', async () => {
+    const user = userEvent.setup()
+    mockGet.mockImplementation((path: string) => {
+      if (path === '/api/energy/costs/summary') return Promise.resolve({ data: SUMMARY })
+      if (path === '/api/energy/meter-costs/summary') return Promise.resolve({ data: THERMAL_SUMMARY })
+      return Promise.resolve({ data: { items: [], total: 0 } })
+    })
+
+    renderWithProviders(<CostView />)
+
+    const electricityToolbar = screen.getByTestId('cost-toolbar')
+    expect(electricityToolbar).toContainElement(screen.getByTestId('costs-scope-selector'))
+    expect(electricityToolbar).toContainElement(screen.getByTestId('cost-range-control'))
+    expect(electricityToolbar).toContainElement(screen.getByTestId('cost-recompute-button'))
+    expect(screen.getByTestId('cost-recompute-button')).toHaveStyle({ marginLeft: 'auto' })
+
+    await user.click(screen.getByTestId('costs-scope-selector'))
+    await user.click(screen.getByText('Thermal'))
+    await waitFor(() => expect(screen.getByTestId('thermal-cost-toolbar')).toBeInTheDocument())
+    const thermalToolbar = screen.getByTestId('thermal-cost-toolbar')
+    expect(thermalToolbar).toContainElement(screen.getByTestId('costs-scope-selector'))
+    expect(thermalToolbar).toContainElement(screen.getByTestId('thermal-cost-range-control'))
+    expect(thermalToolbar).toContainElement(screen.getByTestId('thermal-recompute-button'))
+    expect(screen.getByTestId('thermal-recompute-button')).toHaveStyle({ marginLeft: 'auto' })
+  })
+
   it('calls recompute mutation when confirmed', async () => {
     const user = userEvent.setup()
 
@@ -349,8 +398,8 @@ describe('CostView', () => {
   it.each([
     ['only heating', [ACTIVE_HEATING_METER], 'hot-water meter is not configured', 'Not configured'],
     ['only hot water', [ACTIVE_HOT_WATER_METER], 'heating meter is not configured', 'Not configured'],
-    ['both current meters', [ACTIVE_HEATING_METER, ACTIVE_HOT_WATER_METER], null, '1.10'],
+    ['both current meters', [ACTIVE_HEATING_METER, ACTIVE_HOT_WATER_METER], null, '1.1'],
-    ['a replaced heating meter plus its current epoch', [ENDED_HEATING_METER, ACTIVE_HEATING_METER, ACTIVE_HOT_WATER_METER], null, '1.10'],
+    ['a replaced heating meter plus its current epoch', [ENDED_HEATING_METER, ACTIVE_HEATING_METER, ACTIVE_HOT_WATER_METER], null, '1.1'],
   ])('uses active meter epochs for %s without treating zero amounts as missing', async (_name, meterItems, missingText, heatingValue) => {
     mockGet.mockImplementation((path: string) => {
       if (path === '/api/energy/meters') return Promise.resolve({ data: { items: meterItems, total: meterItems.length } })
@@ -373,6 +422,44 @@ describe('CostView', () => {
     }
   })
 
+  it('rounds ordinary thermal Decimal strings without changing the audit snapshot', async () => {
+    const user = userEvent.setup()
+    mockGet.mockImplementation((path: string) => {
+      if (path === '/api/energy/meters') {
+        return Promise.resolve({ data: { items: [ACTIVE_HEATING_METER, ACTIVE_HOT_WATER_METER], total: 2 } })
+      }
+      if (path === '/api/energy/meter-costs') {
+        return Promise.resolve({ data: { items: [ROUNDED_THERMAL_ROW], total: 1 } })
+      }
+      if (path === '/api/energy/meter-costs/summary') {
+        return Promise.resolve({ data: ROUNDED_THERMAL_SUMMARY })
+      }
+      if (path === '/api/energy/costs/summary') return Promise.resolve({ data: SUMMARY })
+      return Promise.resolve({ data: { items: [], total: 0 } })
+    })
+
+    renderWithProviders(<CostView />)
+    await user.click(screen.getByTestId('costs-scope-selector'))
+    await user.click(screen.getByText('Thermal'))
+    await waitFor(() => expect(screen.getByTestId('thermal-cost-summary')).toBeInTheDocument())
+
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('Heating20.1234')
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('Hot-water heating8.2001')
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('Hot water2')
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('Hot-water tax0.4')
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('Variable subtotal7')
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('Fixed subtotal0')
+    expect(screen.getByTestId('thermal-cost-summary')).toHaveTextContent('All-in total10')
+    expect(screen.getByTestId('thermal-fixed-breakdown')).toHaveTextContent('heating_network 100')
+    expect(screen.getByTestId('thermal-fixed-breakdown')).toHaveTextContent('other 40.4001')
+    expect(screen.getByTestId('thermal-cost-row-0')).toHaveTextContent('1.2346')
+    expect(screen.getByTestId('thermal-cost-row-0')).toHaveTextContent('0.1234 EUR')
+    expect(screen.getByTestId('thermal-cost-row-0')).toHaveTextContent('heating 0.1235, hot_water 0.1')
+
+    await user.click(screen.getByTestId('thermal-cost-expand-0'))
+    expect(screen.getByTestId('thermal-cost-audit-0')).toHaveTextContent('20.123456789123456789')
+  })
+
   it('paginates the complete thermal ledger and resets offset when its range or scope changes', async () => {
     const user = userEvent.setup()
     const lastRow = { ...THERMAL_ROW, period_start: '2026-06-22T12:00:00Z', quantity: '501' }

frontend/src/energy/CostView.tsx

@@ -110,6 +110,49 @@ function SummaryCard({ label, value, sub, testId }: SummaryCardProps) {
 
 type RangePreset = 'today' | 'month' | 'custom'
 
