feat(coder): add LSP code intelligence tools

- lsp/ module: types, config, JSON-RPC client, server-manager, operations
- lsp_diagnostics: TypeScript/JavaScript diagnostics for a file
- lsp_goto_definition: find symbol definition at position
- lsp_find_references: find all references to a symbol
- Registered as READ_TOOLS in tool index

apps/coder/src/services/lsp/client.ts

@@ -0,0 +1,75 @@
+import { createInterface } from 'node:readline';
+import type { Readable, Writable } from 'node:stream';
+
+interface RpcRequest {
+  jsonrpc: '2.0';
+  id: number;
+  method: string;
+  params?: unknown;
+}
+
+interface RpcResponse {
+  jsonrpc: '2.0';
+  id: number;
+  result?: unknown;
+  error?: { code: number; message: string };
+}
+
+export class LspClient {
+  private nextId = 1;
+  private pending = new Map<number, { resolve: (v: RpcResponse) => void; reject: (e: Error) => void }>();
+  private buffer = '';
+
+  constructor(
+    private stdin: Writable,
+    private stdout: Readable,
+  ) {
+    const rl = createInterface({ input: stdout, crlfDelay: Infinity });
+    rl.on('line', (line) => this.handleLine(line));
+  }
+
+  private handleLine(line: string): void {
+    this.buffer += line + '\n';
+    const match = this.buffer.match(/Content-Length: (\d+)\r?\n\r?\n/);
+    if (!match || !match[1]) return;
+    const len = parseInt(match[1], 10);
+    const headerEnd = match.index! + match[0].length;
+    const body = this.buffer.slice(headerEnd, headerEnd + len);
+    if (body.length < len) return;
+    this.buffer = this.buffer.slice(headerEnd + len);
+    try {
+      const msg: RpcResponse = JSON.parse(body);
+      const cb = this.pending.get(msg.id);
+      if (cb) {
+        this.pending.delete(msg.id);
+        cb.resolve(msg);
+      }
+    } catch {
+      // Malformed JSON, ignore
+    }
+  }
+
+  async request(method: string, params?: unknown): Promise<unknown> {
+    const id = this.nextId++;
+    const req: RpcRequest = { jsonrpc: '2.0', id, method, params };
+    const body = JSON.stringify(req);
+    const header = `Content-Length: ${Buffer.byteLength(body, 'utf8')}\r\n\r\n`;
+
+    return new Promise((resolve, reject) => {
+      this.pending.set(id, {
+        resolve: (resp) => {
+          if (resp.error) reject(new Error(resp.error.message));
+          else resolve(resp.result);
+        },
+        reject,
+      });
+      this.stdin.write(header + body);
+    });
+  }
+
+  async notify(method: string, params?: unknown): Promise<void> {
+    const body = JSON.stringify({ jsonrpc: '2.0', method, params });
+    const header = `Content-Length: ${Buffer.byteLength(body, 'utf8')}\r\n\r\n`;
+    this.stdin.write(header + body);
+  }
+}

apps/coder/src/services/lsp/config.ts

@@ -0,0 +1,19 @@
+export interface LspServerConfig {
+  command: string;
+  args: string[];
+  rootPatterns: string[];
+}
+
+const TS_CONFIG: LspServerConfig = {
+  command: 'typescript-language-server',
+  args: ['--stdio'],
+  rootPatterns: ['package.json', 'tsconfig.json'],
+};
+
+const SUPPORTED_EXTS = new Set(['ts', 'tsx', 'js', 'jsx', 'mjs', 'cjs']);
+
+export function getServerConfig(filePath: string): LspServerConfig | null {
+  const ext = filePath.split('.').pop()?.toLowerCase();
+  if (ext && SUPPORTED_EXTS.has(ext)) return TS_CONFIG;
+  return null;
+}

