diff --git a/apps/sim/lib/api/contracts/knowledge/documents.test.ts b/apps/sim/lib/api/contracts/knowledge/documents.test.ts
index 9a12967d460..3bbc3bc7c09 100644
--- a/apps/sim/lib/api/contracts/knowledge/documents.test.ts
+++ b/apps/sim/lib/api/contracts/knowledge/documents.test.ts
@@ -5,11 +5,14 @@ import { describe, expect, it } from 'vitest'
 import { z } from 'zod'
 import {
   bulkCreateDocumentsBodySchema,
+  createDocumentBodySchema,
   documentDataSchema,
   listKnowledgeDocumentsQuerySchema,
   parseDocumentTagFiltersParam,
+  updateDocumentBodySchema,
   upsertDocumentBodySchema,
 } from '@/lib/api/contracts/knowledge/documents'
+import { MAX_DOCUMENT_INDEXED_TEXT_LENGTH } from '@/lib/knowledge/constants'
 import { getDocumentIndexingStatus } from '@/lib/knowledge/documents/types'
 
 describe('document processing response compatibility', () => {
@@ -255,3 +258,39 @@ describe('internal document processingOptions', () => {
     })
   })
 })
+
+describe('document filename and tag bounds', () => {
+  const base = { fileUrl: 'https://example.com/a.txt', fileSize: 1, mimeType: 'text/plain' }
+  const atLimit = 'a'.repeat(MAX_DOCUMENT_INDEXED_TEXT_LENGTH)
+  const overLimit = `${atLimit}a`
+
+  it('accepts a filename and tag exactly at the indexed-text limit', () => {
+    expect(
+      createDocumentBodySchema.safeParse({ ...base, filename: atLimit, tag1: atLimit }).success
+    ).toBe(true)
+  })
+
+  it('rejects a filename over the limit on create, upsert, and update with a descriptive message', () => {
+    for (const schema of [
+      createDocumentBodySchema,
+      upsertDocumentBodySchema,
+      updateDocumentBodySchema,
+    ]) {
+      const result = schema.safeParse({ ...base, filename: overLimit })
+      expect(result.success).toBe(false)
+      expect(result.error?.issues[0]?.message).toBe(
+        `Filename cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+      )
+    }
+  })
+
+  it('rejects a tag value over the limit on create and update', () => {
+    for (const schema of [createDocumentBodySchema, updateDocumentBodySchema]) {
+      const result = schema.safeParse({ ...base, filename: 'a.txt', tag3: overLimit })
+      expect(result.success).toBe(false)
+      expect(result.error?.issues[0]?.message).toBe(
+        `Tag values cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+      )
+    }
+  })
+})
diff --git a/apps/sim/lib/api/contracts/knowledge/documents.ts b/apps/sim/lib/api/contracts/knowledge/documents.ts
index 4b586ff6765..cf61931c859 100644
--- a/apps/sim/lib/api/contracts/knowledge/documents.ts
+++ b/apps/sim/lib/api/contracts/knowledge/documents.ts
@@ -15,7 +15,11 @@ import {
 import { privateSecretProvenanceBundleSchema } from '@/lib/api/contracts/primitives'
 import { defineRouteContract } from '@/lib/api/contracts/types'
 import { PRIVATE_SECRET_PROVENANCE_FIELD } from '@/lib/execution/private-tool-metadata'
-import { getFieldTypeForSlot, MAX_KNOWLEDGE_DOCUMENTS_PER_CREATE } from '@/lib/knowledge/constants'
+import {
+  getFieldTypeForSlot,
+  MAX_DOCUMENT_INDEXED_TEXT_LENGTH,
+  MAX_KNOWLEDGE_DOCUMENTS_PER_CREATE,
+} from '@/lib/knowledge/constants'
 import { DOCUMENT_PROCESSING_STATUSES } from '@/lib/knowledge/documents/types'
 import { getOperatorsForFieldType, isValidFilterValue } from '@/lib/knowledge/filters/types'
 import { knowledgeDocumentUploadMetadataSchema } from '@/lib/knowledge/upload-metadata'
@@ -115,18 +119,32 @@ export function parseDocumentTagFiltersParam(
   return z.array(documentTagFilterSchema).parse(JSON.parse(value))
 }
 
