hyperhive/hive-agent/src/mcp_config.rs

//! Claude launch-config layer: resolves the agent's tool-group / capability
//! set into the `--allowedTools` / `--tools` argument strings and renders the
//! `--mcp-config` blob claude reads at spawn (built-in hyperhive server +
//! any `hyperhive.extraMcpServers`). Pure config-string generation consumed by
//! [`crate::turn`] when it builds the claude command. It never touches the
//! running MCP server (a separate binary) — the `send` allow-list check that
//! server enforces lives alongside it in the `hive-agent-mcp` crate.

/// Name of the hyperhive MCP server inside claude's view. Claude prefixes
/// tools as `mcp__<this>__<tool>` (e.g. `mcp__hyperhive__send`).
pub const SERVER_NAME: &str = "hyperhive";

/// Default loopback port the built-in hyperhive MCP surface is served on
/// (streamable HTTP, via the persistent `hive-mcp-http` daemon). Overridable
/// via `hyperhive.mcp.httpPort`; **must match that option's default** in
/// `nix/templates/harness/`. Safe as a single fixed value across all
/// agents because each container runs in its own private network namespace,
/// so `127.0.0.1:<port>` is per-container-private (no cross-agent collision).
pub const DEFAULT_MCP_HTTP_PORT: u16 = 8790;

/// Built-in claude tools always present in every session. Anything not
/// in this list (or added by `extra_builtin_tools`) literally doesn't
/// exist in the session. Web egress (`WebFetch`/`WebSearch`) are
/// tool-group-gated (`web_tools`) — off by default. Nested agents
/// (`Task`/`Agent`) are intentionally omitted. `Bash` is disallowed — shell
/// execution goes through `mcp__bash__run` (background tasks
/// with structured output via `hive-bash-mcp`) instead of a raw interactive shell. `TodoWrite`
/// is omitted because the todo list lives in claude's in-process session
/// state and silently evaporates on /compact or session reset — agents
/// should plan in /state notes instead. `Skill` is included so installed
/// plugin skills (`base@hyperhive` and friends) are actually invokable —
/// without it here, every `SKILL.md`'s `description` frontmatter is inert:
/// the model never sees the tool that triggers a skill, no matter how well
/// it matches the task at hand.
pub const ALLOWED_BUILTIN_TOOLS: &[&str] = &["Edit", "Glob", "Grep", "Read", "Skill", "Write"];

/// Env var written by the meta renderer with a comma-separated list of
/// `hive_sh4re::permissions::ToolGroup` `snake_case` names (e.g. `"messaging,inbox,meta"`).
/// When present, the harness expands the groups into per-tool allow entries
/// instead of using the hardcoded flavor default. See `docs/conventions.md::Tool groups`.
const TOOL_GROUPS_ENV: &str = "HIVE_TOOL_GROUPS";

/// `HIVE_CAPABILITIES` env var injected by `meta::render_flake` when the
/// operator grants capabilities to this agent. Comma-separated
/// `hive_sh4re::permissions::Capability` `snake_case` names. Absent = no extra capabilities.
const CAPABILITIES_ENV: &str = "HIVE_CAPABILITIES";

/// Returns the MCP tool names (without `mcp__hyperhive__` prefix) that are
/// unlocked by the agent's current capability set. These are added to the
/// `--allowedTools` list so claude can call them without prompting, and
/// hive-c0re performs a second server-side capability check before executing.
fn allowed_capability_tools() -> Vec<String> {
    let raw = match std::env::var(CAPABILITIES_ENV) {
        Ok(v) if !v.trim().is_empty() => v,
        _ => return vec![],
    };
    let mut tools = Vec::new();
    for token in raw.split(',') {
        let t = token.trim().to_ascii_lowercase();
        match t.as_str() {
            "read_host_journal" => tools.push("get_host_journal".to_owned()),
            // infra_admin lets an agent restart hive infrastructure
            // containers (hive-ci / hive-forge / hive-matrix — not the
            // gateway) through the existing `restart` tool. Unlock it here so agents that hold
            // the capability without the full `lifecycle` group can still
            // call it; c0re re-checks the capability server-side and only
            // honours infra-container names via this path.
            "infra_admin" => tools.push("restart".to_owned()),
            // manage_root_agent / query_agent_state don't expose new MCP
            // tools: manage_root_agent gates existing lifecycle tools via
            // topology enforcement; query_agent_state unlocks the `agent`
            // field in get_loose_ends / count_pending_reminders /
            // reminder_rollup (c0re enforces the cap server-side).
            "manage_root_agent" | "query_agent_state" => {}
            unknown => {
                tracing::warn!(capability = %unknown, "unrecognised capability in HIVE_CAPABILITIES — skipped");
            }
        }
    }
    tools
}

