Add swap-acceptance (verified-swap) flow (#87)

/oncall swap no longer reassigns immediately. It now writes a pending SWAP
record and DMs the target Accept/Decline buttons; the shift only moves once
they accept.

- schedule.py: create_pending_swap / get_swap / mark_swap_verified /
  clear_swap (PK=SWAP, date/shift SK mirroring OVERRIDE, status + timestamps
  + expires_at for TTL). A new request supersedes a prior pending one.
- app.py: _handle_swap creates the pending swap + DMs the target (requires the
  target be Slack-linked; rejects self-swap). New module-level
  handle_swap_accept / handle_swap_decline + two @app.action registrations.
  Accept writes the override, repoints 3CX when it's the active shift, marks
  the swap verified, notifies the channel + requester. Decline clears it and
  DMs the requester. Lazy expiry: accept is rejected once the shift has started
  (_shift_start/_shift_started).
- blocks.py: build_swap_request_blocks (Accept/Decline) + build_swap_resolved_blocks.
- template.yaml: enable DynamoDB TTL on expires_at so abandoned pending swaps
  self-clean.
- tests: swap schedule methods, swap blocks, rewritten test_handle_swap
  (pending + DM, no immediate override), new test_swap_accept_decline. 174 passed.
- README: swap behavior + SWAP item type + TTL.

The verified SWAP status is what #84 (24h drop guard) will query.

Closes #83

README.md

@@ -16,7 +16,7 @@ The weekly schedule post is updated live when shifts change, and the previous we
 | `/oncall next` | Show next week's schedule |
 | `/oncall pick <date>` | Pick up an available shift |
 | `/oncall drop <date>` | Drop your shift (marks it available) |
-| `/oncall swap <date> @person` | Hand your shift to someone else |
+| `/oncall swap <date> @person` | Request a swap — the other person gets an Accept/Decline DM and the shift only moves once they accept |
 | `/oncall register <ext>` | Link your Slack account to your phone extension |
 | `/oncall roster` | Show all employees and their link status |
 | `/oncall pay` | Show last week's bonus pay summary |
@@ -79,10 +79,15 @@ Single table with `PK` / `SK` keys:
 | `ROSTER` | `<extension>` | Employee: name, extension, slack_user_id |
 | `WEEKLY` | `<DayName>` | Default weekly schedule: extension, name |
 | `OVERRIDE` | `<YYYY-MM-DD>` | Date override from pickup/drop (or `OPEN`) |
+| `SWAP` | `<YYYY-MM-DD>` | Pending/verified swap request: requester, target, status, `expires_at` (TTL) |
 | `SCHEDULE_POST` | `<channel_id>` | Current schedule message timestamp |
 | `PAY` | `<YYYY-MM-DD>` | Weekly pay record (Monday date key) |
 | `CONFIG` | `CONFIG` | Settings: shift_rate, fallback_extension, admin_users |
 
+Weekend day-shift rows use a `-DAY` suffix on the SK (e.g. `OVERRIDE` / `2026-04-05-DAY`). The table has TTL enabled on `expires_at` so abandoned pending swaps self-clean.
+
+**Swap flow:** `/oncall swap` writes a `pending` `SWAP` record and DMs the target Accept/Decline buttons; it does **not** reassign the shift. On Accept, the override is written, 3CX is repointed if it's the active shift, and the record is marked `verified`. On Decline (or once the shift has started) the request is dropped and the shift stays with the original owner.
+
 ### Secrets Manager
 
 | Secret | Description |

src/shared/shared/blocks.py

@@ -149,6 +149,54 @@ def build_shift_change_message(
     return [{"type": "section", "text": {"type": "mrkdwn", "text": text}}]
 
