diff --git a/.github/actions/build-xcframework/action.yml b/.github/actions/build-xcframework/action.yml
index 9fad0f245..ead5d9516 100644
--- a/.github/actions/build-xcframework/action.yml
+++ b/.github/actions/build-xcframework/action.yml
@@ -5,7 +5,7 @@ inputs:
   xcode-version:
     description: 'Xcode version to use'
     required: false
-    default: '26.3'
+    default: '26.6'
   tag-name:
     description: 'Tag name for release URLs (empty for manual builds)'
     required: false
diff --git a/.github/actions/uitests/action.yml b/.github/actions/uitests/action.yml
index d670a85c0..6b7649355 100644
--- a/.github/actions/uitests/action.yml
+++ b/.github/actions/uitests/action.yml
@@ -5,7 +5,7 @@ inputs:
   xcode-version:
     description: 'Xcode version to use'
     required: false
-    default: '26.3'
+    default: '26.6'
   platform:
     description: 'Platform to test (ios or macos)'
     required: true
@@ -230,8 +230,7 @@ runs:
         set -o pipefail
         record_status=0
         baseline_result_bundle="${RUNNER_TEMP:-/tmp}/swiftui-baseline-${GITHUB_RUN_ID}-${GITHUB_RUN_ATTEMPT:-0}-${{ inputs.artifact-name }}.xcresult"
-        # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-        NSUnbufferedIO=YES tuist_xcodebuild "$baseline_result_bundle" test -IDEPackageEnablePrebuilts=NO \
+        NSUnbufferedIO=YES tuist_xcodebuild "$baseline_result_bundle" test \
           -workspace Example.xcworkspace \
           -scheme SUI_UITests \
           -destination "${{ inputs.destination }}" \
@@ -287,8 +286,7 @@ runs:
         echo "artifact_dir=$uitest_tmp/artifacts" >> "$GITHUB_OUTPUT"
         echo "xcresult_archive=$uitest_tmp/${{ inputs.artifact-name }}.xcresult.zip" >> "$GITHUB_OUTPUT"
         set -o pipefail
-        # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-        NSUnbufferedIO=YES tuist_xcodebuild "$result_bundle" test -IDEPackageEnablePrebuilts=NO \
+        NSUnbufferedIO=YES tuist_xcodebuild "$result_bundle" test \
           -workspace Example.xcworkspace \
           -scheme OSUI_UITests \
           -destination "${{ inputs.destination }}" \
diff --git a/.github/workflows/build_xcframework.yml b/.github/workflows/build_xcframework.yml
index db3625d8c..912af9d40 100644
--- a/.github/workflows/build_xcframework.yml
+++ b/.github/workflows/build_xcframework.yml
@@ -10,7 +10,9 @@ permissions:
 jobs:
   build_xcframework:
     name: Build XCFrameworks
-    runs-on: macos-15
+    runs-on:
+      - macos-15
+      - xcode-26.6
     env:
       OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH: 1
       OPENSWIFTUI_USE_LOCAL_DEPS: 1
diff --git a/.github/workflows/compatibility_tests.yml b/.github/workflows/compatibility_tests.yml
index e97e2b902..d65f1680b 100644
--- a/.github/workflows/compatibility_tests.yml
+++ b/.github/workflows/compatibility_tests.yml
@@ -29,12 +29,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
-    # Limit to self-hosted to reduce action cost
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       OPENSWIFTUI_WERROR: 0 # Disable it to avoid enable OAG's werror and hit conflicts
       OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH: 1
@@ -58,10 +57,8 @@ jobs:
       - name: Run compatibility tests on OpenSwiftUI + macOS
         run: |
           set -o pipefail
-          # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-          # Swift 6.2 also crashes while indexing AppKit with the private framework shims.
+          # Swift 6.3.3 still crashes while indexing AppKit with the private framework shims.
           NSUnbufferedIO=YES swift test \
-            --disable-experimental-prebuilts \
             --disable-index-store \
             --filter OpenSwiftUICompatibilityTests \
             --build-path .build-compatibility-test-debug \
@@ -71,10 +68,8 @@ jobs:
       - name: Run compatibility tests on SwiftUI + macOS
         run: |
           set -o pipefail
-          # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-          # Swift 6.2 also crashes while indexing AppKit with the private framework shims.
+          # Swift 6.3.3 still crashes while indexing AppKit with the private framework shims.
           NSUnbufferedIO=YES swift test \
-            --disable-experimental-prebuilts \
             --disable-index-store \
             --filter OpenSwiftUICompatibilityTests \
             --build-path .build-compatibility-test-debug \
@@ -90,16 +85,15 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
         ios-version: ["18.5"]
         include:
           - ios-version: "18.5"
             ios-simulator-name: "iPhone 16 Pro"
-    # Limit to self-hosted to reduce action cost
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       OPENSWIFTUI_WERROR: 0 # Disable it to avoid enable OAG's werror and hit conflicts
       OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH: 1
@@ -150,19 +144,15 @@ jobs:
         run: |
           set -o pipefail
           source Scripts/Tuist/common.sh
-          # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-          # Xcode 26.3 + iOS 18.5 fails to launch arm64 SwiftPM package test
-          # runners with CoreSimulator codesigning errors; force the x86_64
-          # simulator slice until that launch path is fixed.
+          # Xcode 26.6 can otherwise link the host macro object into the iOS Simulator test bundle.
           NSUnbufferedIO=YES tuist_xcodebuild "$OPENSWIFTUI_RESULT_BUNDLE_PATH" test -IDEPackageEnablePrebuilts=NO \
             -scheme OpenSwiftUI \
             -configuration Debug \
-            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }},arch=x86_64" \
+            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }}" \
             -only-testing:OpenSwiftUICompatibilityTests \
             -derivedDataPath "$OPENSWIFTUI_DERIVED_DATA_PATH" \
             -skipMacroValidation \
             -skipPackagePluginValidation \
-            ONLY_ACTIVE_ARCH=YES \
             2>&1 | xcbeautify --renderer github-actions --preserve-unbeautified
         env:
           OPENSWIFTUI_COMPATIBILITY_TEST: 0
@@ -170,18 +160,15 @@ jobs:
         run: |
           set -o pipefail
           source Scripts/Tuist/common.sh
-          # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-          # See the OpenSwiftUI iOS compatibility step above: force x86_64 to
-          # avoid the arm64 package test runner launch/codesigning failure.
+          # Match the package prebuilt setting used by the OpenSwiftUI compatibility test.
           NSUnbufferedIO=YES tuist_xcodebuild "$SWIFTUI_RESULT_BUNDLE_PATH" test -IDEPackageEnablePrebuilts=NO \
             -scheme OpenSwiftUI \
             -configuration Debug \
-            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }},arch=x86_64" \
+            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }}" \
             -only-testing:OpenSwiftUICompatibilityTests \
             -derivedDataPath "$SWIFTUI_DERIVED_DATA_PATH" \
             -skipMacroValidation \
             -skipPackagePluginValidation \
-            ONLY_ACTIVE_ARCH=YES \
             2>&1 | xcbeautify --renderer github-actions --preserve-unbeautified
         env:
           OPENSWIFTUI_COMPATIBILITY_TEST: 1
diff --git a/.github/workflows/documentation.yml b/.github/workflows/documentation.yml
index 9c8e6ce14..17b74c6f1 100644
--- a/.github/workflows/documentation.yml
+++ b/.github/workflows/documentation.yml
@@ -14,8 +14,8 @@ jobs:
   build:
     name: Build DocC site
     runs-on:
-      - self-hosted
       - macos-15
+      - xcode-26.6
     env:
       OPENSWIFTUI_WERROR: 0
       OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH: 1
@@ -36,7 +36,7 @@ jobs:
       - name: Setup Xcode
