diff --git a/.changeset/add-gpt-5-4.md b/.changeset/add-gpt-5-4.md
new file mode 100644
index 00000000..b38a81e9
--- /dev/null
+++ b/.changeset/add-gpt-5-4.md
@@ -0,0 +1,5 @@
+---
+"perstack": patch
+---
+
+feat: add GPT-5.4, Gemini 3.1 Pro Preview, and Gemini 3.1 Flash Lite Preview to known models
diff --git a/packages/core/src/known-models/index.ts b/packages/core/src/known-models/index.ts
index 7af934df..e0f9ee92 100644
--- a/packages/core/src/known-models/index.ts
+++ b/packages/core/src/known-models/index.ts
@@ -70,6 +70,13 @@ export const knownModels = [
   {
     provider: "google",
     models: [
+      // https://ai.google.dev/gemini-api/docs/models/gemini-3.1-pro-preview
+      {
+        name: "gemini-3.1-pro-preview",
+        tier: "high" as const,
+        contextWindow: 1_048_576,
+        maxOutputTokens: 65_536,
+      },
       // https://ai.google.dev/gemini-api/docs/models#gemini-3-flash
       {
         name: "gemini-3-flash-preview",
@@ -98,6 +105,13 @@ export const knownModels = [
         contextWindow: 1_048_576,
         maxOutputTokens: 65_536,
       },
+      // https://ai.google.dev/gemini-api/docs/models/gemini-3.1-flash-lite-preview
+      {
+        name: "gemini-3.1-flash-lite-preview",
+        tier: "low" as const,
+        contextWindow: 1_048_576,
+        maxOutputTokens: 65_536,
+      },
       // https://ai.google.dev/gemini-api/docs/models#gemini-2.5-flash-lite
       {
         name: "gemini-2.5-flash-lite",
@@ -110,6 +124,13 @@ export const knownModels = [
   {
     provider: "openai",
     models: [
+      // https://developers.openai.com/api/docs/models/gpt-5.4
+      {
+        name: "gpt-5.4",
+        tier: "high" as const,
+        contextWindow: 1_050_000,
+        maxOutputTokens: 128_000,
+      },
       // https://platform.openai.com/docs/models/gpt-5.2-pro
       {
         name: "gpt-5.2-pro",
diff --git a/packages/core/src/known-models/model-tiers.test.ts b/packages/core/src/known-models/model-tiers.test.ts
index b6d0f9ec..2b765c76 100644
--- a/packages/core/src/known-models/model-tiers.test.ts
+++ b/packages/core/src/known-models/model-tiers.test.ts
@@ -27,13 +27,13 @@ describe("@perstack/core: resolveModelTier", () => {
   it("resolves openai tiers", () => {
     expect(resolveModelTier("openai", "low")).toBe("gpt-5-nano")
     expect(resolveModelTier("openai", "middle")).toBe("gpt-5-mini")
-    expect(resolveModelTier("openai", "high")).toBe("gpt-5.2-pro")
+    expect(resolveModelTier("openai", "high")).toBe("gpt-5.4")
   })
 
   it("resolves google tiers", () => {
-    expect(resolveModelTier("google", "low")).toBe("gemini-2.5-flash-lite")
+    expect(resolveModelTier("google", "low")).toBe("gemini-3.1-flash-lite-preview")
     expect(resolveModelTier("google", "middle")).toBe("gemini-3-flash-preview")
-    expect(resolveModelTier("google", "high")).toBe("gemini-3-pro-preview")
+    expect(resolveModelTier("google", "high")).toBe("gemini-3.1-pro-preview")
   })
 
   it("resolves deepseek tiers", () => {
@@ -48,13 +48,13 @@ describe("@perstack/core: resolveModelTier", () => {
   })
 
   it("falls back to base provider for cloud-hosted providers", () => {
-    expect(resolveModelTier("azure-openai", "high")).toBe("gpt-5.2-pro")
+    expect(resolveModelTier("azure-openai", "high")).toBe("gpt-5.4")
     expect(resolveModelTier("azure-openai", "middle")).toBe("gpt-5-mini")
     expect(resolveModelTier("azure-openai", "low")).toBe("gpt-5-nano")
     expect(resolveModelTier("amazon-bedrock", "high")).toBe("claude-opus-4-6")
     expect(resolveModelTier("amazon-bedrock", "low")).toBe("claude-haiku-4-5")
-    expect(resolveModelTier("google-vertex", "high")).toBe("gemini-3-pro-preview")
-    expect(resolveModelTier("google-vertex", "low")).toBe("gemini-2.5-flash-lite")
+    expect(resolveModelTier("google-vertex", "high")).toBe("gemini-3.1-pro-preview")
+    expect(resolveModelTier("google-vertex", "low")).toBe("gemini-3.1-flash-lite-preview")
   })
 
   it("returns undefined for provider with no matching tier", () => {