 
+def build_swap_request_blocks(
+    requester_slack: str, date_str: str, shift_type: str = "night"
+) -> list[dict]:
+    """Build the interactive Accept / Decline message DMed to a swap target."""
+    dt = datetime.strptime(date_str, "%Y-%m-%d")
+    day_label = dt.strftime("%A, %b %-d")
+    type_label = (
+        f" ({SHIFT_LABELS.get(shift_type, shift_type)})"
+        if dt.strftime("%A") in WEEKEND_DAYS
+        else ""
+    )
+    action_suffix = "_day" if shift_type == "day" else ""
+    return [
+        {
+            "type": "section",
+            "text": {
+                "type": "mrkdwn",
+                "text": (
+                    f"<@{requester_slack}> wants you to cover the "
+                    f"*{day_label}*{type_label} shift. Accept to take it on."
+                ),
+            },
+        },
+        {
+            "type": "actions",
+            "elements": [
+                {
+                    "type": "button",
+                    "text": {"type": "plain_text", "text": "Accept"},
+                    "action_id": f"swap_accept_{date_str}{action_suffix}",
+                    "style": "primary",
+                },
+                {
+                    "type": "button",
+                    "text": {"type": "plain_text", "text": "Decline"},
+                    "action_id": f"swap_decline_{date_str}{action_suffix}",
+                    "style": "danger",
+                },
+            ],
+        },
+    ]
+
+
+def build_swap_resolved_blocks(text: str) -> list[dict]:
+    """A plain section used to replace a swap DM's buttons once it's resolved."""
+    return [{"type": "section", "text": {"type": "mrkdwn", "text": text}}]
+
+
 def build_help_blocks(is_admin: bool = False) -> list[dict]:
     """Build help message blocks."""
     text = (

src/shared/shared/schedule.py

@@ -130,6 +130,60 @@ class ShiftSchedule:
         sk = f"{date_str}-DAY" if shift_type == "day" else date_str
         self.table.delete_item(Key={"PK": "OVERRIDE", "SK": sk})
 
+    # ── Swap requests ───────────────────────────────────────────────────
+
+    def create_pending_swap(
+        self,
+        date_str: str,
+        shift_type: str,
+        requester: dict,
+        target: dict,
+        expires_at: int,
+    ) -> None:
+        """Create (or supersede) a pending swap request for a shift.
+
+        One swap per shift (unique SK), so a new request overwrites any prior
+        pending one. ``expires_at`` is an epoch timestamp used for DynamoDB TTL.
+        """
+        sk = f"{date_str}-DAY" if shift_type == "day" else date_str
+        self.table.put_item(
+            Item={
+                "PK": "SWAP",
+                "SK": sk,
+                "shift_type": shift_type,
+                "status": "pending",
+                "requester_ext": requester["extension"],
+                "requester_name": requester["name"],
+                "requester_slack": requester.get("slack_user_id", ""),
+                "target_ext": target["extension"],
+                "target_name": target["name"],
+                "target_slack": target.get("slack_user_id", ""),
+                "created_at": datetime.now(EASTERN).isoformat(),
+                "expires_at": expires_at,
+            }
+        )
+
+    def get_swap(self, date_str: str, shift_type: str = "night") -> dict | None:
+        sk = f"{date_str}-DAY" if shift_type == "day" else date_str
+        resp = self.table.get_item(Key={"PK": "SWAP", "SK": sk})
+        return resp.get("Item")
+
+    def mark_swap_verified(self, date_str: str, shift_type: str = "night") -> None:
+        sk = f"{date_str}-DAY" if shift_type == "day" else date_str
+        self.table.update_item(
+            Key={"PK": "SWAP", "SK": sk},
+            UpdateExpression="SET #s = :v, accepted_at = :a",
+            ExpressionAttributeNames={"#s": "status"},
+            ExpressionAttributeValues={
+                ":v": "verified",
+                ":a": datetime.now(EASTERN).isoformat(),
+            },
+        )
+
+    def clear_swap(self, date_str: str, shift_type: str = "night") -> None:
+        sk = f"{date_str}-DAY" if shift_type == "day" else date_str
+        self.table.delete_item(Key={"PK": "SWAP", "SK": sk})
+
     # ── Resolution ──────────────────────────────────────────────────────
 
     def resolve_shift(

src/slack-bot/app.py

@@ -19,6 +19,8 @@ from shared.blocks import (
     build_pay_summary_blocks,
     build_roster_blocks,
     build_shift_change_message,
+    build_swap_request_blocks,
+    build_swap_resolved_blocks,
     build_week_schedule,
 )
 from shared.ring_scheduler import update_queue_routing
@@ -103,6 +105,16 @@ def _is_active_shift_type(shift_type: str) -> bool:
     return determine_shift_type() == shift_type
 
