diff --git a/packages/omo-opencode/src/config/schema/hooks.ts b/packages/omo-opencode/src/config/schema/hooks.ts
index c243e882356..3deec422228 100644
--- a/packages/omo-opencode/src/config/schema/hooks.ts
+++ b/packages/omo-opencode/src/config/schema/hooks.ts
@@ -58,6 +58,7 @@ export const HookNameSchema = z.enum([
   "webfetch-redirect-guard",
   "fsync-skip-warning",
   "plan-format-validator",
+  "v4-checkpoint-writer",
   "legacy-plugin-toast",
 ])
 
diff --git a/packages/omo-opencode/src/hooks/index.ts b/packages/omo-opencode/src/hooks/index.ts
index 537145e095b..d7501a7dbee 100644
--- a/packages/omo-opencode/src/hooks/index.ts
+++ b/packages/omo-opencode/src/hooks/index.ts
@@ -69,3 +69,4 @@ export { createFsyncSkipWarningHook } from "./fsync-skip-warning"
 export { createNotepadWriteGuardHook } from "./notepad-write-guard"
 export { createPlanFormatValidatorHook } from "./plan-format-validator"
 export { createMonitorStatusInjectorHook } from "./monitor-status-injector"
+export { createV4CheckpointWriterHook } from "./v4-checkpoint-writer"
diff --git a/packages/omo-opencode/src/hooks/v4-checkpoint-writer/hook.test.ts b/packages/omo-opencode/src/hooks/v4-checkpoint-writer/hook.test.ts
new file mode 100644
index 00000000000..a63c3868a43
--- /dev/null
+++ b/packages/omo-opencode/src/hooks/v4-checkpoint-writer/hook.test.ts
@@ -0,0 +1,146 @@
+/// <reference types="bun-types" />
+
+import { describe, expect, test, mock, afterAll, beforeEach, afterEach } from "bun:test"
+import { existsSync, readFileSync, rmSync, mkdtempSync } from "node:fs"
+import { join } from "node:path"
+import { tmpdir } from "node:os"
+
+const logMock = mock(() => {})
+
+mock.module("../../shared/logger", () => ({
+  log: logMock,
+}))
+
+afterAll(() => {
+  mock.restore()
+})
+
+const { createV4CheckpointWriterHook } = await import("./hook")
+
+describe("v4-checkpoint-writer", () => {
+  let tempDir: string
+
+  beforeEach(() => {
+    tempDir = mkdtempSync(join(tmpdir(), "v4-checkpoint-test-"))
+  })
+
+  afterEach(() => {
+    rmSync(tempDir, { recursive: true, force: true })
+  })
+
+  test("#given V4 session reaching 20 tool calls #when tool.execute.after runs #then writes checkpoint file", () => {
+    // given
+    const hook = createV4CheckpointWriterHook({ directory: tempDir })
+    const sessionID = "ses_v4_checkpoint"
+
+    // simulate model detection
+    hook.event({
+      event: {
+        type: "message.updated",
+        properties: {
+          info: { sessionID, modelID: "deepseek/deepseek-v4-pro", role: "assistant" },
+        },
+      },
+    })
+
+    // when — simulate 20 tool calls
+    for (let i = 0; i < 20; i++) {
+      hook["tool.execute.after"](
+        { tool: "bash", sessionID, callID: `call_${i}` },
+        { title: "", output: "result", metadata: null },
+      )
+    }
+
+    // then
+    const checkpointPath = join(tempDir, ".omo/checkpoints", `${sessionID}.json`)
+    expect(existsSync(checkpointPath)).toBe(true)
+    const checkpoint = JSON.parse(readFileSync(checkpointPath, "utf8"))
+    expect(checkpoint.sessionID).toBe(sessionID)
+    expect(checkpoint.modelID).toBe("deepseek/deepseek-v4-pro")
+    expect(checkpoint.toolCallCount).toBe(20)
+    expect(checkpoint.lastToolName).toBe("bash")
+  })
+
+  test("#given V4 session at 19 tool calls #when tool.execute.after runs #then does NOT write checkpoint", () => {
+    // given
+    const hook = createV4CheckpointWriterHook({ directory: tempDir })
+    const sessionID = "ses_v4_no_checkpoint"
+
+    hook.event({
+      event: {
+        type: "message.updated",
+        properties: {
+          info: { sessionID, modelID: "deepseek/deepseek-v4-flash", role: "assistant" },
+        },
+      },
+    })
+
+    // when — 19 tool calls (one short of the 20-call interval)
