Allow multi_agent_v2 features to have its own temporary configuration
under `[features.multi_agent_v2]`
```
[features.multi_agent_v2]
enabled = true
usage_hint_enabled = false
usage_hint_text = "Custom delegation guidance."
hide_spawn_agent_metadata = true
```
Absent `usage_hint_text` means use the default hint.
```
[features]
multi_agent_v2 = true
```
still works as the boolean shorthand.
## Summary
- make `CODEX_EXEC_SERVER_URL=none` map to an explicit disabled
environment mode instead of inferring from a missing URL
- expose environment capabilities (`exec_enabled`, `filesystem_enabled`)
so tool building can gate behavior explicitly and future
multi-environment work has a clearer seam
- suppress env-backed tools when the relevant capability is unavailable,
including exec tools, `js_repl`, `apply_patch`, `list_dir`, and
`view_image`
- keep handler/runtime backstops so disabled environments still reject
execution if a tool path somehow bypasses registration
## Testing
- `just fmt`
- `cargo test -p codex-exec-server`
- `cargo test -p codex-tools
disabled_environment_omits_environment_backed_tools`
- `cargo test -p codex-tools
environment_capabilities_gate_exec_and_filesystem_tools_independently`
- remote devbox Bazel build via `codex-applied-devbox`:
`//codex-rs/cli:cli`
## Why
#16513 moved pure tool-registry planning into `codex-tools`, but much of
the corresponding spec/feature-gating coverage still lived in
`codex-core`. That leaves the tests for planner behavior in the crate
that no longer owns that logic and makes the next extraction steps
harder to review.
## What
Move the planner-only `spec_tests.rs` coverage into
`codex-rs/tools/src/tool_registry_plan_tests.rs` and wire it up from
`codex-rs/tools/src/tool_registry_plan.rs` using the crate-local `#[path
= "tool_registry_plan_tests.rs"] mod tests;` pattern.
The `codex-core` test file now keeps the core-side integration checks:
router-visible model tool lists, namespaced handler alias registration,
shell adapter behavior, and MCP schema edge cases that still exercise
the `core` binding layer.
## Verification
- `cargo test -p codex-tools`
- `cargo test -p codex-core tools::spec::tests`
## Why
This is a larger step in the `codex-core` -> `codex-tools` migration
called out in `AGENTS.md`.
`codex-rs/core/src/tools/spec.rs` had become mostly pure tool-spec
assembly plus handler registration. That made it hard to move more of
the tool-definition layer into `codex-tools`, because the runtime
binding and the crate-independent planning logic were still interleaved
in one function.
Splitting those concerns gives `codex-tools` ownership of the
declarative registry plan while keeping `codex-core` responsible for
instantiating concrete handlers.
## What Changed
- Add a `codex-tools` registry-plan layer in
`codex-rs/tools/src/tool_registry_plan.rs` and
`codex-rs/tools/src/tool_registry_plan_types.rs`.
- Move feature-gated tool-spec assembly, MCP/dynamic tool conversion,
tool-search aliases, and code-mode nested-plan expansion into
`codex-tools`.
- Keep `codex-rs/core/src/tools/spec.rs` as the core-side adapter that
maps each planned handler kind to concrete runtime handler instances.
- Update `spec_tests.rs` to import the moved `codex_tools` symbols
directly instead of relying on top-level `spec.rs` re-exports.
This is intended to be a straight refactor with no behavior change and
no new test surface.
## Verification
- `cargo test -p codex-tools`
- `cargo test -p codex-core tools::spec::tests`
---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/16513).
* #16521
* __->__ #16513
