[tyffical]

Motivation

• [APPS-2953] Fix: check Origin, Host and Content-Type on the apps dev-server routes #588 logs each refusal at debug, below the default logLevel of warn, so a developer behind a tunnel or LAN hostname sees a 403 and nothing in the terminal.
• Jira: APPS-2953

Changes

7 changes across dev-server.ts, dev-server-request-guard.ts, README.md and their tests

What changed	File
Warns the first time it logs a refusal's message, then logs repeats at debug.	dev-server.ts
Caps warnings at MAX_WARNED_REJECTIONS (32) per dev server, with one notice.	dev-server.ts
Escapes a refused hostname's non-ASCII characters, so a Host can't send control bytes to the terminal.	dev-server-request-guard.ts
Moves the host-not-allowed message's server.allowedHosts advice into ALLOWED_HOSTS_HINT.	dev-server-request-guard.ts
Tests warn-once, the cap, per-instance state and credential-free logs.	dev-server.test.ts
Tests the hostname escaping and that a refused-host message ends with ALLOWED_HOSTS_HINT.	dev-server-request-guard.test.ts
Documents the warn-once logging.	README.md

QA Instructions

• All checks below pass, verified at 6d804f4a. Setup: the build-plugins: Testing and QA Guide.

yarn install && yarn build:all
# Expected: exit 0

yarn typecheck:all && yarn lint && yarn cli integrity
# Expected: all exit 0, integrity leaves no changes to commit

yarn test:unit packages/plugins/apps/src/vite/dev-server-request-guard.test.ts packages/plugins/apps/src/vite/dev-server.test.ts
# Expected: both files pass

yarn test:unit
# Expected on macOS: only manifest-tags.integration and parameters.integration fail, because /var is a symlink to /private/var

TMPDIR=/private/tmp yarn test:unit packages/plugins/apps/src/vite/manifest-tags.integration.test.ts packages/plugins/apps/src/vite/parameters.integration.test.ts
# Expected: both files pass

• A real vite dev run (Vite 6.4.3) of the request guard, with outbound sockets blocked and no Datadog credentials:

Check	Result	Evidence
Refused host, 3 times and once on another port	HTTP 403 each with only the server.allowedHosts hint; one warn, the 3 repeats at debug only	qa-guard-logging.sh
Host with C1 control bytes	HTTP 403; the hostname prints each C1 byte as a JSON \u escape, with no raw non-ASCII byte in the terminal	qa-guard-logging.sh
Cross-origin call, twice via localhost and once via 127.0.0.1	HTTP 403 each; one warn, the 2 repeats at debug only	qa-guard-logging.sh
Wrong Content-Type	HTTP 415	qa-guard-logging.sh
Same-origin /__dd/debugBundle call	HTTP 200 with the bundle	qa-guard-logging.sh
34 more refused hosts	29 warns, the last (cap-28) with the cap notice; the other 5 at debug only	qa-guard-logging.sh, both log levels

Real vite dev run: script, app files and output

• Put the files below in one directory, then run:

W=<build-plugins checkout with this branch built> ./qa-guard-logging.sh
W=<build-plugins checkout with this branch built> QA_LOG_LEVEL=debug ./qa-guard-logging.sh

• qa-guard-logging.sh:

