diff --git a/src/tools/grep/cli.ts b/src/tools/grep/cli.ts
index c44bda377..1a6cd89d0 100644
--- a/src/tools/grep/cli.ts
+++ b/src/tools/grep/cli.ts
@@ -1,6 +1,7 @@
 import { spawn } from "bun"
 import {
   resolveGrepCli,
+  type ResolvedCli,
   type GrepBackend,
   DEFAULT_MAX_DEPTH,
   DEFAULT_MAX_FILESIZE,
@@ -148,17 +149,17 @@ function parseCountOutput(output: string): CountResult[] {
   return results
 }
 
-export async function runRg(options: GrepOptions): Promise<GrepResult> {
+export async function runRg(options: GrepOptions, resolvedCli?: ResolvedCli): Promise<GrepResult> {
   await rgSemaphore.acquire()
   try {
-    return await runRgInternal(options)
+    return await runRgInternal(options, resolvedCli)
   } finally {
     rgSemaphore.release()
   }
 }
 
-async function runRgInternal(options: GrepOptions): Promise<GrepResult> {
-  const cli = resolveGrepCli()
+async function runRgInternal(options: GrepOptions, resolvedCli?: ResolvedCli): Promise<GrepResult> {
+  const cli = resolvedCli ?? resolveGrepCli()
   const args = buildArgs(options, cli.backend)
   const timeout = Math.min(options.timeout ?? DEFAULT_TIMEOUT_MS, DEFAULT_TIMEOUT_MS)
 
@@ -224,17 +225,23 @@ async function runRgInternal(options: GrepOptions): Promise<GrepResult> {
   }
 }
 
-export async function runRgCount(options: Omit<GrepOptions, "context">): Promise<CountResult[]> {
+export async function runRgCount(
+  options: Omit<GrepOptions, "context">,
+  resolvedCli?: ResolvedCli
+): Promise<CountResult[]> {
   await rgSemaphore.acquire()
   try {
-    return await runRgCountInternal(options)
+    return await runRgCountInternal(options, resolvedCli)
   } finally {
     rgSemaphore.release()
   }
 }
 
-async function runRgCountInternal(options: Omit<GrepOptions, "context">): Promise<CountResult[]> {
-  const cli = resolveGrepCli()
+async function runRgCountInternal(
+  options: Omit<GrepOptions, "context">,
+  resolvedCli?: ResolvedCli
+): Promise<CountResult[]> {
+  const cli = resolvedCli ?? resolveGrepCli()
   const args = buildArgs({ ...options, context: 0 }, cli.backend)
 