 
+def _shift_start(date_str: str, shift_type: str) -> datetime:
+    """The datetime (ET) a shift begins — weekend day at 08:00, otherwise 17:00."""
+    d = datetime.strptime(date_str, "%Y-%m-%d").replace(tzinfo=EASTERN)
+    return d.replace(hour=8 if shift_type == "day" else 17)
+
+
+def _shift_started(date_str: str, shift_type: str) -> bool:
+    return datetime.now(EASTERN) >= _shift_start(date_str, shift_type)
+
+
 def _shift_type_label(day_name: str, shift_type: str) -> str:
     if day_name not in WEEKEND_DAYS:
         return ""
@@ -580,37 +592,170 @@ def _handle_swap(
             respond(text=f"Extension `{target_text}` not found in the roster.")
             return
 
-    schedule.set_override(date_str, target["extension"], target["name"], shift_type)
+    if target["extension"] == employee["extension"]:
+        respond(text="That shift is already yours — nothing to swap.")
+        return
 
-    if is_today(date_str) and _is_active_shift_type(shift_type):
-        _update_3cx_routing(target["extension"])
+    # The target must be linked to Slack so we can DM them the request.
+    if not target.get("slack_user_id"):
+        respond(
+            text=f"*{target['name']}* (Ext {target['extension']}) isn't linked to Slack yet — "
+            "they need to run `/oncall register <extension>` before they can be swapped a shift."
+        )
+        return
+
+    # Create a pending swap and DM the target Accept/Decline. The shift does NOT
+    # move until they accept — the original owner stays responsible until then.
+    expires_at = int(_shift_start(date_str, shift_type).timestamp())
+    schedule.create_pending_swap(date_str, shift_type, employee, target, expires_at)
 
-    blocks = build_shift_change_message(
-        target.get("slack_user_id", user_id),
-        date_str,
-        "swapped",
-        target["extension"],
-        target["name"],
-        shift_type=shift_type,
-    )
     date_label = date.strftime("%A, %b %-d")
     shift_label = _shift_type_label(day_name, shift_type)
+    try:
+        client.chat_postMessage(
+            channel=target["slack_user_id"],
+            blocks=build_swap_request_blocks(user_id, date_str, shift_type),
+            text=f"{employee['name']} wants to swap you the {date_str} shift",
+        )
+    except Exception:
+        logger.exception("Failed to DM swap request to target")
+        respond(
+            text=f"Couldn't reach *{target['name']}* on Slack to send the request. Try again later."
+        )
+        return
+
     respond(
         text=(
-            f"Swapped *{date_label}*{shift_label} to {target['name']} "
-            f"(Ext {target['extension']})."
+            f"Swap request sent to <@{target['slack_user_id']}> for "
+            f"*{date_label}*{shift_label}. The shift moves to them once they accept."
         )
     )
 
-    try:
-        client.chat_postMessage(
-            channel=channel_id, blocks=blocks, text=f"Shift swapped for {date_str}"
+
+def _parse_swap_action(action_id: str, prefix: str) -> tuple[str, str]:
+    """Split a swap action_id into (date_str, shift_type)."""
+    remainder = action_id[len(prefix) :]
+    if remainder.endswith("_day"):
+        return remainder[:-4], "day"
+    return remainder, "night"
+
+
+def handle_swap_accept(body, respond, client, schedule, schedule_channel):
+    """Target accepted a swap — apply the override and mark it verified."""
+    date_str, shift_type = _parse_swap_action(
+        body["actions"][0]["action_id"], "swap_accept_"
+    )
+    user_id = body["user"]["id"]
+
+    swap = schedule.get_swap(date_str, shift_type)
+    if (
+        not swap
+        or swap.get("status") != "pending"
+        or swap.get("target_slack") != user_id
+    ):
+        respond(
+            replace_original=True,
+            blocks=build_swap_resolved_blocks("This swap request is no longer valid."),
         )
-    except Exception:
-        logger.exception("Failed to post swap notification to channel")
+        return
+
+    if _shift_started(date_str, shift_type):
+        schedule.clear_swap(date_str, shift_type)
+        respond(
+            replace_original=True,
+            blocks=build_swap_resolved_blocks(
+                "This swap request has expired — the shift has already started."
+            ),
+        )
+        return
+
+    schedule.set_override(date_str, swap["target_ext"], swap["target_name"], shift_type)
+    if is_today(date_str) and _is_active_shift_type(shift_type):
+        _update_3cx_routing(swap["target_ext"])
+    schedule.mark_swap_verified(date_str, shift_type)
+
+    day_name = datetime.strptime(date_str, "%Y-%m-%d").strftime("%A")
+    date_label = datetime.strptime(date_str, "%Y-%m-%d").strftime("%A, %b %-d")
+    shift_label = _shift_type_label(day_name, shift_type)
+
+    respond(
+        replace_original=True,
+        blocks=build_swap_resolved_blocks(
+            f"You're now covering the *{date_label}*{shift_label} shift. Thanks!"
+        ),
+    )
+
+    if swap.get("requester_slack"):
+        try:
+            client.chat_postMessage(
+                channel=swap["requester_slack"],
+                text=f"<@{user_id}> accepted your swap — they're now on the *{date_label}*{shift_label} shift.",
+            )
+        except Exception:
+            logger.exception("Failed to DM swap requester on accept")
+
+    if schedule_channel:
+        blocks = build_shift_change_message(
+            user_id,
+            date_str,
+            "swapped",
+            swap["target_ext"],
+            swap["target_name"],
+            shift_type=shift_type,
+        )
+        try:
+            client.chat_postMessage(
+                channel=schedule_channel,
+                blocks=blocks,
+                text=f"Shift swapped for {date_str}",
+            )
+        except Exception:
+            logger.exception("Failed to post swap notification to channel")
     _refresh_schedule_post(schedule, schedule_channel, client)
 
