LSP Phase 8: feature gate + Channels struct refactor

Two related changes — splitting into separate commits would have
required disentangling overlapping diffs in the same files.

## Refactor: build_channels returns Channels struct

10-tuple → `struct Channels { ... }`. Same fields, just named.
build_channels returns Channels; main.rs destructures the same locals
it already used. No behavior change, but the call site is no longer a
positional 10-tuple unpacking that breaks every time we add a slot.

Doc-noted in main.rs: `compile_lsp_commands` currently ignores the
`extensions` field on per-server overrides. The claimed-extensions
list lives in the static `builtin_servers()` registry; making it
instance-overridable requires plumbing a per-session server set down
through LspManager. Follow-up; users who need new extensions today
must edit `server.rs`.

## Phase 8: feature gate

Adds `feature = "lsp"` to Cargo.toml's default set. With it off:
- `lsp` module is not compiled; `lsp-types` dep stays optional + skipped.
- `Channels.lsp_manager` field gated out (also gated out of destructure
  in main.rs).
- `build_agent` / `build_agent_inner` / `run_interactive` drop their
  `lsp_manager` arg via `#[cfg(feature = "lsp")]` on the param.
- Read/Write/Edit tools drop their `lsp_manager` field + integration
  call.
- LspTool not registered; `--no-lsp` CLI flag not exposed.
- `LspConfig` / `LspServerConfig` types gated; `cfg.lsp` field gated.
- ACP / slash sub-rebuilds / plan-switch all use `#[cfg(feature = "lsp")]`
  None args.

Verified:
- `cargo build --no-default-features --features 'loop git-worktree mcp'`
  → clean (no lsp deps pulled in).
- `cargo build` (default) → clean, all 4 LSP servers wired.
- `cargo test --no-default-features --features 'loop git-worktree mcp'`
  → 305 passing (LSP module's 121 tests correctly excluded).
- `cargo test` (default) → 426 passing.

Author: Yogthos

Cargo.toml

@@ -11,7 +11,7 @@ readme = "README.md"
 keywords = ["ai", "cli", "dev"]
 
 [features]
-default = ['loop', 'git-worktree', 'mcp']
+default = ['loop', 'git-worktree', 'mcp', 'lsp']
 loop = []
 git-worktree = []
 mcp = [
@@ -26,6 +26,7 @@ semantic-ts = ["semantic", "dep:tree-sitter-typescript"]
 semantic-python = ["semantic", "dep:tree-sitter-python"]
 semantic-bash = ["semantic", "dep:tree-sitter-bash"]
 plugin = ["dep:janetrs"]
+lsp = ["dep:lsp-types"]
 
 [dependencies]
 rig = { version = "0.37", features = ["rmcp"] }
@@ -66,7 +67,7 @@ streaming-iterator = { version = "0.1", optional = true }
 janetrs = { version = "0.8", optional = true }
 html2text = "0.17"
 indexmap = "2"
-lsp-types = "0.97"
+lsp-types = { version = "0.97", optional = true }
 
 [dev-dependencies]
 tokio = { version = "1", features = ["test-util"] }

src/agent/builder.rs

@@ -37,7 +37,7 @@ pub async fn build_agent_inner<M: CompletionModel + 'static>(
     question_tx: Option<QuestionSender>,
     plan_tx: Option<PlanSwitchSender>,
     bg_store: Option<BackgroundStore>,
-    lsp_manager: Option<std::sync::Arc<crate::lsp::manager::LspManager>>,
+    #[cfg(feature = "lsp")] lsp_manager: Option<std::sync::Arc<crate::lsp::manager::LspManager>>,
     sandbox: Sandbox,
     parent_model: Option<AnyModel>,
     #[cfg(feature = "mcp")] mcp_manager: Option<&McpClientManager>,
@@ -141,20 +141,23 @@ pub async fn build_agent_inner<M: CompletionModel + 'static>(
                 permission.clone(),
                 ask_tx.clone(),
                 cache.clone(),
+                #[cfg(feature = "lsp")]
                 lsp_manager.clone(),
             )),
             Box::new(tools::WriteTool::with_cache(
                 permission.clone(),
                 ask_tx.clone(),
                 plan_file.clone(),
                 cache.clone(),
+                #[cfg(feature = "lsp")]
                 lsp_manager.clone(),
             )),
             Box::new(tools::EditTool::with_cache(
                 permission.clone(),
                 ask_tx.clone(),
                 plan_file.clone(),
                 cache.clone(),
+                #[cfg(feature = "lsp")]
                 lsp_manager.clone(),
             )),
             Box::new(tools::BashTool::with_cache(
@@ -262,6 +265,7 @@ pub async fn build_agent_inner<M: CompletionModel + 'static>(
             builder = builder.tools(vec![task_tool, status_tool]);
         }
 
