Fix empty tool call ID causing API errors when switching providers

packages/opencode/src/session/compaction.ts

@@ -129,6 +129,21 @@ export namespace SessionCompaction {
       model: model.info,
       abort: input.abort,
     })
+    const modelMessages = await MessageV2.toModelMessage(
+      input.messages.filter((m) => {
+        if (m.info.role !== "assistant" || m.info.error === undefined) {
+          return true
+        }
+        if (
+          MessageV2.AbortedError.isInstance(m.info.error) &&
+          m.parts.some((part) => part.type !== "step-start" && part.type !== "reasoning")
+        ) {
+          return true
+        }
+
+        return false
+      }),
+    )
     const result = await processor.process(() =>
       streamText({
         onError(error) {
@@ -157,21 +172,7 @@ export namespace SessionCompaction {
               content: x,
             }),
           ),
-          ...MessageV2.toModelMessage(
-            input.messages.filter((m) => {
-              if (m.info.role !== "assistant" || m.info.error === undefined) {
-                return true
-              }
-              if (
-                MessageV2.AbortedError.isInstance(m.info.error) &&
-                m.parts.some((part) => part.type !== "step-start" && part.type !== "reasoning")
-              ) {
-                return true
-              }
-
-              return false
-            }),
-          ),
+          ...modelMessages,
           {
             role: "user",
             content: [

packages/opencode/src/session/message-v2.ts

@@ -9,6 +9,7 @@ import { Snapshot } from "@/snapshot"
 import { fn } from "@/util/fn"
 import { Storage } from "@/storage/storage"
 import { ProviderTransform } from "@/provider/transform"
+import { ulid } from "ulid"
 
 export namespace MessageV2 {
   export const OutputLengthError = NamedError.create("MessageOutputLengthError", z.object({}))
@@ -549,12 +550,12 @@ export namespace MessageV2 {
     throw new Error("unknown message type")
   }
 
-  export function toModelMessage(
+  export async function toModelMessage(
     input: {
       info: Info
       parts: Part[]
     }[],
-  ): ModelMessage[] {
+  ): Promise<ModelMessage[]> {
     const result: UIMessage[] = []
 
     for (const msg of input) {
@@ -616,6 +617,11 @@ export namespace MessageV2 {
               type: "step-start",
             })
           if (part.type === "tool") {
+            // Fix empty callID from providers that don't generate tool call IDs (e.g. Gemini)
+            if (!part.callID) {
+              part.callID = ulid()
+              await Storage.write(["part", part.messageID, part.id], part)
+            }
             if (part.state.status === "completed") {
               if (part.state.attachments?.length) {
                 result.push({

packages/opencode/src/session/processor.ts

@@ -3,6 +3,7 @@ import { MessageV2 } from "./message-v2"
 import { type StreamTextResult, type Tool as AITool, APICallError } from "ai"
 import { Log } from "@/util/log"
 import { Identifier } from "@/id/id"
+import { ulid } from "ulid"
 import { Session } from "."
 import { Agent } from "@/agent/agent"
 import { Permission } from "@/permission"
@@ -101,7 +102,7 @@ export namespace SessionProcessor {
                     sessionID: input.assistantMessage.sessionID,
                     type: "tool",
                     tool: value.toolName,
-                    callID: value.id,
+                    callID: value.id || ulid(),
                     state: {
                       status: "pending",
                       input: {},

packages/opencode/src/session/prompt.ts

@@ -505,6 +505,22 @@ export namespace SessionPrompt {
         })
       }
 
+      const modelMessages = await MessageV2.toModelMessage(
+        msgs.filter((m) => {
+          if (m.info.role !== "assistant" || m.info.error === undefined) {
+            return true
+          }
+          if (
+            MessageV2.AbortedError.isInstance(m.info.error) &&
+            m.parts.some((part) => part.type !== "step-start" && part.type !== "reasoning")
+          ) {
+            return true
+          }
+
+          return false
+        }),
+      )
+
       const result = await processor.process(() =>
         streamText({
           onError(error) {
@@ -563,21 +579,7 @@ export namespace SessionPrompt {
                 content: x,
               }),
             ),
-            ...MessageV2.toModelMessage(
-              msgs.filter((m) => {
-                if (m.info.role !== "assistant" || m.info.error === undefined) {
-                  return true
-                }
-                if (
-                  MessageV2.AbortedError.isInstance(m.info.error) &&
-                  m.parts.some((part) => part.type !== "step-start" && part.type !== "reasoning")
-                ) {
-                  return true
-                }
-
-                return false
-              }),
-            ),
+            ...modelMessages,
           ],
           tools: model.info.tool_call === false ? undefined : tools,
           model: wrapLanguageModel({
@@ -1431,7 +1433,7 @@ export namespace SessionPrompt {
           role: "user",
           content: "Generate a title for this conversation:\n",
         },
-        ...MessageV2.toModelMessage([
+        ...(await MessageV2.toModelMessage([
           {
             info: {
               id: Identifier.ascending("message"),
@@ -1448,7 +1450,7 @@ export namespace SessionPrompt {
             },
             parts: input.message.parts,
           },
-        ]),
+        ])),
       ],
       headers: small.info.headers,
       model: small.language,

packages/opencode/src/session/summary.ts

@@ -142,7 +142,7 @@ export namespace SessionSummary {
                 content: x,
               }),
             ),
-            ...MessageV2.toModelMessage(messages),
+            ...(await MessageV2.toModelMessage(messages)),
             {
               role: "user",
               content: `Summarize the above conversation according to your system prompts.`,