+/** Format an API Decimal string without converting it through binary floating point. */
+function formatDecimal(value: string): string {
+  const negative = value.startsWith('-')
+  const unsigned = negative ? value.slice(1) : value
+  const [rawWhole = '0', rawFraction = ''] = unsigned.split('.')
+  let whole = rawWhole.replace(/^0+(?=\d)/, '') || '0'
+  let fraction = rawFraction.slice(0, 4)
+
+  if (rawFraction.length > 4 && rawFraction[4] >= '5') {
+    const digits = '0123456789'
+    const fractionDigits = fraction.split('')
+    let carry = true
+    for (let index = fractionDigits.length - 1; index >= 0 && carry; index -= 1) {
+      const digit = fractionDigits[index]
+      if (digit === '9') {
+        fractionDigits[index] = '0'
+      } else {
+        fractionDigits[index] = digits[digits.indexOf(digit) + 1]
+        carry = false
+      }
+    }
+    fraction = fractionDigits.join('')
+
+    if (carry) {
+      const wholeDigits = whole.split('')
+      for (let index = wholeDigits.length - 1; index >= 0 && carry; index -= 1) {
+        const digit = wholeDigits[index]
+        if (digit === '9') {
+          wholeDigits[index] = '0'
+        } else {
+          wholeDigits[index] = digits[digits.indexOf(digit) + 1]
+          carry = false
+        }
+      }
+      whole = `${carry ? '1' : ''}${wholeDigits.join('')}`
+    }
+  }
+
+  fraction = fraction.replace(/0+$/, '')
+  const formatted = fraction ? `${whole}.${fraction}` : whole
+  return negative && formatted !== '0' ? `-${formatted}` : formatted
+}
+
 export function CostView() {
   const [scope, setScope] = useState<'electricity' | 'thermal'>('electricity')
   if (scope === 'thermal') return <ThermalCostView onScopeChange={setScope} />
@@ -155,7 +198,7 @@ function ElectricityCostView({ onScopeChange }: { onScopeChange: (scope: 'electr
   return (
     <Stack gap="lg" data-testid="cost-view">
       {/* Date range selector */}
-      <Group align="flex-start" gap="md" wrap="wrap">
+      <Group align="flex-end" gap="md" wrap="wrap" data-testid="cost-toolbar">
         <ScopeSelector scope="electricity" onScopeChange={onScopeChange} />
         <Stack gap="xs">
           <Text size="sm" fw={500}>
@@ -192,18 +235,17 @@ function ElectricityCostView({ onScopeChange }: { onScopeChange: (scope: 'electr
           </Group>
         )}
 
-        <Group gap="sm" style={{ marginLeft: 'auto' }} align="flex-end">
+        <Button
-          <Button
+          variant="outline"
-            variant="outline"
+          color="orange"
-            color="orange"
+          size="sm"
-            size="sm"
+          onClick={() => setShowRecomputeConfirm(true)}
-            onClick={() => setShowRecomputeConfirm(true)}
+          loading={recomputeMutation.isPending}
-            loading={recomputeMutation.isPending}
+          style={{ marginLeft: 'auto' }}
-            data-testid="cost-recompute-button"
+          data-testid="cost-recompute-button"
-          >
+        >
-            Recompute
+          Recompute
-          </Button>
+        </Button>
-        </Group>
       </Group>
 