/// Resolve the active tool groups for a harness session.
///
/// Reads `HIVE_TOOL_GROUPS` from the environment first. Each comma-separated
/// token is matched (case-insensitive) against the `ToolGroup` serde names
/// (`messaging`, `meta`, `inbox`, `lifecycle`, `approvals`, `scheduling`,
/// `diagnostics`, `execution`). Unrecognised tokens are logged and skipped.
/// Falls back to `AGENT_DEFAULT` when the env var is absent or empty.
fn effective_tool_groups() -> Vec<hive_sh4re::permissions::ToolGroup> {
    let raw = match std::env::var(TOOL_GROUPS_ENV) {
        Ok(v) if !v.trim().is_empty() => v,
        _ => return hive_sh4re::permissions::ToolGroup::AGENT_DEFAULT.to_vec(),
    };
    let mut groups = Vec::new();
    for token in raw.split(',') {
        let t = token.trim().to_ascii_lowercase();
        // Parse via serde_json (the canonical deserialization path).
        if let Ok(g) = serde_json::from_value::<hive_sh4re::permissions::ToolGroup>(
            serde_json::Value::String(t.clone()),
        ) {
            groups.push(g);
        } else {
            tracing::warn!(token = %t, "{TOOL_GROUPS_ENV}: unknown tool group, skipping");
        }
    }
    if groups.is_empty() {
        tracing::warn!(
            "{TOOL_GROUPS_ENV} set but contained no recognised groups; \
             falling back to AGENT_DEFAULT"
        );
        return hive_sh4re::permissions::ToolGroup::AGENT_DEFAULT.to_vec();
    }
    groups
}

/// Tool group an extra (out-of-process) MCP server is gated behind, if any.
///
/// Most `hyperhive.extraMcpServers` entries are ungated — available whenever
/// the operator declares them. The `bash` server is the exception: raw shell
/// execution is a privilege, so it is only exposed when the agent holds the
/// `Execution` tool group. Unlike the in-process hyperhive tools (gated at
/// dispatch) and the capability tools (re-checked server-side by hive-c0re),
/// an out-of-process server has **no** later enforcement point — once it is
/// in the claude MCP config the agent can call it. So this gate, applied at
/// config-render time, is the security boundary for those servers.
fn extra_server_required_group(server: &str) -> Option<hive_sh4re::permissions::ToolGroup> {
    match server {
        "bash" => Some(hive_sh4re::permissions::ToolGroup::Execution),
        _ => None,
    }
}

/// Whether an extra MCP server should be exposed to claude given the active
/// tool `groups`. A gated server (see [`extra_server_required_group`]) is
/// suppressed when the agent lacks its required group.
fn extra_server_enabled(server: &str, groups: &[hive_sh4re::permissions::ToolGroup]) -> bool {
    extra_server_required_group(server).is_none_or(|required| groups.contains(&required))
}

#[cfg(test)]
mod extra_server_gate_tests {
    use super::{extra_server_enabled, extra_server_required_group};
    use hive_sh4re::permissions::ToolGroup;

    #[test]
    fn bash_is_gated_behind_execution() {
        assert_eq!(
            extra_server_required_group("bash"),
            Some(ToolGroup::Execution)
        );
        // Suppressed without Execution, even if other groups are present.
        assert!(!extra_server_enabled(
            "bash",
            &[ToolGroup::Messaging, ToolGroup::Inbox]
        ));
        // Available once Execution is granted.
        assert!(extra_server_enabled("bash", &[ToolGroup::Execution]));
    }

