#22893: Add Z.AI image format support

Z.AI uses a different format for images than OpenAI: - OpenAI: { content: [{ type: image_url, image_url: { url: ... } }] } - Z.AI: { content: [...], files: [{ type: image, file: { url: ..., name: ... } }] } This patch adds a streamFn wrapper that transforms OpenAI-style image_url content blocks to Z.AIs files array format at the payload level. The wrapper is automatically applied for zai and z-ai providers. ## Summary Describe the problem and fix in 2–5 bullets: - Problem: - Why it matters: - What changed: - What did NOT change (scope boundary): ## Change Type (select all) - [ ] Bug fix - [ ] Feature - [ ] Refactor - [ ] 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 # - Related # ## User-visible / Behavior Changes List user-visible changes (including defaults/config). If none, write `None`. ## Security Impact (required) - New permissions/capabilities? (`Yes/No`) - Secrets/tokens handling changed? (`Yes/No`) - New/changed network calls? (`Yes/No`) - Command/tool execution surface changed? (`Yes/No`) - Data access scope changed? (`Yes/No`) - If any `Yes`, explain risk + mitigation: ## Repro + Verification ### Environment - OS: - Runtime/container: - Model/provider: - Integration/channel (if any): - Relevant config (redacted): ### Steps 1. 2. 3. ### Expected - ### Actual - ## Evidence Attach at least one: - [ ] Failing test/log before + passing after - [ ] Trace/log snippets - [ ] Screenshot/recording - [ ] Perf numbers (if relevant) ## Human Verification (required) What you personally verified (not just CI), and how: - Verified scenarios: - Edge cases checked: - What you did **not** verify: ## Compatibility / Migration - Backward compatible? (`Yes/No`) - Config/env changes? (`Yes/No`) - Migration needed? (`Yes/No`) - If yes, exact upgrade steps: ## Failure Recovery (if this breaks) - How to disable/revert this change quickly: - Files/config to restore: - Known bad symptoms reviewers should watch for: ## Risks and Mitigations List only real risks for this PR. Add/remove entries as needed. If none, write `None`. - Risk: - Mitigation: <!-- greptile_comment --> <h3>Greptile Summary</h3> This PR adds a `createZaiImageFormatWrapper` function to transform OpenAI-style `image_url` content blocks into Z.AI's `files` array format. The wrapper hooks into the `onPayload` callback to rewrite messages before they're sent to Z.AI, moving image data from inline content blocks to a top-level `files` array on each message. It is applied for `zai` and `z-ai` providers alongside the existing `createZaiToolStreamWrapper`. - Adds image format translation for Z.AI providers, converting `{ type: "image_url", image_url: { url } }` blocks to `{ type: "image", file: { url, name } }` entries in a `files` array - MIME type is extracted from data URIs to generate appropriate file extensions; HTTP URLs default to `image.png` - When all content blocks are images, a fallback empty text block `{ type: "text", text: "" }` is inserted - **Issue found**: `image_url` blocks with a missing/empty URL are silently dropped from the message (neither added to `files` nor preserved in content) - No tests were added for the new wrapper, though the existing Z.AI test file (`extra-params.zai-tool-stream.test.ts`) provides a pattern that could be followed <h3>Confidence Score: 3/5</h3> - Low-risk feature addition scoped to Z.AI providers only, but has a data-loss edge case and no test coverage - The change is well-scoped (only affects zai/z-ai providers) and follows established patterns in the file (onPayload wrapper). However, there's a logic issue where malformed image_url blocks can be silently dropped from messages, and the PR adds no tests despite the existing test infrastructure supporting this pattern. The comment-only change on line 73 is trivial and fine. - `src/agents/pi-embedded-runner/extra-params.ts` — the `createZaiImageFormatWrapper` function has a logic gap around malformed `image_url` blocks _{Last reviewed commit: 8322565} <!-- greptile_other_comments_section --> _{(3/5) Reply to the agent's comments like "Can you suggest a fix for this @greptileai?" or ask follow-up questions!} <!-- /greptile_comment -->