diff --git a/.env.example b/.env.example
index 27bc16d..8f865f1 100644
--- a/.env.example
+++ b/.env.example
@@ -23,11 +23,22 @@ ANTHROPIC_API_KEY=your-api-key-here
 # ROUTER_DEFAULT=openai,gpt-4o
 
 # --- Google Gemini ---
-GEMINI_API_KEY=your-gemini-key
-ROUTER_DEFAULT=gemini,gemini-2.5-pro
+# GEMINI_API_KEY=your-gemini-key
+# ROUTER_DEFAULT=gemini,gemini-2.5-pro
+
+# --- DeepSeek (cheapest option) ---
+# DEEPSEEK_API_KEY=your-together-or-deepseek-key
+# DEEPSEEK_API_BASE=https://api.together.xyz/v1/chat/completions  # Default: Together.ai
+# ROUTER_DEFAULT=deepseek,deepseek-ai/DeepSeek-V3
+#
+# To use DeepSeek's official API instead:
+# DEEPSEEK_API_BASE=https://api.deepseek.com/chat/completions
+# ROUTER_DEFAULT=deepseek,deepseek-chat
 
 # =============================================================================
 # Available Models
 # =============================================================================
-# OpenAI:  gpt-4o, gpt-4o-mini
-# Gemini:  gemini-2.5-pro, gemini-2.5-flash
+# OpenAI:     gpt-4o, gpt-4o-mini
+# Gemini:     gemini-2.5-pro, gemini-2.5-flash
+# DeepSeek:   (Together.ai) deepseek-ai/DeepSeek-V3, deepseek-ai/DeepSeek-R1
+#             (Official)    deepseek-chat, deepseek-reasoner
diff --git a/configs/router-config.json b/configs/router-config.json
index 8d043e4..6d5213d 100644
--- a/configs/router-config.json
+++ b/configs/router-config.json
@@ -23,6 +23,15 @@
       "transformer": {
         "use": ["gemini"]
       }
+    },
+    {
+      "name": "deepseek",
+      "api_base_url": "$DEEPSEEK_API_BASE",
+      "api_key": "$DEEPSEEK_API_KEY",
+      "models": ["deepseek-ai/DeepSeek-V3", "deepseek-ai/DeepSeek-R1", "deepseek-chat", "deepseek-reasoner"],
+      "transformer": {
+        "use": ["deepseek", "enhancetool"]
+      }
     }
   ],
   "Router": {
diff --git a/docker-compose.yml b/docker-compose.yml
index afb7d3d..664e3b6 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -58,6 +58,8 @@ services:
       - ANTHROPIC_API_KEY=${ANTHROPIC_API_KEY:-}
       - OPENAI_API_KEY=${OPENAI_API_KEY:-}
       - GEMINI_API_KEY=${GEMINI_API_KEY:-}
+      - DEEPSEEK_API_KEY=${DEEPSEEK_API_KEY:-}
+      - DEEPSEEK_API_BASE=${DEEPSEEK_API_BASE:-https://api.together.xyz/v1/chat/completions}
       - ROUTER_DEFAULT=${ROUTER_DEFAULT:-openai,gpt-4o}
     healthcheck:
       test: ["CMD", "node", "-e", "require('http').get('http://localhost:3456/health', r => process.exit(r.statusCode === 200 ? 0 : 1)).on('error', () => process.exit(1))"]
diff --git a/shannon b/shannon
index c979d76..3719a40 100755
--- a/shannon
+++ b/shannon
@@ -123,14 +123,14 @@ cmd_start() {
     exit 1
   fi
 
-  # Check for API key (router mode can use OPENAI_API_KEY or GEMINI_API_KEY instead)
+  # Check for API key (router mode can use alternative provider API keys)
   if [ -z "$ANTHROPIC_API_KEY" ] && [ -z "$CLAUDE_CODE_OAUTH_TOKEN" ]; then
-    if [ "$ROUTER" = "true" ] && { [ -n "$OPENAI_API_KEY" ] || [ -n "$GEMINI_API_KEY" ]; }; then
+    if [ "$ROUTER" = "true" ] && { [ -n "$OPENAI_API_KEY" ] || [ -n "$GEMINI_API_KEY" ] || [ -n "$DEEPSEEK_API_KEY" ]; }; then
       # Router mode with alternative provider - set a placeholder for SDK init
       export ANTHROPIC_API_KEY="router-mode"
     else
       echo "ERROR: Set ANTHROPIC_API_KEY or CLAUDE_CODE_OAUTH_TOKEN in .env"
-      echo "       (or use ROUTER=true with OPENAI_API_KEY or GEMINI_API_KEY)"
+      echo "       (or use ROUTER=true with OPENAI_API_KEY, GEMINI_API_KEY, or DEEPSEEK_API_KEY)"
       exit 1
     fi
   fi
@@ -165,9 +165,9 @@ cmd_start() {
     else
       echo "Starting claude-code-router..."
 
-      # Check for OpenAI API key
-      if [ -z "$OPENAI_API_KEY" ] && [ -z "$GEMINI_API_KEY" ]; then
-        echo "WARNING: Neither OPENAI_API_KEY nor GEMINI_API_KEY set. Router may not work."
+      # Check for provider API keys
+      if [ -z "$OPENAI_API_KEY" ] && [ -z "$GEMINI_API_KEY" ] && [ -z "$DEEPSEEK_API_KEY" ]; then
+        echo "WARNING: No provider API key set (OPENAI_API_KEY, GEMINI_API_KEY, or DEEPSEEK_API_KEY). Router may not work."
       fi
 
       # Start router with profile