Fix pre-turn compaction context handling and remote compact edge cases by charley-oai · Pull Request #11234 · openai/codex

charley-oai · 2026-02-09T21:13:02Z

Note: this PR is not vibe coded and I have carefully self reviewed.

Snapshot/shape test extraction now lives in a separate base PR: #11487.

This PR is stacked on top of cc/compact-context-tests and contains the compaction/context runtime changes only.

Summary

Pre-turn auto-compaction now compacts with incoming turn items (pre_turn_context_items + latest user input), and if that compaction hits context-window limits we return an explicit oversized incoming-items error to the user.
Keep PreTurnCompactionOutcome::CompactedWithoutIncomingItems as a reserved, test-only strategy for future model behavior; production pre-turn flow currently uses CompactedWithIncomingItems.
Preserve structured incoming user items in local compaction history shaping (avoid flattening multimodal user input to plain text).
Persist model-visible pre-turn settings updates in failure-prone paths so diffs are not dropped when previous_context advances:
- empty-input settings-only UserTurn
- pre-turn compaction failure before normal turn execution
- early cancellation paths before skill/app resolution completes
Model-switch pre-pass compaction now reinjects canonical context (TurnContextReinjection::ReinjectAboveLastRealUser) so unchanged instructions remain present if this is the only compaction pass before submission.
Local pre-turn compaction retry/trim logic now protects the incoming tail (incoming items + compaction prompt), so retries trim seeded history rather than dropping current incoming items.
Remote compaction tail trimming now accounts for incoming pre-turn item tokens when deciding whether to trim codex-generated tail items.
Manual /compact now no-ops when there is no user-turn boundary and marks initial context unseeded for the next turn so canonical context is reseeded before future user input.
Both local and remote compaction now persist replacement_history, improving compact/resume/fork reconstruction consistency.

Reviewer Focus

codex-rs/core/src/codex.rs
- run_pre_turn_auto_compaction_if_needed
- persist_pre_turn_items_for_compaction_outcome
- maybe_run_previous_model_inline_compact
- pre-turn update persistence in handlers::user_input_or_turn / run_turn
codex-rs/core/src/compact.rs
- run_compact_task_inner (trim/retry + protected tail semantics)
- build_compacted_history_with_limit
- process_compacted_history
codex-rs/core/src/compact_remote.rs
- run_remote_compact_task_inner_impl
- trim_function_call_history_to_fit_context_window
codex-rs/core/src/tasks/compact.rs
- /compact no-op + reseed semantics when no user-turn boundary exists
codex-rs/core/tests/suite/compact.rs
- pre-turn inclusion, oversize, trim-retry, and persistence regression coverage
codex-rs/core/tests/suite/model_switching.rs
- model-switch compaction/regression coverage

Codex author

codex resume 019c40c5-7867-7843-b487-cce45a86a8bb

charley-oai · 2026-02-09T21:23:24Z

@codex review this

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codex-rs/core/src/codex.rs

charley-oai · 2026-02-10T19:20:29Z

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codex-rs/core/src/codex.rs

charley-oai · 2026-02-11T03:45:17Z

codex-rs/core/tests/suite/compact_resume_fork.rs

@@ -356,24 +356,25 @@ async fn compact_resume_and_fork_preserve_model_history_view() {
      "model": expected_model,


Old expected order was roughly:

permissions -> user_instructions -> environment_context -> last_real_user -> summary -> new_user

New expected order is:

last_real_user -> summary -> permissions -> user_instructions -> environment_context -> new_user

So the tests now expect:

The compaction summary to stay attached to the compacted user history (right after the last real pre-
compaction user message).

Turn context reseeding to be placed above the next user message, not hoisted to the very front.

charley-oai · 2026-02-11T04:13:24Z

codex-rs/core/src/compact.rs

    let rollout_item = RolloutItem::Compacted(CompactedItem {
        message: summary_text.clone(),
-        replacement_history: None,
+        replacement_history: Some(sess.clone_history().await.raw_items().to_vec()),


aligning more with remote compaction behavior

charley-oai · 2026-02-11T04:22:38Z

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codex-rs/core/src/compact.rs

codex-rs/core/src/codex.rs

charley-oai · 2026-02-11T05:12:41Z

codex-rs/app-server/tests/suite/v2/compaction.rs

-        responses::ev_assistant_message("m1", "MANUAL_COMPACT_SUMMARY"),
-        responses::ev_completed_with_tokens("r1", 200),
-    ]);
-    responses::mount_sse_sequence(&server, vec![sse]).await;


This test now exercises the empty-history /compact path, which is intentionally a no-op at the
model/API layer.

