Automate real Claude Code and Codex sessions in headless PTYs.

Write scripts that control normal interactive Claude Code and Codex sessions, which use your regular subscription rather than metered API billing. Elwood starts the actual agent CLI in a hidden terminal and types into it the way you would. The agent keeps its tools, hooks, configuration, and login.

npm install -g @with-logic/elwood
elwood "Explain this project's architecture."

import { ClaudeSession } from "@with-logic/elwood";

const session = new ClaudeSession({ cwd: "/path/to/project" });
console.log(await session.send("Explain this project."));
await session.close();

Why Elwood

The agent should not know it is wrapped.

Headless agent APIs give you a different product than the CLI your team actually uses: different tools, different hooks, different billing. Elwood drives the real interactive CLI instead. The process stays interactive, runs in your normal shell environment, and is controlled through the hooks and transcripts the CLI already provides.

• Your subscription, not an API key. It is the same interactive session you run by hand, so it bills the way that session already bills.
• A small API over a real terminal. send() returns a string. stream() yields typed events. The CLI keeps its own tools and history.
• Typed activity, not screen scraping. Assistant text, reasoning, tool calls and results, hooks, warnings, and lifecycle arrive as one event stream.
• Two ways in. A TypeScript library for applications, and an elwood command for shell scripts and pipelines.

prd/ is the source of truth for observable behavior. If this README, the tests, or the implementation disagree with the PRD, the PRD wins.

Requirements

• macOS. Both adapters reject other platforms at startup with unsupported_platform.
• Node.js 24 or newer.
• Claude Code 2.1.144 or newer, and/or Codex CLI 0.124.0 or newer, installed and authenticated.

An unparseable CLI version becomes a version_unparseable warning and startup continues. Pass strictVersionCheck: true to fail closed instead.

Install

npm install @with-logic/elwood

The package installs an elwood executable for the headless CLI. It ships a prebuilt dist/, so a global install runs no build step and no install scripts of its own. To work from a checkout instead, run npm install && npm run build && npm link; the build is explicit because dist/ is not committed.

Quickstart: library

import { ClaudeSession } from "@with-logic/elwood";

// Construct synchronously; the session starts lazily on the first turn.
const session = new ClaudeSession({ cwd: "/path/to/project", autotrust: true });

// `send` returns the assistant's reply as a string; a follow-up keeps context.
const summary = await session.send("Summarize this repo's test strategy in two sentences.");
const risks = await session.send("Now list the biggest gaps you'd address first.");

// `stream` yields typed events as they happen.
for await (const event of session.stream("Run the test suite and report failures.")) {
  if (event.type === "text") process.stdout.write(event.text);
  // event.type is also "thinking" | "tool_call" | "tool_result"
}

await session.close();

CodexSession has the same shape. autotrust: true lets Elwood answer its allowlisted workspace and extension trust prompts on your behalf; see Security and privacy for the full scope. Leave it off when a human should make those decisions. There is no default turn timeout; pass send(prompt, { timeoutMs }) (a TurnOptions field) to bound one turn.

Quickstart: CLI

elwood "Summarize this repository"
git diff | elwood --agent claude "Review this diff for correctness"
elwood --output json "Run the tests and summarize failures" | jq -r .response
elwood --output json "Remember that the release color is teal"
elwood --resume <sessionId> "What is the release color?"

When nothing selects an agent, Elwood tries claude and then codex in your login shell and uses the first that resolves; if neither does, the run fails with no_agent_found. See docs/cli.md for configuration, output protocols, head mode, and continuation.

Core concepts

Sessions. A session is one agent process in one PTY, identified by an elwoodSessionId. ClaudeSession / CodexSession add send, stream, and close on top of the full control surface (sendMessage, sendPrompt, sendGuidance, sendKeys, interrupt, compact, listModels, setModel, loops, waitForStatus, stop, kill, teardown). The eager startClaude / startCodex factories are deprecated but still available.

Hooks. Claude and Codex hook events are delivered to typed handlers you pass at start. Elwood runs a local bridge that the CLI's hook scripts call over IPC with a per-session token. Handlers can allow, deny, block a stop, or add context; they fail open on error.

