Announce the MCP server to Home Assistant from dev and beta

[bdraco]

Adds mcp to the supervisor discovery: list so the Device Builder can announce its MCP server to Home Assistant's mcp integration (one-click confirm). The supervisor rejects discovery for services not listed here.

• dev + beta only: set as per-app overrides in template/addon_config.yaml. Stable is unchanged until 2026.10 ships, then move mcp into base and drop the overrides.
• Dev config regenerated; the beta config is picked up by the release script on the next beta.

Related: esphome/device-builder#2733 (server), discovery script in esphome, home-assistant/core#180378 (HA side).

[esphbot]

@bdraco: Took the first note in 20bd491: only the dev config is regenerated now, stable and beta wait for t...

Checked it. mcp is now only in esphome-dev/config.yaml:19 and the template. Stable and beta configs don't have it. Noted the core#180378 discovery support. Both notes are resolved.

[esphbot]

Previous review — superseded by a newer review below.

[esphbot]

Tip

No blocking issues found — ready to merge.

[esphbot]

PR Review — Announce the MCP server to Home Assistant from dev and beta

Merge-ready. The per-channel override approach is correct, and I found no new issues.

What works well:

• Since the last review, mcp moved out of base into discovery: overrides on esphome-dev and esphome-beta (template/addon_config.yaml:54-56, :71-73). Stable keeps only esphome until 2026.10 ships, as the description says.
• Each override repeats esphome alongside mcp. That's required: deep_merge in script/generate.py:19-26 merges only dicts, so an override list replaces the base list instead of extending it. Listing mcp alone would have silently dropped esphome discovery.
• Only the dev config is regenerated. esphome-dev/config.yaml:19 is the only generated file that contains mcp, and the only change is the added list entry. Stable and beta configs are untouched and left to the release script, as the template header says.

Follow-up, not a blocker:

• After 2026.10 ships, move mcp into base.discovery and delete both overrides, as the description already plans. Otherwise dev and beta keep their own copy of a list that has to stay in sync with base.

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Checklist

• Generated dev config matches template source of truth
• Stable/beta generated configs left to the release script
• Override lists preserve base esphome discovery (lists replace, not merge)
• No hardcoded secrets or credentials
• Diff matches PR description, no scope creep
• Stable add-on config unchanged

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Automated review by Kōan (Claude) HEAD=b0ece0f 22s

[esphbot]

Tip

No blocking issues found — ready to merge.