Source Atlas

Reading Contract: Use this page as an audit index, not prerequisite reading. Open links only after a claim is clear in prose, then verify owner, function, and line-level evidence against the pinned commit.

All links point to public Codex source pinned at 569ff6a1c400bd514ff79f5f1050a684dc3afde3. The book should stand on its own; this page is for audit.

Use the atlas as an evidence boundary. A linked source line can verify a visible type, function, comment, call site, or record shape. The book’s owner/lifetime diagrams are bounded engineering interpretations of those visible contracts, not claims about provider-internal state or unpublished service behavior.

Source atlas evidence ladder from narrative claim to source map, pinned GitHub line, and audit result — Use this page after the prose has already made a claim: the atlas turns a narrative statement into a subsystem owner, then into a pinned line anchor that can confirm or correct the book.

Context Boundary

Context manager fields and ledger: codex-rs/core/src/context_manager/history.rs
Turn envelope: codex-rs/core/src/session/turn_context.rs
Turn loop: codex-rs/core/src/session/turn.rs

History and Projection

Recording model-visible history: record_items
Preparing prompt input: for_prompt
Paired removal: remove_first_item
Rollback-aware dropping: drop_last_n_user_turns

Typed Context

Context fragment trait: context/fragment.rs
Fragment catalog: context/mod.rs
Settings updates: context_manager/updates.rs
Realtime updates: build_realtime_update_item

Optional Context

Skill rendering and budgets: core-skills/src/render.rs
Skill and plugin injection in the turn loop: session/turn.rs
Memory read prompt injection: memories/read/src/prompts.rs
Memory write truncation: memories/write/src/prompts.rs
Image modality projection: for_prompt
Tool image replacement: replace_last_turn_images

Compaction

Initial context placement modes: InitialContextInjection
Local compaction: compact.rs
Replacement history construction: build_compacted_history
Remote compaction: compact_remote.rs

Replay and Client Surfaces

Rollout reconstruction: session/rollout_reconstruction.rs
Rollout truncation: thread_rollout_truncation.rs
TUI token usage: tui/src/token_usage.rs
App-server token replay: token_usage_replay.rs