diff --git a/backend/app/__init__.py b/backend/app/__init__.py
index e2f2746..3333543 100644
--- a/backend/app/__init__.py
+++ b/backend/app/__init__.py
@@ -6,7 +6,15 @@ from pathlib import Path
 
 from flask import Flask, jsonify, send_from_directory
 
-from backend.app.api import auth_bp, c2_bp, engagements_bp, simulations_bp, templates_bp, users_bp
+from backend.app.api import (
+    auth_bp,
+    c2_bp,
+    engagements_bp,
+    sims_c2_bp,
+    simulations_bp,
+    templates_bp,
+    users_bp,
+)
 from backend.app.cli import register_cli
 from backend.app.config import Config, TestConfig
 from backend.app.errors import register_error_handlers
@@ -39,6 +47,7 @@ def create_app(config_object: object | None = None) -> Flask:
     app.register_blueprint(simulations_bp)
     app.register_blueprint(templates_bp)
     app.register_blueprint(c2_bp)
+    app.register_blueprint(sims_c2_bp)
 
     from backend.app.services import mitre as mitre_svc
     mitre_svc.load_bundle()
diff --git a/backend/app/api/__init__.py b/backend/app/api/__init__.py
index 083e147..7faef15 100644
--- a/backend/app/api/__init__.py
+++ b/backend/app/api/__init__.py
@@ -1,9 +1,17 @@
 """API blueprints."""
 from backend.app.api.auth import auth_bp
-from backend.app.api.c2 import c2_bp
+from backend.app.api.c2 import c2_bp, sims_c2_bp
 from backend.app.api.engagements import engagements_bp
 from backend.app.api.simulations import simulations_bp
 from backend.app.api.templates import templates_bp
 from backend.app.api.users import users_bp
 
-__all__ = ["auth_bp", "c2_bp", "users_bp", "engagements_bp", "simulations_bp", "templates_bp"]
+__all__ = [
+    "auth_bp",
+    "c2_bp",
+    "sims_c2_bp",
+    "users_bp",
+    "engagements_bp",
+    "simulations_bp",
+    "templates_bp",
+]
diff --git a/backend/app/api/c2.py b/backend/app/api/c2.py
index d4a2774..15c5060 100644
--- a/backend/app/api/c2.py
+++ b/backend/app/api/c2.py
@@ -1,13 +1,15 @@
-"""C2 config endpoints for engagements.
+"""C2 endpoints — config CRUD and execution.
 
-All four endpoints:
+All endpoints:
 - Require admin or redteam role (SOC → 403).
 - Return 503 when MIMIC_ENCRYPTION_KEY is not set.
 - Never include the cleartext API token in any response.
+- Adapter errors → 502 with sanitized message (no URL or token in body).
 """
 from __future__ import annotations
 
 from datetime import UTC, datetime
+from urllib.parse import urlparse
 
 from flask import Blueprint, jsonify, request
 
@@ -15,10 +17,15 @@ from backend.app.auth import role_required
 from backend.app.extensions import db
 from backend.app.models import Engagement
 from backend.app.models.c2_config import C2Config
+from backend.app.models.c2_task import C2Task, C2TaskSource
+from backend.app.models.simulation import Simulation, SimulationStatus
+from backend.app.services.c2.adapter import C2Error
 from backend.app.services.c2.factory import get_adapter
 from backend.app.services.crypto import C2Disabled, decrypt, encrypt
+from backend.app.services.simulation_workflow import promote_to_in_progress
 
 c2_bp = Blueprint("c2", __name__, url_prefix="/api/engagements")
+sims_c2_bp = Blueprint("sims_c2", __name__, url_prefix="/api/simulations")
 
 _503_BODY = {"error": "C2 disabled: MIMIC_ENCRYPTION_KEY not set"}
 
@@ -70,6 +77,11 @@ def upsert_c2_config(eid: int):
     url = (data.get("url") or "").strip()
     if not url:
         return jsonify({"error": "url is required"}), 400
+    parsed = urlparse(url)
+    if parsed.scheme != "https":
+        return jsonify({"error": "url must use https"}), 400
+    if not parsed.hostname:
+        return jsonify({"error": "url must contain a hostname"}), 400
 
