diff --git a/fluxer_docs/scripts/VerifyDocsCoverage.ts b/fluxer_docs/scripts/VerifyDocsCoverage.ts
index e74e9e285..24087a652 100644
--- a/fluxer_docs/scripts/VerifyDocsCoverage.ts
+++ b/fluxer_docs/scripts/VerifyDocsCoverage.ts
@@ -1314,6 +1314,33 @@ console.log('self-hosting guide against deploy/self-hosting');
 		}
 	}
 
+	const COMPOSE_DEFAULT_NAMES = ['compose.yaml', 'compose.yml', 'docker-compose.yml', 'docker-compose.yaml'];
+	const shellComposeNames = shellRows('fluxer_compose_names', 'NAMES', 'the install.sh compose name list');
+	const powershellComposeNames: Array<string> = [];
+	for (const row of powershellRows('FluxerComposeNames', 'the install.ps1 compose name list')) {
+		const parsed = row.match(/^\s*'([^']+)'\s*$/u);
+		if (parsed == null) {
+			problems.push(`the install.ps1 compose name list carries \`${row.trim()}\`, which is not a quoted file name`);
+			continue;
+		}
+		powershellComposeNames.push(parsed[1]);
+	}
+	for (const [script, list] of [
+		['install.sh', shellComposeNames],
+		['install.ps1', powershellComposeNames],
+	] as const) {
+		if (list.join(', ') !== COMPOSE_DEFAULT_NAMES.join(', ')) {
+			problems.push(
+				`${script} resolves compose files as [${list.join(', ')}] and Compose resolves them as [${COMPOSE_DEFAULT_NAMES.join(', ')}]`,
+			);
+		}
+	}
+	if (!shellStackFiles.includes('docker-compose.yml') || !COMPOSE_DEFAULT_NAMES.includes('docker-compose.yml')) {
+		problems.push(
+			'the installers no longer download docker-compose.yml, so the name they map onto an instance is unclear',
+		);
+	}
+
 	const PIPE_TO_SHELL =
 		/(?:curl|wget|iwr|Invoke-WebRequest)[^\n|]*\|\s*(?:sudo\s+)?(?:sh|bash|zsh|iex|Invoke-Expression)\b/iu;
 	const docsPages = await walk(DOCS_ROOT);
@@ -1419,10 +1446,15 @@ console.log('self-hosting guide against deploy/self-hosting');
 		await writeFile(path.join(instance, '.env'), 'FLUXER_DOMAIN=x.example\nFLUXER_IMAGE_TAG=2026.813.205040\n');
 		await writeFile(path.join(instance, 'docker-compose.yml'), 'name: fluxer\nservices:\n  api:\n    image: stub\n');
 
-		const plannedRef = (label: string, args: ReadonlyArray<string>): string | null => {
+		const planned = (label: string, args: ReadonlyArray<string>, cwd?: string): string | null => {
 			const run = spawnSync('sh', [path.join(INSTALLER_ROOT, 'install.sh'), ...args], {
+				cwd,
 				encoding: 'utf8',
-				env: {...process.env, PATH: `${stubBin}${path.delimiter}${process.env.PATH ?? ''}`},
+				env: {
+					...process.env,
+					PATH: `${stubBin}${path.delimiter}${process.env.PATH ?? ''}`,
+					...(cwd == null ? {} : {PWD: cwd}),
+				},
 			});
 			if (run.error != null) {
 				problems.push(`install.sh ${label} could not run: ${run.error.message}`);
@@ -1432,7 +1464,15 @@ console.log('self-hosting guide against deploy/self-hosting');
 				problems.push(`install.sh ${label} exited ${String(run.status)}: ${run.stderr.trim()}`);
 				return null;
 			}
-			const line = run.stdout.match(/^ {2}ref\s+(\S+)$/mu);
+			return run.stdout;
+		};
+
+		const plannedRef = (label: string, args: ReadonlyArray<string>): string | null => {
+			const stdout = planned(label, args);
+			if (stdout == null) {
+				return null;
+			}
+			const line = stdout.match(/^ {2}ref\s+(\S+)$/mu);
 			if (line == null) {
 				problems.push(`install.sh ${label} printed no ref line`);
 				return null;
@@ -1472,6 +1512,38 @@ console.log('self-hosting guide against deploy/self-hosting');
 				problems.push(`install.sh ${label} plans ref ${resolved}, and the image tag it pairs with wants ${expected}`);
 			}
 		}
+
+		const composeYmlInstance = path.join(sandbox, 'compose-yml-instance');
+		await mkdir(composeYmlInstance, {recursive: true});
