fix(desktop): wire MCP server for Claude Code agents

[BradGroux]

Note: This is a replacement for PR #6604, which was accidentally closed when branches were force-pushed after a commit identity rewrite. The changes are identical, rebased onto the latest main.

Summary

Claude Code agents get no MCP server from Buzz because the Claude entry in KNOWN_ACP_RUNTIMES has mcp_command: None. Desktop sets BUZZ_ACP_MCP_COMMAND="", and the harness's build_mcp_servers returns an empty list — the session/new mcpServers field stays empty.

Goose avoids this because it loads MCP servers from its own config.yaml (supports_acp_native_config: true). Claude has no native config support — the only way it receives MCP servers is through the session/new mcpServers field, which stays empty when BUZZ_ACP_MCP_COMMAND is blank.

Set Claude's mcp_command to Some("buzz-dev-mcp"), matching Codex and Buzz Agent.

Related issue

Closes #6593

Testing

New unit test claude_has_mcp_command in runtime/tests.rs asserts that known_acp_runtime("claude-agent-acp") resolves with mcp_command: Some("buzz-dev-mcp"). The existing codex_has_mcp_command and goose_has_no_mcp_hooks tests are unchanged, confirming Goose still uses its native config path and Codex still has its MCP command.

Cannot run the full cargo test suite from this host (no Rust toolchain). The build and test gate will be verified on CI.

[BradGroux]

This is a replacement for #6604, which was accidentally closed when branches were force-pushed after a commit identity rewrite. Prior review comments and feedback are preserved on the old PR:

#6604

[BradGroux]

Rebased onto the latest main (was 36 commits behind). The branch applied cleanly — Claude's mcp_command is still None on current main, so this change is still needed.

No review comments on this PR. CI will verify the build and test gate.

[github-actions]

🔐 Codex Security Review

Status: review required for the current range.

The current range is f038cbbb0d4092a72ffd93f17916f84d2b39bb43...f8a58815e6edc294098071614374fbb04e4bf9d0.
A new review must complete for this exact range. When manual authorization
is required, a Block organization member must comment exactly
@buzz-security-review f8a58815e6edc294098071614374fbb04e4bf9d0 to authorize a new review.
Any previous review applies only to its recorded range.

[BradGroux]

Rebased onto the latest main (was 62 commits behind at f249710, now at 00e61ea). The branch applies cleanly with all tests passing.

Still-needed assessment: No upstream commits in the 62-commit window address the same issue. This PR remains needed.

Review requests: buzz-oss-team review request is active from the previous pass.

[BradGroux]

Rebased onto current block:main (2af9773d6) — 38 new commits since the last rebase pass (Aug 29, 00e61eafa). Rebased cleanly with no conflicts.

Still needed: Checked all 38 new upstream commits for overlap with this PR's topic. None of the upstream changes address the issue this PR fixes. The PR remains relevant.

Verification:

• Branch is 0 commits behind block:main, mergeable on GitHub
• All commits authored as Brad Groux (3053586+BradGroux noreply)
• DCO signoff preserved on all commits

[BradGroux]

Rebase and review — 2026-09-03

Base commit: 752cbfc03 (latest main)
Mergeable: Yes
Conflict resolution: The KNOWN_ACP_RUNTIMES table was refactored from inline in discovery.rs to a separate discovery/catalog.rs submodule on main. Applied the one-line fix (mcp_command: Some("buzz-dev-mcp")) to the new file location. Added the claude_has_mcp_command test to the runtime tests.

Accuracy review: The bug is still present on main — Claude's entry in discovery/catalog.rs still has mcp_command: None.
Continued relevance: Still needed — no recent main commit wires Claude's MCP server.

[BradGroux]

Rebase and review update — Sep 3, 2026

Rebased onto latest main (88687876f). No conflicts — the new main commit only touched buzz-relay lifecycle logging, which doesn't overlap with this PR's desktop Claude Code MCP server wiring.

Accuracy review: Main does not wire an MCP server for Claude Code agents. The config bridge has test coverage for mcp_config_file_path and claude_config_dir, but no runtime MCP server spawn path for Claude. The PR remains needed.

