fix(core): omit historical images for text models

tests/test-pure-functions.ts

@@ -161,7 +161,7 @@ describe("projectSlugFromPath()", () => {
 })
 
 describe("text-only image handling", () => {
-  it("rejects image content for models without image support", () => {
+  it("rejects direct image input for models without image support", () => {
     assert.throws(
       () =>
         assertTextOnlyMessages([
@@ -172,16 +172,17 @@ describe("text-only image handling", () => {
         ]),
       /does not support image content/i,
     )
-    assert.throws(
-      () =>
-        assertTextOnlyMessages([
-          {
-            role: "toolResult",
-            toolCallId: "c1",
-            content: [{ type: "image", data: "base64-data", mimeType: "image/png" }],
-          },
-        ]),
-      /does not support image content/i,
+  })
+
+  it("allows historical tool-result images to be omitted for text-only models", () => {
+    assert.doesNotThrow(() =>
+      assertTextOnlyMessages([
+        {
+          role: "toolResult",
+          toolCallId: "c1",
+          content: [{ type: "image", data: "base64-data", mimeType: "image/png" }],
+        },
+      ]),
     )
   })
 })
@@ -597,6 +598,48 @@ describe("messagesToCC()", () => {
     )
   })
 
+  it("omits tool-result images for text-only models while preserving their text", () => {
+    const result = messagesToCC([
+      { role: "user", content: "read image" },
+      {
+        role: "assistant",
+        content: [{ type: "toolCall", id: "c1", name: "read", arguments: {} }],
+      },
+      {
+        role: "toolResult",
+        toolCallId: "c1",
+        toolName: "read",
+        content: [
+          { type: "text", text: "image attached" },
+          { type: "image", data: "aGVsbG8=", mimeType: "image/jpeg" },
+        ],
+      },
+    ])
+
+    assert.equal(objectAt(result, ["2", "content", "0", "output", "value"]), "image attached")
+    assert.equal(objectAt(result, ["3"]), undefined)
+  })
+
+  it("describes an omitted image-only tool result for text-only models", () => {
+    const result = messagesToCC([
+      {
+        role: "assistant",
+        content: [{ type: "toolCall", id: "c1", name: "read", arguments: {} }],
+      },
+      {
+        role: "toolResult",
+        toolCallId: "c1",
+        toolName: "read",
+        content: [{ type: "image", data: "aGVsbG8=", mimeType: "image/jpeg" }],
+      },
+    ])
+
+    assert.equal(
+      objectAt(result, ["1", "content", "0", "output", "value"]),
+      "[Image omitted: model does not support images]",
+    )
+  })
+
   it("preserves tool-result images as a following user image message", () => {
     const result = messagesToCC(
       [

tests/test-stream.ts

@@ -240,12 +240,16 @@ describe("streamCommandCode — successful streams", () => {
     )
   })
 
-  it("rejects a tool-result image before network access for text-only models", async () => {
+  it("omits a historical tool-result image after switching to a text-only model", async () => {
+    server.mockResponse({
+      type: "success",
+      events: [JSON.stringify({ type: "finish", finishReason: "stop" })],
+    })
     const { streamCommandCode } = createTestDeps({ apiBase: server.baseUrl() })
 
     const events = await collectEvents(
       streamCommandCode(
-        makeModel({ id: "deepseek/deepseek-v4-pro" }),
+        makeModel({ id: "deepseek/deepseek-v4-flash" }),
         makeContext({
           messages: [
             { role: "user", content: "read the image" },
@@ -257,19 +261,29 @@ describe("streamCommandCode — successful streams", () => {
               role: "toolResult",
               toolCallId: "c1",
               toolName: "read",
-              content: [{ type: "image", data: "aGVsbG8=", mimeType: "image/png" }],
+              content: [
+                { type: "text", text: "image attached" },
+                { type: "image", data: "aGVsbG8=", mimeType: "image/png" },
+              ],
             },
+            { role: "user", content: "continue without the image" },
           ],
         }),
         { apiKey: "mock-key" },
       ),
     )
 
-    const lastEvent = events.at(-1)
-    assert.equal(lastEvent?.type, "error")
-    if (lastEvent?.type !== "error") throw new Error("expected error event")
-    assert.match(lastEvent.error.errorMessage ?? "", /does not support image content/i)
-    assert.equal(server.requestCount(), 0)
+    assert.equal(events.at(-1)?.type, "done")
+    assert.equal(server.requestCount(), 1)
+    const body = server.lastRequestBody()
+    assert.equal(
+      objectAt(body, ["params", "messages", "2", "content", "0", "output", "value"]),
+      "image attached",
+    )
+    assert.equal(
+      objectAt(body, ["params", "messages", "3", "content"]),
+      "continue without the image",
+    )
   })
 
   it("rejects images before network access for text-only models", async () => {