fix(opencode): fall back for legacy compacted tool evidence

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <[email protected]>

Author: GuestAUser

packages/opencode/src/session/evidence.ts

@@ -32,8 +32,8 @@ export namespace Evidence {
     return [...list.slice(0, FILE_MAX), `+${list.length - FILE_MAX} more`]
   }
 
-  function path(input: MessageV2.ToolStateCompleted["metadata"]) {
-    return typeof input.outputPath === "string" ? input.outputPath : undefined
+  function path(input?: MessageV2.ToolStateCompleted["metadata"]) {
+    return typeof input?.outputPath === "string" ? input.outputPath : undefined
   }
 
   export function tool(input: {

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

@@ -718,13 +718,10 @@ export namespace MessageV2 {
             toolNames.add(part.tool)
             if (part.state.status === "completed") {
               const state = part.state
-              const outputText = state.time.compacted
-                ? Evidence.text(
-                    Evidence.isTool(state.metadata.evidence)
-                      ? state.metadata.evidence
-                      : Evidence.tool({ tool: part.tool, state }),
-                  )
-                : state.output
+              const proof = Evidence.isTool(state.metadata?.evidence)
+                ? state.metadata.evidence
+                : Evidence.tool({ tool: part.tool, state })
+              const outputText = state.time.compacted ? Evidence.text(proof) : state.output
               const attachments = state.time.compacted || options?.stripMedia ? [] : (state.attachments ?? [])
 
               // For providers that don't support media in tool results, extract media files

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

@@ -519,6 +519,53 @@ describe("session.message-v2.toModelMessage", () => {
     expect(text).not.toContain("[Old tool result content cleared]")
   })
 
+  test("replaces compacted tool output when legacy evidence metadata is missing", async () => {
+    const userID = "m-user-legacy"
+    const assistantID = "m-assistant-legacy"
+
+    const input = [
+      {
+        info: userInfo(userID),
+        parts: [
+          {
+            ...basePart(userID, "u1"),
+            type: "text",
+            text: "run tool",
+          },
+        ] as MessageV2.Part[],
+      },
+      {
+        info: assistantInfo(assistantID, userID),
+        parts: [
+          {
+            ...basePart(assistantID, "a1"),
+            type: "tool",
+            callID: "call-legacy",
+            tool: "bash",
+            state: {
+              status: "completed",
+              input: { cmd: "pwd" },
+              output: "legacy compacted output",
+              title: "Bash",
+              metadata: undefined,
+              time: { start: 0, end: 1, compacted: 1 },
+            },
+          },
+        ] as unknown as MessageV2.Part[],
+      },
+    ] satisfies MessageV2.WithParts[]
+
+    const result = await MessageV2.toModelMessages(input, model)
+    const tool = result[2] as {
+      content: Array<{
+        output: { value: string }
+      }>
+    }
+
+    expect(tool.content[0]?.output.value).toContain("tool: bash")
+    expect(tool.content[0]?.output.value).toContain("excerpt:\nlegacy compacted output")
+  })
+
   test("converts assistant tool error into error-text tool result", async () => {
     const userID = "m-user"
     const assistantID = "m-assistant"