What: the metrics lineage no longer keys off the ambient Portal conversation id (it walks every
parent_session_id: gateway reset/idle expiry, /new, /branch). Compression calls
relay_shared_metrics.rotate_segment(old, new) from the committed rotation
(_notify_context_engine_compression_complete) and from a stale agent adopting the live tip
(_adopt_live_compression_child). The hand-off registers the new id in the lineage, moves the
route run and the spent-turn history into it, and closes the old segment now (or when its in-flight
compression turn ends). A rotated-to id closed before serving a turn, or still open at shutdown,
closes too; a 512-lineage backstop flushes conversations a surface never closed.
- m2: /undo or /retry on the new id reaches the turns earlier segments spent (tokens_bucket known).
- m11: /model right after a rotation finds the conversation's turn run.
- m8: background review forks (same session id, no pre_llm_call) add no turns/calls/messages.
Why: one conversation = one session / context_peak / tool_overhead / tool_enabled_unused row, on
time; N gateway conversations collapsed into one row emitted only at process exit, and rotated
segments stayed in memory until exit.
Tests: two existing tests simulated rotation by sharing a conversation context; their contract
changes to the explicit hand-off (test_a_compressed_conversation..., test_context_peak_is_one_row...).
New: reset/branch chain after a compression + tip-first close order, the compression seam, switch/undo
right after a rotation, review fork volume. RED on base (rotate_segment missing / switch_after [] /
turn bucket '2' for one user turn).
Probe (review/engagement/lineage probe_lineage.py -k c2, probe_branch.py; fix-lineage/probe_handoff.py):
before: c2 3 conversations -> session.count 0 until shutdown, then 1; branch -> 1; 50 compressed
conversations -> 0 rows, 50 lineages/sessions live.
after: c2 -> 3 rows before shutdown (turns 2,1,1), lineages=0; branch -> 2; 50 compressed -> 50 rows,
0 lineages, no sessions; tip-first close with the old turn running -> 0 then 1; shutdown with an
open tip -> 1 per conversation.
b3d4865328