Or, for the Project Glasswing model with the same capabilities: changedmodels/fable-5-1/migration-guide
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/
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9191 EOF
9292 ```
9393
94 <MultiFileExample language="cli" label="CLI">
95 ```bash CLI
96 ant messages create < request.yaml
97 ```
94 ```bash CLI
95 ant messages create <<'YAML'
96 model: claude-fable-5
97 max_tokens: 16000
98 tools:
99 - name: record_summary
100 description: Record the structured summary of the document.
101 input_schema:
102 type: object
103 properties:
104 summary:
105 type: string
106 required: [summary]
107 tool_choice:
108 type: tool
109 name: record_summary
110 messages:
111 - role: user
112 content: "Summarize: The meeting moved to Thursday."
113 YAML
114 ```
98115
99 <File filename="request.yaml">
100 ```yaml
101 model: claude-fable-5
102 max_tokens: 16000
103 tools:
104 - name: record_summary
105 description: Record the structured summary of the document.
106 input_schema:
107 type: object
108 properties:
109 summary:
110 type: string
111 required: [summary]
112 tool_choice:
113 type: tool
114 name: record_summary
115 messages:
116 - role: user
117 content: "Summarize: The meeting moved to Thursday."
118 ```
119 </File>
120 </MultiFileExample>
121
122116 ```python Python
123117 client = anthropic.Anthropic()
124118
from line 335
341335 EOF
342336 ```
343337
344 <MultiFileExample language="cli" label="CLI">
345 ```bash CLI
346 ant messages create < request.yaml
347 ```
338 ```bash CLI
339 ant messages create <<'YAML'
340 model: claude-fable-5-1
341 max_tokens: 16000
342 tools:
343 - name: record_summary
344 description: Record the structured summary of the document.
345 strict: true
346 input_schema:
347 type: object
348 properties:
349 summary:
350 type: string
351 required: [summary]
352 additionalProperties: false
353 tool_choice:
354 type: auto
355 messages:
356 - role: user
357 content: "Summarize: The meeting moved to Thursday. Call the record_summary tool with your result."
358 YAML
359 ```
348360
349 <File filename="request.yaml">
350 ```yaml
351 model: claude-fable-5-1
352 max_tokens: 16000
353 tools:
354 - name: record_summary
355 description: Record the structured summary of the document.
356 strict: true
357 input_schema:
358 type: object
359 properties:
360 summary:
361 type: string
362 required: [summary]
363 additionalProperties: false
364 tool_choice:
365 type: auto
366 messages:
367 - role: user
368 content: "Summarize: The meeting moved to Thursday. Call the record_summary tool with your result."
369 ```
370 </File>
371 </MultiFileExample>
372
373361 ```python Python
374362 client = anthropic.Anthropic()
375363
from line 613
625613 EOF
626614 ```
627615
628 <MultiFileExample language="cli" label="CLI">
629 ```bash CLI
630 ant messages create < request.yaml
631 ```
616 ```bash CLI
617 ant messages create <<'YAML'
618 model: claude-fable-5-1
619 max_tokens: 16000
620 system: You are a customer support assistant for an online electronics store.
621 tools:
622 - name: search_help_center
623 description: Search the help center for policy and troubleshooting articles.
624 strict: true
625 input_schema:
626 type: object
627 properties:
628 query:
629 type: string
630 required: [query]
631 additionalProperties: false
632 messages:
633 - role: user
634 content: My headphones from order A1234 arrived yesterday.
635 - role: assistant
636 content: Thanks for confirming. How can I help with order A1234?
637 - role: user
638 content: I opened the box. Can I still return them?
639 - role: system
640 content: >-
641 Tool-use requirement for the current turn: the application requires a call
642 to the search_help_center tool in your response to the user's latest message.
643 Begin your response with the search_help_center tool call. Do not reply with
644 text only.
645 YAML
646 ```
632647
633 <File filename="request.yaml">
634 ```yaml
635 model: claude-fable-5-1
636 max_tokens: 16000
637 system: You are a customer support assistant for an online electronics store.
638 tools:
639 - name: search_help_center
640 description: Search the help center for policy and troubleshooting articles.
641 strict: true
642 input_schema:
643 type: object
644 properties:
645 query:
646 type: string
647 required: [query]
648 additionalProperties: false
649 messages:
650 - role: user
651 content: My headphones from order A1234 arrived yesterday.
652 - role: assistant
653 content: Thanks for confirming. How can I help with order A1234?
654 - role: user
655 content: I opened the box. Can I still return them?
656 - role: system
657 content: >-
658 Tool-use requirement for the current turn: the application requires a call
659 to the search_help_center tool in your response to the user's latest message.
660 Begin your response with the search_help_center tool call. Do not reply with
661 text only.