In codex-rs/app-server/tests/suite/v2/compaction.rs:202,
thread_compact_start_triggers_compaction_and_returns_empty_response starts a fresh thread with no user-turn boundary.

With current behavior, compaction emits started/completed thread items but does not send a /v1/responses
request.

The deleted block (mount_sse_sequence) created a strict mock expecting one SSE request; since no request
is sent, Wiremock fails on drop (“expected 1, got 0”), which is exactly the CI failure you pasted.

So it was removed to align the test with the new semantics: empty-start /compact should no-op remotely, not
hit the responses API.

charley-oai · 2026-02-11T18:20:17Z

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codex-rs/core/src/codex.rs

charley-oai · 2026-02-11T19:29:11Z

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codex-rs/core/src/codex.rs

codex-rs/core/src/compact_remote.rs

charley-oai · 2026-02-11T19:52:48Z

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codex-rs/core/src/compact.rs

codex-rs/core/src/codex.rs

charley-oai · 2026-02-12T09:34:44Z

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codex-rs/core/src/codex.rs

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codex-rs/core/src/compact.rs

charley-oai · 2026-02-18T09:57:08Z

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codex-rs/core/src/compact.rs

charley-oai · 2026-02-18T10:18:32Z

@codex review this

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chatgpt-codex-connector · 2026-02-18T10:29:30Z

codex-rs/core/src/compact_remote.rs

+            new_history
+                .iter()
+                .rposition(|candidate| match (candidate, incoming_item) {
+                    (
+                        ResponseItem::Message {
+                            role: candidate_role,
+                            content: candidate_content,
+                            ..
+                        },
+                        ResponseItem::Message {
+                            role: incoming_role,
+                            content: incoming_content,
+                            ..
+                        },
+                    ) => candidate_role == incoming_role && candidate_content == incoming_content,
+                    (


Preserve historical duplicates when stripping incoming echoes

remove_incoming_echoes_from_compacted_history removes the last item matching each incoming item by role/content. If remote compaction output does not actually echo the incoming item, but an older turn has identical text, this deletes legitimate history. Repeated user messages can be silently dropped after compaction, corrupting conversation context.

Useful? React with 👍 / 👎.

pakrym-oai · 2026-02-18T16:39:40Z

codex-rs/app-server/tests/suite/v2/compaction.rs

@@ -203,11 +203,6 @@ async fn thread_compact_start_triggers_compaction_and_returns_empty_response() -
    skip_if_no_network!(Ok(()));

    let server = responses::start_mock_server().await;


does test need renaming?

pakrym-oai · 2026-02-18T16:49:26Z

codex-rs/core/src/codex.rs

+        &sess,
+        &turn_context,
+        auto_compact_limit,
+        &incoming_turn_items,


The combination of incoming_turn_items and pre_turn_context_items is very confusing. Especiallu considering incoming_turn_items == pre_turn_context_items + input

pakrym-oai · 2026-02-18T16:52:46Z

codex-rs/core/src/codex.rs

-                sess.record_conversation_items(&current_context, &update_items)
+            let has_user_input = !items.is_empty();
+            if !has_user_input && !pre_turn_context_items.is_empty() {
+                // Empty-input UserTurn still needs these model-visible updates persisted now.


