diff --git a/autobot-slm-backend/ansible/roles/backend/defaults/main.yml b/autobot-slm-backend/ansible/roles/backend/defaults/main.yml
index bffc26cbb..14ddcfe68 100644
--- a/autobot-slm-backend/ansible/roles/backend/defaults/main.yml
+++ b/autobot-slm-backend/ansible/roles/backend/defaults/main.yml
@@ -55,6 +55,10 @@ backend_llm_provider: "ollama"  # Default LLM provider for all agents
 backend_llm_endpoint: "http://127.0.0.1:11434"  # Default Ollama endpoint
 backend_llm_model: "qwen3.5:9b"  # Default LLM model
 
+# AI Stack connection (co-located: use 127.0.0.1; WSL2: may need 10.255.255.254)
+backend_ai_stack_host: "127.0.0.1"
+backend_ai_stack_port: 8080
+
 # Service Authentication
 service_auth_service_id: "main-backend"
 service_auth_keys_dir: "/etc/autobot/service-keys"
diff --git a/autobot-slm-backend/ansible/roles/backend/tasks/main.yml b/autobot-slm-backend/ansible/roles/backend/tasks/main.yml
index efba2da1f..b27b2013f 100644
--- a/autobot-slm-backend/ansible/roles/backend/tasks/main.yml
+++ b/autobot-slm-backend/ansible/roles/backend/tasks/main.yml
@@ -27,6 +27,28 @@
     state: present
   tags: ['backend', 'users']
 
+# ==========================================================
+# WSL2 auto-detection (#3503): 127.0.0.1 is ECONNREFUSED on
+# WSL2 mirrored networking — override backend_ai_stack_host
+# per-host at deploy time if it has not been explicitly set.
+# ==========================================================
+- name: "Backend | Read /proc/version to detect WSL2 (#3503)"
+  ansible.builtin.slurp:
+    src: /proc/version
+  register: _proc_version
+  changed_when: false
+  failed_when: false
+  tags: ['backend', 'config']
+
+- name: "Backend | Set backend_ai_stack_host=10.255.255.254 on WSL2 hosts (#3503)"
+  ansible.builtin.set_fact:
+    backend_ai_stack_host: "10.255.255.254"
+  when:
+    - _proc_version.content is defined
+    - (_proc_version.content | b64decode | lower) is search('microsoft')
+    - backend_ai_stack_host == '127.0.0.1'
+  tags: ['backend', 'config']
+
 # ============================================================
 # Per-role env at /etc/autobot/  (#926 Phase 4)
 # ============================================================
diff --git a/autobot-slm-backend/ansible/roles/backend/templates/backend.env.j2 b/autobot-slm-backend/ansible/roles/backend/templates/backend.env.j2
index 39d0f455a..97277914a 100644
--- a/autobot-slm-backend/ansible/roles/backend/templates/backend.env.j2
+++ b/autobot-slm-backend/ansible/roles/backend/templates/backend.env.j2
@@ -44,6 +44,10 @@ AUTOBOT_SLM_TLS_ENABLED=true
 AUTOBOT_TTS_WORKER_HOST={{ tts_host | default('127.0.0.1') }}
 AUTOBOT_TTS_WORKER_PORT={{ tts_port | default(8083) }}
 
+# AI Stack (agent processing service)
+AUTOBOT_AI_STACK_HOST={{ backend_ai_stack_host }}
+AUTOBOT_AI_STACK_PORT={{ backend_ai_stack_port }}
+
 # ChromaDB (remote on AI Stack VM)
 AUTOBOT_CHROMADB_HOST={{ backend_chromadb_host | default(ai_stack_host | default('127.0.0.1')) }}
 AUTOBOT_CHROMADB_PORT={{ backend_chromadb_port | default('8100') }}