Add web search tool (#2371)

Adds web_search tool, enabling the model to use Responses API web_search
tool.
- Disabled by default, enabled by --search flag
- When --search is passed, exposes web_search_request function tool to
the model, which triggers user approval. When approved, the model can
use the web_search tool for the remainder of the turn
<img width="1033" height="294" alt="image"
src="https://github.com/user-attachments/assets/62ac6563-b946-465c-ba5d-9325af28b28f"
/>

---------

Co-authored-by: easong-openai <easong@openai.com>

codex-rs/core/src/config.rs

@@ -169,6 +169,8 @@ pub struct Config {
     /// model family's default preference.
     pub include_apply_patch_tool: bool,
 
+    pub tools_web_search_request: bool,
+
     /// The value for the `originator` header included with Responses API requests.
     pub responses_originator_header: String,
 
@@ -480,6 +482,9 @@ pub struct ConfigToml {
 
     /// If set to `true`, the API key will be signed with the `originator` header.
     pub preferred_auth_method: Option<AuthMode>,
+
+    /// Nested tools section for feature toggles
+    pub tools: Option<ToolsToml>,
 }
 
 #[derive(Deserialize, Debug, Clone, PartialEq, Eq)]
@@ -487,6 +492,13 @@ pub struct ProjectConfig {
     pub trust_level: Option<String>,
 }
 
+#[derive(Deserialize, Debug, Clone, Default)]
+pub struct ToolsToml {
+    // Renamed from `web_search_request`; keep alias for backwards compatibility.
+    #[serde(default, alias = "web_search_request")]
+    pub web_search: Option<bool>,
+}
+
 impl ConfigToml {
     /// Derive the effective sandbox policy from the configuration.
     fn derive_sandbox_policy(&self, sandbox_mode_override: Option<SandboxMode>) -> SandboxPolicy {
@@ -576,6 +588,7 @@ pub struct ConfigOverrides {
     pub include_apply_patch_tool: Option<bool>,
     pub disable_response_storage: Option<bool>,
     pub show_raw_agent_reasoning: Option<bool>,
+    pub tools_web_search_request: Option<bool>,
 }
 
 impl Config {
@@ -602,6 +615,7 @@ impl Config {
             include_apply_patch_tool,
             disable_response_storage,
             show_raw_agent_reasoning,
+            tools_web_search_request: override_tools_web_search_request,
         } = overrides;
 
         let config_profile = match config_profile_key.as_ref().or(cfg.profile.as_ref()) {
@@ -640,7 +654,7 @@ impl Config {
             })?
             .clone();
 
-        let shell_environment_policy = cfg.shell_environment_policy.into();
+        let shell_environment_policy = cfg.shell_environment_policy.clone().into();
 
         let resolved_cwd = {
             use std::env;
@@ -661,7 +675,11 @@ impl Config {
             }
         };
 
-        let history = cfg.history.unwrap_or_default();
+        let history = cfg.history.clone().unwrap_or_default();
+
+        let tools_web_search_request = override_tools_web_search_request
+            .or(cfg.tools.as_ref().and_then(|t| t.web_search))
+            .unwrap_or(false);
 
         let model = model
             .or(config_profile.model)
@@ -735,7 +753,7 @@ impl Config {
             codex_home,
             history,
             file_opener: cfg.file_opener.unwrap_or(UriBasedFileOpener::VsCode),
-            tui: cfg.tui.unwrap_or_default(),
+            tui: cfg.tui.clone().unwrap_or_default(),
             codex_linux_sandbox_exe,
 
             hide_agent_reasoning: cfg.hide_agent_reasoning.unwrap_or(false),
@@ -754,12 +772,13 @@ impl Config {
             model_verbosity: config_profile.model_verbosity.or(cfg.model_verbosity),
             chatgpt_base_url: config_profile
                 .chatgpt_base_url
-                .or(cfg.chatgpt_base_url)
+                .or(cfg.chatgpt_base_url.clone())
                 .unwrap_or("https://chatgpt.com/backend-api/".to_string()),
 
             experimental_resume,
             include_plan_tool: include_plan_tool.unwrap_or(false),
             include_apply_patch_tool: include_apply_patch_tool.unwrap_or(false),
+            tools_web_search_request,
             responses_originator_header,
             preferred_auth_method: cfg.preferred_auth_method.unwrap_or(AuthMode::ChatGPT),
             use_experimental_streamable_shell_tool: cfg
@@ -1129,6 +1148,7 @@ disable_response_storage = true
                 base_instructions: None,
                 include_plan_tool: false,
                 include_apply_patch_tool: false,
+                tools_web_search_request: false,
                 responses_originator_header: "codex_cli_rs".to_string(),
                 preferred_auth_method: AuthMode::ChatGPT,
                 use_experimental_streamable_shell_tool: false,
@@ -1184,6 +1204,7 @@ disable_response_storage = true
             base_instructions: None,
             include_plan_tool: false,
             include_apply_patch_tool: false,
+            tools_web_search_request: false,
             responses_originator_header: "codex_cli_rs".to_string(),
             preferred_auth_method: AuthMode::ChatGPT,
             use_experimental_streamable_shell_tool: false,
@@ -1254,6 +1275,7 @@ disable_response_storage = true
             base_instructions: None,
             include_plan_tool: false,
             include_apply_patch_tool: false,
+            tools_web_search_request: false,
             responses_originator_header: "codex_cli_rs".to_string(),
             preferred_auth_method: AuthMode::ChatGPT,
             use_experimental_streamable_shell_tool: false,