Remove use of Bun.file (#14215)

43 files changed, 634 insertions, 431 deletions

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 5f8a3920d..3ea8826ef 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/frecency.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/frecency.tsx
@@ -1,9 +1,10 @@
 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 } from "fs/promises"
+import { appendFile, writeFile } from "fs/promises"
 
 function calculateFrecency(entry?: { frequency: number; lastOpen: number }): number {
   if (!entry) return 0
@@ -17,9 +18,9 @@ const MAX_FRECENCY_ENTRIES = 1000
 export const { use: useFrecency, provider: FrecencyProvider } = createSimpleContext({
   name: "Frecency",
   init: () => {
-    const frecencyFile = Bun.file(path.join(Global.Path.state, "frecency.jsonl"))
+    const frecencyPath = path.join(Global.Path.state, "frecency.jsonl")
     onMount(async () => {
-      const text = await frecencyFile.text().catch(() => "")
+      const text = await Filesystem.readText(frecencyPath).catch(() => "")
       const lines = text
         .split("\n")
         .filter(Boolean)
@@ -53,7 +54,7 @@ export const { use: useFrecency, provider: FrecencyProvider } = createSimpleCont
 
       if (sorted.length > 0) {
         const content = sorted.map((entry) => JSON.stringify(entry)).join("\n") + "\n"
-        Bun.write(frecencyFile, content).catch(() => {})
+        writeFile(frecencyPath, content).catch(() => {})
       }
     })
 
@@ -68,7 +69,7 @@ export const { use: useFrecency, provider: FrecencyProvider } = createSimpleCont
         lastOpen: Date.now(),
       }
       setStore("data", absolutePath, newEntry)
-      appendFile(frecencyFile.name!, JSON.stringify({ path: absolutePath, ...newEntry }) + "\n").catch(() => {})
+      appendFile(frecencyPath, JSON.stringify({ path: absolutePath, ...newEntry }) + "\n").catch(() => {})
 
       if (Object.keys(store.data).length > MAX_FRECENCY_ENTRIES) {
         const sorted = Object.entries(store.data)
@@ -76,7 +77,7 @@ 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"
-        Bun.write(frecencyFile, content).catch(() => {})
+        writeFile(frecencyPath, content).catch(() => {})
       }
     }
 
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 e90503e9f..c40534e7e 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/history.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/history.tsx
@@ -1,5 +1,6 @@
 import path from "path"
 import { Global } from "@/global"
+import { Filesystem } from "@/util/filesystem"
 import { onMount } from "solid-js"
 import { createStore, produce } from "solid-js/store"
 import { clone } from "remeda"
@@ -30,9 +31,9 @@ const MAX_HISTORY_ENTRIES = 50
 export const { use: usePromptHistory, provider: PromptHistoryProvider } = createSimpleContext({
   name: "PromptHistory",
   init: () => {
-    const historyFile = Bun.file(path.join(Global.Path.state, "prompt-history.jsonl"))
+    const historyPath = path.join(Global.Path.state, "prompt-history.jsonl")
     onMount(async () => {
-      const text = await historyFile.text().catch(() => "")
+      const text = await Filesystem.readText(historyPath).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(historyFile.name!, content).catch(() => {})
+        writeFile(historyPath, content).catch(() => {})
       }
     })
 
@@ -97,11 +98,11 @@ export const { use: usePromptHistory, provider: PromptHistoryProvider } = create
 
         if (trimmed) {
           const content = store.history.map((line) => JSON.stringify(line)).join("\n") + "\n"
-          writeFile(historyFile.name!, content).catch(() => {})
+          writeFile(historyPath, content).catch(() => {})
           return
         }
 
-        appendFile(historyFile.name!, JSON.stringify(entry) + "\n").catch(() => {})
+        appendFile(historyPath, JSON.stringify(entry) + "\n").catch(() => {})
       },
     }
   },
diff --git a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
index 4114daf6c..d63c248fb 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
@@ -1,6 +1,8 @@
 import { BoxRenderable, TextareaRenderable, MouseEvent, PasteEvent, t, dim, fg } from "@opentui/core"
 import { createEffect, createMemo, type JSX, onMount, createSignal, onCleanup, on, Show, Switch, Match } from "solid-js"
 import "opentui-spinner/solid"
+import path from "path"
+import { Filesystem } from "@/util/filesystem"
 import { useLocal } from "@tui/context/local"
 import { useTheme } from "@tui/context/theme"
 import { EmptyBorder } from "@tui/component/border"
@@ -931,26 +933,26 @@ export function Prompt(props: PromptProps) {
                 const isUrl = /^(https?):\/\//.test(filepath)
                 if (!isUrl) {
                   try {
-                    const file = Bun.file(filepath)
+                    const mime = Filesystem.mimeType(filepath)
+                    const filename = path.basename(filepath)
                     // Handle SVG as raw text content, not as base64 image
-                    if (file.type === "image/svg+xml") {
+                    if (mime === "image/svg+xml") {
                       event.preventDefault()
-                      const content = await file.text().catch(() => {})
+                      const content = await Filesystem.readText(filepath).catch(() => {})
                       if (content) {
-                        pasteText(content, `[SVG: ${file.name ?? "image"}]`)
+                        pasteText(content, `[SVG: ${filename ?? "image"}]`)
                         return
                       }
                     }
-                    if (file.type.startsWith("image/")) {
+                    if (mime.startsWith("image/")) {
                       event.preventDefault()
-                      const content = await file
-                        .arrayBuffer()
+                      const content = await Filesystem.readArrayBuffer(filepath)
                         .then((buffer) => Buffer.from(buffer).toString("base64"))
                         .catch(() => {})
                       if (content) {
                         await pasteImage({
-                          filename: file.name,
-                          mime: file.type,
+                          filename,
+                          mime,
                           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 fd1cba86b..d4dc138d8 100644
--- a/packages/opencode/src/cli/cmd/tui/component/prompt/stash.tsx
+++ b/packages/opencode/src/cli/cmd/tui/component/prompt/stash.tsx
@@ -1,5 +1,6 @@
 import path from "path"
 import { Global } from "@/global"
+import { Filesystem } from "@/util/filesystem"
 import { onMount } from "solid-js"
 import { createStore, produce } from "solid-js/store"
 import { clone } from "remeda"
@@ -18,9 +19,9 @@ const MAX_STASH_ENTRIES = 50
 export const { use: usePromptStash, provider: PromptStashProvider } = createSimpleContext({
   name: "PromptStash",
   init: () => {
-    const stashFile = Bun.file(path.join(Global.Path.state, "prompt-stash.jsonl"))
+    const stashPath = path.join(Global.Path.state, "prompt-stash.jsonl")
     onMount(async () => {
-      const text = await stashFile.text().catch(() => "")
+      const text = await Filesystem.readText(stashPath).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(stashFile.name!, content).catch(() => {})
+        writeFile(stashPath, content).catch(() => {})
       }
     })
 
@@ -66,11 +67,11 @@ export const { use: usePromptStash, provider: PromptStashProvider } = createSimp
 
         if (trimmed) {
           const content = store.entries.map((line) => JSON.stringify(line)).join("\n") + "\n"
-          writeFile(stashFile.name!, content).catch(() => {})
+          writeFile(stashPath, content).catch(() => {})
           return
         }
 
-        appendFile(stashFile.name!, JSON.stringify(stash) + "\n").catch(() => {})
+        appendFile(stashPath, JSON.stringify(stash) + "\n").catch(() => {})
       },
       pop() {
         if (store.entries.length === 0) return undefined
@@ -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(stashFile.name!, content).catch(() => {})
+        writeFile(stashPath, content).catch(() => {})
         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(stashFile.name!, content).catch(() => {})
+        writeFile(stashPath, content).catch(() => {})
       },
     }
   },
diff --git a/packages/opencode/src/cli/cmd/tui/context/kv.tsx b/packages/opencode/src/cli/cmd/tui/context/kv.tsx
index 651c2dbc0..7a52156f8 100644
--- a/packages/opencode/src/cli/cmd/tui/context/kv.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/kv.tsx
@@ -1,4 +1,5 @@
 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"
@@ -9,10 +10,9 @@ export const { use: useKV, provider: KVProvider } = createSimpleContext({
   init: () => {
     const [ready, setReady] = createSignal(false)
     const [store, setStore] = createStore<Record<string, any>>()
-    const file = Bun.file(path.join(Global.Path.state, "kv.json"))
+    const filePath = path.join(Global.Path.state, "kv.json")
 
-    file
-      .json()
+    Filesystem.readJson(filePath)
       .then((x) => {
         setStore(x)
       })
@@ -44,7 +44,7 @@ export const { use: useKV, provider: KVProvider } = createSimpleContext({
       },
       set(key: string, value: any) {
         setStore(key, value)
-        Bun.write(file, JSON.stringify(store, null, 2))
+        Filesystem.writeJson(filePath, store)
       },
     }
     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 72c72dc5b..d93079f12 100644
--- a/packages/opencode/src/cli/cmd/tui/context/local.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/local.tsx
@@ -12,6 +12,7 @@ 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",
@@ -119,7 +120,7 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
         variant: {},
       })
 
-      const file = Bun.file(path.join(Global.Path.state, "model.json"))
+      const filePath = path.join(Global.Path.state, "model.json")
       const state = {
         pending: false,
       }
@@ -130,19 +131,15 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
           return
         }
         state.pending = false
-        Bun.write(
-          file,
-          JSON.stringify({
-            recent: modelStore.recent,
-            favorite: modelStore.favorite,
-            variant: modelStore.variant,
-          }),
-        )
+        Filesystem.writeJson(filePath, {
+          recent: modelStore.recent,
+          favorite: modelStore.favorite,
+          variant: modelStore.variant,
+        })
       }
 
-      file
-        .json()
-        .then((x) => {
+      Filesystem.readJson(filePath)
+        .then((x: any) => {
           if (Array.isArray(x.recent)) setModelStore("recent", x.recent)
           if (Array.isArray(x.favorite)) setModelStore("favorite", x.favorite)
           if (typeof x.variant === "object" && x.variant !== null) setModelStore("variant", x.variant)
diff --git a/packages/opencode/src/cli/cmd/tui/context/theme.tsx b/packages/opencode/src/cli/cmd/tui/context/theme.tsx
index 41c5a4a83..f9db1d77c 100644
--- a/packages/opencode/src/cli/cmd/tui/context/theme.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/theme.tsx
@@ -412,7 +412,7 @@ async function getCustomThemes() {
       cwd: dir,
     })) {
       const name = path.basename(item, ".json")
-      result[name] = await Bun.file(item).json()
+      result[name] = await Filesystem.readJson(item)
     }
   }
   return result
diff --git a/packages/opencode/src/cli/cmd/tui/thread.ts b/packages/opencode/src/cli/cmd/tui/thread.ts
index 9eb296032..50f63c3df 100644
--- a/packages/opencode/src/cli/cmd/tui/thread.ts
+++ b/packages/opencode/src/cli/cmd/tui/thread.ts
@@ -3,10 +3,12 @@ import { tui } from "./app"
 import { Rpc } from "@/util/rpc"
 import { type rpc } from "./worker"
 import path from "path"
+import { fileURLToPath } from "url"
 import { UI } from "@/cli/ui"
 import { iife } from "@/util/iife"
 import { Log } from "@/util/log"
 import { withNetworkOptions, resolveNetworkOptions } from "@/cli/network"
+import { Filesystem } from "@/util/filesystem"
 import type { Event } from "@opencode-ai/sdk/v2"
 import type { EventSource } from "./context/sdk"
 import { win32DisableProcessedInput, win32InstallCtrlCGuard } from "./win32"
@@ -99,7 +101,7 @@ export const TuiThreadCommand = cmd({
       const distWorker = new URL("./cli/cmd/tui/worker.js", import.meta.url)
       const workerPath = await iife(async () => {
         if (typeof OPENCODE_WORKER_PATH !== "undefined") return OPENCODE_WORKER_PATH
-        if (await Bun.file(distWorker).exists()) return distWorker
+        if (await Filesystem.exists(fileURLToPath(distWorker))) return distWorker
         return localWorker
       })
       try {
diff --git a/packages/opencode/src/lsp/client.ts b/packages/opencode/src/lsp/client.ts
index 8704b65ac..084ccf831 100644
--- a/packages/opencode/src/lsp/client.ts
+++ b/packages/opencode/src/lsp/client.ts
@@ -147,8 +147,7 @@ export namespace LSPClient {
       notify: {
         async open(input: { path: string }) {
           input.path = path.isAbsolute(input.path) ? input.path : path.resolve(Instance.directory, input.path)
-          const file = Bun.file(input.path)
-          const text = await file.text()
+          const text = await Filesystem.readText(input.path)
           const extension = path.extname(input.path)
           const languageId = LANGUAGE_EXTENSIONS[extension] ?? "plaintext"
 
diff --git a/packages/opencode/src/lsp/server.ts b/packages/opencode/src/lsp/server.ts
index 0200be226..a4ebeb5a2 100644
--- a/packages/opencode/src/lsp/server.ts
+++ b/packages/opencode/src/lsp/server.ts
@@ -131,7 +131,7 @@ export namespace LSPServer {
           "bin",
           "vue-language-server.js",
         )
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "@vue/language-server"], {
             cwd: Global.Path.bin,
@@ -173,14 +173,14 @@ export namespace LSPServer {
       if (!eslint) return
       log.info("spawning eslint server")
       const serverPath = path.join(Global.Path.bin, "vscode-eslint", "server", "out", "eslintServer.js")
-      if (!(await Bun.file(serverPath).exists())) {
+      if (!(await Filesystem.exists(serverPath))) {
         if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
         log.info("downloading and building VS Code ESLint server")
         const response = await fetch("https://github.com/microsoft/vscode-eslint/archive/refs/heads/main.zip")
         if (!response.ok) return
 
         const zipPath = path.join(Global.Path.bin, "vscode-eslint.zip")
-        await Bun.file(zipPath).write(response)
+        if (response.body) await Filesystem.writeStream(zipPath, response.body)
 
         const ok = await Archive.extractZip(zipPath, Global.Path.bin)
           .then(() => true)
@@ -242,7 +242,7 @@ export namespace LSPServer {
 
       const resolveBin = async (target: string) => {
         const localBin = path.join(root, target)
-        if (await Bun.file(localBin).exists()) return localBin
+        if (await Filesystem.exists(localBin)) return localBin
 
         const candidates = Filesystem.up({
           targets: [target],
@@ -326,7 +326,7 @@ export namespace LSPServer {
     async spawn(root) {
       const localBin = path.join(root, "node_modules", ".bin", "biome")
       let bin: string | undefined
-      if (await Bun.file(localBin).exists()) bin = localBin
+      if (await Filesystem.exists(localBin)) bin = localBin
       if (!bin) {
         const found = Bun.which("biome")
         if (found) bin = found
@@ -467,7 +467,7 @@ export namespace LSPServer {
         const potentialPythonPath = isWindows
           ? path.join(venvPath, "Scripts", "python.exe")
           : path.join(venvPath, "bin", "python")
-        if (await Bun.file(potentialPythonPath).exists()) {
+        if (await Filesystem.exists(potentialPythonPath)) {
           initialization["pythonPath"] = potentialPythonPath
           break
         }
@@ -479,7 +479,7 @@ export namespace LSPServer {
           const potentialTyPath = isWindows
             ? path.join(venvPath, "Scripts", "ty.exe")
             : path.join(venvPath, "bin", "ty")
-          if (await Bun.file(potentialTyPath).exists()) {
+          if (await Filesystem.exists(potentialTyPath)) {
             binary = potentialTyPath
             break
           }
@@ -511,7 +511,7 @@ export namespace LSPServer {
       const args = []
       if (!binary) {
         const js = path.join(Global.Path.bin, "node_modules", "pyright", "dist", "pyright-langserver.js")
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "pyright"], {
             cwd: Global.Path.bin,
@@ -536,7 +536,7 @@ export namespace LSPServer {
         const potentialPythonPath = isWindows
           ? path.join(venvPath, "Scripts", "python.exe")
           : path.join(venvPath, "bin", "python")
-        if (await Bun.file(potentialPythonPath).exists()) {
+        if (await Filesystem.exists(potentialPythonPath)) {
           initialization["pythonPath"] = potentialPythonPath
           break
         }
@@ -571,7 +571,7 @@ export namespace LSPServer {
           process.platform === "win32" ? "language_server.bat" : "language_server.sh",
         )
 
