diff --git a/docs/swarm/README.md b/docs/swarm/README.md
index 77c87247..fc6f3c79 100644
--- a/docs/swarm/README.md
+++ b/docs/swarm/README.md
@@ -88,6 +88,12 @@ One authelia, one matrix, one forge per swarm — which host runs them,
 and what a hive that runs none of them configures instead:
 [`services.md`](services.md).
 
+## Single sign-on
+
+Which secrets the SSO provider generates, which one has a reader in
+another container, and the three ways that one gets delivered:
+[`sso.md`](sso.md).
+
 ## The swarm's hive directory
 
 ```nix
diff --git a/docs/swarm/sso.md b/docs/swarm/sso.md
new file mode 100644
index 00000000..0c1c5b61
--- /dev/null
+++ b/docs/swarm/sso.md
@@ -0,0 +1,92 @@
+# Swarm SSO
+
+The swarm runs one authelia, and it is two things at once: the **session
+provider** every protected vhost checks (`auth_request`), and — once any
+client is declared — an **OIDC provider** issuing tokens to relying
+parties like the forge.
+
+The second role is derived rather than switched:
+`services.hyperhive.swarm.authelia.oidc.clients` being non-empty turns it
+on. authelia refuses to start with a provider that has no clients, so a
+separate `enable` would be a second fact free to disagree with the first.
+
+## What secrets exist, and where each one lives
+
+| secret | generated by | rests in | read by |
+|---|---|---|---|
+| `jwt.key`, `session.key`, `storage-encryption.key` | authelia's first-boot unit | `/var/lib/authelia-swarm/` | authelia |
+| `oidc-hmac.key` | same unit | same directory | authelia |
+| `oidc-issuer.key` (RSA) | same unit | same directory | authelia signs with it; clients verify the **public** half at `/jwks.json` |
+| `oidc-clients/<id>.digest` | same unit, via `authelia crypto hash generate` | same directory, merged in through `settingsFiles` | authelia |
+| `oidc-clients/<id>.secret` | the same mint — this is its plaintext half | same directory | **the relying party, in another container** |
+
+Everything above the last row is generated in-container because nothing
+outside that container ever reads it. That is the test worth applying to
+any secret added here. The last row fails it, and that is the entire
+reason a delivery step exists.
+
+**None of it is ever written into a nix expression.** authelia's
+`settings` are rendered into the nix store, which is world-readable and
+permanent, so the client digest reaches authelia through `settingsFiles`
+(merged at runtime) and every other secret through a `*File` option
+carrying a path rather than a value.
+
+## Getting the plaintext to the relying party
+
+Three cases, and they are genuinely different mechanisms rather than one
+mechanism with flags.
+
+### 1. All-local — one host runs both
+
+Nothing to configure beyond `swarm.forge.sso.enable = true`. A host-side
+unit waits for authelia's first boot to mint the secret and copies it
+into the forge container, and the forge module contributes its own client
+entry — callback URL included — to authelia's client list.
+
+The callback is built from the same source name the registration uses, so
+the redirect URI authelia is told to allow and the one forgejo actually
+sends cannot drift apart. A mismatch there is a rejected login with no
+error text worth reading.
+
+⚠️ The delivery is a copy, not a `bindMounts` entry, and deliberately so:
+nixos-container refuses to start a container whose bind source is
+missing, and this secret does not exist until authelia's first boot has
+run. Binding it would make the forge wait on a file that waits on a
+container that starts after it — on a fresh hive, a permanent stall
+presenting as "the forge is broken", several layers from its cause.
+
+### 2. Swarm-managed services
+
+The controller side owns provisioning: `swarmctl` writes both halves, the
+same way it already owns authelia's user store (`users.json` canonical,
+`users.yml` a rendered artifact).
+
+### 3. A hive elsewhere
+
+No shared host, so no automatic path. The operator provides the file and
+names it:
+
+```nix
+services.hyperhive.swarm = {
+  authelia.url = "https://auth.example.com";
+  forge.sso = {
+    enable = true;
+    clientSecretFile = "/var/lib/hyperhive/forge-oidc-secret";
+  };
+};
+```
+
+**Both are asserted at eval.** A hive that boots with SSO
+half-configured shows a login button that always fails — a symptom
+several layers from its cause, and far worse to diagnose than an
+evaluation error.
