diff --git a/install.ps1 b/install.ps1
index a434e78fb..dbdfedb6f 100644
--- a/install.ps1
+++ b/install.ps1
@@ -14,13 +14,18 @@ Add-Type -AssemblyName System.Net.Http
 $Repo = "DeusData/codebase-memory-mcp"
 $InstallDir = "$env:LOCALAPPDATA\Programs\codebase-memory-mcp"
 $BinName = "codebase-memory-mcp.exe"
-$WindowsArchiveNames = @(
+# Core members shipped since the single-binary Windows layout. The integration
+# manifest was added later (externalized runtime assets); published v0.9.0 zips
+# still omit it, so validation accepts either the legacy 4-file core set or the
+# current 5-file set. New releases from package-release.sh always ship both.
+$WindowsCoreArchiveNames = @(
     $BinName,
-    "cbm-integrations.json",
     "LICENSE",
     "install.ps1",
     "THIRD_PARTY_NOTICES.md"
 )
+$WindowsIntegrationArchiveName = "cbm-integrations.json"
+$WindowsArchiveNames = $WindowsCoreArchiveNames + @($WindowsIntegrationArchiveName)
 $UiPackPattern = '^cbm-ui-[0-9a-f]{64}\.pack$'
 $BaseUrl = if ($env:CBM_DOWNLOAD_URL) { $env:CBM_DOWNLOAD_URL } else { "https://github.com/$Repo/releases/latest/download" }
 
@@ -232,8 +237,10 @@ try {
 
 # Validate the zip namespace before extraction. Windows paths are
 # case-insensitive, so two entries that differ only in case are ambiguous and
-# must never be allowed to overwrite each other. The official five entries are
-# required at the archive root; UI adds exactly one hash-shaped pack.
+# must never be allowed to overwrite each other. Core members are always
+# required; cbm-integrations.json is required when present and accepted as
+# absent for legacy published archives (v0.9.0). UI adds exactly one
+# hash-shaped pack on top of either layout.
 try {
     Add-Type -AssemblyName System.IO.Compression.FileSystem
     $zip = [System.IO.Compression.ZipFile]::OpenRead("$TmpDir\$Archive")
@@ -272,17 +279,22 @@ try {
                 throw "archive contains an unexpected root entry: $($entry.FullName)"
             }
         }
-        foreach ($archiveName in $WindowsArchiveNames) {
+        foreach ($archiveName in $WindowsCoreArchiveNames) {
             if ($archiveCounts[$archiveName] -ne 1) {
                 throw "archive must contain exactly one $archiveName"
             }
         }
+        $integrationCount = $archiveCounts[$WindowsIntegrationArchiveName]
+        if ($integrationCount -ne 0 -and $integrationCount -ne 1) {
+            throw "archive must contain exactly one $WindowsIntegrationArchiveName"
+        }
         $expectedUiPackCount = if ($Variant -eq "ui") { 1 } else { 0 }
-        $expectedArchiveCount = $WindowsArchiveNames.Count + $expectedUiPackCount
+        $expectedArchiveCount = $WindowsCoreArchiveNames.Count + $integrationCount + $expectedUiPackCount
         if ($uiPackCount -ne $expectedUiPackCount -or
             $seen.Count -ne $expectedArchiveCount) {
             throw "archive does not match the exact $Variant Windows release allowlist"
         }
+        $script:WindowsHasIntegrationManifest = ($integrationCount -eq 1)
     } finally {
         $zip.Dispose()
     }
@@ -298,7 +310,11 @@ try {
 Write-Host "Extracting..."
 Expand-Archive -Path "$TmpDir\$Archive" -DestinationPath $TmpDir -Force
 
-foreach ($archiveName in $WindowsArchiveNames) {
+$RequiredExtractedMembers = @($WindowsCoreArchiveNames)
+if ($WindowsHasIntegrationManifest) {
+    $RequiredExtractedMembers += $WindowsIntegrationArchiveName
+}
+foreach ($archiveName in $RequiredExtractedMembers) {
     $extractedMember = Join-Path $TmpDir $archiveName
     if (-not (Test-Path -LiteralPath $extractedMember -PathType Leaf)) {
         Write-Host "error: release member is not a regular file: $archiveName" -ForegroundColor Red
diff --git a/install.sh b/install.sh
index b9e9cea3f..8aed6591a 100755
--- a/install.sh
+++ b/install.sh
@@ -232,9 +232,10 @@ fi
 echo "Checksum verified."
 
