Review of PR #615 — fix(docs): unbreak published Fern site

Summary

Two targeted fixes to unbreak the hosted Fern site:

1. fern/scripts/ipynb-to-fern-json.py — adds shrink_inline_b64_in_html() so inline data:image/...;base64,... URIs embedded in IPython.display.HTML outputs are funnelled through the existing shrink_image_b64 pipeline, instead of slipping past the image/png MIME branch and landing in the .ts bundle at full resolution.
2. fern/versions/v0.5.8/pages/concepts/agent-rollout-ingestion.mdx — converts five leftover PyMdown === "Title" tab blocks to Fern <Tabs>/<Tab> JSX (missed during the MkDocs→Fern migration in docs: migrate documentation from MkDocs to Fern #581).
3. fern/components/notebooks/{5,6}-*.{ts,json} — regenerated artifacts showing the payload drop (1.8 MB → 423 KB, 4.6 MB → 1.3 MB).

Scope is narrow and matches the stated root cause. No runtime code paths are touched.

Findings

fern/scripts/ipynb-to-fern-json.py

• Correctness — regex terminators look right. INLINE_DATA_URI_RE uses a non-greedy [A-Za-z0-9+/=\s]+? for the payload with a lookahead (?=[\"'\s)]). That covers the three realistic contexts (HTML attribute quotes, whitespace, CSS url(...)). Because base64 alphabet is A-Za-z0-9+/=, none of the terminator characters can appear inside the payload, so the non-greedy match won't prematurely stop mid-URI. Good.
• Minor — "idempotent" is slightly overstated (fern/scripts/ipynb-to-fern-json.py:99–108 / summary). shrink_image_b64 unconditionally re-encodes to JPEG q=82 even when max(img.size) <= max_dim. On repeat runs of make generate-fern-notebooks-with-outputs, already-shrunk JPEG inline URIs will match INLINE_DATA_URI_RE again (the regex accepts jpeg) and be decoded + re-encoded, accumulating generational loss. Payload size will stabilize, but visual quality slowly degrades. Cheapest fix: short-circuit in shrink_image_b64 when img.format == "JPEG" and max(img.size) <= max_dim — return the original (b64, "image/jpeg") untouched. Not blocking for this PR; worth a follow-up issue.
• Nit — the lookahead class includes \" but not <. If a future cell emits <img src=data:image/png;base64,AAA...> (unquoted attribute), the URI would be followed by > and the regex would greedily consume until a whitespace/quote/paren boundary is found. Current notebook authors always quote attributes, so this is theoretical. Mentioning only because adding > to the terminator class is zero cost.
• Missing — no unit test for shrink_inline_b64_in_html. The project generally tests new logic, but this is a build script under fern/scripts/ (outside the three installable packages) and there's no existing test harness for it. Consistent with the neighboring code; acceptable.
• Docstring style (fern/scripts/ipynb-to-fern-json.py:90–94). Multi-line docstring here is longer than the STYLEGUIDE one-liner preference, but this matches the existing style of shrink_image_b64 directly above it, which is the right call — consistency with the neighbor wins.

fern/versions/v0.5.8/pages/concepts/agent-rollout-ingestion.mdx

• Content preserved. Spot-checked all five tab titles (Claude Code, Codex, Hermes Agent, Pi Coding Agent, ATIF), intro prose, and code blocks — titles and Python snippets are verbatim. Link to Harbor's ATIF docs preserved.
• Indentation removed is correct for Fern. Old PyMdown syntax required 4-space indented content inside === "Title"; Fern <Tab> children sit at column 0. The diff correctly dedents.
• Consistency check. Compared to other pages using <Tabs> under fern/versions/v0.5.8/ — matches the same JSX pattern. Good.

Notebook bundles (5-*.{ts,json}, 6-*.{ts,json})

• Not reviewed line-by-line — these are generator output. Payload reductions in the PR description (1.8→0.4 MB, 4.6→1.3 MB) are consistent with 800 px JPEG q=82 on Flux outputs.
• PR author confirms non-image cells are unmodified; the regex is scoped to inline data URIs only, so this is believable from the code.

Risks

• Low blast radius. No Python package code touched; change is confined to the fern/ docs pipeline. Cannot regress runtime behavior.
• Forward compatibility. The converter change is backward-compatible — notebooks without inline HTML base64 payloads are unaffected (the regex simply never matches).
• Rollback is trivial — revert the script change; re-run the generator; previous bundles restored.

Suggestions (non-blocking)

1. Short-circuit shrink_image_b64 when the decoded image is already JPEG and within size limits, to make the converter truly idempotent across repeat generator runs.
2. Consider widening the lookahead character class to include > for defense against unquoted HTML attributes in future notebook outputs.
3. Follow-up issue: add a lightweight test for ipynb-to-fern-json.py (golden-file or regex-level) so future refactors don't silently regress.

Verdict

Approve intent. The fix is well-scoped, root-caused, and matches the PR description. The idempotency nit and regex-terminator nit are minor follow-ups, not blockers. Recommend merging once the test-plan boxes for the hosted site render are checked post-merge.

Greptile Summary

This PR fixes a broken Fern hosted docs site caused by two migration leftovers: oversized notebook payloads that crashed Fern's SSR bundler, and leftover MkDocs tab and admonition syntax that Fern's MDX runtime couldn't parse.

• Notebook payload shrinking: shrink_inline_b64_in_html() is added to ipynb-to-fern-json.py so that inline data:image/png;base64,... URIs embedded in IPython.display.HTML outputs are downsampled to 800 px JPEG (q=82) via the existing shrink_image_b64 path; notebooks 5 and 6 are regenerated with the fix applied (1.8 MB → 423 KB, 4.6 MB → 1.3 MB).
• MDX syntax migration: agent-rollout-ingestion.mdx five PyMdown === \"Title\" blocks are converted to <Tabs>/<Tab title=\"...\"> JSX, and default-model-settings.mdx one !!! tip admonition is converted to <Tip>, both now valid Fern MDX.

Important Files Changed

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Notebook cell output] --> B{output_type?}
    B -- display_data / execute_result --> C{MIME key?}
    C -- image/png --> D[shrink_image_b64\n→ JPEG ≤800px]
    C -- text/html --> E[shrink_inline_b64_in_html]
    E --> F{inline data: URIs\nin HTML?}
    F -- yes --> G[INLINE_DATA_URI_RE.sub\n→ shrink_image_b64 per match]
    F -- no --> H[pass-through HTML]
    G --> I[emit type=text, format=html]
    H --> I
    C -- text/plain --> J[emit type=text, format=plain]
    D --> K[emit type=image]
    B -- stream --> L[emit type=text, format=plain]

_{Reviews (2): Last reviewed commit: "Merge branch 'main' into lbliii/fix-fern..." | Re-trigger Greptile}