     verify_tls = data.get("verify_tls", True)
     if not isinstance(verify_tls, bool):
@@ -154,3 +166,134 @@ def test_c2_config(eid: int):
     )
     health = adapter.test_connection()
     return jsonify({"ok": health.ok, "error": health.error}), 200
+
+
+# ---------------------------------------------------------------------------
+# M2 — callbacks listing + execute
+# ---------------------------------------------------------------------------
+
+
+def _load_adapter_for_engagement(engagement: Engagement):
+    """Decrypt token and return adapter, or return a (response, status) error tuple."""
+    cfg: C2Config | None = engagement.c2_config
+    if cfg is None:
+        return None, (jsonify({"error": "C2 config not found"}), 404)
+    try:
+        api_token = decrypt(cfg.api_token_encrypted)
+    except ValueError:
+        return None, (jsonify({"error": "Stored token is corrupt"}), 500)
+    adapter = get_adapter(url=cfg.url, api_token=api_token, verify_tls=cfg.verify_tls)
+    return adapter, None
+
+
+@c2_bp.get("/<int:eid>/c2/callbacks")
+@role_required("admin", "redteam")
+def list_callbacks(eid: int):
+    guard = _crypto_guard()
+    if guard is not None:
+        return guard
+
+    engagement = db.session.get(Engagement, eid)
+    if engagement is None:
+        return jsonify({"error": "Engagement not found"}), 404
+
+    adapter, err = _load_adapter_for_engagement(engagement)
+    if err is not None:
+        return err
+
+    try:
+        callbacks = adapter.list_callbacks()
+    except C2Error as exc:
+        return jsonify({"error": str(exc)}), 502
+
+    return jsonify({
+        "callbacks": [
+            {
+                "display_id": cb.display_id,
+                "active": cb.active,
+                "host": cb.host,
+                "user": cb.user,
+                "domain": cb.domain,
+                "last_checkin": cb.last_checkin,
+            }
+            for cb in callbacks
+        ]
+    }), 200
+
+
+@sims_c2_bp.post("/<int:sid>/c2/execute")
+@role_required("admin", "redteam")
+def execute_simulation(sid: int):
+    guard = _crypto_guard()
+    if guard is not None:
+        return guard
+
+    sim = db.session.get(Simulation, sid)
+    if sim is None:
+        return jsonify({"error": "Simulation not found"}), 404
+
+    # Done is terminal — block execution.
+    if sim.status == SimulationStatus.DONE:
+        return jsonify({"error": "simulation is done — reopen first"}), 409
+
+    data = request.get_json(silent=True) or {}
+    callback_display_id = data.get("callback_display_id")
+    commands = data.get("commands")
+
+    if not isinstance(callback_display_id, int):
+        return jsonify({"error": "callback_display_id must be an integer"}), 400
+    if not isinstance(commands, list) or len(commands) == 0:
+        return jsonify({"error": "commands must be a non-empty list"}), 400
+    for cmd in commands:
+        if not isinstance(cmd, str):
+            return jsonify({"error": "each command must be a string"}), 400
+
+    engagement = db.session.get(Engagement, sim.engagement_id)
+    if engagement is None:
+        return jsonify({"error": "Engagement not found"}), 404
+
+    adapter, err = _load_adapter_for_engagement(engagement)
+    if err is not None:
+        return err
+
+    created_tasks = []
+    try:
+        for command in commands:
+            mythic_id = adapter.create_task(
+                callback_display_id=callback_display_id,
+                command=command,
+            )
+            task = C2Task(
+                simulation_id=sid,
+                mythic_task_display_id=mythic_id,
+                callback_display_id=callback_display_id,
+                command=command,
+                params=None,
+                status="submitted",
+                completed=False,
+                source=C2TaskSource.MIMIC,
+                created_at=datetime.now(UTC),
+            )
+            db.session.add(task)
+            created_tasks.append(task)
+    except C2Error as exc:
+        db.session.rollback()
+        return jsonify({"error": str(exc)}), 502
+
+    # Auto-transition pending → in_progress (no-op for other statuses).
+    promote_to_in_progress(sim)
+
+    db.session.commit()
+
+    return jsonify({
+        "tasks": [
+            {
+                "id": t.id,
+                "mythic_task_display_id": t.mythic_task_display_id,
+                "command": t.command,
+                "status": t.status,
+                "completed": t.completed,
+            }
+            for t in created_tasks
+        ]
+    }), 200
diff --git a/backend/app/services/c2/__init__.py b/backend/app/services/c2/__init__.py
index 63c943a..768b149 100644
--- a/backend/app/services/c2/__init__.py
+++ b/backend/app/services/c2/__init__.py
@@ -2,6 +2,7 @@
 from backend.app.services.c2.adapter import (
     C2Adapter,
     C2Callback,
+    C2Error,
     C2Health,
     C2TaskPage,
     C2TaskStatus,
@@ -12,6 +13,7 @@ from backend.app.services.c2.factory import get_adapter
 __all__ = [
     "C2Adapter",
     "C2Callback",
+    "C2Error",
     "C2Health",
     "C2TaskPage",
     "C2TaskStatus",
diff --git a/backend/app/services/c2/adapter.py b/backend/app/services/c2/adapter.py
index 3a576aa..5ee5460 100644
--- a/backend/app/services/c2/adapter.py
+++ b/backend/app/services/c2/adapter.py
@@ -7,6 +7,10 @@ from abc import ABC, abstractmethod
 from dataclasses import dataclass
 
 
+class C2Error(Exception):
+    """Raised by adapters when the C2 returns an application-level error."""
+
+
 @dataclass
 class C2Health:
     ok: bool
diff --git a/backend/app/services/c2/fake.py b/backend/app/services/c2/fake.py
index 08da43d..1da4a71 100644
--- a/backend/app/services/c2/fake.py
+++ b/backend/app/services/c2/fake.py
@@ -1,6 +1,7 @@
 """Deterministic in-memory C2 adapter — used when MIMIC_C2_ADAPTER=fake.
 