 # Validate the complete archive namespace before extraction. Standard releases
-# are the canonical five files; UI releases add exactly one root-level,
-# content-addressed pack. Anything else is a release-integrity failure, not a
-# sidecar to ignore.
+# ship either the current five-file set (with cbm-integrations.json) or the
+# legacy four-file set still published as v0.9.0. UI releases add exactly one
+# root-level, content-addressed pack on top of either layout. Anything else is
+# a release-integrity failure, not a sidecar to ignore.
 if [ "$OS" = "windows" ]; then
     ARCHIVE_BINARY="codebase-memory-mcp.exe"
     ARCHIVE_INSTALLER="install.ps1"
@@ -284,13 +285,24 @@ while IFS= read -r member || [ -n "$member" ]; do
     esac
 done < "$ARCHIVE_MEMBERS_FILE"
 
-EXPECTED_MEMBER_COUNT=5
+# Current releases: 5 members (+1 UI pack). Legacy published archives (v0.9.0)
+# omit cbm-integrations.json and therefore have 4 core members.
+if [ "$INTEGRATION_MEMBERS" -eq 1 ]; then
+    EXPECTED_CORE_COUNT=5
+elif [ "$INTEGRATION_MEMBERS" -eq 0 ]; then
+    EXPECTED_CORE_COUNT=4
+else
+    echo "error: release archive does not match the exact $VARIANT member set" >&2
+    exit 1
+fi
+EXPECTED_MEMBER_COUNT=$EXPECTED_CORE_COUNT
 if [ "$VARIANT" = "ui" ]; then
-    EXPECTED_MEMBER_COUNT=6
+    EXPECTED_MEMBER_COUNT=$((EXPECTED_CORE_COUNT + 1))
 fi
-if [ "$BINARY_MEMBERS" -ne 1 ] || [ "$INTEGRATION_MEMBERS" -ne 1 ] ||
+if [ "$BINARY_MEMBERS" -ne 1 ] ||
     [ "$LICENSE_MEMBERS" -ne 1 ] || [ "$INSTALLER_MEMBERS" -ne 1 ] ||
-    [ "$NOTICE_MEMBERS" -ne 1 ] || [ "$UI_PACK_MEMBERS" -ne $((EXPECTED_MEMBER_COUNT - 5)) ] ||
+    [ "$NOTICE_MEMBERS" -ne 1 ] ||
+    [ "$UI_PACK_MEMBERS" -ne $((EXPECTED_MEMBER_COUNT - EXPECTED_CORE_COUNT)) ] ||
     [ "$ARCHIVE_MEMBER_COUNT" -ne "$EXPECTED_MEMBER_COUNT" ]; then
     echo "error: release archive does not match the exact $VARIANT member set" >&2
     exit 1
@@ -304,8 +316,16 @@ else
     tar -xzf "$DLDIR/$ARCHIVE" -C "$DLDIR"
 fi
 
