## Summary
- Retry transient streamable HTTP failures during RMCP startup when the
failure happens while sending the initialize request.
- Retry transient streamable HTTP failures for tools/list, which is
read-only and safe to replay.
- Cover both retryable HTTP statuses and request-layer failures where no
HTTP status is returned.
- Surface retryable HTTP statuses from the streamable HTTP adapter as
typed client errors.
- Add integration coverage for initialize retry, tools/list retry,
no-status request failure retry, and non-retryable initialize status.
## Root cause
The observed codex_apps failures can happen before normal tool
execution: RMCP startup fails while sending initialize, or the first
read-only tools/list fails after startup. Retrying hosted_apps_bridge
tools/call would not cover initialize and would risk replaying
side-effecting tool calls. This change retries the streamable HTTP
handshake itself, recreates the transport between initialize attempts,
and retries only tools/list among post-initialize service operations.
## Validation
- cargo fmt --package codex-rmcp-client
- cargo test -p codex-rmcp-client --test streamable_http_recovery
## Why
Codex persists OAuth expiry as an absolute `expires_at`, then
reconstructs RMCP’s relative `expires_in` when credentials are loaded.
For an already-expired token, Codex reconstructed `expires_in` as
missing.
[RMCP 0.15 treated a missing `expires_in` as zero when a refresh token
was
present](https://github.com/modelcontextprotocol/rust-sdk/blob/9cfc905a9ef17c8bba6748dc0a9bdd2452681733/crates/rmcp/src/transport/auth.rs#L704-L723),
so this still triggered a refresh. [RMCP 1.7 treats missing expiry
information as unknown and uses the access token
as-is](https://github.com/modelcontextprotocol/rust-sdk/blob/3529c3675ff64db805bd947ca6ece6090809e43d/crates/rmcp/src/transport/auth.rs#L1233-L1265),
causing the stale token to be sent during `initialize`.
## What changed
- Represent a known-expired persisted token as `expires_in = 0`,
preserving `None` for genuinely unknown expiry.
- Add Streamable HTTP coverage requiring the token to refresh before the
startup handshake.
## Validation
- The new regression test fails on RMCP 1.7 before the fix and passes
afterward.
- The same scenario passes on the commit immediately before the RMCP 1.7
update, using RMCP 0.15.
- `just test -p codex-rmcp-client` (63 passed).
WIll make it easier to uprev when the new draft spec is supported.
Also updates reqwest where needed for compatibility but doesn't update
it everywhere since this is already a large diff.
The new version of rmcp handles certain kinds of authentication failures
differently, this patch includes support for identifying the failing scope
in a WWW-Authenticate header.
### Why
The RMCP layer needs a Streamable HTTP client that can talk either
directly over `reqwest` or through the executor HTTP runner without
duplicating MCP session logic higher in the stack. This PR adds that
client-side transport boundary so remote Streamable HTTP MCP can reuse
the same RMCP flow as the local path.
### What
- Add a shared `rmcp-client/src/streamable_http/` module with:
- `transport_client.rs` for the local-or-remote transport enum
- `local_client.rs` for the direct `reqwest` implementation
- `remote_client.rs` for the executor-backed implementation
- `common.rs` for the small shared Streamable HTTP helpers
- Teach `RmcpClient` to build Streamable HTTP transports in either local
or remote mode while keeping the existing OAuth ownership in RMCP.
- Translate remote POST, GET, and DELETE session operations into
executor `http/request` calls.
- Preserve RMCP session expiry handling and reconnect behavior for the
remote transport.
- Add remote transport coverage in
`rmcp-client/tests/streamable_http_remote.rs` and keep the shared test
support in `rmcp-client/tests/streamable_http_test_support.rs`.
### Verification
- `cargo check -p codex-rmcp-client`
- online CI
### Stack
1. #18581 protocol
2. #18582 runner
3. #18583 RMCP client
4. #18584 manager wiring and local/remote coverage
---------
Co-authored-by: Codex <noreply@openai.com>
ssetty-oaiandGitHub
Adam Perry @ OpenAIandGitHub
efrazer-oaiandGitHub