+/** A text tag value that fits its index row; see {@link MAX_DOCUMENT_INDEXED_TEXT_LENGTH}. */
+const documentTagValueSchema = z
+  .string()
+  .max(
+    MAX_DOCUMENT_INDEXED_TEXT_LENGTH,
+    `Tag values cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+  )
+
 export const createDocumentBodySchema = z.object({
-  filename: z.string().min(1, 'Filename is required'),
+  filename: z
+    .string()
+    .min(1, 'Filename is required')
+    .max(
+      MAX_DOCUMENT_INDEXED_TEXT_LENGTH,
+      `Filename cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+    ),
   fileUrl: knowledgeDocumentFileUrlSchema,
   fileSize: z.number().min(1, 'File size must be greater than 0'),
   mimeType: z.string().min(1, 'MIME type is required'),
-  tag1: z.string().optional(),
-  tag2: z.string().optional(),
-  tag3: z.string().optional(),
-  tag4: z.string().optional(),
-  tag5: z.string().optional(),
-  tag6: z.string().optional(),
-  tag7: z.string().optional(),
+  tag1: documentTagValueSchema.optional(),
+  tag2: documentTagValueSchema.optional(),
+  tag3: documentTagValueSchema.optional(),
+  tag4: documentTagValueSchema.optional(),
+  tag5: documentTagValueSchema.optional(),
+  tag6: documentTagValueSchema.optional(),
+  tag7: documentTagValueSchema.optional(),
   documentTagsData: z.string().optional(),
 })
 
@@ -165,7 +183,13 @@ export type SingleCreateDocumentBody = z.input<typeof singleCreateDocumentBodySc
 
 export const upsertDocumentBodySchema = z.object({
   documentId: z.string().optional(),
-  filename: z.string().min(1, 'Filename is required'),
+  filename: z
+    .string()
+    .min(1, 'Filename is required')
+    .max(
+      MAX_DOCUMENT_INDEXED_TEXT_LENGTH,
+      `Filename cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+    ),
   fileUrl: knowledgeDocumentFileUrlSchema,
   fileSize: z.number().min(1, 'File size must be greater than 0'),
   mimeType: z.string().min(1, 'MIME type is required'),
@@ -196,7 +220,14 @@ export const bulkCreateDocumentsResponseSchema = z.object({
 })
 
 export const updateDocumentBodySchema = z.object({
-  filename: z.string().min(1, 'Filename is required').optional(),
+  filename: z
+    .string()
+    .min(1, 'Filename is required')
+    .max(
+      MAX_DOCUMENT_INDEXED_TEXT_LENGTH,
+      `Filename cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+    )
+    .optional(),
   enabled: z.boolean().optional(),
   chunkCount: z.number().min(0).optional(),
   tokenCount: z.number().min(0).optional(),
@@ -205,13 +236,13 @@ export const updateDocumentBodySchema = z.object({
   processingError: z.string().optional(),
   markFailedDueToTimeout: z.boolean().optional(),
   retryProcessing: z.boolean().optional(),
-  tag1: z.string().optional(),
-  tag2: z.string().optional(),
-  tag3: z.string().optional(),
-  tag4: z.string().optional(),
-  tag5: z.string().optional(),
-  tag6: z.string().optional(),
-  tag7: z.string().optional(),
+  tag1: documentTagValueSchema.optional(),
+  tag2: documentTagValueSchema.optional(),
+  tag3: documentTagValueSchema.optional(),
+  tag4: documentTagValueSchema.optional(),
+  tag5: documentTagValueSchema.optional(),
+  tag6: documentTagValueSchema.optional(),
+  tag7: documentTagValueSchema.optional(),
   number1: z.string().optional(),
   number2: z.string().optional(),
   number3: z.string().optional(),
diff --git a/apps/sim/lib/knowledge/application/documents.ts b/apps/sim/lib/knowledge/application/documents.ts
index dc584acb7ac..036aa97aea2 100644
--- a/apps/sim/lib/knowledge/application/documents.ts
+++ b/apps/sim/lib/knowledge/application/documents.ts
@@ -68,7 +68,7 @@ import {
   toKnowledgeTagFilterConditions,
 } from '@/lib/knowledge/tags/filter-resolution'
 import { getDocumentTagDefinitions } from '@/lib/knowledge/tags/service'
-import { validateTagValue } from '@/lib/knowledge/tags/utils'
+import { validateTagValue, validateTagValueLength } from '@/lib/knowledge/tags/utils'
 import { StorageService } from '@/lib/uploads'
 import { generateKnowledgeBaseFileKey } from '@/lib/uploads/contexts/knowledge-base/knowledge-base-file-manager'
 import { recordKnowledgeBaseFileOwnership } from '@/lib/uploads/server/metadata'
@@ -252,7 +252,9 @@ async function resolveKnowledgeDocumentTagValueUpdates(
         `Tag "${definition.displayName}" requires a value; use null to clear it`
       )
     }
-    const validationError = validateTagValue(definition.displayName, value, definition.fieldType)
+    const validationError =
+      validateTagValueLength(definition.displayName, value) ??
+      validateTagValue(definition.displayName, value, definition.fieldType)
     if (validationError) {
       throw new OrchestrationError('validation', validationError)
     }
diff --git a/apps/sim/lib/knowledge/connectors/sync-persistence.test.ts b/apps/sim/lib/knowledge/connectors/sync-persistence.test.ts
index 34c9e6a2423..fd90b59c1d4 100644
--- a/apps/sim/lib/knowledge/connectors/sync-persistence.test.ts
+++ b/apps/sim/lib/knowledge/connectors/sync-persistence.test.ts
@@ -27,7 +27,16 @@ vi.mock('@/lib/knowledge/documents/storage-cleanup', () => ({
   }),
   isKnowledgeBaseOwnedStorageKey: (key: string) => key.startsWith('kb/'),
 }))
-vi.mock('@/connectors/registry.server', () => ({ CONNECTOR_REGISTRY: {} }))
+vi.mock('@/connectors/registry.server', () => ({
+  CONNECTOR_REGISTRY: {
+    fixture: {
+      mapTags: (metadata: Record<string, unknown>) => ({
+        label: metadata.label,
+        owner: metadata.owner,
+      }),
+    },
+  },
+}))
 
