diff --git a/web/app.js b/web/app.js
index 4830f5d..62a6866 100644
--- a/web/app.js
+++ b/web/app.js
@@ -2,6 +2,7 @@ let state;
 let groups = [];
 let selectedIndex = -1;
 let pdfViewer = null;
+let currentPdfKey = null;
 let loadRequestId = 0;
 
 const people = document.querySelector("#people");
@@ -112,69 +113,23 @@ function renderList() {
   updateStatus(shown.length);
 }
 
-async function loadPdf(index) {
+async function openDocument(index, { force = false } = {}) {
   const doc = state.documents[index];
   if (!doc) return;
 
-  // Deduplicate: don't reload the same document
-  if (index === selectedIndex && pdfViewer) {
+  const key = `${doc._letter}/${doc.file_name}`;
+
+  // Deduplicate: ignore click on already-loaded document unless forced
+  if (!force && key === currentPdfKey) {
     return;
   }
 
-  if (pdfViewer) {
-    pdfViewer.destroy();
-  }
-  pdfViewer = new PdfViewer(pdfContainer);
-  viewer.classList.remove("loaded");
-  pdfMessage.hidden = false;
-  pdfMessage.textContent = "Loading PDF\u2026";
-
-  const reqId = "pdf-" + (++loadRequestId);
-  console.log(
-    `[BizMatch QC] PDF ${reqId} selection: ${doc._letter}/${doc.file_name}`,
-  );
-  console.log(`[BizMatch QC] PDF ${reqId} prepare requested`);
-
-  const startTime = performance.now();
-  try {
-    const response = await fetch("/api/pdf/prepare", {
-      method: "POST",
-      headers: { "content-type": "application/json" },
-      body: JSON.stringify({ index, requestId: reqId }),
-    });
-    if (!response.ok) {
-      const body = await response.json().catch(() => ({}));
-      throw new Error(body.error || `Prepare failed: HTTP ${response.status}`);
-    }
-    const data = await response.json();
-    const prepareMs = Math.round(performance.now() - startTime);
-    console.log(
-      `[BizMatch QC] PDF ${reqId} prepare: ${prepareMs}ms, disk cache ${data.cacheStatus}`,
-    );
-
-    if (index !== selectedIndex) {
-      // A newer selection happened while preparing, don't show stale result
-      return;
-    }
-
-    viewer.classList.add("loaded");
-    pdfMessage.hidden = true;
-    console.log(`[BizMatch QC] PDF ${reqId} viewer load started`);
-    await pdfViewer.load(data.url, data.size);
-    console.log(`[BizMatch QC] PDF ${reqId} rendering complete`);
-  } catch (error) {
-    if (index !== selectedIndex) return;
-    const message = error instanceof Error ? error.message : String(error);
-    pdfMessage.textContent = `Cannot open PDF: ${message}`;
-    pdfMessage.hidden = false;
-  }
-}
-
-function select(index) {
+  // Mark as loading this document
+  currentPdfKey = key;
   selectedIndex = index;
-  const doc = state.documents[index];
-  if (!doc) return;
+  renderList();
 
+  // Update detail panel
   let rowIdx = 0;
   fields.innerHTML = `
     <h2>${esc(doc.name_from_filename)}</h2>
@@ -202,8 +157,64 @@ function select(index) {
     }).join("")
   }
   `;
-  void loadPdf(index);
-  renderList();
+
+  // Load PDF
+  if (pdfViewer) {
+    pdfViewer.destroy();
+  }
+  pdfViewer = new PdfViewer(pdfContainer);
+  viewer.classList.remove("loaded");
+  pdfMessage.hidden = false;
+  pdfMessage.textContent = "Loading PDF\u2026";
+
+  const reqId = "pdf-" + (++loadRequestId);
+  console.log(
+    `[BizMatch QC] Document selected: ${key}`,
+  );
+  console.log(`[BizMatch QC] PDF prepare starting: ${reqId}`);
+
+  const startTime = performance.now();
+  try {
+    const response = await fetch("/api/pdf/prepare", {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ index, requestId: reqId }),
+    });
+    if (!response.ok) {
+      const body = await response.json().catch(() => ({}));
+      throw new Error(body.error || `Prepare failed: HTTP ${response.status}`);
+    }
+    const data = await response.json();
+    const prepareMs = Math.round(performance.now() - startTime);
+    console.log(
+      `[BizMatch QC] PDF prepare: ${prepareMs}ms, disk cache ${data.cacheStatus}`,
+    );
+    console.log(`[BizMatch QC] PDF viewer URL received: ${reqId}`);
+
+    if (key !== currentPdfKey) {
+      // A newer document was selected while preparing
+      return;
+    }
+
+    viewer.classList.add("loaded");
+    pdfMessage.hidden = true;
+    await pdfViewer.load(data.url, data.size);
+    console.log(`[BizMatch QC] PDF ${reqId} rendering complete`);
+  } catch (error) {
+    if (key !== currentPdfKey) return;
+    const message = error instanceof Error ? error.message : String(error);
+    pdfMessage.textContent = `Cannot open PDF: ${message}`;
+    pdfMessage.hidden = false;
+  }
+}
+
+function select(index) {
+  openDocument(index);
+}
+
+// Exposed for future retry from viewer; use openDocument(_, {force:true})
+function _selectForced(index) {
+  openDocument(index, { force: true });
 }
 
 people.addEventListener("click", (event) => {
diff --git a/web/pdf_viewer.js b/web/pdf_viewer.js
index 570de0c..d59d622 100644
--- a/web/pdf_viewer.js
+++ b/web/pdf_viewer.js
@@ -39,10 +39,8 @@ class PdfViewer {
   }
 
