[prompts] Add <environment_context> (#1869)

## Summary
Includes a new user message in the api payload which provides useful
environment context for the model, so it knows about things like the
current working directory and the sandbox.

## Testing
Updated unit tests

codex-rs/core/src/chat_completions.rs

@@ -41,11 +41,9 @@ pub(crate) async fn stream_chat_completions(
     let full_instructions = prompt.get_full_instructions(model_family);
     messages.push(json!({"role": "system", "content": full_instructions}));
 
-    if let Some(instr) = &prompt.get_formatted_user_instructions() {
-        messages.push(json!({"role": "user", "content": instr}));
-    }
+    let input = prompt.get_formatted_input();
 
-    for item in &prompt.input {
+    for item in &input {
         match item {
             ResponseItem::Message { role, content, .. } => {
                 let mut text = String::new();

codex-rs/core/src/client.rs

@@ -34,7 +34,6 @@ use crate::error::Result;
 use crate::flags::CODEX_RS_SSE_FIXTURE;
 use crate::model_provider_info::ModelProviderInfo;
 use crate::model_provider_info::WireApi;
-use crate::models::ContentItem;
 use crate::models::ResponseItem;
 use crate::openai_tools::create_tools_json_for_responses_api;
 use crate::protocol::TokenUsage;
@@ -146,15 +145,7 @@ impl ModelClient {
             vec![]
         };
 
-        let mut input_with_instructions = Vec::with_capacity(prompt.input.len() + 1);
-        if let Some(ui) = prompt.get_formatted_user_instructions() {
-            input_with_instructions.push(ResponseItem::Message {
-                id: None,
-                role: "user".to_string(),
-                content: vec![ContentItem::InputText { text: ui }],
-            });
-        }
-        input_with_instructions.extend(prompt.input.clone());
+        let input_with_instructions = prompt.get_formatted_input();
 
         let payload = ResponsesApiRequest {
             model: &self.config.model,

codex-rs/core/src/client_common.rs

@@ -1,14 +1,20 @@
 use crate::config_types::ReasoningEffort as ReasoningEffortConfig;
 use crate::config_types::ReasoningSummary as ReasoningSummaryConfig;
 use crate::error::Result;
+use crate::git_info::GitInfo;
 use crate::model_family::ModelFamily;
+use crate::models::ContentItem;
 use crate::models::ResponseItem;
 use crate::openai_tools::OpenAiTool;
+use crate::protocol::AskForApproval;
+use crate::protocol::SandboxPolicy;
 use crate::protocol::TokenUsage;
 use codex_apply_patch::APPLY_PATCH_TOOL_INSTRUCTIONS;
 use futures::Stream;
 use serde::Serialize;
 use std::borrow::Cow;
+use std::fmt::Display;
+use std::path::PathBuf;
 use std::pin::Pin;
 use std::task::Context;
 use std::task::Poll;
@@ -18,10 +24,49 @@ use tokio::sync::mpsc;
 /// with this content.
 const BASE_INSTRUCTIONS: &str = include_str!("../prompt.md");
 
+/// wraps environment context message in a tag for the model to parse more easily.
+const ENVIRONMENT_CONTEXT_START: &str = "<environment_context>\n\n";
+const ENVIRONMENT_CONTEXT_END: &str = "\n\n</environment_context>";
+
 /// wraps user instructions message in a tag for the model to parse more easily.
 const USER_INSTRUCTIONS_START: &str = "<user_instructions>\n\n";
 const USER_INSTRUCTIONS_END: &str = "\n\n</user_instructions>";
 