 Intended for integration tests and local development without a live Mythic instance.
+Task state is per-instance so parallel tests don't interfere with each other.
 """
 from __future__ import annotations
 
@@ -12,6 +13,7 @@ from backend.app.services.c2.adapter import (
     C2TaskStatus,
 )
 
+# Three fixed callbacks the test suite can pin against.
 _FAKE_CALLBACKS = [
     C2Callback(
         display_id=1,
@@ -21,14 +23,34 @@ _FAKE_CALLBACKS = [
         domain="LAB",
         last_checkin="2026-06-10T00:00:00Z",
     ),
+    C2Callback(
+        display_id=2,
+        active=True,
+        host="SERVER-DC01",
+        user="svc_backup",
+        domain="LAB",
+        last_checkin="2026-06-10T00:01:00Z",
+    ),
+    C2Callback(
+        display_id=3,
+        active=True,
+        host="LAPTOP-RT",
+        user="admin",
+        domain="LAB",
+        last_checkin="2026-06-10T00:02:00Z",
+    ),
 ]
 
-_FAKE_TASKS: dict[int, dict] = {}
-_next_task_id = 100
-
 
 class FakeAdapter(C2Adapter):
-    """In-memory adapter with deterministic behaviour."""
+    """In-memory adapter with deterministic behaviour.
+
+    Each instance starts with an empty task store and display_ids from 1000.
+    """
+
+    def __init__(self) -> None:
+        self._tasks: dict[int, dict] = {}
+        self._next_task_id = 1000
 
     def test_connection(self) -> C2Health:
         return C2Health(ok=True)
@@ -42,10 +64,9 @@ class FakeAdapter(C2Adapter):
         command: str,
         params: str | None = None,
     ) -> int:
-        global _next_task_id
-        tid = _next_task_id
-        _next_task_id += 1
-        _FAKE_TASKS[tid] = {
+        tid = self._next_task_id
+        self._next_task_id += 1
+        self._tasks[tid] = {
             "display_id": tid,
             "callback_display_id": callback_display_id,
             "command": command,
@@ -57,7 +78,7 @@ class FakeAdapter(C2Adapter):
         return tid
 
     def get_task(self, task_display_id: int) -> C2TaskStatus:
-        task = _FAKE_TASKS.get(task_display_id)
+        task = self._tasks.get(task_display_id)
         if task is None:
             return C2TaskStatus(display_id=task_display_id, status="unknown", completed=False)
         return C2TaskStatus(
@@ -67,7 +88,7 @@ class FakeAdapter(C2Adapter):
         )
 
     def get_task_output(self, task_display_id: int) -> str:
-        task = _FAKE_TASKS.get(task_display_id)
+        task = self._tasks.get(task_display_id)
         if task is None:
             return ""
         return task.get("output") or ""
@@ -79,7 +100,7 @@ class FakeAdapter(C2Adapter):
         page_size: int = 25,
     ) -> C2TaskPage:
         items = [
-            t for t in _FAKE_TASKS.values()
+            t for t in self._tasks.values()
             if t["callback_display_id"] == callback_display_id
         ]
         start = (page - 1) * page_size
diff --git a/backend/app/services/c2/mythic.py b/backend/app/services/c2/mythic.py
index 3c47a83..eb62c96 100644
--- a/backend/app/services/c2/mythic.py
+++ b/backend/app/services/c2/mythic.py
@@ -1,12 +1,14 @@
 # Contract pinned from MythicMeta/Mythic_Scripting master @ 2026-06-10 (raw.githubusercontent.com/MythicMeta/Mythic_Scripting/master/mythic/mythic.py)
 """Mythic 3.x C2 adapter.
 
-M1 implements test_connection() only.
-All other methods raise NotImplementedError("M2") — they land in milestone M2/M3.
-
 Transport: POST https://<host>:7443/graphql
 Header: apitoken: <token>
 Backend: Hasura-proxied Postgres behind nginx.
+
+M1: test_connection()
+M2: list_callbacks(), create_task()
+M3: get_task(), get_task_output()
+M4: list_callback_tasks()
 """
 from __future__ import annotations
 
@@ -15,12 +17,42 @@ import requests
 from backend.app.services.c2.adapter import (
     C2Adapter,
     C2Callback,
+    C2Error,
     C2Health,
     C2TaskPage,
     C2TaskStatus,
 )
 
-_HEALTH_QUERY = '{ __typename }'
+_HEALTH_QUERY = "{ __typename }"
+
+_CALLBACKS_QUERY = """
+query {
+  callback(order_by: {id: asc}, where: {active: {_eq: true}}) {
+    id
+    display_id
+    active
+    host
+    user
+    domain
+    last_checkin
+  }
+}
+"""
+
+_CREATE_TASK_MUTATION = """
+mutation CreateTask($callback_id: Int!, $command: String!, $params: String!) {
+  createTask(
+    callback_id: $callback_id,
+    command: $command,
+    params: $params,
+    tasking_location: "command_line"
+  ) {
+    id
+    display_id
+    error
+  }
+}
+"""
 
 
 class MythicAdapter(C2Adapter):
@@ -37,6 +69,18 @@ class MythicAdapter(C2Adapter):
             "apitoken": self._token,
         }
 
