diff --git a/.changeset/setup-runtime-selection.md b/.changeset/setup-runtime-selection.md
new file mode 100644
index 0000000..d492e36
--- /dev/null
+++ b/.changeset/setup-runtime-selection.md
@@ -0,0 +1,5 @@
+---
+"@gh-symphony/cli": patch
+---
+
+Add runtime selection to `gh-symphony setup` so issue #390 users can choose Codex or Claude Code during onboarding, pass `--runtime` in non-interactive setup, and receive a clear install hint when the selected runtime command is missing from `PATH`.
diff --git a/packages/cli/src/commands/doctor.ts b/packages/cli/src/commands/doctor.ts
index f70605a..98db75d 100644
--- a/packages/cli/src/commands/doctor.ts
+++ b/packages/cli/src/commands/doctor.ts
@@ -1,7 +1,7 @@
 import { constants } from "node:fs";
 import { execFileSync, spawnSync } from "node:child_process";
 import { access, mkdir, readFile, stat } from "node:fs/promises";
-import { delimiter, isAbsolute, join, resolve } from "node:path";
+import { isAbsolute, join, resolve } from "node:path";
 import {
   parseWorkflowMarkdown,
   type ParsedWorkflow,
@@ -56,6 +56,7 @@ import {
   readGitHubProjectBinding,
   renderIssueWorkflowPreview,
 } from "./workflow.js";
+import { commandExistsOnPath } from "../utils/command-exists-on-path.js";
 
 type DoctorStatus = "pass" | "warn" | "fail";
 type DoctorRemediationStatus = "applied" | "skipped" | "manual";
@@ -583,69 +584,6 @@ function formatGhSymphonyCommand(
   return `gh-symphony ${commandArgs.join(" ")}`;
 }
 
-function getCommandCandidates(
-  binary: string,
-  deps: Pick<DoctorDependencies, "platform" | "pathExtEnv">
-): string[] {
-  if (deps.platform !== "win32") {
-    return [binary];
-  }
-
-  const pathExts = (deps.pathExtEnv ?? ".COM;.EXE;.BAT;.CMD")
-    .split(";")
-    .map((ext) => ext.trim())
-    .filter(Boolean);
-  const normalizedBinary = binary.toLowerCase();
-  if (pathExts.some((ext) => normalizedBinary.endsWith(ext.toLowerCase()))) {
-    return [binary];
-  }
-
-  return [binary, ...pathExts.map((ext) => `${binary}${ext}`)];
-}
-
-async function commandExistsOnPath(
-  binary: string,
-  deps: Pick<
-    DoctorDependencies,
-    "access" | "pathEnv" | "pathExtEnv" | "platform"
-  >
-): Promise<boolean> {
-  if (!binary) {
-    return false;
-  }
-
-  const candidates = getCommandCandidates(binary, deps);
-  if (isAbsolute(binary) || binary.includes("/") || binary.includes("\\")) {
-    for (const candidate of candidates) {
-      try {
-        await deps.access(resolve(candidate), constants.X_OK);
-        return true;
-      } catch {
-        continue;
-      }
-    }
-
-    return false;
-  }
-
-  for (const segment of (deps.pathEnv ?? "").split(delimiter)) {
-    if (!segment) {
-      continue;
-    }
-    for (const command of candidates) {
-      const candidate = join(segment, command);
-      try {
-        await deps.access(candidate, constants.X_OK);
-        return true;
-      } catch {
-        continue;
-      }
-    }
-  }
-
-  return false;
-}
-
 function toDoctorClaudeCheck(check: ClaudePreflightCheck): DoctorCheckResult {
   const id: DoctorCheckId = check.id;
   if (check.status === "pass") {
diff --git a/packages/cli/src/commands/setup.test.ts b/packages/cli/src/commands/setup.test.ts
index 27d83ee..f40e86c 100644
--- a/packages/cli/src/commands/setup.test.ts
+++ b/packages/cli/src/commands/setup.test.ts
@@ -36,6 +36,7 @@ import * as p from "@clack/prompts";
 import setupCommand from "./setup.js";
 import * as ghAuth from "../github/gh-auth.js";
 import * as githubClient from "../github/client.js";
+import * as commandExists from "../utils/command-exists-on-path.js";
 
