diff --git a/static/app/utils/analytics/seerAnalyticsEvents.tsx b/static/app/utils/analytics/seerAnalyticsEvents.tsx
index 7563d68da037..cec533d69d2c 100644
--- a/static/app/utils/analytics/seerAnalyticsEvents.tsx
+++ b/static/app/utils/analytics/seerAnalyticsEvents.tsx
@@ -1,4 +1,5 @@
 import type {Organization} from 'sentry/types/organization';
+import type {SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 
 export type SeerAnalyticsEventsParameters = {
   'ai_query.applied': {
@@ -142,7 +143,7 @@ export type SeerAnalyticsEventsParameters = {
     conversations_url: string | undefined;
     explorer_url: string | undefined;
     langfuse_url: string | undefined;
-    run_id: number | undefined;
+    run_id: SeerExplorerRunId | undefined;
     type: 'positive' | 'negative';
   };
   'seer.explorer.global_panel.opened': {
@@ -164,7 +165,7 @@ export type SeerAnalyticsEventsParameters = {
   };
   'seer.explorer.session_link_copied': Record<string, unknown>;
   'seer.explorer.timed_out': {
-    run_id: number | null;
+    run_id: SeerExplorerRunId | null;
   };
 };
 
diff --git a/static/app/views/dashboards/createFromSeerUtils.spec.tsx b/static/app/views/dashboards/createFromSeerUtils.spec.tsx
index 3505581ac8cd..45ef1c079db1 100644
--- a/static/app/views/dashboards/createFromSeerUtils.spec.tsx
+++ b/static/app/views/dashboards/createFromSeerUtils.spec.tsx
@@ -31,7 +31,6 @@ function makeSession(
   overrides: Partial<NonNullable<SeerExplorerResponse['session']>> = {}
 ): NonNullable<SeerExplorerResponse['session']> {
   return {
-    run_id: 1,
     status: 'completed',
     updated_at: new Date().toISOString(),
     blocks: [],
diff --git a/static/app/views/seerExplorer/components/chat/assistant.tsx b/static/app/views/seerExplorer/components/chat/assistant.tsx
index abfd99011636..4264b2d21539 100644
--- a/static/app/views/seerExplorer/components/chat/assistant.tsx
+++ b/static/app/views/seerExplorer/components/chat/assistant.tsx
@@ -11,7 +11,7 @@ import {trackAnalytics} from 'sentry/utils/analytics';
 import {useOrganization} from 'sentry/utils/useOrganization';
 import {useSessionStorage} from 'sentry/utils/useSessionStorage';
 import {getConversationsUrlForExternalUse} from 'sentry/views/explore/conversations/utils/urlParams';
-import type {Block} from 'sentry/views/seerExplorer/types';
+import type {Block, SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 import {getExplorerUrl, getLangfuseUrl} from 'sentry/views/seerExplorer/utils';
 
 import type {AssistantBlockProps} from './shared';
@@ -53,7 +53,11 @@ export function AssistantBlock({
   );
 }
 
-function useBlockFeedback(block: Block, blockIndex: number, runId: number | undefined) {
+function useBlockFeedback(
+  block: Block,
+  blockIndex: number,
+  runId: SeerExplorerRunId | undefined
+) {
   const organization = useOrganization();
   const [feedbackSubmitted, setFeedbackSubmitted] = useSessionStorage(
     `seer-explorer-feedback:run-${runId ?? 'null'}:block-${block.id}`,
diff --git a/static/app/views/seerExplorer/components/chat/index.tsx b/static/app/views/seerExplorer/components/chat/index.tsx
index 3e0318fbd437..4406c6ff16c0 100644
--- a/static/app/views/seerExplorer/components/chat/index.tsx
+++ b/static/app/views/seerExplorer/components/chat/index.tsx
@@ -3,7 +3,7 @@ import {motion} from 'framer-motion';
 import {Container} from '@sentry/scraps/layout';
 