-for extracted_member in "$ARCHIVE_BINARY" cbm-integrations.json LICENSE \
-    "$ARCHIVE_INSTALLER" THIRD_PARTY_NOTICES.md; do
+REQUIRED_EXTRACTED_MEMBERS=(
+    "$ARCHIVE_BINARY"
+    LICENSE
+    "$ARCHIVE_INSTALLER"
+    THIRD_PARTY_NOTICES.md
+)
+if [ "$INTEGRATION_MEMBERS" -eq 1 ]; then
+    REQUIRED_EXTRACTED_MEMBERS+=(cbm-integrations.json)
+fi
+for extracted_member in "${REQUIRED_EXTRACTED_MEMBERS[@]}"; do
     if [ ! -f "$DLDIR/$extracted_member" ] || [ -L "$DLDIR/$extracted_member" ]; then
         echo "error: release member is not a regular file: $extracted_member" >&2
         exit 1
diff --git a/tests/test_install_archive_layout_compat.sh b/tests/test_install_archive_layout_compat.sh
new file mode 100755
index 000000000..fa0c7aa09
--- /dev/null
+++ b/tests/test_install_archive_layout_compat.sh
@@ -0,0 +1,189 @@
+#!/usr/bin/env bash
+# Regression for #1499: published v0.9.0 Windows/Unix archives omit
+# cbm-integrations.json, while main installers initially required it. Install
+# scripts must accept both the legacy four-file core layout and the current
+# five-file layout (core + cbm-integrations.json). package-release.sh still
+# ships the five-file set for new builds.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+python3 - "$ROOT" <<'PY'
+from __future__ import annotations
+
+import pathlib
+import re
+import sys
+import tempfile
+import zipfile
+
+
+root = pathlib.Path(sys.argv[1])
+failures: list[str] = []
+
+
+def require(condition: bool, message: str) -> None:
+    if not condition:
+        failures.append(message)
+
+
+install_ps1 = (root / "install.ps1").read_text(encoding="utf-8")
+install_sh = (root / "install.sh").read_text(encoding="utf-8")
+package_release = (root / "scripts/package-release.sh").read_text(encoding="utf-8")
+
+require(
+    "WindowsCoreArchiveNames" in install_ps1
+    and "WindowsIntegrationArchiveName" in install_ps1
+    and "WindowsHasIntegrationManifest" in install_ps1,
+    "install.ps1 must split core members from the optional integration manifest",
+)
+require(
+    "EXPECTED_CORE_COUNT=4" in install_sh and "EXPECTED_CORE_COUNT=5" in install_sh,
+    "install.sh must accept both the legacy 4-file and current 5-file layouts",
+)
+require(
+    "INTEGRATION_MEMBERS\" -eq 0" in install_sh
+    or '[ "$INTEGRATION_MEMBERS" -eq 0 ]' in install_sh,
+    "install.sh must treat a missing cbm-integrations.json as the legacy layout",
+)
+require(
+    "cbm-integrations.json LICENSE install.ps1" in package_release
+    and "cbm-integrations.json LICENSE install.sh" in package_release,
+    "package-release.sh must keep shipping cbm-integrations.json in new archives",
+)
+
+# Extract the PowerShell validation core into a tiny harness that mirrors the
+# allowlist logic without downloading anything.
+core = [
+    "codebase-memory-mcp.exe",
+    "LICENSE",
+    "install.ps1",
+    "THIRD_PARTY_NOTICES.md",
+]
+integration = "cbm-integrations.json"
+ui_pack = "cbm-ui-" + ("a" * 64) + ".pack"
+
+
+def validate(names: list[str], variant: str = "standard") -> str | None:
+    """Return None on success, else the error string."""
+    archive_names = core + [integration]
+    counts = {name: 0 for name in archive_names}
+    seen: set[str] = set()
+    ui_pack_count = 0
+    ui_pattern = re.compile(r"^cbm-ui-[0-9a-f]{64}\.pack$")
+    for entry_name in names:
+        if entry_name in seen:
+            return f"duplicate or case-conflicting zip entry: {entry_name}"
+        seen.add(entry_name)
+        if entry_name in counts:
+            counts[entry_name] += 1
+        elif variant == "ui" and ui_pattern.match(entry_name):
+            ui_pack_count += 1
+        else:
+            return f"archive contains an unexpected root entry: {entry_name}"
+    for name in core:
+        if counts[name] != 1:
+            return f"archive must contain exactly one {name}"
+    integration_count = counts[integration]
+    if integration_count not in (0, 1):
+        return f"archive must contain exactly one {integration}"
+    expected_ui = 1 if variant == "ui" else 0
+    expected = len(core) + integration_count + expected_ui
+    if ui_pack_count != expected_ui or len(seen) != expected:
+        return f"archive does not match the exact {variant} Windows release allowlist"
+    return None
+
+
+legacy = list(core)
+current = list(core) + [integration]
+legacy_ui = list(core) + [ui_pack]
+current_ui = list(core) + [integration, ui_pack]
+
+require(validate(legacy) is None, f"legacy 4-file layout must pass: {validate(legacy)}")
+require(validate(current) is None, f"current 5-file layout must pass: {validate(current)}")
+require(
+    validate(legacy_ui, "ui") is None,
+    f"legacy UI layout must pass: {validate(legacy_ui, 'ui')}",
+)
+require(
+    validate(current_ui, "ui") is None,
+    f"current UI layout must pass: {validate(current_ui, 'ui')}",
+)
+require(
+    validate(core[:3]) is not None,
+    "incomplete core layout must still fail",
+)
+require(
+    validate(current + ["extra.txt"]) is not None,
+    "unexpected extra root entry must still fail",
+)
+require(
+    validate(core + [integration, integration]) is not None,
+    "duplicate integration manifest must still fail",
+)
+
+# install.sh acceptance matrix for INTEGRATION_MEMBERS
+sh_cases = [
+    # binary, integration, license, installer, notice, ui, variant, expect_ok
+    (1, 1, 1, 1, 1, 0, "standard", True),
+    (1, 0, 1, 1, 1, 0, "standard", True),
+    (1, 1, 1, 1, 1, 1, "ui", True),
+    (1, 0, 1, 1, 1, 1, "ui", True),
+    (1, 2, 1, 1, 1, 0, "standard", False),
+    (1, 1, 1, 1, 0, 0, "standard", False),
+    (1, 0, 1, 1, 1, 0, "ui", False),  # ui without pack
+]
+
+
+def sh_ok(
+    binary: int,
+    integration: int,
+    license_n: int,
+    installer: int,
+    notice: int,
+    ui: int,
+    variant: str,
+) -> bool:
+    if integration == 1:
+        expected_core = 5
+    elif integration == 0:
+        expected_core = 4
+    else:
+        return False
+    expected_member = expected_core + (1 if variant == "ui" else 0)
+    archive_member = binary + integration + license_n + installer + notice + ui
+    return (
+        binary == 1
+        and license_n == 1
+        and installer == 1
+        and notice == 1
+        and ui == (expected_member - expected_core)
+        and archive_member == expected_member
+    )
+
+
+for case in sh_cases:
+    *counts, variant, expect = case
+    got = sh_ok(*counts, variant)
+    require(
+        got is expect,
+        f"install.sh matrix {case} expected {expect}, got {got}",
+    )
+
+# Prove a real zip with the legacy layout enumerates the way install.ps1 expects.
+with tempfile.TemporaryDirectory() as tmp:
+    path = pathlib.Path(tmp) / "legacy.zip"
+    with zipfile.ZipFile(path, "w") as zf:
+        for name in legacy:
+            zf.writestr(name, b"x")
+    names = zipfile.ZipFile(path).namelist()
+    require(validate(names) is None, f"zip legacy layout failed: {validate(names)}")
+
+if failures:
+    print("test_install_archive_layout_compat FAILED:")
+    for failure in failures:
+        print(f"  - {failure}")
+    sys.exit(1)
+
+print("test_install_archive_layout_compat: ok")
+PY
diff --git a/tests/test_smoke_fixture_contract.sh b/tests/test_smoke_fixture_contract.sh
index f793b299b..90f911656 100755
--- a/tests/test_smoke_fixture_contract.sh
+++ b/tests/test_smoke_fixture_contract.sh
@@ -195,8 +195,9 @@ require(
     "fixture checksums must name exact artifact basenames, never ./-prefixed paths",
 )
 
