diff --git a/.superpowers/sdd/task-7-report.md b/.superpowers/sdd/task-7-report.md
index a25de52c..ca384282 100644
--- a/.superpowers/sdd/task-7-report.md
+++ b/.superpowers/sdd/task-7-report.md
@@ -66,3 +66,14 @@ An operator must still choose the three reviewed legacy IDs, materialize real ru
 secrets, deploy Task 4 and Task 5 together in a maintenance window, apply the one-shot migrator,
 and run the documented authenticated smoke. The guarded helper has not been invoked with
 `--delete`.
+
+## P1 correction — migrator TLS validation
+
+The original migrator Compose command interpolated `THT_SESSION_DB_SSLMODE` into its URL without
+checking it. `docker/session-migrate.sh` now rejects every value except `verify-ca` and
+`verify-full` before reading the password file or building that URL; the Compose service invokes
+this helper. `docker/session-migrate.test.sh` first established RED because the helper did not
+exist, then verified that `prefer` is rejected before `tht` can run and that `verify-full` reaches
+a fake `tht` binary with the expected TLS URL. The helper and test pass `bash -n`; the focused
+backend config/health suite remains green, and the base-plus-overlay Compose configuration renders
+with temporary empty secret files.
diff --git a/README.md b/README.md
index cb3b79d9..7d23e7fa 100644
--- a/README.md
+++ b/README.md
@@ -230,6 +230,8 @@ The overlay mounts the runtime password at `/run/secrets/session_runtime_passwor
 It mounts `session_migrator_password` only to `session-migrate`. The backend refuses a server
 session store without upstream authentication, direct DB host/name/runtime user/password-file,
 `verify-ca` or `verify-full`, and an absolute CA path.
+The migrator independently rejects every other TLS mode before reading its password secret or
+constructing a database URL.
 
 Perform the cutover in one maintenance window, with the Task 4 portal proxy headers and Task 5
 backend principal parser deployed together. Neither change is safe to deploy independently: Task
diff --git a/deploy/compose.session-server.yaml.example b/deploy/compose.session-server.yaml.example
index afae607c..fbb1bc4f 100644
--- a/deploy/compose.session-server.yaml.example
+++ b/deploy/compose.session-server.yaml.example
@@ -27,18 +27,15 @@ services:
   session-migrate:
     image: thothii-core:local
     profiles: [session-migrate]
-    entrypoint: [/bin/sh, -ec]
-    command: >-
-      export PGPASSWORD="$$(cat /run/secrets/session_migrator_password)";
-      exec /opt/venv/bin/tht session migrate --database-url
-      "postgresql+psycopg2://$${THT_SESSION_MIGRATOR_USER}@$${THT_SESSION_DB_HOST}:$${THT_SESSION_DB_PORT}/$${THT_SESSION_DB_NAME}?sslmode=$${THT_SESSION_DB_SSLMODE}&sslrootcert=/run/secrets/session_ca.pem"
-      --json
+    entrypoint: [/app/docker/session-migrate.sh]
     environment:
       THT_SESSION_DB_HOST: ${THT_SESSION_DB_HOST:?set THT_SESSION_DB_HOST}
       THT_SESSION_DB_PORT: ${THT_SESSION_DB_PORT:-5432}
       THT_SESSION_DB_NAME: ${THT_SESSION_DB_NAME:?set THT_SESSION_DB_NAME}
       THT_SESSION_MIGRATOR_USER: ${THT_SESSION_MIGRATOR_USER:?set THT_SESSION_MIGRATOR_USER}
+      THT_SESSION_MIGRATOR_PASSWORD_FILE: /run/secrets/session_migrator_password
       THT_SESSION_DB_SSLMODE: ${THT_SESSION_DB_SSLMODE:-verify-full}
+      THT_SESSION_DB_SSLROOTCERT: /run/secrets/session_ca.pem
     secrets:
       - source: session_migrator_password
         target: session_migrator_password
diff --git a/docker/core.Dockerfile b/docker/core.Dockerfile
index 7abb1088..db75fe6d 100644
--- a/docker/core.Dockerfile
+++ b/docker/core.Dockerfile
@@ -63,8 +63,8 @@ ENV PATH="/opt/venv/bin:/usr/local/bin:$PATH" \
     PI_BIN=pi \
     HOME=/home/thoth
 
