diff --git a/application/alembic/versions/0026_stack_logs_agent_id.py b/application/alembic/versions/0026_stack_logs_agent_id.py
new file mode 100644
index 00000000..8e365d9a
--- /dev/null
+++ b/application/alembic/versions/0026_stack_logs_agent_id.py
@@ -0,0 +1,52 @@
+"""0026 stack_logs.agent_id — stable per-agent attribution for activity logs.
+
+``stack_logs`` (webhook + system-error activity logs) previously carried only
+the agent's ``api_key`` string, so it could be joined to an agent only through
+that key. Now that agents can rotate their key, a key-only join would orphan
+history on rotation. This adds a nullable ``agent_id`` UUID (no FK, mirroring
+``token_usage.agent_id`` so a stray/legacy id can never block a log write),
+indexes it, and backfills existing rows by matching the stored ``api_key`` to
+``agents.key``. The backfill is exhaustive today because no key has been
+rotated yet. Idempotent both ways.
+
+Revision ID: 0026_stack_logs_agent_id
+Revises: 0025_artifacts
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+
+
+revision: str = "0026_stack_logs_agent_id"
+down_revision: Union[str, None] = "0025_artifacts"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute("ALTER TABLE stack_logs ADD COLUMN IF NOT EXISTS agent_id uuid;")
+    op.execute(
+        """
+        CREATE INDEX IF NOT EXISTS ix_stack_logs_agent_id
+            ON stack_logs (agent_id)
+            WHERE agent_id IS NOT NULL;
+        """
+    )
+    # Backfill from the still-current key mapping. ``agents.key`` is CITEXT and
+    # unique, so each api_key resolves to at most one agent.
+    op.execute(
+        """
+        UPDATE stack_logs s
+           SET agent_id = a.id
+          FROM agents a
+         WHERE s.agent_id IS NULL
+           AND s.api_key IS NOT NULL
+           AND a.key = s.api_key;
+        """
+    )
+
+
+def downgrade() -> None:
+    op.execute("DROP INDEX IF EXISTS ix_stack_logs_agent_id;")
+    op.execute("ALTER TABLE stack_logs DROP COLUMN IF EXISTS agent_id;")
diff --git a/application/api/user/agents/routes.py b/application/api/user/agents/routes.py
index a58f526c..2104788b 100644
--- a/application/api/user/agents/routes.py
+++ b/application/api/user/agents/routes.py
@@ -28,6 +28,12 @@ from application.api.user.team_sharing import (
 )
 from application.storage.db.repositories.agent_folders import AgentFoldersRepository
 from application.storage.db.repositories.agents import AgentsRepository
+from application.storage.db.repositories.conversations import ConversationsRepository
+from application.storage.db.repositories.shared_conversations import (
+    SharedConversationsRepository,
+)
+from application.storage.db.repositories.stack_logs import StackLogsRepository
+from application.storage.db.repositories.token_usage import TokenUsageRepository
 from application.storage.db.repositories.users import UsersRepository
 from application.storage.db.repositories.workflow_edges import WorkflowEdgesRepository
 from application.storage.db.repositories.workflow_nodes import WorkflowNodesRepository
@@ -1293,6 +1299,106 @@ class UpdateAgent(Resource):
         return make_response(jsonify(response_data), 200)
 
 
+@agents_ns.route("/regenerate_agent_key/<string:agent_id>")
+class RegenerateAgentKey(Resource):
+    @api.doc(
+        params={"agent_id": "ID of the agent"},
+        description=(
+            "Rotate an agent's API key. The previous key is invalidated "
+            "immediately and a fresh key is returned once. Historical logging "
+            "and usage records are re-pointed to the new key so analytics stay "
+            "intact. Owner only."
+        ),
+    )
+    def post(self, agent_id):
+        if not (decoded_token := request.decoded_token):
+            return make_response(
+                jsonify({"success": False, "message": "Unauthorized"}), 401
+            )
+        user = decoded_token.get("sub")
+
+        try:
+            with db_session() as conn:
+                agents_repo = AgentsRepository(conn)
+                # Owner-only: rotating a credential is destructive to live
+                # integrations, so this is intentionally stricter than
+                # update_agent (which also allows team editors).
+                existing_agent = agents_repo.get_any(agent_id, user)
+                if not existing_agent:
+                    return make_response(
+                        jsonify(
+                            {
+                                "success": False,
+                                "message": "Agent not found or not authorized",
+                            }
+                        ),
+                        404,
+                    )
+
+                pg_agent_id = str(existing_agent["id"])
+                old_key = existing_agent.get("key")
+                if not old_key:
+                    # Draft agents have no key; the first key is minted on
+                    # publish. Nothing to rotate.
+                    return make_response(
+                        jsonify(
+                            {
+                                "success": False,
+                                "message": "Publish the agent before resetting its key",
+                            }
+                        ),
+                        400,
+                    )
+
+                new_key = str(uuid.uuid4())
+                updated = agents_repo.update(pg_agent_id, user, {"key": new_key})
+                if not updated:
+                    return make_response(
+                        jsonify(
+                            {
+                                "success": False,
+                                "message": "Failed to regenerate key",
+                            }
+                        ),
+                        500,
+                    )
+
+                # Re-point every api_key reference to the new key so rotation
+                # doesn't break history or live links. token_usage/stack_logs
+                # (0026) carry agent_id, but rows can still be api_key-only:
+                # conversations set api_key without an agent_id unless the caller
+                # passes one, stack_logs rows may have a NULL agent_id, and the
+                # 24h rate-limit window is keyed by api_key only (token_usage).
+                # shared_conversations is functional, not just analytics: the
+                # public share endpoint hands its stored api_key to the widget,
+                # so a stale key would break promptable shared links.
+                # All rewrites run in the same transaction as the key swap.
+                StackLogsRepository(conn).reassign_api_key(
+                    old_key=old_key, new_key=new_key
+                )
+                TokenUsageRepository(conn).reassign_api_key(
+                    old_key=old_key, new_key=new_key
+                )
+                ConversationsRepository(conn).reassign_api_key(
+                    old_key=old_key, new_key=new_key
+                )
+                SharedConversationsRepository(conn).reassign_api_key(
+                    old_key=old_key, new_key=new_key
+                )
+        except Exception as err:
+            current_app.logger.error(
+                f"Error regenerating agent key: {err}", exc_info=True
+            )
+            return make_response(
+                jsonify(
+                    {"success": False, "message": "Error regenerating agent key"}
+                ),
+                500,
+            )
+
+        return make_response(jsonify({"success": True, "key": new_key}), 200)
+
+
 @agents_ns.route("/delete_agent")
 class DeleteAgent(Resource):
     @api.doc(params={"id": "ID of the agent"}, description="Delete an agent by ID")
diff --git a/application/api/user/analytics/routes.py b/application/api/user/analytics/routes.py
index 9bf3ba1a..9a193068 100644
--- a/application/api/user/analytics/routes.py
+++ b/application/api/user/analytics/routes.py
@@ -801,15 +801,23 @@ class GetUserLogs(Resource):
                         "(l.data->>'api_key' = :api_key"
                         " OR l.data->>'agent_id' = :agent_pg_id)"
                     ]
+                    # ``stack_logs.agent_id`` (0026) is the stable join key;
+                    # ``api_key`` is mutable (agents rotate keys), so match the
+                    # id first and keep the key arm for rows predating the
+                    # backfill / any null agent_id.
+                    stack_agent_match = (
+                        "(s.agent_id = CAST(:agent_pg_id AS uuid)"
+                        " OR s.api_key = :api_key)"
+                    )
                     webhook_where = [
                         "COALESCE(s.endpoint, '') = 'webhook'",
-                        "s.api_key = :api_key",
+                        stack_agent_match,
                         webhook_dedupe,
                     ]
                     system_where = [
                         "s.level = 'error'",
                         "COALESCE(s.endpoint, '') NOT IN ('webhook', 'schedule')",
-                        "s.api_key = :api_key",
+                        stack_agent_match,
                     ]
                     # Owner-gated agent match: drop the user clause so a
                     # shared agent's runs (stamped with the caller's
diff --git a/application/logging.py b/application/logging.py
index d9f5b768..5c03f2a2 100644
--- a/application/logging.py
+++ b/application/logging.py
@@ -5,7 +5,7 @@ import time
 
