The whole hunk
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lines
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44description: Get up to 2.5x higher output tokens per second from supported Claude Opus models.
55---
66
7Fast mode delivers up to 2.5x higher output tokens per second from Claude Opus 5 and Claude Opus 4.8 at premium pricing. Set `speed: "fast"` with the `fast-mode-2026-02-01` beta header on your request to opt in.
7Fast mode delivers up to 2.5x higher output tokens per second from Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8 at premium pricing. Set `speed: "fast"` with the `fast-mode-2026-02-01` beta header on your request to opt in.
88
99<Note>
1010 Fast mode is in research preview. Contact your account manager to request access. If you do not have an account manager, [join the waitlist](https://claude.com/fast-mode) for fast mode.
from line 18
1818
1919Fast mode is supported on the following models:
2020
21* Claude Opus 5.5 (claude-opus-5-5)
2122* Claude Opus 5 (claude-opus-5)
2223* Claude Opus 4.8 (claude-opus-4-8)
2324
2425<Note>
25 Fast mode for Claude Opus 5 and Claude Opus 4.8 is available as a research preview on the Claude API, including [Claude Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview), only. It is not available on Amazon Bedrock, Claude Platform on AWS, Google Cloud, or Microsoft Foundry.
26 Fast mode for Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8 is available as a research preview on the Claude API, including [Claude Managed Agents](https://platform.claude.com/docs/en/managed-agents/overview), only. It is not available on Amazon Bedrock, Claude Platform on AWS, Google Cloud, or Microsoft Foundry.
2627</Note>
2728
2829<Note>
29 Fast mode is not available on Claude Opus 4.7. Requests to `claude-opus-4-7` with `speed: "fast"` return an error; unlike Claude Opus 4.6 (see the following note), requests do not fall back to standard speed. The model itself remains available at standard speed. To continue using fast mode, migrate to [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/migration-guide#migrating-from-claude-opus-47) or Claude Opus 4.8.
30 Fast mode is not available on Claude Opus 4.7. Requests to `claude-opus-4-7` with `speed: "fast"` return an error; unlike Claude Opus 4.6 (see the following note), requests do not fall back to standard speed. The model itself remains available at standard speed. To continue using fast mode, migrate to Claude Opus 5.5, [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/migration-guide#migrating-from-claude-opus-47), or Claude Opus 4.8.
3031</Note>
3132
3233<Note>
33 Fast mode is not available on Claude Opus 4.6. Requests to `claude-opus-4-6` with `speed: "fast"` do not return an error: they run at standard speed and are billed at [standard rates](https://platform.claude.com/docs/en/about-claude/pricing) rather than fast mode's premium rates, and the response reports [`usage.speed: "standard"`](https://platform.claude.com/docs/en/build-with-claude/fast-mode#checking-which-speed-was-used). To continue using fast mode, migrate to [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/migration-guide#migrating-from-claude-opus-46) or Claude Opus 4.8.
34 Fast mode is not available on Claude Opus 4.6. Requests to `claude-opus-4-6` with `speed: "fast"` do not return an error: they run at standard speed and are billed at [standard rates](https://platform.claude.com/docs/en/about-claude/pricing) rather than fast mode's premium rates, and the response reports [`usage.speed: "standard"`](https://platform.claude.com/docs/en/build-with-claude/fast-mode#checking-which-speed-was-used). To continue using fast mode, migrate to Claude Opus 5.5, [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/migration-guide#migrating-from-claude-opus-46), or Claude Opus 4.8.
