diff --git a/CLAUDE.md b/CLAUDE.md
index 60b54ad..92542a4 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -4,7 +4,8 @@
 Multi-agent orchestrator that runs parallel Claude Code agents in git worktrees. Tasks submitted via REST API, monitored via SSE, agents auto-commit and merge to main.
 
 ## Architecture
-- **src/index.ts** — CLI entry point (Commander.js)
+- **src/index.ts** — Server entry point (Commander.js)
+- **src/cli.ts** — CLI client commands (submit, list, status, diff, logs, stats, workers, search, cancel, retry, watch)
 - **src/server.ts** — Hono REST API + SSE
 - **src/scheduler.ts** — Task queue, priority dispatch, retry logic, stale worker recovery
 - **src/agent-runner.ts** — Multi-agent CLI spawning (Claude, Codex, generic), cost tracking, code review
@@ -29,7 +30,7 @@ node dist/index.js --repo /path/to/repo --workers 5 --port 8080
 ```
 
 ```bash
-# Run tests (255 tests across 6 suites)
+# Run tests (282 tests across 8 suites)
 node --import tsx --test src/__tests__/*.test.ts
 ```
 
@@ -37,7 +38,7 @@ node --import tsx --test src/__tests__/*.test.ts
 - Always use `.js` extensions in TypeScript imports (ESM)
 - Run `npx tsc` after changes to verify compilation
 - Only modify core files — do NOT create standalone utility modules
-- Core files: server.ts, scheduler.ts, store.ts, agent-runner.ts, worktree-pool.ts, index.ts, types.ts, logger.ts
+- Core files: server.ts, scheduler.ts, store.ts, agent-runner.ts, worktree-pool.ts, index.ts, cli.ts, types.ts, logger.ts
 - Keep changes minimal and focused — one concern per change
 - Always `git add -A && git commit` after successful changes
 
@@ -139,7 +140,9 @@ pending → running → success (branch merged to main)
 - `src/__tests__/scheduler.test.ts` — Submit, cancel, stats, queue position
 - `src/__tests__/agent-runner.test.ts` — Cost estimation, code review, system prompt, CLI dispatch
 - `src/__tests__/server.test.ts` — API input validation (prompt, timeout, priority, tags, webhookUrl)
-- `src/__tests__/cli.test.ts` — CLI commands, fetch mocking, output formatting, error handling
+- `src/__tests__/cli.test.ts` — CLI commands (all 12), fetch mocking, output formatting, error handling
+- `src/__tests__/logger.test.ts` — Structured logger: JSON format, level filtering, stream routing
+- `src/__tests__/index.test.ts` — Entry point validation: repo, workers, port, system prompt (subprocess)
 
 ## Repository
 - **GitHub**: `agent-next/cc-manager` (private)
diff --git a/src/__tests__/cli.test.ts b/src/__tests__/cli.test.ts
index 4d129d4..9907d5f 100644
--- a/src/__tests__/cli.test.ts
+++ b/src/__tests__/cli.test.ts
@@ -473,6 +473,66 @@ describe("cli", () => {
     });
   });
 
+  // ─── watch ───────────────────────────────────────────────────────────────────
+
+  describe("watch command", () => {
+    function mockSSEFetch(chunks: string[]) {
+      fetchCalls = [];
+      let chunkIndex = 0;
+      (globalThis as any).fetch = async (url: string | URL, init?: RequestInit) => {
+        fetchCalls.push({ url: String(url), init });
+        return {
+          ok: true,
+          status: 200,
+          body: {
+            getReader: () => ({
+              read: async () => {
+                if (chunkIndex < chunks.length) {
+                  const encoder = new TextEncoder();
+                  return { done: false, value: encoder.encode(chunks[chunkIndex++]) };
+                }
+                return { done: true, value: undefined };
+              },
+            }),
+          },
+        };
+      };
+    }
+
+    it("connects to /api/events", async () => {
+      mockSSEFetch([]);
+      await run("watch");
+
+      assert.ok(fetchCalls[0].url.includes("/api/events"));
+    });
+
+    it("parses SSE data lines and logs events", async () => {
+      const event = JSON.stringify({ type: "task_started", taskId: "t1", status: "running" });
+      mockSSEFetch([`data: ${event}\n\n`]);
+      await run("watch");
+
+      const output = logs.join("\n");
+      assert.ok(output.includes("task_started"), "should log event type");
+      assert.ok(output.includes("t1"), "should log task ID");
+    });
+
+    it("skips malformed SSE data", async () => {
+      mockSSEFetch(["data: not-valid-json\n\n"]);
+      await run("watch");
+
+      // Should not throw, just silently skip
+      assert.ok(true);
+    });
+
+    it("prints connection message", async () => {
+      mockSSEFetch([]);
+      await run("watch");
+
+      const output = logs.join("\n");
+      assert.ok(output.includes("Watching events"), "should show connection message");
+    });
+  });
+
   // ─── api() Content-Type header ──────────────────────────────────────────────
 
   describe("api() helper behavior", () => {
diff --git a/src/__tests__/index.test.ts b/src/__tests__/index.test.ts
