Finishing from a subdirectory inside an agent worktree made the active-worktree check compare the source worktree root against the physical subdirectory. That let cleanup remove the caller's cwd after a successful merge, which then surfaced as a false background-command failure.

Constraint: Preserve active shell cwd even if this leaves the detached worktree for a later gx cleanup pass.

Rejected: Always pivot prune to the primary checkout | it can delete the caller's active shell cwd and recreate the false failure.

Confidence: high

Scope-risk: narrow

Directive: Active-cwd cleanup must compare worktree roots, not raw pwd values.

Tested: node --test test/finish.test.js; node --test --test-name-pattern 'agent-branch-finish pivots' test/metadata.test.js; bash -n scripts/agent-branch-finish.sh; bash -n templates/scripts/agent-branch-finish.sh; git diff --check; openspec validate --specs

Not-tested: Live Claude background shell prompt refresh after finish.