diff --git a/DECISIONS.md b/DECISIONS.md
index 2e5121b6..81861706 100644
--- a/DECISIONS.md
+++ b/DECISIONS.md
@@ -1337,3 +1337,4 @@ One line per decision: `[YYYY-MM-DD] <decision>: <why>`. Appended by agents and
 [2026-08-28] /migrate SIE guard skips company-info-only runs (all entity flags false) and the wizard derives "SIE already imported" from the preview OR this session's successful /import-sie results: company info writes no accounts, balances or subledger rows, so the BFL rationale does not apply; and the one-shot preview went stale after phase 1 succeeded and phase 2 failed, falsely blocking an entities-only retry (#2000 review).
 [2026-08-28] get_vat_ruta_source_lines (the VAT ruta drill-down) now applies the same four exclusions as get_vat_declaration_totals (the filed figure): posted closing entries, source_type 'vat_settlement', the two kontantmetod year-end reversals, and settlement-SHAPED entries (a line on a ruta account plus a line on 2650/1650). It previously filtered on company, status and date only, so expanding a ruta listed verifikat that are not in the number it claims to explain, with no total on the panel to reveal the mismatch. Measured on prod 2026-08-28: 322 posted/reversed entries carrying 26xx lines across 214 companies sit in those excluded classes. A momsdeklaration is räkenskapsinformation (BFL 5 kap.) and this drill-down is what substantiates a filed figure, so the two must agree exactly. The exclusion CTEs are lifted VERBATIM from the figure rather than re-derived: any divergence reintroduces exactly this bug, and an identical copy is easy to diff when the figure changes. Settlement-shape is detected against journal_entry_lines directly instead of through the figure's vat_lines CTE, which is EQUIVALENT not a shortcut (p_ruta_accounts = VAT_ACCOUNTS and p_net_accounts = ['2650','1650'] are both strict subsets of the figure's p_accounts, so restricting to vat_lines first cannot change which entries match); that keeps p_accounts meaning "the accounts of the ruta being expanded" without a fourth account parameter. opening_balance entries are deliberately NOT excluded: the figure exempts them from `shaped`, which keeps their lines IN the totals, so dropping them here would break the equality in the other direction (pinned by its own test). VAT_ACCOUNTS is now exported from lib/reports/vat-declaration.ts so the route detects shape from the same list the figure uses; a second copy is what let the two disagree. DROP + CREATE OR REPLACE, not CREATE OR REPLACE alone: the signature gains p_ruta_accounts/p_net_accounts and adding parameters registers a second overload PostgREST cannot choose between (trap documented in 20260421140000); OR REPLACE on the new arity keeps the file re-runnable. Verified the new pg test actually catches the bug by reinstalling the old body and watching 3 of 4 tests fail with the real misreporting (2611: drill-down 250/240 vs figure 0/200), then restoring.
 [2026-08-28] Bankavstamning NULL-link fix scoped to transfer legs with contradicting sign (20260828220000): the naive rule (NULL counts only for the primary account) and the formula-only variant (drop far-leg-settled vouchers from unexplained) were both simulated against prod and rejected; the naive rule worsened 4 of 11 affected cards (worst -37 000 kr false alarm on single-leg vouchers with no user action available), the formula variant blew up healthy cards by up to 474 550 kr. The shipped three-condition rule changes 24 vouchers on 7 cards in 6 companies, all verified per-card.
+[2026-08-29] Database errors now keep their SQLSTATE: new lib/errors/db-error.ts (dbError/errorCauseTag), applied at the 54 `throw new Error(\`Database error: ${err.message}\`)` sites in the MCP server AND, far more importantly, at lib/supabase/fetch-all.ts:74 where `throw new Error(error.message)` was the single highest-traffic strip point in the codebase (31 callers; every paginated read). isTransientFailure() checks the driver code FIRST and 57014 (statement timeout) is already in TRANSIENT_SQLSTATES, so discarding it turned a retryable timeout into UNKNOWN_ERROR ("Något gick fel. Försök igen."), which an agent cannot dispatch on. Traced end to end: gnubok_query_journal -> fetchEntryLines -> fetchAllRows (code stripped here) -> the tool's own sanitizeDbError, which ALREADY had a correct TRANSIENT_ERROR branch with a "retry or narrow with date_from/date_to" hint that could never fire because getStructuredError saw an anonymous Error. Measured on prod over 60 days with bot actors excluded: 1 024 real-agent failures, 645 UNKNOWN_ERROR across 60 actors and 57 companies; query_journal failed 164 times at p50 8 110 ms while every other failing tool sat at 1-315 ms; 82 retry streaks, 462 wasted repeat calls, 53.1% of error calls inside a streak. fetch-all passes context=null so the driver message stays VERBATIM (sanitizeDbError and other callers match on the existing text; this change adds the code, it does not reword). Attaching `code` is safe because extractCode() only accepts /^[A-Z_]+$/ and every SQLSTATE/PostgREST code contains digits, so it cannot hijack the application error registry (pinned by a test). dbError also never renders the literal "undefined": a driver-level failure with no message produced "Database error: undefined", the string that made these unsearchable. errorCauseTag() returns a PII-safe SQLSTATE for telemetry; the raw driver message can quote row values in a constraint violation and belongs in the server log, never in event_log. NOT ratcheted: check:types reports 538 vs baseline 539 because main fixed an unrelated error in own-account-detector.test.ts after the baseline was set; the gate only fails on an INCREASE, so the baseline is left alone rather than adding unrelated churn to this diff.
diff --git a/extensions/general/mcp-server/server.ts b/extensions/general/mcp-server/server.ts
index 2903bc1b..6068006b 100644
--- a/extensions/general/mcp-server/server.ts
+++ b/extensions/general/mcp-server/server.ts
@@ -47,6 +47,7 @@ import { applyAccountOverride } from '@/lib/bookkeeping/account-override'
 import { ACCOUNT_NUMBER_RE } from '@/lib/invariants/account-number'
 import { isSlpPensionAccount } from '@/lib/bookkeeping/slp-lines'
 import { getErrorEntry } from '@/lib/errors/structured-errors'
+import { dbError } from '@/lib/errors/db-error'
 import { getStructuredError } from '@/lib/errors/get-structured-error'
 import { applySettlementAccount } from '@/lib/bookkeeping/mapping-engine'
 import { resolveSettlementAccount } from '@/lib/bookkeeping/settlement-account'
@@ -1055,7 +1056,7 @@ async function resolveJournalEntryRef(
     .order('entry_date', { ascending: false })
 
