fix(opencode): debug paths runs once per binary and home in a process (Issue #60, Linux item 6)

Every run appends a line to opencode's log, and one discover resolved the
database once per candidate. A successful answer is kept per (binary, HOME,
XDG_DATA_HOME) - the values the run sees; a failed run is not remembered.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_issue60_linux_fixes.py

@@ -5,6 +5,8 @@
 5. The adapter's queries neither create nor remove anything beside
    opencode's database (a read-write open checkpoints the WAL and deletes
    the sidecars on close; a plain mode=ro open creates missing ones).
+6. `debug paths` (which writes a line to opencode's log) runs once per
+   (binary, HOME, XDG_DATA_HOME) in a process.
 """
 
 from __future__ import annotations
@@ -28,6 +30,8 @@ from lib_py import stall_watch  # noqa: E402
 from lib_py.agents.base import DiscoveryContext  # noqa: E402
 from lib_py.agents.input_region import extract_input_region  # noqa: E402
 from lib_py.agents.registry import get_adapter  # noqa: E402
+from lib_py.agents.adapters import opencode as opencode_mod  # noqa: E402
+import _fake_opencode  # noqa: E402
 
 # 140 columns (herdr capture) and 60 columns, where the example loses its
 # closing quote.
@@ -35,6 +39,11 @@ HOME_SCREENS = ("opencode_idle_2x_home.txt", "opencode_idle_2x_home_narrow.txt")
 PLACEHOLDER_LINE = re.compile(r'^(\s*┃\s*)Ask anything… ".*$', re.M)
 
 
+@pytest.fixture(autouse=True)
+def _no_cached_db_paths(monkeypatch):
+    monkeypatch.setattr(opencode_mod, "_DB_PATHS", {}, raising=False)
+
+
 def _pane(name: str) -> str:
     return "".join(l for l in (PANES / name).read_text(encoding="utf-8").splitlines(True) if not l.startswith("# "))
 
@@ -165,3 +174,42 @@ def test_a_query_reads_right_and_leaves_the_sidecars_alone(wal_home, state, list
     run, expected = QUERIES[query]
     assert run(adapter, ctx, db) == expected
     assert sorted(os.listdir(os.path.dirname(db))) == listing
+
+
+# ---------------------------------------------------------------------------
+# 6. `debug paths` once per (binary, HOME, XDG_DATA_HOME)
+# ---------------------------------------------------------------------------
+def test_debug_paths_runs_once_per_home(tmp_path, monkeypatch):
+    log = tmp_path / "calls.log"
+    fake = _fake_opencode.write(tmp_path / "fakebin" / "opencode-real")
+    wrapper = tmp_path / "fakebin" / "opencode"
+    wrapper.write_text(f'#!/bin/sh\necho "$*" >> "{log}"\nexec "{fake}" "$@"\n')
+    wrapper.chmod(0o755)
+    adapter = get_adapter("opencode")
+    monkeypatch.setattr(adapter, "_bin", lambda ctx: str(wrapper))
+    homes = [tmp_path / "home1", tmp_path / "home2"]
+    ctxs = [DiscoveryContext(workspace=str(tmp_path), agent_name="opencode", home_dir=str(h)) for h in homes]
+
+    def calls():
+        return log.read_text().splitlines() if log.exists() else []
+
+    want = [str(h / ".local" / "share" / "opencode" / "opencode.db") for h in homes]
+    assert [adapter._resolve_db(ctxs[0]) for _ in range(2)] == [want[0]] * 2
+    assert calls() == ["debug paths"]
+    assert adapter._resolve_db(ctxs[1]) == want[1]
+    assert adapter._resolve_db(ctxs[0]) == want[0]
+    assert calls() == ["debug paths"] * 2
+
+
+def test_a_failed_debug_paths_is_not_remembered(tmp_path, monkeypatch):
+    log = tmp_path / "calls.log"
+    failing = tmp_path / "fakebin" / "opencode"
+    failing.parent.mkdir()
+    failing.write_text(f'#!/bin/sh\necho "$*" >> "{log}"\nexit 3\n')
+    failing.chmod(0o755)
+    adapter = get_adapter("opencode")
+    monkeypatch.setattr(adapter, "_bin", lambda ctx: str(failing))
+    ctx = DiscoveryContext(workspace=str(tmp_path), agent_name="opencode", home_dir=str(tmp_path / "home"))
+    default = str(tmp_path / "home" / ".local" / "share" / "opencode" / "opencode.db")
+    assert [adapter._resolve_db(ctx) for _ in range(2)] == [default] * 2
+    assert log.read_text().splitlines() == ["debug paths"] * 2