 const MOCK_PROJECT_SUMMARY = {
   id: "PVT_setup_1",
@@ -167,10 +168,12 @@ describe("setup command", () => {
     vi.spyOn(githubClient, "getProjectDetail").mockResolvedValue(
       MOCK_PROJECT_DETAIL
     );
+    vi.spyOn(commandExists, "commandExistsOnPath").mockResolvedValue(true);
   });
 
   afterEach(() => {
     process.chdir(originalCwd);
+    vi.unstubAllEnvs();
   });
 
   it("reports removed project/workspace setup flags with migration guidance", async () => {
@@ -193,7 +196,7 @@ describe("setup command", () => {
     );
     expect(stderrWrite).toHaveBeenCalledWith(
       expect.stringContaining(
-        "Supported flags: --non-interactive, --output, --skip-skills. Deprecated no-op: --skip-context."
+        "Supported flags: --non-interactive, --output, --runtime, --skip-skills. Deprecated no-op: --skip-context."
       )
     );
   });
@@ -258,6 +261,7 @@ describe("setup command", () => {
         expect(errorOutput).toContain("gh-symphony setup");
       }
       expect(errorOutput).not.toMatch(/[가-힣]/);
+      expect(p.select).not.toHaveBeenCalled();
       expect(githubClient.listUserProjects).not.toHaveBeenCalled();
       expect(process.exitCode).toBe(1);
     }
@@ -305,6 +309,99 @@ describe("setup command", () => {
     expect(project).not.toHaveProperty("repositories");
   });
 
+  it("writes Claude runtime config from non-interactive --runtime claude-code", async () => {
+    const cwd = await mkdtemp(join(tmpdir(), "setup-non-interactive-claude-"));
+    const configDir = await mkdtemp(
+      join(tmpdir(), "setup-non-interactive-claude-config-")
+    );
+    initializeGitRemote(cwd);
+    process.chdir(cwd);
+    vi.mocked(commandExists.commandExistsOnPath).mockResolvedValueOnce(false);
+
+    const stdoutWrite = vi
+      .spyOn(process.stdout, "write")
+      .mockImplementation(() => true);
+
+    await setupCommand(["--non-interactive", "--runtime", "claude-code"], {
+      configDir,
+      verbose: false,
+      json: false,
+      noColor: true,
+    });
+
+    const workflow = await readFile(join(cwd, "WORKFLOW.md"), "utf8");
+    const stdout = stdoutWrite.mock.calls
+      .map(([chunk]) => String(chunk))
+      .join("");
+
+    expect(workflow).toContain("kind: claude-print");
+    expect(workflow).toContain("command: claude");
+    expect(stdout).toContain("Agent runtime    claude-print");
+    expect(p.log.warn).toHaveBeenCalledWith(
+      expect.stringContaining(
+        "Selected runtime 'claude-print' requires the 'claude' command"
+      )
+    );
+  });
+
+  it("keeps non-interactive JSON setup output parseable when the runtime is missing", async () => {
+    const cwd = await mkdtemp(join(tmpdir(), "setup-json-runtime-cwd-"));
+    const configDir = await mkdtemp(
+      join(tmpdir(), "setup-json-runtime-config-")
+    );
+    initializeGitRemote(cwd);
+    process.chdir(cwd);
+    vi.mocked(commandExists.commandExistsOnPath).mockResolvedValueOnce(false);
+
+    const stdoutWrite = vi
+      .spyOn(process.stdout, "write")
+      .mockImplementation(() => true);
+    const stderrWrite = vi
+      .spyOn(process.stderr, "write")
+      .mockImplementation(() => true);
+
+    await setupCommand(["--non-interactive", "--runtime", "claude-code"], {
+      configDir,
+      verbose: false,
+      json: true,
+      noColor: true,
+    });
+
+    const stdout = stdoutWrite.mock.calls
+      .map(([chunk]) => String(chunk))
+      .join("");
+
+    expect(JSON.parse(stdout)).toMatchObject({
+      status: "created",
+      runtime: "claude-print",
+    });
+    expect(p.log.warn).not.toHaveBeenCalled();
+    expect(stderrWrite).toHaveBeenCalledWith(
+      expect.stringContaining(
+        "Warning: Selected runtime 'claude-print' requires the 'claude' command"
+      )
+    );
+  });
+
+  it("rejects unsupported setup runtime presets", async () => {
+    const stderrWrite = vi
+      .spyOn(process.stderr, "write")
+      .mockImplementation(() => true);
+
+    await setupCommand(["--non-interactive", "--runtime", "claud-print"], {
+      configDir: "/tmp/unused",
+      verbose: false,
+      json: false,
+      noColor: true,
+    });
+
+    expect(process.exitCode).toBe(1);
+    expect(stderrWrite).toHaveBeenCalledWith(
+      "Error: Unsupported runtime 'claud-print'. Choose one of: codex-app-server, claude-print.\n"
+    );
+    expect(githubClient.listUserProjects).not.toHaveBeenCalled();
+  });
+
   it("shows a final summary and writes the selected repositories in interactive mode", async () => {
     const cwd = await mkdtemp(join(tmpdir(), "setup-interactive-cwd-"));
     const configDir = await mkdtemp(
@@ -314,6 +411,7 @@ describe("setup command", () => {
     process.chdir(cwd);
 
