diff --git a/open-sse/config/providerModels.js b/open-sse/config/providerModels.js
index 5accb7fe..c1456db9 100644
--- a/open-sse/config/providerModels.js
+++ b/open-sse/config/providerModels.js
@@ -10,11 +10,20 @@ export const PROVIDER_MODELS = {
     { id: "claude-haiku-4-5-20251001", name: "Claude 4.5 Haiku" },
   ],
   cx: [  // OpenAI Codex
+    // GPT 5.3 Codex - all thinking levels
+    { id: "gpt-5.3-codex", name: "GPT 5.3 Codex" },
+    { id: "gpt-5.3-codex-xhigh", name: "GPT 5.3 Codex (xHigh)" },
+    { id: "gpt-5.3-codex-high", name: "GPT 5.3 Codex (High)" },
+    { id: "gpt-5.3-codex-low", name: "GPT 5.3 Codex (Low)" },
+    { id: "gpt-5.3-codex-none", name: "GPT 5.3 Codex (None)" },
+    // Mini - medium and high only
+    { id: "gpt-5.1-codex-mini", name: "GPT 5.1 Codex Mini" },
+    { id: "gpt-5.1-codex-mini-high", name: "GPT 5.1 Codex Mini (High)" },
+    // Other models
     { id: "gpt-5.2-codex", name: "GPT 5.2 Codex" },
     { id: "gpt-5.2", name: "GPT 5.2" },
     { id: "gpt-5.1-codex-max", name: "GPT 5.1 Codex Max" },
     { id: "gpt-5.1-codex", name: "GPT 5.1 Codex" },
-    { id: "gpt-5.1-codex-mini", name: "GPT 5.1 Codex Mini" },
     { id: "gpt-5.1", name: "GPT 5.1" },
     { id: "gpt-5-codex", name: "GPT 5 Codex" },
     { id: "gpt-5-codex-mini", name: "GPT 5 Codex Mini" },
diff --git a/open-sse/executors/codex.js b/open-sse/executors/codex.js
index 5c8b7934..dd65fd41 100644
--- a/open-sse/executors/codex.js
+++ b/open-sse/executors/codex.js
@@ -23,6 +23,26 @@ export class CodexExecutor extends BaseExecutor {
     // Ensure store is false (Codex requirement)
     body.store = false;
 
+    // Extract thinking level from model name suffix
+    // e.g., gpt-5.3-codex-high → high, gpt-5.3-codex → medium (default)
+    const effortLevels = ['none', 'low', 'medium', 'high', 'xhigh'];
+    let modelEffort = null;
+    for (const level of effortLevels) {
+      if (model.endsWith(`-${level}`)) {
+        modelEffort = level;
+        // Strip suffix from model name for actual API call
+        body.model = body.model.replace(`-${level}`, '');
+        break;
+      }
+    }
+
+    // Priority: explicit reasoning.effort > reasoning_effort param > model suffix > default (medium)
+    if (!body.reasoning) {
+      const effort = body.reasoning_effort || modelEffort || 'medium';
+      body.reasoning = { effort };
+    }
+    delete body.reasoning_effort;
+
     // Remove unsupported parameters for Codex API
     delete body.temperature;
     delete body.top_p;
diff --git a/open-sse/handlers/chatCore.js b/open-sse/handlers/chatCore.js
index 88dc9096..5bb2caf3 100644
--- a/open-sse/handlers/chatCore.js
+++ b/open-sse/handlers/chatCore.js
@@ -468,16 +468,22 @@ export async function handleChatCore({ body, modelInfo, credentials, log, onCred
 
   // Create transform stream with logger for streaming response
   let transformStream;
-  // For Codex provider, always translate response from openai-responses to openai format
-  // This ensures clients like Cursor get the expected chat completions format
-  // BUT: skip translation if client already sent in openai-responses format (like Droid CLI)
-  const needsCodexTranslation = (provider === 'codex' || provider === 'openai') && targetFormat === 'openai-responses' && sourceFormat !== 'openai-responses';
-  if (needsCodexTranslation || needsTranslation(targetFormat, sourceFormat)) {
-    // For Codex, translate FROM openai-responses TO openai (client's expected format)
-    const responseSourceFormat = needsCodexTranslation ? 'openai-responses' : targetFormat;
-    const responseTargetFormat = needsCodexTranslation ? 'openai' : sourceFormat;
-    transformStream = createSSETransformStreamWithLogger(responseSourceFormat, responseTargetFormat, provider, reqLogger, toolNameMap, model, connectionId, body);
+  // For Codex provider, translate response from openai-responses to openai (Chat Completions) format
+  // UNLESS client originally sent in openai-responses format (like Droid CLI) - they expect same format back
+  const needsCodexTranslation = provider === 'codex' 
+    && targetFormat === 'openai-responses' 
+    && sourceFormat !== 'openai-responses';
+
+  if (needsCodexTranslation) {
+    // Codex returns openai-responses, translate to openai (Chat Completions) that clients expect
+    log?.debug?.("STREAM", `Codex translation mode: openai-responses → openai`);
+    transformStream = createSSETransformStreamWithLogger('openai-responses', 'openai', provider, reqLogger, toolNameMap, model, connectionId, body);
+  } else if (needsTranslation(targetFormat, sourceFormat)) {
+    // Standard translation for other providers
+    log?.debug?.("STREAM", `Translation mode: ${targetFormat} → ${sourceFormat}`);
+    transformStream = createSSETransformStreamWithLogger(targetFormat, sourceFormat, provider, reqLogger, toolNameMap, model, connectionId, body);
   } else {
+    log?.debug?.("STREAM", `Standard passthrough mode`);
     transformStream = createPassthroughStreamWithLogger(provider, reqLogger, model, connectionId, body);
   }
 
diff --git a/src/sse/handlers/chat.js b/src/sse/handlers/chat.js
index b9674147..49f9b907 100644
--- a/src/sse/handlers/chat.js
+++ b/src/sse/handlers/chat.js
@@ -38,7 +38,8 @@ export async function handleChat(request, clientRawRequest = null) {
   // Count messages (support both messages[] and input[] formats)
   const msgCount = body.messages?.length || body.input?.length || 0;
   const toolCount = body.tools?.length || 0;
-  log.request("POST", `${url.pathname} | ${modelStr} | ${msgCount} msgs${toolCount ? ` | ${toolCount} tools` : ""}`);
+  const effort = body.reasoning_effort || body.reasoning?.effort || null;
+  log.request("POST", `${url.pathname} | ${modelStr} | ${msgCount} msgs${toolCount ? ` | ${toolCount} tools` : ""}${effort ? ` | effort=${effort}` : ""}`);
 
   // Log API key (masked)
   const apiKey = request.headers.get("Authorization");