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/tui/src/chatwidget.rs

@@ -28,6 +28,7 @@ use codex_core::protocol::TaskCompleteEvent;
 use codex_core::protocol::TokenUsage;
 use codex_core::protocol::TurnAbortReason;
 use codex_core::protocol::TurnDiffEvent;
+use codex_core::protocol::WebSearchBeginEvent;
 use codex_protocol::parse_command::ParsedCommand;
 use crossterm::event::KeyEvent;
 use crossterm::event::KeyEventKind;
@@ -308,6 +309,11 @@ impl ChatWidget {
         self.defer_or_handle(|q| q.push_mcp_end(ev), |s| s.handle_mcp_end_now(ev2));
     }
 
+    fn on_web_search_begin(&mut self, ev: WebSearchBeginEvent) {
+        self.flush_answer_stream_with_separator();
+        self.add_to_history(history_cell::new_web_search_call(ev.query));
+    }
+
     fn on_get_history_entry_response(
         &mut self,
         event: codex_core::protocol::GetHistoryEntryResponseEvent,
@@ -839,6 +845,7 @@ impl ChatWidget {
             EventMsg::ExecCommandEnd(ev) => self.on_exec_command_end(ev),
             EventMsg::McpToolCallBegin(ev) => self.on_mcp_tool_call_begin(ev),
             EventMsg::McpToolCallEnd(ev) => self.on_mcp_tool_call_end(ev),
+            EventMsg::WebSearchBegin(ev) => self.on_web_search_begin(ev),
             EventMsg::GetHistoryEntryResponse(ev) => self.on_get_history_entry_response(ev),
             EventMsg::McpListToolsResponse(ev) => self.on_list_mcp_tools(ev),
             EventMsg::ShutdownComplete => self.on_shutdown_complete(),

codex-rs/tui/src/cli.rs

@@ -54,6 +54,10 @@ pub struct Cli {
     #[clap(long = "cd", short = 'C', value_name = "DIR")]
     pub cwd: Option<PathBuf>,
 
+    /// Enable web search (off by default). When enabled, the native Responses `web_search` tool is available to the model (no per‑call approval).
+    #[arg(long = "search", default_value_t = false)]
+    pub web_search: bool,
+
     #[clap(skip)]
     pub config_overrides: CliConfigOverrides,
 }

codex-rs/tui/src/history_cell.rs

@@ -445,6 +445,12 @@ pub(crate) fn new_active_mcp_tool_call(invocation: McpInvocation) -> PlainHistor
     PlainHistoryCell { lines }
 }
 
+pub(crate) fn new_web_search_call(query: String) -> PlainHistoryCell {
+    let lines: Vec<Line<'static>> =
+        vec![Line::from(""), Line::from(vec!["🌐 ".into(), query.into()])];
+    PlainHistoryCell { lines }
+}
+
 /// If the first content is an image, return a new cell with the image.
 /// TODO(rgwood-dd): Handle images properly even if they're not the first result.
 fn try_new_completed_mcp_tool_call_with_image_output(

codex-rs/tui/src/lib.rs

@@ -128,10 +128,11 @@ pub async fn run_main(
         include_apply_patch_tool: None,
         disable_response_storage: cli.oss.then_some(true),
         show_raw_agent_reasoning: cli.oss.then_some(true),
+        tools_web_search_request: cli.web_search.then_some(true),
     };
-
-    // Parse `-c` overrides from the CLI.
-    let cli_kv_overrides = match cli.config_overrides.parse_overrides() {
+    let raw_overrides = cli.config_overrides.raw_overrides.clone();
+    let overrides_cli = codex_common::CliConfigOverrides { raw_overrides };
+    let cli_kv_overrides = match overrides_cli.parse_overrides() {
         Ok(v) => v,
         #[allow(clippy::print_stderr)]
         Err(e) => {