claude-code-proxy-patterns

Claude Code Proxy Patterns

Multi-provider proxy that routes Claude Code model tiers to different backends. Haiku to a cheaper Anthropic-compatible provider (cost/speed), Sonnet/Opus to Anthropic (native OAuth passthrough). Includes Go binary proxy with launchd auto-restart and failover wrapper for resilience.

Scope: Local reverse proxy for Claude Code with OAuth subscription (Max plan). Routes based on model name in request body.

Reference implementations:

• Go proxy binary: /usr/local/bin/claude-proxy (port 8082)

---

Self-Evolving Skill: This skill improves through use. If instructions are wrong, parameters drifted, or a workaround was needed — fix this file immediately, don't defer. Only update for real, reproducible issues.

When to Use This Skill

• Building or debugging a Claude Code multi-provider proxy
• Setting up ANTHROPIC_BASE_URL with OAuth subscription mode
• Integrating Anthropic-compatible providers
• Diagnosing "OAuth not supported" or auth failures through a proxy
• Understanding how Claude Code stores and transmits OAuth tokens

Do NOT use for: Claude API key-only setups (no proxy needed), MCP server development, Claude Code hooks (operate at tool level, not API level), or corporate HTTPS proxy traversal.

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Architecture

Claude Code (OAuth/Max subscription)
    |
    |  ANTHROPIC_BASE_URL=http://127.0.0.1:8082 (Go proxy)
    |  (unset ANTHROPIC_API_KEY to avoid auth conflict)
    v
+----------------------------------+
| Go proxy (:8082)                 |
| launchd managed, auto-restart   |
+----------------------------------+
    |
    | model =
    | claude-haiku-
    | 4-5-20251001
    v
+-----------+
| 3rd-party |
| provider  |
+-----------+

Port Configuration:

• :8082 - Go proxy (entry point, launchd-managed, auto-restart)

The Go proxy uses cenkalti/backoff/v4 for built-in retry logic.

The proxy reads the model field from each /v1/messages request body. If it matches the configured Haiku model ID, the request goes to the configured provider. Everything else falls through to real Anthropic with OAuth passthrough.

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Working Patterns

WP-01: Keychain OAuth Token Reading

Read OAuth tokens from macOS Keychain where Claude Code stores them.

Service: "Claude Code-credentials" (note the space before the hyphen) Account: Current username via getpass.getuser()

import subprocess, json, getpass

result = subprocess.run(
    ["security", "find-generic-password",
     "-s", "Claude Code-credentials",
     "-a", getpass.getuser(), "-w"],
    capture_output=True, text=True, timeout=5, check=False,
)
if result.returncode == 0:
    data = json.loads(result.stdout.strip())
    oauth = data.get("claudeAiOauth")

See references/oauth-internals.md for the full deep dive.

WP-02: Token JSON Structure

The Keychain stores a JSON envelope with the claudeAiOauth key.

{
  "claudeAiOauth": {
    "accessToken": "eyJhbG...",
    "refreshToken": "rt_...",
    "expiresAt": 1740268800000,
    "subscriptionType": "claude_pro_2025"
  }
}

Note: expiresAt is in milliseconds (Unix epoch _ 1000). Compare with time.time() _ 1000 or divide by 1000 for seconds.

WP-03: OAuth Beta Header

The anthropic-beta: oauth-2025-04-20 header is required for OAuth token authentication. Without it, Anthropic rejects the Bearer token.

Critical: APPEND to existing beta headers, do not replace them.

# proxy.py:304-308
existing_beta = original_headers.get("anthropic-beta", "")
beta_parts = [b.strip() for b in existing_beta.split(",") if b.strip()] if existing_beta else []
if "oauth-2025-04-20" not in beta_parts:
    beta_parts.append("oauth-2025-04-20")
target_headers["anthropic-beta"] = ",".join(beta_parts)

WP-04: ANTHROPIC_API_KEY=proxy-managed

Setting ANTHROPIC_BASE_URL alone is insufficient in OAuth mode. Claude Code must also see ANTHROPIC_API_KEY set to switch from OAuth-only mode to API-key mode, which then honors ANTHROPIC_BASE_URL.

# In .zshenv (managed by proxy-toggle)
export ANTHROPIC_BASE_URL="http://127.0.0.1:8082"
export ANTHROPIC_API_KEY="proxy-managed"

The value "proxy-managed" is a dummy sentinel. The proxy intercepts it (line 324) and never forwards it to providers.