     vi.mocked(p.select)
+      .mockResolvedValueOnce("codex-app-server" as never)
       .mockResolvedValueOnce(MOCK_PROJECT_SUMMARY.id as never)
       .mockResolvedValueOnce("wait" as never)
       .mockResolvedValueOnce("active" as never)
@@ -348,6 +446,25 @@ describe("setup command", () => {
       expect.stringContaining("Repository:     current working directory"),
       "Final summary"
     );
+    expect(p.outro).toHaveBeenCalledWith(
+      expect.stringContaining(
+        "Repository runtime is ready for codex-app-server."
+      )
+    );
+    const selectMessages = vi
+      .mocked(p.select)
+      .mock.calls.map(([input]) => input.message);
+    expect(selectMessages).toEqual(
+      expect.arrayContaining([
+        "Step 1/5 — Select the agent runtime:",
+        "Step 2/5 — Select a GitHub Project board:",
+        expect.stringContaining("Step 3/5 — Map column"),
+        expect.stringContaining("Step 5/5 — Choose one priority source:"),
+      ])
+    );
+    expect(vi.mocked(p.confirm).mock.calls[0]?.[0]).toMatchObject({
+      message: expect.stringContaining("Step 4/5 — Enable blocker check?"),
+    });
   });
 
   it("validates state mappings before prompting for blocker checks", async () => {
@@ -359,6 +476,7 @@ describe("setup command", () => {
     process.chdir(cwd);
 
     vi.mocked(p.select)
+      .mockResolvedValueOnce("codex-app-server" as never)
       .mockResolvedValueOnce(MOCK_PROJECT_SUMMARY.id as never)
       .mockResolvedValueOnce("wait" as never)
       .mockResolvedValueOnce("wait" as never)
@@ -390,6 +508,7 @@ describe("setup command", () => {
       { name: "priority: p1", color: "ffaa00", description: null },
     ]);
     vi.mocked(p.select)
+      .mockResolvedValueOnce("codex-app-server" as never)
       .mockResolvedValueOnce(MOCK_PROJECT_SUMMARY.id as never)
       .mockResolvedValueOnce("wait" as never)
       .mockResolvedValueOnce("active" as never)
@@ -486,6 +605,7 @@ describe("setup command", () => {
     process.chdir(cwd);
 
