Provider: OpenAI Codex CLI

Process guidance for keeping the gateway's Codex (codex) integration aligned with the upstream CLI. This skill does not define argv/env behaviour; the single mechanical source of truth is UPSTREAM_CLI_CONTRACTS.codex in src/upstream-contracts.ts, enforced by validateUpstreamCliArgs / validateUpstreamCliEnv. Never re-encode flags, sandbox/approval modes, or resume rules here or in TOML.

Identity

These values mirror UPSTREAM_CLI_CONTRACTS.codex.upstreamMetadata and docs/upstream/provider-sources.dag.toml ([providers.codex]). The TypeScript metadata is authoritative; the TOML is scanner input only.

When to use

• An OpenAI Codex CLI release lands and you need to check for contract drift.
• A codex request fails the upstream contract check before spawn.
• npm run upstream:scan -- --live reports a change on the Codex release notes

or changelog.

How LLM agents should use Codex through the gateway

1. Discover the live gateway/provider surface before relying on Codex-specific

controls:

   provider_tool_capabilities({cli:"codex"})

For a cached read-only resource, use provider-tools://codex.

1. Use codex_request for normal implementation/review turns and

codex_request_async for long-running work. To continue an existing Codex conversation, pass codex_request a real Codex session UUID from ~/.codex/sessions/, or resumeLatest:true; both route through codex exec resume and work headlessly. codex_fork_session is registered but cannot run from the gateway: codex fork is interactive and requires a controlling terminal, and Codex exposes no non-interactive equivalent (codex exec has only resume/review/help). Re-check that on each Codex release; if a headless fork lands, codexForkCanRunHeadless in src/index.ts is the single predicate to flip.

1. Omit model unless the caller explicitly asked for a specific variant; the

gateway resolves the configured Codex default/profile.

1. Prefer sandboxMode:"workspace-write" when Codex needs a writable

workspace. fullAuto:true is the deprecated compatibility shorthand. Use approvalStrategy:"legacy": Codex rejects mcp_managed before launch because its ambient MCP configuration cannot be isolated, and approvalPolicy has no effect for Codex.

1. Do not pass Claude-style allowedTools or disallowedTools; Codex does not

expose those request fields through the gateway. Codex owns its MCP configuration, and a gateway mcpServers list is descriptive metadata, not an enforceable allowlist.

1. Use sandboxMode, profile, configOverrides, oss, images,

outputFormat, and outputSchema only as reported by provider_tool_capabilities. askForApproval and useLegacyFullAutoFlag are deprecated compatibility inputs: current Codex emits no corresponding argv and the gateway returns a warning. fullAuto:true remains a compatibility shorthand for sandboxMode:"workspace-write". These are provider-native legacy controls, not inputs to the Claude-only gateway approval boundary.

1. Codex continuity is real through codex exec resume: pass a real Codex UUID

from ~/.codex/sessions/, or resumeLatest:true. Gateway gw-* IDs are not Codex sessions. sandboxMode and its deprecated fullAuto:true shorthand are dropped on resume, so those fields cannot select a posture there. That is not a guarantee that the original posture is retained: configOverrides is not filtered and can set sandbox_mode, and Codex re-resolves configuration on a cold resume. resumeLatest is under review (#258): --last is cwd-filtered upstream unless --all is passed, which the gateway does not emit, and the child is still spawned with the gateway-resolved cwd. Do not rely on which session it selects or on the resumed working directory. The provider-native workingDir and addDir flags scope new sessions only; the gateway accepts but omits those fields on resume. Omitting them does not pin the resumed directory: the child is still spawned with the gateway-resolved cwd. A verified workspace or gateway worktree can still select the child process launch cwd and bind gateway tracking. Do not rely on a resumed session's directory in any resume form, including a direct UUID resume: the child is spawned with the gateway-resolved cwd even though the flags are filtered.

1. Codex new and resume requests send the exact prompt through stdin with the

native - marker. They do not consume the platform's single-argv prompt allowance and are never truncated. codex_fork_session uses the distinct codex fork contract, remains argv-bound, and rejects oversized UTF-8 prompts as non-retryable input_too_large. That rejection is deliberately evaluated before the tool's availability check, so argv admission stays observable even though the call cannot ultimately run. An otherwise unscoped child still runs in a fresh neutral temporary cwd, not the gateway repository. All other caller-controlled argv values are admitted in their final encoded form before spawn. Embedded NUL bytes return non-retryable invalid_input without exposing the rejected value. New and resumed stdin requests complete only after the full payload write callback succeeds; a clean child exit with closed or pending delivery is a fixed non-sensitive failure.

Full-access review handoff

For a user-authorized exhaustive review that needs full provider permissions and native MCP access, do not infer the launch controls from this maintenance guide. Follow multi-llm-review's full-access protocol, inspect the current request schema and live capability response, and use a fresh target-checkout node dist/index.js --transport=stdio gateway rather than a global process. Reapply the grant on every new job, preserve native MCP configuration without a pretend gateway allowlist, send the corrective-program report and exact diff/file identity, set no caller caps, and honor a user-required 90-second progress cadence. The reviewer must independently inspect code, docs, tests, and commands before it can approve.

Scan for upstream change

npm run upstream:scan -- --provider codex
npm run upstream:scan -- --live --provider codex --fail-on-critical
npm run upstream:scan -- --live --provider codex --write-snapshot --write-report

A failed fetch is advisory (exit 0) unless --fail-on-critical is passed.

Update procedure when the upstream CLI changes

1. Edit the contract in src/upstream-contracts.ts (UPSTREAM_CLI_CONTRACTS.codex):

the exec / exec resume command shape, flag arities/enums, and the resumeOnlyFlags / resumeForbiddenFlags lists all live here.

1. Add a conformance fixture proving the new accept/reject behaviour

(mirror the existing codex-* fixtures, including resume cases).

1. If a source URL or watch category changed, update upstreamMetadata and

mirror it into docs/upstream/provider-sources.dag.toml.

1. Verify: npm run build && npm run upstream:contracts and npm test.

Codex-specific notes (see the contract for exact rules)

• Tested against codex-cli 0.153.0. Codex advertises mcp-server / app-server transports, not a native ACP entrypoint, so provider-acp://codex reports native:false (no methods, no adapter-as-native masquerade) and codex_request exposes no transport:"acp" selector.
• argv must start with exec; exec resume enters resume context.
• --last is resume-only. In resume context, --sandbox, -C, --cd,

--add-dir, and --profile are forbidden (per resumeForbiddenFlags). --ask-for-approval, --full-auto, and --search are unsupported by the current codex exec command on every path.

• --output-schema, -c key=value, --ephemeral, safety bypasses (on review), --json etc. are accepted on resume/review (codex-cli 0.153.0). Example (resume):

  codex exec resume --ephemeral --json <UUID> "follow up"

• Sandbox and approval values are closed enums; extend the enum in the contract.
• Continuity is real via codex exec resume <UUID> / --last; sessionId must be a real Codex UUID (gateway gw-* IDs rejected).
• Top-level interactive resume and destructive delete are catalogued for drift monitoring, not request argv. Keep them unexposed unless a separately reviewed gateway surface is added.