fix(reliability): preflight inline image decoded size

[seonghobae]

Problem

Closes #165.
Closes #274.

Inline-image validation must reject oversized decoded payloads without materializing the base64 payload, must avoid whole-source regex validation over attacker-controlled oversized input, preserve malformed-source precedence, and fail closed on malformed public byte ceilings rather than silently disabling the resource policy.

Product test-first lineage

• RED bb93115e3059c8fb54fa08ca6e41e500233cee45 established that a valid four-byte raster data URI under maxSizeBytes: 3 must raise Base64SizeError without calling Buffer.from(payload, 'base64').
• RED ad6fb67a3ed56c4509e634d37895699be18f7d0f plus hosted CI 31794000599 / job 94746933626 proved the implementation still ran whole-source regex validation over a 65,536-code-unit valid raster candidate.
• e0a92157263b2ad1627d8ea356072629e6487baf moved decoded-size preflight ahead of the whole-source regex; hosted CI 31794194653 correctly rejected that intermediate attempt at the repository 100% coverage gate.
• fa7c46e4cd27bba89bbac82cab672e9f23b2d151 added the missing coverage.
• Test-only 450847bda35b5950e8521255583afbda2af717d6 captured the semantic regression that malformed oversized payloads must still classify as Base64ImageSourceError before size policy.
• Product repair 7701b9d35efa26284b4e0894b24cf050e3994031 replaced whole-source regex validation with a bounded MIME/prefix recognizer plus incremental canonical-base64 code-unit validation, then derives decoded length from validated source length/padding.

Public byte-limit contract (#274)

Issue #274 was opened against predecessor edcaf2e6afa013990b7e7bc8ce96eb9a32b41520, where the public validator only interpreted maxSizeBytes > 0 and invalid JavaScript numbers could bypass the intended finite byte policy.

RED 08257617c496b639d44be09f1a510f9bffa5ef02. Hosted CI 31591393025 passed immutable install/typecheck, Office Python 3.11–3.14, and cross-engine clipboard evidence, then failed exactly at repository Test with 100% coverage for the malformed public-byte-limit regressions. Security/SAST on that immediately superseded test-only generation were cancelled and remain historical non-passing evidence.

GREEN 1c0b2546ce5d8ec152286e392b5d3d7c958c9a25 and descendants. assertValidInlineImageByteLimit() accepts only non-negative safe integers, preserving 0 as the documented size-limit disable value. NaN, negatives, fractional values, infinities, and unsafe integers fail closed with one payload-redacted RangeError before source-size comparison. The strict raster grammar, decoded-size derivation without base64 allocation, and Base64SizeError behavior for valid ceilings remain unchanged.

Later commits on this long-lived branch included privacy/data-integrity hardening and temporary release-control parity work. Those commits are ancestry only after synchronization; the current effective delta no longer carries release workflow/docs changes.

Protected-main synchronization and current scope

Protected shipped truth is independently resolved as main@3b38ead2d00f44eb578d0689087b9293b3dabe1e. Current exact Draft head is f0e1a2e641d5372b4e333361ee015593caeb7cc9 on fix/inline-image-size-preflight-20260811, a non-destructive synchronization commit whose first parent is predecessor 6f17bc31c84b6522ee709d4cce076a3e9b270002 and whose second parent is exact protected main.

Fresh exact comparison resolves protected main as the merge base and reports ahead_by=24, behind_by=0. Despite the long branch history, the effective current diff is exactly two Inkspan-owned product/test paths:

• src/policy/inlineImagePolicy.ts;
• src/policy/inlineImagePolicyPreflight.test.ts.

Protected-main release workflow, release-contract tests, release-security documentation, and exact-checkout fixes are inherited from protected main and are not changed by this PR. No force push or destructive rebase is represented by the synchronization.

Exact-current-head evidence

For unchanged exact head f0e1a2e641d5372b4e333361ee015593caeb7cc9:

• CI 32073713863: completed / success;
• Security Scan 32073713918: completed / success;
• SAST Semgrep 32073713735: completed / success;
• formal submitted reviews: 0;
• unresolved inline review threads: 0;
• GitHub reports the Draft mergeable.

These exact-head repository results are technical evidence only. They do not establish separately applicable central required workflows or qualifying independent approval. No predecessor-head, status-only, model-only, skipped, absent, cancelled, queued, or stale result transfers lifecycle authority to this head.

Product and integration boundary

The current diff adds no transport, persistence, credential, model, tenant, deployment, durable-audit, or release-publication authority. Inkspan owns deterministic local inline-image validation only; hosts retain their established service/runtime authorities.

Keep this PR Draft and unmerged while #118 owns exact protected v0.6.0 tag/publication/provenance/registry-digest operational acceptance. Live governance, required workflow identities, review requirements and permissions must be independently refetched before any lifecycle action. Do not self-approve, transfer predecessor evidence, weaken gates, or substitute a branch ref for release identity.

[coderabbitai]

Important

Draft PR not reviewed

Draft PRs are not automatically reviewed by default.

• Trigger a manual review

To automatically review draft PRs, update your CodeRabbit configuration:

reviews:
  auto_review:
    drafts: true

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[seonghobae]

Exact-head local validation for 8f0d1f7: inline-image decoded-size preflight and the related Base64Image MIME/source contracts passed in a detached worktree, 4/4 files and 82/82 tests. This is focused local evidence only; the PR remains Draft and this is not approval or merge evidence.

[seonghobae]

Restacked the inline-image decoded-size preflight onto exact main@a40b9489665bed7d95af619a6079b9c51cab299a and propagated the event-specific Python matrix contract. Exact head: f5d08bcb0959ed2d772b4a7b3f983f6b340052bb. Fresh local proof: focused inline-image policy suite 4 files / 100 tests; TypeScript typecheck; full Vitest 157 files / 898 tests with 100% statements, branches, functions, and lines; production build; all packed package consumers; Python support contract 4/4. The shared validator remains the single enforcement point. Draft and independent-approval gates remain unchanged.

[seonghobae]

@codex review

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.
To continue using code reviews, add credits to your account and enable them for code reviews in your settings.