     vi.mocked(p.select)
+      .mockResolvedValueOnce("codex-app-server" as never)
       .mockResolvedValueOnce(MOCK_PROJECT_SUMMARY.id as never)
       .mockResolvedValueOnce("wait" as never)
       .mockResolvedValueOnce("active" as never)
diff --git a/packages/cli/src/commands/setup.ts b/packages/cli/src/commands/setup.ts
index d8a3acc..aaa5680 100644
--- a/packages/cli/src/commands/setup.ts
+++ b/packages/cli/src/commands/setup.ts
@@ -1,4 +1,5 @@
 import * as p from "@clack/prompts";
+import { access } from "node:fs/promises";
 import { resolve } from "node:path";
 import type { GlobalOptions } from "../index.js";
 import {
@@ -35,19 +36,29 @@ import {
   promptLegacyGhSymphonyCleanup,
   warnDeprecatedSkipContext,
 } from "./workflow-init.js";
+import { commandExistsOnPath } from "../utils/command-exists-on-path.js";
 import {
   toWorkflowLifecycleConfig,
   validateStateMapping,
 } from "../mapping/smart-defaults.js";
 import { initRepoRuntime } from "../repo-runtime.js";
+import {
+  isSupportedInitRuntime,
+  normalizeInitRuntime,
+  resolveRuntimeCommand,
+  type InitRuntimeKind,
+} from "../workflow/workflow-runtime.js";
 
 type SetupFlags = {
   nonInteractive: boolean;
   output?: string;
+  runtime?: string;
   skipSkills: boolean;
   skipContext: boolean;
 };
 
+const SETUP_RUNTIME_CHOICES = "codex-app-server, claude-print";
+
 function parseSetupFlags(args: string[]): SetupFlags {
   const flags: SetupFlags = {
     nonInteractive: false,
@@ -64,9 +75,19 @@ function parseSetupFlags(args: string[]): SetupFlags {
         flags.nonInteractive = true;
         break;
       case "--output":
+        if (!next || next.startsWith("-")) {
+          throw new Error("Option '--output' argument missing");
+        }
         flags.output = next;
         i += 1;
         break;
+      case "--runtime":
+        if (!next || next.startsWith("-")) {
+          throw new Error("Option '--runtime' argument missing");
+        }
+        flags.runtime = next;
+        i += 1;
+        break;
       case "--skip-skills":
         flags.skipSkills = true;
         break;
@@ -76,7 +97,7 @@ function parseSetupFlags(args: string[]): SetupFlags {
       default:
         if (arg?.startsWith("-")) {
           throw new Error(
-            `Unknown option '${arg}'. Removed project/workspace flags are no longer supported; run 'gh-symphony setup' from inside the target repository. Supported flags: --non-interactive, --output, --skip-skills. Deprecated no-op: --skip-context.`
+            `Unknown option '${arg}'. Removed project/workspace flags are no longer supported; run 'gh-symphony setup' from inside the target repository. Supported flags: --non-interactive, --output, --runtime, --skip-skills. Deprecated no-op: --skip-context.`
           );
         }
     }
@@ -85,6 +106,69 @@ function parseSetupFlags(args: string[]): SetupFlags {
   return flags;
 }
 
