fix(selfhost): preserve legacy dual-review behavior for multi-provider AI_PROVIDER

apps/gittensory-ui/src/lib/selfhost-env-reference.ts

@@ -7,11 +7,11 @@ export type SelfHostEnvReferenceRow = {
 export const SELFHOST_ENV_REFERENCE_ROWS: SelfHostEnvReferenceRow[] = [
   {
     name: "AI_COMBINE",
-    firstReference: "src/selfhost/ai.ts:1173",
+    firstReference: "src/selfhost/ai.ts:1149",
   },
   {
     name: "AI_DUAL_REVIEW",
-    firstReference: "src/selfhost/ai.ts:1148",
+    firstReference: "src/selfhost/ai.ts:1151",
   },
   {
     name: "AI_EMBED_API_KEY",
@@ -27,7 +27,7 @@ export const SELFHOST_ENV_REFERENCE_ROWS: SelfHostEnvReferenceRow[] = [
   },
   {
     name: "AI_ON_MERGE",
-    firstReference: "src/selfhost/ai.ts:1175",
+    firstReference: "src/selfhost/ai.ts:1149",
   },
   {
     name: "AI_PROVIDER",
@@ -394,12 +394,12 @@ export const SELFHOST_ENV_REFERENCE_ROWS: SelfHostEnvReferenceRow[] = [
 export const SELFHOST_ENV_REFERENCE_MARKDOWN = [
   "| Name | First reference |",
   "| --- | --- |",
-  "| `AI_COMBINE` | `src/selfhost/ai.ts:1173` |",
-  "| `AI_DUAL_REVIEW` | `src/selfhost/ai.ts:1148` |",
+  "| `AI_COMBINE` | `src/selfhost/ai.ts:1149` |",
+  "| `AI_DUAL_REVIEW` | `src/selfhost/ai.ts:1151` |",
   "| `AI_EMBED_API_KEY` | `src/server.ts:443` |",
   "| `AI_EMBED_BASE_URL` | `src/server.ts:440` |",
   "| `AI_EMBED_MODEL` | `src/selfhost/ai.ts:1045` |",
-  "| `AI_ON_MERGE` | `src/selfhost/ai.ts:1175` |",
+  "| `AI_ON_MERGE` | `src/selfhost/ai.ts:1149` |",
   "| `AI_PROVIDER` | `src/selfhost/ai-config.ts:43` |",
   "| `ANTHROPIC_AI_BASE_URL` | `src/selfhost/ai.ts:1049` |",
   "| `ANTHROPIC_AI_MODEL` | `src/selfhost/ai.ts:109` |",

src/selfhost/ai.ts

@@ -1138,14 +1138,17 @@ function enabledEnvFlag(value: string | undefined): boolean {
 
 /** Resolve the self-host review plan from env. By default, `AI_PROVIDER=a,b` means one reviewer using `a` with
  *  `b` as the per-review fallback, so a Codex quota/auth outage can fall through to Claude Code without paying
- *  for two simultaneous reviewers. `AI_DUAL_REVIEW=1` opts back into the explicit two-reviewer mode where the
- *  first two providers run independently and `AI_COMBINE` / `AI_ON_MERGE` decide how to merge them. */
+ *  for two simultaneous reviewers. Existing multi-provider configs that explicitly set `AI_COMBINE` or
+ *  `AI_ON_MERGE` keep their two-reviewer behavior; `AI_DUAL_REVIEW=1` is the explicit opt-in for new dual
+ *  review configs. */
 export function resolveAiReviewerPlan(
   env: Record<string, string | undefined>,
 ): { reviewers: Array<{ model: string; fallback?: string | null | undefined }>; combine: CombineStrategy; onMerge: OnMerge | undefined } | undefined {
   const names = resolveProviderNames(env);
   if (names.length === 0) return undefined;
-  if (!enabledEnvFlag(env.AI_DUAL_REVIEW)) {
+  const hasLegacyDualReviewConfig = (env.AI_COMBINE ?? "").trim() !== "" || (env.AI_ON_MERGE ?? "").trim() !== "";
+  if (names.length === 1) return { reviewers: [{ model: names[0] as string }], combine: "single", onMerge: undefined };
+  if (!enabledEnvFlag(env.AI_DUAL_REVIEW) && !hasLegacyDualReviewConfig) {
     const primary = names[0] as string;
     const fallback = names.find((name) => name !== primary);
     return {
@@ -1159,7 +1162,6 @@ export function resolveAiReviewerPlan(
       onMerge: undefined,
     };
   }
-  if (names.length === 1) return { reviewers: [{ model: names[0] as string }], combine: "single", onMerge: undefined };
   // Fail loud when the two SLOTS the dual-review plan actually uses (the first two names) are the same
   // provider: routeProviders' `byName` map collapses duplicate provider names to one runtime instance, so
   // "dual review" would silently become "one provider called twice" -- no independent second opinion, and

test/unit/selfhost-ai.test.ts

@@ -675,13 +675,26 @@ describe("resolveProviderNames + resolveAiReviewerPlan (#dual-ai-combiner)", ()
       combine: "single",
       onMerge: undefined,
     });
-    expect(resolveAiReviewerPlan({ AI_PROVIDER: "codex,claude-code,ollama", AI_COMBINE: "consensus", AI_ON_MERGE: "both" })).toEqual({
+    expect(resolveAiReviewerPlan({ AI_PROVIDER: "codex,claude-code,ollama" })).toEqual({
       reviewers: [{ model: "codex", fallback: "claude-code" }],
       combine: "single",
       onMerge: undefined,
     });
   });
 
+  it("resolveAiReviewerPlan: legacy multi-provider combine/on-merge configs remain dual-review", () => {
+    expect(resolveAiReviewerPlan({ AI_PROVIDER: "codex,claude-code,ollama", AI_COMBINE: "consensus", AI_ON_MERGE: "both" })).toEqual({
+      reviewers: [{ model: "codex" }, { model: "claude-code" }],
+      combine: "consensus",
+      onMerge: "both",
+    });
+    expect(resolveAiReviewerPlan({ AI_PROVIDER: "codex,claude-code", AI_ON_MERGE: "either" })).toMatchObject({
+      reviewers: [{ model: "codex" }, { model: "claude-code" }],
+      combine: "synthesis",
+      onMerge: "either",
+    });
+  });
+
   it("resolveAiReviewerPlan: AI_DUAL_REVIEW=1 restores two independent reviewers and combine controls", () => {
     expect(resolveAiReviewerPlan({ AI_PROVIDER: "claude-code,codex", AI_DUAL_REVIEW: "1" })).toEqual({
       reviewers: [{ model: "claude-code" }, { model: "codex" }],