diff --git a/bin/fm-afk-launch.sh b/bin/fm-afk-launch.sh
index 57b7f6590d..c84137ee19 100755
--- a/bin/fm-afk-launch.sh
+++ b/bin/fm-afk-launch.sh
@@ -48,6 +48,28 @@ set -u
 FM_AFK_LAUNCH_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 FM_ROOT="${FM_ROOT_OVERRIDE:-$(cd "$FM_AFK_LAUNCH_DIR/.." && pwd)}"
 FM_HOME="${FM_HOME:-${FM_ROOT_OVERRIDE:-$FM_ROOT}}"
+case "$FM_HOME" in
+  /*) ;;
+  *)
+    FM_AFK_LAUNCH_HOME_INPUT=$FM_HOME
+    FM_HOME=$(cd "$FM_AFK_LAUNCH_HOME_INPUT" 2>/dev/null && pwd -P) || {
+      echo "error: FM_HOME directory cannot be resolved: $FM_AFK_LAUNCH_HOME_INPUT" >&2
+      exit 1
+    }
+    ;;
+esac
+if [ -n "${FM_STATE_OVERRIDE:-}" ]; then
+  case "$FM_STATE_OVERRIDE" in
+    /*) ;;
+    *)
+      FM_AFK_LAUNCH_STATE_INPUT=$FM_STATE_OVERRIDE
+      FM_STATE_OVERRIDE=$(cd "$FM_AFK_LAUNCH_STATE_INPUT" 2>/dev/null && pwd -P) || {
+        echo "error: FM_STATE_OVERRIDE directory cannot be resolved: $FM_AFK_LAUNCH_STATE_INPUT" >&2
+        exit 1
+      }
+      ;;
+  esac
+fi
 FM_AFK_LAUNCH_STATE="${FM_STATE_OVERRIDE:-$FM_HOME/state}"
 FM_AFK_LAUNCH_RECORD="$FM_AFK_LAUNCH_STATE/.afk-daemon-terminal"
 FM_AFK_LAUNCH_LOCK="$FM_AFK_LAUNCH_STATE/.afk-launch.lock"
diff --git a/bin/fm-bootstrap.sh b/bin/fm-bootstrap.sh
index c86b7e839a..ce12529b3f 100755
--- a/bin/fm-bootstrap.sh
+++ b/bin/fm-bootstrap.sh
@@ -620,7 +620,7 @@ x_mode_remove_artifact() {
 # applying a cadence transition to a running watcher is the caller's job via
 # the emitted harness-aware supervision repair instruction.
 x_mode_setup() {
-  local env_file token shim cadence shim_body cadence_body tool missing
+  local env_file token shim cadence shim_body cadence_body tool missing shim_home
   env_file="$FM_HOME/.env"
   shim="$STATE/x-watch.check.sh"
   cadence="$CONFIG/x-mode.env"
@@ -683,9 +683,16 @@ x_mode_setup() {
 
   mkdir -p "$STATE" "$CONFIG" 2>/dev/null || { fmx_arm_failed; return 0; }
 
-  shim_body=$(fmx_poll_shim_content "$FM_HOME" "$FM_ROOT")
+  case "$FM_HOME" in
+    /*) shim_home=$FM_HOME ;;
+    *)
+      shim_home=$(cd "$FM_HOME" 2>/dev/null && pwd -P) \
+        || { fmx_arm_failed; return 0; }
+      ;;
+  esac
+  shim_body=$(fmx_poll_shim_content "$shim_home" "$FM_ROOT")
   x_mode_write_if_changed "$shim" "$shim_body" 700 || { fmx_arm_failed; return 0; }
-  fmx_poll_shim_valid "$shim" "$FM_HOME" "$FM_ROOT" \
+  fmx_poll_shim_valid "$shim" "$shim_home" "$FM_ROOT" \
     || { fmx_arm_failed; return 0; }
 
   cadence_body=$(cat <<'EOF'
diff --git a/bin/fm-brief.sh b/bin/fm-brief.sh
index 8125aa2e9e..d296c3badc 100755