+function resolveSetupRuntime(runtime: string | undefined): string {
+  return normalizeInitRuntime(runtime ?? "codex-app-server");
+}
+
+function validateSetupRuntime(runtime: string): string | null {
+  if (isSupportedInitRuntime(runtime)) {
+    return null;
+  }
+  return `Unsupported runtime '${runtime}'. Choose one of: ${SETUP_RUNTIME_CHOICES}.`;
+}
+
+async function promptRuntimeSelection(): Promise<InitRuntimeKind> {
+  return abortIfCancelled(
+    p.select({
+      message: "Step 1/5 — Select the agent runtime:",
+      options: [
+        {
+          value: "codex-app-server",
+          label: "codex-app-server",
+          hint: "Codex app-server JSON-RPC runtime",
+        },
+        {
+          value: "claude-print",
+          label: "claude-print",
+          hint: "Claude Code non-interactive stream-json runtime",
+        },
+      ],
+    })
+  );
+}
+
+function runtimeInstallHint(runtime: string): string {
+  const command = resolveRuntimeCommand(runtime);
+  if (runtime === "claude-print") {
+    return `Selected runtime '${runtime}' requires the '${command}' command, but it was not found on PATH. Install Claude Code and confirm '${command} --version' works before running 'gh-symphony repo start'.`;
+  }
+  return `Selected runtime '${runtime}' requires the '${command}' command, but it was not found on PATH. Install Codex and confirm '${command} --version' works before running 'gh-symphony repo start'.`;
+}
+
+async function checkRuntimeInstall(runtime: string): Promise<boolean> {
+  const command = resolveRuntimeCommand(runtime);
+  return commandExistsOnPath(command, {
+    access,
+    pathEnv: process.env.PATH,
+    pathExtEnv: process.env.PATHEXT,
+    platform: process.platform,
+  });
+}
+
+async function warnIfRuntimeMissing(
+  runtime: string,
+  options: Pick<GlobalOptions, "json">
+): Promise<void> {
+  if (!(await checkRuntimeInstall(runtime))) {
+    const hint = runtimeInstallHint(runtime);
+    if (options.json) {
+      process.stderr.write(`Warning: ${hint}\n`);
+      return;
+    }
+    p.log.warn(hint);
+  }
+}
+
 function displayScopeError(
   error: GitHubScopeError,
   retryCommand: string
@@ -146,7 +230,7 @@ async function selectProjectSummary(
 
   const selectedProjectId = await abortIfCancelled(
     p.select({
-      message: "Step 1/4 — Select a GitHub Project board:",
+      message: "Step 2/5 — Select a GitHub Project board:",
       options: projects.map((project) => ({
         value: project.id,
         label: `${project.owner.login}/${project.title}`,
@@ -164,6 +248,7 @@ function printNonInteractiveSummary(input: {
   githubProjectId: string;
   workflowPath: string;
   runtimeDir: string;
+  runtime: string;
   repository: string;
 }): void {
   process.stdout.write(
@@ -171,6 +256,7 @@ function printNonInteractiveSummary(input: {
       `GitHub Project   ${input.githubProjectTitle}  (${input.githubProjectId})`,
       `Repository       ${input.repository}`,
       `WORKFLOW.md      ${input.workflowPath}`,
+      `Agent runtime    ${input.runtime}`,
       `Runtime          ${input.runtimeDir}`,
       "Ready. Run 'gh-symphony repo start' to begin orchestration.",
     ]
@@ -211,6 +297,14 @@ async function runNonInteractive(
   flags: SetupFlags,
   options: GlobalOptions
 ): Promise<void> {
+  const selectedRuntime = resolveSetupRuntime(flags.runtime);
+  const runtimeError = validateSetupRuntime(selectedRuntime);
+  if (runtimeError) {
+    process.stderr.write(`Error: ${runtimeError}\n`);
+    process.exitCode = 1;
+    return;
+  }
+
   let token: string;
   try {
     token = getGhToken();
@@ -296,7 +390,7 @@ async function runNonInteractive(
     priority,
     includePriorityTemplates: !priorityField,
     mappings,
-    runtime: "codex",
+    runtime: selectedRuntime,
     skipSkills: flags.skipSkills,
     skipContext: flags.skipContext,
   });
@@ -309,7 +403,7 @@ async function runNonInteractive(
     priorityField,
     priority,
     includePriorityTemplates: !priorityField,
-    runtime: "codex",
+    runtime: selectedRuntime,
     skipSkills: flags.skipSkills,
     skipContext: flags.skipContext,
   });
@@ -319,11 +413,13 @@ async function runNonInteractive(
     workflowFile: workflowPath,
   });
 