    #[test]
    fn other_servers_are_ungated() {
        assert_eq!(extra_server_required_group("matrix"), None);
        assert_eq!(extra_server_required_group("scraper"), None);
        // An ungated server is available regardless of (even empty) groups.
        assert!(extra_server_enabled("matrix", &[]));
        assert!(extra_server_enabled("scraper", &[ToolGroup::Messaging]));
    }
}

/// MCP tools claude is allowed to call without prompting, derived from
/// the supplied tool groups. Adding a new `#[tool]` fn to a server impl
/// requires updating the matching `ToolGroup::tools()` slice in hive-sh4re
/// (single source of truth). See `docs/conventions.md::Tool groups`.
#[must_use]
pub fn allowed_mcp_tools(groups: &[hive_sh4re::permissions::ToolGroup]) -> Vec<String> {
    // Collect all tool names, deduplicating while preserving order.
    // Always-on tools (e.g. `set_status`) come first so they're present
    // regardless of which groups the agent is granted — a misconfigured
    // agent still has to be able to report its dashboard status.
    let mut seen = std::collections::HashSet::new();
    let mut out: Vec<String> = hive_sh4re::permissions::ToolGroup::ALWAYS_ON_TOOLS
        .iter()
        .copied()
        .chain(groups.iter().flat_map(|g| g.tools().iter().copied()))
        .filter(|t| seen.insert(*t))
        .map(|t| format!("mcp__{SERVER_NAME}__{t}"))
        .collect();
    // Extra MCP servers declared via `hyperhive.extraMcpServers` in
    // the agent's NixOS config. Each entry maps its `allowedTools`
    // pattern list to `mcp__<server>__<pattern>` so claude can call
    // them without per-tool operator approval. `["*"]` (the default)
    // expands to `mcp__<server>__*` — every tool from that server.
    for (server, spec) in load_extra_mcp() {
        if server == SERVER_NAME || !extra_server_enabled(&server, groups) {
            continue;
        }
        for pat in spec.allowed_tools() {
            out.push(format!("mcp__{server}__{pat}"));
        }
    }
    out
}

/// Combined allow-list passed to `--allowedTools` (auto-approve) — covers
/// both the built-ins and the MCP surface.
#[must_use]
pub fn allowed_tools_arg() -> String {
    let groups = effective_tool_groups();
    // Base built-ins always present.
    let mut all: Vec<String> = ALLOWED_BUILTIN_TOOLS
        .iter()
        .map(|s| (*s).to_owned())
        .collect();
    // Extra built-ins gated by tool groups (e.g. WebFetch/WebSearch via web_tools).
    for group in &groups {
        for tool in group.builtin_tools() {
            if !all.iter().any(|t| t == *tool) {
                all.push((*tool).to_owned());
            }
        }
    }
    all.extend(allowed_mcp_tools(&groups));
    // Capability-gated MCP tools: added to --allowedTools when HIVE_CAPABILITIES
    // includes the corresponding capability. hive-c0re performs a second
    // server-side check, so this is a usability gate (no annoying prompts),
    // not the security boundary.
    for tool in allowed_capability_tools() {
        all.push(format!("mcp__{SERVER_NAME}__{tool}"));
    }
    all.join(",")
}

/// Built-in tools list for `--tools` (which built-ins exist in this
/// session). Base set plus any group-gated built-ins (e.g.
/// `WebFetch`/`WebSearch` when the `web_tools` group is active).
#[must_use]
pub fn builtin_tools_arg() -> String {
    let groups = effective_tool_groups();
    let mut tools: Vec<&str> = ALLOWED_BUILTIN_TOOLS.to_vec();
    for group in &groups {
        for t in group.builtin_tools() {
            if !tools.contains(t) {
                tools.push(t);
            }
        }
    }
    tools.join(",")
}

/// Where the NixOS module writes the per-agent extra-MCP spec (see
/// `nix/templates/harness/`). Each entry becomes an additional
/// `mcpServers.<key>` block in the rendered claude config + a
/// `mcp__<key>__<tool>` pattern in `--allowedTools`.
const EXTRA_MCP_PATH: &str = "/etc/hyperhive/extra-mcp.json";

