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Update claude-api skill: Claude Opus 5 (#1476)
* Update claude-api skill: Claude Opus 5 - Add Claude Opus 5 (`claude-opus-5`) as the default model across all SDK examples, model tables, pricing, and migration guidance. - Add an Opus 5 migration section covering the API changes that come with it, and move Opus 4.8 into the previous-generation slot. - Drop the Opus 4.7 fast-mode guidance, which no longer applies. - Scope the server-side fallbacks beta header to the current version. * Update claude-api skill: Opus 5 fast-follow corrections - Server-side refusal fallbacks are available on Claude Platform on AWS, not just the Claude API. Correct the availability statements in SKILL.md, the migration guide, and the platform-availability table. - Simplify the effort guidance: start at `high` (the API default) and sweep down, rather than starting at `xhigh` for coding work. - Add a time-to-first-token section with the prompt instruction that reduces pre-answer thinking on latency-sensitive routes. - Replace the two separate thinking-disabled mitigations with the single combined instruction that covers both failure modes.
This commit is contained in:
Lance Martin
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-25
@@ -32,7 +32,7 @@ Never mix the two — don't reach for `requests`/`fetch` in a Python or TypeScri
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Unless the user requests otherwise:
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For the Claude model version, please use Claude Opus 4.8, which you can access via the exact model string `claude-opus-4-8`. Please default to using adaptive thinking (`thinking: {type: "adaptive"}`) for anything remotely complicated. And finally, please default to streaming for any request that may involve long input, long output, or high `max_tokens` — it prevents hitting request timeouts. Use the SDK's `.get_final_message()` / `.finalMessage()` helper to get the complete response if you don't need to handle individual stream events
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For the Claude model version, please use Claude Opus 5, which you can access via the exact model string `claude-opus-5`. Please default to using adaptive thinking (`thinking: {type: "adaptive"}`) for anything remotely complicated. And finally, please default to streaming for any request that may involve long input, long output, or high `max_tokens` — it prevents hitting request timeouts. Use the SDK's `.get_final_message()` / `.finalMessage()` helper to get the complete response if you don't need to handle individual stream events
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## ⚠️ API Drift — Your Training Prior May Be Stale
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@@ -40,8 +40,8 @@ Several common Claude API shapes changed in 2025–2026. If you recall a pattern
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| Area | Stale prior | Current API |
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|---|---|---|
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| Extended thinking | `thinking: {type: "enabled", budget_tokens: N}` | On Claude 4.6+ models: `thinking: {type: "adaptive"}`. `budget_tokens` is deprecated on Opus 4.6 / Sonnet 4.6 and **rejected with a 400** on Fable 5 / Sonnet 5 / Opus 4.8 / 4.7. Pre-4.6 models still use `budget_tokens`. |
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| Web search / web fetch tool type | `web_search_20250305`, `web_fetch_20250910` | `web_search_20260209`, `web_fetch_20260209` (dynamic filtering) on Opus 4.8/4.7/4.6, Sonnet 5, and Sonnet 4.6. Older models keep the basic variants; on Vertex AI only basic `web_search_20250305` is available (web fetch is not on Vertex) — see the Server Tools QR below. |
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| Extended thinking | `thinking: {type: "enabled", budget_tokens: N}` | On Claude 4.6+ models: `thinking: {type: "adaptive"}`. `budget_tokens` is deprecated on Opus 4.6 / Sonnet 4.6 and **rejected with a 400** on Fable 5 / Sonnet 5 / Opus 5 / 4.8 / 4.7. Pre-4.6 models still use `budget_tokens`. |
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| Web search / web fetch tool type | `web_search_20250305`, `web_fetch_20250910` | `web_search_20260209`, `web_fetch_20260209` (dynamic filtering) on Opus 5/4.8/4.7/4.6, Sonnet 5, and Sonnet 4.6. Older models keep the basic variants; on Vertex AI only basic `web_search_20250305` is available (web fetch is not on Vertex) — see the Server Tools QR below. |
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| PHP parameter names | snake_case wire names as named args (`max_tokens`) | Top-level named args are camelCase (`maxTokens`). Nested array keys vary by feature (e.g. `'taskBudget'`, `'skillID'`, `'mcp_server_name'`) — copy the exact key from the documented example; do not bulk-convert. |
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| Managed Agents credentials | Keep secrets host-side via custom tools (the only option before vaults shipped) | Vault `environment_variable` credentials — stored by Anthropic, substituted at egress, never visible in the sandbox (`shared/managed-agents-tools.md` → Vaults). Host-side custom tools remain the fallback for self-hosted sandboxes. |
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@@ -174,7 +174,8 @@ Everything goes through `POST /v1/messages`. Tools and output constraints are fe
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| ----------------- | ------------------- | -------------- | ---------- | ----------- |
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| Claude Fable 5 | `claude-fable-5` | 1M | $10.00 | $50.00 |
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| Claude Mythos 5 (Project Glasswing only) | `claude-mythos-5` | 1M | $10.00 | $50.00 |
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| Claude Opus 4.8 | `claude-opus-4-8` | 1M | $5.00 | $25.00 |
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| Claude Opus 5 | `claude-opus-5` | 1M | $5.00 | $25.00 |
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| Claude Opus 4.8 | `claude-opus-4-8` | 1M | $5.00 | $25.00 |
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| Claude Opus 4.7 | `claude-opus-4-7` | 1M | $5.00 | $25.00 |
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| Claude Opus 4.6 | `claude-opus-4-6` | 1M | $5.00 | $25.00 |
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| Claude Sonnet 5 | `claude-sonnet-5` | 1M | $3.00 ($2.00 intro through 2026-08-31) | $15.00 ($10.00 intro) |
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@@ -183,7 +184,7 @@ Everything goes through `POST /v1/messages`. Tools and output constraints are fe
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**Partner pricing:** The prices above are Anthropic first-party API rates — they also apply to Claude on Microsoft Foundry, which is billed through the Microsoft Marketplace at standard API rates. Claude on Amazon Bedrock and Vertex AI is partner-operated with separate pricing — see [Bedrock](https://aws.amazon.com/bedrock/pricing/) or [Vertex AI](https://cloud.google.com/vertex-ai/generative-ai/pricing#claude-models). For WebFetch, use the Pricing row in `shared/live-sources.md`.
