Add OpenCode Go as a cleanup and agent provider

OpenCode Go serves open coding models from an OpenAI-compatible endpoint. It cannot transcribe, so it joins
the two LLM jobs: transcript cleanup and the plain-chat agent. The key
falls back to OPENCODE_API_KEY, and api.chat() stops hardcoding the
OpenRouter name so the same call serves both.

tests/test_assistant.py

@@ -59,6 +59,7 @@ class Provider(DikteTest):
         self.assertEqual(assistant.executable("claude"), "claude")
         self.assertEqual(assistant.executable("codex"), "codex")
         self.assertEqual(assistant.executable("openrouter"), "")
+        self.assertEqual(assistant.executable("opencode"), "")
 
     def test_what_each_one_is_called(self):
         self.assertEqual(assistant.display_name(self.config()), "Claude")
@@ -67,6 +68,9 @@ class Provider(DikteTest):
         self.assertEqual(
             assistant.display_name(self.config(assistant_provider="openrouter")),
             "OpenRouter")
+        self.assertEqual(
+            assistant.display_name(self.config(assistant_provider="opencode")),
+            "OpenCode Go")
 
 
 class Effort(unittest.TestCase):
@@ -507,6 +511,41 @@ class AskOpenRouter(DikteTest):
             assistant.ask("when is it", conf)
 
 
+class AskOpenCode(DikteTest):
+    def test_a_question_and_an_answer(self):
+        conf = self.config(assistant_provider="opencode",
+                           opencode_api_key="opencode-test-key")
+        with fake_urlopen({"choices": [{"message": {"content": "on Thursday"}}]}):
+            answer, warning = assistant.ask("when is it", conf)
+        self.assertEqual(answer, "on Thursday")
+        self.assertEqual(warning, "")
+
+    def test_the_conversation_is_ours_to_keep(self):
+        conf = self.config(assistant_provider="opencode",
+                           opencode_api_key="opencode-test-key")
+        with fake_urlopen({"choices": [{"message": {"content": "on Thursday"}}]}):
+            assistant.ask("when is it", conf)
+        stored = assistant.read_messages("opencode", 1800)
+        self.assertEqual([row["content"] for row in stored],
+                         ["when is it", "on Thursday"])
+
+    def test_the_model_and_endpoint_are_opencode_s_own(self):
+        conf = self.config(assistant_provider="opencode",
+                           opencode_api_key="opencode-test-key",
+                           assistant_opencode_model="glm-5.3")
+        with fake_urlopen({"choices": [{"message": {"content": "on Thursday"}}]}) as calls:
+            assistant.ask("when is it", conf)
+        sent = json.loads(calls[0].data.decode("utf-8"))
+        self.assertEqual(sent["model"], "glm-5.3")
+        self.assertIn("https://opencode.ai/zen/go/v1/chat/completions",
+                      calls[0].full_url)
+
+    def test_an_api_failure_reads_as_an_assistant_failure(self):
+        conf = self.config(assistant_provider="opencode")
+        with self.assertRaises(assistant.AssistantError):
+            assistant.ask("when is it", conf)
+
+
 class Ask(DikteTest):
     def test_a_cli_that_is_not_installed_says_where_to_change_it(self):
         with only_these_tools(), \

tests/test_cleanup.py

@@ -50,6 +50,7 @@ class Provider(DikteTest):
         self.assertEqual(cleanup.executable("claude"), "claude")
         self.assertEqual(cleanup.executable("codex"), "codex")
         self.assertEqual(cleanup.executable("openrouter"), "")
+        self.assertEqual(cleanup.executable("opencode"), "")
 
     def test_the_model_named_in_the_history_is_the_one_that_did_it(self):
         self.assertEqual(cleanup.model(self.config(cleanup_model="some/model")),
@@ -65,6 +66,9 @@ class Provider(DikteTest):
         self.assertEqual(
             cleanup.model(self.config(cleanup_provider="codex",
                                       cleanup_codex_model="gpt-5.4")), "gpt-5.4")
+        self.assertEqual(
+            cleanup.model(self.config(cleanup_provider="opencode",
+                                      cleanup_opencode_model="glm-5.3")), "glm-5.3")
 
 
 class OpenRouter(DikteTest):
@@ -86,6 +90,32 @@ class OpenRouter(DikteTest):
         self.assertEqual(calls, [])
 
 
+class OpenCode(DikteTest):
+    def test_it_is_one_request_with_the_settings_as_they_were(self):
+        conf = self.config(cleanup_provider="opencode",
+                           opencode_api_key="opencode-test-key",
+                           cleanup_opencode_model="some/model",
+                           cleanup_reasoning="low")
+        with mock.patch.object(api, "cleanup", return_value="Done.") as call:
+            self.assertEqual(cleanup.run("uh, done", conf, "the rules"), "Done.")
+        text, key, model, prompt = call.call_args.args
+        self.assertEqual((text, key, model, prompt),
+                         ("uh, done", "opencode-test-key", "some/model", "the rules"))
+        self.assertEqual(call.call_args.kwargs["reasoning"], "low")
+        self.assertEqual(call.call_args.kwargs["provider"], "opencode")
+        self.assertEqual(call.call_args.kwargs["service"], "OpenCode Go")
+        self.assertEqual(call.call_args.kwargs["base_url"],
+                         "https://opencode.ai/zen/go/v1")
+
+    def test_no_cli_is_started_for_it(self):
+        conf = self.config(cleanup_provider="opencode",
+                           opencode_api_key="opencode-test-key")
+        patcher, calls = fake_run(stdout="never")
+        with patcher, mock.patch.object(api, "cleanup", return_value="Done."):
+            cleanup.run("uh, done", conf, "the rules")
+        self.assertEqual(calls, [])
+
+
 class ClaudeCode(DikteTest):
     def setUp(self):
         super().setUp()