   _setState(state) {
-    this.loadingDiv.hidden = true;
-    this.errorDiv.hidden = true;
-    if (state === "loading") this.loadingDiv.hidden = false;
-    if (state === "error") this.errorDiv.hidden = false;
+    this.loadingDiv.hidden = state !== "loading";
+    this.errorDiv.hidden = state !== "error";
     this._viewerState = state;
   }
 
@@ -59,7 +57,6 @@ class PdfViewer {
       `[BizMatch QC] PDF viewer load started: generation ${generation}`,
     );
 
-    // Await cleanup of previous document (promises may be involved)
     await this._disposeCurrentDocument();
     if (generation !== this.generation) return;
 
@@ -90,14 +87,14 @@ class PdfViewer {
       const viewerWidth = this._getViewportWidth();
       console.log(`[BizMatch QC] PDF usable render width: ${viewerWidth}px`);
 
-      const pageStart = performance.now();
+      // Render page 1 -- MUST succeed before we show ready state
       await this._renderPage(doc, 1, viewerWidth, generation);
       if (generation !== this.generation) return;
-
-      this._setState(null); // Remove loading overlay
-      const firstPageMs = Math.round(performance.now() - pageStart);
+      this._setState("ready");
       console.log(
-        `[BizMatch QC] PDF page 1 rendered in ${firstPageMs}ms`,
+        `[BizMatch QC] PDF page 1 rendered in ${
+          Math.round(performance.now() - loadStart)
+        }ms`,
       );
       console.log(
         `[BizMatch QC] First page visible after ${
@@ -127,15 +124,12 @@ class PdfViewer {
       );
     } catch (err) {
       if (generation !== this.generation) return;
-      // Distinguish cancellation from real errors
       if (isCancellationError(err)) {
-        console.log(
-          `[BizMatch QC] PDF generation ${generation} cancelled`,
-        );
+        console.log(`[BizMatch QC] PDF generation ${generation} cancelled`);
         return;
       }
       const msg = errorMsg(err);
-      console.error(`[BizMatch QC] PDF load failed:`, msg);
+      console.error(`[BizMatch QC] PDF load failed:`, msg, err?.stack);
       this.errorMsg.textContent = `Unable to open PDF: ${msg}`;
       this._setState("error");
     }
@@ -197,19 +191,20 @@ class PdfViewer {
       const fitScale = viewerWidth / vp1.width;
       const viewport = page.getViewport({ scale: fitScale });
 
-      const dpr = Math.min(globalThis.devicePixelRatio || 1, 2);
+      // Use DPR 1 for initial diagnosis; restore DPR scaling after content renders
+      const dpr = 1;
       canvas.width = Math.floor(viewport.width * dpr);
       canvas.height = Math.floor(viewport.height * dpr);
       canvas.style.width = `${Math.floor(viewport.width)}px`;
       canvas.style.height = `${Math.floor(viewport.height)}px`;
 
       const ctx = canvas.getContext("2d");
-      const transform = dpr !== 1 ? [dpr, 0, 0, dpr, 0, 0] : undefined;
+      if (!ctx) throw new Error("2D canvas context is unavailable");
 
       const renderTask = page.render({
-        canvasContext: ctx,
+        canvas,
         viewport,
-        transform,
+        transform: undefined,
       });
       this.renderTasks.add(renderTask);
 
@@ -220,21 +215,27 @@ class PdfViewer {
       pageDiv.dataset.renderState = "rendered";
     } catch (err) {
       if (generation !== this.generation) return;
-      if (isCancellationError(err)) return;
-      pageDiv.dataset.renderState = "error";
+      if (isCancellationError(err)) throw err;
+
       console.error(
-        `[BizMatch QC] Failed to render PDF page ${pageNum}`,
+        `[BizMatch QC] Page ${pageNum} render failed`,
         err,
+        err?.stack,
       );
+
       if (pageNum === 1) {
-        this.errorMsg.textContent = `Unable to open PDF: ${errorMsg(err)}`;
-        this._setState("error");
-      } else {
-        pageDiv.textContent = `Error rendering page ${pageNum}`;
-        pageDiv.style.padding = "20px";
-        pageDiv.style.color = "#f88";
-        pageDiv.style.textAlign = "center";
+        throw new Error(
+          `Failed to render page 1: ${errorMsg(err)}`,
+          { cause: err },
+        );
       }
+
+      // Inline error for later pages
+      pageDiv.textContent = `Error rendering page ${pageNum}`;
+      pageDiv.style.padding = "20px";
+      pageDiv.style.color = "#f88";
+      pageDiv.style.textAlign = "center";
+      pageDiv.dataset.renderState = "error";
     }
   }