## Why
`selectedCapabilityRoots` is durable thread intent: “use this capability
root from environment `worker`.”
The important product assumption is:
> One environment ID always names the same logical executor and stable
contents.
`worker` does not silently change from executor A to an unrelated
executor B. The process-local connection handle for `worker` can still
be replaced while Codex is running, though, for example when
`environment/add` registers a fresh handle for the same logical
environment.
The thread should persist only the stable selection. Each model step
should pair that selection with the exact ready handle captured for that
step.
## The boundary
```text
persisted thread intent
plugin@1 -> environment "worker"
|
| capture the current step
v
model-step view
unavailable, or
plugin@1 + worker's exact captured ready handle
```
The environment ID is the stable identity and cache key. The
`Arc<Environment>` is only a process-local handle retained so consumers
of one model step use the same captured environment. It is never
persisted and it does not imply different environment contents.
## What changes
### Persist the stable selection
Selected roots are written into `SessionMeta` and restored with the
thread. Forked subagents inherit the same selections, including
bounded-history forks.
Only stable data is persisted: root ID, environment ID, and root path.
### Capture readiness together with the exact handle
The environment snapshot records:
```rust
environment_id -> Some(Arc<Environment>) // ready in this step
environment_id -> None // still starting in this step
```
This prevents readiness and execution from coming from different
registry snapshots.
For example:
```text
step snapshot: worker -> handle A, ready
environment/add: worker -> fresh handle B for the same logical environment
current step: plugin@1 still uses captured handle A
```
Without carrying handle A in the snapshot, the resolver could combine “A
was ready” with handle B and treat B as ready before it had finished
starting.
This does not change cache invalidation. Stable capability metadata
remains identified by environment ID and capability root. Replacing a
process-local handle under the same stable environment ID does not
invalidate or rediscover that metadata.
### Resolve availability per model step
- A ready captured environment produces resolved roots using its
captured handle.
- A starting, missing, or failed environment is omitted from that step.
- A selected lazy environment that is outside the turn's captured
environment set is asked to start, and a later step can observe it as
ready.
- No capability files are scanned here.
Transient transport disconnects remain the remote client's reconnect
concern. This PR models initial attachment/readiness; it does not add
live socket-connectivity state.
## Example
```text
thread selection: plugin@1 -> environment "worker"
step 1: worker is starting -> plugin@1 unavailable
step 2: worker is ready -> plugin@1 resolves through worker's captured handle
step 3: fresh local handle -> current step remains pinned; a later step captures its own view
```
Temporary unavailability does not discard the durable selection. Later
PRs can retain stable metadata caches while projecting only currently
available capabilities into model-visible World State.
## Compatibility
The app-server request shape does not change. Older rollouts without
`selected_capability_roots` deserialize to an empty list.
## Stack
1. **This PR:** persist stable selected roots and resolve them through
an exact model-step handle.
2. #29960: cache stable skill metadata and project available skills into
World State.
3. #29946: cache stable plugin declarations and manage the separate live
MCP runtime.
## Why
PR #29494 made context-window IDs visible to the model by wrapping the
token-budget window payload in `<context_window>`, but rollout JSONL
consumers still could not see the initial window identity by tailing the
session file. Compacted rollout items carry window IDs only after
compaction has happened, so a session with no compaction had no durable
JSONL record for window 0.
This change gives tailing consumers a stable initial-window record at
session creation time.
## What Changed
- Added `session_meta.context_window.window_id` for the initial
context-window identity.
- `CreateThreadParams` now requires `initial_window_id: String`, so
thread-store callers cannot accidentally create new threads without
window-0 metadata.
- Live thread creation derives the persisted initial window ID from the
same `AutoCompactWindowIds` used to initialize `SessionState`, keeping
runtime state and JSONL metadata aligned.
- Rollout reconstruction uses `session_meta.context_window.window_id` as
the initial-window fallback and derives `window_number = 0`,
`first_window_id = window_id`, and `previous_window_id = None`
internally.
