diff --git a/bwh_hive/bwh_hive/doctype/hive_project/hive_project.json b/bwh_hive/bwh_hive/doctype/hive_project/hive_project.json
index a2194f0..de4d3ae 100644
--- a/bwh_hive/bwh_hive/doctype/hive_project/hive_project.json
+++ b/bwh_hive/bwh_hive/doctype/hive_project/hive_project.json
@@ -24,6 +24,7 @@
   "github_repo",
   "agent_section",
   "agent_enabled",
+  "agent_engine",
   "github_pat",
   "agent_template_slug",
   "target_app_name",
@@ -139,6 +140,15 @@
    "fieldtype": "Check",
    "label": "Agent Enabled"
   },
+  {
+   "default": "Claude Code",
+   "depends_on": "agent_enabled",
+   "description": "Coding agent that runs inside the box. Codex uses the OpenAI API key; Claude Code uses the Anthropic key or subscription token (both in Hive Settings).",
+   "fieldname": "agent_engine",
+   "fieldtype": "Select",
+   "label": "Agent Engine",
+   "options": "Claude Code\nCodex"
+  },
   {
    "depends_on": "agent_enabled",
    "description": "Project PAT used inside the box for gh / git push (GIT_PAT).",
diff --git a/bwh_hive/bwh_hive/doctype/hive_settings/hive_settings.json b/bwh_hive/bwh_hive/doctype/hive_settings/hive_settings.json
index a4e4573..3d7c402 100644
--- a/bwh_hive/bwh_hive/doctype/hive_settings/hive_settings.json
+++ b/bwh_hive/bwh_hive/doctype/hive_settings/hive_settings.json
@@ -27,6 +27,7 @@
   "skills_repo",
   "anthropic_api_key",
   "claude_code_oauth_token",
+  "openai_api_key",
   "agent_prompts_section",
   "agent_spec_prompt",
   "agent_implement_prompt",
@@ -182,6 +183,12 @@
    "fieldtype": "Password",
    "label": "Claude Code OAuth Token"
   },
+  {
+   "description": "OpenAI API key, injected as OPENAI_API_KEY into boxes whose project uses the Codex engine.",
+   "fieldname": "openai_api_key",
+   "fieldtype": "Password",
+   "label": "OpenAI API Key"
+  },
   {
    "collapsible": 1,
    "fieldname": "agent_prompts_section",
diff --git a/bwh_hive/bwh_hive/orchestrator/service.py b/bwh_hive/bwh_hive/orchestrator/service.py
index 973aa29..f5bd289 100644
--- a/bwh_hive/bwh_hive/orchestrator/service.py
+++ b/bwh_hive/bwh_hive/orchestrator/service.py
@@ -120,14 +120,20 @@ def build_boot_env(task: Document) -> dict:
 	spec_run_timeout = max(spec_min - 5, 5) * 60
 	impl_run_timeout = max(impl_min - 5, 5) * 60
 
-	# Claude auth: an Anthropic API key (API billing) OR a subscription OAuth token from
-	# `claude setup-token`. The box's claude falls back to the OAuth token when
-	# ANTHROPIC_API_KEY is empty, so only forward the token when no API key is set —
-	# never both, to avoid an ambiguous auth mode.
+	# Coding-agent engine (per-project): "codex" or "claude" (default). Drives which CLI the
+	# box runs (AGENT_ENGINE) and which auth key it needs.
+	engine = "codex" if (project.get("agent_engine") or "").strip().lower().startswith("codex") else "claude"
+
+	# Auth keys (global, Hive Settings). Only the chosen engine's key(s) are forwarded.
+	# Claude: an Anthropic API key (API billing) OR a subscription OAuth token from
+	# `claude setup-token` — the box falls back to the token when ANTHROPIC_API_KEY is empty,
+	# so forward the token only when no API key is set (never both). Codex: OPENAI_API_KEY.
 	anthropic_api_key = settings.get_password("anthropic_api_key", raise_exception=False) or ""
 	oauth_token = settings.get_password("claude_code_oauth_token", raise_exception=False) or ""
+	openai_api_key = settings.get_password("openai_api_key", raise_exception=False) or ""
 
