docs: add anthropic auth error troubleshooting

docs/gateway/troubleshooting.md

@@ -31,6 +31,24 @@ See also: [Health checks](/gateway/health) and [Logging](/logging).
 
 ## Common Issues
 
+### No API key found for provider "anthropic"
+
+This means the **agent’s auth store is empty** or missing Anthropic credentials.
+Auth is **per agent**, so a new agent won’t inherit the main agent’s keys.
+
+Fix options:
+- Re-run onboarding and choose **Anthropic** for that agent.
+- Or paste a setup-token on the **gateway host**:
+  ```bash
+  clawdbot models auth setup-token --provider anthropic
+  ```
+- Or copy `auth-profiles.json` from the main agent dir to the new agent dir.
+
+Verify:
+```bash
+clawdbot models status
+```
+
 ### OAuth token refresh failed (Anthropic Claude subscription)
 
 This means the stored Anthropic OAuth token expired and the refresh failed.

docs/providers/anthropic.md

@@ -114,6 +114,11 @@ clawdbot onboard --auth-choice claude-cli
 - If the Claude CLI login lives on a different machine, use
   `clawdbot models auth paste-token --provider anthropic` on the gateway host.
 
+**No API key found for provider "anthropic"**
+- Auth is **per agent**. New agents don’t inherit the main agent’s keys.
+- Re-run onboarding for that agent, or paste a setup-token / API key on the
+  gateway host, then verify with `clawdbot models status`.
+
 **No credentials found for profile `anthropic:default` or `anthropic:claude-cli`**
 - Run `clawdbot models status` to see which auth profile is active.
 - Re-run onboarding, or paste a setup-token / API key for that profile.