@halo-sdk/strategies

Pluggable strategies for context management and tool-call repair in Halo AI SDK.

Installation

npm install @halo-sdk/strategies

Requires @halo-sdk/core as a peer dependency.

TruncateStrategy

Automatically truncates MessageLog when approaching the context window limit. Drops discardable messages first (e.g. skill bodies), then oldest messages.

import { Halo } from "@halo-sdk/core";
import { TruncateStrategy } from "@halo-sdk/strategies";

const agent = halo.agent({
  messages: [{ role: "system", content: "You are helpful." }],
  context: new TruncateStrategy({ maxTokens: 102_400 }), // default: 80% of 128K
});

Important: The strategy is read-only on StablePrefix — it only modifies MessageLog. This preserves prefix caching.

BasicRepair

Fixes truncated JSON in tool-call arguments. Counts unbalanced braces/brackets and closes them.

import { BasicRepair } from "@halo-sdk/strategies";

const agent = halo.agent({
  messages: [...],
  repair: new BasicRepair(),
});

When the model's tool-call JSON is cut off mid-generation, BasicRepair tries to salvage it rather than discarding the call.

Custom Strategies

Implement ContextStrategy or RepairStrategy from @halo-sdk/core for custom behavior:

import type { ContextStrategy, ChatMessage } from "@halo-sdk/core";

class MyStrategy implements ContextStrategy {
  prepare(prefix: ChatMessage[], history: ChatMessage[], ctxMax: number) {
    return { history, modified: false, droppedCount: 0 };
  }
}

Documentation

See the Halo SDK docs for full API reference.