fix(wrap): set ANTHROPIC_HOST so wrap goose actually proxies Anthropic

[filipkujawa]

Description

headroom wrap goose never proxied Anthropic traffic. Goose's Anthropic provider reads ANTHROPIC_HOST, not ANTHROPIC_BASE_URL, so the wrapper started the proxy, printed the banner, and then sent every request straight to api.anthropic.com — silently, with no error and zero compression.

ANTHROPIC_BASE_URL appears in no .rs file in the goose repo. The provider reads ANTHROPIC_HOST at crates/goose/src/providers/anthropic_def.rs#L38-L40 and appends /v1/messages itself, so _claude_proxy_base_url(port) is already the correct value.

Note the README currently advertises headroom wrap goose -- --provider anthropic as an example — that is the exact invocation that bypasses the proxy. The OpenAI path was unaffected: goose does honour OPENAI_BASE_URL.

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Changes Made

• Set ANTHROPIC_HOST alongside the existing vars in wrap goose (headroom/cli/wrap.py), and show it in the launch banner.
• Extend test_wrap_goose_sets_provider_envs to assert the value. This test fails before the change with a KeyError.
• Update the command docstring.

Testing

• Unit tests pass (pytest)
• Linting passes (ruff check .)
• Type checking passes (mypy headroom)
• New tests added for new functionality
• Manual testing performed

Test Output

# Test A - the env vars `wrap goose` sets today (ANTHROPIC_HOST explicitly unset)
$ env -u ANTHROPIC_HOST ANTHROPIC_API_KEY=*** \
    OPENAI_BASE_URL=http://127.0.0.1:8787/v1 \
    OPENAI_API_BASE=http://127.0.0.1:8787/v1 \
    ANTHROPIC_BASE_URL=http://127.0.0.1:8787 \
    goose run --no-session -t "Reply with exactly: PONG"

● new session · anthropic claude-haiku-4-5
PONG
===== LISTENER HITS =====
(hit count:        0)

# Test B - same, plus ANTHROPIC_HOST (this change)
(hit count: 7)
2026-07-27T12:13:09.381232 HIT POST /v1/messages host=127.0.0.1:8787
2026-07-27T12:13:09.382744 HIT POST /v1/messages host=127.0.0.1:8787
2026-07-27T12:13:10.245477 HIT POST /v1/messages host=127.0.0.1:8787
...

# Test C - OpenAI path, unchanged env (confirms scope is Anthropic-only)
(hit count: 8)  POST /v1/chat/completions

Real Behavior Proof

• Environment: macOS 15 arm64, goose v1.44.0 built from source, headroom main @ e530de5, provider anthropic / claude-haiku-4-5, isolated goose config via GOOSE_PATH_ROOT, stub HTTP listener on 127.0.0.1:8787 standing in for the proxy.
• Exact command / steps: Ran goose run --no-session -t "Reply with exactly: PONG" three times against the stub listener — (A) with the env vars wrap goose sets today and ANTHROPIC_HOST explicitly unset, (B) identical but with ANTHROPIC_HOST added, (C) OpenAI provider with unchanged env. Full commands and output in the Test Output block above.
• Observed result: A got 0 requests at the listener and goose returned a real completion from api.anthropic.com, so the bypass is silent rather than a failure; B got 7 requests at the listener, proving the fix; C got 8 requests on /v1/chat/completions, confirming the OpenAI path already worked and the scope is Anthropic-only.
• Not tested: pytest, ruff and mypy were not run locally because my corporate network blocks files.pythonhosted.org so the dev environment will not install — those three boxes are deliberately left unchecked and CI should be the authority on them; the new assertion mirrors the adjacent ANTHROPIC_BASE_URL one against the same anthropic_base value.

Review Readiness

• I have performed a self-review
• This PR is ready for human review

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I did not edit CHANGELOG.md

Additional Notes

• Folded the assertion into the existing env-fan-out test rather than adding a near-duplicate, to match the file's stated organisation.
• On port fallback, _launch_tool rewrites the child environment (including the new var) but not env_vars_display, so the printed value can show the requested port. Pre-existing for the other displayed URLs; not addressed here.
• Possible follow-ups, happy to file separately: wrap aider sets OPENAI_API_BASE but not OPENAI_BASE_URL; and wrap goose does not call with_project_prefix(), so goose traffic isn't attributed per project.

[github-actions]

PR governance

This PR follows the template and is marked ready for human review.

[JerrettDavis]

Reviewed the latest commit 6e85f45. The fix correctly adds ANTHROPIC_HOST using the Anthropic proxy base (without the OpenAI /v1 suffix) while preserving the existing OpenAI envs, and the test now locks that behavior. I ran the focused Goose wrapper tests on the PR worktree: tests/test_cli/test_wrap_goose.py passed (2 passed).