Or, for Claude Mythos 5.1, which offers the same capabilities to verified organizations: changedmodels/fable-5-1/migration-guide
Nearest release: v2.1.307, published 4 hours after this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
Recorded here
Lines+15added
Lines−24removed
From line
182
where the diff opens
First seen
1 Sep 2026
this site's first read of the page
Recorded edits25to this page, all time
The whole hunk
from line 182, old and new numbered
/
from line 182
182182 }),
183183 ],
184184 ToolChoice = new ToolChoiceTool { Name = "record_summary" },
185 Messages = [
186 new() { Role = Role.User, Content = "Summarize: The meeting moved to Thursday." }
187 ]
185 Messages = [new UserMessageParam { Content = "Summarize: The meeting moved to Thursday." }]
188186 };
189187
190188 var message = await client.Messages.Create(parameters);
from line 441
443441 ],
444442 ToolChoice = new ToolChoiceAuto(),
445443 Messages = [
446 new() { Role = Role.User, Content = "Summarize: The meeting moved to Thursday. Call the record_summary tool with your result." }
444 new UserMessageParam { Content = "Summarize: The meeting moved to Thursday. Call the record_summary tool with your result." }
447445 ]
448446 };
449447
from line 744
746744 }),
747745 ],
748746 Messages = [
749 new() { Role = Role.User, Content = "My headphones from order A1234 arrived yesterday." },
750 new() { Role = Role.Assistant, Content = "Thanks for confirming. How can I help with order A1234?" },
751 new() { Role = Role.User, Content = "I opened the box. Can I still return them?" },
747 new UserMessageParam { Content = "My headphones from order A1234 arrived yesterday." },
748 new AssistantMessageParam { Content = "Thanks for confirming. How can I help with order A1234?" },
749 new UserMessageParam { Content = "I opened the box. Can I still return them?" },
752750 // The application requires a help center lookup before any policy
753751 // answer. Appending the requirement as a system message leaves the
754752 // earlier turns unchanged.
755 new()
753 new SystemMessageParam
756754 {
757 Role = Role.System,
758755 Content = "Tool-use requirement for the current turn: the application requires a call to the search_help_center tool in your response to the user's latest message. Begin your response with the search_help_center tool call. Do not reply with text only."
759756 }
760757 ]
from line 832
835832 // The application requires a help center lookup before any policy
836833 // answer. Appending the requirement as a system message leaves the
837834 // earlier turns unchanged.
838 .addMessage(MessageParam.builder()
839 .role(MessageParam.Role.SYSTEM)
840 .content("Tool-use requirement for the current turn: the application requires a call to the search_help_center tool in your response to the user's latest message. Begin your response with the search_help_center tool call. Do not reply with text only.")
841 .build())
835 .addSystemMessage("Tool-use requirement for the current turn: the application requires a call to the search_help_center tool in your response to the user's latest message. Begin your response with the search_help_center tool call. Do not reply with text only.")
842836 .build();
843837
844838 Message response = client.messages().create(params);
from line 1040
10461040 },
10471041 Messages =
10481042 [
1049 new()
1043 new BetaUserMessageParam
10501044 {
1051 Role = Role.User,
10521045 Content = "What is the greatest common divisor of 1071 and 462?",
10531046 },
10541047 ],
from line 1338
13451338 OutputConfig = new() { Effort = Effort.High },
13461339 Messages =
13471340 [
1348 new() { Role = Role.User, Content = "Plan a migration from SQLite to PostgreSQL in three short steps." },
1349 new() { Role = Role.Assistant, Content = "1. Export the SQLite data. 2. Create the PostgreSQL schema. 3. Import the data and verify row counts." },
1341 new BetaUserMessageParam { Content = "Plan a migration from SQLite to PostgreSQL in three short steps." },
1342 new BetaAssistantMessageParam { Content = "1. Export the SQLite data. 2. Create the PostgreSQL schema. 3. Import the data and verify row counts." },
13501343 // Effort-only system message: the new level takes effect from the next user turn.
1351 new()
1344 new BetaSystemMessageParam
13521345 {
1353 Role = Role.System,
13541346 Content = new([]),
13551347 OutputConfig = new() { Effort = BetaSystemMessageOutputConfigEffort.Low },
13561348 },
1357 new() { Role = Role.User, Content = "Summarize the plan in one sentence." },
1349 new BetaUserMessageParam { Content = "Summarize the plan in one sentence." },
13581350 ],
13591351 Betas = [AnthropicBeta.MidConversationOutputConfig2026_07_01],
13601352 });
from line 1397
14051397 ```java Java
14061398 import com.anthropic.models.beta.AnthropicBeta;
14071399 import com.anthropic.models.beta.messages.BetaMessage;
1408 import com.anthropic.models.beta.messages.BetaMessageParam;
14091400 import com.anthropic.models.beta.messages.BetaOutputConfig;
14101401 import com.anthropic.models.beta.messages.BetaSystemMessageOutputConfig;
1402 import com.anthropic.models.beta.messages.BetaSystemMessageParam;
14111403 import com.anthropic.models.beta.messages.MessageCreateParams;
14121404 import com.anthropic.models.messages.Model;
14131405
from line 1416
14241416 .addUserMessage("Plan a migration from SQLite to PostgreSQL in three short steps.")
14251417 .addAssistantMessage("1. Export the SQLite data. 2. Create the PostgreSQL schema. 3. Import the data and verify row counts.")
14261418 // Effort-only system message: the new level takes effect from the next user turn.
1427 .addMessage(BetaMessageParam.builder()
1428 .role(BetaMessageParam.Role.SYSTEM)
1429 .contentOfBetaContentBlockParams(List.of())
1419 .addMessage(BetaSystemMessageParam.builder()
1420 .contentOfBlocks(List.of())
14301421 .outputConfig(BetaSystemMessageOutputConfig.builder()
14311422 .effort(BetaSystemMessageOutputConfig.Effort.LOW)
14321423 .build())
No line in this hunk matches that.