Activity stream. The activity event is one adapter-neutral timeline: assistant messages, reasoning, tool calls and results, web searches, hooks, warnings, and lifecycle. Most host UIs render this and nothing else.

Terminal stream. terminal:data carries the raw PTY bytes so a host can mirror the agent in its own xterm. A late subscriber first receives up to 128 KB of replayed history as one chunk. sendKeys(Uint8Array) forwards a user's keystrokes verbatim.

Status lifecycle. status moves through starting, ready, running, and blocked (a dialog needs a human) and ends in stopped, exited, killed, or torn_down. Every real turn is a running to ready beat.

State directory. Elwood keeps a minimal session record under <cwd>/.elwood by default, or under an explicit stateDir. It holds what resume needs and nothing else.

Headless CLI

Live terminal view

Add --head when you want to watch the real agent interface while retaining a pipeline-friendly final result:

elwood --head "Run the test suite and fix the failure"
elwood --head --output json "Review this repository" >result.json
elwood --head --agent claude "Explain the architecture"

The display stays in the current terminal and receives the raw PTY byte stream on stderr. It is a real VT/ANSI mirror, so full-screen layouts, cursor-addressed updates, alternate-screen buffers, colors, spinners, and title changes render as they do in the underlying Claude or Codex client. Stdout remains only the final text or JSON protocol and can be redirected independently. Pending display work is capped at 4 MiB or 1,024 frames; a terminal that remains backpressured fails the run cleanly after draining accepted bytes instead of growing memory without bound.

Head mode is deliberately view-only: while attached, ordinary keyboard, mouse, paste, and terminal-response bytes are discarded; Ctrl-C still interrupts using Elwood's normal first-interrupt/repeated-force-kill lifecycle. Terminal resizes propagate to the agent. Elwood restores raw/cooked input state, mouse and paste modes, attributes, cursor visibility, and the main screen before printing the final result. Both stdin and stderr must be terminals, and --head cannot be combined with --stream, --verbose, --debug, or --output jsonl.

Continuation and cleanup

New and resumed headless runs preserve Elwood state by default. A resumable session ID is reported on stderr for text output and in the terminal record for JSON and JSONL. --keep explicitly selects the default; use --ephemeral for one-off runs that should remove their Elwood state afterward:

first=$(elwood --output json "Remember that the release color is teal")
id=$(printf '%s' "$first" | jq -r .sessionId)
elwood --resume "$id" "What is the release color?"
elwood --resume "$id" --ephemeral "Finish this conversation"

Resume uses the exact stored agent and workspace; conflicting --agent and any --cwd are rejected. Resumed sessions stay preserved after success or failure unless --ephemeral requests teardown. Ephemeral teardown removes Elwood's session record and loop definitions; it does not undo workspace changes or delete conversation history owned by Claude or Codex. CLI state defaults to absolute $XDG_STATE_HOME/elwood or ~/.local/state/elwood; its private records contain resume metadata, not ordinary prompts or output.

Before launching, elwood config effective [run options] prints the resolved settings and where each came from. The JSON includes head and, for Claude, the effective permissionMode, allowedTools, disallowedTools, and tools; resume inspection reports persisted tool rules with stored-session provenance.

Exit status is 0 for success or a closed consumer, 1 for agent/runtime or cleanup failure, 2 for usage/configuration failure, 124 for timeout, and 130 for interruption. The first Ctrl-C requests a clean interrupt; a repeated Ctrl-C force-kills before cleanup.

--persona runs an actual extra agent turn before the requested turn. Elwood discards that setup turn's answer, but any tools it invokes or files it changes remain. It is therefore supported only for new sessions, never --resume.

Sessions, resume, and interactive mode

elwood sessions lists the Elwood-owned session records in the effective state directory without starting an agent, and elwood resume <id> is the subcommand form of --resume <id>:

elwood sessions
elwood sessions --state-dir ./state --output json | jq -r '.sessions[] | .id'
elwood resume "$id" "What is the release color?"
git diff | elwood resume "$id" --ephemeral "Does this diff match what we agreed?"

