fix: cross-session file change leak in Files Changed tab

packages/app/src/i18n/ar.ts

@@ -643,6 +643,7 @@ export const dict = {
   "session.share.action.view": "عرض",
   "session.share.copy.copied": "تم النسخ",
   "session.share.copy.copyLink": "نسخ الرابط",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "لا توجد خوادم LSP",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "جارٍ تحميل الموجه...",

packages/app/src/i18n/br.ts

@@ -651,6 +651,7 @@ export const dict = {
   "session.share.action.view": "Ver",
   "session.share.copy.copied": "Copiado",
   "session.share.copy.copyLink": "Copiar link",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "Nenhum servidor LSP",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "Carregando prompt...",

packages/app/src/i18n/bs.ts

@@ -708,6 +708,7 @@ export const dict = {
   "session.share.action.view": "Prikaži",
   "session.share.copy.copied": "Kopirano",
   "session.share.copy.copyLink": "Kopiraj link",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "Nema LSP servera",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/da.ts

@@ -705,6 +705,7 @@ export const dict = {
   "session.share.action.view": "Vis",
   "session.share.copy.copied": "Kopieret",
   "session.share.copy.copyLink": "Kopier link",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "Ingen LSP-servere",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/de.ts

@@ -660,6 +660,7 @@ export const dict = {
   "session.share.action.view": "Ansehen",
   "session.share.copy.copied": "Kopiert",
   "session.share.copy.copyLink": "Link kopieren",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "Keine LSP-Server",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "Lade Prompt...",

packages/app/src/i18n/es.ts

@@ -711,6 +711,7 @@ export const dict = {
   "session.share.action.view": "Ver",
   "session.share.copy.copied": "Copiado",
   "session.share.copy.copyLink": "Copiar enlace",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "Sin servidores LSP",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/fr.ts

@@ -656,6 +656,7 @@ export const dict = {
   "session.share.action.view": "Voir",
   "session.share.copy.copied": "Copié",
   "session.share.copy.copyLink": "Copier le lien",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "Aucun serveur LSP",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "Chargement du prompt...",

packages/app/src/i18n/ja.ts

@@ -647,6 +647,7 @@ export const dict = {
   "session.share.action.view": "表示",
   "session.share.copy.copied": "コピーしました",
   "session.share.copy.copyLink": "リンクをコピー",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "LSPサーバーなし",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "プロンプトを読み込み中...",

packages/app/src/i18n/ko.ts

@@ -523,6 +523,7 @@ export const dict = {
   "session.share.action.view": "보기",
   "session.share.copy.copied": "복사됨",
   "session.share.copy.copyLink": "링크 복사",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "LSP 서버 없음",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "프롬프트 로드 중...",

packages/app/src/i18n/no.ts

@@ -589,6 +589,7 @@ export const dict = {
   "session.share.action.view": "Vis",
   "session.share.copy.copied": "Kopiert",
   "session.share.copy.copyLink": "Kopier lenke",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "Ingen LSP-servere",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/pl.ts

@@ -651,6 +651,7 @@ export const dict = {
   "session.share.action.view": "Widok",
   "session.share.copy.copied": "Skopiowano",
   "session.share.copy.copyLink": "Kopiuj link",
+  "session.exportTrace": "Export trace",
   "lsp.tooltip.none": "Brak serwerów LSP",
   "lsp.label.connected": "{{count}} LSP",
   "prompt.loading": "Ładowanie promptu...",

packages/app/src/i18n/ru.ts

@@ -708,6 +708,7 @@ export const dict = {
   "session.share.action.view": "Посмотреть",
   "session.share.copy.copied": "Скопировано",
   "session.share.copy.copyLink": "Копировать ссылку",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "Нет LSP серверов",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/th.ts

@@ -702,6 +702,7 @@ export const dict = {
   "session.share.action.view": "ดู",
   "session.share.copy.copied": "คัดลอกแล้ว",
   "session.share.copy.copyLink": "คัดลอกลิงก์",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "ไม่มีเซิร์ฟเวอร์ LSP",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/tr.ts

@@ -713,6 +713,7 @@ export const dict = {
   "session.share.action.view": "Görüntüle",
   "session.share.copy.copied": "Kopyalandı",
   "session.share.copy.copyLink": "Bağlantı kopyala",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "LSP sunucusu yok",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/uk.ts

@@ -756,6 +756,7 @@ export const dict = {
   "session.share.action.view": "Переглянути",
   "session.share.copy.copied": "Скопійовано",
   "session.share.copy.copyLink": "Копіювати посилання",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "Немає серверів LSP",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/zh.ts

@@ -698,6 +698,7 @@ export const dict = {
   "session.share.action.view": "查看",
   "session.share.copy.copied": "已复制",
   "session.share.copy.copyLink": "复制链接",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "没有 LSP 服务器",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/i18n/zht.ts