 import logging
 import uuid
-from typing import Any, Callable, Dict, Generator, List
+from typing import Any, Callable, Dict, Generator, List, Optional
 
 from application.core import log_context
 from application.storage.db.repositories.stack_logs import StackLogsRepository
@@ -17,11 +17,12 @@ logging.basicConfig(
 
 
 class LogContext:
-    def __init__(self, endpoint, activity_id, user, api_key, query):
+    def __init__(self, endpoint, activity_id, user, api_key, query, agent_id=None):
         self.endpoint = endpoint
         self.activity_id = activity_id
         self.user = user
         self.api_key = api_key
+        self.agent_id = agent_id
         self.query = query
         self.stacks = []
         # Per-activity response aggregates populated by ``_consume_and_log``
@@ -100,7 +101,9 @@ def log_activity() -> Callable:
             # so nested activities record the parent → child link.
             parent_activity_id = log_context.snapshot().get("activity_id")
 
-            context = LogContext(endpoint, activity_id, user, api_key, query)
+            context = LogContext(
+                endpoint, activity_id, user, api_key, query, agent_id=agent_id
+            )
             kwargs["log_context"] = context
 
             ctx_token = log_context.bind(
@@ -217,6 +220,7 @@ def _consume_and_log(generator: Generator, context: "LogContext"):
             activity_id=context.activity_id,
             user=context.user,
             api_key=context.api_key,
+            agent_id=context.agent_id,
             query=context.query,
             stacks=context.stacks,
             level="error",
@@ -228,6 +232,7 @@ def _consume_and_log(generator: Generator, context: "LogContext"):
             activity_id=context.activity_id,
             user=context.user,
             api_key=context.api_key,
+            agent_id=context.agent_id,
             query=context.query,
             stacks=context.stacks,
             level="info",
@@ -242,6 +247,7 @@ def _log_activity_to_db(
     query: str,
     stacks: List[Dict],
     level: str,
+    agent_id: Optional[str] = None,
 ) -> None:
     """Append a per-request activity log row to Postgres (``stack_logs``)."""
     try:
@@ -259,6 +265,7 @@ def _log_activity_to_db(
                 level=_truncate(level),
                 user_id=_truncate(user),
                 api_key=_truncate(api_key),
+                agent_id=agent_id,
                 query=_truncate(query),
                 stacks=stacks,
                 timestamp=datetime.datetime.now(datetime.timezone.utc),
diff --git a/application/storage/db/models.py b/application/storage/db/models.py
index 261e5c1b..bdde2263 100644
--- a/application/storage/db/models.py
+++ b/application/storage/db/models.py
@@ -255,6 +255,11 @@ stack_logs_table = Table(
     Column("level", Text),
     Column("user_id", Text),
     Column("api_key", Text),
+    # Stable per-agent attribution. ``api_key`` is mutable (agents can rotate
+    # their key), so analytics join on this UUID first and fall back to the
+    # key string. No FK (mirrors ``token_usage.agent_id``) so a stray/legacy
+    # id can never block an activity-log write. Added in ``0026``.
+    Column("agent_id", UUID(as_uuid=True)),
     Column("query", Text),
     Column("stacks", JSONB, nullable=False, server_default="[]"),
     Column("timestamp", DateTime(timezone=True), nullable=False, server_default=func.now()),
diff --git a/application/storage/db/repositories/conversations.py b/application/storage/db/repositories/conversations.py
index dc652c99..97f8c56f 100644
--- a/application/storage/db/repositories/conversations.py
+++ b/application/storage/db/repositories/conversations.py
@@ -574,6 +574,27 @@ class ConversationsRepository:
         self._reap_artifact_storage(paths)
         return result.rowcount
 
+    def reassign_api_key(self, *, old_key: str, new_key: str) -> int:
+        """Re-point conversation rows from ``old_key`` to ``new_key``.
+
+        Called when an agent's key is rotated. Per-agent analytics match
+        ``c.api_key = :api_key OR c.agent_id = :agent_pg_id``, but a
+        conversation created from api-key traffic may have ``api_key`` set and
+        ``agent_id`` NULL (``conversation_service`` only sets ``agent_id`` when
+        the caller passes one). Rewriting ``api_key`` keeps those rows attached
+        to the agent after rotation instead of orphaning them.
+
+        Matched by ``api_key`` only — ``agents.key`` is globally unique so a key
+        maps to exactly one agent. Returns the number of rows updated.
+        """
+        if not old_key or not new_key:
+            return 0
+        result = self._conn.execute(
+            text("UPDATE conversations SET api_key = :new_key WHERE api_key = :old_key"),
+            {"old_key": old_key, "new_key": new_key},
+        )
+        return result.rowcount
+
     @staticmethod
     def _reap_artifact_storage(paths: list) -> None:
         """Best-effort delete artifact bytes whose rows were cascade-removed; never raises."""
diff --git a/application/storage/db/repositories/shared_conversations.py b/application/storage/db/repositories/shared_conversations.py
index 4d3bf40f..5681cbef 100644
--- a/application/storage/db/repositories/shared_conversations.py
+++ b/application/storage/db/repositories/shared_conversations.py
@@ -211,3 +211,31 @@ class SharedConversationsRepository:
             {"conv_id": conversation_id},
         )
         return [row_to_dict(r) for r in result.fetchall()]
+
+    def reassign_api_key(self, *, old_key: str, new_key: str) -> int:
+        """Re-point promptable share rows from ``old_key`` to ``new_key``.
+
+        A *promptable* shared-conversation link stores the backing agent's key
+        in ``api_key`` and the public share endpoint returns it so the shared
+        widget can keep prompting. If that agent's key is rotated without this
+        rewrite, the endpoint would hand out an invalidated key and break every
+        existing shared link. Rewriting keeps those links working with the new
+        key.
+
+        Matched by ``api_key`` only — ``agents.key`` is globally unique, so a
+        key maps to exactly one agent. The uniform rewrite cannot violate the
+        ``(conversation_id, user_id, is_promptable, first_n_queries,
+        COALESCE(api_key, ''))`` partial unique index: rows already differ on
+        the non-key columns, and ``new_key`` is freshly generated so no row
+        already holds it. Returns the number of rows updated.
+        """
+        if not old_key or not new_key:
+            return 0
+        result = self._conn.execute(
+            text(
+                "UPDATE shared_conversations SET api_key = :new_key "
+                "WHERE api_key = :old_key"
+            ),
+            {"old_key": old_key, "new_key": new_key},
+        )
+        return result.rowcount
diff --git a/application/storage/db/repositories/stack_logs.py b/application/storage/db/repositories/stack_logs.py
index a5ac17fc..750376d6 100644
--- a/application/storage/db/repositories/stack_logs.py
+++ b/application/storage/db/repositories/stack_logs.py
@@ -10,6 +10,7 @@ Covers the single operation the legacy Mongo code performs:
 from __future__ import annotations
 