+
+## What this does not do
+
+- **It does not disable local login.** The forge keeps its password
+  database and gains a second door. An identity provider that can take
+  the forge offline when it hiccups is a worse forge than one with two
+  ways in.
+- **It does not provision users.** Agents are created and destroyed
+  continuously, so the subject set belongs to a program rather than to a
+  config file; today that program is `swarmctl`.
diff --git a/nix/host-modules/hive-forge/default.nix b/nix/host-modules/hive-forge/default.nix
index 7a59a3ce..518a63a0 100644
--- a/nix/host-modules/hive-forge/default.nix
+++ b/nix/host-modules/hive-forge/default.nix
@@ -23,6 +23,38 @@ let
   # that make the CA reachable are shared with hive-ci via the
   # `hive-ca-trust` helper; only the Go SSL_CERT_FILE concat below is
   # hive-forge-specific.
+  # Forgejo's name for the login source. A constant, not an option: it
+  # is the key this module's own idempotency check looks up, so making
+  # it configurable would buy nothing and add a way for the lookup and
+  # the row to disagree.
+  ssoSourceName = "authelia";
+
+  # `url` is the half of the authelia module that exists on EVERY hive —
+  # null when no SSO provider is configured anywhere, which the
+  # assertion below turns into an eval failure rather than a discovery
+  # request to `null/.well-known/...`.
+  autheliaCfg = config.services.hyperhive.swarm.authelia;
+  autheliaUrl = autheliaCfg.url;
+  autheliaDiscoveryUrl = "${toString autheliaUrl}/.well-known/openid-configuration";
+
+  # The all-local case: this host runs BOTH the forge and the swarm's
+  # authelia, so the secret can be moved without an operator. The other
+  # two cases (swarm side via swarmctl, remote hive) leave
+  # `clientSecretFile` to be set explicitly — see docs/swarm/.
+  ssoLocal = cfg.sso.enable && autheliaCfg.enable;
+
+  # Where the plaintext lands inside the forge container. Under
+  # /var/lib rather than /run: the forge may start before the delivery
+  # unit on a later boot, and a secret that evaporates on reboot turns a
+  # working login into an intermittent one.
+  forgeSecretPath = "/var/lib/forgejo-oidc/${cfg.sso.clientId}.secret";
+
+  # Forgejo's OAuth2 callback shape. Built from the SAME `ssoSourceName`
+  # the registration uses, so the redirect URI authelia is told to allow
+  # and the one forgejo will actually send cannot drift apart — a
+  # mismatch there is a rejected login with no error text worth reading.
+  ssoRedirectUri = "${effectiveRootUrl}user/oauth2/${ssoSourceName}/callback";
+
   caTrust = import ../lib/hive-ca-trust.nix { inherit lib tlsCfg gatewayCfg; };
   useSelfSigned = caTrust.useSelfSigned;
   caContainerPath = caTrust.caContainerPath;
@@ -314,10 +346,86 @@ in
         external DNS, but that's off the CI path).
       '';
     };
+
+    sso = {
+      enable = lib.mkOption {
+        type = lib.types.bool;
+        default = false;
+        example = true;
+        description = ''
+          Register the swarm's authelia as an OpenID Connect login
+          source on this forge.
+
+          **Additive, never exclusive.** Forgejo keeps its local
+          password database and gains an extra "sign in with" button;
+          this does not disable local login. Deliberate: an identity
+          provider that can take the forge offline when it hiccups is a
+          worse forge than one with two ways in.
+        '';
+      };
+
+      clientId = lib.mkOption {
+        type = lib.types.str;
+        default = "forgejo";
+        description = ''
+          OAuth2 client id this forge identifies itself with. Must match
+          the `id` of the corresponding entry in
+          `services.hyperhive.swarm.authelia.oidc.clients`.
+        '';
+      };
+
+      clientSecretFile = lib.mkOption {
+        type = lib.types.nullOr lib.types.str;
+        default = null;
+        example = "/var/lib/hyperhive/forge-oidc-secret";
+        description = ''
+          Path **inside the forge container** holding the client
+          secret's plaintext.
+
+          A path, never a value: an OIDC client secret has two holders
+          in two containers (authelia keeps a hash, this forge needs the
+          plaintext), and a literal written here would be rendered into
+          the world-readable nix store.
