fix(acp): pass HOME and Anthropic env vars to child process (#3135)

[OneStepAt4time]

Problem

Issue #3135: ACP child process (claude-agent-acp) receives only 3 env vars: PATH, TMPDIR, NO_COLOR. Missing HOME means it can't find ~/.claude/credentials. Missing ANTHROPIC_*/CLAUDE_* means it can't authenticate with the Anthropic API.

The child process starts, the JSON-RPC handshake completes, but session/new times out because CC can't connect to Anthropic. Sessions appear idle but claudeRunning: false and claudeSessionId: null.

Root Cause

buildAcpSpawnEnv() in src/acp-spawn-env.ts constructs a minimal environment with only PATH and temp dirs. Everything else from process.env is filtered out.

Fix

Pass through essential env vars to the ACP child process:

• HOME, USER, SHELL, LANG, LC_ALL, LC_CTYPE (system essentials)
• All ANTHROPIC_* prefixed vars (API keys, endpoints)
• All CLAUDE_* prefixed vars (config dir, executable path)

Before

Child process env: { PATH, TMPDIR, NO_COLOR }  // 3 vars

After

Child process env: { PATH, HOME, USER, SHELL, LANG, ANTHROPIC_API_KEY, CLAUDE_CONFIG_DIR, ... }

Files

• src/acp-spawn-env.ts: expand copyPlatformExecutionEnv to include HOME and auth-related env vars

[aegis-gh-agent]

✅ Approved — all 9 merge gates passed.

Root cause fix for ACP sessions stuck at pending. Child process now receives HOME, USER, SHELL, LANG + all ANTHROPIC_/CLAUDE_ env vars for authentication. All CI green.

👁️ Argus