diff --git a/TODO.md b/TODO.md
index ec3fe77..5e13fc6 100644
--- a/TODO.md
+++ b/TODO.md
@@ -39,12 +39,13 @@ compute of its own yet.
       502 is no longer cached. Whatever raises its hand for the api host
       should raise it for this too.
 - [ ] **Nothing says which index a deployed site expects.** The site pins a
-      MegaMek version in its own source and fetches `/assets/helm/<that>/…`;
-      nothing here fails when that version has no index published. The check
+      MegaMek version in its own source and fetches `/assets/helm/…`; nothing
+      here fails when the pinned pair has no index published. The check
       belongs at deploy time, where the release id and the bucket are both in
-      reach. `megamek_index_version` is now a second place the same version is
-      written down — the api's, for the match report — so the check has two
-      values to answer for rather than one.
+      reach, and it now has a second reader to answer for: the api reads
+      `<releases.helm>/<megamek_index_version>/units.json`, and an apply that
+      names a prefix helm never wrote leaves every match report with no
+      machine pictures until somebody looks at a log.
 - [ ] **Nothing prunes an old MegaMek's art.** Each release writes a prefix in
       the assets-megamek bucket and nothing removes one, deliberately — a match started
       under the old image still draws from it. 39MB a version is cheap enough
diff --git a/envs/lance.blue/main.tf b/envs/lance.blue/main.tf
index 2312ba1..a1d7d19 100644
--- a/envs/lance.blue/main.tf
+++ b/envs/lance.blue/main.tf
@@ -172,15 +172,27 @@ module "api_host" {
     # advertise api.lance.blue, which is the one thing the behaviour exists
     # to avoid.
     SHARE_ORIGIN = "https://${var.domain_name}"
-
-    # helm's index of the unit library, read once at api startup: it is what
-    # says which of MegaMek's pictures each design is drawn with, so a match
-    # report shows the machines that fought rather than one silhouette per
-    # weight class. Served from the distribution below, beside the art it
-    # names. Empty when no version is set, which the api reads as "no index".
-    UNIT_INDEX_URL = var.megamek_index_version == "" ? "" : "https://${var.domain_name}/assets/helm/${var.megamek_index_version}/units.json"
   }
 
+  # helm's index of the unit library, read once at api startup: it is what
+  # says which of MegaMek's pictures each design is drawn with, so a match
+  # report shows the machines that fought rather than one silhouette per
+  # class. Served from the distribution below, beside the art it names.
+  #
+  # Not part of match_env, which rides in user_data and replaces the instance
+  # when it changes. A helm release is a routine deploy and must not cost a
+  # new box, so this goes the way the image and arena tags go: a parameter the
+  # host's poller watches, which restarts the container within ten seconds.
+  #
+  # Both halves of the path or none of it. helm keys its artifacts by its own
+  # release and then by the MegaMek they describe, so an address built from
+  # one of them alone names a file that was never written.
+  unit_index_url = (
+    var.megamek_index_version == "" || var.releases.helm == ""
+    ? ""
+    : "https://${var.domain_name}/assets/helm/${var.releases.helm}/${var.megamek_index_version}/units.json"
+  )
+
   tags = { Component = "api", Environment = local.env }
 }
 
@@ -198,7 +210,8 @@ module "assets_megamek" {
 
 # helm's generated index of MegaMek's unit library: what a force-building
 # screen filters on, keyed by the MegaMek release it describes so it cannot
-# drift from the art beside it. scripts/assets-helm.sh publishes one.
+# drift from the art beside it. helm's own scripts/deploy.sh publishes one,
+# under a prefix named for the helm release that built it.
 module "assets_helm" {
   source = "../../modules/asset-bucket"
 
diff --git a/envs/lance.blue/variables.tf b/envs/lance.blue/variables.tf
index 240e43a..aa0d051 100644
--- a/envs/lance.blue/variables.tf
+++ b/envs/lance.blue/variables.tf
@@ -45,6 +45,9 @@ variable "releases" {
       arena - arena image tag a match task runs.
       site  - release id headquarters pushed the built site under. CloudFront
               serves releases/<id> in the site bucket; empty serves the root.
+      helm  - release id helm published its browser artifacts under. The
+              index and the wasm live at assets/helm/<id>/..., written by
+              helm's own scripts/deploy.sh, which also writes this value.
 
     A deploy is changing one of these and applying.
   EOT
@@ -53,6 +56,7 @@ variable "releases" {
     api   = string
     arena = string
     site  = string
+    helm  = string
   })
 
   validation {
@@ -172,7 +176,7 @@ variable "posthog_salt" {
 }
 
 variable "megamek_index_version" {
-  description = "The MegaMek release whose published unit index the api reads, e.g. \"0.51.0\". scripts/assets-helm.sh puts one at /assets/helm/<version>/units.json, and helm resolved the picture for every design in it; the api uses that to draw a machine on a match report as its own design rather than as its weight class. Empty means no index, and the reports draw silhouettes. Only a release whose index has actually been published belongs here - a version that was never synced is a report full of broken images."
+  description = "The MegaMek release the api reads an index for, e.g. \"0.51.0\". helm publishes its artifacts under assets/helm/<releases.helm>/<this>/units.json - two levels, because the index is a function of both helm's code and a particular MegaMek - and the api uses it to draw a machine on a match report as its own design rather than as its class. Must be a release helm has actually published an index for under the current releases.helm; empty means no index, and the reports draw no machine pictures at all."
   type        = string
   default     = ""
 }
diff --git a/modules/api-host/main.tf b/modules/api-host/main.tf
index b7d712e..d4c5196 100644
--- a/modules/api-host/main.tf
+++ b/modules/api-host/main.tf
@@ -143,6 +143,17 @@ resource "aws_ssm_parameter" "arena_tag" {
   value = var.arena_tag
 }
 
