fix(app): model selection persist by session (#17348)

1 files changed, 13 insertions, 120 deletions

diff --git a/packages/app/src/pages/session/session-model-helpers.test.ts b/packages/app/src/pages/session/session-model-helpers.test.ts
index 5f554dcd3..319db805d 100644
--- a/packages/app/src/pages/session/session-model-helpers.test.ts
+++ b/packages/app/src/pages/session/session-model-helpers.test.ts
@@ -14,145 +14,38 @@ const message = (input?: Partial<Pick<UserMessage, "agent" | "model" | "variant"
   }) as UserMessage
 
 describe("syncSessionModel", () => {
-  test("restores the last message model and variant", () => {
+  test("restores the last message through session state", () => {
     const calls: unknown[] = []
 
     syncSessionModel(
       {
-        agent: {
-          current() {
-            return undefined
-          },
-          set(value) {
-            calls.push(["agent", value])
-          },
-        },
-        model: {
-          set(value) {
-            calls.push(["model", value])
-          },
-          current() {
-            return { id: "claude-sonnet-4", provider: { id: "anthropic" } }
-          },
-          variant: {
-            set(value) {
-              calls.push(["variant", value])
-            },
-          },
-        },
-      },
-      message({ variant: "high" }),
-    )
-
-    expect(calls).toEqual([
-      ["agent", "build"],
-      ["model", { providerID: "anthropic", modelID: "claude-sonnet-4" }],
-      ["variant", "high"],
-    ])
-  })
-
-  test("skips variant when the model falls back", () => {
-    const calls: unknown[] = []
-
-    syncSessionModel(
-      {
-        agent: {
-          current() {
-            return undefined
-          },
-          set(value) {
-            calls.push(["agent", value])
-          },
-        },
-        model: {
-          set(value) {
-            calls.push(["model", value])
-          },
-          current() {
-            return { id: "gpt-5", provider: { id: "openai" } }
-          },
-          variant: {
-            set(value) {
-              calls.push(["variant", value])
-            },
+        session: {
+          restore(value) {
+            calls.push(value)
           },
+          reset() {},
         },
       },
       message({ variant: "high" }),
     )
 
-    expect(calls).toEqual([
-      ["agent", "build"],
-      ["model", { providerID: "anthropic", modelID: "claude-sonnet-4" }],
-    ])
+    expect(calls).toEqual([message({ variant: "high" })])
   })
 })
 
 describe("resetSessionModel", () => {
-  test("restores the current agent defaults", () => {
-    const calls: unknown[] = []
+  test("clears draft session state", () => {
+    const calls: string[] = []
 
     resetSessionModel({
-      agent: {
-        current() {
-          return {
-            model: { providerID: "anthropic", modelID: "claude-sonnet-4" },
-            variant: "high",
-          }
-        },
-        set() {},
-      },
-      model: {
-        set(value) {
-          calls.push(["model", value])
-        },
-        current() {
-          return undefined
-        },
-        variant: {
-          set(value) {
-            calls.push(["variant", value])
-          },
-        },
-      },
-    })
-
-    expect(calls).toEqual([
-      ["model", { providerID: "anthropic", modelID: "claude-sonnet-4" }],
-      ["variant", "high"],
-    ])
-  })
-
-  test("clears the variant when the agent has none", () => {
-    const calls: unknown[] = []
-
-    resetSessionModel({
-      agent: {
-        current() {
-          return {
-            model: { providerID: "anthropic", modelID: "claude-sonnet-4" },
-          }
-        },
-        set() {},
-      },
-      model: {
-        set(value) {
-          calls.push(["model", value])
-        },
-        current() {
-          return undefined
-        },
-        variant: {
-          set(value) {
-            calls.push(["variant", value])
-          },
+      session: {
+        reset() {
+          calls.push("reset")
         },
+        restore() {},
       },
     })
 
-    expect(calls).toEqual([
-      ["model", { providerID: "anthropic", modelID: "claude-sonnet-4" }],
-      ["variant", undefined],
-    ])
+    expect(calls).toEqual(["reset"])
   })
 })