- Fork reconstruction intentionally uses the same rollout reconstruction
path; consumers that need to distinguish copied initial-window metadata
can use the rollout `thread_id`.
- Legacy compactions without `window_number` still use compaction-count
fallback accounting instead of being reset to window 0 by the
initial-window fallback.
- Compacted rollout metadata still takes precedence once compaction
records exist, preserving the richer chain fields there.
## JSONL Shape
Real rollout JSONL is one object per line. This example is expanded for
readability, but shows the new initial `session_meta.context_window`
record followed by the existing compacted rollout item shape that also
carries window IDs:
```jsonl
{
"timestamp": "2026-06-22T12:00:00.000Z",
"type": "session_meta",
"payload": {
"session_id": "<THREAD_ID>",
"id": "<THREAD_ID>",
"timestamp": "2026-06-22T12:00:00.000Z",
"cwd": "/repo",
"originator": "codex",
"cli_version": "0.0.0",
"source": "cli",
"model_provider": "<MODEL_PROVIDER>",
"context_window": {
"window_id": "<INITIAL_WINDOW_ID>"
}
}
}
...
{
"timestamp": "2026-06-22T12:34:56.000Z",
"type": "compacted",
"payload": {
"message": "<COMPACTION_SUMMARY>",
"replacement_history": [
"..."
],
"window_number": 1,
"first_window_id": "<INITIAL_WINDOW_ID>",
"previous_window_id": "<INITIAL_WINDOW_ID>",
"window_id": "<NEXT_WINDOW_ID>"
}
}
```
The nested `context_window` object is intentional: it gives rollout
consumers a stable namespace for context-window metadata while only
writing the non-derivable initial `window_id`. For the initial window,
`window_number`, `first_window_id`, and `previous_window_id` are derived
internally instead of being written to the rollout.
## Verification
- `just test -p codex-protocol`
- `just test -p codex-rollout
recorder_materializes_on_flush_with_pending_items`
- `just test -p codex-core reconstruct_history`
- `just test -p codex-core
record_initial_history_reconstructs_forked_transcript`
- `just test -p codex-thread-store`
- `just test -p codex-state`
- `just test -p codex-app-server
thread_read_returns_summary_without_turns`
- `just test -p codex-rollout persistence_metrics`
## Summary
A cold-resumed subagent kept its durable thread ID but could receive a
new session ID, splitting one agent tree across multiple sessions after
a restart.
Persist the root session ID in every rollout `SessionMeta`, carry it
through thread creation, and restore it before initializing the resumed
`Session` and `AgentControl`.
## Behavior
For a nested agent tree:
```text
root session R
parent thread P
child thread C
```
The child rollout stores:
```text
session_id: R
parent_thread_id: P
id: C
```
After a cold resume, the child still belongs to root session `R` while
its immediate parent remains `P`. The integration coverage uses distinct
values for all three IDs so it catches restoring the session from
`parent_thread_id`.
## Legacy rollouts
Previous rollouts have `id` but no `session_id`. `SessionMetaLine`
deserialization treats a missing `session_id` as `id`, keeping those
files readable, listable, and resumable. When a legacy subagent is
resumed through its root, that synthesized child ID no longer overrides
the inherited root-scoped `AgentControl`. New rollouts always persist
the explicit root session ID.
## Why
The local rollout compression worker currently scans only
`archived_sessions`, so cold unarchived thread history remains expanded
indefinitely.
## What changed
- Scan `sessions` after `archived_sessions` within the existing worker
runtime budget.
- Update rollout compression coverage to require both cold active and
archived rollouts to be compressed while fresh active rollouts remain
plain.
The worker remains behind the disabled-by-default
`local_thread_store_compression` feature, and the existing seven-day
cold-file threshold is unchanged.