WP-05: OAuth Token Cache with TTL

Avoid repeated Keychain subprocess calls by caching the token for 5 minutes.

# proxy.py:117-118
_oauth_cache: dict = {"token": None, "expires_at": 0.0, "fetched_at": 0.0}
_OAUTH_CACHE_TTL = 300  # Re-read from Keychain every 5 minutes

Cache invalidation triggers:

• TTL expired (5 minutes since last fetch)
• Token's expiresAt has passed
• Proxy restart

WP-06: Auth Priority Chain

The proxy tries multiple auth sources in order for Anthropic-bound requests.

1. REAL_ANTHROPIC_API_KEY env var   -> x-api-key header (explicit config)
2. Keychain OAuth token             -> Authorization: Bearer + anthropic-beta
3. ~/.claude/.credentials.json      -> Authorization: Bearer (plaintext fallback)
4. Forward client Authorization     -> Pass through whatever Claude Code sent
5. No auth                          -> Will 401 (expected)

See proxy.py:293-314 for the implementation.

WP-07: count_tokens Endpoint Auth

The /v1/messages/count_tokens endpoint needs the same auth as /v1/messages. Claude Code calls this for preflight token counting. Missing auth here causes silent failures. Returns 501 for non-Anthropic providers that do not implement it.

WP-08: Anthropic-Compatible Provider URLs

Third-party providers that support the Anthropic /v1/messages API format.

Provider	Base URL	Notes
(your provider)	https://<provider-host>/anthropic	Check: model echo, extra content blocks, cache_control, count_tokens

See references/provider-compatibility.md for the full matrix.

WP-09: Concurrency Semaphore

Per-provider rate limiting prevents overwhelming third-party APIs. No semaphore for Anthropic (they handle their own rate limiting).

# proxy.py:207-209
MAX_CONCURRENT_REQUESTS = int(os.getenv("MAX_CONCURRENT_REQUESTS", "5"))
haiku_semaphore = asyncio.Semaphore(MAX_CONCURRENT_REQUESTS)
opus_semaphore = asyncio.Semaphore(MAX_CONCURRENT_REQUESTS)
sonnet_semaphore = asyncio.Semaphore(MAX_CONCURRENT_REQUESTS)

WP-10: proxy-toggle Enable/Disable

The proxy-toggle script manages .zshenv entries and a flag file atomically.

~/.claude/bin/proxy-toggle enable    # Adds env vars, creates flag file, checks health
~/.claude/bin/proxy-toggle disable   # Removes env vars, removes flag file
~/.claude/bin/proxy-toggle status    # Shows routing flag, proxy process, .zshenv state

Important: Claude Code must be restarted after toggling because ANTHROPIC_BASE_URL is read at startup.

WP-11: Health Endpoint

The /health endpoint returns provider configuration state for monitoring.

curl -s http://127.0.0.1:8082/health | jq .

WP-12: Go Proxy with Retry

Go proxy with built-in retry using cenkalti/backoff/v4 (exponential backoff: 500ms -> 1s -> 2s, max 5s elapsed).

import "github.com/cenkalti/backoff/v4"

backoffConfig := backoff.NewExponentialBackOff(
    backoff.WithInitialInterval(500 * time.Millisecond),
    backoff.WithMultiplier(2),
    backoff.WithMaxInterval(2 * time.Second),
    backoff.WithMaxElapsedTime(5 * time.Second),
)
err := backoff.Retry(operation, backoffConfig)

Location: /usr/local/bin/claude-proxy | Environment: ANTHROPIC_BASE_URL=http://127.0.0.1:8082 in .zshenv

WP-13: Launchd Service Configuration

The Go proxy runs as a macOS launchd daemon for auto-restart on crash and boot persistence.

Plist: /Library/LaunchDaemons/com.example.claude-proxy.plist

Full plist configuration, commands, verification checklist, and debugging: references/launchd-configuration.md

WP-14: OAuth Token Auto-Refresh

Background goroutine refreshes OAuth tokens every 30 minutes, 5 minutes before expiry. Falls back to Keychain if API refresh fails.