         uses: OpenSwiftUIProject/setup-xcode@v2
         with:
-          xcode-version: "26.3"
+          xcode-version: "26.6"
       - name: Set up build environment
         run: Scripts/CI/darwin_setup_build.sh
         shell: bash
diff --git a/.github/workflows/ios.yml b/.github/workflows/ios.yml
index 865d4604d..fb6b6c210 100644
--- a/.github/workflows/ios.yml
+++ b/.github/workflows/ios.yml
@@ -32,16 +32,15 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
         ios-version: ["18.5"]
         include:
           - ios-version: "18.5"
             ios-simulator-name: "iPhone 16 Pro"
-    # Limit to self-hosted to reduce action cost
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       OPENSWIFTUI_WERROR: 0 # Disable it to avoid enable OAG's werror and hit conflicts
       OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH: 1
@@ -93,34 +92,27 @@ jobs:
         run: |
           set -o pipefail
           source Scripts/Tuist/common.sh
-          # Xcode 26.3 + iOS 18.5 fails to launch arm64 SwiftPM package test
-          # runners with CoreSimulator codesigning errors. Build the x86_64
-          # simulator slice to match the test command below until that is fixed.
-          # Swift 6.2 macro prebuilts do not support the x86_64 simulator
-          # testable macro target, so build SwiftSyntax from source instead.
+          # Xcode 26.6 can otherwise link the host macro object into the iOS Simulator test bundle.
           NSUnbufferedIO=YES tuist_xcodebuild "$BUILD_RESULT_BUNDLE_PATH" build -IDEPackageEnablePrebuilts=NO \
             -scheme OpenSwiftUI \
             -configuration Debug \
-            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }},arch=x86_64" \
+            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }}" \
             -derivedDataPath "$DERIVED_DATA_PATH" \
             -skipMacroValidation \
             -skipPackagePluginValidation \
-            ONLY_ACTIVE_ARCH=YES \
             2>&1 | xcbeautify --renderer github-actions --preserve-unbeautified
       - name: Run test target in debug mode
         run: |
           set -o pipefail
           source Scripts/Tuist/common.sh
-          # See the build step above: force x86_64 to avoid the arm64 package
-          # test runner launch/codesigning failure on this Xcode/iOS pair.
+          # Match the package prebuilt setting used by the build step.
           NSUnbufferedIO=YES tuist_xcodebuild "$TEST_RESULT_BUNDLE_PATH" test -IDEPackageEnablePrebuilts=NO \
             -scheme OpenSwiftUI \
             -configuration Debug \
-            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }},arch=x86_64" \
+            -destination "platform=iOS Simulator,OS=${{ matrix.ios-version }},name=${{ matrix.ios-simulator-name }}" \
             -derivedDataPath "$DERIVED_DATA_PATH" \
             -skipMacroValidation \
             -skipPackagePluginValidation \
-            ONLY_ACTIVE_ARCH=YES \
             2>&1 | xcbeautify --renderer github-actions --preserve-unbeautified
       - name: Clean up isolated DerivedData
         if: always()
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 0e14ef396..22c4455d2 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -25,12 +25,11 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
-    # Limit to self-hosted to reduce action cost
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       OPENSWIFTUI_WERROR: 0 # Disable it to avoid enable OAG's werror and hit conflicts
       OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH: 1
@@ -57,10 +56,8 @@ jobs:
       - name: Build and run tests in debug mode with coverage
         run: |
           set -o pipefail
-          # Swift 6.2 can duplicate-link swift-syntax macro prebuilts; Swift 6.3 fixes this.
-          # Swift 6.2 also crashes while indexing AppKit with the private framework shims.
+          # Swift 6.3.3 still crashes while indexing AppKit with the private framework shims.
           NSUnbufferedIO=YES swift test \
-            --disable-experimental-prebuilts \
             --disable-index-store \
             -c debug \
             --filter OpenSwiftUITests \
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 923dcffdf..61936bbbe 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -12,7 +12,9 @@ permissions:
 jobs:
   build-xcframeworks:
     name: Build and Upload XCFrameworks
-    runs-on: macos-15
+    runs-on:
+      - macos-15
+      - xcode-26.6
     outputs:
       checksum_OpenSwiftUI: ${{ steps.build.outputs.checksum_OpenSwiftUI }}
       checksum_OpenSwiftUICore: ${{ steps.build.outputs.checksum_OpenSwiftUICore }}
diff --git a/.github/workflows/stdout_renderer.yml b/.github/workflows/stdout_renderer.yml
index 456aa0a1a..ff57320bd 100644
--- a/.github/workflows/stdout_renderer.yml
+++ b/.github/workflows/stdout_renderer.yml
@@ -24,7 +24,7 @@ jobs:
   # stdout_renderer_linux:
   #   name: Run stdout renderer on Linux
   #   runs-on: ubuntu-22.04
-  #   container: swift:6.2.4-jammy
+  #   container: swift:6.3.3-jammy
   #   env:
   #     OPENSWIFTUI_WERROR: 0
   #     OPENSWIFTUI_SWIFT_LOG: 1
@@ -40,7 +40,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
         backend: [AttributeGraph, Compute]
         include:
@@ -51,8 +51,8 @@ jobs:
             attributegraph: "0"
             compute: "1"
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       OPENSWIFTUI_WERROR: 0
       OPENSWIFTUI_TARGET_RELEASE: ${{ matrix.release }}
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
index 76a412cea..153b8b8ba 100644
--- a/.github/workflows/ubuntu.yml
+++ b/.github/workflows/ubuntu.yml
@@ -22,7 +22,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        swift_version: ["6.2.4"]
+        swift_version: ["6.3.3"]
     runs-on: ubuntu-22.04
     env:
       OPENSWIFTUI_WERROR: 0 # Disable it to avoid enable OAG's werror and hit conflicts
diff --git a/.github/workflows/uitests.yml b/.github/workflows/uitests.yml
index a187a7de6..b82de7834 100644
--- a/.github/workflows/uitests.yml
+++ b/.github/workflows/uitests.yml
@@ -271,17 +271,16 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
         ios-version: ["18.5"]
         configuration: ${{ fromJSON(needs.prepare_uitests.outputs.configuration-matrix) }}
         include:
           - ios-version: "18.5"
             ios-simulator-name: "iPhone 16 Pro"
-    # Limit to self-hosted to reduce action cost
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       STATUS_CONTEXT: UI Tests / iOS / ${{ matrix.configuration.id }}
       STATUS_ENABLED: ${{ needs.prepare_uitests.outputs.status-enabled }}
@@ -370,13 +369,12 @@ jobs:
       fail-fast: false
       matrix:
         os: [macos-15]
-        xcode-version: ["26.3"]
+        xcode-version: ["26.6"]
         release: [2024]
         configuration: ${{ fromJSON(needs.prepare_uitests.outputs.configuration-matrix) }}
-    # Limit to self-hosted to reduce action cost
     runs-on:
-      - self-hosted
       - ${{ matrix.os }}
+      - xcode-26.6
     env:
       STATUS_CONTEXT: UI Tests / macOS / ${{ matrix.configuration.id }}
       STATUS_ENABLED: ${{ needs.prepare_uitests.outputs.status-enabled }}
diff --git a/.vdc.json b/.vdc.json
index 842a8f390..caab96c11 100644
--- a/.vdc.json
+++ b/.vdc.json
@@ -67,9 +67,6 @@
     "openobservation": "../OpenObservation",
     "openrenderbox": "../OpenRenderBox"
   },
-  "buildArguments": [
-    "--disable-index-store"
-  ],
   "doccArguments": [
     "--emit-digest"
   ]
diff --git a/Docs/Toolchain/CHANGELOG.md b/Docs/Toolchain/CHANGELOG.md
index fcd8d065f..9bae44382 100644
--- a/Docs/Toolchain/CHANGELOG.md
+++ b/Docs/Toolchain/CHANGELOG.md
@@ -5,6 +5,7 @@ found while validating CI, package dependencies, and platform-specific tests.
 
