feat: adopt active sessions across repos and worktrees

CLAUDE.md

@@ -29,12 +29,15 @@ pointing at the canonical group form. Newer experimental command families are
 discoverable through `entire labs` and may remain hidden from root help while
 their canonical paths are still runnable.
 
-- `session` (alias: `sessions`): `list`, `info`, `tokens`, `stop`, `attach`, `resume`, `current`.
+- `session` (alias: `sessions`): `list`, `info`, `tokens`, `stop`, `attach`, `adopt`, `resume`, `current`.
   `resume` with a branch arg switches to it and resumes its session; with no arg
   it opens an interactive picker of stopped sessions (across all worktrees),
   resolving each to its branch and pointing at the owning worktree when the
   branch is checked out elsewhere. Resume keeps an existing local session log
   as-is by default (`--force` overwrites it from the checkpoint).
+  `adopt` moves an active session from another repo or worktree into the current
+  worktree and resets target-local checkpoint bookkeeping so future commits link
+  to the adopted session from the new location.
 - `checkpoint` (aliases: `cp`, `checkpoints`): `list`, `explain`, `tokens`, `search`, plus
   the deprecated `rewind` (functional, prints a cobra deprecation message, will
   be removed in a future release)

cmd/entire/cli/lifecycle.go

@@ -242,6 +242,11 @@ func handleLifecycleSessionStart(ctx context.Context, ag agent.Agent, event *age
 	// so ErrStateNotFound is the normal first-session path — only warn on
 	// genuinely unexpected errors, matching the rest of this file.
 	mutErr := strategy.MutateSessionState(ctx, event.SessionID, func(state *strategy.SessionState) error {
+		if state.AdoptedIntoWorktreePath != "" {
+			logging.Info(logCtx, "skipping adopted-away source session start",
+				slog.String("adopted_into_worktree", state.AdoptedIntoWorktreePath))
+			return strategy.ErrMutationSkip
+		}
 		persistEventMetadataToState(event, state)
 		if transErr := strategy.TransitionAndLog(ctx, state, session.EventSessionStart, session.TransitionContext{}, session.NoOpActionHandler{}); transErr != nil {
 			logging.Warn(logCtx, "session start transition failed",

cmd/entire/cli/session/state.go

@@ -113,6 +113,16 @@ type State struct {
 	// Derived from .git/worktrees/<name>/, stable across git worktree move
 	WorktreeID string `json:"worktree_id,omitempty"`
 
+	// AdoptedIntoWorktreePath marks a source-side tombstone left behind after
+	// `entire session adopt` moves this session into another repository/worktree.
+	// Hook TurnStart must not reactivate tombstoned source records, otherwise the
+	// same session ID can diverge in two session stores.
+	AdoptedIntoWorktreePath string `json:"adopted_into_worktree_path,omitempty"`
+
+	// AdoptedIntoWorktreeID is the target worktree ID paired with
+	// AdoptedIntoWorktreePath when available.
+	AdoptedIntoWorktreeID string `json:"adopted_into_worktree_id,omitempty"`
+
 	// Branch is the git branch HEAD pointed at the last time this session took a
 	// turn. Captured on each turn start so it tracks branches created or renamed
 	// after the session began. Empty when HEAD was detached or for sessions
@@ -384,8 +394,7 @@ func (s *State) NormalizeAfterLoad(ctx context.Context) {
 	// will see 0 for these fields and fall back to scoping from the transcript start.
 	// This is acceptable since CLI upgrades are monotonic and the worst case is
 	// redundant transcript content in a condensation, not data loss.
-	s.CondensedTranscriptLines = 0
-	s.TranscriptLinesAtStart = 0
+	s.ClearLegacyTranscriptOffsets()
 
 	// Backfill AttributionBaseCommit for sessions created before this field existed.
 	// Without this, a mid-turn commit would migrate BaseCommit and the fallback in
@@ -402,6 +411,14 @@ func (s *State) NormalizeAfterLoad(ctx context.Context) {
 	}
 }
 
+// ClearLegacyTranscriptOffsets clears deprecated transcript offset fields so
+// callers that intentionally reset CheckpointTranscriptStart do not re-persist
+// stale legacy state.
+func (s *State) ClearLegacyTranscriptOffsets() {
+	s.CondensedTranscriptLines = 0
+	s.TranscriptLinesAtStart = 0
+}
+
 // RealignAttributionBase sets AttributionBaseCommit to newBase and clears any
 // bookkeeping whose meaning depends on attribution being diverged from the
 // shadow-branch base. Call this every time a code path intentionally brings