diff --git a/api/config.py b/api/config.py
index 23f67b0..e7bbd17 100644
--- a/api/config.py
+++ b/api/config.py
@@ -415,8 +415,8 @@ _FALLBACK_MODELS = [
     {"provider": "Anthropic", "id": "anthropic/claude-sonnet-4-5",        "label": "Claude Sonnet 4.5"},
     {"provider": "Anthropic", "id": "anthropic/claude-haiku-4-5",         "label": "Claude Haiku 4.5"},
     # Google
-    {"provider": "Google",    "id": "google/gemini-3.1-pro",              "label": "Gemini 3.1 Pro"},
-    {"provider": "Google",    "id": "google/gemini-3-flash",              "label": "Gemini 3 Flash"},
+    {"provider": "Google",    "id": "google/gemini-3.1-pro-preview",              "label": "Gemini 3.1 Pro Preview"},
+    {"provider": "Google",    "id": "google/gemini-3-flash-preview",              "label": "Gemini 3 Flash Preview"},
     # DeepSeek
     {"provider": "DeepSeek",  "id": "deepseek/deepseek-chat-v3-0324",     "label": "DeepSeek V3"},
     {"provider": "DeepSeek",  "id": "deepseek/deepseek-r1",               "label": "DeepSeek R1"},
@@ -424,7 +424,7 @@ _FALLBACK_MODELS = [
     {"provider": "Qwen",      "id": "qwen/qwen3-coder",                   "label": "Qwen3 Coder"},
     {"provider": "Qwen",      "id": "qwen/qwen3.6-plus",                  "label": "Qwen3.6 Plus"},
     # xAI
-    {"provider": "xAI",       "id": "x-ai/grok-4-20",                    "label": "Grok 4.20"},
+    {"provider": "xAI",       "id": "x-ai/grok-4.20",                    "label": "Grok 4.20"},
     # Mistral
     {"provider": "Mistral",   "id": "mistralai/mistral-large-latest",     "label": "Mistral Large"},
 ]
@@ -476,8 +476,8 @@ _PROVIDER_MODELS = {
         {"id": "codex-mini-latest", "label": "Codex Mini (latest)"},
     ],
     "google": [
-        {"id": "gemini-3.1-pro",   "label": "Gemini 3.1 Pro"},
-        {"id": "gemini-3-flash", "label": "Gemini 3 Flash"},
+        {"id": "gemini-3.1-pro-preview",   "label": "Gemini 3.1 Pro Preview"},
+        {"id": "gemini-3-flash-preview", "label": "Gemini 3 Flash Preview"},
     ],
     "deepseek": [
         {"id": "deepseek-chat-v3-0324", "label": "DeepSeek V3"},
@@ -487,7 +487,7 @@ _PROVIDER_MODELS = {
         {"id": "claude-opus-4.6", "label": "Claude Opus 4.6 (via Nous)"},
         {"id": "claude-sonnet-4.6", "label": "Claude Sonnet 4.6 (via Nous)"},
         {"id": "gpt-5.4-mini", "label": "GPT-5.4 Mini (via Nous)"},
-        {"id": "gemini-3.1-pro", "label": "Gemini 2.5 Pro (via Nous)"},
+        {"id": "gemini-3.1-pro-preview", "label": "Gemini 3.1 Pro Preview (via Nous)"},
     ],
     "zai": [
         {"id": "glm-5.1", "label": "GLM-5.1"},
@@ -517,7 +517,7 @@ _PROVIDER_MODELS = {
         {"id": "gpt-4o", "label": "GPT-4o"},
         {"id": "claude-opus-4.6", "label": "Claude Opus 4.6"},
         {"id": "claude-sonnet-4.6", "label": "Claude Sonnet 4.6"},
-        {"id": "gemini-3.1-pro", "label": "Gemini 3.1 Pro"},
+        {"id": "gemini-3.1-pro-preview", "label": "Gemini 3.1 Pro Preview"},
     ],
     # OpenCode Zen — curated models via opencode.ai/zen (pay-as-you-go credits)
     "opencode-zen": [
@@ -544,8 +544,8 @@ _PROVIDER_MODELS = {
         {"id": "claude-sonnet-4", "label": "Claude Sonnet 4"},
         {"id": "claude-haiku-4-5", "label": "Claude Haiku 4.5"},
         {"id": "claude-3-5-haiku", "label": "Claude 3.5 Haiku"},
-        {"id": "gemini-3.1-pro", "label": "Gemini 3.1 Pro"},
-        {"id": "gemini-3-flash", "label": "Gemini 3 Flash"},
+        {"id": "gemini-3.1-pro-preview", "label": "Gemini 3.1 Pro Preview"},
+        {"id": "gemini-3-flash-preview", "label": "Gemini 3 Flash Preview"},
         {"id": "glm-5.1", "label": "GLM-5.1"},
         {"id": "glm-5", "label": "GLM-5"},
         {"id": "kimi-k2.5", "label": "Kimi K2.5"},
@@ -566,8 +566,8 @@ _PROVIDER_MODELS = {
     ],
     # 'gemini' is the hermes_cli provider ID for Google AI Studio
     "gemini": [
-        {"id": "gemini-3.1-pro", "label": "Gemini 3.1 Pro"},
-        {"id": "gemini-3-flash", "label": "Gemini 3 Flash"},
+        {"id": "gemini-3.1-pro-preview", "label": "Gemini 3.1 Pro Preview"},
+        {"id": "gemini-3-flash-preview", "label": "Gemini 3 Flash Preview"},
     ],
     # Mistral — prefix used in OpenRouter model IDs (mistralai/mistral-large-latest)
     "mistralai": [
@@ -581,7 +581,7 @@ _PROVIDER_MODELS = {
     ],
     # xAI — prefix used in OpenRouter model IDs (x-ai/grok-4-20)
     "x-ai": [
-        {"id": "grok-4-20", "label": "Grok 4.20"},
+        {"id": "grok-4.20", "label": "Grok 4.20"},
     ],
 }