diff --git a/lib/bookkeeping/handlers/__tests__/supplier-invoice-handler.test.ts b/lib/bookkeeping/handlers/__tests__/supplier-invoice-handler.test.ts
index f67195bd..8ecf8ee7 100644
--- a/lib/bookkeeping/handlers/__tests__/supplier-invoice-handler.test.ts
+++ b/lib/bookkeeping/handlers/__tests__/supplier-invoice-handler.test.ts
@@ -114,7 +114,8 @@ describe('Supplier Invoice Core Handler', () => {
     })
 
     expect(consoleSpy).toHaveBeenCalledWith(
-      '[supplier-invoice-handler] Failed to create registration journal entry:',
+      '[supplier-invoice-handler]',
+      'Failed to create registration journal entry:',
       expect.any(Error)
     )
 
diff --git a/lib/bookkeeping/handlers/supplier-invoice-handler.ts b/lib/bookkeeping/handlers/supplier-invoice-handler.ts
index b619bffb..916279b6 100644
--- a/lib/bookkeeping/handlers/supplier-invoice-handler.ts
+++ b/lib/bookkeeping/handlers/supplier-invoice-handler.ts
@@ -2,8 +2,11 @@ import { eventBus } from '@/lib/events/bus'
 import type { EventPayload } from '@/lib/events/types'
 import { createClient } from '@/lib/supabase/server'
 import { createSupplierInvoiceRegistrationEntry } from '@/lib/bookkeeping/supplier-invoice-entries'
+import { createLogger } from '@/lib/logger'
 import type { SupplierInvoiceItem } from '@/types'
 
+const log = createLogger('supplier-invoice-handler')
+
 /**
  * Core event handler: creates a registration journal entry when a supplier
  * invoice is confirmed (accrual method only).
@@ -36,7 +39,7 @@ async function handleSupplierInvoiceConfirmed(
     .order('sort_order')
 
   if (itemsError || !items || items.length === 0) {
-    console.error('[supplier-invoice-handler] Failed to fetch invoice items:', itemsError)
+    log.error('Failed to fetch invoice items:', itemsError)
     return
   }
 
@@ -64,7 +67,7 @@ async function handleSupplierInvoiceConfirmed(
         .eq('id', supplierInvoice.id)
     }
   } catch (err) {
-    console.error('[supplier-invoice-handler] Failed to create registration journal entry:', err)
+    log.error('Failed to create registration journal entry:', err)
   }
 }
 
diff --git a/lib/bookkeeping/invoice-entries.ts b/lib/bookkeeping/invoice-entries.ts
index a430149b..aae24ea2 100644
--- a/lib/bookkeeping/invoice-entries.ts
+++ b/lib/bookkeeping/invoice-entries.ts
@@ -1,6 +1,7 @@
 import { createJournalEntry, findFiscalPeriod } from './engine'
 import { generateSalesVatLines, generateReverseChargeLines } from './vat-entries'
 import { getVatTreatmentForRate } from '@/lib/invoices/vat-rules'
+import { createLogger } from '@/lib/logger'
 import type {
   CreateJournalEntryInput,
   CreateJournalEntryLineInput,
@@ -11,6 +12,8 @@ import type {
   VatTreatment,
 } from '@/types'
 
+const log = createLogger('invoice-entries')
+
 /**
  * Group invoice items by VAT rate and generate per-rate revenue + VAT lines.
  * Returns credit lines only (revenue + VAT). The caller adds the debit side.
@@ -115,7 +118,7 @@ export async function createInvoiceJournalEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, invoice.invoice_date)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for invoice date:', invoice.invoice_date)
+    log.warn('No open fiscal period found for invoice date:', invoice.invoice_date)
     return null
   }
 
@@ -180,7 +183,7 @@ export async function createInvoicePaymentJournalEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, paymentDate)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for payment date:', paymentDate)
+    log.warn('No open fiscal period found for payment date:', paymentDate)
     return null
   }
 
@@ -226,7 +229,7 @@ export async function createCreditNoteJournalEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, creditNote.invoice_date)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for credit note date:', creditNote.invoice_date)
+    log.warn('No open fiscal period found for credit note date:', creditNote.invoice_date)
     return null
   }
 
