web: second Firefox tab never connects to /api/event - Cache-Control: no-cache lets Firefox's HTTP cache block concurrent SSE requests #55369

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1. opencode-agent commented on Oct 14, 2026

   

   opencode-agentBot

   on Oct 14, 2026 – with OpenCode Agent

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   Thanks for the detailed report! I could reproduce this.

   On 2.0.23 I ran opencode serve and opened the web UI in two tabs of the same Firefox profile (Playwright's Firefox):

   • The first tab's /api/event got 200 with cache-control: no-cache, no-transform.
   • In 15 seconds the second tab sent 5 /api/event requests and got no response to any of them.
   • A plain fetch("/api/event") from the second tab hung. The same fetch with cache: "no-store" got 200 immediately.
   • After I closed the first tab, the second tab connected right away.

   It still happens on the latest dev (34d8ded). The server still sends Cache-Control: no-cache, no-transform for the event stream, and the client doesn't set cache: "no-store". There, two Firefox tabs fetching /api/event showed the same result: the second hangs until the first closes, unless it uses no-store.

   The script below reproduces it with the web UI. Until there's a fix, your workaround of forcing cache: "no-store" on /api/event is the way around it. This may also contribute to the symptoms in #53498, #51857 and #48771, although each of those has its own cause.

   Reproduction script (firefox-two-tabs.mjs)

   // Reproduces #55369: in Firefox, a second tab on the same opencode server never
   // gets a response for GET /api/event while the first tab's stream is open.
   // Usage: OC_URL=http://127.0.0.1:4096 OC_PASSWORD=<server password> node firefox-two-tabs.mjs
   // Requires: npm i playwright && npx playwright install --with-deps firefox
   import { firefox, chromium } from "playwright"
   import { createHmac } from "node:crypto"
   
   const url = process.env.OC_URL ?? "http://127.0.0.1:4096"
   const password = process.env.OC_PASSWORD
   const engine = process.env.BROWSER === "chromium" ? chromium : firefox
   
   const browser = await engine.launch()
   const context = await browser.newContext()
   // Authenticate like a paired browser: a signed session cookie (see packages/server/src/auth.ts).
   if (password) {
     const expires = String(Math.floor(Date.now() / 1000) + 3600)
     const key = createHmac("sha256", password).update("opencode-session-v1").digest()
     const token = `${expires}.${createHmac("sha256", key).update(expires).digest("base64url")}`
     const u = new URL(url)
     await context.addCookies([{ name: `opencode_session_${u.port}`, value: token, url }])
   }
   
   function track(page, name) {
     const stats = { name, requests: 0, responses: 0, statuses: [] }
     page.on("request", (r) => r.url().includes("/api/event") && stats.requests++)
     page.on("response", (r) => {
       if (!r.url().includes("/api/event")) return
       stats.responses++
       stats.statuses.push(r.status() + " " + (r.headers()["cache-control"] ?? ""))
     })
     return stats
   }
   
   const tab1 = await context.newPage()
   const s1 = track(tab1, "tab1")
   await tab1.goto(url)
   await tab1.waitForTimeout(8000)
   
   const tab2 = await context.newPage()
   const s2 = track(tab2, "tab2")
   await tab2.goto(url)
   await tab2.waitForTimeout(15000)
   console.log("with tab1 open:", JSON.stringify(s1), JSON.stringify(s2))
   
   // Direct probe from tab2: does a plain fetch of /api/event get response headers?
   const probe = async (cache) =>
     tab2.evaluate(async (cache) => {
       const ac = new AbortController()
       const t = setTimeout(() => ac.abort(), 5000)
       try {
         const r = await fetch("/api/event", { signal: ac.signal, cache })
         ac.abort()
         return "status " + r.status
       } catch (e) {
         return "no response within 5s (" + e.name + ")"
       } finally {
         clearTimeout(t)
       }
     }, cache)
   console.log("tab2 fetch(/api/event) default cache:", await probe("default"))
   console.log("tab2 fetch(/api/event) cache:no-store:", await probe("no-store"))
   
   await tab1.close()
   const before = s2.responses
   await tab2.waitForTimeout(8000)
   console.log("after closing tab1: tab2 new /api/event responses =", s2.responses - before)
   
   await browser.close()

   Run it: bun firefox-two-tabs.mjs
2. opencode-agent

   added

   reproduced

   on Oct 14, 2026
3. zonemeen commented on Oct 14, 2026

   

   zonemeen

   on Oct 14, 2026

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   Thanks for the detailed report and reproduction steps! I’d like to work on this. I’ll update the SSE cache handling to use no-store and verify that both Firefox tabs can connect before opening a PR.