+  await warnIfRuntimeMissing(selectedRuntime, options);
   if (options.json) {
     process.stdout.write(
       JSON.stringify({
         status: "created",
         output: workflowPath,
+        runtime: selectedRuntime,
         runtimeDir: runtime.configDir,
         repository: `${runtime.repository.owner}/${runtime.repository.name}`,
         githubProjectId: projectDetail.id,
@@ -336,6 +432,7 @@ async function runNonInteractive(
     githubProjectTitle: projectDetail.title,
     githubProjectId: projectDetail.id,
     workflowPath,
+    runtime: selectedRuntime,
     runtimeDir: runtime.configDir,
     repository: `${runtime.repository.owner}/${runtime.repository.name}`,
   });
@@ -343,7 +440,7 @@ async function runNonInteractive(
 
 async function runInteractive(
   flags: SetupFlags,
-  _options: GlobalOptions
+  options: GlobalOptions
 ): Promise<void> {
   p.intro("gh-symphony — One-command Setup");
 
@@ -369,6 +466,8 @@ async function runInteractive(
     return;
   }
 
+  const selectedRuntime = await promptRuntimeSelection();
+
   const projectsSpinner = p.spinner();
   projectsSpinner.start("Loading GitHub Project boards...");
 
@@ -416,7 +515,7 @@ async function runInteractive(
     projectDetail.linkedRepositories
   );
   const mappings = await promptStateMappings(statusField, {
-    stepLabel: "Step 2/4",
+    stepLabel: "Step 3/5",
   });
   const workflowValidation = validateStateMapping(mappings);
   if (!workflowValidation.valid) {
@@ -433,7 +532,7 @@ async function runInteractive(
 
   const lifecycleBase = toWorkflowLifecycleConfig(statusField.name, mappings);
   const blockerCheckStates = await promptBlockerCheck(lifecycleBase, {
-    stepLabel: "Step 3/4",
+    stepLabel: "Step 4/5",
   });
   const lifecycle = toWorkflowLifecycleConfig(statusField.name, mappings, {
     blockerCheckStates,
@@ -443,7 +542,7 @@ async function runInteractive(
   const { priority, priorityField } = await promptPriorityConfig({
     priorityResolution,
     labelNames: priorityLabelNames,
-    stepLabel: "Step 4/4",
+    stepLabel: "Step 5/5",
   });
 
   const workflowPath = resolve(flags.output ?? "WORKFLOW.md");
@@ -457,7 +556,7 @@ async function runInteractive(
     includePriorityTemplates: priority.source === "disabled",
     mappings,
     lifecycle,
-    runtime: "codex",
+    runtime: selectedRuntime,
     skipSkills: flags.skipSkills,
     skipContext: flags.skipContext,
   });
@@ -466,6 +565,7 @@ async function runInteractive(
     [
       `GitHub Project: ${projectDetail.title}`,
       `Authenticated:  ${login}`,
+      `Agent runtime:  ${selectedRuntime}`,
       `Repository:     current working directory`,
       "",
       renderDryRunPreview(workflowPath, workflowPlan, ecosystemPlan).trimEnd(),
@@ -498,7 +598,7 @@ async function runInteractive(
       priority,
       lifecycle,
       includePriorityTemplates: priority.source === "disabled",
-      runtime: "codex",
+      runtime: selectedRuntime,
       skipSkills: flags.skipSkills,
       skipContext: flags.skipContext,
     });
@@ -516,7 +616,8 @@ async function runInteractive(
     return;
   }
 
