assistant: Partial fix for HTML entities in tools params (#32148)

This problem seems to be specific to Opus 4. Eval shows improvement from
89% to 97%.

Closes: https://github.com/zed-industries/zed/issues/32060

Release Notes:

- N/A

Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>

crates/eval/src/examples/grep_params_escapement.rs

@@ -0,0 +1,59 @@
+use agent_settings::AgentProfileId;
+use anyhow::Result;
+use assistant_tools::GrepToolInput;
+use async_trait::async_trait;
+
+use crate::example::{Example, ExampleContext, ExampleMetadata};
+
+pub struct GrepParamsEscapementExample;
+
+/*
+
+This eval checks that the model doesn't use HTML escapement for characters like `<` and
+`>` in tool parameters.
+
+                      original     +system_prompt change    +tool description
+  claude-opus-4        89%          92%                     97%+
+  claude-sonnet-4      100%
+  gpt-4.1-mini         100%
+  gemini-2.5-pro                    98%
+
+*/
+
+#[async_trait(?Send)]
+impl Example for GrepParamsEscapementExample {
+    fn meta(&self) -> ExampleMetadata {
+        ExampleMetadata {
+            name: "grep_params_escapement".to_string(),
+            url: "https://github.com/octocat/hello-world".to_string(),
+            revision: "7fd1a60b01f91b314f59955a4e4d4e80d8edf11d".to_string(),
+            language_server: None,
+            max_assertions: Some(1),
+            profile_id: AgentProfileId::default(),
+            existing_thread_json: None,
+            max_turns: Some(2),
+        }
+    }
+
+    async fn conversation(&self, cx: &mut ExampleContext) -> Result<()> {
+        // cx.push_user_message("How does the precedence/specificity work with Keymap contexts? I am seeing that `MessageEditor > Editor` is lower precendence than `Editor` which is surprising to me, but might be how it works");
+        cx.push_user_message("Search for files containing the characters `>` or `<`");
+        let response = cx.run_turns(2).await?;
+        let grep_input = response
+            .find_tool_call("grep")
+            .and_then(|tool_use| tool_use.parse_input::<GrepToolInput>().ok());
+
+        cx.assert_some(grep_input.as_ref(), "`grep` tool should be called")?;
+
+        cx.assert(
+            !contains_html_entities(&grep_input.unwrap().regex),
+            "Tool parameters should not be escaped",
+        )
+    }
+}
+
+fn contains_html_entities(pattern: &str) -> bool {
+    regex::Regex::new(r"&[a-zA-Z]+;|&#[0-9]+;|&#x[0-9a-fA-F]+;")
+        .unwrap()
+        .is_match(pattern)
+}

crates/eval/src/examples/mod.rs

@@ -16,6 +16,7 @@ mod add_arg_to_trait_method;
 mod code_block_citations;
 mod comment_translation;
 mod file_search;
+mod grep_params_escapement;
 mod overwrite_file;
 mod planets;
 
@@ -27,6 +28,7 @@ pub fn all(examples_dir: &Path) -> Vec<Rc<dyn Example>> {
         Rc::new(planets::Planets),
         Rc::new(comment_translation::CommentTranslation),
         Rc::new(overwrite_file::FileOverwriteExample),
+        Rc::new(grep_params_escapement::GrepParamsEscapementExample),
     ];
 
     for example_path in list_declarative_examples(examples_dir).unwrap() {