 import {unreachable} from 'sentry/utils/unreachable';
-import type {Block} from 'sentry/views/seerExplorer/types';
+import type {Block, SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 
 import {AssistantBlock} from './assistant';
 import {ToolUseBlock} from './toolUse';
@@ -18,7 +18,7 @@ interface BlockProps {
   onClick?: () => void;
   readOnly?: boolean;
   ref?: React.Ref<HTMLDivElement>;
-  runId?: number;
+  runId?: SeerExplorerRunId;
   showThinking?: boolean;
 }
 
diff --git a/static/app/views/seerExplorer/components/chat/shared.tsx b/static/app/views/seerExplorer/components/chat/shared.tsx
index e31916e7815d..6b3348d6eaf0 100644
--- a/static/app/views/seerExplorer/components/chat/shared.tsx
+++ b/static/app/views/seerExplorer/components/chat/shared.tsx
@@ -8,7 +8,7 @@ import {Link} from '@sentry/scraps/link';
 import {Markdown, type MarkdownProps} from '@sentry/scraps/markdown';
 import {Heading} from '@sentry/scraps/text';
 
-import type {Block} from 'sentry/views/seerExplorer/types';
+import type {Block, SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 
 interface BlockVariantProps {
   block: Block;
@@ -20,7 +20,7 @@ export interface AssistantBlockProps extends BlockVariantProps {
   blockIndex: number;
   interactionPending?: boolean;
   readOnly?: boolean;
-  runId?: number;
+  runId?: SeerExplorerRunId;
 }
 
 export interface ToolUseBlockProps extends BlockVariantProps {
diff --git a/static/app/views/seerExplorer/components/drawer/useSeerExplorerDrawer.tsx b/static/app/views/seerExplorer/components/drawer/useSeerExplorerDrawer.tsx
index 6f14ed9e5588..b650f1b0f65a 100644
--- a/static/app/views/seerExplorer/components/drawer/useSeerExplorerDrawer.tsx
+++ b/static/app/views/seerExplorer/components/drawer/useSeerExplorerDrawer.tsx
@@ -7,6 +7,7 @@ import {trackAnalytics} from 'sentry/utils/analytics';
 import {useOrganization} from 'sentry/utils/useOrganization';
 import {ExplorerDrawerContent} from 'sentry/views/seerExplorer/components/drawer/explorerDrawerContent';
 import {useSeerExplorerChatDispatch} from 'sentry/views/seerExplorer/seerExplorerChatStateContext';
+import type {SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 import {isSeerExplorerEnabled, usePageReferrer} from 'sentry/views/seerExplorer/utils';
 
 const SEER_EXPLORER_DRAWER_KEY = 'seer-explorer-drawer';
@@ -21,7 +22,7 @@ export type OpenSeerExplorerDrawerOptions = {
    * Optional run ID to open. If provided, opens an existing session.
    * Cannot be used together with `startNewRun`.
    */
-  runId?: number;
+  runId?: SeerExplorerRunId;
   /**
    * If true, switches to a new session before opening.
    * Cannot be used together with `runId`.
diff --git a/static/app/views/seerExplorer/components/emptyState.tsx b/static/app/views/seerExplorer/components/emptyState.tsx
index 4f7270c579c4..562eced7bb19 100644
--- a/static/app/views/seerExplorer/components/emptyState.tsx
+++ b/static/app/views/seerExplorer/components/emptyState.tsx
@@ -7,6 +7,7 @@ import {Flex} from '@sentry/scraps/layout';
 import {LoadingIndicator} from 'sentry/components/loadingIndicator';
 import {IconSeer} from 'sentry/icons';
 import {t, tct} from 'sentry/locale';
+import type {SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 
 const SUGGESTED_QUESTIONS = [
   t('Which of my open issues are getting worse, not better?'),
@@ -19,7 +20,7 @@ interface EmptyStateProps {
   isError?: boolean;
   isLoading?: boolean;
   onSuggestionClick?: (question: string) => void;
-  runId?: number | null;
+  runId?: SeerExplorerRunId | null;
 }
 
