fix: address code review findings for URL routing (#180)

- Decode URI-encoded session IDs in parsePath (copilot:abc → works)
- Use router.navigateToSession directly in callers to avoid race with
  route-change effect when navigating from non-session pages
- Respect basePath in SubagentInline href via buildSessionHref helper
- Preserve filter params when deselecting session (navigateFromSession)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mariusvniekerk

frontend/src/App.svelte

@@ -236,6 +236,25 @@
     });
   });
 
+  // Build URL params from current session filters.
+  function buildFilterParams(): Record<string, string> {
+    const f = sessions.filters;
+    const p: Record<string, string> = {};
+    if (f.project) p.project = f.project;
+    if (f.machine) p.machine = f.machine;
+    if (f.agent) p.agent = f.agent;
+    if (f.date) p.date = f.date;
+    if (f.dateFrom) p.date_from = f.dateFrom;
+    if (f.dateTo) p.date_to = f.dateTo;
+    if (f.recentlyActive) p.active_since = "true";
+    if (f.hideUnknownProject) p.exclude_project = "unknown";
+    if (f.minMessages > 0) p.min_messages = String(f.minMessages);
+    if (f.maxMessages > 0) p.max_messages = String(f.maxMessages);
+    if (f.minUserMessages > 0) p.min_user_messages = String(f.minUserMessages);
+    if (f.includeOneShot) p.include_one_shot = "true";
+    return p;
+  }
+
   // Sync active session to URL.
   $effect(() => {
     const activeId = sessions.activeSessionId;
@@ -247,7 +266,7 @@
       if (activeId) {
         router.navigateToSession(activeId);
       } else {
-        router.navigateFromSession();
+        router.navigateFromSession(buildFilterParams());
       }
     });
   });

frontend/src/lib/components/analytics/TopSessions.svelte

@@ -17,13 +17,7 @@
   }
 
   function handleSessionClick(id: string) {
-    if (router.route !== "sessions") {
-      const params: Record<string, string> = {};
-      if (analytics.includeOneShot) {
-        params["include_one_shot"] = "true";
-      }
-      router.navigate("sessions", params);
-    }
+    router.navigateToSession(id);
     sessions.selectSession(id);
   }
 </script>

frontend/src/lib/components/content/SubagentInline.svelte

@@ -6,7 +6,7 @@
   import { formatTokenCount } from "../../utils/format.js";
   import { computeMainModel } from "../../utils/model.js";
   import { sessions } from "../../stores/sessions.svelte.js";
-  import { router } from "../../stores/router.svelte.js";
+  import { router, buildSessionHref } from "../../stores/router.svelte.js";
   import MessageContent from "./MessageContent.svelte";
 
   interface Props {
@@ -45,9 +45,7 @@
   async function openAsSession(e: MouseEvent) {
     e.preventDefault();
     e.stopPropagation();
-    if (router.route !== "sessions") {
-      router.navigate("sessions");
-    }
+    router.navigateToSession(sessionId);
     await sessions.navigateToSession(sessionId);
   }
 
@@ -86,7 +84,7 @@
       {/if}
     </button>
     <a
-      href="/sessions/{sessionId}"
+      href={buildSessionHref(sessionId)}
       class="open-session-link"
       onclick={openAsSession}
       title="Open as full session"

frontend/src/lib/components/pinned/PinnedPage.svelte

@@ -24,9 +24,7 @@
 
   function navigateToPin(sessionId: string, ordinal: number) {
     ui.scrollToOrdinal(ordinal, sessionId);
-    if (router.route !== "sessions") {
-      router.navigate("sessions");
-    }
+    router.navigateToSession(sessionId);
     sessions.navigateToSession(sessionId);
   }
 

frontend/src/lib/stores/router.svelte.ts

@@ -15,13 +15,18 @@ const VALID_ROUTES: ReadonlySet<string> = new Set<Route>([
 
 const DEFAULT_ROUTE: Route = "sessions";
 
-function getBasePath(): string {
+export function getBasePath(): string {
   const base = document.querySelector("base");
   if (!base) return "";
   const href = base.getAttribute("href") ?? "";
   return href.replace(/\/+$/, "");
 }
 
+/** Build a full URL path for a session, respecting basePath. */
+export function buildSessionHref(id: string): string {
+  return `${getBasePath()}/sessions/${encodeURIComponent(id)}`;
+}
+
 export function parsePath(): {
   route: Route;
   sessionId: string | null;
@@ -44,7 +49,7 @@ export function parsePath(): {
 
   const sessionId =
     route === "sessions" && segments.length >= 2
-      ? segments[1]!
+      ? decodeURIComponent(segments[1]!)
       : null;
 
   const params = Object.fromEntries(

frontend/src/lib/stores/router.test.ts

@@ -82,6 +82,12 @@ describe("parsePath", () => {
     expect(result.sessionId).toBeNull();
   });
 
+  it("decodes encoded session IDs", () => {
+    setURL("/sessions/copilot%3Aabc123");
+    const result = parsePath();
+    expect(result.sessionId).toBe("copilot:abc123");
+  });
+
   it("strips basePath from pathname", () => {
     const base = document.createElement("base");
     base.href = "/agentsview/";