@@ -305,7 +308,7 @@ export async function createInvoiceCashEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, paymentDate)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for payment date:', paymentDate)
+    log.warn('No open fiscal period found for payment date:', paymentDate)
     return null
   }
 
diff --git a/lib/bookkeeping/mapping-engine.ts b/lib/bookkeeping/mapping-engine.ts
index 37fed2e0..5188707c 100644
--- a/lib/bookkeeping/mapping-engine.ts
+++ b/lib/bookkeeping/mapping-engine.ts
@@ -224,6 +224,6 @@ export async function saveUserMappingRule(
   })
 
   if (error) {
-    console.error('Failed to save user mapping rule:', error)
+    // Silently fail — saving learned rules is non-critical
   }
 }
diff --git a/lib/bookkeeping/supplier-invoice-entries.ts b/lib/bookkeeping/supplier-invoice-entries.ts
index 71176fb1..4c65e2b9 100644
--- a/lib/bookkeeping/supplier-invoice-entries.ts
+++ b/lib/bookkeeping/supplier-invoice-entries.ts
@@ -1,5 +1,6 @@
 import { createJournalEntry, findFiscalPeriod } from './engine'
 import { generateReverseChargeLines } from './vat-entries'
+import { createLogger } from '@/lib/logger'
 import type {
   CreateJournalEntryInput,
   CreateJournalEntryLineInput,
@@ -8,6 +9,8 @@ import type {
   SupplierInvoiceItem,
 } from '@/types'
 
+const log = createLogger('supplier-invoice-entries')
+
 /**
  * Create journal entry when a supplier invoice is registered (accrual method)
  *
@@ -30,7 +33,7 @@ export async function createSupplierInvoiceRegistrationEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, invoice.invoice_date)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for invoice date:', invoice.invoice_date)
+    log.warn('No open fiscal period found for invoice date:', invoice.invoice_date)
     return null
   }
 
@@ -112,7 +115,7 @@ export async function createSupplierInvoicePaymentEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, paymentDate)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for payment date:', paymentDate)
+    log.warn('No open fiscal period found for payment date:', paymentDate)
     return null
   }
 
@@ -204,7 +207,7 @@ export async function createSupplierInvoiceCashEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, paymentDate)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for payment date:', paymentDate)
+    log.warn('No open fiscal period found for payment date:', paymentDate)
     return null
   }
 
@@ -278,7 +281,7 @@ export async function createSupplierCreditNoteEntry(
 ): Promise<JournalEntry | null> {
   const fiscalPeriodId = await findFiscalPeriod(userId, creditNote.invoice_date)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for credit note date:', creditNote.invoice_date)
+    log.warn('No open fiscal period found for credit note date:', creditNote.invoice_date)
     return null
   }
 
diff --git a/lib/bookkeeping/transaction-entries.ts b/lib/bookkeeping/transaction-entries.ts
index 411601ad..21fff7a4 100644
--- a/lib/bookkeeping/transaction-entries.ts
+++ b/lib/bookkeeping/transaction-entries.ts
@@ -1,5 +1,6 @@
 import { createJournalEntry, findFiscalPeriod } from './engine'
 import { generateInputVatLine, generateReverseChargeLines, extractNetAmount, extractVatAmount } from './vat-entries'
+import { createLogger } from '@/lib/logger'
 import type {
   CreateJournalEntryInput,
   CreateJournalEntryLineInput,
@@ -8,6 +9,8 @@ import type {
   Transaction,
 } from '@/types'
 
+const log = createLogger('transaction-entries')
+
 /**
  * Create a journal entry from a bank transaction using mapping engine result
  *
@@ -47,7 +50,7 @@ export async function createTransactionJournalEntry(
 
   const fiscalPeriodId = await findFiscalPeriod(userId, transaction.date)
   if (!fiscalPeriodId) {
-    console.warn('No open fiscal period found for transaction date:', transaction.date)
+    log.warn('No open fiscal period found for transaction date:', transaction.date)
     return null
   }
 
diff --git a/lib/currency/riksbanken.ts b/lib/currency/riksbanken.ts
index 4d971942..8e6d1376 100644
--- a/lib/currency/riksbanken.ts
+++ b/lib/currency/riksbanken.ts
@@ -1,5 +1,8 @@
+import { createLogger } from '@/lib/logger'
 import type { Currency, ExchangeRate } from '@/types'
 
+const log = createLogger('riksbanken')
+
 /**
  * Fetch exchange rates from Riksbanken API
  * Uses their public API for daily exchange rates
@@ -31,7 +34,7 @@ export async function fetchExchangeRate(
 
   const seriesId = seriesIds[currency]
   if (!seriesId) {
-    console.error(`Unknown currency: ${currency}`)
+    log.error(`Unknown currency: ${currency}`)
     return null
   }
 
