PR #73005: Fix: Issue 72905 cloudflare ai gateway prefill

• Repository: openclaw/openclaw
• Author: sahilsatralkar
• State: closed | merged: False
• Link: https://github.com/openclaw/openclaw/pull/73005

Description (problem / solution / changelog)

Summary

Describe the problem and fix in 2–5 bullets:

If this PR fixes a plugin beta-release blocker, title it fix(<plugin-id>): beta blocker - <summary> and link the matching Beta blocker: <plugin-name> - <summary> issue labeled beta-blocker. Contributors cannot label PRs, so the title is the PR-side signal for maintainers and automation.

• Problem: Cloudflare AI Gateway requests using Anthropic Messages could fail when extended thinking was enabled because OpenClaw preserved trailing assistant prefill turns that Anthropic rejects for thinking requests.
• Why it matters: Claude requests routed through Cloudflare AI Gateway could fail even though the native Anthropic provider already handled this payload rule.
• What changed: Added Cloudflare AI Gateway stream wrapping for Anthropic-style thinking payloads, extracted the shared prefill-stripping helper into the plugin SDK, added focused tests, updated changelog, and refreshed the SDK API baseline.
• What did NOT change (scope boundary): No provider auth, model catalog, gateway routing, non-Anthropic payload behavior, or Cloudflare AI Gateway network behavior changed.

Change Type (select all)

• Bug fix
• Feature
• Refactor required for the fix
• Docs
• Security hardening
• Chore/infra

Scope (select all touched areas)

• Gateway / orchestration
• Skills / tool execution
• Auth / tokens
• Memory / storage
• Integrations
• API / contracts
• UI / DX
• CI/CD / infra

Linked Issue/PR

• Closes #72905
• Related #
• This PR fixes a bug or regression

Root Cause (if applicable)

For bug fixes or regressions, explain why this happened, not just what changed. Otherwise write N/A. If the cause is unclear, write Unknown.

• Root cause: The native Anthropic provider stripped trailing assistant prefill messages when thinking was enabled, but the Cloudflare AI Gateway provider did not apply the same Anthropic payload normalization before forwarding the request.
• Missing detection / guardrail: Cloudflare AI Gateway had discovery/registration coverage, but no stream-wrapper coverage for Anthropic thinking payload validation.
• Contributing context (if known): Anthropic rejects thinking-enabled Messages requests when the final assistant turn is text prefill rather than a valid user/tool-use conversation boundary.

Regression Test Plan (if applicable)

For bug fixes or regressions, name the smallest reliable test coverage that should catch this. Otherwise write N/A.

• Coverage level that should have caught this:
  • Unit test
  • Seam / integration test
  • End-to-end test
  • Existing coverage already sufficient
  • Target test or file: extensions/cloudflare-ai-gateway/stream-wrappers.test.ts, extensions/cloudflare-ai-gateway/index.test.ts, src/plugin-sdk/provider-stream-shared.test.ts
  • Scenario the test should lock in: Thinking-enabled Anthropic Messages payloads routed through Cloudflare AI Gateway strip trailing assistant text prefill turns while preserving assistant tool-use turns and non-thinking payloads.
  • Why this is the smallest reliable guardrail: The bug is payload shaping before provider streaming, so unit and provider-registration seam tests cover the failing behavior without needing live Cloudflare or Anthropic credentials.
  • Existing test that already covers this (if any): Native Anthropic wrapper behavior had related coverage, but Cloudflare AI Gateway did not.
  • If no new test is added, why not: N/A

User-visible / Behavior Changes

Cloudflare AI Gateway users sending Claude requests with thinking enabled should no longer hit Anthropic conversation-ending validation failures caused by trailing assistant text prefill turns.

Diagram (if applicable)

For UI changes or non-trivial logic flows, include a small ASCII diagram reviewers can scan quickly. Otherwise write N/A.

