Preserve double dash values during flag alias parsing

docs/roadmap/remediation.md

@@ -215,7 +215,7 @@ passed on Go 1.26.8.
 
 ## R-6: Keep the flag interpretation pass consistent with value consumption
 
-Status: open. Priority: P2. Category: canonical/alias parsing divergence.
+Status: complete. Priority: P2. Category: canonical/alias parsing divergence.
 
 **Evidence:** [interpretFlagTokens](../../internal/cobra/flags.go#L28) refuses to
 consume a following `--` as the value of a value-taking flag in both the long
@@ -242,6 +242,13 @@ introducing a different operand/option convention.
 values. Cover canonical and aliased long/short spellings, and preserve ordinary
 termination when `--` occurs after a completed value or boolean flag.
 
+**Completed:** The alias interpretation pass now consumes the next token for
+value-taking long and short flags even when that value is `--`, matching backend
+arity. All four canonical/alias long/short regressions failed before the fix and
+now retain the value, later alias occurrences, original spellings, and genuine
+post-value terminators. Boolean/value termination cases also pass. No accepted
+value was prohibited. The complete offline root suite passed on Go 1.26.8.
+
 ## R-7: Retain entered flag spellings in parser-level usage failures
 
 Status: open. Priority: P3. Category: incomplete diagnostic adaptation.

internal/cobra/flags.go

@@ -56,7 +56,7 @@ func interpretFlagTokens(argv []string, flags []commandmeta.Flag, aliases []comm
 				index++
 				continue
 			}
-			if !flag.Boolean && index+1 < len(argv) && argv[index+1] != "--" {
+			if !flag.Boolean && index+1 < len(argv) {
 				interpreted = append(interpreted, "--"+flag.Name+"="+argv[index+1])
 				index += 2
 				continue
@@ -101,7 +101,7 @@ func interpretFlagTokens(argv []string, flags []commandmeta.Flag, aliases []comm
 					interpreted = append(interpreted, "--"+flag.Name+"="+value)
 					break
 				}
-				if index+1 < len(argv) && argv[index+1] != "--" {
+				if index+1 < len(argv) {
 					interpreted = append(interpreted, "--"+flag.Name+"="+argv[index+1])
 					index += 2
 					consumedNext = true

internal/cobra/flags_test.go

@@ -92,6 +92,29 @@ func TestParseFlagAliasesPreserveValuesAndTerminators(t *testing.T) {
 	}
 }
 
+func TestParseConsumesDoubleDashAsAFlagValue(t *testing.T) {
+	for _, spelling := range []string{"--color", "--colour", "-c", "-C"} {
+		t.Run(spelling, func(t *testing.T) {
+			result := Parse(flagGrammarTree(), []string{"run", spelling, "--", "--taggy=one", "--colour=red", "--", "--taggy=operand"}, flagGrammarOptions())
+			if result.Failure != nil {
+				t.Fatalf("parse failed: %s", result.Failure.Message)
+			}
+			if !reflect.DeepEqual(result.FlagValues[0], []string{"--", "red"}) || !reflect.DeepEqual(result.FlagValues[4], []string{"one"}) {
+				t.Errorf("flag values = %#v", result.FlagValues)
+			}
+			if !reflect.DeepEqual(result.FlagSpellings[0], []string{spelling, "--colour"}) || !reflect.DeepEqual(result.Operands, []string{"--taggy=operand"}) {
+				t.Errorf("spellings = %#v, operands = %#v", result.FlagSpellings, result.Operands)
+			}
+		})
+	}
+	for _, args := range [][]string{{"run", "-v", "--", "--colour"}, {"run", "--color", "blue", "--", "--colour"}} {
+		result := Parse(flagGrammarTree(), args, flagGrammarOptions())
+		if result.Failure != nil || !reflect.DeepEqual(result.Operands, []string{"--colour"}) {
+			t.Errorf("Parse(%q) = %#v", args, result)
+		}
+	}
+}
+
 func TestParseHelpAliasAndUnknownShortMembers(t *testing.T) {
 	result := Parse(flagGrammarTree(), []string{"run", "--hlep"}, flagGrammarOptions())
 	if result.Failure != nil || !result.HelpRequested {