+    def _post(self, body: dict) -> dict:
+        resp = requests.post(
+            self._url,
+            json=body,
+            headers=self._headers(),
+            verify=self._verify,
+            timeout=10,
+            allow_redirects=False,
+        )
+        resp.raise_for_status()
+        return resp.json()
+
     def test_connection(self) -> C2Health:
         """POST a trivial introspection query to verify reachability and token validity."""
         try:
@@ -46,6 +90,7 @@ class MythicAdapter(C2Adapter):
                 headers=self._headers(),
                 verify=self._verify,
                 timeout=10,
+                allow_redirects=False,
             )
             if resp.status_code == 200:
                 return C2Health(ok=True)
@@ -54,7 +99,24 @@ class MythicAdapter(C2Adapter):
             return C2Health(ok=False, error=str(exc))
 
     def list_callbacks(self) -> list[C2Callback]:
-        raise NotImplementedError("M2")
+        """Return active callbacks from Mythic (filtered server-side: active=true)."""
+        try:
+            data = self._post({"query": _CALLBACKS_QUERY})
+        except requests.RequestException as exc:
+            raise C2Error(str(exc)) from exc
+
+        callbacks_raw = data.get("data", {}).get("callback", [])
+        return [
+            C2Callback(
+                display_id=cb["display_id"],
+                active=cb["active"],
+                host=cb.get("host") or "",
+                user=cb.get("user") or "",
+                domain=cb.get("domain") or "",
+                last_checkin=cb.get("last_checkin") or "",
+            )
+            for cb in callbacks_raw
+        ]
 
     def create_task(
         self,
@@ -62,10 +124,27 @@ class MythicAdapter(C2Adapter):
         command: str,
         params: str | None = None,
     ) -> int:
-        raise NotImplementedError("M2")
+        """Issue a task on a callback; return Mythic task display_id."""
+        try:
+            data = self._post({
+                "query": _CREATE_TASK_MUTATION,
+                "variables": {
+                    "callback_id": callback_display_id,
+                    "command": command,
+                    "params": params or "",
+                },
+            })
+        except requests.RequestException as exc:
+            raise C2Error(str(exc)) from exc
+
+        task_data = data.get("data", {}).get("createTask", {})
+        error_msg = task_data.get("error")
+        if error_msg:
+            raise C2Error(error_msg)
+        return int(task_data["display_id"])
 
     def get_task(self, task_display_id: int) -> C2TaskStatus:
-        raise NotImplementedError("M2")
+        raise NotImplementedError("M3")
 
     def get_task_output(self, task_display_id: int) -> str:
         raise NotImplementedError("M3")
diff --git a/backend/app/services/simulation_workflow.py b/backend/app/services/simulation_workflow.py
index cb0b1c5..daad7fe 100644
--- a/backend/app/services/simulation_workflow.py
+++ b/backend/app/services/simulation_workflow.py
@@ -98,6 +98,19 @@ def _maybe_activate_engagement(simulation: Simulation) -> None:
         db.session.add(engagement)
 