+		await writeFile(
+			path.join(composeYmlInstance, '.env'),
+			'FLUXER_DOMAIN=x.example\nFLUXER_IMAGE_TAG=2026.813.205040\n',
+		);
+		await writeFile(path.join(composeYmlInstance, 'compose.yml'), 'name: fluxer\nservices:\n  api:\n    image: stub\n');
+		const COMPOSE_NAME_CASES: ReadonlyArray<readonly [string, ReadonlyArray<string>, string | undefined]> = [
+			[
+				'under --update against a compose.yml instance',
+				['--update', '--dry-run', '--allow-root', '--dir', composeYmlInstance],
+				undefined,
+			],
+			[
+				'under --update standing in a compose.yml instance',
+				['--update', '--dry-run', '--allow-root'],
+				composeYmlInstance,
+			],
+		];
+		for (const [label, args, cwd] of COMPOSE_NAME_CASES) {
+			const stdout = planned(label, args, cwd);
+			if (stdout == null) {
+				continue;
+			}
+			if (!/^ {4}compose\.yml is unchanged$/mu.test(stdout)) {
+				problems.push(`install.sh ${label} does not plan the refreshed stack file onto compose.yml`);
+			}
+			if (/^ {4}docker-compose\.yml is new$/mu.test(stdout)) {
+				problems.push(`install.sh ${label} plans a docker-compose.yml that Compose would never load there`);
+			}
+		}
 	} finally {
 		await rm(sandbox, {recursive: true, force: true});
 	}
diff --git a/fluxer_docs/src/installer/install.ps1 b/fluxer_docs/src/installer/install.ps1
index 6a6ee864e..e623e6e3d 100644
--- a/fluxer_docs/src/installer/install.ps1
+++ b/fluxer_docs/src/installer/install.ps1
@@ -108,6 +108,32 @@ $FluxerStackFiles = @(
 	'.env.example'
 )
 
+$FluxerComposeNames = @(
+	'compose.yaml'
+	'compose.yml'
+	'docker-compose.yml'
+	'docker-compose.yaml'
+)
+
+$script:FluxerComposeBase = 'docker-compose.yml'
+$script:FluxerComposeBaseFrom = ''
+
+function Get-FluxerComposeNameIn([string]$Directory) {
+	foreach ($name in $FluxerComposeNames) {
+		if (Test-Path -LiteralPath (Join-Path $Directory $name)) {
+			return $name
+		}
+	}
+	return ''
+}
+
+function Get-FluxerPlacedName([string]$Name) {
+	if ($Name -eq 'docker-compose.yml') {
+		return $script:FluxerComposeBase
+	}
+	return $Name
+}
+
 # The file Compose bind-mounts from the working directory, with the service that mounts it.
 # Compose decides whether to recreate a container by comparing its configuration, and the
 # contents of a bind-mounted file are not part of that comparison, so a changed Caddyfile survives
@@ -641,7 +667,7 @@ function Get-FluxerStackFiles([string]$StagingDir, [string]$RefValue) {
 # for an edit.
 function Move-FluxerStackFiles([string]$StagingDir, [string]$TargetDir) {
 	foreach ($name in $FluxerStackFiles) {
-		Move-Item -LiteralPath (Join-Path $StagingDir $name) -Destination (Join-Path $TargetDir $name) -Force
+		Move-Item -LiteralPath (Join-Path $StagingDir $name) -Destination (Join-Path $TargetDir (Get-FluxerPlacedName $name)) -Force
 	}
 }
 
@@ -840,7 +866,7 @@ function Get-FluxerComposeProject([string]$TargetDir) {
 	if ($null -ne $env:COMPOSE_PROJECT_NAME -and $env:COMPOSE_PROJECT_NAME.Length -gt 0) {
 		return $env:COMPOSE_PROJECT_NAME
 	}
-	foreach ($line in [System.IO.File]::ReadAllText((Join-Path $TargetDir 'docker-compose.yml')).Split("`n")) {
+	foreach ($line in [System.IO.File]::ReadAllText((Join-Path $TargetDir $script:FluxerComposeBase)).Split("`n")) {
 		if ($line -match '^name:\s*(\S+)') {
 			return $Matches[1]
 		}
@@ -1046,7 +1072,7 @@ function Restart-FluxerMounts($Entries, [string]$TargetDir) {
 	$services = @(Get-FluxerComposeServices)
 	foreach ($entry in $Entries) {
 		if ($services -notcontains $entry.Service) {
-			Write-FluxerLine "Skipping the restart of $($entry.Service), because the docker-compose.yml in $TargetDir defines no service by that name."
