fix(oauth): restore identity block required by Anthropic API

Anthropic now requires OAuth requests to include an approved identity
string as a separate first content block in the system prompt array.
Without it, Sonnet/Opus models return 400 invalid_request_error.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nanobot/providers/anthropic_oauth.py

@@ -11,7 +11,7 @@ import httpx
 from loguru import logger
 
 from nanobot.providers.base import LLMProvider, LLMResponse, ToolCallRequest
-from nanobot.providers.oauth_utils import get_auth_headers
+from nanobot.providers.oauth_utils import get_auth_headers, get_claude_code_system_prefix
 
 
 class AnthropicOAuthProvider(LLMProvider):
@@ -377,7 +377,10 @@ class AnthropicOAuthProvider(LLMProvider):
             payload["temperature"] = temperature
 
         if system:
-            payload["system"] = [{"type": "text", "text": system, "cache_control": {"type": "ephemeral", "ttl": "1h"}}]
+            payload["system"] = [
+                {"type": "text", "text": get_claude_code_system_prefix()},
+                {"type": "text", "text": system, "cache_control": {"type": "ephemeral", "ttl": "1h"}},
+            ]
 
         if tools:
             cached_tools = list(tools)
@@ -424,70 +427,109 @@ class AnthropicOAuthProvider(LLMProvider):
 
         import asyncio
         import time as _time
-        _t0 = _time.monotonic()
-        try:
-            response = await client.post(
-                self._get_api_url(),
-                headers=headers,
-                json=payload,
-            )
-        except httpx.ConnectTimeout:
-            elapsed = _time.monotonic() - _t0
-            logger.error(f"ConnectTimeout after {elapsed:.1f}s — running diagnostics")
-            await self._diagnose_connectivity()
-            await self._reset_client()
-            raise
-        except httpx.PoolTimeout:
-            elapsed = _time.monotonic() - _t0
-            logger.error(f"PoolTimeout after {elapsed:.1f}s — resetting client")
-            await self._reset_client()
-            raise
-        except (httpx.ConnectError, httpx.TimeoutException) as e:
-            elapsed = _time.monotonic() - _t0
-            logger.error(f"{type(e).__name__} after {elapsed:.1f}s")
-            raise
-        elapsed = _time.monotonic() - _t0
-        if elapsed > 30:
-            logger.warning(f"Anthropic API slow response: {elapsed:.1f}s")
 
-        # Dump rate limit headers for analysis
-        try:
-            import datetime
-            import os
-            header_dump = {
-                "timestamp": datetime.datetime.now(datetime.UTC).isoformat(),
-                "status_code": response.status_code,
-                "model": payload.get("model"),
-                "headers": dict(response.headers),
-            }
-            dump_path = "/root/.nanobot/workspace/api_headers.jsonl"
-            with open(dump_path, "a") as f:
-                f.write(json.dumps(header_dump) + "\n")
-            # Capture rate limit state for quota-based model switching
-            hdrs = response.headers
-            rate_limit_state = {
-                "updated_at": datetime.datetime.utcnow().isoformat(),
-                "model": payload.get("model"),
-                "weekly_all_models": float(hdrs["anthropic-ratelimit-unified-7d-utilization"]) if hdrs.get("anthropic-ratelimit-unified-7d-utilization") else None,
-                "weekly_sonnet": float(hdrs["anthropic-ratelimit-unified-7d_sonnet-utilization"]) if hdrs.get("anthropic-ratelimit-unified-7d_sonnet-utilization") else None,
-                "session_5h": float(hdrs["anthropic-ratelimit-unified-5h-utilization"]) if hdrs.get("anthropic-ratelimit-unified-5h-utilization") else None,
-                "weekly_reset": int(hdrs["anthropic-ratelimit-unified-7d-reset"]) if hdrs.get("anthropic-ratelimit-unified-7d-reset") else None,
-                "session_reset": int(hdrs["anthropic-ratelimit-unified-5h-reset"]) if hdrs.get("anthropic-ratelimit-unified-5h-reset") else None,
-                "binding_limit": hdrs.get("anthropic-ratelimit-unified-representative-claim"),
-                "sonnet_fallback": hdrs.get("anthropic-ratelimit-unified-fallback"),
-            }
-            state_path = "/root/.nanobot/workspace/memory/rate_limits.json"
-            os.makedirs(os.path.dirname(state_path), exist_ok=True)
-            with open(state_path, "w") as f:
-                json.dump(rate_limit_state, f, indent=2)
-        except Exception as e:
-            logger.warning("Rate limit header capture failed: {}", e)
+        max_retries = 3
+        base_delay = 2.0  # seconds
 