@@ -696,6 +696,7 @@ export const dict = {
   "session.share.action.view": "檢視",
   "session.share.copy.copied": "已複製",
   "session.share.copy.copyLink": "複製連結",
+  "session.exportTrace": "Export trace",
 
   "lsp.tooltip.none": "沒有 LSP 伺服器",
   "lsp.label.connected": "{{count}} LSP",

packages/app/src/pages/session.tsx

@@ -1,7 +1,7 @@
 import type { FilePart, Project, SnapshotFileDiff, UserMessage } from "@opencode-ai/sdk/v2"
 import { getFilename } from "@opencode-ai/core/util/path"
 import { useDialog } from "@opencode-ai/ui/context/dialog"
-import { createQuery, keepPreviousData, skipToken, useMutation } from "@tanstack/solid-query"
+import { createQuery, skipToken, useMutation } from "@tanstack/solid-query"
 import {
   batch,
   ErrorBoundary,
@@ -695,7 +695,14 @@ export default function Page() {
     return {
       queryKey: sessionDiffKey(),
       enabled: !!sessionID,
-      placeholderData: keepPreviousData,
+      // Keep previous data only for intra-session refetches (e.g. diff_version
+      // bumps), NOT across session switches. Cross-session keepPreviousData was
+      // the secondary leak vector: the old session's diffs appeared as
+      // placeholder in the new session's review panel.
+      placeholderData: (prev: SnapshotFileDiff[] | undefined, prevQuery: { queryKey?: readonly unknown[] } | undefined) => {
+        if (prevQuery?.queryKey?.[1] === sessionID) return prev
+        return undefined
+      },
       queryFn: sessionID
         ? () =>
             sdk()
@@ -765,7 +772,10 @@ export default function Page() {
     return {
       queryKey: ["session-touched-files", sessionID ?? "", sessionDiffVersion()] as const,
       enabled: !!sessionID,
-      placeholderData: keepPreviousData,
+      placeholderData: (prev: Array<{ file: string; status: string }> | undefined, prevQuery: { queryKey?: readonly unknown[] } | undefined) => {
+        if (prevQuery?.queryKey?.[1] === sessionID) return prev
+        return undefined
+      },
       staleTime: 30_000,
       queryFn: sessionID
         ? async () => {

packages/app/src/pages/session/v2/accumulate-diffs.test.ts

@@ -108,7 +108,9 @@ describe("accumulateDiffs", () => {
     expect(result[0].additions).toBe(6)
     expect(result[0].deletions).toBe(5)
     // A hypothetical net diff would be lower — the client must never show
-    // this stale/inflated data during a refetch. The fix is keepPreviousData
-    // on the query so the fallback never fires while server data exists.
+    // this stale/inflated data during a refetch. The fix is scoped
+    // placeholderData on the query (keep previous data only for the SAME
+    // session) so the fallback never fires during intra-session refetches,
+    // while inter-session switches correctly drop the stale data.
   })
 })

packages/opencode/src/session/session.ts

@@ -946,6 +946,12 @@ const layer: Layer.Layer<
         }
       }
 
+      // Snapshots exist but the agent touched no files (e.g. plan-only session).
+      // Return empty — do NOT fall through to the legacy fallbacks, whose
+      // summary.diffs are unfiltered snapshot diffs that include cross-session
+      // changes (the computeDiff contamination vector from #733).
+      if (from) return [] as Snapshot.FileDiff[]
+
       // Fallback 1: aggregate stored per-message summary diffs across the session.
       const seen = new Map<string, Snapshot.FileDiff>()
       for (const msg of all) {