-# Native Windows packages and serves the exact five-file standard bundle or
-# six-file UI bundle (one native binary), then runs the full smoke from a
+# Native Windows packages and serves the current five-file standard bundle
+# (or legacy four-file / matching UI +1 layouts) with one native binary, then
+# runs the full smoke from a
 # protected profile-rooted directory/cache.
 for name in (
     "codebase-memory-mcp.exe",
@@ -380,13 +381,15 @@ require(
         needle in unix_installer
         for needle in (
             "ARCHIVE_MEMBER_COUNT",
-            "EXPECTED_MEMBER_COUNT=5",
-            "EXPECTED_MEMBER_COUNT=6",
+            "EXPECTED_CORE_COUNT=4",
+            "EXPECTED_CORE_COUNT=5",
+            "EXPECTED_MEMBER_COUNT=$EXPECTED_CORE_COUNT",
             "^cbm-ui-[0-9a-f]{64}\\.pack$",
             "release archive contains unexpected member",
         )
     ),
-    "install.sh must validate the exact five-member standard or six-member UI archive",
+    "install.sh must validate legacy 4-file and current 5-file standard archives "
+    "(plus optional UI pack on either layout)",
 )
 unix_binary_publish = unix_installer.find('"$DLBIN" install "${INSTALL_ARGS[@]}"')
 require(
diff --git a/tests/test_windows_bundle_contract.sh b/tests/test_windows_bundle_contract.sh
index 1661dfeda..7f89dce4c 100644
--- a/tests/test_windows_bundle_contract.sh
+++ b/tests/test_windows_bundle_contract.sh
@@ -279,7 +279,8 @@ for relative, patterns in single_binary_contracts.items():
 
 # All package downloaders parse the Windows archive against an exact official
 # root allowlist; direct install.ps1 additionally distinguishes standard from
-# UI by the single hash-shaped pack.
+# UI by the single hash-shaped pack. install.ps1 also accepts the legacy
+# four-file core set (no cbm-integrations.json) still published as v0.9.0.
 exact_archive_guards = {
     "install.ps1": (
         "$seen.Count -ne $expectedArchiveCount",
@@ -288,6 +289,8 @@ exact_archive_guards = {
         '"LICENSE"',
         '"install.ps1"',
         "THIRD_PARTY_NOTICES.md",
+        "WindowsCoreArchiveNames",
+        "WindowsIntegrationArchiveName",
     ),
     "pkg/npm/install.js": (
         "seen.size !== expectedCount",