## Summary
This PR adds `memchr` for some low-hanging performance improvements
(namely, in MCP stdio, Ollama streaming, and full message-history
newline counts).
Codex produced the following release benchmarks:
| Operation | Before | After | Speedup |
| --- | ---: | ---: | ---: |
| MCP 1 MiB chunked line | 2.172 s | 3.984 ms | 545x |
| Ollama 1 MiB chunked line | 1.673 s | 2.790 ms | 600x |
| Count newlines in 10 MiB history | 132.83 ms | 20.05 ms | 6.6x |
With a "real" MCP setup (`ExecutorStdioServerLauncher` started a Python
MCP server, completed `initialize`, requested `tools/list`, and
deserialized a 1 MiB tool description over newline-delimited stdio),
it's about 16x faster end-to-end:
| Branch | 50 calls | Per call |
| --- | ---: | ---: |
| `main` | 862.53 ms | 17.25 ms |
| this branch | 53.89 ms | 1.08 ms |
`memchr` is already in our dependency tree and extremely widely used for
this kind of optimized scanning.
## Why
Message history was implemented inside `codex-core` and surfaced through
core protocol ops and `SessionConfiguredEvent` fields even though the
current consumer is TUI-local prompt recall. That made core own UI
history persistence and exposed `history_log_id` / `history_entry_count`
through surfaces that app-server and other clients do not need.
This change moves message history persistence out of core and keeps the
recall plumbing local to the TUI.
## What changed
- Added a new `codex-message-history` crate for appending, looking up,
trimming, and reading metadata from `history.jsonl`.
- Removed core protocol history ops/events: `AddToHistory`,
`GetHistoryEntryRequest`, and `GetHistoryEntryResponse`.
- Removed `history_log_id` and `history_entry_count` from
`SessionConfiguredEvent` and updated exec/MCP/test fixtures accordingly.
- Updated the TUI to dispatch local app events for message-history
append/lookup and keep its persistent-history metadata in TUI session
state.
## Validation
- `cargo test -p codex-message-history -p codex-protocol`
- `cargo test -p codex-exec event_processor_with_json_output`
- `cargo test -p codex-mcp-server outgoing_message`
- `cargo test -p codex-tui`
- `just fix -p codex-message-history -p codex-protocol -p codex-core -p
codex-tui -p codex-exec -p codex-mcp-server`
Charlie MarshandGitHub
pakrym-oaiandGitHub