diff --git a/gitgalaxy/core/detector.py b/gitgalaxy/core/detector.py
index 429144085..0e2b55831 100644
--- a/gitgalaxy/core/detector.py
+++ b/gitgalaxy/core/detector.py
@@ -3377,6 +3377,45 @@ def _count_haskell_pattern_list(self, text: str) -> int:
             i += 1
         return count
 
+    def _count_tcl_arg_list(self, text: str) -> int:
+        """
+        Counts Tcl argument list parameters, aware of brace nesting.
+        Tcl uses {name default_value} for optional arguments. This entire
+        nested brace structure counts as a single parameter.
+        Whitespace separates parameters only at depth 0.
+        """
+        depth = 0
+        count = 0
+        at_boundary = True
+        i = 0
+        while i < len(text):
+            ch = text[i]
+            if ch == "\\":
+                i += 2
+                continue
+            if ch == "{":
+                if depth == 0 and at_boundary:
+                    count += 1
+                    at_boundary = False
+                depth += 1
+                i += 1
+                continue
+            if ch == "}":
+                if depth > 0:
+                    depth -= 1
+                i += 1
+                continue
+            if ch in " \t\r\n":
+                if depth == 0:
+                    at_boundary = True
+                i += 1
+                continue
+            if depth == 0 and at_boundary:
+                count += 1
+                at_boundary = False
+            i += 1
+        return count
+
     def _calculate_block_metrics(
         self,
         name: str,
@@ -3479,6 +3518,7 @@ def _calculate_block_metrics(
                     arrow_count_groups = rules.get("_args_arrow_count_groups")
                     colon_selector_groups = rules.get("_args_colon_selector_groups")
                     pattern_list_groups = rules.get("_args_pattern_list_groups")
+                    tcl_pattern_list_groups = rules.get("_args_tcl_pattern_list_groups")
                     findall_max_groups = rules.get("_args_findall_max_groups")
                     findall_sum_groups = rules.get("_args_findall_sum_groups")
                     if findall_max_groups and arg_match.lastindex in findall_max_groups:
@@ -3526,6 +3566,11 @@ def _calculate_block_metrics(
                             else:
                                 total += 1
                         args_count = total
+                    elif tcl_pattern_list_groups and arg_match.lastindex in tcl_pattern_list_groups:
+                        # Tcl default-value braces (#1512):
+                        # Tcl allows nested braces like {db db} for default
+                        # parameter values, which should count as a single argument.
+                        args_count = self._count_tcl_arg_list(stripped)
                     elif pattern_list_groups and arg_match.lastindex in pattern_list_groups:
                         # Haskell signature-less equation LHS (#1505 follow-up):
                         # a naive whitespace split would wrongly split a single
diff --git a/gitgalaxy/standards/language_standards.py b/gitgalaxy/standards/language_standards.py
index 197527cad..0cf5d4018 100644
--- a/gitgalaxy/standards/language_standards.py
+++ b/gitgalaxy/standards/language_standards.py
@@ -12734,6 +12734,8 @@ class PrismConfigSchema(TypedDict):
                 r"^[ \t]*proc[ \t\n]+[a-zA-Z0-9_:\-!?]+[ \t\n]+\{((?:[^{}]|\{(?:[^{}]|\{(?:[^{}]|\{[^{}]*\})*\})*\})*)\}",
                 re.M,
             ),
+            # Tcl default-value argument lists (#1512): opt-in for depth-aware braced parameter parsing.
+            "_args_tcl_pattern_list_groups": {1},
             # 3. linear (Sequential Boundaries)
             # Structural boundaries. EXCLUDES: global/upvar (globals/heat).
             "structural_boundaries": re.compile(r"\b(?:proc|return|break|continue|namespace|variable|yield)\b"),
diff --git a/tests/extraction/languages/test_tcl.py b/tests/extraction/languages/test_tcl.py
index 55423d7a0..d756f752f 100644
--- a/tests/extraction/languages/test_tcl.py
+++ b/tests/extraction/languages/test_tcl.py
@@ -54,6 +54,8 @@
         ("proc TargetFunc {a b} {", "a b"),
         ("proc ::namespace::TargetFunc {args} {", "args"),
         ("proc TargetFunc {{a 1} b} {", "{a 1} b"),
+        ("proc faultsim_integrity_check {{db db}} {", "{db db}"),
+        ("proc TargetFunc {a {b 2} {c {nested list}}} {", "a {b 2} {c {nested list}}"),
     ],
     "invalid": [
         "TargetFunc a b",