 export function EmptyState({
diff --git a/static/app/views/seerExplorer/components/seerExplorerHeader.tsx b/static/app/views/seerExplorer/components/seerExplorerHeader.tsx
index bc16aa3cefe0..5bd5ffbfcf12 100644
--- a/static/app/views/seerExplorer/components/seerExplorerHeader.tsx
+++ b/static/app/views/seerExplorer/components/seerExplorerHeader.tsx
@@ -26,7 +26,10 @@ import {
 import {t} from 'sentry/locale';
 import {useDebouncedValue} from 'sentry/utils/useDebouncedValue';
 import {useSeerExplorerSessionsQuery} from 'sentry/views/seerExplorer/seerExplorerSessionContext';
-import type {SeerExplorerSidebarPosition} from 'sentry/views/seerExplorer/types';
+import type {
+  SeerExplorerRunId,
+  SeerExplorerSidebarPosition,
+} from 'sentry/views/seerExplorer/types';
 
 const POSITION_ICON_DIRECTION = {
   auto: undefined,
@@ -44,7 +47,7 @@ const POSITION_ICON_DIRECTION = {
 interface SeerExplorerHeaderProps {
   isPipSupported: boolean;
   isPoppedOut: boolean;
-  onChangeSession: (runId: number) => void;
+  onChangeSession: (runId: SeerExplorerRunId) => void;
   onCopyLinkClick: (() => void) | undefined;
   onCopySessionClick: (() => void) | undefined;
   onNewChatClick: () => void;
@@ -92,7 +95,7 @@ export function SeerExplorerHeader({
     }
     return (
       data?.data.map(session => ({
-        value: session.run_id,
+        value: session.sentry_run_id ?? session.run_id,
         label: session.title,
         details: (
           <TimeSince
diff --git a/static/app/views/seerExplorer/hooks/useSeerExplorer.spec.tsx b/static/app/views/seerExplorer/hooks/useSeerExplorer.spec.tsx
index 751f412ed83b..3edf8f7ca962 100644
--- a/static/app/views/seerExplorer/hooks/useSeerExplorer.spec.tsx
+++ b/static/app/views/seerExplorer/hooks/useSeerExplorer.spec.tsx
@@ -343,6 +343,43 @@ describe('useSeerExplorer', () => {
         expect(result.current.hasSentInterrupt).toBe(false);
       });
     });
+
+    it('URL-encodes the runId when building explorer-update URLs', async () => {
+      // A runId carrying path separators must be encoded so the same-origin
+      // POST can't traverse to another endpoint.
+      const maliciousRunId = '../../foo';
+      MockApiClient.addMockResponse({
+        url: `/organizations/${organization.slug}/seer/explorer-chat/..%2F..%2Ffoo/`,
+        method: 'GET',
+        body: {session: {blocks: [], status: 'processing'}},
+      });
+      const updateMock = MockApiClient.addMockResponse({
+        url: `/organizations/${organization.slug}/seer/explorer-update/..%2F..%2Ffoo/`,
+        method: 'POST',
+        body: {run_id: 123},
+      });
+
+      const {result} = renderHookWithProviders(() => useSeerExplorer(), {
+        organization,
+        additionalWrapper: SeerExplorerChatStateProvider,
+      });
+
+      act(() => {
+        result.current.switchToRun(maliciousRunId);
+      });
+
+      await waitFor(() => {
+        expect(result.current.runId).toBe(maliciousRunId);
+      });
+
+      act(() => {
+        result.current.interruptRun();
+      });
+
+      await waitFor(() => {
+        expect(updateMock).toHaveBeenCalled();
+      });
+    });
   });
 
   describe('Polling Logic', () => {
diff --git a/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx b/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx
index 2f8af474b517..71c0a0db1cfb 100644
--- a/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx
+++ b/static/app/views/seerExplorer/hooks/useSeerExplorer.tsx
@@ -20,6 +20,7 @@ import type {
   Block,
   RepoPRState,
   SeerExplorerResponse,
+  SeerExplorerRunId,
 } from 'sentry/views/seerExplorer/types';
 import {
   isSeerExplorerEnabled,
@@ -30,12 +31,21 @@ import {
 type SeerExplorerChatResponse = {
   message: Block;
   run_id: number;
+  sentry_run_id?: string | null;
 };
 
 type SeerExplorerUpdateResponse = {
   run_id: number;
 };
 