       {/* Summary cards */}
@@ -483,16 +525,16 @@ function ThermalCostView({ onScopeChange }: { onScopeChange: (scope: 'electricit
   const shownStart = totalRows === 0 ? 0 : ledgerOffset + 1
   const shownEnd = Math.min(ledgerOffset + (rows.data?.items.length ?? 0), totalRows)
   return <Stack gap="lg" data-testid="thermal-cost-view">
-    <Group align="flex-start" gap="md" wrap="wrap"><ScopeSelector scope="thermal" onScopeChange={onScopeChange} /><Stack gap="xs"><Text size="sm" fw={500}>Date range</Text><SegmentedControl value={rangePreset} onChange={(value) => { resetLedgerPage(); setRangePreset(value as RangePreset) }} data={[{ label: 'Today', value: 'today' }, { label: 'This month', value: 'month' }, { label: 'Custom', value: 'custom' }]} data-testid="thermal-cost-range-control" /></Stack>{rangePreset === 'custom' && <Group gap="sm" align="flex-end"><TextInput label="From" type="date" value={customStartStr} onChange={(event) => { resetLedgerPage(); setCustomStartStr(event.currentTarget.value) }} data-testid="thermal-cost-custom-start" /><TextInput label="To" type="date" value={customEndStr} onChange={(event) => { resetLedgerPage(); setCustomEndStr(event.currentTarget.value) }} data-testid="thermal-cost-custom-end" /></Group>}<Button variant="outline" color="orange" onClick={() => { setRecomputeError(null); setRecomputeSuccess(null); setShowConfirm(true) }} disabled={!recomputeAvailable} data-testid="thermal-recompute-button">Recompute</Button></Group>
+    <Group align="flex-end" gap="md" wrap="wrap" data-testid="thermal-cost-toolbar"><ScopeSelector scope="thermal" onScopeChange={onScopeChange} /><Stack gap="xs"><Text size="sm" fw={500}>Date range</Text><SegmentedControl value={rangePreset} onChange={(value) => { resetLedgerPage(); setRangePreset(value as RangePreset) }} data={[{ label: 'Today', value: 'today' }, { label: 'This month', value: 'month' }, { label: 'Custom', value: 'custom' }]} data-testid="thermal-cost-range-control" /></Stack>{rangePreset === 'custom' && <Group gap="sm" align="flex-end"><TextInput label="From" type="date" value={customStartStr} onChange={(event) => { resetLedgerPage(); setCustomStartStr(event.currentTarget.value) }} data-testid="thermal-cost-custom-start" /><TextInput label="To" type="date" value={customEndStr} onChange={(event) => { resetLedgerPage(); setCustomEndStr(event.currentTarget.value) }} data-testid="thermal-cost-custom-end" /></Group>}<Button variant="outline" color="orange" onClick={() => { setRecomputeError(null); setRecomputeSuccess(null); setShowConfirm(true) }} disabled={!recomputeAvailable} style={{ marginLeft: 'auto' }} data-testid="thermal-recompute-button">Recompute</Button></Group>
     {(rows.isLoading || summary.isLoading) && <Center><Loader size="sm" /></Center>}
     {(rows.isError || summary.isError) && <Alert color="red">Failed to load thermal costs.</Alert>}
     {recomputeError && <Alert color="red" data-testid="thermal-recompute-error">{recomputeError}</Alert>}
     {recomputeSuccess && <Alert color="green" data-testid="thermal-recompute-success">{recomputeSuccess}</Alert>}
     {summary.data && <Stack gap="xs" data-testid="thermal-cost-summary"><Title order={6}>{rangePreset === 'today' ? 'Today' : rangePreset === 'month' ? 'This month' : 'Custom range'} ({currency})</Title><Text size="sm" data-testid="thermal-cost-range">{start ?? 'Select a start date'} — {end ?? 'Select an end date'}</Text><SimpleGrid cols={{ base: 2, sm: 3 }}>
-      <SummaryCard label="Heating" value={hasCurrentHeatingMeter === false ? 'Not configured' : summary.data.heating} /><SummaryCard label="Hot-water heating" value={hasCurrentHotWaterMeter === false ? 'Not configured' : summary.data.hot_water_heating} /><SummaryCard label="Hot water" value={hasCurrentHotWaterMeter === false ? 'Not configured' : summary.data.hot_water} /><SummaryCard label="Hot-water tax" value={hasCurrentHotWaterMeter === false ? 'Not configured' : summary.data.hot_water_tax} /><SummaryCard label="Variable subtotal" value={summary.data.variable_subtotal} /><SummaryCard label="Fixed subtotal" value={summary.data.fixed_subtotal} /><SummaryCard label="All-in total" value={summary.data.all_in} />
+      <SummaryCard label="Heating" value={hasCurrentHeatingMeter === false ? 'Not configured' : formatDecimal(summary.data.heating)} /><SummaryCard label="Hot-water heating" value={hasCurrentHotWaterMeter === false ? 'Not configured' : formatDecimal(summary.data.hot_water_heating)} /><SummaryCard label="Hot water" value={hasCurrentHotWaterMeter === false ? 'Not configured' : formatDecimal(summary.data.hot_water)} /><SummaryCard label="Hot-water tax" value={hasCurrentHotWaterMeter === false ? 'Not configured' : formatDecimal(summary.data.hot_water_tax)} /><SummaryCard label="Variable subtotal" value={formatDecimal(summary.data.variable_subtotal)} /><SummaryCard label="Fixed subtotal" value={formatDecimal(summary.data.fixed_subtotal)} /><SummaryCard label="All-in total" value={formatDecimal(summary.data.all_in)} />
-    </SimpleGrid>{missingCurrentMeters.length > 0 && <Alert color="yellow" data-testid="thermal-missing-current-meter">Current {missingCurrentMeters.join(' and ')} meter{missingCurrentMeters.length > 1 ? 's are' : ' is'} not configured. Historical ledger rows do not establish a current meter.</Alert>}<Text size="sm" data-testid="thermal-period-count">{summary.data.period_count} periods; {summary.data.degraded_count} degraded</Text>{summary.data.degraded_count > 0 && <Alert color="orange" data-testid="thermal-summary-degraded">Some totals include degraded periods. Expand a row to see its recorded reason.</Alert>}{fixed && <Text size="sm" data-testid="thermal-fixed-breakdown">Fixed once per settled local day (summary only): {Object.entries(fixed).map(([key, value]) => `${key} ${value}`).join(' · ')}</Text>}</Stack>}
+    </SimpleGrid>{missingCurrentMeters.length > 0 && <Alert color="yellow" data-testid="thermal-missing-current-meter">Current {missingCurrentMeters.join(' and ')} meter{missingCurrentMeters.length > 1 ? 's are' : ' is'} not configured. Historical ledger rows do not establish a current meter.</Alert>}<Text size="sm" data-testid="thermal-period-count">{summary.data.period_count} periods; {summary.data.degraded_count} degraded</Text>{summary.data.degraded_count > 0 && <Alert color="orange" data-testid="thermal-summary-degraded">Some totals include degraded periods. Expand a row to see its recorded reason.</Alert>}{fixed && <Text size="sm" data-testid="thermal-fixed-breakdown">Fixed once per settled local day (summary only): {Object.entries(fixed).map(([key, value]) => `${key} ${formatDecimal(value)}`).join(' · ')}</Text>}</Stack>}
     {rows.data?.items.length === 0 && <Alert color="gray" data-testid="thermal-costs-empty">No thermal cost data for this range. Check that heating or hot-water meters are bound and have settled readings.</Alert>}
-    {rows.data && <Stack gap="xs"><Text size="sm" c="dimmed" data-testid="thermal-ledger-count">Showing {shownStart}-{shownEnd} of {totalRows}</Text>{rows.data.items.length > 0 && <ScrollArea><Table striped withTableBorder data-testid="thermal-costs-table"><Table.Thead><Table.Tr><Table.Th>Time</Table.Th><Table.Th>Commodity</Table.Th><Table.Th>Quantity</Table.Th><Table.Th>Cost</Table.Th><Table.Th>Breakdown</Table.Th><Table.Th>Status</Table.Th><Table.Th></Table.Th></Table.Tr></Table.Thead><Table.Tbody>{rows.data.items.flatMap((item, index) => [<Table.Tr key={`${item.commodity}-${item.period_start}`} data-testid={`thermal-cost-row-${index}`}><Table.Td>{formatLocalTime(item.period_start)}</Table.Td><Table.Td>{item.commodity}</Table.Td><Table.Td>{item.quantity}</Table.Td><Table.Td>{item.cost} {item.currency}</Table.Td><Table.Td>{Object.entries(item.cost_breakdown).map(([key, value]) => `${key} ${value}`).join(', ')}</Table.Td><Table.Td>{item.degraded ? <Badge color="orange" data-testid={`thermal-degraded-${index}`}>{item.degraded_reason ?? 'degraded'}</Badge> : 'normal'}</Table.Td><Table.Td><Button size="xs" variant="subtle" onClick={() => setExpandedRows((current) => { const next = new Set(current); if (next.has(index)) next.delete(index); else next.add(index); return next })} data-testid={`thermal-cost-expand-${index}`}>{expandedRows.has(index) ? 'Hide audit' : 'Audit'}</Button></Table.Td></Table.Tr>, ...(expandedRows.has(index) ? [<Table.Tr key={`audit-${item.commodity}-${item.period_start}`} data-testid={`thermal-cost-audit-${index}`}><Table.Td colSpan={7}><Text size="xs">Contract version: {item.contract_version_id ?? 'none'}</Text><Text size="xs">Pricing snapshot: {JSON.stringify(item.pricing_snapshot)}</Text></Table.Td></Table.Tr>] : [])])}</Table.Tbody></Table></ScrollArea>}<Group justify="flex-end"><Button size="xs" variant="default" disabled={ledgerOffset === 0} onClick={() => { setExpandedRows(new Set()); setLedgerOffset((current) => Math.max(0, current - COSTS_MAX_LIMIT)) }} data-testid="thermal-ledger-prev">Previous</Button><Button size="xs" variant="default" disabled={ledgerOffset + (rows.data.items.length ?? 0) >= totalRows} onClick={() => { setExpandedRows(new Set()); setLedgerOffset((current) => current + COSTS_MAX_LIMIT) }} data-testid="thermal-ledger-next">Next</Button></Group></Stack>}
+    {rows.data && <Stack gap="xs"><Text size="sm" c="dimmed" data-testid="thermal-ledger-count">Showing {shownStart}-{shownEnd} of {totalRows}</Text>{rows.data.items.length > 0 && <ScrollArea><Table striped withTableBorder data-testid="thermal-costs-table"><Table.Thead><Table.Tr><Table.Th>Time</Table.Th><Table.Th>Commodity</Table.Th><Table.Th>Quantity</Table.Th><Table.Th>Cost</Table.Th><Table.Th>Breakdown</Table.Th><Table.Th>Status</Table.Th><Table.Th></Table.Th></Table.Tr></Table.Thead><Table.Tbody>{rows.data.items.flatMap((item, index) => [<Table.Tr key={`${item.commodity}-${item.period_start}`} data-testid={`thermal-cost-row-${index}`}><Table.Td>{formatLocalTime(item.period_start)}</Table.Td><Table.Td>{item.commodity}</Table.Td><Table.Td>{formatDecimal(item.quantity)}</Table.Td><Table.Td>{formatDecimal(item.cost)} {item.currency}</Table.Td><Table.Td>{Object.entries(item.cost_breakdown).map(([key, value]) => `${key} ${formatDecimal(value)}`).join(', ')}</Table.Td><Table.Td>{item.degraded ? <Badge color="orange" data-testid={`thermal-degraded-${index}`}>{item.degraded_reason ?? 'degraded'}</Badge> : 'normal'}</Table.Td><Table.Td><Button size="xs" variant="subtle" onClick={() => setExpandedRows((current) => { const next = new Set(current); if (next.has(index)) next.delete(index); else next.add(index); return next })} data-testid={`thermal-cost-expand-${index}`}>{expandedRows.has(index) ? 'Hide audit' : 'Audit'}</Button></Table.Td></Table.Tr>, ...(expandedRows.has(index) ? [<Table.Tr key={`audit-${item.commodity}-${item.period_start}`} data-testid={`thermal-cost-audit-${index}`}><Table.Td colSpan={7}><Text size="xs">Contract version: {item.contract_version_id ?? 'none'}</Text><Text size="xs">Pricing snapshot: {JSON.stringify(item.pricing_snapshot)}</Text></Table.Td></Table.Tr>] : [])])}</Table.Tbody></Table></ScrollArea>}<Group justify="flex-end"><Button size="xs" variant="default" disabled={ledgerOffset === 0} onClick={() => { setExpandedRows(new Set()); setLedgerOffset((current) => Math.max(0, current - COSTS_MAX_LIMIT)) }} data-testid="thermal-ledger-prev">Previous</Button><Button size="xs" variant="default" disabled={ledgerOffset + (rows.data.items.length ?? 0) >= totalRows} onClick={() => { setExpandedRows(new Set()); setLedgerOffset((current) => current + COSTS_MAX_LIMIT) }} data-testid="thermal-ledger-next">Next</Button></Group></Stack>}
     {showConfirm && <Modal opened onClose={() => setShowConfirm(false)} title="Recompute thermal costs?" data-testid="thermal-recompute-confirm-modal"><Stack><Text>This explicitly overwrites closed 15-minute thermal ledger rows for {recomputeStart ?? 'the selected start'} — {closedEnd}. Continue?</Text>{!recomputeAvailable && <Alert color="yellow">Select a range containing at least one closed UTC quarter.</Alert>}<Group justify="flex-end"><Button variant="default" onClick={() => setShowConfirm(false)} data-testid="thermal-recompute-cancel">Cancel</Button><Button color="orange" loading={recompute.isPending} disabled={!recomputeAvailable} onClick={async () => { try { await recompute.mutateAsync(); setShowConfirm(false) } catch { setRecomputeError('Failed to recompute thermal costs. Please try again.'); setShowConfirm(false) } }} data-testid="thermal-recompute-confirm">Recompute</Button></Group></Stack></Modal>}
   </Stack>
 }