new file mode 100644
index 0000000..a577c3f
--- /dev/null
+++ b/src/__tests__/index.test.ts
@@ -0,0 +1,122 @@
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { execFile } from "node:child_process";
+import { promisify } from "node:util";
+import { mkdtempSync, mkdirSync, writeFileSync, rmSync } from "fs";
+import { join } from "path";
+import { tmpdir } from "os";
+
+// =============================================================================
+// index.ts entry point tests — subprocess validation of CLI args and startup
+// =============================================================================
+
+const exec = promisify(execFile);
+
+async function runServer(...args: string[]): Promise<{ stdout: string; stderr: string; exitCode: number }> {
+  try {
+    const { stdout, stderr } = await exec("node", ["--import", "tsx", "src/index.ts", ...args], {
+      timeout: 5000,
+      env: { ...process.env, NODE_NO_WARNINGS: "1" },
+    });
+    return { stdout, stderr, exitCode: 0 };
+  } catch (err: any) {
+    return { stdout: err.stdout ?? "", stderr: err.stderr ?? "", exitCode: err.code ?? 1 };
+  }
+}
+
+describe("index.ts entry point", () => {
+
+  // ─── required options ───────────────────────────────────────────────────────
+
+  describe("required options", () => {
+    it("exits with error when --repo is missing", async () => {
+      const result = await runServer();
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("--repo"), "should mention --repo in error");
+    });
+  });
+
+  // ─── repo validation ────────────────────────────────────────────────────────
+
+  describe("repo validation", () => {
+    it("exits with error for nonexistent repo path", async () => {
+      const result = await runServer("--repo", "/nonexistent/path/to/repo");
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("not a git repository"), "should report invalid repo");
+    });
+
+    it("exits with error for directory without .git", async () => {
+      const tmp = mkdtempSync(join(tmpdir(), "cc-test-"));
+      try {
+        const result = await runServer("--repo", tmp);
+        assert.notStrictEqual(result.exitCode, 0);
+        assert.ok(result.stderr.includes("not a git repository"));
+      } finally {
+        rmSync(tmp, { recursive: true });
+      }
+    });
+  });
+
+  // ─── workers validation ─────────────────────────────────────────────────────
+
+  describe("workers validation", () => {
+    let fakeRepo: string;
+
+    // Create a minimal fake git repo for validation tests that pass repo check
+    fakeRepo = mkdtempSync(join(tmpdir(), "cc-test-repo-"));
+    mkdirSync(join(fakeRepo, ".git"), { recursive: true });
+
+    it("exits with error for --workers 0", async () => {
+      const result = await runServer("--repo", fakeRepo, "--workers", "0");
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("--workers must be between 1 and 20"));
+    });
+
+    it("exits with error for --workers 25", async () => {
+      const result = await runServer("--repo", fakeRepo, "--workers", "25");
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("--workers must be between 1 and 20"));
+    });
+
+    it("exits with error for --workers abc", async () => {
+      const result = await runServer("--repo", fakeRepo, "--workers", "abc");
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("--workers must be between 1 and 20"));
+    });
+  });
+
+  // ─── port validation ────────────────────────────────────────────────────────
+
+  describe("port validation", () => {
+    let fakeRepo: string;
+    fakeRepo = mkdtempSync(join(tmpdir(), "cc-test-repo-"));
+    mkdirSync(join(fakeRepo, ".git"), { recursive: true });
+
+    it("exits with error for --port 80", async () => {
+      const result = await runServer("--repo", fakeRepo, "--port", "80");
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("--port must be between 1024 and 65535"));
+    });
+
+    it("exits with error for --port 99999", async () => {
+      const result = await runServer("--repo", fakeRepo, "--port", "99999");
+      assert.notStrictEqual(result.exitCode, 0);
+      assert.ok(result.stderr.includes("--port must be between 1024 and 65535"));
+    });
+  });
+
+  // ─── system prompt file ─────────────────────────────────────────────────────
+
+  describe("system prompt file", () => {
+    it("exits with error for nonexistent --system-prompt-file", async () => {
+      const fakeRepo = mkdtempSync(join(tmpdir(), "cc-test-repo-"));
+      mkdirSync(join(fakeRepo, ".git"), { recursive: true });
+      try {
+        const result = await runServer("--repo", fakeRepo, "--system-prompt-file", "/nonexistent/file.txt");
+        assert.notStrictEqual(result.exitCode, 0);
+      } finally {