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**ALWAYS use `claude-opus-4-8` unless the user explicitly names a different model.** This is non-negotiable. Do not use `claude-sonnet-5`, `claude-sonnet-4-6`, or any other model unless the user literally says "use sonnet" or "use haiku". Never downgrade for cost — that's the user's decision, not yours. Use `claude-fable-5` only when the user explicitly asks for Claude Fable 5, "fable", or Anthropic's most capable model — it has different API behavior than the Opus family (see below) and pricing that exceeds Opus-tier. **Use only the exact model ID strings from the table — they are complete as-is; never append date suffixes** (`claude-sonnet-4-6`, never `claude-sonnet-4-6-20251114` or any other date-suffixed variant you might recall from training data). If the user requests an older model not in the table (e.g., "opus 4.5", "sonnet 3.7"), read `shared/models.md` for the exact ID — do not construct one yourself.
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**ALWAYS use `claude-opus-5` unless the user explicitly names a different model.** This is non-negotiable. Do not use `claude-sonnet-5`, `claude-sonnet-4-6`, or any other model unless the user literally says "use sonnet" or "use haiku". Never downgrade for cost — that's the user's decision, not yours. Use `claude-fable-5` only when the user explicitly asks for Claude Fable 5, "fable", or Anthropic's most capable model — it has different API behavior than the Opus family (see below) and pricing that exceeds Opus-tier. **Use only the exact model ID strings from the table — they are complete as-is; never append date suffixes** (`claude-sonnet-4-6`, never `claude-sonnet-4-6-20251114` or any other date-suffixed variant you might recall from training data). If the user requests an older model not in the table (e.g., "opus 4.5", "sonnet 3.7"), read `shared/models.md` for the exact ID — do not construct one yourself.
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### Claude Fable 5 (`claude-fable-5`) — most capable widely released model
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@@ -192,7 +193,7 @@ Claude Fable 5 is Anthropic's most capable widely released model, for the most d
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- **Thinking is always on** — omit the `thinking` parameter entirely (or send `{type: "adaptive"}`). Any other explicit configuration is rejected: `{type: "disabled"}` and `{type: "enabled", budget_tokens: N}` both return a 400. Control depth with `output_config.effort` (supports `low` through `xhigh` and `max`).
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- **The raw chain of thought is never returned** — responses carry regular `thinking` blocks (not `redacted_thinking`): `display: "summarized"` returns a readable summary, `"omitted"` (the default) leaves the `thinking` field as an empty string. Replay rules: pass thinking blocks back unchanged on the same model; other models drop them silently (unbilled — nothing to strip); details in `shared/model-migration.md`.
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- **Tokenizer** — same tokenizer as Opus 4.8 (introduced with Opus 4.7). Token counts are roughly unchanged when migrating from Opus 4.7/4.8; per-token pricing differs. Coming from Opus 4.6, Sonnet, Haiku, or older, re-baseline with `count_tokens` (the Opus 4.7 tokenizer uses ~1×–1.35× as many tokens).
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- **`refusal` stop reason — handle it, and opt into fallbacks by default** — safety classifiers may decline a request (HTTP 200, `stop_reason: "refusal"`, with a `stop_details` category); always check `stop_reason` before reading `content`. **When you write `claude-fable-5` code, include the server-side `fallbacks` parameter by default** (`betas: ["server-side-fallback-2026-06-01"]` + `fallbacks: [{"model": "claude-opus-4-8"}]`; Claude API and Claude Platform on AWS — elsewhere, incl. Bedrock/Vertex/Foundry, use the SDKs' client-side `BetaRefusalFallbackMiddleware` + `BetaFallbackState`). Tell the user you've enabled it; drop it only if they decline. Full semantics (billing, mid-stream refusals, credit repricing) in `shared/model-migration.md` → refusal section; code examples in `{lang}/claude-api/README.md` § Refusal Fallbacks.
