fix(fetch): apply proxy.bypass to redirect targets

[Yury Semikhatsky (yury-s)]

Summary

• Resolve the proxy agent per redirect hop instead of reusing the one chosen for the original URL, so proxy.bypass applies to redirect targets.
• Resolve client certificates in the same place, so all URL-scoped request options are derived per hop.

Fixes #42815

[github-actions]

Test results for "tests 1"

9 flaky

⚠️ [chromium-library] › library/beforeunload.spec.ts:130 › should support dismissing the dialog multiple times `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/video.spec.ts:690 › screencast › should capture full viewport `@chromium-ubuntu-22.04-node24`
⚠️ [chromium-library] › library/chromium/chromium.spec.ts:373 › should produce network events, routing, and annotations for Service Worker `@chromium-ubuntu-22.04-node20`
⚠️ [chromium-library] › library/video.spec.ts:725 › screencast › should capture full viewport on hidpi `@chromium-ubuntu-22.04-node22`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:257 › third party 'Partitioned;' cookies `@firefox-ubuntu-22.04-node20`
⚠️ [firefox-library] › library/browsercontext-cookies-third-party.spec.ts:470 › top level 'Partitioned;' cookie and same origin iframe `@firefox-ubuntu-22.04-node20`
⚠️ [playwright-test] › ui-mode-test-watch.spec.ts:96 › should batch watch updates `@windows-latest-node22`
⚠️ [playwright-test] › ui-mode-trace.spec.ts:778 › should partition action tree state by test `@windows-latest-node22`
⚠️ [playwright-test] › ui-mode-trace.spec.ts:827 › should update state on subsequent run `@windows-latest-node22`

52084 passed, 1252 skipped

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Merge workflow run.

[github-actions]

Test results for "MCP"

2 failed
❌ [chrome] › mcp/cli-webmcp.spec.ts:188 › webmcp-call disambiguates same-name tools in identical same-origin frames @mcp-ubuntu-latest-chrome
❌ [firefox] › mcp/cli-session.spec.ts:54 › idle timeout shuts the session down @mcp-windows-latest-firefox

8690 passed, 1474 skipped

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Merge workflow run.

[github-actions]

Hi, I am the Playwright bot and I took a first look at the red CI here.

🟢 Both failures are known flakes — this PR is clear

cli-webmcp.spec.ts:188 and cli-session.spec.ts:54 both flip verdict across unrelated SHAs in the CI results database, and neither goes anywhere near fetch.ts proxy resolution. The tests 1 report has no failures at all, only 9 flaky.

Details

This PR touches packages/playwright-core/src/server/fetch.ts (per-redirect-hop proxy agent and client-cert resolution) and tests/library/fetch-proxy.spec.ts. That code path is only reachable from APIRequestContext; the MCP CLI tests that failed do not exercise it. The PR's own new proxy tests passed.

Pre-existing flake / infra

• [chrome] › mcp/cli-webmcp.spec.ts:188 › webmcp-call disambiguates same-name tools in identical same-origin frames — fails on and off across several bots on SHAs unrelated to this PR: 4/55 runs on mcp-macos-latest-chrome, 3/57 on mcp-ubuntu-latest-chrome, 3/54 on mcp-macos-latest-chromium, green the rest of the time. Last 30 runs on mcp-ubuntu-latest-chrome:

  🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟩🟥

• [firefox] › mcp/cli-session.spec.ts:54 › idle timeout shuts the session down — a long-standing Windows/Firefox flake: failed 50 of 156 runs (32%) on mcp-windows-latest-firefox, while the same test is 0-failure on every other bot (chromium, webkit, chrome, msedge, and Firefox on Ubuntu/macOS). A timing-sensitive idle-timeout test failing only on the slowest bot. Last 30 runs:

  🟩🟩🟥🟩🟩🟩🟥🟩🟥🟩🟥🟩🟩🟩🟩🟩🟥🟥🟥🟩🟥🟥🟩🟩🟩🟩🟥🟩🟩🟥

_{Triaged by the Playwright bot - agent run}