 | Date | OpenSwiftUI PR | Toolchain move | Notes |
 | --- | --- | --- | --- |
+| 2026-07-27 | [#987](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/987) | Xcode 26.3 / Swift 6.2.4 to Xcode 26.6 / Swift 6.3.3 | Updated package manifests and CI, retained the targeted index-store and package-prebuilt workarounds required by Xcode 26.6, and refreshed SDK-linked test expectations. |
 | 2026-06-09 | [#902](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/902) | Add Xcode 27 / SDK 27 support | Added SDK 26/27 addition guards and updated UIFoundation shims while keeping Xcode 26.3 / macOS 26.2 compatibility. |
 | 2026-06-07 | [#899](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/899) | Xcode 16.4 / Swift 6.1 to Xcode 26.3 / Swift 6.2.4 | Kept `macos-15` and iOS 18.5 while documenting the Linux compiler crash, index store, prebuilt package, runtime issue, and Linux dyld shim workarounds. |
 | 2025-11-18 | [#634](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/634) | Initial Xcode 26 SDK support | Added SDK 26 compatibility without moving CI to iOS 26 or macOS 26 destinations. |
@@ -12,6 +13,106 @@ found while validating CI, package dependencies, and platform-specific tests.
 | 2025-04-05 | [#241](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/241) | Xcode version selector cleanup | `16.0` resolved to Xcode 16.3 in setup tooling, so CI was changed to use a precise Xcode version. |
 | 2024-09-17 | [#118](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/118) | Add Xcode 16 and Swift 6 support on macOS | Closed [#117](https://github.com/OpenSwiftUIProject/OpenSwiftUI/issues/117). Also updated Linux/Wasm Swift 6 nightly jobs and fixed several Swift 6 warnings and iOS 18 test issues. |
 