--- a/bin/fm-brief.sh
+++ b/bin/fm-brief.sh
@@ -66,10 +66,31 @@ esac
 # shellcheck source=bin/fm-classify-lib.sh
 . "$SCRIPT_DIR/fm-classify-lib.sh"
 PAUSED_VERB=${FM_CLASSIFY_PAUSED_VERB:-$FM_CLASSIFY_PAUSED_VERB_DEFAULT}
+
+resolve_directory_input() {
+  local name=$1 path=$2 resolved
+  case "$path" in
+    /*) printf '%s\n' "$path"; return 0 ;;
+  esac
+  resolved=$(cd "$path" 2>/dev/null && pwd -P) || {
+    echo "error: $name directory cannot be resolved: $path" >&2
+    return 1
+  }
+  printf '%s\n' "$resolved"
+}
+
 FM_ROOT="${FM_ROOT_OVERRIDE:-$(cd "$SCRIPT_DIR/.." && pwd)}"
-FM_HOME="${FM_HOME:-${FM_ROOT_OVERRIDE:-$FM_ROOT}}"
-DATA="${FM_DATA_OVERRIDE:-$FM_HOME/data}"
-STATE="${FM_STATE_OVERRIDE:-$FM_HOME/state}"
+FM_HOME=$(resolve_directory_input FM_HOME "${FM_HOME:-${FM_ROOT_OVERRIDE:-$FM_ROOT}}") || exit 1
+if [ -n "${FM_DATA_OVERRIDE:-}" ]; then
+  DATA=$(resolve_directory_input FM_DATA_OVERRIDE "$FM_DATA_OVERRIDE") || exit 1
+else
+  DATA="$FM_HOME/data"
+fi
+if [ -n "${FM_STATE_OVERRIDE:-}" ]; then
+  STATE=$(resolve_directory_input FM_STATE_OVERRIDE "$FM_STATE_OVERRIDE") || exit 1
+else
+  STATE="$FM_HOME/state"
+fi
 KIND=ship
 HERDR_LAB=0
 NO_PROJECTS=0
diff --git a/bin/fm-spawn.sh b/bin/fm-spawn.sh
index 76eed3e736..d545b9e70b 100755
--- a/bin/fm-spawn.sh
+++ b/bin/fm-spawn.sh
@@ -124,6 +124,26 @@ esac
 
 FM_ROOT="${FM_ROOT_OVERRIDE:-$(cd "$SCRIPT_DIR/.." && pwd)}"
 FM_HOME="${FM_HOME:-${FM_ROOT_OVERRIDE:-$FM_ROOT}}"
+
+resolve_directory_input() {
+  local name=$1 path=$2 resolved
+  case "$path" in
+    /*) printf '%s\n' "$path"; return 0 ;;
+  esac
+  resolved=$(cd "$path" 2>/dev/null && pwd -P) || {
+    echo "error: $name directory cannot be resolved: $path" >&2
+    return 1
+  }
+  printf '%s\n' "$resolved"
+}
+
+FM_HOME=$(resolve_directory_input FM_HOME "$FM_HOME") || exit 1
+if [ -n "${FM_STATE_OVERRIDE:-}" ]; then
+  FM_STATE_OVERRIDE=$(resolve_directory_input FM_STATE_OVERRIDE "$FM_STATE_OVERRIDE") || exit 1
+fi
+if [ -n "${FM_DATA_OVERRIDE:-}" ]; then
+  FM_DATA_OVERRIDE=$(resolve_directory_input FM_DATA_OVERRIDE "$FM_DATA_OVERRIDE") || exit 1
+fi
 STATE="${FM_STATE_OVERRIDE:-$FM_HOME/state}"
 DATA="${FM_DATA_OVERRIDE:-$FM_HOME/data}"
 PROJECTS="${FM_PROJECTS_OVERRIDE:-$FM_HOME/projects}"
diff --git a/docs/configuration.md b/docs/configuration.md
index c5215512b2..adf215b408 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -169,6 +169,8 @@ When it is unset, most scripts use the repo root as the home; when it is set, sc
 When `FM_HOME` is unset, it also behaves as the old whole-root override.