## Validation
- `just test -p codex-rollout` (69 passed)
- `just fmt`
- `git diff --check`
## Why
`thread/search` found content inside compressed rollouts but could drop
the result when joining it with SQLite-backed thread metadata. Search
returned the physical `.jsonl.zst` path while SQLite retained the
logical `.jsonl` path, so exact path matching failed.
## What changed
- Key rollout search matches by their canonical logical `.jsonl` path,
independent of the on-disk representation.
- Canonicalize thread-list paths before joining them with content-search
matches.
- Update compressed-rollout coverage to assert the logical-path
contract.
## Validation
- Ran `just fmt`.
- Ran `git diff --check`.
- Tests and Clippy were intentionally left to CI.
Stack split from #25708. Original PR intentionally left open. This first
PR adds the multi-agent runtime metadata types and catalog plumbing used
by the rest of the stack.
## Summary
- teach rollout search to return precomputed snippets for compressed
rollouts
- reuse those snippets in local thread search instead of reopening
matching compressed files
- keep the no-`rg` fallback single-pass and add regression coverage for
the compressed path
## Why
`thread/search` currently decodes matching compressed rollouts twice:
once to discover the matching path and again to extract the snippet
shown in results. That defeats a meaningful part of the compressed-read
optimization work.
## Impact
Compressed rollout hits now pay one decode pass on the search path while
plain `.jsonl` hits keep the existing ripgrep-driven flow.
## Validation
- `just test -p codex-rollout`
- `just test -p codex-thread-store`
- `just fix -p codex-rollout`
- `just fix -p codex-thread-store`
- `just fmt`
## Why
[#25089](https://github.com/openai/codex/pull/25089) introduced the
background worker that compresses cold archived rollouts, and
[#25654](https://github.com/openai/codex/pull/25654) made that pass
faster once it starts. But the worker still deleted
`rollout-compression.lock` on successful exit, so the existing six-hour
staleness window only helped with overlapping or crashed workers. Each
new local thread-store initialization could immediately rescan archived
rollouts even if a full pass had just finished.
This change keeps the existing marker around long enough to throttle
redundant reruns. The worker is still best-effort, but it no longer does
repeated startup scans when nothing new is eligible for compression.
## What Changed
- Replace the drop-scoped `CompressionLock` with a
`CompressionRunMarker` that claims the existing
`.tmp/rollout-compression.lock` path and leaves it in place after
success.
- Reuse the existing six-hour staleness window to block both overlapping
starts and immediate reruns, while still letting a stale marker be
reclaimed.
- Update the worker docs and debug logging to describe the new "already
running or recently ran" behavior.
- Extend the rollout compression tests to assert that a successful run
leaves the marker behind and that a fresh marker suppresses a new run.
## Validation
- `just test -p codex-rollout`
## Rollout compression stack
This stack splits #24941 into reviewable steps for local rollout
compression. The design is intentionally staged:
1. Teach readers, listing, search, and lookup to understand compressed
rollouts.
2. Make append and resume paths materialize compressed rollouts back to
plain JSONL before writing.
3. Add a disabled-by-default worker that can compress cold archived
rollouts behind `local_thread_store_compression`.
The key invariant is that writers append to plain `.jsonl`. A
`.jsonl.zst` file is a cold/read representation; if a write is needed,
the compressed file is materialized back to plain JSONL first. Readers
prefer plain `.jsonl` when both forms exist and can fall back to the
compressed sibling during transitions.
The worker is deliberately the last PR and remains behind an
under-development feature flag. It currently scans only
`archived_sessions`, not active `sessions`, because active sessions have
the highest resume/append race risk. That means this stack does not yet
compress most unarchived local history.
## Known race / follow-up
The remaining unresolved design question is writer/compressor
coordination. Even for archived rollouts, a resume or metadata update
can append while the worker is replacing the plain file with
`.jsonl.zst`; the current double-stat checks narrow but do not fully
eliminate the window where a writer has opened the plain file before
unlink. Do not treat the worker PR as production-ready until we either:
- prevent append/resume paths from racing archived compression, or
- introduce a shared representation/append lock or equivalent
coordination.
