fix(cmux): classify borderless Claude composers

bin/backends/cmux.sh

@@ -535,38 +535,62 @@ fm_backend_cmux_capture() {  # <target> <lines> [expected-label]
 # explicit direction - this is the highest-risk piece of a new backend's
 # send-and-verify logic, and cmux's `read-screen` gives plain-text capture
 # with no cursor-row primitive and no ANSI style channel like herdr's newer
-# `pane read --format ansi` path. The cmux classifier intentionally remains
-# border-row based: locate the
-# composer row as the only captured line whose TRIMMED content both STARTS and
-# ENDS with the same border glyph (│, ┃, or a plain ASCII |), scanning forward
-# and keeping the LAST match so an earlier border-shaped line (scrollback, a
-# popup) never outranks the real bottom-anchored composer row.
+# `pane read --format ansi` path. Locate the LAST bordered composer row when
+# one exists. Current Claude Code also renders a borderless composer as a bare
+# agent-prompt row bounded by horizontal rules, which is the only bare shape
+# accepted here because cmux cannot identify a cursor row.
 FM_BACKEND_CMUX_COMPOSER_LINES=${FM_BACKEND_CMUX_COMPOSER_LINES:-20}
 FM_BACKEND_CMUX_IDLE_RE=${FM_BACKEND_CMUX_IDLE_RE:-'^Type a message\.\.\.$'}
 
+fm_backend_cmux_horizontal_rule() {  # <trimmed-line>
+  local remaining=$1
+  remaining=${remaining//─/}
+  remaining=${remaining//[[:space:]]/}
+  [ -n "$1" ] && [ -z "$remaining" ]
+}
+
 fm_backend_cmux_composer_state() {  # <target> [expected-label] -> empty|pending|unknown
-  local target=$1 expected_label=${2:-} cap line trimmed stripped="" found=0
+  local target=$1 expected_label=${2:-} cap line trimmed stripped="" bare="" bordered_index=-1 bare_index=-1 i
+  local -a rows=()
   cap=$(fm_backend_cmux_capture "$target" "$FM_BACKEND_CMUX_COMPOSER_LINES" "$expected_label") || { printf 'unknown'; return 0; }
   while IFS= read -r line; do
     trimmed="${line#"${line%%[![:space:]]*}"}"
     trimmed="${trimmed%"${trimmed##*[![:space:]]}"}"
     [ -n "$trimmed" ] || continue
+    rows+=("$trimmed")
     case "$trimmed" in
-      '│'*'│'|'┃'*'┃'|'|'*'|') : ;;
-      *) continue ;;
+      '│'*'│'|'┃'*'┃'|'|'*'|')
+        stripped=$trimmed
+        bordered_index=$((${#rows[@]} - 1))
+        ;;
     esac
-    stripped=$trimmed
-    found=1
   done < <(printf '%s\n' "$cap")
-  [ "$found" -eq 1 ] || { printf 'unknown'; return 0; }
+  for ((i = 1; i + 1 < ${#rows[@]}; i++)); do
+    fm_backend_cmux_horizontal_rule "${rows[i - 1]}" || continue
+    fm_backend_cmux_horizontal_rule "${rows[i + 1]}" || continue
+    case "${rows[i]}" in
+      '❯'*|'›'*|'⟩'*)
+        bare=${rows[i]}
+        bare_index=$i
+        ;;
+    esac
+  done
+  if [ "$bare_index" -gt "$bordered_index" ]; then
+    # cmux has no cursor-position primitive. The horizontal-rule container plus
+    # an agent-only prompt glyph is the structural proof for this bare row.
+    case "$bare" in
+      $'❯\302\240') bare="" ;;
+    esac
+    fm_composer_classify_content 0 "$bare" "$FM_BACKEND_CMUX_IDLE_RE"
+    return 0
+  fi
+  [ "$bordered_index" -ge 0 ] || { printf 'unknown'; return 0; }
   stripped=${stripped//│/}
   stripped=${stripped//┃/}
   stripped=${stripped//|/}
   stripped="${stripped#"${stripped%%[![:space:]]*}"}"
   stripped="${stripped%"${stripped##*[![:space:]]}"}"
-  # A row was found only by the bordered shape above, so content came from a
-  # genuine composer box - delegate to the shared owner with bordered=1. A bare
-  # dead-shell prompt has no bordered row and already returned 'unknown' above.
+  # A bordered row is a genuine composer box.
   fm_composer_classify_content 1 "$stripped" "$FM_BACKEND_CMUX_IDLE_RE"
 }
 