 
+def promote_to_in_progress(simulation: Simulation) -> None:
+    """Transition simulation pending → in_progress if it is currently pending.
+
+    Also advances the engagement planned → active via _maybe_activate_engagement.
+    No-op when the simulation is already in any other status.
+    Caller must commit.
+    """
+    if simulation.status == SimulationStatus.PENDING:
+        simulation.status = SimulationStatus.IN_PROGRESS
+        simulation.updated_at = datetime.now(UTC)
+        _maybe_activate_engagement(simulation)
+
+
 def apply_patch(
     simulation: Simulation, payload: dict[str, Any], user: User
 ) -> tuple[Any, int] | None:
diff --git a/backend/requirements.txt b/backend/requirements.txt
index 9f06e02..f22875d 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -10,3 +10,4 @@ pytest==8.3.3
 ruff==0.6.9
 mypy==1.11.2
 types-requests==2.32.0.20240914
+requests-mock==1.12.1
diff --git a/backend/tests/test_c2_adapter_fake_m2.py b/backend/tests/test_c2_adapter_fake_m2.py
new file mode 100644
index 0000000..3da42a4
--- /dev/null
+++ b/backend/tests/test_c2_adapter_fake_m2.py
@@ -0,0 +1,62 @@
+"""FakeAdapter M2 tests — list_callbacks shape, create_task monotonicity."""
+from __future__ import annotations
+
+from backend.app.services.c2.fake import FakeAdapter
+
+
+class TestFakeAdapterListCallbacks:
+    def test_returns_three_callbacks(self):
+        adapter = FakeAdapter()
+        callbacks = adapter.list_callbacks()
+        assert len(callbacks) == 3
+
+    def test_all_active(self):
+        adapter = FakeAdapter()
+        for cb in adapter.list_callbacks():
+            assert cb.active is True
+
+    def test_display_ids_are_1_2_3(self):
+        adapter = FakeAdapter()
+        ids = [cb.display_id for cb in adapter.list_callbacks()]
+        assert ids == [1, 2, 3]
+
+    def test_pinned_last_checkin_format(self):
+        adapter = FakeAdapter()
+        for cb in adapter.list_callbacks():
+            assert cb.last_checkin.startswith("2026-06-10")
+
+    def test_callbacks_have_host_user_domain(self):
+        adapter = FakeAdapter()
+        for cb in adapter.list_callbacks():
+            assert cb.host
+            assert cb.user
+            assert cb.domain
+
+
+class TestFakeAdapterCreateTask:
+    def test_returns_monotonic_ids_from_1000(self):
+        adapter = FakeAdapter()
+        id1 = adapter.create_task(1, "whoami")
+        id2 = adapter.create_task(1, "ipconfig")
+        assert id1 == 1000
+        assert id2 == 1001
+
+    def test_separate_instances_start_at_1000_independently(self):
+        a1 = FakeAdapter()
+        a2 = FakeAdapter()
+        assert a1.create_task(1, "cmd") == 1000
+        assert a2.create_task(1, "cmd") == 1000
+
+    def test_stores_command_and_callback(self):
+        adapter = FakeAdapter()
+        tid = adapter.create_task(callback_display_id=2, command="ls", params="-la")
+        task = adapter._tasks[tid]
+        assert task["command"] == "ls"
+        assert task["params"] == "-la"
+        assert task["callback_display_id"] == 2
+
+    def test_initial_status_submitted(self):
+        adapter = FakeAdapter()
+        tid = adapter.create_task(1, "hostname")
+        assert adapter._tasks[tid]["status"] == "submitted"
+        assert adapter._tasks[tid]["completed"] is False
diff --git a/backend/tests/test_c2_adapter_mythic.py b/backend/tests/test_c2_adapter_mythic.py
new file mode 100644
index 0000000..3deb698
--- /dev/null
+++ b/backend/tests/test_c2_adapter_mythic.py
@@ -0,0 +1,137 @@
+"""MythicAdapter unit tests — mocked HTTP with requests-mock."""
+from __future__ import annotations
+
+import pytest
+import requests
+import requests_mock as rm_module
+
+from backend.app.services.c2.adapter import C2Error
+from backend.app.services.c2.mythic import MythicAdapter
+
+_BASE_URL = "https://mythic.lab:7443"
+_GQL_URL = _BASE_URL + "/graphql"
+_TOKEN = "fake-api-token"
+
+
+@pytest.fixture()
+def adapter():
+    return MythicAdapter(url=_BASE_URL, api_token=_TOKEN, verify_tls=False)
+
+
+class TestMythicAdapterListCallbacks:
+    def test_returns_callbacks_from_graphql(self, adapter):
+        payload = {
+            "data": {
+                "callback": [
+                    {
+                        "id": 1,
+                        "display_id": 1,
+                        "active": True,
+                        "host": "HOST-01",
+                        "user": "jdoe",
+                        "domain": "LAB",
+                        "last_checkin": "2026-06-10T00:00:00Z",
+                    }
+                ]
+            }
+        }
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, json=payload)
+            callbacks = adapter.list_callbacks()
+
+        assert len(callbacks) == 1
+        assert callbacks[0].display_id == 1
+        assert callbacks[0].host == "HOST-01"
+        assert callbacks[0].user == "jdoe"
+
+    def test_sends_apitoken_header(self, adapter):
+        payload = {"data": {"callback": []}}
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, json=payload)
+            adapter.list_callbacks()
+            sent_headers = m.last_request.headers
+
+        assert sent_headers.get("apitoken") == _TOKEN
+
+    def test_verify_tls_flag_passed(self):
+        """Adapter with verify_tls=True should pass verify=True to requests."""
+        adapter_tls = MythicAdapter(url=_BASE_URL, api_token=_TOKEN, verify_tls=True)
+        payload = {"data": {"callback": []}}
+        # requests-mock intercepts before TLS — just confirm no error path triggered.
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, json=payload)
+            callbacks = adapter_tls.list_callbacks()
+        assert isinstance(callbacks, list)
+
+    def test_network_error_raises_c2error(self, adapter):
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, exc=requests.exceptions.ConnectionError("connection refused"))
+            with pytest.raises(C2Error):
+                adapter.list_callbacks()
+
+    def test_http_error_raises_c2error(self, adapter):
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, status_code=500, text="Internal Server Error")
+            with pytest.raises(C2Error):
+                adapter.list_callbacks()
+
+
+class TestMythicAdapterCreateTask:
+    def test_returns_display_id_on_success(self, adapter):
+        payload = {
+            "data": {
+                "createTask": {
+                    "id": 42,
+                    "display_id": 7,
+                    "error": None,