+/**
+ * Build the explorer-update endpoint URL. `runId` can originate from an
+ * attacker-controlled `explorerRunId` deep link, so it must be encoded to
+ * prevent path traversal in the resulting same-origin POST.
+ */
+const makeExplorerUpdateUrl = (orgSlug: string, runId: SeerExplorerRunId | null) =>
+  `/organizations/${orgSlug}/seer/explorer-update/${encodeURIComponent(String(runId))}/`;
+
 /** Routes where the LLMContext tree provides structured page context. */
 const STRUCTURED_CONTEXT_ROUTES = new Set([
   '/dashboard/:dashboardId/',
@@ -101,7 +111,6 @@ const getOptimisticAssistantTexts = () => [
 
 const makeErrorSeerExplorerData = (errorMessage: string): SeerExplorerResponse => ({
   session: {
-    run_id: undefined,
     blocks: [
       {
         id: 'error',
@@ -170,7 +179,7 @@ export const useSeerExplorer = () => {
       overrideCtxEngEnable: boolean;
       pageName: string;
       query: string;
-      runId: number | null;
+      runId: SeerExplorerRunId | null;
       screenshot: string | undefined;
     }
   >({
@@ -209,8 +218,11 @@ export const useSeerExplorer = () => {
     },
     onSuccess: (response, params) => {
       if (params.runId === null) {
-        // set run ID if this is a new session
-        dispatch({type: 'set run id', payload: response.run_id});
+        // Prefer the UUID; fall back to the numeric run_id for legacy runs.
+        dispatch({
+          type: 'set run id',
+          payload: response.sentry_run_id ?? response.run_id,
+        });
       } else {
         // invalidate the query so fresh data is fetched
         queryClient.invalidateQueries({
@@ -237,13 +249,17 @@ export const useSeerExplorer = () => {
     },
   });
 
-  const {mutate: userInputMutate} = useMutation({
-    mutationFn: async (params: {
+  const {mutate: userInputMutate} = useMutation<
+    SeerExplorerUpdateResponse,
+    RequestError,
+    {
       inputId: string;
       orgSlug: string;
-      runId: number | null;
+      runId: SeerExplorerRunId | null;
       responseData?: Record<string, unknown>;
-    }) => {
+    }
+  >({
+    mutationFn: async params => {
       setHasSentInterrupt(false);
 
       // Set optimistic status and updated_at to prevent isPolling flicker on new message.
@@ -264,8 +280,8 @@ export const useSeerExplorer = () => {
               : prev
         );
       }
-      return fetchMutation<SeerExplorerUpdateResponse>({
-        url: `/organizations/${params.orgSlug}/seer/explorer-update/${params.runId}/`,
+      return fetchMutation({
+        url: makeExplorerUpdateUrl(params.orgSlug, params.runId),
         method: 'POST',
         data: {
           payload: {
@@ -305,7 +321,7 @@ export const useSeerExplorer = () => {
   const {mutate: createPRMutate} = useMutation<
     SeerExplorerUpdateResponse,
     RequestError,
-    {orgSlug: string; runId: number | null; repoName?: string}
+    {orgSlug: string; runId: SeerExplorerRunId | null; repoName?: string}
   >({
     mutationFn: async params => {
       setHasSentInterrupt(false);
@@ -329,7 +345,7 @@ export const useSeerExplorer = () => {
         );
       }
       return fetchMutation({
-        url: `/organizations/${params.orgSlug}/seer/explorer-update/${params.runId}/`,
+        url: makeExplorerUpdateUrl(params.orgSlug, params.runId),
         method: 'POST',
         data: {
           payload: {
@@ -363,13 +379,13 @@ export const useSeerExplorer = () => {
     RequestError,
     {
       orgSlug: string;
-      runId: number | null;
+      runId: SeerExplorerRunId | null;
     }
   >({
     mutationFn: async params => {
       setHasSentInterrupt(true);
       return fetchMutation({
-        url: `/organizations/${params.orgSlug}/seer/explorer-update/${params.runId}/`,
+        url: makeExplorerUpdateUrl(params.orgSlug, params.runId),
         method: 'POST',
         data: {
           payload: {
@@ -401,7 +417,7 @@ export const useSeerExplorer = () => {
 