 	env = {
+		"AGENT_ENGINE": engine,
 		"AGENT_MODE": "1",
 		"HIVE_BASE_URL": frappe.utils.get_url(),
 		"HIVE_API_KEY": settings.agent_callback_api_key or "",
@@ -141,8 +147,9 @@ def build_boot_env(task: Document) -> dict:
 		"TARGET_APP_REPO": project.get("target_app_repo") or "",
 		"TARGET_APP_BRANCH": project.get("target_app_branch") or "develop",
 		"SKILLS_REPO": skills_repo or "",
-		"ANTHROPIC_API_KEY": anthropic_api_key,
-		"CLAUDE_CODE_OAUTH_TOKEN": oauth_token if not anthropic_api_key else "",
+		"ANTHROPIC_API_KEY": anthropic_api_key if engine == "claude" else "",
+		"CLAUDE_CODE_OAUTH_TOKEN": oauth_token if (engine == "claude" and not anthropic_api_key) else "",
+		"OPENAI_API_KEY": openai_api_key if engine == "codex" else "",
 		"SPEC_RUN_TIMEOUT": spec_run_timeout,
 		"IMPL_RUN_TIMEOUT": impl_run_timeout,
 	}
diff --git a/frontend/src/components/project/AgentSettingsTab.tsx b/frontend/src/components/project/AgentSettingsTab.tsx
index 2d65b73..1b012ad 100644
--- a/frontend/src/components/project/AgentSettingsTab.tsx
+++ b/frontend/src/components/project/AgentSettingsTab.tsx
@@ -10,6 +10,7 @@ import {
   SwitchField,
   SecretField,
   PromptField,
+  SelectField,
 } from "@/components/settings/agent-fields"
 import { PROMPT_TOKENS } from "@/lib/agent"
 import type { HiveProject } from "@/types"
@@ -70,6 +71,7 @@ export function AgentSettingsTab({ projectId, onSaved }: AgentSettingsTabProps)
     // eslint-disable-next-line react-hooks/set-state-in-effect
     setForm({
       agent_enabled: data.agent_enabled ?? 0,
+      agent_engine: data.agent_engine ?? "Claude Code",
       agent_template_slug: data.agent_template_slug ?? "",
       target_app_name: data.target_app_name ?? "",
       target_app_repo: data.target_app_repo ?? "",
@@ -128,6 +130,17 @@ export function AgentSettingsTab({ projectId, onSaved }: AgentSettingsTabProps)
       {enabled && (
         <>
           <div className="space-y-4">
+            <SelectField
+              id="proj-agent-engine"
+              label="Agent engine"
+              hint="Codex uses the OpenAI API key; Claude Code uses the Anthropic key or subscription token (both in global Agent settings)."
+              value={s("agent_engine") || "Claude Code"}
+              onChange={set("agent_engine")}
+              options={[
+                { value: "Claude Code", label: "Claude Code" },
+                { value: "Codex", label: "Codex" },
+              ]}
+            />
             <TextField id="proj-agent-template" label="Template slug" hint="Blank = the global default template." value={s("agent_template_slug")} onChange={set("agent_template_slug")} placeholder="Inherit global default" />
           </div>
 
diff --git a/frontend/src/components/settings/AgentSection.tsx b/frontend/src/components/settings/AgentSection.tsx
index 4e6138b..74701f1 100644
--- a/frontend/src/components/settings/AgentSection.tsx
+++ b/frontend/src/components/settings/AgentSection.tsx
@@ -23,6 +23,8 @@ interface HiveSettings {
   default_agent_template_slug?: string | null
   skills_repo?: string | null
   anthropic_api_key?: string | null
+  claude_code_oauth_token?: string | null
+  openai_api_key?: string | null
   agent_spec_prompt?: string | null
   agent_implement_prompt?: string | null
   agent_changes_prompt?: string | null
@@ -43,6 +45,8 @@ const SECRET_FIELDS = [
   "benchspace_api_secret",
   "agent_callback_api_secret",
   "anthropic_api_key",
+  "claude_code_oauth_token",
+  "openai_api_key",
   "telegram_bot_token",
 ] as const
 