 `bin/fm-send.sh` is intentionally stricter than that general fallback: it requires `FM_HOME` to be set before resolving a target, so operator steers cannot silently resolve against the wrong home.
 `FM_STATE_OVERRIDE`, `FM_DATA_OVERRIDE`, `FM_PROJECTS_OVERRIDE`, and `FM_CONFIG_OVERRIDE` override individual operational directories for tests and specialized harness setup.
+Before `fm-brief.sh`, `fm-spawn.sh`, or `fm-afk-launch.sh` persists a path or passes it to another process, it resolves each applicable relative `FM_HOME`, `FM_STATE_OVERRIDE`, or `FM_DATA_OVERRIDE` directory against the caller's working directory, preserves absolute spellings unchanged, and rejects an unresolvable relative directory with the offending variable named.
+Bootstrap applies the same relative `FM_HOME` resolution only when embedding that home in the generated X-mode poll shim; other transient consumers retain their existing shell-relative behavior.
 For the herdr backend, `FM_HOME` also determines the workspace label used by the adapter.
 For the zellij backend, `FM_HOME` does not split containers, but it determines the readable home prefix embedded in visible tab titles; use `FM_ZELLIJ_SESSION` when a separate zellij session is needed.
 The full zellij home label also includes a short hash of the resolved `FM_ROOT` path.
diff --git a/tests/fm-afk-launch.test.sh b/tests/fm-afk-launch.test.sh
index 8075d7067a..2fd3cbe0fa 100755
--- a/tests/fm-afk-launch.test.sh
+++ b/tests/fm-afk-launch.test.sh
@@ -70,6 +70,54 @@ unit_clear_stale() {
   rm -rf "$st"
 }
 
+unit_relative_paths_are_absolute_before_daemon_launch() {
+  local root home state out status linked_home
+  root=$(mktemp -d "${TMPDIR:-/tmp}/fm-afk-relative-home.XXXXXX")
+  mkdir -p "$root/home/state"
+  home=$(cd "$root/home" && pwd -P)
+  state="$home/state"
+  out=$(
+    cd "$root" || exit 1
+    FM_HOME=home FM_STATE_OVERRIDE=home/state \
+      bash -c '. "$1"; printf "%s\n%s\n" "$FM_HOME" "$FM_AFK_LAUNCH_STATE"' _ "$LAUNCH"
+  )
+  if [ "$out" = "$home"$'\n'"$state" ]; then
+    pass "launcher paths: relative home and state are absolute before daemon command construction"
+  else
+    fail "launcher paths: relative home or state remained cwd-dependent ($out)"
+  fi
+  linked_home="$root/home-link"
+  ln -s "$root/home" "$linked_home"
+  out=$(FM_HOME="$linked_home" FM_STATE_OVERRIDE="$linked_home/state" \
+    bash -c '. "$1"; printf "%s\n%s\n" "$FM_HOME" "$FM_AFK_LAUNCH_STATE"' _ "$LAUNCH")
+  if [ "$out" = "$linked_home"$'\n'"$linked_home/state" ]; then
+    pass "launcher paths: absolute symlink spellings are preserved"
+  else
+    fail "launcher paths: absolute symlink spelling changed ($out)"
+  fi
+  out=$(
+    cd "$root" || exit 1
+    FM_HOME=missing-home "$LAUNCH" help 2>&1
+  )
+  status=$?
+  if [ "$status" -ne 0 ] && printf '%s\n' "$out" | grep -F "FM_HOME directory cannot be resolved: missing-home" >/dev/null; then
+    pass "launcher paths: unresolved relative FM_HOME fails loudly"
+  else
+    fail "launcher paths: unresolved relative FM_HOME did not name the bad input ($out)"
+  fi
+  out=$(
+    cd "$root" || exit 1
+    FM_HOME=home FM_STATE_OVERRIDE=missing-state "$LAUNCH" help 2>&1
+  )
+  status=$?