 
+def handle_swap_decline(body, respond, client, schedule, schedule_channel):
+    """Target declined a swap — clear it and notify the requester."""
+    date_str, shift_type = _parse_swap_action(
+        body["actions"][0]["action_id"], "swap_decline_"
+    )
+    user_id = body["user"]["id"]
+
+    swap = schedule.get_swap(date_str, shift_type)
+    if (
+        not swap
+        or swap.get("status") != "pending"
+        or swap.get("target_slack") != user_id
+    ):
+        respond(
+            replace_original=True,
+            blocks=build_swap_resolved_blocks("This swap request is no longer valid."),
+        )
+        return
+
+    schedule.clear_swap(date_str, shift_type)
+
+    day_name = datetime.strptime(date_str, "%Y-%m-%d").strftime("%A")
+    date_label = datetime.strptime(date_str, "%Y-%m-%d").strftime("%A, %b %-d")
+    shift_label = _shift_type_label(day_name, shift_type)
+
+    respond(
+        replace_original=True,
+        blocks=build_swap_resolved_blocks(
+            f"You declined the *{date_label}*{shift_label} swap. No change."
+        ),
+    )
+
+    if swap.get("requester_slack"):
+        try:
+            client.chat_postMessage(
+                channel=swap["requester_slack"],
+                text=f"<@{user_id}> declined your swap for *{date_label}*{shift_label} — it's still your shift.",
+            )
+        except Exception:
+            logger.exception("Failed to DM swap requester on decline")
+
+
 def _handle_admin(respond, schedule, user_id, text, is_admin, client, schedule_channel):
     if not is_admin:
         respond(text="Admin commands are restricted. Contact an administrator.")
@@ -784,4 +929,14 @@ def create_app(
         ack()
         handle_pickup(body, respond, client, schedule, schedule_channel)
 
+    @app.action(re.compile(r"^swap_accept_"))
+    def handle_swap_accept_button(ack, body, client, respond):
+        ack()
+        handle_swap_accept(body, respond, client, schedule, schedule_channel)
+
+    @app.action(re.compile(r"^swap_decline_"))
+    def handle_swap_decline_button(ack, body, client, respond):
+        ack()
+        handle_swap_decline(body, respond, client, schedule, schedule_channel)
+
     return app

template.yaml

@@ -53,6 +53,9 @@ Resources:
           KeyType: HASH
         - AttributeName: SK
           KeyType: RANGE
+      TimeToLiveSpecification:
+        AttributeName: expires_at
+        Enabled: true
 
   # --- Slack Bot Lambda ---
   SlackBotFunction:

tests/shared/test_blocks.py

@@ -7,6 +7,8 @@ from shared.blocks import (
     build_pay_summary_blocks,
     build_roster_blocks,
     build_shift_change_message,
+    build_swap_request_blocks,
+    build_swap_resolved_blocks,
     build_week_schedule,
 )
 
@@ -93,6 +95,43 @@ class TestBuildPaySummaryBlocks:
         assert "Alice" in text and "$50.00" in text and "1 shift" in text
 