-        if (!(await Bun.file(binary).exists())) {
+        if (!(await Filesystem.exists(binary))) {
           const elixir = Bun.which("elixir")
           if (!elixir) {
             log.error("elixir is required to run elixir-ls")
@@ -584,7 +584,7 @@ export namespace LSPServer {
           const response = await fetch("https://github.com/elixir-lsp/elixir-ls/archive/refs/heads/master.zip")
           if (!response.ok) return
           const zipPath = path.join(Global.Path.bin, "elixir-ls.zip")
-          await Bun.file(zipPath).write(response)
+          if (response.body) await Filesystem.writeStream(zipPath, response.body)
 
           const ok = await Archive.extractZip(zipPath, Global.Path.bin)
             .then(() => true)
@@ -692,7 +692,7 @@ export namespace LSPServer {
         }
 
         const tempPath = path.join(Global.Path.bin, assetName)
-        await Bun.file(tempPath).write(downloadResponse)
+        if (downloadResponse.body) await Filesystem.writeStream(tempPath, downloadResponse.body)
 
         if (ext === "zip") {
           const ok = await Archive.extractZip(tempPath, Global.Path.bin)
@@ -710,7 +710,7 @@ export namespace LSPServer {
 
         bin = path.join(Global.Path.bin, "zls" + (platform === "win32" ? ".exe" : ""))
 
-        if (!(await Bun.file(bin).exists())) {
+        if (!(await Filesystem.exists(bin))) {
           log.error("Failed to extract zls binary")
           return
         }
@@ -857,7 +857,7 @@ export namespace LSPServer {
         // Stop at filesystem root
         const cargoTomlPath = path.join(currentDir, "Cargo.toml")
         try {
-          const cargoTomlContent = await Bun.file(cargoTomlPath).text()
+          const cargoTomlContent = await Filesystem.readText(cargoTomlPath)
           if (cargoTomlContent.includes("[workspace]")) {
             return currentDir
           }
@@ -907,7 +907,7 @@ export namespace LSPServer {
 
       const ext = process.platform === "win32" ? ".exe" : ""
       const direct = path.join(Global.Path.bin, "clangd" + ext)
-      if (await Bun.file(direct).exists()) {
+      if (await Filesystem.exists(direct)) {
         return {
           process: spawn(direct, args, {
             cwd: root,
@@ -920,7 +920,7 @@ export namespace LSPServer {
         if (!entry.isDirectory()) continue
         if (!entry.name.startsWith("clangd_")) continue
         const candidate = path.join(Global.Path.bin, entry.name, "bin", "clangd" + ext)
-        if (await Bun.file(candidate).exists()) {
+        if (await Filesystem.exists(candidate)) {
           return {
             process: spawn(candidate, args, {
               cwd: root,
@@ -990,7 +990,7 @@ export namespace LSPServer {
         log.error("Failed to write clangd archive")
         return
       }
-      await Bun.write(archive, buf)
+      await Filesystem.write(archive, Buffer.from(buf))
 
       const zip = name.endsWith(".zip")
       const tar = name.endsWith(".tar.xz")
@@ -1014,7 +1014,7 @@ export namespace LSPServer {
       await fs.rm(archive, { force: true })
 
       const bin = path.join(Global.Path.bin, "clangd_" + tag, "bin", "clangd" + ext)
-      if (!(await Bun.file(bin).exists())) {
+      if (!(await Filesystem.exists(bin))) {
         log.error("Failed to extract clangd binary")
         return
       }
@@ -1045,7 +1045,7 @@ export namespace LSPServer {
       const args: string[] = []
       if (!binary) {
         const js = path.join(Global.Path.bin, "node_modules", "svelte-language-server", "bin", "server.js")
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "svelte-language-server"], {
             cwd: Global.Path.bin,
@@ -1092,7 +1092,7 @@ export namespace LSPServer {
       const args: string[] = []
       if (!binary) {
         const js = path.join(Global.Path.bin, "node_modules", "@astrojs", "language-server", "bin", "nodeServer.js")
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "@astrojs/language-server"], {
             cwd: Global.Path.bin,
@@ -1248,7 +1248,7 @@ export namespace LSPServer {
       const distPath = path.join(Global.Path.bin, "kotlin-ls")
       const launcherScript =
         process.platform === "win32" ? path.join(distPath, "kotlin-lsp.cmd") : path.join(distPath, "kotlin-lsp.sh")
-      const installed = await Bun.file(launcherScript).exists()
+      const installed = await Filesystem.exists(launcherScript)
       if (!installed) {
         if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
         log.info("Downloading Kotlin Language Server from GitHub.")
@@ -1307,7 +1307,7 @@ export namespace LSPServer {
         }
         log.info("Installed Kotlin Language Server", { path: launcherScript })
       }
-      if (!(await Bun.file(launcherScript).exists())) {
+      if (!(await Filesystem.exists(launcherScript))) {
         log.error(`Failed to locate the Kotlin LS launcher script in the installed directory: ${distPath}.`)
         return
       }
@@ -1336,7 +1336,7 @@ export namespace LSPServer {
           "src",
           "server.js",
         )
-        const exists = await Bun.file(js).exists()
+        const exists = await Filesystem.exists(js)
         if (!exists) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "yaml-language-server"], {
@@ -1443,7 +1443,7 @@ export namespace LSPServer {
         }
 
         const tempPath = path.join(Global.Path.bin, assetName)
-        await Bun.file(tempPath).write(downloadResponse)
+        if (downloadResponse.body) await Filesystem.writeStream(tempPath, downloadResponse.body)
 
         // Unlike zls which is a single self-contained binary,
         // lua-language-server needs supporting files (meta/, locale/, etc.)
@@ -1482,7 +1482,7 @@ export namespace LSPServer {
         // Binary is located in bin/ subdirectory within the extracted archive
         bin = path.join(installDir, "bin", "lua-language-server" + (platform === "win32" ? ".exe" : ""))
 
-        if (!(await Bun.file(bin).exists())) {
+        if (!(await Filesystem.exists(bin))) {
           log.error("Failed to extract lua-language-server binary")
           return
         }
@@ -1516,7 +1516,7 @@ export namespace LSPServer {
       const args: string[] = []
       if (!binary) {
         const js = path.join(Global.Path.bin, "node_modules", "intelephense", "lib", "intelephense.js")
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "intelephense"], {
             cwd: Global.Path.bin,
@@ -1613,7 +1613,7 @@ export namespace LSPServer {
       const args: string[] = []
       if (!binary) {
         const js = path.join(Global.Path.bin, "node_modules", "bash-language-server", "out", "cli.js")
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "bash-language-server"], {
             cwd: Global.Path.bin,
@@ -1654,22 +1654,17 @@ export namespace LSPServer {
 
       if (!bin) {
         if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
-        log.info("downloading terraform-ls from GitHub releases")
+        log.info("downloading terraform-ls from HashiCorp releases")
 
-        const releaseResponse = await fetch("https://api.github.com/repos/hashicorp/terraform-ls/releases/latest")
+        const releaseResponse = await fetch("https://api.releases.hashicorp.com/v1/releases/terraform-ls/latest")
         if (!releaseResponse.ok) {
           log.error("Failed to fetch terraform-ls release info")
           return
         }
 
         const release = (await releaseResponse.json()) as {
-          tag_name?: string
-          assets?: { name?: string; browser_download_url?: string }[]
-        }
-        const version = release.tag_name?.replace("v", "")
-        if (!version) {
-          log.error("terraform-ls release did not include a version tag")
-          return
+          version?: string
+          builds?: { arch?: string; os?: string; url?: string }[]
         }
 
         const platform = process.platform
@@ -1678,23 +1673,21 @@ export namespace LSPServer {
         const tfArch = arch === "arm64" ? "arm64" : "amd64"
         const tfPlatform = platform === "win32" ? "windows" : platform
 
-        const assetName = `terraform-ls_${version}_${tfPlatform}_${tfArch}.zip`
-
-        const assets = release.assets ?? []
-        const asset = assets.find((a) => a.name === assetName)
-        if (!asset?.browser_download_url) {
-          log.error(`Could not find asset ${assetName} in terraform-ls release`)
+        const builds = release.builds ?? []
+        const build = builds.find((b) => b.arch === tfArch && b.os === tfPlatform)
+        if (!build?.url) {
+          log.error(`Could not find build for ${tfPlatform}/${tfArch} terraform-ls release version ${release.version}`)
           return
         }
 
-        const downloadResponse = await fetch(asset.browser_download_url)
+        const downloadResponse = await fetch(build.url)
         if (!downloadResponse.ok) {
           log.error("Failed to download terraform-ls")
           return
         }
 
-        const tempPath = path.join(Global.Path.bin, assetName)
-        await Bun.file(tempPath).write(downloadResponse)
+        const tempPath = path.join(Global.Path.bin, "terraform-ls.zip")
+        if (downloadResponse.body) await Filesystem.writeStream(tempPath, downloadResponse.body)
 
         const ok = await Archive.extractZip(tempPath, Global.Path.bin)
           .then(() => true)
@@ -1707,7 +1700,7 @@ export namespace LSPServer {
 
         bin = path.join(Global.Path.bin, "terraform-ls" + (platform === "win32" ? ".exe" : ""))
 
-        if (!(await Bun.file(bin).exists())) {
+        if (!(await Filesystem.exists(bin))) {
           log.error("Failed to extract terraform-ls binary")
           return
         }
@@ -1784,7 +1777,7 @@ export namespace LSPServer {
         }
 
         const tempPath = path.join(Global.Path.bin, assetName)
-        await Bun.file(tempPath).write(downloadResponse)
+        if (downloadResponse.body) await Filesystem.writeStream(tempPath, downloadResponse.body)
 
         if (ext === "zip") {
           const ok = await Archive.extractZip(tempPath, Global.Path.bin)
@@ -1803,7 +1796,7 @@ export namespace LSPServer {
 
         bin = path.join(Global.Path.bin, "texlab" + (platform === "win32" ? ".exe" : ""))
 
-        if (!(await Bun.file(bin).exists())) {
+        if (!(await Filesystem.exists(bin))) {
           log.error("Failed to extract texlab binary")
           return
         }
@@ -1832,7 +1825,7 @@ export namespace LSPServer {
       const args: string[] = []
       if (!binary) {
         const js = path.join(Global.Path.bin, "node_modules", "dockerfile-language-server-nodejs", "lib", "server.js")
-        if (!(await Bun.file(js).exists())) {
+        if (!(await Filesystem.exists(js))) {
           if (Flag.OPENCODE_DISABLE_LSP_DOWNLOAD) return
           await Bun.spawn([BunProc.which(), "install", "dockerfile-language-server-nodejs"], {
             cwd: Global.Path.bin,
@@ -1990,7 +1983,7 @@ export namespace LSPServer {
         }
 
         const tempPath = path.join(Global.Path.bin, assetName)
-        await Bun.file(tempPath).write(downloadResponse)
+        if (downloadResponse.body) await Filesystem.writeStream(tempPath, downloadResponse.body)
 
         if (ext === "zip") {
           const ok = await Archive.extractZip(tempPath, Global.Path.bin)
@@ -2008,7 +2001,7 @@ export namespace LSPServer {
 
         bin = path.join(Global.Path.bin, "tinymist" + (platform === "win32" ? ".exe" : ""))
 
-        if (!(await Bun.file(bin).exists())) {
+        if (!(await Filesystem.exists(bin))) {
           log.error("Failed to extract tinymist binary")
           return
         }
diff --git a/packages/opencode/src/mcp/auth.ts b/packages/opencode/src/mcp/auth.ts
index 0f91a35b8..399986376 100644
--- a/packages/opencode/src/mcp/auth.ts
+++ b/packages/opencode/src/mcp/auth.ts
@@ -1,6 +1,7 @@
 import path from "path"
 import z from "zod"
 import { Global } from "../global"
+import { Filesystem } from "../util/filesystem"
 
 export namespace McpAuth {
   export const Tokens = z.object({
@@ -53,25 +54,22 @@ export namespace McpAuth {
   }
 
   export async function all(): Promise<Record<string, Entry>> {
-    const file = Bun.file(filepath)
-    return file.json().catch(() => ({}))
+    return Filesystem.readJson<Record<string, Entry>>(filepath).catch(() => ({}))
   }
 
   export async function set(mcpName: string, entry: Entry, serverUrl?: string): Promise<void> {
-    const file = Bun.file(filepath)
     const data = await all()
     // Always update serverUrl if provided
     if (serverUrl) {
       entry.serverUrl = serverUrl
     }
-    await Bun.write(file, JSON.stringify({ ...data, [mcpName]: entry }, null, 2), { mode: 0o600 })
+    await Filesystem.writeJson(filepath, { ...data, [mcpName]: entry }, 0o600)
   }
 
   export async function remove(mcpName: string): Promise<void> {
-    const file = Bun.file(filepath)
     const data = await all()
     delete data[mcpName]
-    await Bun.write(file, JSON.stringify(data, null, 2), { mode: 0o600 })
+    await Filesystem.writeJson(filepath, data, 0o600)
   }
 
   export async function updateTokens(mcpName: string, tokens: Tokens, serverUrl?: string): Promise<void> {
diff --git a/packages/opencode/src/project/project.ts b/packages/opencode/src/project/project.ts
index 8fa0f6c6f..63c1c4cad 100644
--- a/packages/opencode/src/project/project.ts
+++ b/packages/opencode/src/project/project.ts
@@ -86,8 +86,7 @@ export namespace Project {
         const gitBinary = Bun.which("git")
 
         // cached id calculation
-        let id = await Bun.file(path.join(dotgit, "opencode"))
-          .text()
+        let id = await Filesystem.readText(path.join(dotgit, "opencode"))
           .then((x) => x.trim())
           .catch(() => undefined)
 
@@ -125,9 +124,7 @@ export namespace Project {
 
           id = roots[0]
           if (id) {
-            void Bun.file(path.join(dotgit, "opencode"))
-              .write(id)
-              .catch(() => undefined)
+            void Filesystem.write(path.join(dotgit, "opencode"), id).catch(() => undefined)
           }
         }
 
