## Why
Device-key providers should only own platform key material. The
account/client binding used to authorize a signing payload is app-server
state, and keeping that state in provider-specific metadata makes the
same check harder to audit and harder to share across platform
implementations.
Persisting the binding in the shared state database gives the device-key
crate a platform-neutral source of truth before it asks a provider to
sign. It also lets app-server move potentially blocking key operations
off the main message processor path, which matters once providers may
wait for OS authentication prompts.
## What changed
- Add a `device_key_bindings` state migration plus `StateRuntime`
helpers keyed by `key_id`.
- Add an async `DeviceKeyBindingStore` abstraction to `codex-device-key`
and use it from `DeviceKeyStore::create` and `DeviceKeyStore::sign`.
- Keep provider calls behind async store methods and run the synchronous
provider work through `spawn_blocking`.
- Wire app-server device-key RPC handling to the SQLite-backed binding
store and spawn response/error delivery tasks for device-key requests.
- Run the turn-start tracing test on the existing larger current-thread
test harness after the larger async surface made the default test stack
too small locally.
## Validation
- `cargo test -p codex-device-key`
- `cargo test -p codex-state device_key`
- `cargo test -p codex-state`
- `cargo test -p codex-app-server device_key`
- `cargo test -p codex-app-server
message_processor::tracing_tests::turn_start_jsonrpc_span_parents_core_turn_spans`
- `cargo test -p codex-app-server`
- `just fix -p codex-device-key`
- `just fix -p codex-state`
- `just fix -p codex-app-server`
- `just bazel-lock-update`
- `just bazel-lock-check`
- `git diff --check`
## Why
Device-key storage and signing are local security-sensitive operations
with platform-specific behavior. Keeping the core API in
`codex-device-key` keeps app-server focused on routing and business
logic instead of owning key-management details.
The crate keeps the signing surface intentionally narrow: callers can
create a bound key, fetch its public key, or sign one of the structured
payloads accepted by the crate. It does not expose a generic
arbitrary-byte signing API.
Key IDs cross into platform-specific labels, tags, and metadata paths,
so externally supplied IDs are constrained to the same auditable
namespace created by the crate: `dk_` followed by unpadded base64url for
32 bytes. Remote-control target paths are also tied to each signed
payload shape so connection proofs cannot be reused for enrollment
endpoints, or vice versa.
## What changed
- Added the `codex-device-key` workspace crate.
- Added account/client-bound key creation with stable `dk_` key IDs.
- Added strict `key_id` validation before public-key lookup or signing
reaches a provider.
- Added public-key lookup and structured signing APIs.
- Split remote-control client endpoint allowlists by connection vs
enrollment payload shape.
- Added validation for key bindings, accepted payload fields, token
expiration, and payload/key binding mismatches.
- Added flow-oriented docs on the validation helpers that gate provider
signing.
- Added protection policy and protection-class types without wiring a
platform provider yet.
- Added an unsupported default provider so platforms without an
implementation fail explicitly instead of silently falling back to
software-backed keys.
- Updated Cargo and Bazel lock metadata for the new crate and
non-platform-specific dependencies.
## Stack
This is stacked on #18428.
## Validation
- `cargo test -p codex-device-key`
- Added unit coverage for strict `key_id` validation before provider
use.
- Added unit coverage that rejects remote-control paths from the wrong
signed payload shape.
- `just bazel-lock-update`
- `just bazel-lock-check`