+  if [ "$status" -ne 0 ] && printf '%s\n' "$out" | grep -F "FM_STATE_OVERRIDE directory cannot be resolved: missing-state" >/dev/null; then
+    pass "launcher paths: unresolved relative FM_STATE_OVERRIDE fails loudly"
+  else
+    fail "launcher paths: unresolved relative FM_STATE_OVERRIDE did not name the bad input ($out)"
+  fi
+  rm -rf "$root"
+}
+
 # ---------------------------------------------------------------------------
 # UNIT 2: a FRESH entry clears; a REFRESH (daemon already alive) preserves the
 # current session's buffered escalations.
@@ -861,6 +909,7 @@ e2e_tmux() {
 }
 
 unit_clear_stale
+unit_relative_paths_are_absolute_before_daemon_launch
 unit_fresh_vs_refresh
 unit_stop_ordering
 unit_stop_rejects_reused_pid
diff --git a/tests/fm-brief.test.sh b/tests/fm-brief.test.sh
index bed170b741..8ea4fc396f 100755
--- a/tests/fm-brief.test.sh
+++ b/tests/fm-brief.test.sh
@@ -436,6 +436,95 @@ test_secondmate_marked_request_reporting_contract() {
   pass "fm-brief.sh: marked requests avoid generic acknowledgements and preserve material reporting"
 }
 
+test_secondmate_directory_paths_are_absolute_and_output_is_stable() {
+  local root home data_override state_override brief baseline err status
+  root="$TMP_ROOT/relative-directory-inputs"
+  mkdir -p "$root"
+  root=$(cd "$root" && pwd -P)
+  home="$root/home"
+  data_override="$root/data-override"
+  state_override="$root/state-override"
+  mkdir -p "$home/data" "$home/state" "$data_override" "$state_override"
+
+  brief="$home/data/relative-home/brief.md"
+  FM_HOME="$home" FM_SECONDMATE_CHARTER=x \
+    "$ROOT/bin/fm-brief.sh" relative-home --secondmate --no-projects >/dev/null 2>&1
+  baseline="$root/absolute-home-charter"
+  cp "$brief" "$baseline"
+  rm -f "$brief"
+  (
+    cd "$root" || exit 1
+    FM_HOME=home FM_SECONDMATE_CHARTER=x \
+      "$ROOT/bin/fm-brief.sh" relative-home --secondmate --no-projects >/dev/null 2>&1
+  )
+  cmp -s "$baseline" "$brief" \
+    || fail "relative FM_HOME changed charter bytes compared with the same absolute home"
+  assert_grep ">> '$home/state/relative-home.status'" "$brief" \
+    "relative FM_HOME did not render an absolute secondmate status path"
+
+  brief="$home/data/relative-state/brief.md"
+  FM_HOME="$home" FM_STATE_OVERRIDE="$state_override" FM_SECONDMATE_CHARTER=x \
+    "$ROOT/bin/fm-brief.sh" relative-state --secondmate --no-projects >/dev/null 2>&1
+  baseline="$root/absolute-state-charter"
+  cp "$brief" "$baseline"
+  rm -f "$brief"
+  (
+    cd "$root" || exit 1
+    FM_HOME="$home" FM_STATE_OVERRIDE=state-override FM_SECONDMATE_CHARTER=x \
+      "$ROOT/bin/fm-brief.sh" relative-state --secondmate --no-projects >/dev/null 2>&1
+  )
+  cmp -s "$baseline" "$brief" \
+    || fail "relative FM_STATE_OVERRIDE changed charter bytes compared with the same absolute state directory"
+  assert_grep ">> '$state_override/relative-state.status'" "$brief" \
+    "relative FM_STATE_OVERRIDE did not render an absolute secondmate status path"
+
+  brief="$data_override/relative-data/brief.md"
+  FM_HOME="$home" FM_DATA_OVERRIDE="$data_override" FM_SECONDMATE_CHARTER=x \