@@ -277,10 +274,9 @@ export namespace Project {
     )
     const shortest = matches.sort((a, b) => a.length - b.length)[0]
     if (!shortest) return
-    const file = Bun.file(shortest)
-    const buffer = await file.arrayBuffer()
-    const base64 = Buffer.from(buffer).toString("base64")
-    const mime = file.type || "image/png"
+    const buffer = await Filesystem.readBytes(shortest)
+    const base64 = buffer.toString("base64")
+    const mime = Filesystem.mimeType(shortest) || "image/png"
     const url = `data:${mime};base64,${base64}`
     await update({
       projectID: input.id,
@@ -381,10 +377,8 @@ export namespace Project {
     const data = fromRow(row)
     const valid: string[] = []
     for (const dir of data.sandboxes) {
-      const stat = await Bun.file(dir)
-        .stat()
-        .catch(() => undefined)
-      if (stat?.isDirectory()) valid.push(dir)
+      const s = Filesystem.stat(dir)
+      if (s?.isDirectory()) valid.push(dir)
     }
     return valid
   }
diff --git a/packages/opencode/src/provider/models.ts b/packages/opencode/src/provider/models.ts
index 0960176e2..bae331784 100644
--- a/packages/opencode/src/provider/models.ts
+++ b/packages/opencode/src/provider/models.ts
@@ -5,6 +5,7 @@ import z from "zod"
 import { Installation } from "../installation"
 import { Flag } from "../flag/flag"
 import { lazy } from "@/util/lazy"
+import { Filesystem } from "../util/filesystem"
 
 // Try to import bundled snapshot (generated at build time)
 // Falls back to undefined in dev mode when snapshot doesn't exist
@@ -85,8 +86,7 @@ export namespace ModelsDev {
   }
 
   export const Data = lazy(async () => {
-    const file = Bun.file(Flag.OPENCODE_MODELS_PATH ?? filepath)
-    const result = await file.json().catch(() => {})
+    const result = await Filesystem.readJson(Flag.OPENCODE_MODELS_PATH ?? filepath).catch(() => {})
     if (result) return result
     // @ts-ignore
     const snapshot = await import("./models-snapshot")
@@ -104,7 +104,6 @@ export namespace ModelsDev {
   }
 
   export async function refresh() {
-    const file = Bun.file(filepath)
     const result = await fetch(`${url()}/api.json`, {
       headers: {
         "User-Agent": Installation.USER_AGENT,
@@ -116,7 +115,7 @@ export namespace ModelsDev {
       })
     })
     if (result && result.ok) {
-      await Bun.write(file, await result.text())
+      await Filesystem.write(filepath, await result.text())
       ModelsDev.Data.reset()
     }
   }
diff --git a/packages/opencode/src/provider/provider.ts b/packages/opencode/src/provider/provider.ts
index f1871ddb6..022ec3167 100644
--- a/packages/opencode/src/provider/provider.ts
+++ b/packages/opencode/src/provider/provider.ts
@@ -16,6 +16,7 @@ import { Flag } from "../flag/flag"
 import { iife } from "@/util/iife"
 import { Global } from "../global"
 import path from "path"
+import { Filesystem } from "../util/filesystem"
 
 // Direct imports for bundled providers
 import { createAmazonBedrock, type AmazonBedrockProviderSettings } from "@ai-sdk/amazon-bedrock"
@@ -1289,8 +1290,9 @@ export namespace Provider {
     if (cfg.model) return parseModel(cfg.model)
 
     const providers = await list()
-    const recent = (await Bun.file(path.join(Global.Path.state, "model.json"))
-      .json()
+    const recent = (await Filesystem.readJson<{ recent?: { providerID: string; modelID: string }[] }>(
+      path.join(Global.Path.state, "model.json"),
+    )
       .then((x) => (Array.isArray(x.recent) ? x.recent : []))
       .catch(() => [])) as { providerID: string; modelID: string }[]
     for (const entry of recent) {
diff --git a/packages/opencode/src/session/instruction.ts b/packages/opencode/src/session/instruction.ts
index 6fb2a7aeb..d65ada278 100644
--- a/packages/opencode/src/session/instruction.ts
+++ b/packages/opencode/src/session/instruction.ts
@@ -85,7 +85,7 @@ export namespace InstructionPrompt {
     }
 
     for (const file of globalFiles()) {
-      if (await Bun.file(file).exists()) {
+      if (await Filesystem.exists(file)) {
         paths.add(path.resolve(file))
         break
       }
@@ -120,9 +120,7 @@ export namespace InstructionPrompt {
     const paths = await systemPaths()
 
     const files = Array.from(paths).map(async (p) => {
-      const content = await Bun.file(p)
-        .text()
-        .catch(() => "")
+      const content = await Filesystem.readText(p).catch(() => "")
       return content ? "Instructions from: " + p + "\n" + content : ""
     })
 
@@ -164,7 +162,7 @@ export namespace InstructionPrompt {
   export async function find(dir: string) {
     for (const file of FILES) {
       const filepath = path.resolve(path.join(dir, file))
-      if (await Bun.file(filepath).exists()) return filepath
+      if (await Filesystem.exists(filepath)) return filepath
     }
   }
 
@@ -182,9 +180,7 @@ export namespace InstructionPrompt {
 
       if (found && found !== target && !system.has(found) && !already.has(found) && !isClaimed(messageID, found)) {
         claim(messageID, found)
-        const content = await Bun.file(found)
-          .text()
-          .catch(() => undefined)
+        const content = await Filesystem.readText(found).catch(() => undefined)
         if (content) {
           results.push({ filepath: found, content: "Instructions from: " + found + "\n" + content })
         }
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index d1f407258..6ca93979e 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -2,6 +2,7 @@ import path from "path"
 import os from "os"
 import fs from "fs/promises"
 import z from "zod"
+import { Filesystem } from "../util/filesystem"
 import { Identifier } from "../id/id"
 import { MessageV2 } from "./message-v2"
 import { Log } from "../util/log"
@@ -1082,11 +1083,9 @@ export namespace SessionPrompt {
               // have to normalize, symbol search returns absolute paths
               // Decode the pathname since URL constructor doesn't automatically decode it
               const filepath = fileURLToPath(part.url)
-              const stat = await Bun.file(filepath)
-                .stat()
-                .catch(() => undefined)
+              const s = Filesystem.stat(filepath)
 
-              if (stat?.isDirectory()) {
+              if (s?.isDirectory()) {
                 part.mime = "application/x-directory"
               }
 
@@ -1233,14 +1232,13 @@ export namespace SessionPrompt {
                 ]
               }
 
-              const file = Bun.file(filepath)
               FileTime.read(input.sessionID, filepath)
               return [
                 {
                   messageID: info.id,
                   sessionID: input.sessionID,
                   type: "text",
-                  text: `Called the Read tool with the following input: {\"filePath\":\"${filepath}\"}`,
+                  text: `Called the Read tool with the following input: {"filePath":"${filepath}"}`,
                   synthetic: true,
                 },
                 {
@@ -1248,7 +1246,7 @@ export namespace SessionPrompt {
                   messageID: info.id,
                   sessionID: input.sessionID,
                   type: "file",
-                  url: `data:${part.mime};base64,` + Buffer.from(await file.bytes()).toString("base64"),
+                  url: `data:${part.mime};base64,` + (await Filesystem.readBytes(filepath)).toString("base64"),
                   mime: part.mime,
                   filename: part.filename!,
                   source: part.source,
@@ -1354,7 +1352,7 @@ export namespace SessionPrompt {
     // Switching from plan mode to build mode
     if (input.agent.name !== "plan" && assistantMessage?.info.agent === "plan") {
       const plan = Session.plan(input.session)
-      const exists = await Bun.file(plan).exists()
+      const exists = await Filesystem.exists(plan)
       if (exists) {
         const part = await Session.updatePart({
           id: Identifier.ascending("part"),
@@ -1373,7 +1371,7 @@ export namespace SessionPrompt {
     // Entering plan mode
     if (input.agent.name === "plan" && assistantMessage?.info.agent !== "plan") {
       const plan = Session.plan(input.session)
-      const exists = await Bun.file(plan).exists()
+      const exists = await Filesystem.exists(plan)
       if (!exists) await fs.mkdir(path.dirname(plan), { recursive: true })
       const part = await Session.updatePart({
         id: Identifier.ascending("part"),
diff --git a/packages/opencode/src/shell/shell.ts b/packages/opencode/src/shell/shell.ts
index 2e8d48bfd..e7b7cdb3e 100644
--- a/packages/opencode/src/shell/shell.ts
+++ b/packages/opencode/src/shell/shell.ts
@@ -1,5 +1,6 @@
 import { Flag } from "@/flag/flag"
 import { lazy } from "@/util/lazy"
+import { Filesystem } from "@/util/filesystem"
 import path from "path"
 import { spawn, type ChildProcess } from "child_process"
 
@@ -43,7 +44,7 @@ export namespace Shell {
         // git.exe is typically at: C:\Program Files\Git\cmd\git.exe
         // bash.exe is at: C:\Program Files\Git\bin\bash.exe
         const bash = path.join(git, "..", "..", "bin", "bash.exe")
-        if (Bun.file(bash).size) return bash
+        if (Filesystem.stat(bash)?.size) return bash
       }
       return process.env.COMSPEC || "cmd.exe"
     }
diff --git a/packages/opencode/src/skill/discovery.ts b/packages/opencode/src/skill/discovery.ts
index a4bf97d7a..846002cda 100644
--- a/packages/opencode/src/skill/discovery.ts
+++ b/packages/opencode/src/skill/discovery.ts
@@ -2,6 +2,7 @@ import path from "path"
 import { mkdir } from "fs/promises"
 import { Log } from "../util/log"
 import { Global } from "../global"
+import { Filesystem } from "../util/filesystem"
 
 export namespace Discovery {
   const log = Log.create({ service: "skill-discovery" })
@@ -19,14 +20,14 @@ export namespace Discovery {
   }
 
   async function get(url: string, dest: string): Promise<boolean> {
-    if (await Bun.file(dest).exists()) return true
+    if (await Filesystem.exists(dest)) return true
     return fetch(url)
       .then(async (response) => {
         if (!response.ok) {
           log.error("failed to download", { url, status: response.status })
           return false
         }
-        await Bun.write(dest, await response.text())
+        if (response.body) await Filesystem.writeStream(dest, response.body)
         return true
       })
       .catch((err) => {
@@ -88,7 +89,7 @@ export namespace Discovery {
         )
 
         const md = path.join(root, "SKILL.md")
-        if (await Bun.file(md).exists()) result.push(root)
+        if (await Filesystem.exists(md)) result.push(root)
       }),
     )
 
diff --git a/packages/opencode/src/storage/db.ts b/packages/opencode/src/storage/db.ts
index 0974cbe7b..6d7bfd728 100644
--- a/packages/opencode/src/storage/db.ts
+++ b/packages/opencode/src/storage/db.ts
@@ -10,7 +10,7 @@ import { Log } from "../util/log"
 import { NamedError } from "@opencode-ai/util/error"
 import z from "zod"
 import path from "path"
-import { readFileSync, readdirSync } from "fs"
+import { readFileSync, readdirSync, existsSync } from "fs"
 import * as schema from "./schema"
 
 declare const OPENCODE_MIGRATIONS: { sql: string; timestamp: number }[] | undefined
@@ -54,7 +54,7 @@ export namespace Database {
     const sql = dirs
       .map((name) => {
         const file = path.join(dir, name, "migration.sql")
-        if (!Bun.file(file).size) return
+        if (!existsSync(file)) return
         return {
           sql: readFileSync(file, "utf-8"),
           timestamp: time(name),
diff --git a/packages/opencode/src/storage/json-migration.ts b/packages/opencode/src/storage/json-migration.ts
index e0684ce3c..268442dcf 100644
--- a/packages/opencode/src/storage/json-migration.ts
+++ b/packages/opencode/src/storage/json-migration.ts
@@ -7,6 +7,7 @@ import { SessionTable, MessageTable, PartTable, TodoTable, PermissionTable } fro
 import { SessionShareTable } from "../share/share.sql"
 import path from "path"
 import { existsSync } from "fs"
+import { Filesystem } from "../util/filesystem"
 
 export namespace JsonMigration {
   const log = Log.create({ service: "json-migration" })
@@ -82,7 +83,7 @@ export namespace JsonMigration {
       const count = end - start
       const tasks = new Array(count)
       for (let i = 0; i < count; i++) {
-        tasks[i] = Bun.file(files[start + i]).json()
+        tasks[i] = Filesystem.readJson(files[start + i])
       }
       const results = await Promise.allSettled(tasks)
       const items = new Array(count)
diff --git a/packages/opencode/src/storage/storage.ts b/packages/opencode/src/storage/storage.ts
index 18f2d67e7..691ce3c53 100644
--- a/packages/opencode/src/storage/storage.ts
+++ b/packages/opencode/src/storage/storage.ts
@@ -39,7 +39,7 @@ export namespace Storage {
             cwd: path.join(project, projectDir),
             absolute: true,
           })) {
-            const json = await Bun.file(msgFile).json()
+            const json = await Filesystem.readJson<any>(msgFile)
             worktree = json.path?.root
             if (worktree) break
           }
@@ -60,18 +60,15 @@ export namespace Storage {
           if (!id) continue
           projectID = id
 
-          await Bun.write(
-            path.join(dir, "project", projectID + ".json"),
-            JSON.stringify({
-              id,
-              vcs: "git",
-              worktree,
-              time: {
-                created: Date.now(),
-                initialized: Date.now(),
-              },
-            }),
-          )
+          await Filesystem.writeJson(path.join(dir, "project", projectID + ".json"), {
+            id,
+            vcs: "git",
+            worktree,
+            time: {
+              created: Date.now(),
+              initialized: Date.now(),
+            },
+          })
 
           log.info(`migrating sessions for project ${projectID}`)
           for await (const sessionFile of new Bun.Glob("storage/session/info/*.json").scan({
@@ -83,8 +80,8 @@ export namespace Storage {
               sessionFile,
               dest,
             })
-            const session = await Bun.file(sessionFile).json()
-            await Bun.write(dest, JSON.stringify(session))
+            const session = await Filesystem.readJson<any>(sessionFile)
+            await Filesystem.writeJson(dest, session)
             log.info(`migrating messages for session ${session.id}`)
             for await (const msgFile of new Bun.Glob(`storage/session/message/${session.id}/*.json`).scan({
               cwd: fullProjectDir,
@@ -95,8 +92,8 @@ export namespace Storage {
                 msgFile,
                 dest,
               })
-              const message = await Bun.file(msgFile).json()
-              await Bun.write(dest, JSON.stringify(message))
+              const message = await Filesystem.readJson<any>(msgFile)
+              await Filesystem.writeJson(dest, message)
 
               log.info(`migrating parts for message ${message.id}`)
               for await (const partFile of new Bun.Glob(`storage/session/part/${session.id}/${message.id}/*.json`).scan(
@@ -106,12 +103,12 @@ export namespace Storage {
                 },
               )) {
                 const dest = path.join(dir, "part", message.id, path.basename(partFile))
-                const part = await Bun.file(partFile).json()
+                const part = await Filesystem.readJson(partFile)
                 log.info("copying", {
                   partFile,
                   dest,
                 })
-                await Bun.write(dest, JSON.stringify(part))
+                await Filesystem.writeJson(dest, part)
               }
             }
           }
@@ -123,35 +120,32 @@ export namespace Storage {
         cwd: dir,
         absolute: true,
       })) {
-        const session = await Bun.file(item).json()
+        const session = await Filesystem.readJson<any>(item)
         if (!session.projectID) continue
         if (!session.summary?.diffs) continue
         const { diffs } = session.summary
-        await Bun.file(path.join(dir, "session_diff", session.id + ".json")).write(JSON.stringify(diffs))
-        await Bun.file(path.join(dir, "session", session.projectID, session.id + ".json")).write(
-          JSON.stringify({
-            ...session,
-            summary: {
-              additions: diffs.reduce((sum: any, x: any) => sum + x.additions, 0),
-              deletions: diffs.reduce((sum: any, x: any) => sum + x.deletions, 0),
-            },
-          }),
-        )
+        await Filesystem.write(path.join(dir, "session_diff", session.id + ".json"), JSON.stringify(diffs))
+        await Filesystem.writeJson(path.join(dir, "session", session.projectID, session.id + ".json"), {
+          ...session,
+          summary: {
+            additions: diffs.reduce((sum: any, x: any) => sum + x.additions, 0),
+            deletions: diffs.reduce((sum: any, x: any) => sum + x.deletions, 0),
+          },
+        })
       }
     },
   ]
 
   const state = lazy(async () => {
     const dir = path.join(Global.Path.data, "storage")
-    const migration = await Bun.file(path.join(dir, "migration"))
-      .json()
+    const migration = await Filesystem.readJson<string>(path.join(dir, "migration"))
       .then((x) => parseInt(x))
       .catch(() => 0)
     for (let index = migration; index < MIGRATIONS.length; index++) {
       log.info("running migration", { index })
       const migration = MIGRATIONS[index]
       await migration(dir).catch(() => log.error("failed to run migration", { index }))
-      await Bun.write(path.join(dir, "migration"), (index + 1).toString())
+      await Filesystem.write(path.join(dir, "migration"), (index + 1).toString())
     }
     return {
       dir,
@@ -171,7 +165,7 @@ export namespace Storage {
     const target = path.join(dir, ...key) + ".json"
     return withErrorHandling(async () => {
       using _ = await Lock.read(target)
-      const result = await Bun.file(target).json()
+      const result = await Filesystem.readJson<T>(target)
       return result as T
     })
   }
@@ -181,10 +175,10 @@ export namespace Storage {
     const target = path.join(dir, ...key) + ".json"
     return withErrorHandling(async () => {
       using _ = await Lock.write(target)
-      const content = await Bun.file(target).json()
-      fn(content)
-      await Bun.write(target, JSON.stringify(content, null, 2))
-      return content as T
+      const content = await Filesystem.readJson<T>(target)
+      fn(content as T)
+      await Filesystem.writeJson(target, content)
+      return content
     })
   }
 