@@ -82,6 +86,8 @@ export function AgentSection() {
       default_agent_template_slug: data.default_agent_template_slug ?? "",
       skills_repo: data.skills_repo ?? "",
       anthropic_api_key: "",
+      claude_code_oauth_token: "",
+      openai_api_key: "",
       agent_spec_prompt: data.agent_spec_prompt ?? "",
       agent_implement_prompt: data.agent_implement_prompt ?? "",
       agent_changes_prompt: data.agent_changes_prompt ?? "",
@@ -163,7 +169,9 @@ export function AgentSection() {
           <SecretField id="agent-bs-secret" label="BenchSpace API Secret" isSet={secretsSet.benchspace_api_secret} value={s("benchspace_api_secret")} onChange={set("benchspace_api_secret")} />
           <TextField id="agent-cb-key" label="Agent Callback API Key" value={s("agent_callback_api_key")} onChange={set("agent_callback_api_key")} />
           <SecretField id="agent-cb-secret" label="Agent Callback API Secret" isSet={secretsSet.agent_callback_api_secret} value={s("agent_callback_api_secret")} onChange={set("agent_callback_api_secret")} />
-          <SecretField id="agent-anthropic-key" label="Anthropic API Key" isSet={secretsSet.anthropic_api_key} value={s("anthropic_api_key")} onChange={set("anthropic_api_key")} />
+          <SecretField id="agent-anthropic-key" label="Anthropic API Key" hint="Claude Code (API billing)." isSet={secretsSet.anthropic_api_key} value={s("anthropic_api_key")} onChange={set("anthropic_api_key")} />
+          <SecretField id="agent-claude-oauth" label="Claude Code OAuth Token" hint="claude setup-token — used when no Anthropic API key is set (subscription auth)." isSet={secretsSet.claude_code_oauth_token} value={s("claude_code_oauth_token")} onChange={set("claude_code_oauth_token")} />
+          <SecretField id="agent-openai-key" label="OpenAI API Key" hint="Used by projects on the Codex engine." isSet={secretsSet.openai_api_key} value={s("openai_api_key")} onChange={set("openai_api_key")} />
           <TextField id="agent-skills-repo" label="Skills Repo" value={s("skills_repo")} onChange={set("skills_repo")} placeholder="owner/repo" />
         </div>
 
diff --git a/frontend/src/components/settings/agent-fields.tsx b/frontend/src/components/settings/agent-fields.tsx
index a58af87..70381e7 100644
--- a/frontend/src/components/settings/agent-fields.tsx
+++ b/frontend/src/components/settings/agent-fields.tsx
@@ -2,6 +2,7 @@ import { Input } from "@/components/ui/input"
 import { Label } from "@/components/ui/label"
 import { Switch } from "@/components/ui/switch"
 import { Textarea } from "@/components/ui/textarea"
+import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from "@/components/ui/select"
 
 export function FieldLabel({ label, hint }: { label: string; hint?: string }) {
   return (
@@ -36,6 +37,41 @@ export function TextField({
   )
 }
 
+export function SelectField({
+  id,
+  label,
+  hint,
+  value,
+  onChange,
+  options,
+}: {
+  id: string
+  label: string
+  hint?: string
+  value: string
+  onChange: (v: string) => void
+  options: { value: string; label: string }[]
+}) {
+  return (
+    <div className="grid gap-1.5">
+      <Label htmlFor={id}>{label}</Label>
+      {hint && <p className="text-xs text-muted-foreground">{hint}</p>}
+      <Select value={value} onValueChange={onChange}>
+        <SelectTrigger id={id} className="h-8 text-sm">
+          <SelectValue />
+        </SelectTrigger>
+        <SelectContent>
+          {options.map((o) => (
+            <SelectItem key={o.value} value={o.value}>
+              {o.label}
+            </SelectItem>
+          ))}
+        </SelectContent>
+      </Select>
+    </div>
+  )
+}
+
 export function IntField({
   id,
   label,
diff --git a/frontend/src/types.ts b/frontend/src/types.ts
index 9176434..abe4a71 100644
--- a/frontend/src/types.ts
+++ b/frontend/src/types.ts
@@ -13,6 +13,7 @@ export interface HiveProject {
   links?: HiveProjectLink[]
   // Agent settings (specs/v2 09 — surface 3)
   agent_enabled?: 0 | 1
+  agent_engine?: "Claude Code" | "Codex" | null
   github_pat?: string | null
   agent_template_slug?: string | null
   target_app_name?: string | null