diff --git a/CMakeLists.txt b/CMakeLists.txt
index b294f27ba..97b87a1d8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -337,6 +337,15 @@ elseif(WIN32)
   # Configure file with custom definitions for NSIS.
   configure_file("${COCKATRICE_CMAKE_PATH}/NSIS.definitions.nsh.in" "${PROJECT_BINARY_DIR}/NSIS.definitions.nsh")
 
+  # Installer-log sender for the AbortInstall Sentry hook (values parsed out of COCKATRICE_SENTRY_DSN in
+  # cmake/CrashReporting.cmake). Generated only when a DSN was parsed: cmake/NSIS.template.in embeds it under
+  # the same CPACK_SENTRY_ENABLED check, so a build without reporting never references or carries the helper.
+  if(CPACK_SENTRY_ENABLED)
+    configure_file(
+      "${COCKATRICE_CMAKE_PATH}/SendInstallerLog.ps1.in" "${PROJECT_BINARY_DIR}/SendInstallerLog.ps1" @ONLY
+    )
+  endif()
+
   # Every runtime DLL a Windows install has to contain, as paths relative to the
   # install root. .ci/compile.sh reads this and fails the build when the packaged
   # installer is missing one of them, or carries a runtime it does not know about.
diff --git a/cmake/CrashReporting.cmake b/cmake/CrashReporting.cmake
index db016269f..6f9cf4849 100644
--- a/cmake/CrashReporting.cmake
+++ b/cmake/CrashReporting.cmake
@@ -179,3 +179,34 @@ if(WITH_CRASH_REPORTING
     )
   endif()
 endif()
+
+# Installer failure reporting (increment 4): parse COCKATRICE_SENTRY_DSN into the parts the Windows installer
+# needs. These are CPACK_* so CPack snapshots them at include(CPack) time and substitutes them into
+# cmake/NSIS.template.in at package time; on non-Windows they are inert (only the NSIS template consumes them).
+# Set from COCKATRICE_SENTRY_DSN on every configure, so a changed or removed DSN can never leave a stale value
+# behind. Plain variables, not CACHE: they only need to be in scope when include(CPack) later snapshots every
+# CPACK_* variable into CPackConfig.cmake.
+set(CPACK_SENTRY_ENABLED "0")
+set(CPACK_SENTRY_KEY "")
+set(CPACK_SENTRY_ENVELOPE_URL "")
+set(CPACK_SENTRY_DSN_FULL "")
+# Deliberately PROJECT_VERSION: that is what the client bakes as its Sentry release and what CI passes to
+# `sentry-cli debug-files upload`, so installer and client events group under one release. It is not the
+# CPACK_PACKAGE_VERSION the installer logs in its own log line — on Development tags PROJECT_VERSION carries a
+# "-<label>" suffix (getversion.cmake) while CPACK_PACKAGE_VERSION is only MAJOR.MINOR.PATCH.
+set(CPACK_SENTRY_RELEASE "${PROJECT_VERSION}")
+
+# Canonical <scheme>://<key>@<host>/<project-id>. Deliberately unanchored, so a trailing slash still matches.
+# A self-hosted DSN with a path prefix (e.g. GlitchTip behind a subpath) does not match and falls through to the
+# disabled-and-warn branch instead of deriving a wrong endpoint from the tail of the path.
+if(COCKATRICE_SENTRY_DSN MATCHES "(https?)://([^@]+)@([^/]+)/([0-9]+)")
+  set(CPACK_SENTRY_ENABLED "1")
+  set(CPACK_SENTRY_KEY "${CMAKE_MATCH_2}")
+  # Scheme comes from the DSN, not an assumption: self-hosted (GlitchTip) DSNs may be plain http.