apps/coder/src/services/lsp/operations.ts

@@ -0,0 +1,86 @@
+import type { LspClient } from './client.js';
+import type { Diagnostic, Location } from './types.js';
+
+function fileUri(filePath: string): string {
+  return `file://${filePath.startsWith('/') ? '' : '/'}${filePath}`;
+}
+
+export async function openDocument(
+  client: LspClient,
+  filePath: string,
+  content: string,
+  version: number = 1,
+): Promise<void> {
+  const uri = fileUri(filePath);
+  await client.notify('textDocument/didOpen', {
+    textDocument: { uri, languageId: 'typescript', version, text: content },
+  });
+}
+
+export async function closeDocument(client: LspClient, filePath: string): Promise<void> {
+  await client.notify('textDocument/didClose', {
+    textDocument: { uri: fileUri(filePath) },
+  });
+}
+
+export async function getDiagnostics(
+  client: LspClient,
+  filePath: string,
+  content: string,
+): Promise<Diagnostic[]> {
+  const uri = fileUri(filePath);
+  await openDocument(client, filePath, content);
+  const result: any = await client.request('textDocument/diagnostic', {
+    textDocument: { uri },
+  });
+  await closeDocument(client, filePath);
+  const diagnostics: Diagnostic[] = [];
+  if (result?.diagnostics) {
+    for (const d of result.diagnostics) {
+      diagnostics.push({
+        range: d.range,
+        severity: d.severity ?? 1,
+        message: d.message,
+        source: d.source,
+      });
+    }
+  }
+  return diagnostics;
+}
+
+export async function gotoDefinition(
+  client: LspClient,
+  filePath: string,
+  content: string,
+  line: number,
+  character: number,
+): Promise<Location | null> {
+  const uri = fileUri(filePath);
+  await openDocument(client, filePath, content);
+  const result: any = await client.request('textDocument/definition', {
+    textDocument: { uri },
+    position: { line, character },
+  });
+  await closeDocument(client, filePath);
+  if (!result) return null;
+  const loc = Array.isArray(result) ? result[0] : result;
+  return loc ? { uri: loc.uri, range: loc.range } : null;
+}
+
+export async function findReferences(
+  client: LspClient,
+  filePath: string,
+  content: string,
+  line: number,
+  character: number,
+): Promise<Location[]> {
+  const uri = fileUri(filePath);
+  await openDocument(client, filePath, content);
+  const result: any = await client.request('textDocument/references', {
+    textDocument: { uri },
+    position: { line, character },
+    context: { includeDeclaration: true },
+  });
+  await closeDocument(client, filePath);
+  return (result ?? []).map((loc: any) => ({ uri: loc.uri, range: loc.range }));
+}

apps/coder/src/services/lsp/server-manager.ts

@@ -0,0 +1,119 @@
+import { spawn, type ChildProcess } from 'node:child_process';
+import { join } from 'node:path';
+import { existsSync } from 'node:fs';
+import { LspClient } from './client.js';
+import { getServerConfig } from './config.js';
+
+const IDLE_TIMEOUT_MS = 5 * 60 * 1000;
+const SWEEP_INTERVAL_MS = 30_000;
+
+interface LspInstance {
+  client: LspClient;
+  proc: ChildProcess;
+  lastUsed: number;
+  timer: ReturnType<typeof setTimeout>;
+}
+
+export class LspServerManager {
+  private instances = new Map<string, LspInstance>();
+  private sweepTimer: ReturnType<typeof setInterval> | null = null;
+
+  constructor() {
+    this.startSweeper();
+  }
+
+  private startSweeper(): void {
+    this.sweepTimer = setInterval(() => this.sweep(), SWEEP_INTERVAL_MS);
+    this.sweepTimer.unref?.();
+  }
+
+  private findProjectRoot(filePath: string): string | null {
+    let dir = filePath;
+    const config = getServerConfig(filePath);
+    if (!config) return null;
+    while (true) {
+      for (const pattern of config.rootPatterns) {
+        if (existsSync(join(dir, pattern))) return dir;
+      }
+      const parent = join(dir, '..');
+      if (parent === dir) return dir;
+      dir = parent;
+    }
+  }
+
+  async getClient(filePath: string): Promise<LspClient | null> {
+    const config = getServerConfig(filePath);
+    if (!config) return null;
+    const projectRoot = this.findProjectRoot(filePath);
+    if (!projectRoot) return null;
+
+    const existing = this.instances.get(projectRoot);
+    if (existing) {
+      existing.lastUsed = Date.now();
+      clearTimeout(existing.timer);
+      existing.timer = setTimeout(() => this.kill(projectRoot), IDLE_TIMEOUT_MS);
+      existing.timer.unref?.();
+      return existing.client;
+    }
+
+    return this.spawn(projectRoot, config.command, config.args);
+  }
+
+  private async spawn(projectRoot: string, command: string, args: string[]): Promise<LspClient> {
+    const proc = spawn(command, args, { stdio: ['pipe', 'pipe', 'pipe'], cwd: projectRoot });
+    const client = new LspClient(proc.stdin!, proc.stdout!);
+
+    await client.request('initialize', {
+      processId: process.pid,
+      rootUri: `file://${projectRoot}`,
+      capabilities: {
+        textDocument: {
+          diagnostic: { dynamicRegistration: false },
+          definition: { dynamicRegistration: false },
+          references: { dynamicRegistration: false },
+        },
+      },
+    });
+    await client.notify('initialized', {});
+
+    const timer = setTimeout(() => this.kill(projectRoot), IDLE_TIMEOUT_MS);
+    timer.unref?.();
+
+    this.instances.set(projectRoot, { client, proc, lastUsed: Date.now(), timer });
+    proc.on('exit', () => this.instances.delete(projectRoot));
+
+    return client;
+  }
+
+  private kill(projectRoot: string): void {
+    const inst = this.instances.get(projectRoot);
+    if (!inst) return;
+    this.instances.delete(projectRoot);
+    inst.proc.kill('SIGTERM');
+    setTimeout(() => {
+      if (inst.proc.exitCode === null) inst.proc.kill('SIGKILL');
+    }, 5000);
+  }
+
+  private sweep(): void {
+    const now = Date.now();
+    for (const [root, inst] of this.instances) {
+      if (now - inst.lastUsed > IDLE_TIMEOUT_MS) {
+        this.kill(root);
+      }
+    }
+  }
+
+  shutdown(): void {
+    if (this.sweepTimer) clearInterval(this.sweepTimer);
+    for (const root of [...this.instances.keys()]) {
+      this.kill(root);
+    }
+  }
+
+  getActiveCount(): number {
+    return this.instances.size;
+  }
+}
+
+export const lspManager = new LspServerManager();

