diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/frecency.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/frecency.tsx
index 3ea8826ef8bd..052f33ca54d6 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/frecency.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/frecency.tsx
@@ -1,10 +1,9 @@
 import path from "path"
 import { Global } from "@/global"
-import { Filesystem } from "@/util/filesystem"
 import { onMount } from "solid-js"
 import { createStore } from "solid-js/store"
 import { createSimpleContext } from "../../context/helper"
-import { appendFile, writeFile } from "fs/promises"
+import { appendFile } from "fs/promises"
 
 function calculateFrecency(entry?: { frequency: number; lastOpen: number }): number {
   if (!entry) return 0
@@ -20,7 +19,9 @@ export const { use: useFrecency, provider: FrecencyProvider } = createSimpleCont
   init: () => {
     const frecencyPath = path.join(Global.Path.state, "frecency.jsonl")
     onMount(async () => {
-      const text = await Filesystem.readText(frecencyPath).catch(() => "")
+      const text = await Bun.file(frecencyPath)
+        .text()
+        .catch(() => "")
       const lines = text
         .split("\n")
         .filter(Boolean)
@@ -54,7 +55,7 @@ export const { use: useFrecency, provider: FrecencyProvider } = createSimpleCont
 
       if (sorted.length > 0) {
         const content = sorted.map((entry) => JSON.stringify(entry)).join("\n") + "\n"
-        writeFile(frecencyPath, content).catch(() => {})
+        void Bun.write(frecencyPath, content)
       }
     })
 
@@ -77,7 +78,7 @@ export const { use: useFrecency, provider: FrecencyProvider } = createSimpleCont
           .slice(0, MAX_FRECENCY_ENTRIES)
         setStore("data", Object.fromEntries(sorted))
         const content = sorted.map(([path, entry]) => JSON.stringify({ path, ...entry })).join("\n") + "\n"
-        writeFile(frecencyPath, content).catch(() => {})
+        void Bun.write(frecencyPath, content)
       }
     }
 
diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/history.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/history.tsx
index d49dd5c7b699..f9aa97f9e302 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/history.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/history.tsx
@@ -1,10 +1,9 @@
 import path from "path"
 import { Global } from "@/global"
-import { Filesystem } from "@/util/filesystem"
 import { onMount } from "solid-js"
 import { createStore, produce, unwrap } from "solid-js/store"
 import { createSimpleContext } from "../../context/helper"
-import { appendFile, writeFile } from "fs/promises"
+import { appendFile } from "fs/promises"
 import type { AgentPart, FilePart, TextPart } from "@opencode-ai/sdk/v2"
 
 export type PromptInfo = {
@@ -32,7 +31,9 @@ export const { use: usePromptHistory, provider: PromptHistoryProvider } = create
   init: () => {
     const historyPath = path.join(Global.Path.state, "prompt-history.jsonl")
     onMount(async () => {
-      const text = await Filesystem.readText(historyPath).catch(() => "")
+      const text = await Bun.file(historyPath)
+        .text()
+        .catch(() => "")
       const lines = text
         .split("\n")
         .filter(Boolean)
@@ -51,7 +52,7 @@ export const { use: usePromptHistory, provider: PromptHistoryProvider } = create
       // Rewrite file with only valid entries to self-heal corruption
       if (lines.length > 0) {
         const content = lines.map((line) => JSON.stringify(line)).join("\n") + "\n"
-        writeFile(historyPath, content).catch(() => {})
+        void Bun.write(historyPath, content)
       }
     })
 
@@ -97,7 +98,7 @@ export const { use: usePromptHistory, provider: PromptHistoryProvider } = create
 
         if (trimmed) {
           const content = store.history.map((line) => JSON.stringify(line)).join("\n") + "\n"
-          writeFile(historyPath, content).catch(() => {})
+          void Bun.write(historyPath, content)
           return
         }
 
diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/stash.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/stash.tsx
index ef3eb329a995..8b155ecc1200 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/stash.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/stash.tsx
@@ -1,10 +1,9 @@
 import path from "path"
 import { Global } from "@/global"
-import { Filesystem } from "@/util/filesystem"
 import { onMount } from "solid-js"
 import { createStore, produce, unwrap } from "solid-js/store"
 import { createSimpleContext } from "../../context/helper"
-import { appendFile, writeFile } from "fs/promises"
+import { appendFile } from "fs/promises"
 import type { PromptInfo } from "./history"
 