packages/opencode/src/session/summary.ts

@@ -82,6 +82,9 @@ const layer = Layer.effect(
     const computeDiff = Effect.fn("SessionSummary.computeDiff")(function* (input: { messages: SessionV1.WithParts[] }) {
       let from: string | undefined
       let to: string | undefined
+      const EDIT_TOOLS = new Set(["edit", "write", "patch", "apply_patch"])
+      const agentFiles = new Set<string>()
+      let hasAnyTool = false
       for (const item of input.messages) {
         if (!from) {
           for (const part of item.parts) {
@@ -93,9 +96,43 @@ const layer = Layer.effect(
         }
         for (const part of item.parts) {
           if (part.type === "step-finish" && part.snapshot) to = part.snapshot
+          if (part.type === "tool") {
+            hasAnyTool = true
+            // Collect agent-touched files from completed edit tools (#733 follow-up).
+            // Without this filter, diffFull captures ALL worktree changes between
+            // the two tree hashes — including edits from concurrent sessions.
+            const toolPart = part as { tool?: string; state?: { status?: string; metadata?: Record<string, unknown> } }
+            if (toolPart.tool && EDIT_TOOLS.has(toolPart.tool) && toolPart.state?.status === "completed") {
+              const filediff = toolPart.state?.metadata?.filediff as { file?: string } | undefined
+              if (filediff?.file) agentFiles.add(filediff.file)
+            }
+          }
+        }
+      }
+      if (from && to) {
+        const allDiffs = yield* snapshot.diffFull(from, to)
+        // If filediff-tracked agent files exist, filter the diff to only
+        // those files (prevents cross-session contamination).
+        if (agentFiles.size > 0) {
+          // Agent files are absolute paths (from tool filediff metadata);
+          // diff files are relative to the worktree. Match by suffix.
+          return allDiffs.filter((d: Snapshot.FileDiff) => {
+            if (!d.file) return false
+            const suffix = "/" + d.file
+            for (const af of agentFiles) {
+              if (af.endsWith(suffix) || af === d.file) return true
+            }
+            return false
+          })
         }
+        // Tools ran but none had filediff metadata (e.g. bash creating
+        // files) — return the full diff since we can't determine which
+        // files the agent touched.
+        if (hasAnyTool) return allDiffs
+        // No tools at all (plan-only session) — the diff is entirely
+        // from external sources (other sessions). Return empty.
+        return [] as Snapshot.FileDiff[]
       }
-      if (from && to) return yield* snapshot.diffFull(from, to)
       return []
     })
 

packages/opencode/test/server/session-diff-scoped.test.ts

@@ -456,4 +456,88 @@ describe("Session.diff — session-scoped agent diffs (#174)", () => {
       }),
     { git: true, config: { formatter: false, lsp: false } },
   )
+
+  it.instance(
+    "returns [] for session with snapshots but no tool edits (plan-mode cross-session leak fix)",
+    () =>
+      Effect.gen(function* () {
+        const test = yield* TestInstance
+        const session = yield* withSession({ title: "plan-mode-leak" })
+        const snapshotSvc = yield* Snapshot.Service
+        const fs = yield* FSUtil.Service
+
+        // Take the session-start snapshot (before any external edits)
+        const startHash = yield* snapshotSvc.track()
+        expect(startHash).toBeTruthy()
+
+        // Create a user message
+        const userMsgID = MessageID.ascending()
+        yield* Session.use.updateMessage({
+          id: userMsgID,
+          sessionID: session.id,
+          role: "user",
+          time: { created: Date.now() },
+          agent: "plan",
+          model: { providerID: ProviderV2.ID.make("test"), modelID: ModelV2.ID.make("model") },
+        } satisfies SessionV1.User)
+
+        // Attach step-start part (records session-start snapshot)
+        yield* Session.use.updatePart({
+          id: PartID.ascending(),
+          sessionID: session.id,
+          messageID: userMsgID,
+          type: "step-start",
+          snapshot: startHash!,
+        })
+
+        // Simulate an external change (another session editing a file)
+        yield* fs.writeWithDirs(path.join(test.directory, "foreign-edit.ts"), "edited by another session")
+
+        // Take the step-finish snapshot (captures the foreign edit)
+        const endHash = yield* snapshotSvc.track()
+        expect(endHash).toBeTruthy()
+        expect(endHash).not.toBe(startHash)
+
+        // Attach step-finish part
+        yield* Session.use.updatePart({
+          id: PartID.ascending(),
+          sessionID: session.id,
+          messageID: userMsgID,
+          type: "step-finish",
+          snapshot: endHash!,
+          reason: "done",
+          cost: 0,
+          tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+        } as any)
+
+        // Store contaminated summary.diffs (simulating what computeDiff produces)
+        // This is what summarize() does after step-finish — unfiltered snapshot diff
+        yield* Session.use.updateMessage({
+          id: userMsgID,
+          sessionID: session.id,
+          role: "user",
+          time: { created: Date.now() },
+          agent: "plan",
+          model: { providerID: ProviderV2.ID.make("test"), modelID: ModelV2.ID.make("model") },
+          summary: {
+            diffs: [
+              { file: "foreign-edit.ts", additions: 1, deletions: 0, status: "added" as const },
+            ],
+          },
+        } satisfies SessionV1.User)
+
+        // NO tool parts with filediff — this is a plan-mode session
+
+        // The diff should be empty: snapshots exist, so Fallback 1 should NOT
+        // serve contaminated summary.diffs from computeDiff
+        const response = yield* requestInDirectory(
+          pathFor(SessionPaths.diff, { sessionID: session.id }),
+          test.directory,
+        )
+        expect(response.status).toBe(200)
+        const diffs = (yield* response.json) as Array<{ file: string }>
+        expect(diffs).toEqual([])
+      }),
+    { git: true, config: { formatter: false, lsp: false } },
+  )
 })