## Summary
- add an `EncodedFrame` type so IPC payloads are serialized and
size-checked before entering bounded queues
- add the V1 `operation/cancel` client-to-host message
- pin the new wire shape with protocol tests
## Why
The process-owned code-mode host needs bounded, pre-encoded outbound
messages and a best-effort cancellation signal. Keeping these wire
primitives in a protocol-only change lets their compatibility contract
be reviewed independently from either endpoint.
## Stack
This is **1 of 4** in the process-owned code-mode session stack. The
next PR targets this branch.
## Validation
- `just test -p codex-code-mode-protocol` — 22 passed
- `just fix -p codex-code-mode-protocol`
- `just fmt`
## Why
The process-owned code mode implementation needs an explicit, bounded
wire contract before either side depends on it. Keeping framing and
message semantics in `codex-code-mode-protocol` gives the client and
sidecar one shared source of truth and makes compatibility failures
detectable during connection setup.
## What changed
- adds a versioned client/host handshake with required and optional
capabilities
- defines operation requests and responses for session lifecycle and
cell control
- defines reverse delegate request, response, cancellation, and
cell-closure messages
- adds a four-byte little-endian length-prefixed JSON codec with a hard
frame cap
- rejects malformed frames, unknown fields, invalid identifiers, and
unsupported protocol states
- locks the wire representation down with explicit JSON round-trip tests
## Testing
- `just test -p codex-code-mode-protocol`
## Stack
Part 1 of 6. Followed by
[#29805](https://github.com/openai/codex/pull/29805).
Remove this unused API. This API is insidious in that it implies that
alive state should be determinable from the caller, and implies that a
preflight should indicate routing. Lets drop this, and handle errors
correctly from a failed session in the future.
## Summary
- add validated protocol-version, capability, and session identifier
types
- define explicit `ClientToHost` and `HostToClient` JSON envelopes for
connection negotiation and session open/close acknowledgements
- reject invalid states and unknown fields during decoding, with
explicit wire-format and round-trip coverage
## Why
This establishes the transport-neutral encoding shape needed to build
and test the new code-mode host incrementally. Cell, tool callback, and
failure-domain messages are intentionally deferred until their actors
and behavior tests establish the required semantics.
This is additive protocol scaffolding and does not change the current
production code-mode implementation.
## Validation
## Summary
- reject HTTP(S) image URLs from the shared code-mode output-image
normalization path
- return a concise model-visible tool error so the model can recover on
its next turn
- apply the targeted rejection to both `image()` and `generatedImage()`
- leave other non-empty image URL values to existing downstream handling
The returned error is:
> Tool call failed: remote image URLs are not supported in tool outputs.
Pass a base64 data URI instead
## Why
Responses Lite cannot lower a remote image URL emitted from a structured
tool output. Rejecting HTTP(S) values in the Codex harness preserves the
tool-call metadata and gives the model a recoverable next turn instead
of invalidating the sample.
## Test coverage
The regression is covered primarily by a `test_codex()` agent
integration test that simulates the Responses API exchange and asserts
the failed model-visible exec output. A supplemental runtime test covers
both `http://` and `https://` inputs across both image output helpers.
## Test plan
- `cd codex-rs && just test -p codex-code-mode`
- `cd codex-rs && just test -p codex-code-mode-protocol`
- `cd codex-rs && just test -p codex-core
code_mode_image_helper_rejects_remote_url`
- `cd codex-rs && just fmt`
- `git diff --check origin/main...HEAD`
Related context: https://github.com/openai/openai/pull/1022346
This is phase 1 of a 4 phase stack:
1. **Add protocol and host crates for new IPC code mode implementation**
2. Create the new standalone binary
3. Create a new IPC `CodeModeSessionProvider` to use new binary
4. Remove v8 from core and only use IPC provider
## Add protocol and host crates for new IPC code mode implementation
Establish a clean process boundary without changing the existing
in-process behavior.
- Add the codex-code-mode-protocol crate for shared session, runtime,
response, and tool-definition types.
- Move protocol-facing code out of the V8-backed implementation.
- Add a buildable codex-code-mode-host crate as the foundation for the
standalone process.
- Keep the existing in-process runtime as the active implementation.
Channing CongerandGitHub
rka-oaiandGitHub