+    "$ROOT/bin/fm-brief.sh" relative-data --secondmate --no-projects >/dev/null 2>&1
+  baseline="$root/absolute-data-charter"
+  cp "$brief" "$baseline"
+  rm -f "$brief"
+  (
+    cd "$root" || exit 1
+    FM_HOME="$home" FM_DATA_OVERRIDE=data-override FM_SECONDMATE_CHARTER=x \
+      "$ROOT/bin/fm-brief.sh" relative-data --secondmate --no-projects >/dev/null 2>&1
+  )
+  cmp -s "$baseline" "$brief" \
+    || fail "relative FM_DATA_OVERRIDE changed charter bytes compared with the same absolute data directory"
+  assert_grep ">> '$home/state/relative-data.status'" "$brief" \
+    "relative FM_DATA_OVERRIDE changed the absolute default status path"
+
+  err="$root/unresolved.err"
+  (
+    cd "$root" || exit 1
+    FM_HOME=missing-home FM_SECONDMATE_CHARTER=x \
+      "$ROOT/bin/fm-brief.sh" unresolved-home --secondmate --no-projects >/dev/null 2>"$err"
+  ); status=$?
+  expect_code 1 "$status" "an unresolved relative FM_HOME must fail"
+  assert_grep "FM_HOME directory cannot be resolved: missing-home" "$err" \
+    "unresolved relative FM_HOME did not fail loudly"
+
+  (
+    cd "$root" || exit 1
+    FM_HOME="$home" FM_STATE_OVERRIDE=missing-state FM_SECONDMATE_CHARTER=x \
+      "$ROOT/bin/fm-brief.sh" unresolved-state --secondmate --no-projects >/dev/null 2>"$err"
+  ); status=$?
+  expect_code 1 "$status" "an unresolved relative FM_STATE_OVERRIDE must fail"
+  assert_grep "FM_STATE_OVERRIDE directory cannot be resolved: missing-state" "$err" \
+    "unresolved relative FM_STATE_OVERRIDE did not fail loudly"
+
+  (
+    cd "$root" || exit 1
+    FM_HOME="$home" FM_DATA_OVERRIDE=missing-data FM_SECONDMATE_CHARTER=x \
+      "$ROOT/bin/fm-brief.sh" unresolved-data --secondmate --no-projects >/dev/null 2>"$err"
+  ); status=$?
+  expect_code 1 "$status" "an unresolved relative FM_DATA_OVERRIDE must fail"
+  assert_grep "FM_DATA_OVERRIDE directory cannot be resolved: missing-data" "$err" \
+    "unresolved relative FM_DATA_OVERRIDE did not fail loudly"
+
+  pass "fm-brief.sh: relative directory inputs render stable absolute charter paths or fail loudly"
+}
+
 test_herdr_lab_contract_applies_to_scouts_but_not_secondmates() {
   local home brief status=0
   home="$TMP_ROOT/herdr-kind-home"
@@ -540,6 +629,7 @@ test_herdr_lab_omission_is_loud_for_ship_and_scout
 test_herdr_lab_contract_applies_to_scouts_but_not_secondmates
 test_secondmate_no_projects_charter
 test_secondmate_marked_request_reporting_contract
+test_secondmate_directory_paths_are_absolute_and_output_is_stable
 test_pause_verb_override_renders_all_brief_scaffolds
 test_scout_and_secondmate_load_decision_hold_policy
 test_scout_and_secondmate_scaffold
diff --git a/tests/fm-spawn-dispatch-profile.test.sh b/tests/fm-spawn-dispatch-profile.test.sh
index 4f0695e7e5..c022f53c6d 100755
--- a/tests/fm-spawn-dispatch-profile.test.sh
+++ b/tests/fm-spawn-dispatch-profile.test.sh
@@ -128,6 +128,152 @@ test_no_profile_keeps_claude_profile_defaults() {
   pass "no --model/--effort records defaults and types the claude launch instructions"
 }
 
+test_relative_home_overrides_launch_with_absolute_cross_process_paths() {