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- **`refusal` stop reason — handle it, and opt into fallbacks by default** — safety classifiers may decline a request (HTTP 200, `stop_reason: "refusal"`, with a `stop_details` category); always check `stop_reason` before reading `content`. **When you write `claude-fable-5` or `claude-opus-5` code, include the server-side `fallbacks` parameter by default.** Simplest form: `betas: ["server-side-fallback-2026-07-01"]` + `fallbacks: "default"`, which routes by refusal category so you never maintain a model list. (The older array form — `betas: ["server-side-fallback-2026-06-01"]` + `fallbacks: [{"model": "claude-opus-4-8"}]` — still works; Claude API and Claude Platform on AWS — on Bedrock, Vertex and Foundry, use the SDKs' client-side `BetaRefusalFallbackMiddleware` + `BetaFallbackState` instead). Tell the user you've enabled it; drop it only if they decline. Full semantics (billing, mid-stream refusals, credit repricing) in `shared/model-migration.md` → refusal section. **Per-language code examples in `{lang}/claude-api/README.md` § Refusal Fallbacks cover the array form only** — for the `"default"` mode, follow the raw-HTTP shape in `shared/model-migration.md` → Migrating to Claude Opus 5 → New API features and swap `fallbacks: [{...}]` for `fallbacks: "default"` plus the `-2026-07-01` header; the rest of the request is unchanged.
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- **No assistant prefill** — same as the rest of the 4.6+ family.
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- **30-day data retention required** — Claude Fable 5 is not available under zero data retention; requests from an org whose retention configuration doesn't meet the requirement return `400 invalid_request_error`.
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- **Longer turns, different prompting** — single requests on hard tasks can run many minutes (plan timeouts/streaming/progress UX); effort sweeps should include low/medium for routine work; prompts written for prior models are often too prescriptive and reduce output quality. See `shared/model-migration.md` → Migrating to Claude Fable 5 → Behavioral shifts (prompt-tunable) for the recommended prompt snippets.
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@@ -225,6 +226,7 @@ Use adaptive thinking (`thinking: {type: "adaptive"}`) on every current model
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| Model | Thinking config | Omitting `thinking` | `budget_tokens` | Sampling (`temperature`/`top_p`/`top_k`) | Effort levels |
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|---|---|---|---|---|---|
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| Fable 5 | `{type: "adaptive"}` or omit; explicit `{type: "disabled"}` returns 400 — omit the param instead | Runs adaptive (thinking is always on) | Removed — `{type: "enabled", budget_tokens: N}` returns 400 | Removed — 400 | `low`/`medium`/`high`/`xhigh`/`max` |
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| Claude Opus 5 | `{type: "adaptive"}` or omit; `{type: "disabled"}` accepted **only at effort `high` or below** — 400 at `xhigh`/`max`, and see the disabled-thinking pitfall below | Runs **adaptive** (thinking is on by default — unlike Opus 4.8/4.7) | Removed — 400 | Removed — 400 | `low`–`max` (all five) |
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| Opus 4.8 / 4.7 | `{type: "adaptive"}` is the only on-mode; `{type: "disabled"}` accepted | Runs **without** thinking — set `{type: "adaptive"}` explicitly | Removed — 400 | Removed — 400 | `low`/`medium`/`high`/`xhigh`/`max` |
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| Sonnet 5 | `{type: "adaptive"}` is the only on-mode; `{type: "disabled"}` accepted | Runs adaptive | Removed — 400 | Removed — 400 | `low`/`medium`/`high`/`xhigh`/`max` |
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| Opus 4.6 / Sonnet 4.6 | `{type: "adaptive"}` (recommended; auto-enables interleaved thinking, no beta header) | Set `{type: "adaptive"}` explicitly | Deprecated — do not use in new code; transitional escape hatch only (see below) | Allowed | `low`/`medium`/`high`/`max` (`xhigh` arrived with Opus 4.7) |
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@@ -233,14 +235,14 @@ Use adaptive thinking (`thinking: {type: "adaptive"}`) on every current model
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Opus 4.8 keeps the same request surface as 4.7 (no new breaking changes) — see `shared/model-migration.md` → Migrating to Opus 4.8 for the behavioral re-tuning, and → Migrating to Opus 4.7 for the full breaking-change list when coming from 4.6 or earlier. With `thinking` disabled, Opus 4.8 may write longer reasoning into the visible response — leave adaptive thinking on, or add a final-answer-only instruction (see the migration guide).
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- **Effort (GA, no beta header):** `output_config: {effort: "low"|"medium"|"high"|"xhigh"|"max"}` — inside `output_config`, not top-level; default `high` (equivalent to omitting it). Controls thinking depth and overall token spend; combine with adaptive thinking for the best cost-quality tradeoffs. `xhigh` (added on Opus 4.7, between `high` and `max`) is the best setting for most coding and agentic use cases on Fable 5 / Opus 4.7/4.8 / Sonnet 5, and the default in Claude Code; effort matters more on those models than on any prior model in their tier — re-tune it when migrating, and run long-horizon/agentic tasks at `high`/`xhigh` with the full task spec given up front. Use a minimum of `high` for intelligence-sensitive work, `max` when correctness matters more than cost, and `low` for subagents or simple tasks — lower effort means fewer and more-consolidated tool calls, less preamble, and terser confirmations (`high` is often the sweet spot balancing quality and token efficiency).
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- **Thinking display — `"omitted"` by default on Fable 5 / Mythos 5 / Opus 4.8 / 4.7 / Sonnet 5:** `display: "summarized"` returns a readable summary of the reasoning; `"omitted"` (the default on all five — a silent change from Opus 4.6 and Sonnet 4.6, where it was `"summarized"`) streams `thinking` blocks with empty text. `display` controls visibility only — thinking happens and is billed the same under every setting; the raw chain of thought is never exposed on any model. If you stream reasoning to users, the default looks like a long pause before output — set `thinking: {type: "adaptive", display: "summarized"}` explicitly. (Independent of display, echo thinking blocks back unchanged when continuing on the same model; other models silently ignore them — see the migration guide.)