 import json
+import uuid
 from datetime import datetime
 from typing import Optional
 
@@ -52,16 +53,28 @@ class StackLogsRepository:
         level: Optional[str] = None,
         user_id: Optional[str] = None,
         api_key: Optional[str] = None,
+        agent_id: Optional[str] = None,
         query: Optional[str] = None,
         stacks: Optional[list] = None,
         timestamp: Optional[datetime] = None,
     ) -> None:
+        # ``agent_id`` is a UUID column. Parse it with ``uuid.UUID`` and coerce
+        # anything that isn't a valid UUID (e.g. a 24-hex legacy Mongo ObjectId)
+        # to NULL so a stray/legacy id never reaches ``CAST(... AS uuid)`` and
+        # breaks the activity-log write.
+        agent_id_uuid: Optional[str] = None
+        if agent_id:
+            try:
+                agent_id_uuid = str(uuid.UUID(str(agent_id)))
+            except (ValueError, AttributeError, TypeError):
+                agent_id_uuid = None
         self._conn.execute(
             text(
                 """
-                INSERT INTO stack_logs (activity_id, endpoint, level, user_id, api_key, query, stacks, timestamp)
+                INSERT INTO stack_logs (activity_id, endpoint, level, user_id, api_key, agent_id, query, stacks, timestamp)
                 VALUES (
-                    :activity_id, :endpoint, :level, :user_id, :api_key, :query,
+                    :activity_id, :endpoint, :level, :user_id, :api_key,
+                    CAST(:agent_id AS uuid), :query,
                     CAST(:stacks AS jsonb),
                     COALESCE(:timestamp, now())
                 )
@@ -73,6 +86,7 @@ class StackLogsRepository:
                 "level": strip_null_bytes(level),
                 "user_id": strip_null_bytes(user_id),
                 "api_key": strip_null_bytes(api_key),
+                "agent_id": agent_id_uuid,
                 "query": strip_null_bytes(query),
                 "stacks": json.dumps(
                     redact_secrets(
@@ -83,3 +97,28 @@ class StackLogsRepository:
                 "timestamp": timestamp,
             },
         )
+
+    def reassign_api_key(self, *, old_key: str, new_key: str) -> int:
+        """Re-point historical rows from ``old_key`` to ``new_key``.
+
+        Since migration 0026 ``stack_logs`` has an ``agent_id`` column and the
+        analytics ``webhook_where`` / ``system_where`` clauses match
+        ``agent_id`` first with ``api_key`` as a fallback, so most rows already
+        survive a key rotation via ``agent_id``. This rewrite still runs to keep
+        the ``api_key`` column consistent and to re-attach any rows whose
+        ``agent_id`` is NULL (e.g. a log written without agent context).
+
+        Matched by ``api_key`` only — deliberately NOT scoped by ``user_id``:
+        ``agents.key`` is globally unique, so a key maps to exactly one agent,
+        and rows are stamped with the *caller's* user_id (which is not the
+        owner for webhook / external-api-key traffic). Scoping by owner would
+        skip precisely the rows this rewrite exists to preserve.
+        Returns the number of rows updated.
+        """
+        if not old_key or not new_key:
+            return 0
+        result = self._conn.execute(
+            text("UPDATE stack_logs SET api_key = :new_key WHERE api_key = :old_key"),
+            {"old_key": old_key, "new_key": new_key},
+        )
+        return result.rowcount
diff --git a/application/storage/db/repositories/token_usage.py b/application/storage/db/repositories/token_usage.py
index 127d213e..c23ec90b 100644
--- a/application/storage/db/repositories/token_usage.py
+++ b/application/storage/db/repositories/token_usage.py
@@ -83,6 +83,25 @@ class TokenUsageRepository:
             },
         )
 