+#[derive(Debug, Clone)]
+pub(crate) struct EnvironmentContext {
+    pub cwd: PathBuf,
+    pub git_info: Option<GitInfo>,
+    pub approval_policy: AskForApproval,
+    pub sandbox_policy: SandboxPolicy,
+}
+
+impl Display for EnvironmentContext {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        writeln!(
+            f,
+            "Current working directory: {}",
+            self.cwd.to_string_lossy()
+        )?;
+        writeln!(f, "Is directory a git repo: {}", self.git_info.is_some())?;
+        writeln!(f, "Approval policy: {}", self.approval_policy)?;
+        writeln!(f, "Sandbox policy: {}", self.sandbox_policy)?;
+
+        let network_access = match self.sandbox_policy.clone() {
+            SandboxPolicy::DangerFullAccess => "enabled",
+            SandboxPolicy::ReadOnly => "restricted",
+            SandboxPolicy::WorkspaceWrite { network_access, .. } => {
+                if network_access {
+                    "enabled"
+                } else {
+                    "restricted"
+                }
+            }
+        };
+        writeln!(f, "Network access: {network_access}")?;
+        Ok(())
+    }
+}
+
 /// API request payload for a single model turn.
 #[derive(Default, Debug, Clone)]
 pub struct Prompt {
@@ -33,6 +78,10 @@ pub struct Prompt {
     /// Whether to store response on server side (disable_response_storage = !store).
     pub store: bool,
 
+    /// A list of key-value pairs that will be added as a developer message
+    /// for the model to use
+    pub environment_context: Option<EnvironmentContext>,
+
     /// Tools available to the model, including additional tools sourced from
     /// external MCP servers.
     pub tools: Vec<OpenAiTool>,
@@ -54,11 +103,37 @@ impl Prompt {
         Cow::Owned(sections.join("\n"))
     }
 
-    pub(crate) fn get_formatted_user_instructions(&self) -> Option<String> {
+    fn get_formatted_user_instructions(&self) -> Option<String> {
         self.user_instructions
             .as_ref()
             .map(|ui| format!("{USER_INSTRUCTIONS_START}{ui}{USER_INSTRUCTIONS_END}"))
     }
+
+    fn get_formatted_environment_context(&self) -> Option<String> {
+        self.environment_context
+            .as_ref()
+            .map(|ec| format!("{ENVIRONMENT_CONTEXT_START}{ec}{ENVIRONMENT_CONTEXT_END}"))
+    }
+
+    pub(crate) fn get_formatted_input(&self) -> Vec<ResponseItem> {
+        let mut input_with_instructions = Vec::with_capacity(self.input.len() + 2);
+        if let Some(ec) = self.get_formatted_environment_context() {
+            input_with_instructions.push(ResponseItem::Message {
+                id: None,
+                role: "user".to_string(),
+                content: vec![ContentItem::InputText { text: ec }],
+            });
+        }
+        if let Some(ui) = self.get_formatted_user_instructions() {
+            input_with_instructions.push(ResponseItem::Message {
+                id: None,
+                role: "user".to_string(),
+                content: vec![ContentItem::InputText { text: ui }],
+            });
+        }
+        input_with_instructions.extend(self.input.clone());
+        input_with_instructions
+    }
 }
 
 #[derive(Debug)]

codex-rs/core/src/codex.rs

@@ -37,6 +37,7 @@ use crate::apply_patch::convert_apply_patch_to_protocol;
 use crate::apply_patch::get_writable_roots;
 use crate::apply_patch::{self};
 use crate::client::ModelClient;
+use crate::client_common::EnvironmentContext;
 use crate::client_common::Prompt;
 use crate::client_common::ResponseEvent;
 use crate::config::Config;
@@ -51,6 +52,7 @@ use crate::exec::SandboxType;
 use crate::exec::StdoutStream;
 use crate::exec::process_exec_tool_call;
 use crate::exec_env::create_env;
+use crate::git_info::collect_git_info;
 use crate::mcp_connection_manager::McpConnectionManager;
 use crate::mcp_tool_call::handle_mcp_tool_call;
 use crate::models::ContentItem;
@@ -1224,6 +1226,12 @@ async fn run_turn(
         store: !sess.disable_response_storage,
         tools,
         base_instructions_override: sess.base_instructions.clone(),
+        environment_context: Some(EnvironmentContext {
+            cwd: sess.cwd.clone(),
+            git_info: collect_git_info(&sess.cwd).await,
+            approval_policy: sess.approval_policy,
+            sandbox_policy: sess.sandbox_policy.clone(),
+        }),
     };
 