bin/fm-test-run.sh

@@ -180,6 +180,7 @@ family_for_basename() {
       printf '%s\n' session-bootstrap
       ;;
     fm-afk-pi-herdr-return-e2e.test.sh|\
+    fm-cmux-claude-composer-live-e2e.test.sh|\
     fm-codex-continuity-live-e2e.test.sh|fm-grok-continuity-live-e2e.test.sh|\
     fm-grok-stop-live-e2e.test.sh|fm-harness-liveness-drift-live-e2e.test.sh|\
     fm-muse-signals-live-e2e.test.sh|\

docs/cmux-backend.md

@@ -92,8 +92,9 @@ Spawn-time worktree discovery sends begin and end markers around `pwd`, captures
 
 Literal send and Enter are separate calls.
 Enter, Escape, and Ctrl-C are supported.
-The composer verifier locates the last bordered composer row and delegates the content decision to `bin/fm-composer-lib.sh`.
-A bare shell prompt is `unknown`, and a slash-popup placeholder remains `pending`, so only Enter is retried and text is never retyped.
+The composer verifier locates the last bordered composer row or a later bare agent-prompt row bounded by horizontal rules, then delegates the content decision to `bin/fm-composer-lib.sh`.
+The bounded bare shape supports Claude's borderless `❯` composer, with or without a trailing U+00A0 non-breaking space, without relying on a cursor primitive that `read-screen` does not provide.
+An unstructured bare prompt is `unknown`, and a slash-popup placeholder remains `pending`, so only Enter is retried and text is never retyped.
 cmux exposes no native generic agent busy signal, so supervision uses capture/hash polling for screen changes and each harness adapter's semantic lifecycle for worker state.
 Grok alone retains its isolated rendered-tail fallback.
 

docs/verification/runtime-backends.md

@@ -674,6 +674,20 @@ tests/fm-backend-cmux-smoke.test.sh
 
 The real smoke proves socket access, fresh readiness, current-path probing, send and keys, bounded capture, title identity, and guarded exact cleanup.
 
+### Claude composer confirmation
+
+The borderless Claude composer confirmation was verified on 2026-08-09 with cmux 0.64.22 build 102 and Claude Code 2.1.226 on macOS aarch64.
+An isolated real Claude worker rendered a bare `❯` plus U+00A0 row between horizontal rules.
+The cmux classifier returned `empty`, and one `fm-send.sh --resolve-key <key> ALBATROSS` command appended the matching `resolved` event before the worker reported completion.
+The terminal capture contained exactly one submitted `❯ ALBATROSS` row.
+Refresh this harness-dependent proof with an isolated cmux Claude worker before accepting a Claude or cmux upgrade:
+
+```sh
+FM_CMUX_CLAUDE_COMPOSER_LIVE=1 bin/fm-test-run.sh tests/fm-cmux-claude-composer-live-e2e.test.sh
+```
+
+The portable classifier regression is `tests/fm-backend-cmux.test.sh`.
+
 ## Codex App host tools
 
 A reusable Desktop host-tool smoke ran on 2026-07-06 against Codex Desktop bundle version 26.623.101652, build 4674, bundle id `com.openai.codex`.

tests/fm-backend-cmux.test.sh

@@ -726,6 +726,54 @@ test_composer_state_bare_prompt_is_empty() {
   pass "fm_backend_cmux_composer_state: a bare '❯' composer row reads empty"
 }
 
