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9router/open-sse/translator/concerns/eosStrip.js
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// EOS sentinel strip for translated streaming text.
//
// Some upstream executors/providers (observed: opencode/big-pickle behind a
// claude transport) append their special end-of-stream token verbatim to the
// final text delta — e.g. "OK<|im_end|>" — because the tokenizer emits it and
// the executor's OpenAI-compatible decoder passes it through as content. An
// Anthropic client receiving such a delta renders the literal marker in the
// transcript (and a strict schema check flags the unknown character run).
// Stripping is safe: these tokens only ever appear exactly once, as a suffix
// of the final chunk, and never carry meaning in a translated stream.
const EOS_SENTINELS = [
"<|im_end|>",
"<|endoftext|>",
"<|eot_id|>",
"<|end|>",
];
/** Remove a trailing EOS sentinel from streaming text (suffix-only, once). */
export function stripEosSentinel(text) {
if (!text || typeof text !== "string") return text;
for (const sentinel of EOS_SENTINELS) {
if (text.endsWith(sentinel)) {
return text.slice(0, -sentinel.length);
}
}
// Some providers emit it mid-chunk boundary (sentinel split across two
// deltas) — strip any occurrence, since these tokens have no legitimate
// place in model output.
const hasAny = EOS_SENTINELS.find((s) => text.includes(s));
if (hasAny) return text.split(hasAny).join("");
return text;
}