   if (error) {
-    throw new Error(`Database error resolving voucher "${series}-${number}": ${error.message}`)
+    throw dbError(error, `Database error resolving voucher "${series}-${number}"`)
   }
 
   const matches = (data ?? []) as Array<{ id: string; entry_date: string; description: string }>
@@ -3799,7 +3800,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!data) throw new Error('Company settings not found.')
 
       return {
@@ -3916,7 +3917,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!current) throw new Error('Company settings not found.')
 
       const currentPreview = {
@@ -5041,7 +5042,7 @@ export const tools: McpTool[] = [
       if (cashAccountId) countQuery = countQuery.eq('cash_account_id', cashAccountId)
       const { count: totalCount, error: countError } = await countQuery
 
-      if (countError) throw new Error(`Database error: ${countError.message}`)
+      if (countError) throw dbError(countError)
 
       let listQuery = supabase
         .from('transactions')
@@ -5055,7 +5056,7 @@ export const tools: McpTool[] = [
         .order('date', { ascending: false })
         .range(offset, offset + limit - 1)
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       // Resolve the bank account's BAS ledger for the rows on this page so a
       // per-account reconciliation can be driven from outside (customer
@@ -5070,7 +5071,7 @@ export const tools: McpTool[] = [
           .select('id, ledger_account')
           .eq('company_id', companyId)
           .in('id', cashAccountIds)
-        if (cashError) throw new Error(`Database error: ${cashError.message}`)
+        if (cashError) throw dbError(cashError)
         for (const c of (cashRows ?? []) as Array<{ id: string; ledger_account: string }>) {
           ledgerByCashAccount.set(c.id, c.ledger_account)
         }
@@ -5150,7 +5151,7 @@ export const tools: McpTool[] = [
         p_limit: limit,
         p_offset: offset,
       })
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       const result = data as {
         ok: boolean
@@ -5228,7 +5229,7 @@ export const tools: McpTool[] = [
         p_limit: limit,
         p_offset: offset,
       })
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       const result = data as {
         ok: boolean
@@ -5490,7 +5491,7 @@ export const tools: McpTool[] = [
         .order('date', { ascending: false })
         .limit(limit)
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       return {
         transactions: data ?? [],
@@ -5551,7 +5552,7 @@ export const tools: McpTool[] = [
             .range(from, to)
         })
       } catch (error) {
-        throw new Error(`Database error: ${error instanceof Error ? error.message : 'unknown error'}`)
+        throw dbError(error)
       }
       rows.sort((a, b) => a.name.localeCompare(b.name, 'sv') || a.id.localeCompare(b.id))
 
@@ -5843,7 +5844,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!current) throw new Error('Customer not found.')
 