+			Write-FluxerLine "Skipping the restart of $($entry.Service), because the $($script:FluxerComposeBase) in $TargetDir defines no service by that name."
 			continue
 		}
 		Write-FluxerLine "Restarting $($entry.Service), because $($entry.Name) is mounted into it and up -d does not reload a mounted file."
@@ -1225,7 +1251,7 @@ function Save-FluxerCurrentFiles([string]$Record, [string]$TargetDir, [string]$E
 	Copy-Item -LiteralPath $EnvPath -Destination $envCopy -Force
 	Set-FluxerPrivateFile $envCopy
 	foreach ($name in $FluxerStackFiles) {
-		$source = Join-Path $TargetDir $name
+		$source = Join-Path $TargetDir (Get-FluxerPlacedName $name)
 		$length = Get-FluxerFileLength $source
 		if ($length -gt 0) {
 			Copy-Item -LiteralPath $source -Destination (Join-Path $Record $name) -Force
@@ -1427,7 +1453,7 @@ function Backup-FluxerInstance([string]$Record, [string]$TargetDir, [string]$Pro
 # The refreshed file is still staged when this runs, so a refusal here leaves the instance exactly
 # as it was.
 function Assert-FluxerPostgresMajor([string]$TargetDir, [string]$StagingDir) {
-	$old = Get-FluxerPostgresMajor (Join-Path $TargetDir 'docker-compose.yml')
+	$old = Get-FluxerPostgresMajor (Join-Path $TargetDir $script:FluxerComposeBase)
 	$new = Get-FluxerPostgresMajor (Join-Path $StagingDir 'docker-compose.yml')
 	if ($old.Length -eq 0 -or $new.Length -eq 0 -or $old -eq $new) {
 		return
@@ -1515,21 +1541,22 @@ function Show-FluxerUpdatePlan([string]$TargetDir, [string]$EnvPath, [string]$Ba
 		Write-FluxerLine '  File changes:'
 		$changed = 0
 		foreach ($name in $FluxerStackFiles) {
-			$current = Join-Path $TargetDir $name
+			$placed = Get-FluxerPlacedName $name
+			$current = Join-Path $TargetDir $placed
 			if (-not (Test-Path -LiteralPath $current)) {
-				Write-FluxerLine "    $name is new"
+				Write-FluxerLine "    $placed is new"
 				$changed++
 			} elseif (Test-FluxerSameFile $current (Join-Path $staging $name)) {
-				Write-FluxerLine "    $name is unchanged"
+				Write-FluxerLine "    $placed is unchanged"
 			} else {
-				Write-FluxerLine "    $name changes"
+				Write-FluxerLine "    $placed changes"
 				$changed++
 			}
 		}
 		if ($changed -eq 0) {
 			Write-FluxerLine "  Note:       ref $Ref moves no stack file"
 		}
-		$old = Get-FluxerPostgresMajor (Join-Path $TargetDir 'docker-compose.yml')
+		$old = Get-FluxerPostgresMajor (Join-Path $TargetDir $script:FluxerComposeBase)
 		$new = Get-FluxerPostgresMajor (Join-Path $staging 'docker-compose.yml')
 		if ($old.Length -gt 0 -and $new.Length -gt 0 -and $old -ne $new) {
 			Write-FluxerLine "  Refusal:    postgres moves from $old to $new, which this script does not do"
@@ -1706,7 +1733,7 @@ function Invoke-FluxerRollback([string]$TargetDir, [string]$EnvPath, [string]$Ba
 		$source = Join-Path $record $name
 		$length = Get-FluxerFileLength $source
 		if ($length -gt 0) {
-			Copy-Item -LiteralPath $source -Destination (Join-Path $TargetDir $name) -Force
+			Copy-Item -LiteralPath $source -Destination (Join-Path $TargetDir (Get-FluxerPlacedName $name)) -Force
 		} elseif (Test-Path -LiteralPath $source) {
 			Stop-Fluxer "$source is empty, so restoring it would replace a working file with nothing. Nothing was restored. Take the file from another record or from the ref the record names." $FluxerExitRefused
 		}
@@ -1739,13 +1766,20 @@ function Assert-FluxerInstance([string]$TargetDir, [string]$EnvPath) {
 	if (-not (Test-Path -LiteralPath $EnvPath)) {
 		Stop-Fluxer "No .env in $TargetDir. That directory holds no instance. Run install.ps1 with neither -Update nor -Rollback to set one up." $FluxerExitPrerequisite
 	}
-	$compose = Join-Path $TargetDir 'docker-compose.yml'
+	Resolve-FluxerComposeBase $TargetDir $EnvPath