+  await warnIfRuntimeMissing(selectedRuntime, options);
   p.outro(
-    "Repository runtime is ready.\n  Run 'gh-symphony repo start' to begin orchestration."
+    `Repository runtime is ready for ${selectedRuntime}.\n  Run 'gh-symphony repo start' to begin orchestration.`
   );
 }
diff --git a/packages/cli/src/completion.ts b/packages/cli/src/completion.ts
index 915a31f..01c33c0 100644
--- a/packages/cli/src/completion.ts
+++ b/packages/cli/src/completion.ts
@@ -42,6 +42,7 @@ const COMMAND_OPTIONS: Record<string, readonly string[]> = {
   setup: [
     "--non-interactive",
     "--output",
+    "--runtime",
     "--skip-skills",
     "--skip-context",
     ...GLOBAL_OPTIONS,
diff --git a/packages/cli/src/index.ts b/packages/cli/src/index.ts
index 1a09754..ba5f744 100644
--- a/packages/cli/src/index.ts
+++ b/packages/cli/src/index.ts
@@ -335,6 +335,10 @@ function createProgram(): { program: Command; wasInvoked: () => boolean } {
       .description("Run the one-command first-run setup flow")
       .option("--non-interactive", "Run without prompts")
       .option("--output <path>", "Write WORKFLOW.md to a custom path")
+      .option(
+        "--runtime <kind>",
+        "Runtime preset: codex-app-server or claude-print"
+      )
       .option("--skip-skills", "Skip runtime skill generation")
       .option("--skip-context", "Deprecated no-op")
       .allowExcessArguments(false)
@@ -344,6 +348,7 @@ function createProgram(): { program: Command; wasInvoked: () => boolean } {
     const args: string[] = [];
     pushOption(args, "--non-interactive", values.nonInteractive);
     pushOption(args, "--output", values.output);
+    pushOption(args, "--runtime", values.runtime);
     pushOption(args, "--skip-skills", values.skipSkills);
     pushOption(args, "--skip-context", values.skipContext);
     await invokeHandler("setup", args, values);
diff --git a/packages/cli/src/utils/command-exists-on-path.ts b/packages/cli/src/utils/command-exists-on-path.ts
new file mode 100644
index 0000000..ba739fa
--- /dev/null
+++ b/packages/cli/src/utils/command-exists-on-path.ts
@@ -0,0 +1,71 @@
+import { constants } from "node:fs";
+import { delimiter, isAbsolute, join, resolve } from "node:path";
+
+type AccessFn = typeof import("node:fs/promises").access;
+
+type CommandExistsDependencies = {
+  access: AccessFn;
+  pathEnv: string | undefined;
+  pathExtEnv: string | undefined;
+  platform: NodeJS.Platform;
+};
+
+function getCommandCandidates(
+  binary: string,
+  deps: Pick<CommandExistsDependencies, "platform" | "pathExtEnv">
+): string[] {
+  if (deps.platform !== "win32") {
+    return [binary];
+  }
+
+  const pathExts = (deps.pathExtEnv ?? ".COM;.EXE;.BAT;.CMD")
+    .split(";")
+    .map((ext) => ext.trim())
+    .filter(Boolean);
+  const normalizedBinary = binary.toLowerCase();
+  if (pathExts.some((ext) => normalizedBinary.endsWith(ext.toLowerCase()))) {
+    return [binary];
+  }
+
+  return [binary, ...pathExts.map((ext) => `${binary}${ext}`)];
+}
+
+export async function commandExistsOnPath(
+  binary: string,
+  deps: CommandExistsDependencies
+): Promise<boolean> {
+  if (!binary) {
+    return false;
+  }
+
+  const candidates = getCommandCandidates(binary, deps);
+  if (isAbsolute(binary) || binary.includes("/") || binary.includes("\\")) {
+    for (const candidate of candidates) {
+      try {
+        await deps.access(resolve(candidate), constants.X_OK);
+        return true;
+      } catch {
+        continue;
+      }
+    }
+
+    return false;
+  }
+
+  for (const segment of (deps.pathEnv ?? "").split(delimiter)) {
+    if (!segment) {
+      continue;
+    }
+    for (const command of candidates) {
+      const candidate = join(segment, command);
+      try {
+        await deps.access(candidate, constants.X_OK);
+        return true;
+      } catch {
+        continue;
+      }
+    }
+  }
+
+  return false;
+}