       // Same guard as gnubok_create_customer and the REST PATCH route: only
@@ -5971,7 +5972,7 @@ export const tools: McpTool[] = [
           return q.order('id', { ascending: true }).range(from, to)
         })
       } catch (error) {
-        throw new Error(`Database error: ${error instanceof Error ? error.message : 'unknown error'}`)
+        throw dbError(error)
       }
       articles.sort((a, b) => a.name.localeCompare(b.name, 'sv') || a.id.localeCompare(b.id))
 
@@ -6157,7 +6158,7 @@ export const tools: McpTool[] = [
         .order('id', { ascending: false })
         .range(offset, offset + limit)
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       const rows = data ?? []
       const invoices = rows.slice(0, limit).map((inv: Record<string, unknown>) => ({
@@ -6285,7 +6286,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!invoice) throw new Error('Invoice not found. Use gnubok_list_invoices to find valid IDs.')
 
       type InvoiceLineRow = {
@@ -7258,7 +7259,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (invoiceError) throw new Error(`Database error: ${invoiceError.message}`)
+      if (invoiceError) throw dbError(invoiceError)
       if (!invoice) throw new Error('Invoice not found')
 
       // Never read invoice_deliveries directly: the row carries the exact
@@ -7270,7 +7271,7 @@ export const tools: McpTool[] = [
         'list_invoice_delivery_summaries_for_service',
         { p_company_id: companyId, p_user_id: userId, p_invoice_id: invoiceId },
       )
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       // Mirrors the RETURNS TABLE of the RPC. body_html, body_text and
       // bcc_addresses are absent by construction, not filtered here.
@@ -7411,7 +7412,7 @@ export const tools: McpTool[] = [
             .range(from, to)
         })
       } catch (error) {
-        throw new Error(`Database error: ${error instanceof Error ? error.message : 'unknown error'}`)
+        throw dbError(error)
       }
       suppliers.sort((a, b) => a.name.localeCompare(b.name, 'sv') || a.id.localeCompare(b.id))
 
@@ -7605,7 +7606,7 @@ export const tools: McpTool[] = [
 
       const { data, error } = await query.order('due_date', { ascending: true }).limit(limit)
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       return { invoices: data ?? [], count: data?.length ?? 0 }
     },
@@ -7650,7 +7651,7 @@ export const tools: McpTool[] = [
         .order('occurrence_count', { ascending: false })
         .limit(limit)
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       return {
         templates: (data ?? []).map((t) => ({
@@ -7710,7 +7711,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .in('id', limitedIds)
 
-      if (txError) throw new Error(`Database error: ${txError.message}`)
+      if (txError) throw dbError(txError)
       if (!transactions || transactions.length === 0) throw new Error('No transactions found')
 
       // Fetch mapping rules
@@ -7846,7 +7847,7 @@ export const tools: McpTool[] = [
           return query.order('account_number', { ascending: true }).range(from, to)
         })
       } catch (error) {
-        throw new Error(`Database error: ${error instanceof Error ? error.message : 'unknown error'}`)
+        throw dbError(error)
       }
 
       // Postgres ordered by sort_order ascending with nulls last; keep that
@@ -7917,7 +7918,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .eq('account_number', accountNumber)
         .maybeSingle()
-      if (existingErr) throw new Error(`Database error: ${existingErr.message}`)
+      if (existingErr) throw dbError(existingErr)
       if (existing) {
         throw new Error(
           existing.is_active
@@ -8038,7 +8039,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .eq('account_number', accountNumber)
         .maybeSingle()
-      if (fetchErr) throw new Error(`Database error: ${fetchErr.message}`)
+      if (fetchErr) throw dbError(fetchErr)
       if (!current) {
         throw new Error(`Konto ${accountNumber} finns inte i kontoplanen. Skapa det med gnubok_create_account.`)
       }
@@ -8240,7 +8241,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .eq('sie_dim_no', sieDimNo)
         .maybeSingle()
-      if (dimError) throw new Error(`Database error: ${dimError.message}`)
+      if (dimError) throw dbError(dimError)
       if (!dimension) {
         throw new Error(
           `Dimension ${sieDimNo} finns inte i registret. Anropa gnubok_list_dimensions för att se registrerade dimensioner.`,
@@ -8256,7 +8257,7 @@ export const tools: McpTool[] = [
       if (!includeInactive) valuesQuery = valuesQuery.eq('is_active', true)
 
       const { data: rows, error: valuesError } = await valuesQuery
-      if (valuesError) throw new Error(`Database error: ${valuesError.message}`)
+      if (valuesError) throw dbError(valuesError)
       const all = (rows ?? []) as Array<{
         id: string
         code: string
@@ -8350,7 +8351,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .eq('sie_dim_no', params.sie_dim_no)
         .maybeSingle()
-      if (dimError) throw new Error(`Database error: ${dimError.message}`)
+      if (dimError) throw dbError(dimError)
       if (!dimension) {
         throw new Error(
           `Okänd dimension ${params.sie_dim_no}. Endast registrerade dimensioner kan få nya värden: ` +
@@ -8370,7 +8371,7 @@ export const tools: McpTool[] = [
         .eq('dimension_id', dimension.id)
         .eq('code', params.code)
         .maybeSingle()
-      if (existingError) throw new Error(`Database error: ${existingError.message}`)
+      if (existingError) throw dbError(existingError)
       if (existing?.is_active) {
         throw new Error(
           `Värdet "${params.code}" (${existing.name}) finns redan i ${dimension.name}: använd koden direkt i dimensions-baggen.`,
@@ -10925,7 +10926,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .order('period_start', { ascending: false })
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       const periods = (data ?? []).map((p) => ({
         id: p.id,
@@ -11719,7 +11720,7 @@ export const tools: McpTool[] = [
       }
 