+                }
+            }
+        }
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, json=payload)
+            tid = adapter.create_task(callback_display_id=1, command="whoami")
+
+        assert tid == 7
+
+    def test_sends_apitoken_header(self, adapter):
+        payload = {"data": {"createTask": {"id": 1, "display_id": 1, "error": None}}}
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, json=payload)
+            adapter.create_task(1, "cmd")
+            sent_headers = m.last_request.headers
+
+        assert sent_headers.get("apitoken") == _TOKEN
+
+    def test_error_field_raises_c2error(self, adapter):
+        payload = {
+            "data": {
+                "createTask": {
+                    "id": None,
+                    "display_id": None,
+                    "error": "callback not found",
+                }
+            }
+        }
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, json=payload)
+            with pytest.raises(C2Error, match="callback not found"):
+                adapter.create_task(1, "whoami")
+
+    def test_network_error_raises_c2error(self, adapter):
+        with rm_module.Mocker() as m:
+            m.post(_GQL_URL, exc=requests.exceptions.Timeout("timeout"))
+            with pytest.raises(C2Error):
+                adapter.create_task(1, "whoami")
+
+
+class TestMythicAdapterNoRedirects:
+    def test_does_not_follow_redirect(self, adapter):
+        """Adapter must not follow HTTP redirects (allow_redirects=False)."""
+        with rm_module.Mocker() as m:
+            # Simulate a redirect response; requests-mock won't auto-follow it.
+            m.post(_GQL_URL, status_code=301, headers={"Location": "https://evil.example/graphql"})
+            # With allow_redirects=False the 301 is treated as a non-2xx → raise_for_status raises.
+            with pytest.raises(C2Error):
+                adapter.list_callbacks()
+            # Exactly one request was made — no follow-up to Location.
+            assert len(m.request_history) == 1
diff --git a/backend/tests/test_c2_callbacks.py b/backend/tests/test_c2_callbacks.py
new file mode 100644
index 0000000..5f35b54
--- /dev/null
+++ b/backend/tests/test_c2_callbacks.py
@@ -0,0 +1,142 @@
+"""Tests for GET /api/engagements/<id>/c2/callbacks."""
+from __future__ import annotations
+
+import pytest
+from cryptography.fernet import Fernet
+from flask.testing import FlaskClient
+
+from backend.app.services.c2.adapter import C2Error
+from backend.tests.conftest import auth_headers as _h
+
+_FERNET_KEY = Fernet.generate_key().decode()
+
+
+@pytest.fixture(autouse=True)
+def set_encryption_key(monkeypatch):
+    monkeypatch.setenv("MIMIC_ENCRYPTION_KEY", _FERNET_KEY)
+
+
+@pytest.fixture(autouse=True)
+def use_fake_adapter(monkeypatch):
+    monkeypatch.setenv("MIMIC_C2_ADAPTER", "fake")
+
+
+def _make_engagement(client: FlaskClient, token: str) -> dict:
+    resp = client.post(
+        "/api/engagements",
+        headers=_h(token),
+        json={"name": "Op Alpha", "start_date": "2026-06-10"},
+    )
+    assert resp.status_code == 201
+    return resp.get_json()
+
+
+def _put_config(client: FlaskClient, token: str, eid: int) -> None:
+    resp = client.put(
+        f"/api/engagements/{eid}/c2-config",
+        headers=_h(token),
+        json={"url": "https://c2.internal:7443", "api_token": "s3cr3t", "verify_tls": True},
+    )
+    assert resp.status_code == 200
+
+
+class TestGetCallbacksHappyPath:
+    def test_returns_3_callbacks_with_fake_adapter(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(admin_token),
+        )
+        assert resp.status_code == 200
+        body = resp.get_json()
+        assert "callbacks" in body
+        assert len(body["callbacks"]) == 3
+
+    def test_callback_shape(self, client: FlaskClient, admin_token: str) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(admin_token),
+        )
+        cb = resp.get_json()["callbacks"][0]
+        assert "display_id" in cb
+        assert "active" in cb
+        assert "host" in cb
+        assert "user" in cb
+        assert "domain" in cb
+        assert "last_checkin" in cb
+
+    def test_redteam_allowed(
+        self, client: FlaskClient, admin_token: str, redteam_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(redteam_token),
+        )
+        assert resp.status_code == 200
+
+
+class TestGetCallbacksErrorCases:
+    def test_404_when_no_config(self, client: FlaskClient, admin_token: str) -> None:
+        eng = _make_engagement(client, admin_token)
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(admin_token),
+        )
+        assert resp.status_code == 404
+
+    def test_404_engagement_not_found(self, client: FlaskClient, admin_token: str) -> None:
+        resp = client.get(
+            "/api/engagements/9999/c2/callbacks",
+            headers=_h(admin_token),
+        )
+        assert resp.status_code == 404
+
+    def test_403_soc(
+        self, client: FlaskClient, admin_token: str, soc_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(soc_token),
+        )
+        assert resp.status_code == 403
+
+    def test_503_no_key(
+        self, monkeypatch, client: FlaskClient, admin_token: str
+    ) -> None:
+        monkeypatch.delenv("MIMIC_ENCRYPTION_KEY", raising=False)
+        eng = _make_engagement(client, admin_token)
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(admin_token),
+        )
+        assert resp.status_code == 503
+
+    def test_502_when_adapter_raises(
+        self, monkeypatch, client: FlaskClient, admin_token: str
+    ) -> None:
+        from backend.app.services.c2 import fake as fake_mod
+
+        def _boom(self):
+            raise C2Error("mythic unreachable")
+
+        monkeypatch.setattr(fake_mod.FakeAdapter, "list_callbacks", _boom)
+
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+
+        resp = client.get(
+            f"/api/engagements/{eng['id']}/c2/callbacks",
+            headers=_h(admin_token),
+        )
+        assert resp.status_code == 502
+        assert "mythic unreachable" in resp.get_json().get("error", "")
diff --git a/backend/tests/test_c2_config.py b/backend/tests/test_c2_config.py
index f5f76ca..fd2c617 100644
--- a/backend/tests/test_c2_config.py
+++ b/backend/tests/test_c2_config.py
@@ -95,6 +95,21 @@ def test_get_config_engagement_not_found(client: FlaskClient, admin_token: str)
 # ---------------------------------------------------------------------------
 