The table (or the sessions array in JSON) reports each session's id, agent, workspace, createdAt/lastUsedAt timestamps, whether it is resumable (the agent's own conversation id is stored), and live — whether a launch's bridge socket file is currently present. live is a cheap file-presence signal: a socket left behind by a force-killed owner reads as live until that session is next started or torn down. Unreadable records are skipped with a stderr warning, and an empty state directory is a normal empty result. resume <id> follows every --resume rule: stored agent and workspace, no --cwd, no persona, and piped stdin composes the same way.

elwood interactive [id] opens the real claude or codex TUI in the current terminal — no hidden PTY, no automation, no observation, no Elwood state — with Elwood's resolved agent, model, reasoning effort, workspace, and posture passed as the agent's own flags. It exits with the agent's exit status and needs a terminal on stdin and stdout:

elwood interactive                      # the configured agent, its own defaults
elwood interactive --agent claude --model opus --claude-permission-mode plan
elwood interactive "$id"                # the stored conversation, workspace, and posture

Built-in headless posture defaults (Claude dontAsk, Codex workspace-write and never) are not applied unless a flag, environment variable, config key, or stored record selected them, so an unconfigured launch is the agent's own default experience. A session kept by a headless run does store its headless posture; pass --claude-permission-mode default (or the Codex flags) to get the agent's prompts back when resuming one interactively. Because the agent owns the resumed conversation, a later elwood resume <id> sees what you said. The command rejects --output json|jsonl, --stream, --verbose, --debug, --head, --timeout, --persona, --image, --keep, --ephemeral, and --resume.

Listing models

elwood models lists Claude and Codex models, with each model's agent noted. It probes Claude then Codex, briefly opening and cancelling each model picker, and removes both probe sessions afterward. --agent limits the listing to one agent; saved configuration and ELWOOD_AGENT do not narrow the bare command. Text marks the current model with * and the default with (default).

elwood models
elwood models --output json | jq '.agents[] | {agent, models}'
elwood models --agent claude --output json | jq -r '.models[] | select(.isCurrent) | .id'

JSON is one {"schemaVersion":1,"type":"models",...} document. Combined listings contain agents: [{agent, models}] and errors: [...]; explicit --agent retains the single agent and models fields. If one agent fails or is unavailable, the other catalog remains available and the command exits nonzero. --timeout is one budget shared by both probes, and Ctrl-C stops further probes. Workspace, model, reasoning, trust, state-directory, and matching adapter posture settings apply; the configured model stays unchanged.

Trust and security

Headless mode is non-interactive. With the default --trust, Elwood answers only its allowlisted workspace-directory and extension trust dialogs. Codex hook trust is bypassed session-wide, including hooks beyond Elwood’s own hooks. --no-trust disables the workspace/extension approvals. Any other recognized dialog fails safely as blocked_prompt instead of hanging or guessing.

Piped text and image paths are prompt input with the same authority as text typed by the caller. Do not combine untrusted input with broad filesystem permissions. Global config is never loaded from the repository being opened.

Head mode renders agent-controlled terminal escape sequences verbatim, just as running the selected interactive CLI directly would. Use it only with agents and workspaces you trust to control the current terminal display.

Try It Locally

Elwood includes two local test apps.

# Terminal smoke app, Claude by default.
npm run dev:app -- --cwd /path/to/project

# Terminal smoke app with Codex.
npm run dev:app -- --agent codex --cwd /path/to/project

# Resume from Elwood metadata.
npm run dev:app -- --cwd /path/to/project --resume <elwoodSessionId>

# Browser debugger with xterm.js terminal mirror and structured event inspector.
npm run dev:web

dev:web serves http://localhost:4317. It shows the live terminal on the left and a structured event timeline on the right. Use it to inspect hooks, activities, warnings, startup automation, status changes, and raw event payloads.

The script is still invoked through npm, but the browser dev server process runs under Node so node-pty can own a real interactive PTY reliably.

Runnable Examples

For the smallest real usage sample, run the minimal example. It constructs a CodexSession, which starts Codex lazily on the first send, then makes two ergonomic send calls — an initial prompt and a follow-up that refers back to it — printing each assistant response, and closes the session:

npm run example:minimal

For a fuller sample with Claude/Codex selection, custom prompts, richer logging, timeouts, and cleanup options, run examples/full.ts:

npm run example:full
npm run example:full -- --agent codex --cwd . --prompt "Summarize this repo in one paragraph."

