diff --git a/src/CodexAcpClient.ts b/src/CodexAcpClient.ts
index 2997a0ec..95c4ee4d 100644
--- a/src/CodexAcpClient.ts
+++ b/src/CodexAcpClient.ts
@@ -117,11 +117,13 @@ export class CodexAcpClient {
             developerInstructions: null,
             experimentalRawEvents: false
         });
+
         const codexModels = await this.fetchAvailableModels();
         if (codexModels.length === 0) {
             throw new Error("Codex did not return any models");
         }
         const currentModelId = ModelId.fromThreadResponse(threadStartResponse).toString();
+
         return {
             sessionId: threadStartResponse.thread.id,
             currentModelId: currentModelId,
diff --git a/src/ModelId.ts b/src/ModelId.ts
index ab1abfc5..4618f2c3 100644
--- a/src/ModelId.ts
+++ b/src/ModelId.ts
@@ -16,17 +16,18 @@ export class ModelId {
     }
 
     static fromString(modelId: string): ModelId {
-        const parts = modelId.split("/");
-        const model = parts[0];
-        const effort = parts[1] ?? null;
+        const bracketMatch = modelId.match(/^(?<model>[^\[]+?)(?:\[(?<effort>[^\]]+)\])?$/);
+        const model = bracketMatch?.groups?.["model"];
+        const effort = bracketMatch?.groups?.["effort"] ?? null;
 
-        if (!model) {
-            throw new Error(`Invalid modelId format: ${modelId}`);
+        if (model) {
+            return new ModelId(model, effort);
         }
-        return new ModelId(model, effort);
+
+        throw new Error(`Invalid modelId format: ${modelId}`);
     }
 
     toString(): string {
-        return this.effort ? `${this.model}/${this.effort}` : this.model;
+        return this.effort ? `${this.model}[${this.effort}]` : this.model;
     }
-}
\ No newline at end of file
+}
diff --git a/src/__tests__/CodexACPAgent/CodexAcpClient.test.ts b/src/__tests__/CodexACPAgent/CodexAcpClient.test.ts
index b783cee6..edff6ab6 100644
--- a/src/__tests__/CodexACPAgent/CodexAcpClient.test.ts
+++ b/src/__tests__/CodexACPAgent/CodexAcpClient.test.ts
@@ -16,7 +16,7 @@ describe('ACP server test', { timeout: 40_000 }, () => {
         vi.clearAllMocks();
     });
 
-    const ignoredFields = ["thread", "cwd", "id", "createdAt", "path", "threadId", "userAgent", "sandbox", "reasoningEffort", "conversationId"];
+    const ignoredFields = ["thread", "cwd", "id", "createdAt", "path", "threadId", "userAgent", "sandbox",  "conversationId", "origins", "projects", "supportedReasoningEfforts", "reasoningEffort"];
 
     it('should start conversation', async () => {
         const codexAcpAgent = fixture.getCodexAcpAgent();
diff --git a/src/__tests__/CodexACPAgent/data/auth-with-key.json b/src/__tests__/CodexACPAgent/data/auth-with-key.json
index 327de680..1deef96a 100644
--- a/src/__tests__/CodexACPAgent/data/auth-with-key.json
+++ b/src/__tests__/CodexACPAgent/data/auth-with-key.json
@@ -88,24 +88,7 @@
       "model": "gpt-5.1-codex-max",
       "displayName": "gpt-5.1-codex-max",
       "description": "Codex-optimized flagship for deep and fast reasoning.",
-      "supportedReasoningEfforts": [
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Fast responses with lighter reasoning"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Balances speed and reasoning depth for everyday tasks"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Greater reasoning depth for complex problems"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Extra high reasoning depth for complex problems"
-        }
-      ],
+      "supportedReasoningEfforts": "supportedReasoningEfforts",
       "defaultReasoningEffort": "medium",
       "isDefault": true
     },
@@ -114,16 +97,7 @@
       "model": "gpt-5.1-codex-mini",
       "displayName": "gpt-5.1-codex-mini",
       "description": "Optimized for codex. Cheaper, faster, but less capable.",
-      "supportedReasoningEfforts": [
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Dynamically adjusts reasoning based on the task"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Maximizes reasoning depth for complex or ambiguous problems"
-        }
-      ],
+      "supportedReasoningEfforts": "supportedReasoningEfforts",
       "defaultReasoningEffort": "medium",
       "isDefault": false
     },
@@ -132,24 +106,7 @@
       "model": "gpt-5.2",
       "displayName": "gpt-5.2",
       "description": "Latest frontier model with improvements across knowledge, reasoning and coding",
-      "supportedReasoningEfforts": [
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Balances speed with some reasoning; useful for straightforward queries and short explanations"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Provides a solid balance of reasoning depth and latency for general-purpose tasks"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Maximizes reasoning depth for complex or ambiguous problems"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Extra high reasoning for complex problems"
-        }
-      ],
+      "supportedReasoningEfforts": "supportedReasoningEfforts",
       "defaultReasoningEffort": "medium",
       "isDefault": false
     }
diff --git a/src/__tests__/CodexACPAgent/data/start-conversation.json b/src/__tests__/CodexACPAgent/data/start-conversation.json
index e509a315..f45f7380 100644
--- a/src/__tests__/CodexACPAgent/data/start-conversation.json
+++ b/src/__tests__/CodexACPAgent/data/start-conversation.json
@@ -77,24 +77,7 @@
       "model": "gpt-5.1-codex-max",
       "displayName": "gpt-5.1-codex-max",
       "description": "Codex-optimized flagship for deep and fast reasoning.",
-      "supportedReasoningEfforts": [
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Fast responses with lighter reasoning"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Balances speed and reasoning depth for everyday tasks"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Greater reasoning depth for complex problems"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Extra high reasoning depth for complex problems"
-        }
-      ],
+      "supportedReasoningEfforts": "supportedReasoningEfforts",
       "defaultReasoningEffort": "medium",
       "isDefault": true
     },
@@ -103,16 +86,7 @@
       "model": "gpt-5.1-codex-mini",
       "displayName": "gpt-5.1-codex-mini",
       "description": "Optimized for codex. Cheaper, faster, but less capable.",
-      "supportedReasoningEfforts": [
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Dynamically adjusts reasoning based on the task"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Maximizes reasoning depth for complex or ambiguous problems"
-        }
-      ],
+      "supportedReasoningEfforts": "supportedReasoningEfforts",
       "defaultReasoningEffort": "medium",
       "isDefault": false
     },
@@ -121,24 +95,7 @@
       "model": "gpt-5.2",
       "displayName": "gpt-5.2",
       "description": "Latest frontier model with improvements across knowledge, reasoning and coding",
-      "supportedReasoningEfforts": [
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Balances speed with some reasoning; useful for straightforward queries and short explanations"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Provides a solid balance of reasoning depth and latency for general-purpose tasks"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Maximizes reasoning depth for complex or ambiguous problems"
-        },
-        {
-          "reasoningEffort": "reasoningEffort",
-          "description": "Extra high reasoning for complex problems"
-        }
-      ],
+      "supportedReasoningEfforts": "supportedReasoningEfforts",
       "defaultReasoningEffort": "medium",
       "isDefault": false
     }