migration-guide changedmodels/opus-5-5/migration-guide
Nearest release: v2.1.318, published 4 hours before this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
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Lines−12removed
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37
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First seen
23 Sep 2026
this site's first read of the page
Recorded edits28to this page, all time
The whole hunk
from line 37, old and new numbered
/
from line 37
3737 ```bash cURL
3838 curl https://api.anthropic.com/v1/messages \
3939 -H "x-api-key: $ANTHROPIC_API_KEY" \
40 -H "anthropic-version: 2023-06-01" \
40 -H "anthropic-version: 2026-10-21" \
4141 -H "content-type: application/json" \
4242 -d '{
4343 "model": "claude-opus-5-5",
from line 334
334334* Handle the `refusal` stop reason.
335335* Handle the `model_context_window_exceeded` stop reason.
336336* Verify tool string parameter handling for trailing newlines.
337* Remove legacy beta headers (`token-efficient-tools-2025-02-19`, `output-128k-2025-02-19`).
337* Remove the `token-efficient-tools-2025-02-19` and `output-128k-2025-02-19` beta headers.
338338* Review and update prompts following [prompting best practices](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/claude-prompting-best-practices).
339339
340340### Claude Sonnet 5 only
from line 369
369369 ```bash cURL
370370 curl https://api.anthropic.com/v1/messages \
371371 -H "x-api-key: $ANTHROPIC_API_KEY" \
372 -H "anthropic-version: 2023-06-01" \
372 -H "anthropic-version: 2026-10-21" \
373373 -H "content-type: application/json" \
374374 -d '{
375375 "model": "claude-opus-5",
from line 465
465465 # thinking is always on; effort is the control
466466 curl https://api.anthropic.com/v1/messages \
467467 -H "x-api-key: $ANTHROPIC_API_KEY" \
468 -H "anthropic-version: 2023-06-01" \
468 -H "anthropic-version: 2026-10-21" \
469469 -H "content-type: application/json" \
470470 -d '{
471471 "model": "claude-opus-5-5",
from line 570
570570 ```bash cURL
571571 curl https://api.anthropic.com/v1/messages \
572572 -H "x-api-key: $ANTHROPIC_API_KEY" \
573 -H "anthropic-version: 2023-06-01" \
573 -H "anthropic-version: 2026-10-21" \
574574 -H "content-type: application/json" \
575575 -d '{
576576 "model": "claude-opus-5",
from line 702
702702 # strict tool use: every call matches the tool's input_schema
703703 curl https://api.anthropic.com/v1/messages \
704704 -H "x-api-key: $ANTHROPIC_API_KEY" \
705 -H "anthropic-version: 2023-06-01" \
705 -H "anthropic-version: 2026-10-21" \
706706 -H "content-type: application/json" \
707707 -d '{
708708 "model": "claude-opus-5-5",
from line 890
890890 ```bash cURL
891891 curl https://api.anthropic.com/v1/messages \
892892 -H "x-api-key: $ANTHROPIC_API_KEY" \
893 -H "anthropic-version: 2023-06-01" \
893 -H "anthropic-version: 2026-10-21" \
894894 -H "anthropic-beta: computer-use-2025-11-24" \
895895 -H "content-type: application/json" \
896896 -d '{
from line 1043
10431043 # no beta header; the toolset entry takes no name or display size
10441044 curl https://api.anthropic.com/v1/messages \
10451045 -H "x-api-key: $ANTHROPIC_API_KEY" \
1046 -H "anthropic-version: 2023-06-01" \
1046 -H "anthropic-version: 2026-10-21" \
10471047 -H "content-type: application/json" \
10481048 -d '{
10491049 "model": "claude-opus-5-5",
from line 1178
11781178
117911791. **Consider task budgets (beta):** For agentic workloads, [task budgets](https://platform.claude.com/docs/en/build-with-claude/task-budgets) tell the model how many tokens it has for a full agentic loop. They require the `task-budgets-2026-03-13` beta header.
11801180
11812. **Consider mid-conversation tool changes (beta):** Mid-conversation tool changes let you add or remove tools between turns of a conversation without invalidating [prompt cache](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) hits on earlier turns. Changing the `tools` array itself invalidates the cached prefix. On the Claude API, Claude Platform on AWS, and Claude Models on Google Cloud (Anthropic managed), send the `inline-tools-2026-09-15` beta header. The older `mid-conversation-tool-changes-2026-07-01` header still works for changes that name a tool by reference, on the Claude API, Amazon Bedrock, Claude Platform on AWS, Claude Models on Google Cloud (Anthropic managed), and Claude Models on Google Cloud (Google managed).
11812. **Consider mid-conversation tool changes (beta):** Mid-conversation tool changes let you add or remove tools between turns of a conversation without invalidating [prompt cache](https://platform.claude.com/docs/en/build-with-claude/prompt-caching) hits on earlier turns. Changing the `tools` array itself invalidates the cached prefix. On the Claude API, Claude Platform on AWS, and Claude Models on Google Cloud (Anthropic managed), send the `inline-tools-2026-09-15` beta header. The `mid-conversation-tool-changes-2026-07-01` header works for changes that name a tool by reference, on the Claude API, Amazon Bedrock, Claude Platform on AWS, Claude Models on Google Cloud (Anthropic managed), and Claude Models on Google Cloud (Google managed).
11821182
11831183## Migrating to Claude Opus 5.5 from Claude Opus 4.7
11841184
from line 1218
12181218 ```bash cURL
12191219 curl https://api.anthropic.com/v1/messages \
12201220 -H "x-api-key: $ANTHROPIC_API_KEY" \
1221 -H "anthropic-version: 2023-06-01" \
1221 -H "anthropic-version: 2026-10-21" \
12221222 -H "content-type: application/json" \
12231223 -d '{
12241224 "model": "claude-opus-4-6",
from line 1350
13501350 ```bash cURL
13511351 curl https://api.anthropic.com/v1/messages \
13521352 -H "x-api-key: $ANTHROPIC_API_KEY" \
1353 -H "anthropic-version: 2023-06-01" \
1353 -H "anthropic-version: 2026-10-21" \
13541354 -H "content-type: application/json" \
13551355 -d '{
13561356 "model": "claude-opus-5-5",
from line 1773
17731773
17741774#### Additional recommended changes
17751775
1776* **Remove legacy beta headers:** Remove `token-efficient-tools-2025-02-19` and `output-128k-2025-02-19`. All Claude 4 and later models have built-in token-efficient tool use and these headers have no effect.
1776* **Beta headers:** Remove `token-efficient-tools-2025-02-19` and `output-128k-2025-02-19`. All Claude 4 and later models have built-in token-efficient tool use and these headers have no effect.
17771777
17781778## Migrating to Claude Opus 5.5 from Claude Sonnet 5
17791779
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