Support adaptive thinking for Claude Opus 4.6

[leeweisern]

Anthropic has deprecated thinking.type: "enabled" with budget_tokens on Opus 4.6 and will remove it in a future release. The recommended replacement is adaptive thinking:

{
  "thinking": { "type": "adaptive" },
  "output_config": { "effort": "high" }
}

Docs: https://platform.claude.com/docs/en/build-with-claude/adaptive-thinking

Currently variants() in transform.ts uses the deprecated config for all Anthropic models, including Opus 4.6:

high: { thinking: { type: "enabled", budgetTokens: ... } },
max:  { thinking: { type: "enabled", budgetTokens: ... } },

A few things to consider:

• Only Opus 4.6 supports adaptive — older models still need type: "enabled"
• effort: "max" is Opus 4.6 exclusive
• maxOutputTokens() assumes a known budgetTokens for the subtraction — adaptive doesn't have one
• Depends on @ai-sdk/anthropic supporting type: "adaptive" upstream

[BouquetAntoine]

OpenCode currently depends on @ai-sdk/anthropic v2.x. Simply bumping the dependency to v3.x and rebuilding isn't enough — there are several breaking changes in the SDK that need to be addressed in the codebase.

Below is a summary of every breaking change identified so far, tried different fixes in my codebase but that's a lot of work.

---

1. finishReason format change

v2.x returns a plain string:

finishReason: "end_turn" | "tool_use" | "stop_sequence" | ...

v3.x returns an object with unified and raw properties:

finishReason: {
  unified: "stop" | "tool-calls" | "error" | "other" | ...
  raw: string | undefined
}

---

2. usage token counts format change

v2.x returns flat numbers:

usage: {
  inputTokens: 1234,
  outputTokens: 567,
  cachedInputTokens: 100,
  reasoningTokens: 200,
}

v3.x returns nested objects:

usage: {
  inputTokens:    { total: 1234, noCache: 1034, cacheRead: 200 },
  outputTokens:   { total: 567, text: undefined },
  reasoningTokens: 200, // may also be an object
}

---

3. New providerOptions schema (thinking / effort)

v2.x supports a limited thinking config:

thinking: {
  type: "enabled" | "disabled",
  budgetTokens?: number,
}
// No "effort" field

v3.x adds an adaptive mode and a new top-level effort field:

thinking: {
  type: "adaptive" | "enabled" | "disabled",
  budgetTokens?: number, // only required when type is "enabled"
}
effort: "low" | "medium" | "high" | "max" // NEW

Fix

Update config schema validation (e.g. Zod schemas or type definitions) to accept the new "adaptive" type and the effort field.

---

Problem is that we probably need to update all ai-sdk to last version for compatibility across models

[avarayr]

I was able to temporarily hack this to work until fix is in place.

Note: this is not a long term solution, just an unblocker until this issue is fixed.

// File: ~/.opencode/plugins/adaptiveThinking.ts
export const adaptiveThinking: import("@opencode-ai/plugin").Plugin =
  async () => ({
      loader: async () => {
        return {
          fetch: async (url: RequestInfo | URL, init?: RequestInit) => {
            const body = init?.body
              ? JSON.parse(init.body as string)
              : undefined;
              
            if (body?.thinking?.budget_tokens === -1) {
              body.thinking = { type: "adaptive" };
              return fetch(url, { ...init, body: JSON.stringify(body) });
            }
            return fetch(url, init);
          },
        };
      },
    },

    // Shim: rewrite adaptive -> enabled with sentinel budget so SDK Zod passes,
    // then the custom fetch above detects budget_tokens:-1 and patches to adaptive.
    "chat.params": async (_input, output) => {
      if (output.options?.thinking?.type === "adaptive") {
        output.options.thinking = { type: "enabled", budgetTokens: -1 };
      }
    },
  });

// File: ~/.config/opencode/opencode.jsonc
{
   "plugin": [
        "file:///Users/<USERNAME>/.opencode/plugin/adaptiveThinking.ts",
    ],
	"provider": {
	        "anthropic": { // <-- replace with your provider of choice
	            "models": {
	                "claude-opus-4-6@20260205": { // might need replacement based on provider
	                    "id": "claude-opus-4-6",
	                    "name": "Claude Opus 4.6",
	                    "family": "claude-opus",
	                    "attachment": true,
	                    "reasoning": true,
	                    "tool_call": true,
	                    "temperature": true,
	                    "knowledge": "2025-05",
	                    "release_date": "2026-02-05",
	                    "last_updated": "2026-02-05",
	                    "modalities": {
	                        "input": [
	                            "text",
	                            "image",
	                            "pdf"
	                        ],
	                        "output": [
	                            "text"
	                        ]
	                    },
	                    "open_weights": false,
	                    "cost": {
	                        "input": 5,
	                        "output": 25,
	                        "cache_read": 0.5,
	                        "cache_write": 6.25,
	                        "context_over_200k": {
	                            "input": 10,
	                            "output": 37.5,
	                            "cache_read": 1,
	                            "cache_write": 12.5
	                        }
	                    },
	                    "limit": {
	                        "context": 200000,
	                        "output": 128000
	                    },
	                    "variants": {
	                        "adaptive": {
	                            "thinking": {
	                                "type": "adaptive" // special case handled by plugin
	                            }
	                        },
	                        "high": {
	                            "thinking": {
	                                "type": "enabled",
	                                "budgetTokens": 16000
	                            }
	                        },
	                        "max": {
	                            "thinking": {
	                                "type": "enabled",
	                                "budgetTokens": 128000
	                            }
	                        }
	                    }
	                }
	            }
	        }
	    },
}

[BouquetAntoine]

#12342 will fix this soon