The agent factory carries two ids for each live agent/session pair: `agentId`, the `AgentRegistry` routing handle, and `sessionId`, the event-sourced and persisted-log identity. `CreateAgentOptions` takes both; `ResumeAgentOptions` takes `agentId` plus `resumeSessionId`; in-process subagents mint two independent UUIDs despite recording lineage separately.
ACP already uses the same value for both identities. They diverge for config-created agents, resumed sessions, and in-process children, but no production path reattaches one live agent to several sessions or drives one session through several agent ids. Stdio keeps `labelBySession` only to recover an agent label from session events, and hooks expose both values for authors to reconcile.
The [agent-scope runtime](../../implemented/architecture/2026-07-12-agent-scope-runtime-design.md) has no identity-specific reservation state: create and resume use one `AgentCreationTransaction`, and both registry entries use the same final-entry collision rule. Separate ids do not duplicate liveness, rollback, or quiescence machinery. Unification deletes one caller-supplied id, one UUID per in-process child, and the remaining translation paths without changing the transaction lifecycle; it also makes the live-agent registry enforce the session identity used by background-task ownership.
`Session` separately exposes `Session.id` and `Session.header.id` even though construction requires them to match. The durable boundary must validate the duplicate, and consumers must choose between two homes for one fact.
Use one id for the agent registry entry and `session.header.id`. `CreateAgentOptions` accepts one identity for both final entries; resume registers the agent under the resumed session id; subagent creation mints one combined id; and `Session` keeps one identity home. Preserve the current transaction, final-entry collision checks, exact-entry detach, rollback, and quiescence; remove only maps and fields whose sole job is translating between the ids.
The config-driven path must first settle its resume-or-create policy. Today it uses a stable agent label and a fresh UUID-suffixed session id to avoid colliding with an existing durable log on the next run. Under unification it must deliberately resume a fixed id, mint a fresh combined id, or expose that policy; implementation must not choose silently.
`agent/created` and `agent/disposed` remain outside this proposal. They are publication lifecycle events rather than identity aliases; removing them requires a separate production-consumer audit and decision.
**Keep separate routing and log identities.** A stable configured agent label paired with a fresh conversation is a real use of the distinction. If that display or routing identity is required, reject this proposal and enforce session-id uniqueness explicitly instead of hiding the translation in another map.
Unification forecloses a stable actor identity spanning several session logs, including a future handoff or fork that preserves the actor while changing the session. Reintroducing that design would require a new explicit actor identity. It also makes a persisted, possibly client-chosen session id the registry handle and changes every create/resume call site and fixture.
The config restart policy is the blocking design decision: a fixed combined id may collide with its existing log, while a per-run id gives up the stable configured label. If either independent actor identity or the stable-label/fresh-session pairing is required, reject this proposal and retain the separate ids with an explicit uniqueness guard.