/// An extra MCP server declared via `hyperhive.extraMcpServers`. Two
/// transports: `Stdio` (claude spawns `command` fresh each turn, talks
/// JSON-RPC over its stdin/stdout) and `Http` (claude points at a
/// long-lived streamable-http `url` instead — no per-turn spawn, no
/// re-registration race, same shape as the built-in hyperhive surface).
/// Internally tagged on the nix-rendered `type` field; unrecognised
/// fields for the inactive variant (e.g. `command` on an `Http` entry)
/// are ignored by serde's default struct deserialization.
#[derive(Debug, serde::Deserialize)]
#[serde(tag = "type", rename_all = "snake_case")]
enum ExtraMcpServer {
    Stdio {
        command: String,
        #[serde(default)]
        args: Vec<String>,
        #[serde(default)]
        env: std::collections::BTreeMap<String, String>,
        #[serde(default = "default_allowed_tools")]
        #[serde(rename = "allowedTools")]
        allowed_tools: Vec<String>,
    },
    Http {
        url: String,
        #[serde(default = "default_allowed_tools")]
        #[serde(rename = "allowedTools")]
        allowed_tools: Vec<String>,
    },
}

impl ExtraMcpServer {
    fn allowed_tools(&self) -> &[String] {
        match self {
            Self::Stdio { allowed_tools, .. } | Self::Http { allowed_tools, .. } => allowed_tools,
        }
    }
}

fn default_allowed_tools() -> Vec<String> {
    vec!["*".to_owned()]
}

/// Read + parse the extra-MCP spec. Returns an empty map when
/// the file is missing or unparsable (the agent has none configured,
/// or the file is malformed — both cases degrade to "no extra servers").
fn load_extra_mcp() -> std::collections::BTreeMap<String, ExtraMcpServer> {
    let Ok(raw) = std::fs::read_to_string(EXTRA_MCP_PATH) else {
        return std::collections::BTreeMap::new();
    };
    serde_json::from_str(&raw).unwrap_or_else(|e| {
        tracing::warn!(
            path = EXTRA_MCP_PATH,
            error = ?e,
            "extra-mcp spec parse failed; ignoring",
        );
        std::collections::BTreeMap::new()
    })
}

/// Render the MCP config blob claude reads from `--mcp-config <path>`.
/// The built-in `hyperhive` surface is an HTTP entry pointing at the
/// persistent `hive-mcp-http` daemon (see [`DEFAULT_MCP_HTTP_PORT`]); there
/// is no per-turn stdio child for it. Merges in any extra MCP servers
/// declared via `hyperhive.extraMcpServers` — each one is either a
/// per-turn stdio bridge or another persistent HTTP entry, per its own
/// `type`.
#[must_use]
pub fn render_claude_config() -> String {
    let config = serde_json::json!({ "mcpServers": build_mcp_servers() });
    serde_json::to_string_pretty(&config).unwrap_or_else(|_| "{}".into())
}

/// The set of MCP server names claude is configured with this turn — the
/// keys of the rendered `--mcp-config` (built-in hyperhive HTTP surface +
/// any tool-group-permitted extra servers). The harness compares
/// this against the per-turn `system`/`init` event's `mcp_servers` to
/// detect a configured server that failed to connect or was dropped
/// (the MCP-health instrumentation).
#[must_use]
pub fn configured_server_names() -> Vec<String> {
    build_mcp_servers().into_iter().map(|(k, _)| k).collect()
}