 import { MAX_ACL_TOKENS } from '@/lib/knowledge/access/tokens'
 import { getConnectorFailureDiagnostic } from '@/lib/knowledge/connectors/connector-error'
@@ -35,6 +44,7 @@ import {
   addDocument,
   persistDocumentAcls,
   persistSourceDocumentFailures,
+  resolveTagMapping,
 } from '@/lib/knowledge/connectors/sync-persistence'
 
 const CONNECTOR = 'connector-1'
@@ -350,6 +360,18 @@ describe('persistSourceDocumentFailures', () => {
     expect(JSON.stringify(dbChainMockFns.set.mock.calls)).not.toContain('private body')
     expect(dbChainMockFns.delete).not.toHaveBeenCalled()
   })
+  it('bounds a source title that would exceed the filename index row limit', async () => {
+    leaseHeld()
+    const title = 'x'.repeat(5000)
+    await persistSourceDocumentFailures({
+      ...input,
+      documents: [{ ...input.documents[0], title }],
+      priorByExternalId: new Map(),
+    })
+    const [rows] = dbChainMockFns.values.mock.calls[0] as [Array<{ filename: string }>]
+    expect(rows[0].filename).toBe(`${'x'.repeat(509)}...`)
+    expect(rows[0].filename.length).toBe(512)
+  })
   it('refuses to commit a failure under a reclaimed lease', async () => {
     queueTableRows(schemaMock.knowledgeBase, [{ id: 'kb' }])
     await expect(
@@ -416,3 +438,35 @@ describe('organization source cache persistence', () => {
     expect(mockUploadFile).not.toHaveBeenCalled()
   })
 })
+
+describe('resolveTagMapping', () => {
+  it('bounds a mapped tag value that would exceed its index row limit and keeps a short one intact', () => {
+    const tags = resolveTagMapping(
+      'fixture',
+      { label: 'y'.repeat(5000), owner: 'Purchasing' },
+      { tagSlotMapping: { label: 'tag1', owner: 'tag2' } }
+    )
+    expect(tags?.tag1).toBe(`${'y'.repeat(509)}...`)
+    expect(tags?.tag2).toBe('Purchasing')
+  })
+
+  it('keeps a value exactly at the limit untouched', () => {
+    const atLimit = 'z'.repeat(512)
+    const tags = resolveTagMapping(
+      'fixture',
+      { label: atLimit },
+      { tagSlotMapping: { label: 'tag1' } }
+    )
+    expect(tags?.tag1).toBe(atLimit)
+  })
+
+  it('cuts by code point so a bounded value never ends in half a surrogate pair', () => {
+    const tags = resolveTagMapping(
+      'fixture',
+      { label: '\u{1F600}'.repeat(600) },
+      { tagSlotMapping: { label: 'tag1' } }
+    )
+    expect(tags?.tag1).toBe(`${'\u{1F600}'.repeat(254)}...`)
+    expect(tags?.tag1?.length).toBeLessThanOrEqual(512)
+  })
+})
diff --git a/apps/sim/lib/knowledge/connectors/sync-persistence.ts b/apps/sim/lib/knowledge/connectors/sync-persistence.ts
index 33b53184ac2..48946ea7067 100644
--- a/apps/sim/lib/knowledge/connectors/sync-persistence.ts
+++ b/apps/sim/lib/knowledge/connectors/sync-persistence.ts
@@ -3,6 +3,7 @@ import { document, embedding, knowledgeBase, knowledgeConnector } from '@sim/db/
 import { createLogger } from '@sim/logger'
 import { chunkArray } from '@sim/utils/helpers'
 import { generateId } from '@sim/utils/id'
+import { truncateAtCodePoint } from '@sim/utils/string'
 import { and, eq, exists, inArray, isNull, lt, or, sql } from 'drizzle-orm'
 import { getInternalApiBaseUrl } from '@/lib/core/utils/urls'
 import type { DbOrTx } from '@/lib/db/types'
@@ -18,6 +19,7 @@ import type { ConnectorFailureDiagnostic } from '@/lib/knowledge/connectors/conn
 import { resolveSourceModifiedAt } from '@/lib/knowledge/connectors/source-modified-at'
 import { SOURCE_CONTENT_ERROR } from '@/lib/knowledge/connectors/sync-limits'
 import { assertSyncLeaseHeldInTx, type SyncWriteLease } from '@/lib/knowledge/connectors/sync-lock'
+import { MAX_DOCUMENT_INDEXED_TEXT_LENGTH } from '@/lib/knowledge/constants'
 import type { DocumentData } from '@/lib/knowledge/documents/service'
 import { enqueueKnowledgeStorageCleanup } from '@/lib/knowledge/documents/storage-cleanup'
 import {
@@ -173,6 +175,23 @@ export async function persistDocumentAcls(
 
