Always expose view_image and return unsupported image-input error (#11336)

- Keep `view_image` in the advertised tool list for all models.
- Return a clear error when the current model does not support image
inputs, and cover it with a unit test.

codex-rs/core/src/tools/handlers/view_image.rs

@@ -1,5 +1,6 @@
 use async_trait::async_trait;
 use codex_protocol::models::FunctionCallOutputBody;
+use codex_protocol::openai_models::InputModality;
 use serde::Deserialize;
 use tokio::fs;
 
@@ -18,6 +19,9 @@ use codex_protocol::models::local_image_content_items_with_label_number;
 
 pub struct ViewImageHandler;
 
+const VIEW_IMAGE_UNSUPPORTED_MESSAGE: &str =
+    "view_image is not allowed because you do not support image inputs";
+
 #[derive(Deserialize)]
 struct ViewImageArgs {
     path: String,
@@ -30,6 +34,17 @@ impl ToolHandler for ViewImageHandler {
     }
 
     async fn handle(&self, invocation: ToolInvocation) -> Result<ToolOutput, FunctionCallError> {
+        if !invocation
+            .turn
+            .model_info
+            .input_modalities
+            .contains(&InputModality::Image)
+        {
+            return Err(FunctionCallError::RespondToModel(
+                VIEW_IMAGE_UNSUPPORTED_MESSAGE.to_string(),
+            ));
+        }
+
         let ToolInvocation {
             session,
             turn,

codex-rs/core/src/tools/spec.rs

@@ -17,7 +17,6 @@ use codex_protocol::dynamic_tools::DynamicToolSpec;
 use codex_protocol::models::VIEW_IMAGE_TOOL_NAME;
 use codex_protocol::openai_models::ApplyPatchToolType;
 use codex_protocol::openai_models::ConfigShellToolType;
-use codex_protocol::openai_models::InputModality;
 use codex_protocol::openai_models::ModelInfo;
 use serde::Deserialize;
 use serde::Serialize;
@@ -31,7 +30,6 @@ pub(crate) struct ToolsConfig {
     pub shell_type: ConfigShellToolType,
     pub apply_patch_tool_type: Option<ApplyPatchToolType>,
     pub web_search_mode: Option<WebSearchMode>,
-    pub supports_image_input: bool,
     pub search_tool: bool,
     pub collab_tools: bool,
     pub collaboration_modes_tools: bool,
@@ -87,7 +85,6 @@ impl ToolsConfig {
             shell_type,
             apply_patch_tool_type,
             web_search_mode: *web_search_mode,
-            supports_image_input: model_info.input_modalities.contains(&InputModality::Image),
             search_tool: include_search_tool,
             collab_tools: include_collab_tools,
             collaboration_modes_tools: include_collaboration_modes_tools,
@@ -1498,10 +1495,8 @@ pub(crate) fn build_specs(
         Some(WebSearchMode::Disabled) | None => {}
     }
 
-    if config.supports_image_input {
-        builder.push_spec_with_parallel_support(create_view_image_tool(), true);
-        builder.register_handler("view_image", view_image_handler);
-    }
+    builder.push_spec_with_parallel_support(create_view_image_tool(), true);
+    builder.register_handler("view_image", view_image_handler);
 
     if config.collab_tools {
         let collab_handler = Arc::new(CollabHandler);
@@ -2076,29 +2071,6 @@ mod tests {
         );
     }
 
-    #[test]
-    fn test_non_multimodal_models_exclude_view_image() {
-        let config = test_config();
-        let mut model_info = ModelsManager::construct_model_info_offline("gpt-5.1", &config);
-        model_info.input_modalities = vec![InputModality::Text];
-        let mut features = Features::with_defaults();
-        features.enable(Feature::CollaborationModes);
-        let tools_config = ToolsConfig::new(&ToolsConfigParams {
-            model_info: &model_info,
-            features: &features,
-            web_search_mode: Some(WebSearchMode::Cached),
-        });
-        let (tools, _) = build_specs(&tools_config, Some(HashMap::new()), &[]).build();
-
-        assert!(
-            !tools
-                .iter()
-                .map(|t| t.spec.name())
-                .any(|name| name == VIEW_IMAGE_TOOL_NAME),
-            "view_image should be excluded for non-multimodal models"
-        );
-    }
-
     #[test]
     fn test_gpt_5_1_codex_max_unified_exec_web_search() {
         let mut features = Features::with_defaults();

codex-rs/core/tests/suite/view_image.rs

@@ -2,17 +2,28 @@
 
 use base64::Engine;
 use base64::engine::general_purpose::STANDARD as BASE64_STANDARD;
+use codex_core::CodexAuth;
+use codex_core::features::Feature;
 use codex_core::protocol::AskForApproval;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::Op;
 use codex_core::protocol::SandboxPolicy;
 use codex_protocol::config_types::ReasoningSummary;
+use codex_protocol::openai_models::ConfigShellToolType;
+use codex_protocol::openai_models::InputModality;
+use codex_protocol::openai_models::ModelInfo;
+use codex_protocol::openai_models::ModelVisibility;
+use codex_protocol::openai_models::ModelsResponse;
+use codex_protocol::openai_models::ReasoningEffort;
+use codex_protocol::openai_models::ReasoningEffortPreset;
+use codex_protocol::openai_models::TruncationPolicyConfig;
 use codex_protocol::user_input::UserInput;
 use core_test_support::responses;
 use core_test_support::responses::ev_assistant_message;
 use core_test_support::responses::ev_completed;
 use core_test_support::responses::ev_function_call;
 use core_test_support::responses::ev_response_created;
+use core_test_support::responses::mount_models_once;
 use core_test_support::responses::sse;
 use core_test_support::responses::start_mock_server;
 use core_test_support::skip_if_no_network;
@@ -26,6 +37,8 @@ use image::Rgba;
 use image::load_from_memory;
 use serde_json::Value;
 use tokio::time::Duration;
+use wiremock::BodyPrintLimit;
+use wiremock::MockServer;
 