3435</Note>
3536
3637## How fast mode works
from line 53
5253 -H "anthropic-beta: fast-mode-2026-02-01" \
5354 -H "content-type: application/json" \
5455 -d '{
55 "model": "claude-opus-5",
56 "model": "claude-opus-5-5",
5657 "max_tokens": 4096,
5758 "speed": "fast",
5859 "messages": [{
from line 68
6768 --beta fast-mode-2026-02-01 \
6869 --transform 'content.#(type=="text").text' \
6970 --raw-output <<'YAML'
70 model: claude-opus-5
71 model: claude-opus-5-5
7172 max_tokens: 4096
7273 speed: fast
7374 messages:
from line 81
8081 client = anthropic.Anthropic()
8182
8283 response = client.beta.messages.create(
83 model="claude-opus-5",
84 model="claude-opus-5-5",
8485 max_tokens=4096,
8586 speed="fast",
8687 betas=["fast-mode-2026-02-01"],
from line 99
9899 const client = new Anthropic();
99100
100101 const response = await client.beta.messages.create({
101 model: "claude-opus-5",
102 model: "claude-opus-5-5",
102103 max_tokens: 4096,
103104 speed: "fast",
104105 betas: ["fast-mode-2026-02-01"],
from line 122
121122
122123 var response = await client.Beta.Messages.Create(new MessageCreateParams
123124 {
124 Model = "claude-opus-5",
125 Model = "claude-opus-5-5",
125126 MaxTokens = 4096,
126127 Speed = Speed.Fast,
127128 Betas = ["fast-mode-2026-02-01"],
from line 144
143144 client := anthropic.NewClient()
144145
145146 response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
146 Model: anthropic.ModelClaudeOpus5,
147 Model: anthropic.ModelClaudeOpus5_5,
147148 MaxTokens: 4096,
148149 Speed: anthropic.BetaMessageNewParamsSpeedFast,
149150 Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaFastMode2026_02_01},
from line 167
166167
167168 BetaMessage response = client.beta().messages().create(
168169 MessageCreateParams.builder()
169 .model(Model.CLAUDE_OPUS_5)
170 .model(Model.CLAUDE_OPUS_5_5)
170171 .maxTokens(4096L)
171172 .speed(MessageCreateParams.Speed.FAST)
172173 .addBeta(AnthropicBeta.FAST_MODE_2026_02_01)
from line 183
182183 $client = new Client();
183184
184185 $response = $client->beta->messages->create(
185 model: 'claude-opus-5',
186 model: 'claude-opus-5-5',
186187 maxTokens: 4096,
187188 speed: 'fast',
188189 betas: ['fast-mode-2026-02-01'],
from line 203
202203 client = Anthropic::Client.new
203204
204205 response = client.beta.messages.create(
205 model: "claude-opus-5",
206 model: "claude-opus-5-5",
206207 max_tokens: 4096,
207208 speed: "fast",
208209 betas: ["fast-mode-2026-02-01"],
from line 222
221222
222223| Model | Input | Output |
223224| ------------------------------- | -------------- | -------------- |
225| Claude Opus 5.5 | $8 USD / MTok | $40 USD / MTok |
224226| Claude Opus 5 / Claude Opus 4.8 | $10 USD / MTok | $50 USD / MTok |
225227
226228Fast mode pricing stacks with other pricing modifiers:
from line 261
259261 -H "anthropic-beta: fast-mode-2026-02-01" \
260262 -H "content-type: application/json" \
261263 -d '{
262 "model": "claude-opus-5",
264 "model": "claude-opus-5-5",
263265 "max_tokens": 1024,
264266 "speed": "fast",
265267 "messages": [{"role": "user", "content": "Hello"}]
from line 273
271273 --beta fast-mode-2026-02-01 \
272274 --transform usage.speed \
273275 --raw-output <<'YAML'
274 model: claude-opus-5
276 model: claude-opus-5-5
275277 max_tokens: 1024
276278 speed: fast
277279 messages:
from line 286
284286 client = anthropic.Anthropic()
285287
286288 response = client.beta.messages.create(
287 model="claude-opus-5",
289 model="claude-opus-5-5",
288290 max_tokens=1024,
289291 speed="fast",
290292 betas=["fast-mode-2026-02-01"],
from line 300
298300 const client = new Anthropic();
299301
300302 const response = await client.beta.messages.create({
301 model: "claude-opus-5",
303 model: "claude-opus-5-5",
302304 max_tokens: 1024,
303305 speed: "fast",
304306 betas: ["fast-mode-2026-02-01"],
from line 315
313315
314316 var response = await client.Beta.Messages.Create(new MessageCreateParams
315317 {
316 Model = "claude-opus-5",
318 Model = "claude-opus-5-5",
317319 MaxTokens = 1024,
318320 Speed = Speed.Fast,
319321 Betas = ["fast-mode-2026-02-01"],
from line 329
327329 client := anthropic.NewClient()
328330
329331 response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
330 Model: anthropic.ModelClaudeOpus5,
