## Why
A [Windows Cargo
build](https://github.com/openai/codex/actions/runs/24754807756/job/72425641062)
on `main` timed out in several unrelated-looking suites at the same
time:
- `codex-app-server` account tests failed before account logic, while
`mcp.initialize()` was waiting for the first JSON-RPC response.
- `codex-core` `apply_patch_cli` tests timed out while running full
Codex/apply_patch turns.
- `codex-windows-sandbox` legacy session tests timed out while creating
restricted-token child processes and private desktops.
The app-server log reached the test harness write path in
[`McpProcess::initialize_with_params`](731b54d08f/codex-rs/app-server/tests/common/mcp_process.rs (L244-L263)),
but never printed the matching stdout read from
[`read_jsonrpc_message`](731b54d08f/codex-rs/app-server/tests/common/mcp_process.rs (L1123-L1128)).
The server initialize handler is a small bookkeeping/response path
([`message_processor.rs`](731b54d08f/codex-rs/app-server/src/message_processor.rs (L601-L728))),
so the failure looks like Windows runner process/pipe scheduling
starvation rather than account-specific behavior.
## What Changed
This updates `.config/nextest.toml` to serialize two process-heavy sets:
- `codex-core` tests matching `package(codex-core) & kind(test) &
test(apply_patch_cli)`
- `codex-windows-sandbox` tests matching `package(codex-windows-sandbox)
& test(legacy_)`
`codex-app-server` integration tests were already serialized inside
their own package; this change reduces overlap with the other suites
that were saturating the runner at the same time.
## Verification
- `cargo nextest list --filterset "package(codex-core) & kind(test) &
test(apply_patch_cli)"`
- `cargo nextest list --filterset "package(codex-windows-sandbox) &
test(legacy_)"`
The Windows sandbox filter naturally lists no tests on macOS, but it
validates the nextest filter/config syntax locally.
## What changed
- TypeScript schema fixture generation now goes through in-memory tree
helpers rather than a heavier on-disk generation path.
- The comparison logic normalizes generated banner and path differences
that are not semantically relevant to the exported schema.
- TypeScript and JSON fixture coverage are split into separate tests,
and the expensive schema-export tests are serialized in `nextest`.
## Why this fixes the flake
- The original fixture coverage mixed several heavy codegen paths into
one monolithic test and then compared generated output that included
incidental banner/path differences.
- On Windows CI, that combination created both runtime pressure and
output variance unrelated to the schema shapes we actually care about.
- Splitting the coverage isolates failures by format, in-memory
generation reduces filesystem churn, normalization strips generator
noise, and serializing the heavy tests removes parallel resource
contention.
## Scope
- Production helper change plus test changes.