       const { data, error } = await query
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       const mapped = (data || []).map((item) => {
         const extracted = item.extracted_data as Record<string, unknown> | null
@@ -11819,7 +11820,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .single()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!data) throw new Error('Inbox item not found')
 
       return data
@@ -12275,7 +12276,7 @@ export const tools: McpTool[] = [
       }
 
       const { data: inboxRows, error: inboxError } = await inboxQuery
-      if (inboxError) throw new Error(`Database error: ${inboxError.message}`)
+      if (inboxError) throw dbError(inboxError)
       if (!inboxRows || inboxRows.length === 0) {
         return { items: [], count: 0 }
       }
@@ -12287,7 +12288,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .in('document_id', docIds)
 
-      if (txError) throw new Error(`Database error: ${txError.message}`)
+      if (txError) throw dbError(txError)
       const matchedDocIds = new Set((txMatches || []).map((t) => t.document_id))
 
       const unmatched = inboxRows
@@ -12402,7 +12403,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (docError) throw new Error(`Database error: ${docError.message}`)
+      if (docError) throw dbError(docError)
       if (!doc) throw new Error('Document not found')
 
       const ttlSeconds = 300
@@ -12717,7 +12718,7 @@ export const tools: McpTool[] = [
         .from('fiscal_periods')
         .select('id, period_start, period_end')
         .eq('company_id', companyId)
-      if (periodsError) throw new Error(`Database error: ${periodsError.message}`)
+      if (periodsError) throw dbError(periodsError)
 
       const periodsByYear = new Map<number, Array<{ id: string; period_start: string; period_end: string }>>()
       for (const p of periods ?? []) {
@@ -12734,7 +12735,7 @@ export const tools: McpTool[] = [
         .select('id, file_name, mime_type, journal_entry_id')
         .in('id', documentIds)
         .eq('company_id', companyId)
-      if (docsError) throw new Error(`Database error: ${docsError.message}`)
+      if (docsError) throw dbError(docsError)
       const docsById = new Map((docs ?? []).map((d) => [d.id as string, d as {
         id: string; file_name: string; mime_type: string; journal_entry_id: string | null
       }]))
@@ -12820,7 +12821,7 @@ export const tools: McpTool[] = [
           .select('id, status')
           .eq('company_id', companyId)
           .in('id', existingJeIds)
-        if (existingErr) throw new Error(`Database error: ${existingErr.message}`)
+        if (existingErr) throw dbError(existingErr)
         for (const je of existingJes ?? []) {
           if ((je as { status: string }).status === 'posted') postedExistingJeIds.add(je.id as string)
         }
@@ -13185,7 +13186,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
       if (activeOnly) query = query.eq('is_active', true)
       const { data, error } = await query.order('last_name')
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       // Shared masking helper: strips personnummer (ciphertext) AND
       // personnummer_last4, exposing only personnummer_masked: same shape as
       // the app routes and the other MCP payroll tools.
@@ -13370,7 +13371,7 @@ export const tools: McpTool[] = [
         .eq('id', id)
         .eq('company_id', companyId)
         .maybeSingle()
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!run) throw new Error('Salary run not found')
       if (run.status === 'booked') throw new Error('Salary run is already booked')
       if (!['draft', 'review', 'approved', 'paid'].includes(run.status as string)) {
@@ -13383,7 +13384,7 @@ export const tools: McpTool[] = [
         .from('salary_run_employees')
         .select('id, calculation_breakdown')
         .eq('salary_run_id', id)
-      if (rosterError) throw new Error(`Database error: ${rosterError.message}`)
+      if (rosterError) throw dbError(rosterError)
       const rosterRows = roster ?? []
       const uncalculated = rosterRows.filter((r) => !r.calculation_breakdown).length
       if (uncalculated > 0) {
@@ -13880,7 +13881,7 @@ export const tools: McpTool[] = [
         .eq('id', employeeId)
         .eq('company_id', companyId)
         .maybeSingle()
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!e) throw new Error('Employee not found')
       // LLM context is a leak surface: personnummer is ALWAYS masked on MCP,
       // there is no full-value drill-in on this surface.
@@ -13977,7 +13978,7 @@ export const tools: McpTool[] = [
         .eq('employee_id', employeeId)
         .eq('company_id', companyId)
         .maybeSingle()
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!sre) throw new Error('Employee not found in this salary run')
       const emp = sre.employee as { first_name: string; last_name: string; personnummer: string } | null
       const lineItems = ((sre.line_items ?? []) as Array<Record<string, unknown>>)
@@ -14593,7 +14594,7 @@ export const tools: McpTool[] = [
         .eq('id', employee_id)
         .eq('company_id', companyId)
         .maybeSingle()
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!existing) throw new Error('Employee not found')
 
