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527527| `400` errors naming `context_management`, `Extra inputs are not permitted`, or other unrecognized fields | The gateway forwards requests to an upstream that rejects fields Claude Code sends to Anthropic-format endpoints | Set `CLAUDE_CODE_DISABLE_EXPERIMENTAL_BETAS=1`, which suppresses most pre-release fields; see [feature pass-through](/docs/en/llm-gateway-protocol#feature-pass-through). Some betas aren't gated by this flag; for those, set the matching `CLAUDE_CODE_USE_*` provider variable so Claude Code sends only what that provider accepts |
528528| `400` errors naming `thinking` or `adaptive`, such as `Input tag 'adaptive' found` | The upstream model build doesn't accept adaptive reasoning, which Claude Code requests for Claude 4.6 and later models | Upgrade the gateway's upstream. On Opus 4.6 and Sonnet 4.6, `CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING=1` works instead. The [model configuration](/docs/en/model-config) capability variables apply only to the provider configurations, such as `CLAUDE_CODE_USE_BEDROCK` and `CLAUDE_CODE_USE_VERTEX`, not behind an `ANTHROPIC_BASE_URL` gateway |
529529| `400` errors stating a context or token limit in the gateway's own words, such as `ContextWindowExceededError` or `prompt token count of N exceeds the limit of M` | The gateway enforces a smaller context than the model's native window and rewrites the upstream error, so Claude Code doesn't recognize it as a [too-long error](/docs/en/errors#prompt-is-too-long) and doesn't compact and retry automatically | Run `/compact` to recover the session. To prevent it, set `CLAUDE_CODE_AUTO_COMPACT_WINDOW` to the gateway's limit; Claude Code clamps the value to at least 100,000 tokens and at most the model's context window, so you can't match a gateway limit below 100,000, and `/compact` remains the recovery there. Also set `CLAUDE_CODE_MAX_OUTPUT_TOKENS` below the gateway model's output limit |
530| `400` errors on every request, in the gateway's own words rejecting a tool's input schema or its `pattern`, on Claude Code v2.1.265 through v2.1.267 | In a gradual rollout on those versions, the [Artifact tool](/docs/en/artifacts#availability) schema carries a regular expression with `\p{...}` Unicode character classes. The Anthropic API accepts it, but a gateway or upstream that checks each tool schema's `pattern` with its own regex engine rejects the whole request | Update to v2.1.268 or later, which doesn't send the regular expression. On an affected version, [turn artifacts off](/docs/en/artifacts#disable-artifacts), which removes the tool and its schema from requests |
530531| Models missing from the `/model` picker | Gateway model names aren't in Claude Code's built-in list, or Claude Code is showing a [`modelPicker`](/docs/en/settings-reference#modelpicker) lineup that replaces the built-in options | Enable [gateway model discovery](#add-gateway-models-to-the-model-picker) or add names with the [model configuration](/docs/en/model-config) variables. If Claude Code shows a replacing `modelPicker` lineup, add the gateway models to it, or ask your administrator to add them when managed settings supply it |
531532| `/fast` reports `Fast mode unavailable due to network connectivity issues` while inference requests work | The [fast mode](/docs/en/fast-mode) availability check goes directly to `api.anthropic.com` and doesn't follow `ANTHROPIC_BASE_URL`, so blocked direct egress fails the check. The same message appears on an open network when the check presents a gateway-issued key from `ANTHROPIC_API_KEY` or an `apiKeyHelper` and Anthropic rejects it | Allowlist `api.anthropic.com` if egress is blocked, or set a skip variable; for a rejected gateway key only the skip variables help. See [use fast mode behind proxies and LLM gateways](/docs/en/fast-mode#use-fast-mode-behind-proxies-and-llm-gateways) |
532533| `/fast` reports `Fast mode has been disabled by your organization` in a session authenticated with `ANTHROPIC_AUTH_TOKEN`, even though the organization has fast mode enabled | The availability check requires a claude.ai login or an Anthropic API key; with only a bearer token, Claude Code treats fast mode as disabled without sending the check | Set `CLAUDE_CODE_SKIP_FAST_MODE_ORG_CHECK=1`; see [use fast mode behind proxies and LLM gateways](/docs/en/fast-mode#use-fast-mode-behind-proxies-and-llm-gateways) |