fix(server): log underlying cause chain for failed D1 queries

Drizzle wraps the real D1 error in DrizzleQueryError.cause; both the access
log and the origin-detect catch only logged .message, surfacing just
"Failed query: <sql>" with no reason. Add formatError() to flatten the cause
chain and use it at both sites so D1 failures are diagnosable.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/app.ts

@@ -3,6 +3,7 @@ import type { Context } from 'hono'
 import { Hono } from 'hono'
 import { cors } from 'hono/cors'
 import type { Auth } from './auth'
+import { formatError } from './lib/errors'
 import { authMiddleware } from './middleware/auth'
 import { imageHostingDomain } from './middleware/image-hosting-domain'
 import { accessLog } from './middleware/logger'
@@ -50,8 +51,7 @@ export function createApp(platform: Platform, auth: Auth) {
   app.use('/*', platformMiddleware(platform, auth))
   app.use('/*', async (c, next) => {
     const result = await ensureSitePublicOrigin(platform.db, c.req.url).catch((err) => {
-      const code = err instanceof Error ? err.message : String(err)
-      console.error(`site.public_origin.detect.error code=${code}`)
+      console.error(`site.public_origin.detect.error code=${formatError(err)}`)
       return { origin: null, created: false }
     })
 
@@ -66,8 +66,7 @@ export function createApp(platform: Platform, auth: Auth) {
         trigger: 'runtime',
         runtime: instanceTelemetryRuntime(platform),
       }).catch((err) => {
-        const code = err instanceof Error ? err.message : String(err)
-        console.error(`instance.telemetry.initial_report.error code=${code}`)
+        console.error(`instance.telemetry.initial_report.error code=${formatError(err)}`)
       })
       waitUntil(c, task)
     }

server/lib/errors.test.ts

@@ -0,0 +1,23 @@
+import { describe, expect, it } from 'vitest'
+import { formatError } from './errors'
+
+describe('formatError', () => {
+  it('returns the message for a plain error', () => {
+    expect(formatError(new Error('boom'))).toBe('boom')
+  })
+
+  it('flattens the cause chain (drizzle wraps the real D1 error in cause)', () => {
+    const d1 = new Error('D1_ERROR: Network connection lost')
+    const wrapped = new Error('Failed query: update "download_tasks" ...', { cause: d1 })
+    expect(formatError(wrapped)).toBe('Failed query: update "download_tasks" ... <- D1_ERROR: Network connection lost')
+  })
+
+  it('appends a non-Error cause', () => {
+    const err = new Error('outer', { cause: 'inner string' })
+    expect(formatError(err)).toBe('outer <- inner string')
+  })
+
+  it('stringifies a non-Error value', () => {
+    expect(formatError('plain string')).toBe('plain string')
+  })
+})

server/lib/errors.ts

@@ -0,0 +1,20 @@
+/**
+ * Flatten an error and its `cause` chain into a single string.
+ *
+ * Drizzle wraps the underlying driver error in `DrizzleQueryError`, whose
+ * `message` is only `Failed query: <sql>`; the real D1 error lives in `.cause`.
+ * Logging just `.message` hides why the query failed — this surfaces the chain.
+ */
+export function formatError(error: unknown): string {
+  if (!(error instanceof Error)) return String(error)
+
+  const parts: string[] = [error.message]
+  let cause = (error as { cause?: unknown }).cause
+  while (cause instanceof Error) {
+    parts.push(cause.message)
+    cause = (cause as { cause?: unknown }).cause
+  }
+  if (cause !== undefined) parts.push(String(cause))
+
+  return parts.join(' <- ')
+}

server/middleware/logger.ts

@@ -1,5 +1,6 @@
 import type { Context } from 'hono'
 import { createMiddleware } from 'hono/factory'
+import { formatError } from '../lib/errors'
 import type { Env } from './platform'
 
 export const accessLog = createMiddleware<Env>(async (c, next) => {
@@ -44,10 +45,8 @@ function accessLogFields(
     )
   }
 
-  if (error instanceof Error) {
-    fields.push(['error', error.message])
-  } else if (error) {
-    fields.push(['error', String(error)])
+  if (error !== undefined) {
+    fields.push(['error', formatError(error)])
   }
 
   return fields