The first two PRs are useful independently: they make compressed
rollouts readable and make append paths safely recover back to plain
JSONL. The third PR isolates the worker behavior so that coordination
issue is reviewable separately.
## Validation
Focused local validation for the stack includes:
- `just test -p codex-rollout`
- `just test -p codex-thread-store` where thread-store paths were
touched
- `just test -p codex-features` for the feature flag slice
- `just bazel-lock-check` after dependency graph changes
- scoped `just fix -p ...` passes for changed crates
CI is still the source of truth for the full platform matrix.
## This PR in the stack
This is PR 3/3, based on #25088. It adds the under-development feature
flag and starts the best-effort background worker when enabled. The
worker currently compresses only cold archived rollouts, skips active
sessions, verifies compressed output, preserves mtime and permissions,
keeps a store-level lock heartbeat, and cleans stale temp files.
Stack order:
1. #25087: read compressed local rollouts.
2. #25088: materialize compressed rollouts before append.
3. This PR: add the disabled local compression worker.
## Summary
- initialize `parent_thread_id` in the compressed rollout test fixture's
`SessionMeta`
- restore rollout test compilation across Bazel test, clippy,
release-build, and argument-comment-lint jobs
## Root cause
PR #25087 (`Read compressed rollouts and materialize before append`)
added `codex-rs/rollout/src/compression_tests.rs` in merge commit
`a8a6071279b6f3112fcc5fc3fee69c48473d7149`. Its `write_rollout` fixture
constructs `SessionMeta` without the required `parent_thread_id` field,
causing `error[E0063]` when Bazel compiles `rollout-unit-tests-bin` on
`main` and downstream PRs.
## Validation
- `UV_CACHE_DIR=/private/tmp/codex-uv-cache just fmt`
- `just test -p codex-rollout` (`59` tests passed; bench smoke passed)
- `git diff --check`
- manually audited the touched Rust diff for positional literal argument
comments; the change adds no positional callsite
## Local lint blocker
- `just argument-comment-lint` could not reach source inspection locally
because Bazel's LLVM dependency fails analysis:
`compiler-rt/BUILD.bazel` glob `include/sanitizer/*.h` matched no files.
## Why
Local rollout compression needs a cold `.jsonl.zst` representation
without letting compressed physical paths leak into append-mode writers.
The unsafe case is resume or metadata update code successfully reading a
compressed rollout and then appending raw JSONL bytes to the zstd file.
This PR folds the former #25088 materialization slice into the
read-support PR so the reader changes and append-safety invariant land
together.
## What Changed
- Teach rollout readers, discovery, listing, search, and ID lookup to
understand compressed `.jsonl.zst` rollouts.
- Keep `.jsonl` as the logical/stored rollout path while allowing read
paths to open either plain or compressed storage.
- Materialize compressed rollouts back to plain `.jsonl` before
append-mode writes, including resume and direct metadata append paths.
- Preserve compressed-file permissions when materializing back to plain
JSONL.
- Refresh thread-store resolved rollout paths after compatibility
metadata writes so reconciliation follows the materialized file.
- Avoid treating transient compression temp files as real rollout lookup
results.
## Remaining Stack
#25089 remains the separate worker PR. It is based directly on this PR
and stays behind the disabled `local_thread_store_compression` feature
flag.
The worker still has a broader coordination question: a resume or
metadata update can race with background compression while a plain file
is being replaced by `.jsonl.zst`. This PR handles the read and
materialize-before-append primitives; it does not make the worker
production-ready.
## Validation
- `just test -p codex-rollout`
- `just test -p codex-thread-store`
- `just fix -p codex-rollout`
- `just fix -p codex-thread-store`
- `just bazel-lock-check`
jif ·
Michael Bolin ·
Felipe Coury ·