+        #[cfg(feature = "lsp")]
         if let Some(manager) = &lsp_manager {
             let cwd = std::env::current_dir().unwrap_or_else(|_| ".".into());
             let lsp_tool = Box::new(tools::LspTool::new(

src/agent/tools/edit.rs

@@ -1,11 +1,13 @@
 use std::path::PathBuf;
+#[cfg(feature = "lsp")]
 use std::sync::Arc;
 
 use rig::completion::ToolDefinition;
 use rig::tool::Tool;
 
 use crate::agent::tools::cache::ToolCache;
 use crate::agent::tools::{AskSender, EditArgs, PermCheck, ToolError, check_perm_path};
+#[cfg(feature = "lsp")]
 use crate::lsp::manager::LspManager;
 
 pub struct EditTool {
@@ -16,6 +18,7 @@ pub struct EditTool {
     /// When set, the tool touches the edited file on the LSP server and
     /// appends any diagnostic block to its output. `None` reproduces the
     /// pre-LSP behaviour.
+    #[cfg(feature = "lsp")]
     lsp_manager: Option<Arc<LspManager>>,
 }
 
@@ -31,6 +34,7 @@ impl EditTool {
             ask_tx,
             plan_file,
             cache: None,
+            #[cfg(feature = "lsp")]
             lsp_manager: None,
         }
     }
@@ -40,13 +44,14 @@ impl EditTool {
         ask_tx: Option<AskSender>,
         plan_file: Option<PathBuf>,
         cache: ToolCache,
-        lsp_manager: Option<Arc<LspManager>>,
+        #[cfg(feature = "lsp")] lsp_manager: Option<Arc<LspManager>>,
     ) -> Self {
         EditTool {
             permission,
             ask_tx,
             plan_file,
             cache: Some(cache),
+            #[cfg(feature = "lsp")]
             lsp_manager,
         }
     }
@@ -212,6 +217,7 @@ impl Tool for EditTool {
             new_content
         };
 
+        #[cfg(feature = "lsp")]
         let write_at = std::time::Instant::now();
         tokio::fs::write(&args.path, &output).await?;
         // File mutated → invalidate cached reads/greps/listings for this turn.
@@ -236,15 +242,18 @@ impl Tool for EditTool {
             ));
         }
 
-        let path = std::path::Path::new(&args.path);
-        result.push_str(
-            &crate::agent::tools::write::append_lsp_block(
-                self.lsp_manager.as_ref(),
-                path,
-                write_at,
-            )
-            .await,
-        );
+        #[cfg(feature = "lsp")]
+        {
+            let path = std::path::Path::new(&args.path);
+            result.push_str(
+                &crate::agent::tools::write::append_lsp_block(
+                    self.lsp_manager.as_ref(),
+                    path,
+                    write_at,
+                )
+                .await,
+            );
+        }
         Ok(result)
     }
 }

src/agent/tools/mod.rs

@@ -7,6 +7,7 @@ mod find_files;
 mod glob;
 mod grep;
 mod list_dir;
+#[cfg(feature = "lsp")]
 mod lsp;
 mod memory;
 pub(crate) mod plan;
@@ -30,6 +31,7 @@ pub use find_files::FindFilesTool;
 pub use glob::GlobTool;
 pub use grep::GrepTool;
 pub use list_dir::ListDirTool;
+#[cfg(feature = "lsp")]
 pub use lsp::LspTool;
 pub use memory::MemoryTool;
 pub use plan::{PlanEnterTool, PlanExitTool};

src/agent/tools/read.rs

@@ -1,10 +1,12 @@
+#[cfg(feature = "lsp")]
 use std::sync::Arc;
 