+## Swift 6.3
+
+OpenSwiftUI PR: [#987](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/987)
+
+Dependency PRs:
+
+- OpenSwiftUIProject/DarwinPrivateFrameworks#TBD
+- OpenSwiftUIProject/OpenAttributeGraph#234
+- OpenSwiftUIProject/OpenRenderBox#TBD
+- jcmosc/Compute#TBD
+
+Use the following dependency section in the OpenSwiftUI PR body:
+
+```markdown
+## Dependency
+
+- OpenSwiftUIProject/DarwinPrivateFrameworks#TBD
+- OpenSwiftUIProject/OpenAttributeGraph#234
+- OpenSwiftUIProject/OpenRenderBox#TBD
+- jcmosc/Compute#TBD
+```
+
+### Version Targets
+
+- Apple platforms: Xcode 26.6 / Swift 6.3.3.
+- Linux: Swift 6.3.3.
+- Swift tools version: 6.3 for the root and nested packages updated by this
+  bump.
+- Runner and destinations: require `macos-15` and `xcode-26.6` runner labels,
+  and keep iOS simulator tests on iOS 18.5.
+
+### Package Manifests
+
+Update the root and nested package entry points together:
+
+- `Package.swift`
+- `Example/Tuist/Package.swift`
+- `Renderer/Stdout/Package.swift`
+- `Renderer/Stdout/Tuist/Package.swift`
+
+The corresponding DarwinPrivateFrameworks, OpenAttributeGraph, and
+OpenRenderBox manifests also move to Swift tools version 6.3.
+
+### Swift 6.2 Workaround Audit
+
+Xcode 26.6 and Swift 6.3.3 make several workarounds from the previous toolchain
+bump unnecessary, while CI validation shows that two targeted workarounds are
+still required:
+
+- Retain `--disable-index-store` in OpenSwiftUI macOS SwiftPM test jobs and the
+  Stdout renderer because Swift 6.3.3 still crashes while indexing AppKit with
+  the private framework shims.
+- Retain `-IDEPackageEnablePrebuilts=NO` in OpenSwiftUI iOS package build and
+  test jobs because Xcode 26.6 otherwise links the host macOS macro object into
+  the iOS Simulator test bundle.
+- Remove `--disable-index-store` and `COMPILER_INDEX_STORE_ENABLE=NO` from
+  OpenAttributeGraph test and Tuist configurations.
+- Remove the documentation-specific OpenSwiftUI index-store configuration and
+  the package-prebuilt override from the UI test action.
+- Remove `--disable-experimental-prebuilts` from OpenSwiftUI SwiftPM jobs and
+  remove compiler-version guards made redundant by the Swift 6.3 requirement.
+- Use the default iOS Simulator architecture rather than forcing `x86_64` and
+  `ONLY_ACTIVE_ARCH=YES`.
+
+### SDK-Linked Test Expectations
+
+Xcode 26.6 ships an `xctest` binary linked against SDK 26.4:
+
+- iPhone Simulator: SDK 26.4, minimum iOS 13.0 on x86_64 and iOS 14.0 on
+  arm64.
+- macOS: SDK 26.4, minimum macOS 14.0.
+
+Update the dyld shim constants and tests accordingly:
+
+- Add iOS and macOS 26.4 and 26.5 version constants.
+- Expect `dyld_program_sdk_at_least(26.5)` to be `false`.
+- Expect `dyld_program_sdk_at_least(26.4)` to be `true`.
+- Enable the 2025 semantic version on 26.x runtimes while keeping it disabled
+  on the macOS 15 and iOS 18.5 CI runtimes, whose dyld does not recognize the
+  2025 version-set token even though active-platform SDK checks report 26.4.
+
+### Swift Testing Exit-Test Arguments
+
+Swift Testing serializes values captured by exit-test closures as JSON, which
+cannot represent non-finite floating-point values:
+
+- Capture dimension inputs as codable floating-point bit patterns and
+  reconstruct their `CGFloat` values inside the exit-test process.
+
+### Validation
+
+- Parse all changed workflow YAML files.
+- Run `swift package dump-package` with Xcode 26.6 for each updated root and
+  nested package.
+- Inspect the Xcode 26.6 `xctest` Mach-O build-version commands for SDK and
+  minimum deployment versions.
+- Run `git diff --check` in each changed repository.
+- Do not run full OpenSwiftUI builds by default for this metadata and
+  compatibility update.
+
 ## Xcode 27 SDK
 