 fn find_image_message(body: &Value) -> Option<&Value> {
     body.get("input")
@@ -521,6 +534,120 @@ async fn view_image_tool_errors_when_file_missing() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn view_image_tool_returns_unsupported_message_for_text_only_model() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    // Use MockServer directly (not start_mock_server) so the first /models request returns our
+    // text-only model. start_mock_server mounts empty models first, causing get_model_info to
+    // fall back to model_info_from_slug with default_input_modalities (Text+Image), which would
+    // incorrectly allow view_image.
+    let server = MockServer::builder()
+        .body_print_limit(BodyPrintLimit::Limited(80_000))
+        .start()
+        .await;
+    let model_slug = "text-only-view-image-test-model";
+    let text_only_model = ModelInfo {
+        slug: model_slug.to_string(),
+        display_name: "Text-only view_image test model".to_string(),
+        description: Some("Remote model for view_image unsupported-path coverage".to_string()),
+        default_reasoning_level: Some(ReasoningEffort::Medium),
+        supported_reasoning_levels: vec![ReasoningEffortPreset {
+            effort: ReasoningEffort::Medium,
+            description: ReasoningEffort::Medium.to_string(),
+        }],
+        shell_type: ConfigShellToolType::ShellCommand,
+        visibility: ModelVisibility::List,
+        supported_in_api: true,
+        input_modalities: vec![InputModality::Text],
+        priority: 1,
+        upgrade: None,
+        base_instructions: "base instructions".to_string(),
+        model_messages: None,
+        supports_reasoning_summaries: false,
+        support_verbosity: false,
+        default_verbosity: None,
+        apply_patch_tool_type: None,
+        truncation_policy: TruncationPolicyConfig::bytes(10_000),
+        supports_parallel_tool_calls: false,
+        context_window: Some(272_000),
+        auto_compact_token_limit: None,
+        effective_context_window_percent: 95,
+        experimental_supported_tools: Vec::new(),
+    };
+    mount_models_once(
+        &server,
+        ModelsResponse {
+            models: vec![text_only_model],
+        },
+    )
+    .await;
+
+    let TestCodex { codex, cwd, .. } = test_codex()
+        .with_auth(CodexAuth::create_dummy_chatgpt_auth_for_testing())
+        .with_config(|config| {
+            config.features.enable(Feature::RemoteModels);
+            config.model = Some(model_slug.to_string());
+        })
+        .build(&server)
+        .await?;
+
+    let rel_path = "assets/example.png";
+    let abs_path = cwd.path().join(rel_path);
+    if let Some(parent) = abs_path.parent() {
+        std::fs::create_dir_all(parent)?;
+    }
+    let image = ImageBuffer::from_pixel(20, 20, Rgba([255u8, 0, 0, 255]));
+    image.save(&abs_path)?;
+
+    let call_id = "view-image-unsupported-model";
+    let arguments = serde_json::json!({ "path": rel_path }).to_string();
+    let first_response = sse(vec![
+        ev_response_created("resp-1"),
+        ev_function_call(call_id, "view_image", &arguments),
+        ev_completed("resp-1"),
+    ]);
+    responses::mount_sse_once(&server, first_response).await;
+
+    let second_response = sse(vec![
+        ev_assistant_message("msg-1", "done"),
+        ev_completed("resp-2"),
+    ]);
+    let mock = responses::mount_sse_once(&server, second_response).await;
+
+    codex
+        .submit(Op::UserTurn {
+            items: vec![UserInput::Text {
+                text: "please attach the image".into(),
+                text_elements: Vec::new(),
+            }],
+            final_output_json_schema: None,
+            cwd: cwd.path().to_path_buf(),
+            approval_policy: AskForApproval::Never,
+            sandbox_policy: SandboxPolicy::DangerFullAccess,
+            model: model_slug.to_string(),
+            effort: None,
+            summary: ReasoningSummary::Auto,
+            collaboration_mode: None,
+            personality: None,
+        })
+        .await?;
+
+    wait_for_event(&codex, |event| matches!(event, EventMsg::TurnComplete(_))).await;
+
+    let output_text = mock
+        .single_request()
+        .function_call_output_content_and_success(call_id)
+        .and_then(|(content, _)| content)
+        .expect("output text present");
+    assert_eq!(
+        output_text,
+        "view_image is not allowed because you do not support image inputs"
+    );
+
+    Ok(())
+}
+
 #[cfg(not(debug_assertions))]
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn replaces_invalid_local_image_after_bad_request() -> anyhow::Result<()> {