fix(wrap/opencode): verify the opencode binary before mutating config

Verify the OpenCode executable before changing configuration.

headroom/cli/wrap.py

@@ -6947,6 +6947,20 @@ def opencode(
             )
         subscription_resolution = _require_copilot_subscription_resolution()
 
+    # Verify the opencode binary exists BEFORE mutating any config. Otherwise a
+    # missing binary leaves headroom MCP/Serena/memory entries in the user's
+    # opencode config and an injected AGENTS.md, then errors with no cleanup --
+    # the config-before-verify anti-pattern (#1614). Siblings (claude, codex,
+    # goose, omp) already check first. `--prepare-only` intentionally writes
+    # config without launching, so it is exempt.
+    opencode_bin: str | None = None
+    if not prepare_only:
+        opencode_bin = shutil.which("opencode")
+        if not opencode_bin:
+            click.echo("Error: 'opencode' not found in PATH.")
+            click.echo("Install OpenCode: https://opencode.ai")
+            raise SystemExit(1)
+
     # Snapshot OpenCode config.json BEFORE any wrap-time mutation so
     # `headroom unwrap opencode` can restore the user's pre-wrap state.
     _opencode_config_file, _opencode_backup_file = opencode_config_paths()
@@ -6987,11 +7001,9 @@ def opencode(
         inject_opencode_provider_config(port)
         return
 
-    opencode_bin = shutil.which("opencode")
-    if not opencode_bin:
-        click.echo("Error: 'opencode' not found in PATH.")
-        click.echo("Install OpenCode: https://opencode.ai")
-        raise SystemExit(1)
+    # Past the prepare-only return the launch path always ran the binary check
+    # above, so opencode_bin is resolved.
+    assert opencode_bin is not None
 
     # Register our proxy client marker BEFORE _ensure_proxy so that another
     # wrapper's cleanup sees us as an active client and doesn't terminate a

tests/test_cli/test_wrap_opencode.py

@@ -364,6 +364,35 @@ def test_wrap_opencode_missing_binary_errors_clearly(
     assert "'opencode' not found in PATH" in result.output
 
 
+def test_wrap_opencode_missing_binary_does_not_mutate_config(
+    runner: CliRunner,
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """A missing opencode binary must not leave memory side-effects behind (#1614 class).
+
+    The MCP/Serena registrations are already gated on ``registrar.detect()``, but
+    the ``--memory`` injections (AGENTS.md, the .headroom dir, the memory MCP
+    config) are not -- they ran unconditionally before the binary check. Verify
+    the binary first, like claude/codex/goose/omp, so an absent tool cannot write
+    those and then error with nothing launched.
+    """
+    monkeypatch.chdir(tmp_path)
+    monkeypatch.delenv("HEADROOM_CONTEXT_TOOL", raising=False)
+    _set_test_home(monkeypatch, tmp_path)
+
+    agents_md = tmp_path / "AGENTS.md"
+    headroom_dir = tmp_path / ".headroom"
+
+    with patch.object(wrap_mod.shutil, "which", return_value=None):
+        result = runner.invoke(main, ["wrap", "opencode", "--memory"])
+
+    assert result.exit_code == 1
+    assert "'opencode' not found in PATH" in result.output
+    assert not agents_md.exists(), "AGENTS.md was created before the missing-binary check"
+    assert not headroom_dir.exists(), ".headroom dir was created before the missing-binary check"
+
+
 def test_wrap_opencode_prepare_only_injects_config(
     runner: CliRunner,
     tmp_path: Path,