2026-10-24-codex-runtime-signing-is-present-but-default-off-with-ephemeral-keys

Runtime signing is present but default-off, with ephemeral keys. The runtime can generate an Ed25519 key, register an instance, and sign agent assertions. In the implementation read, the key is generated for registration and retained in memory; it is not a durable private key written to disk. Registration uses a restricted HTTPS or loopback endpoint with redirects disabled. Dual-header and assertion-only authorization modes exist, while runtime_agent_instances remains default-off. Code presence does not establish server enforcement against third-party clients.

Channel: tagged-release. Half: capability. Date: 2026-10-23.

Operator consequence: Authentication adapters should watch this protocol and test it only when intentionally enabled. Do not report the social prediction of durable-key client lockout as shipped fact. The useful question is whether a named service begins requiring these assertions and under which account contract; neither service-side enforcement nor a lockout test was observed.

Receipt

• https://github.com/openai/codex/blob/rust-v0.164.0/codex-rs/runtime-agent-instance/src/runtime.rs
• https://github.com/openai/codex/blob/rust-v0.164.0/codex-rs/runtime-agent-instance/src/registration.rs
• https://github.com/openai/codex/blob/rust-v0.164.0/codex-rs/runtime-agent-instance/src/auth.rs
• https://github.com/openai/codex/blob/rust-v0.164.0/codex-rs/features/src/lib.rs