patch-claude-proxy

name	patch-claude-proxy
description	Patch the claude-code binary to route Vertex API traffic through http://localhost:13128 proxy, scoped only to ANTHROPIC_VERTEX_BASE_URL traffic. Use when user says "patch claude", "apply proxy patch", "claude upgrade", or "patch claude.exe". Also handles copying the patched binary as a versioned backup.

patch-claude-proxy

Patches the claude.exe SEA (Single Executable Application) binary in-place so that Vertex API traffic is routed through http://localhost:13128 only, without affecting any other HTTPS traffic in the process.

What the patch does

Replaces the proxy env-reader function (historically named vp, rS, or PR depending on version) with a scoped version:

// BEFORE
function PR(H=process.env){return H.https_proxy||H.HTTPS_PROXY||H.http_proxy||H.HTTP_PROXY}

// AFTER
function PR(){return process.env.ANTHROPIC_VERTEX_BASE_URL&&"http://localhost:13128"}

This function is the single chokepoint all proxy logic flows through (getProxyFetchOptions/s3, configureGlobalAgents, etc.). When ANTHROPIC_VERTEX_BASE_URL is not set, it returns undefined → direct connection.

Patch script location

/home/kent/Project/Issues/claude_https_proxy/patch-claude.py

Versioned backup binaries are stored in the same folder as claude-<version>-patched.exe.

Workflow

Step 1 — Determine current binary state

python3 /home/kent/Project/Issues/claude_https_proxy/patch-claude.py --verify

Output will be:

• status : patched → nothing to do
• status : original → ready to patch
• status : unknown → function was renamed in this version (see Step 3)

Step 2 — Apply the patch (if status is "original")

python3 /home/kent/Project/Issues/claude_https_proxy/patch-claude.py

Step 3 — Handle "unknown" status (function renamed after upgrade)

Find the current function name:

python3 -c "
import re
data = open('/home/kent/.nvm/versions/node/v20.19.3/lib/node_modules/@anthropic-ai/claude-code/bin/claude.exe','rb').read()
for m in re.finditer(rb'function \w+\(H=process\.env\)\{return H\.https_proxy\|\|H\.HTTPS_PROXY', data):
    print(repr(data[m.start():m.start()+150]))
"

Then update the OLD/NEW constants in patch-claude.py with the new function name:

# Calculate correct padding
OLD_len = len(b'function XX(H=process.env){return H.https_proxy||H.HTTPS_PROXY||H.http_proxy||H.HTTP_PROXY}')
NEW_body = b'function XX(){return process.env.ANTHROPIC_VERTEX_BASE_URL&&"http://localhost:13128"}'
padding = OLD_len - len(NEW_body)
print(f'need {padding} spaces of padding')

Update patch-claude.py replacing XX with the actual function name found, and set padding accordingly.

Step 4 — Copy patched binary as versioned backup

# Get version
VERSION=$(claude --version 2>/dev/null | awk '{print $1}')
cp /home/kent/.nvm/versions/node/v20.19.3/lib/node_modules/@anthropic-ai/claude-code/bin/claude.exe \
   /home/kent/Project/Issues/claude_https_proxy/claude-${VERSION}-patched.exe

After every npm update -g @anthropic-ai/claude-code

1. Run --verify → if "original", patch directly
2. If "unknown", find the new function name, update patch-claude.py, then patch
3. Copy versioned backup

Reverting

python3 /home/kent/Project/Issues/claude_https_proxy/patch-claude.py --revert

Key technical facts

• Binary: ~/.nvm/versions/node/v20.19.3/lib/node_modules/@anthropic-ai/claude-code/bin/claude.exe
• The JS is embedded as a plain-text blob inside the ELF — patch must be exact same byte length
• The proxy function name has changed across versions: vp → rS → PR (track with --verify)
• Native fetch() (used by Vertex SDK) ignores proxy/agent fields; only HTTPS_PROXY env var works via undici's EnvHttpProxyAgent
• Patching vp/rS/PR scopes it without setting any global env vars