+test_composer_state_borderless_claude_prompt_is_empty() {
+  local dir fb out
+  dir="$TMP_ROOT/composer-borderless-claude"; mkdir -p "$dir/responses"
+  cmux_panes_response "$dir" 1 "bbbbbbbb-1111-1111-1111-111111111111"
+  cmux_read_screen_response "$dir" 2 $'────────────────────────\n❯\n────────────────────────\nHaiku 4.5'
+  fb=$(make_cmux_fakebin "$dir")
+  out=$( PATH="$fb:$PATH" FM_CMUX_LOG="$dir/log" FM_CMUX_RESPONSES="$dir/responses" \
+    bash -c '. "$0/bin/backends/cmux.sh"; fm_backend_cmux_composer_state "aaaaaaaa-0000-0000-0000-000000000000:bbbbbbbb-1111-1111-1111-111111111111"' "$ROOT" )
+  [ "$out" = empty ] || fail "a borderless Claude '❯' row bounded by horizontal rules should read empty, got '$out'"
+  pass "fm_backend_cmux_composer_state: a borderless Claude '❯' composer row reads empty"
+}
+
+test_composer_state_borderless_claude_prompt_outranks_stale_bordered_row() {
+  local dir fb out
+  dir="$TMP_ROOT/composer-borderless-claude-after-bordered"; mkdir -p "$dir/responses"
+  cmux_panes_response "$dir" 1 "bbbbbbbb-1111-1111-1111-111111111111"
+  cmux_read_screen_response "$dir" 2 $'│ ❯ stale input │\n────────────────────────\n❯\n────────────────────────\nHaiku 4.5'
+  fb=$(make_cmux_fakebin "$dir")
+  out=$( PATH="$fb:$PATH" FM_CMUX_LOG="$dir/log" FM_CMUX_RESPONSES="$dir/responses" \
+    bash -c '. "$0/bin/backends/cmux.sh"; fm_backend_cmux_composer_state "aaaaaaaa-0000-0000-0000-000000000000:bbbbbbbb-1111-1111-1111-111111111111"' "$ROOT" )
+  [ "$out" = empty ] || fail "a current borderless Claude row should outrank stale bordered scrollback, got '$out'"
+  pass "fm_backend_cmux_composer_state: a borderless Claude row outranks stale bordered scrollback"
+}
+
+test_composer_state_borderless_claude_nbsp_prompt_is_empty() {
+  local dir fb out
+  dir="$TMP_ROOT/composer-borderless-claude-nbsp"; mkdir -p "$dir/responses"
+  cmux_panes_response "$dir" 1 "bbbbbbbb-1111-1111-1111-111111111111"
+  cmux_read_screen_response "$dir" 2 $'────────────────────────\n❯\302\240\n────────────────────────\nHaiku 4.5'
+  fb=$(make_cmux_fakebin "$dir")
+  out=$( LC_ALL=C PATH="$fb:$PATH" FM_CMUX_LOG="$dir/log" FM_CMUX_RESPONSES="$dir/responses" \
+    bash -c '. "$0/bin/backends/cmux.sh"; fm_backend_cmux_composer_state "aaaaaaaa-0000-0000-0000-000000000000:bbbbbbbb-1111-1111-1111-111111111111"' "$ROOT" )
+  [ "$out" = empty ] || fail "a borderless Claude '❯'+NBSP row bounded by horizontal rules should read empty under LC_ALL=C, got '$out'"
+  pass "fm_backend_cmux_composer_state: a borderless Claude '❯'+NBSP composer row reads empty under LC_ALL=C"
+}
+
+test_composer_state_borderless_claude_text_is_pending() {
+  local dir fb out
+  dir="$TMP_ROOT/composer-borderless-claude-text"; mkdir -p "$dir/responses"
+  cmux_panes_response "$dir" 1 "bbbbbbbb-1111-1111-1111-111111111111"
+  cmux_read_screen_response "$dir" 2 $'────────────────────────\n❯ retain this message\n────────────────────────\nHaiku 4.5'
+  fb=$(make_cmux_fakebin "$dir")
+  out=$( PATH="$fb:$PATH" FM_CMUX_LOG="$dir/log" FM_CMUX_RESPONSES="$dir/responses" \
+    bash -c '. "$0/bin/backends/cmux.sh"; fm_backend_cmux_composer_state "aaaaaaaa-0000-0000-0000-000000000000:bbbbbbbb-1111-1111-1111-111111111111"' "$ROOT" )
+  [ "$out" = pending ] || fail "a borderless Claude row with typed text should read pending, got '$out'"
+  pass "fm_backend_cmux_composer_state: a borderless Claude row with typed text reads pending"
+}
+
 test_composer_state_ghost_placeholder_is_empty() {
   local dir fb out
   dir="$TMP_ROOT/composer-ghost"; mkdir -p "$dir/responses"
@@ -1087,6 +1135,10 @@ test_send_text_line_clears_partial_input_when_enter_fails
 test_send_text_line_reports_unsafe_input_when_cleanup_fails
 test_current_path_probes_with_marker
 test_composer_state_bare_prompt_is_empty
+test_composer_state_borderless_claude_prompt_is_empty
+test_composer_state_borderless_claude_prompt_outranks_stale_bordered_row
+test_composer_state_borderless_claude_nbsp_prompt_is_empty
+test_composer_state_borderless_claude_text_is_pending
 test_composer_state_ghost_placeholder_is_empty
 test_composer_state_real_text_is_pending
 test_composer_state_popup_placeholder_fill_is_pending