@@ -193,7 +187,7 @@ export namespace Storage {
     const target = path.join(dir, ...key) + ".json"
     return withErrorHandling(async () => {
       using _ = await Lock.write(target)
-      await Bun.write(target, JSON.stringify(content, null, 2))
+      await Filesystem.writeJson(target, content)
     })
   }
 
diff --git a/packages/opencode/src/tool/edit.ts b/packages/opencode/src/tool/edit.ts
index d84f6ec34..7a097d3fe 100644
--- a/packages/opencode/src/tool/edit.ts
+++ b/packages/opencode/src/tool/edit.ts
@@ -49,7 +49,7 @@ export const EditTool = Tool.define("edit", {
     let contentNew = ""
     await FileTime.withLock(filePath, async () => {
       if (params.oldString === "") {
-        const existed = await Bun.file(filePath).exists()
+        const existed = await Filesystem.exists(filePath)
         contentNew = params.newString
         diff = trimDiff(createTwoFilesPatch(filePath, filePath, contentOld, contentNew))
         await ctx.ask({
@@ -61,7 +61,7 @@ export const EditTool = Tool.define("edit", {
             diff,
           },
         })
-        await Bun.write(filePath, params.newString)
+        await Filesystem.write(filePath, params.newString)
         await Bus.publish(File.Event.Edited, {
           file: filePath,
         })
@@ -73,12 +73,11 @@ export const EditTool = Tool.define("edit", {
         return
       }
 
-      const file = Bun.file(filePath)
-      const stats = await file.stat().catch(() => {})
+      const stats = Filesystem.stat(filePath)
       if (!stats) throw new Error(`File ${filePath} not found`)
       if (stats.isDirectory()) throw new Error(`Path is a directory, not a file: ${filePath}`)
       await FileTime.assert(ctx.sessionID, filePath)
-      contentOld = await file.text()
+      contentOld = await Filesystem.readText(filePath)
       contentNew = replace(contentOld, params.oldString, params.newString, params.replaceAll)
 
       diff = trimDiff(
@@ -94,7 +93,7 @@ export const EditTool = Tool.define("edit", {
         },
       })
 
-      await file.write(contentNew)
+      await Filesystem.write(filePath, contentNew)
       await Bus.publish(File.Event.Edited, {
         file: filePath,
       })
@@ -102,7 +101,7 @@ export const EditTool = Tool.define("edit", {
         file: filePath,
         event: "change",
       })
-      contentNew = await file.text()
+      contentNew = await Filesystem.readText(filePath)
       diff = trimDiff(
         createTwoFilesPatch(filePath, filePath, normalizeLineEndings(contentOld), normalizeLineEndings(contentNew)),
       )
diff --git a/packages/opencode/src/tool/glob.ts b/packages/opencode/src/tool/glob.ts
index 9df1eedca..a2611246c 100644
--- a/packages/opencode/src/tool/glob.ts
+++ b/packages/opencode/src/tool/glob.ts
@@ -1,6 +1,7 @@
 import z from "zod"
 import path from "path"
 import { Tool } from "./tool"
+import { Filesystem } from "../util/filesystem"
 import DESCRIPTION from "./glob.txt"
 import { Ripgrep } from "../file/ripgrep"
 import { Instance } from "../project/instance"
@@ -45,10 +46,7 @@ export const GlobTool = Tool.define("glob", {
         break
       }
       const full = path.resolve(search, file)
-      const stats = await Bun.file(full)
-        .stat()
-        .then((x) => x.mtime.getTime())
-        .catch(() => 0)
+      const stats = Filesystem.stat(full)?.mtime.getTime() ?? 0
       files.push({
         path: full,
         mtime: stats,
diff --git a/packages/opencode/src/tool/grep.ts b/packages/opencode/src/tool/grep.ts
index 41ed494de..00497d4e3 100644
--- a/packages/opencode/src/tool/grep.ts
+++ b/packages/opencode/src/tool/grep.ts
@@ -1,5 +1,6 @@
 import z from "zod"
 import { Tool } from "./tool"
+import { Filesystem } from "../util/filesystem"
 import { Ripgrep } from "../file/ripgrep"
 
 import DESCRIPTION from "./grep.txt"
@@ -83,8 +84,7 @@ export const GrepTool = Tool.define("grep", {
       const lineNum = parseInt(lineNumStr, 10)
       const lineText = lineTextParts.join("|")
 
-      const file = Bun.file(filePath)
-      const stats = await file.stat().catch(() => null)
+      const stats = Filesystem.stat(filePath)
       if (!stats) continue
 
       matches.push({
diff --git a/packages/opencode/src/tool/lsp.ts b/packages/opencode/src/tool/lsp.ts
index ca352280b..52aef0f9e 100644
--- a/packages/opencode/src/tool/lsp.ts
+++ b/packages/opencode/src/tool/lsp.ts
@@ -6,6 +6,7 @@ import DESCRIPTION from "./lsp.txt"
 import { Instance } from "../project/instance"
 import { pathToFileURL } from "url"
 import { assertExternalDirectory } from "./external-directory"
+import { Filesystem } from "../util/filesystem"
 
 const operations = [
   "goToDefinition",
@@ -47,7 +48,7 @@ export const LspTool = Tool.define("lsp", {
     const relPath = path.relative(Instance.worktree, file)
     const title = `${args.operation} ${relPath}:${args.line}:${args.character}`
 
-    const exists = await Bun.file(file).exists()
+    const exists = await Filesystem.exists(file)
     if (!exists) {
       throw new Error(`File not found: ${file}`)
     }
diff --git a/packages/opencode/src/tool/read.ts b/packages/opencode/src/tool/read.ts
index 80ca95900..c981ac16e 100644
--- a/packages/opencode/src/tool/read.ts
+++ b/packages/opencode/src/tool/read.ts
@@ -10,6 +10,7 @@ import DESCRIPTION from "./read.txt"
 import { Instance } from "../project/instance"
 import { assertExternalDirectory } from "./external-directory"
 import { InstructionPrompt } from "../session/instruction"
+import { Filesystem } from "../util/filesystem"
 
 const DEFAULT_READ_LIMIT = 2000
 const MAX_LINE_LENGTH = 2000
@@ -34,8 +35,7 @@ export const ReadTool = Tool.define("read", {
     }
     const title = path.relative(Instance.worktree, filepath)
 
-    const file = Bun.file(filepath)
-    const stat = await file.stat().catch(() => undefined)
+    const stat = Filesystem.stat(filepath)
 
     await assertExternalDirectory(ctx, filepath, {
       bypass: Boolean(ctx.extra?.["bypassCwdCheck"]),
@@ -118,11 +118,10 @@ export const ReadTool = Tool.define("read", {
     const instructions = await InstructionPrompt.resolve(ctx.messages, filepath, ctx.messageID)
 
     // Exclude SVG (XML-based) and vnd.fastbidsheet (.fbs extension, commonly FlatBuffers schema files)
-    const isImage =
-      file.type.startsWith("image/") && file.type !== "image/svg+xml" && file.type !== "image/vnd.fastbidsheet"
-    const isPdf = file.type === "application/pdf"
+    const mime = Filesystem.mimeType(filepath)
+    const isImage = mime.startsWith("image/") && mime !== "image/svg+xml" && mime !== "image/vnd.fastbidsheet"
+    const isPdf = mime === "application/pdf"
     if (isImage || isPdf) {
-      const mime = file.type
       const msg = `${isImage ? "Image" : "PDF"} read successfully`
       return {
         title,
@@ -136,13 +135,13 @@ export const ReadTool = Tool.define("read", {
           {
             type: "file",
             mime,
-            url: `data:${mime};base64,${Buffer.from(await file.bytes()).toString("base64")}`,
+            url: `data:${mime};base64,${Buffer.from(await Filesystem.readBytes(filepath)).toString("base64")}`,
           },
         ],
       }
     }
 
-    const isBinary = await isBinaryFile(filepath, stat.size)
+    const isBinary = await isBinaryFile(filepath, Number(stat.size))
     if (isBinary) throw new Error(`Cannot read binary file: ${filepath}`)
 
     const stream = createReadStream(filepath, { encoding: "utf8" })
diff --git a/packages/opencode/src/tool/truncation.ts b/packages/opencode/src/tool/truncation.ts
index 84e799c13..4cc524aee 100644
--- a/packages/opencode/src/tool/truncation.ts
+++ b/packages/opencode/src/tool/truncation.ts
@@ -5,6 +5,7 @@ import { Identifier } from "../id/id"
 import { PermissionNext } from "../permission/next"
 import type { Agent } from "../agent/agent"
 import { Scheduler } from "../scheduler"
+import { Filesystem } from "../util/filesystem"
 
 export namespace Truncate {
   export const MAX_LINES = 2000
@@ -91,7 +92,7 @@ export namespace Truncate {
 
     const id = Identifier.ascending("tool")
     const filepath = path.join(DIR, id)
-    await Bun.write(Bun.file(filepath), text)
+    await Filesystem.write(filepath, text)
 
     const hint = hasTaskTool(agent)
       ? `The tool call succeeded but the output was truncated. Full output saved to: ${filepath}\nUse the Task tool to have explore agent process this file with Grep and Read (with offset/limit). Do NOT read the full file yourself - delegate to save context.`
diff --git a/packages/opencode/src/tool/write.ts b/packages/opencode/src/tool/write.ts
index eca64d303..8c1e53cca 100644
--- a/packages/opencode/src/tool/write.ts
+++ b/packages/opencode/src/tool/write.ts
@@ -26,9 +26,8 @@ export const WriteTool = Tool.define("write", {
     const filepath = path.isAbsolute(params.filePath) ? params.filePath : path.join(Instance.directory, params.filePath)
     await assertExternalDirectory(ctx, filepath)
 
-    const file = Bun.file(filepath)
-    const exists = await file.exists()
-    const contentOld = exists ? await file.text() : ""
+    const exists = await Filesystem.exists(filepath)
+    const contentOld = exists ? await Filesystem.readText(filepath) : ""
     if (exists) await FileTime.assert(ctx.sessionID, filepath)
 
     const diff = trimDiff(createTwoFilesPatch(filepath, filepath, contentOld, params.content))
@@ -42,7 +41,7 @@ export const WriteTool = Tool.define("write", {
       },
     })
 
-    await Bun.write(filepath, params.content)
+    await Filesystem.write(filepath, params.content)
     await Bus.publish(File.Event.Edited, {
       file: filepath,
     })
diff --git a/packages/opencode/src/util/filesystem.ts b/packages/opencode/src/util/filesystem.ts
index 7b196eb84..575e61406 100644
--- a/packages/opencode/src/util/filesystem.ts
+++ b/packages/opencode/src/util/filesystem.ts
@@ -1,8 +1,10 @@
-import { mkdir, readFile, writeFile } from "fs/promises"
-import { existsSync, statSync } from "fs"
+import { chmod, mkdir, readFile, writeFile } from "fs/promises"
+import { createWriteStream, existsSync, statSync } from "fs"
 import { lookup } from "mime-types"
 import { realpathSync } from "fs"
 import { dirname, join, relative } from "path"
+import { Readable } from "stream"
+import { pipeline } from "stream/promises"
 
 export namespace Filesystem {
   // Fast sync version for metadata checks
@@ -39,11 +41,16 @@ export namespace Filesystem {
     return readFile(p)
   }
 
+  export async function readArrayBuffer(p: string): Promise<ArrayBuffer> {
+    const buf = await readFile(p)
+    return buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength) as ArrayBuffer
+  }
+
   function isEnoent(e: unknown): e is { code: "ENOENT" } {
     return typeof e === "object" && e !== null && "code" in e && (e as { code: string }).code === "ENOENT"
   }
 
-  export async function write(p: string, content: string | Buffer, mode?: number): Promise<void> {
+  export async function write(p: string, content: string | Buffer | Uint8Array, mode?: number): Promise<void> {
     try {
       if (mode) {
         await writeFile(p, content, { mode })
@@ -68,6 +75,25 @@ export namespace Filesystem {
     return write(p, JSON.stringify(data, null, 2), mode)
   }
 
+  export async function writeStream(
+    p: string,
+    stream: ReadableStream<Uint8Array> | Readable,
+    mode?: number,
+  ): Promise<void> {
+    const dir = dirname(p)
+    if (!existsSync(dir)) {
+      await mkdir(dir, { recursive: true })
+    }
+
+    const nodeStream = stream instanceof ReadableStream ? Readable.fromWeb(stream as any) : stream
+    const writeStream = createWriteStream(p)
+    await pipeline(nodeStream, writeStream)
+
+    if (mode) {
+      await chmod(p, mode)
+    }
+  }
+
   export function mimeType(p: string): string {
     return lookup(p) || "application/octet-stream"
   }
diff --git a/packages/opencode/src/util/log.ts b/packages/opencode/src/util/log.ts
index 6941310bb..c62d59299 100644
--- a/packages/opencode/src/util/log.ts
+++ b/packages/opencode/src/util/log.ts
@@ -1,5 +1,6 @@
 import path from "path"
 import fs from "fs/promises"
+import { createWriteStream } from "fs"
 import { Global } from "../global"
 import z from "zod"
 
@@ -63,13 +64,15 @@ export namespace Log {
       Global.Path.log,
       options.dev ? "dev.log" : new Date().toISOString().split(".")[0].replace(/:/g, "") + ".log",
     )
-    const logfile = Bun.file(logpath)
     await fs.truncate(logpath).catch(() => {})
-    const writer = logfile.writer()
+    const stream = createWriteStream(logpath, { flags: "a" })
     write = async (msg: any) => {
-      const num = writer.write(msg)
-      writer.flush()
-      return num
+      return new Promise((resolve, reject) => {
+        stream.write(msg, (err) => {
+          if (err) reject(err)
+          else resolve(msg.length)
+        })
+      })
     }
   }
 
diff --git a/packages/opencode/test/config/config.test.ts b/packages/opencode/test/config/config.test.ts
index 836a3f5d1..56773570a 100644
--- a/packages/opencode/test/config/config.test.ts
+++ b/packages/opencode/test/config/config.test.ts
@@ -7,6 +7,7 @@ import path from "path"
 import fs from "fs/promises"
 import { pathToFileURL } from "url"
 import { Global } from "../../src/global"
+import { Filesystem } from "../../src/util/filesystem"
 
