fix(server): default to loopback with explicit deployment binding

[deepujain]

What

Running switchyard-server --config routes.toml now listens on 127.0.0.1. To accept remote clients, pass --host 0.0.0.0.

The Docker image and checked-in systemd service explicitly select 0.0.0.0, so container port publishing and remote service traffic keep working. A later --host argument can override the image's choice. The getting-started guide, server README, CLI reference and changelog explain the migration. The three DeepSWE profile launch examples also bind explicitly for Pier access.

Why

Fixes #596, following @grahamking's agreement with the local-only default. The earlier #584 proposal was closed because changing only the binary would break the deployment paths. This patch covers those paths together: a first standalone run stays local, while deployments deliberately expose the listener. Loopback does not add authentication.

Notes for reviewers

The default-host regression fails with the old wildcard address and passes after the change. The actual native binary also passed three socket checks: default loopback, explicit all-interface binding, and an explicit override after the container-style arguments. Each served /health successfully.

I built the root Dockerfile and ran that image with a published host port; /health returned 200 through the published port. The container was stopped after the check. The systemd unit's command is updated, but systemd itself was not run on this macOS host.

Local checks passed: formatting, workspace tests and Clippy, the CI prefill-router test/Clippy commands, Ruff, mypy, Python tests on a fresh 3.11 native build, and a strict MkDocs build. No provider credentials are needed for the listener checks.

The documentation follow-up was checked by running all three DeepSWE launch commands with --dry-run and rebuilding the strict documentation site. It changes comments and the CLI reference only.

Summary by CodeRabbit

• Changed
  • The standalone server now listens on 127.0.0.1 by default. To accept remote connections, specify --host 0.0.0.0 and secure access appropriately.
  • The provided Docker image and systemd service explicitly bind to 0.0.0.0 to allow network access. You can override the Docker image’s host setting with a later --host argument.
  • When multiple --host values are supplied, the last value takes precedence.

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📒 Files selected for processing (4)

• benchmark/routing-profiles/deepswe-v11-advisor-gate-luna-sol.toml
• benchmark/routing-profiles/deepswe-v11-plan-execute-luna-sol.toml
• benchmark/routing-profiles/deepswe-v11-stage-router-luna-sol.toml
• docs/cli_reference.md

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Walkthrough

The standalone server now binds to 127.0.0.1 by default. The Docker image and systemd service pass --host 0.0.0.0. Repeated --host arguments use the last value. Benchmark server commands also specify --host 0.0.0.0.

Changes

Server binding behavior

Layer / File(s)	Summary
CLI host selection crates/switchyard-server/src/cli.rs	The default host changes to IPv4 localhost. The last repeated --host value takes precedence. Tests cover the default and repeated values for IPv4, IPv6, and 0.0.0.0.
Deployment host settings Dockerfile, dev-server/switchyard.service, benchmark/routing-profiles/*	The Docker entrypoint, systemd service, and benchmark server commands specify --host 0.0.0.0.
Binding guidance and reference crates/switchyard-server/README.md, docs/getting_started.md, docs/cli_reference.md, CHANGELOG.md	The documentation and changelog state the standalone default, describe --host overrides, and identify deployment settings.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 47bc6

Standalone server use now stays local by default, while deployments that need remote access opt in explicitly. No merge-blocking issue was identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Issue #596 requires a local-only default with coordinated deployment updates. crates/switchyard-server/src/cli.rs now defaults to 127.0.0.1 and tests the default and later --host precedence. `Do…
Out of Scope Changes check	✅ Passed	The changes support issue #596. The DeepSWE profile updates preserve remote access after the default changes. The other changes update the server behavior, deployment configuration, regression tests, …
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 1 files. (4 skipped: 4 …
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: the server now defaults to loopback, while deployments must set an explicit binding.

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_{A rabbit checks the host address,
Loopback keeps the bind in place.
A flag opens the wider door,
Last host wins when flags are more.
Docker and systemd set the score,
Then hops away across the floor.}

_{Comment @coderabbitai help to get the list of available commands.}

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Actionable comments posted: 1

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• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at @crates/switchyard-server/src/cli.rs:
- Around line 16-17: Update the DeepSWE launch-command comments associated with
DEFAULT_HOST and DEFAULT_PORT to include --host 0.0.0.0 for each listed Pier
workflow profile, so the documented commands bind to an address reachable from
Pier.

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📒 Files selected for processing (6)

• CHANGELOG.md
• Dockerfile
• crates/switchyard-server/README.md
• crates/switchyard-server/src/cli.rs
• dev-server/switchyard.service
• docs/getting_started.md

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