+	$compose = Join-Path $TargetDir $script:FluxerComposeBase
 	if (-not (Test-Path -LiteralPath $compose)) {
-		Stop-Fluxer "No docker-compose.yml in $TargetDir. That directory does not hold an instance." $FluxerExitPrerequisite
+		if ($script:FluxerComposeBaseFrom.Length -gt 0) {
+			Stop-Fluxer "$($script:FluxerComposeBaseFrom) names $($script:FluxerComposeBase) first, and $compose is not there. Put that file back, or name the file the instance runs on first in COMPOSE_FILE." $FluxerExitPrerequisite
+		}
+		Stop-Fluxer "No compose file in $TargetDir. Compose looks for compose.yaml, compose.yml, docker-compose.yml and docker-compose.yaml there, and that directory holds none of them, so it does not hold an instance." $FluxerExitPrerequisite
 	}
 	if ((Get-FluxerFileLength $compose) -eq 0) {
 		Stop-Fluxer "$compose is empty. A redirect that captured a failed download leaves that, and Compose refuses an empty compose file. Put the file back from a backup or from the record of the last upgrade, then run this again." $FluxerExitPrerequisite
 	}
+	if ($script:FluxerComposeBase -ne 'docker-compose.yml') {
+		Write-FluxerLine "Compose loads $($script:FluxerComposeBase) in $TargetDir, so the stack's docker-compose.yml is written to that name."
+	}
 }
 
 # Compose reads COMPOSE_FILE from .env and loads every file it names before it answers anything, so
@@ -1776,7 +1810,7 @@ function Get-FluxerEnvScalar([string]$EnvPath, [string]$Name) {
 	return $raw
 }
 
-function Assert-FluxerComposeFiles([string]$TargetDir, [string]$EnvPath) {
+function Get-FluxerComposeSetting([string]$EnvPath) {
 	$value = ''
 	$source = 'the environment'
 	if ($null -ne $env:COMPOSE_FILE) {
@@ -1786,9 +1820,6 @@ function Assert-FluxerComposeFiles([string]$TargetDir, [string]$EnvPath) {
 		$value = Get-FluxerEnvScalar $EnvPath 'COMPOSE_FILE'
 		$source = $EnvPath
 	}
-	if ($value.Length -eq 0) {
-		return
-	}
 	$separator = ''
 	if ($null -ne $env:COMPOSE_PATH_SEPARATOR) {
 		$separator = [string]$env:COMPOSE_PATH_SEPARATOR
@@ -1799,6 +1830,50 @@ function Assert-FluxerComposeFiles([string]$TargetDir, [string]$EnvPath) {
 	if ($separator.Length -eq 0) {
 		$separator = [System.IO.Path]::PathSeparator
 	}
+	return [pscustomobject]@{Value = $value; Source = $source; Separator = $separator}
+}
+
+function Resolve-FluxerComposeBase([string]$TargetDir, [string]$EnvPath) {
+	$setting = Get-FluxerComposeSetting $EnvPath
+	$script:FluxerComposeBaseFrom = ''
+	foreach ($name in $setting.Value.Split([string[]]$setting.Separator, [System.StringSplitOptions]::None)) {
+		if ($name.Length -eq 0) {
+			continue
+		}
+		$base = $name
+		foreach ($prefix in @('./', '.\')) {
+			if ($base.StartsWith($prefix, [System.StringComparison]::Ordinal)) {
+				$base = $base.Substring($prefix.Length)
+			}
+		}
+		foreach ($root in @("$TargetDir/", "$TargetDir\")) {
+			if ($base.StartsWith($root, [System.StringComparison]::OrdinalIgnoreCase)) {
+				$base = $base.Substring($root.Length)
+			}
+		}
+		$script:FluxerComposeBaseFrom = "COMPOSE_FILE from $($setting.Source)"
+		if ($base.Contains('/') -or $base.Contains('\')) {
+			Stop-Fluxer "$($script:FluxerComposeBaseFrom) names $name first, and that file is not directly in $TargetDir. This script refreshes only the files in the directory it acts on, so the upgrade would leave the file Compose loads on the old stack. Move it into $TargetDir and name it there, or upgrade by hand." $FluxerExitPrerequisite
+		}
+		$script:FluxerComposeBase = $base
+		return
+	}
+	$found = Get-FluxerComposeNameIn $TargetDir
+	if ($found.Length -gt 0) {
+		$script:FluxerComposeBase = $found
+	} else {
+		$script:FluxerComposeBase = 'docker-compose.yml'
+	}
+}
+
+function Assert-FluxerComposeFiles([string]$TargetDir, [string]$EnvPath) {