Hooks and policy

Handlers return undefined for "no decision". Claude:

const claude = new ClaudeSession({
  cwd,
  autotrust: true,
  hooks: {
    PreToolUse(event) {
      if (event.tool_name === "Bash" && event.tool_input.command.includes("rm -rf")) {
        return { permissionDecision: "deny", permissionDecisionReason: "Dangerous shell command." };
      }
      return undefined;
    },
    Stop(event) {
      if (event.last_assistant_message?.includes("tests are failing")) {
        return { decision: "block", reason: "Tests are still failing." };
      }
      return undefined;
    },
  },
});

Codex:

const codex = new CodexSession({
  cwd,
  autotrust: true,
  approvalPolicy: "never",
  hooks: {
    PermissionRequest(event) {
      if (event.tool_name === "Bash") return { behavior: "allow", message: "Approved by policy." };
      return { behavior: "deny", message: "Only Bash is allowed in this mode." };
    },
    Stop(event) {
      if (event.last_assistant_message?.includes("TODO")) {
        return { decision: "block", reason: "Do not stop with TODOs remaining." };
      }
      return undefined;
    },
  },
});

Hooks fail open: a handler that throws, times out, returns an invalid result, or receives invalid input is reported as a hookError event and the agent proceeds as if no handler ran. Empty objects are invalid Codex results and fail open the same way.

Events

Subscribe with session.on(eventName, handler); on returns an unsubscribe function and may be called before the session starts.

session.on("activity", (event) => {
  switch (event.kind) {
    case "assistant_message":
    case "reasoning":
    case "tool_call":
    case "tool_result":
    case "web_search":
      renderTimelineItem(event);
      break;
  }
});

| Event | Purpose | |---|---| | activity | Adapter-neutral live stream for messages, reasoning, tools, warnings, hooks, hook results, and lifecycle. | | hook | Every parsed and validated adapter hook event. | | hook:<Name> | Hook-specific handler registration with typed response guidance. | | hookError | Handler timeout, thrown handler, invalid input, invalid response, or bridge error. Hooks fail open. | | warning | Non-fatal environment issue, such as an unparseable version or a failed autoupdate. | | loop | Redacted lifecycle for persisted recurring prompts. | | terminal:data | Raw PTY output for a visual terminal renderer. | | terminal:exit | PTY process exit, emitted exactly once. | | status | Session status change. | | codex:transcript | Codex-only best-effort transcript observations not covered by hooks. |

activity events carry normalized fields for timeline rendering: hookEventName, turnId, toolName, toolUseId, toolInput, toolOutput, status, exitCode, failedOpen, and transcriptPath when Elwood can derive them. raw is available for deep inspection.

Resume and teardown

Persist two things: the elwoodSessionId and the stateDir it lives in. At boot, let Elwood decide whether to resume:

import { startOrResumeClaude } from "@with-logic/elwood";

const { session, resumed } = await startOrResumeClaude({
  cwd,
  stateDir,
  elwoodSessionId: persisted?.elwoodSessionId,
  autotrust: true,
});
if (!resumed) persist({ elwoodSessionId: session.elwoodSessionId });

startOrResumeClaude / startOrResumeCodex fall back to a fresh start only on state_not_found, resume_unavailable (the CLI never reported a conversation id), or adapter_mismatch, and rethrow anything else. Resume restores the persisted launch posture (permission mode and tool rules for Claude, sandbox and approval policy for Codex); model, hooks, and trust options are per call.

teardown() removes only Elwood-owned files: the session record, loop sidecar, generated settings, bridge script, and socket home. It never touches the agent CLI's own auth, transcripts, or settings. stop() is graceful; kill() is immediate; both are safe after the process has already exited.

