diff --git a/CHANGELOG.md b/CHANGELOG.md
index 70889d14..aa2786a5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,12 +4,14 @@ All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
-## Version 4.0.0 - TBD
+## Version 4.0.0 - 2026-08-03
 
 **BREAKING CHANGE: The attachments plugin comes now without hyperscaler dependencies, please make sure to install them accordingly!**
+**BREAKING CHANGE: Projects that explicitly set `attachments.outbox: true` in their own CDS configuration must rename the key to `outboxed`.**
 
 ### Changed
 
+- The `outbox` configuration key under `cds.requires.attachments` has been renamed to `outboxed`. A deprecation warning is logged at startup when the old key is detected.
 - Cloud storage SDKs (`@aws-sdk/client-s3`, `@aws-sdk/lib-storage`, `@azure/storage-blob`, `@google-cloud/storage`) are now optional peer dependencies. Install only the SDK(s) for the provider you use (e.g. `npm install @aws-sdk/client-s3 @aws-sdk/lib-storage` for AWS S3). A clear error message with the exact install command is shown if a required SDK is missing at runtime.
 
 ### Fixed
diff --git a/lib/generic-handlers.js b/lib/generic-handlers.js
index 3665542e..05728034 100644
--- a/lib/generic-handlers.js
+++ b/lib/generic-handlers.js
@@ -1,12 +1,7 @@
 const cds = require("@sap/cds")
 const LOG = cds.log("attachments")
 const { extname } = require("path")
-const {
-  MAX_FILE_SIZE,
-  sizeInBytes,
-  checkMimeTypeMatch,
-  inferTargetCAP8,
-} = require("./helper")
+const { MAX_FILE_SIZE, sizeInBytes, checkMimeTypeMatch } = require("./helper")
 const { getMime } = require("./mime")
 
 /**
@@ -40,13 +35,7 @@ async function finalizePrepareAttachment(data, req, prefix) {
     // Only try to populate parent keys if there is a parent reference
     if (parentRef && parentRef.length > 0) {
       let target
-      if (cds.infer?.target) {
-        // CAP 9+: Use cds.infer.target
-        target = cds.infer.target({ SELECT: { from: { ref: parentRef } } })
-      } else {
-        // CAP 8 fallback: Use inferTargetCAP8 helper
-        target = inferTargetCAP8(req, parentRef)
-      }
+      target = cds.infer.target({ SELECT: { from: { ref: parentRef } } })
 
       if (target?.keys) {
         LOG.info(`Populating parent keys for attachment upload`, target)
diff --git a/lib/helper.js b/lib/helper.js
index 6d4d1c5f..58c96af8 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -484,40 +484,6 @@ async function computeHash(input) {
   return hash.digest("hex")
 }
 
-/**
- * Resolves the target entity definition from a subject ref in CAP 8 (fallback for CAP 9+ cds.infer).
- * Walks the ref path through the model and returns the draft entity if draft-enabled.
- * @param {import('@sap/cds').Request} req - The current request (unused, kept for API symmetry with cds.infer)
- * @param {Array<string|{id: string}>} ref - The subject ref array from req.subject
- * @returns {import('@sap/cds').entity|null} The resolved entity definition, or null if not found
- */
-function inferTargetCAP8(req, ref) {
-  const model = cds.context?.model || cds.model
-
-  // Extract entity/navigation names from ref array
-  // Handle both simple strings and objects with .id property
-  const names = ref
-    .map((part) => {
-      if (typeof part === "string") return part
-      if (typeof part === "object" && part.id) return part.id
-      return null
-    })
-    .filter(Boolean)
-
-  const name = names.join(".")
-
-  let target = model.definitions[name]
-  if (!target) return null
-
-  // draft fallback
-  if (target["@odata.draft.enabled"]) {
-    const draft = model.definitions[`${name}.drafts`]
-    if (draft) target = draft
-  }
-
-  return target
-}
-
 const multipliers = {}
 multipliers.B = 1
 multipliers.KB = multipliers.B * 1024
@@ -952,7 +918,6 @@ module.exports = {
   traverseEntity,
   buildBackAssocChain,
   MAX_FILE_SIZE,
-  inferTargetCAP8,
   getAttachmentKind,
   handleDuplicates,
   createSizeCheckHandler,
diff --git a/lib/plugin.js b/lib/plugin.js
index 37e5231e..02052334 100644
--- a/lib/plugin.js
+++ b/lib/plugin.js
@@ -7,18 +7,11 @@ const {
   validateAttachmentMimeType,
   validateAndInsertAttachmentFromDBHandler,
 } = require("./generic-handlers")
-const {
-  inferTargetCAP8,
-  getAttachmentKind,
-  handleDuplicates,
-} = require("./helper")
+const { getAttachmentKind, handleDuplicates } = require("./helper")
 require("./csn-runtime-extension")
 const LOG = cds.log("attachments")
 
-cds.on(
-  cds.version.split(".")[0] >= 8 ? "compile.to.edmx" : "loaded",
-  unfoldModel,
-)
+cds.on("compile.to.edmx", unfoldModel)
 
