diff --git a/static/js/compare/sse.js b/static/js/compare/sse.js
new file mode 100644
index 000000000..7e60b0e12
--- /dev/null
+++ b/static/js/compare/sse.js
@@ -0,0 +1,65 @@
+function streamError(payload) {
+ const detail = payload?.data ?? payload;
+ const candidates = [detail?.message, detail?.text, detail?.error?.message,
+ detail?.error, payload?.message, payload?.text, payload?.error?.message,
+ payload?.error, typeof payload === 'string' ? payload : null];
+ const message = candidates.find(value => typeof value === 'string' && value.trim());
+ return new Error(message || 'Model request failed.');
+}
+
+/** Decode complete SSE frames, requiring the backend's terminal DONE event. */
+export async function consumeCompareEvents(response, onEvent, onActivity) {
+ const reader = response.body.getReader();
+ const decoder = new TextDecoder();
+ let line = '', event = 'message', data = [], skipLF = false;
+ try {
+ while (true) {
+ const { done, value } = await reader.read();
+ if (!done) onActivity?.();
+ let chunk = decoder.decode(value, { stream: !done });
+ if (skipLF && chunk.length) {
+ if (chunk.startsWith('\n')) chunk = chunk.slice(1);
+ skipLF = false;
+ }
+ const separators = /\r\n|\r|\n/g;
+ let start = 0, separator;
+ while ((separator = separators.exec(chunk))) {
+ line += chunk.slice(start, separator.index);
+ start = separator.index + separator[0].length;
+ skipLF = separator[0] === '\r' && start === chunk.length;
+ if (!line) {
+ if (data.length || event === 'error') {
+ const raw = data.join('\n');
+ if (event !== 'error' && raw === '[DONE]') return;
+ let payload;
+ try { payload = JSON.parse(raw); }
+ catch (_) {
+ if (event === 'error') throw streamError(raw);
+ throw new Error('Invalid model stream data.');
+ }
+ if (event === 'error' || payload?.type === 'error') throw streamError(payload);
+ if (!payload || typeof payload !== 'object' || Array.isArray(payload)) {
+ throw new Error('Invalid model stream data.');
+ }
+ await onEvent(payload);
+ }
+ event = 'message';
+ data = [];
+ } else if (!line.startsWith(':')) {
+ const colon = line.indexOf(':');
+ const field = colon < 0 ? line : line.slice(0, colon);
+ let value = colon < 0 ? '' : line.slice(colon + 1);
+ if (value.startsWith(' ')) value = value.slice(1);
+ if (field === 'data') data.push(value);
+ else if (field === 'event') event = value || 'message';
+ }
+ line = '';
+ }
+ line += chunk.slice(start);
+ if (done) throw new Error('Stream ended before completion.');
+ }
+ } finally {
+ try { await reader.cancel(); } catch (_) {}
+ reader.releaseLock();
+ }
+}
diff --git a/static/js/compare/stream.js b/static/js/compare/stream.js
index 4ea5c4e74..c2577cbed 100644
--- a/static/js/compare/stream.js
+++ b/static/js/compare/stream.js
@@ -1,5 +1,6 @@
// compare/stream.js — SSE streaming to panes
import state from './state.js';
+import { consumeCompareEvents } from './sse.js';
import { addFinishBadge } from './vote.js?v=20260828resendcaldrag1';
import { getModelCost, renderAskUserCard, safeDisplayImageSrc } from '../chatRenderer.js?v=20260914metricssummary1';
import markdownModule from '../markdown.js';
@@ -472,25 +473,9 @@ async function streamToPane(paneIdx, sessionId, message, aiMsgEl, opts) {
});
if (!response.ok) throw new Error(`HTTP ${response.status}`);
- const reader = response.body.getReader();
- const decoder = new TextDecoder();
- let buffer = '';
-
- while (true) {
- const { done, value } = await reader.read();
- if (done) break;
- _resetIdleTimeout(); // any chunk = stream is alive
-
- buffer += decoder.decode(value, { stream: true });
- const lines = buffer.split('\n');
- buffer = lines.pop() || '';
-
- for (const line of lines) {
- if (!line.startsWith('data: ')) continue;
- const data = line.slice(6);
- if (data === '[DONE]') break;
+ await consumeCompareEvents(response,
+ (json) => {
try {
- const json = JSON.parse(data);
if (json.type === 'metrics') {
metrics = json.data;
@@ -672,7 +657,7 @@ async function streamToPane(paneIdx, sessionId, message, aiMsgEl, opts) {
if (hist) hist.scrollTop = hist.scrollHeight;
} else if (json.delta) {
// Skip text deltas if we already rendered an image
- if (aiMsgEl._imageData) continue;
+ if (aiMsgEl._imageData) return;
// Capture TTFT on very first text delta
if (!accumulated && !_ttft) _ttft = performance.now() - _timerStart;
// On first delta, destroy spinner and prepare text area
@@ -701,8 +686,7 @@ async function streamToPane(paneIdx, sessionId, message, aiMsgEl, opts) {
_scheduleLiveRender(target);
}
} catch (e) { console.warn('Compare stream render error:', e); }
- }
- }
+ }, _resetIdleTimeout);
streamOk = true;
// Destroy any remaining spinner
@@ -900,9 +884,15 @@ async function streamToPane(paneIdx, sessionId, message, aiMsgEl, opts) {
}
} else {
console.error('Compare stream error:', error);
- aiBody.innerHTML = 'Error: ' + escapeHtml(error.message) + '';
+ awaitingChoice = false;
+ const message = state._blindMode ? 'Model request failed. Try again.' : error.message;
+ aiBody.innerHTML = 'Error: ' + escapeHtml(message) + '';
}
} finally {
+ if (aiMsgEl._spinner) {
+ aiMsgEl._spinner.destroy();
+ aiMsgEl._spinner = null;
+ }
clearTimeout(timeoutId);
_timerDone = true;
cancelAnimationFrame(_rafId);
diff --git a/static/sw.js b/static/sw.js
index de964dd14..a3feba04a 100644
--- a/static/sw.js
+++ b/static/sw.js
@@ -7,7 +7,7 @@
// - Other static assets (images/fonts/libs): cache-first with bg refresh.
