diff --git a/apps/coder/src/index.ts b/apps/coder/src/index.ts
index 4de35df..78a69de 100644
--- a/apps/coder/src/index.ts
+++ b/apps/coder/src/index.ts
@@ -23,7 +23,11 @@ import { setInferenceContext, clearInferenceContext } from './services/tools/inf
 // Routes
 import { registerMessageRoutes } from './routes/messages.js';
 import { registerPendingRoutes } from './routes/pending.js';
+import { registerTaskRoutes } from './routes/tasks.js';
 import { registerWebSocket } from './routes/ws.js';
+// Phase 4: dispatcher + agent probe
+import { createDispatcher } from './services/dispatcher.js';
+import { probeAgents } from './services/agent-probe.js';
 
 async function main() {
   const config = loadConfig();
@@ -113,9 +117,18 @@ async function main() {
     });
   });
 
+  // Phase 4: probe available agents on startup
+  await probeAgents(sql, app.log);
+
+  // Phase 4: dispatcher — polls tasks table and runs inference
+  const dispatcher = createDispatcher({ sql, inference: inferenceApi, broker, log: app.log, config });
+  dispatcher.start();
+  app.addHook('onClose', () => dispatcher.stop());
+
   // Register routes
   registerMessageRoutes(app, sql, broker, inferenceApi);
   registerPendingRoutes(app, sql);
+  registerTaskRoutes(app, sql, inferenceApi);
   registerWebSocket(app, sql, broker);
 
   // Serve static frontend (built web app). In production, the dist/ is
diff --git a/apps/coder/src/routes/tasks.ts b/apps/coder/src/routes/tasks.ts
new file mode 100644
index 0000000..021d1e3
--- /dev/null
+++ b/apps/coder/src/routes/tasks.ts
@@ -0,0 +1,138 @@
+import type { FastifyInstance } from 'fastify';
+import { z } from 'zod';
+import type { Sql } from '../db.js';
+
+interface InferenceApi {
+  cancel: (sessionId: string, chatId: string) => Promise<boolean>;
+}
+
+const CreateBody = z.object({
+  project_id: z.string().uuid(),
+  input: z.string().min(1).max(64_000),
+  agent: z.string().max(100).optional(),
+  model: z.string().max(200).optional(),
+});
+
+const ListQuery = z.object({
+  state: z.enum(['pending', 'running', 'completed', 'failed', 'blocked', 'cancelled']).optional(),
+  project_id: z.string().uuid().optional(),
+});
+
+export function registerTaskRoutes(app: FastifyInstance, sql: Sql, inference: InferenceApi): void {
+  // POST /api/tasks — create a new task
+  app.post('/api/tasks', async (req, reply) => {
+    const parsed = CreateBody.safeParse(req.body);
+    if (!parsed.success) {
+      reply.code(400);
+      return { error: 'invalid body', details: parsed.error.flatten() };
+    }
+
+    const { project_id, input, agent, model } = parsed.data;
+
+    const [task] = await sql<{ id: string; state: string }[]>`
+      INSERT INTO tasks (project_id, input, agent, model)
+      VALUES (${project_id}, ${input}, ${agent ?? null}, ${model ?? null})
+      RETURNING id, state
+    `;
+
+    reply.code(201);
+    return { id: task!.id, state: task!.state };
+  });
+
+  // GET /api/tasks — list tasks with optional filters
+  app.get('/api/tasks', async (req, _reply) => {
+    const parsed = ListQuery.safeParse(req.query);
+    if (!parsed.success) {
+      return { error: 'invalid query', details: parsed.error.flatten() };
+    }
+
+    const { state, project_id } = parsed.data;
+
+    // Build query with optional filters
+    if (state && project_id) {
+      return sql`