apps/coder/src/services/lsp/types.ts

@@ -0,0 +1,28 @@
+export interface Position {
+  line: number;
+  character: number;
+}
+
+export interface Range {
+  start: Position;
+  end: Position;
+}
+
+export interface Location {
+  uri: string;
+  range: Range;
+}
+
+export interface Diagnostic {
+  range: Range;
+  severity: number;
+  message: string;
+  source?: string;
+}
+
+export interface TextDocumentItem {
+  uri: string;
+  languageId: string;
+  version: number;
+  text: string;
+}

apps/coder/src/services/tools/index.ts

@@ -7,6 +7,9 @@ import { rewindTool } from './rewind.js';
 import { newTaskTool } from './new_task.js';
 import { listTasksTool } from './list_tasks.js';
 import { checkTaskStatusTool } from './check_task_status.js';
+import { lspDiagnosticsTool } from './lsp_diagnostics.js';
+import { lspGotoDefinitionTool } from './lsp_goto_definition.js';
+import { lspFindReferencesTool } from './lsp_find_references.js';
 
 export type { ToolDef, ToolContext, ToolJsonSchema } from './types.js';
 
@@ -26,4 +29,16 @@ export const WRITE_TOOLS: readonly ToolDef<any>[] = [
   checkTaskStatusTool,
 ];
 
-export { editFileTool, createFileTool, deleteFileTool, applyPendingTool, rewindTool, newTaskTool, listTasksTool, checkTaskStatusTool };
+// Read-only agent tools for code intelligence.
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+export const READ_TOOLS: readonly ToolDef<any>[] = [
+  lspDiagnosticsTool,
+  lspGotoDefinitionTool,
+  lspFindReferencesTool,
+];
+
+export {
+  editFileTool, createFileTool, deleteFileTool, applyPendingTool, rewindTool,
+  newTaskTool, listTasksTool, checkTaskStatusTool,
+  lspDiagnosticsTool, lspGotoDefinitionTool, lspFindReferencesTool,
+};

apps/coder/src/services/tools/lsp_diagnostics.ts

@@ -0,0 +1,48 @@
+import { z } from 'zod';
+import { readFile } from 'node:fs/promises';
+import type { ToolDef, ToolContext } from './types.js';
+import { resolveWritePath } from '../write_guard.js';
+import { lspManager } from '../lsp/server-manager.js';
+import { getDiagnostics } from '../lsp/operations.js';
+
+const LspDiagnosticsInput = z.object({
+  file_path: z.string().describe('Path to the file to check for diagnostics'),
+});
+
+type InputT = z.infer<typeof LspDiagnosticsInput>;
+
+export const lspDiagnosticsTool: ToolDef<InputT> = {
+  name: 'lsp_diagnostics',
+  description: 'Get TypeScript/JavaScript diagnostics (errors, warnings) for a file. Returns diagnostic messages with severity and location.',
+  inputSchema: LspDiagnosticsInput,
+  jsonSchema: {
+    type: 'function',
+    function: {
+      name: 'lsp_diagnostics',
+      description: 'Get TypeScript/JavaScript diagnostics for a file',
+      parameters: {
+        type: 'object',
+        properties: {
+          file_path: { type: 'string', description: 'Path to the file' },
+        },
+        required: ['file_path'],
+      },
+    },
+  },
+
+  async execute(input: InputT, projectRoot: string, _context: ToolContext): Promise<unknown> {
+    const resolved = await resolveWritePath(projectRoot, input.file_path);
+    const content = await readFile(resolved, 'utf8');
+    const client = await lspManager.getClient(resolved);
+    if (!client) return { error: 'Unsupported file type for LSP diagnostics' };
+
+    const diagnostics = await getDiagnostics(client, resolved, content);
+    if (diagnostics.length === 0) return { result: 'No diagnostics found.' };
+
+    const lines = diagnostics.map((d) => {
+      const sev = ['', 'error', 'warning', 'info', 'hint'][d.severity] ?? 'unknown';
+      return `[${sev}] line ${d.range.start.line + 1}:${d.range.start.character + 1} - ${d.message}`;
+    });
+    return { result: lines.join('\n') };
+  },
+};