+  local rec id out status launch home_real
+  id=profile-relative-paths-z1b
+  rec=$(make_spawn_case profile-relative-paths pi "$id")
+  read_case_record "$rec"
+  home_real=$(cd "$HOME_DIR" && pwd -P)
+  : > "$LAUNCH_LOG"
+
+  out=$(
+    cd "$CASE_DIR" || exit 1
+    FM_ROOT_OVERRIDE='' FM_HOME=home \
+      FM_STATE_OVERRIDE=home/state FM_DATA_OVERRIDE=home/data \
+      FM_PROJECTS_OVERRIDE=home/projects FM_CONFIG_OVERRIDE=home/config \
+      FM_SPAWN_NO_GUARD=1 FM_FAKE_PANE_PATH="$WT_DIR" TMUX="fake,1,0" \
+      CLAUDE_CONFIG_DIR='' FM_FAKE_LAUNCH_LOG="$LAUNCH_LOG" \
+      GROK_HOME=home/grok-home PATH="$FAKEBIN_DIR:$PATH" \
+      "$SPAWN" "$id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 0 "$status" "spawn with relative home overrides should succeed"
+  launch=$(cat "$LAUNCH_LOG")
+  assert_contains "$launch" "-e '$home_real/state/$id.pi-ext.ts'" \
+    "relative FM_STATE_OVERRIDE leaked into Pi's cross-process extension path"
+  assert_contains "$launch" "< '$home_real/data/$id/brief.md'" \
+    "relative FM_DATA_OVERRIDE leaked into the cross-process brief path"
+  pass "relative home overrides become absolute before spawn launch construction"
+}
+
+test_home_defaults_preserve_absolute_or_resolve_relative_paths() {
+  local rec relative_id absolute_id out status launch home_real linked_home
+  relative_id=profile-relative-home-defaults-z1c
+  absolute_id=profile-absolute-home-defaults-z1d
+  rec=$(make_spawn_case profile-home-defaults pi "$relative_id" "$absolute_id")
+  read_case_record "$rec"
+  home_real=$(cd "$HOME_DIR" && pwd -P)
+
+  : > "$LAUNCH_LOG"
+  out=$(
+    cd "$CASE_DIR" || exit 1
+    FM_ROOT_OVERRIDE='' FM_HOME=home \
+      FM_STATE_OVERRIDE='' FM_DATA_OVERRIDE='' \
+      FM_PROJECTS_OVERRIDE=home/projects FM_CONFIG_OVERRIDE=home/config \
+      FM_SPAWN_NO_GUARD=1 FM_FAKE_PANE_PATH="$WT_DIR" TMUX="fake,1,0" \
+      CLAUDE_CONFIG_DIR='' FM_FAKE_LAUNCH_LOG="$LAUNCH_LOG" \
+      GROK_HOME=home/grok-home PATH="$FAKEBIN_DIR:$PATH" \
+      "$SPAWN" "$relative_id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 0 "$status" "spawn with relative FM_HOME defaults should succeed"
+  launch=$(cat "$LAUNCH_LOG")
+  assert_contains "$launch" "-e '$home_real/state/$relative_id.pi-ext.ts'" \
+    "relative FM_HOME leaked into Pi's default cross-process extension path"
+  assert_contains "$launch" "< '$home_real/data/$relative_id/brief.md'" \
+    "relative FM_HOME leaked into the default cross-process brief path"
+
+  linked_home="$CASE_DIR/home-link"
+  ln -s "$HOME_DIR" "$linked_home"
+  : > "$LAUNCH_LOG"
+  out=$(
+    FM_ROOT_OVERRIDE='' FM_HOME="$linked_home" \
+      FM_STATE_OVERRIDE='' FM_DATA_OVERRIDE='' \
+      FM_PROJECTS_OVERRIDE="$linked_home/projects" FM_CONFIG_OVERRIDE="$linked_home/config" \
+      FM_SPAWN_NO_GUARD=1 FM_FAKE_PANE_PATH="$WT_DIR" TMUX="fake,1,0" \
+      CLAUDE_CONFIG_DIR='' FM_FAKE_LAUNCH_LOG="$LAUNCH_LOG" \
+      GROK_HOME="$linked_home/grok-home" PATH="$FAKEBIN_DIR:$PATH" \
+      "$SPAWN" "$absolute_id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 0 "$status" "spawn with absolute symlink-spelled FM_HOME defaults should succeed"