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- **When the user asks for "extended thinking", a "thinking budget", or `budget_tokens`:** always use Fable 5, Opus 4.8, 4.7, or 4.6 with `thinking: {type: "adaptive"}` — the fixed thinking-token-budget concept is deprecated and adaptive thinking replaces it. Do NOT use `budget_tokens` for new 4.6/4.7/4.8 code and do NOT switch to an older model just because the user mentions it. *Gradual-migration carve-out:* `budget_tokens` is still functional on Opus 4.6 and Sonnet 4.6 only, as a transitional escape hatch for existing code that needs a hard token ceiling before you've tuned `effort` — see `shared/model-migration.md` → Transitional escape hatch. It is fully removed on Fable 5, Opus 4.7/4.8, and Sonnet 5.
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- **Thinking display — `"omitted"` by default on Fable 5 / Mythos 5 / Opus 5 / 4.8 / 4.7 / Sonnet 5:** `display: "summarized"` returns a readable summary of the reasoning; `"omitted"` (the default on all six — a silent change from Opus 4.6 and Sonnet 4.6, where it was `"summarized"`) streams `thinking` blocks with empty text. `display` controls visibility only — thinking happens and is billed the same under every setting; the raw chain of thought is never exposed on any model. If you stream reasoning to users, the default looks like a long pause before output — set `thinking: {type: "adaptive", display: "summarized"}` explicitly. (Independent of display, echo thinking blocks back unchanged when continuing on the same model; other models silently ignore them — see the migration guide.)
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- **When the user asks for "extended thinking", a "thinking budget", or `budget_tokens`:** always use Fable 5, Opus 5, 4.8, 4.7, or 4.6 with `thinking: {type: "adaptive"}` — the fixed thinking-token-budget concept is deprecated and adaptive thinking replaces it. Do NOT use `budget_tokens` for new 4.6/4.7/4.8 code and do NOT switch to an older model just because the user mentions it. *Gradual-migration carve-out:* `budget_tokens` is still functional on Opus 4.6 and Sonnet 4.6 only, as a transitional escape hatch for existing code that needs a hard token ceiling before you've tuned `effort` — see `shared/model-migration.md` → Transitional escape hatch. It is fully removed on Fable 5, Opus 5/4.7/4.8, and Sonnet 5.
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---
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## Compaction (Quick Reference)
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**Beta, Fable 5, Opus 4.8, Opus 4.7, Opus 4.6, Sonnet 5, and Sonnet 4.6.** For long-running conversations that may exceed the 1M context window, enable server-side compaction. The API automatically summarizes earlier context when it approaches the trigger threshold (default: 150K tokens). Requires beta header `compact-2026-01-12`.
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**Beta, Fable 5, Opus 5, Opus 4.8, Opus 4.7, Opus 4.6, Sonnet 5, and Sonnet 4.6.** For long-running conversations that may exceed the 1M context window, enable server-side compaction. The API automatically summarizes earlier context when it approaches the trigger threshold (default: 150K tokens). Requires beta header `compact-2026-01-12`.
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**Critical:** Append `response.content` (not just the text) back to your messages on every turn. Compaction blocks in the response must be preserved — the API uses them to replace the compacted history on the next request. Extracting only the text string and appending that will silently lose the compaction state.
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@@ -252,7 +254,7 @@ See `{lang}/claude-api/README.md` (Compaction section) for code examples. Full d
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**Prefix match.** Any byte change anywhere in the prefix invalidates everything after it. Render order is `tools` → `system` → `messages`. Keep stable content first (frozen system prompt, deterministic tool list), put volatile content (timestamps, per-request IDs, varying questions) after the last `cache_control` breakpoint.
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**Mid-conversation operator instructions** (Claude Opus 4.8 only; no beta header): append `{"role": "system", ...}` to `messages[]` instead of editing top-level `system`. Preserves the cached history prefix and is the prompt-injection-safe operator channel. See `shared/prompt-caching.md` § Mid-conversation system messages.
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**Mid-conversation operator instructions** (Claude Opus 5, Claude Opus 4.8, Claude Fable 5, Claude Mythos 5; not Claude Sonnet 5; no beta header): append `{"role": "system", ...}` to `messages[]` instead of editing top-level `system`. Preserves the cached history prefix and is the prompt-injection-safe operator channel. See `shared/prompt-caching.md` § Mid-conversation system messages.
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**Top-level auto-caching** (`cache_control: {type: "ephemeral"}` on `messages.create()`) is the simplest option when you don't need fine-grained placement. Max 4 breakpoints per request. Minimum cacheable prefix is ~1024 tokens — shorter prefixes silently won't cache.
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@@ -264,11 +266,11 @@ For placement patterns, architectural guidance, and the silent-invalidator audit
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## Fast Mode (Quick Reference)
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**Research preview, Opus 4.8 / 4.7 only.** Opus 4.7 fast mode is deprecated — after removal, `speed: "fast"` on 4.7 returns an error. Opus 4.8 is the durable fast-capable tier. Fast mode runs the same model at up to 2.5x higher output tokens per second, at premium pricing. Three things are required on every request: use the **beta** messages endpoint (`client.beta.messages.…`), pass the beta flag `fast-mode-2026-02-01`, and set `speed: "fast"` as a top-level request parameter (not a header, not in `extra_body`).