#!/bin/bash
# Run: W=<build-plugins checkout with this branch built> [VITE_BIN=<vite.js>] [QA_LOG_LEVEL=debug] ./qa-guard-logging.sh
set -u
cd "$(dirname "$0")"; QA_DIR=$PWD
PORT=5297
BASE="http://127.0.0.1:${PORT}"
VITE_BIN=${VITE_BIN:-$W/node_modules/vite/bin/vite.js}
LOG="vite-dev-${QA_LOG_LEVEL:-warn}.log"
(cd app && exec env -u DD_API_KEY -u DD_APP_KEY -u DATADOG_API_KEY -u DATADOG_APP_KEY -u DD_OAUTH_ACCESS_TOKEN -u DATADOG_OAUTH_ACCESS_TOKEN \
    NODE_OPTIONS="-r $QA_DIR/loopback-only.cjs" W="$W" node "$VITE_BIN" > "../$LOG" 2>&1) &
PID=$!
echo "== vite pid $PID, $(node "$VITE_BIN" --version 2>/dev/null)"
for _ in $(seq 1 90); do grep -q 'Local:' "$LOG" && break; sleep 1; done
FN=$(node -e "const c=require('crypto');console.log(c.createHash('sha256').update('backend/greet').digest('hex')+'.greet')")
# Vite registers backend functions when it transforms the importing module.
curl -s -o /dev/null "${BASE}/main.js" -H "Host: localhost:${PORT}"
curl -s -o /dev/null "${BASE}/backend/greet.backend.ts" -H "Host: localhost:${PORT}"
post() { # $1 label, $2 route, $3 Host, $4 Origin, $5 Content-Type
    local out
    out=$(curl -s -w '\n%{http_code}' -X POST "${BASE}$2" -H "Host: $3" -H "Origin: $4" \
        -H "Content-Type: $5" --data "{\"functionName\":\"${FN}\",\"args\":[\"x\"]}")
    printf '%-26s %s  %s\n' "$1" "${out##*$'\n'}" "$(printf '%s' "${out%$'\n'*}" | tr '\n' ' ' | cut -c1-230)"
}
OWN="localhost:${PORT}"
echo "== Responses"
for i in 1 2 3; do post "refused host #$i" /__dd/executeAction "evil.example" "http://evil.example" application/json; done
post "refused host, other port" /__dd/executeAction "evil.example:8080" "http://evil.example:8080" application/json
post "C1 bytes in Host" /__dd/executeAction "$(printf 'evil\x9b2J\x85.example')" "http://x.example" application/json | LC_ALL=C sed 's/[^[:print:]]/?/g'
for i in 1 2; do post "cross-origin #$i" /__dd/executeAction "$OWN" "http://attacker.example" application/json; done
post "cross-origin, 127.0.0.1" /__dd/executeAction "127.0.0.1:${PORT}" "http://attacker.example" application/json
post "wrong content-type" /__dd/executeAction "$OWN" "http://${OWN}" text/plain
post "same origin" /__dd/debugBundle "$OWN" "http://${OWN}" application/json
for i in $(seq 0 33); do
    post "cap host #$i" /__dd/executeAction "cap-${i}.example:${PORT}" "http://cap-${i}.example:${PORT}" application/json > /dev/null
done
sleep 1
kill "$PID"; wait 2>/dev/null
plain() { sed 's/\x1b\[[0-9;]*m//g' "$LOG"; }
echo "== Dev server terminal, excluding the cap hosts"
plain | grep -a -E 'Rejected|BLOCKED' | grep -v 'cap-[0-9]*\.example'
echo "== Raw non-ASCII bytes in rejection lines: $(plain | grep -a 'Rejected' | LC_ALL=C grep -c '[^ -~]')"
echo "== Rejection lines by level"
for level in warn debug; do
    printf '%-5s refused-host=%s  cross-origin=%s  cap-hosts=%s\n' "$level" \
        "$(plain | grep -c "\[$level|vite|apps\] Rejected.*\"evil.example\"")" \
        "$(plain | grep -c "\[$level|vite|apps\] Rejected.*own origin")" \
        "$(plain | grep -c "\[$level|vite|apps\] Rejected.*cap-[0-9]*\.example")"
done
echo "== Cap notice"
plain | grep -a "Further rejections" | sed -E 's/^(\[[^]]*\]).*This host \(("[^"]*")\).*(Further rejections.*)/\1 host \2 ... \3/'

• app/index.html:

<!doctype html>
<html><body><script type="module" src="/main.js"></script></body></html>

• app/main.js:

import { greet } from './backend/greet.backend.ts';
window.__greet = greet;

• app/backend/greet.backend.ts:

export async function greet(name: string) {
    return `hello ${name}`;
}

• app/vite.config.mjs:

// The built plugin is loaded from the checkout named by W.
const { datadogVitePlugin } = await import(`${process.env.W}/packages/published/vite-plugin/dist/src/index.mjs`);

export default {
    server: { host: '127.0.0.1', port: 5297, strictPort: true },
    plugins: [
        datadogVitePlugin({ logLevel: process.env.QA_LOG_LEVEL ?? 'warn', apps: { enable: true } }),
    ],
};

