# Side effects — pre-merge review fixes (Multi-Machine Session Pool, PR #506)

## Context
A 23-agent adversarial review of the session-pool components (each finding verified against the code) confirmed 14 issues. This commit fixes the genuine CORRECTNESS bugs in the dark code before #506 merges; the integration-wiring findings (load-broker → router, isolation-at-join) are the L6 activation phase (D11), tracked separately.

## Fixes (4 correctness bugs)
- **`src/core/SessionOwnership.ts` (CRITICAL):** `release` now requires `status === 'active'`. Previously a source could release WHILE transferring, advancing the record to `released` before the target T claimed — T's claim was then rejected (claim-out-of-sequence), orphaning the session. New reason `release-requires-active`. Matches the §L3 handoff order (release is the last step, after T is active).
- **`src/core/PlacementExecutor.ts` (high):** `validateTopicPlacement` now rejects `pinned:true` without a `preferredMachine` (`pinned-without-target`) → placement-blocked, instead of silently treating it as unpinned and letting placement drift off the intended machine.
- **`src/core/StageAdvancer.ts` (high):** `reconcile()` only reverts on a `red` E2E for the CURRENT commit — a stale red from a prior commit is no longer a false regression signal.
- **`src/core/SessionRouter.ts` (high #7):** on a stale-ownership ACK, the router now re-forwards to the current owner when the owner OR the epoch changed (previously only on a different owner) — so a SAME-owner epoch advance re-delivers at the corrected epoch instead of needlessly re-placing. A spurious same-owner/same-epoch stale ACK still falls through to re-place (bounded by maxReResolveDepth).

## Risk / blast radius
None at runtime — all four files are dark (the pool is enabled:false). These are pure-logic corrections with regression tests; no behavior change for a single-machine agent.

## Tests (regression, both sides)
- SessionOwnership: rejects release-while-transferring (+ T can still claim); allows release from active.
- PlacementExecutor: pinned-without-target → blocked; pinned+target → placed.
- StageAdvancer: reconcile does NOT revert on a stale-commit red.
- SessionRouter: same-owner epoch-advance re-forwards at the new epoch; spurious same-epoch stale → re-place (no loop).
- Plus closed two flagged test gaps: TransferOrchestrator transport-failed sendTransferRpc → sync-corrupted (no claim); RebalancePlanner spreads moves across free targets (pile-on guard).

## Tracked (activation phase — D11)
Load-broker → router integration (computeMachineLoad feeding placement weight), checkAgentIsolation at join, sessionCountTrustworthy consumption, and the persistent NonceStore for mesh (vs in-memory) land when the live router/registration is wired during activation.