 
+class TestBuildSwapRequestBlocks:
+    def _action_ids(self, blocks):
+        return [
+            e["action_id"]
+            for b in blocks
+            if b["type"] == "actions"
+            for e in b["elements"]
+        ]
+
+    def test_weekday_request_has_accept_decline(self):
+        blocks = build_swap_request_blocks("U_REQ", "2026-06-03", "night")
+        assert "<@U_REQ>" in blocks[0]["text"]["text"]
+        ids = self._action_ids(blocks)
+        assert ids == ["swap_accept_2026-06-03", "swap_decline_2026-06-03"]
+
+    def test_weekend_day_request_uses_day_suffix_and_label(self):
+        blocks = build_swap_request_blocks("U_REQ", "2026-06-06", "day")
+        assert "Day (8am" in blocks[0]["text"]["text"]
+        ids = self._action_ids(blocks)
+        assert ids == ["swap_accept_2026-06-06_day", "swap_decline_2026-06-06_day"]
+
+    def test_button_styles(self):
+        elements = build_swap_request_blocks("U_REQ", "2026-06-03", "night")[1][
+            "elements"
+        ]
+        assert elements[0]["style"] == "primary"  # Accept
+        assert elements[1]["style"] == "danger"  # Decline
+
+
+class TestBuildSwapResolvedBlocks:
+    def test_renders_text_no_buttons(self):
+        blocks = build_swap_resolved_blocks("All done.")
+        assert blocks == [
+            {"type": "section", "text": {"type": "mrkdwn", "text": "All done."}}
+        ]
+
+
 class TestBuildHelpBlocks:
     def test_non_admin_excludes_admin_section(self):
         text = build_help_blocks(is_admin=False)[0]["text"]["text"]

tests/shared/test_schedule.py

@@ -218,3 +218,43 @@ class TestPayAndConfigAndPosts:
 def test_shiftschedule_uses_env_table_name(monkeypatch, dynamodb_table):
     # Constructed with no arg → reads SHIFT_TABLE.
     assert ShiftSchedule().table.name == "afterhours-shifts"
+
+
+class TestSwaps:
+    REQ = {"extension": "114", "name": "Alice", "slack_user_id": "U_ALICE"}
+    TGT = {"extension": "115", "name": "Bob", "slack_user_id": "U_BOB"}
+
+    def test_create_and_get_pending_swap(self, schedule):
+        schedule.create_pending_swap(WED, "night", self.REQ, self.TGT, 1_900_000_000)
+        swap = schedule.get_swap(WED)
+        assert swap["status"] == "pending"
+        assert swap["requester_ext"] == "114" and swap["requester_slack"] == "U_ALICE"
+        assert swap["target_ext"] == "115" and swap["target_slack"] == "U_BOB"
+        assert swap["expires_at"] == 1_900_000_000
+        assert swap["created_at"]  # stamped
+
+    def test_get_missing_swap(self, schedule):
+        assert schedule.get_swap(WED) is None
+
+    def test_create_supersedes_existing(self, schedule):
+        schedule.create_pending_swap(WED, "night", self.REQ, self.TGT, 1)
+        other = {"extension": "116", "name": "Carol", "slack_user_id": "U_CAROL"}
+        schedule.create_pending_swap(WED, "night", self.REQ, other, 2)
+        swap = schedule.get_swap(WED)
+        assert swap["target_ext"] == "116"  # overwritten, only one record
+
+    def test_day_and_night_swaps_independent(self, schedule):
+        schedule.create_pending_swap(SAT, "day", self.REQ, self.TGT, 1)
+        assert schedule.get_swap(SAT, "day")["target_ext"] == "115"
+        assert schedule.get_swap(SAT, "night") is None
+
+    def test_mark_verified(self, schedule):
+        schedule.create_pending_swap(WED, "night", self.REQ, self.TGT, 1)
+        schedule.mark_swap_verified(WED)
+        swap = schedule.get_swap(WED)
+        assert swap["status"] == "verified" and swap["accepted_at"]
+
+    def test_clear_swap(self, schedule):
+        schedule.create_pending_swap(WED, "night", self.REQ, self.TGT, 1)
+        schedule.clear_swap(WED)
+        assert schedule.get_swap(WED) is None

tests/slack_bot/test_handle_swap.py

@@ -1,4 +1,5 @@
-"""Tests for slack-bot _handle_swap."""
+"""Tests for slack-bot _handle_swap — now creates a pending swap + DMs the target
+instead of reassigning immediately."""
 