     let mut retries = 0;
@@ -1449,6 +1457,7 @@ async fn run_compact_task(
         input: turn_input,
         user_instructions: None,
         store: !sess.disable_response_storage,
+        environment_context: None,
         tools: Vec::new(),
         base_instructions_override: Some(compact_instructions.clone()),
     };

codex-rs/core/src/git_info.rs

@@ -9,7 +9,7 @@ use tokio::time::timeout;
 /// Timeout for git commands to prevent freezing on large repositories
 const GIT_COMMAND_TIMEOUT: TokioDuration = TokioDuration::from_secs(5);
 
-#[derive(Serialize, Deserialize, Clone)]
+#[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct GitInfo {
     /// Current commit hash (SHA)
     #[serde(skip_serializing_if = "Option::is_none")]

codex-rs/core/src/protocol.rs

@@ -159,7 +159,8 @@ pub enum AskForApproval {
 }
 
 /// Determines execution restrictions for model shell commands.
-#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Display)]
+#[strum(serialize_all = "kebab-case")]
 #[serde(tag = "mode", rename_all = "kebab-case")]
 pub enum SandboxPolicy {
     /// No restrictions whatsoever. Use with caution.

codex-rs/core/tests/client.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::expect_used)]
+#![allow(clippy::unwrap_used)]
 use std::path::PathBuf;
 
 use chrono::Utc;
@@ -32,6 +34,32 @@ fn sse_completed(id: &str) -> String {
     load_sse_fixture_with_id("tests/fixtures/completed_template.json", id)
 }
 
+fn assert_message_role(request_body: &serde_json::Value, role: &str) {
+    assert_eq!(request_body["role"].as_str().unwrap(), role);
+}
+
+fn assert_message_starts_with(request_body: &serde_json::Value, text: &str) {
+    let content = request_body["content"][0]["text"]
+        .as_str()
+        .expect("invalid message content");
+
+    assert!(
+        content.starts_with(text),
+        "expected message content '{content}' to start with '{text}'"
+    );
+}
+
+fn assert_message_ends_with(request_body: &serde_json::Value, text: &str) {
+    let content = request_body["content"][0]["text"]
+        .as_str()
+        .expect("invalid message content");
+
+    assert!(
+        content.ends_with(text),
+        "expected message content '{content}' to end with '{text}'"
+    );
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn includes_session_id_and_model_headers_in_request() {
     #![allow(clippy::unwrap_used)]
@@ -371,19 +399,12 @@ async fn includes_user_instructions_message_in_request() {
             .unwrap()
             .contains("be nice")
     );
-    assert_eq!(request_body["input"][0]["role"], "user");
-    assert!(
-        request_body["input"][0]["content"][0]["text"]
-            .as_str()
-            .unwrap()
-            .starts_with("<user_instructions>\n\nbe nice")
-    );
-    assert!(
-        request_body["input"][0]["content"][0]["text"]
-            .as_str()
-            .unwrap()
-            .ends_with("</user_instructions>")
-    );
+    assert_message_role(&request_body["input"][0], "user");
+    assert_message_starts_with(&request_body["input"][0], "<environment_context>\n\n");
+    assert_message_ends_with(&request_body["input"][0], "</environment_context>");
+    assert_message_role(&request_body["input"][1], "user");
+    assert_message_starts_with(&request_body["input"][1], "<user_instructions>\n\n");
+    assert_message_ends_with(&request_body["input"][1], "</user_instructions>");
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]

codex-rs/mcp-server/tests/send_message.rs

@@ -99,7 +99,7 @@ async fn test_send_message_success() {
         response
     );
     // wait for the server to hear the user message
-    sleep(Duration::from_secs(1));
+    sleep(Duration::from_secs(10));
 
     // Ensure the server and tempdir live until end of test
     drop(server);