fix(provider): scope Anthropic context-1m beta header to 1M models

[Olusammytee]

Summary

• remove unconditional context-1m-2025-08-07 beta from default Anthropic headers
• add model-aware loader logic that only re-adds the 1M beta for Anthropic model IDs containing 1m
• keep all other Anthropic beta headers intact to preserve existing behavior

Fixes #482

[github-actions]

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[kiloconnect]

CRITICAL: This creates a brand-new createAnthropic() SDK using only the raw provider.options, discarding the pre-built sdk parameter (renamed _sdk on line 110). Every other getModel implementation in this file (openai, github-copilot, azure, amazon-bedrock, etc.) uses the passed sdk parameter.

The sdk passed to getModel is built by getSDK() which enriches provider.options with apiKey, baseURL, model-specific headers, and a custom fetch wrapper (with timeout logic, OpenAI ID stripping, etc.). By creating a new SDK here, all of those are lost.

This means Anthropic 1M-context models will likely fail or behave incorrectly because the new SDK won't have the API key, base URL, or timeout handling.

Consider modifying the headers on the existing sdk or restructuring so the beta header is applied at the getSDK level based on the model ID, rather than creating a separate SDK instance.

[kiloconnect]

WARNING: The check modelID.toLowerCase().includes("1m") is fragile. It would match any model ID containing "1m" anywhere (e.g., a hypothetical model like claude-21march or claude-v1mini). Consider a more specific pattern like checking for -1m- or a suffix match to reduce false positives.

[kiloconnect]

Code Review Summary

Status: 2 Issues Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	1
WARNING	1
SUGGESTION	0

Issue Details (click to expand)

CRITICAL

File	Line	Issue
packages/opencode/src/provider/provider.ts	125	New createAnthropic() SDK discards the pre-built sdk (with apiKey, baseURL, fetch wrapper, timeout). Anthropic 1M-context models will likely fail or lose timeout/auth handling.

WARNING

File	Line	Issue
packages/opencode/src/provider/provider.ts	120	modelID.toLowerCase().includes("1m") is a fragile check that could match unintended model IDs

Files Reviewed (1 files)

• packages/opencode/src/provider/provider.ts - 2 issues

Fix these issues in Kilo Cloud

[Copilot]

Pull request overview

This PR fixes a bug where the context-1m-2025-08-07 Anthropic beta header was being sent unconditionally for all Anthropic API requests, causing errors for users on plans without long context access (like Claude Max plan) when using standard 200K context models.

Changes:

• Removed context-1m-2025-08-07 from the default Anthropic beta headers
• Added a custom getModel() function that conditionally includes the 1M context beta header only for models with "1m" in their ID
• Preserved all other Anthropic beta headers (claude-code, interleaved-thinking, fine-grained-tool-streaming)

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