diff --git a/packages/opencode/src/cli/cmd/tui/worker.ts b/packages/opencode/src/cli/cmd/tui/worker.ts
index e63f10ba80c..e0c0786bf0a 100644
--- a/packages/opencode/src/cli/cmd/tui/worker.ts
+++ b/packages/opencode/src/cli/cmd/tui/worker.ts
@@ -18,6 +18,11 @@ await Log.init({
     if (Installation.isLocal()) return "DEBUG"
     return "INFO"
   })(),
+  path: process.env.OPENCODE_LOG_PATH || undefined,
+  rotate:
+    process.env.OPENCODE_LOG_ROTATE === "daily"
+      ? { kind: "daily", retention: Number(process.env.OPENCODE_LOG_RETENTION) || undefined }
+      : undefined,
 })
 
 process.on("unhandledRejection", (e) => {
diff --git a/packages/opencode/src/index.ts b/packages/opencode/src/index.ts
index 6dc5e99e91e..a4beec3e167 100644
--- a/packages/opencode/src/index.ts
+++ b/packages/opencode/src/index.ts
@@ -65,6 +65,11 @@ const cli = yargs(hideBin(process.argv))
         if (Installation.isLocal()) return "DEBUG"
         return "INFO"
       })(),
+      path: process.env.OPENCODE_LOG_PATH || undefined,
+      rotate:
+        process.env.OPENCODE_LOG_ROTATE === "daily"
+          ? { kind: "daily", retention: Number(process.env.OPENCODE_LOG_RETENTION) || undefined }
+          : undefined,
     })
 
     process.env.AGENT = "1"
diff --git a/packages/opencode/src/util/log.ts b/packages/opencode/src/util/log.ts
index 6941310bbbd..47a82492a69 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 { openSync, writeSync, closeSync } from "fs"
 import { Global } from "../global"
 import z from "zod"
 
@@ -40,10 +41,22 @@ export namespace Log {
 
   export const Default = create({ service: "default" })
 
+  export type Rotate =
+    | {
+        kind: "startup"
+        retention?: number
+      }
+    | {
+        kind: "daily"
+        retention?: number
+      }
+
   export interface Options {
     print: boolean
     dev?: boolean
     level?: Level
+    path?: string
+    rotate?: Rotate
   }
 
   let logpath = ""
@@ -55,35 +68,78 @@ export namespace Log {
     return msg.length
   }
 
+  let fd: number | undefined
+  let deadline = 0
+
+  function today() {
+    const d = new Date()
+    return (
+      d.getFullYear() + "-" + String(d.getMonth() + 1).padStart(2, "0") + "-" + String(d.getDate()).padStart(2, "0")
+    )
+  }
+
+  function midnight() {
+    const d = new Date()
+    d.setHours(24, 0, 0, 0)
+    return d.getTime()
+  }
+
+  function rotate(dir: string) {
+    if (Date.now() < deadline && fd !== undefined) return
+    if (fd !== undefined) closeSync(fd)
+    deadline = midnight()
+    logpath = path.join(dir, `opencode-${today()}.log`)
+    fd = openSync(logpath, "a")
+  }
+
+  const writeStrategies: Record<Rotate["kind"], (options: Options) => Promise<void>> = {
+    async startup(options) {
+      const dir = options.path ?? Global.Path.log
+      const retention = options.rotate?.retention ?? 10
+      cleanup(dir, retention)
+      const name = options.dev ? "dev.log" : new Date().toISOString().split(".")[0].replace(/:/g, "") + ".log"
+      logpath = path.join(dir, name)
+      await fs.truncate(logpath).catch(() => {})
+      const writer = Bun.file(logpath).writer()
+      write = (msg: any) => {
+        const num = writer.write(msg)
+        writer.flush()
+        return num
+      }
+    },
+    async daily(options) {
+      const dir = options.path ?? Global.Path.log
+      const retention = options.rotate?.retention ?? 7
+      await fs.mkdir(dir, { recursive: true })
+      if (fd !== undefined) closeSync(fd)
+      fd = undefined
+      deadline = 0
+      rotate(dir)
+      cleanup(dir, retention)
+      write = (msg: any) => {
+        rotate(dir)
+        return writeSync(fd!, msg)
+      }
+    },
+  }
+
   export async function init(options: Options) {
     if (options.level) level = options.level
-    cleanup(Global.Path.log)
     if (options.print) return
-    logpath = path.join(
-      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()
-    write = async (msg: any) => {
-      const num = writer.write(msg)
-      writer.flush()
-      return num
-    }
+    return writeStrategies[options.rotate?.kind ?? "startup"](options)
   }
 