+  set(CPACK_SENTRY_ENVELOPE_URL "${CMAKE_MATCH_1}://${CMAKE_MATCH_3}/api/${CMAKE_MATCH_4}/envelope/")
+  set(CPACK_SENTRY_DSN_FULL "${COCKATRICE_SENTRY_DSN}")
+elseif(NOT COCKATRICE_SENTRY_DSN STREQUAL "")
+  message(WARNING "COCKATRICE_SENTRY_DSN is set but malformed "
+                  "(expected <scheme>://<key>@<host>/<project-id>); installer log reporting disabled"
+  )
+endif()
diff --git a/cmake/NSIS.template.in b/cmake/NSIS.template.in
index 3647303b9..0ef746430 100644
--- a/cmake/NSIS.template.in
+++ b/cmake/NSIS.template.in
@@ -37,6 +37,9 @@ Var LogFindHandle
 Var LogFindName
 Var LogMatchLabel
 Var LogMatchPattern
+; Sentry installer-log hook state (see AbortInstall)
+Var SentryResult
+Var SentryOutput
 
 !include LogicLib.nsh
 !include FileFunc.nsh
@@ -909,6 +912,48 @@ Function AbortInstall
     ${If} $ReinstallMode = 1
     ${OrIfNot} ${Silent}
         MessageBox MB_OK|MB_ICONEXCLAMATION "$AbortReason$\r$\n$\r$\nA detailed installer log was written to:$\r$\n$InstallLogPath"
+        ; Offer to send the installer log to Sentry so aborted installs can be diagnosed. This block already runs
+        ; only when someone is at the keyboard (attended install, or the updater's /R upgrade whose launcher has
+        ; quit), so a silent or package-manager install never reaches the prompt and its behavior is unchanged.
+        ; Only a package built with a baked DSN offers to send, so the prompt can only appear when a send
+        ; can actually go out. A preprocessor guard rather than a runtime test: a package built without a
+        ; DSN compiles the block out entirely, so it cannot even carry the helper or its baked endpoint.
+        ; No /SD here: a /SD would suppress this prompt on the silent /R upgrade, which is exactly the
+        ; attended-update case this offer exists for. The runtime gate above (ReinstallMode/Silent) is the
+        ; hang protection — a package-manager /S install without /R never reaches this box, matching the
+        ; two sibling MessageBox sites in this file.
+        !if "@CPACK_SENTRY_ENABLED@" == "1"
+            MessageBox MB_YESNO|MB_ICONQUESTION "Send the installer log to the developers to help fix this? The log contains file paths from this machine, which may include your Windows user name." IDYES sentry_send
+            !insertmacro CockLog "sentry send: declined by user"
+            Goto sentry_done
+            sentry_send:
+            ; The abort reason is already in the log file (CockLog writes "ABORT: ..." as the
+            ; first thing AbortInstall does), so the helper reads it from there. Nothing
+            ; reason-shaped crosses the command line, which keeps quoting trivial and needs
+            ; no NSIS string functions.
+            InitPluginsDir
+            ; Embedded by the same relative path that resolves NSIS.definitions.nsh above (both are
+            ; configure_file'd into the build root, which is three levels up from project.nsi). An
+            ; absolute CMake path here carries forward slashes, which makensis does not treat as
+            ; absolute and so fails to find the file at package time.
+            File "/oname=$PLUGINSDIR\send-installer-log.ps1" "..\..\..\SendInstallerLog.ps1"
+            ; The send can take up to the /TIMEOUT below, so put something on the details pane
+            ; the moment the user says yes rather than leaving the window blank until it returns.
+            DetailPrint "Sending installer log..."
+            nsExec::ExecToStack /TIMEOUT=60000 'powershell -NoProfile -NonInteractive -ExecutionPolicy Bypass -File "$PLUGINSDIR\send-installer-log.ps1" -LogPath "$InstallLogPath"'
+            Pop $SentryResult
+            Pop $SentryOutput
+            ; $SentryOutput is a single line by construction: the helper flattens its message
+            ; and this log file is uploaded verbatim, so a stray newline must not be able to
+            ; forge extra lines into the artifact we send.
