From 23bb524973d67a783911980d25460833f03befc3 Mon Sep 17 00:00:00 2001
From: Abhinav <abhinav@openai.com>
Date: Wed, 13 May 2026 15:21:31 -0700
Subject: [PATCH] Spill oversized PreToolUse additionalContext (#22529)

# Why

`PreToolUse.additionalContext` became model-visible after #20692, but
the hook-output spilling path from #21069 never picked up that newer
lane. As a result, oversized `PreToolUse` context could bypass the
truncation/spill treatment that already applies to the other hook
outputs Codex forwards to the model.

# What

- Run `PreToolUseOutcome.additional_contexts` through
`maybe_spill_texts(...)`
- Add an integration test proving a large `PreToolUse.additionalContext`
is replaced with a truncated preview plus spill-file pointer, while the
full text is preserved on disk.
---
 codex-rs/core/tests/suite/hooks.rs | 61 ++++++++++++++++++++++++++++++
 codex-rs/hooks/src/engine/mod.rs   | 11 ++++--
 2 files changed, 69 insertions(+), 3 deletions(-)

diff --git a/codex-rs/core/tests/suite/hooks.rs b/codex-rs/core/tests/suite/hooks.rs
index 635aeaf488..f059998052 100644
--- a/codex-rs/core/tests/suite/hooks.rs
+++ b/codex-rs/core/tests/suite/hooks.rs
@@ -1064,6 +1064,67 @@ async fn session_start_hook_spills_large_additional_context() -> Result<()> {
     Ok(())
 }
 
+#[tokio::test]
+async fn pre_tool_use_hook_spills_large_additional_context() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = start_mock_server().await;
+    let call_id = "pretooluse-shell-command-large-context";
+    let command = "printf pre-tool-output".to_string();
+    let args = serde_json::json!({ "command": command });
+    let responses = mount_sse_sequence(
+        &server,
+        vec![
+            sse(vec![
+                ev_response_created("resp-1"),
+                core_test_support::responses::ev_function_call(
+                    call_id,
+                    "shell_command",
+                    &serde_json::to_string(&args)?,
+                ),
+                ev_completed("resp-1"),
+            ]),
+            sse(vec![
+                ev_response_created("resp-2"),
+                ev_assistant_message("msg-1", "pre hook context observed"),
+                ev_completed("resp-2"),
+            ]),
+        ],
+    )
+    .await;
+    let additional_context = "remember the pre tool reef ".repeat(800);
+
+    let mut builder = test_codex()
+        .with_pre_build_hook({
+            let additional_context = additional_context.clone();
+            move |home| {
+                if let Err(error) =
+                    write_pre_tool_use_hook(home, Some("^Bash$"), "context", &additional_context)
+                {
+                    panic!("failed to write pre tool use hook test fixture: {error}");
+                }
+            }
+        })
+        .with_config(trust_discovered_hooks);
+    let test = builder.build(&server).await?;
+
+    test.submit_turn("run the shell command with large pre hook context")
+        .await?;
+
+    let requests = responses.requests();
+    assert_eq!(requests.len(), 2);
+    let developer_messages = requests[1].message_input_texts("developer");
+    let developer_message = developer_messages
+        .iter()
+        .find(|message| spilled_hook_output_path(message).is_some())
+        .context("spilled developer hook message")?;
+    assert!(developer_message.contains("tokens truncated"));
+    let path = spilled_hook_output_path(developer_message).context("spill path")?;
+    assert_eq!(fs::read_to_string(path)?, additional_context);
+
+    Ok(())
+}
+
 #[tokio::test]
 async fn stop_hook_spills_large_continuation_prompt() -> Result<()> {
     skip_if_no_network!(Ok(()));
diff --git a/codex-rs/hooks/src/engine/mod.rs b/codex-rs/hooks/src/engine/mod.rs
index 441c24314c..8a4a11a5d4 100644
--- a/codex-rs/hooks/src/engine/mod.rs
+++ b/codex-rs/hooks/src/engine/mod.rs
@@ -4,8 +4,6 @@ pub(crate) mod dispatcher;
 pub(crate) mod output_parser;
 pub(crate) mod schema_loader;
 
-use std::collections::HashMap;
-
 use crate::events::compact::PostCompactRequest;
 use crate::events::compact::PreCompactOutcome;
 use crate::events::compact::PreCompactRequest;
@@ -32,6 +30,7 @@ use codex_protocol::protocol::HookRunSummary;
 use codex_protocol::protocol::HookSource;
 use codex_protocol::protocol::HookTrustStatus;
 use codex_utils_absolute_path::AbsolutePathBuf;
+use std::collections::HashMap;
 
 #[derive(Debug, Clone)]
 pub(crate) struct CommandShell {
@@ -180,7 +179,13 @@ impl ClaudeHooksEngine {
     }
 
     pub(crate) async fn run_pre_tool_use(&self, request: PreToolUseRequest) -> PreToolUseOutcome {
-        crate::events::pre_tool_use::run(&self.handlers, &self.shell, request).await
+        let session_id = request.session_id;
+        let mut outcome =
+            crate::events::pre_tool_use::run(&self.handlers, &self.shell, request).await;
+        outcome.additional_contexts = self
+            .maybe_spill_texts(session_id, outcome.additional_contexts)
+            .await;
+        outcome
     }
 
     pub(crate) async fn run_permission_request(