Add an operation to override current task context

codex-rs/core/src/client.rs

@@ -33,6 +33,7 @@ use crate::error::CodexErr;
 use crate::error::Result;
 use crate::error::UsageLimitReachedError;
 use crate::flags::CODEX_RS_SSE_FIXTURE;
+use crate::model_family::ModelFamily;
 use crate::model_provider_info::ModelProviderInfo;
 use crate::model_provider_info::WireApi;
 use crate::models::ResponseItem;
@@ -311,6 +312,30 @@ impl ModelClient {
     pub fn get_provider(&self) -> ModelProviderInfo {
         self.provider.clone()
     }
+
+    /// Returns the currently configured model slug.
+    pub fn get_model(&self) -> String {
+        self.config.model.clone()
+    }
+
+    /// Returns the currently configured model family.
+    pub fn get_model_family(&self) -> ModelFamily {
+        self.config.model_family.clone()
+    }
+
+    /// Returns the current reasoning effort setting.
+    pub fn get_reasoning_effort(&self) -> ReasoningEffortConfig {
+        self.effort
+    }
+
+    /// Returns the current reasoning summary setting.
+    pub fn get_reasoning_summary(&self) -> ReasoningSummaryConfig {
+        self.summary
+    }
+
+    pub fn get_auth(&self) -> Option<CodexAuth> {
+        self.auth.clone()
+    }
 }
 
 #[derive(Debug, Deserialize, Serialize)]

codex-rs/core/src/codex.rs

@@ -989,14 +989,91 @@ async fn submission_loop(
     rx_sub: Receiver<Submission>,
 ) {
     // Wrap once to avoid cloning TurnContext for each task.
-    let turn_context = Arc::new(turn_context);
+    let mut turn_context = Arc::new(turn_context);
     // To break out of this loop, send Op::Shutdown.
     while let Ok(sub) = rx_sub.recv().await {
         debug!(?sub, "Submission");
         match sub.op {
             Op::Interrupt => {
                 sess.interrupt_task();
             }
+            Op::OverrideTurnContext {
+                cwd,
+                approval_policy,
+                sandbox_policy,
+                model,
+                effort,
+                summary,
+            } => {
+                // Recalculate the persistent turn context with provided overrides.
+                let prev = Arc::clone(&turn_context);
+                let provider = prev.client.get_provider();
+
+                // Effective model + family
+                let (effective_model, effective_family) = if let Some(m) = model {
+                    let fam =
+                        find_family_for_model(&m).unwrap_or_else(|| config.model_family.clone());
+                    (m, fam)
+                } else {
+                    (prev.client.get_model(), prev.client.get_model_family())
+                };
+
+                // Effective reasoning settings
+                let effective_effort = effort.unwrap_or(prev.client.get_reasoning_effort());
+                let effective_summary = summary.unwrap_or(prev.client.get_reasoning_summary());
+
+                let auth = prev.client.get_auth();
+                // Build updated config for the client
+                let mut updated_config = (*config).clone();
+                updated_config.model = effective_model.clone();
+                updated_config.model_family = effective_family.clone();
+
+                let client = ModelClient::new(
+                    Arc::new(updated_config),
+                    auth,
+                    provider,
+                    effective_effort,
+                    effective_summary,
+                    sess.session_id,
+                );
+
+                let new_approval_policy = approval_policy.unwrap_or(prev.approval_policy);
+                let new_sandbox_policy = sandbox_policy
+                    .clone()
+                    .unwrap_or(prev.sandbox_policy.clone());
+                let new_cwd = cwd.clone().unwrap_or_else(|| prev.cwd.clone());
+
+                let tools_config = ToolsConfig::new(
+                    &effective_family,
+                    new_approval_policy,
+                    new_sandbox_policy.clone(),
+                    config.include_plan_tool,
+                    config.include_apply_patch_tool,
+                );
+
+                let new_turn_context = TurnContext {
+                    client,
+                    tools_config,
+                    user_instructions: prev.user_instructions.clone(),
+                    base_instructions: prev.base_instructions.clone(),
+                    approval_policy: new_approval_policy,
+                    sandbox_policy: new_sandbox_policy.clone(),
+                    shell_environment_policy: prev.shell_environment_policy.clone(),
+                    cwd: new_cwd.clone(),
+                    disable_response_storage: prev.disable_response_storage,
+                };
+
+                // Install the new persistent context for subsequent tasks/turns.
+                turn_context = Arc::new(new_turn_context);
+                if cwd.is_some() || approval_policy.is_some() || sandbox_policy.is_some() {
+                    sess.record_conversation_items(&[ResponseItem::from(EnvironmentContext::new(
+                        new_cwd,
+                        new_approval_policy,
+                        new_sandbox_policy,
+                    ))])
+                    .await;
+                }
+            }
             Op::UserInput { items } => {
                 // attempt to inject input into current task
                 if let Err(items) = sess.inject_input(items) {
@@ -1057,7 +1134,7 @@ async fn submission_loop(
                         cwd,
                         disable_response_storage: turn_context.disable_response_storage,
                     };
-
+                    // TODO: record the new environment context in the conversation history
                     // no current task, spawn a new one with the per‑turn context
                     let task =
                         AgentTask::spawn(sess.clone(), Arc::new(fresh_turn_context), sub.id, items);

