## What changed
Add `model_post_turn_compact_threshold_percent` to trigger compaction after a final response when context usage reaches the configured percentage of the usable window or an existing auto-compaction limit. Accept values from `0` to `100`; omitted or zero disables the feature.
Skip post-turn compaction when input is pending, the turn is cancelled, or token-budget mode is enabled. Disable it for approval reviewers to avoid delaying approval completion, and record a distinct `PostTurn` analytics phase.
Buffer local post-turn summaries until compaction succeeds and require a nonempty assistant summary before replacing history. Log compaction failures without failing the completed turn, while still propagating interruptions and turn aborts.
GitOrigin-RevId: b616994175829bd83b5d7974f95dabb042a39a89
## What changed
Resolve the review model's token budget from the parent turn's original
configuration and model-default setting when deciding whether a Guardian
follow-up review needs context rollover. This preserves explicit token-budget
preferences instead of unconditionally applying the review model's defaults.
GitOrigin-RevId: cb3adaea7dad22f4975d84c6ee62dfc2bfbddbb9
## Why
Long-lived Guardian sessions can exhaust the review model's context window. After
a rollover, a transcript delta is insufficient because the new window no longer
contains the original transcript or persistent review instructions.
## What changed
- Compact an exhausted Guardian session before submitting the next review while
respecting the review model's token-budget configuration.
- Detect whether the full transcript remains in the reviewer history. If it does
not, reset transcript and Node REPL evidence cursors so the next review replays
the complete transcript and associated image evidence.
- Restore the follow-up reminder and Node REPL policy when compaction removes
them.
## Testing
- Cover rollover both when the reviewer window is already exhausted and when a
follow-up reminder crosses the limit.
- Verify that multimodal reviews preserve the fallback buffer and replay browser
evidence after rollover.
GitOrigin-RevId: f2a02a84e1f25d15c6e2b8eddb93e2d1805449f5
## Why
Thread settings can change while a turn is running, and delegated review or
compaction steps can select a different model. Each request needs a consistent
set of settings resolved against the model that will execute it.
## What changed
- Capture immutable resolved settings for each model step, including model
metadata, reasoning options, service tier, approvals, and personality.
- Keep in-flight steps on their captured settings while applying thread updates
to subsequent work.
- Resolve inherited reasoning summaries and filter service tiers against the
selected model and feature configuration for review and compaction steps.
## Testing
Added coverage for settings updates during paused turns, model changes,
previous-model compaction, review-model defaults, and service-tier filtering.
GitOrigin-RevId: fca4b3b305379f1bf26a5cac75ee0dd1747ac1f6
## Why
Token-budget sessions need a final opportunity to preserve important state before the current context is compacted.
## What changed
- When `auto_compact_fallback_prompt` is configured, reserve `auto_compact_fallback_buffer_tokens` beyond the base auto-compaction limit.
- At the base limit, inject the fallback prompt once as a developer message while keeping the normal tool surface available. Continue reporting zero base-window tokens during this reserve.
- Roll over when the reserve or full model context is exhausted, and skip the fallback when a new context was already requested.
## Testing
Added coverage for using the fallback reserve, rolling over after it is exhausted, and bypassing the fallback for an explicit `new_context` request.
GitOrigin-RevId: 32983ecadc5cb4927e15ecd7b1e896cb52a9ad3b
## Why
With `model_auto_compact_token_limit_scope = "body_after_prefix"`, the
persistent prefix should not count against the active body window.
`get_context_remaining` and the token-budget reminder should report the
same usable body-after-prefix window that auto-compaction uses, rather
than the total token count since the session began.
This is stacked on #29664 so the mechanical move from `turn.rs` is
isolated from the behavior fix.
## What
- Extends `ContextWindowTokenStatus` with `context_remaining_tokens`.
- Updates `get_context_remaining` to use the shared context-window
accounting.
- Adds integration coverage for body-after-prefix reminder timing and
`get_context_remaining` output.
## Testing
- `just test -p codex-core body_after_prefix_window`
- `just test -p codex-core auto_compact_body_after_prefix`
- `just fix -p codex-core`
## Why
This PR keeps the mechanical helper extraction separate from the
behavior change in #29665. The follow-up needs the token-window
accounting from `turn.rs` in another call path, but reviewing that is
much easier when the helper extraction is separate from the semantic
change.
## What
- Adds `session/context_window.rs` with `ContextWindowTokenStatus`.
- Moves the existing auto-compaction token-status calculation out of
`session/turn.rs`.
- Replaces the duplicated inline remaining-token calculation in
`turn.rs` with `tokens_until_compaction()`.
This PR is intended to be behavior-preserving. The
`get_context_remaining` behavior change is stacked separately in #29665.
## Testing
- `just test -p codex-core auto_compact_body_after_prefix`
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/29664).
* #29665
* __->__ #29664
Henry Levy