+	$setting = Get-FluxerComposeSetting $EnvPath
+	$value = $setting.Value
+	$source = $setting.Source
+	$separator = $setting.Separator
+	if ($value.Length -eq 0) {
+		return
+	}
 	foreach ($name in $value.Split([string[]]$separator, [System.StringSplitOptions]::None)) {
 		if ($name.Length -eq 0) {
 			continue
@@ -1855,15 +1930,18 @@ function Invoke-FluxerInstall {
 
 	$targetPath = $Dir
 	$adoptedCwd = $false
+	$fellBack = $false
 	if ($targetPath.Length -eq 0) {
 		$here = (Get-Location).Path
 		$hereEnv = Join-Path $here '.env'
 		$hereIsFluxer = (Test-Path -LiteralPath $hereEnv) -and (@(Get-FluxerEnvLines $hereEnv | Where-Object {$_.StartsWith('FLUXER_')}).Count -gt 0)
-		if (($Update -or $Rollback) -and (Get-FluxerFileLength (Join-Path $here 'docker-compose.yml')) -gt 0 -and $hereIsFluxer) {
+		$hereCompose = Get-FluxerComposeNameIn $here
+		if (($Update -or $Rollback) -and $hereCompose.Length -gt 0 -and (Get-FluxerFileLength (Join-Path $here $hereCompose)) -gt 0 -and $hereIsFluxer) {
 			$targetPath = $here
 			$adoptedCwd = $true
 		} else {
 			$targetPath = Join-Path $HOME 'fluxer'
+			$fellBack = $Update -or $Rollback
 		}
 	}
 	$targetDir = $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath($targetPath)
@@ -1876,6 +1954,9 @@ function Invoke-FluxerInstall {
 	if ($adoptedCwd) {
 		Write-FluxerLine "Acting on the instance in $targetDir, the working directory. Pass -Dir to name another."
 	}
+	if ($fellBack) {
+		Write-FluxerLine "The working directory holds no instance, so this acts on $targetDir. Pass -Dir to name another."
+	}
 
 	if ($Update -or $Rollback) {
 		Assert-FluxerInstance $targetDir $envPath
@@ -1886,7 +1967,7 @@ function Invoke-FluxerInstall {
 		Assert-FluxerComposeFiles $targetDir $envPath
 		$project = Get-FluxerComposeProject $targetDir
 		if ($project.Length -eq 0) {
-			Stop-Fluxer "docker-compose.yml in $targetDir declares no project name, so the volume names cannot be derived." $FluxerExitPrerequisite
+			Stop-Fluxer "$($script:FluxerComposeBase) in $targetDir declares no project name, so the volume names cannot be derived." $FluxerExitPrerequisite
 		}
 		Push-Location -LiteralPath $targetDir
 		try {
diff --git a/fluxer_docs/src/installer/install.sh b/fluxer_docs/src/installer/install.sh
index c43f0e478..b4b47b548 100644
--- a/fluxer_docs/src/installer/install.sh
+++ b/fluxer_docs/src/installer/install.sh
@@ -131,6 +131,36 @@ Caddyfile
 FILES
 }
 
+fluxer_compose_names() {
+	cat <<'NAMES'
+compose.yaml
+compose.yml
+docker-compose.yml
+docker-compose.yaml
+NAMES
+}
+
+fluxer_compose_name_in() {
+	for fluxer_candidate in $(fluxer_compose_names); do
+		if [ -e "$1/$fluxer_candidate" ]; then
+			printf '%s' "$fluxer_candidate"
+			return 0
+		fi
+	done
+	return 1
+}
+
+fluxer_compose_base='docker-compose.yml'
+fluxer_compose_base_from=''
+
+fluxer_placed_name() {
+	if [ "$1" = 'docker-compose.yml' ]; then
+		printf '%s' "$fluxer_compose_base"
+	else
+		printf '%s' "$1"
+	fi
+}
+
 # The file Compose bind-mounts from the working directory, with the service that
 # mounts it.
 #
@@ -372,15 +402,21 @@ done
 #
 # An install writes a new instance, so it never adopts the working directory.
 if [ -z "$opt_dir" ]; then
+	fluxer_here_compose=$(fluxer_compose_name_in "$(pwd)" || true)
 	if { [ "$opt_update" -eq 1 ] || [ "$opt_rollback" -eq 1 ]; } &&
-		[ -s "$(pwd)/docker-compose.yml" ] && [ -e "$(pwd)/.env" ] &&
-		grep -q '^FLUXER_' "$(pwd)/.env" 2>/dev/null; then
+		[ -n "$fluxer_here_compose" ] && [ -s "$(pwd)/$fluxer_here_compose" ] &&
+		[ -e "$(pwd)/.env" ] && grep -q '^FLUXER_' "$(pwd)/.env" 2>/dev/null; then
 		opt_dir="$(pwd)"
 		fluxer_say "Acting on the instance in $opt_dir, the working directory. Pass --dir to name another."