+
+          Required when `enable` is set — deliberately no fallback. A
+          forge that boots with SSO half-configured presents as a login
+          button that always fails, which is harder to diagnose than an
+          eval error.
+        '';
+      };
+    };
   };
 
   config = lib.mkIf config.services.hyperhive.enable {
     assertions = [
+      {
+        # Fail at EVAL, not at boot. The alternative failure is a login
+        # button that always 401s, three layers from the missing file.
+        assertion = !cfg.sso.enable || cfg.sso.clientSecretFile != null;
+        message = ''
+          services.hyperhive.swarm.forge.sso.enable requires
+          sso.clientSecretFile — the path (inside the forge container)
+          holding the OIDC client secret's plaintext.
+
+          On a hive that also runs the swarm's authelia this is wired up
+          for you. Set it explicitly when authelia lives on another
+          host: see docs/swarm/ for which secret goes where.
+        '';
+      }
+      {
+        # Without a provider URL there is nothing to discover against,
+        # and the rendered unit would ask `null/.well-known/…`.
+        assertion = !cfg.sso.enable || autheliaUrl != null;
+        message = ''
+          services.hyperhive.swarm.forge.sso.enable requires
+          services.hyperhive.swarm.authelia.url — the base URL of the
+          swarm's SSO provider.
+
+          It defaults to this host's own instance only when this host
+          runs authelia. A hive that federates with a swarm sets it
+          explicitly to wherever that provider lives.
+        '';
+      }
       {
         assertion = cfg.rootUrl == null || lib.hasSuffix "/" cfg.rootUrl;
         message = ''
@@ -648,9 +756,155 @@ in
               fi
             '';
           };
+
+          # Register authelia as an OIDC login source.
+          #
+          # ⚠️ Ordered AFTER forgejo, unlike forgejo-gpg-init above, and
+          # the difference is not stylistic: a login source is a row in
+          # forgejo's database, and on a fresh hive that database does
+          # not exist until forgejo has started and run its migrations.
+          # Running first would either fail or let the CLI initialise a
+          # schema behind the server's back.
+          #
+          # Idempotency is by QUERY, not by a stamp file — same reason
+          # spelled out for the GPG key above: a stamp survives a state
+          # wipe that took the thing it claims exists, and then suppresses
+          # the repair.
+          systemd.services.forgejo-sso-source = lib.mkIf cfg.sso.enable {
+            description = "register authelia as Forgejo's OIDC login source";
+            after = [ "forgejo.service" ];
+            requires = [ "forgejo.service" ];
+            wantedBy = [ "multi-user.target" ];
+            serviceConfig = {
+              Type = "oneshot";
+              RemainAfterExit = true;
+              User = "forgejo";
+              Group = "forgejo";
+              SyslogIdentifier = "forgejo-sso-source";
+            };
+            # `FORGEJO_CUSTOM` (not `GITEA_CUSTOM` — forgejo renamed it)
+            # is how the CLI finds the app.ini upstream's module wrote.
+            environment.FORGEJO_CUSTOM = "/var/lib/forgejo/custom";
+            path = [
+              cfg.package
+              pkgs.coreutils
+              pkgs.gnugrep
+            ];
+            script = ''
+              set -euo pipefail
+
+              secret=$(cat ${lib.escapeShellArg cfg.sso.clientSecretFile})
+              if [ -z "$secret" ]; then
+                echo "empty OIDC client secret at ${cfg.sso.clientSecretFile}" >&2
+                exit 1
+              fi
+
+              # `--secret` is the only input forgejo offers: there is no
+              # --secret-file and no env var, though its sibling
+              # `forgejo-cli actions register` has both. So the value is
+              # on this argv for the length of one exec, inside this
+              # container, where forgejo already stores it at rest in the
+              # login-source row — root and forgejo are the only
+              # principals here, and root can read the resting copy
+              # anyway. Accepted deliberately (see docs/swarm/), not
+              # overlooked; upstream gap filed.