   /** Switches to a different run and fetches its latest state. */
   const switchToRun = useCallback(
-    (newRunId: number | null, {onSuccess}: {onSuccess?: () => void} = {}) => {
+    (newRunId: SeerExplorerRunId | null, {onSuccess}: {onSuccess?: () => void} = {}) => {
       if (newRunId === runId) {
         return;
       }
@@ -432,7 +448,11 @@ export const useSeerExplorer = () => {
   );
 
   const sendMessage = useCallback(
-    (query: string, explicitInsertIndex?: number, explicitRunId?: number | null) => {
+    (
+      query: string,
+      explicitInsertIndex?: number,
+      explicitRunId?: SeerExplorerRunId | null
+    ) => {
       if (!orgSlug) {
         return;
       }
@@ -639,7 +659,6 @@ export const useSeerExplorer = () => {
     ];
 
     const baseSession = rawSessionData ?? {
-      run_id: runId ?? undefined,
       blocks: [],
       status: 'processing' as const,
       updated_at: new Date().toISOString(),
diff --git a/static/app/views/seerExplorer/hooks/useSeerExplorerPolling.tsx b/static/app/views/seerExplorer/hooks/useSeerExplorerPolling.tsx
index d6fe3cdacbe7..1f00b9dfe5d3 100644
--- a/static/app/views/seerExplorer/hooks/useSeerExplorerPolling.tsx
+++ b/static/app/views/seerExplorer/hooks/useSeerExplorerPolling.tsx
@@ -5,7 +5,10 @@ import {useApiQuery} from 'sentry/utils/queryClient';
 import {useOrganization} from 'sentry/utils/useOrganization';
 import {useTimeout} from 'sentry/utils/useTimeout';
 import type {PollingState} from 'sentry/views/seerExplorer/seerExplorerChatStateContext';
-import type {SeerExplorerResponse} from 'sentry/views/seerExplorer/types';
+import type {
+  SeerExplorerResponse,
+  SeerExplorerRunId,
+} from 'sentry/views/seerExplorer/types';
 import type {Block} from 'sentry/views/seerExplorer/types';
 import {
   isSeerExplorerEnabled,
@@ -36,7 +39,7 @@ const getTimestampAge = (updatedAt: string | undefined): number | null => {
 };
 
 const getPollingState = (
-  runId: number | null,
+  runId: SeerExplorerRunId | null,
   sessionData: SeerExplorerResponse['session'] | undefined,
   isError: boolean,
   errorStatusCode: number | undefined,
@@ -70,7 +73,7 @@ const getPollingState = (
  * Called exclusively by `SeerExplorerChatStateProvider`, which dispatches the
  * derived polling state into context for all consumers.
  */
-export const useSeerExplorerPolling = ({runId}: {runId: number | null}) => {
+export const useSeerExplorerPolling = ({runId}: {runId: SeerExplorerRunId | null}) => {
   const organization = useOrganization({allowNull: true});
   const orgSlug = organization?.slug;
   const errorPollCountRef = useRef(0);
diff --git a/static/app/views/seerExplorer/seerExplorerChatStateContext.tsx b/static/app/views/seerExplorer/seerExplorerChatStateContext.tsx
index c00dffcdbff0..b53c9ac89cbf 100644
--- a/static/app/views/seerExplorer/seerExplorerChatStateContext.tsx
+++ b/static/app/views/seerExplorer/seerExplorerChatStateContext.tsx
@@ -10,6 +10,7 @@ import {
 