   if (cli.backend === "rg") {
diff --git a/src/tools/grep/constants.test.ts b/src/tools/grep/constants.test.ts
new file mode 100644
index 000000000..717398e0b
--- /dev/null
+++ b/src/tools/grep/constants.test.ts
@@ -0,0 +1,166 @@
+import { afterEach, beforeEach, describe, expect, mock, test } from "bun:test"
+
+type SpawnResult = {
+  status: number | null
+  stdout: string
+}
+
+describe("grep constants", () => {
+  let originalPlatform: NodeJS.Platform
+
+  beforeEach(() => {
+    originalPlatform = process.platform
+    mock.restore()
+  })
+
+  afterEach(() => {
+    Object.defineProperty(process, "platform", { value: originalPlatform, configurable: true })
+    mock.restore()
+  })
+
+  function mockPlatform(platform: NodeJS.Platform): void {
+    Object.defineProperty(process, "platform", { value: platform, configurable: true })
+  }
+
+  function createSpawnSyncMock(paths: { rg?: string; grep?: string }) {
+    return mock((_command: string, args: string[]): SpawnResult => {
+      const binaryName = args[0]
+
+      if (binaryName === "rg" && paths.rg) {
+        return { status: 0, stdout: `${paths.rg}\n` }
+      }
+
+      if (binaryName === "grep" && paths.grep) {
+        return { status: 0, stdout: `${paths.grep}\n` }
+      }
+
+      return { status: 1, stdout: "" }
+    })
+  }
+
+  async function importConstantsModule(tag: string) {
+    return import(new URL(`./constants.ts?${tag}`, import.meta.url).href)
+  }
+
+  test("#given only GNU grep is available #when auto-install succeeds #then it caches the downloaded ripgrep path", async () => {
+    // given
+    const spawnSyncMock = createSpawnSyncMock({ grep: "/usr/bin/grep" })
+    const existsSyncMock = mock(() => false)
+    const downloadAndInstallRipgrepMock = mock(async () => "/tmp/oh-my-opencode/bin/rg")
+    const getInstalledRipgrepPathMock = mock(() => null)
+    const logMock = mock(() => {})
+
+    mock.module("node:child_process", () => ({ spawnSync: spawnSyncMock }))
+    mock.module("node:fs", () => ({ existsSync: existsSyncMock }))
+    mock.module("./downloader", () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module("./downloader.ts", () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module(new URL("./downloader.ts", import.meta.url).href, () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module("../../shared/logger", () => ({ log: logMock }))
+    mock.module("../../shared/logger.ts", () => ({ log: logMock }))
+    mock.module(new URL("../../shared/logger.ts", import.meta.url).href, () => ({ log: logMock }))
+
+    const { resolveGrepCliWithAutoInstall } = await importConstantsModule("grep-cache-success")
+
+    // when
+    const firstResult = await resolveGrepCliWithAutoInstall()
+    const secondResult = await resolveGrepCliWithAutoInstall()
+
+    // then
+    expect(firstResult).toEqual({ path: "/tmp/oh-my-opencode/bin/rg", backend: "rg" })
+    expect(secondResult).toEqual({ path: "/tmp/oh-my-opencode/bin/rg", backend: "rg" })
+    expect(downloadAndInstallRipgrepMock).toHaveBeenCalledTimes(1)
+    expect(logMock).not.toHaveBeenCalled()
+  })
+
+  test("#given Windows resolves to placeholder rg #when auto-install succeeds #then it still downloads ripgrep", async () => {
+    // given
+    mockPlatform("win32")
+
+    const spawnSyncMock = createSpawnSyncMock({})
+    const existsSyncMock = mock(() => false)