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**Research preview, Claude Opus 5 / Opus 4.8 only** — Claude API and Managed Agents, not Bedrock / Google Cloud / Foundry. Opus 4.7 fast mode has been removed: `speed: "fast"` on 4.7 returns an error. Fast mode on Claude Opus 5 is priced at $10 / $50 per MTok. Fast mode runs the same model at up to 2.5x higher output tokens per second, at premium pricing. Three things are required on every request: use the **beta** messages endpoint (`client.beta.messages.…`), pass the beta flag `fast-mode-2026-02-01`, and set `speed: "fast"` as a top-level request parameter (not a header, not in `extra_body`).
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```python
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client.beta.messages.create(
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model="claude-opus-4-8", max_tokens=4096,
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model="claude-opus-5", max_tokens=4096,
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speed="fast", betas=["fast-mode-2026-02-01"],
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messages=[...],
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)
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@@ -286,15 +288,17 @@ client.beta.messages.create(
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`response.usage.speed` reports which speed was used. Fast mode has its own rate limit separate from standard Opus; on 429, either retry after the `retry-after` delay or drop `speed` and fall back to standard (note: switching speed invalidates prompt cache). Not available with Batch API, Priority Tier, Claude Platform on AWS, or third-party platforms.
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**Priority Tier does not cover Claude Opus 5.** It is supported on every other current model, including Claude Fable 5 and Opus 4.8, but Claude Opus 5, Claude Sonnet 5, Claude Mythos 5, and Mythos Preview are excluded — a Priority Tier request naming one of them fails validation.
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---
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## Task Budgets (Quick Reference)
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**Beta, Fable 5 / Sonnet 5 / Opus 4.8 / 4.7.** A task budget gives Claude a token ceiling for an agentic loop so it paces itself and finishes gracefully instead of being cut off — distinct from `max_tokens`, which is an enforced per-response ceiling the model is not aware of. Minimum `total`: 20,000. Set `task_budget` inside `output_config` on `client.beta.messages.stream(...)` with beta flag `task-budgets-2026-03-13` — use streaming so the large `max_tokens` doesn't hit HTTP timeouts (full details: `shared/model-migration.md` → Task Budgets):
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**Beta, Claude Opus 5 / Fable 5 / Sonnet 5 / Opus 4.8 / 4.7.** A task budget gives Claude a token ceiling for an agentic loop so it paces itself and finishes gracefully instead of being cut off — distinct from `max_tokens`, which is an enforced per-response ceiling the model is not aware of. Minimum `total`: 20,000. Set `task_budget` inside `output_config` on `client.beta.messages.stream(...)` with beta flag `task-budgets-2026-03-13` — use streaming so the large `max_tokens` doesn't hit HTTP timeouts (full details: `shared/model-migration.md` → Task Budgets):
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```python
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with client.beta.messages.stream(
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model="claude-opus-4-8", max_tokens=128000,
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model="claude-opus-5", max_tokens=128000,
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output_config={"effort": "high", "task_budget": {"type": "tokens", "total": 64000}},
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betas=["task-budgets-2026-03-13"],
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messages=[...], tools=[...],
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@@ -314,7 +318,7 @@ When targeting Claude on a third-party platform, use that platform's dedicated c
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### Amazon Bedrock
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Use the **Mantle** client (Messages-API Bedrock endpoint). Bedrock model IDs take an `anthropic.` prefix (e.g. `"anthropic.claude-opus-4-8"`). Region is required.
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Use the **Mantle** client (Messages-API Bedrock endpoint). Bedrock model IDs take an `anthropic.` prefix (e.g. `"anthropic.claude-opus-5"`). Region is required.
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| Language | Client |
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|---|---|
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@@ -342,7 +346,7 @@ The Go and Ruby SDKs do not currently support Foundry. For Ruby, use the standar
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### Google Cloud Vertex AI
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Two required constructor args: GCP `project_id` and `region`. Vertex model IDs take **no prefix** — current-generation models (Opus 4.8/4.7/4.6, Sonnet 5, Sonnet 4.6) use the bare first-party ID (e.g. `"claude-opus-4-8"`); dated-snapshot models use an `@` version separator (e.g. `claude-opus-4-5@20251101`, **not** `claude-opus-4-5-20251101`). Auth is GCP ADC (`gcloud auth application-default login`); no Anthropic API key. `region` can be `"global"` (recommended), a multi-region (`"us"`/`"eu"`), or a specific region. After construction, use the same `messages.create` / `.stream` surface.
|
||||
Two required constructor args: GCP `project_id` and `region`. Vertex model IDs take **no prefix** — current-generation models (Opus 4.8/4.7/4.6, Sonnet 5, Sonnet 4.6) use the bare first-party ID (e.g. `"claude-opus-5"`); dated-snapshot models use an `@` version separator (e.g. `claude-opus-4-5@20251101`, **not** `claude-opus-4-5-20251101`). Auth is GCP ADC (`gcloud auth application-default login`); no Anthropic API key. `region` can be `"global"` (recommended), a multi-region (`"us"`/`"eu"`), or a specific region. After construction, use the same `messages.create` / `.stream` surface.