+  launch=$(cat "$LAUNCH_LOG")
+  assert_contains "$launch" "-e '$linked_home/state/$absolute_id.pi-ext.ts'" \
+    "absolute FM_HOME spelling changed in Pi's default cross-process extension path"
+  assert_contains "$launch" "< '$linked_home/data/$absolute_id/brief.md'" \
+    "absolute FM_HOME spelling changed in the default cross-process brief path"
+  pass "FM_HOME defaults resolve relative paths and preserve absolute spellings"
+}
+
+test_absolute_override_spelling_is_preserved_in_launch_paths() {
+  local rec id out status launch linked_home
+  id=profile-absolute-paths-z1c
+  rec=$(make_spawn_case profile-absolute-paths pi "$id")
+  read_case_record "$rec"
+  linked_home="$CASE_DIR/home-link"
+  ln -s "$HOME_DIR" "$linked_home"
+  : > "$LAUNCH_LOG"
+
+  out=$(
+    FM_ROOT_OVERRIDE='' FM_HOME="$linked_home" \
+      FM_STATE_OVERRIDE="$linked_home/state" FM_DATA_OVERRIDE="$linked_home/data" \
+      FM_PROJECTS_OVERRIDE="$linked_home/projects" FM_CONFIG_OVERRIDE="$linked_home/config" \
+      FM_SPAWN_NO_GUARD=1 FM_FAKE_PANE_PATH="$WT_DIR" TMUX="fake,1,0" \
+      CLAUDE_CONFIG_DIR='' FM_FAKE_LAUNCH_LOG="$LAUNCH_LOG" \
+      GROK_HOME="$linked_home/grok-home" PATH="$FAKEBIN_DIR:$PATH" \
+      "$SPAWN" "$id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 0 "$status" "spawn with absolute symlink-spelled overrides should succeed"
+  launch=$(cat "$LAUNCH_LOG")
+  assert_contains "$launch" "-e '$linked_home/state/$id.pi-ext.ts'" \
+    "absolute FM_STATE_OVERRIDE spelling changed in Pi's cross-process extension path"
+  assert_contains "$launch" "< '$linked_home/data/$id/brief.md'" \
+    "absolute FM_DATA_OVERRIDE spelling changed in the cross-process brief path"
+  pass "absolute override spellings are preserved in spawn launch paths"
+}
+
+test_unresolvable_relative_overrides_fail_loudly() {
+  local rec id out status
+  id=profile-unresolvable-paths-z1d
+  rec=$(make_spawn_case profile-unresolvable-paths pi "$id")
+  read_case_record "$rec"
+
+  out=$(
+    cd "$CASE_DIR" || exit 1
+    FM_ROOT_OVERRIDE='' FM_HOME=missing-home \
+      FM_STATE_OVERRIDE='' FM_DATA_OVERRIDE='' \
+      "$SPAWN" "$id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 1 "$status" "spawn with an unresolvable relative home should fail"
+  assert_contains "$out" "FM_HOME directory cannot be resolved: missing-home" \
+    "spawn did not name the unresolvable FM_HOME"
+
+  out=$(
+    cd "$CASE_DIR" || exit 1
+    FM_ROOT_OVERRIDE='' FM_HOME=home \
+      FM_STATE_OVERRIDE=missing-state FM_DATA_OVERRIDE=home/data \
+      "$SPAWN" "$id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 1 "$status" "spawn with an unresolvable relative state override should fail"
+  assert_contains "$out" "FM_STATE_OVERRIDE directory cannot be resolved: missing-state" \
+    "spawn did not name the unresolvable FM_STATE_OVERRIDE"
+
+  out=$(
+    cd "$CASE_DIR" || exit 1
+    FM_ROOT_OVERRIDE='' FM_HOME=home \
+      FM_STATE_OVERRIDE=home/state FM_DATA_OVERRIDE=missing-data \
+      "$SPAWN" "$id" "$PROJ_DIR" 2>&1
+  )
+  status=$?