+        SELECT id, project_id, state, input, output_summary, agent, model, execution_path, session_id, started_at, ended_at, created_at
+        FROM tasks
+        WHERE state = ${state} AND project_id = ${project_id}
+        ORDER BY created_at DESC
+        LIMIT 100
+      `;
+    } else if (state) {
+      return sql`
+        SELECT id, project_id, state, input, output_summary, agent, model, execution_path, session_id, started_at, ended_at, created_at
+        FROM tasks
+        WHERE state = ${state}
+        ORDER BY created_at DESC
+        LIMIT 100
+      `;
+    } else if (project_id) {
+      return sql`
+        SELECT id, project_id, state, input, output_summary, agent, model, execution_path, session_id, started_at, ended_at, created_at
+        FROM tasks
+        WHERE project_id = ${project_id}
+        ORDER BY created_at DESC
+        LIMIT 100
+      `;
+    } else {
+      return sql`
+        SELECT id, project_id, state, input, output_summary, agent, model, execution_path, session_id, started_at, ended_at, created_at
+        FROM tasks
+        ORDER BY created_at DESC
+        LIMIT 100
+      `;
+    }
+  });
+
+  // GET /api/tasks/:id — single task detail
+  app.get<{ Params: { id: string } }>('/api/tasks/:id', async (req, reply) => {
+    const rows = await sql`
+      SELECT id, project_id, parent_task_id, state, input, output_summary, agent, model, execution_path, worktree_path, session_id, cost_tokens, started_at, ended_at, created_at
+      FROM tasks
+      WHERE id = ${req.params.id}
+    `;
+    if (rows.length === 0) {
+      reply.code(404);
+      return { error: 'task not found' };
+    }
+    return rows[0];
+  });
+
+  // POST /api/tasks/:id/cancel — cancel a pending or running task
+  app.post<{ Params: { id: string } }>('/api/tasks/:id/cancel', async (req, reply) => {
+    const taskId = req.params.id;
+
+    // Get current task state + session info
+    const rows = await sql<{ id: string; state: string; session_id: string | null }[]>`
+      SELECT id, state, session_id FROM tasks WHERE id = ${taskId}
+    `;
+    if (rows.length === 0) {
+      reply.code(404);
+      return { error: 'task not found' };
+    }
+
+    const task = rows[0]!;
+    if (task.state !== 'pending' && task.state !== 'running') {
+      reply.code(409);
+      return { error: `cannot cancel task in state '${task.state}'` };
+    }
+
+    // If running, try to cancel inference
+    if (task.state === 'running' && task.session_id) {
+      // Find active chat in the task's session
+      const chats = await sql<{ id: string }[]>`
+        SELECT id FROM chats WHERE session_id = ${task.session_id} AND status = 'open'
+      `;
+      for (const chat of chats) {
+        await inference.cancel(task.session_id, chat.id);
+      }
+    }
+
+    await sql`
+      UPDATE tasks
+      SET state = 'cancelled', ended_at = clock_timestamp()
+      WHERE id = ${taskId} AND state IN ('pending', 'running')
+    `;
+
+    return { cancelled: true };
+  });
+}
diff --git a/apps/coder/src/schema.sql b/apps/coder/src/schema.sql
index 76ac92f..63f8de1 100644
--- a/apps/coder/src/schema.sql
+++ b/apps/coder/src/schema.sql
@@ -43,6 +43,9 @@ CREATE TABLE IF NOT EXISTS available_agents (
   last_probed_at TIMESTAMPTZ
 );
 
+-- v2.0.0 Phase 4: link tasks to their inference sessions.