|
||||
|
||||
| Language | Client |
|
||||
|---|---|
|
||||
@@ -362,7 +366,7 @@ Two required constructor args: GCP `project_id` and `region`. Vertex model IDs t
|
||||
|
||||
```python
|
||||
client.beta.messages.create(
|
||||
model="claude-opus-4-8", max_tokens=4096,
|
||||
model="claude-opus-5", max_tokens=4096,
|
||||
betas=["context-management-2025-06-27"],
|
||||
context_management={"edits": [{"type": "clear_tool_uses_20250919"}]},
|
||||
tools=[...], messages=[...],
|
||||
@@ -375,7 +379,7 @@ Strategy types: `clear_tool_uses_20250919` (clears old tool results; optional `c
|
||||
|
||||
## Mid-Conversation System Messages (Quick Reference)
|
||||
|
||||
**Claude Opus 4.8 only; no beta header.** Append `{"role": "system", "content": "…"}` to the `messages` array (not the top-level `system` field) to add an operator instruction mid-conversation without invalidating the cached prefix. Use the regular `client.messages.create` — there is no beta. A mid-conversation system message must follow a `user` message (or an `assistant` message ending in server-tool use), and must be either the last entry in `messages` or be followed by an `assistant` turn — it cannot be `messages[0]`. Availability: `shared/platform-availability.md`. See `shared/prompt-caching.md` § Mid-conversation system messages.
|
||||
**Claude Opus 5, Claude Opus 4.8, Claude Fable 5, and Claude Mythos 5; not Claude Sonnet 5; no beta header.** Append `{"role": "system", "content": "…"}` to the `messages` array (not the top-level `system` field) to add an operator instruction mid-conversation without invalidating the cached prefix. Use the regular `client.messages.create` — there is no beta. A mid-conversation system message must follow a `user` message (or an `assistant` message ending in server-tool use), and must be either the last entry in `messages` or be followed by an `assistant` turn — it cannot be `messages[0]`. Availability: `shared/platform-availability.md`. See `shared/prompt-caching.md` § Mid-conversation system messages.
|
||||
|
||||
---
|
||||
|
||||
@@ -407,7 +411,7 @@ Availability: `shared/platform-availability.md`. For agents on Bedrock / Vertex
|
||||
|
||||
## Server Tools (Quick Reference)
|
||||
|
||||
Server-side tools run on Anthropic's infrastructure — no client-side execution loop. Declare in `tools`; results arrive as content blocks in the same response. **No beta header** unless noted. **Prefer the latest type variant your model supports.** The `_20260209` web search / web fetch variants below (dynamic filtering) require Opus 4.8/4.7/4.6, Sonnet 5, or Sonnet 4.6; the basic variants for older models are listed after the table.
|
||||
Server-side tools run on Anthropic's infrastructure — no client-side execution loop. Declare in `tools`; results arrive as content blocks in the same response. **No beta header** unless noted. **Prefer the latest type variant your model supports.** The `_20260209` web search / web fetch variants below (dynamic filtering) require Opus 5/4.8/4.7/4.6, Sonnet 5, or Sonnet 4.6; the basic variants for older models are listed after the table.
|
||||
|
||||
| Tool | `type` | `name` | Key optional params | Result block type |
|
||||
|---|---|---|---|---|
|
||||
@@ -441,7 +445,7 @@ Server-side tools run on Anthropic's infrastructure — no client-side execution
|
||||
|
||||
**Message Batches (no beta; availability: `shared/platform-availability.md`):** `client.messages.batches.create(requests=[{custom_id, params}, ...])` → poll `client.messages.batches.retrieve(id).processing_status` until `"ended"` → stream `client.messages.batches.results(id)`. Each result has `.custom_id` + `.result.type` (`succeeded`/`errored`/`canceled`/`expired`); on success read `.result.message.content`. Python wraps requests as `Request(custom_id=..., params=MessageCreateParamsNonStreaming(...))`. Results arrive in **any order** — key by `custom_id`, never by position.
|
||||
|
||||
**Models API (no beta; availability: `shared/platform-availability.md`):** `client.models.list()` (auto-paginates) and `client.models.retrieve("claude-opus-4-8")`. Each model object has `id`, `display_name`, `created_at`, and — since Mar 2026 — `max_input_tokens` (the context window), `max_tokens` (the output cap), and `capabilities`. There is no `context_window` field.
|
||||
**Models API (no beta; availability: `shared/platform-availability.md`):** `client.models.list()` (auto-paginates) and `client.models.retrieve("claude-opus-5")`. Each model object has `id`, `display_name`, `created_at`, and — since Mar 2026 — `max_input_tokens` (the context window), `max_tokens` (the output cap), and `capabilities`. There is no `context_window` field.
|
||||
|
||||
**Stop details (GA, Opus 4.7+):** `response.stop_details` is populated **only when `stop_reason == "refusal"`** (fields: `type: "refusal"`, `category: "cyber"|"bio"|null`, `explanation`). It is `null` for every other `stop_reason` (`end_turn`, `max_tokens`, `tool_use`, `pause_turn`, …) — always guard before reading.