+    const downloadAndInstallRipgrepMock = mock(async () => "C:/Users/test/.cache/oh-my-opencode/bin/rg.exe")
+    const getInstalledRipgrepPathMock = mock(() => null)
+    const logMock = mock(() => {})
+
+    mock.module("node:child_process", () => ({ spawnSync: spawnSyncMock }))
+    mock.module("node:fs", () => ({ existsSync: existsSyncMock }))
+    mock.module("./downloader", () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module("./downloader.ts", () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module(new URL("./downloader.ts", import.meta.url).href, () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module("../../shared/logger", () => ({ log: logMock }))
+    mock.module("../../shared/logger.ts", () => ({ log: logMock }))
+    mock.module(new URL("../../shared/logger.ts", import.meta.url).href, () => ({ log: logMock }))
+
+    const { resolveGrepCliWithAutoInstall } = await importConstantsModule("grep-win32-placeholder")
+
+    // when
+    const result = await resolveGrepCliWithAutoInstall()
+
+    // then
+    expect(result).toEqual({ path: "C:/Users/test/.cache/oh-my-opencode/bin/rg.exe", backend: "rg" })
+    expect(downloadAndInstallRipgrepMock).toHaveBeenCalledTimes(1)
+    expect(logMock).not.toHaveBeenCalled()
+  })
+
+  test("#given only GNU grep is available #when auto-install fails #then it logs and falls back to GNU grep", async () => {
+    // given
+    const spawnSyncMock = createSpawnSyncMock({ grep: "/usr/bin/grep" })
+    const existsSyncMock = mock(() => false)
+    const downloadAndInstallRipgrepMock = mock(async () => {
+      throw new Error("network down")
+    })
+    const getInstalledRipgrepPathMock = mock(() => null)
+    const logMock = mock(() => {})
+
+    mock.module("node:child_process", () => ({ spawnSync: spawnSyncMock }))
+    mock.module("node:fs", () => ({ existsSync: existsSyncMock }))
+    mock.module("./downloader", () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module("./downloader.ts", () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module(new URL("./downloader.ts", import.meta.url).href, () => ({
+      downloadAndInstallRipgrep: downloadAndInstallRipgrepMock,
+      getInstalledRipgrepPath: getInstalledRipgrepPathMock,
+    }))
+    mock.module("../../shared/logger", () => ({ log: logMock }))
+    mock.module("../../shared/logger.ts", () => ({ log: logMock }))
+    mock.module(new URL("../../shared/logger.ts", import.meta.url).href, () => ({ log: logMock }))
+
+    const { resolveGrepCliWithAutoInstall } = await importConstantsModule("grep-grep-fallback")
+
+    // when
+    const result = await resolveGrepCliWithAutoInstall()
+
+    // then
+    expect(result).toEqual({ path: "/usr/bin/grep", backend: "grep" })
+    expect(logMock).toHaveBeenCalledWith(
+      "[oh-my-opencode] Failed to auto-install ripgrep. Falling back to GNU grep.",
+      {
+        error: "network down",
+        grep_path: "/usr/bin/grep",
+      }
+    )
+  })
+})
diff --git a/src/tools/grep/constants.ts b/src/tools/grep/constants.ts
index 524fddd4b..f41284324 100644
--- a/src/tools/grep/constants.ts
+++ b/src/tools/grep/constants.ts
@@ -3,10 +3,11 @@ import { join, dirname } from "node:path"
 import { spawnSync } from "node:child_process"
 import { getInstalledRipgrepPath, downloadAndInstallRipgrep } from "./downloader"
 import { getDataDir } from "../../shared/data-path"
+import { log } from "../../shared/logger"
 