-        if response.status_code != 200:
-            error_text = response.text
-            raise Exception(f"Anthropic API error {response.status_code}: {error_text}")
+        for attempt in range(max_retries + 1):
+            _t0 = _time.monotonic()
+            try:
+                response = await client.post(
+                    self._get_api_url(),
+                    headers=headers,
+                    json=payload,
+                )
+            except httpx.ConnectTimeout:
+                elapsed = _time.monotonic() - _t0
+                logger.error(f"ConnectTimeout after {elapsed:.1f}s (attempt {attempt+1}/{max_retries+1})")
+                if attempt == 0:
+                    await self._diagnose_connectivity()
+                await self._reset_client()
+                if attempt < max_retries:
+                    delay = base_delay * (2 ** attempt)
+                    logger.info(f"Retrying in {delay:.1f}s...")
+                    await asyncio.sleep(delay)
+                    continue
+                raise
+            except httpx.PoolTimeout:
+                elapsed = _time.monotonic() - _t0
+                logger.error(f"PoolTimeout after {elapsed:.1f}s (attempt {attempt+1}/{max_retries+1})")
+                await self._reset_client()
+                if attempt < max_retries:
+                    delay = base_delay * (2 ** attempt)
+                    logger.info(f"Retrying in {delay:.1f}s...")
+                    await asyncio.sleep(delay)
+                    continue
+                raise
+            except (httpx.ConnectError, httpx.TimeoutException) as e:
+                elapsed = _time.monotonic() - _t0
+                logger.error(f"{type(e).__name__} after {elapsed:.1f}s (attempt {attempt+1}/{max_retries+1})")
+                if attempt < max_retries:
+                    delay = base_delay * (2 ** attempt)
+                    logger.info(f"Retrying in {delay:.1f}s...")
+                    await asyncio.sleep(delay)
+                    continue
+                raise
+            elapsed = _time.monotonic() - _t0
+            if elapsed > 30:
+                logger.warning(f"Anthropic API slow response: {elapsed:.1f}s")
 
-        return response.json()
+            # Dump rate limit headers for analysis
+            try:
+                import datetime
+                import os
+                header_dump = {
+                    "timestamp": datetime.datetime.now(datetime.UTC).isoformat(),
+                    "status_code": response.status_code,
+                    "model": payload.get("model"),
+                    "headers": dict(response.headers),
+                }
+                dump_path = "/root/.nanobot/workspace/api_headers.jsonl"
+                with open(dump_path, "a") as f:
+                    f.write(json.dumps(header_dump) + "\n")
+                # Capture rate limit state for quota-based model switching
+                hdrs = response.headers
+                rate_limit_state = {
+                    "updated_at": datetime.datetime.utcnow().isoformat(),
+                    "model": payload.get("model"),
+                    "weekly_all_models": float(hdrs["anthropic-ratelimit-unified-7d-utilization"]) if hdrs.get("anthropic-ratelimit-unified-7d-utilization") else None,
+                    "weekly_sonnet": float(hdrs["anthropic-ratelimit-unified-7d_sonnet-utilization"]) if hdrs.get("anthropic-ratelimit-unified-7d_sonnet-utilization") else None,
+                    "session_5h": float(hdrs["anthropic-ratelimit-unified-5h-utilization"]) if hdrs.get("anthropic-ratelimit-unified-5h-utilization") else None,
+                    "weekly_reset": int(hdrs["anthropic-ratelimit-unified-7d-reset"]) if hdrs.get("anthropic-ratelimit-unified-7d-reset") else None,
+                    "session_reset": int(hdrs["anthropic-ratelimit-unified-5h-reset"]) if hdrs.get("anthropic-ratelimit-unified-5h-reset") else None,
+                    "binding_limit": hdrs.get("anthropic-ratelimit-unified-representative-claim"),
+                    "sonnet_fallback": hdrs.get("anthropic-ratelimit-unified-fallback"),
+                }
+                state_path = "/root/.nanobot/workspace/memory/rate_limits.json"
+                os.makedirs(os.path.dirname(state_path), exist_ok=True)
+                with open(state_path, "w") as f:
+                    json.dump(rate_limit_state, f, indent=2)
+            except Exception as e:
+                logger.warning("Rate limit header capture failed: {}", e)
+
+            # Retry on 5xx server errors and 429 rate limits
+            if response.status_code >= 500 or response.status_code == 429:
+                error_text = response.text
+                logger.warning(f"Anthropic API {response.status_code} (attempt {attempt+1}/{max_retries+1}): {error_text[:200]}")
+                if attempt < max_retries:
+                    if response.status_code == 429:
+                        retry_after = response.headers.get("retry-after")
+                        delay = float(retry_after) if retry_after else base_delay * (2 ** attempt)
+                    else:
+                        delay = base_delay * (2 ** attempt)
+                    logger.info(f"Retrying in {delay:.1f}s...")
+                    await asyncio.sleep(delay)
+                    continue
+                raise Exception(f"Anthropic API error {response.status_code}: {error_text}")
+
+            if response.status_code != 200:
+                error_text = response.text
+                raise Exception(f"Anthropic API error {response.status_code}: {error_text}")
+
+            return response.json()
+
+        # Should not reach here, but just in case
+        raise Exception("Exhausted all retry attempts")
 
     async def chat(
         self,

nanobot/providers/oauth_utils.py

@@ -36,3 +36,11 @@ def get_auth_headers(token: str, is_oauth: bool = False) -> dict[str, str]:
         headers["x-api-key"] = token
 
     return headers
+
+
+def get_claude_code_system_prefix() -> str:
+    """Get the required system prompt prefix for OAuth tokens.
+
+    Anthropic requires this identity declaration for OAuth auth.
+    """
+    return "You are a Claude agent, built on Anthropic's Claude Agent SDK."