apps/coder/src/services/tools/lsp_find_references.ts

@@ -0,0 +1,49 @@
+import { z } from 'zod';
+import { readFile } from 'node:fs/promises';
+import type { ToolDef, ToolContext } from './types.js';
+import { resolveWritePath } from '../write_guard.js';
+import { lspManager } from '../lsp/server-manager.js';
+import { findReferences } from '../lsp/operations.js';
+
+const LspFindReferencesInput = z.object({
+  file_path: z.string().describe('Path to the source file'),
+  line: z.number().int().nonnegative().describe('0-based line number'),
+  character: z.number().int().nonnegative().describe('0-based character offset'),
+});
+
+type InputT = z.infer<typeof LspFindReferencesInput>;
+
+export const lspFindReferencesTool: ToolDef<InputT> = {
+  name: 'lsp_find_references',
+  description: 'Find all references to a symbol at a given position in a file.',
+  inputSchema: LspFindReferencesInput,
+  jsonSchema: {
+    type: 'function',
+    function: {
+      name: 'lsp_find_references',
+      description: 'Find all references to symbol at position',
+      parameters: {
+        type: 'object',
+        properties: {
+          file_path: { type: 'string' },
+          line: { type: 'number' },
+          character: { type: 'number' },
+        },
+        required: ['file_path', 'line', 'character'],
+      },
+    },
+  },
+
+  async execute(input: InputT, projectRoot: string, _context: ToolContext): Promise<unknown> {
+    const resolved = await resolveWritePath(projectRoot, input.file_path);
+    const content = await readFile(resolved, 'utf8');
+    const client = await lspManager.getClient(resolved);
+    if (!client) return { error: 'Unsupported file type' };
+
+    const refs = await findReferences(client, resolved, content, input.line, input.character);
+    if (refs.length === 0) return { result: 'No references found.' };
+
+    const lines = refs.map((r) => `${r.uri}:${r.range.start.line + 1}:${r.range.start.character + 1}`);
+    return { result: `Found ${refs.length} reference(s):\n${lines.join('\n')}` };
+  },
+};

apps/coder/src/services/tools/lsp_goto_definition.ts

@@ -0,0 +1,48 @@
+import { z } from 'zod';
+import { readFile } from 'node:fs/promises';
+import type { ToolDef, ToolContext } from './types.js';
+import { resolveWritePath } from '../write_guard.js';
+import { lspManager } from '../lsp/server-manager.js';
+import { gotoDefinition } from '../lsp/operations.js';
+
+const LspGotoDefinitionInput = z.object({
+  file_path: z.string().describe('Path to the source file'),
+  line: z.number().int().nonnegative().describe('0-based line number'),
+  character: z.number().int().nonnegative().describe('0-based character offset'),
+});
+
+type InputT = z.infer<typeof LspGotoDefinitionInput>;
+
+export const lspGotoDefinitionTool: ToolDef<InputT> = {
+  name: 'lsp_goto_definition',
+  description: 'Find the definition of a symbol at a given position in a file.',
+  inputSchema: LspGotoDefinitionInput,
+  jsonSchema: {
+    type: 'function',
+    function: {
+      name: 'lsp_goto_definition',
+      description: 'Find definition of symbol at position',
+      parameters: {
+        type: 'object',
+        properties: {
+          file_path: { type: 'string' },
+          line: { type: 'number' },
+          character: { type: 'number' },
+        },
+        required: ['file_path', 'line', 'character'],
+      },
+    },
+  },
+
+  async execute(input: InputT, projectRoot: string, _context: ToolContext): Promise<unknown> {
+    const resolved = await resolveWritePath(projectRoot, input.file_path);
+    const content = await readFile(resolved, 'utf8');
+    const client = await lspManager.getClient(resolved);
+    if (!client) return { error: 'Unsupported file type' };
+
+    const loc = await gotoDefinition(client, resolved, content, input.line, input.character);
+    if (!loc) return { result: 'No definition found.' };
+
+    return { result: `Defined at ${loc.uri}:${loc.range.start.line + 1}:${loc.range.start.character + 1}` };
+  },
+};