diff --git a/src/mcp/mcp.c b/src/mcp/mcp.c
index 75ff8e396c..4df0a4ffeb 100644
--- a/src/mcp/mcp.c
+++ b/src/mcp/mcp.c
@@ -1481,24 +1481,50 @@ static bool repo_path_is_absolute(const char *path) {
 #endif
 }
 
+bool cbm_validate_project_name(const char *project);
+
+static bool has_non_ascii_byte(const char *s) {
+    for (; *s; s++) {
+        if ((unsigned char)*s >= 0x80) {
+            return true;
+        }
+    }
+    return false;
+}
+
+/* #1827: a bare non-ASCII selector, typically the real folder name of a repo
+ * under a CJK path, is encoded exactly like the path segment it came from
+ * (non-ASCII bytes -> hex, #571), so the exact/tail lookup matches the stored
+ * identity. Stored names never change; ASCII selectors keep their existing
+ * validation; a selector that collapses to the "root" fallback is left alone
+ * so it never selects the root project. */
+static bool bare_project_encoding_usable(const char *encoded) {
+    return strcmp(encoded, "root") != 0 && cbm_validate_project_name(encoded);
+}
+
 static char *normalize_project_arg(char *project) {
-    if (!project || (!strchr(project, '/') && !strchr(project, '\\'))) {
+    if (!project) {
         return project;
     }
-
-    project = canonicalize_repo_path_if_exists(project);
-    char *normalized = cbm_project_name_from_path(project);
-    if (normalized) {
-        free(project);
-        return normalized;
+    char *normalized = NULL;
+    bool bare = !strchr(project, '/') && !strchr(project, '\\');
+    if (bare) {
+        if (has_non_ascii_byte(project)) {
+            normalized = cbm_project_name_sanitize(project);
+        }
+    } else {
+        project = canonicalize_repo_path_if_exists(project);
+        normalized = cbm_project_name_from_path(project);
     }
-    return project;
+    /* Keep exactly one of the two strings and release the other. */
+    bool use_normalized = normalized && (!bare || bare_project_encoding_usable(normalized));
+    free(use_normalized ? project : normalized);
+    return use_normalized ? normalized : project;
 }
 
 /* Forward decls — defined below alongside store resolution. */
 static const char *cache_dir(char *buf, size_t bufsz);
 static bool is_project_db_file(const char *name, size_t len);
-bool cbm_validate_project_name(const char *project);
 
 /* #1025: agents naturally pass the repo FOLDER name ("codebase-memory-mcp"),
  * but indexed project names derive from the full path
diff --git a/src/pipeline/fqn.c b/src/pipeline/fqn.c
index 9d0861155e..96e959a0be 100644
--- a/src/pipeline/fqn.c
+++ b/src/pipeline/fqn.c
@@ -428,9 +428,13 @@ char *cbm_project_name_from_path(const char *abs_path) {
         cbm_normalize_path_sep(real);
         name_path = real;
     }
+    return cbm_project_name_sanitize(name_path);
+}
 
-    /* Work on mutable copy */
-    char *path = strdup(name_path);
+char *cbm_project_name_sanitize(const char *name_path) {
+    /* Work on mutable copy. NULL and "" map to "" and fall through to the
+     * empty-after-trim "root" return below. */
+    char *path = strdup(name_path ? name_path : "");
     if (!path) {
         return NULL;
     }
diff --git a/src/pipeline/pipeline.h b/src/pipeline/pipeline.h
index e5a672cb0b..8cff690643 100644
--- a/src/pipeline/pipeline.h
+++ b/src/pipeline/pipeline.h
@@ -206,6 +206,13 @@ char *cbm_pipeline_resolve_relative_import(const char *source_rel, const char *m
  * Caller must free() the returned string. */
 char *cbm_project_name_from_path(const char *abs_path);
 
+/* The name-mapping half of cbm_project_name_from_path, WITHOUT path
+ * canonicalization: maps any string to the stored project-name form (unsafe
+ * ASCII -> '-', non-ASCII bytes -> two hex digits, dash/dot collapse, trim,
+ * #624 length cap). Lets a selector such as a bare non-ASCII folder name be
+ * encoded exactly like the segment it came from (#1827). Caller frees. */
+char *cbm_project_name_sanitize(const char *name_path);
+
 /* ── Function Registry ──────────────────────────────────────────── */
 
 typedef struct cbm_registry cbm_registry_t;
diff --git a/tests/test_mcp.c b/tests/test_mcp.c
index ffa9ea3a3b..5ad8a6b928 100644
--- a/tests/test_mcp.c
+++ b/tests/test_mcp.c
@@ -8382,6 +8382,91 @@ TEST(tool_project_arg_resolves_unique_tail_issue1025) {
     PASS();
 }
 