 const MAX_SAFE_TITLE_LENGTH = 200
 
+/** The suffix a cut value carries, counted inside {@link MAX_DOCUMENT_INDEXED_TEXT_LENGTH}. */
+const INDEXED_TEXT_CUT_SUFFIX = '...'
+
+/**
+ * Source titles and mapped tag values are untrusted machine input with no caller to refuse them,
+ * so they are cut to {@link MAX_DOCUMENT_INDEXED_TEXT_LENGTH} code units, suffix included, and
+ * never inside a surrogate pair. The result always passes the document APIs' own bound.
+ */
+function boundIndexedText(value: string): string {
+  if (value.length <= MAX_DOCUMENT_INDEXED_TEXT_LENGTH) return value
+  return truncateAtCodePoint(
+    value,
+    MAX_DOCUMENT_INDEXED_TEXT_LENGTH - INDEXED_TEXT_CUT_SUFFIX.length,
+    INDEXED_TEXT_CUT_SUFFIX
+  )
+}
+
 function sanitizeStorageTitle(title: string): string {
   return title.replace(/[^a-zA-Z0-9.-]/g, '_').slice(0, MAX_SAFE_TITLE_LENGTH)
 }
@@ -250,7 +269,8 @@ export function resolveTagMapping(
   const result: Partial<DocumentTags> = {}
   for (const [semanticKey, slot] of Object.entries(mapping)) {
     const value = semanticTags[semanticKey]
-    ;(result as Record<string, unknown>)[slot] = value != null ? value : null
+    ;(result as Record<string, unknown>)[slot] =
+      typeof value === 'string' ? boundIndexedText(value) : (value ?? null)
   }
   return result
 }
@@ -278,7 +298,7 @@ function buildSkippedDocumentRow(
   return {
     id: generateId(),
     knowledgeBaseId,
-    filename: extDoc.title,
+    filename: boundIndexedText(extDoc.title),
     fileUrl: '',
     storageKey: null,
     /** No artifact was stored; a provider's reported source size is not local storage usage. */
@@ -630,7 +650,7 @@ export async function addDocument(
     await tx.insert(document).values({
       id: documentId,
       knowledgeBaseId,
-      filename: extDoc.title,
+      filename: boundIndexedText(extDoc.title),
       fileUrl,
       storageKey: fileInfo.key,
       fileSize: artifact.bytes.length,
@@ -745,7 +765,7 @@ export async function updateDocument(
     await tx
       .update(document)
       .set({
-        filename: extDoc.title,
+        filename: boundIndexedText(extDoc.title),
         fileUrl,
         storageKey: fileInfo.key,
         fileSize: artifact.bytes.length,
diff --git a/apps/sim/lib/knowledge/constants.ts b/apps/sim/lib/knowledge/constants.ts
index b65aa6bd77f..f6de98cf0a0 100644
--- a/apps/sim/lib/knowledge/constants.ts
+++ b/apps/sim/lib/knowledge/constants.ts
@@ -3,6 +3,14 @@ import { MAX_FOLDERS_PER_WORKSPACE } from '@/lib/folders/constants'
 /** Max character length for a knowledge base description, enforced at every layer (UI, internal API, v1 API). */
 export const KNOWLEDGE_BASE_DESCRIPTION_MAX_LENGTH = 10_000
 