+              args="--provider openidConnect \
+                --key ${lib.escapeShellArg cfg.sso.clientId} \
+                --auto-discover-url ${lib.escapeShellArg autheliaDiscoveryUrl} \
+                --scopes ${lib.escapeShellArg "openid profile email groups"}"
+
+              # shellcheck disable=SC2086
+              if forgejo admin auth list | grep -q "[[:space:]]${ssoSourceName}[[:space:]]"; then
+                id=$(forgejo admin auth list \
+                  | grep "[[:space:]]${ssoSourceName}[[:space:]]" \
+                  | cut -f1)
+                forgejo admin auth update-oauth --id "$id" \
+                  --name ${lib.escapeShellArg ssoSourceName} \
+                  --secret "$secret" $args
+                echo "updated OIDC login source ${ssoSourceName} (id $id)"
+              else
+                forgejo admin auth add-oauth \
+                  --name ${lib.escapeShellArg ssoSourceName} \
+                  --secret "$secret" $args
+                echo "added OIDC login source ${ssoSourceName}"
+              fi
+            '';
+          };
         };
     };
 
+    # One declaration, two readers. The forge knows its own callback URL;
+    # making the operator restate it in authelia's client list would be a
+    # second source of truth for a string whose mismatch is a silent
+    # rejected login.
+    services.hyperhive.swarm.authelia.oidc.clients = lib.mkIf ssoLocal [
+      {
+        id = cfg.sso.clientId;
+        description = "HyperHive forge";
+        redirectUris = [ ssoRedirectUri ];
+      }
+    ];
+
+    # Same case, same reasoning: this host minted the secret, so it can
+    # say where the forge will find it.
+    services.hyperhive.swarm.forge.sso.clientSecretFile = lib.mkIf ssoLocal (
+      lib.mkDefault forgeSecretPath
+    );
+
+    # The delivery. It runs on the HOST because that is the only place
+    # both container trees are addressable: they share this host's
+    # network namespace, which makes them feel co-located, but their
+    # filesystem roots are separate — the forge cannot open a path inside
+    # authelia's tree however local the port looks.
+    #
+    # ⚠️ Deliberately a copy and not a `bindMounts` entry.
+    # nixos-container refuses to start when a bind source is missing, and
+    # this secret does not exist until authelia's first boot has minted
+    # it — so binding it would make the forge wait on a file that waits
+    # on a container that starts after it. On a fresh hive that is a
+    # permanent stall presenting as "the forge is broken", several layers
+    # from its cause.
+    systemd.services.hive-forge-oidc-secret = lib.mkIf ssoLocal {
+      description = "deliver the forge's OIDC client secret from authelia";
+      after = [ "container@${autheliaCfg.machine}.service" ];
+      requires = [ "container@${autheliaCfg.machine}.service" ];
+      before = [ "container@hive-forge.service" ];
+      wantedBy = [ "container@hive-forge.service" ];
+      serviceConfig = {
+        Type = "oneshot";
+        RemainAfterExit = true;
+        SyslogIdentifier = "hive-forge-oidc-secret";
+      };
+      path = [ pkgs.coreutils ];
+      script = ''
+        set -euo pipefail
+
+        src=${lib.escapeShellArg "${autheliaCfg.hostClientSecretDir}/${cfg.sso.clientId}.secret"}
+        dst=${lib.escapeShellArg "/var/lib/nixos-containers/hive-forge${forgeSecretPath}"}
+
+        # authelia's container is up, but its first-boot generator may
+        # still be minting. Bounded wait, then fail: a silent skip here
+        # produces a forge whose SSO button 401s, which is the failure
+        # this whole design is trying not to ship.
+        for _ in $(seq 1 60); do
+          [ -s "$src" ] && break
+          sleep 2
+        done
+        if [ ! -s "$src" ]; then
+          echo "authelia has not minted $src after 120s" >&2
+          exit 1
+        fi
+
+        # The owning uid is DISCOVERED, not assumed: read it off the
+        # forge container's own state dir. Whatever uid maps to forgejo
+        # inside that container is by definition the one that owns the
+        # directory it was created with, and hardcoding a number here
+        # would be a second place for it to be wrong.