We were already persisting these items for empty user turn before. Why the extra condition?

pakrym-oai · 2026-02-18T16:54:00Z

codex-rs/core/src/codex.rs

+                sess.take_startup_regular_task()
+                    .await
+                    .unwrap_or_default()
+                    .with_pre_turn_context_items(pre_turn_context_items)


I really don't love how sometimes we directly inject history items and sometimes we carry them separately

pakrym-oai · 2026-02-18T16:57:51Z

codex-rs/core/src/codex.rs

+        None,
+    )
+    .await
+    {


There is a lot of new error reporting in many places. Should it be part of this PR and should it be done more centally?

pakrym-oai · 2026-02-18T17:02:53Z

...x-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_with_history_shapes.snap

-04:message/user:<COMPACTION_SUMMARY>\nFIRST_MANUAL_SUMMARY
+00:message/user:first manual turn
+01:message/user:<COMPACTION_SUMMARY>\nFIRST_MANUAL_SUMMARY
+02:message/developer:<PERMISSIONS_INSTRUCTIONS>


didn't we want these pre summary?

I guess not for manual compact.

pakrym-oai · 2026-02-18T17:04:59Z

...core/tests/suite/snapshots/all__suite__compact__manual_compact_without_prev_user_shapes.snap

-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
-03:message/user:<SUMMARIZATION_PROMPT>
+Scenario: Manual /compact with no prior user turn is a no-op; follow-up turn carries canonical context and the new user message.


Do we special case the logic to skip compaction without user turns anywhere? Do we need to? Feels pretty rare.

pakrym-oai · 2026-02-18T17:15:36Z

...e/snapshots/all__suite__compact_remote__remote_mid_turn_compaction_multi_summary_shapes.snap

-03:message/user:<AGENTS_MD>
-04:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
-05:message/user:<COMPACTION_SUMMARY>\nREMOTE_LATEST_SUMMARY
+02:message/user:<COMPACTION_SUMMARY>\nREMOTE_LATEST_SUMMARY


I don't think we'll ever have two summaries.

pakrym-oai · 2026-02-18T17:24:56Z

codex-rs/core/src/codex.rs

-            if !update_items.is_empty() {
-                sess.record_conversation_items(&current_context, &update_items)
+            let has_user_input = !items.is_empty();
+            if !has_user_input && !pre_turn_context_items.is_empty() {


Is not content use turn a thing?

pakrym-oai · 2026-02-18T17:35:17Z

codex-rs/core/src/codex.rs

+    incoming_user_tokens_estimate: i64,
+    auto_compact_limit: i64,
+) -> bool {
+    if auto_compact_limit == i64::MAX {


isn't this an effective noop?

charley-oai · 2026-02-20T07:31:28Z

Closing in favor of simpler approach

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charley-oai changed the title ~~Fix auto-compaction phase reinjection and pre-turn threshold checks~~ Unify auto-compaction callsites and pre-turn fallback handling Feb 11, 2026

charley-oai changed the title ~~Unify auto-compaction callsites and pre-turn fallback handling~~ Fix pre-turn auto-compaction and fallback context leakage bugs Feb 11, 2026

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charley-oai changed the title ~~Fix pre-turn auto-compaction and fallback context leakage bugs~~ Fix pre-turn compaction context handling and remote compact edge cases Feb 11, 2026

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charley-oai added 6 commits February 18, 2026 01:41

Rename compact callsite vars and document reinjection policy

4c0ca09

Clarify compaction reinjection rationale comments

0fbc4c7

Reinject context for summary-only mid-turn compaction

96b88ae

Update compaction test for canonical context reinjection

5ae08bc

Document user-anchor behavior for context reinjection

7476184

Reuse summary-user helper in compaction anchoring

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charley-oai added 4 commits February 18, 2026 02:09

Move pre-turn context persistence to run_turn callsite

16285c1

nit

0c53637

Remove redundant developer-role check in compaction filter

7b4e4b5

Fix clippy doc list formatting for anchor helper

6901781

edge case

ca84df3

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Avoid dropping historical duplicates in remote echo stripping

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Rename /compact start test for no-history semantics

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charley-oai closed this Feb 20, 2026

		@@ -356,24 +356,25 @@ async fn compact_resume_and_fork_preserve_model_history_view() {
		"model": expected_model,

		@@ -203,11 +203,6 @@ async fn thread_compact_start_triggers_compaction_and_returns_empty_response() -
		skip_if_no_network!(Ok(()));

		let server = responses::start_mock_server().await;

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