 // Get managed config directory from environment (set in preload.ts)
 const managedConfigDir = process.env.OPENCODE_TEST_MANAGED_CONFIG_DIR!
@@ -17,11 +18,11 @@ afterEach(async () => {
 
 async function writeManagedSettings(settings: object, filename = "opencode.json") {
   await fs.mkdir(managedConfigDir, { recursive: true })
-  await Bun.write(path.join(managedConfigDir, filename), JSON.stringify(settings))
+  await Filesystem.write(path.join(managedConfigDir, filename), JSON.stringify(settings))
 }
 
 async function writeConfig(dir: string, config: object, name = "opencode.json") {
-  await Bun.write(path.join(dir, name), JSON.stringify(config))
+  await Filesystem.write(path.join(dir, name), JSON.stringify(config))
 }
 
 test("loads config with defaults when no files exist", async () => {
@@ -58,7 +59,7 @@ test("loads JSON config file", async () => {
 test("loads JSONC config file", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.jsonc"),
         `{
         // This is a comment
@@ -144,7 +145,7 @@ test("preserves env variables when adding $schema to config", async () => {
     await using tmp = await tmpdir({
       init: async (dir) => {
         // Config without $schema - should trigger auto-add
-        await Bun.write(
+        await Filesystem.write(
           path.join(dir, "opencode.json"),
           JSON.stringify({
             theme: "{env:PRESERVE_VAR}",
@@ -159,7 +160,7 @@ test("preserves env variables when adding $schema to config", async () => {
         expect(config.theme).toBe("secret_value")
 
         // Read the file to verify the env variable was preserved
-        const content = await Bun.file(path.join(tmp.path, "opencode.json")).text()
+        const content = await Filesystem.readText(path.join(tmp.path, "opencode.json"))
         expect(content).toContain("{env:PRESERVE_VAR}")
         expect(content).not.toContain("secret_value")
         expect(content).toContain("$schema")
@@ -177,7 +178,7 @@ test("preserves env variables when adding $schema to config", async () => {
 test("handles file inclusion substitution", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(path.join(dir, "included.txt"), "test_theme")
+      await Filesystem.write(path.join(dir, "included.txt"), "test_theme")
       await writeConfig(dir, {
         $schema: "https://opencode.ai/config.json",
         theme: "{file:included.txt}",
@@ -196,7 +197,7 @@ test("handles file inclusion substitution", async () => {
 test("handles file inclusion with replacement tokens", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(path.join(dir, "included.md"), "const out = await Bun.$`echo hi`")
+      await Filesystem.write(path.join(dir, "included.md"), "const out = await Bun.$`echo hi`")
       await writeConfig(dir, {
         $schema: "https://opencode.ai/config.json",
         theme: "{file:included.md}",
@@ -233,7 +234,7 @@ test("validates config schema and throws on invalid fields", async () => {
 test("throws error for invalid JSON", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(path.join(dir, "opencode.json"), "{ invalid json }")
+      await Filesystem.write(path.join(dir, "opencode.json"), "{ invalid json }")
     },
   })
   await Instance.provide({
@@ -336,7 +337,7 @@ test("handles command configuration", async () => {
 test("migrates autoshare to share field", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -358,7 +359,7 @@ test("migrates autoshare to share field", async () => {
 test("migrates mode field to agent field", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -395,7 +396,7 @@ test("loads config from .opencode directory", async () => {
       const agentDir = path.join(opencodeDir, "agent")
       await fs.mkdir(agentDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentDir, "test.md"),
         `---
 model: test/model
@@ -428,7 +429,7 @@ test("loads agents from .opencode/agents (plural)", async () => {
       const agentsDir = path.join(opencodeDir, "agents")
       await fs.mkdir(path.join(agentsDir, "nested"), { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentsDir, "helper.md"),
         `---
 model: test/model
@@ -437,7 +438,7 @@ mode: subagent
 Helper agent prompt`,
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentsDir, "nested", "child.md"),
         `---
 model: test/model
@@ -479,7 +480,7 @@ test("loads commands from .opencode/command (singular)", async () => {
       const commandDir = path.join(opencodeDir, "command")
       await fs.mkdir(path.join(commandDir, "nested"), { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandDir, "hello.md"),
         `---
 description: Test command
@@ -487,7 +488,7 @@ description: Test command
 Hello from singular command`,
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandDir, "nested", "child.md"),
         `---
 description: Nested command
@@ -524,7 +525,7 @@ test("loads commands from .opencode/commands (plural)", async () => {
       const commandsDir = path.join(opencodeDir, "commands")
       await fs.mkdir(path.join(commandsDir, "nested"), { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandsDir, "hello.md"),
         `---
 description: Test command
@@ -532,7 +533,7 @@ description: Test command
 Hello from plural commands`,
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(commandsDir, "nested", "child.md"),
         `---
 description: Nested command
@@ -568,7 +569,7 @@ test("updates config and writes to file", async () => {
       const newConfig = { model: "updated/model" }
       await Config.update(newConfig as any)
 
-      const writtenConfig = JSON.parse(await Bun.file(path.join(tmp.path, "config.json")).text())
+      const writtenConfig = await Filesystem.readJson(path.join(tmp.path, "config.json"))
       expect(writtenConfig.model).toBe("updated/model")
     },
   })
@@ -639,8 +640,8 @@ test("installs dependencies in writable OPENCODE_CONFIG_DIR", async () => {
       },
     })
 
-    expect(await Bun.file(path.join(tmp.extra, "package.json")).exists()).toBe(true)
-    expect(await Bun.file(path.join(tmp.extra, ".gitignore")).exists()).toBe(true)
+    expect(await Filesystem.exists(path.join(tmp.extra, "package.json"))).toBe(true)
+    expect(await Filesystem.exists(path.join(tmp.extra, ".gitignore"))).toBe(true)
   } finally {
     if (prev === undefined) delete process.env.OPENCODE_CONFIG_DIR
     else process.env.OPENCODE_CONFIG_DIR = prev
@@ -653,12 +654,12 @@ test("resolves scoped npm plugins in config", async () => {
       const pluginDir = path.join(dir, "node_modules", "@scope", "plugin")
       await fs.mkdir(pluginDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "package.json"),
         JSON.stringify({ name: "config-fixture", version: "1.0.0", type: "module" }, null, 2),
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(pluginDir, "package.json"),
         JSON.stringify(
           {
@@ -672,9 +673,9 @@ test("resolves scoped npm plugins in config", async () => {
         ),
       )
 
-      await Bun.write(path.join(pluginDir, "index.js"), "export default {}\n")
+      await Filesystem.write(path.join(pluginDir, "index.js"), "export default {}\n")
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({ $schema: "https://opencode.ai/config.json", plugin: ["@scope/plugin"] }, null, 2),
       )
@@ -708,7 +709,7 @@ test("merges plugin arrays from global and local configs", async () => {
       await fs.mkdir(opencodeDir, { recursive: true })
 
       // Global config with plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -717,7 +718,7 @@ test("merges plugin arrays from global and local configs", async () => {
       )
 
       // Local .opencode config with different plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -753,7 +754,7 @@ test("does not error when only custom agent is a subagent", async () => {
       const agentDir = path.join(opencodeDir, "agent")
       await fs.mkdir(agentDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(agentDir, "helper.md"),
         `---
 model: test/model
@@ -784,7 +785,7 @@ test("merges instructions arrays from global and local configs", async () => {
       const opencodeDir = path.join(projectDir, ".opencode")
       await fs.mkdir(opencodeDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -792,7 +793,7 @@ test("merges instructions arrays from global and local configs", async () => {
         }),
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -823,7 +824,7 @@ test("deduplicates duplicate instructions from global and local configs", async
       const opencodeDir = path.join(projectDir, ".opencode")
       await fs.mkdir(opencodeDir, { recursive: true })
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -831,7 +832,7 @@ test("deduplicates duplicate instructions from global and local configs", async
         }),
       )
 
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -867,7 +868,7 @@ test("deduplicates duplicate plugins from global and local configs", async () =>
       await fs.mkdir(opencodeDir, { recursive: true })
 
       // Global config with plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -876,7 +877,7 @@ test("deduplicates duplicate plugins from global and local configs", async () =>
       )
 
       // Local .opencode config with some overlapping plugins
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -915,7 +916,7 @@ test("deduplicates duplicate plugins from global and local configs", async () =>
 test("migrates legacy tools config to permissions - allow", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -946,7 +947,7 @@ test("migrates legacy tools config to permissions - allow", async () => {
 test("migrates legacy tools config to permissions - deny", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -977,7 +978,7 @@ test("migrates legacy tools config to permissions - deny", async () => {
 test("migrates legacy write tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1086,7 +1087,7 @@ test("missing managed settings file is not an error", async () => {
 test("migrates legacy edit tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1115,7 +1116,7 @@ test("migrates legacy edit tool to edit permission", async () => {
 test("migrates legacy patch tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1144,7 +1145,7 @@ test("migrates legacy patch tool to edit permission", async () => {
 test("migrates legacy multiedit tool to edit permission", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1173,7 +1174,7 @@ test("migrates legacy multiedit tool to edit permission", async () => {
 test("migrates mixed legacy tools config", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1208,7 +1209,7 @@ test("migrates mixed legacy tools config", async () => {
 test("merges legacy tools with existing permission config", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1241,7 +1242,7 @@ test("merges legacy tools with existing permission config", async () => {
 test("permission config preserves key order", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1289,7 +1290,7 @@ test("project config can override MCP server enabled status", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
       // Simulates a base config (like from remote .well-known) with disabled MCP
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.jsonc"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1308,7 +1309,7 @@ test("project config can override MCP server enabled status", async () => {
         }),
       )
       // Project config enables just jira
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1347,7 +1348,7 @@ test("MCP config deep merges preserving base config properties", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
       // Base config with full MCP definition
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.jsonc"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1364,7 +1365,7 @@ test("MCP config deep merges preserving base config properties", async () => {
         }),
       )
       // Override just enables it, should preserve other properties
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1399,7 +1400,7 @@ test("local .opencode config can override MCP from project config", async () =>
   await using tmp = await tmpdir({
     init: async (dir) => {
       // Project config with disabled MCP
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1415,7 +1416,7 @@ test("local .opencode config can override MCP from project config", async () =>
       // Local .opencode directory config enables it
       const opencodeDir = path.join(dir, ".opencode")
       await fs.mkdir(opencodeDir, { recursive: true })
-      await Bun.write(
+      await Filesystem.write(
         path.join(opencodeDir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -1483,7 +1484,7 @@ test("project config overrides remote well-known config", async () => {
       git: true,
       init: async (dir) => {
         // Project config enables jira (overriding remote default)
-        await Bun.write(
+        await Filesystem.write(
           path.join(dir, "opencode.json"),
           JSON.stringify({
             $schema: "https://opencode.ai/config.json",
@@ -1576,7 +1577,7 @@ describe("deduplicatePlugins", () => {
         const pluginDir = path.join(opencodeDir, "plugin")
         await fs.mkdir(pluginDir, { recursive: true })
 
-        await Bun.write(
+        await Filesystem.write(
           path.join(dir, "opencode.json"),
           JSON.stringify({
             $schema: "https://opencode.ai/config.json",
@@ -1584,7 +1585,7 @@ describe("deduplicatePlugins", () => {
           }),
         )
 
-        await Bun.write(path.join(pluginDir, "my-plugin.js"), "export default {}")
+        await Filesystem.write(path.join(pluginDir, "my-plugin.js"), "export default {}")
       },
     })
 
@@ -1611,7 +1612,7 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
       await using tmp = await tmpdir({
         init: async (dir) => {
           // Create a project config that would normally be loaded
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://opencode.ai/config.json",
@@ -1649,7 +1650,7 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
           // Create a .opencode directory with a command
           const opencodeDir = path.join(dir, ".opencode", "command")
           await fs.mkdir(opencodeDir, { recursive: true })
-          await Bun.write(path.join(opencodeDir, "test-cmd.md"), "# Test Command\nThis is a test command.")
+          await Filesystem.write(path.join(opencodeDir, "test-cmd.md"), "# Test Command\nThis is a test command.")
         },
       })
       await Instance.provide({
@@ -1706,7 +1707,7 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
       await using tmp = await tmpdir({
         init: async (dir) => {
           // Create a config with relative instruction path
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://opencode.ai/config.json",
@@ -1714,7 +1715,7 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
             }),
           )
           // Create the instruction file (should be skipped)
-          await Bun.write(path.join(dir, "CUSTOM.md"), "# Custom Instructions")
+          await Filesystem.write(path.join(dir, "CUSTOM.md"), "# Custom Instructions")
         },
       })
 
@@ -1752,7 +1753,7 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
       await using configDirTmp = await tmpdir({
         init: async (dir) => {
           // Create config in the custom config dir
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://opencode.ai/config.json",
@@ -1765,7 +1766,7 @@ describe("OPENCODE_DISABLE_PROJECT_CONFIG", () => {
       await using projectTmp = await tmpdir({
         init: async (dir) => {
           // Create config in project (should be ignored)
-          await Bun.write(
+          await Filesystem.write(
             path.join(dir, "opencode.json"),
             JSON.stringify({
               $schema: "https://opencode.ai/config.json",
diff --git a/packages/opencode/test/file/index.test.ts b/packages/opencode/test/file/index.test.ts
index 053a64e20..f269926b5 100644
--- a/packages/opencode/test/file/index.test.ts
+++ b/packages/opencode/test/file/index.test.ts
@@ -3,11 +3,12 @@ import path from "path"
 import fs from "fs/promises"
 import { File } from "../../src/file"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 
-describe("file/index Bun.file patterns", () => {
+describe("file/index Filesystem patterns", () => {
   describe("File.read() - text content", () => {
-    test("reads text file via Bun.file().text()", async () => {
+    test("reads text file via Filesystem.readText()", async () => {
       await using tmp = await tmpdir()
       const filepath = path.join(tmp.path, "test.txt")
       await fs.writeFile(filepath, "Hello World", "utf-8")
@@ -22,7 +23,7 @@ describe("file/index Bun.file patterns", () => {
       })
     })
 
-    test("reads with Bun.file().exists() check", async () => {
+    test("reads with Filesystem.exists() check", async () => {
       await using tmp = await tmpdir()
 
       await Instance.provide({
@@ -81,7 +82,7 @@ describe("file/index Bun.file patterns", () => {
   })
 
   describe("File.read() - binary content", () => {
-    test("reads binary file via Bun.file().arrayBuffer()", async () => {
+    test("reads binary file via Filesystem.readArrayBuffer()", async () => {
       await using tmp = await tmpdir()
       const filepath = path.join(tmp.path, "image.png")
       const binaryContent = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])
@@ -115,8 +116,8 @@ describe("file/index Bun.file patterns", () => {
     })
   })
 