-  async function cleanup(dir: string) {
-    const glob = new Bun.Glob("????-??-??T??????.log")
+  async function cleanup(dir: string, retention: number) {
+    const glob = new Bun.Glob("*[0-9]*.log")
     const files = await Array.fromAsync(
       glob.scan({
         cwd: dir,
         absolute: true,
       }),
     )
-    if (files.length <= 5) return
-
-    const filesToDelete = files.slice(0, -10)
+    if (files.length <= retention) return
+    files.sort()
+    const filesToDelete = files.slice(0, -retention)
     await Promise.all(filesToDelete.map((file) => fs.unlink(file).catch(() => {})))
   }
 
diff --git a/packages/opencode/test/util/log.test.ts b/packages/opencode/test/util/log.test.ts
new file mode 100644
index 00000000000..5c899022bc8
--- /dev/null
+++ b/packages/opencode/test/util/log.test.ts
@@ -0,0 +1,206 @@
+import os from "os"
+import path from "path"
+import fs from "fs/promises"
+import { afterEach, beforeEach, describe, expect, test } from "bun:test"
+import { Log } from "../../src/util/log"
+
+let tmpDir: string
+
+beforeEach(async () => {
+  tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "log-test-"))
+})
+
+afterEach(async () => {
+  await fs.rm(tmpDir, { recursive: true, force: true })
+})
+
+describe("startup strategy", () => {
+  test("each init creates a new file", async () => {
+    const dir1 = path.join(tmpDir, "run1")
+    const dir2 = path.join(tmpDir, "run2")
+    await fs.mkdir(dir1, { recursive: true })
+    await fs.mkdir(dir2, { recursive: true })
+
+    await Log.init({ print: false, path: dir1, rotate: { kind: "startup" } })
+    const first = Log.file()
+
+    await Log.init({ print: false, path: dir2, rotate: { kind: "startup" } })
+    const second = Log.file()
+
+    expect(first).toBeTruthy()
+    expect(second).toBeTruthy()
+    expect(first).not.toBe(second)
+  })
+
+  test("file name matches YYYY-MM-DDTHHMMSS.log format", async () => {
+    const dir = path.join(tmpDir, "startup-fmt")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, path: dir, rotate: { kind: "startup" } })
+    const file = path.basename(Log.file())
+
+    expect(file).toMatch(/^\d{4}-\d{2}-\d{2}T\d{6}\.log$/)
+  })
+
+  test("dev mode uses dev.log as file name", async () => {
+    const dir = path.join(tmpDir, "startup-dev")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, dev: true, path: dir, rotate: { kind: "startup" } })
+    expect(path.basename(Log.file())).toBe("dev.log")
+  })
+
+  test("cleans up old files beyond retention", async () => {
+    const dir = path.join(tmpDir, "startup-retention")
+    await fs.mkdir(dir, { recursive: true })
+
+    // create 5 old log files that match the cleanup glob (*[0-9]*.log)
+    const oldFiles = Array.from({ length: 5 }, (_, i) => {
+      const name = `2024-01-0${i + 1}T000000.log`
+      return path.join(dir, name)
+    })
+    await Promise.all(oldFiles.map((f) => fs.writeFile(f, "old")))
+
+    // init with retention=3: cleanup runs before new file is created,
+    // so it sees 5 old files and deletes the 2 oldest
+    await Log.init({ print: false, path: dir, rotate: { kind: "startup", retention: 3 } })
+
+    // poll until the 2 oldest files are deleted
+    const oldest = [oldFiles[0], oldFiles[1]]
+    const end = Date.now() + 2000
+    while (Date.now() < end) {
+      const gone = await Promise.all(oldest.map((f) => fs.access(f).then(() => false).catch(() => true)))
+      if (gone.every(Boolean)) break
+      await Bun.sleep(50)
+    }
+
+    // the 2 oldest files should be deleted
+    for (const f of oldest) {
+      await expect(fs.access(f)).rejects.toThrow()
+    }
+    // the 3 newest old files should still exist
+    for (const f of oldFiles.slice(2)) {
+      await expect(fs.stat(f)).resolves.toBeTruthy()
+    }
+  })
+
+  test("log.info writes content to file", async () => {
+    const dir = path.join(tmpDir, "startup-write")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, level: "DEBUG", path: dir, rotate: { kind: "startup" } })