/// Build the `mcpServers` map claude gets in its `--mcp-config`: the
/// built-in hyperhive HTTP surface plus any tool-group-permitted extra
/// servers (stdio or http, per each entry's `type`). Shared by
/// [`render_claude_config`] (serialises it) and [`configured_server_names`]
/// (lists its keys) so the two never drift.
fn build_mcp_servers() -> serde_json::Map<String, serde_json::Value> {
    let mut servers = serde_json::Map::new();
    // The built-in hyperhive surface is served exclusively over streamable
    // HTTP by the persistent `hive-mcp-http` daemon (loopback, inside the
    // agent's private network namespace). Point claude at the stable URL
    // rather than respawning a fresh stdio child each turn: the URL survives
    // the per-turn claude re-spawn, so there is no per-turn re-registration
    // race for the hyperhive surface. The port comes from
    // `HYPERHIVE_MCP_HTTP_PORT` (always set by the harness);
    // `DEFAULT_MCP_HTTP_PORT` is the fallback matching the nix default.
    let port = std::env::var("HYPERHIVE_MCP_HTTP_PORT")
        .ok()
        .and_then(|p| p.trim().parse::<u16>().ok())
        .unwrap_or(DEFAULT_MCP_HTTP_PORT);
    let hyperhive_entry = serde_json::json!({
        "type": "http",
        "url": format!("http://127.0.0.1:{port}/mcp"),
    });
    servers.insert(SERVER_NAME.to_owned(), hyperhive_entry);
    // Auto-inject HYPERHIVE_STATE_DIR so extra stdio MCP servers can resolve
    // the agent's durable state dir without the agent author hard-coding it.
    // User-supplied env takes precedence — we only fill in the missing key.
    // (Http entries have no child-process env to inject into — the daemon
    // behind the URL resolves its own state dir independently.)
    let state_dir = crate::paths::state_dir();
    // Gate tool-group-restricted extra servers (e.g. `bash` → `Execution`).
    // This is the security boundary for them: an out-of-process server the
    // agent isn't entitled to must not even appear in the MCP config, or the
    // agent could call it directly (there is no later enforcement point).
    let groups = effective_tool_groups();
    for (name, spec) in load_extra_mcp() {
        if name == SERVER_NAME {
            tracing::warn!(
                "extra MCP server name `{SERVER_NAME}` collides with the built-in surface; ignoring",
            );
            continue;
        }
        if !extra_server_enabled(&name, &groups) {
            tracing::info!(
                server = %name,
                "extra MCP server suppressed: agent lacks the required tool group"
            );
            continue;
        }
        let entry = match spec {
            ExtraMcpServer::Stdio {
                command,
                args,
                mut env,
                ..
            } => {
                env.entry("HYPERHIVE_STATE_DIR".to_owned())
                    .or_insert_with(|| state_dir.display().to_string());
                serde_json::json!({ "command": command, "args": args, "env": env })
            }
            ExtraMcpServer::Http { url, .. } => serde_json::json!({ "type": "http", "url": url }),
        };
        servers.insert(name, entry);
    }
    servers
}

#[cfg(test)]
mod tests {
    use super::{SERVER_NAME, allowed_mcp_tools};
    use hive_sh4re::permissions::ToolGroup;

    fn qualified(tool: &str) -> String {
        format!("mcp__{SERVER_NAME}__{tool}")
    }

    #[test]
    fn set_status_present_with_no_groups() {
        // An agent with zero tool groups (or any group set that omits
        // `meta`) must still be able to report its dashboard status.
        let tools = allowed_mcp_tools(&[]);
        assert!(
            tools.contains(&qualified("set_status")),
            "set_status missing from empty-group allow-list: {tools:?}"
        );
    }

    #[test]
    fn mark_todos_done_present_with_no_groups() {
        // Regression: mark_todos_done was declared as a
        // tool but never added to any ToolGroup, so no agent could ever
        // get it into --allowedTools regardless of which groups it held —
        // including `inbox`, which only gates get_loose_ends/
        // cancel_loose_end/remind.
        let tools = allowed_mcp_tools(&[]);
        assert!(
            tools.contains(&qualified("mark_todos_done")),
            "mark_todos_done missing from empty-group allow-list: {tools:?}"
        );
        let tools = allowed_mcp_tools(&[ToolGroup::Inbox]);
        assert!(tools.contains(&qualified("mark_todos_done")));
    }

    #[test]
    fn set_status_present_without_meta_group() {
        let tools = allowed_mcp_tools(&[ToolGroup::Messaging, ToolGroup::Inbox]);
        assert!(tools.contains(&qualified("set_status")));
        // get_agent_meta stays gated behind `meta` — only set_status is always-on.
        assert!(!tools.contains(&qualified("get_agent_meta")));
    }

    #[test]
    fn no_duplicate_set_status_when_meta_granted() {
        let tools = allowed_mcp_tools(&[ToolGroup::Meta]);
        let count = tools
            .iter()
            .filter(|t| **t == qualified("set_status"))
            .count();
        assert_eq!(count, 1, "set_status duplicated: {tools:?}");
        assert!(tools.contains(&qualified("get_agent_meta")));
    }
}