-COPY docker/core-entrypoint.sh docker/ensure-pi-trust.mjs /app/docker/
-RUN chmod +x /app/docker/core-entrypoint.sh
+COPY docker/core-entrypoint.sh docker/session-migrate.sh docker/ensure-pi-trust.mjs /app/docker/
+RUN chmod +x /app/docker/core-entrypoint.sh /app/docker/session-migrate.sh
 
 WORKDIR /app/backend
 USER thoth
diff --git a/docker/session-migrate.sh b/docker/session-migrate.sh
new file mode 100755
index 00000000..7e040ce7
--- /dev/null
+++ b/docker/session-migrate.sh
@@ -0,0 +1,40 @@
+#!/bin/sh
+# One-shot schema migration only. Validate TLS before reading a secret or composing a URL.
+set -eu
+
+case "${THT_SESSION_DB_SSLMODE:-}" in
+  verify-ca|verify-full) ;;
+  *)
+    echo "THT_SESSION_DB_SSLMODE must be verify-ca or verify-full" >&2
+    exit 2
+    ;;
+esac
+
+require_env() {
+  eval "value=\${$1:-}"
+  if [ -z "$value" ]; then
+    echo "missing required session migrator configuration" >&2
+    exit 2
+  fi
+}
+
+require_env THT_SESSION_DB_HOST
+require_env THT_SESSION_DB_PORT
+require_env THT_SESSION_DB_NAME
+require_env THT_SESSION_MIGRATOR_USER
+require_env THT_SESSION_MIGRATOR_PASSWORD_FILE
+require_env THT_SESSION_DB_SSLROOTCERT
+
+if [ ! -r "$THT_SESSION_MIGRATOR_PASSWORD_FILE" ]; then
+  echo "session migrator credential is unavailable" >&2
+  exit 2
+fi
+export PGPASSWORD="$(cat "$THT_SESSION_MIGRATOR_PASSWORD_FILE")"
+if [ -z "$PGPASSWORD" ]; then
+  echo "session migrator credential is unavailable" >&2
+  exit 2
+fi
+
+exec "${THT_BIN:-/opt/venv/bin/tht}" session migrate --database-url \
+  "postgresql+psycopg2://${THT_SESSION_MIGRATOR_USER}@${THT_SESSION_DB_HOST}:${THT_SESSION_DB_PORT}/${THT_SESSION_DB_NAME}?sslmode=${THT_SESSION_DB_SSLMODE}&sslrootcert=${THT_SESSION_DB_SSLROOTCERT}" \
+  --json
diff --git a/docker/session-migrate.test.sh b/docker/session-migrate.test.sh
new file mode 100755
index 00000000..1891d21f
--- /dev/null
+++ b/docker/session-migrate.test.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+root=$(cd "$(dirname "$0")/.." && pwd)
+helper="$root/docker/session-migrate.sh"
+tmp=$(mktemp -d)
+trap 'rm -rf "$tmp"' EXIT HUP INT TERM
+
+if THT_SESSION_DB_SSLMODE=prefer sh "$helper" >"$tmp/invalid.out" 2>&1; then
+  echo "session migrator accepted an unverified TLS mode" >&2
+  exit 1
+fi
+grep -qx 'THT_SESSION_DB_SSLMODE must be verify-ca or verify-full' "$tmp/invalid.out"
+
+printf '%s' password >"$tmp/password"
+cat >"$tmp/tht" <<'EOF'
+#!/bin/sh
+printf '%s\n' "$@" >"$ARGS_FILE"
+EOF
+chmod +x "$tmp/tht"
+
+ARGS_FILE="$tmp/args" \
+THT_BIN="$tmp/tht" \
+THT_SESSION_DB_HOST=sessions-db.internal \
+THT_SESSION_DB_PORT=5432 \
+THT_SESSION_DB_NAME=thoth \
+THT_SESSION_MIGRATOR_USER=thoth_sessions_migrate \
+THT_SESSION_MIGRATOR_PASSWORD_FILE="$tmp/password" \
+THT_SESSION_DB_SSLMODE=verify-full \
+THT_SESSION_DB_SSLROOTCERT=/run/secrets/session_ca.pem \
+sh "$helper"
+
+grep -qx 'session' "$tmp/args"
+grep -qx 'migrate' "$tmp/args"
+grep -qx -- '--database-url' "$tmp/args"
+grep -Fxq 'postgresql+psycopg2://thoth_sessions_migrate@sessions-db.internal:5432/thoth?sslmode=verify-full&sslrootcert=/run/secrets/session_ca.pem' "$tmp/args"
+
+echo "session migrator TLS contract passed."