 from freezegun import freeze_time
 
@@ -12,87 +13,127 @@ def _setup(seed):
 
 
 @freeze_time(MON)
-def test_swap_to_mention(
+def test_request_creates_pending_and_dms_target(
     slackbot_app, schedule, seed, respond, client, routing_spy, text_of
 ):
     _setup(seed)
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap today <@U_BOB>", "C1", client, None
+        respond, schedule, "U_ALICE", "swap today <@U_BOB>", "C1", client, "C_TEST"
     )
-    override = schedule.get_override("2026-06-01")
-    assert override["extension"] == "115" and override["name"] == "Bob"
-    assert "Swapped" in text_of(respond)
-    routing_spy.assert_called_once_with("115")
-    client.chat_postMessage.assert_called_once()
+
+    swap = schedule.get_swap("2026-06-01")
+    assert swap["status"] == "pending" and swap["target_ext"] == "115"
+    # Not applied yet — the shift still belongs to Alice.
+    assert schedule.get_override("2026-06-01") is None
+    routing_spy.assert_not_called()
+    # DM'd the target, told the requester.
+    assert client.chat_postMessage.call_args.kwargs["channel"] == "U_BOB"
+    assert "Swap request sent" in text_of(respond)
 
 
 @freeze_time(MON)
-def test_swap_to_extension(slackbot_app, schedule, seed, respond, client, routing_spy):
+def test_request_by_extension(
+    slackbot_app, schedule, seed, respond, client, routing_spy
+):
     _setup(seed)
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap today 115", "C1", client, None
+        respond, schedule, "U_ALICE", "swap today 115", "C1", client, "C_TEST"
     )
-    assert schedule.get_override("2026-06-01")["extension"] == "115"
+    assert schedule.get_swap("2026-06-01")["target_ext"] == "115"
 
 
 @freeze_time(MON)
-def test_swap_not_your_shift(
-    slackbot_app, schedule, seed, respond, client, routing_spy, text_of
+def test_later_request_supersedes(slackbot_app, schedule, seed, respond, client):
+    _setup(seed)
+    seed.roster("116", "Carol", slack_user_id="U_CAROL")
+    slackbot_app._handle_swap(
+        respond, schedule, "U_ALICE", "swap today <@U_BOB>", "C1", client, "C_TEST"
+    )
+    slackbot_app._handle_swap(
+        respond, schedule, "U_ALICE", "swap today <@U_CAROL>", "C1", client, "C_TEST"
+    )
+    assert schedule.get_swap("2026-06-01")["target_ext"] == "116"
+
+
+@freeze_time(MON)
+def test_target_not_linked_to_slack(
+    slackbot_app, schedule, seed, respond, client, text_of
 ):
+    seed.roster("114", "Alice", slack_user_id="U_ALICE")
+    seed.roster("115", "Bob")  # registered but never linked Slack
+    seed.weekly("Monday", "114", "Alice")
+    slackbot_app._handle_swap(
+        respond, schedule, "U_ALICE", "swap today 115", "C1", client, "C_TEST"
+    )
+    assert "isn't linked to Slack" in text_of(respond)
+    assert schedule.get_swap("2026-06-01") is None
+
+
+@freeze_time(MON)
+def test_swap_to_self_rejected(slackbot_app, schedule, seed, respond, client, text_of):
+    _setup(seed)
+    slackbot_app._handle_swap(
+        respond, schedule, "U_ALICE", "swap today 114", "C1", client, "C_TEST"
+    )
+    assert "already yours" in text_of(respond).lower()
+
+
+@freeze_time(MON)
+def test_not_your_shift(slackbot_app, schedule, seed, respond, client, text_of):
     seed.roster("114", "Alice", slack_user_id="U_ALICE")
     seed.roster("115", "Bob", slack_user_id="U_BOB")
     seed.weekly("Monday", "115", "Bob")  # Bob's shift, not Alice's
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap today <@U_BOB>", "C1", client, None
+        respond, schedule, "U_ALICE", "swap today <@U_BOB>", "C1", client, "C_TEST"
     )
     assert "not your shift" in text_of(respond).lower()
-    routing_spy.assert_not_called()
+    assert schedule.get_swap("2026-06-01") is None
 