 use rig::completion::ToolDefinition;
 use rig::tool::Tool;
 
 use crate::agent::tools::cache::ToolCache;
 use crate::agent::tools::{AskSender, PermCheck, ReadArgs, ToolError, check_perm_path};
+#[cfg(feature = "lsp")]
 use crate::lsp::manager::{LspManager, TouchMode};
 
 pub struct ReadTool {
@@ -14,6 +16,7 @@ pub struct ReadTool {
     /// When set, the tool fires off a `touch_file` to warm the LSP server
     /// so subsequent edits surface diagnostics quickly. Fire-and-forget:
     /// the read tool does not wait or surface diagnostics in its output.
+    #[cfg(feature = "lsp")]
     pub lsp_manager: Option<Arc<LspManager>>,
 }
 
@@ -24,6 +27,7 @@ impl ReadTool {
             permission,
             ask_tx,
             cache: None,
+            #[cfg(feature = "lsp")]
             lsp_manager: None,
         }
     }
@@ -32,12 +36,13 @@ impl ReadTool {
         permission: Option<PermCheck>,
         ask_tx: Option<AskSender>,
         cache: ToolCache,
-        lsp_manager: Option<Arc<LspManager>>,
+        #[cfg(feature = "lsp")] lsp_manager: Option<Arc<LspManager>>,
     ) -> Self {
         ReadTool {
             permission,
             ask_tx,
             cache: Some(cache),
+            #[cfg(feature = "lsp")]
             lsp_manager,
         }
     }
@@ -122,6 +127,7 @@ impl Tool for ReadTool {
         // Fire-and-forget LSP warmup so the server already has the file
         // open by the time the agent edits it (and we can wait_for_push
         // quickly). No diagnostic surfacing on read.
+        #[cfg(feature = "lsp")]
         if let Some(manager) = self.lsp_manager.clone() {
             let path = std::path::PathBuf::from(&args.path);
             tokio::spawn(async move {

src/agent/tools/write.rs

@@ -1,18 +1,23 @@
 use std::path::{Path, PathBuf};
+#[cfg(feature = "lsp")]
 use std::sync::Arc;
+#[cfg(feature = "lsp")]
 use std::time::{Duration, Instant};
 
 use rig::completion::ToolDefinition;
 use rig::tool::Tool;
 
 use crate::agent::tools::cache::ToolCache;
 use crate::agent::tools::{AskSender, PermCheck, ToolError, WriteArgs, check_perm_path};
+#[cfg(feature = "lsp")]
 use crate::lsp::diagnostic;
+#[cfg(feature = "lsp")]
 use crate::lsp::manager::{LspManager, TouchMode};
 
 /// How long to wait for the LSP server to publish fresh diagnostics after
 /// a write. Matches opencode's `DIAGNOSTICS_FULL_WAIT_TIMEOUT_MS`. Bounded
 /// so a stuck server doesn't hold up the agent's turn.
+#[cfg(feature = "lsp")]
 const DIAGNOSTIC_WAIT: Duration = Duration::from_secs(10);
 
 pub struct WriteTool {
@@ -23,6 +28,7 @@ pub struct WriteTool {
     /// When set, the tool touches the file on the LSP server after writing
     /// and appends any resulting diagnostic block to its output. `None`
     /// reproduces the pre-LSP behaviour exactly.
+    #[cfg(feature = "lsp")]
     lsp_manager: Option<Arc<LspManager>>,
 }
 
@@ -38,6 +44,7 @@ impl WriteTool {
             ask_tx,
             plan_file,
             cache: None,
+            #[cfg(feature = "lsp")]
             lsp_manager: None,
         }
     }
@@ -47,13 +54,14 @@ impl WriteTool {
         ask_tx: Option<AskSender>,
         plan_file: Option<PathBuf>,
         cache: ToolCache,
-        lsp_manager: Option<Arc<LspManager>>,
+        #[cfg(feature = "lsp")] lsp_manager: Option<Arc<LspManager>>,
     ) -> Self {
         WriteTool {
             permission,
             ask_tx,
             plan_file,
             cache: Some(cache),
+            #[cfg(feature = "lsp")]
             lsp_manager,
         }
     }
@@ -106,14 +114,17 @@ impl Tool for WriteTool {
             tokio::fs::create_dir_all(parent).await?;
         }
         let bytes = args.content.len();
+        #[cfg(feature = "lsp")]
         let write_at = Instant::now();
         tokio::fs::write(path, &args.content).await?;
         // File mutated → invalidate cached reads/greps/listings for this turn.
         if let Some(ref cache) = self.cache {
             cache.clear();
         }
 
