fix(cli): install into an existing opencode.jsonc instead of a second file (#1560)

OpenCode reads either opencode.json or opencode.jsonc. We always wrote the
.json name, so a user whose real config is opencode.jsonc got a SECOND config
file that OpenCode ignores: the MCP server never appeared, while the installer
reported success. Silent, and indistinguishable from "the tool is broken".

The install target is now whichever file already exists, .jsonc first since it
is the one we used to miss. With neither present, .json is created exactly as
before, so fresh installs are unchanged. Other clients in this file (pochi,
kilo) already resolve .jsonc paths — OpenCode was the gap, not the exception.

Reported by @iandol in discussion #1560, who noticed their config was .jsonc
while the installer named .json. Verified by revert: the test fails without
the fix and passes with it.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

src/cli/cli.c

@@ -2432,6 +2432,20 @@ static void cbm_opencode_config_path(const char *home_dir, char *out, size_t out
         snprintf(out, out_sz, "%s", custom);
         return;
     }
+    /* OpenCode reads either opencode.json or opencode.jsonc. We always wrote
+     * the .json name, so a user whose real config is .jsonc got a SECOND file
+     * that OpenCode ignores — their MCP server silently never appeared, and the
+     * install looked like it had succeeded (discussion #1560). Prefer whichever
+     * file already exists, .jsonc first since it is the one we used to miss;
+     * with neither present, create .json as before. Other clients in this file
+     * (pochi, kilo) already carry .jsonc paths — OpenCode was the gap. */
+    char candidate[CLI_BUF_1K];
+    int written = snprintf(candidate, sizeof(candidate), "%s/.config/opencode/opencode.jsonc",
+                           home_dir ? home_dir : "");
+    if (written > 0 && (size_t)written < sizeof(candidate) && cbm_file_exists(candidate)) {
+        snprintf(out, out_sz, "%s", candidate);
+        return;
+    }
     snprintf(out, out_sz, "%s/.config/opencode/opencode.json", home_dir);
 }
 

tests/test_cli.c

@@ -7349,6 +7349,40 @@ TEST(cli_opencode_honors_custom_config) {
     PASS();
 }
 
+/* Discussion #1560: OpenCode reads either opencode.json or opencode.jsonc, but
+ * we always wrote the .json name. A user whose real config is .jsonc got a
+ * SECOND file that OpenCode ignores — the MCP server silently never appeared
+ * while the install reported success. Prefer an existing .jsonc; with neither
+ * present, .json is still created, so fresh installs are unchanged. */
+TEST(cli_opencode_prefers_existing_jsonc_config_discussion1560) {
+    char tmpdir[256];
+    snprintf(tmpdir, sizeof(tmpdir), "/tmp/cli-opencode-jsonc-XXXXXX");
+    if (!cbm_mkdtemp(tmpdir))
+        FAIL("cbm_mkdtemp failed");
+    char config_dir[512];
+    snprintf(config_dir, sizeof(config_dir), "%s/.config/opencode", tmpdir);
+    test_mkdirp(config_dir);
+    char jsonc_path[640];
+    snprintf(jsonc_path, sizeof(jsonc_path), "%s/opencode.jsonc", config_dir);
+    write_test_file(jsonc_path, "{\n  // user's hand-written config\n  \"theme\": \"dark\"\n}\n");
+
+    char *saved_path = save_test_env("PATH");
+    char *saved_file = save_test_env("OPENCODE_CONFIG");
+    cbm_setenv("PATH", tmpdir, 1);
+    cbm_unsetenv("OPENCODE_CONFIG");
+
+    char *json = cbm_build_install_plan_json(tmpdir, "/usr/local/bin/codebase-memory-mcp");
+    bool targets_jsonc = json && strstr(json, "/.config/opencode/opencode.jsonc") != NULL;
+
+    free(json);
+    restore_test_env("PATH", saved_path);
+    restore_test_env("OPENCODE_CONFIG", saved_file);
+    test_rmdir_r(tmpdir);
+    if (!targets_jsonc)
+        FAIL("an existing opencode.jsonc must be the install target, not a new opencode.json");
+    PASS();
+}
+
 TEST(cli_opencode_config_dir_detects_without_retargeting_global_json) {
     char tmpdir[256];
     snprintf(tmpdir, sizeof(tmpdir), "/tmp/cli-opencode-dir-XXXXXX");
@@ -12416,6 +12450,7 @@ SUITE(cli) {
     RUN_TEST(cli_antigravity_does_not_imply_gemini);
     RUN_TEST(cli_antigravity_plan_uses_documented_global_files);
     RUN_TEST(cli_opencode_honors_custom_config);
+    RUN_TEST(cli_opencode_prefers_existing_jsonc_config_discussion1560);
     RUN_TEST(cli_opencode_config_dir_detects_without_retargeting_global_json);
     RUN_TEST(cli_kiro_and_hermes_homes_are_honored);
     RUN_TEST(cli_detect_agents_finds_official_kiro_cli_executable);