332 Model: anthropic.ModelClaudeOpus5_5,
331333 MaxTokens: 1024,
332334 Speed: anthropic.BetaMessageNewParamsSpeedFast,
333335 Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaFastMode2026_02_01},
from line 347
345347 AnthropicClient client = AnthropicOkHttpClient.fromEnv();
346348
347349 MessageCreateParams params = MessageCreateParams.builder()
348 .model(Model.CLAUDE_OPUS_5)
350 .model(Model.CLAUDE_OPUS_5_5)
349351 .maxTokens(1024L)
350352 .speed(MessageCreateParams.Speed.FAST)
351353 .addBeta(AnthropicBeta.FAST_MODE_2026_02_01)
from line 362
360362 $client = new Client();
361363
362364 $response = $client->beta->messages->create(
363 model: 'claude-opus-5',
365 model: 'claude-opus-5-5',
364366 maxTokens: 1024,
365367 speed: 'fast',
366368 betas: ['fast-mode-2026-02-01'],
from line 376
374376 client = Anthropic::Client.new
375377
376378 response = client.beta.messages.create(
377 model: "claude-opus-5",
379 model: "claude-opus-5-5",
378380 max_tokens: 1024,
379381 speed: "fast",
380382 betas: ["fast-mode-2026-02-01"],
from line 454
452454
453455 MESSAGE=$(
454456 create_message_with_fast_fallback fast <<'YAML'
455 model: claude-opus-5
457 model: claude-opus-5-5
456458 max_tokens: 1024
457459 messages:
458460 - role: user
from line 491
489491
490492
491493 message = create_message_with_fast_fallback(
492 model="claude-opus-5",
494 model="claude-opus-5-5",
493495 max_tokens=1024,
494496 messages=[{"role": "user", "content": "Hello"}],
495497 betas=["fast-mode-2026-02-01"],
from line 529
527529
528530 const message = await createMessageWithFastFallback(
529531 {
530 model: "claude-opus-5",
532 model: "claude-opus-5-5",
531533 max_tokens: 1024,
532534 messages: [{ role: "user", content: "Hello" }],
533535 betas: ["fast-mode-2026-02-01"],
from line 577
575577 var message = await CreateMessageWithFastFallback(
576578 new MessageCreateParams
577579 {
578 Model = "claude-opus-5",
580 Model = "claude-opus-5-5",
579581 MaxTokens = 1024,
580582 Messages = [new() { Role = Role.User, Content = "Hello" }],
581583 Betas = ["fast-mode-2026-02-01"],
from line 617
615617 context.TODO(),
616618 &client,
617619 anthropic.BetaMessageNewParams{
618 Model: anthropic.ModelClaudeOpus5,
620 Model: anthropic.ModelClaudeOpus5_5,
619621 MaxTokens: 1024,
620622 Messages: []anthropic.BetaMessageParam{
621623 anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello")),
from line 666
664666 void main() {
665667 BetaMessage message = createMessageWithFastFallback(
666668 MessageCreateParams.builder()
667 .model(Model.CLAUDE_OPUS_5)
669 .model(Model.CLAUDE_OPUS_5_5)
668670 .maxTokens(1024L)
669671 .addUserMessage("Hello")
670672 .addBeta(AnthropicBeta.FAST_MODE_2026_02_01)
from line 717
715717 $message = createMessageWithFastFallback(
716718 $client,
717719 [
718 'model' => 'claude-opus-5',
720 'model' => 'claude-opus-5-5',
719721 'maxTokens' => 1024,
720722 'messages' => [['role' => 'user', 'content' => 'Hello']],
721723 'betas' => ['fast-mode-2026-02-01'],
from line 743
741743
742744 message = create_message_with_fast_fallback(
743745 client,
744 model: "claude-opus-5",
746 model: "claude-opus-5-5",
745747 max_tokens: 1024,
746748 messages: [{ role: "user", content: "Hello" }],
747749 betas: ["fast-mode-2026-02-01"],
from line 756
754756## Considerations
755757
756758* **Prompt caching:** Switching between fast and standard speed invalidates the prompt cache. Requests at different speeds do not share cached prefixes.
757* **Supported models:** Fast mode is supported on Claude Opus 5 and Claude Opus 4.8. See [Supported models](https://platform.claude.com/docs/en/build-with-claude/fast-mode#supported-models).
759* **Supported models:** Fast mode is supported on Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8. See [Supported models](https://platform.claude.com/docs/en/build-with-claude/fast-mode#supported-models).
758760* **TTFT:** Fast mode's benefits are focused on output tokens per second (OTPS), not time to first token (TTFT).
759761* **Batch API:** Fast mode is not available with the [Batch API](https://platform.claude.com/docs/en/build-with-claude/batch-processing).
760762* **Priority Tier:** Fast mode is not available with a [Priority Tier](https://platform.claude.com/docs/en/api/service-tiers) commitment.