 import {sessionStorageWrapper} from 'sentry/utils/sessionStorage';
 import {useSeerExplorerPolling} from 'sentry/views/seerExplorer/hooks/useSeerExplorerPolling';
+import type {SeerExplorerRunId} from 'sentry/views/seerExplorer/types';
 
 export type PollingState =
   | 'polling'
@@ -22,24 +23,24 @@ type ChatState = {
 };
 
 type SeerExplorerChatState = {
-  chatStates: Record<number, ChatState>;
-  runId: number | null;
+  chatStates: Record<SeerExplorerRunId, ChatState>;
+  runId: SeerExplorerRunId | null;
 };
 
 type ChatStateAction =
-  | {payload: {polling: PollingState; runId: number}; type: 'set polling'}
-  | {payload: number | null; type: 'set run id'};
+  | {payload: {polling: PollingState; runId: SeerExplorerRunId}; type: 'set polling'}
+  | {payload: SeerExplorerRunId | null; type: 'set run id'};
 
 const RUN_ID_STORAGE_KEY = 'seer-explorer-run-id';
 
-function readRunIdFromStorage(): number | null {
+function readRunIdFromStorage(): SeerExplorerRunId | null {
   const raw = sessionStorageWrapper.getItem(RUN_ID_STORAGE_KEY);
   if (raw === null || raw === 'undefined') {
     return null;
   }
   try {
     const parsed: unknown = JSON.parse(raw);
-    return typeof parsed === 'number' ? parsed : null;
+    return typeof parsed === 'number' || typeof parsed === 'string' ? parsed : null;
   } catch {
     return null;
   }
@@ -121,7 +122,7 @@ function SeerExplorerChatStatePolling({
 }: {
   children: ReactNode;
   dispatch: Dispatch<ChatStateAction>;
-  runId: number | null;
+  runId: SeerExplorerRunId | null;
 }) {
   const {pollingState} = useSeerExplorerPolling({runId});
 
diff --git a/static/app/views/seerExplorer/types.tsx b/static/app/views/seerExplorer/types.tsx
index 7cadb15f954a..c9b744eb1aef 100644
--- a/static/app/views/seerExplorer/types.tsx
+++ b/static/app/views/seerExplorer/types.tsx
@@ -114,6 +114,7 @@ export interface ExplorerSession {
   last_triggered_at: string;
   run_id: number;
   title: string;
+  sentry_run_id?: string | null;
 }
 
 export interface Artifact<T = Record<string, unknown>> {
@@ -148,6 +149,8 @@ export type PendingUserInput = {
   input_type: 'file_change_approval' | 'ask_user_question';
 };
 
+export type SeerExplorerRunId = number | string;
+
 export type SeerExplorerResponse = {
   session: {
     blocks: Block[];
@@ -156,6 +159,6 @@ export type SeerExplorerResponse = {
     owner_user_id?: number | null;
     pending_user_input?: PendingUserInput | null;
     repo_pr_states?: Record<string, RepoPRState>;
-    run_id?: number;
   } | null;
+  sentry_run_id?: string | null;
 };
diff --git a/static/app/views/seerExplorer/useSeerExplorerContext.tsx b/static/app/views/seerExplorer/useSeerExplorerContext.tsx
index 413765da8cda..364053fab145 100644
--- a/static/app/views/seerExplorer/useSeerExplorerContext.tsx
+++ b/static/app/views/seerExplorer/useSeerExplorerContext.tsx
@@ -32,7 +32,10 @@ import {
   useSeerExplorerChatDispatch,
   useSeerExplorerChatState,
 } from 'sentry/views/seerExplorer/seerExplorerChatStateContext';
-import type {SeerExplorerSidebarPosition} from 'sentry/views/seerExplorer/types';
+import type {
+  SeerExplorerRunId,
+  SeerExplorerSidebarPosition,
+} from 'sentry/views/seerExplorer/types';
 import {
   useIsSeerExplorerSidebarEnabled,
   usePageReferrer,
@@ -361,7 +364,7 @@ export function SeerExplorerContextProvider({children}: {children: ReactNode}) {
   // Deep link effect while Seer isn't already showing (the drawer content
   // handles deep links itself when open or popped out).
   const deepLinkCallback = useCallback(
-    (_runId: number) => openSeerExplorer({runId: _runId}),
+    (_runId: SeerExplorerRunId) => openSeerExplorer({runId: _runId}),
     [openSeerExplorer]
   );
 
