fix: resolve silent agent termination on stream drop

packages/opencode/src/provider/sdk/copilot/chat/map-openai-compatible-finish-reason.ts

@@ -14,6 +14,6 @@ export function mapOpenAICompatibleFinishReason(
     case "tool_calls":
       return "tool-calls"
     default:
-      return "other"
+      return "unknown"
   }
 }

packages/opencode/src/provider/sdk/copilot/chat/openai-compatible-chat-language-model.ts

@@ -345,6 +345,7 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV3 {
       unified: "other",
       raw: undefined,
     }
+    let receivedFinishReason = false
     const usage: {
       completionTokens: number | undefined
       completionTokensDetails: {
@@ -453,6 +454,7 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV3 {
             const choice = value.choices[0]
 
             if (choice?.finish_reason != null) {
+              receivedFinishReason = true
               finishReason = {
                 unified: mapOpenAICompatibleFinishReason(choice.finish_reason),
                 raw: choice.finish_reason ?? undefined,
@@ -645,6 +647,10 @@ export class OpenAICompatibleChatLanguageModel implements LanguageModelV3 {
           },
 
           flush(controller) {
+            if (!receivedFinishReason && !isFirstChunk) {
+              finishReason = { unified: "unknown", raw: undefined }
+            }
+
             if (isActiveReasoning) {
               controller.enqueue({
                 type: "reasoning-end",

packages/opencode/src/provider/sdk/copilot/responses/map-openai-responses-finish-reason.ts

@@ -17,6 +17,6 @@ export function mapOpenAIResponseFinishReason({
     case "content_filter":
       return "content-filter"
     default:
-      return hasFunctionCall ? "tool-calls" : "other"
+      return hasFunctionCall ? "tool-calls" : "unknown"
   }
 }

packages/opencode/src/provider/sdk/copilot/responses/openai-responses-language-model.ts

@@ -803,6 +803,7 @@ export class OpenAIResponsesLanguageModel implements LanguageModelV3 {
       unified: "other",
       raw: undefined,
     }
+    let receivedFinishChunk = false
     const usage: {
       inputTokens: number | undefined
       outputTokens: number | undefined
@@ -1259,6 +1260,7 @@ export class OpenAIResponsesLanguageModel implements LanguageModelV3 {
                 })
               }
             } else if (isResponseFinishedChunk(value)) {
+              receivedFinishChunk = true
               finishReason = {
                 unified: mapOpenAIResponseFinishReason({
                   finishReason: value.response.incomplete_details?.reason,
@@ -1305,6 +1307,10 @@ export class OpenAIResponsesLanguageModel implements LanguageModelV3 {
               currentTextId = null
             }
 
+            if (!receivedFinishChunk && responseId !== null) {
+              finishReason = { unified: "unknown", raw: undefined }
+            }
+
             const providerMetadata: SharedV3ProviderMetadata = {
               openai: {
                 responseId,

packages/opencode/src/session/processor.ts

@@ -625,6 +625,18 @@ export const layer: Layer.Layer<
               Stream.takeUntil(() => ctx.needsCompaction),
               Stream.runDrain,
             )
+
+            if (ctx.assistantMessage.finish === "unknown") {
+              const parts = MessageV2.parts(ctx.assistantMessage.id)
+              if (!parts.some((p) => p.type === "tool")) {
+                yield* Effect.fail(
+                  new MessageV2.APIError({
+                    message: "Stream terminated prematurely without a finish reason",
+                    isRetryable: true,
+                  }).toObject()
+                )
+              }
+            }
           }).pipe(
             Effect.onInterrupt(() =>
               Effect.gen(function* () {

packages/opencode/src/session/prompt.ts

@@ -1592,7 +1592,7 @@ NOTE: At any point in time through this workflow you should feel free to ask the
               return "break" as const
             }
 
-            const finished = handle.message.finish && !["tool-calls", "unknown"].includes(handle.message.finish)
+            const finished = handle.message.finish && !["tool-calls", "unknown", "other"].includes(handle.message.finish)
             if (finished && !handle.message.error) {
               if (format.type === "json_schema") {
                 handle.message.error = new MessageV2.StructuredOutputError({