fix(session): preserve context after user interrupts

STATS.md

@@ -80,3 +80,9 @@
 | 2025-09-13 | 324,894 (+3,848) | 245,539 (+4,811) | 570,433 (+8,659)  |
 | 2025-09-14 | 328,876 (+3,982) | 248,245 (+2,706) | 577,121 (+6,688)  |
 | 2025-09-15 | 334,201 (+5,325) | 250,983 (+2,738) | 585,184 (+8,063)  |
+| 2025-09-16 | 342,613 (+8,412) | 255,264 (+4,281) | 597,877 (+12,693) |
+| 2025-09-17 | 351,118 (+8,505) | 260,970 (+5,706) | 612,088 (+14,211) |
+| 2025-09-18 | 358,718 (+7,600) | 266,922 (+5,952) | 625,640 (+13,552) |
+| 2025-09-19 | 365,402 (+6,684) | 271,859 (+4,937) | 637,261 (+11,621) |
+| 2025-09-20 | 372,092 (+6,690) | 276,917 (+5,058) | 649,009 (+11,748) |
+| 2025-09-21 | 377,083 (+4,991) | 280,261 (+3,344) | 657,344 (+8,335)  |

packages/opencode/src/session/index.ts

@@ -301,7 +301,7 @@ export namespace Session {
     let sum = 0
     for (let msgIndex = msgs.length - 2; msgIndex >= 0; msgIndex--) {
       const msg = msgs[msgIndex]
-      if (msg.info.role === "assistant" && msg.info.summary) return
+      if (msg.info.role === "assistant" && msg.info.summary && !msg.info.error) return
       for (let partIndex = msg.parts.length - 1; partIndex >= 0; partIndex--) {
         const part = msg.parts[partIndex]
         if (part.type === "tool")

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

@@ -569,7 +569,7 @@ export namespace MessageV2 {
   }
 
   export function filterSummarized(msgs: { info: MessageV2.Info; parts: MessageV2.Part[] }[]) {
-    const i = msgs.findLastIndex((m) => m.info.role === "assistant" && !!m.info.summary)
+    const i = msgs.findLastIndex((m) => m.info.role === "assistant" && !!m.info.summary && !m.info.error)
     if (i === -1) return msgs.slice()
     return msgs.slice(i)
   }

packages/opencode/src/tool/task.ts

@@ -75,12 +75,25 @@ export const TaskTool = Tool.define("task", async () => {
         ],
       })
       unsub()
+      const outputText = (result.parts.findLast((x: any) => x.type === "text") as any)?.text ?? ""
+      const err = (result as any).info?.error
+      if (err) {
+        const isAborted = MessageV2.AbortedError.isInstance(err)
+        const name = typeof err === "object" && err && "name" in err ? (err as any).name : "Error"
+        const msg =
+          typeof err === "object" && err && "data" in err && (err as any).data && "message" in (err as any).data
+            ? ((err as any).data as any).message
+            : name
+        const partial = outputText ? `\nPartial output from subagent before interruption:\n${outputText}` : ""
+        const text = isAborted ? `Subagent task was interrupted by user.` : `Subagent encountered an error: ${msg}`
+        throw new Error(`${text}${partial}`)
+      }
       return {
         title: params.description,
         metadata: {
           summary: result.parts.filter((x: any) => x.type === "tool"),
         },
-        output: (result.parts.findLast((x: any) => x.type === "text") as any)?.text ?? "",
+        output: outputText,
       }
     },
   }