## Summary This PR consolidates base_instructions onto SessionMeta / SessionConfiguration, so we ensure `base_instructions` is set once per session and should be (mostly) immutable, unless: - overridden by config on resume / fork - sub-agent tasks, like review or collab In a future PR, we should convert all references to `base_instructions` to consistently used the typed struct, so it's less likely that we put other strings there. See #9423. However, this PR is already quite complex, so I'm deferring that to a follow-up. ## Testing - [x] Added a resume test to assert that instructions are preserved. In particular, `resume_switches_models_preserves_base_instructions` fails against main. Existing test coverage thats assert base instructions are preserved across multiple requests in a session: - Manual compact keeps baseline instructions: core/tests/suite/compact.rs:199 - Auto-compact keeps baseline instructions: core/tests/suite/compact.rs:1142 - Prompt caching reuses the same instructions across two requests: core/tests/suite/prompt_caching.rs:150 and core/tests/suite/prompt_caching.rs:157 - Prompt caching with explicit expected string across two requests: core/tests/suite/prompt_caching.rs:213 and core/tests/suite/prompt_caching.rs:222 - Resume with model switch keeps original instructions: core/tests/suite/resume.rs:136 - Compact/resume/fork uses request 0 instructions for later expected payloads: core/tests/suite/compact_resume_fork.rs:215
codex-core
This crate implements the business logic for Codex. It is designed to be used by the various Codex UIs written in Rust.
Dependencies
Note that codex-core makes some assumptions about certain helper utilities being available in the environment. Currently, this support matrix is:
macOS
Expects /usr/bin/sandbox-exec to be present.
When using the workspace-write sandbox policy, the Seatbelt profile allows
writes under the configured writable roots while keeping .git (directory or
pointer file), the resolved gitdir: target, and .codex read-only.
Linux
Expects the binary containing codex-core to run the equivalent of codex sandbox linux (legacy alias: codex debug landlock) when arg0 is codex-linux-sandbox. See the codex-arg0 crate for details.
All Platforms
Expects the binary containing codex-core to simulate the virtual apply_patch CLI when arg1 is --codex-run-as-apply-patch. See the codex-arg0 crate for details.