 
 @freeze_time(MON)
-def test_swap_target_mention_unregistered(
+def test_target_mention_unregistered(
     slackbot_app, schedule, seed, respond, client, text_of
 ):
     seed.roster("114", "Alice", slack_user_id="U_ALICE")
     seed.weekly("Monday", "114", "Alice")
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap today <@U_GHOST>", "C1", client, None
+        respond, schedule, "U_ALICE", "swap today <@U_GHOST>", "C1", client, "C_TEST"
     )
     assert "isn't registered" in text_of(respond)
 
 
 @freeze_time(MON)
-def test_swap_target_extension_not_found(
+def test_target_extension_not_found(
     slackbot_app, schedule, seed, respond, client, text_of
 ):
     seed.roster("114", "Alice", slack_user_id="U_ALICE")
     seed.weekly("Monday", "114", "Alice")
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap today 999", "C1", client, None
+        respond, schedule, "U_ALICE", "swap today 999", "C1", client, "C_TEST"
     )
     assert "not found" in text_of(respond).lower()
 
 
 @freeze_time(MON)
-def test_swap_past_date(slackbot_app, schedule, seed, respond, client, text_of):
+def test_past_date(slackbot_app, schedule, seed, respond, client, text_of):
     _setup(seed)
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap 2026-05-01 <@U_BOB>", "C1", client, None
+        respond, schedule, "U_ALICE", "swap 2026-05-01 <@U_BOB>", "C1", client, "C_TEST"
     )
     assert "past" in text_of(respond).lower()
 
 
 @freeze_time(MON)
-def test_swap_unregistered_requester(slackbot_app, schedule, respond, client, text_of):
+def test_unregistered_requester(slackbot_app, schedule, respond, client, text_of):
     slackbot_app._handle_swap(
-        respond, schedule, "U_NOBODY", "swap today 115", "C1", client, None
+        respond, schedule, "U_NOBODY", "swap today 115", "C1", client, "C_TEST"
     )
     assert "not registered" in text_of(respond).lower()
 
 
 @freeze_time(MON)
-def test_swap_usage(slackbot_app, schedule, respond, client, text_of):
+def test_usage(slackbot_app, schedule, respond, client, text_of):
     slackbot_app._handle_swap(
-        respond, schedule, "U_ALICE", "swap today", "C1", client, None
+        respond, schedule, "U_ALICE", "swap today", "C1", client, "C_TEST"
     )
     assert "Usage" in text_of(respond)