Security and privacy

• With autotrust, Elwood answers allowlisted workspace, skill/plugin/MCP, and Claude bypass-permissions acceptance dialogs. The library defaults to autotrust: false; the CLI defaults to --trust. Codex hook trust is bypassed for the entire launched session even without autotrust. Codex update dialogs are skipped, and Claude browser-tools onboarding is dismissed. Other recognized dialogs leave the session blocked for a human; the CLI fails such runs as blocked_prompt.
• --high-trust (library highTrust: true) is the agent-neutral "never ask" switch: Claude bypassPermissions, or Codex danger-full-access with approval policy never. It removes the agent's own guardrails, so point it only at work you would let run unattended. Combining it with an explicit per-agent posture is a usage error rather than a silent override.
• autotrust changes the security posture of the launched agent. Point it only at directories you already trust. The standalone listClaudeModels / listCodexModels probes always start with autotrust: true.
• The persisted session record holds schema version, elwoodSessionId, adapter, cwd, and per-adapter resume state. Loop definitions are the only persisted prompt text, in an owner-only 0600 sidecar.
• Elwood does not persist ordinary prompts, terminal output, hook payloads, hook responses, transcripts, or warnings. Fresh bridge tokens and socket paths are embedded in generated owner-only bridge scripts (0600), but excluded from session records and never read back as credentials on resume. teardown() removes these scripts; stop() preserves them with the session's runtime files.
• Hook bridge traffic stays on local IPC with a per-session token and an 8 MiB request cap.
• Elwood does not modify the user's global agent configuration. Claude gets session-scoped --settings; Codex gets session-scoped -c overrides, and Elwood restores config.toml after setModel.
• Codex image attachment goes through the macOS clipboard; the injected image is briefly the clipboard's contents. See docs/images.md.
• ClaudeSession.login() drives /login with a human-supplied code and validates the URL and code it handles, but should only run at a genuine login prompt. See docs/login-recovery.md.
• CLI output excludes ANSI frames, hook payloads, screen contents, credentials, and stack traces. Head mode renders agent-controlled escape sequences verbatim, so use it only with agents and workspaces you trust.

Limitations

• macOS only.
• Codex transcript observation is best-effort because not every TUI-visible activity is exposed as a hook.
• Codex subagent transcripts are not observed. A Codex SubagentStop still carries agent_transcript_path, so a host that wants those records reads the file itself. Claude subagent transcripts are observed.
• Model picker automation (listModels / setModel) is pinned to current CLI picker layouts; drift surfaces as model_automation_failed.
• The /login recovery flow needs a human to supply the authorization code.
• Screen matchers (trust prompts, update dialogs, login banners) are version-coupled to the CLIs; docs/cli-behavior.md records what has been verified against which versions.

Documentation

• docs/cli.md: the elwood command, configuration, head mode, continuation, and trust.
• docs/cli-output.md: text, JSON, and JSONL output fields, exit codes, and shell recipes.
• docs/api.md: the low-level session API, send semantics, commands, and model listing.
• docs/lifecycle.md: event delivery guarantees, terminal size, and persisting/resuming.
• docs/embedding.md: wiring a session into a host application (Electron and similar).
• docs/loops.md: recurring prompts and /loop parsing.
• docs/images.md: attaching images to a turn.
• docs/login-recovery.md: detecting and recovering an expired Claude login.
• docs/design-notes.md: design decisions and the state, privacy, and safety model.
• docs/cli-behavior.md: empirically verified real-CLI behavior that unit tests cannot catch.
• docs/codex/: short sourced notes on the Codex CLI, config, and hooks.
• examples/README.md: runnable minimal, streaming, and low-level examples.
• prd/: the behavior specification and conformance criteria.
• CHANGELOG.md: consumer-facing changes.
• site/: the landing page and the generated documentation site.

The website

site/ is the landing page and the generated documentation site, deployed to Vercel from this repository and served at elwood.bot. It is a static site with no framework and no build step: HTML, CSS, ES modules, and the robot's sprite sheets.

cd site && python3 -m http.server 8766 --bind 127.0.0.1

The documentation page is generated from Markdown sources in site/docs/guide/ and reads the CLI's help text out of src/cli/help.ts, so the published flag reference cannot drift from the code:

cd site
uv run scripts/build_docs.py        # regenerate guide/, llms.txt, llms-full.txt
python3 scripts/check_doc_examples.py   # typecheck every documented example
node --test tests/*.test.mjs        # the landing page's own tests

License

MIT. See LICENSE.

Contributing

Setup, the merge gate, the e2e suite, the dev apps, and the repository map are in CONTRIBUTING.md. Report vulnerabilities privately as described in SECURITY.md.