fix(checkin): skip empty AI work and rejected MCP probes

layers/registry/server/utils/ai-generation-work.ts

@@ -121,6 +121,8 @@ const ELIGIBLE_SKILL_SQL = `
   WHERE r.broken_since IS NULL
     AND s.current_sha IS NOT NULL
     AND s.rendered_raw IS NOT NULL
+    -- Match String.trim(): empty content cannot produce an embedding or classification.
+    AND LENGTH(TRIM(s.rendered_raw, char(9, 10, 11, 12, 13, 32, 160, 5760, 8192, 8193, 8194, 8195, 8196, 8197, 8198, 8199, 8200, 8201, 8202, 8232, 8233, 8239, 8287, 12288, 65279))) > 0
     AND s.rendered_status = 'ok'
     AND s.seo_indexable = 1
 `

server/plugins/sentry.ts

@@ -1,10 +1,10 @@
 import { createSentryInitOptions } from '@harlan-zw/nuxt-sentry/server'
 import { SDK_VERSION } from '@sentry/cloudflare'
 import { sentryCloudflareNitroPlugin } from '@sentry/nuxt/module/plugins'
-import { isBestEffortCacheWriteError, isExpectedUpstreamOutageError, isMcpAcceptProbeError, scrubSentryBreadcrumb, scrubSentryEvent } from '../../shared/sentry'
+import { isBestEffortCacheWriteError, isExpectedUpstreamOutageError, isMcpAcceptProbeError, isMcpProtocolProbeError, scrubSentryBreadcrumb, scrubSentryEvent } from '../../shared/sentry'
 
 function isDroppedSignature(error: unknown): boolean {
-  return isBestEffortCacheWriteError(error) || isExpectedUpstreamOutageError(error) || isMcpAcceptProbeError(error)
+  return isBestEffortCacheWriteError(error) || isExpectedUpstreamOutageError(error) || isMcpAcceptProbeError(error) || isMcpProtocolProbeError(error)
 }
 
 export default defineNitroPlugin((nitroApp) => {
@@ -28,7 +28,7 @@ export default defineNitroPlugin((nitroApp) => {
     // Nitro's route cache catches its own KV write failures and forwards the
     // caught error here as unhandled (SKILLD-17). The registry handlers'
     // intended upstream-outage 503s land here the same way (SKILLD-11,
-    // SKILLD-1E), as does the MCP transport's intended probe 406 (SKILLD-35).
+    // SKILLD-1E), as do MCP probe rejections: 406 (SKILLD-35) and 400 (SKILLD-3H).
     // All are failure classes already answered or recorded, so drop the
     // duplicates and keep the wide events as the visibility path.
     beforeSend(event, hint) {

shared/sentry.ts

@@ -123,6 +123,12 @@ export function isMcpAcceptProbeError(error: unknown): boolean {
   return typeof message === 'string' && message.startsWith('Not Acceptable: Client must accept')
 }
 
+/** MCP answers unsupported protocol probes with 400 before running a tool (SKILLD-3H). */
+export function isMcpProtocolProbeError(error: unknown): boolean {
+  const message = sentryExceptionMessage(error)
+  return typeof message === 'string' && message.startsWith('Bad Request: Unsupported protocol version:')
+}
+
 /**
  * A URL without its query string or fragment. Query strings carry OAuth codes,
  * signed tokens, and search terms, so no URL reaches Sentry with one.

test/unit/ai-generation-work.test.ts

@@ -73,6 +73,12 @@ describe('ai generation work', () => {
 
   afterEach(() => sqlite.close())
 
+  it.each(['', ' \t\n\r', '\u00A0\u2003\uFEFF'])('keeps empty source out of runtime generation work: %j', async (source) => {
+    sqlite.prepare('UPDATE skills SET rendered_raw = ?').run(source)
+    expect(await selectMissingGeneratedSkills(db, 'abstractness', 50)).toEqual([])
+    expect(await selectMissingGeneratedSkills(db, 'embedding', 50)).toEqual([])
+  })
+
   it('does not select current runtime kinds because paused batch kinds are missing', async () => {
     const embeddings = await selectMissingGeneratedSkills(db, 'embedding', 50)
     const abstractness = await selectMissingGeneratedSkills(db, 'abstractness', 50)

test/unit/sentry-cache-write-filter.nuxt.test.ts

@@ -196,4 +196,15 @@ describe('sentry beforeSend cache-write filter', () => {
     }
     expect(beforeSend(page406Event, {})).toBe(page406Event)
   })
+
+  it.each([true, false])('drops rejected MCP protocol probes with original exception: %s', (original) => {
+    const message = 'Bad Request: Unsupported protocol version: 2026-07-28 (supported versions: 2025-11-25, 2025-06-18)'
+    const event: SentryEventFixture = { exception: { values: [{ type: 'Error', value: message }] } }
+    expect(beforeSend(event, original ? { originalException: new Error(message) } : {})).toBeNull()
+  })
+
+  it('keeps other protocol errors', () => {
+    const event: SentryEventFixture = { exception: { values: [{ type: 'Error', value: 'Unsupported protocol version in database connection' }] } }
+    expect(beforeSend(event, {})).toBe(event)
+  })
 })