+    def reassign_api_key(self, *, old_key: str, new_key: str) -> int:
+        """Re-point historical rows from ``old_key`` to ``new_key``.
+
+        Called when an agent's key is rotated. Although per-agent analytics
+        also match on ``agent_id``, the 24h rate-limit window
+        (``sum_tokens_in_range`` / ``count_in_range``) and any legacy rows with
+        a NULL ``agent_id`` are keyed by the api-key string only. Rewriting the
+        key here preserves the running rate-limit window across a rotation (so
+        rotating cannot be used to reset it) and keeps legacy rows attributed.
+        Returns the number of rows updated.
+        """
+        if not old_key or not new_key:
+            return 0
+        result = self._conn.execute(
+            text("UPDATE token_usage SET api_key = :new_key WHERE api_key = :old_key"),
+            {"old_key": old_key, "new_key": new_key},
+        )
+        return result.rowcount
+
     def sum_tokens_in_range(
         self,
         *,
diff --git a/frontend/src/agents/NewAgent.tsx b/frontend/src/agents/NewAgent.tsx
index c12ba288..1f93efe2 100644
--- a/frontend/src/agents/NewAgent.tsx
+++ b/frontend/src/agents/NewAgent.tsx
@@ -1455,6 +1455,7 @@ export default function NewAgent({ mode }: { mode: 'new' | 'edit' | 'draft' }) {
         mode={effectiveMode}
         modalState={agentDetails}
         setModalState={setAgentDetails}
+        onKeyRegenerated={(key) => setAgent((prev) => ({ ...prev, key }))}
       />
       {shareModalOpen && agent.id && (
         <ShareToTeamModal
diff --git a/frontend/src/agents/workflow/WorkflowBuilder.tsx b/frontend/src/agents/workflow/WorkflowBuilder.tsx
index d821d9f8..a2dca188 100644
--- a/frontend/src/agents/workflow/WorkflowBuilder.tsx
+++ b/frontend/src/agents/workflow/WorkflowBuilder.tsx
@@ -3077,6 +3077,9 @@ function WorkflowBuilderInner() {
             mode="edit"
             modalState={agentDetails}
             setModalState={setAgentDetails}
+            onKeyRegenerated={(key) =>
+              setCurrentAgent((prev) => ({ ...prev, key }))
+            }
           />
         )}
       </div>
diff --git a/frontend/src/api/endpoints.ts b/frontend/src/api/endpoints.ts
index edc89b97..c32d62e9 100644
--- a/frontend/src/api/endpoints.ts
+++ b/frontend/src/api/endpoints.ts
@@ -27,6 +27,7 @@ const endpoints = {
     TEMPLATE_AGENTS: '/api/template_agents',
     ADOPT_AGENT: (id: string) => `/api/adopt_agent?id=${id}`,
     AGENT_WEBHOOK: (id: string) => `/api/agent_webhook?id=${id}`,
+    REGENERATE_AGENT_KEY: (id: string) => `/api/regenerate_agent_key/${id}`,
     EXPORT_AGENT: (id: string) => `/api/export_agent?id=${id}`,
     IMPORT_AGENT_PLAN: '/api/import_agent/plan',
     IMPORT_AGENT: '/api/import_agent',
diff --git a/frontend/src/api/services/userService.ts b/frontend/src/api/services/userService.ts
index 563743b5..c4aef35b 100644
--- a/frontend/src/api/services/userService.ts
+++ b/frontend/src/api/services/userService.ts
@@ -66,6 +66,8 @@ const userService = {
     apiClient.post(endpoints.USER.ADOPT_AGENT(id), {}, token),
   getAgentWebhook: (id: string, token: string | null): Promise<any> =>
     apiClient.get(endpoints.USER.AGENT_WEBHOOK(id), token),
+  regenerateAgentKey: (id: string, token: string | null): Promise<any> =>
+    apiClient.post(endpoints.USER.REGENERATE_AGENT_KEY(id), {}, token),
   getPrompts: (token: string | null): Promise<any> =>
     apiClient.get(endpoints.USER.PROMPTS, token),
   createPrompt: (data: any, token: string | null): Promise<any> =>
diff --git a/frontend/src/locale/de.json b/frontend/src/locale/de.json
index 60e40eee..ebfdc15e 100644
--- a/frontend/src/locale/de.json
+++ b/frontend/src/locale/de.json
@@ -1001,7 +1001,9 @@
       "webhookUrl": "Webhook-URL",
       "generate": "Generieren",
       "test": "Testen",
-      "learnMore": "Mehr erfahren"
+      "learnMore": "Mehr erfahren",
+      "resetKey": "Schlüssel zurücksetzen",
+      "resetKeyConfirm": "Möchten Sie den API-Schlüssel wirklich zurücksetzen? Der aktuelle Schlüssel funktioniert sofort nicht mehr und diese Aktion kann nicht rückgängig gemacht werden."
     },
     "importSpec": {
       "title": "API-Spezifikation importieren",
diff --git a/frontend/src/locale/en.json b/frontend/src/locale/en.json
index 472961b0..b3bf62dc 100644
--- a/frontend/src/locale/en.json
+++ b/frontend/src/locale/en.json
@@ -1002,7 +1002,9 @@
       "webhookUrl": "Webhook URL",
       "generate": "Generate",
       "test": "Test",
-      "learnMore": "Learn more"
+      "learnMore": "Learn more",
+      "resetKey": "Reset key",
+      "resetKeyConfirm": "Are you sure you want to reset the API key? The current key will stop working immediately and this action cannot be undone."
     },
     "importSpec": {
       "title": "Import API Specification",
diff --git a/frontend/src/locale/es.json b/frontend/src/locale/es.json
index 700d8732..f3f577c9 100644
--- a/frontend/src/locale/es.json
+++ b/frontend/src/locale/es.json
@@ -1001,7 +1001,9 @@
       "webhookUrl": "Webhook URL",
       "generate": "Generate",
       "test": "Test",
-      "learnMore": "Learn more"
+      "learnMore": "Learn more",
+      "resetKey": "Restablecer clave",
+      "resetKeyConfirm": "¿Seguro que quieres restablecer la clave de API? La clave actual dejará de funcionar de inmediato y esta acción no se puede deshacer."
     },
     "importSpec": {
       "title": "Importar especificación de API",
diff --git a/frontend/src/locale/jp.json b/frontend/src/locale/jp.json
index 02157c05..5fbae862 100644
--- a/frontend/src/locale/jp.json
+++ b/frontend/src/locale/jp.json
@@ -1001,7 +1001,9 @@
       "webhookUrl": "Webhook URL",
       "generate": "Generate",
       "test": "Test",
-      "learnMore": "Learn more"
+      "learnMore": "Learn more",
+      "resetKey": "キーをリセット",
+      "resetKeyConfirm": "APIキーをリセットしてもよろしいですか？現在のキーは直ちに無効になり、この操作は元に戻せません。"
     },
     "importSpec": {
       "title": "API仕様のインポート",
diff --git a/frontend/src/locale/ru.json b/frontend/src/locale/ru.json
index df5d395f..da2c418e 100644
--- a/frontend/src/locale/ru.json
+++ b/frontend/src/locale/ru.json
@@ -1001,7 +1001,9 @@
       "webhookUrl": "Webhook URL",
       "generate": "Generate",
       "test": "Test",
-      "learnMore": "Learn more"
+      "learnMore": "Learn more",
+      "resetKey": "Сбросить ключ",
+      "resetKeyConfirm": "Вы уверены, что хотите сбросить API-ключ? Текущий ключ немедленно перестанет работать, и это действие нельзя отменить."
     },
     "importSpec": {
       "title": "Импорт спецификации API",
diff --git a/frontend/src/locale/zh-TW.json b/frontend/src/locale/zh-TW.json
index 03087484..1a56a7b5 100644
--- a/frontend/src/locale/zh-TW.json
+++ b/frontend/src/locale/zh-TW.json
@@ -1001,7 +1001,9 @@
       "webhookUrl": "Webhook URL",
       "generate": "Generate",
       "test": "Test",
-      "learnMore": "Learn more"
+      "learnMore": "Learn more",
+      "resetKey": "重設金鑰",
+      "resetKeyConfirm": "確定要重設 API 金鑰嗎？目前的金鑰將立即停止運作，此操作無法復原。"
     },
     "importSpec": {
       "title": "匯入 API 規格",
diff --git a/frontend/src/locale/zh.json b/frontend/src/locale/zh.json
index 202ff839..c1a4db88 100644
--- a/frontend/src/locale/zh.json
+++ b/frontend/src/locale/zh.json
@@ -1001,7 +1001,9 @@
       "webhookUrl": "Webhook URL",
       "generate": "Generate",
       "test": "Test",
-      "learnMore": "Learn more"
+      "learnMore": "Learn more",
+      "resetKey": "重置密钥",
+      "resetKeyConfirm": "确定要重置 API 密钥吗？当前密钥将立即停止工作，此操作无法撤销。"
     },
     "importSpec": {
       "title": "导入 API 规范",
diff --git a/frontend/src/modals/AgentDetailsModal.tsx b/frontend/src/modals/AgentDetailsModal.tsx
index 5b95c950..b2bb8ee3 100644
--- a/frontend/src/modals/AgentDetailsModal.tsx
+++ b/frontend/src/modals/AgentDetailsModal.tsx
@@ -11,6 +11,7 @@ import { Button } from '../components/ui/button';
 import { Modal } from '../components/ui/modal';
 import { ActiveState } from '../models/misc';
 import { selectToken } from '../preferences/preferenceSlice';
+import ConfirmationModal from './ConfirmationModal';
 
 const baseURL = import.meta.env.VITE_BASE_URL;
 
