diff --git a/install.sh b/install.sh
index b80a411..d5e0b62 100755
--- a/install.sh
+++ b/install.sh
@@ -1104,10 +1104,26 @@ collect_security_config() {
 # Parameter source-of-truth: single mapping for CFN Console, CFN CLI, Terraform
 # ============================================================================
 # ⚠ KEEP THESE THREE ARRAYS IN SYNC — same order, same count
-PARAM_CFN_NAMES=(EnvironmentName PackName ProfileName InstanceType ModelMode BedrockRegion LokiWatermark EnableBedrockForm EnableSecurityHub EnableGuardDuty EnableInspector EnableAccessAnalyzer EnableConfigRecorder ExistingVpcId ExistingSubnetId RepoBranch)
-PARAM_TF_NAMES=(environment_name pack_name profile_name instance_type model_mode bedrock_region loki_watermark enable_bedrock_form enable_security_hub enable_guardduty enable_inspector enable_access_analyzer enable_config_recorder existing_vpc_id existing_subnet_id repo_branch)
+PARAM_CFN_NAMES=(EnvironmentName PackName ProfileName InstanceType DefaultModel ModelMode BedrockRegion LokiWatermark EnableBedrockForm EnableSecurityHub EnableGuardDuty EnableInspector EnableAccessAnalyzer EnableConfigRecorder ExistingVpcId ExistingSubnetId RepoBranch)
+PARAM_TF_NAMES=(environment_name pack_name profile_name instance_type default_model model_mode bedrock_region loki_watermark enable_bedrock_form enable_security_hub enable_guardduty enable_inspector enable_access_analyzer enable_config_recorder existing_vpc_id existing_subnet_id repo_branch)
 PARAM_VALUES=()  # populated by build_deploy_params()
 
+# Per-pack default model (passed to CFN DefaultModel / bootstrap.sh --model).
+# Packs that use AWS Bedrock get Bedrock model IDs; packs that use provider
+# APIs (OpenAI, etc.) get provider-native model IDs. Without this mapping
+# every pack inherits the template's Bedrock default, which breaks codex-cli
+# (OpenAI rejects Bedrock ids with HTTP 400).
+pack_default_model() {
+  case "$1" in
+    codex-cli)                     echo "gpt-5.4" ;;
+    openclaw|claude-code|kiro-cli) echo "us.anthropic.claude-opus-4-6-v1" ;;
+    nemoclaw)                      echo "us.anthropic.claude-opus-4-6-v1" ;;
+    hermes)                        echo "NousResearch/Hermes-3-Llama-3.1-8B" ;;
+    pi|ironclaw)                   echo "us.anthropic.claude-opus-4-6-v1" ;;
+    *)                             echo "us.anthropic.claude-opus-4-6-v1" ;;
+  esac
+}
+
 # Populate PARAM_VALUES from user config (call after collect_config)
 build_deploy_params() {
   PARAM_VALUES=(
@@ -1115,6 +1131,7 @@ build_deploy_params() {
     "$PACK_NAME"
     "$PROFILE_NAME"
     "$INSTANCE_TYPE"
+    "${DEFAULT_MODEL:-$(pack_default_model "$PACK_NAME")}"
     "bedrock"
     "$DEPLOY_REGION"
     "$LOKI_WATERMARK"
diff --git a/packs/codex-cli/install.sh b/packs/codex-cli/install.sh
index 0ac404e..885b586 100755
--- a/packs/codex-cli/install.sh
+++ b/packs/codex-cli/install.sh
@@ -78,6 +78,19 @@ done
 REGION="${PACK_ARG_REGION}"
 MODEL="${PACK_ARG_MODEL}"
 
+# ── Guard against Bedrock model IDs leaking in via CFN's DefaultModel ────────────────────────────────────
+# install.sh / CFN template ship with a Bedrock-style DefaultModel
+# (e.g. us.anthropic.claude-opus-4-6-v1) that's great for openclaw/claude-code
+# but poison for codex-cli — OpenAI's API rejects it with HTTP 400.
+# If the caller hands us a Bedrock-style ID, fall back to the pack default
+# instead of writing a broken config.
+CODEX_DEFAULT_MODEL="gpt-5.4"
+if [[ "${MODEL}" =~ ^(us\.|eu\.|ap\.|anthropic\.|amazon\.|meta\.|mistral\.|cohere\.|ai21\.) ]]; then
+  warn "ignoring Bedrock-style model id '${MODEL}' — Codex CLI talks to OpenAI, not Bedrock"
+  warn "falling back to ${CODEX_DEFAULT_MODEL} (override with: bash install.sh --model <openai-model>)"
+  MODEL="${CODEX_DEFAULT_MODEL}"
+fi
+
 pack_banner "codex-cli"
 log "region=${REGION} model=${MODEL} sandbox=danger-full-access approval=never"