 
+def test_put_rejects_http_scheme(client: FlaskClient, admin_token: str) -> None:
+    eng = _make_engagement(client, admin_token)
+    resp = _put_config(client, admin_token, eng["id"], url="http://c2.internal:7443")
+    assert resp.status_code == 400
+    assert "https" in resp.get_json().get("error", "").lower()
+
+
+def test_put_rejects_missing_hostname(client: FlaskClient, admin_token: str) -> None:
+    eng = _make_engagement(client, admin_token)
+    # urlparse("https://:7443") produces an empty hostname
+    resp = _put_config(client, admin_token, eng["id"], url="https://:7443")
+    assert resp.status_code == 400
+    assert "hostname" in resp.get_json().get("error", "").lower()
+
+
 def test_put_creates_config(client: FlaskClient, admin_token: str) -> None:
     eng = _make_engagement(client, admin_token)
     resp = _put_config(client, admin_token, eng["id"])
diff --git a/backend/tests/test_c2_execute.py b/backend/tests/test_c2_execute.py
new file mode 100644
index 0000000..8b632cc
--- /dev/null
+++ b/backend/tests/test_c2_execute.py
@@ -0,0 +1,324 @@
+"""Tests for POST /api/simulations/<id>/c2/execute."""
+from __future__ import annotations
+
+import pytest
+from cryptography.fernet import Fernet
+from flask import Flask
+from flask.testing import FlaskClient
+
+from backend.app.extensions import db
+from backend.app.models.c2_task import C2Task
+from backend.app.models.simulation import Simulation, SimulationStatus
+from backend.app.services.c2.adapter import C2Error
+from backend.tests.conftest import auth_headers as _h
+
+_FERNET_KEY = Fernet.generate_key().decode()
+
+
+@pytest.fixture(autouse=True)
+def set_encryption_key(monkeypatch):
+    monkeypatch.setenv("MIMIC_ENCRYPTION_KEY", _FERNET_KEY)
+
+
+@pytest.fixture(autouse=True)
+def use_fake_adapter(monkeypatch):
+    monkeypatch.setenv("MIMIC_C2_ADAPTER", "fake")
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _make_engagement(client: FlaskClient, token: str) -> dict:
+    resp = client.post(
+        "/api/engagements",
+        headers=_h(token),
+        json={"name": "Op Alpha", "start_date": "2026-06-10"},
+    )
+    assert resp.status_code == 201
+    return resp.get_json()
+
+
+def _put_config(client: FlaskClient, token: str, eid: int) -> None:
+    resp = client.put(
+        f"/api/engagements/{eid}/c2-config",
+        headers=_h(token),
+        json={"url": "https://c2.internal:7443", "api_token": "s3cr3t", "verify_tls": True},
+    )
+    assert resp.status_code == 200
+
+
+def _make_sim(client: FlaskClient, token: str, eid: int) -> dict:
+    resp = client.post(
+        f"/api/engagements/{eid}/simulations",
+        headers=_h(token),
+        json={"name": "Sim Alpha"},
+    )
+    assert resp.status_code == 201
+    return resp.get_json()
+
+
+def _execute(
+    client: FlaskClient,
+    token: str,
+    sid: int,
+    commands: list,
+    callback_display_id: int = 1,
+):
+    return client.post(
+        f"/api/simulations/{sid}/c2/execute",
+        headers=_h(token),
+        json={"callback_display_id": callback_display_id, "commands": commands},
+    )
+
+
+def _advance_to_in_progress(client: FlaskClient, token: str, sid: int) -> None:
+    client.patch(
+        f"/api/simulations/{sid}",
+        headers=_h(token),
+        json={"name": "Sim Alpha"},
+    )
+
+
+def _advance_to_review_required(client: FlaskClient, token: str, sid: int) -> None:
+    _advance_to_in_progress(client, token, sid)
+    client.post(
+        f"/api/simulations/{sid}/transition",
+        headers=_h(token),
+        json={"to": "review_required"},
+    )
+
+
+def _advance_to_done(client: FlaskClient, redteam_token: str, soc_token: str, sid: int) -> None:
+    _advance_to_review_required(client, redteam_token, sid)
+    client.post(
+        f"/api/simulations/{sid}/transition",
+        headers=_h(soc_token),
+        json={"to": "done"},
+    )
+
+
+# ---------------------------------------------------------------------------
+# Happy path
+# ---------------------------------------------------------------------------
+
+
+class TestExecuteHappyPath:
+    def test_two_commands_create_two_tasks(
+        self, app: Flask, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["whoami", "ipconfig"])
+        assert resp.status_code == 200
+        body = resp.get_json()
+        assert len(body["tasks"]) == 2
+        assert body["tasks"][0]["command"] == "whoami"
+        assert body["tasks"][1]["command"] == "ipconfig"
+
+        with app.app_context():
+            rows = C2Task.query.filter_by(simulation_id=sim["id"]).all()
+            assert len(rows) == 2
+
+    def test_task_response_shape(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["hostname"])
+        task = resp.get_json()["tasks"][0]
+        assert "id" in task
+        assert "mythic_task_display_id" in task
+        assert "command" in task
+        assert "status" in task
+        assert "completed" in task
+
+    def test_pending_sim_transitions_to_in_progress(
+        self, app: Flask, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+        assert sim["status"] == "pending"