-  describe("File.read() - Bun.file().type", () => {
-    test("detects MIME type via Bun.file().type", async () => {
+  describe("File.read() - Filesystem.mimeType()", () => {
+    test("detects MIME type via Filesystem.mimeType()", async () => {
       await using tmp = await tmpdir()
       const filepath = path.join(tmp.path, "test.json")
       await fs.writeFile(filepath, '{"key": "value"}', "utf-8")
@@ -124,8 +125,7 @@ describe("file/index Bun.file patterns", () => {
       await Instance.provide({
         directory: tmp.path,
         fn: async () => {
-          const bunFile = Bun.file(filepath)
-          expect(bunFile.type).toContain("application/json")
+          expect(Filesystem.mimeType(filepath)).toContain("application/json")
 
           const result = await File.read("test.json")
           expect(result.type).toBe("text")
@@ -149,16 +149,15 @@ describe("file/index Bun.file patterns", () => {
         await Instance.provide({
           directory: tmp.path,
           fn: async () => {
-            const bunFile = Bun.file(filepath)
-            expect(bunFile.type).toContain(mime)
+            expect(Filesystem.mimeType(filepath)).toContain(mime)
           },
         })
       }
     })
   })
 
-  describe("File.list() - Bun.file().exists() and .text()", () => {
-    test("reads .gitignore via Bun.file().exists() and .text()", async () => {
+  describe("File.list() - Filesystem.exists() and readText()", () => {
+    test("reads .gitignore via Filesystem.exists() and readText()", async () => {
       await using tmp = await tmpdir({ git: true })
 
       await Instance.provide({
@@ -168,10 +167,9 @@ describe("file/index Bun.file patterns", () => {
           await fs.writeFile(gitignorePath, "node_modules\ndist\n", "utf-8")
 
           // This is used internally in File.list()
-          const bunFile = Bun.file(gitignorePath)
-          expect(await bunFile.exists()).toBe(true)
+          expect(await Filesystem.exists(gitignorePath)).toBe(true)
 
-          const content = await bunFile.text()
+          const content = await Filesystem.readText(gitignorePath)
           expect(content).toContain("node_modules")
         },
       })
@@ -186,9 +184,8 @@ describe("file/index Bun.file patterns", () => {
           const ignorePath = path.join(tmp.path, ".ignore")
           await fs.writeFile(ignorePath, "*.log\n.env\n", "utf-8")
 
-          const bunFile = Bun.file(ignorePath)
-          expect(await bunFile.exists()).toBe(true)
-          expect(await bunFile.text()).toContain("*.log")
+          expect(await Filesystem.exists(ignorePath)).toBe(true)
+          expect(await Filesystem.readText(ignorePath)).toContain("*.log")
         },
       })
     })
@@ -200,8 +197,7 @@ describe("file/index Bun.file patterns", () => {
         directory: tmp.path,
         fn: async () => {
           const gitignorePath = path.join(tmp.path, ".gitignore")
-          const bunFile = Bun.file(gitignorePath)
-          expect(await bunFile.exists()).toBe(false)
+          expect(await Filesystem.exists(gitignorePath)).toBe(false)
 
           // File.list() should still work
           const nodes = await File.list()
@@ -211,8 +207,8 @@ describe("file/index Bun.file patterns", () => {
     })
   })
 
-  describe("File.changed() - Bun.file().text() for untracked files", () => {
-    test("reads untracked files via Bun.file().text()", async () => {
+  describe("File.changed() - Filesystem.readText() for untracked files", () => {
+    test("reads untracked files via Filesystem.readText()", async () => {
       await using tmp = await tmpdir({ git: true })
 
       await Instance.provide({
@@ -222,8 +218,7 @@ describe("file/index Bun.file patterns", () => {
           await fs.writeFile(untrackedPath, "new content\nwith multiple lines", "utf-8")
 
           // This is how File.changed() reads untracked files
-          const bunFile = Bun.file(untrackedPath)
-          const content = await bunFile.text()
+          const content = await Filesystem.readText(untrackedPath)
           const lines = content.split("\n").length
           expect(lines).toBe(2)
         },
@@ -232,7 +227,7 @@ describe("file/index Bun.file patterns", () => {
   })
 
   describe("Error handling", () => {
-    test("handles errors gracefully in Bun.file().text()", async () => {
+    test("handles errors gracefully in Filesystem.readText()", async () => {
       await using tmp = await tmpdir()
       const filepath = path.join(tmp.path, "readonly.txt")
       await fs.writeFile(filepath, "content", "utf-8")
@@ -240,9 +235,9 @@ describe("file/index Bun.file patterns", () => {
       await Instance.provide({
         directory: tmp.path,
         fn: async () => {
-          const nonExistentFile = Bun.file(path.join(tmp.path, "does-not-exist.txt"))
-          // Bun.file().text() on non-existent file throws
-          await expect(nonExistentFile.text()).rejects.toThrow()
+          const nonExistentPath = path.join(tmp.path, "does-not-exist.txt")
+          // Filesystem.readText() on non-existent file throws
+          await expect(Filesystem.readText(nonExistentPath)).rejects.toThrow()
 
           // But File.read() handles this gracefully
           const result = await File.read("does-not-exist.txt")
@@ -251,14 +246,14 @@ describe("file/index Bun.file patterns", () => {
       })
     })
 
-    test("handles errors in Bun.file().arrayBuffer()", async () => {
+    test("handles errors in Filesystem.readArrayBuffer()", async () => {
       await using tmp = await tmpdir()
 
       await Instance.provide({
         directory: tmp.path,
         fn: async () => {
-          const nonExistentFile = Bun.file(path.join(tmp.path, "does-not-exist.bin"))
-          const buffer = await nonExistentFile.arrayBuffer().catch(() => new ArrayBuffer(0))
+          const nonExistentPath = path.join(tmp.path, "does-not-exist.bin")
+          const buffer = await Filesystem.readArrayBuffer(nonExistentPath).catch(() => new ArrayBuffer(0))
           expect(buffer.byteLength).toBe(0)
         },
       })
@@ -272,7 +267,6 @@ describe("file/index Bun.file patterns", () => {
       await Instance.provide({
         directory: tmp.path,
         fn: async () => {
-          const bunFile = Bun.file(filepath)
           // File.read() handles missing images gracefully
           const result = await File.read("broken.png")
           expect(result.type).toBe("text")
diff --git a/packages/opencode/test/file/time.test.ts b/packages/opencode/test/file/time.test.ts
index ab7451276..e46d5229b 100644
--- a/packages/opencode/test/file/time.test.ts
+++ b/packages/opencode/test/file/time.test.ts
@@ -3,6 +3,7 @@ import path from "path"
 import fs from "fs/promises"
 import { FileTime } from "../../src/file/time"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 
 describe("file/time", () => {
@@ -312,8 +313,8 @@ describe("file/time", () => {
     })
   })
 
-  describe("stat() Bun.file pattern", () => {
-    test("reads file modification time via Bun.file().stat()", async () => {
+  describe("stat() Filesystem.stat pattern", () => {
+    test("reads file modification time via Filesystem.stat()", async () => {
       await using tmp = await tmpdir()
       const filepath = path.join(tmp.path, "file.txt")
       await fs.writeFile(filepath, "content", "utf-8")
@@ -323,9 +324,9 @@ describe("file/time", () => {
         fn: async () => {
           FileTime.read(sessionID, filepath)
 
-          const stats = await Bun.file(filepath).stat()
-          expect(stats.mtime).toBeInstanceOf(Date)
-          expect(stats.mtime.getTime()).toBeGreaterThan(0)
+          const stats = Filesystem.stat(filepath)
+          expect(stats?.mtime).toBeInstanceOf(Date)
+          expect(stats!.mtime.getTime()).toBeGreaterThan(0)
 
           // FileTime.assert uses this stat internally
           await FileTime.assert(sessionID, filepath)
@@ -343,14 +344,14 @@ describe("file/time", () => {
         fn: async () => {
           FileTime.read(sessionID, filepath)
 
-          const originalStat = await Bun.file(filepath).stat()
+          const originalStat = Filesystem.stat(filepath)
 
           // Wait and modify
           await new Promise((resolve) => setTimeout(resolve, 100))
           await fs.writeFile(filepath, "modified", "utf-8")
 
-          const newStat = await Bun.file(filepath).stat()
-          expect(newStat.mtime.getTime()).toBeGreaterThan(originalStat.mtime.getTime())
+          const newStat = Filesystem.stat(filepath)
+          expect(newStat!.mtime.getTime()).toBeGreaterThan(originalStat!.mtime.getTime())
 
           await expect(FileTime.assert(sessionID, filepath)).rejects.toThrow()
         },
diff --git a/packages/opencode/test/project/project.test.ts b/packages/opencode/test/project/project.test.ts
index 19f9821c4..fef9e4190 100644
--- a/packages/opencode/test/project/project.test.ts
+++ b/packages/opencode/test/project/project.test.ts
@@ -4,6 +4,7 @@ import { Log } from "../../src/util/log"
 import { $ } from "bun"
 import path from "path"
 import { tmpdir } from "../fixture/fixture"
+import { Filesystem } from "../../src/util/filesystem"
 import { GlobalBus } from "../../src/bus/global"
 
 Log.init({ print: false })
@@ -78,7 +79,7 @@ describe("Project.fromDirectory", () => {
     expect(project.worktree).toBe(tmp.path)
 
     const opencodeFile = path.join(tmp.path, ".git", "opencode")
-    const fileExists = await Bun.file(opencodeFile).exists()
+    const fileExists = await Filesystem.exists(opencodeFile)
     expect(fileExists).toBe(false)
   })
 
@@ -94,7 +95,7 @@ describe("Project.fromDirectory", () => {
     expect(project.worktree).toBe(tmp.path)
 
     const opencodeFile = path.join(tmp.path, ".git", "opencode")
-    const fileExists = await Bun.file(opencodeFile).exists()
+    const fileExists = await Filesystem.exists(opencodeFile)
     expect(fileExists).toBe(true)
   })
 
diff --git a/packages/opencode/test/project/worktree-remove.test.ts b/packages/opencode/test/project/worktree-remove.test.ts
index 32d38fe84..e17a5392b 100644
--- a/packages/opencode/test/project/worktree-remove.test.ts
+++ b/packages/opencode/test/project/worktree-remove.test.ts
@@ -4,6 +4,7 @@ import fs from "fs/promises"
 import path from "path"
 import { Instance } from "../../src/project/instance"
 import { Worktree } from "../../src/worktree"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 
 describe("Worktree.remove", () => {
@@ -53,7 +54,7 @@ describe("Worktree.remove", () => {
     })()
 
     expect(ok).toBe(true)
-    expect(await Bun.file(dir).exists()).toBe(false)
+    expect(await Filesystem.exists(dir)).toBe(false)
 
     const list = await $`git worktree list --porcelain`.cwd(root).quiet().text()
     expect(list).not.toContain(`worktree ${dir}`)
diff --git a/packages/opencode/test/provider/amazon-bedrock.test.ts b/packages/opencode/test/provider/amazon-bedrock.test.ts
index d1d3cc41c..cb64455b4 100644
--- a/packages/opencode/test/provider/amazon-bedrock.test.ts
+++ b/packages/opencode/test/provider/amazon-bedrock.test.ts
@@ -7,11 +7,12 @@ import { Instance } from "../../src/project/instance"
 import { Provider } from "../../src/provider/provider"
 import { Env } from "../../src/env"
 import { Global } from "../../src/global"
+import { Filesystem } from "../../src/util/filesystem"
 
 test("Bedrock: config region takes precedence over AWS_REGION env var", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -43,7 +44,7 @@ test("Bedrock: config region takes precedence over AWS_REGION env var", async ()
 test("Bedrock: falls back to AWS_REGION env var when no config region", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -68,7 +69,7 @@ test("Bedrock: falls back to AWS_REGION env var when no config region", async ()
 test("Bedrock: loads when bearer token from auth.json is present", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -89,14 +90,14 @@ test("Bedrock: loads when bearer token from auth.json is present", async () => {
   // Save original auth.json if it exists
   let originalAuth: string | undefined
   try {
-    originalAuth = await Bun.file(authPath).text()
+    originalAuth = await Filesystem.readText(authPath)
   } catch {
     // File doesn't exist, that's fine
   }
 
   try {
     // Write test auth.json
-    await Bun.write(
+    await Filesystem.write(
       authPath,
       JSON.stringify({
         "amazon-bedrock": {
@@ -122,7 +123,7 @@ test("Bedrock: loads when bearer token from auth.json is present", async () => {
   } finally {
     // Restore original or delete
     if (originalAuth !== undefined) {
-      await Bun.write(authPath, originalAuth)
+      await Filesystem.write(authPath, originalAuth)
     } else {
       try {
         await unlink(authPath)
@@ -136,7 +137,7 @@ test("Bedrock: loads when bearer token from auth.json is present", async () => {
 test("Bedrock: config profile takes precedence over AWS_PROFILE env var", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -169,7 +170,7 @@ test("Bedrock: config profile takes precedence over AWS_PROFILE env var", async
 test("Bedrock: includes custom endpoint in options when specified", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -202,7 +203,7 @@ test("Bedrock: includes custom endpoint in options when specified", async () =>
 test("Bedrock: autoloads when AWS_WEB_IDENTITY_TOKEN_FILE is present", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -240,7 +241,7 @@ test("Bedrock: autoloads when AWS_WEB_IDENTITY_TOKEN_FILE is present", async ()
 test("Bedrock: model with us. prefix should not be double-prefixed", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -277,7 +278,7 @@ test("Bedrock: model with us. prefix should not be double-prefixed", async () =>
 test("Bedrock: model with global. prefix should not be prefixed", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -313,7 +314,7 @@ test("Bedrock: model with global. prefix should not be prefixed", async () => {
 test("Bedrock: model with eu. prefix should not be double-prefixed", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
@@ -349,7 +350,7 @@ test("Bedrock: model with eu. prefix should not be double-prefixed", async () =>
 test("Bedrock: model without prefix in US region should get us. prefix added", async () => {
   await using tmp = await tmpdir({
     init: async (dir) => {
-      await Bun.write(
+      await Filesystem.write(
         path.join(dir, "opencode.json"),
         JSON.stringify({
           $schema: "https://opencode.ai/config.json",
diff --git a/packages/opencode/test/session/llm.test.ts b/packages/opencode/test/session/llm.test.ts
index be0b8e520..d7af9908f 100644
--- a/packages/opencode/test/session/llm.test.ts
+++ b/packages/opencode/test/session/llm.test.ts
@@ -7,6 +7,7 @@ import { Instance } from "../../src/project/instance"
 import { Provider } from "../../src/provider/provider"
 import { ProviderTransform } from "../../src/provider/transform"
 import { ModelsDev } from "../../src/provider/models"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 import type { Agent } from "../../src/agent/agent"
 import type { MessageV2 } from "../../src/session/message-v2"
@@ -185,7 +186,7 @@ function createChatStream(text: string) {
 
 async function loadFixture(providerID: string, modelID: string) {
   const fixturePath = path.join(import.meta.dir, "../tool/fixtures/models-api.json")
-  const data = (await Bun.file(fixturePath).json()) as Record<string, ModelsDev.Provider>
+  const data = await Filesystem.readJson<Record<string, ModelsDev.Provider>>(fixturePath)
   const provider = data[providerID]
   if (!provider) {
     throw new Error(`Missing provider in fixture: ${providerID}`)
diff --git a/packages/opencode/test/skill/discovery.test.ts b/packages/opencode/test/skill/discovery.test.ts
index 90759fa3c..f78c6623b 100644
--- a/packages/opencode/test/skill/discovery.test.ts
+++ b/packages/opencode/test/skill/discovery.test.ts
@@ -1,5 +1,6 @@
 import { describe, test, expect } from "bun:test"
 import { Discovery } from "../../src/skill/discovery"
+import { Filesystem } from "../../src/util/filesystem"
 import path from "path"
 
 const CLOUDFLARE_SKILLS_URL = "https://developers.cloudflare.com/.well-known/skills/"
@@ -11,7 +12,7 @@ describe("Discovery.pull", () => {
     for (const dir of dirs) {
       expect(dir).toStartWith(Discovery.dir())
       const md = path.join(dir, "SKILL.md")
-      expect(await Bun.file(md).exists()).toBe(true)
+      expect(await Filesystem.exists(md)).toBe(true)
     }
   }, 30_000)
 