Full implementation and refresh logic: references/oauth-auto-refresh.md

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Anti-Patterns Summary

Full details with code examples: references/anti-patterns.md

ID	Severity	Gotcha	Fix
CCP-01	HIGH	ANTHROPIC_BASE_URL alone without ANTHROPIC_API_KEY	Set ANTHROPIC_API_KEY=proxy-managed
CCP-02	HIGH	Missing anthropic-beta: oauth-2025-04-20 header	Append to existing beta headers
CCP-03	MEDIUM	Using /api/oauth/claude_cli/create_api_key endpoint	Requires org:create_api_key scope (users only have user:inference)
CCP-04	HIGH	Lowercase keychain service "claude-code-credentials"	Actual name has space: "Claude Code-credentials"
CCP-05	MEDIUM	Reading ~/.claude/.credentials.json as primary	Keychain is SSoT; credential file is stale fallback
CCP-06	HIGH	Hardcoding OAuth tokens	Tokens expire; read dynamically with cache
CCP-07	HIGH	Using gh auth token in proxy/hooks	Causes process storms (recursive spawning)
CCP-08	HIGH	ANTHROPIC_API_KEY set in env while having OAuth token	Auth conflict warning in Claude Code; unset it
CCP-09	MEDIUM	cache_control param sent to a provider lacking it	Provider rejects it; remove from allowedParams
CCP-10	MEDIUM	Setting ANTHROPIC_API_KEY to real key while proxy runs	Proxy forwards it to all providers, leaking key
CCP-11	MEDIUM	Not handling /v1/messages/count_tokens	Causes auth failures on preflight requests
CCP-12	LOW	Running proxy on 0.0.0.0	Bind to 127.0.0.1 for security

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TodoWrite Task Templates

Setup, provider addition, diagnostics, and disable templates: references/task-templates.md

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Reference Implementation

The working production deployment (Go proxy is primary):

File	Purpose
/usr/local/bin/claude-proxy	Go proxy binary (~960 lines)
~/.claude/tools/claude-code-proxy-go/main.go	Go proxy source
~/.claude/tools/claude-code-proxy-go/oauth_refresh.go	OAuth auto-refresh (80 lines)
~/.claude/tools/claude-code-proxy-go/.env	Provider config (chmod 600)
/Library/LaunchDaemons/com.example.claude-proxy.plist	launchd config
~/.zshenv	Environment (ANTHROPIC_BASE_URL)

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Post-Change Checklist

After modifying this skill:

1. Anti-patterns table matches references/anti-patterns.md
2. Working patterns verified against proxy.py source
3. No hardcoded OAuth tokens in examples
4. Beta header version current (oauth-2025-04-20)
5. All internal links use relative paths (./references/...)
6. Link validator passes
7. Skill validator passes
8. Append changes to references/evolution-log.md

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Troubleshooting

Issue	Cause	Solution
Claude Code ignores ANTHROPIC_BASE_URL	Missing ANTHROPIC_API_KEY (CCP-01)	Set ANTHROPIC_API_KEY=proxy-managed in .zshenv
401 Unauthorized from Anthropic	Missing anthropic-beta header (CCP-02)	Ensure proxy appends oauth-2025-04-20
Keychain read returns empty	Wrong service name (CCP-04)	Use "Claude Code-credentials" (with space)
Proxy forwards real API key	ANTHROPIC_API_KEY set to real key (CCP-10)	Use proxy-managed sentinel value
count_tokens auth failure	Missing endpoint handler (CCP-11)	Proxy must handle /v1/messages/count_tokens
Proxy accessible from network	Bound to 0.0.0.0 (CCP-12)	Bind to 127.0.0.1 only
Process storms on enable	gh auth token in hooks (CCP-07)	Never call gh CLI from hooks/credential helpers
Token expired after 5 min	Cache TTL (WP-05)	Normal behavior; proxy re-reads from Keychain
Auth conflict warning in Claude Code	ANTHROPIC_API_KEY set (CCP-08)	Unset ANTHROPIC_API_KEY in .zshenv
cache_control.ephemeral.scope error	Provider lacks cache_control (CCP-09)	Remove cache_control from allowedParams

Post-Execution Reflection

After this skill completes, check before closing:

1. Did the command succeed? — If not, fix the instruction or error table that caused the failure.
2. Did parameters or output change? — If the underlying tool's interface drifted, update Usage examples and Parameters table to match.
3. Was a workaround needed? — If you had to improvise (different flags, extra steps), update this SKILL.md so the next invocation doesn't need the same workaround.

Only update if the issue is real and reproducible — not speculative.