tests/fm-cmux-claude-composer-live-e2e.test.sh

@@ -0,0 +1,110 @@
+#!/usr/bin/env bash
+# Real Claude Code plus cmux submit-confirmation drift guard.
+# Run explicitly with FM_CMUX_CLAUDE_COMPOSER_LIVE=1; it creates and cleans up
+# only one exact fm-test- workspace through the normal scout lifecycle.
+set -u
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+TASK="fm-test-cmux-claude-composer-$$"
+LAB=
+SPAWNED=0
+
+fail() { printf 'not ok - %s\n' "$1" >&2; exit 1; }
+pass() { printf 'ok - %s\n' "$1"; }
+
+cleanup() {
+  [ "$SPAWNED" -eq 0 ] || {
+    mkdir -p "$LAB/data/$TASK"
+    : > "$LAB/data/$TASK/report.md"
+    if grep -q '^needs-decision \[key=probe-decision\]' "$LAB/state/$TASK.status" 2>/dev/null \
+      && ! grep -q '^resolved \[key=probe-decision\]' "$LAB/state/$TASK.status" 2>/dev/null; then
+      printf '%s\n' 'resolved [key=probe-decision]: live guard cleanup' >> "$LAB/state/$TASK.status"
+    fi
+    FM_HOME="$LAB" "$ROOT/bin/fm-decision-hold.sh" complete "$TASK" --none >/dev/null 2>&1 || true
+    FM_HOME="$LAB" "$ROOT/bin/fm-teardown.sh" "$TASK" >/dev/null 2>&1 || true
+  }
+  [ -z "$LAB" ] || rm -rf -- "$LAB"
+}
+
+if [ "${FM_CMUX_CLAUDE_COMPOSER_LIVE:-0}" != 1 ]; then
+  echo "skip: set FM_CMUX_CLAUDE_COMPOSER_LIVE=1 to run the real cmux Claude composer drift guard"
+  exit 0
+fi
+
+command -v claude >/dev/null 2>&1 || fail "FM_CMUX_CLAUDE_COMPOSER_LIVE=1 but Claude Code is not installed"
+command -v cmux >/dev/null 2>&1 || fail "FM_CMUX_CLAUDE_COMPOSER_LIVE=1 but cmux is not installed"
+command -v jq >/dev/null 2>&1 || fail "FM_CMUX_CLAUDE_COMPOSER_LIVE=1 but jq is not installed"
+command -v treehouse >/dev/null 2>&1 || fail "FM_CMUX_CLAUDE_COMPOSER_LIVE=1 but treehouse is not installed"
+command -v python3 >/dev/null 2>&1 || fail "FM_CMUX_CLAUDE_COMPOSER_LIVE=1 but python3 is not installed"
+cmux ping >/dev/null 2>&1 || fail "FM_CMUX_CLAUDE_COMPOSER_LIVE=1 but the cmux socket is unavailable"
+
+LAB=$(mktemp -d "${TMPDIR:-/tmp}/fm-cmux-claude-composer.XXXXXX") || fail "could not create an isolated cmux Claude lab"
+trap cleanup EXIT
+mkdir -p "$LAB/config" "$LAB/data/$TASK" "$LAB/projects/comms" "$LAB/state"
+printf 'cmux\n' > "$LAB/config/backend"
+
+git -C "$LAB/projects/comms" init -q -b main || fail "could not initialize the isolated probe repository"
+git -C "$LAB/projects/comms" config user.email 'cmux-composer-test@example.invalid'
+git -C "$LAB/projects/comms" config user.name 'cmux composer test'
+printf 'cmux Claude composer probe\n' > "$LAB/projects/comms/README.md"
+git -C "$LAB/projects/comms" add README.md
+git -C "$LAB/projects/comms" commit -qm 'fixture: initialize cmux Claude composer probe'
+
+STATUS="$LAB/state/$TASK.status"
+FM_HOME="$LAB" "$ROOT/bin/fm-brief.sh" "$TASK" comms --scout || fail "could not scaffold the Claude probe brief"