       const changes = Object.entries(patch).map(([field, to]) => ({
@@ -14714,7 +14715,7 @@ export const tools: McpTool[] = [
         .select(`employee_id, ${MERGEABLE_FIELDS.join(', ')}`)
         .eq('company_id', companyId)
         .in('employee_id', employeeIds)
-      if (storedErr) throw new Error(`Database error: ${storedErr.message}`)
+      if (storedErr) throw dbError(storedErr)
       const storedByEmployee = new Map(
         ((storedRows ?? []) as unknown as Array<Record<string, unknown>>).map((r) => [
           r.employee_id as string,
@@ -14837,7 +14838,7 @@ export const tools: McpTool[] = [
         .order('vacation_year_start', { ascending: false })
         .limit(1)
         .maybeSingle()
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!balance) throw new Error('No vacation balance exists for the employee yet (the ledger seeds on first booking)')
       const { id, ...rest } = balance as { id: string } & Record<string, unknown>
       const entitled = (rest.entitled_days as number) ?? 0
@@ -14855,7 +14856,7 @@ export const tools: McpTool[] = [
         .eq('id', employeeId)
         .eq('company_id', companyId)
         .maybeSingle()
-      if (empErr) throw new Error(`Database error: ${empErr.message}`)
+      if (empErr) throw dbError(empErr)
       if (!employee) throw new Error(`Employee ${employeeId} not found for this company`)
       const savedTotal = Object.values((rest.saved_days as Record<string, number> | null) ?? {})
         .reduce((s, d) => s + (Number(d) || 0), 0)
@@ -16121,7 +16122,7 @@ export const tools: McpTool[] = [
         .eq('id', journalEntryId)
         .eq('company_id', companyId)
         .maybeSingle()
-      if (fetchErr) throw new Error(`Database error: ${fetchErr.message}`)
+      if (fetchErr) throw dbError(fetchErr)
       if (!entry) throw new Error('Verifikationen hittades inte.')
 
       const voucherLabel = entry.voucher_number
@@ -16555,7 +16556,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!invoice) throw new Error('Invoice not found. Use gnubok_list_invoices to find valid IDs.')
 
       // Editable drafts only: the shared predicate the web PATCH route gates
@@ -16700,7 +16701,7 @@ export const tools: McpTool[] = [
           .select('line_type, description, quantity, unit, unit_price, line_total, vat_rate, revenue_account, article_id, deduction_type, accrual_period_start, accrual_period_end')
           .eq('invoice_id', invoice.id)
           .order('sort_order', { ascending: true })
-        if (currentError) throw new Error(`Database error: ${currentError.message}`)
+        if (currentError) throw dbError(currentError)
         currentItems = (currentRows ?? []).map((row: Record<string, unknown>) => ({
           line_type: row.line_type ?? 'product',
           description: row.description,
@@ -17715,7 +17716,7 @@ export const tools: McpTool[] = [
       const original = data as OriginalRow | null
 
       if (origErr) {
-        throw new Error(`Database error looking up journal entry ${entryId}: ${origErr.message}`)
+        throw dbError(origErr, `Database error looking up journal entry ${entryId}`)
       }
       if (!original) {
         throw new Error(
@@ -17883,7 +17884,7 @@ export const tools: McpTool[] = [
       const original = data as OriginalRow | null
 
       if (origErr) {
-        throw new Error(`Database error looking up journal entry ${entryId}: ${origErr.message}`)
+        throw dbError(origErr, `Database error looking up journal entry ${entryId}`)
       }
       if (!original) {
         throw new Error(
@@ -18897,7 +18898,7 @@ export const tools: McpTool[] = [
         .order('id', { ascending: false })
         .range(offset, offset + limit)
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
 
       const rows = data ?? []
       const schedules = rows.slice(0, limit).map((row: Record<string, unknown>) => {
@@ -19095,7 +19096,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!customer) throw new Error('Customer not found. Use gnubok_list_customers to find IDs.')
       if (params.auto_send && !customer.email) {
         throw new Error('Customer has no email address: auto_send requires one. Stage with auto_send=false or add an email first.')
@@ -19290,7 +19291,7 @@ export const tools: McpTool[] = [
         .eq('company_id', companyId)
         .maybeSingle()
 
-      if (error) throw new Error(`Database error: ${error.message}`)
+      if (error) throw dbError(error)
       if (!current) throw new Error('Recurring schedule not found. Use gnubok_list_recurring_schedules to find IDs.')
 