+# The unit index the api reads. Same delivery as the tags above and for the
+# same reason: helm publishes a release, this value moves, and the poller
+# restarts the container - where a user_data change would replace the host.
+resource "aws_ssm_parameter" "unit_index_url" {
+  name = "${local.ssm_prefix}/unit-index-url"
+  type = "String"
+  # SSM has no empty string. "none" is the absent value, and the host turns it
+  # back into an unset variable, which is what the api reads as "no index".
+  value = var.unit_index_url == "" ? "none" : var.unit_index_url
+}
+
 resource "aws_iam_instance_profile" "this" {
   name = "${var.name_prefix}-api-host-${var.environment}"
   role = aws_iam_role.this.name
diff --git a/modules/api-host/user_data.sh.tpl b/modules/api-host/user_data.sh.tpl
index 4516014..e5c3e62 100644
--- a/modules/api-host/user_data.sh.tpl
+++ b/modules/api-host/user_data.sh.tpl
@@ -39,9 +39,10 @@ mkdir -p /data/api /data/caddy
 docker network create web
 
 # Everything about how the api container runs, in one place. Idempotent: it
-# exits immediately when the running container already matches the image-tag
-# and arena-tag parameters. Secrets are fetched into shell variables and passed
-# to docker as env - they never land on disk.
+# exits immediately when the running container already matches every parameter
+# it is converged on - the image tag, the arena tag and the unit index.
+# Secrets are fetched into shell variables and passed to docker as env - they
+# never land on disk.
 cat > /usr/local/bin/api-deploy <<'DEPLOY'
 #!/bin/bash
 set -euo pipefail
@@ -55,12 +56,28 @@ image="${image_repo}:$tag"
 arena=$(aws ssm get-parameter --region ${region} \
   --name "${ssm_prefix}/arena-tag" --query Parameter.Value --output text)
 
+# helm's unit index, the same shape of value: env only, never pulled here, and
+# read by the api once at startup - so a new helm release moves this and the
+# container has to come back for it. "none" is how an absent index is spelt,
+# because SSM has no empty string.
+index=$(aws ssm get-parameter --region ${region} \
+  --name "${ssm_prefix}/unit-index-url" --query Parameter.Value --output text)
+if [ "$index" = "none" ]; then
+  index=""
+fi
+
 current=$(docker inspect -f '{{.Config.Image}}' api 2>/dev/null || true)
-current_arena=$(docker inspect -f '{{range .Config.Env}}{{println .}}{{end}}' api 2>/dev/null \
-  | sed -n 's/^ARENA_VERSION=//p' || true)
-[ "$image" = "$current" ] && [ "$arena" = "$current_arena" ] && exit 0
+env_of() {
+  docker inspect -f '{{range .Config.Env}}{{println .}}{{end}}' api 2>/dev/null \
+    | sed -n "s/^$1=//p" || true
+}
+current_arena=$(env_of ARENA_VERSION)
+current_index=$(env_of UNIT_INDEX_URL)
+[ "$image" = "$current" ] && [ "$arena" = "$current_arena" ] &&
+  [ "$index" = "$current_index" ] && exit 0
 
 echo "api-deploy: $current -> $image (arena $current_arena -> $arena)"
+[ "$index" = "$current_index" ] || echo "api-deploy: unit index $current_index -> $index"
 aws ecr get-login-password --region ${region} \
   | docker login --username AWS --password-stdin "${registry}"
 docker pull "$image"
@@ -86,6 +103,7 @@ docker run -d --restart always --name api --network web \
   -e WEB_ORIGIN="${web_origin}" \
   -e DB_PATH=/data/api/headquarters.sqlite \
   -e ARENA_VERSION="$arena" \
+  -e UNIT_INDEX_URL="$index" \
 %{ for k, v in match_env ~}
   -e ${k}="${v}" \
 %{ endfor ~}
diff --git a/modules/api-host/variables.tf b/modules/api-host/variables.tf
index 514a093..6783aed 100644
--- a/modules/api-host/variables.tf
+++ b/modules/api-host/variables.tf
@@ -65,6 +65,12 @@ variable "match_policy_arns" {
   default     = {}
 }
 
+variable "unit_index_url" {
+  description = "Address of helm's unit index, which the api reads once at startup to draw each machine on a match report as its own design. Delivered as an SSM parameter rather than in user_data: a helm release changes this, and a release must not replace the instance. Empty means no index, which the api accepts and reports."
+  type        = string
+  default     = ""
+}
+
 variable "match_env" {
   description = "Extra environment for the api container: the match set (cluster, task family, subnets, task security group, artifacts bucket - empty disables match launching) plus standalone api settings like the cookie domain and the flare space."
   type        = map(string)