From 8efaa547dd46917bd0ffabe1b7963f47b03e1381 Mon Sep 17 00:00:00 2001
From: Vincent Koc <vincentkoc@ieee.org>
Date: Fri, 6 Mar 2026 00:29:02 -0500
Subject: [PATCH] Models: resolve GPT-5.3 Codex Spark fallback

---
 src/agents/model-compat.test.ts                      | 12 ++++++++++++
 src/agents/model-forward-compat.ts                   |  8 ++++++++
 .../pi-embedded-runner/model.forward-compat.test.ts  | 10 ++++++++++
 src/agents/pi-embedded-runner/model.test.ts          | 11 +++++++++++
 4 files changed, 41 insertions(+)

diff --git a/src/agents/model-compat.test.ts b/src/agents/model-compat.test.ts
index 232543ce86d..c8a0491dda3 100644
--- a/src/agents/model-compat.test.ts
+++ b/src/agents/model-compat.test.ts
@@ -368,6 +368,18 @@ describe("resolveForwardCompatModel", () => {
     expect(model?.maxTokens).toBe(128_000);
   });
 
+  it("resolves openai-codex gpt-5.3-codex-spark via codex template fallback", () => {
+    const registry = createRegistry({
+      "openai-codex/gpt-5.2-codex": createOpenAICodexTemplateModel("gpt-5.2-codex"),
+    });
+    const model = resolveForwardCompatModel("openai-codex", "gpt-5.3-codex-spark", registry);
+    expectResolvedForwardCompat(model, { provider: "openai-codex", id: "gpt-5.3-codex-spark" });
+    expect(model?.api).toBe("openai-codex-responses");
+    expect(model?.baseUrl).toBe("https://chatgpt.com/backend-api");
+    expect(model?.contextWindow).toBe(272_000);
+    expect(model?.maxTokens).toBe(128_000);
+  });
+
   it("resolves anthropic opus 4.6 via 4.5 template", () => {
     const registry = createRegistry({
       "anthropic/claude-opus-4-5": createTemplateModel("anthropic", "claude-opus-4-5"),
diff --git a/src/agents/model-forward-compat.ts b/src/agents/model-forward-compat.ts
index 95d13832cc7..558eb6624d2 100644
--- a/src/agents/model-forward-compat.ts
+++ b/src/agents/model-forward-compat.ts
@@ -275,6 +275,7 @@ export function augmentKnownForwardCompatModels(models: Model<Api>[]): Model<Api
 }
 
 const CODEX_GPT54_ELIGIBLE_PROVIDERS = new Set(["openai-codex"]);
+const CODEX_GPT53_SPARK_ELIGIBLE_PROVIDERS = new Set(["openai-codex"]);
 const CODEX_GPT53_ELIGIBLE_PROVIDERS = new Set(["openai-codex", "github-copilot"]);
 
 function resolveOpenAICodexForwardCompatModel(
@@ -291,6 +292,9 @@ function resolveOpenAICodexForwardCompatModel(
   if (lower === OPENAI_CODEX_GPT_54_MODEL_ID) {
     templateIds = OPENAI_CODEX_GPT_54_TEMPLATE_MODEL_IDS;
     eligibleProviders = CODEX_GPT54_ELIGIBLE_PROVIDERS;
+  } else if (lower === OPENAI_CODEX_GPT_53_SPARK_MODEL_ID) {
+    templateIds = [OPENAI_CODEX_GPT_53_MODEL_ID, ...OPENAI_CODEX_TEMPLATE_MODEL_IDS];
+    eligibleProviders = CODEX_GPT53_SPARK_ELIGIBLE_PROVIDERS;
   } else if (lower === OPENAI_CODEX_GPT_53_MODEL_ID) {
     templateIds = OPENAI_CODEX_TEMPLATE_MODEL_IDS;
     eligibleProviders = CODEX_GPT53_ELIGIBLE_PROVIDERS;
@@ -314,6 +318,10 @@ function resolveOpenAICodexForwardCompatModel(
     } as Model<Api>);
   }
 
+  if (lower === OPENAI_CODEX_GPT_53_SPARK_MODEL_ID) {
+    return buildOpenAICodexSparkFallbackModel();
+  }
+
   return normalizeModelCompat({
     id: trimmedModelId,
     name: trimmedModelId,
diff --git a/src/agents/pi-embedded-runner/model.forward-compat.test.ts b/src/agents/pi-embedded-runner/model.forward-compat.test.ts
index 56fd4654e91..50ac667a37e 100644
--- a/src/agents/pi-embedded-runner/model.forward-compat.test.ts
+++ b/src/agents/pi-embedded-runner/model.forward-compat.test.ts
@@ -57,6 +57,16 @@ describe("pi embedded model e2e smoke", () => {
     expect(result.model).toMatchObject(buildOpenAICodexForwardCompatExpectation("gpt-5.4"));
   });
 
+  it("builds an openai-codex forward-compat fallback for gpt-5.3-codex-spark", () => {
+    mockOpenAICodexTemplateModel();
+
+    const result = resolveModel("openai-codex", "gpt-5.3-codex-spark", "/tmp/agent");
+    expect(result.error).toBeUndefined();
+    expect(result.model).toMatchObject(
+      buildOpenAICodexForwardCompatExpectation("gpt-5.3-codex-spark"),
+    );
+  });
+
   it("keeps unknown-model errors for non-forward-compat IDs", () => {
     const result = resolveModel("openai-codex", "gpt-4.1-mini", "/tmp/agent");
     expect(result.model).toBeUndefined();
diff --git a/src/agents/pi-embedded-runner/model.test.ts b/src/agents/pi-embedded-runner/model.test.ts
index 25936e3d444..1697e812214 100644
--- a/src/agents/pi-embedded-runner/model.test.ts
+++ b/src/agents/pi-embedded-runner/model.test.ts
@@ -407,6 +407,17 @@ describe("resolveModel", () => {
     expect(result.model).toMatchObject(buildOpenAICodexForwardCompatExpectation("gpt-5.4"));
   });
 
+  it("builds an openai-codex fallback for gpt-5.3-codex-spark", () => {
+    mockOpenAICodexTemplateModel();
+
+    const result = resolveModel("openai-codex", "gpt-5.3-codex-spark", "/tmp/agent");
+
+    expect(result.error).toBeUndefined();
+    expect(result.model).toMatchObject(
+      buildOpenAICodexForwardCompatExpectation("gpt-5.3-codex-spark"),
+    );
+  });
+
   it("applies provider overrides to openai gpt-5.4 forward-compat models", () => {
     mockDiscoveredModel({
       provider: "openai",