+  expect_code 1 "$status" "spawn with an unresolvable relative data override should fail"
+  assert_contains "$out" "FM_DATA_OVERRIDE directory cannot be resolved: missing-data" \
+    "spawn did not name the unresolvable FM_DATA_OVERRIDE"
+  pass "unresolvable relative spawn overrides fail with named diagnostics"
+}
+
 test_active_dispatch_profile_requires_explicit_harness_for_ship() {
   local rec id out status
   id=profile-required-ship-z11
@@ -509,6 +655,10 @@ test_active_dispatch_profile_does_not_block_secondmate_launch() {
 }
 
 test_no_profile_keeps_claude_profile_defaults
+test_relative_home_overrides_launch_with_absolute_cross_process_paths
+test_home_defaults_preserve_absolute_or_resolve_relative_paths
+test_absolute_override_spelling_is_preserved_in_launch_paths
+test_unresolvable_relative_overrides_fail_loudly
 test_active_dispatch_profile_requires_explicit_harness_for_ship
 test_active_dispatch_profile_requires_explicit_harness_for_scout
 test_active_dispatch_profile_allows_explicit_harness
diff --git a/tests/fm-x-mode.test.sh b/tests/fm-x-mode.test.sh
index 505860689d..1ebdf944cb 100755
--- a/tests/fm-x-mode.test.sh
+++ b/tests/fm-x-mode.test.sh
@@ -700,6 +700,23 @@ test_bootstrap_activates_on_env_token() {
   pass "bootstrap activates X mode from an .env token, idempotently"
 }
 
+test_bootstrap_relative_home_writes_absolute_poll_shim() {
+  local root home out quoted_home
+  root="$TMP_ROOT/boot-relative-home"
+  mkdir -p "$root/home"
+  home=$(cd "$root/home" && pwd -P)
+  printf 'FMX_PAIRING_TOKEN=tok-relative\n' > "$home/.env"
+  out=$(
+    cd "$root" || exit 1
+    FM_HOME=home "$ROOT/bin/fm-bootstrap.sh" 2>/dev/null
+  )
+  assert_contains "$out" "FMX: X mode on" "relative-home bootstrap must announce X mode"
+  quoted_home=$(printf '%q' "$home")
+  assert_grep "export FM_HOME=$quoted_home" "$home/state/x-watch.check.sh" \
+    "relative FM_HOME leaked into the durable X-mode poll shim"
+  pass "bootstrap writes an absolute FM_HOME into the durable X-mode poll shim"
+}
+
 test_bootstrap_reports_missing_x_dependency() {
   local home fakebin out tool tool_path
   home="$TMP_ROOT/boot-missing-x"; mkdir -p "$home"
@@ -2862,6 +2879,7 @@ test_followup_post_dry_run_increments_counter_keeps_link
 test_followup_post_dry_run_final_clears_link
 test_followup_usage_errors
 test_bootstrap_activates_on_env_token
+test_bootstrap_relative_home_writes_absolute_poll_shim
 test_bootstrap_reports_missing_x_dependency
 test_bootstrap_does_not_announce_when_arm_fails
 test_bootstrap_does_not_follow_x_artifact_symlinks