• loopback-only.cjs:

// Preloaded with `node -r`: fails and logs any outbound socket that isn't loopback.
const net = require('net');
const original = net.Socket.prototype.connect;
net.Socket.prototype.connect = function (...args) {
    const options = typeof args[0] === 'object' ? args[0] : { port: args[0], host: args[1] };
    const host = options.host ?? 'localhost';
    if (!options.path && !['127.0.0.1', '::1', 'localhost'].includes(host)) {
        console.log(`[qa] BLOCKED outbound connection to ${host}:${options.port}`);
        process.nextTick(() => this.destroy(new Error(`blocked outbound connection to ${host}`)));
        return this;
    }
    return original.apply(this, args);
};

• Output at the default log level; GitHub rewrites C1 escape text in PR bodies, so each escape below has a space after \u:

== Responses
refused host #1            403  {"success":false,"error":"Blocked request. This host (\"evil.example\") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js."}
refused host #2            403  {"success":false,"error":"Blocked request. This host (\"evil.example\") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js."}
refused host #3            403  {"success":false,"error":"Blocked request. This host (\"evil.example\") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js."}
refused host, other port   403  {"success":false,"error":"Blocked request. This host (\"evil.example\") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js."}
C1 bytes in Host           403  {"success":false,"error":"Blocked request. This host (\"evil\\u 009b2J\\u 0085.example\") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js."}
cross-origin #1            403  {"success":false,"error":"Blocked request. Only the dev server's own origin can call this endpoint."}
cross-origin #2            403  {"success":false,"error":"Blocked request. Only the dev server's own origin can call this endpoint."}
cross-origin, 127.0.0.1    403  {"success":false,"error":"Blocked request. Only the dev server's own origin can call this endpoint."}
wrong content-type         415  {"success":false,"error":"Requests must use Content-Type: application/json."}
same origin                200  var s=Object.defineProperty;var c=(t,o)=>s(t,"name",{value:o,configurable:!0});async function u(t){return`hello ${t}`}c(u,"greet");async function h(t){globalThis.$=t,typeof setExecuteActionImplementation=="function"&&setExecuteAct
== Dev server terminal, excluding the cap hosts
[qa] BLOCKED outbound connection to browser-http-intake.logs.datadoghq.com:443
[warn|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[warn|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil\u 009b2J\u 0085.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[warn|vite|apps] Rejected POST /__dd/executeAction: Blocked request. Only the dev server's own origin can call this endpoint.
[warn|vite|apps] Rejected POST /__dd/executeAction: Requests must use Content-Type: application/json.
== Raw non-ASCII bytes in rejection lines: 0
== Rejection lines by level
warn  refused-host=1  cross-origin=1  cap-hosts=29
debug refused-host=0  cross-origin=0  cap-hosts=0
== Cap notice
[warn|vite|apps] host "cap-28.example" ... Further rejections are only logged with the Datadog plugin's `logLevel: 'debug'`.

• With QA_LOG_LEVEL=debug, the responses and cap notice match the default run; the terminal and counts become:

== Dev server terminal, excluding the cap hosts
[qa] BLOCKED outbound connection to browser-http-intake.logs.datadoghq.com:443
[warn|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[debug|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[debug|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[debug|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[warn|vite|apps] Rejected POST /__dd/executeAction: Blocked request. This host ("evil\u 009b2J\u 0085.example") is not allowed. If you trust this host, add it to `server.allowedHosts` in vite.config.js.
[warn|vite|apps] Rejected POST /__dd/executeAction: Blocked request. Only the dev server's own origin can call this endpoint.
[debug|vite|apps] Rejected POST /__dd/executeAction: Blocked request. Only the dev server's own origin can call this endpoint.
[debug|vite|apps] Rejected POST /__dd/executeAction: Blocked request. Only the dev server's own origin can call this endpoint.
[warn|vite|apps] Rejected POST /__dd/executeAction: Requests must use Content-Type: application/json.
== Raw non-ASCII bytes in rejection lines: 0
== Rejection lines by level
warn  refused-host=1  cross-origin=1  cap-hosts=29
debug refused-host=3  cross-origin=2  cap-hosts=5

• Four refusal messages plus 28 cap hosts fill the 32-entry set, so cap-28 carries the notice.