|
||||
|
||||
@@ -471,7 +475,7 @@ The Quick Task Reference below uses the `{lang}/claude-api/FILE.md` path notatio
|
||||
|
||||
**Long-running conversations (may exceed context window):**
|
||||
→ Read `{lang}/claude-api/README.md` — see Compaction section
|
||||
**Migrating to a newer model (Fable 5 / Opus 4.8 / Opus 4.7 / Opus 4.6 / Sonnet 5 / Sonnet 4.6), replacing a retired model, or translating `budget_tokens` / prefill patterns to the current API:**
|
||||
**Migrating to a newer model (Fable 5 / Opus 5 / Opus 4.8 / Opus 4.7 / Opus 4.6 / Sonnet 5 / Sonnet 4.6), replacing a retired model, or translating `budget_tokens` / prefill patterns to the current API:**
|
||||
→ Read `shared/model-migration.md`
|
||||
**Prompting or tuning Fable 5 (long turns, effort, verbosity, autonomous runs, sub-agents):**
|
||||
→ Read `shared/model-migration.md` → Migrating to Fable 5 → Behavioral shifts (prompt-tunable) + Long-running agent recommendations
|
||||
@@ -516,11 +520,12 @@ Live documentation URLs are in `shared/live-sources.md`.
|
||||
## Common Pitfalls
|
||||
|
||||
- Don't truncate inputs when passing files or content to the API. If the content is too long to fit in the context window, notify the user and discuss options (chunking, summarization, etc.) rather than silently truncating.
|
||||
- **Prefill removed (Fable 5 and the 4.6/4.7/4.8 family):** Assistant message prefills (last-assistant-turn prefills) return a 400 error on Fable 5, Opus 4.6, Opus 4.7, Opus 4.8, and Sonnet 4.6. Use structured outputs (`output_config.format`) or system prompt instructions to control response format instead. (One exception: the fallback-credit prefill claim — when redeeming a credit with `fallback_has_prefill_claim: true`, the server accepts the echoed assistant message; see the migration guide's refusal section.)
|
||||
- **Prefill removed (Fable 5, Opus 5, and the 4.6/4.7/4.8 family):** Assistant message prefills (last-assistant-turn prefills) return a 400 error on Fable 5, Opus 5, Opus 4.6, Opus 4.7, Opus 4.8, and Sonnet 4.6. Use structured outputs (`output_config.format`) or system prompt instructions to control response format instead. (One exception: the fallback-credit prefill claim — when redeeming a credit with `fallback_has_prefill_claim: true`, the server accepts the echoed assistant message; see the migration guide's refusal section.)
|
||||
- **Confirm migration scope before editing:** When a user asks to migrate code to a newer Claude model without naming a specific file, directory, or file list, **ask which scope to apply first** — the entire working directory, a specific subdirectory, or a specific set of files. Do not start editing until the user confirms. Imperative phrasings like "migrate my codebase", "move my project to X", "upgrade to Sonnet 4.6", or bare "migrate to Opus 4.8" are **still ambiguous** — they tell you what to do but not where, so ask. Proceed without asking only when the prompt names an exact file, a specific directory, or an explicit file list ("migrate `app.py`", "migrate everything under `services/`", "update `a.py` and `b.py`"). See `shared/model-migration.md` Step 0.
|
||||
- **`max_tokens` defaults:** Don't lowball `max_tokens` — hitting the cap truncates output mid-thought and requires a retry. For non-streaming requests, default to `~16000` (keeps responses under SDK HTTP timeouts). For streaming requests, default to `~64000` (timeouts aren't a concern, so give the model room). Only go lower when you have a hard reason: classification (`~256`), cost caps, deliberately short outputs, or **`max_tokens: 0`** for cache pre-warming (see `shared/prompt-caching.md` → Pre-warming).
|
||||
- **128K output tokens:** Fable 5, Opus 4.6, Opus 4.7, Opus 4.8, Sonnet 5, and Sonnet 4.6 support up to 128K `max_tokens`, but the SDKs require streaming for values that large to avoid HTTP timeouts. Use `.stream()` with `.get_final_message()` / `.finalMessage()`.
|
||||
- **Tool call JSON parsing (Fable 5 and the 4.6/4.7/4.8 family):** Fable 5, Opus 4.6, Opus 4.7, Opus 4.8, and Sonnet 4.6 may produce different JSON string escaping in tool call `input` fields (e.g., Unicode or forward-slash escaping). Always parse tool inputs with `json.loads()` / `JSON.parse()` — never do raw string matching on the serialized input.
|
||||
- **Disabling thinking on Claude Opus 5 has two failure modes — prefer low/medium effort instead.** Only affects code that explicitly opts out; thinking is on by default, so watch for a disabled-thinking setting carried forward from Opus 4.8. With `thinking: {type: "disabled"}`, the model occasionally writes a tool call into its **visible text** instead of a `tool_use` block: the turn succeeds, the call never runs, no error is raised, and in an agentic loop that text pollutes later turns. It can also leak `<thinking>` tags into the response. Turning thinking on and lowering `effort` fixes both and still cuts cost. If a route must stay thinking-off: **delete** any don't-think/don't-reason rule (it makes tag leakage worse), don't name thinking tags, and add the combined instruction *"When you use a tool, you may say a brief sentence first. If no tool can express what the user asked for, say so instead of guessing. Do not include internal or system XML tags in your response."* Details: `shared/model-migration.md` → Two failure modes when thinking is disabled.