 export type GrepBackend = "rg" | "grep"
 
-interface ResolvedCli {
+export interface ResolvedCli {
   path: string
   backend: GrepBackend
 }
@@ -89,7 +90,7 @@ export function resolveGrepCli(): ResolvedCli {
 export async function resolveGrepCliWithAutoInstall(): Promise<ResolvedCli> {
   const current = resolveGrepCli()
 
-  if (current.backend === "rg") {
+  if (current.backend === "rg" && current.path !== "rg") {
     return current
   }
 
@@ -103,7 +104,18 @@ export async function resolveGrepCliWithAutoInstall(): Promise<ResolvedCli> {
     const rgPath = await downloadAndInstallRipgrep()
     cachedCli = { path: rgPath, backend: "rg" }
     return cachedCli
-  } catch {
+  } catch (error) {
+    if (current.backend === "grep") {
+      log("[oh-my-opencode] Failed to auto-install ripgrep. Falling back to GNU grep.", {
+        error: error instanceof Error ? error.message : String(error),
+        grep_path: current.path,
+      })
+    } else {
+      log("[oh-my-opencode] Failed to auto-install ripgrep and GNU grep was not found.", {
+        error: error instanceof Error ? error.message : String(error),
+      })
+    }
+
     return current
   }
 }
diff --git a/src/tools/grep/tools.test.ts b/src/tools/grep/tools.test.ts
new file mode 100644
index 000000000..1404672b3
--- /dev/null
+++ b/src/tools/grep/tools.test.ts
@@ -0,0 +1,139 @@
+import { afterEach, beforeEach, describe, expect, mock, test } from "bun:test"
+import type { PluginInput } from "@opencode-ai/plugin"
+import type { ToolContext } from "@opencode-ai/plugin/tool"
+
+const projectDir = "/private/tmp/work-3003"
+
+const mockCtx = { directory: projectDir } as PluginInput
+
+const mockContext: ToolContext = {
+  sessionID: "test-session",
+  messageID: "test-message",
+  agent: "test-agent",
+  directory: projectDir,
+  worktree: projectDir,
+  abort: new AbortController().signal,
+  metadata: () => {},
+  ask: async () => {},
+}
+
+describe("grep tools", () => {
+  beforeEach(() => {
+    mock.restore()
+  })
+
+  afterEach(() => {
+    mock.restore()
+  })
+
+  async function importToolsModule(tag: string) {
+    return import(new URL(`./tools.ts?${tag}`, import.meta.url).href)
+  }
+
+  test("#given content mode #when grep executes #then it resolves the CLI with auto-install before runRg", async () => {
+    // given
+    const cli = { path: "/tmp/oh-my-opencode/bin/rg", backend: "rg" as const }
+    const resolveGrepCliWithAutoInstallMock = mock(async () => cli)
+    const runRgMock = mock(async () => ({
+      matches: [{ file: "src/tools/grep/tools.ts", line: 12, text: "resolveGrepCliWithAutoInstall" }],
+      totalMatches: 1,
+      filesSearched: 1,
+      truncated: false,
+    }))
+    const runRgCountMock = mock(async () => [])
+    const formatGrepResultMock = mock(() => "formatted grep result")
+    const formatCountResultMock = mock(() => "formatted count result")
+
+    mock.module("./constants", () => ({ resolveGrepCliWithAutoInstall: resolveGrepCliWithAutoInstallMock }))
+    mock.module("./constants.ts", () => ({ resolveGrepCliWithAutoInstall: resolveGrepCliWithAutoInstallMock }))
+    mock.module(new URL("./constants.ts", import.meta.url).href, () => ({ resolveGrepCliWithAutoInstall: resolveGrepCliWithAutoInstallMock }))
+    mock.module("./cli", () => ({ runRg: runRgMock, runRgCount: runRgCountMock }))
+    mock.module("./cli.ts", () => ({ runRg: runRgMock, runRgCount: runRgCountMock }))
+    mock.module(new URL("./cli.ts", import.meta.url).href, () => ({ runRg: runRgMock, runRgCount: runRgCountMock }))
+    mock.module("./result-formatter", () => ({
+      formatGrepResult: formatGrepResultMock,
+      formatCountResult: formatCountResultMock,
+    }))
+    mock.module("./result-formatter.ts", () => ({
+      formatGrepResult: formatGrepResultMock,
+      formatCountResult: formatCountResultMock,
+    }))
+    mock.module(new URL("./result-formatter.ts", import.meta.url).href, () => ({
+      formatGrepResult: formatGrepResultMock,
+      formatCountResult: formatCountResultMock,
+    }))
+
+    const { createGrepTools } = await importToolsModule("grep-tools-content")
+    const { grep } = createGrepTools(mockCtx)
+
+    // when
+    const result = await grep.execute({ pattern: "resolveGrepCliWithAutoInstall" }, mockContext)
+
+    // then