 // Register the db handler ONCE (not per-service) to intercept attachment INSERT
 // and handle it through the attachments service instead of native DB insert
@@ -27,6 +20,11 @@ cds.on(
 // NOTE: Must use db.prepend() to ensure handlers run before existing ones
 cds.once("served", () => {
   if (!cds.env.requires.attachments) return
+  if (cds.env.requires.attachments?.outbox !== undefined) {
+    LOG.warn(
+      "`cds.requires.attachments.outbox` is deprecated; use `outboxed` instead.",
+    )
+  }
   const { db } = cds.services
 
   db.prepend(() => {
@@ -853,8 +851,7 @@ cds.ApplicationService.handle_attachments = cds.service.impl(async function () {
     if (req.query?.INSERT?.into.ref.length > 1) {
       const ref = req.query.INSERT.into.ref.slice(0, -1)
       const parentQuery = { SELECT: { from: { ref: ref }, one: true } }
-      const parent =
-        cds.infer?.target?.(parentQuery) || inferTargetCAP8(req, ref)
+      const parent = cds.infer.target(parentQuery)
       if (!parent) {
         LOG.warn(
           `Could not determine parent target. Ref: ${JSON.stringify(ref)}`,
@@ -935,8 +932,7 @@ cds.ApplicationService.handle_attachments = cds.service.impl(async function () {
     if (req.query?.DELETE?.from?.ref.length > 1) {
       const ref = req.query.DELETE.from.ref.slice(0, -1)
       const parentQuery = { SELECT: { from: { ref: ref }, one: true } }
-      const parent =
-        cds.infer?.target?.(parentQuery) || inferTargetCAP8(req, ref)
+      const parent = cds.infer.target(parentQuery)
       if (!parent) {
         LOG.warn(
           `Could not determine parent target. Ref: ${JSON.stringify(ref)}`,
diff --git a/package.json b/package.json
index 2371596d..6a9dbc15 100644
--- a/package.json
+++ b/package.json
@@ -35,7 +35,7 @@
     "@aws-sdk/lib-storage": "^3",
     "@azure/storage-blob": "^12",
     "@google-cloud/storage": "^7",
-    "@sap/cds": ">=8"
+    "@sap/cds": ">=9"
   },
   "peerDependenciesMeta": {
     "@aws-sdk/client-s3": {
@@ -101,7 +101,7 @@
         }
       },
       "attachments": {
-        "outbox": true,
+        "outboxed": true,
         "scan": true,
         "deduplicateFileNames": true,
         "scanExpiryMs": 259200000,
diff --git a/srv/attachments/gcp.js b/srv/attachments/gcp.js
index 4d48cc12..9454a724 100644
--- a/srv/attachments/gcp.js
+++ b/srv/attachments/gcp.js
@@ -414,17 +414,8 @@ module.exports = class GoogleAttachmentsService extends (
     )
 
     const file = bucket.file(blobName)
-    let response
-    try {
-      response = await file.delete()
-    } catch (error) {
-      if (error.statusCode === 404) {
-        response = error
-      } else {
-        throw error
-      }
-    }
-    if (response?.[0]?.statusCode !== 204) {
+    const [response] = await file.delete({ ignoreNotFound: true })
+    if (response?.statusCode !== 204) {
       LOG.warn("File has not been deleted from Google Cloud Storage", {
         blobName,
         bucketName: bucket.name,
diff --git a/tests/integration/attachments-non-draft.test.js b/tests/integration/attachments-non-draft.test.js
index ac87c452..478df2f2 100644
--- a/tests/integration/attachments-non-draft.test.js
+++ b/tests/integration/attachments-non-draft.test.js
@@ -1,5 +1,4 @@
 const cds = require("@sap/cds")
-const { test } = cds.test()
 const {
   waitForScanStatus,
   newIncident,
@@ -10,10 +9,7 @@ const {
 const path = require("path")
 
 const app = path.resolve(__dirname, "../incidents-app")
-const { GET, POST, PATCH, DELETE, PUT } = withUser(
-  "alice",
-  require("@cap-js/cds-test")(app),
-)
+const { GET, POST, PATCH, DELETE, PUT } = withUser("alice", cds.test(app))
 const { join } = cds.utils.path
 const { createReadStream, readFileSync, statSync } = cds.utils.fs
 
@@ -32,7 +28,7 @@ describe("Tests for uploading/deleting and fetching attachments through API call
       originalDeduplicateFileNames
   })
 
-  let log = test.log()
+  let log = cds.test.log()
   const { createAttachmentMetadata, uploadAttachmentContent } = createHelpers()
 
   // Allow background operations (malware scan status updates) to complete before teardown
@@ -1059,7 +1055,7 @@ describe("Testing max and min amounts of attachments", () => {
     })
   })
 
-  it("custom error message can be specified targeting composition property", async () => {
+  it("Custom error message can be specified targeting composition property", async () => {
     await POST(`odata/v4/validation-test-non-draft/Incidents`, {
       customer_ID: "1004155",
       title: "ABC",
@@ -1081,7 +1077,7 @@ describe("Testing max and min amounts of attachments", () => {
     })
   })
 
-  it("custom error message can be specified for entity", async () => {
+  it("Custom error message can be specified for entity", async () => {
     await POST(`odata/v4/validation-test-non-draft/Incidents`, {
       customer_ID: "1004155",
       title: "ABC",