OpenShell/examples/multi-agent-notepad

Multi-Agent Shared Notepad Demo

Run multiple Codex coding agents in parallel OpenShell sandboxes, with a GitHub repository as the durable shared notepad they coordinate through.

Why GitHub as a shared notepad?

Long-running agents that produce artifacts — research notes, memory entries, reports, decision logs — need somewhere durable to write them. The store has to survive individual sandbox death, accept many concurrent writers safely, and stay inspectable after the fact. GitHub provides all three for free:

• Durable across sandbox restarts. A sandbox can crash mid-run; the committed artifact persists.
• Concurrency control built in. Every PUT must include the current file SHA, and the branch ref serializes commits. Racing writers see HTTP 409 and retry instead of silently overwriting each other.
• Auditable. Every write is a commit with author, message, diff, and timestamp. Free observability.
• Reviewable. Humans review agent output with the same PR/diff tooling they already use for code.
• No new infra. Most teams already have a GitHub org.

The pattern works best when artifacts are markdown or other text (so diffs are useful) and when write rates are moderate (commits per minute, not per second). For higher rates or structured queries, graduate to a real datastore — see Beyond map/reduce below.

What this demo shows

The simplest useful shape: map/reduce. N worker agents fan out and write one note each; one synthesis agent reads them and writes a summary.

runs/<run-id>/notes/agent-1.md   ← worker 1 writes
runs/<run-id>/notes/agent-2.md   ← worker 2 writes
...
runs/<run-id>/summary.md         ← synthesis agent writes

Each worker gets a different research angle on the same topic. Workers share neither filesystem nor container — only the GitHub repository.

The demo also exercises two OpenShell features:

• Provider-backed credentials. Sandboxes get placeholders, not the real Codex OAuth tokens or the GitHub token. The proxy resolves them at the network boundary.
• Scoped network policy. Each sandbox can only GET and PUT paths under /repos/<owner>/<repo>/contents/runs/<run-id>/**.

Files in this example

• demo.sh — host orchestration. Validates env, creates providers, launches sandboxes, waits for completion. Read this to understand how the run is driven from the host.
• runner.sh — the script that runs inside each sandbox. Bootstraps Codex OAuth, calls codex exec, and writes the result to GitHub. Read this to understand the agent side.
• policy.template.yaml — the network policy applied to every sandbox in the run. Renders to a concrete policy with the configured owner, repo, and run id.
• prompts/worker.md, prompts/synthesis.md — agent instructions.

Prerequisites

• OpenShell CLI from current main (or set OPENSHELL_BIN to the binary path)
• A running OpenShell gateway: mise run gateway:docker for local development
• Local Codex sign-in on the host: codex login
• gh (GitHub CLI) signed in, or a GitHub PAT with contents:write
• jq on the host
• A disposable or demo-only GitHub repository

The demo writes under runs/<run-id>/. Use a repository created specifically for this demo, or one you're comfortable with the demo creating files in.

Quick start

export DEMO_GITHUB_OWNER=<owner>
export DEMO_GITHUB_REPO=<repo>
export DEMO_GITHUB_TOKEN="$(gh auth token)"
export DEMO_AGENT_IMAGE="registry.example.com/your-org/codex-agent:latest"

bash examples/multi-agent-notepad/demo.sh

gh auth token returns a token with whatever scopes you logged in with — usually broader than contents:write. If you'd rather use a scope-limited PAT, set DEMO_GITHUB_TOKEN to that value instead.

The selected image must contain Codex, curl, and Bash. The script launches five worker agents and one synthesis agent by default. To run a faster smoke test:

export DEMO_AGENT_COUNT=2
bash examples/multi-agent-notepad/demo.sh

Optional settings:

export DEMO_TOPIC="How should teams evaluate sandboxed coding agents?"
export DEMO_AGENT_COUNT=5
export DEMO_BRANCH=main
export DEMO_RUN_ID="$(date +%Y%m%d-%H%M%S)"
export DEMO_KEEP_SANDBOXES=0

DEMO_RUN_ID is used in sandbox names and policy paths, so keep it lowercase letters, numbers, and -. Use a fresh DEMO_RUN_ID per run unless you intentionally want to overwrite a previous run's files.

DEMO_BRANCH may contain only letters, numbers, ., _, and -.

If a worker fails, the script prints the relevant log tail and keeps full logs in a temporary directory. Set DEMO_KEEP_SANDBOXES=1 to inspect sandboxes after the run; temporary providers are still removed.

How credential protection works

The host script reads your local Codex sign-in and creates a temporary OpenShell provider for the OAuth tokens. It also creates a temporary provider for the GitHub token. Sandboxes receive provider placeholders, not the real credential values.

When codex or curl inside a sandbox sends an authorized request, the OpenShell proxy resolves the placeholder at the network boundary and forwards the request upstream with the real credential. The credential values never sit in the sandbox filesystem.

Network policy

The script renders policy.template.yaml for the configured GitHub repository and run id. The policy allows:

• Codex traffic to OpenAI and ChatGPT endpoints used by the selected workload image
• Limited Codex plugin metadata reads from github.com/openai/plugins.git
• GitHub REST GET and PUT calls scoped to /repos/<owner>/<repo>/contents/runs/<run-id>/**

The policy does not grant broad GitHub API access.

Beyond map/reduce: memory architecture variants

The pile-and-reduce shape in this demo is one of several useful patterns for using a Git repository as durable agent memory. Each is a different tradeoff between contention, complexity, and what you can ask of the artifact afterwards.

Pile (this demo)

Each agent writes its own file at a unique path. A reducer reads them all and writes a summary.

• Best for: parallel exploration with bounded fan-in (research, multi-perspective analysis, code review across files).
• Contention: low. Different files have independent SHAs, so the only source of 409s is branch-ref locking when many commits land at once. The retry loop in put_contents handles it.
• Extension: hierarchical reduce — k workers per reducer, log(N) levels — for runs that exceed what one synthesis agent can chew through.

Append journal

A long-lived agent (or small team) appends entries to a shared journal.md across many sessions. Useful as chronological memory: "decisions made", "things learned", "open questions".

• Best for: a single agent or a small group continuously writing an ordered log.
• Contention: high if many writers; the GET-PUT-409-retry pattern is load-bearing here. For high-write-rate journals, switch to the Git Data API — create blobs concurrently, build one tree, commit once — to avoid branch-ref serialization.
• Extension: split by month (journal/2026-05.md) to bound file size and spread contention across files.

Indexed memory

Agents read and write keyed entries — memory/<topic>.md per key. Higher- level agents look up "what do we know about X?" by reading the relevant file directly.

• Best for: keyed memory that survives across runs and is queried by topic.
• Contention: per-key, which is usually what you want. Hot keys still benefit from the retry loop.
• Extension: maintain a index.md listing all keys. The index becomes the hot spot — update it lazily, or rebuild it from a directory listing when needed.

When to graduate beyond GitHub

GitHub stops being the right backend when you need sustained write rates above roughly 10/sec, sub-100ms reads, structured queries, or vector search. At that point reach for Postgres, a KV store, or a vector DB. The shape of the agent code stays similar — only the storage primitive changes.