-	elif [ -n "${HOME:-}" ]; then
-		opt_dir="$HOME/fluxer"
 	else
-		opt_dir="$(pwd)/fluxer"
+		if [ -n "${HOME:-}" ]; then
+			opt_dir="$HOME/fluxer"
+		else
+			opt_dir="$(pwd)/fluxer"
+		fi
+		if [ "$opt_update" -eq 1 ] || [ "$opt_rollback" -eq 1 ]; then
+			fluxer_say "The working directory holds no instance, so this acts on $opt_dir. Pass --dir to name another."
+		fi
 	fi
 fi
 case $opt_dir in
@@ -749,7 +785,7 @@ fluxer_fetch_stack() {
 fluxer_place_stack() {
 	while read -r fluxer_file; do
 		[ -n "$fluxer_file" ] || continue
-		mv "$fluxer_scratch/$fluxer_file.part" "$opt_dir/$fluxer_file"
+		mv "$fluxer_scratch/$fluxer_file.part" "$opt_dir/$(fluxer_placed_name "$fluxer_file")"
 	done < "$fluxer_scratch/files"
 	fluxer_say "Stack files in $opt_dir are at ref $opt_ref."
 }
@@ -759,7 +795,7 @@ fluxer_compose_project() {
 		printf '%s' "$COMPOSE_PROJECT_NAME"
 		return 0
 	fi
-	sed -n 's/^name: *//p' "$opt_dir/docker-compose.yml" | head -n 1
+	sed -n 's/^name: *//p' "$opt_dir/$fluxer_compose_base" | head -n 1
 }
 
 fluxer_project=''
@@ -767,7 +803,7 @@ fluxer_project=''
 fluxer_set_project() {
 	fluxer_project=$(fluxer_compose_project)
 	if [ -z "$fluxer_project" ]; then
-		fluxer_fail 2 "docker-compose.yml in $opt_dir declares no project name, so the volume names cannot be derived."
+		fluxer_fail 2 "$fluxer_compose_base in $opt_dir declares no project name, so the volume names cannot be derived."
 	fi
 }
 
@@ -1104,11 +1140,18 @@ fluxer_require_instance() {
 	if [ ! -e "$opt_dir/.env" ]; then
 		fluxer_fail 2 "No .env in $opt_dir. That directory holds no instance. Run install.sh with neither --update nor --rollback to set one up."
 	fi
-	if [ ! -e "$opt_dir/docker-compose.yml" ]; then
-		fluxer_fail 2 "No docker-compose.yml in $opt_dir. That directory does not hold an instance."
+	fluxer_resolve_compose_base
+	if [ ! -e "$opt_dir/$fluxer_compose_base" ]; then
+		if [ -n "$fluxer_compose_base_from" ]; then
+			fluxer_fail 2 "$fluxer_compose_base_from names $fluxer_compose_base first, and $opt_dir/$fluxer_compose_base is not there. Put that file back, or name the file the instance runs on first in COMPOSE_FILE."
+		fi
+		fluxer_fail 2 "No compose file in $opt_dir. Compose looks for compose.yaml, compose.yml, docker-compose.yml and docker-compose.yaml there, and that directory holds none of them, so it does not hold an instance."
 	fi
-	if [ ! -s "$opt_dir/docker-compose.yml" ]; then
-		fluxer_fail 2 "$opt_dir/docker-compose.yml is empty. A redirect that captured a failed download leaves that, and Compose refuses an empty compose file. Put the file back from a backup or from the record of the last upgrade, then run this again."
+	if [ ! -s "$opt_dir/$fluxer_compose_base" ]; then
+		fluxer_fail 2 "$opt_dir/$fluxer_compose_base is empty. A redirect that captured a failed download leaves that, and Compose refuses an empty compose file. Put the file back from a backup or from the record of the last upgrade, then run this again."
