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fix: strip trailing mXXXX</parameter> hallucinations #600

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Merged
Tarquinen merged 1 commit into from
Aug 16, 2026
+10 −1
Merged

fix: strip trailing mXXXX</parameter> hallucinations #600

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4 changes: 3 additions & 1 deletion lib/messages/utils.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ const SUMMARY_ID_HASH_LENGTH = 16
const DCP_BLOCK_ID_TAG_REGEX = /(<dcp-message-id(?=[\s>])[^>]*>)b\d+(<\/dcp-message-id>)/g
const DCP_PAIRED_TAG_REGEX = /<dcp[^>]*>[\s\S]*?<\/dcp[^>]*>/gi
const DCP_UNPAIRED_TAG_REGEX = /<\/?dcp[^>]*>/gi
const HALLUCINATED_PARAMETER_SUFFIX_REGEX = /\nm\d+<\/parameter>\s*$/

const generateStableId = (prefix: string, seed: string): string => {
const hash = createHash("sha256").update(seed).digest("hex").slice(0, SUMMARY_ID_HASH_LENGTH)
Expand Down Expand Up @@ -163,7 +164,8 @@ export const replaceBlockIdsWithBlocked = (text: string): string => {
}

export const stripHallucinationsFromString = (text: string): string => {
return text.replace(DCP_PAIRED_TAG_REGEX, "").replace(DCP_UNPAIRED_TAG_REGEX, "")
const withoutHallucinatedParameter = text.replace(HALLUCINATED_PARAMETER_SUFFIX_REGEX, "")
return withoutHallucinatedParameter.replace(DCP_PAIRED_TAG_REGEX, "").replace(DCP_UNPAIRED_TAG_REGEX, "")
}

export const stripHallucinations = (messages: WithParts[]): void => {
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7 changes: 7 additions & 0 deletions tests/message-priority.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -814,6 +814,13 @@ test("hallucination stripping does not affect non-dcp tags", async () => {
)
})

test("hallucination stripping removes trailing mXXXX</parameter> artifact (issue #555)", () => {
assert.equal(
stripHallucinationsFromString("Total: maybe 20 lines changed.\n\nm0340</parameter>\n\n"),
"Total: maybe 20 lines changed.\n\n",
)
})

test("injectMessageIds skips empty assistant messages to avoid prefill (issue #463)", () => {
const sessionID = "ses_empty_assistant"
const messages: WithParts[] = [
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