@@ -20,7 +21,7 @@ describe("Discovery.pull", () => {
     expect(dirs.length).toBeGreaterThan(0)
     for (const dir of dirs) {
       const md = path.join(dir, "SKILL.md")
-      expect(await Bun.file(md).exists()).toBe(true)
+      expect(await Filesystem.exists(md)).toBe(true)
     }
   }, 30_000)
 
@@ -40,7 +41,7 @@ describe("Discovery.pull", () => {
     const agentsSdk = dirs.find((d) => d.endsWith("/agents-sdk"))
     if (agentsSdk) {
       const refs = path.join(agentsSdk, "references")
-      expect(await Bun.file(path.join(agentsSdk, "SKILL.md")).exists()).toBe(true)
+      expect(await Filesystem.exists(path.join(agentsSdk, "SKILL.md"))).toBe(true)
       // agents-sdk has reference files per the index
       const refDir = await Array.fromAsync(new Bun.Glob("**/*.md").scan({ cwd: refs, onlyFiles: true }))
       expect(refDir.length).toBeGreaterThan(0)
diff --git a/packages/opencode/test/snapshot/snapshot.test.ts b/packages/opencode/test/snapshot/snapshot.test.ts
index 091469ec7..b54cb8b8a 100644
--- a/packages/opencode/test/snapshot/snapshot.test.ts
+++ b/packages/opencode/test/snapshot/snapshot.test.ts
@@ -1,7 +1,9 @@
 import { test, expect } from "bun:test"
 import { $ } from "bun"
+import fs from "fs/promises"
 import { Snapshot } from "../../src/snapshot"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 
 async function bootstrap() {
@@ -11,8 +13,8 @@ async function bootstrap() {
       const unique = Math.random().toString(36).slice(2)
       const aContent = `A${unique}`
       const bContent = `B${unique}`
-      await Bun.write(`${dir}/a.txt`, aContent)
-      await Bun.write(`${dir}/b.txt`, bContent)
+      await Filesystem.write(`${dir}/a.txt`, aContent)
+      await Filesystem.write(`${dir}/b.txt`, bContent)
       await $`git add .`.cwd(dir).quiet()
       await $`git commit --no-gpg-sign -m init`.cwd(dir).quiet()
       return {
@@ -46,11 +48,16 @@ test("revert should remove new files", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/new.txt`, "NEW")
+      await Filesystem.write(`${tmp.path}/new.txt`, "NEW")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/new.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/new.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -64,11 +71,16 @@ test("revert in subdirectory", async () => {
       expect(before).toBeTruthy()
 
       await $`mkdir -p ${tmp.path}/sub`.quiet()
-      await Bun.write(`${tmp.path}/sub/file.txt`, "SUB")
+      await Filesystem.write(`${tmp.path}/sub/file.txt`, "SUB")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/sub/file.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/sub/file.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
       // Note: revert currently only removes files, not directories
       // The empty subdirectory will remain
     },
@@ -84,18 +96,23 @@ test("multiple file operations", async () => {
       expect(before).toBeTruthy()
 
       await $`rm ${tmp.path}/a.txt`.quiet()
-      await Bun.write(`${tmp.path}/c.txt`, "C")
+      await Filesystem.write(`${tmp.path}/c.txt`, "C")
       await $`mkdir -p ${tmp.path}/dir`.quiet()
-      await Bun.write(`${tmp.path}/dir/d.txt`, "D")
-      await Bun.write(`${tmp.path}/b.txt`, "MODIFIED")
+      await Filesystem.write(`${tmp.path}/dir/d.txt`, "D")
+      await Filesystem.write(`${tmp.path}/b.txt`, "MODIFIED")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(tmp.extra.aContent)
-      expect(await Bun.file(`${tmp.path}/c.txt`).exists()).toBe(false)
+      expect(await fs.readFile(`${tmp.path}/a.txt`, "utf-8")).toBe(tmp.extra.aContent)
+      expect(
+        await fs
+          .access(`${tmp.path}/c.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
       // Note: revert currently only removes files, not directories
       // The empty directory will remain
-      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(tmp.extra.bContent)
+      expect(await fs.readFile(`${tmp.path}/b.txt`, "utf-8")).toBe(tmp.extra.bContent)
     },
   })
 })
@@ -123,13 +140,18 @@ test("binary file handling", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/image.png`, new Uint8Array([0x89, 0x50, 0x4e, 0x47]))
+      await Filesystem.write(`${tmp.path}/image.png`, new Uint8Array([0x89, 0x50, 0x4e, 0x47]))
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(`${tmp.path}/image.png`)
 
       await Snapshot.revert([patch])
-      expect(await Bun.file(`${tmp.path}/image.png`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/image.png`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -157,7 +179,7 @@ test("large file handling", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/large.txt`, "x".repeat(1024 * 1024))
+      await Filesystem.write(`${tmp.path}/large.txt`, "x".repeat(1024 * 1024))
 
       expect((await Snapshot.patch(before!)).files).toContain(`${tmp.path}/large.txt`)
     },
@@ -173,11 +195,16 @@ test("nested directory revert", async () => {
       expect(before).toBeTruthy()
 
       await $`mkdir -p ${tmp.path}/level1/level2/level3`.quiet()
-      await Bun.write(`${tmp.path}/level1/level2/level3/deep.txt`, "DEEP")
+      await Filesystem.write(`${tmp.path}/level1/level2/level3/deep.txt`, "DEEP")
 
       await Snapshot.revert([await Snapshot.patch(before!)])
 
-      expect(await Bun.file(`${tmp.path}/level1/level2/level3/deep.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/level1/level2/level3/deep.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -190,9 +217,9 @@ test("special characters in filenames", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/file with spaces.txt`, "SPACES")
-      await Bun.write(`${tmp.path}/file-with-dashes.txt`, "DASHES")
-      await Bun.write(`${tmp.path}/file_with_underscores.txt`, "UNDERSCORES")
+      await Filesystem.write(`${tmp.path}/file with spaces.txt`, "SPACES")
+      await Filesystem.write(`${tmp.path}/file-with-dashes.txt`, "DASHES")
+      await Filesystem.write(`${tmp.path}/file_with_underscores.txt`, "UNDERSCORES")
 
       const files = (await Snapshot.patch(before!)).files
       expect(files).toContain(`${tmp.path}/file with spaces.txt`)
@@ -225,7 +252,7 @@ test("patch with invalid hash", async () => {
       expect(before).toBeTruthy()
 
       // Create a change
-      await Bun.write(`${tmp.path}/test.txt`, "TEST")
+      await Filesystem.write(`${tmp.path}/test.txt`, "TEST")
 
       // Try to patch with invalid hash - should handle gracefully
       const patch = await Snapshot.patch("invalid-hash-12345")
@@ -273,7 +300,7 @@ test("unicode filenames", async () => {
       ]
 
       for (const file of unicodeFiles) {
-        await Bun.write(file.path, file.content)
+        await Filesystem.write(file.path, file.content)
       }
 
       const patch = await Snapshot.patch(before!)
@@ -286,7 +313,12 @@ test("unicode filenames", async () => {
       await Snapshot.revert([patch])
 
       for (const file of unicodeFiles) {
-        expect(await Bun.file(file.path).exists()).toBe(false)
+        expect(
+          await fs
+            .access(file.path)
+            .then(() => true)
+            .catch(() => false),
+        ).toBe(false)
       }
     },
   })
@@ -300,14 +332,14 @@ test.skip("unicode filenames modification and restore", async () => {
       const chineseFile = `${tmp.path}/文件.txt`
       const cyrillicFile = `${tmp.path}/файл.txt`
 
-      await Bun.write(chineseFile, "original chinese")
-      await Bun.write(cyrillicFile, "original cyrillic")
+      await Filesystem.write(chineseFile, "original chinese")
+      await Filesystem.write(cyrillicFile, "original cyrillic")
 
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(chineseFile, "modified chinese")
-      await Bun.write(cyrillicFile, "modified cyrillic")
+      await Filesystem.write(chineseFile, "modified chinese")
+      await Filesystem.write(cyrillicFile, "modified cyrillic")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(chineseFile)
@@ -315,8 +347,8 @@ test.skip("unicode filenames modification and restore", async () => {
 
       await Snapshot.revert([patch])
 
-      expect(await Bun.file(chineseFile).text()).toBe("original chinese")
-      expect(await Bun.file(cyrillicFile).text()).toBe("original cyrillic")
+      expect(await fs.readFile(chineseFile, "utf-8")).toBe("original chinese")
+      expect(await fs.readFile(cyrillicFile, "utf-8")).toBe("original cyrillic")
     },
   })
 })
@@ -331,13 +363,18 @@ test("unicode filenames in subdirectories", async () => {
 
       await $`mkdir -p "${tmp.path}/目录/подкаталог"`.quiet()
       const deepFile = `${tmp.path}/目录/подкаталог/文件.txt`
-      await Bun.write(deepFile, "deep unicode content")
+      await Filesystem.write(deepFile, "deep unicode content")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(deepFile)
 
       await Snapshot.revert([patch])
-      expect(await Bun.file(deepFile).exists()).toBe(false)
+      expect(
+        await fs
+          .access(deepFile)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -353,13 +390,18 @@ test("very long filenames", async () => {
       const longName = "a".repeat(200) + ".txt"
       const longFile = `${tmp.path}/${longName}`
 
-      await Bun.write(longFile, "long filename content")
+      await Filesystem.write(longFile, "long filename content")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(longFile)
 
       await Snapshot.revert([patch])
-      expect(await Bun.file(longFile).exists()).toBe(false)
+      expect(
+        await fs
+          .access(longFile)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -372,9 +414,9 @@ test("hidden files", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/.hidden`, "hidden content")
-      await Bun.write(`${tmp.path}/.gitignore`, "*.log")
-      await Bun.write(`${tmp.path}/.config`, "config content")
+      await Filesystem.write(`${tmp.path}/.hidden`, "hidden content")
+      await Filesystem.write(`${tmp.path}/.gitignore`, "*.log")
+      await Filesystem.write(`${tmp.path}/.config`, "config content")
 
       const patch = await Snapshot.patch(before!)
       expect(patch.files).toContain(`${tmp.path}/.hidden`)
@@ -393,7 +435,7 @@ test("nested symlinks", async () => {
       expect(before).toBeTruthy()
 
       await $`mkdir -p ${tmp.path}/sub/dir`.quiet()
-      await Bun.write(`${tmp.path}/sub/dir/target.txt`, "target content")
+      await Filesystem.write(`${tmp.path}/sub/dir/target.txt`, "target content")
       await $`ln -s ${tmp.path}/sub/dir/target.txt ${tmp.path}/sub/dir/link.txt`.quiet()
       await $`ln -s ${tmp.path}/sub ${tmp.path}/sub-link`.quiet()
 
@@ -450,9 +492,9 @@ test("gitignore changes", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/.gitignore`, "*.ignored")
-      await Bun.write(`${tmp.path}/test.ignored`, "ignored content")
-      await Bun.write(`${tmp.path}/normal.txt`, "normal content")
+      await Filesystem.write(`${tmp.path}/.gitignore`, "*.ignored")
+      await Filesystem.write(`${tmp.path}/test.ignored`, "ignored content")
+      await Filesystem.write(`${tmp.path}/normal.txt`, "normal content")
 
       const patch = await Snapshot.patch(before!)
 
@@ -477,7 +519,7 @@ test("concurrent file operations during patch", async () => {
       // Start creating files
       const createPromise = (async () => {
         for (let i = 0; i < 10; i++) {
-          await Bun.write(`${tmp.path}/concurrent${i}.txt`, `concurrent${i}`)
+          await Filesystem.write(`${tmp.path}/concurrent${i}.txt`, `concurrent${i}`)
           // Small delay to simulate concurrent operations
           await new Promise((resolve) => setTimeout(resolve, 1))
         }
@@ -504,7 +546,7 @@ test("snapshot state isolation between projects", async () => {
     directory: tmp1.path,
     fn: async () => {
       const before1 = await Snapshot.track()
-      await Bun.write(`${tmp1.path}/project1.txt`, "project1 content")
+      await Filesystem.write(`${tmp1.path}/project1.txt`, "project1 content")
       const patch1 = await Snapshot.patch(before1!)
       expect(patch1.files).toContain(`${tmp1.path}/project1.txt`)
     },
@@ -514,7 +556,7 @@ test("snapshot state isolation between projects", async () => {
     directory: tmp2.path,
     fn: async () => {
       const before2 = await Snapshot.track()
-      await Bun.write(`${tmp2.path}/project2.txt`, "project2 content")
+      await Filesystem.write(`${tmp2.path}/project2.txt`, "project2 content")
       const patch2 = await Snapshot.patch(before2!)
       expect(patch2.files).toContain(`${tmp2.path}/project2.txt`)
 
@@ -544,7 +586,7 @@ test("patch detects changes in secondary worktree", async () => {
         expect(before).toBeTruthy()
 
         const worktreeFile = `${worktreePath}/worktree.txt`
-        await Bun.write(worktreeFile, "worktree content")
+        await Filesystem.write(worktreeFile, "worktree content")
 
         const patch = await Snapshot.patch(before!)
         expect(patch.files).toContain(worktreeFile)
@@ -569,7 +611,7 @@ test("revert only removes files in invoking worktree", async () => {
       },
     })
     const primaryFile = `${tmp.path}/worktree.txt`
-    await Bun.write(primaryFile, "primary content")
+    await Filesystem.write(primaryFile, "primary content")
 
     await Instance.provide({
       directory: worktreePath,
@@ -578,16 +620,21 @@ test("revert only removes files in invoking worktree", async () => {
         expect(before).toBeTruthy()
 
         const worktreeFile = `${worktreePath}/worktree.txt`
-        await Bun.write(worktreeFile, "worktree content")
+        await Filesystem.write(worktreeFile, "worktree content")
 
         const patch = await Snapshot.patch(before!)
         await Snapshot.revert([patch])
 
-        expect(await Bun.file(worktreeFile).exists()).toBe(false)
+        expect(
+          await fs
+            .access(worktreeFile)
+            .then(() => true)
+            .catch(() => false),
+        ).toBe(false)
       },
     })
 
-    expect(await Bun.file(primaryFile).text()).toBe("primary content")
+    expect(await fs.readFile(primaryFile, "utf-8")).toBe("primary content")
   } finally {
     await $`git worktree remove --force ${worktreePath}`.cwd(tmp.path).quiet().nothrow()
     await $`rm -rf ${worktreePath}`.quiet()
@@ -614,10 +661,10 @@ test("diff reports worktree-only/shared edits and ignores primary-only", async (
         const before = await Snapshot.track()
         expect(before).toBeTruthy()
 
-        await Bun.write(`${worktreePath}/worktree-only.txt`, "worktree diff content")
-        await Bun.write(`${worktreePath}/shared.txt`, "worktree edit")
-        await Bun.write(`${tmp.path}/shared.txt`, "primary edit")
-        await Bun.write(`${tmp.path}/primary-only.txt`, "primary change")
+        await Filesystem.write(`${worktreePath}/worktree-only.txt`, "worktree diff content")
+        await Filesystem.write(`${worktreePath}/shared.txt`, "worktree edit")
+        await Filesystem.write(`${tmp.path}/shared.txt`, "primary edit")
+        await Filesystem.write(`${tmp.path}/primary-only.txt`, "primary change")
 
         const diff = await Snapshot.diff(before!)
         expect(diff).toContain("worktree-only.txt")
@@ -662,8 +709,8 @@ test("diff function with various changes", async () => {
 