       // Turning auto_send on, or moving the schedule to another customer,
@@ -19305,7 +19306,7 @@ export const tools: McpTool[] = [
           .eq('id', parsedChanges.customer_id)
           .eq('company_id', companyId)
           .maybeSingle()
-        if (targetError) throw new Error(`Database error: ${targetError.message}`)
+        if (targetError) throw dbError(targetError)
         if (!target) throw new Error('Customer not found. Use gnubok_list_customers to find IDs.')
         if (effectiveAutoSend && !target.email) {
           throw new Error('Customer has no email address: auto_send requires one.')
diff --git a/lib/errors/__tests__/db-error.test.ts b/lib/errors/__tests__/db-error.test.ts
new file mode 100644
index 00000000..ae1367e5
--- /dev/null
+++ b/lib/errors/__tests__/db-error.test.ts
@@ -0,0 +1,110 @@
+/**
+ * The database-error wrapper, and the classification it exists to unlock.
+ *
+ * The idiom `throw new Error(\`Database error: ${error.message}\`)` kept the
+ * prose and dropped `code`. `isTransientFailure()` checks that SQLSTATE FIRST,
+ * and 57014 (statement timeout) is already in its transient set, so stripping
+ * it turned a retryable timeout into UNKNOWN_ERROR: "Något gick fel. Försök
+ * igen." Agents cannot dispatch on that, so they retried: on production over
+ * 60 days, 462 wasted repeat calls, with 53.1% of all real-agent error calls
+ * sitting inside a repeat streak.
+ *
+ * The headline test is the last one: it asserts the OLD shape still resolves
+ * to UNKNOWN_ERROR and the new one resolves to TRANSIENT_ERROR, so it fails if
+ * the wrapper ever stops preserving the code.
+ */
+import { describe, it, expect } from 'vitest'
+import { dbError, errorCauseTag } from '../db-error'
+import { getStructuredError } from '../get-structured-error'
+
+/** What supabase-js hands back when Postgres cancels on statement_timeout. */
+const TIMEOUT_ERROR = {
+  message: 'canceling statement due to statement timeout',
+  code: '57014',
+  details: null,
+  hint: null,
+}
+
+describe('dbError', () => {
+  it('preserves the SQLSTATE, which is the whole point', () => {
+    const wrapped = dbError(TIMEOUT_ERROR)
+    expect(wrapped.code).toBe('57014')
+  })
+
+  it('preserves details and hint for the server log', () => {
+    const wrapped = dbError({
+      message: 'duplicate key value violates unique constraint',
+      code: '23505',
+      details: 'Key (company_id, account_number) already exists.',
+      hint: 'Use upsert.',
+    })
+    expect(wrapped.details).toContain('already exists')
+    expect(wrapped.hint).toBe('Use upsert.')
+  })
+
+  it('never renders the literal "undefined"', () => {
+    // A driver-level failure (aborted fetch, gateway timeout) can arrive with
+    // no message at all. "Database error: undefined" is the string that made
+    // these unsearchable in production.
+    for (const shape of [{}, { message: undefined }, { message: '' }, { message: '   ' }, null]) {
+      expect(dbError(shape).message).not.toContain('undefined')
+    }
+  })
+
+  it('prefixes with the historical context by default', () => {
+    expect(dbError({ message: 'boom' }).message).toBe('Database error: boom')
+  })
+
+  it('keeps the driver message verbatim when context is null', () => {
+    // fetchAllRows passes null: callers such as query_journal's
+    // sanitizeDbError already match on the exact text, and this change is
+    // meant to add the code, not reword anything.
+    expect(dbError({ message: 'boom' }, null).message).toBe('boom')
+  })
+
+  it('accepts a custom context', () => {
+    expect(dbError({ message: 'boom' }, 'Database error resolving voucher "A-7"').message).toBe(
+      'Database error resolving voucher "A-7": boom',
+    )
+  })
+})
+
+describe('errorCauseTag', () => {
+  it('returns the SQLSTATE, which carries no tenant data', () => {
+    expect(errorCauseTag(dbError(TIMEOUT_ERROR))).toBe('57014')
+  })
+
+  it('falls back to the error name when there is no code', () => {
+    expect(errorCauseTag(new TypeError('nope'))).toBe('TypeError')
+  })
+
+  it('returns null rather than inventing a tag', () => {
+    expect(errorCauseTag(new Error('plain'))).toBeNull()
+    expect(errorCauseTag(null)).toBeNull()
+  })
+})
+
+describe('classification: the regression this prevents', () => {
+  it('classifies a wrapped statement timeout as retryable', () => {
+    expect(getStructuredError(dbError(TIMEOUT_ERROR)).code).toBe('TRANSIENT_ERROR')
+  })
+
+  it('would classify the OLD bare-Error shape as UNKNOWN_ERROR', () => {
+    // The bug, pinned. `new Error(error.message)` is what fetchAllRows threw,
+    // and PostgREST does not always put the word "timeout" in the message it
+    // returns, so message-pattern matching cannot be relied on. Only the code
+    // is durable, which is why the wrapper must carry it.
+    const stripped = new Error('some driver text that names no timeout')
+    expect(getStructuredError(stripped).code).toBe('UNKNOWN_ERROR')
+
+    // Same failure, code intact: now dispatchable.
+    const preserved = dbError({ message: 'some driver text that names no timeout', code: '57014' })
+    expect(getStructuredError(preserved).code).toBe('TRANSIENT_ERROR')
+  })
+
+  it('does not mistake a SQLSTATE for one of our own stable codes', () => {