// - API / non-GET: never cached.
// Bump CACHE_NAME whenever the precache list or SW logic changes.
-const CACHE_NAME = 'odysseus-v1114-pr40-editor-precache';
+const CACHE_NAME = 'odysseus-v1115-pr40-editor-precache';
// KaTeX resolves these from its own stylesheet, so caching the CSS without them
// gives offline math fallback glyphs instead of proper typesetting.
@@ -38,6 +38,7 @@ const KATEX_FONTS = [
// Both are fetched at install time, in the background. Entries must match the
// exact URL the browser requests, query string included.
const PRECACHE = [
+ '/static/js/compare/sse.js',
'/',
'/static/css/00-tokens.css?v=20260929csssplit',
'/static/css/01-agent-chat.css?v=20260929csssplit',
diff --git a/tests/test_compare_stream_contract_browser.py b/tests/test_compare_stream_contract_browser.py
new file mode 100644
index 000000000..620a1768d
--- /dev/null
+++ b/tests/test_compare_stream_contract_browser.py
@@ -0,0 +1,70 @@
+"""Compare's actual stream consumer must preserve evidence and terminal state."""
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[1]
+
+CASES = [
+ ("lf", 'data: {"delta":"Hello"}\n\ndata: [DONE]\n\n', False, True, "Hello"),
+ ("crlf", 'data:{"delta":"Héllö"}\r\n\r\ndata:[DONE]\r\n\r\n', False, True, "Héllö"),
+ ("multiline", 'data: {"delta":\ndata: "Hello"}\n\ndata: [DONE]\n\n', False, True, "Hello"),
+ ("eof", 'data: {"delta":"Partial"}\n\n', False, False, "ended before completion"),
+ ("named-error", 'event: error\ndata: {"text":"Provider Z private-model failed"}\n\n', False, False, "Provider Z private-model failed"),
+ ("typed-error", 'data: {"type":"error","data":{"message":"Provider Z 
"}}\n\ndata: [DONE]\n\n', False, False, "Provider Z {
+ const browser=await chromium.launch({headless:true});
+ try{
+ const page=await browser.newPage();
+ await page.goto(process.env.ODYSSEUS_TEST_STATIC_ORIGIN+'/static/js/storage.js');
+ await page.setContent('');
+ const result=await page.evaluate(async(data)=>{
+ const {default:state}=await import('/static/js/compare/state.js');
+ const {streamToPane}=await import('/static/js/compare/stream.js');
+ Object.assign(state,{isActive:true,_selectedModels:[{model:'fixture',name:'Fixture'}],_paneSessionIds:['session'],_compareMode:'chat',_parallel:true,_blindMode:data.blind,_timeout:data.kind==='heartbeat'?1:5});
+ const nativeFetch=window.fetch,bytes=new TextEncoder().encode(data.wire);let index=0,cancelled=false,context=null;
+ window.fetch=async(url,options)=>{
+ if(!String(url).endsWith('/api/chat_stream'))return nativeFetch(url,options);
+ context=options.body.get('search_context');
+ const heartbeats=[...Array(6).fill(': ping\n\n'),data.wire];
+ return new Response(new ReadableStream({start(controller){options.signal.addEventListener('abort',()=>controller.error(new DOMException('Stopped','AbortError')),{once:true});},async pull(controller){if(data.kind==='heartbeat'){if(indexsetTimeout(r,200));controller.enqueue(new TextEncoder().encode(heartbeats[index++]));}else controller.close();}else if(indexsetTimeout(()=>reject(Error('Consumer did not finish at DONE')),data.kind==='heartbeat'?6000:1500))]);
+ const pane=document.querySelector('.compare-pane');
+ return {done:pane.classList.contains('is-done'),failed:pane.classList.contains('is-failed'),text:pane.innerText,images:pane.querySelectorAll('img').length,cancelled,spinnerDestroyed,spinnerOwned:!!message._spinner};
+ },JSON.parse(process.argv[1]));
+ const expected=JSON.parse(process.argv[1]);
+ assert.equal(result.done,expected.success);assert.equal(result.failed,!expected.success);assert(result.text.includes(expected.text),JSON.stringify(result));assert.equal(result.images,0);
+ assert(result.spinnerDestroyed);assert(!result.spinnerOwned);
+ if(expected.blind)assert(!/Provider Z|private-model/.test(result.text),JSON.stringify(result));
+ if(expected.kind==='done-open')assert(result.cancelled);
+ console.log(JSON.stringify(result));
+ }finally{await browser.close();}
+})().catch(e=>{console.error(e);process.exitCode=1;});
+"""
+ data = dict(kind=kind, wire=wire, blind=blind, success=success, text=text)
+ result = subprocess.run(["node", "-e", script, json.dumps(data)], cwd=ROOT,
+ capture_output=True, text=True, timeout=30)
+ if result.returncode == 77:
+ pytest.skip("playwright not installed")
+ assert result.returncode == 0, result.stdout + result.stderr