review: pin off-value wire contract, scope compat inheritance to the entry's api, update the superseded note

Review findings on #1977, each verified before acting: the 2026-08-03
declared-provider-catalog note is updated in place and cross-linked both
ways now that reasoningEfforts/compat reopened half of its rejected
alternative; resolveModelCompat inherits the catalog entry's compat only
while the resolved api still is the entry's own, so a route-level api
repoint no longer merges another protocol's shape as a completions base;
the off-with-value promise gains a request-boundary test proving pi-ai
reads thinkingLevelMap.off when the reasoning option is absent (and the
catalog-level test name stops overclaiming); the cannot-stop-thinking
wording narrows to what is actually enforced (no Off offered, explicit
Off refused — an effortless request goes out bare); the z.const(null)
comment attributes null passthrough to schemastery's nullable
short-circuit; the baseten drift-gate claim names its verification
source; and the layered-merge delete gap for dict keys is documented
under Known Limitations with the atomic-leaf follow-up in #2003.

packages/llm/llm-pi-ai/src/catalog.ts

@@ -347,9 +347,13 @@ function resolveModelCompat(
     }
     return {}
   }
-  // The installed entry's compat matches its own api, so on an
-  // openai-completions model it is the completions shape.
-  const inherited: OpenAICompletionsCompat | undefined = base?.compat
+  // The installed entry's compat matches the entry's OWN api — a route-level
+  // `api` repoint (an anthropic catalog served through an OpenAI-compatible
+  // gateway) leaves `base.compat` in the other protocol's shape, so it is
+  // inherited only while the resolved api still is the entry's. A repointed
+  // model starts from pi-ai's baseURL-derived detection instead, which is
+  // what a protocol change means for every other compat field too.
+  const inherited: OpenAICompletionsCompat | undefined = base?.api === api ? base.compat : undefined
   return {
     compat: {
       ...inherited,

packages/llm/llm-pi-ai/src/config.ts

@@ -161,12 +161,14 @@ const compatProfile: z<PiAiCompatProfile> = z.object({
 })
 
 /**
- * Keys are the offered levels, values their wire spellings. `z.const(null)`
- * keeps a valueless key (`off:`) alive through validation — only resolution
- * decides which levels may leave the value empty, so the diagnostic can name
- * the route and model. The assertion narrows schemastery's `Dict`, which
- * types every literal key as required; dict validation is per-present-key, so
- * the runtime shape is the partial record.
+ * Keys are the offered levels, values their wire spellings. A valueless key
+ * (`off:`) survives validation because schemastery passes nullable data
+ * through before any member schema runs — `z.const(null)` only shapes the
+ * error for non-null wrong values and what a configuration surface renders.
+ * Only resolution decides which levels may leave the value empty, so the
+ * diagnostic can name the route and model. The assertion narrows
+ * schemastery's `Dict`, which types every literal key as required; dict
+ * validation is per-present-key, so the runtime shape is the partial record.
  */
 const reasoningEfforts = z.dict(
   z.union([z.string(), z.const(null)]),