 export type StashEntry = {
@@ -20,7 +19,9 @@ export const { use: usePromptStash, provider: PromptStashProvider } = createSimp
   init: () => {
     const stashPath = path.join(Global.Path.state, "prompt-stash.jsonl")
     onMount(async () => {
-      const text = await Filesystem.readText(stashPath).catch(() => "")
+      const text = await Bun.file(stashPath)
+        .text()
+        .catch(() => "")
       const lines = text
         .split("\n")
         .filter(Boolean)
@@ -39,7 +40,7 @@ export const { use: usePromptStash, provider: PromptStashProvider } = createSimp
       // Rewrite file with only valid entries to self-heal corruption
       if (lines.length > 0) {
         const content = lines.map((line) => JSON.stringify(line)).join("\n") + "\n"
-        writeFile(stashPath, content).catch(() => {})
+        void Bun.write(stashPath, content)
       }
     })
 
@@ -66,7 +67,7 @@ export const { use: usePromptStash, provider: PromptStashProvider } = createSimp
 
         if (trimmed) {
           const content = store.entries.map((line) => JSON.stringify(line)).join("\n") + "\n"
-          writeFile(stashPath, content).catch(() => {})
+          void Bun.write(stashPath, content)
           return
         }
 
@@ -82,7 +83,7 @@ export const { use: usePromptStash, provider: PromptStashProvider } = createSimp
         )
         const content =
           store.entries.length > 0 ? store.entries.map((line) => JSON.stringify(line)).join("\n") + "\n" : ""
-        writeFile(stashPath, content).catch(() => {})
+        void Bun.write(stashPath, content)
         return entry
       },
       remove(index: number) {
@@ -94,7 +95,7 @@ export const { use: usePromptStash, provider: PromptStashProvider } = createSimp
         )
         const content =
           store.entries.length > 0 ? store.entries.map((line) => JSON.stringify(line)).join("\n") + "\n" : ""
-        writeFile(stashPath, content).catch(() => {})
+        void Bun.write(stashPath, content)
       },
     }
   },
diff --git a/packages/opencode/src/cli/cmd/tui/context/kv.tsx b/packages/opencode/src/cli/cmd/tui/context/kv.tsx
index 7a52156f8823..6016a3fee1bb 100644
--- a/packages/opencode/src/cli/cmd/tui/context/kv.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/kv.tsx
@@ -1,5 +1,4 @@
 import { Global } from "@/global"
-import { Filesystem } from "@/util/filesystem"
 import { createSignal, type Setter } from "solid-js"
 import { createStore } from "solid-js/store"
 import { createSimpleContext } from "./helper"
@@ -12,9 +11,10 @@ export const { use: useKV, provider: KVProvider } = createSimpleContext({
     const [store, setStore] = createStore<Record<string, any>>()
     const filePath = path.join(Global.Path.state, "kv.json")
 
-    Filesystem.readJson(filePath)
+    Bun.file(filePath)
+      .json()
       .then((x) => {
-        setStore(x)
+        if (typeof x === "object" && x !== null) setStore(x as Record<string, any>)
       })
       .catch(() => {})
       .finally(() => {
@@ -44,7 +44,7 @@ export const { use: useKV, provider: KVProvider } = createSimpleContext({
       },
       set(key: string, value: any) {
         setStore(key, value)
-        Filesystem.writeJson(filePath, store)
+        void Bun.write(filePath, JSON.stringify(store, null, 2))
       },
     }
     return result
diff --git a/packages/opencode/src/cli/cmd/tui/context/local.tsx b/packages/opencode/src/cli/cmd/tui/context/local.tsx
index ec3931b209ad..7c58f195e048 100644
--- a/packages/opencode/src/cli/cmd/tui/context/local.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/local.tsx
@@ -12,7 +12,6 @@ import { Provider } from "@/provider/provider"
 import { useArgs } from "./args"
 import { useSDK } from "./sdk"
 import { RGBA } from "@opentui/core"
-import { Filesystem } from "@/util/filesystem"
 
 export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
   name: "Local",
@@ -131,14 +130,22 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
           return
         }
         state.pending = false
-        Filesystem.writeJson(filePath, {
-          recent: modelStore.recent,
-          favorite: modelStore.favorite,
-          variant: modelStore.variant,
-        })
+        void Bun.write(
+          filePath,
+          JSON.stringify(
+            {
+              recent: modelStore.recent,
+              favorite: modelStore.favorite,
+              variant: modelStore.variant,
+            },
+            null,
+            2,
+          ),
+        )
       }
 