+        rmSync(fakeRepo, { recursive: true });
+      }
+    });
+  });
+});
diff --git a/src/__tests__/logger.test.ts b/src/__tests__/logger.test.ts
new file mode 100644
index 0000000..1365a0a
--- /dev/null
+++ b/src/__tests__/logger.test.ts
@@ -0,0 +1,145 @@
+import { describe, it, beforeEach, afterEach } from "node:test";
+import assert from "node:assert/strict";
+import { log, setLogLevel } from "../logger.js";
+
+// =============================================================================
+// Logger tests — verify structured JSON output, level filtering, stream routing
+// =============================================================================
+
+let stdoutWrites: string[] = [];
+let stderrWrites: string[] = [];
+const originalStdoutWrite = process.stdout.write;
+const originalStderrWrite = process.stderr.write;
+
+function captureStreams() {
+  stdoutWrites = [];
+  stderrWrites = [];
+  process.stdout.write = ((chunk: string) => {
+    stdoutWrites.push(chunk);
+    return true;
+  }) as typeof process.stdout.write;
+  process.stderr.write = ((chunk: string) => {
+    stderrWrites.push(chunk);
+    return true;
+  }) as typeof process.stderr.write;
+}
+
+function restoreStreams() {
+  process.stdout.write = originalStdoutWrite;
+  process.stderr.write = originalStderrWrite;
+}
+
+describe("logger", () => {
+  beforeEach(() => {
+    setLogLevel("info"); // reset to default
+    captureStreams();
+  });
+
+  afterEach(() => {
+    restoreStreams();
+  });
+
+  // ─── JSON format ────────────────────────────────────────────────────────────
+
+  describe("JSON format", () => {
+    it("outputs valid JSON with ts, level, and msg fields", () => {
+      log("info", "hello world");
+
+      assert.strictEqual(stdoutWrites.length, 1);
+      const entry = JSON.parse(stdoutWrites[0]);
+      assert.strictEqual(entry.level, "info");
+      assert.strictEqual(entry.msg, "hello world");
+      assert.ok(entry.ts, "should have timestamp");
+    });
+
+    it("includes extra data fields", () => {
+      log("info", "task start", { taskId: "abc", agent: "claude" });
+
+      const entry = JSON.parse(stdoutWrites[0]);
+      assert.strictEqual(entry.taskId, "abc");
+      assert.strictEqual(entry.agent, "claude");
+    });
+
+    it("produces ISO 8601 timestamp", () => {
+      log("info", "check ts");
+
+      const entry = JSON.parse(stdoutWrites[0]);
+      assert.ok(/^\d{4}-\d{2}-\d{2}T/.test(entry.ts), "should be ISO format");
+    });
+
+    it("appends newline after JSON", () => {
+      log("info", "newline check");
+
+      assert.ok(stdoutWrites[0].endsWith("\n"));
+    });
+  });
+
+  // ─── stream routing ─────────────────────────────────────────────────────────
+
+  describe("stream routing", () => {
+    it("writes info to stdout", () => {
+      log("info", "info msg");
+      assert.strictEqual(stdoutWrites.length, 1);
+      assert.strictEqual(stderrWrites.length, 0);
+    });
+
+    it("writes warn to stdout", () => {
+      log("warn", "warn msg");
+      assert.strictEqual(stdoutWrites.length, 1);
+      assert.strictEqual(stderrWrites.length, 0);
+    });
+
+    it("writes error to stderr", () => {
+      log("error", "error msg");
+      assert.strictEqual(stderrWrites.length, 1);
+      assert.strictEqual(stdoutWrites.length, 0);
+    });
+
+    it("writes debug to stdout when level is debug", () => {
+      setLogLevel("debug");
+      log("debug", "debug msg");
+      assert.strictEqual(stdoutWrites.length, 1);
+      assert.strictEqual(stderrWrites.length, 0);
+    });
+  });
+
+  // ─── level filtering ────────────────────────────────────────────────────────
+
+  describe("level filtering", () => {
+    it("suppresses debug at default info level", () => {
+      log("debug", "should not appear");
+      assert.strictEqual(stdoutWrites.length, 0);
+      assert.strictEqual(stderrWrites.length, 0);
+    });
+
+    it("emits debug when level set to debug", () => {
+      setLogLevel("debug");
+      log("debug", "visible");
+      assert.strictEqual(stdoutWrites.length, 1);
+    });
+
+    it("suppresses info when level set to warn", () => {
+      setLogLevel("warn");
+      log("info", "hidden");
+      assert.strictEqual(stdoutWrites.length, 0);
+    });
+
+    it("emits warn when level set to warn", () => {
+      setLogLevel("warn");
+      log("warn", "visible");
+      assert.strictEqual(stdoutWrites.length, 1);
+    });
+
+    it("suppresses warn when level set to error", () => {
+      setLogLevel("error");
+      log("warn", "hidden");
+      assert.strictEqual(stdoutWrites.length, 0);
+    });
+
+    it("emits error at any level", () => {
+      setLogLevel("error");
+      log("error", "always visible");
+      assert.strictEqual(stderrWrites.length, 1);
+    });
+  });
+});