+
+        _execute(client, admin_token, sim["id"], ["whoami"])
+
+        with app.app_context():
+            updated = db.session.get(Simulation, sim["id"])
+            assert updated is not None
+            assert updated.status == SimulationStatus.IN_PROGRESS
+
+    def test_already_in_progress_stays_in_progress(
+        self, app: Flask, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+        _advance_to_in_progress(client, admin_token, sim["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["whoami"])
+        assert resp.status_code == 200
+
+        with app.app_context():
+            updated = db.session.get(Simulation, sim["id"])
+            assert updated is not None
+            assert updated.status == SimulationStatus.IN_PROGRESS
+
+    def test_review_required_sim_still_allowed(
+        self, app: Flask, client: FlaskClient, admin_token: str, soc_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+        _advance_to_review_required(client, admin_token, sim["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["net use"])
+        assert resp.status_code == 200
+
+        # Status stays review_required — no regression to in_progress.
+        with app.app_context():
+            updated = db.session.get(Simulation, sim["id"])
+            assert updated is not None
+            assert updated.status == SimulationStatus.REVIEW_REQUIRED
+
+    def test_redteam_can_execute(
+        self, client: FlaskClient, admin_token: str, redteam_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, redteam_token, sim["id"], ["whoami"])
+        assert resp.status_code == 200
+
+    def test_mythic_task_display_id_stored(
+        self, app: Flask, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        _execute(client, admin_token, sim["id"], ["whoami"])
+
+        with app.app_context():
+            task = C2Task.query.filter_by(simulation_id=sim["id"]).first()
+            assert task is not None
+            assert task.mythic_task_display_id == 1000  # FakeAdapter starts at 1000
+
+
+# ---------------------------------------------------------------------------
+# Error cases
+# ---------------------------------------------------------------------------
+
+
+class TestExecuteValidation:
+    def test_400_empty_commands(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, admin_token, sim["id"], [])
+        assert resp.status_code == 400
+
+    def test_400_non_string_command(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = client.post(
+            f"/api/simulations/{sim['id']}/c2/execute",
+            headers=_h(admin_token),
+            json={"callback_display_id": 1, "commands": [42]},
+        )
+        assert resp.status_code == 400
+
+    def test_400_missing_callback_display_id(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = client.post(
+            f"/api/simulations/{sim['id']}/c2/execute",
+            headers=_h(admin_token),
+            json={"commands": ["whoami"]},
+        )
+        assert resp.status_code == 400
+
+    def test_409_done_sim(
+        self,
+        client: FlaskClient,
+        admin_token: str,
+        soc_token: str,
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+        _advance_to_done(client, admin_token, soc_token, sim["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["whoami"])
+        assert resp.status_code == 409
+        assert "done" in resp.get_json().get("error", "").lower()
+
+    def test_404_simulation_not_found(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        resp = _execute(client, admin_token, 9999, ["whoami"])
+        assert resp.status_code == 404
+
+    def test_404_no_c2_config(
+        self, client: FlaskClient, admin_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["whoami"])
+        assert resp.status_code == 404
+
+    def test_403_soc(
+        self, client: FlaskClient, admin_token: str, soc_token: str
+    ) -> None:
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, soc_token, sim["id"], ["whoami"])
+        assert resp.status_code == 403
+
+    def test_503_no_key(
+        self, monkeypatch, client: FlaskClient, admin_token: str
+    ) -> None:
+        monkeypatch.delenv("MIMIC_ENCRYPTION_KEY", raising=False)
+        eng = _make_engagement(client, admin_token)
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["whoami"])
+        assert resp.status_code == 503
+
+    def test_502_adapter_error(
+        self, monkeypatch, client: FlaskClient, admin_token: str
+    ) -> None:
+        from backend.app.services.c2 import fake as fake_mod
+
+        def _boom(self, callback_display_id, command, params=None):
+            raise C2Error("task queue full")
+
+        monkeypatch.setattr(fake_mod.FakeAdapter, "create_task", _boom)
+
+        eng = _make_engagement(client, admin_token)
+        _put_config(client, admin_token, eng["id"])
+        sim = _make_sim(client, admin_token, eng["id"])
+
+        resp = _execute(client, admin_token, sim["id"], ["whoami"])
+        assert resp.status_code == 502
+        assert "task queue full" in resp.get_json().get("error", "")