662 ```
663 </File>
664 </MultiFileExample>
665
666648 ```python Python
667649 client = anthropic.Anthropic()
668650
from line 965
983965 }'
984966 ```
985967
986 <MultiFileExample language="cli" label="CLI">
987 ```bash CLI
988 ant beta:messages create \
989 --beta thinking-binding-controls-2026-08-01 \
990 --transform '{content.#(type=="text")#.text,input_transformations}' \
991 --format yaml < request.yaml
992 ```
968 ```bash CLI
969 ant beta:messages create \
970 --beta thinking-binding-controls-2026-08-01 \
971 --transform '{content.#(type=="text")#.text,input_transformations}' \
972 --format yaml <<'YAML'
973 model: claude-fable-5-1
974 max_tokens: 16000
975 thinking:
976 type: adaptive
977 block_binding:
978 prefix_mismatch_behavior: drop_block
979 messages:
980 - role: user
981 content: What is the greatest common divisor of 1071 and 462?
982 YAML
983 ```
993984
994 <File filename="request.yaml">
995 ```yaml
996 model: claude-fable-5-1
997 max_tokens: 16000
998 thinking:
999 type: adaptive
1000 block_binding:
1001 prefix_mismatch_behavior: drop_block
1002 messages:
1003 - role: user
1004 content: What is the greatest common divisor of 1071 and 462?
1005 ```
1006 </File>
1007 </MultiFileExample>
1008
1009985 ```python Python
1010986 client = anthropic.Anthropic()
1011987
from line 1255
12791255 }'
12801256 ```
12811257
1282 <MultiFileExample language="cli" label="CLI">
1283 ```bash CLI
1284 ant beta:messages create \
1285 --beta mid-conversation-output-config-2026-07-01 \
1286 --transform 'content.#(type=="text").text' \
1287 --raw-output < request.yaml
1288 ```
1289
1290 <File filename="request.yaml">
1291 ```yaml
1292 model: claude-fable-5-1
1293 max_tokens: 4096
1258 ```bash CLI
1259 ant beta:messages create \
1260 --beta mid-conversation-output-config-2026-07-01 \
1261 --transform 'content.#(type=="text").text' \
1262 --raw-output <<'YAML'
1263 model: claude-fable-5-1
1264 max_tokens: 4096
1265 output_config:
1266 effort: high
1267 messages:
1268 - role: user
1269 content: Plan a migration from SQLite to PostgreSQL in three short steps.
1270 - role: assistant
1271 content: "1. Export the SQLite data. 2. Create the PostgreSQL schema. 3. Import the data and verify row counts."
1272 # Effort-only system message: the new level takes effect from the next user turn.
1273 - role: system
1274 content: []
12941275 output_config:
1295 effort: high
1296 messages:
1297 - role: user
1298 content: Plan a migration from SQLite to PostgreSQL in three short steps.
1299 - role: assistant
1300 content: "1. Export the SQLite data. 2. Create the PostgreSQL schema. 3. Import the data and verify row counts."
1301 # Effort-only system message: the new level takes effect from the next user turn.
1302 - role: system
1303 content: []
1304 output_config:
1305 effort: low
1306 - role: user
1307 content: Summarize the plan in one sentence.
1308 ```
1309 </File>
1310 </MultiFileExample>
1276 effort: low
1277 - role: user
1278 content: Summarize the plan in one sentence.
1279 YAML
1280 ```
13111281
13121282 ```python Python
13131283 client = anthropic.Anthropic()
from line 1575
16051575
16061576## Migrating to Claude Fable 5.1 from Claude Opus 4.8 or earlier
16071577
1608First apply [Migrating to Claude Mythos 5 and Claude Fable 5 from Claude Opus 4.8](https://platform.claude.com/docs/en/models/fable-5/migration-guide#migrating-from-claude-opus-48) for the API-level changes from Claude Opus 4.8. It covers adaptive thinking, thinking output, refusals, effort, the caching minimum, pricing, and data retention. Then apply the remaining delta in [Migrating to Claude Fable 5.1 from Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5-1/migration-guide#migrating-from-claude-fable-5-to-claude-fable-5-1). On Claude Opus 4.7 or earlier, start with the matching [Migrating to Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/migration-guide) section.
1578First apply [Migrating to Claude Mythos 5 and Claude Fable 5 from Claude Opus 4.8](https://platform.claude.com/docs/en/models/fable-5/migration-guide#migrating-from-claude-opus-48) for the API-level changes from Claude Opus 4.8. It covers adaptive thinking, thinking output, refusals, effort, the caching minimum, pricing, and data retention. Then apply the remaining delta in [Migrating to Claude Fable 5.1 from Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5-1/migration-guide#migrating-from-claude-fable-5-to-claude-fable-5-1). On Claude Opus 4.7 or earlier, start with the matching [Migrating to Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/migration-guide) section.
16091579
16101580### Update your model name
16111581
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