frontend/src/energy/MeterManager.test.tsx

@@ -209,14 +209,55 @@ describe('MeterManager — meter list', () => {
         { uuid: 'binding-active', source_uuid: 'source-new', source_channel_uuid: 'channel-new', started_at: '2025-02-01T00:00:00Z', ended_at: null },
       ],
     }
-    mockGet.mockResolvedValue({ data: { items: [meterWithBindings], total: 1 } })
+    mockGet.mockImplementation((path: string) => {
+      if (path === '/api/energy/meters') return Promise.resolve({ data: { items: [meterWithBindings], total: 1 } })
+      if (path === '/api/energy/sources') return Promise.resolve({ data: { items: [
+        { uuid: 'source-old', name: 'Old source' }, { uuid: 'source-new', name: 'New source' },
+      ], total: 2 } })
+      if (path === '/api/energy/sources/{source_uuid}/channels') return Promise.resolve({ data: { items: [
+        { uuid: 'channel-old', label: 'Old channel', unit: 'kWh' }, { uuid: 'channel-new', label: 'New channel', unit: 'kWh' },
+      ], total: 2 } })
+      return Promise.resolve({ data: { items: [] } })
+    })
     renderWithProviders(<MeterManager />)
     const closed = await screen.findByTestId('binding-timeline-binding-closed')
+    await waitFor(() => expect(closed).toHaveTextContent('Old source → Old channel'))
     const active = screen.getByTestId('binding-timeline-binding-active')
-    expect(closed).toHaveTextContent('source-old → channel-old')
+    expect(closed).toHaveTextContent('Old source → Old channel')
     expect(closed).toHaveTextContent('[1/1/2025, 00:00:00, 2/1/2025, 00:00:00) (closed)')
-    expect(active).toHaveTextContent('source-new → channel-new')
+    expect(active).toHaveTextContent('New source → New channel')
     expect(active).toHaveTextContent('[2/1/2025, 00:00:00, open-ended) (active)')
+    expect(closed).not.toHaveTextContent('source-old')
+    expect(active).not.toHaveTextContent('channel-new')
+  })
+
+  it('uses UUID-free honest binding fallbacks while source details load or fail', async () => {
+    const meter = { ...ACTIVE_METER, bindings: [{ uuid: 'binding-visible-id-only', source_uuid: 'private-source-id', source_channel_uuid: 'private-channel-id', started_at: '2025-01-01T00:00:00Z', ended_at: null }] }
+    mockGet.mockImplementation((path: string) => {
+      if (path === '/api/energy/meters') return Promise.resolve({ data: { items: [meter], total: 1 } })
+      if (path === '/api/energy/sources') return new Promise(() => {})
+      return Promise.resolve({ data: { items: [] } })
+    })
+    renderWithProviders(<MeterManager />)
+    const timeline = await screen.findByTestId('binding-timeline-binding-visible-id-only')
+    expect(timeline).toHaveTextContent('Loading source details… → Channel details unavailable')
+    expect(timeline).not.toHaveTextContent('private-source-id')
+    expect(timeline).not.toHaveTextContent('private-channel-id')
+  })
+
+  it('keeps meter row actions in the shared light, xs order', async () => {
+    const binding = { uuid: 'ordered-binding', source_uuid: 'source-1', source_channel_uuid: 'channel-1', started_at: '2024-01-15T00:00:00Z', ended_at: null }
+    mockGet.mockImplementation((path: string) => {
+      if (path === '/api/energy/meters') return Promise.resolve({ data: { items: [{ ...ACTIVE_METER, bindings: [binding] }], total: 1 } })
+      if (path === '/api/energy/sources') return Promise.resolve({ data: { items: [{ uuid: 'source-1', name: 'DSMR' }], total: 1 } })
+      if (path === '/api/energy/sources/{source_uuid}/channels') return Promise.resolve({ data: { items: [{ uuid: 'channel-1', label: 'Total import', unit: 'kWh' }], total: 1 } })
+      return Promise.resolve({ data: { items: [] } })
+    })
+    renderWithProviders(<MeterManager />)
+    const row = await screen.findByTestId(`meter-row-${ACTIVE_METER.id}`)
+    const buttons = Array.from(row.querySelectorAll('button'))
+    expect(buttons.map((button) => button.textContent)).toEqual(['Edit', 'Transfer source', 'Unbind', 'Close meter'])
+    expect(buttons).toHaveLength(4)
   })
 
