diff --git a/codex-rs/core/src/models_manager/manager.rs b/codex-rs/core/src/models_manager/manager.rs
index 2d8518507..a3c6df633 100644
--- a/codex-rs/core/src/models_manager/manager.rs
+++ b/codex-rs/core/src/models_manager/manager.rs
@@ -137,10 +137,8 @@ impl ModelsManager {
     /// Look up model metadata, applying remote overrides and config adjustments.
     pub async fn get_model_info(&self, model: &str, config: &Config) -> ModelInfo {
         let remote = self
-            .get_remote_models(config)
-            .await
-            .into_iter()
-            .find(|m| m.slug == model);
+            .find_remote_model_by_longest_prefix(model, config)
+            .await;
         let model = if let Some(remote) = remote {
             remote
         } else {
@@ -149,6 +147,28 @@ impl ModelsManager {
         model_info::with_config_overrides(model, config)
     }
 
+    async fn find_remote_model_by_longest_prefix(
+        &self,
+        model: &str,
+        config: &Config,
+    ) -> Option<ModelInfo> {
+        let mut best: Option<ModelInfo> = None;
+        for candidate in self.get_remote_models(config).await {
+            if !model.starts_with(&candidate.slug) {
+                continue;
+            }
+            let is_better_match = if let Some(current) = best.as_ref() {
+                candidate.slug.len() > current.slug.len()
+            } else {
+                true
+            };
+            if is_better_match {
+                best = Some(candidate);
+            }
+        }
+        best
+    }
+
     /// Refresh models if the provided ETag differs from the cached ETag.
     ///
     /// Uses `Online` strategy to fetch latest models when ETags differ.
diff --git a/codex-rs/core/tests/suite/remote_models.rs b/codex-rs/core/tests/suite/remote_models.rs
index ed46855f9..202ba412a 100644
--- a/codex-rs/core/tests/suite/remote_models.rs
+++ b/codex-rs/core/tests/suite/remote_models.rs
@@ -55,6 +55,69 @@ use wiremock::MockServer;
 
 const REMOTE_MODEL_SLUG: &str = "codex-test";
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn remote_models_get_model_info_uses_longest_matching_prefix() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+    skip_if_sandbox!(Ok(()));
+
+    let server = MockServer::start().await;
+    let generic = test_remote_model_with_policy(
+        "gpt-5.3",
+        ModelVisibility::List,
+        1_000,
+        TruncationPolicyConfig::bytes(10_000),
+    );
+    let specific = test_remote_model_with_policy(
+        "gpt-5.3-codex",
+        ModelVisibility::List,
+        1_000,
+        TruncationPolicyConfig::bytes(10_000),
+    );
+    let specific = ModelInfo {
+        display_name: "GPT 5.3 Codex".to_string(),
+        base_instructions: "use specific prefix".to_string(),
+        ..specific
+    };
+    let generic = ModelInfo {
+        display_name: "GPT 5.3".to_string(),
+        base_instructions: "use generic prefix".to_string(),
+        ..generic
+    };
+    mount_models_once(
+        &server,
+        ModelsResponse {
+            models: vec![generic.clone(), specific.clone()],
+        },
+    )
+    .await;
+
+    let codex_home = TempDir::new()?;
+    let mut config = load_default_config_for_test(&codex_home).await;
+    config.features.enable(Feature::RemoteModels);
+
+    let auth = CodexAuth::create_dummy_chatgpt_auth_for_testing();
+    let provider = ModelProviderInfo {
+        base_url: Some(format!("{}/v1", server.uri())),
+        ..built_in_model_providers()["openai"].clone()
+    };
+    let manager = ModelsManager::with_provider(
+        codex_home.path().to_path_buf(),
+        codex_core::auth::AuthManager::from_auth_for_testing(auth),
+        provider,
+    );
+
+    manager
+        .list_models(&config, RefreshStrategy::OnlineIfUncached)
+        .await;
+
+    let model_info = manager.get_model_info("gpt-5.3-codex-test", &config).await;
+
+    assert_eq!(model_info.slug, specific.slug);
+    assert_eq!(model_info.base_instructions, specific.base_instructions);
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn remote_models_remote_model_uses_unified_exec() -> Result<()> {
     skip_if_no_network!(Ok(()));