+ALTER TABLE tasks ADD COLUMN IF NOT EXISTS session_id UUID REFERENCES sessions(id);
+
 -- Human inbox: tasks needing attention
 CREATE OR REPLACE VIEW human_inbox AS
   SELECT * FROM tasks WHERE state IN ('blocked', 'failed');
diff --git a/apps/coder/src/services/agent-probe.ts b/apps/coder/src/services/agent-probe.ts
new file mode 100644
index 0000000..cbdb841
--- /dev/null
+++ b/apps/coder/src/services/agent-probe.ts
@@ -0,0 +1,51 @@
+import { execFile } from 'node:child_process';
+import { promisify } from 'node:util';
+import type { Sql } from '../db.js';
+import type { FastifyBaseLogger } from 'fastify';
+
+const execFileAsync = promisify(execFile);
+
+const KNOWN_AGENTS: Array<{ name: string; supportsAcp: boolean }> = [
+  { name: 'opencode', supportsAcp: true },
+  { name: 'goose', supportsAcp: true },
+  { name: 'claude', supportsAcp: false },
+  { name: 'pi', supportsAcp: false },
+];
+
+export async function probeAgents(sql: Sql, log: FastifyBaseLogger): Promise<void> {
+  log.info('agent-probe: scanning PATH for known agents');
+
+  for (const agent of KNOWN_AGENTS) {
+    try {
+      // Check if the agent binary is on PATH
+      const { stdout: whichOut } = await execFileAsync('which', [agent.name], { timeout: 5_000 });
+      const installPath = whichOut.trim();
+      if (!installPath) continue;
+
+      // Get version
+      let version: string | null = null;
+      try {
+        const { stdout: verOut } = await execFileAsync(agent.name, ['--version'], { timeout: 10_000 });
+        version = verOut.trim().slice(0, 100);
+      } catch {
+        // Some agents may not support --version — that's fine
+      }
+
+      // UPSERT into available_agents
+      await sql`
+        INSERT INTO available_agents (name, install_path, version, supports_acp, last_probed_at)
+        VALUES (${agent.name}, ${installPath}, ${version}, ${agent.supportsAcp}, clock_timestamp())
+        ON CONFLICT (name) DO UPDATE SET
+          install_path = EXCLUDED.install_path,
+          version = EXCLUDED.version,
+          supports_acp = EXCLUDED.supports_acp,
+          last_probed_at = EXCLUDED.last_probed_at
+      `;
+      log.info({ agent: agent.name, version, installPath }, 'agent-probe: found');
+    } catch {
+      // Agent not found on PATH — skip silently
+    }
+  }
+
+  log.info('agent-probe: scan complete');
+}
diff --git a/apps/coder/src/services/dispatcher.ts b/apps/coder/src/services/dispatcher.ts
new file mode 100644
index 0000000..9117f88
--- /dev/null
+++ b/apps/coder/src/services/dispatcher.ts
@@ -0,0 +1,191 @@
+import type { Sql } from '../db.js';
+import type { FastifyBaseLogger } from 'fastify';
+import type { Broker } from '@boocode/server/broker';
+import type { Config } from '../config.js';
+
+interface InferenceRunner {
+  enqueue: (sessionId: string, chatId: string, assistantId: string, user: string) => void;
+  cancel: (sessionId: string, chatId: string) => Promise<boolean>;
+  hasActive: (chatId: string) => boolean;
+}
+
+interface Deps {
+  sql: Sql;
+  inference: InferenceRunner;
+  broker: Broker;
+  log: FastifyBaseLogger;
+  config: Config;
+}
+
+const POLL_INTERVAL_MS = 5_000;
+const COMPLETION_POLL_MS = 2_000;
+
+export function createDispatcher(deps: Deps): { start(): void; stop(): Promise<void> } {
+  const { sql, inference, log, config } = deps;
+  let timer: ReturnType<typeof setInterval> | null = null;
+  let running = false;
+  let stopping = false;
+  let inflightPromise: Promise<void> | null = null;
+
+  async function poll(): Promise<void> {
+    if (running || stopping) return;
+
+    // Grab one pending task
+    const rows = await sql<{ id: string; project_id: string; input: string; agent: string | null; model: string | null }[]>`
+      SELECT id, project_id, input, agent, model
+      FROM tasks
+      WHERE state = 'pending'
+      ORDER BY created_at
+      LIMIT 1
+    `;
+    if (rows.length === 0) return;
+
+    const task = rows[0]!;
+    running = true;
+    inflightPromise = runTask(task).finally(() => {
+      running = false;
+      inflightPromise = null;
+    });
+  }
+
+  async function runTask(task: { id: string; project_id: string; input: string; agent: string | null; model: string | null }): Promise<void> {
+    const taskId = task.id;
+    log.info({ taskId }, 'dispatcher: starting task');
+
+    try {
+      // Mark running
+      await sql`
+        UPDATE tasks
+        SET state = 'running', started_at = clock_timestamp(), execution_path = 'native'
+        WHERE id = ${taskId}