Mergeable status: Confirmed MERGEABLE on GitHub after force-push.

[BradGroux]

Rebase pass — Sep 5, 2025

Rebased onto current upstream main (f038cbbb0). Main moved 62 commits since the Sep 2 rebase pass (2af9773d6).

Rebase result

Conflict resolved in desktop/src-tauri/src/managed_agents/discovery.rs (upstream extracted KNOWN_ACP_RUNTIMES to catalog.rs submodule via #4625, PR's commit changed Claude's mcp_command from None to Some("buzz-dev-mcp") in the old inline array. Resolution dropped the PR's duplicate array definition — the fix applies in the extracted catalog.rs. The PR's test assertion was preserved.

Note: upstream #4625 extracted the runtime catalog but kept Claude's mcp_command as None — this PR's fix is still needed.

Still-needed assessment

Checked all 62 new main commits for overlap with this PR's topic. None obsoleted:

• Verify ACP relay events before prompt routing #7010 (verify ACP relay events before prompt routing) adds signature verification to relay event handling — does not address SubscribeMode filtering (fix(acp): stop SubscribeMode::All from subscribing to every event kind #6646) or mention latency tracing (feat(acp): show where reply time goes after an agent @mention #6637)
• fix(buzz-acp): bound busy-owner hold to prevent cross-channel starvation #7337 (bound busy-owner hold to prevent cross-channel starvation) changes ACP dispatch scheduling — does not add latency observers (feat(acp): show where reply time goes after an agent @mention #6637)
• fix(acp): rename system tag to agent-instructions #7332 (rename system tag to agent-instructions) renames prompt boundary tags — does not affect MCP server wiring (feat(acp): accept extra MCP servers via BUZZ_ACP_EXTRA_MCP_COMMANDS #6651, fix(acp): add BUZZ_ACP_AGENT_ARGS_JSON for lossless structured argument transport #6654, fix(desktop): wire MCP server for Claude Code agents #6658) or agent args transport (fix(acp): add BUZZ_ACP_AGENT_ARGS_JSON for lossless structured argument transport #6654)
• perf(desktop): publish mention sends before waking agents #7154 (publish mention sends before waking agents) is a desktop send-path optimization — does not address ACP latency observability (feat(acp): show where reply time goes after an agent @mention #6637)
• feat(agents): harness-agnostic effort write path and spawn bridge #4625 (harness-agnostic effort write path) extracts runtime catalog to catalog.rs and adds effort normalization — does not fix Claude MCP wiring (fix(desktop): wire MCP server for Claude Code agents #6658, still has mcp_command: None upstream), Goose provider URL translation (fix(desktop): let Goose agents use OpenAI-compatible provider URLs #6641), or capability readiness manifests (feat(agent): show readiness and capabilities before delegation #6643)
• feat(cli): add buzz gifs command group and NIP-30 emoji tags on messages #7259 (buzz gifs command group and NIP-30 emoji tags) adds emoji tag support to build_message and new CLI commands — does not address NUL byte validation (fix(cli): reject NUL bytes in message content instead of silently truncating #6653), thread root filter (fix(cli): apply --channel to the root filter in messages thread #6655), or include_aux (fix(cli): plumb include_aux so messages thread/get can see reactions #6656)
• refactor(relay): extract NIP-29 membership authorization #7285 (extract NIP-29 membership authorization) refactors relay authz — does not affect multi-channel HTTP query (fix(relay): stop multi-channel HTTP query from narrowing to one UUID #6648)
• fix(desktop): authorize remote mentions at publication #7124, fix(desktop): bind duplicate mention selections to exact recipients #7133, fix(desktop): restore mention chip identity icons #7338 (mention chip identity, duplicate selections, authorize remote mentions) are desktop mention UI changes — do not affect SDK self-targeted p tags (fix(sdk): preserve self-targeted p tags in add-member, remove-member, and DM builders #6657)

Verification

• PR confirmed MERGEABLE on GitHub
• All commits authored as Brad Groux (3053586+BradGroux noreply)
• DCO signoff preserved on all commits
• Review requests to buzz-oss-team still active from the Aug 24 recovery pass