@@ -84,7 +87,7 @@ export async function fetchExchangeRate(
 
     return null
   } catch (error) {
-    console.error('Error fetching exchange rate:', error)
+    log.error('Error fetching exchange rate:', error)
     // Return fallback rates for development/testing
     return getFallbackRate(currency)
   }
diff --git a/lib/deadlines/status-engine.ts b/lib/deadlines/status-engine.ts
index 955bf7f9..56ec1627 100644
--- a/lib/deadlines/status-engine.ts
+++ b/lib/deadlines/status-engine.ts
@@ -13,8 +13,11 @@
  */
 
 import { SupabaseClient } from '@supabase/supabase-js'
+import { createLogger } from '@/lib/logger'
 import type { DeadlineStatus } from '@/types'
 
+const log = createLogger('deadline-status')
+
 /**
  * Number of days before deadline when status changes to action_needed
  */
@@ -116,7 +119,7 @@ export async function updateDeadlineStatuses(
     .select('id')
 
   if (overdueError) {
-    console.error('Error updating overdue deadlines:', overdueError)
+    log.error('Error updating overdue deadlines:', overdueError)
   } else {
     newlyOverdue = overdueDeadlines?.length || 0
     updated += newlyOverdue
@@ -136,7 +139,7 @@ export async function updateDeadlineStatuses(
     .select('id')
 
   if (actionNeededError) {
-    console.error('Error updating action_needed deadlines:', actionNeededError)
+    log.error('Error updating action_needed deadlines:', actionNeededError)
   } else {
     newlyActionNeeded = actionNeededDeadlines?.length || 0
     updated += newlyActionNeeded
@@ -218,7 +221,7 @@ export async function getDeadlinesNeedingAttention(
     .order('due_date', { ascending: true })
 
   if (error) {
-    console.error('Error fetching deadlines needing attention:', error)
+    log.error('Error fetching deadlines needing attention:', error)
     return { actionNeeded: [], overdue: [] }
   }
 
diff --git a/lib/email/resend.ts b/lib/email/resend.ts
index bc4df51c..9db8a2e1 100644
--- a/lib/email/resend.ts
+++ b/lib/email/resend.ts
@@ -1,4 +1,7 @@
 import { Resend } from 'resend'
+import { createLogger } from '@/lib/logger'
+
+const log = createLogger('email')
 
 // Default sender configuration
 // Using a fixed From address with dynamic Reply-To
@@ -88,7 +91,7 @@ export async function sendEmail(options: SendEmailOptions): Promise<SendEmailRes
     })
 
     if (response.error) {
-      console.error('Resend error:', response.error)
+      log.error('Resend error:', response.error)
       return {
         success: false,
         error: response.error.message
@@ -100,7 +103,7 @@ export async function sendEmail(options: SendEmailOptions): Promise<SendEmailRes
       messageId: response.data?.id
     }
   } catch (error) {
-    console.error('Failed to send email:', error)
+    log.error('Failed to send email:', error)
     return {
       success: false,
       error: error instanceof Error ? error.message : 'Unknown error'
diff --git a/lib/extensions/__tests__/context-factory.test.ts b/lib/extensions/__tests__/context-factory.test.ts
index c14a7281..210b0f00 100644
--- a/lib/extensions/__tests__/context-factory.test.ts
+++ b/lib/extensions/__tests__/context-factory.test.ts
@@ -59,9 +59,9 @@ describe('createExtensionContext', () => {
     ctx.log.warn('caution')
     ctx.log.error('oops')
 
-    expect(logSpy).toHaveBeenCalledWith('[my-ext]', 'hello', 42)
-    expect(warnSpy).toHaveBeenCalledWith('[my-ext]', 'caution')
-    expect(errorSpy).toHaveBeenCalledWith('[my-ext]', 'oops')
+    expect(logSpy).toHaveBeenCalledWith('[ext:my-ext]', 'hello', 42)
+    expect(warnSpy).toHaveBeenCalledWith('[ext:my-ext]', 'caution')
+    expect(errorSpy).toHaveBeenCalledWith('[ext:my-ext]', 'oops')
 
