fix(agents): disable agy implementation dispatch

Codex handoff could not write .agents in its sandbox, so the orchestrator applied the intended fail-fast change: agy remains available for dry-run prompt inspection but non-dry-run dispatch exits before worktree or PR side effects.

.agents/README.md

@@ -24,7 +24,7 @@ bin/dev          CLI: `dev implement <issue#> --harness <name> [--dry-run]`
 - **Groom** (interactive, Claude): `/groom <issue#>` runs a seeded grill-me → writes a
   Ready spec into the issue body → sets Effort/Priority → leaves Stage at `Research`.
   You review and flip to `Ready`.
-- **Implement** (any harness): `.agents/bin/dev implement <issue#> --harness <name>`
+- **Implement** (recommended harnesses: `codex` or `cursor`): `.agents/bin/dev implement <issue#> --harness <name>`
   (or `/implement …` in Claude to supervise) → isolated worktree → runs the harness
   headless on the spec → build gate → opens a PR → sets Stage `In Review`.
 - **Review + merge**: use the `review` skill from a harness different from the
@@ -42,8 +42,17 @@ local adapter state.
 ## Adding / fixing a harness
 
 Edit one function in `harnesses.sh`: `harness_<name> <workdir> <promptfile>`, running the
-tool non-interactively in `<workdir>` on the prompt. `claude`/`codex`/`opencode` are
-wired; `pi`/`cursor` are stubs — confirm their headless flags before trusting.
+tool non-interactively in `<workdir>` on the prompt. For current implementation
+dispatch, prefer `codex` or `cursor`; `claude` and `opencode` remain available, and
+`pi` still needs flag verification before trusting.
+
+`agy` / Antigravity is deliberately disabled for non-dry-run dispatch as of
+2026-07-04. Phase 1 testing found the headless path unreliable: with
+`--new-project` it ignored the prompt and tried to scaffold, while without it the CLI
+could resume a stale conversation and hang past the print timeout. Keep using
+`.agents/bin/dev implement <issue#> --harness agy --dry-run` for prompt inspection
+only; real dispatch should use `codex` or `cursor` until a fresh Antigravity
+headless invocation is verified and documented.
 
 Always `--dry-run` a new harness first: it renders the exact prompt and plan, touching
 nothing (no worktree, PR, or state change).

.agents/bin/dev

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 # .agents/bin/dev — box-box agentic dev CLI. Works from any harness's shell.
 #
-#   dev implement <issue#> --harness <claude|codex|opencode|pi|cursor> [--dry-run] [--base <branch>]
+#   dev implement <issue#> --harness <codex|cursor|claude|opencode|pi|agy> [--dry-run] [--base <branch>]
 #
 # Grooming is driven interactively via the Claude Code /groom skill; this CLI covers
 # the implement lane (dispatch a Ready issue to a harness → worktree → gate → PR).
@@ -15,7 +15,7 @@ box-box dev CLI
 
   dev implement <issue#> --harness <name> [--dry-run] [--base <branch>]
 
-harnesses: claude, codex, opencode (supported) · pi, cursor (verify flags in .agents/harnesses.sh)
+harnesses: codex, cursor (recommended) · claude, opencode (available) · agy (dry-run only, disabled for dispatch) · pi (verify flags)
   --dry-run   render the prompt + plan, touch nothing (no worktree/PR/state change)
   --base      base branch for the worktree/PR (default: main)
 EOF

.agents/harnesses.sh

@@ -11,6 +11,18 @@
 
 # ---- MUST-HAVE ----
 
+harness_disabled_reason() {              # <name> -> reason on stdout; 0 means disabled
+  case "$1" in
+    agy)
+      cat <<'EOF'
+agy is disabled for implementation dispatch as of 2026-07-04: Antigravity headless mode was observed to ignore prompts with --new-project, resume stale conversations without it, and hang past print timeouts. Use codex or cursor until a fresh headless invocation is verified.
+EOF
+      return 0
+      ;;
+    *) return 1 ;;
+  esac
+}
+
 harness_claude() {                      # Claude Code — print mode, auto-accept edits
   local dir="$1" prompt="$2"
   ( cd "$dir" && claude -p "$(cat "$prompt")" --permission-mode acceptEdits )
@@ -31,14 +43,11 @@ harness_cursor() {                      # Cursor CLI agent — composer-2.5, hea
   ( cd "$dir" && cursor-agent -p "$(cat "$prompt")" --model composer-2.5 --force --trust )
 }
 
