Buzz Desktop 0.5.2: agent_args reset to [] and missing_binary setup payload error prevents OpenCode ACP integration

[m-faizan-tariq]

Summary

Buzz Desktop v0.5.2 has two bugs that prevent OpenCode (and other ACP-based agents) from working properly as agents.

Bug 1: agent_args silently reset to [] by Buzz Desktop

Observed behavior:
When configuring an agent to use OpenCode via the Buzz Desktop UI, the agent_args field in managed-agents.json keeps getting silently reset to [] (empty array) after being set to ["acp"].

Impact:
OpenCode requires the acp subcommand to start in ACP server mode (e.g., opencode acp). Without it, Buzz Desktop launches opencode with no arguments, which starts in interactive mode instead of ACP mode. buzz-acp waits 60s and times out with:

agent initialize failed: Request timeout — agent did not respond within 60s

Root cause:
Buzz Desktop's internal state management overrides the agent_args value in managed-agents.json on every restart/sync, discarding any user-set value.

Expected behavior:
When a user explicitly sets agent_args through the UI or directly in the config file, Buzz Desktop should preserve that value.

Workaround discovered:
Replace the opencode binary with a wrapper script that detects buzz-acp as its parent process and auto-injects the acp argument:

#!/bin/bash
if [ \$# -eq 0 ] || { [ \$# -eq 1 ] && [ -z "\$1" ]; }; then
    PARENT_NAME=\$(ps -p \$PPID -o comm= 2>/dev/null)
    case "\$PARENT_NAME" in
        *buzz*)
            exec /path/to/opencode-real acp
            ;;
    esac
fi
exec /path/to/opencode-real "\$@"

Bug 2: missing_binary unknown variant in setup payload

Observed behavior:
When provider and/or provider_binary_path are set in the agent config, buzz-acp crashes with:

Error: setup payload error: malformed BUZZ_ACP_SETUP_PAYLOAD: unknown variant `missing_binary`, expected one of `normalized_field`, `env_key`, `cli_login`, `cli_config_invalid`, `git_bash`

Root cause:
The setup payload format sent by Buzz Desktop or the relay contains a missing_binary variant that the buzz-acp binary (v0.5.2) does not recognize. This suggests a version mismatch — buzz-acp's setup payload parser does not include missing_binary in its valid variants enum.

Environment

• Buzz Desktop version: 0.5.2 (bundle xyz.block.buzz.app)
• OS: macOS (arm64)
• Agent runtime: OpenCode 1.18.9-fork
• Relay: WebSocket relay (tested with wss://kamil22.communities.buzz.xyz)

Steps to Reproduce (Bug 1)

1. Install Buzz Desktop 0.5.2 and OpenCode CLI
2. Create a team with agents (e.g., Fizz, Bumble, Honey personas)
3. Configure an agent to use OpenCode runtime via UI
4. Edit managed-agents.json to set agent_args: ["acp"]
5. Restart Buzz Desktop or toggle the agent
6. Observe that agent_args reverts to []

Steps to Reproduce (Bug 2)

1. In managed-agents.json, set provider and/or provider_binary_path on an agent
2. Toggle the agent on
3. Observe the missing_binary error in agent logs

Suggested Fixes

1. For Bug 1: Ensure Buzz Desktop preserves agent_args when syncing agent configuration. The args array should only be modified through intentional user action.

2. For Bug 2: Add missing_binary to the valid variants enum in buzz-acp's setup payload parser, or ensure the relay does not emit this variant to older clients.

[iroiro147]

Cross-reference for reviewers — both halves of this issue appear to be covered by open PRs, so likely no independent fix needed here.

Bug 1 (agent_args silently [] → interactive mode → 60s timeout): Root cause is opencode missing from the default_agent_args identity table used by the Tauri spawn path (desktop/src-tauri/src/managed_agents/discovery.rs). Open PR #3706 already adds exactly "opencode" => Some(vec!["acp"]) to that table — the same fix class as #3793 (omp) / #3458 (grok). That preserves the user's "no args → acp" intent without needing the wrapper-script workaround.

Bug 2 (missing_binary unknown variant): Buzz Desktop serializes Requirement::MissingBinary into BUZZ_ACP_SETUP_PAYLOAD, but buzz-acp v0.5.2's SetupPayload has no matching variant. Open PR #3598 adds the missing_binary variant + rendering to crates/buzz-acp/src/setup_mode.rs directly.

Suggest holding this issue for #3706 + #3598 to land rather than duplicating effort. cc @m-faizan-tariq