   it('renders "Declare New Meter" button', async () => {

frontend/src/energy/MeterManager.tsx

@@ -167,6 +167,34 @@ function recoveryTargetFor(meter: MeterResponse, meters: MeterResponse[]): Meter
   return target
 }
 
+function BindingTimeline({ binding, sources }: {
+  binding: NonNullable<MeterResponse['bindings']>[number]
+  sources: ReturnType<typeof useSources>
+}) {
+  const source = sources.data?.items.find((item) => item.uuid === binding.source_uuid)
+  const channels = useSourceChannels(source?.uuid ?? null)
+  const channel = channels.data?.items.find((item) => item.uuid === binding.source_channel_uuid)
+  let endpoint = 'Source details unavailable'
+  if (sources.isLoading) endpoint = 'Loading source details…'
+  else if (!sources.isError && source) endpoint = source.name
+  else if (!sources.isError) endpoint = 'Source unavailable'
+
+  let channelName = 'Channel details unavailable'
+  if (source && channels.isLoading) channelName = 'Loading channel details…'
+  else if (source && !channels.isError && channel) channelName = channel.label
+  else if (source && !channels.isError) channelName = 'Channel unavailable'
+
+  return (
+    <Stack gap={0} mb="xs" data-testid={`binding-timeline-${binding.uuid}`}>
+      <Text size="xs">{endpoint} → {channelName}</Text>
+      <Text size="xs" c="dimmed">
+        [{formatLocalDateTime(binding.started_at)}, {binding.ended_at ? formatLocalDateTime(binding.ended_at) : 'open-ended'})
+        {' '}({binding.ended_at ? 'closed' : 'active'})
+      </Text>
+    </Stack>
+  )
+}
+
 // ---------------------------------------------------------------------------
 // Declare meter form (modal)
 // ---------------------------------------------------------------------------
@@ -515,11 +543,12 @@ function EditMeterForm({ meter, onClose, onSaved }: EditMeterFormProps) {
 
 interface MeterTableProps {
   meters: MeterResponse[]
+  sources: ReturnType<typeof useSources>
   onEdit: (meter: MeterResponse) => void
   onClose: (meter: MeterResponse) => void
 }
 
-function MeterTable({ meters, onEdit, onClose }: MeterTableProps) {
+function MeterTable({ meters, sources, onEdit, onClose }: MeterTableProps) {
   if (meters.length === 0) {
     return (
       <Text c="dimmed" ta="center" size="sm" data-testid="meters-empty">
@@ -585,30 +614,24 @@ function MeterTable({ meters, onEdit, onClose }: MeterTableProps) {
                 </Table.Td>
                 <Table.Td>
                   {meter.bindings?.length ? meter.bindings.map((binding) => (
-                    <Stack key={binding.uuid} gap={0} mb="xs" data-testid={`binding-timeline-${binding.uuid}`}>
+                    <BindingTimeline key={binding.uuid} binding={binding} sources={sources} />
-                      <Text size="xs">{binding.source_uuid} → {binding.source_channel_uuid}</Text>
-                      <Text size="xs" c="dimmed">
-                        [{formatLocalDateTime(binding.started_at)}, {binding.ended_at ? formatLocalDateTime(binding.ended_at) : 'open-ended'})
-                        {' '}({binding.ended_at ? 'closed' : 'active'})
-                      </Text>
-                    </Stack>
                   )) : <Text size="xs" c="dimmed">Unbound</Text>}
                 </Table.Td>
                 <Table.Td>
                   <Group justify="flex-end" gap="xs">
-                    {meter.bindings?.filter((binding) => binding.ended_at === null).map((binding) => (
-                      <BindingActions key={binding.uuid} meter={meter} binding={binding} meters={meters} />
-                    ))}
-                    {isActive && !meter.bindings?.some((binding) => binding.ended_at === null) && <DirectBindButton meter={meter} meters={meters} />}
-                    {isActive && <Button size="xs" color="red" variant="light" onClick={() => onClose(meter)}>Close meter</Button>}
                     <Button
                       size="xs"
-                      variant="outline"
+                      variant="light"
                       onClick={() => onEdit(meter)}
                       data-testid={`meter-edit-${meter.id}`}
                     >
                       Edit
                     </Button>
+                    {meter.bindings?.filter((binding) => binding.ended_at === null).map((binding) => (
+                      <BindingActions key={binding.uuid} meter={meter} binding={binding} meters={meters} />
+                    ))}
+                    {isActive && !meter.bindings?.some((binding) => binding.ended_at === null) && <DirectBindButton meter={meter} meters={meters} />}
+                    {isActive && <Button size="xs" color="red" variant="light" onClick={() => onClose(meter)}>Close meter</Button>}
                   </Group>
                 </Table.Td>
               </Table.Tr>
@@ -622,7 +645,7 @@ function MeterTable({ meters, onEdit, onClose }: MeterTableProps) {
 