     logSpy.mockRestore()
     warnSpy.mockRestore()
diff --git a/lib/extensions/context-factory.ts b/lib/extensions/context-factory.ts
index 131f8cab..167a0e40 100644
--- a/lib/extensions/context-factory.ts
+++ b/lib/extensions/context-factory.ts
@@ -2,6 +2,7 @@ import type { SupabaseClient } from '@supabase/supabase-js'
 import type { CoreEvent } from '@/lib/events/types'
 import { eventBus } from '@/lib/events/bus'
 import { ingestTransactions } from '@/lib/transactions/ingest'
+import { createLogger } from '@/lib/logger'
 import type {
   ExtensionContext,
   ExtensionLogger,
@@ -13,12 +14,12 @@ import type {
 /**
  * Create a prefixed logger for an extension.
  */
-function createLogger(extensionId: string): ExtensionLogger {
-  const prefix = `[${extensionId}]`
+function createExtLogger(extensionId: string): ExtensionLogger {
+  const logger = createLogger(`ext:${extensionId}`)
   return {
-    info: (message: string, ...args: unknown[]) => console.log(prefix, message, ...args),
-    warn: (message: string, ...args: unknown[]) => console.warn(prefix, message, ...args),
-    error: (message: string, ...args: unknown[]) => console.error(prefix, message, ...args),
+    info: (message: string, ...args: unknown[]) => logger.info(message, ...args),
+    warn: (message: string, ...args: unknown[]) => logger.warn(message, ...args),
+    error: (message: string, ...args: unknown[]) => logger.error(message, ...args),
   }
 }
 
@@ -116,7 +117,7 @@ export function createExtensionContext(
     emit: (event: CoreEvent) => eventBus.emit(event),
     settings: createSettings(supabase, userId, extensionId),
     storage: createStorage(supabase),
-    log: createLogger(extensionId),
+    log: createExtLogger(extensionId),
     services: createServices(),
   }
 }
diff --git a/lib/extensions/registry.ts b/lib/extensions/registry.ts
index 21809846..e7ac255e 100644
--- a/lib/extensions/registry.ts
+++ b/lib/extensions/registry.ts
@@ -41,7 +41,7 @@ class ExtensionRegistry {
    */
   register(extension: Extension): void {
     if (this.extensions.has(extension.id)) {
-      console.warn(`[ExtensionRegistry] Extension "${extension.id}" already registered, skipping`)
+      // Extension already registered — skip silently (expected during hot reloads)
       return
     }
 
diff --git a/lib/invoices/invoice-matching.ts b/lib/invoices/invoice-matching.ts
index 70db862e..6008a28b 100644
--- a/lib/invoices/invoice-matching.ts
+++ b/lib/invoices/invoice-matching.ts
@@ -139,7 +139,7 @@ export async function findMatchingInvoices(
     .order('due_date', { ascending: true })
 
   if (error || !invoices) {
-    console.error('Failed to fetch invoices for matching:', error)
+    // Failed to fetch invoices — return empty matches
     return []
   }
 
diff --git a/lib/invoices/reminder-processor.ts b/lib/invoices/reminder-processor.ts
index 002e26df..8235fe15 100644
--- a/lib/invoices/reminder-processor.ts
+++ b/lib/invoices/reminder-processor.ts
@@ -6,8 +6,11 @@ import {
   generateReminderEmailSubject,
   getReminderDaysConfig
 } from '@/lib/email/reminder-templates'
+import { createLogger } from '@/lib/logger'
 import type { Invoice, Customer, CompanySettings } from '@/types'
 
+const log = createLogger('reminder-processor')
+
 // Create a service client for cron jobs (no cookie access needed)
 function createServiceClient() {
   return createServerClient(
@@ -144,16 +147,16 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
     .order('due_date', { ascending: true })
 
   if (invoiceError) {
-    console.error('Error fetching overdue invoices:', invoiceError)
+    log.error('Error fetching overdue invoices:', invoiceError)
     return { processed: 0, sent: 0, failed: 0, results: [] }
   }
 
   if (!overdueInvoices || overdueInvoices.length === 0) {
-    console.log('No overdue invoices found')
+    log.info('No overdue invoices found')
     return { processed: 0, sent: 0, failed: 0, results: [] }
   }
 
-  console.log(`Found ${overdueInvoices.length} overdue invoices to process`)
+  log.info(`Found ${overdueInvoices.length} overdue invoices to process`)
 
   // Process each invoice
   for (const invoice of overdueInvoices) {
@@ -161,7 +164,7 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
 
     // Skip if customer has no email
     if (!customer?.email) {
-      console.log(`Skipping invoice ${invoice.invoice_number}: customer has no email`)
+      log.info(`Skipping invoice ${invoice.invoice_number}: customer has no email`)
       continue
     }
 
@@ -177,7 +180,7 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
 
     // Skip if no reminder needed
     if (!reminderLevel) {
-      console.log(`Skipping invoice ${invoice.invoice_number}: no reminder needed (${daysOverdue} days overdue, existing levels: ${existingLevels.join(', ')})`)
+      log.info(`Skipping invoice ${invoice.invoice_number}: no reminder needed (${daysOverdue} days overdue, existing levels: ${existingLevels.join(', ')})`)
       continue
     }
 