+            !insertmacro CockLog "sentry send: result=$SentryResult output=$SentryOutput"
+            ${If} $SentryResult == "0"
+                MessageBox MB_OK|MB_ICONINFORMATION "The installer log was sent. Thank you for helping improve Cockatrice!"
+            ${Else}
+                MessageBox MB_OK|MB_ICONEXCLAMATION "The installer log could not be sent. You can still share it manually; it was written to:$\r$\n$InstallLogPath"
+            ${EndIf}
+            sentry_done:
+        !endif
     ${EndIf}
     SetErrorLevel 1
     Abort
diff --git a/cmake/SendInstallerLog.ps1.in b/cmake/SendInstallerLog.ps1.in
new file mode 100644
index 000000000..dfb8c3d63
--- /dev/null
+++ b/cmake/SendInstallerLog.ps1.in
@@ -0,0 +1,120 @@
+# Sends the NSIS installer log to Sentry as an envelope carrying one error
+# event plus the log as an attachment.
+#
+# Generated at configure time from this template by CMake configure_file: the
+# CPACK_SENTRY_* placeholders are baked in then, so the real values only ever
+# exist in the build directory and the packaged installer, never in the repo.
+# Runs on stock Windows PowerShell 5.1 with no extra modules.
+param(
+    [Parameter(Mandatory = $true)][string]$LogPath
+)
+
+$ErrorActionPreference = 'Stop'
+
+$EnvelopeUrl = '@CPACK_SENTRY_ENVELOPE_URL@'
+$SentryKey = '@CPACK_SENTRY_KEY@'
+$Release = '@CPACK_SENTRY_RELEASE@'
+$Dsn = '@CPACK_SENTRY_DSN_FULL@'
+
+try {
+    # The envelope endpoint is TLS-only; stock powershell.exe on older systems
+    # still negotiates TLS 1.0 otherwise, so opt into 1.2 explicitly.
+    try {
+        [Net.ServicePointManager]::SecurityProtocol = [Net.ServicePointManager]::SecurityProtocol -bor [Net.SecurityProtocolType]::Tls12
+    } catch {
+    }
+
+    # --- Log payload, tail-capped at 128 KiB ---------------------------------
+    $MaxLogBytes = 128 * 1024
+    $TruncNotice = '[log truncated to last 128 KB]'
+    if (Test-Path -LiteralPath $LogPath) {
+        $raw = [System.IO.File]::ReadAllBytes($LogPath)
+    } else {
+        $raw = [System.Text.Encoding]::UTF8.GetBytes('(installer log not found: ' + $LogPath + ')')
+    }
+    if ($raw.Length -gt $MaxLogBytes) {
+        $tail = New-Object byte[] $MaxLogBytes
+        [System.Buffer]::BlockCopy($raw, $raw.Length - $MaxLogBytes, $tail, 0, $MaxLogBytes)
+        $prefix = [System.Text.Encoding]::UTF8.GetBytes($TruncNotice + "`r`n")
+        $logBytes = New-Object byte[] ($prefix.Length + $tail.Length)
+        [System.Buffer]::BlockCopy($prefix, 0, $logBytes, 0, $prefix.Length)
+        [System.Buffer]::BlockCopy($tail, 0, $logBytes, $prefix.Length, $tail.Length)
+    } else {
+        $logBytes = $raw
+    }
+
+    # --- Abort reason, read from the log itself --------------------------------
+    # AbortInstall logs "ABORT: ..." first, so the reason travels inside the file
+    # and nothing reason-shaped crosses the command line (no quoting hazards).
+    # Select-String yields the matching line alone, so the reason is already one
+    # physical line for the message; anything else stays in the attached log.
+    # Non-ASCII paths may garble here; the attachment is byte-exact regardless.