+/* #1827: a repo under a non-ASCII folder ("中文测试仓库") gets a project name
+ * whose non-ASCII bytes are hex-transliterated (#571), e.g.
+ * "...-e4b8ade69687e6b58be8af95e4bb93e5ba93". That stored identity stays
+ * stable (it is the cache DB file name), but the project must stay reachable
+ * by what the user actually knows: the real path (already normalized) AND the
+ * real folder name, which the #1025 tail match skipped because the raw
+ * non-ASCII name fails the project-name validator before any lookup. */
+TEST(tool_project_arg_resolves_non_ascii_folder_issue1827) {
+    char parent[CBM_SZ_256];
+    char cache[CBM_SZ_256];
+    snprintf(parent, sizeof(parent), "/tmp/cbm-i1827a-XXXXXX");
+    snprintf(cache, sizeof(cache), "/tmp/cbm-i1827c-XXXXXX");
+    if (!cbm_mkdtemp(parent) || !cbm_mkdtemp(cache)) {
+        FAIL("mkdtemp failed");
+    }
+    const char *folder = "\xe4\xb8\xad\xe6\x96\x87\xe6\xb5\x8b\xe8\xaf\x95\xe4\xbb\x93\xe5\xba\x93";
+    char repo[CBM_SZ_512];
+    snprintf(repo, sizeof(repo), "%s/%s", parent, folder);
+    ASSERT_TRUE(cbm_mkdir_p(repo, 0755));
+    char file[CBM_SZ_1K];
+    snprintf(file, sizeof(file), "%s/hello.js", repo);
+    FILE *f = cbm_fopen(file, "w");
+    ASSERT_NOT_NULL(f);
+    fprintf(f, "function greet_1827(){return 'hi';}\n");
+    fclose(f);
+
+    const char *saved_cache = getenv("CBM_CACHE_DIR");
+    char *saved_cache_copy = saved_cache ? cbm_strdup(saved_cache) : NULL;
+    cbm_setenv("CBM_CACHE_DIR", cache, 1);
+    cbm_setenv("CBM_INDEX_SUPERVISOR", "0", 1);
+
+    cbm_mcp_server_t *srv = cbm_mcp_server_new(NULL);
+    ASSERT_NOT_NULL(srv);
+    char args[CBM_SZ_2K];
+    snprintf(args, sizeof(args), "{\"repo_path\":\"%s\"}", repo);
+    char *r = cbm_mcp_handle_tool(srv, "index_repository", args);
+    ASSERT_NOT_NULL(r);
+    free(r);
+
+    /* The stored identity keeps its existing hex form (no DB rename). */
+    char *stored = cbm_project_name_from_path(repo);
+    ASSERT_NOT_NULL(stored);
+    ASSERT_NOT_NULL(strstr(stored, "-e4b8ade69687e6b58be8af95e4bb93e5ba93"));
+    free(stored);
+
+    /* 1. The real folder name resolves (RED before: "project not found"). */
+    snprintf(args, sizeof(args), "{\"project\":\"%s\",\"name_pattern\":\".*greet_1827.*\"}",
+             folder);
+    r = cbm_mcp_handle_tool(srv, "search_graph", args);
+    ASSERT_NOT_NULL(r);
+    if (strstr(r, "project not found")) {
+        fprintf(stderr, "  [1827] FAIL folder name did not resolve: %.200s\n", r);
+    }
+    ASSERT_NULL(strstr(r, "project not found"));
+    ASSERT_NOT_NULL(strstr(r, "greet_1827"));
+    free(r);
+
+    /* 2. The real path keeps resolving. */
+    snprintf(args, sizeof(args), "{\"project\":\"%s\",\"name_pattern\":\".*greet_1827.*\"}", repo);
+    r = cbm_mcp_handle_tool(srv, "search_graph", args);
+    ASSERT_NOT_NULL(r);
+    ASSERT_NULL(strstr(r, "project not found"));
+    ASSERT_NOT_NULL(strstr(r, "greet_1827"));
+    free(r);
+
+    /* 3. A non-ASCII name matching nothing stays a not-found error. */
+    r = cbm_mcp_handle_tool(srv, "search_graph",
+                            "{\"project\":\"\xe4\xb8\x8d\xe5\xad\x98\xe5\x9c\xa8\","
+                            "\"name_pattern\":\".*\"}");
+    ASSERT_NOT_NULL(r);
+    ASSERT_NOT_NULL(strstr(r, "project not found"));
+    free(r);
+
+    cbm_mcp_server_free(srv);
+    if (saved_cache_copy) {
+        cbm_setenv("CBM_CACHE_DIR", saved_cache_copy, 1);
+        free(saved_cache_copy);
+    } else {
+        cbm_unsetenv("CBM_CACHE_DIR");
+    }
+    th_rmtree(parent);
+    th_rmtree(cache);
+    PASS();
+}
+
 /* Regression for #604: path scopes architecture totals and content. */
 TEST(tool_get_architecture_path_scoping) {
     cbm_mcp_server_t *srv = cbm_mcp_server_new(NULL);
@@ -20597,6 +20682,7 @@ SUITE(mcp) {
     RUN_TEST(tool_get_architecture_accepts_project_name_alias_issue640);
     RUN_TEST(tool_search_graph_accepts_project_name_alias_issue640);
     RUN_TEST(tool_project_arg_resolves_unique_tail_issue1025);
+    RUN_TEST(tool_project_arg_resolves_non_ascii_folder_issue1827);
     RUN_TEST(tool_get_architecture_path_scoping);
     RUN_TEST(tool_query_graph_missing_query);