fix: preserve PR monitoring after task relaunch

bin/fm-spawn.sh

@@ -5509,12 +5509,14 @@ preserve_relaunch_meta() {
     echo "home=$PROJ_ABS"
     echo "projects=$SECONDMATE_PROJECTS"
   fi
-  if [ "$RELAUNCH" -eq 1 ]; then
-    preserve_relaunch_meta
-  fi
+  # Keep relaunch fields before the preserved PR block so monitoring can parse it;
+  # fm_pr_metadata_identity_parse owns the allowed fields following pr=.
   if [ "$SPAWN_CONTROL_PARENT" = 1 ] && [ -n "${FM_CONTROL_RELAUNCH_TX:-}" ]; then
     echo "control_relaunch_tx=$FM_CONTROL_RELAUNCH_TX"
   fi
+  if [ "$RELAUNCH" -eq 1 ]; then
+    preserve_relaunch_meta
+  fi
 } >"$SPAWN_META_PATH" || {
   echo "error: task record for $ID could not be prepared at $SPAWN_META_PATH" >&2
   exit 1
@@ -5863,8 +5865,12 @@ spawn_record_traceparent() {
   fi
   SPAWN_META_TMP="$STATE/.$ID.meta.trace.${BASHPID:-$$}"
   if [ ! -f "$meta" ] || [ ! -w "$meta" ] ||
-    ! awk -F= '$1 != "traceparent"' "$meta" >"$SPAWN_META_TMP" ||
-    ! printf 'traceparent=%s\n' "$SPAWN_TRACEPARENT" >>"$SPAWN_META_TMP" ||
+    ! awk -F= -v carrier="$SPAWN_TRACEPARENT" '
+      $1 == "traceparent" { next }
+      $1 == "pr" && !written { print "traceparent=" carrier; written = 1 }
+      { print }
+      END { if (!written) print "traceparent=" carrier }
+    ' "$meta" >"$SPAWN_META_TMP" ||
     ! fm_backlog_atomic_transition publish "$SPAWN_META_TMP" "$meta" "task record" "$STATE"; then
     status=1
     rm -f "$SPAWN_META_TMP" 2>/dev/null || true

docs/trace-context.md

@@ -52,6 +52,9 @@ Because ambient `TRACEPARENT` is never read, the environment a supervisor happen
 Disabling propagation is an intentional trace boundary: a disabled home injects no carrier into a newly launched or relaunched agent even when the task meta already contains a valid `traceparent=`.
 An actual disabled relaunch regenerates the task meta without `traceparent=`, so a later enabled relaunch roots a new trace instead of resuming the identity from before the boundary; reusing an already-alive remote endpoint is not a relaunch and preserves the carrier that agent already holds.
 
+Carrier publication removes prior `traceparent=` lines and writes one replacement before the first `pr=` line, or at the end of a record without a PR.
+PR monitoring can still parse the preserved identity after relaunch with tracing on or off; [`tests/fm-control-relaunch.test.sh`](../tests/fm-control-relaunch.test.sh)'s `test_relaunch_keeps_a_recorded_pr_parseable_for_monitoring` covers both paths.
+
 ### Enablement is home-session-scoped
 
 Each locked `bin/fm-session-start.sh` run resolves that home's `config/trace-context` plus `FM_TRACE_CONTEXT` exactly once into session-scoped effective state.

tests/fm-control-relaunch.test.sh

@@ -729,6 +729,43 @@ test_relaunch_preserves_durable_task_metadata() {
   pass "fm-control relaunch: durable task metadata survives replacement launch publication"
 }
 
+test_relaunch_keeps_a_recorded_pr_parseable_for_monitoring() {
+  local dir out rc parsed tracing
+  for tracing in off on; do
+    dir=$(new_case "pr-parse-$tracing" rl90)
+    add_ship_task "$dir" rl90 claude
+    printf '%s\n' "$$" > "$dir/home/state/.lock"
+    printf '%s %s\n' "$$" "$tracing" > "$dir/home/state/.trace-context-effective"
+    {
+      printf '%s\n' 'traceparent=00-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbb-01'
+      printf '%s\n' 'pr=https://github.com/example/repo/pull/90'
+      printf '%s\n' 'pr_head=0123456789abcdef0123456789abcdef01234567'
+      printf '%s\n' 'x_request=request-90'
+    } >> "$dir/home/state/rl90.meta"
+
+    out=$(run_control "$dir" rl90 relaunch --note "keep PR monitoring alive"); rc=$?
+    expect_code 0 "$rc" "relaunch of a task with a recorded PR and tracing $tracing should succeed"$'\n'"$out"
+    [ -n "$(meta_field "$dir" rl90 control_relaunch_tx)" ] \
+      || fail "the published record should still identify its relaunch transaction"
+    parsed=$(bash -c '
+      . "$1/bin/fm-pr-lib.sh"
+      fm_pr_metadata_identity_parse "$2" && printf "%s\n" "$FM_PR_META_URL"
+    ' _ "$ROOT" "$dir/home/state/rl90.meta")
+    [ "$parsed" = "https://github.com/example/repo/pull/90" ] \
+      || fail "PR monitoring must still parse the relaunched task record with tracing $tracing (got: ${parsed:-rejected})"
+    if [ "$tracing" = on ]; then
+      [ "$(awk -F= '$1 == "traceparent" { count++ } END { print count+0 }' "$dir/home/state/rl90.meta")" = 1 ] \
+        || fail "traced relaunch must publish exactly one trace carrier"
+      [ "$(meta_field "$dir" rl90 traceparent)" = "00-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa-bbbbbbbbbbbbbbbb-01" ] \
+        || fail "traced relaunch must preserve the task's recorded carrier"
+    else
+      [ -z "$(meta_field "$dir" rl90 traceparent)" ] \
+        || fail "untraced relaunch must remove the task's recorded carrier"
+    fi
+    pass "fm-control relaunch: a recorded PR stays parseable for PR monitoring with tracing $tracing"
+  done
+}
+
 test_relaunch_serializes_concurrent_durable_metadata_publication() {
   local dir control_pid link_pid rc i=0 traceparent prepare launch_release waiting ready release
   dir=$(new_case metadata-race rl28)
@@ -4140,6 +4177,7 @@ test_relaunch_refuses_before_exit_when_the_composer_holds_pending_text
 test_relaunch_refuses_before_exit_when_the_composer_state_is_unproven
 test_relaunch_from_linked_home_preserves_recorded_worktree
 test_relaunch_preserves_durable_task_metadata
+test_relaunch_keeps_a_recorded_pr_parseable_for_monitoring
 test_relaunch_serializes_concurrent_durable_metadata_publication
 test_disabled_relaunch_clears_prior_trace_context
 test_relaunch_appends_the_progress_note_to_the_instructions