+	fi
+	if [ "$fluxer_compose_base" != 'docker-compose.yml' ]; then
+		fluxer_say "Compose loads $fluxer_compose_base in $opt_dir, so the stack's docker-compose.yml is written to that name."
 	fi
 }
 
@@ -1141,14 +1184,13 @@ fluxer_env_scalar() {
 	printf '%s' "$fluxer_scalar"
 }
 
-fluxer_require_compose_files() {
+fluxer_read_compose_setting() {
 	fluxer_compose_file=${COMPOSE_FILE:-}
 	fluxer_compose_from="the environment"
 	if [ -z "$fluxer_compose_file" ]; then
 		fluxer_compose_file=$(fluxer_env_scalar COMPOSE_FILE)
 		fluxer_compose_from="$opt_dir/.env"
 	fi
-	[ -n "$fluxer_compose_file" ] || return 0
 	fluxer_path_sep=${COMPOSE_PATH_SEPARATOR:-}
 	if [ -z "$fluxer_path_sep" ]; then
 		fluxer_path_sep=$(fluxer_env_scalar COMPOSE_PATH_SEPARATOR)
@@ -1156,6 +1198,36 @@ fluxer_require_compose_files() {
 	if [ -z "$fluxer_path_sep" ]; then
 		fluxer_path_sep=':'
 	fi
+}
+
+fluxer_resolve_compose_base() {
+	fluxer_read_compose_setting
+	fluxer_compose_base_from=''
+	fluxer_rest=$fluxer_compose_file
+	while [ -n "$fluxer_rest" ]; do
+		fluxer_name=${fluxer_rest%%"$fluxer_path_sep"*}
+		case $fluxer_rest in
+			*"$fluxer_path_sep"*) fluxer_rest=${fluxer_rest#*"$fluxer_path_sep"} ;;
+			*) fluxer_rest='' ;;
+		esac
+		[ -n "$fluxer_name" ] || continue
+		fluxer_compose_base=${fluxer_name#./}
+		fluxer_compose_base=${fluxer_compose_base#"$opt_dir"/}
+		fluxer_compose_base_from="COMPOSE_FILE from $fluxer_compose_from"
+		break
+	done
+	if [ -z "$fluxer_compose_base_from" ]; then
+		fluxer_compose_base=$(fluxer_compose_name_in "$opt_dir" || printf '%s' 'docker-compose.yml')
+		return 0
+	fi
+	case $fluxer_compose_base in
+		*/*) fluxer_fail 2 "$fluxer_compose_base_from names $fluxer_name first, and that file is not directly in $opt_dir. This script refreshes only the files in the directory it acts on, so the upgrade would leave the file Compose loads on the old stack. Move it into $opt_dir and name it there, or upgrade by hand." ;;
+	esac
+}
+
+fluxer_require_compose_files() {
+	fluxer_read_compose_setting
+	[ -n "$fluxer_compose_file" ] || return 0
 	fluxer_compose_count=0
 	fluxer_rest=$fluxer_compose_file
 	while [ -n "$fluxer_rest" ]; do
@@ -1185,7 +1257,7 @@ Leave the COMPOSE_FILE line as it is. Without $fluxer_name the edge container bi
 	done
 	if [ "$fluxer_compose_count" -gt 1 ] &&
 		! fluxer_version_ge "$fluxer_compose_version" "$FLUXER_MIN_COMPOSE_OVERLAY"; then
-		fluxer_fail 2 "COMPOSE_FILE from $fluxer_compose_from loads $fluxer_compose_count files and this host runs Compose $fluxer_compose_version. Every overlay this script downloads uses the !override tag, which needs Compose $FLUXER_MIN_COMPOSE_OVERLAY or newer. Upgrade Compose, or load only docker-compose.yml."
+		fluxer_fail 2 "COMPOSE_FILE from $fluxer_compose_from loads $fluxer_compose_count files and this host runs Compose $fluxer_compose_version. Every overlay this script downloads uses the !override tag, which needs Compose $FLUXER_MIN_COMPOSE_OVERLAY or newer. Upgrade Compose, or load only $fluxer_compose_base."
 	fi
 }
 
@@ -1315,10 +1387,11 @@ fluxer_save_current_files() {
 	chmod 600 "$fluxer_record/.env"
 	while read -r fluxer_file; do
 		[ -n "$fluxer_file" ] || continue
-		if [ -s "$opt_dir/$fluxer_file" ]; then
-			cp -p "$opt_dir/$fluxer_file" "$fluxer_record/$fluxer_file"
-		elif [ -e "$opt_dir/$fluxer_file" ]; then
-			fluxer_fail 7 "$opt_dir/$fluxer_file is empty, so the record would hold a file a rollback could not use. Put the file back before upgrading."