@@ -19,6 +20,7 @@ type AgentDetailsModalProps = {
   mode: 'new' | 'edit' | 'draft';
   modalState: ActiveState;
   setModalState: (state: ActiveState) => void;
+  onKeyRegenerated?: (key: string) => void;
 };
 
 export default function AgentDetailsModal({
@@ -26,6 +28,7 @@ export default function AgentDetailsModal({
   mode,
   modalState,
   setModalState,
+  onKeyRegenerated,
 }: AgentDetailsModalProps) {
   const { t } = useTranslation();
   const token = useSelector(selectToken);
@@ -35,6 +38,8 @@ export default function AgentDetailsModal({
   );
   const [apiKey, setApiKey] = useState<string | null>(null);
   const [webhookUrl, setWebhookUrl] = useState<string | null>(null);
+  const [resetKeyConfirmState, setResetKeyConfirmState] =
+    useState<ActiveState>('INACTIVE');
   const [loadingStates, setLoadingStates] = useState({
     publicLink: false,
     apiKey: false,
@@ -75,12 +80,29 @@ export default function AgentDetailsModal({
     setLoading('webhook', false);
   };
 
+  const handleRegenerateKey = async () => {
+    setLoading('apiKey', true);
+    try {
+      const response = await userService.regenerateAgentKey(
+        agent.id ?? '',
+        token,
+      );
+      if (!response.ok) return;
+      const data = await response.json();
+      setApiKey(data.key);
+      onKeyRegenerated?.(data.key);
+    } finally {
+      setLoading('apiKey', false);
+    }
+  };
+
   useEffect(() => {
     setSharedToken(agent.shared_token ?? null);
     setApiKey(agent.key ?? null);
   }, [agent]);
 
   return (
+    <>
     <Modal
       open={modalState === 'ACTIVE'}
       onOpenChange={(o) => !o && setModalState('INACTIVE')}
@@ -174,6 +196,20 @@ export default function AgentDetailsModal({
                       />
                     </a>
                   )}
+                  {apiKey.includes('...') && (
+                    <button
+                      type="button"
+                      onClick={() => setResetKeyConfirmState('ACTIVE')}
+                      disabled={loadingStates.apiKey}
+                      className="border-primary text-primary hover:bg-primary/90 ml-8 flex items-center justify-center gap-1 rounded-full border px-5 py-1.5 text-sm font-medium transition-colors hover:text-white disabled:opacity-60"
+                    >
+                      {loadingStates.apiKey ? (
+                        <Spinner size="small" />
+                      ) : (
+                        t('modals.agentDetails.resetKey')
+                      )}
+                    </button>
+                  )}
                 </div>
               </div>
             ) : (
@@ -238,5 +274,14 @@ export default function AgentDetailsModal({
         </div>
       </div>
     </Modal>
+    <ConfirmationModal
+      message={t('modals.agentDetails.resetKeyConfirm')}
+      modalState={resetKeyConfirmState}
+      setModalState={setResetKeyConfirmState}
+      submitLabel={t('modals.agentDetails.resetKey')}
+      handleSubmit={handleRegenerateKey}
+      variant="danger"
+    />
+    </>
   );
 }
diff --git a/tests/api/user/agents/test_routes_happy.py b/tests/api/user/agents/test_routes_happy.py
index c483da35..079fec1c 100644
--- a/tests/api/user/agents/test_routes_happy.py
+++ b/tests/api/user/agents/test_routes_happy.py
@@ -1252,6 +1252,187 @@ class TestPinAgentMore:
         assert response.status_code == 500
 
