add user-agent header to all http clients

[dapplion]

Issue Addressed

Closes #7963

Proposed Changes

Adds a User-Agent HTTP header to all outgoing HTTP requests. The header format is Lighthouse/v<version>-<commit> (e.g., Lighthouse/v8.0.0-67da032).

This helps distributed validator middleware operators identify what their peers are running.

Clients updated:

• BeaconNodeHttpClient (BN API client)
• ValidatorClientHttpClient (VC API client)
• HttpJsonRpc (execution layer engine API)
• BuilderHttpClient (already had user-agent)
• MonitoringHttpClient (metrics endpoint)
• Web3Signer client
• ProductionValidatorClient beacon node builder

Key design decision: the user_agent is passed as a &str constructor parameter rather than having library crates depend on lighthouse_version directly. This avoids cargo cache invalidation cascading through the dependency tree on every git change, since lighthouse_version uses git_version!().

Only top-level/binary crates reference lighthouse_version::VERSION. Library crates (eth2, initialized_validators, beacon_node_fallback) receive it as a parameter.

Related PRs

• Add User-Agent header to validator client HTTP requests #8481 — initial implementation for BeaconNodeHttpClient only
• add user agent in http requests #7990 — broader implementation with tests (stalled)

Test plan

• cargo check passes
• cargo fmt --all clean
• make lint-fix passes

[chong-he]

If I understand correctly, after this change, when the VC calls the HTTP requests to the BN, it should include its version.

I tested a running BN and VC and run: sudo tcpdump -A -i lo port 5052, I see the request sent by VC does not contain the user-agent, only has accept and host:

22:04:47.429301 IP localhost.54174 > localhost.5052: Flags [.], ack 32, win 510, options [nop,nop,TS val 3648558767 ecr 3648558767], length 0
E..4..@.@.D>..............A.!..c.....(.....
.x...x..
22:04:51.803986 IP localhost.54184 > localhost.5052: Flags [P.], seq 3425:3497, ack 105371, win 881, options [nop,nop,TS val 3648563141 ecr 3648558342], length 72
E..|..@.@.^..............v4..R.....q.p.....
.x...x..GET /eth/v1/node/version HTTP/1.1
accept: */*
host: localhost:5052


22:04:51.804203 IP localhost.5052 > localhost.54184: Flags [P.], seq 105371:105588, ack 3497, win 512, options [nop,nop,TS val 3648563142 ecr 3648563141], length 217
E.... @.@................R...v4H...........
.x...x..HTTP/1.1 200 OK
content-type: application/json
server: Lighthouse/v8.1.0-39edcf2/x86_64-linux
content-length: 61
date: Fri, 13 Feb 2026 14:04:51 GMT

{"data":{"version":"Lighthouse/v8.1.0-39edcf2/x86_64-linux"}}

[macladson]

I believe the reason it isn't working is because we never actually set the user agent when constructing the BeaconNodeHttpClient instance that is used by the VC on startup. We need to add a

.user_agent(&config.user_agent)

here:

lighthouse/validator_client/src/lib.rs

Lines 287 to 291 in edba56b

	let beacon_node_http_client = beacon_node_http_client_builder
	// Set default timeout to be the full slot duration.
	.timeout(slot_duration)
	.build()
	.map_err(|e| format!("Unable to build HTTP client: {:?}", e))?;

Also, I noticed that while the PR mentions updating HttpJsonRpc and MonitoringHttpClient (and web3signer) but I don't see any diffs for those. Are those still required?

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 3 committers have signed the CLA.

✅ chong-he
✅ dapplion
❌ Clawdia

---

Clawdia seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
1 out of 2 committers have signed the CLA.

✅ dapplion
❌ Clawdia

---

Clawdia seems not to be a GitHub user. You need a GitHub account to be able to sign the CLA. If you have already a GitHub account, please add the email address used for this commit to your account.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[KaloyanTanev]

Hey @dapplion, is there an update on this one?

[mergify]

Hi @dapplion, this pull request has been closed automatically due to 30 days of inactivity. If you’d like to continue working on it, feel free to reopen at any time.

[chong-he]

Just did some minor fix. I believe @dapplion has addressed the comments. I tested with BN + VC and ca see that the user-agent requests now has Lighthouse version:

accept: */*
user-agent: Lighthouse/v8.1.3-c6bfbc9
host: localhost:5052

This PR is ready for another review.

[michaelsproul]

For testing we might need to take off serde(skip).

[michaelsproul]

For testing:

• One BN test
• One VC test

Check that all "downstream" configs with user_agent are initialised when the top-level config is initialised.

[chong-he]

Added some tests in add test

[mergify]

Some required checks have failed. Could you please take a look @dapplion? 🙏

[KaloyanTanev]

Hey guys, is there any chance we can get this merged and tagged before gloas? We'd love to keep get data of node operators which are on pre-gloas versions of their VCs and raise warnings to update.

[macladson]

Hi @KaloyanTanev, most of the team is pretty flat out with Gloas at the moment but I'll try to review this by the end of the week and try to get this over the line