-harness_agy() {                         # Antigravity CLI — UNRELIABLE headless (2026-07): with
-  # --new-project it ignores the prompt and asks to scaffold a project; without it, it
-  # resumes the previous conversation (silently keeping its old model — --model only
-  # applies to new conversations) and can hang past the print timeout. Do not trust for
-  # dispatch until fixed upstream; verify with a trivial prompt first.
-  local dir="$1" prompt="$2"
-  ( cd "$dir" && agy --print --print-timeout 60m \
-      --model="Gemini 3.1 Pro (High)" --dangerously-skip-permissions "$(cat "$prompt")" )
+harness_agy() {                         # Antigravity CLI — disabled until headless is verified
+  local reason
+  reason="$(harness_disabled_reason agy)"
+  echo "harness_agy: $reason" >&2
+  return 2
 }
 
 # ---- NICE-TO-HAVE (verify the exact invocation for your version before trusting) ----

.agents/lib/dispatch.sh

@@ -52,6 +52,15 @@ dispatch() { # <issue#> <harness> [--dry-run] [--base <branch>]
   if ! declare -f "harness_$harness" >/dev/null 2>&1; then
     echo "no adapter for harness '$harness' — add harness_$harness() to .agents/harnesses.sh" >&2; return 2
   fi
+  if [ "$dry" != 1 ] && declare -f harness_disabled_reason >/dev/null 2>&1; then
+    local disabled_reason
+    if disabled_reason="$(harness_disabled_reason "$harness")"; then
+      echo "harness '$harness' is disabled for non-dry-run dispatch." >&2
+      echo "  $disabled_reason" >&2
+      echo "  Use --dry-run for prompt inspection, or dispatch with --harness codex/cursor." >&2
+      return 2
+    fi
+  fi
 
   local repo_root title body slug branch wt prompt
   repo_root="$(git rev-parse --show-toplevel)" || return 1

.agents/test/dispatch_disabled_harness_test.sh

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+cd "$ROOT"
+
+# shellcheck source=/dev/null
+source "$ROOT/.agents/lib/dispatch.sh"
+
+issue_title() { echo "Disable agy harness smoke"; }
+issue_body() { echo "## Spec"; echo; echo "Smoke prompt body"; }
+get_field() { echo "Ready"; }
+set_stage() { echo "unexpected set_stage $*" >&2; return 99; }
+run_gate() { echo "unexpected run_gate $*" >&2; return 99; }
+
+unexpected_git_file="$(mktemp "${TMPDIR:-/tmp}/boxbox-agy-git.XXXX")"
+rm -f "$unexpected_git_file"
+git() {
+  if [ "${1:-}" = "rev-parse" ]; then
+    command git "$@"
+    return
+  fi
+  echo "unexpected git $*" >&2
+  touch "$unexpected_git_file"
+  return 99
+}
+
+set +e
+non_dry_output="$(dispatch 47 agy 2>&1)"
+non_dry_status=$?
+set -e
+
+[ "$non_dry_status" -eq 2 ] || {
+  echo "expected agy non-dry-run to exit 2, got $non_dry_status" >&2
+  echo "$non_dry_output" >&2
+  exit 1
+}
+[[ "$non_dry_output" == *"harness 'agy' is disabled"* ]] || {
+  echo "expected disabled-harness message" >&2
+  echo "$non_dry_output" >&2
+  exit 1
+}
+[ ! -e "$unexpected_git_file" ] || {
+  echo "agy non-dry-run reached git before failing" >&2
+  echo "$non_dry_output" >&2
+  exit 1
+}
+
+dry_output="$(dispatch 47 agy --dry-run 2>&1)"
+[[ "$dry_output" == *"[dry-run] no worktree / harness / PR / state change"* ]] || {
+  echo "expected agy dry-run to render dispatch preview" >&2
+  echo "$dry_output" >&2
+  exit 1
+}
+[[ "$dry_output" == *"Smoke prompt body"* ]] || {
+  echo "expected agy dry-run prompt body" >&2
+  echo "$dry_output" >&2
+  exit 1
+}