|
||||
- **128K output tokens:** Fable 5, Opus 5, Opus 4.6, Opus 4.7, Opus 4.8, Sonnet 5, and Sonnet 4.6 support up to 128K `max_tokens`, but the SDKs require streaming for values that large to avoid HTTP timeouts. Use `.stream()` with `.get_final_message()` / `.finalMessage()`.
|
||||
- **Tool call JSON parsing (Fable 5, Opus 5, and the 4.6/4.7/4.8 family):** Fable 5, Opus 5, Opus 4.6, Opus 4.7, Opus 4.8, and Sonnet 4.6 may produce different JSON string escaping in tool call `input` fields (e.g., Unicode or forward-slash escaping). Always parse tool inputs with `json.loads()` / `JSON.parse()` — never do raw string matching on the serialized input.
|
||||
- **Structured outputs (all models):** Use `output_config: {format: {...}}` instead of the deprecated `output_format` parameter on `messages.create()`. This is a general API change, not 4.6-specific.
|
||||
- **Don't reimplement SDK functionality:** The SDK provides high-level helpers — use them instead of building from scratch. Specifically: use `stream.finalMessage()` instead of wrapping `.on()` events in `new Promise()`; use typed exception classes (`Anthropic.RateLimitError`, etc.) instead of string-matching error messages; use SDK types (`Anthropic.MessageParam`, `Anthropic.Tool`, `Anthropic.Message`, etc.) instead of redefining equivalent interfaces.
|
||||
- **Error handling — catch a chain, not one broad class.** A single `except APIStatusError` / `catch (AnthropicServiceException)` / `rescue APIError` loses the distinction between retryable (429, ≥500, network) and non-retryable (400/404) failures. Write a most-specific-first chain — e.g. `NotFoundError` → `RateLimitError` → `APIStatusError` → `APIConnectionError` (or the Go equivalent: `errors.As` into `*anthropic.Error` then `switch apierr.StatusCode { case 404: …; case 429: …; default: … }`). Per-language class names and namespaces are in `shared/error-codes.md`.
|
||||
@@ -533,7 +538,7 @@ Live documentation URLs are in `shared/live-sources.md`.
|
||||
- **Fine-grained tool streaming is not a beta feature.** Set `eager_input_streaming: true` on the tool definition and call the regular `client.messages.stream(...)`. There is no beta header and no `client.beta.*` path.
|
||||
- **Cache diagnostics is beta.** Use `client.beta.messages.*` with beta `cache-diagnosis-2026-04-07`. Pass `diagnostics: {previous_message_id: null}` on the first turn and `diagnostics: {previous_message_id: <previous response id>}` on subsequent turns; the result is on `response.diagnostics`. Availability: `shared/platform-availability.md`.
|
||||
- **Memory tool type is `memory_20250818`.** Declare `{"type": "memory_20250818", "name": "memory"}`. Go uses the beta-namespace type `{OfMemoryTool20250818: &anthropic.BetaMemoryTool20250818Param{}}` on `client.Beta.Messages.New`; Python/TypeScript/Ruby/PHP/C# use the non-beta `client.messages.create`; Java has both a non-beta `MemoryTool20250818` and a beta tool-runner path. Python/TypeScript provide `BetaAbstractMemoryTool` / `betaMemoryTool` helpers for implementing the backend.
|
||||
- **Use a model the feature actually supports.** Some features are restricted to specific model tiers — fast mode is Opus 4.8 / 4.7 only, task budgets are Fable 5 / Sonnet 5 / Opus 4.8 / 4.7 only, and the advisor tool requires a valid executor↔advisor pair. If the user's prompt names a model that the feature doesn't support, use a supported model instead and note the substitution in the output.
|
||||
- **Use a model the feature actually supports.** Some features are restricted to specific model tiers — fast mode is Claude Opus 5 / Opus 4.8 only (and Claude API only), task budgets are Claude Opus 5 / Fable 5 / Sonnet 5 / Opus 4.8 / 4.7 only, and the advisor tool requires a valid executor↔advisor pair. If the user's prompt names a model that the feature doesn't support, use a supported model instead and note the substitution in the output.
|
||||
- **Don't define custom types for SDK data structures:** The SDK exports types for all API objects. Use `Anthropic.MessageParam` for messages, `Anthropic.Tool` for tool definitions, `Anthropic.ToolUseBlock` / `Anthropic.ToolResultBlockParam` for tool results, `Anthropic.Message` for responses. Defining your own `interface ChatMessage { role: string; content: unknown }` duplicates what the SDK already provides and loses type safety.
|
||||
- **Report and document output:** For tasks that produce reports, documents, or visualizations, the code execution sandbox has `python-docx`, `python-pptx`, `matplotlib`, `pillow`, and `pypdf` pre-installed. Claude can generate formatted files (DOCX, PDF, charts) and return them via the Files API — consider this for "report" or "document" type requests instead of plain stdout text.
|
||||
- **Server-tool errors don't raise.** Web search and web fetch errors return HTTP 200 with a `web_search_tool_result` / `web_fetch_tool_result` block whose `content` is a single error object (e.g. `{error_code: "max_uses_exceeded"}`) — not a raised exception. For web search, a success `content` is a *list*; an error `content` is an *object* — branch on that before indexing.
|
||||
|
||||
Reference in New Issue
Block a user