[Bug] WebFetch does not return response body on HTTP error codes

Bug Description
WebFetch does not return the response body to the agent on HTTP error codes. This is hurting agent cages which limit the requests a Claude session is allowed to make (e.g. using a proxy) and causes issues in filtered environments (e.g. organization proxies with filter rules). The agent tries to circumvent the block instead of understanding that the website trying to be accessed is intentionally filtered. With presenting the response body to the agent, WebFetch would allow the agent to understand the reason why a website is not available, when the blocking instance explains that in the response (which is the case for agent cages and many organization proxies).

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.175
• Feedback ID: 0b19a9d3-79b0-41f7-a150-a539cdb54f75

Errors

[{"error":"Error: Tool Grep not found\n    at byK (/$bunfs/root/src/entrypoints/cli.js:4147:15832)\n    at e_ (/$bunfs/root/src/entrypoints/cli.js:594:21157)\n    at XK (/$bunfs/root/src/entrypoints/cli.js:594:39927)\n    at xo (/$bunfs/root/src/entrypoints/cli.js:594:50741)\n    at mA (/$bunfs/root/src/entrypoints/cli.js:594:87761)\n    at iK (/$bunfs/root/src/entrypoints/cli.js:594:86731)\n    at kK (/$bunfs/root/src/entrypoints/cli.js:594:86553)\n    at Qo (/$bunfs/root/src/entrypoints/cli.js:594:82894)\n    at sH (/$bunfs/root/src/entrypoints/cli.js:594:6446)\n    at LV8 (/$bunfs/root/src/entrypoints/cli.js:587:5415)","timestamp":"2026-06-12T17:10:23.736Z"},{"error":"Error: Tool Grep not found\n    at byK (/$bunfs/root/src/entrypoints/cli.js:4147:15832)\n    at e_ (/$bunfs/root/src/entrypoints/cli.js:594:21157)\n    at XK (/$bunfs/root/src/entrypoints/cli.js:594:39927)\n    at xo (/$bunfs/root/src/entrypoints/cli.js:594:50741)\n    at mA (/$bunfs/root/src/entrypoints/cli.js:594:87761)\n    at iK (/$bunfs/root/src/entrypoints/cli.js:594:86731)\n    at kK (/$bunfs/root/src/entrypoints/cli.js:594:86553)\n    at Qo (/$bunfs/root/src/entrypoints/cli.js:594:82894)\n    at sH (/$bunfs/root/src/entrypoints/cli.js:594:6446)\n    at LV8 (/$bunfs/root/src/entrypoints/cli.js:587:5415)","timestamp":"2026-06-12T17:10:24.201Z"},{"error":"Error: Tool Grep not found\n    at byK (/$bunfs/root/src/entrypoints/cli.js:4147:15832)\n    at e_ (/$bunfs/root/src/entrypoints/cli.js:594:21157)\n    at XK (/$bunfs/root/src/entrypoints/cli.js:594:39927)\n    at xo (/$bunfs/root/src/entrypoints/cli.js:594:50741)\n    at mA (/$bunfs/root/src/entrypoints/cli.js:594:87761)\n    at iK (/$bunfs/root/src/entrypoints/cli.js:594:86731)\n    at kK (/$bunfs/root/src/entrypoints/cli.js:594:86553)\n    at Qo (/$bunfs/root/src/entrypoints/cli.js:594:82894)\n    at sH (/$bunfs/root/src/entrypoints/cli.js:594:6446)\n    at LV8 (/$bunfs/root/src/entrypoints/cli.js:587:5415)","timestamp":"2026-06-12T17:10:25.272Z"},{"error":"Error: Tool Grep not found\n    at byK (/$bunfs/root/src/entrypoints/cli.js:4147:15832)\n    at e_ (/$bunfs/root/src/entrypoints/cli.js:594:21157)\n    at XK (/$bunfs/root/src/entrypoints/cli.js:594:39927)\n    at xo (/$bunfs/root/src/entrypoints/cli.js:594:50741)\n    at mA (/$bunfs/root/src/entrypoints/cli.js:594:87761)\n    at iK (/$bunfs/root/src/entrypoints/cli.js:594:86731)\n    at kK (/$bunfs/root/src/entrypoints/cli.js:594:86553)\n    at Qo (/$bunfs/root/src/entrypoints/cli.js:594:82894)\n    at sH (/$bunfs/root/src/entrypoints/cli.js:594:6446)\n    at LV8 (/$bunfs/root/src/entrypoints/cli.js:587:5415)","timestamp":"2026-06-12T17:10:25.425Z"},{"error":"Error: Tool Grep not found\n    at byK (/$bunfs/root/src/entrypoints/cli.js:4147:15832)\n    at e_ (/$bunfs/root/src/entrypoints/cli.js:594:21157)\n    at XK (/$bunfs/root/src/entrypoints/cli.js:594:39927)\n    at xo (/$bunfs/root/src/entrypoints/cli.js:594:50741)\n    at mA (/$bunfs/root/src/entrypoints/cli.js:594:87761)\n    at iK (/$bunfs/root/src/entrypoints/cli.js:594:86731)\n    at kK (/$bunfs/root/src/entrypoints/cli.js:594:86553)\n    at Qo (/$bunfs/root/src/entrypoints/cli.js:594:82894)\n    at sH (/$bunfs/root/src/entrypoints/cli.js:594:6446)\n    at LV8 (/$bunfs/root/src/entrypoints/cli.js:587:5415)","timestamp":"2026-06-12T17:10:41.798Z"},{"error":"Error: Tool Grep not found\n    at byK (/$bunfs/root/src/entrypoints/cli.js:4147:15832)\n    at e_ (/$bunfs/root/src/entrypoints/cli.js:594:21157)\n    at XK (/$bunfs/root/src/entrypoints/cli.js:594:39927)\n    at xo (/$bunfs/root/src/entrypoints/cli.js:594:50741)\n    at mA (/$bunfs/root/src/entrypoints/cli.js:594:87761)\n    at iK (/$bunfs/root/src/entrypoints/cli.js:594:86731)\n    at kK (/$bunfs/root/src/entrypoints/cli.js:594:86553)\n    at Qo (/$bunfs/root/src/entrypoints/cli.js:594:82894)\n…

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