 function DirectBindButton({ meter, meters }: { meter: MeterResponse; meters: MeterResponse[] }) {
   const [opened, setOpened] = useState(false)
-  return <>{<Button size="xs" variant="subtle" onClick={() => setOpened(true)}>Bind source</Button>}{opened && <DirectBindModal meter={meter} meters={meters} onClose={() => setOpened(false)} />}</>
+  return <>{<Button size="xs" variant="light" onClick={() => setOpened(true)}>Bind source</Button>}{opened && <DirectBindModal meter={meter} meters={meters} onClose={() => setOpened(false)} />}</>
 }
 
 function DirectBindModal({ meter, meters, onClose }: { meter: MeterResponse; meters: MeterResponse[]; onClose: () => void }) {
@@ -676,8 +699,8 @@ function BindingActions({ meter, binding, meters }: { meter: MeterResponse; bind
   const recoverySourceIsClosable = meter.ended_at === null ||
     parseBackendTimestamp(binding.started_at).getTime() < parseBackendTimestamp(meter.ended_at).getTime()
   return <>
-    <Button size="xs" variant="subtle" onClick={() => setUnbindOpened(true)}>Unbind</Button>
+    {meter.ended_at === null ? <Button size="xs" variant="light" onClick={() => setTransferOpened(true)}>Transfer source</Button> : recoveryTarget && recoverySourceIsClosable && <Button size="xs" variant="light" onClick={() => setTransferOpened(true)}>Recover binding</Button>}
-    {meter.ended_at === null ? <Button size="xs" variant="subtle" onClick={() => setTransferOpened(true)}>Transfer source</Button> : recoveryTarget && recoverySourceIsClosable && <Button size="xs" variant="light" onClick={() => setTransferOpened(true)}>Recover binding</Button>}
+    <Button size="xs" variant="light" onClick={() => setUnbindOpened(true)}>Unbind</Button>
     {meter.ended_at !== null && recoveryTarget && !recoverySourceIsClosable && <Text size="xs" c="red">Cannot recover: the source binding starts at or after this Meter ended.</Text>}
     {unbindOpened && <UnbindModal meter={meter} binding={binding} onClose={() => setUnbindOpened(false)} />}
     {transferOpened && <TransferModal target={recoveryTarget ?? meter} sourceBinding={binding} meters={meters} recovery={!!recoveryTarget} onClose={() => setTransferOpened(false)} />}
@@ -793,6 +816,7 @@ function CloseMeterModal({ meter, onClose }: { meter: MeterResponse; onClose: ()
 
 export function MeterManager() {
   const metersQuery = useMeters()
+  const sources = useSources()
 
   const [showDeclareForm, setShowDeclareForm] = useState(false)
   const [editMeter, setEditMeter] = useState<MeterResponse | null>(null)
@@ -845,7 +869,7 @@ export function MeterManager() {
         </Notification>
       )}
 
-      <MeterTable meters={meters} onEdit={(m) => setEditMeter(m)} onClose={(m) => setCloseMeter(m)} />
+      <MeterTable meters={meters} sources={sources} onEdit={(m) => setEditMeter(m)} onClose={(m) => setCloseMeter(m)} />
 
       {/* Declare new meter */}
       {showDeclareForm && (

frontend/src/energy/TibberPrices.test.tsx

@@ -245,7 +245,7 @@ describe('TibberPrices', () => {
     expect(screen.getByTestId('tariff-sell-dal')).toHaveTextContent('0.0900')
   })
 
-  it('keeps thermal prices scoped and renders the complete D11 Decimal snapshot with units', async () => {
+  it('keeps thermal prices scoped and renders the complete D11 Decimal snapshot as a table', async () => {
     const user = userEvent.setup()
     const thermal = {
       kind: 'district_heating', currency: 'EUR', points: [], tariff: null,
@@ -273,15 +273,19 @@ describe('TibberPrices', () => {
     await waitFor(() => expect(screen.getByTestId('thermal-price-snapshot')).toBeInTheDocument())
 
     const snapshot = screen.getByTestId('thermal-price-snapshot')
+    const table = screen.getByTestId('thermal-price-table')
     expect(snapshot).toHaveTextContent('Version 42')
     expect(snapshot).toHaveTextContent('effective 2026-01-01T00:00:00Z to 2026-12-31T00:00:00Z')
     expect(snapshot).toHaveTextContent('not a 15-minute market spot price')
-    expect(snapshot).toHaveTextContent('20.123456789123456789 EUR/GJ')
+    expect(screen.getAllByRole('columnheader').map((header) => header.textContent)).toEqual([
-    expect(snapshot).toHaveTextContent('8.200000000000000001 EUR/m³')
+      'Category', 'Charge', 'Rate', 'Unit',
-    expect(snapshot).toHaveTextContent('1.234567890123456789 EUR/m³')
+    ])
-    expect(snapshot).toHaveTextContent('0.456789012345678901 EUR/m³')
+    expect(table.querySelectorAll('tbody tr')).toHaveLength(9)
+    expect(screen.getByTestId('thermal-price-row-variable-heating')).toHaveTextContent('VariableHeating20.123456789123456789EUR/GJ')
+    expect(screen.getByTestId('thermal-price-row-variable-hot_water_heating')).toHaveTextContent('Hot Water Heating8.200000000000000001EUR/m³')
+    expect(screen.getByTestId('thermal-price-row-standing-heating_network')).toHaveTextContent('StandingHeating Network100.000000000000000001EUR/year')
     for (const value of Object.values(thermal.values.standing)) {
-      expect(snapshot).toHaveTextContent(`${value} EUR/year`)
+      expect(table).toHaveTextContent(value)
     }
     expect(mockGet).toHaveBeenCalledWith('/api/energy/prices', expect.objectContaining({
       params: { query: expect.objectContaining({ scope: 'thermal' }) },
@@ -292,6 +296,19 @@ describe('TibberPrices', () => {
     expect(screen.queryByTestId('thermal-price-snapshot')).not.toBeInTheDocument()
   })
 
