How Codex handles this
Codex sits in your repository, so the question comes with a diff attached. You changed how a theme loads its scripts, you pushed it to the live site, and you want a number to put in the pull request. Ask Codex for the PageSpeed history of the site, and it calls get_score_history through the xspeedhub server: score, LCP, FCP, CLS, TBT, Speed Index and TTFB for mobile and desktop. Then it can start run_speed_test for a fresh reading, mobile or desktop, which takes up to about two minutes.
One thing is easy to miss. The Hub tests the address of the site you connected, which is the live site, not the branch on your machine and not a local dev server. PageSpeed Insights runs on Google's side and cannot reach an address that only exists on your computer. So the order is deploy first, test second, and the test result is a reading of what is live.
For something quicker, run_benchmark times the home page cached and uncached, with no Lighthouse score, and get_benchmark_history shows earlier runs on the same timeline as your settings changes. Ask Codex to format the result as a small before and after table you can paste straight into the pull request description. A test started through the Hub is saved to the Hub's own report history, which the dashboard shows on its Reports tab. get_score_history reads the plugin's stored runs, so the fresh run may not appear there. Each call tests one device only.
Set up Codex once
Already connected? Skip to the prompts. Alternatives and troubleshooting are on the Codex guide.
1Put your sites in xSpeed Hub
Sign in at app.xspeedcache.com with Google or email; the Hub is free and has no site cap. Then connect each WordPress site from its own dashboard: click Connect Hub in the xSpeed Cache top bar, then Connect via xSpeed Hub. Each site needs the free xSpeed Cache plugin.
2Add xSpeed Hub and sign in
Add the server with its URL, then log in. The login opens an xSpeed Hub page in your browser; approve access there. There is no token to paste, and Codex keeps the credentials it receives. Start Codex and type /mcp to see the server.
codex mcp add xspeedhub --url https://app.xspeedcache.com/xspeed/mcp codex mcp login xspeedhub
3Keep the Hub's tools on a prompt
Open ~/.codex/config.toml. Set the server to prompt for every tool, then let one read tool run without a question. The tool timeout defaults to 60 seconds, and a PageSpeed test can take up to about two minutes, so raise it.
[mcp_servers.xspeedhub] url = "https://app.xspeedcache.com/xspeed/mcp" default_tools_approval_mode = "prompt" tool_timeout_sec = 150 [mcp_servers.xspeedhub.tools.get_cache_status] approval_mode = "approve"
Full Codex setup, sign-in options and FAQ
Before you send a prompt that changes something
Reads change nothing on your sites, though contact_support emails xSpeed support. Writes run once your connection allows them, so your client's approval prompt and a read-only connection (the token's Read-only everywhere switch, or a Viewer sign-in) are the gates that matter. Codex has two layers for shell work: the sandbox mode limits what commands can touch, and the approval policy sets when Codex stops to ask. MCP tools have their own settings. Each server takes default_tools_approval_mode (auto, prompt, writes or approve) and each tool can override it with approval_mode. Codex also asks about MCP calls that advertise side effects or a destructive annotation, but xSpeed Hub's tool definitions do not declare either, so do not rely on that default for the Hub; set the server to prompt. approval_policy never, --yolo and an auto_review reviewer take the human out of the loop. xSpeed Hub has no confirmation step of its own, so an approved or auto-approved write runs as soon as your connection allows writes.
What do I ask?
Three prompts written for Codex. More for this job are below.
Use xSpeed Hub to read the PageSpeed history for shop and give me a before and after table for the PR description.
I deployed to the live blog site just now. With xSpeed Hub, run one mobile test and compare it with the last stored mobile run.
Ask xSpeed Hub for the benchmark history on shop and tell me whether response time changed after the settings change I made on Monday.
What happens, step by step
PageSpeed Insights is Google's Lighthouse audit, and its score and Core Web Vitals are the numbers most people mean by "my speed". Through xSpeed Hub an agent can read the scores a site has already stored, run a new PageSpeed test on mobile or desktop, and read or run a separate benchmark of cached against uncached response time. The three answer different questions, and the Hub tells the agent which to use for each.
01
Read before you test
get_score_history returns the stored PageSpeed Insights and GTmetrix runs for a site: the score per run, with LCP, FCP, CLS, TBT, Speed Index and TTFB, mobile and desktop. It starts nothing. The Hub tells the agent to use it whenever you ask what your score is, or whether it improved, because a new test spends a shared allowance.
02
Run a new test when you need one
run_speed_test runs a real PageSpeed Insights audit on the site from the Hub and returns the score, the Core Web Vitals and the top opportunities. strategy is mobile (the default) or desktop, and one call tests one of them. It can take up to about 2 minutes, so the agent should say it is running before it calls.