+python3 - "$LAB/data/$TASK/brief.md" "$STATUS" <<'PY'
+from pathlib import Path
+import sys
+
+brief = Path(sys.argv[1])
+status = sys.argv[2]
+brief.write_text(brief.read_text().replace("{TASK}", f'''Run a cmux communication probe.
+
+Immediately append `working: cmux composer probe ready` to `{status}`.
+Then append exactly `needs-decision [key=probe-decision]: awaiting codeword` to that file and stop to wait for a firstmate message.
+When you receive a firstmate message containing `ALBATROSS`, append `done: received ALBATROSS` to that status file and stop.
+Do not change project files or make a commit.'''))
+PY
+
+FM_HOME="$LAB" "$ROOT/bin/fm-spawn.sh" "$TASK" "$LAB/projects/comms" --scout --harness claude --model haiku --backend cmux \
+  || fail "could not launch the real Claude cmux probe"
+SPAWNED=1
+
+# shellcheck source=bin/fm-backend.sh
+FM_HOME="$LAB"
+export FM_HOME
+. "$ROOT/bin/fm-backend.sh"
+fm_backend_source cmux || fail "could not source the cmux adapter"
+TARGET=$(awk -F= '/^window=/{print $2}' "$LAB/state/$TASK.meta")
+[ -n "$TARGET" ] || fail "the cmux probe did not record its endpoint"
+
+for _ in $(seq 1 45); do
+  CAPTURE=$(fm_backend_cmux_capture "$TARGET" 200 "$TASK" 2>/dev/null || true)
+  case "$CAPTURE" in
+    *'Yes, I trust this folder'*) FM_HOME="$LAB" "$ROOT/bin/fm-send.sh" "$TASK" --key Enter || fail "could not accept Claude's folder-trust prompt" ;;
+  esac
+  grep -q '^needs-decision \[key=probe-decision\]' "$STATUS" 2>/dev/null && break
+  sleep 2
+done
+grep -q '^needs-decision \[key=probe-decision\]' "$STATUS" 2>/dev/null \
+  || fail "Claude $(claude --version) did not reach the communication decision"
+
+COMPOSER=$(fm_backend_cmux_composer_state "$TARGET" "$TASK")
+[ "$COMPOSER" = empty ] || fail "cmux classified the real Claude $(claude --version) idle composer as '$COMPOSER'"
+pass "cmux classifies the real Claude borderless composer as empty"
+
+FM_SEND_SETTLE=0 FM_HOME="$LAB" "$ROOT/bin/fm-send.sh" "$TASK" --resolve-key probe-decision ALBATROSS \
+  || fail "cmux did not confirm the real Claude steer"
+for _ in $(seq 1 30); do
+  grep -q '^done: received ALBATROSS' "$STATUS" 2>/dev/null && break
+  sleep 2
+done
+grep -q '^resolved \[key=probe-decision\]: answered: ALBATROSS' "$STATUS" \
+  || fail "confirmed cmux delivery did not close the keyed decision"
+grep -q '^done: received ALBATROSS' "$STATUS" \
+  || fail "the real Claude worker did not complete after the confirmed steer"
+
+CAPTURE=$(fm_backend_cmux_capture "$TARGET" 200 "$TASK")
+COUNT=$(printf '%s\n' "$CAPTURE" | grep -cF '❯ ALBATROSS' || true)
+[ "$COUNT" -eq 1 ] || fail "expected exactly one submitted ALBATROSS steer, found $COUNT"
+pass "cmux confirms one steer, closes the keyed decision, and leaves no duplicate"