-      Filesystem.readJson(filePath)
+      Bun.file(filePath)
+        .json()
         .then((x: any) => {
           if (Array.isArray(x.recent)) setModelStore("recent", x.recent)
           if (Array.isArray(x.favorite)) setModelStore("favorite", x.favorite)
diff --git a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
index c7790006f41a..584d0edcc64e 100644
--- a/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/routes/session/index.tsx
@@ -74,8 +74,8 @@ import { Editor } from "../../util/editor"
 import stripAnsi from "strip-ansi"
 import { usePromptRef } from "../../context/prompt"
 import { useExit } from "../../context/exit"
-import { Filesystem } from "@/util/filesystem"
 import { Global } from "@/global"
+import { AppFileSystem } from "@opencode-ai/shared/filesystem"
 import { PermissionPrompt } from "./permission"
 import { QuestionPrompt } from "./question"
 import { DialogExportOptions } from "../../ui/dialog-export-options"
@@ -916,12 +916,12 @@ export function Session() {
             const filename = options.filename.trim()
             const filepath = path.join(exportDir, filename)
 
-            await Filesystem.write(filepath, transcript)
+            await Bun.write(filepath, transcript)
 
             // Open with EDITOR if available
             const result = await Editor.open({ value: transcript, renderer })
             if (result !== undefined) {
-              await Filesystem.write(filepath, result)
+              await Bun.write(filepath, result)
             }
 
             toast.show({ message: `Session exported to ${filename}`, variant: "success" })
@@ -2236,7 +2236,7 @@ function Skill(props: ToolProps<typeof SkillTool>) {
 function Diagnostics(props: { diagnostics?: Record<string, Record<string, any>[]>; filePath: string }) {
   const { theme } = useTheme()
   const errors = createMemo(() => {
-    const normalized = Filesystem.normalizePath(props.filePath)
+    const normalized = AppFileSystem.normalizePath(props.filePath)
     const arr = props.diagnostics?.[normalized] ?? []
     return arr.filter((x) => x.severity === 1).slice(0, 3)
   })
diff --git a/packages/opencode/src/cli/cmd/tui/util/clipboard.ts b/packages/opencode/src/cli/cmd/tui/util/clipboard.ts
index 87c0a63abc82..4533ff919464 100644
--- a/packages/opencode/src/cli/cmd/tui/util/clipboard.ts
+++ b/packages/opencode/src/cli/cmd/tui/util/clipboard.ts
@@ -4,7 +4,6 @@ import { lazy } from "../../../../util/lazy.js"
 import { tmpdir } from "os"
 import path from "path"
 import fs from "fs/promises"
-import { Filesystem } from "../../../../util/filesystem"
 import { Process } from "../../../../util/process"
 import { which } from "../../../../util/which"
 
@@ -58,8 +57,7 @@ export namespace Clipboard {
           ],
           { nothrow: true },
         )
-        const buffer = await Filesystem.readBytes(tmpfile)
-        return { data: buffer.toString("base64"), mime: "image/png" }
+        return { data: Buffer.from(await Bun.file(tmpfile).arrayBuffer()).toString("base64"), mime: "image/png" }
       } catch {
       } finally {
         await fs.rm(tmpfile, { force: true }).catch(() => {})
diff --git a/packages/opencode/src/cli/cmd/tui/util/editor.ts b/packages/opencode/src/cli/cmd/tui/util/editor.ts
index 9eaae99fce78..15bb07c579aa 100644
--- a/packages/opencode/src/cli/cmd/tui/util/editor.ts
+++ b/packages/opencode/src/cli/cmd/tui/util/editor.ts
@@ -3,7 +3,6 @@ import { rm } from "node:fs/promises"
 import { tmpdir } from "node:os"
 import { join } from "node:path"
 import { CliRenderer } from "@opentui/core"
-import { Filesystem } from "@/util/filesystem"
 import { Process } from "@/util/process"
 
 export namespace Editor {
@@ -14,7 +13,7 @@ export namespace Editor {
     const filepath = join(tmpdir(), `${Date.now()}.md`)
     await using _ = defer(async () => rm(filepath, { force: true }))
 
-    await Filesystem.write(filepath, opts.value)
+    await Bun.write(filepath, opts.value)
     opts.renderer.suspend()
     opts.renderer.currentRenderBuffer.clear()
     try {
@@ -26,7 +25,7 @@ export namespace Editor {
         shell: process.platform === "win32",
       })
       await proc.exited
-      const content = await Filesystem.readText(filepath)
+      const content = await Bun.file(filepath).text()
       return content || undefined
     } finally {
       opts.renderer.currentRenderBuffer.clear()