 
+class TestRegenerateAgentKey:
+    def _seed_published_with_key(self, pg_conn, user, key):
+        from application.storage.db.repositories.agents import AgentsRepository
+
+        agent = _seed_agent(pg_conn, user=user, status="published")
+        AgentsRepository(pg_conn).update(str(agent["id"]), user, {"key": key})
+        return agent
+
+    def test_returns_401_unauthenticated(self, app):
+        from application.api.user.agents.routes import RegenerateAgentKey
+
+        with app.test_request_context(
+            "/api/regenerate_agent_key/abc", method="POST"
+        ):
+            from flask import request
+            request.decoded_token = None
+            response = RegenerateAgentKey().post("abc")
+        status = (
+            response[1] if isinstance(response, tuple) else response.status_code
+        )
+        assert status == 401
+
+    def test_returns_404_when_missing(self, app, pg_conn):
+        from application.api.user.agents.routes import RegenerateAgentKey
+
+        with _patch_db(pg_conn), app.test_request_context(
+            "/api/regenerate_agent_key/00000000-0000-0000-0000-000000000000",
+            method="POST",
+        ):
+            from flask import request
+            request.decoded_token = {"sub": "u"}
+            response = RegenerateAgentKey().post(
+                "00000000-0000-0000-0000-000000000000"
+            )
+        assert response.status_code == 404
+
+    def test_returns_404_for_non_owner(self, app, pg_conn):
+        """Owner-only: another user cannot rotate someone else's key."""
+        from application.api.user.agents.routes import RegenerateAgentKey
+
+        owner = "u-owner-key"
+        agent = self._seed_published_with_key(pg_conn, owner, "owner-old-key")
+
+        with _patch_db(pg_conn), app.test_request_context(
+            f"/api/regenerate_agent_key/{agent['id']}", method="POST"
+        ):
+            from flask import request
+            request.decoded_token = {"sub": "u-intruder"}
+            response = RegenerateAgentKey().post(str(agent["id"]))
+        assert response.status_code == 404
+
+    def test_returns_400_for_draft_without_key(self, app, pg_conn):
+        from application.api.user.agents.routes import RegenerateAgentKey
+
+        user = "u-draft-key"
+        agent = _seed_agent(pg_conn, user=user, status="draft")
+
+        with _patch_db(pg_conn), app.test_request_context(
+            f"/api/regenerate_agent_key/{agent['id']}", method="POST"
+        ):
+            from flask import request
+            request.decoded_token = {"sub": user}
+            response = RegenerateAgentKey().post(str(agent["id"]))
+        assert response.status_code == 400
+
+    def test_regenerates_key_and_invalidates_old(self, app, pg_conn):
+        from application.api.user.agents.routes import RegenerateAgentKey
+        from application.storage.db.repositories.agents import AgentsRepository
+
+        user = "u-regen"
+        old_key = "regen-old-key"
+        agent = self._seed_published_with_key(pg_conn, user, old_key)
+
+        with _patch_db(pg_conn), app.test_request_context(
+            f"/api/regenerate_agent_key/{agent['id']}", method="POST"
+        ):
+            from flask import request
+            request.decoded_token = {"sub": user}
+            response = RegenerateAgentKey().post(str(agent["id"]))
+
+        assert response.status_code == 200
+        new_key = response.json["key"]
+        assert new_key and new_key != old_key
+
+        repo = AgentsRepository(pg_conn)
+        # Persisted key is the new one; the old key no longer resolves.
+        assert repo.get(str(agent["id"]), user)["key"] == new_key
+        assert repo.find_by_key(old_key) is None
+        assert repo.find_by_key(new_key)["id"] == agent["id"]
+
+    def test_migrates_historical_logs_and_usage(self, app, pg_conn):
+        """stack_logs + token_usage + conversations + shared_conversations rows
+        follow the key so analytics, the rate-limit window, and promptable shared
+        links are not orphaned/broken. The stack_logs row is stamped with a
+        *different* user_id (a caller, not the owner) to prove the migration is
+        not owner-scoped, and the conversation is created with api_key set but
+        agent_id NULL to prove the api_key-only path is covered.
+        """
+        from application.api.user.agents.routes import RegenerateAgentKey
+        from application.storage.db.repositories.conversations import (
+            ConversationsRepository,
+        )
+        from application.storage.db.repositories.shared_conversations import (
+            SharedConversationsRepository,
+        )
+        from application.storage.db.repositories.stack_logs import (
+            StackLogsRepository,
+        )
+        from application.storage.db.repositories.token_usage import (
+            TokenUsageRepository,
+        )
+
+        user = "u-regen-hist"
+        old_key = "regen-hist-old-key"
+        agent = self._seed_published_with_key(pg_conn, user, old_key)
+
+        StackLogsRepository(pg_conn).insert(
+            activity_id="regen-act-1",
+            endpoint="webhook",
+            level="info",
+            user_id="external-caller",
+            api_key=old_key,
+        )
+        TokenUsageRepository(pg_conn).insert(
+            api_key=old_key, prompt_tokens=7, generated_tokens=3,
+        )
+        # api_key set, agent_id intentionally omitted (NULL) — the orphan case.
+        conv = ConversationsRepository(pg_conn).create(
+            user, "conv", api_key=old_key,
+        )
+        # A promptable shared link stores the agent key; rotation must not
+        # leave it pointing at an invalidated key.
+        SharedConversationsRepository(pg_conn).create(
+            conv["id"], user, is_promptable=True, api_key=old_key,
+        )
+
+        with _patch_db(pg_conn), app.test_request_context(
+            f"/api/regenerate_agent_key/{agent['id']}", method="POST"
+        ):
+            from flask import request
+            request.decoded_token = {"sub": user}
+            response = RegenerateAgentKey().post(str(agent["id"]))
+        assert response.status_code == 200
+        new_key = response.json["key"]
+
+        from sqlalchemy import text
+
+        def _count(table, key):
+            return pg_conn.execute(
+                text(f"SELECT COUNT(*) FROM {table} WHERE api_key = :k"),
+                {"k": key},
+            ).scalar()
+
+        assert _count("stack_logs", old_key) == 0
+        assert _count("stack_logs", new_key) == 1
+        assert _count("token_usage", old_key) == 0
+        assert _count("token_usage", new_key) == 1
+        assert _count("conversations", old_key) == 0
+        assert _count("conversations", new_key) == 1
+        assert _count("shared_conversations", old_key) == 0
+        assert _count("shared_conversations", new_key) == 1
+
+    def test_db_error_returns_500(self, app):
+        from application.api.user.agents.routes import RegenerateAgentKey
+
+        @contextmanager
+        def _broken():
+            raise RuntimeError("boom")
+            yield
+
+        with patch(
+            "application.api.user.agents.routes.db_session", _broken
+        ), app.test_request_context(
+            "/api/regenerate_agent_key/abc", method="POST"
+        ):
+            from flask import request
+            request.decoded_token = {"sub": "u"}
+            response = RegenerateAgentKey().post("abc")
+        assert response.status_code == 500
+
+
 class TestPinnedAgentsListing:
     def test_returns_pinned_after_pinning(self, app, pg_conn):
         from application.api.user.agents.routes import PinAgent, PinnedAgents
diff --git a/tests/api/user/test_analytics.py b/tests/api/user/test_analytics.py
index 4afd3aec..4c47490c 100644
--- a/tests/api/user/test_analytics.py
+++ b/tests/api/user/test_analytics.py
@@ -413,6 +413,55 @@ class TestGetUserLogs:
         assert response.status_code == 200
         assert len(response.json["logs"]) == 1
 
+    def test_webhook_logs_match_by_agent_id_after_key_rotation(
+        self, app, pg_conn,
+    ):
+        """A webhook activity-log row stamped with the agent's id but an
+        *old* api_key (the state after a key rotation) must still surface on
+        the agent's timeline via the stable agent_id join."""
+        from application.api.user.analytics.routes import GetUserLogs
+        from application.storage.db.repositories.agents import AgentsRepository
+        from application.storage.db.repositories.stack_logs import (
+            StackLogsRepository,
+        )
+
+        user = "u-logs-rotate"
+        agent = AgentsRepository(pg_conn).create(
+            user, "a", "published", key="current-key",
+        )
+        stack_repo = StackLogsRepository(pg_conn)
+        # Written under the previous key, but carries the stable agent_id.
+        stack_repo.insert(
+            activity_id="wh-rotated",
+            endpoint="webhook",
+            level="info",
+            user_id="external-caller",
+            api_key="rotated-away-key",
+            agent_id=str(agent["id"]),
+        )
+        # A different agent's webhook log must NOT leak in.
+        stack_repo.insert(
+            activity_id="wh-other",
+            endpoint="webhook",
+            level="info",
+            user_id="external-caller",
+            api_key="unrelated-key",
+            agent_id="99999999-9999-9999-9999-999999999999",
+        )
+
+        with _patch_analytics_db(pg_conn), app.test_request_context(
+            "/api/get_user_logs",
+            method="POST",
+            json={"api_key_id": str(agent["id"]), "event_type": "webhook"},
+        ):
+            from flask import request
+            request.decoded_token = {"sub": user}
+            response = GetUserLogs().post()
+        assert response.status_code == 200
+        logs = response.json["logs"]
+        assert len(logs) == 1
+        assert logs[0]["id"]  # the rotated-away row surfaced via agent_id
+
     def test_db_error_returns_400(self, app):
         from application.api.user.analytics.routes import GetUserLogs
 
