refactor(sse): extract shared Claude effort-model predicate

open-sse/utils/claudeEffortVariants.ts

@@ -64,6 +64,17 @@ export function formatClaudeEffortLabel(level: string): string {
   return level.charAt(0).toUpperCase() + level.slice(1);
 }
 
+/**
+ * Whether `bareModelId` (no provider prefix, no effort suffix) is a real,
+ * effort-capable Claude-family model — the single source of truth used both to
+ * decide whether the catalog should advertise an effort variant AND whether
+ * dispatch-time stripping should unwind one back to this model.
+ */
+export function isKnownClaudeEffortBaseModel(bareModelId: string): boolean {
+  const spec = getModelSpec(bareModelId);
+  return spec?.supportsThinking === true && CLAUDE_NAME_RE.test(bareModelId);
+}
+
 /**
  * Whether the catalog should advertise reasoning-effort variants for this entry.
  *
@@ -84,10 +95,7 @@ export function shouldExposeClaudeEffortVariants(
   if (CLAUDE_EFFORT_SUFFIX_RE.test(id)) return false;
 
   const name = bareModelName(id);
-  const spec = getModelSpec(name);
-  if (!spec) return false;
-
-  return spec.supportsThinking === true && CLAUDE_NAME_RE.test(name);
+  return isKnownClaudeEffortBaseModel(name);
 }
 
 /**

tests/unit/claude-effort-variants.test.ts

@@ -6,6 +6,7 @@ import {
   CLAUDE_XHIGH_EFFORT_LEVEL,
   formatClaudeEffortLabel,
   shouldExposeClaudeEffortVariants,
+  isKnownClaudeEffortBaseModel,
   claudeEffortLevelsFor,
   appendClaudeEffortVariants,
 } from "../../open-sse/utils/claudeEffortVariants.ts";
@@ -63,6 +64,26 @@ test("non-string / empty / non-object ids never match", () => {
   assert.equal(shouldExposeClaudeEffortVariants({ id: 42 as never }), false);
 });
 
+// ── isKnownClaudeEffortBaseModel ─────────────────────────────────────────────
+
+test("isKnownClaudeEffortBaseModel returns true for a real effort-capable Claude model", () => {
+  assert.equal(isKnownClaudeEffortBaseModel("claude-fable-5"), true);
+});
+
+test("isKnownClaudeEffortBaseModel returns false for a non-Claude model", () => {
+  assert.equal(isKnownClaudeEffortBaseModel("gpt-4o"), false);
+});
+
+test("isKnownClaudeEffortBaseModel returns false for an unregistered model id", () => {
+  assert.equal(isKnownClaudeEffortBaseModel("totally-unregistered-model-xyz"), false);
+});
+
+test("isKnownClaudeEffortBaseModel returns false for a non-Claude model that also supports thinking (SC-1)", () => {
+  // gpt-5.5 has supportsThinking:true in MODEL_SPECS (like 36+ other non-Claude models) —
+  // the /claude/i name check is the only thing excluding it, not the thinking flag alone.
+  assert.equal(isKnownClaudeEffortBaseModel("gpt-5.5"), false);
+});
+
 // ── claudeEffortLevelsFor ────────────────────────────────────────────────────
 
 test("xHigh is added only for models that support it", () => {