+    for (let i = 0; i < 19; i++) {
+      hook["tool.execute.after"](
+        { tool: "read", sessionID, callID: `call_${i}` },
+        { title: "", output: "result", metadata: null },
+      )
+    }
+
+    // then
+    const checkpointPath = join(tempDir, ".omo/checkpoints", `${sessionID}.json`)
+    expect(existsSync(checkpointPath)).toBe(false)
+  })
+
+  test("#given non-V4 session at 20 tool calls #when tool.execute.after runs #then does NOT write checkpoint", () => {
+    // given
+    const hook = createV4CheckpointWriterHook({ directory: tempDir })
+    const sessionID = "ses_non_v4"
+
+    hook.event({
+      event: {
+        type: "message.updated",
+        properties: {
+          info: { sessionID, modelID: "anthropic/claude-sonnet-4-6", role: "assistant" },
+        },
+      },
+    })
+
+    // when
+    for (let i = 0; i < 20; i++) {
+      hook["tool.execute.after"](
+        { tool: "bash", sessionID, callID: `call_${i}` },
+        { title: "", output: "result", metadata: null },
+      )
+    }
+
+    // then
+    const checkpointPath = join(tempDir, ".omo/checkpoints", `${sessionID}.json`)
+    expect(existsSync(checkpointPath)).toBe(false)
+  })
+
+  test("#given V4 session reaching 40 tool calls #when tool.execute.after runs #then writes 2nd checkpoint", () => {
+    // given
+    const hook = createV4CheckpointWriterHook({ directory: tempDir })
+    const sessionID = "ses_v4_40"
+
+    hook.event({
+      event: {
+        type: "message.updated",
+        properties: {
+          info: { sessionID, modelID: "deepseek/deepseek-v4-pro", role: "assistant" },
+        },
+      },
+    })
+
+    // when — 40 tool calls (two intervals)
+    for (let i = 0; i < 40; i++) {
+      hook["tool.execute.after"](
+        { tool: "edit", sessionID, callID: `call_${i}` },
+        { title: "", output: "result", metadata: null },
+      )
+    }
+
+    // then — checkpoint should show 40 calls
+    const checkpointPath = join(tempDir, ".omo/checkpoints", `${sessionID}.json`)
+    expect(existsSync(checkpointPath)).toBe(true)
+    const checkpoint = JSON.parse(readFileSync(checkpointPath, "utf8"))
+    expect(checkpoint.toolCallCount).toBe(40)
+  })
+})
diff --git a/packages/omo-opencode/src/hooks/v4-checkpoint-writer/hook.ts b/packages/omo-opencode/src/hooks/v4-checkpoint-writer/hook.ts
new file mode 100644
index 00000000000..91c64574651
--- /dev/null
+++ b/packages/omo-opencode/src/hooks/v4-checkpoint-writer/hook.ts
@@ -0,0 +1,104 @@
+import { writeFileSync, mkdirSync, existsSync } from "node:fs"
+import { join, dirname } from "node:path"
+import { homedir } from "node:os"
+import { log } from "../../shared/logger"
+
+const CHECKPOINT_INTERVAL = 20
+const CHECKPOINT_DIR_NAME = ".omo/checkpoints"
+
+function isV4Model(modelID: string): boolean {
+  const lower = modelID.toLowerCase()
+  return lower.includes("deepseek-v4") || lower.includes("deepseek_v4")
+}
+
+function resolveCheckpointDir(directory?: string): string {
+  if (directory) return join(directory, CHECKPOINT_DIR_NAME)
+  return join(homedir(), ".omo", "checkpoints")
+}
+
+type SessionState = {
+  modelID: string
+  toolCallCount: number
+  lastToolName: string
+  lastCheckpointAt: number
+}
+
+type SessionStateCache = Map<string, SessionState>
+
+export function createV4CheckpointWriterHook(options?: { directory?: string }) {
+  const sessionStates: SessionStateCache = new Map()
+  const checkpointDir = resolveCheckpointDir(options?.directory)
+
+  return {
+    event: (input: {
+      event: {
+        type: string
+        properties: {
+          info?: {
+            sessionID?: string
+            modelID?: string
+            role?: string
+          }
+        }
+      }
+    }): void => {