tests/slack_bot/test_swap_accept_decline.py

@@ -0,0 +1,162 @@
+"""Tests for slack-bot handle_swap_accept / handle_swap_decline."""
+
+from freezegun import freeze_time
+
+# Monday 2026-06-01 08:00 ET — weekday, active shift is night, before 17:00 start.
+MON = "2026-06-01 12:00:00"
+# Same Monday but 18:00 ET — the night shift has already started.
+MON_AFTER_START = "2026-06-01 22:00:00"
+
+REQ = {"extension": "114", "name": "Alice", "slack_user_id": "U_ALICE"}
+TGT = {"extension": "115", "name": "Bob", "slack_user_id": "U_BOB"}
+
+
+def _accept_body(date_str, user_id="U_BOB", suffix=""):
+    return {
+        "actions": [{"action_id": f"swap_accept_{date_str}{suffix}"}],
+        "user": {"id": user_id},
+        "channel": {"id": "D1"},
+    }
+
+
+def _decline_body(date_str, user_id="U_BOB", suffix=""):
+    return {
+        "actions": [{"action_id": f"swap_decline_{date_str}{suffix}"}],
+        "user": {"id": user_id},
+        "channel": {"id": "D1"},
+    }
+
+
+def _pending(schedule, date_str, shift_type="night", target=TGT):
+    schedule.create_pending_swap(date_str, shift_type, REQ, target, 1_900_000_000)
+
+
+def _resolved_text(respond):
+    return respond.call_args.kwargs["blocks"][0]["text"]["text"]
+
+
+def _channels(client):
+    return [c.kwargs.get("channel") for c in client.chat_postMessage.call_args_list]
+
+
+class TestAccept:
+    @freeze_time(MON)
+    def test_applies_override_marks_verified_notifies(
+        self, slackbot_app, schedule, respond, client, routing_spy
+    ):
+        _pending(schedule, "2026-06-01")
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-01"), respond, client, schedule, "C_TEST"
+        )
+        assert schedule.get_override("2026-06-01")["extension"] == "115"
+        assert schedule.get_swap("2026-06-01")["status"] == "verified"
+        # Today + active night → 3CX repointed to the new holder.
+        routing_spy.assert_called_once_with("115")
+        # Channel notification + requester DM both sent.
+        assert "C_TEST" in _channels(client) and "U_ALICE" in _channels(client)
+        assert "now covering" in _resolved_text(respond).lower()
+
+    @freeze_time(MON)
+    def test_future_shift_no_3cx(
+        self, slackbot_app, schedule, respond, client, routing_spy
+    ):
+        _pending(schedule, "2026-06-03")  # Wednesday
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-03"), respond, client, schedule, "C_TEST"
+        )
+        assert schedule.get_override("2026-06-03")["extension"] == "115"
+        routing_spy.assert_not_called()
+
+    @freeze_time(MON)
+    def test_wrong_clicker_rejected(
+        self, slackbot_app, schedule, respond, client, routing_spy
+    ):
+        _pending(schedule, "2026-06-01")
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-01", user_id="U_STRANGER"),
+            respond,
+            client,
+            schedule,
+            "C_TEST",
+        )
+        assert schedule.get_override("2026-06-01") is None
+        assert "no longer valid" in _resolved_text(respond).lower()
+        routing_spy.assert_not_called()
+
+    @freeze_time(MON)
+    def test_no_pending_swap(self, slackbot_app, schedule, respond, client):
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-01"), respond, client, schedule, "C_TEST"
+        )
+        assert "no longer valid" in _resolved_text(respond).lower()
+
+    @freeze_time(MON)
+    def test_already_verified_swap_not_reapplied(
+        self, slackbot_app, schedule, respond, client
+    ):
+        _pending(schedule, "2026-06-01")
+        schedule.mark_swap_verified("2026-06-01")
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-01"), respond, client, schedule, "C_TEST"
+        )
+        assert "no longer valid" in _resolved_text(respond).lower()
+        assert schedule.get_override("2026-06-01") is None
+
+    @freeze_time(MON_AFTER_START)
+    def test_expired_after_shift_start(
+        self, slackbot_app, schedule, respond, client, routing_spy
+    ):
+        _pending(schedule, "2026-06-01")
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-01"), respond, client, schedule, "C_TEST"
+        )
+        assert "expired" in _resolved_text(respond).lower()
+        assert schedule.get_override("2026-06-01") is None
+        assert schedule.get_swap("2026-06-01") is None  # cleared
+        routing_spy.assert_not_called()
+
+    @freeze_time(MON)
+    def test_weekend_day_suffix(self, slackbot_app, schedule, respond, client):
+        _pending(schedule, "2026-06-06", shift_type="day")
+        slackbot_app.handle_swap_accept(
+            _accept_body("2026-06-06", suffix="_day"),
+            respond,
+            client,
+            schedule,
+            "C_TEST",
+        )
+        assert schedule.get_override("2026-06-06", "day")["extension"] == "115"
+        assert schedule.get_swap("2026-06-06", "day")["status"] == "verified"
+
+
+class TestDecline:
+    @freeze_time(MON)
+    def test_clears_and_dms_requester(self, slackbot_app, schedule, respond, client):
+        _pending(schedule, "2026-06-01")
+        slackbot_app.handle_swap_decline(
+            _decline_body("2026-06-01"), respond, client, schedule, "C_TEST"
+        )
+        assert schedule.get_swap("2026-06-01") is None
+        assert schedule.get_override("2026-06-01") is None  # never applied
+        assert "declined" in _resolved_text(respond).lower()
+        assert "U_ALICE" in _channels(client)  # requester notified
+
+    @freeze_time(MON)
+    def test_wrong_clicker_rejected(self, slackbot_app, schedule, respond, client):
+        _pending(schedule, "2026-06-01")
+        slackbot_app.handle_swap_decline(
+            _decline_body("2026-06-01", user_id="U_STRANGER"),
+            respond,
+            client,
+            schedule,
+            "C_TEST",
+        )
+        assert "no longer valid" in _resolved_text(respond).lower()
+        assert schedule.get_swap("2026-06-01") is not None  # untouched
+
+    @freeze_time(MON)
+    def test_no_pending_swap(self, slackbot_app, schedule, respond, client):
+        slackbot_app.handle_swap_decline(
+            _decline_body("2026-06-01"), respond, client, schedule, "C_TEST"
+        )
+        assert "no longer valid" in _resolved_text(respond).lower()