[pacocartones]

Summary

• Some Cloudflare Workers AI models stream a digit as a JSON number in choices[].delta.content ({"delta":{"content":7}}) instead of a string. The OpenAI passthrough only counted string content as text, so those chunks were dropped and the digits vanished from the reply: A B 7 . 1 . 9 came out as AB...
• Root cause: hasValuableContent and the stream collectors check typeof content === "string", so a chunk whose only content is a number is discarded (stream.ts continues when the chunk has no valuable content). normalizeArrayContentDelta already folds non-string delta.content (Mistral part arrays) into a string for every stream path; it now also turns a finite number into its decimal string.

Related Issues

• Closes fix(providers): Cloudflare numeric SSE content loses digits #16554

Target Branch

• Base is the active release/v3.8.x branch (the highest open release/v*), not main

Proof Of Fix (required)

• TDD (preferred) — a test that fails before the fix and passes after it.
  • Test file(s): tests/unit/openai-numeric-delta-content.test.ts
  • Failing output before the fix:

    passthrough keeps numeric delta.content as string text
      actual:   'AB..'
      expected: 'AB7.1.90'
    normalizeArrayContentDelta turns a finite number into its decimal string
      actual: false
    

Tests Added Or Updated

• tests/unit/openai-numeric-delta-content.test.ts: (1) a stream through createSSEStream in passthrough mode with string and numeric deltas, including a 0, concatenates to AB7.1.90 and every forwarded content is a string; (2) normalizeArrayContentDelta converts 7 and 0, leaves NaN and plain strings alone.

Coverage Notes

• Covers the shared normalizer and the passthrough path (mode: "passthrough", OpenAI client format). The Responses translator and the other stream modes call the same normalizer; they have no dedicated test for numeric content.

Scope

• Only the files the failing test proves need changing are touched (open-sse/utils/arrayContentDelta.ts, the test and the changelog fragment)
• No test was weakened or deleted to make the suite pass

Validation

• Change type: other (SSE passthrough)
• Focused tests and category gates from the golden path: the tests that use createSSEStream, arrayContentDelta or responseSanitizer pass (438); check:ai-attribution and check:changelog-integrity pass; eslint is clean on the touched files
• npm run lint (the repository-wide run is left to CI). check:file-size reports the same five violations on the base and on this branch; none of those files is touched here.

Reviewer Notes

• Limitation: a number cannot carry what the provider already lost before serialising it. 7.10 arrives as the JSON number 7.1, and leading zeros disappear in the same way, so a numeric chunk is recovered as the digits the number holds, not as the text the model produced. Cloudflare should emit strings; this only stops OmniRoute from discarding the chunk. The upstream report is Workers AI OpenAI-compatible streaming: delta.content sometimes arrives as a JSON number instead of a string cloudflare/ai#651.
• Only finite numbers are converted; NaN and Infinity (not valid JSON anyway) are left as they were.