Blast Radius

• Only the apps plugin's dev-server /__dd routes change.
• A refusal's first occurrence prints a warn line, at most 33 per dev server.
• No feature flag. Risk: Low.

Documentation

• Vite server.allowedHosts

🤖 Generated with Claude Code

[tyffical]

@codex review

[Copilot]

🟢 Approval recommended

The focused logging and message changes have targeted test coverage and no identified blocking issues.

0 open findings

What changed in this PR

Improves visibility of rejected requests to the apps plugin’s Vite dev-server routes without flooding default logs.

Changes:

• Warns once per Host/reason pair, with a per-server cap and debug logging afterward.
• Adds stable rejection reasons and upgrade guidance for older Vite versions.
• Tests deduplication, warning limits, instance isolation, and credential exclusion.

File	Description
packages/​plugins/​apps/​src/​vite/​dev-server.ts	Adds bounded, per-server refusal warnings.
packages/​plugins/​apps/​src/​vite/​dev-server.test.ts	Tests refusal logging and deduplication.
packages/​plugins/​apps/​src/​vite/​dev-server-request-guard.ts	Adds rejection reasons, shared Host extraction, and upgrade guidance.
packages/​plugins/​apps/​src/​vite/​dev-server-request-guard.test.ts	Verifies rejection reasons and guidance.

🧠 Review effort: Balanced

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Chef's kiss.

Reviewed commit: 2a840694e8

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Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-16T19:16:46.073744Z	2a84069	Manual request

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[datadog-datadog-prod-us1]

 

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.
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Live Debugger Runtime Benchmark

SDK-loaded dormant-probe runtime overhead, measured against an uninstrumented bundle in the same browser session.

Browser	Workload	Quality	Per-call overhead upper
chrome	Hot	clean	<= 2.56 ns
chrome	Tiny	clean	<= 0.02 ns
firefox	Hot	clean	<= 9.47 ns
firefox	Tiny	clean	<= 0.04 ns
safari	Hot	clean	<= 5.54 ns
safari	Tiny	clean	<= 0.97 ns

What do the Tiny and Hot workloads represent?

Browser Debugger SDK: 7.16.2 · built 2026-10-27 · S3 ETag 872de873

Full diagnostics

browser  workload  quality  per-call overhead upper  overhead upper          95% CI        A/A diag        block CI  acf(1)   baseline  instrumented                         samples
-------  --------  -------  -----------------------  --------------  --------------  --------------  --------------  ------  ---------  ------------  ------------------------------
chrome   Hot       clean                 <= 2.56 ns        <= 5.14%   2.52..2.56 ns  -0.02..0.01 ns   2.51..2.56 ns    0.21  52.683 ms     55.365 ms   102 (trim 20%, outliers 4.9%)
chrome   Tiny      clean                 <= 0.02 ns        <= 0.24%  -0.03..0.01 ns  -0.01..0.03 ns  -0.03..0.02 ns    0.03  56.540 ms     56.583 ms  102 (trim 20%, outliers 13.7%)
firefox  Hot       clean                 <= 9.47 ns       <= 37.59%   9.44..9.47 ns  -0.01..0.00 ns   9.44..9.47 ns   -0.01  40.200 ms     55.300 ms   102 (trim 20%, outliers 7.8%)
firefox  Tiny      clean                 <= 0.04 ns        <= 0.24%   0.02..0.04 ns  -0.00..0.01 ns   0.02..0.03 ns    0.06  53.760 ms     53.860 ms  102 (trim 20%, outliers 10.8%)
safari   Hot       clean                 <= 5.54 ns       <= 22.11%   5.52..5.54 ns  -0.01..0.01 ns   5.52..5.54 ns   -0.20  45.390 ms     55.400 ms   102 (trim 20%, outliers 4.9%)
safari   Tiny      clean                 <= 0.97 ns       <= 25.97%   0.96..0.97 ns  -0.00..0.00 ns   0.96..0.97 ns    0.23  41.120 ms     51.770 ms   102 (trim 20%, outliers 3.9%)

Raw samples are in the live-debugger-runtime-bench-results artifact.