+  it('keeps unknown thermal snapshot fields with safe human-readable labels', async () => {
+    const user = userEvent.setup()
+    mockGet.mockImplementation((_path: string, options?: { params?: { query?: { scope?: string } } }) => Promise.resolve({
+      data: options?.params?.query?.scope === 'thermal'
+        ? { kind: 'district_heating', currency: 'EUR', values: { future_fee: { experimental_charge: '1.000000000000000001' } } }
+        : { kind: 'manual', currency: 'EUR', points: [], tariff: { buy_dal: 0.1, buy_normal: 0.2, sell_dal: 0.03, sell_normal: 0.04 } },
+    }))
+    renderWithProviders(<TibberPrices />)
+    await user.click(await screen.findByText('Thermal'))
+    const row = await screen.findByTestId('thermal-price-row-future_fee-experimental_charge')
+    expect(row).toHaveTextContent('Future FeeExperimental Charge1.000000000000000001EUR')
+  })
+
   it('marks the currently active price slot with a dot and a caption', async () => {
     installChartSize()
 

frontend/src/energy/TibberPrices.tsx

@@ -23,6 +23,7 @@ import {
   Group,
   Paper,
   SegmentedControl,
+  ScrollArea,
 } from '@mantine/core'
 import {
   LineChart,
@@ -60,6 +61,19 @@ function thermalUnit(section: string, key: string, currency: string): string {
   return currency
 }
 
+function humanizeThermalField(value: string): string {
+  return value
+    .replace(/_/g, ' ')
+    .replace(/\b\w/g, (letter) => letter.toUpperCase())
+}
+
+function thermalSections(values: Record<string, Record<string, string>>): string[] {
+  const preferred = ['variable', 'standing']
+  return [...preferred.filter((section) => section in values), ...Object.keys(values)
+    .filter((section) => !preferred.includes(section))
+    .sort()]
+}
+
 // ---------------------------------------------------------------------------
 // Time range helpers
 // ---------------------------------------------------------------------------
@@ -399,13 +413,28 @@ export function TibberPrices() {
             <Text fw={500}>Thermal contract snapshot</Text>
             <Text size="sm">Version {data.contract_version_id ?? '—'} · effective {data.effective_from ?? '—'} to {data.effective_to ?? 'open'}</Text>
             <Text size="sm" c="dimmed">This is a contract snapshot, not a 15-minute market spot price.</Text>
-            {Object.entries(data.values).map(([section, values]) => (
+            <ScrollArea type="auto">
-              <Text size="sm" key={section} data-testid={`thermal-price-section-${section}`}>
+              <Table withTableBorder withColumnBorders data-testid="thermal-price-table">
-                {section}: {Object.entries(values).map(([key, value]) =>
+                <Table.Thead>
-                  `${key} ${value} ${thermalUnit(section, key, currency)}`,
+                  <Table.Tr>
-                ).join(', ')}
+                    <Table.Th>Category</Table.Th>
-              </Text>
+                    <Table.Th>Charge</Table.Th>
-            ))}
+                    <Table.Th>Rate</Table.Th>
+                    <Table.Th>Unit</Table.Th>
+                  </Table.Tr>
+                </Table.Thead>
+                <Table.Tbody>
+                  {thermalSections(data.values!).flatMap((section) => Object.entries(data.values![section]).map(([key, rate]) => (
+                    <Table.Tr key={`${section}-${key}`} data-testid={`thermal-price-row-${section}-${key}`}>
+                      <Table.Td>{humanizeThermalField(section)}</Table.Td>
+                      <Table.Td>{humanizeThermalField(key)}</Table.Td>
+                      <Table.Td>{rate}</Table.Td>
+                      <Table.Td>{thermalUnit(section, key, currency)}</Table.Td>
+                    </Table.Tr>
+                  )))}
+                </Table.Tbody>
+              </Table>
+            </ScrollArea>
           </Stack>
         </Paper>
       )}

tests/test_deployment.py

@@ -72,6 +72,21 @@ def test_compose_uses_migration_job_before_app() -> None:
     assert dev["services"]["app"]["build"] == "."
 
 
+def test_compose_defaults_business_timezone_and_dev_inherits_it() -> None:
+    """Both production services receive an overridable Amsterdam timezone.
+
+    Compose merges service ``environment`` mappings, and the dev override does
+    not replace either mapping, so the base default applies to base+dev too.
+    """
+    base = _read_yaml("docker-compose.yml")
+    dev = _read_yaml("docker-compose.dev.yml")
+    default_tz = "${TZ:-Europe/Amsterdam}"
+
+    for service_name in ("migration", "app"):
+        assert base["services"][service_name]["environment"]["TZ"] == default_tz
+        assert "TZ" not in dev["services"].get(service_name, {}).get("environment", {})
+
+
 def test_compose_keeps_app_non_root_and_maps_minimal_warmtelink_serial_access() -> None:
     """Base Compose maps the configured device with only pyserial's required access.
 

tests/test_dsmr_source_migration.py

@@ -12,6 +12,8 @@ from alembic import command
 from alembic.config import Config
 from sqlalchemy import create_engine, event, inspect, text
 
+from app.integrations.meter_sources import sanitize_source_config, validate_source_config
+
 
 def _config(database_url: str) -> Config:
     config = Config("alembic_app.ini")
@@ -108,7 +110,7 @@ def test_populated_revision_14_adopts_dsmr_history_at_revision_16(tmp_path: Path
                     {"key": "DSMR_INGEST_ENABLED", "value": "true", "at": start},
                     {"key": "DSMR_MQTT_TOPIC", "value": "historic/dsmr", "at": start},
                     {"key": "DSMR_TARIFF_TOPIC", "value": "historic/tariff", "at": start},
-                    {"key": "DSMR_SAMPLE_INTERVAL_S", "value": "15", "at": start},
+                    {"key": "DSMR_SAMPLE_INTERVAL_S", "value": "0", "at": start},
                     {"key": "MQTT_BROKER_HOST", "value": "mqtt.example.invalid", "at": start},
                     {"key": "MQTT_BROKER_PORT", "value": "1884", "at": start},
                     {"key": "MQTT_USERNAME", "value": "historic-user", "at": start},
@@ -159,11 +161,14 @@ def test_populated_revision_14_adopts_dsmr_history_at_revision_16(tmp_path: Path
                 text("SELECT id, enabled, config FROM meter_source WHERE kind = 'dsmr_mqtt'")
             ).one()
             assert source.enabled == 1
-            assert json.loads(source.config) == {
+            source_config = json.loads(source.config)
+            assert source_config == {
                 "broker_host": "mqtt.example.invalid", "broker_port": 1884,
                 "username": "historic-user", "password": "historic-password", "tls_enabled": True,
-                "topic": "historic/dsmr", "tariff_topic": "historic/tariff", "sample_interval_s": 15,
+                "topic": "historic/dsmr", "tariff_topic": "historic/tariff", "sample_interval_s": 0,
             }
+            assert validate_source_config("dsmr_mqtt", source_config) == source_config
+            assert sanitize_source_config("dsmr_mqtt", source_config)["sample_interval_s"] == 0
             assert connection.execute(text("SELECT value FROM app_config WHERE key = 'DSMR_MQTT_TOPIC'")).scalar_one() == "historic/dsmr"
             assert dict(connection.execute(text("SELECT key, value FROM app_config")).all()) == config_before
             assert connection.execute(text("SELECT group_concat(telegram_id) FROM dsmr_reading")).scalar_one() == "77,78,77"

