fix(api): enforce API_TIMEOUT_MS for OpenAI-compatible headers (#1940)

* fix(api): enforce API_TIMEOUT_MS for OpenAI-compatible headers

* test(api): cover Copilot responses fallback deadlines

* fix(api): redact secrets in timeout URL paths

* fix(api): harden Copilot response deadlines

* fix(api): prevent header-timeout request replay

* fix(api): harden timeout cleanup and redaction

* fix(api): redact encoded transport credentials

* fix(api): harden deadline retries and URL redaction

* fix(api): preserve aborted fetch reasons

* fix(api): preserve caller abort reasons

* test(api): clear caller abort timer

* docs(api): clarify API_TIMEOUT_MS transport scope

* docs(api): explain timeout env loading

* fix(api): reset deadline for proxy retries

* fix(api): type deadline fetch adapter

* fix(api): honor abort cleanup and request signals

* fix(api): do not block proxy retries on body cancellation

---------

Co-authored-by: jatmn <the@jat.mn>

.env.example

@@ -439,8 +439,15 @@ ANTHROPIC_API_KEY=sk-ant-your-key-here
 # Turn on whichever audience you're debugging; both can run together.
 # OPENCLAUDE_LOG_TOKEN_USAGE=verbose
 
-# Custom timeout for API requests in milliseconds (default: varies)
-# API_TIMEOUT_MS=60000
+# Time-to-response-headers deadline for OpenAI-compatible API requests
+# in milliseconds (default: 600000, or 10 minutes). Use a safe positive
+# integer; invalid values use the default and values above 2147483647 are capped.
+# This runtime setting must be exported from your shell or launcher; the
+# provider env-file loader intentionally ignores runtime/debug knobs.
+# This covers generic OpenAI-compatible requests, direct GitHub Copilot
+# Responses, and Copilot chat-to-Responses fallback requests. First-party
+# Codex OAuth Responses and the Anthropic SDK retain their existing handling.
+# API_TIMEOUT_MS=600000
 
 # Enable debug logging
 # CLAUDE_DEBUG=1