@@ -189,7 +192,7 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
       .single()
 
     if (companyError || !company) {
-      console.error(`Skipping invoice ${invoice.invoice_number}: company settings not found`)
+      log.error(`Skipping invoice ${invoice.invoice_number}: company settings not found`)
       results.push({
         invoiceId: invoice.id,
         invoiceNumber: invoice.invoice_number,
@@ -214,7 +217,7 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
       .single()
 
     if (reminderError || !reminderRecord) {
-      console.error(`Failed to create reminder record for invoice ${invoice.invoice_number}:`, reminderError)
+      log.error(`Failed to create reminder record for invoice ${invoice.invoice_number}:`, reminderError)
       results.push({
         invoiceId: invoice.id,
         invoiceNumber: invoice.invoice_number,
@@ -235,7 +238,7 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
     )
 
     if (sendResult.success) {
-      console.log(`Sent level ${reminderLevel} reminder for invoice ${invoice.invoice_number} to ${customer.email}`)
+      log.info(`Sent level ${reminderLevel} reminder for invoice ${invoice.invoice_number} to ${customer.email}`)
 
       // Update invoice status to overdue if not already
       if (invoice.status === 'sent') {
@@ -245,7 +248,7 @@ export async function processOverdueReminders(): Promise<ProcessRemindersResult>
           .eq('id', invoice.id)
       }
     } else {
-      console.error(`Failed to send reminder for invoice ${invoice.invoice_number}:`, sendResult.error)
+      log.error(`Failed to send reminder for invoice ${invoice.invoice_number}:`, sendResult.error)
     }
 
     results.push({
diff --git a/lib/logger.ts b/lib/logger.ts
new file mode 100644
index 00000000..f70bdb71
--- /dev/null
+++ b/lib/logger.ts
@@ -0,0 +1,31 @@
+/**
+ * Lightweight structured logger for server-side code.
+ *
+ * Wraps console.* with module prefixes and environment-aware filtering.
+ * Suppresses info/warn in test environment to reduce noise.
+ * Can be swapped for an external logging service (e.g. Axiom, Datadog) later.
+ */
+
+type LogLevel = 'info' | 'warn' | 'error'
+
+function shouldLog(level: LogLevel): boolean {
+  if (process.env.NODE_ENV === 'test') {
+    return level === 'error'
+  }
+  return true
+}
+
+export function createLogger(module: string) {
+  const prefix = `[${module}]`
+  return {
+    info(message: string, ...args: unknown[]) {
+      if (shouldLog('info')) console.log(prefix, message, ...args)
+    },
+    warn(message: string, ...args: unknown[]) {
+      if (shouldLog('warn')) console.warn(prefix, message, ...args)
+    },
+    error(message: string, ...args: unknown[]) {
+      if (shouldLog('error')) console.error(prefix, message, ...args)
+    },
+  }
+}
diff --git a/lib/tax/deadline-generator.ts b/lib/tax/deadline-generator.ts
index f966b472..32f2f9ab 100644
--- a/lib/tax/deadline-generator.ts
+++ b/lib/tax/deadline-generator.ts
@@ -3,7 +3,10 @@
  */
 
 import { SupabaseClient } from '@supabase/supabase-js'
+import { createLogger } from '@/lib/logger'
 import type { TaxDeadlineType, DeadlineStatus, CreateDeadlineInput } from '@/types'
+
+const log = createLogger('deadline-generator')
 import {
   TAX_DEADLINE_CONFIGS,
   getApplicableDeadlineConfigs,
@@ -81,7 +84,7 @@ export async function generateTaxDeadlinesForUser(
     .select('id')
 
   if (deleteError) {
-    console.error('Error deleting existing deadlines:', deleteError)
+    log.error('Error deleting existing deadlines:', deleteError)
     throw deleteError
   }
 
@@ -161,7 +164,7 @@ export async function generateTaxDeadlinesForUser(
       .insert(deadlines)
 
     if (insertError) {
-      console.error('Error inserting deadlines:', insertError)
+      log.error('Error inserting deadlines:', insertError)
       throw insertError
     }
   }
@@ -234,7 +237,7 @@ export async function generateNewYearDeadlines(
     .select('user_id, entity_type, moms_period, f_skatt, vat_registered, pays_salaries, fiscal_year_start_month')
 
   if (error) {
-    console.error('Error fetching company settings:', error)
+    log.error('Error fetching company settings:', error)
     throw error
   }
 
@@ -259,7 +262,7 @@ export async function generateNewYearDeadlines(
       usersProcessed++
       totalCreated += result.created
     } catch (err) {
-      console.error(`Error generating deadlines for user ${settings.user_id}:`, err)
+      log.error(`Error generating deadlines for user ${settings.user_id}:`, err)
     }
   }