 OpenSwiftUI PR: [#902](https://github.com/OpenSwiftUIProject/OpenSwiftUI/pull/902)
diff --git a/Example/Tuist/Package.swift b/Example/Tuist/Package.swift
index ce5b7ceae..2f0b9fda4 100644
--- a/Example/Tuist/Package.swift
+++ b/Example/Tuist/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 6.2
+// swift-tools-version: 6.3
 
 import PackageDescription
 
diff --git a/INTEGRATION.md b/INTEGRATION.md
index 9c24afa30..24aa56483 100644
--- a/INTEGRATION.md
+++ b/INTEGRATION.md
@@ -4,8 +4,8 @@ This guide walks you through the steps to integrate OpenSwiftUI into your projec
 
 ## Prerequisites
 
-- Xcode 26.3
-- Swift 6.2.4+
+- Xcode 26.6
+- Swift 6.3.3+
 
 ## Important Notes
 
diff --git a/Package.resolved b/Package.resolved
index 1c6392c7d..46a5150d3 100644
--- a/Package.resolved
+++ b/Package.resolved
@@ -7,7 +7,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/DarwinPrivateFrameworks.git",
       "state" : {
         "branch" : "main",
-        "revision" : "d93839821ebebdab22081fbc0f3d0b8cb0e30b2f"
+        "revision" : "b7e6ba165f3763dd477f55cc55b4a63f51385571"
       }
     },
     {
@@ -16,7 +16,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/OpenAttributeGraph",
       "state" : {
         "branch" : "main",
-        "revision" : "49a40098fc0b41c6f9e686ef4218b4895fe513f9"
+        "revision" : "65e7cbf19c2c2797d3c5eaafcb19190130c8ad47"
       }
     },
     {
diff --git a/Package.swift b/Package.swift
index 3f7c56bb7..735d3b9bf 100644
--- a/Package.swift
+++ b/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 6.2
+// swift-tools-version: 6.3
 
 import CompilerPluginSupport
 import Foundation
diff --git a/README.md b/README.md
index 32f45c35a..10b78ced8 100644
--- a/README.md
+++ b/README.md
@@ -58,7 +58,7 @@ See Example folder and try it with ExampleApp
 
 ## Build
 
-The current suggested toolchain to build the project is Swift 6.2.4 / Xcode 26.3 with macOS 15.5 or iOS 18.5 Simulator.
+The current suggested toolchain to build the project is Swift 6.3.3 / Xcode 26.6.
 