+    // extractCode() only accepts /^[A-Z_]+$/. Every SQLSTATE contains digits,
+    // so attaching one cannot hijack the application error registry.
+    expect(getStructuredError(dbError({ message: 'x', code: '23505' })).code).not.toBe('23505')
+  })
+})
diff --git a/lib/errors/db-error.ts b/lib/errors/db-error.ts
new file mode 100644
index 00000000..74eb82ff
--- /dev/null
+++ b/lib/errors/db-error.ts
@@ -0,0 +1,97 @@
+/**
+ * Wrap a Supabase/PostgREST error without throwing away its identity.
+ *
+ * ## The bug this exists to prevent
+ *
+ * The idiom across the MCP tools was:
+ *
+ *     if (error) throw new Error(`Database error: ${error.message}`)
+ *
+ * which keeps the prose and discards `code`. That matters because `code` is
+ * the SQLSTATE, and `isTransientFailure()` in lib/errors/get-structured-error.ts
+ * checks it FIRST: `57014` (statement timeout), `40001`, `40P01`, `53300` and
+ * friends are already in its TRANSIENT_SQLSTATES set. Strip the code and a
+ * retryable timeout arrives as an anonymous Error, misses every transient
+ * check, and resolves to UNKNOWN_ERROR: "Något gick fel. Försök igen."
+ *
+ * Measured on production over 60 days (bot actors excluded): 1 024 real-agent
+ * tool failures, 645 of them UNKNOWN_ERROR across 60 actors and 57 companies,
+ * 537 carrying that exact generic string. `gnubok_query_journal` alone failed
+ * 164 times at a p50 of 8 110 ms while every other failing tool sat between 1
+ * and 315 ms: a timeout signature that should have been TRANSIENT_ERROR all
+ * along. Agents cannot dispatch on "something went wrong", so they retried:
+ * 82 streaks of three or more identical failures, 462 wasted repeat calls,
+ * 53.1% of all real-agent error calls sitting inside a streak.
+ *
+ * ## Why attaching `code` is safe
+ *
+ * `extractCode()` only treats a code as an application error code when it
+ * matches /^[A-Z_]+$/. Every SQLSTATE contains digits (`57014`, `42P01`,
+ * `23505`), and so does every PostgREST code (`PGRST200`), so none of them can
+ * be mistaken for one of our own stable codes. The only behaviour this unlocks
+ * is the transient check that was always meant to run.
+ */
+
+/** The shape of a PostgrestError, narrowed to what we read. */
+interface DatabaseErrorLike {
+  message?: string | null
+  code?: string | null
+  details?: string | null
+  hint?: string | null
+}
+
+/**
+ * An Error carrying the driver's SQLSTATE and diagnostics.
+ *
+ * `details` and `hint` are preserved for the server log, not for the agent:
+ * `getStructuredError` never reads them, so they cannot leak into a tool
+ * result. They are what makes a production failure debuggable after the fact.
+ */
+export interface DatabaseError extends Error {
+  code?: string
+  details?: string
+  hint?: string
+}
+
+/**
+ * @param error   the `error` half of a supabase-js `{ data, error }` result
+ * @param context prefix for the message; defaults to the historical
+ *                "Database error" so existing message-pattern matching in
+ *                `inferCode()` keeps working unchanged. Pass `null` to keep
+ *                the driver's message verbatim, for call sites whose exact
+ *                text callers already depend on.
+ */
+export function dbError(error: unknown, context: string | null = 'Database error'): DatabaseError {
+  const source = (error ?? {}) as DatabaseErrorLike
+  const raw = typeof source.message === 'string' && source.message.trim() ? source.message.trim() : null
+
+  // Never render the literal "undefined". A driver-level failure (an aborted
+  // fetch, a gateway timeout) can arrive with no `message` at all, and
+  // "Database error: undefined" is the string that made these unsearchable in
+  // the first place.
+  const prefix = context ?? ''
+  const message = raw
+    ? (prefix ? `${prefix}: ${raw}` : raw)
+    : `${prefix || 'Database error'}: no message from the database driver`
+
+  const wrapped = new Error(message) as DatabaseError
+  if (typeof source.code === 'string' && source.code) wrapped.code = source.code
+  if (typeof source.details === 'string' && source.details) wrapped.details = source.details
+  if (typeof source.hint === 'string' && source.hint) wrapped.hint = source.hint
+  return wrapped
+}
+
+/**
+ * A PII-safe identifier for what failed, for telemetry.
+ *
+ * A SQLSTATE is five characters of protocol vocabulary and carries no tenant
+ * data. A raw driver message can quote row values in a constraint violation,
+ * so it belongs in the server log, never in `event_log`.
+ */
+export function errorCauseTag(error: unknown): string | null {
+  if (error === null || error === undefined) return null
+  const source = error as DatabaseErrorLike & { name?: unknown }
+  if (typeof source.code === 'string' && source.code) return source.code
+  if (error instanceof Error && error.name && error.name !== 'Error') return error.name
+  return null
+}
diff --git a/lib/supabase/__tests__/fetch-all.test.ts b/lib/supabase/__tests__/fetch-all.test.ts
index ba655043..2d9fd0ac 100644
--- a/lib/supabase/__tests__/fetch-all.test.ts
+++ b/lib/supabase/__tests__/fetch-all.test.ts
@@ -41,6 +41,31 @@ describe('fetchAllRows', () => {
     ).rejects.toThrow('boom')
   })
 
