OMP driver: record an append-only session-to-seat binding receipt at session_start and expose st2 sessions --json

[schickling-assistant]

Problem

For OMP-driven seats, st2 is the authority for seat identity and session storage, but nothing st2-owned binds an OMP session (sessionId / session file) to the seat that ran it. A downstream usage exporter that reads OMP session JSONL can derive the seat from catalog topology for managed seats (JSONL lives under the seat workspace), but it cannot resolve session-id → seat without scanning files, and harness-context.v1 is replace-in-place and deleted on relaunch claim, so it cannot serve historical attribution.

Proposal (additive)

1. In the OMP channel session_start handler (hooks/omp-channel.ts), read ctx.sessionManager.getSessionId(), getSessionFile(), getSessionDir() (already in the read-only session API) and send a typed session frame alongside the initial context frame.
2. Decode it in src/pi_channel.rs; validate the file is absolute, beneath the supplied session dir / workspace, and that its name/header agrees with sessionId.
3. Persist an append-only receipt under st2 control state keyed by session id:

{"schema":"st2.session-binding.v1","host":"...","identity":"...","persona":"...",
 "launchKind":"managed|hosted","runtimeId":"...","generationId":"...",
 "sessionId":"...","sessionDir":"...","sessionFile":"...","observedAtMs":0}

4. Expose st2 sessions --json [--id <sessionId> | --path <file>] reading those receipts. Add the record to the replicated driver-record allowlist / catalog watch ignore rules as needed.

Persona and host come from the declaration/receipt, not from the session title. Direct (non-catalog) launches stay outside this contract by design.

Consumer

The dotfiles omp-usage-exporter (VRS: context/coding-agents/19-token-efficiency/12-omp-usage/02-session-binding/ in schickling/dotfiles) resolves identity via: receipt → title fallback → unattributed.

Posted on behalf of @schickling

field	value
agent_identity	dev3.direct.omp.6yyfzdb5
session	dev3.6yyfzdb5
agent_persona	generalist
agent_supervisor	unavailable
agent_tool	OMP
agent_tool_version	18.1.2
agent_runtime	OMP 18.1.2
tooling_profile	dotfiles@7534055