+    expect(result).toBe("formatted grep result")
+    expect(resolveGrepCliWithAutoInstallMock).toHaveBeenCalledTimes(1)
+    expect(runRgMock).toHaveBeenCalledWith(
+      {
+        pattern: "resolveGrepCliWithAutoInstall",
+        paths: [projectDir],
+        globs: undefined,
+        context: 0,
+        outputMode: "files_with_matches",
+        headLimit: 0,
+      },
+      cli
+    )
+  })
+
+  test("#given count mode #when grep executes #then it resolves the CLI with auto-install before runRgCount", async () => {
+    // given
+    const cli = { path: "/tmp/oh-my-opencode/bin/rg", backend: "rg" as const }
+    const resolveGrepCliWithAutoInstallMock = mock(async () => cli)
+    const runRgMock = mock(async () => ({
+      matches: [],
+      totalMatches: 0,
+      filesSearched: 0,
+      truncated: false,
+    }))
+    const runRgCountMock = mock(async () => [{ file: "src/tools/grep/tools.ts", count: 2 }])
+    const formatGrepResultMock = mock(() => "formatted grep result")
+    const formatCountResultMock = mock(() => "formatted count result")
+
+    mock.module("./constants", () => ({ resolveGrepCliWithAutoInstall: resolveGrepCliWithAutoInstallMock }))
+    mock.module("./constants.ts", () => ({ resolveGrepCliWithAutoInstall: resolveGrepCliWithAutoInstallMock }))
+    mock.module(new URL("./constants.ts", import.meta.url).href, () => ({ resolveGrepCliWithAutoInstall: resolveGrepCliWithAutoInstallMock }))
+    mock.module("./cli", () => ({ runRg: runRgMock, runRgCount: runRgCountMock }))
+    mock.module("./cli.ts", () => ({ runRg: runRgMock, runRgCount: runRgCountMock }))
+    mock.module(new URL("./cli.ts", import.meta.url).href, () => ({ runRg: runRgMock, runRgCount: runRgCountMock }))
+    mock.module("./result-formatter", () => ({
+      formatGrepResult: formatGrepResultMock,
+      formatCountResult: formatCountResultMock,
+    }))
+    mock.module("./result-formatter.ts", () => ({
+      formatGrepResult: formatGrepResultMock,
+      formatCountResult: formatCountResultMock,
+    }))
+    mock.module(new URL("./result-formatter.ts", import.meta.url).href, () => ({
+      formatGrepResult: formatGrepResultMock,
+      formatCountResult: formatCountResultMock,
+    }))
+
+    const { createGrepTools } = await importToolsModule("grep-tools-count")
+    const { grep } = createGrepTools(mockCtx)
+
+    // when
+    const result = await grep.execute({ pattern: "resolveGrepCliWithAutoInstall", output_mode: "count" }, mockContext)
+
+    // then
+    expect(result).toBe("formatted count result")
+    expect(resolveGrepCliWithAutoInstallMock).toHaveBeenCalledTimes(1)
+    expect(runRgCountMock).toHaveBeenCalledWith(
+      {
+        pattern: "resolveGrepCliWithAutoInstall",
+        paths: [projectDir],
+        globs: undefined,
+      },
+      cli
+    )
+  })
+})
diff --git a/src/tools/grep/tools.ts b/src/tools/grep/tools.ts
index b00c47540..eaf8a3972 100644
--- a/src/tools/grep/tools.ts
+++ b/src/tools/grep/tools.ts
@@ -2,6 +2,7 @@ import { resolve } from "node:path"
 import type { PluginInput } from "@opencode-ai/plugin"
 import { tool, type ToolDefinition } from "@opencode-ai/plugin/tool"
 import { runRg, runRgCount } from "./cli"
+import { resolveGrepCliWithAutoInstall } from "./constants"
 import { formatGrepResult, formatCountResult } from "./result-formatter"
 
 export function createGrepTools(ctx: PluginInput): Record<string, ToolDefinition> {
@@ -42,13 +43,14 @@ export function createGrepTools(ctx: PluginInput): Record<string, ToolDefinition
         const paths = [searchPath]
         const outputMode = args.output_mode ?? "files_with_matches"
         const headLimit = args.head_limit ?? 0
+        const cli = await resolveGrepCliWithAutoInstall()
 
         if (outputMode === "count") {
           const results = await runRgCount({
             pattern: args.pattern,
             paths,
             globs,
-          })
+          }, cli)
           const limited = headLimit > 0 ? results.slice(0, headLimit) : results
           return formatCountResult(limited)
         }
@@ -60,7 +62,7 @@ export function createGrepTools(ctx: PluginInput): Record<string, ToolDefinition
           context: 0,
           outputMode,
           headLimit,
-        })
+        }, cli)
 
         return formatGrepResult(result)
       } catch (e) {