+  it('propagates the driver SQLSTATE so a timeout stays dispatchable', async () => {
+    // This is the highest-traffic error strip point in the codebase: every
+    // paginated read goes through it. It used to throw `new Error(msg)`, which
+    // dropped `code`, so a statement timeout (57014) reached the structured
+    // error layer anonymous and resolved to UNKNOWN_ERROR instead of the
+    // retryable TRANSIENT_ERROR. gnubok_query_journal failed this way 164
+    // times in 60 days at a p50 of 8 110 ms.
+    const failure = fetchAllRows<Row>(() =>
+      Promise.resolve({
+        data: null,
+        error: { message: 'canceling statement due to statement timeout', code: '57014' },
+      }),
+    )
+    await expect(failure).rejects.toMatchObject({ code: '57014' })
+    // And the message stays verbatim: query_journal's sanitizeDbError matches
+    // on the existing text.
+    await expect(failure).rejects.toThrow('canceling statement due to statement timeout')
+  })
+
+  it('does not render "undefined" when the driver sends no message', async () => {
+    await expect(
+      fetchAllRows<Row>(() => Promise.resolve({ data: null, error: { code: '08006' } as never })),
+    ).rejects.toThrow(/^(?!.*undefined).*$/)
+  })
+
   it('returns [] when the first page is empty', async () => {
     const out = await fetchAllRows<Row>(pagedQuery({ 0: [] }))
     expect(out).toEqual([])
diff --git a/lib/supabase/fetch-all.ts b/lib/supabase/fetch-all.ts
index 10ca479a..12968f33 100644
--- a/lib/supabase/fetch-all.ts
+++ b/lib/supabase/fetch-all.ts
@@ -1,4 +1,5 @@
 import { createLogger } from '@/lib/logger'
+import { dbError } from '@/lib/errors/db-error'
 
 const log = createLogger('fetch-all')
 
@@ -71,7 +72,19 @@ export async function fetchAllRows<T>(
 
   while (true) {
     const { data, error } = await queryFn({ from, to: from + PAGE_SIZE - 1 })
-    if (error) throw new Error(error.message)
+    // dbError, not `new Error(error.message)`: the bare form discarded the
+    // driver's SQLSTATE, and `isTransientFailure()` checks that code FIRST.
+    // A statement timeout (57014) therefore arrived as an anonymous Error and
+    // resolved to UNKNOWN_ERROR ("Något gick fel. Försök igen.") instead of
+    // the retryable TRANSIENT_ERROR. This is the single highest-traffic strip
+    // point in the codebase: every paginated read goes through it, including
+    // gnubok_query_journal, which failed 164 times in 60 days at a p50 of
+    // 8 110 ms while every other failing tool sat between 1 and 315 ms.
+    //
+    // The message is kept VERBATIM (context: null). Callers such as
+    // query_journal's sanitizeDbError already match on it, and this change is
+    // meant to add the code, not to reword anything.
+    if (error) throw dbError(error, null)
     if (!data || data.length === 0) break
     allRows.push(...data)
     pages += 1