+        uid=$(stat -c %u /var/lib/nixos-containers/hive-forge/var/lib/forgejo)
+        install -D -m 0400 -o "$uid" -g "$uid" "$src" "$dst"
+      '';
+    };
+
     networking.firewall = lib.mkIf cfg.openFirewall {
       allowedTCPPorts = [
         cfg.httpPort
diff --git a/nix/host-modules/swarm-authelia.nix b/nix/host-modules/swarm-authelia.nix
index 49ad4d07..8aca2d44 100644
--- a/nix/host-modules/swarm-authelia.nix
+++ b/nix/host-modules/swarm-authelia.nix
@@ -18,6 +18,10 @@
 # for LDAP: what makes a directory necessary is the size of the subject
 # set, and this deployment's is bounded by one swarm.
 #
+# Two roles: a **session** provider always, an **OIDC** provider when
+# `oidc.clients` is non-empty (derived, not flagged — authelia will not
+# start with a clientless provider). Secrets map: docs/swarm/sso.md.
+#
 # Per-service integration — putting authelia's `auth_request` in front
 # of the gateway's existing `auth_basic` locations — is deliberately NOT
 # here. Standing an SSO provider up is reversible; cutting every
@@ -52,6 +56,118 @@ let
   # below are: the required-domain assertion in hive-network.nix should
   # be what an operator sees, not a coercion error from here.
   cookieDomain = if swarmDomain == null then "invalid" else swarmDomain;
+
+  # authelia refuses to start with an OIDC provider that has no clients,
+  # so the provider is derived from the client list rather than carrying
+  # its own `enable`: one fact, and it cannot contradict itself. An empty
+  # list is the default, which makes every hive that has not opted in
+  # byte-identical to before.
+  oidcEnabled = cfg.oidc.clients != [ ];
+
+  # Secrets that are 64 random bytes of hex and nothing more. The OIDC
+  # hmac key joins them; the issuer key does not (see below — it is RSA).
+  randomKeys = [
+    "jwt"
+    "session"
+    "storage-encryption"
+  ]
+  ++ lib.optional oidcEnabled "oidc-hmac";
+
+  # Per-client material lives beside the rest of authelia's state, one
+  # file per half: the relying party needs the PLAINTEXT, authelia keeps
+  # only a DIGEST. Splitting them is what lets the clients file below be
+  # re-rendered on every boot from a secret that was minted once.
+  clientsDir = "${stateDir}/oidc-clients";
+  clientsFile = "${stateDir}/oidc-clients.yml";
+
+  # Rendered at RUNTIME, not evaluated: the digest is read from disk by
+  # the script, so nothing secret ever enters a nix expression (and
+  # therefore the store). Everything else here is public metadata that
+  # nix is the right place for.
+  renderClient = c: ''
+    printf -- '      - client_id: %s\n' ${lib.escapeShellArg c.id}
+    printf -- '        client_name: %s\n' ${lib.escapeShellArg c.description}
+    printf -- "        client_secret: '%s'\n" "$(cat ${lib.escapeShellArg "${clientsDir}/${c.id}.digest"})"
+    printf -- '        authorization_policy: one_factor\n'
+    printf -- '        scopes: [openid, profile, email, groups]\n'
+    printf -- '        redirect_uris:\n'
+    ${lib.concatMapStrings (u: ''
+      printf -- '          - %s\n' ${lib.escapeShellArg u}
+    '') c.redirectUris}
+  '';
+
+  # The OIDC half of the first-boot generator, kept out of the script
+  # body so neither is read through the other's indentation.
+  oidcGenScript = lib.optionalString oidcEnabled ''
+    # The issuer key is the one secret here that is NOT interchangeable
+    # with a random blob: it *signs* id tokens, and every relying party
+    # verifies them against the public half served at `/jwks.json`. A
+    # symmetric secret cannot do that, so this one is an RSA pair.
+    #
+    # Rotating it invalidates every token already issued, which is why
+    # it is generated once and left alone — same reason as the session
+    # and storage keys above.
+    issuer=${lib.escapeShellArg stateDir}/oidc-issuer.key
+    if [ ! -s "$issuer" ]; then
+      openssl genrsa -out "$issuer" 4096
+      echo "generated $issuer"
+    fi
+    chmod 0600 "$issuer"
+
+    # Each client's secret, minted once and kept as two files: the
+    # plaintext its relying party authenticates with, and the digest
+    # authelia compares against. The two live in different containers,
+    # so neither side can generate it alone — this is the only place
+    # that sees both.
+    #
+    # `--random` is why no plaintext ever reaches an argv: authelia
+    # generates the password itself and prints it beside its digest,
+    # so nothing has to be handed to a second process on a command
+    # line.