+    const logger = Log.create({ service: "test-startup-write" })
+    logger.info("hello startup")
+
+    // flush happens synchronously via writer.flush()
+    await Bun.sleep(50)
+    const content = await fs.readFile(Log.file(), "utf-8")
+    expect(content).toContain("hello startup")
+  })
+})
+
+describe("daily strategy", () => {
+  test("same day init uses the same file", async () => {
+    const dir = path.join(tmpDir, "daily-same")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, path: dir, rotate: { kind: "daily" } })
+    const first = Log.file()
+
+    await Log.init({ print: false, path: dir, rotate: { kind: "daily" } })
+    const second = Log.file()
+
+    expect(first).toBeTruthy()
+    expect(second).toBeTruthy()
+    expect(path.basename(first)).toBe(path.basename(second))
+  })
+
+  test("file name matches opencode-YYYY-MM-DD.log format", async () => {
+    const dir = path.join(tmpDir, "daily-fmt")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, path: dir, rotate: { kind: "daily" } })
+    const file = path.basename(Log.file())
+
+    expect(file).toMatch(/^opencode-\d{4}-\d{2}-\d{2}\.log$/)
+  })
+
+  test("cleans up old files beyond retention", async () => {
+    const dir = path.join(tmpDir, "daily-retention")
+    await fs.mkdir(dir, { recursive: true })
+
+    // create 10 old daily log files
+    const oldFiles = Array.from({ length: 10 }, (_, i) => {
+      const day = String(i + 1).padStart(2, "0")
+      return path.join(dir, `opencode-2024-01-${day}.log`)
+    })
+    await Promise.all(oldFiles.map((f) => fs.writeFile(f, "old")))
+
+    // init with retention=5
+    await Log.init({ print: false, path: dir, rotate: { kind: "daily", retention: 5 } })
+
+    // wait for async cleanup
+    await Bun.sleep(100)
+
+    const remaining = await fs.readdir(dir)
+    const logFiles = remaining.filter((f) => f.endsWith(".log"))
+    // 5 old + 1 today = 6, but cleanup keeps only retention=5
+    expect(logFiles.length).toBeLessThanOrEqual(5)
+  })
+
+  test("log.info writes content to file", async () => {
+    const dir = path.join(tmpDir, "daily-write")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, level: "DEBUG", path: dir, rotate: { kind: "daily" } })
+    const logger = Log.create({ service: "test-daily-write" })
+    logger.info("hello daily")
+
+    await Bun.sleep(50)
+    const content = await fs.readFile(Log.file(), "utf-8")
+    expect(content).toContain("hello daily")
+  })
+
+  test("appends to existing file on re-init same day", async () => {
+    const dir = path.join(tmpDir, "daily-append")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, level: "DEBUG", path: dir, rotate: { kind: "daily" } })
+    const logger1 = Log.create({ service: "test-daily-append-1" })
+    logger1.info("first message")
+    await Bun.sleep(50)
+
+    const filePath = Log.file()
+    const contentAfterFirst = await fs.readFile(filePath, "utf-8")
+    expect(contentAfterFirst).toContain("first message")
+
+    // re-init same day same dir
+    await Log.init({ print: false, level: "DEBUG", path: dir, rotate: { kind: "daily" } })
+    const logger2 = Log.create({ service: "test-daily-append-2" })
+    logger2.info("second message")
+    await Bun.sleep(50)
+
+    const contentAfterSecond = await fs.readFile(Log.file(), "utf-8")
+    expect(contentAfterSecond).toContain("second message")
+  })
+})
+
+describe("Log.file()", () => {
+  test("returns non-empty path after startup init", async () => {
+    const dir = path.join(tmpDir, "file-path-startup")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, path: dir, rotate: { kind: "startup" } })
+    expect(Log.file()).toBeTruthy()
+    expect(Log.file()).toContain(dir)
+  })
+
+  test("returns non-empty path after daily init", async () => {
+    const dir = path.join(tmpDir, "file-path-daily")
+    await fs.mkdir(dir, { recursive: true })
+
+    await Log.init({ print: false, path: dir, rotate: { kind: "daily" } })
+    expect(Log.file()).toBeTruthy()
+    expect(Log.file()).toContain(dir)
+  })
+})