## Why
MCP catalog discovery must not allow a server to keep pagination running or
growing without bounds.
## What changed
- Apply the shared pagination collector to tool, resource, and resource-template
discovery.
- Limit each catalog to 100 pages and 1,024 items, and reject pagination cursors
larger than 64 KiB or any repeated cursor.
- Bound the entire pagination operation by the configured tool timeout, falling
back to 30 seconds when no timeout is configured.
## Testing
Add unit coverage for every limit and an end-to-end MCP test that preserves
valid multi-page tools while excluding a server that returns an oversized
cursor.
GitOrigin-RevId: 961a1bfa5fe8a265daf56e342a919c980cd720fa
## What changed
- Add an opt-in `mcp_2026_07_28` protocol mode while preserving the legacy
lifecycle by default.
- Negotiate the new protocol over streamable HTTP with `server/discover`,
including bounded responses, redirect protection, and fallback only when a
response establishes that the endpoint is legacy-only.
- Require stdio servers to opt in with
`CODEX_MCP_PROTOCOL_VERSION=2026-07-28`, and add a bounded local stdio
transport for the modern lifecycle.
- Consume paginated tool, resource, and resource-template catalogs in modern
mode, reject repeated cursors, and retain discovered server identity.
- Reconnect reusable MCP clients when their selected protocol mode changes.
## Testing
- Cover HTTP JSON and SSE discovery, legacy fallback and rejection cases,
redirects, retries, response limits, and pagination.
- Cover local and executor stdio discovery, protocol markers, message limits,
and legacy compatibility.
GitOrigin-RevId: f6a78816e127d2a482292d63b91c8384f1595903
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