tests/test_meter_cost_api.py

@@ -5,6 +5,7 @@ from __future__ import annotations
 from datetime import UTC, datetime, timedelta
 from decimal import Decimal
 from unittest.mock import patch
+from zoneinfo import ZoneInfo
 
 import pytest
 from fastapi.testclient import TestClient
@@ -139,7 +140,9 @@ def test_meter_cost_summary_empty_and_recompute_csrf_window_validation(meter_cos
     ).status_code == 422
 
 
-def test_meter_cost_summary_returns_five_fixed_components_and_totals(meter_cost_client) -> None:
+def test_meter_cost_summary_returns_five_fixed_components_and_totals(
+    meter_cost_client, monkeypatch: pytest.MonkeyPatch
+) -> None:
     client, engine = meter_cost_client
     now = datetime.now(UTC)
     values = {
@@ -166,8 +169,10 @@ def test_meter_cost_summary_returns_five_fixed_components_and_totals(meter_cost_
         db.add_all((heating, water))
         db.commit()
     _login(client)
-    with patch("app.api.routes.api.meter_costs.local_now", return_value=datetime(2026, 6, 25, 2, tzinfo=UTC)):
+    monkeypatch.setattr("app.services.timezone.local_tz", lambda: ZoneInfo("Europe/Amsterdam"))
-        response = client.get("/api/energy/meter-costs/summary?scope=thermal&start=2026-06-23T00:00:00Z&end=2026-06-24T00:00:00Z")
+    response = client.get(
+        "/api/energy/meter-costs/summary?scope=thermal&start=2026-06-23T00:00:00Z&end=2026-06-24T00:00:00Z"
+    )
     assert response.status_code == 200
     body = response.json()
     assert body["heating"] == "1.000000000" and body["hot_water_heating"] == "0.8"

tests/test_meter_source_services.py

@@ -68,6 +68,32 @@ def test_secret_sanitize_and_mask_merge_keep_old_value():
     assert merged["topic"] == "new/topic"
 
 
+def test_dsmr_zero_interval_validates_sanitizes_and_merges_unchanged():
+    config = validate_source_config("dsmr_mqtt", {"sample_interval_s": 0})
+
+    assert config["sample_interval_s"] == 0
+    assert sanitize_source_config("dsmr_mqtt", config)["sample_interval_s"] == 0
+    assert merge_source_config("dsmr_mqtt", config, {"topic": "new/topic"})["sample_interval_s"] == 0
+
+
+@pytest.mark.parametrize(
+    ("kind", "config"),
+    [
+        ("dsmr_mqtt", {"sample_interval_s": -1}),
+        ("dsmr_mqtt", {"sample_interval_s": False}),
+        ("dsmr_mqtt", {"broker_port": 0}),
+        ("dsmr_mqtt", {"broker_port": -1}),
+        ("dsmr_mqtt", {"broker_port": False}),
+        ("warmtelink_serial", {"path": "/dev/warmtelink", "baudrate": 0}),
+        ("warmtelink_serial", {"path": "/dev/warmtelink", "baudrate": -1}),
+        ("warmtelink_serial", {"path": "/dev/warmtelink", "baudrate": False}),
+    ],
+)
+def test_numeric_source_profile_constraints_still_reject_invalid_values(kind, config):
+    with pytest.raises(SourceProfileError):
+        validate_source_config(kind, config)
+
+
 @pytest.fixture()
 def session(tmp_path):
     engine = create_engine(f"sqlite:///{tmp_path / 'source_services.db'}")

tests/test_timezone.py

@@ -7,7 +7,7 @@ on any CI host timezone.
 from __future__ import annotations
 
 from datetime import UTC, date, datetime
-from zoneinfo import ZoneInfo
+from zoneinfo import ZoneInfo, ZoneInfoNotFoundError
 
 import pytest
 
@@ -56,6 +56,38 @@ def test_local_tz_env_var_overrides(monkeypatch):
     monkeypatch.delenv("TZ")
 
 
+@pytest.mark.parametrize("value", [None, "", "   "])
+def test_local_tz_defaults_to_dst_aware_amsterdam(monkeypatch, value: str | None):
+    """Unset or blank TZ must use the deterministic Amsterdam business zone."""
+    if value is None:
+        monkeypatch.delenv("TZ", raising=False)
+    else:
+        monkeypatch.setenv("TZ", value)
+
+    tz = tz_mod.local_tz()
+    assert isinstance(tz, ZoneInfo)
+    assert tz.key == "Europe/Amsterdam"
+    winter = datetime(2026, 1, 15, 12, tzinfo=tz)
+    summer = datetime(2026, 7, 15, 12, tzinfo=tz)
+    assert winter.utcoffset().total_seconds() == 3600
+    assert summer.utcoffset().total_seconds() == 7200
+
+
+def test_local_tz_explicit_utc_override(monkeypatch):
+    """A non-empty TZ remains an operator-controlled override."""
+    monkeypatch.setenv("TZ", "UTC")
+    tz = tz_mod.local_tz()
+    assert isinstance(tz, ZoneInfo)
+    assert tz.key == "UTC"
+
+
+def test_local_tz_invalid_explicit_override_fails_loudly(monkeypatch):
+    """A non-empty invalid override must not silently become Amsterdam."""
+    monkeypatch.setenv("TZ", "Invalid/Timezone")
+    with pytest.raises(ZoneInfoNotFoundError):
+        tz_mod.local_tz()
+
+
 # ---------------------------------------------------------------------------
 # to_local() — conversion correctness
 # ---------------------------------------------------------------------------