diff --git a/static/app/views/seerExplorer/utils.spec.tsx b/static/app/views/seerExplorer/utils.spec.tsx
index 881d155e9045..d18e8603663c 100644
--- a/static/app/views/seerExplorer/utils.spec.tsx
+++ b/static/app/views/seerExplorer/utils.spec.tsx
@@ -1,9 +1,15 @@
 import {OrganizationFixture} from 'sentry-fixture/organization';
 
+import {renderHookWithProviders, waitFor} from 'sentry-test/reactTestingLibrary';
+
 import {decodeMetricsQueryParams} from 'sentry/views/explore/metrics/metricQuery';
 import {Mode} from 'sentry/views/explore/queryParams/mode';
 import {VisualizeFunction} from 'sentry/views/explore/queryParams/visualize';
-import {buildToolLinkUrl} from 'sentry/views/seerExplorer/utils';
+import {
+  buildToolLinkUrl,
+  parseRunIdParam,
+  useSeerExplorerDeepLink,
+} from 'sentry/views/seerExplorer/utils';
 
 describe('buildToolLinkUrl', () => {
   const organization = OrganizationFixture({slug: 'org-slug'});
@@ -74,3 +80,70 @@ describe('buildToolLinkUrl', () => {
     expect(result).toBeNull();
   });
 });
+
+describe('parseRunIdParam', () => {
+  it('parses a legacy numeric run ID into a number', () => {
+    expect(parseRunIdParam('123')).toBe(123);
+  });
+
+  it('accepts a UUID run ID as a string', () => {
+    const uuid = '0fd9e7a2-1c3b-4d5e-8f90-abcdef012345';
+    expect(parseRunIdParam(uuid)).toBe(uuid);
+  });
+
+  it('rejects values that are neither numeric nor a UUID', () => {
+    expect(parseRunIdParam('../../foo')).toBeNull();
+    expect(parseRunIdParam('not-a-uuid')).toBeNull();
+    expect(parseRunIdParam('')).toBeNull();
+    expect(parseRunIdParam('12.5')).toBeNull();
+  });
+});
+
+describe('useSeerExplorerDeepLink', () => {
+  const UUID = '0fd9e7a2-1c3b-4d5e-8f90-abcdef012345';
+
+  function renderDeepLink(explorerRunId: string | undefined, enabled = true) {
+    const callback = jest.fn();
+    const {router} = renderHookWithProviders(
+      () => useSeerExplorerDeepLink({callback, enabled}),
+      {
+        initialRouterConfig: {
+          location: {
+            pathname: '/issues/',
+            query: explorerRunId === undefined ? {} : {explorerRunId},
+          },
+        },
+      }
+    );
+    return {callback, router};
+  }
+
+  it('opens a UUID run from the deep link and strips the param', async () => {
+    const {callback, router} = renderDeepLink(UUID);
+
+    await waitFor(() => expect(callback).toHaveBeenCalledWith(UUID));
+    expect(router.location.query.explorerRunId).toBeUndefined();
+  });
+
+  it('opens a legacy numeric run as a number', async () => {
+    const {callback, router} = renderDeepLink('123');
+
+    await waitFor(() => expect(callback).toHaveBeenCalledWith(123));
+    expect(router.location.query.explorerRunId).toBeUndefined();
+  });
+
+  it('ignores a malformed param without navigating or invoking the callback', async () => {
+    const {callback, router} = renderDeepLink('../../foo');
+
+    // Nothing valid to do, so the param is left in place and untouched.
+    await waitFor(() => expect(router.location.query.explorerRunId).toBe('../../foo'));
+    expect(callback).not.toHaveBeenCalled();
+  });
+
+  it('does nothing when disabled, even with a valid param', async () => {
+    const {callback, router} = renderDeepLink(UUID, false);
+
+    await waitFor(() => expect(router.location.query.explorerRunId).toBe(UUID));
+    expect(callback).not.toHaveBeenCalled();
+  });
+});
diff --git a/static/app/views/seerExplorer/utils.tsx b/static/app/views/seerExplorer/utils.tsx
index 832964075fb8..bb5e65d34ed3 100644
--- a/static/app/views/seerExplorer/utils.tsx
+++ b/static/app/views/seerExplorer/utils.tsx
@@ -13,6 +13,7 @@ import {getApiUrl} from 'sentry/utils/api/getApiUrl';
 import type {Sort} from 'sentry/utils/discover/fields';
 import {SavedQueryDatasets} from 'sentry/utils/discover/types';
 import {getRouteStringFromRoutes} from 'sentry/utils/getRouteStringFromRoutes';
+import {isUUID} from 'sentry/utils/string/isUUID';
 import {useLocation} from 'sentry/utils/useLocation';
 import {useMedia} from 'sentry/utils/useMedia';
 import {useNavigate} from 'sentry/utils/useNavigate';
@@ -38,6 +39,7 @@ import {VisualizeFunction} from 'sentry/views/explore/queryParams/visualize';
 import {makeReplaysPathname} from 'sentry/views/explore/replays/pathnames';
 import type {
   Block,
+  SeerExplorerRunId,
   SeerExplorerSidebarPosition,
   ToolCall,
   ToolLink,
@@ -57,7 +59,7 @@ type ToolFormatter = (
 