+		fluxer_placed="$opt_dir/$(fluxer_placed_name "$fluxer_file")"
+		if [ -s "$fluxer_placed" ]; then
+			cp -p "$fluxer_placed" "$fluxer_record/$fluxer_file"
+		elif [ -e "$fluxer_placed" ]; then
+			fluxer_fail 7 "$fluxer_placed is empty, so the record would hold a file a rollback could not use. Put the file back before upgrading."
 		fi
 	done < "$fluxer_scratch/files"
 }
@@ -1499,7 +1572,7 @@ fluxer_postgres_major() {
 # The refreshed file is still in the scratch directory when this runs, so a
 # refusal here leaves the instance exactly as it was.
 fluxer_guard_postgres_major() {
-	fluxer_old_major=$(fluxer_postgres_major "$opt_dir/docker-compose.yml")
+	fluxer_old_major=$(fluxer_postgres_major "$opt_dir/$fluxer_compose_base")
 	fluxer_new_major=$(fluxer_postgres_major "$fluxer_scratch/docker-compose.yml.part")
 	if [ -z "$fluxer_old_major" ] || [ -z "$fluxer_new_major" ]; then
 		return 0
@@ -1550,7 +1623,7 @@ $(fluxer_compose_error '  ')"
 	while read -r fluxer_file fluxer_service; do
 		[ -n "$fluxer_service" ] || continue
 		if ! grep -qxF "$fluxer_service" "$fluxer_scratch/services"; then
-			fluxer_say "Skipping the restart of $fluxer_service, because the docker-compose.yml in $opt_dir defines no service by that name."
+			fluxer_say "Skipping the restart of $fluxer_service, because the $fluxer_compose_base in $opt_dir defines no service by that name."
 			continue
 		fi
 		fluxer_say "Restarting $fluxer_service, because $fluxer_file is mounted into it and up -d does not reload a mounted file."
@@ -1656,20 +1729,21 @@ fluxer_plan_update() {
 	fluxer_changed=0
 	while read -r fluxer_file; do
 		[ -n "$fluxer_file" ] || continue
-		if [ ! -e "$opt_dir/$fluxer_file" ]; then
-			fluxer_say "    $fluxer_file is new"
+		fluxer_placed=$(fluxer_placed_name "$fluxer_file")
+		if [ ! -e "$opt_dir/$fluxer_placed" ]; then
+			fluxer_say "    $fluxer_placed is new"
 			fluxer_changed=1
-		elif cmp -s "$opt_dir/$fluxer_file" "$fluxer_scratch/$fluxer_file.part"; then
-			fluxer_say "    $fluxer_file is unchanged"
+		elif cmp -s "$opt_dir/$fluxer_placed" "$fluxer_scratch/$fluxer_file.part"; then
+			fluxer_say "    $fluxer_placed is unchanged"
 		else
-			fluxer_say "    $fluxer_file changes"
+			fluxer_say "    $fluxer_placed changes"
 			fluxer_changed=1
 		fi
 	done < "$fluxer_scratch/files"
 	if [ "$fluxer_changed" -eq 0 ]; then
 		fluxer_say "  note          ref $opt_ref moves no stack file"
 	fi
-	fluxer_old_major=$(fluxer_postgres_major "$opt_dir/docker-compose.yml")
+	fluxer_old_major=$(fluxer_postgres_major "$opt_dir/$fluxer_compose_base")
 	fluxer_new_major=$(fluxer_postgres_major "$fluxer_scratch/docker-compose.yml.part")
 	if [ -n "$fluxer_old_major" ] && [ -n "$fluxer_new_major" ] && [ "$fluxer_old_major" != "$fluxer_new_major" ]; then
 		fluxer_say "  refusal       postgres moves from $fluxer_old_major to $fluxer_new_major, which this script does not do"
@@ -1862,7 +1936,7 @@ fluxer_run_rollback() {
 	while read -r fluxer_file; do
 		[ -n "$fluxer_file" ] || continue
 		if [ -s "$fluxer_rollback_dir/$fluxer_file" ]; then
-			cp -p "$fluxer_rollback_dir/$fluxer_file" "$opt_dir/$fluxer_file"
+			cp -p "$fluxer_rollback_dir/$fluxer_file" "$opt_dir/$(fluxer_placed_name "$fluxer_file")"
 		elif [ -e "$fluxer_rollback_dir/$fluxer_file" ]; then
 			fluxer_fail 3 "$fluxer_rollback_dir/$fluxer_file is empty, so restoring it would replace a working file with nothing. Nothing was restored. Take the file from another record or from the ref the record names."
 		fi