 ### Build without testing framework
 
diff --git a/Renderer/Stdout/Package.swift b/Renderer/Stdout/Package.swift
index 0bbde667a..7b2021419 100644
--- a/Renderer/Stdout/Package.swift
+++ b/Renderer/Stdout/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 6.2
+// swift-tools-version: 6.3
 
 import PackageDescription
 
diff --git a/Renderer/Stdout/Tuist/Package.swift b/Renderer/Stdout/Tuist/Package.swift
index 419905d7a..a103850c2 100644
--- a/Renderer/Stdout/Tuist/Package.swift
+++ b/Renderer/Stdout/Tuist/Package.swift
@@ -1,4 +1,4 @@
-// swift-tools-version: 6.2
+// swift-tools-version: 6.3
 
 import PackageDescription
 
diff --git a/Renderer/Stdout/run-example.sh b/Renderer/Stdout/run-example.sh
index ed9926ead..699319056 100755
--- a/Renderer/Stdout/run-example.sh
+++ b/Renderer/Stdout/run-example.sh
@@ -10,7 +10,7 @@ case "$(uname -s)" in
 Darwin)
     export OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH="${OPENSWIFTUI_OPENATTRIBUTESHIMS_ATTRIBUTEGRAPH:-1}"
     export OPENSWIFTUI_OPENATTRIBUTESHIMS_COMPUTE="${OPENSWIFTUI_OPENATTRIBUTESHIMS_COMPUTE:-0}"
-    # Swift 6.2 crashes while indexing AppKit with the local private framework shims.
+    # Swift 6.3.3 still crashes while indexing AppKit with the local private framework shims.
     swift_run_options+=(--disable-index-store)
     ;;
 *)
diff --git a/Scripts/build-documentation.sh b/Scripts/build-documentation.sh
index c1ac8a9fd..491066983 100755
--- a/Scripts/build-documentation.sh
+++ b/Scripts/build-documentation.sh
@@ -262,9 +262,7 @@ if [[ "$REBUILD_NEEDED" == true ]] || [[ "$CLEAN_BUILD" == true ]]; then
     fi
 
     log_info "Generating symbol graphs..."
-    # Swift 6.2 crashes while indexing AppKit with the local private framework shims.
     swift build \
-        --disable-index-store \
         --target "$TARGET_NAME" \
         -Xswiftc -emit-symbol-graph \
         -Xswiftc -emit-symbol-graph-dir \
diff --git a/Sources/OpenSwiftUICore/View/View.swift b/Sources/OpenSwiftUICore/View/View.swift
index 8586cd0bd..22bae44e6 100644
--- a/Sources/OpenSwiftUICore/View/View.swift
+++ b/Sources/OpenSwiftUICore/View/View.swift
@@ -45,7 +45,7 @@ import OpenSwiftUI_SPI
 /// You can also collect groups of default modifiers into new,
 /// custom view modifiers for easy reuse.
 @available(OpenSwiftUI_v1_0, *)
-#if OPENSWIFTUI_SUPPORT_2025_API && compiler(>=6.2)
+#if OPENSWIFTUI_SUPPORT_2025_API
 @_typeEraser(DebugReplaceableView)
 #endif
 @_typeEraser(AnyView)
diff --git a/Sources/OpenSwiftUI_SPI/Shims/dyld/dyld_Private.h b/Sources/OpenSwiftUI_SPI/Shims/dyld/dyld_Private.h
index a1b878e94..ba5809998 100644
--- a/Sources/OpenSwiftUI_SPI/Shims/dyld/dyld_Private.h
+++ b/Sources/OpenSwiftUI_SPI/Shims/dyld/dyld_Private.h
@@ -102,6 +102,8 @@ typedef OPENSWIFTUI_ENUM(uint32_t, DYLD_MACOSX_VERSION) {
     DYLD_MACOSX_VERSION_26_1 = 0x001A0100,
     DYLD_MACOSX_VERSION_26_2 = 0x001A0200,
     DYLD_MACOSX_VERSION_26_3 = 0x001A0300,
+    DYLD_MACOSX_VERSION_26_4 = 0x001A0400,
+    DYLD_MACOSX_VERSION_26_5 = 0x001A0500,
 };
 
 typedef OPENSWIFTUI_ENUM(uint32_t, DYLD_IOS_VERSION) {
@@ -133,6 +135,8 @@ typedef OPENSWIFTUI_ENUM(uint32_t, DYLD_IOS_VERSION) {
     DYLD_IOS_VERSION_26_1 = 0x001A0100,
     DYLD_IOS_VERSION_26_2 = 0x001A0200,
     DYLD_IOS_VERSION_26_3 = 0x001A0300,
+    DYLD_IOS_VERSION_26_4 = 0x001A0400,
+    DYLD_IOS_VERSION_26_5 = 0x001A0500,
 };
 
