## Why
Synchronous auth header construction could silently return no credentials when managed authentication became unavailable. Callers need an error to avoid sending requests with missing or partial authentication.
## What changed
- Make `AuthProvider::add_auth_headers`, `to_auth_headers`, and auth header telemetry fallible, and propagate failures through request and WebSocket setup.
- Return a transient error when managed authentication is unavailable, and preserve network policy denials through auth error conversion.
- Retry transient MCP authentication errors while treating build errors and policy denials as terminal.
- Cancel local MCP event streams before resolving authentication so cleanup still works when credentials become unavailable.
## Testing
Add regression coverage for rejected partial authentication, async header resolution, terminal auth errors without sending requests, managed account changes, MCP retry classification, and local stream cancellation after authentication becomes unavailable.
GitOrigin-RevId: 39d981e232cba1e302de502a2fa6239101114ed1
## Why
Remote executors need to recover from confirmed authentication-service outages and spread reconnect attempts after a shared outage. Registration retries must remain limited to confirmed failures before a write, since replaying an ambiguous request can replace a newer registration.
## What changed
- Retry registry responses with HTTP 502 and `authentication_service_unavailable`, alongside the existing HTTP 503 `registration_conflict` retries.
- Accept structured registry errors in `detail`, keeping the canonical `error` authoritative when both are present.
- Randomize reconnect delays between half and all of the current exponential backoff, retaining the 30-second cap.
## Testing
Add coverage for reconnect jitter bounds, authentication-outage retry cancellation, error-envelope precedence, and preservation of Noise identity and initialized sessions across retries. Make the HTTP-header helper cleanup test wait for the helper PID before cancellation and verify process termination when the provider is dropped.
GitOrigin-RevId: 35fdb57732d17b0bbfeca8a4dc557a0988e29a31
## Why
Remote environment registration can return an explicit `503` `registration_conflict` after the registry finishes its own recovery attempts. Retrying ambiguous failures is unsafe because a timed-out request may still have replaced a newer registration.
## What changed
- Retry only explicit `registration_conflict` responses with jittered backoff, both during initial registration and after a rejected relay connection.
- Apply the existing connection timeout to the complete registration attempt, including response-body diagnostics.
- Keep retry waits and in-flight requests cancellable while preserving the Noise identity and initialized session across successful recovery.
## Testing
Added unit coverage for retry eligibility and timeout handling, plus relay tests for identity and session preservation and prompt shutdown during registration.
GitOrigin-RevId: 374e6fdac4755f377cbea9400c76a228b790945a
cooper-oai