diff --git a/tests/storage/db/repositories/test_conversations.py b/tests/storage/db/repositories/test_conversations.py
index 5ca3475d..21b1c544 100644
--- a/tests/storage/db/repositories/test_conversations.py
+++ b/tests/storage/db/repositories/test_conversations.py
@@ -885,3 +885,32 @@ class TestUuidShapeGate:
         msg = repo.get_message_at(conv["id"], 0)
         assert msg is not None
         assert msg["prompt"] == "q"
+
+
+class TestReassignApiKey:
+    def test_rewrites_matching_rows_including_null_agent(self, pg_conn):
+        # A conversation created from api-key traffic can have api_key set and
+        # agent_id NULL; on key rotation it must follow the key so per-agent
+        # analytics (api_key OR agent_id) don't orphan it.
+        repo = _repo(pg_conn)
+        repo.create("owner", "c1", api_key="conv-old")
+        repo.create("caller", "c2", api_key="conv-old")
+        repo.create("owner", "c3", api_key="conv-other")
+
+        moved = repo.reassign_api_key(old_key="conv-old", new_key="conv-new")
+        assert moved == 2
+
+        assert pg_conn.execute(
+            text("SELECT COUNT(*) FROM conversations WHERE api_key = 'conv-old'")
+        ).scalar() == 0
+        assert pg_conn.execute(
+            text("SELECT COUNT(*) FROM conversations WHERE api_key = 'conv-new'")
+        ).scalar() == 2
+        assert pg_conn.execute(
+            text("SELECT COUNT(*) FROM conversations WHERE api_key = 'conv-other'")
+        ).scalar() == 1
+
+    def test_noop_on_blank_keys(self, pg_conn):
+        repo = _repo(pg_conn)
+        assert repo.reassign_api_key(old_key="", new_key="x") == 0
+        assert repo.reassign_api_key(old_key="x", new_key="") == 0
diff --git a/tests/storage/db/repositories/test_shared_conversations.py b/tests/storage/db/repositories/test_shared_conversations.py
index 3bb12e96..b7fd939b 100644
--- a/tests/storage/db/repositories/test_shared_conversations.py
+++ b/tests/storage/db/repositories/test_shared_conversations.py
@@ -115,3 +115,34 @@ class TestFindByUuidShapeGate:
         share = repo.create(conv["id"], "user-1", first_n_queries=1)
         found = repo.find_by_uuid(str(share["uuid"]))
         assert found is not None
+
+
+class TestReassignApiKey:
+    def test_rewrites_promptable_share_keys(self, pg_conn):
+        # A promptable share stores the backing agent's key; on rotation it must
+        # follow the key so the public share endpoint keeps returning a valid one.
+        from sqlalchemy import text
+
+        repo = _repo(pg_conn)
+        c1, c2, c3 = _conv(pg_conn), _conv(pg_conn), _conv(pg_conn)
+        repo.create(c1["id"], "u", is_promptable=True, api_key="sc-old")
+        repo.create(c2["id"], "u", is_promptable=True, api_key="sc-old")
+        repo.create(c3["id"], "u", is_promptable=True, api_key="sc-other")
+
+        moved = repo.reassign_api_key(old_key="sc-old", new_key="sc-new")
+        assert moved == 2
+
+        def _count(key):
+            return pg_conn.execute(
+                text("SELECT COUNT(*) FROM shared_conversations WHERE api_key = :k"),
+                {"k": key},
+            ).scalar()
+
+        assert _count("sc-old") == 0
+        assert _count("sc-new") == 2
+        assert _count("sc-other") == 1
+
+    def test_noop_on_blank_keys(self, pg_conn):
+        repo = _repo(pg_conn)
+        assert repo.reassign_api_key(old_key="", new_key="x") == 0
+        assert repo.reassign_api_key(old_key="x", new_key="") == 0
diff --git a/tests/storage/db/repositories/test_stack_logs.py b/tests/storage/db/repositories/test_stack_logs.py
index 300ad5e1..e77286dc 100644
--- a/tests/storage/db/repositories/test_stack_logs.py
+++ b/tests/storage/db/repositories/test_stack_logs.py
@@ -33,6 +33,32 @@ class TestInsert:
         assert mapping["user_id"] == "u1"
         assert mapping["stacks"] == [{"component": "retriever", "data": {"docs": 3}}]
 
+    def test_inserts_with_agent_id(self, pg_conn):
+        repo = _repo(pg_conn)
+        agent_uuid = "11111111-1111-1111-1111-111111111111"
+        repo.insert(
+            activity_id="act-agent",
+            api_key="k-agent",
+            agent_id=agent_uuid,
+        )
+        row = pg_conn.execute(
+            text("SELECT agent_id FROM stack_logs WHERE activity_id = 'act-agent'")
+        ).fetchone()
+        assert str(dict(row._mapping)["agent_id"]) == agent_uuid
+
+    def test_non_uuid_agent_id_coerced_to_null(self, pg_conn):
+        # A stray/legacy (non-UUID) id must not break the activity-log write.
+        repo = _repo(pg_conn)
+        repo.insert(
+            activity_id="act-badid",
+            api_key="k-badid",
+            agent_id="507f1f77bcf86cd799439011",  # 24-hex Mongo ObjectId
+        )
+        row = pg_conn.execute(
+            text("SELECT agent_id FROM stack_logs WHERE activity_id = 'act-badid'")
+        ).fetchone()
+        assert dict(row._mapping)["agent_id"] is None
+
     def test_inserts_with_empty_stacks(self, pg_conn):
         repo = _repo(pg_conn)
         repo.insert(activity_id="act-2", level="error")
@@ -171,3 +197,35 @@ class TestInsert:
             text("SELECT stacks FROM stack_logs WHERE activity_id = 'act-small'")
         ).fetchone()
         assert dict(row._mapping)["stacks"][0]["data"]["result"] == "ok"
+
+
+class TestReassignApiKey:
+    def test_rewrites_matching_rows_regardless_of_user(self, pg_conn):
+        # On key rotation the rewrite is intentionally NOT scoped by user_id:
+        # agents.key is unique so a key maps to one agent, and rows are stamped
+        # with the caller's user_id (not the owner), so scoping by owner would
+        # skip caller-logged rows. (Rows also carry agent_id since 0026, but
+        # this rewrite still covers api_key consistency and NULL-agent_id rows.)
+        repo = _repo(pg_conn)
+        repo.insert(activity_id="ra-1", api_key="old-k", user_id="owner")
+        repo.insert(activity_id="ra-2", api_key="old-k", user_id="a-caller")
+        repo.insert(activity_id="ra-3", api_key="other-k", user_id="owner")
+
+        moved = repo.reassign_api_key(old_key="old-k", new_key="new-k")
+        assert moved == 2
+
+        assert pg_conn.execute(
+            text("SELECT COUNT(*) FROM stack_logs WHERE api_key = 'old-k'")
+        ).scalar() == 0
+        assert pg_conn.execute(
+            text("SELECT COUNT(*) FROM stack_logs WHERE api_key = 'new-k'")
+        ).scalar() == 2
+        # Unrelated key untouched.
+        assert pg_conn.execute(
+            text("SELECT COUNT(*) FROM stack_logs WHERE api_key = 'other-k'")
+        ).scalar() == 1
+
+    def test_noop_on_blank_keys(self, pg_conn):
+        repo = _repo(pg_conn)
+        assert repo.reassign_api_key(old_key="", new_key="x") == 0
+        assert repo.reassign_api_key(old_key="x", new_key="") == 0
diff --git a/tests/storage/db/repositories/test_token_usage.py b/tests/storage/db/repositories/test_token_usage.py
index 39975095..c4781b4c 100644
--- a/tests/storage/db/repositories/test_token_usage.py
+++ b/tests/storage/db/repositories/test_token_usage.py
@@ -36,6 +36,31 @@ class TestInsert:
         assert total == 30
 
