docs(agent): say which side of a fallback the catalog may not know

The tuning doc read as if an unknown primary's values passed through. They
do not: the block never shows a graded knob for a model outside the
catalog, so a value stored under one is stale and the row's own field
decides. A test now pins that.

Author: mzxchandra

apps/sim/lib/workflows/blocks/fallback-models.test.ts

@@ -265,6 +265,22 @@ describe('resolveFallbackTuning', () => {
     expect(resolved.thinkingLevel).toBeUndefined()
   })
 
+  it('treats a value stored under an uncatalogued primary as stale, and lets the row decide', () => {
+    /** The block never shows a graded knob for a model outside the catalog. */
+    const stale = resolveFallbackTuning({ model: 'gpt-small' }, 'openrouter/custom', {
+      reasoningEffort: 'high',
+    })
+    expect(stale.reasoningEffort).toBeUndefined()
+    expect(stale.adjustments).toEqual(['reasoningEffort: high -> provider default'])
+
+    const own = resolveFallbackTuning(
+      { model: 'gpt-small', reasoningEffort: 'low' },
+      'openrouter/custom',
+      { reasoningEffort: 'high' }
+    )
+    expect(own.reasoningEffort).toBe('low')
+  })
+
   it('clamps temperature and max tokens to the fallback caps, keeping the input type', () => {
     const resolved = resolveFallbackTuning({ model: 'claude-sonnet-5' }, 'gpt-big', {
       temperature: '1.5',

apps/sim/lib/workflows/blocks/fallback-models.ts

@@ -310,8 +310,11 @@ function clampToCap(
  * Temperature and max output tokens are caps in the primary's terms, so they
  * are clamped to what the fallback allows rather than dropped: a low
  * temperature chosen for repeatability must survive, and "no more than N" still
- * holds under a smaller ceiling. A model the catalog does not know has no caps
- * and no lists, so everything passes through unchanged.
+ * holds under a smaller ceiling. A fallback the catalog does not know has no
+ * caps and no lists, so everything passes through to it unchanged. A primary
+ * the catalog does not know never showed a graded knob in the editor, so a
+ * value stored under it is stale and is not inherited; the row shows the field
+ * instead, and its own value is what applies.
  */
 export function resolveFallbackTuning(
   candidate: FallbackModelCandidate,