Development

How to drive the CLI from a checkout and where the repository's own rules live. Users install a release instead (getting started); agent update refuses to overwrite a checkout unless you pass --force.

Deps install into the checkout (deno install --frozen); the proxy floats into the copilot-env data home on the first agent start, the same as a release.

git clone https://github.com/Vivswan/copilot-env.git
cd copilot-env
bash scripts/setup-env.sh   # one-shot env/worktree init (deno install --frozen)
./bin/agent --help          # or: powershell -File bin\agent.ps1 --help

• Tasks: run deno task for the list (typecheck, test, bench, lint, check). They are defined in deno.json.
• Env init: scripts/setup-env.sh (setup-env.ps1 on Windows) is the single initializer. The Copilot coding agent and Codespaces / Dev Containers both run it.
• Checks before a push: the tasks and the pre-commit hook are listed in CONTRIBUTING.md.
• Rules and decisions: the conventions, the hard rules, and the decisions a reader would otherwise reverse (the proxy float, one credential, atomic profiles) live in AGENTS.md.
• Layering: the layers, the edges they draw, and the decisions as diagrams are on the architecture page; architecture.json declares the edges and deno task test fails on any import it does not declare.

Test fakes

Two loopback fakes let the suite and CI run with no Copilot credential and no network:

Fake	Stands in for	Used by
test/copilot-api-fake.mjs	the copilot-api daemon: its admin routes and the Listening on: marker	the start/stop lifecycle smoke (COPILOT_API_ENTRY)
test/helpers/fake_model_endpoint.ts	the model endpoint: Anthropic Messages, OpenAI Responses and chat completions (streaming and not), Copilot's /models	the Direct smoke test, the real-CLI tests

The fake model endpoint

aimock (npm:@copilotkit/aimock, pinned in deno.json, zero runtime deps) behind a thin front. aimock's request and stream shapes are validated daily against the real vendors by its own drift job (the test-drift.yml workflow in CopilotKit/aimock).

The front serves the one route aimock lacks in Copilot's shape, the root /models catalog with the picker fields both smoke pickers read, and proxies everything else byte for byte. The real claude and codex binaries talk to it over ANTHROPIC_BASE_URL / a Codex provider base_url.

A scenario selects one request's reply through the header aimock matches exactly, X-AIMock-Context: <name>; claude forwards it from ANTHROPIC_CUSTOM_HEADERS, codex from model_providers.<id>.http_headers. The table lives in test/helpers/fake_endpoint.ts:

Scenario	Reply
ok	the text OK
unauthorized	401 in the wire's own error envelope
model-not-found	404, the vendor's unknown-model rejection
tier-rejected	400 service_tier is not supported, Copilot's answer to a Codex tier it does not take
truncate-after-first-delta	the connection drops right after the first content delta of a codex-shaped Responses stream
(none)	a default line

Facts the tests rest on, verified against the installed releases:

• claude never calls /v1/messages/count_tokens in --print mode, and tolerates a 404 on its HEAD /api/hello reachability probe.
• Both CLIs retry 429 and 5xx with backoff; claude also retries 401 (10 attempts, about 3 minutes), so an auth failure on Direct ends at the probe's own timeout.
• A connection dropped mid-stream: codex reconnects five times within seconds and fails the turn (exercised); claude reads it as a connection error it retries 10 times (about 6 minutes) before re-asking without streaming (recorded, never exercised: no test may take that long).
• aimock's truncateAfterChunks counts SSE frames from the first one, prelude included; its journal (GET /__aimock/journal) redacts credential header values, so a test asserts their presence there and their value only on the catalog request the front journals in full.

Real CLIs against the fake

test/claude_cli_live.test.ts and test/codex_cli_live.test.ts run the installed CLIs with the Direct probe's own argv against the fake, in a scratch HOME, and pin the output shapes our probe and health checks parse. On a machine without a binary they skip; CI installs both through .github/actions/install-agent-clis and sets COPILOT_ENV_LIVE_CLIS=1, which turns a missing binary into a failure.

The nightly runs through repo-platform's fleet nightly module (nightly in .repo-platform.yml; the repo-owned .github/workflows/nightly.yml). It installs the latest CLI releases and runs only those two files.

A red night opens or refreshes one nightly-failure issue naming the run; the next green night closes it. It gates no merge, but an open nightly issue blocks release-please releases until fixed or overridden (repo-platform docs/nightly.md, docs/tracking-issues.md).

What a red means: usually a claude or codex release changed the shape our probe parses; an install or deno ci failure reads red too. Read the run's nightly-evidence artifact (the CLI versions and the test log; present once the test step ran), then fix the parser or record the change.

• The header comment of .github/workflows/nightly.yml lists what each red step points at.