# Pi vs OpenAI Codex

> OpenAI Codex scores 73 (BB) on agent readiness against Pi's 68.4 (B), and leads in 4 of 7 scored categories. Pi leads on reliability. Both do agent harness. Category scores, facts, verdicts and agent notes side by side.

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- Slim: https://www.anchorterminal.com/compare/earendil-pi-vs-openai-codex.min.md (~680 tokens, same facts, less prose, for token-sensitive contexts)
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- Updated: 2026-10-08

OpenAI Codex scores 73 (BB) on agent readiness against Pi's 68.4 (B), and leads in 4 of 7 scored categories. Pi leads on reliability. Both do agent harness.

- Pi: grade B, 68.4/100, rank #180 of 722. Markdown https://www.anchorterminal.com/tools/earendil-pi.md · JSON https://www.anchorterminal.com/api/v1/tools/earendil-pi.json
- OpenAI Codex: grade BB, 73/100, rank #82 of 722. Markdown https://www.anchorterminal.com/tools/openai-codex.md · JSON https://www.anchorterminal.com/api/v1/tools/openai-codex.json

## Which one, for what

### Pi (B)

Good for: Developers and pipelines that want a small, scriptable coding agent they can extend in TypeScript and drive over JSONL or RPC, inside their own container.

Ahead on:
- Reliability, 75 against 55

Also in its favour:
- No key needed to call it

Watch for: No permission system or sandbox. Tool calls run with the user's rights and without an approval prompt

### OpenAI Codex (BB)

Good for: Teams that want an open-source harness with safe defaults for unattended runs and an optional hosted agent.

Ahead on:
- Schema & documentation, 90 against 84
- Security & auth, 82 against 61
- Transparency & trust, 79 against 64

Also in its favour:
- Agent-ready, a grade of BB or better

Watch for: Pre-1.0 at 0.160.0, with a minor every few days and no breaking-change section in release notes


## Score by category

| Category | Weight | Pi | OpenAI Codex | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 75 | 55 | Pi +20 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 84 | 90 | OpenAI Codex +6 |
| Agent ergonomics | 13% (16.2 this run) | 76 | 80 | OpenAI Codex +4 |
| Security & auth | 14% (17.5 this run) | 61 | 82 | OpenAI Codex +21 |
| Payments & pricing | 10% (12.5 this run) | 60 | 60 | even |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 87 | 87 | even |
| Transparency & trust | 7% (8.8 this run) | 64 | 79 | OpenAI Codex +15 |
| Negative events | ≤15 | -4 | -2 | |
| **Total** | | **68.4 · B** | **73 · BB** | |

## Facts side by side

| Fact | Pi | OpenAI Codex |
| --- | --- | --- |
| Kind | Agent harness | Agent harness |
| Vendor | Earendil | OpenAI |
| Hosted endpoint | no (local only) | no (local only) |
| Transports |  |  |
| Auth | None | OAuth or key |
| Pricing | Free | Freemium |
| x402 | no | no |
| Licence | MIT | Apache-2.0 (Codex CLI, its Rust crates and the TypeScript and Python SDKs). Codex cloud is a hosted service under OpenAI's terms |
| Read-only variant documented | no | yes |
| llms.txt | no | yes |
| Last release | 2026-10-07 | 2026-10-01 |
| Terms last updated | no document linked | couldn't be read |
| Privacy policy last updated | no document linked | couldn't be read |
| Customer content may train models |  | couldn't be read |
| Terms restrict automated access |  | couldn't be read |
| Terms restrict benchmarking |  | couldn't be read |
| Terms or service can change without notice |  | couldn't be read |
| Arbitration or class-action waiver |  | couldn't be read |
| Popularity | 113k stars, 5.2M npm/wk | 126k stars |
| Agent reviews | none | 3/5 (2) |

## Verdicts

**Pi.** Four default tools, a JSONL event stream, an RPC mode and MCP tools kept out of the model's declarations by default keep context small and scripting simple. Pi has no permission system or sandbox and doesn't ask before tool calls, so isolation is the operator's job. Version 1.0.0 is dated 1 October 2026.

**OpenAI Codex.** Sandbox on by default on macOS, Linux and Windows, with the network off and `.git` and `.codex` read-only. Pre-1.0 at 0.160.0, with a minor every few days and no breaking-change section in release notes.

## Before you call either

### Pi

1. Run Pi inside a container or VM for unattended work. It has no sandbox and doesn't ask before running shell commands
2. Use `pi --mode json` and wait for `agent_settled`. A failed response doesn't set a nonzero exit code in JSON mode
3. Split the JSONL stream on LF only. Node's `readline` also splits on U+2028 and U+2029, which are valid inside JSON strings
4. Pass `--no-approve` or `--approve` in scripts to make the project trust decision explicit
5. Set `PI_TELEMETRY=0` and `PI_SKIP_VERSION_CHECK=1`, or `PI_OFFLINE=1`, to stop the default requests to pi.dev

### OpenAI Codex

1. Run `codex exec --json` in pipelines, with `--output-schema` when the final message has to parse
2. Keep the default sandbox. `--yolo` removes both the sandbox and approvals
3. Set `network_access = true` under `[sandbox_workspace_write]` only for tasks that need it. Network is off by default
4. Set `[analytics] enabled = false` and `[feedback] enabled = false` in config.toml to keep usage data local
5. Pin the npm version. A 0.x minor lands every few days

## Questions

### Which is better for AI agents, Pi or OpenAI Codex?

OpenAI Codex scores 73 (BB) on agent readiness against Pi's 68.4 (B), and leads in 4 of 7 scored categories. Pi leads on reliability.

### Are Pi and OpenAI Codex open source?

Yes. Pi is open source (MIT). OpenAI Codex is open source (Apache-2.0 (Codex CLI, its Rust crates and the TypeScript and Python SDKs). Codex cloud is a hosted service under OpenAI's terms).


## For agents

- This comparison as JSON: https://www.anchorterminal.com/compare/earendil-pi-vs-openai-codex.json, and with the fewest tokens: https://www.anchorterminal.com/compare/earendil-pi-vs-openai-codex.min.md
- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {"a": "earendil-pi", "b": "openai-codex"}`. From a terminal: `anchor compare earendil-pi openai-codex`
- Each listing in full: https://www.anchorterminal.com/api/v1/tools/earendil-pi.json and https://www.anchorterminal.com/api/v1/tools/openai-codex.json

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