+    clients=${lib.escapeShellArg clientsDir}
+    mkdir -p "$clients"
+    chmod 0700 "$clients"
+
+    mint() {
+      sec="$clients/$1.secret"
+      dig="$clients/$1.digest"
+      if [ -s "$sec" ] && [ -s "$dig" ]; then
+        chmod 0600 "$sec" "$dig"
+        return
+      fi
+      out=$(authelia crypto hash generate pbkdf2 --variant sha512 --random)
+      printf '%s' "$out" | sed -n 's/^Random Password: *//p' > "$sec"
+      printf '%s' "$out" | sed -n 's/^Digest: *//p' > "$dig"
+      chmod 0600 "$sec" "$dig"
+      # Fail closed. An empty secret is a client that can never
+      # authenticate, and it surfaces three layers away as an opaque
+      # 401 from the token endpoint — refusing to start is by far the
+      # cheaper failure to diagnose.
+      if [ ! -s "$sec" ] || [ ! -s "$dig" ]; then
+        echo "authelia crypto hash generate produced no secret/digest for $1" >&2
+        exit 1
+      fi
+      echo "minted client secret for $1"
+    }
+
+    ${lib.concatMapStrings (c: ''
+      mint ${lib.escapeShellArg c.id}
+    '') cfg.oidc.clients}
+
+    # Re-rendered every boot, deliberately: the secret is minted once,
+    # but the metadata around it (a new redirect URI, a renamed client)
+    # comes from nix and has to be able to change without disturbing
+    # the secret. Written through a temp file so a crash mid-write
+    # cannot leave authelia half a file to parse.
+    {
+      printf -- 'identity_providers:\n'
+      printf -- '  oidc:\n'
+      printf -- '    clients:\n'
+      ${lib.concatMapStrings renderClient cfg.oidc.clients}
+    } > ${lib.escapeShellArg "${clientsFile}.tmp"}
+    chmod 0600 ${lib.escapeShellArg "${clientsFile}.tmp"}
+    mv ${lib.escapeShellArg "${clientsFile}.tmp"} ${lib.escapeShellArg clientsFile}
+  '';
 in
 {
   options.services.hyperhive.swarm.authelia = {
@@ -151,6 +267,59 @@ in
       '';
     };
 
+    oidc.clients = lib.mkOption {
+      type = lib.types.listOf (
+        lib.types.submodule {
+          options = {
+            id = lib.mkOption {
+              type = lib.types.str;
+              example = "forgejo";
+              description = ''
+                OAuth2 client id, as the relying party knows itself.
+              '';
+            };
+
+            description = lib.mkOption {
+              type = lib.types.str;
+              example = "HyperHive forge";
+              description = ''
+                Human-readable name, shown on authelia's consent screen.
+                This is the string a person reads when deciding whether
+                to hand an application their identity, so it should name
+                the application rather than the protocol.
+              '';
+            };
+
+            redirectUris = lib.mkOption {
+              type = lib.types.listOf lib.types.str;
+              example = [ "https://forge.example.com/user/oauth2/authelia/callback" ];
+              description = ''
+                Exact callback URLs the provider will redirect to.
+                Matched literally by authelia — a trailing-slash
+                difference is a rejected login, not a warning.
+              '';
+            };
+          };
+        }
+      );
+      default = [ ];
+      description = ''
+        OIDC relying parties this provider will issue tokens to.
+        Declaring one turns the provider on; the default empty list
+        leaves this module exactly as it was — a session provider and
+        nothing else.
+
+        ⚠️ **There is deliberately no secret here.** A client secret has
+        two holders in two containers (authelia keeps a *hash*, the
+        relying party the *plaintext*), and
+        `services.authelia.instances.<n>.settings` is rendered into the
+        **nix store**, which is world-readable and permanent. So this
+        option carries only the parts that are safe to evaluate: the
+        secret is minted on first boot and never passes through a nix
+        expression. See `docs/swarm/` for what goes where.