 
+class TestReassignApiKey:
+    def test_rewrites_and_preserves_rate_limit_window(self, pg_conn):
+        # Rotating an agent key must carry the running 24h usage window over
+        # to the new key so rotation cannot be used to reset the limit.
+        repo = _repo(pg_conn)
+        repo.insert(api_key="tu-old", prompt_tokens=20, generated_tokens=10)
+        repo.insert(api_key="tu-other", prompt_tokens=1, generated_tokens=1)
+
+        moved = repo.reassign_api_key(old_key="tu-old", new_key="tu-new")
+        assert moved == 1
+
+        window = dict(
+            start=_now() - timedelta(minutes=1), end=_now() + timedelta(minutes=1)
+        )
+        assert repo.sum_tokens_in_range(api_key="tu-old", **window) == 0
+        assert repo.sum_tokens_in_range(api_key="tu-new", **window) == 30
+        # Unrelated key untouched.
+        assert repo.sum_tokens_in_range(api_key="tu-other", **window) == 2
+
+    def test_noop_on_blank_keys(self, pg_conn):
+        repo = _repo(pg_conn)
+        assert repo.reassign_api_key(old_key="", new_key="x") == 0
+        assert repo.reassign_api_key(old_key="x", new_key="") == 0
+
+
 class TestModelId:
     def _latest_model_id(self, conn, user_id):
         return conn.execute(
diff --git a/tests/storage/db/test_migration_0026.py b/tests/storage/db/test_migration_0026.py
new file mode 100644
index 00000000..4a3d68e2
--- /dev/null
+++ b/tests/storage/db/test_migration_0026.py
@@ -0,0 +1,138 @@
+"""Migration round-trip + backfill test for 0026_stack_logs_agent_id."""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+from sqlalchemy import text
+
+
+pytestmark = pytest.mark.integration
+
+
+def _alembic_ini() -> Path:
+    return Path(__file__).resolve().parents[3] / "application" / "alembic.ini"
+
+
+def _run_alembic(url: str, *args: str) -> None:
+    subprocess.check_call(
+        [sys.executable, "-m", "alembic", "-c", str(_alembic_ini()), *args],
+        timeout=60,
+        env={**os.environ, "POSTGRES_URI": url},
+    )
+
+
+def _alembic_heads(url: str) -> list[str]:
+    out = subprocess.check_output(
+        [sys.executable, "-m", "alembic", "-c", str(_alembic_ini()), "heads"],
+        timeout=60,
+        env={**os.environ, "POSTGRES_URI": url},
+        text=True,
+    )
+    return [line for line in out.splitlines() if line.strip()]
+
+
+def _alembic_version(conn) -> str:
+    return conn.execute(text("SELECT version_num FROM alembic_version")).scalar()
+
+
+def _column_exists(conn, table: str, column: str) -> bool:
+    row = conn.execute(
+        text(
+            "SELECT 1 FROM information_schema.columns "
+            "WHERE table_name = :t AND column_name = :c AND table_schema = 'public'"
+        ),
+        {"t": table, "c": column},
+    ).fetchone()
+    return row is not None
+
+
+def _index_exists(conn, name: str) -> bool:
+    row = conn.execute(
+        text("SELECT 1 FROM pg_indexes WHERE indexname = :n"),
+        {"n": name},
+    ).fetchone()
+    return row is not None
+
+
+_0026 = "0026_stack_logs_agent_id"
+_0025 = "0025_artifacts"
+
+
+class TestMigration0026RoundTrip:
+    def test_single_head(self, pg_engine):
+        url = pg_engine.url.render_as_string(hide_password=False)
+        assert len(_alembic_heads(url)) == 1
+
+    def test_head_has_agent_id_column_and_index(self, pg_engine):
+        with pg_engine.connect() as conn:
+            assert _alembic_version(conn) >= _0026
+            assert _column_exists(conn, "stack_logs", "agent_id")
+            assert _index_exists(conn, "ix_stack_logs_agent_id")
+
+    def test_downgrade_drops_then_upgrade_restores(self, pg_engine):
+        url = pg_engine.url.render_as_string(hide_password=False)
+        _run_alembic(url, "downgrade", _0025)
+        with pg_engine.connect() as conn:
+            assert _alembic_version(conn) == _0025
+            assert not _column_exists(conn, "stack_logs", "agent_id")
+            assert not _index_exists(conn, "ix_stack_logs_agent_id")
+        _run_alembic(url, "upgrade", "head")
+        with pg_engine.connect() as conn:
+            assert _alembic_version(conn) >= _0026
+            assert _column_exists(conn, "stack_logs", "agent_id")
+
+    def test_upgrade_backfills_agent_id_from_api_key(self, pg_engine):
+        """A legacy stack_logs row (written before the column existed) is
+        attributed to its agent by matching the stored api_key to
+        ``agents.key`` during the upgrade."""
+        from application.storage.db.repositories.agents import AgentsRepository
+
+        url = pg_engine.url.render_as_string(hide_password=False)
+        _run_alembic(url, "downgrade", _0025)
+
+        with pg_engine.begin() as conn:
+            agent = AgentsRepository(conn).create(
+                "u-mig26", "a", "published", key="mig26-key",
+            )
+            agent_id = str(agent["id"])
+            # Pre-0026 shape: no agent_id column.
+            conn.execute(
+                text(
+                    "INSERT INTO stack_logs "
+                    "(activity_id, endpoint, level, api_key, stacks) "
+                    "VALUES ('mig26-act', 'webhook', 'info', 'mig26-key', "
+                    "'[]'::jsonb)"
+                )
+            )
+            # A row whose key matches no agent must stay NULL.
+            conn.execute(
+                text(
+                    "INSERT INTO stack_logs "
+                    "(activity_id, endpoint, level, api_key, stacks) "
+                    "VALUES ('mig26-orphan', 'webhook', 'info', 'no-such-key', "
+                    "'[]'::jsonb)"
+                )
+            )
+
+        _run_alembic(url, "upgrade", "head")
+
+        with pg_engine.connect() as conn:
+            matched = conn.execute(
+                text(
+                    "SELECT agent_id FROM stack_logs "
+                    "WHERE activity_id = 'mig26-act'"
+                )
+            ).fetchone()
+            orphan = conn.execute(
+                text(
+                    "SELECT agent_id FROM stack_logs "
+                    "WHERE activity_id = 'mig26-orphan'"
+                )
+            ).fetchone()
+        assert str(matched._mapping["agent_id"]) == agent_id
+        assert orphan._mapping["agent_id"] is None