+/**
+ * Max character length for a document's filename and text tag values. Both sit under btree
+ * indexes, and Postgres refuses an index row past about 2.7 KB (SQLSTATE 54000); 512 characters
+ * keeps a four-byte-per-character value inside that ceiling. Connectors truncate source titles to
+ * it; the document APIs reject longer input.
+ */
+export const MAX_DOCUMENT_INDEXED_TEXT_LENGTH = 512
+
 /** Hard bound for path-indexed knowledge folder trees and recursive cascades. */
 export const MAX_KNOWLEDGE_FOLDERS_PER_WORKSPACE = MAX_FOLDERS_PER_WORKSPACE
 
diff --git a/apps/sim/lib/knowledge/documents/service.ts b/apps/sim/lib/knowledge/documents/service.ts
index 3d6820369cf..36732b8e036 100644
--- a/apps/sim/lib/knowledge/documents/service.ts
+++ b/apps/sim/lib/knowledge/documents/service.ts
@@ -179,6 +179,7 @@ import {
   parseNumberValue,
   uncompilableTagFilterError,
   validateTagValue,
+  validateTagValueLength,
 } from '@/lib/knowledge/tags/utils'
 import type { ProcessedDocumentTags } from '@/lib/knowledge/types'
 import { embeddingVectorValues } from '@/lib/knowledge/vector-columns'
@@ -552,7 +553,9 @@ function resolveDocumentTags(
 
     const rawValue = typeof tag.value === 'string' ? tag.value.trim() : tag.value
     const actualFieldType = existingDef.fieldType || fieldType
-    const validationError = validateTagValue(tagName, String(rawValue), actualFieldType)
+    const validationError =
+      validateTagValueLength(tagName, String(rawValue)) ??
+      validateTagValue(tagName, String(rawValue), actualFieldType)
     if (validationError) {
       typeErrors.push(validationError)
     }
diff --git a/apps/sim/lib/knowledge/tags/utils.test.ts b/apps/sim/lib/knowledge/tags/utils.test.ts
index d99b080eecc..078e7c563d6 100644
--- a/apps/sim/lib/knowledge/tags/utils.test.ts
+++ b/apps/sim/lib/knowledge/tags/utils.test.ts
@@ -2,7 +2,11 @@
  * @vitest-environment node
  */
 import { describe, expect, it } from 'vitest'
-import { coerceTagFilterValue, validateTagValue } from '@/lib/knowledge/tags/utils'
+import {
+  coerceTagFilterValue,
+  validateTagValue,
+  validateTagValueLength,
+} from '@/lib/knowledge/tags/utils'
 
 describe('coerceTagFilterValue', () => {
   it('accepts exactly what validateTagValue accepts', () => {
@@ -68,3 +72,12 @@ describe('validateTagValue', () => {
     expect(validateTagValue('name', 'anything', 'json')).toBeNull()
   })
 })
+
+describe('validateTagValueLength', () => {
+  it('accepts a value at the indexed-text limit and names the tag past it', () => {
+    expect(validateTagValueLength('Labels', 'a'.repeat(512))).toBeNull()
+    expect(validateTagValueLength('Labels', 'a'.repeat(513))).toBe(
+      'Tag "Labels" cannot exceed 512 characters'
+    )
+  })
+})
diff --git a/apps/sim/lib/knowledge/tags/utils.ts b/apps/sim/lib/knowledge/tags/utils.ts
index 1d00da28889..4cd7ec4b869 100644
--- a/apps/sim/lib/knowledge/tags/utils.ts
+++ b/apps/sim/lib/knowledge/tags/utils.ts
@@ -1,4 +1,5 @@
 import { OrchestrationError } from '@/lib/core/orchestration/types'
+import { MAX_DOCUMENT_INDEXED_TEXT_LENGTH } from '@/lib/knowledge/constants'
 