+      '';
+    };
+
     # Derived facts, exposed for consumers that have to act on this
     # container **from outside it** — `swarmctl` is the first, and it
     # needs all three. Read-only options rather than literals repeated at
@@ -179,6 +348,28 @@ in
       '';
     };
 
+    hostClientSecretDir = lib.mkOption {
+      type = lib.types.str;
+      readOnly = true;
+      default = "/var/lib/nixos-containers/${cfg.machine}${clientsDir}";
+      description = ''
+        Where the minted client secrets sit **as seen from the host** —
+        `<id>.secret` holds a plaintext, `<id>.digest` the hash authelia
+        itself reads.
+
+        Published for the same reason as `hostUsersFile`: the plaintext's
+        other reader lives in a **different container**, and containers
+        that share this host's network namespace still have separate
+        filesystem roots. The host is the only place both trees are
+        addressable, so the host is where a delivery step has to run.
+
+        ⚠️ Nothing here exists until authelia's **first boot** has run.
+        A consumer must wait for it — it cannot be a `bindMounts` source,
+        because nixos-container refuses to start when a bind source is
+        missing, and that turns a fresh hive into a boot-order deadlock.
+      '';
+    };
+
     hostUsersFile = lib.mkOption {
       type = lib.types.str;
       readOnly = true;
@@ -242,7 +433,17 @@ in
             wantedBy = [ "multi-user.target" ];
             before = [ "${unitName}.service" ];
             requiredBy = [ "${unitName}.service" ];
-            path = [ pkgs.coreutils ];
+            # `cfg.package` is here for its CLI, not its daemon: the
+            # client secrets are minted with `authelia crypto hash
+            # generate`, which is the only way to produce a digest in
+            # the exact form authelia will later verify.
+            path = [
+              pkgs.coreutils
+            ]
+            ++ lib.optionals oidcEnabled [
+              pkgs.openssl
+              cfg.package
+            ];
             serviceConfig = {
               Type = "oneshot";
               RemainAfterExit = true;
@@ -260,7 +461,7 @@ in
               # session and storage keys are load-bearing for data
               # already written (sessions, the encrypted store), so
               # replacing one is an operator action, not a boot action.
-              for f in jwt session storage-encryption; do
+              for f in ${lib.concatStringsSep " " randomKeys}; do
                 p=${lib.escapeShellArg stateDir}/"$f".key
                 if [ ! -s "$p" ]; then
                   head -c 64 /dev/urandom | od -An -tx1 | tr -d ' \n' > "$p"
@@ -268,6 +469,7 @@ in
                 fi
                 chmod 0600 "$p"
               done
+              ${oidcGenScript}
 
               # A users database that exists and parses, with nobody in
               # it. authelia refuses to start without one, and the
@@ -286,10 +488,37 @@ in
             enable = true;
             package = cfg.package;
 
+            # Merged at RUNTIME alongside the nix-generated config, which
+            # is the whole reason the client digests can exist at all:
+            # `settings` below is rendered into the world-readable nix
+            # store, and a client secret's digest may not go there.
+            # Empty (and inert) on a hive with no clients declared.
+            settingsFiles = lib.optional oidcEnabled clientsFile;
+
             secrets = {
               jwtSecretFile = "${stateDir}/jwt.key";
               sessionSecretFile = "${stateDir}/session.key";
               storageEncryptionKeyFile = "${stateDir}/storage-encryption.key";
+            }
+            // lib.optionalAttrs oidcEnabled {
+              # Both are `LoadCredential`-delivered by upstream's module,
+              # so they reach authelia as `AUTHELIA_*_FILE` env and never
+              # as values. Same by-path discipline as the three above —
+              # which is what lets the provider's own secrets stay
+              # in-container: nothing outside this container reads them.
+              #
+              # ⚠️ The issuer key is NOT passed as the deprecated
+              # `issuer_private_key`: on 4.38+ the config key is the
+              # `jwks` *list*, and a list element cannot take the
+              # `_FILE` env treatment. Upstream's module bridges that
+              # by generating a small settings file that templates the
+              # PEM in (`{{ secret "<path>" }}`) and prepending it to
+              # `settingsFiles`. So handing it a path here is the
+              # modern shape, not the legacy one — checked against the
+              # pin (nixpkgs `services/security/authelia.nix`), because
+              # the option name alone reads like the old key.
+              oidcHmacSecretFile = "${stateDir}/oidc-hmac.key";
+              oidcIssuerPrivateKeyFile = "${stateDir}/oidc-issuer.key";
             };
 
             # Small-deployment defaults, and the scope is the