+      `;
+
+      // Create session + chat for this task
+      const model = task.model ?? config.DEFAULT_MODEL;
+      const sessionName = 'Task: ' + task.input.slice(0, 40);
+
+      const [session] = await sql<{ id: string }[]>`
+        INSERT INTO sessions (project_id, name, model, status)
+        VALUES (${task.project_id}, ${sessionName}, ${model}, 'open')
+        RETURNING id
+      `;
+      const sessionId = session!.id;
+
+      const [chat] = await sql<{ id: string }[]>`
+        INSERT INTO chats (session_id, name, status)
+        VALUES (${sessionId}, 'Task execution', 'open')
+        RETURNING id
+      `;
+      const chatId = chat!.id;
+
+      // Link task to session
+      await sql`UPDATE tasks SET session_id = ${sessionId} WHERE id = ${taskId}`;
+
+      // Create user message + streaming assistant
+      await sql<{ id: string }[]>`
+        INSERT INTO messages (session_id, chat_id, role, content, status, created_at)
+        VALUES (${sessionId}, ${chatId}, 'user', ${task.input}, 'complete', clock_timestamp())
+        RETURNING id
+      `;
+      const [assistantMsg] = await sql<{ id: string }[]>`
+        INSERT INTO messages (session_id, chat_id, role, content, status, created_at)
+        VALUES (${sessionId}, ${chatId}, 'assistant', '', 'streaming', clock_timestamp())
+        RETURNING id
+      `;
+      const assistantId = assistantMsg!.id;
+
+      // Enqueue inference
+      inference.enqueue(sessionId, chatId, assistantId, 'default');
+
+      // Wait for inference to complete (poll message status)
+      const finalStatus = await waitForCompletion(assistantId);
+
+      if (stopping) {
+        // Graceful shutdown — mark cancelled
+        await sql`
+          UPDATE tasks
+          SET state = 'cancelled', ended_at = clock_timestamp()
+          WHERE id = ${taskId}
+        `;
+        return;
+      }
+
+      if (finalStatus === 'complete') {
+        // Grab assistant content for output_summary
+        const [msg] = await sql<{ content: string | null }[]>`
+          SELECT content FROM messages WHERE id = ${assistantId}
+        `;
+        const summary = (msg?.content ?? '').slice(0, 500);
+        await sql`
+          UPDATE tasks
+          SET state = 'completed', ended_at = clock_timestamp(), output_summary = ${summary}
+          WHERE id = ${taskId}
+        `;
+        log.info({ taskId }, 'dispatcher: task completed');
+      } else {
+        // failed or cancelled
+        const [msg] = await sql<{ content: string | null }[]>`
+          SELECT content FROM messages WHERE id = ${assistantId}
+        `;
+        const summary = (msg?.content ?? 'Inference failed').slice(0, 500);
+        await sql`
+          UPDATE tasks
+          SET state = 'failed', ended_at = clock_timestamp(), output_summary = ${summary}
+          WHERE id = ${taskId}
+        `;
+        log.warn({ taskId, finalStatus }, 'dispatcher: task failed');
+      }
+    } catch (err) {
+      const errMsg = err instanceof Error ? err.message : String(err);
+      log.error({ taskId, err: errMsg }, 'dispatcher: task error');
+      await sql`
+        UPDATE tasks
+        SET state = 'failed', ended_at = clock_timestamp(), output_summary = ${errMsg.slice(0, 500)}
+        WHERE id = ${taskId}
+      `.catch(() => {}); // best-effort
+    }
+  }
+
+  async function waitForCompletion(assistantId: string): Promise<string> {
+    // Poll until the assistant message is no longer streaming
+    for (;;) {
+      if (stopping) return 'cancelled';
+
+      const [row] = await sql<{ status: string }[]>`
+        SELECT status FROM messages WHERE id = ${assistantId}
+      `;
+      const status = row?.status ?? 'failed';
+      if (status !== 'streaming') return status;
+
+      await sleep(COMPLETION_POLL_MS);
+    }
+  }
+
+  function sleep(ms: number): Promise<void> {
+    return new Promise((resolve) => setTimeout(resolve, ms));
+  }
+
+  return {
+    start() {
+      log.info('dispatcher: starting poll loop');
+      timer = setInterval(() => {
+        poll().catch((err) => {
+          log.error({ err }, 'dispatcher: poll error');
+        });
+      }, POLL_INTERVAL_MS);
+    },
+
+    async stop() {
+      stopping = true;
+      if (timer) {
+        clearInterval(timer);
+        timer = null;
+      }
+      if (inflightPromise) {
+        log.info('dispatcher: waiting for in-flight task');
+        await inflightPromise;
+      }
+      log.info('dispatcher: stopped');
+    },
+  };
+}