  Before:
  OpenClaw Claude request with thinking -> Cloudflare AI Gateway -> Anthropic rejects trailing assistant prefill

  After:
  OpenClaw Claude request with thinking -> strip trailing assistant text prefill -> Cloudflare AI Gateway -> Anthropic-compatible payload

Security Impact (required)

• New permissions/capabilities? (Yes/No): No
• Secrets/tokens handling changed? (Yes/No): No
• New/changed network calls? (Yes/No): No
• Command/tool execution surface changed? (Yes/No): No
• Data access scope changed? (Yes/No): No
• If any Yes, explain risk + mitigation: N/A

Repro + Verification

Environment

• OS: macOS
• Runtime/container: Node 22 / pnpm
• Model/provider: Anthropic Messages via Cloudflare AI Gateway
• Integration/channel (if any): Cloudflare AI Gateway plugin
• Relevant config (redacted): Thinking-enabled Anthropic Messages payload with trailing assistant text prefill

Steps

1. Configure a Claude request through Cloudflare AI Gateway with thinking enabled.
2. Include one or more trailing assistant text prefill messages in the Anthropic Messages payload.
3. Send the request through the Cloudflare AI Gateway provider stream wrapper.

Expected

• The trailing assistant text prefill turns are removed before the request is sent.
• Assistant tool-use turns are preserved.
• Payloads without thinking enabled are unchanged.

Actual

• Before this fix, Cloudflare AI Gateway forwarded the trailing assistant text prefill turns and Anthropic rejected the request.
• After this fix, the Cloudflare AI Gateway wrapper applies the same Anthropic thinking prefill normalization as the native Anthropic provider.

Evidence

Attach at least one:

• Failing test/log before + passing after

• Trace/log snippets

• Screenshot/recording

• Perf numbers (if relevant)

  pnpm test src/plugin-sdk/provider-stream-shared.test.ts extensions/anthropic/stream-wrappers.test.ts extensions/cloudflare-ai-gateway pnpm check:changed pnpm build pnpm plugin-sdk:api:check git diff --check codex review --base origin/main

  Final Codex review result: no correctness issues found.

Human Verification (required)

What you personally verified (not just CI), and how:

• Verified scenarios: Cloudflare AI Gateway strips trailing assistant text prefill when thinking is enabled; multiple trailing assistant prefill turns are stripped; assistant tool-use turns are preserved; non-thinking payloads are unchanged; plugin registration wires the wrapper.
• Edge cases checked: payload without a messages array, OpenAI-shaped tool-use fields, Anthropic content-block tool-use fields, shared helper compatibility with the native Anthropic provider.
• What you did not verify: Live Cloudflare AI Gateway or Anthropic network request with real credentials.

Review Conversations

• I replied to or resolved every bot review conversation I addressed in this PR.
• I left unresolved only the conversations that still need reviewer or maintainer judgment.

If a bot review conversation is addressed by this PR, resolve that conversation yourself. Do not leave bot review conversation cleanup for maintainers.

Compatibility / Migration

• Backward compatible? (Yes/No): Yes
• Config/env changes? (Yes/No): No
• Migration needed? (Yes/No): No
• If yes, exact upgrade steps: N/A

Risks and Mitigations

List only real risks for this PR. Add/remove entries as needed. If none, write None.

• Risk: Shared helper behavior could accidentally diverge from the native Anthropic provider’s previous local implementation.
  • Mitigation: Preserved the native Anthropic wrapper callback behavior and added shared-helper tests covering Anthropic and OpenAI-shaped tool-use turns, plus reran Anthropic wrapper tests.

Built with Codex

Changed files

• CHANGELOG.md (modified, +1/-0)
• extensions/anthropic/stream-wrappers.ts (modified, +11/-56)
• extensions/cloudflare-ai-gateway/index.test.ts (added, +46/-0)
• extensions/cloudflare-ai-gateway/index.ts (modified, +3/-0)
• extensions/cloudflare-ai-gateway/stream-wrappers.test.ts (added, +110/-0)
• extensions/cloudflare-ai-gateway/stream-wrappers.ts (added, +15/-0)
• src/plugin-sdk/provider-stream-shared.test.ts (modified, +55/-0)
• src/plugin-sdk/provider-stream-shared.ts (modified, +62/-0)