 // Returns the active platform of the process
diff --git a/Tests/OpenSwiftUICoreTests/Layout/Geometry/LayoutTraitsTests.swift b/Tests/OpenSwiftUICoreTests/Layout/Geometry/LayoutTraitsTests.swift
index a770965bf..8620f6486 100644
--- a/Tests/OpenSwiftUICoreTests/Layout/Geometry/LayoutTraitsTests.swift
+++ b/Tests/OpenSwiftUICoreTests/Layout/Geometry/LayoutTraitsTests.swift
@@ -86,9 +86,18 @@ struct LayoutTraitsTests {
         ])
         func exitTest(_ min: CGFloat, _ ideal: CGFloat, _ max: CGFloat, _ expectedFailure: Bool) async {
             if expectedFailure {
-                #if compiler(>=6.3) // ST-12
                 #if !os(iOS) && !os(visionOS)
-                await #expect(processExitsWith: .failure) { [min, ideal, max] in
+                // Work around https://github.com/swiftlang/swift-testing/issues/1836:
+                // exit tests cannot JSON-encode captured non-finite floating-point values.
+                await #expect(processExitsWith: .failure) {
+                    [
+                        minBitPattern = Double(min).bitPattern as UInt64,
+                        idealBitPattern = Double(ideal).bitPattern as UInt64,
+                        maxBitPattern = Double(max).bitPattern as UInt64,
+                    ] in
+                    let min = CGFloat(Double(bitPattern: minBitPattern))
+                    let ideal = CGFloat(Double(bitPattern: idealBitPattern))
+                    let max = CGFloat(Double(bitPattern: maxBitPattern))
                     _ = Dimension(min: min, ideal: ideal, max: max)
                     var d = Dimension.fixed(.zero)
                     d.max = ideal
@@ -96,7 +105,6 @@ struct LayoutTraitsTests {
                     d.min = min
                 }
                 #endif
-                #endif
             } else {
                 _ = Dimension(min: min, ideal: ideal, max: max)
                 var d = Dimension.fixed(.zero)
diff --git a/Tests/OpenSwiftUICoreTests/Semantic/SemanticsTests.swift b/Tests/OpenSwiftUICoreTests/Semantic/SemanticsTests.swift
index 51bd30298..79238b586 100644
--- a/Tests/OpenSwiftUICoreTests/Semantic/SemanticsTests.swift
+++ b/Tests/OpenSwiftUICoreTests/Semantic/SemanticsTests.swift
@@ -83,6 +83,34 @@ struct SemanticsTests {
         #expect(isDeployedOnOrAfter(.v5) == false)
         #expect(isDeployedOnOrAfter(.v6) == false)
         #expect(isDeployedOnOrAfter(.v7) == false)
+        #elseif compiler(>=6.3)
+        // Path: Xcode-26.6.0.app Platforms/iPhoneSimulator.platform/Developer/Library/Xcode/Agents/xctest
+        // SDK version: iOS 26.4
+        // min version: iOS 13.0 (x86_64) & iOS 14.0 (arm64)
+        #expect(isLinkedOnOrAfter(.v1) == true)
+        #expect(isLinkedOnOrAfter(.v2) == true)
+        #expect(isLinkedOnOrAfter(.v3) == true)
+        #expect(isLinkedOnOrAfter(.v4) == true)
+        #expect(isLinkedOnOrAfter(.v5) == true)
+        #expect(isLinkedOnOrAfter(.v6) == true)
+        // FIXME: Temporary compatibility for Xcode 26.6 CI running on macOS 15 and iOS 18.5.
+        let v7LinkedOnOrAfter = if #available(iOS 26.0, visionOS 26.0, *) {
+            true
+        } else {
+            false
+        }
+        #expect(isLinkedOnOrAfter(.v7) == v7LinkedOnOrAfter)
+        #expect(isDeployedOnOrAfter(.v1) == true)
+        #if arch(arm64)
+        #expect(isDeployedOnOrAfter(.v2) == true)
+        #else
+        #expect(isDeployedOnOrAfter(.v2) == false)
+        #endif
+        #expect(isDeployedOnOrAfter(.v3) == false)
+        #expect(isDeployedOnOrAfter(.v4) == false)
+        #expect(isDeployedOnOrAfter(.v5) == false)
+        #expect(isDeployedOnOrAfter(.v6) == false)
+        #expect(isDeployedOnOrAfter(.v7) == false)
         #endif
         #elseif os(macOS)
         #if compiler(<6.2) && compiler(>=6.1)
@@ -121,6 +149,30 @@ struct SemanticsTests {
         #expect(isDeployedOnOrAfter(.v5) == true)
         #expect(isDeployedOnOrAfter(.v6) == false)
         #expect(isDeployedOnOrAfter(.v7) == false)
+        #elseif compiler(>=6.3)
+        // Path: Xcode-26.6.0.app Platforms/MacOSX.platform/Developer/Library/Xcode/Agents/xctest
+        // SDK version: macOS 26.4
+        // min version: macOS 14.0
+        #expect(isLinkedOnOrAfter(.v1) == true)
+        #expect(isLinkedOnOrAfter(.v2) == true)
+        #expect(isLinkedOnOrAfter(.v3) == true)
+        #expect(isLinkedOnOrAfter(.v4) == true)
+        #expect(isLinkedOnOrAfter(.v5) == true)
+        #expect(isLinkedOnOrAfter(.v6) == true)
+        // FIXME: Temporary compatibility for Xcode 26.6 CI running on macOS 15.
+        let v7LinkedOnOrAfter = if #available(macOS 26.0, *) {
+            true
+        } else {
+            false
+        }
+        #expect(isLinkedOnOrAfter(.v7) == v7LinkedOnOrAfter)
+        #expect(isDeployedOnOrAfter(.v1) == true)
+        #expect(isDeployedOnOrAfter(.v2) == true)
+        #expect(isDeployedOnOrAfter(.v3) == true)
+        #expect(isDeployedOnOrAfter(.v4) == true)
+        #expect(isDeployedOnOrAfter(.v5) == true)
+        #expect(isDeployedOnOrAfter(.v6) == false)
+        #expect(isDeployedOnOrAfter(.v7) == false)
         #endif
         #endif
     }
diff --git a/Tests/OpenSwiftUI_SPITests/Shims/DyldPrivateTests.swift b/Tests/OpenSwiftUI_SPITests/Shims/DyldPrivateTests.swift
index 4ac138cb3..7c484b3ec 100644
--- a/Tests/OpenSwiftUI_SPITests/Shims/DyldPrivateTests.swift
+++ b/Tests/OpenSwiftUI_SPITests/Shims/DyldPrivateTests.swift
@@ -20,16 +20,16 @@ struct DyldPrivateTests {
         #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(.min)) == true)
 