+      if (input.event.type !== "message.updated") return
+      const info = input.event.properties?.info
+      if (!info?.modelID || !info?.sessionID) return
+      if (!isV4Model(info.modelID)) return
+
+      const existing = sessionStates.get(info.sessionID)
+      if (!existing) {
+        sessionStates.set(info.sessionID, {
+          modelID: info.modelID,
+          toolCallCount: 0,
+          lastToolName: "",
+          lastCheckpointAt: 0,
+        })
+      } else {
+        existing.modelID = info.modelID
+      }
+    },
+
+    "tool.execute.after": (
+      input: { tool: string; sessionID: string; callID: string },
+      _output?: { title?: string; output?: string; metadata?: unknown },
+    ): void => {
+      const state = sessionStates.get(input.sessionID)
+      if (!state) return
+
+      state.toolCallCount++
+      state.lastToolName = input.tool
+
+      if (state.toolCallCount % CHECKPOINT_INTERVAL !== 0) return
+
+      const now = Date.now()
+      state.lastCheckpointAt = now
+
+      const checkpoint = {
+        sessionID: input.sessionID,
+        modelID: state.modelID,
+        toolCallCount: state.toolCallCount,
+        lastToolName: state.lastToolName,
+        timestamp: new Date(now).toISOString(),
+      }
+
+      try {
+        if (!existsSync(checkpointDir)) {
+          mkdirSync(checkpointDir, { recursive: true })
+        }
+        const filePath = join(checkpointDir, `${input.sessionID}.json`)
+        writeFileSync(filePath, JSON.stringify(checkpoint, null, 2) + "\n", "utf8")
+        log("[v4-checkpoint-writer] Checkpoint written", {
+          sessionID: input.sessionID,
+          toolCallCount: state.toolCallCount,
+        })
+      } catch (error) {
+        log("[v4-checkpoint-writer] Failed to write checkpoint", {
+          sessionID: input.sessionID,
+          error: String(error),
+        })
+      }
+    },
+  }
+}
diff --git a/packages/omo-opencode/src/hooks/v4-checkpoint-writer/index.ts b/packages/omo-opencode/src/hooks/v4-checkpoint-writer/index.ts
new file mode 100644
index 00000000000..38bfb2fe112
--- /dev/null
+++ b/packages/omo-opencode/src/hooks/v4-checkpoint-writer/index.ts
@@ -0,0 +1 @@
+export { createV4CheckpointWriterHook } from "./hook"
diff --git a/packages/omo-opencode/src/plugin/hooks/create-tool-guard-hooks.ts b/packages/omo-opencode/src/plugin/hooks/create-tool-guard-hooks.ts
index 0ddfea11815..a01862de22e 100644
--- a/packages/omo-opencode/src/plugin/hooks/create-tool-guard-hooks.ts
+++ b/packages/omo-opencode/src/plugin/hooks/create-tool-guard-hooks.ts
@@ -21,6 +21,7 @@ import {
   createFsyncSkipWarningHook,
   createNotepadWriteGuardHook,
   createPlanFormatValidatorHook,
+  createV4CheckpointWriterHook,
 } from "../../hooks"
 import {
   getOpenCodeVersion,
@@ -49,6 +50,7 @@ export type ToolGuardHooks = {
   teamToolGating: ReturnType<typeof createTeamToolGating> | null
   notepadWriteGuard: ReturnType<typeof createNotepadWriteGuardHook> | null
   planFormatValidator: ReturnType<typeof createPlanFormatValidatorHook> | null
+  v4CheckpointWriter: ReturnType<typeof createV4CheckpointWriterHook> | null
 }
 
 export function createToolGuardHooks(args: {
@@ -157,6 +159,10 @@ export function createToolGuardHooks(args: {
     ? safeHook("notepad-write-guard", () => createNotepadWriteGuardHook())
     : null
 
+  const v4CheckpointWriter = isHookEnabled("v4-checkpoint-writer")
+    ? safeHook("v4-checkpoint-writer", () => createV4CheckpointWriterHook({ directory: ctx.directory }))
+    : null
+
   return {
     commentChecker,
     toolOutputTruncator,
@@ -176,5 +182,6 @@ export function createToolGuardHooks(args: {
     teamToolGating,
     notepadWriteGuard,
     planFormatValidator,
+    v4CheckpointWriter,
   }
 }