codex-rs/core/tests/prompt_caching.rs

@@ -1,9 +1,13 @@
 use codex_core::ConversationManager;
 use codex_core::ModelProviderInfo;
 use codex_core::built_in_model_providers;
+use codex_core::protocol::AskForApproval;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::InputItem;
 use codex_core::protocol::Op;
+use codex_core::protocol::SandboxPolicy;
+use codex_core::protocol_config_types::ReasoningEffort as ReasoningEffortConfig;
+use codex_core::protocol_config_types::ReasoningSummary as ReasoningSummaryConfig;
 use codex_login::CodexAuth;
 use core_test_support::load_default_config_for_test;
 use core_test_support::load_sse_fixture_with_id;
@@ -129,3 +133,126 @@ async fn prefixes_context_and_instructions_once_and_consistently_across_requests
     );
     assert_eq!(body2["input"], expected_body2);
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn overrides_turn_context_but_keeps_cached_prefix_and_key_constant() {
+    use pretty_assertions::assert_eq;
+
+    let server = MockServer::start().await;
+
+    let sse = sse_completed("resp");
+    let template = ResponseTemplate::new(200)
+        .insert_header("content-type", "text/event-stream")
+        .set_body_raw(sse, "text/event-stream");
+
+    // Expect two POSTs to /v1/responses
+    Mock::given(method("POST"))
+        .and(path("/v1/responses"))
+        .respond_with(template)
+        .expect(2)
+        .mount(&server)
+        .await;
+
+    let model_provider = ModelProviderInfo {
+        base_url: Some(format!("{}/v1", server.uri())),
+        ..built_in_model_providers()["openai"].clone()
+    };
+
+    let cwd = TempDir::new().unwrap();
+    let codex_home = TempDir::new().unwrap();
+    let mut config = load_default_config_for_test(&codex_home);
+    config.cwd = cwd.path().to_path_buf();
+    config.model_provider = model_provider;
+    config.user_instructions = Some("be consistent and helpful".to_string());
+
+    let conversation_manager = ConversationManager::default();
+    let codex = conversation_manager
+        .new_conversation_with_auth(config, Some(CodexAuth::from_api_key("Test API Key")))
+        .await
+        .expect("create new conversation")
+        .conversation;
+
+    // First turn
+    codex
+        .submit(Op::UserInput {
+            items: vec![InputItem::Text {
+                text: "hello 1".into(),
+            }],
+        })
+        .await
+        .unwrap();
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
+
+    // Change everything about the turn context.
+    let new_cwd = TempDir::new().unwrap();
+    let writable = TempDir::new().unwrap();
+    codex
+        .submit(Op::OverrideTurnContext {
+            cwd: Some(new_cwd.path().to_path_buf()),
+            approval_policy: Some(AskForApproval::Never),
+            sandbox_policy: Some(SandboxPolicy::WorkspaceWrite {
+                writable_roots: vec![writable.path().to_path_buf()],
+                network_access: true,
+                exclude_tmpdir_env_var: true,
+                exclude_slash_tmp: true,
+            }),
+            model: Some("o3".to_string()),
+            effort: Some(ReasoningEffortConfig::High),
+            summary: Some(ReasoningSummaryConfig::Detailed),
+        })
+        .await
+        .unwrap();
+
+    // Second turn after overrides
+    codex
+        .submit(Op::UserInput {
+            items: vec![InputItem::Text {
+                text: "hello 2".into(),
+            }],
+        })
+        .await
+        .unwrap();
+    wait_for_event(&codex, |ev| matches!(ev, EventMsg::TaskComplete(_))).await;
+
+    // Verify we issued exactly two requests, and the cached prefix stayed identical.
+    let requests = server.received_requests().await.unwrap();
+    assert_eq!(requests.len(), 2, "expected two POST requests");
+
+    let body1 = requests[0].body_json::<serde_json::Value>().unwrap();
+    let body2 = requests[1].body_json::<serde_json::Value>().unwrap();
+
+    // prompt_cache_key should remain constant across overrides
+    assert_eq!(
+        body1["prompt_cache_key"], body2["prompt_cache_key"],
+        "prompt_cache_key should not change across overrides"
+    );
+
+    // The entire prefix from the first request should be identical and reused
+    // as the prefix of the second request, ensuring cache hit potential.
+    let expected_user_message_2 = serde_json::json!({
+        "type": "message",
+        "id": serde_json::Value::Null,
+        "role": "user",
+        "content": [ { "type": "input_text", "text": "hello 2" } ]
+    });
+    // After overriding the turn context, the environment context should be emitted again
+    // reflecting the new cwd, approval policy and sandbox settings.
+    let expected_env_text_2 = format!(
+        "<environment_context>\nCurrent working directory: {}\nApproval policy: never\nSandbox mode: workspace-write\nNetwork access: enabled\n</environment_context>",
+        new_cwd.path().to_string_lossy()
+    );
+    let expected_env_msg_2 = serde_json::json!({
+        "type": "message",
+        "id": serde_json::Value::Null,
+        "role": "user",
+        "content": [ { "type": "input_text", "text": expected_env_text_2 } ]
+    });
+    let expected_body2 = serde_json::json!(
+        [
+            body1["input"].as_array().unwrap().as_slice(),
+            [expected_env_msg_2, expected_user_message_2].as_slice(),
+        ]
+        .concat()
+    );
+    assert_eq!(body2["input"], expected_body2);
+}