03
Test the other device
Mobile and desktop scores differ, often by a lot. For both, the agent makes two calls, one per strategy. A failure is reported with its reason: PageSpeed not configured, quota reached, a timeout, or a site the audit cannot reach.
04
Measure the cache on its own
run_benchmark times the home page with the cache bypassed and again served from cache, and returns the response times. It is a read tool, and it accepts site: "all" for every site. It does not return a Lighthouse score, so the agent must not use it to answer a PageSpeed question.
05
Compare over time
get_benchmark_history returns past benchmark runs, uncached against cached, together with the settings changes on the same timeline, which is how you answer "did that change help?". For PageSpeed scores over time, use get_score_history.
Reference
| Read stored scores | get_score_history (read): PageSpeed Insights and GTmetrix runs, starts nothing |
|---|---|
| Metrics per run | Score, LCP, FCP, CLS, TBT, Speed Index, TTFB, for mobile and desktop |
| Run a new test | run_speed_test (write, uses the shared allowance): one PageSpeed Insights run per call |
| strategy | mobile (default) or desktop |
| Duration | Up to about 2 minutes per run |
| Why a test is a write | It spends a shared PageSpeed allowance and stores a report; it changes nothing on the site |
| Read-only access | A connection token with Read-only everywhere on, or a Viewer member's sign-in: run_speed_test is refused; get_score_history, run_benchmark and get_benchmark_history still work. An OAuth sign-in gets the scopes the client asks for |
| Benchmark | run_benchmark (read): cached against uncached response time for the home page, no Lighthouse score |
| Benchmark history | get_benchmark_history (read): past runs plus settings changes on the same timeline |
| Scheduling | The Hub does not schedule PageSpeed tests itself; its daily pass only reads reports the plugin already stored |
| Where a new test is stored | In the Hub's own report history, the one the Hub dashboard shows |
Rules worth keeping
- Check the history first. Ask for stored scores before starting a test, and run a new one only when you want a fresh measurement or something changed.
- Never answer a PageSpeed or Lighthouse question with run_benchmark. It times your own cache and carries no score.
- run_speed_test changes nothing on your site, but the Hub classes it a write because it spends a shared allowance. A connection token with Read-only everywhere on, or a Viewer sign-in, refuses it. An OAuth sign-in gets the scopes the client asks for, so there your client's approval prompt is the gate.
- Lab scores move a few points between runs of the same page. The agent should compare like with like, same site, same strategy, and not report one run's difference as a trend.
- A new test does not run on a timer. If you want a regular test, the agent has to be started by something else, such as a scheduled job in your client, and a scheduled run that spends the allowance should be one you are comfortable leaving unattended.
Good to know with Codex
Codex asks by default about MCP calls that advertise side effects, and the Hub's tools advertise none, so that default does not cover run_speed_test. Set the server to prompt for every tool and let only the read tools you trust run without a question. Approval policy never, the yolo flag and an auto-approving reviewer remove the prompt, and then a request such as "keep retesting until the score improves" would run run_speed_test over and over. Each run spends the shared allowance and the Hub has no confirmation step to slow it. Also raise the tool timeout: it defaults to 60 seconds and a test can take up to about two minutes. Give Codex a fixed number of runs in the same prompt.
More prompts for this job
They work in any client connected to xSpeed Hub.
Using xSpeed Hub, what is the mobile PageSpeed score for shop? Check the stored history before you run anything.
Use xSpeed Hub to run a new mobile PageSpeed test on blog and tell me the score, LCP and the top opportunities.
With xSpeed Hub, test shop on desktop and mobile and tell me which one is worse.
Using xSpeed Hub, has the PageSpeed score on docs improved over the last few runs?
Use xSpeed Hub to benchmark the cache on every site and tell me which one saves the least time.
Did turning on minification on shop help? Use xSpeed Hub to compare the benchmark history around that change.
My PageSpeed test failed on staging. Use xSpeed Hub to tell me why.
Frequently asked questions
Keep going
Track PageSpeed scores with other agents
More with Codex
Documentation
- How to run a speed test
- PageSpeed Insights integration
- Running speed tests in xSpeed Hub
- How to run a PageSpeed audit
- How to write prompts for xSpeed Hub
- Codex + xSpeed
- Every AI agent that works with xSpeed
From the blog
- Reading a PageSpeed Report in 2026: 30% of the Score Is a Metric Google Does Not Rank You On
- 45% of the WordPress Sites Our Scan Calls Clean Are Failing Google in 2026: Lab Scores Against Field Data
- The Same Page Scored 61 and 73 Twelve Minutes Apart: How to Benchmark WordPress Caching Plugins in 2026