 export const makeSeerExplorerQueryKey = (
   orgSlug: string,
-  runId: number | null
+  runId: SeerExplorerRunId | null
 ): ApiQueryKey => [
   runId
     ? getApiUrl('/organizations/$organizationIdOrSlug/seer/explorer-chat/$runId/', {
@@ -1064,6 +1066,13 @@ function locationToUrl(location: LocationDescriptor): string | null {
 
 const RUN_ID_QUERY_PARAM = 'explorerRunId';
 
+export function parseRunIdParam(value: string): SeerExplorerRunId | null {
+  if (/^\d+$/.test(value)) {
+    return Number(value);
+  }
+  return isUUID(value) ? value : null;
+}
+
 /**
  * useEffect which listens for run ID query param in the current location. If found, it removes the query param and runs a callback.
  */
@@ -1071,7 +1080,7 @@ export function useSeerExplorerDeepLink({
   callback,
   enabled = true,
 }: {
-  callback: (runId: number) => void;
+  callback: (runId: SeerExplorerRunId) => void;
   enabled?: boolean;
 }) {
   const location = useLocation();
@@ -1087,12 +1096,14 @@ export function useSeerExplorerDeepLink({
       return;
     }
 
-    const parsedRunId = Number(paramValue);
-    if (!Number.isNaN(parsedRunId)) {
-      const {[RUN_ID_QUERY_PARAM]: _removed, ...restQuery} = location.query ?? {};
-      navigate({...location, query: restQuery}, {replace: true});
-      callback(parsedRunId);
+    const runId = parseRunIdParam(paramValue);
+    if (runId === null) {
+      return;
     }
+
+    const {[RUN_ID_QUERY_PARAM]: _removed, ...restQuery} = location.query ?? {};
+    navigate({...location, query: restQuery}, {replace: true});
+    callback(runId);
   }, [location, navigate, callback, enabled]);
 }
 
@@ -1109,7 +1120,9 @@ export function getLangfuseUrl(runId: number | string): string {
   return `https://langfuse.getsentry.net/project/clx9kma1k0001iebwrfw4oo0z/sessions/${runId}`;
 }
 
-export function getExplorerFeedbackOptions(runId: number | null): UseFeedbackOptions {
+export function getExplorerFeedbackOptions(
+  runId: SeerExplorerRunId | null
+): UseFeedbackOptions {
   return {
     formTitle: 'Seer Agent Feedback',
     messagePlaceholder: 'How can we make Seer better for you?',