 const DATE_ONLY_PATTERN = /^\d{4}-\d{2}-\d{2}$/
 
@@ -94,6 +95,17 @@ export function uncompilableTagFilterError(filter: {
  * Validate a tag value against its expected field type
  * Returns an error message if invalid, or null if valid
  */
+/**
+ * Text tag values sit under an index whose rows Postgres caps in size; a value past
+ * {@link MAX_DOCUMENT_INDEXED_TEXT_LENGTH} would fail the document write itself, so it is
+ * refused with a message naming the tag instead.
+ */
+export function validateTagValueLength(tagName: string, value: string): string | null {
+  return value.length > MAX_DOCUMENT_INDEXED_TEXT_LENGTH
+    ? `Tag "${tagName}" cannot exceed ${MAX_DOCUMENT_INDEXED_TEXT_LENGTH} characters`
+    : null
+}
+
 export function validateTagValue(tagName: string, value: string, fieldType: string): string | null {
   if (fieldType !== 'boolean' && fieldType !== 'number' && fieldType !== 'date') return null
 
diff --git a/packages/utils/src/string.test.ts b/packages/utils/src/string.test.ts
index 1a33db3ce04..b817c2fff8b 100644
--- a/packages/utils/src/string.test.ts
+++ b/packages/utils/src/string.test.ts
@@ -16,6 +16,7 @@ import {
   slugify,
   stripVersionSuffix,
   truncate,
+  truncateAtCodePoint,
 } from './string.js'
 
 describe('slugify', () => {
@@ -304,3 +305,19 @@ describe('hasRegexMetacharacter', () => {
     }
   })
 })
+
+describe('truncateAtCodePoint', () => {
+  it('returns the input untouched when it fits', () => {
+    expect(truncateAtCodePoint('ab😀cd', 10)).toBe('ab😀cd')
+  })
+
+  it('cuts like truncate when the cut lands between code points', () => {
+    expect(truncateAtCodePoint('ab😀cd', 4)).toBe('ab😀...')
+    expect(truncateAtCodePoint('hello world', 8, ' …')).toBe('hello wo …')
+  })
+
+  it('moves the cut back one unit rather than splitting a surrogate pair', () => {
+    expect(truncateAtCodePoint('ab😀cd', 3)).toBe('ab...')
+    expect(truncateAtCodePoint('😀'.repeat(3), 3)).toBe('😀...')
+  })
+})
diff --git a/packages/utils/src/string.ts b/packages/utils/src/string.ts
index 5518821940f..8cf8dbb5c33 100644
--- a/packages/utils/src/string.ts
+++ b/packages/utils/src/string.ts
@@ -33,6 +33,21 @@ export function truncate(str: string, sliceLength: number, suffix = '...'): stri
   return str.length > sliceLength ? str.slice(0, sliceLength) + suffix : str
 }
 
+/**
+ * Like {@link truncate}, but never cuts inside a surrogate pair: when the code unit at the cut
+ * would split an astral character, the cut moves one unit earlier. Lengths are still counted in
+ * UTF-16 code units, so the result of a cut is at most `sliceLength + suffix.length` units.
+ *
+ * @example
+ * truncateAtCodePoint('ab😀cd', 3)   // 'ab...' (the cut at 3 would split the emoji)
+ * truncateAtCodePoint('ab😀cd', 4)   // 'ab😀...'
+ */
+export function truncateAtCodePoint(str: string, sliceLength: number, suffix = '...'): string {
+  if (str.length <= sliceLength) return str
+  const splitsPair = sliceLength > 0 && (str.charCodeAt(sliceLength - 1) & 0xfc00) === 0xd800
+  return str.slice(0, splitsPair ? sliceLength - 1 : sliceLength) + suffix
+}
+
 /**
  * Lowercases `value` into the `[a-z0-9-]` charset: every run of other characters
  * becomes one hyphen, and leading and trailing hyphens are dropped.