         #if os(iOS) || os(visionOS)
-        // Path: Xcode-26.3.0.app Platforms/iPhoneSimulator.platform/Developer/Library/Xcode/Agents/xctest
-        // SDK version: iOS 26.2
-        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._26_3.rawValue)) == false)
-        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._26_2.rawValue)) == true)
+        // Path: Xcode-26.6.0.app Platforms/iPhoneSimulator.platform/Developer/Library/Xcode/Agents/xctest
+        // SDK version: iOS 26.4
+        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._26_5.rawValue)) == false)
+        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._26_4.rawValue)) == true)
         #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._26_0.rawValue)) == true)
         #elseif os(macOS)
-        // Path: Xcode-26.3.0.app Platforms/MacOSX.platform/Developer/Library/Xcode/Agents/xctest
-        // SDK version: macOS 26.2
-        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._26_3.rawValue)) == false)
-        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._26_2.rawValue)) == true)
+        // Path: Xcode-26.6.0.app Platforms/MacOSX.platform/Developer/Library/Xcode/Agents/xctest
+        // SDK version: macOS 26.4
+        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._26_5.rawValue)) == false)
+        #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._26_4.rawValue)) == true)
         #expect(dyld_program_sdk_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._26_0.rawValue)) == true)
         #else
         preconditionFailure("Unsupported Darwin platform")
@@ -47,7 +47,7 @@ struct DyldPrivateTests {
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(.max)) == false)
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(.min)) == true)
         #if os(iOS) || os(visionOS)
-        // Path: Xcode-26.3.0.app Platforms/iPhoneSimulator.platform/Developer/Library/Xcode/Agents/xctest
+        // Path: Xcode-26.6.0.app Platforms/iPhoneSimulator.platform/Developer/Library/Xcode/Agents/xctest
         // min version: iOS 13.0 (x86_64) & iOS 14.0 (arm64)
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._26_0.rawValue)) == false)
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._15_0.rawValue)) == false)
@@ -58,7 +58,7 @@ struct DyldPrivateTests {
         #endif
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(DYLD_IOS_VERSION._13_0.rawValue)) == true)
         #elseif os(macOS)
-        // Path: Xcode-26.3.0.app Platforms/MacOSX.platform/Developer/Library/Xcode/Agents/xctest
+        // Path: Xcode-26.6.0.app Platforms/MacOSX.platform/Developer/Library/Xcode/Agents/xctest
         // min version: macOS 14.0
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._26_0.rawValue)) == false)
         #expect(dyld_program_minos_at_least(activePlatformBuildVersion(DYLD_MACOSX_VERSION._15_0.rawValue)) == false)
diff --git a/mise.compute.toml b/mise.compute.toml
index ea288356c..cfdc082ab 100644
--- a/mise.compute.toml
+++ b/mise.compute.toml
@@ -1,5 +1,5 @@
 [tools]
-tuist = "4.203.1"
+tuist = "4.203.4"
 
 [env]
 TUIST_USE_SWIFTERPM=1
diff --git a/mise.toml b/mise.toml
index df8cdc78c..8952e958a 100644
--- a/mise.toml
+++ b/mise.toml
@@ -1,5 +1,5 @@
 [tools]
-tuist = "4.203.1"
+tuist = "4.203.4"
 
 [env]
 TUIST_USE_SWIFTERPM=1