codex-rs/protocol/src/protocol.rs

@@ -75,6 +75,38 @@ pub enum Op {
         summary: ReasoningSummaryConfig,
     },
 
+    /// Override parts of the persistent turn context for subsequent turns.
+    ///
+    /// All fields are optional; when omitted, the existing value is preserved.
+    /// This does not enqueue any input – it only updates defaults used for
+    /// future `UserInput` turns.
+    OverrideTurnContext {
+        /// Updated `cwd` for sandbox/tool calls.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        cwd: Option<PathBuf>,
+
+        /// Updated command approval policy.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        approval_policy: Option<AskForApproval>,
+
+        /// Updated sandbox policy for tool calls.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        sandbox_policy: Option<SandboxPolicy>,
+
+        /// Updated model slug. When set, the model family is derived
+        /// automatically.
+        #[serde(skip_serializing_if = "Option::is_none")]
+        model: Option<String>,
+
+        /// Updated reasoning effort (honored only for reasoning-capable models).
+        #[serde(skip_serializing_if = "Option::is_none")]
+        effort: Option<ReasoningEffortConfig>,
+
+        /// Updated reasoning summary preference (honored only for reasoning-capable models).
+        #[serde(skip_serializing_if = "Option::is_none")]
+        summary: Option<ReasoningSummaryConfig>,
+    },
+
     /// Approve a command execution
     ExecApproval {
         /// The id of the submission we are approving