       // Make various changes
       await $`rm ${tmp.path}/a.txt`.quiet()
-      await Bun.write(`${tmp.path}/new.txt`, "new content")
-      await Bun.write(`${tmp.path}/b.txt`, "modified content")
+      await Filesystem.write(`${tmp.path}/new.txt`, "new content")
+      await Filesystem.write(`${tmp.path}/b.txt`, "modified content")
 
       const diff = await Snapshot.diff(before!)
       expect(diff).toContain("a.txt")
@@ -683,16 +730,26 @@ test("restore function", async () => {
 
       // Make changes
       await $`rm ${tmp.path}/a.txt`.quiet()
-      await Bun.write(`${tmp.path}/new.txt`, "new content")
-      await Bun.write(`${tmp.path}/b.txt`, "modified")
+      await Filesystem.write(`${tmp.path}/new.txt`, "new content")
+      await Filesystem.write(`${tmp.path}/b.txt`, "modified")
 
       // Restore to original state
       await Snapshot.restore(before!)
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).exists()).toBe(true)
-      expect(await Bun.file(`${tmp.path}/a.txt`).text()).toBe(tmp.extra.aContent)
-      expect(await Bun.file(`${tmp.path}/new.txt`).exists()).toBe(true) // New files should remain
-      expect(await Bun.file(`${tmp.path}/b.txt`).text()).toBe(tmp.extra.bContent)
+      expect(
+        await fs
+          .access(`${tmp.path}/a.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(true)
+      expect(await fs.readFile(`${tmp.path}/a.txt`, "utf-8")).toBe(tmp.extra.aContent)
+      expect(
+        await fs
+          .access(`${tmp.path}/new.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(true) // New files should remain
+      expect(await fs.readFile(`${tmp.path}/b.txt`, "utf-8")).toBe(tmp.extra.bContent)
     },
   })
 })
@@ -710,14 +767,19 @@ test("revert should not delete files that existed but were deleted in snapshot",
       const snapshot2 = await Snapshot.track()
       expect(snapshot2).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/a.txt`, "recreated content")
+      await Filesystem.write(`${tmp.path}/a.txt`, "recreated content")
 
       const patch = await Snapshot.patch(snapshot2!)
       expect(patch.files).toContain(`${tmp.path}/a.txt`)
 
       await Snapshot.revert([patch])
 
-      expect(await Bun.file(`${tmp.path}/a.txt`).exists()).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/a.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
     },
   })
 })
@@ -727,14 +789,14 @@ test("revert preserves file that existed in snapshot when deleted then recreated
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      await Bun.write(`${tmp.path}/existing.txt`, "original content")
+      await Filesystem.write(`${tmp.path}/existing.txt`, "original content")
 
       const snapshot = await Snapshot.track()
       expect(snapshot).toBeTruthy()
 
       await $`rm ${tmp.path}/existing.txt`.quiet()
-      await Bun.write(`${tmp.path}/existing.txt`, "recreated")
-      await Bun.write(`${tmp.path}/newfile.txt`, "new")
+      await Filesystem.write(`${tmp.path}/existing.txt`, "recreated")
+      await Filesystem.write(`${tmp.path}/newfile.txt`, "new")
 
       const patch = await Snapshot.patch(snapshot!)
       expect(patch.files).toContain(`${tmp.path}/existing.txt`)
@@ -742,9 +804,19 @@ test("revert preserves file that existed in snapshot when deleted then recreated
 
       await Snapshot.revert([patch])
 
-      expect(await Bun.file(`${tmp.path}/newfile.txt`).exists()).toBe(false)
-      expect(await Bun.file(`${tmp.path}/existing.txt`).exists()).toBe(true)
-      expect(await Bun.file(`${tmp.path}/existing.txt`).text()).toBe("original content")
+      expect(
+        await fs
+          .access(`${tmp.path}/newfile.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(false)
+      expect(
+        await fs
+          .access(`${tmp.path}/existing.txt`)
+          .then(() => true)
+          .catch(() => false),
+      ).toBe(true)
+      expect(await fs.readFile(`${tmp.path}/existing.txt`, "utf-8")).toBe("original content")
     },
   })
 })
@@ -754,17 +826,17 @@ test("diffFull sets status based on git change type", async () => {
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      await Bun.write(`${tmp.path}/grow.txt`, "one\n")
-      await Bun.write(`${tmp.path}/trim.txt`, "line1\nline2\n")
-      await Bun.write(`${tmp.path}/delete.txt`, "gone")
+      await Filesystem.write(`${tmp.path}/grow.txt`, "one\n")
+      await Filesystem.write(`${tmp.path}/trim.txt`, "line1\nline2\n")
+      await Filesystem.write(`${tmp.path}/delete.txt`, "gone")
 
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/grow.txt`, "one\ntwo\n")
-      await Bun.write(`${tmp.path}/trim.txt`, "line1\n")
+      await Filesystem.write(`${tmp.path}/grow.txt`, "one\ntwo\n")
+      await Filesystem.write(`${tmp.path}/trim.txt`, "line1\n")
       await $`rm ${tmp.path}/delete.txt`.quiet()
-      await Bun.write(`${tmp.path}/added.txt`, "new")
+      await Filesystem.write(`${tmp.path}/added.txt`, "new")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -803,7 +875,7 @@ test("diffFull with new file additions", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/new.txt`, "new content")
+      await Filesystem.write(`${tmp.path}/new.txt`, "new content")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -829,7 +901,7 @@ test("diffFull with file modifications", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/b.txt`, "modified content")
+      await Filesystem.write(`${tmp.path}/b.txt`, "modified content")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -881,7 +953,7 @@ test("diffFull with multiple line additions", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/multi.txt`, "line1\nline2\nline3")
+      await Filesystem.write(`${tmp.path}/multi.txt`, "line1\nline2\nline3")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -907,7 +979,7 @@ test("diffFull with addition and deletion", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/added.txt`, "added content")
+      await Filesystem.write(`${tmp.path}/added.txt`, "added content")
       await $`rm ${tmp.path}/a.txt`.quiet()
 
       const after = await Snapshot.track()
@@ -941,8 +1013,8 @@ test("diffFull with multiple additions and deletions", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/multi1.txt`, "line1\nline2\nline3")
-      await Bun.write(`${tmp.path}/multi2.txt`, "single line")
+      await Filesystem.write(`${tmp.path}/multi1.txt`, "line1\nline2\nline3")
+      await Filesystem.write(`${tmp.path}/multi2.txt`, "single line")
       await $`rm ${tmp.path}/a.txt`.quiet()
       await $`rm ${tmp.path}/b.txt`.quiet()
 
@@ -1000,7 +1072,7 @@ test("diffFull with binary file changes", async () => {
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/binary.bin`, new Uint8Array([0x00, 0x01, 0x02, 0x03]))
+      await Filesystem.write(`${tmp.path}/binary.bin`, new Uint8Array([0x00, 0x01, 0x02, 0x03]))
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
@@ -1020,11 +1092,11 @@ test("diffFull with whitespace changes", async () => {
   await Instance.provide({
     directory: tmp.path,
     fn: async () => {
-      await Bun.write(`${tmp.path}/whitespace.txt`, "line1\nline2")
+      await Filesystem.write(`${tmp.path}/whitespace.txt`, "line1\nline2")
       const before = await Snapshot.track()
       expect(before).toBeTruthy()
 
-      await Bun.write(`${tmp.path}/whitespace.txt`, "line1\n\nline2\n")
+      await Filesystem.write(`${tmp.path}/whitespace.txt`, "line1\n\nline2\n")
 
       const after = await Snapshot.track()
       expect(after).toBeTruthy()
diff --git a/packages/opencode/test/tool/bash.test.ts b/packages/opencode/test/tool/bash.test.ts
index fd03b7f98..3bd923b60 100644
--- a/packages/opencode/test/tool/bash.test.ts
+++ b/packages/opencode/test/tool/bash.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, test } from "bun:test"
 import path from "path"
 import { BashTool } from "../../src/tool/bash"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 import type { PermissionNext } from "../../src/permission/next"
 import { Truncate } from "../../src/tool/truncation"
@@ -388,7 +389,7 @@ describe("tool.bash truncation", () => {
         const filepath = (result.metadata as any).outputPath
         expect(filepath).toBeTruthy()
 
-        const saved = await Bun.file(filepath).text()
+        const saved = await Filesystem.readText(filepath)
         const lines = saved.trim().split("\n")
         expect(lines.length).toBe(lineCount)
         expect(lines[0]).toBe("1")
diff --git a/packages/opencode/test/tool/read.test.ts b/packages/opencode/test/tool/read.test.ts
index cc9d1a33e..88228f14e 100644
--- a/packages/opencode/test/tool/read.test.ts
+++ b/packages/opencode/test/tool/read.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, test } from "bun:test"
 import path from "path"
 import { ReadTool } from "../../src/tool/read"
 import { Instance } from "../../src/project/instance"
+import { Filesystem } from "../../src/util/filesystem"
 import { tmpdir } from "../fixture/fixture"
 import { PermissionNext } from "../../src/permission/next"
 import { Agent } from "../../src/agent/agent"
@@ -199,10 +200,10 @@ describe("tool.read truncation", () => {
   test("truncates large file by bytes and sets truncated metadata", async () => {
     await using tmp = await tmpdir({
       init: async (dir) => {
-        const base = await Bun.file(path.join(FIXTURES_DIR, "models-api.json")).text()
+        const base = await Filesystem.readText(path.join(FIXTURES_DIR, "models-api.json"))
         const target = 60 * 1024
         const content = base.length >= target ? base : base.repeat(Math.ceil(target / base.length))
-        await Bun.write(path.join(dir, "large.json"), content)
+        await Filesystem.write(path.join(dir, "large.json"), content)
       },
     })
     await Instance.provide({
diff --git a/packages/opencode/test/tool/truncation.test.ts b/packages/opencode/test/tool/truncation.test.ts
index 09222f279..9e141b205 100644
--- a/packages/opencode/test/tool/truncation.test.ts
+++ b/packages/opencode/test/tool/truncation.test.ts
@@ -1,6 +1,7 @@
 import { describe, test, expect, afterAll } from "bun:test"
 import { Truncate } from "../../src/tool/truncation"
 import { Identifier } from "../../src/id/id"
+import { Filesystem } from "../../src/util/filesystem"
 import fs from "fs/promises"
 import path from "path"
 
@@ -9,7 +10,7 @@ const FIXTURES_DIR = path.join(import.meta.dir, "fixtures")
 describe("Truncate", () => {
   describe("output", () => {
     test("truncates large json file by bytes", async () => {
-      const content = await Bun.file(path.join(FIXTURES_DIR, "models-api.json")).text()
+      const content = await Filesystem.readText(path.join(FIXTURES_DIR, "models-api.json"))
       const result = await Truncate.output(content)
 
       expect(result.truncated).toBe(true)
@@ -69,7 +70,7 @@ describe("Truncate", () => {
     })
 
     test("large single-line file truncates with byte message", async () => {
-      const content = await Bun.file(path.join(FIXTURES_DIR, "models-api.json")).text()
+      const content = await Filesystem.readText(path.join(FIXTURES_DIR, "models-api.json"))
       const result = await Truncate.output(content)
 
       expect(result.truncated).toBe(true)
@@ -88,7 +89,7 @@ describe("Truncate", () => {
       expect(result.outputPath).toBeDefined()
       expect(result.outputPath).toContain("tool_")
 
-      const written = await Bun.file(result.outputPath).text()
+      const written = await Filesystem.readText(result.outputPath!)
       expect(written).toBe(lines)
     })
 
@@ -139,21 +140,21 @@ describe("Truncate", () => {
       const oldTimestamp = Date.now() - 10 * DAY_MS
       const oldId = Identifier.create("tool", false, oldTimestamp)
       oldFile = path.join(Truncate.DIR, oldId)
-      await Bun.write(Bun.file(oldFile), "old content")
+      await Filesystem.write(oldFile, "old content")
 
       // Create a recent file (3 days ago)
       const recentTimestamp = Date.now() - 3 * DAY_MS
       const recentId = Identifier.create("tool", false, recentTimestamp)
       recentFile = path.join(Truncate.DIR, recentId)
-      await Bun.write(Bun.file(recentFile), "recent content")
+      await Filesystem.write(recentFile, "recent content")
 
       await Truncate.cleanup()
 
       // Old file should be deleted
-      expect(await Bun.file(oldFile).exists()).toBe(false)
+      expect(await Filesystem.exists(oldFile)).toBe(false)
 
       // Recent file should still exist
-      expect(await Bun.file(recentFile).exists()).toBe(true)
+      expect(await Filesystem.exists(recentFile)).toBe(true)
     })
   })
 })
diff --git a/packages/opencode/test/util/filesystem.test.ts b/packages/opencode/test/util/filesystem.test.ts
index 3c3da0fc7..0f5447937 100644
--- a/packages/opencode/test/util/filesystem.test.ts
+++ b/packages/opencode/test/util/filesystem.test.ts
@@ -285,4 +285,125 @@ describe("filesystem", () => {
       expect(Filesystem.mimeType("Makefile")).toBe("application/octet-stream")
     })
   })
+
+  describe("writeStream()", () => {
+    test("writes from Web ReadableStream", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "streamed.txt")
+      const content = "Hello from stream!"
+      const encoder = new TextEncoder()
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(encoder.encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes from Node.js Readable stream", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "node-streamed.txt")
+      const content = "Hello from Node stream!"
+      const { Readable } = await import("stream")
+      const stream = Readable.from([content])
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes binary data from Web ReadableStream", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "binary.dat")
+      const binaryData = new Uint8Array([0x00, 0x01, 0x02, 0x03, 0xff])
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(binaryData)
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      const read = await fs.readFile(filepath)
+      expect(Buffer.from(read)).toEqual(Buffer.from(binaryData))
+    })
+
+    test("writes large content in chunks", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "large.txt")
+      const chunks = ["chunk1", "chunk2", "chunk3", "chunk4", "chunk5"]
+      const stream = new ReadableStream({
+        start(controller) {
+          for (const chunk of chunks) {
+            controller.enqueue(new TextEncoder().encode(chunk))
+          }
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(chunks.join(""))
+    })
+
+    test("creates parent directories", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "nested", "deep", "streamed.txt")
+      const content = "nested stream content"
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream)
+
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+
+    test("writes with permissions", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "protected-stream.txt")
+      const content = "secret stream content"
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream, 0o600)
+
+      const stats = await fs.stat(filepath)
+      if (process.platform !== "win32") {
+        expect(stats.mode & 0o777).toBe(0o600)
+      }
+    })
+
+    test("writes executable with permissions", async () => {
+      await using tmp = await tmpdir()
+      const filepath = path.join(tmp.path, "script.sh")
+      const content = "#!/bin/bash\necho hello"
+      const stream = new ReadableStream({
+        start(controller) {
+          controller.enqueue(new TextEncoder().encode(content))
+          controller.close()
+        },
+      })
+
+      await Filesystem.writeStream(filepath, stream, 0o755)
+
+      const stats = await fs.stat(filepath)
+      if (process.platform !== "win32") {
+        expect(stats.mode & 0o777).toBe(0o755)
+      }
+      expect(await fs.readFile(filepath, "utf-8")).toBe(content)
+    })
+  })
 })