+    $Reason = 'unknown (no ABORT line in log)'
+    if (Test-Path -LiteralPath $LogPath) {
+        $abortLine = Select-String -LiteralPath $LogPath -Pattern '^ABORT: ' | Select-Object -Last 1
+        if ($abortLine) {
+            $Reason = ($abortLine.Line -replace '^ABORT:\s*', '')
+        }
+    }
+
+    # --- Event ---------------------------------------------------------------
+    $eventId = [guid]::NewGuid().ToString('N')
+    $now = (Get-Date).ToUniversalTime().ToString('yyyy-MM-ddTHH:mm:ssZ')
+    # $Event is an automatic variable (Microsoft.PowerShell.Utility\Register-ObjectEvent),
+    # so the local is named $sentryEvent to avoid shadowing it.
+    $sentryEvent = [ordered]@{
+        event_id = $eventId
+        timestamp = $now
+        platform = 'other'
+        level = 'error'
+        logger = 'cockatrice-installer'
+        release = $Release
+        environment = 'installer'
+        sdk = @{ name = 'cockatrice.installer'; version = $Release }
+        message = @{ formatted = 'Installer aborted: ' + $Reason }
+        extra = @{
+            reason = $Reason
+            os = [System.Environment]::OSVersion.VersionString
+        }
+    }
+    $eventJson = $sentryEvent | ConvertTo-Json -Compress -Depth 6
+    $eventBytes = [System.Text.Encoding]::UTF8.GetBytes($eventJson)
+
+    # --- Envelope, assembled as bytes (the log is opaque binary) -------------
+    $sentAt = (Get-Date).ToUniversalTime().ToString('yyyy-MM-ddTHH:mm:ssZ')
+    $headerLine = '{"event_id":"' + $eventId + '","sent_at":"' + $sentAt + '","dsn":"' + $Dsn + '"}'
+    $eventHeader = '{"type":"event","length":' + $eventBytes.Length + '}'
+    $attachHeader = '{"type":"attachment","filename":"Cockatrice-installer.log","content_type":"text/plain","length":' + $logBytes.Length + '}'
+    $enc = [System.Text.Encoding]::UTF8
+    $lf = [byte[]]@(10)
+    $body = New-Object System.IO.MemoryStream
+    foreach ($chunk in @($enc.GetBytes($headerLine), $lf, $enc.GetBytes($eventHeader), $lf, $eventBytes, $lf, $enc.GetBytes($attachHeader), $lf, $logBytes)) {
+        $body.Write($chunk, 0, $chunk.Length)
+    }
+    $bodyBytes = $body.ToArray()
+    $body.Close()
+
+    # --- Send ----------------------------------------------------------------
+    # The key travels in the auth header only; stdout below never contains it.
+    $auth = 'Sentry sentry_version=7, sentry_client=cockatrice.installer/' + $Release + ', sentry_key=' + $SentryKey
+    Invoke-RestMethod -Uri $EnvelopeUrl -Method Post -TimeoutSec 45 -ContentType 'application/x-sentry-envelope' -Headers @{ 'X-Sentry-Auth' = $auth } -Body $bodyBytes | Out-Null
+    Write-Output ('SENT ' + $eventId)
+    exit 0
+} catch {
+    # Scrub the key/DSN out of the failure text in case a transport error echoes them.
+    $msg = $_.Exception.Message
+    if ($msg -and $SentryKey) {
+        $msg = $msg.Replace($SentryKey, '<redacted>')
+    }
+    if ($msg -and $Dsn) {
+        $msg = $msg.Replace($Dsn, '<redacted>')
+    }
+    # Flatten to one line: this text is echoed into the installer log, which is
+    # itself uploaded as an attachment, so a multi-line transport error must not
+    # be able to forge extra lines in the artifact we send.
+    if ($msg) {
+        $msg = ($msg -replace '\s+', ' ').Trim()
+    }
+    Write-Output ('FAILED: ' + $msg)
+    exit 1
+}