+        #[allow(unused_mut)]
         let mut output = format!("Written {} bytes to {}", bytes, args.path);
+        #[cfg(feature = "lsp")]
         output.push_str(&append_lsp_block(self.lsp_manager.as_ref(), path, write_at).await);
         Ok(output)
     }
@@ -124,6 +135,7 @@ impl Tool for WriteTool {
 /// Errors during touch/wait are intentionally swallowed — diagnostic
 /// surfacing is a side-effect; the write tool's primary contract is
 /// "wrote the file".
+#[cfg(feature = "lsp")]
 pub(crate) async fn append_lsp_block(
     manager: Option<&Arc<LspManager>>,
     path: &Path,
@@ -145,7 +157,7 @@ pub(crate) async fn append_lsp_block(
     diagnostic::build_report_block(path, &diagnostics)
 }
 
-#[cfg(test)]
+#[cfg(all(test, feature = "lsp"))]
 mod tests {
     use super::*;
     use crate::agent::tools::cache::ToolCache;

src/cli.rs

@@ -48,6 +48,7 @@ pub struct Cli {
     #[arg(long = "no-tools", help = "Disable all tools")]
     pub no_tools: bool,
 
+    #[cfg(feature = "lsp")]
     #[arg(
         long = "no-lsp",
         help = "Disable LSP integration (no diagnostics on edit/write, no `lsp` agent tool)"
@@ -167,6 +168,7 @@ impl Cli {
         self.no_tools || cfg.no_tools.unwrap_or(false)
     }
 
+    #[cfg(feature = "lsp")]
     pub fn resolve_lsp_enabled(&self, cfg: &config::Config) -> bool {
         if self.no_lsp || self.no_tools {
             return false;

src/config/mod.rs

@@ -32,6 +32,7 @@ pub struct ToolsConfig {
 /// - `{ "disabled": true }` to turn off a built-in server entirely.
 /// - any subset of `{ command, extensions, env, initialization, disabled }`
 ///   to override pieces of the default.
+#[cfg(feature = "lsp")]
 #[derive(Debug, Default, Clone, Deserialize)]
 #[serde(default)]
 pub struct LspServerConfig {
@@ -46,13 +47,15 @@ pub struct LspServerConfig {
 /// `lsp = false` → disable LSP entirely.
 /// `lsp = { server-id = { … } }` → enable defaults, overriding the named
 ///   servers with the provided config.
+#[cfg(feature = "lsp")]
 #[derive(Debug, Clone, Deserialize)]
 #[serde(untagged)]
 pub enum LspConfig {
     Enabled(bool),
     Servers(HashMap<String, LspServerConfig>),
 }
 
+#[cfg(feature = "lsp")]
 impl LspConfig {
     /// `true` when LSP should be on. Defaults to enabled.
     pub fn is_enabled(&self) -> bool {
@@ -102,6 +105,7 @@ pub struct Config {
     pub tool_result_max_chars: Option<usize>,
     pub default_prompt: Option<String>,
     pub tools: Option<ToolsConfig>,
+    #[cfg(feature = "lsp")]
     pub lsp: Option<LspConfig>,
     #[cfg(feature = "mcp")]
     pub mcp_servers: Option<HashMap<String, McpServerConfig>>,
@@ -194,7 +198,7 @@ pub fn load() -> Config {
     cfg
 }
 
-#[cfg(test)]
+#[cfg(all(test, feature = "lsp"))]
 mod tests {
     use super::*;
 

src/extras/acp/mod.rs

@@ -170,6 +170,7 @@ async fn run_prompt(
         None,
         None,
         None,
+        #[cfg(feature = "lsp")]
         None,
         sandbox,
         #[cfg(feature = "mcp")]