Fix broken ICO + restore animation for WebP and APNG sources

[adityaverm-a]

Summary

Three production bugs reported on image-transformation.punchh.io come down to two root causes — both in image-processor / origin-fetcher. Two commits.

Root causes:

1. origin-fetcher.ts whitelists eight image MIME types in isValidImageContentType(); image/x-icon is absent. When origin sends that type the fetcher returns HTTP 415, more commonly S3 serves .ico with a generic content-type, the bytes pass through, Sharp has no ICO decoder, and ErrorMapper.mapError() falls through to a default ImageProcessingError(500, 'ProcessingFailure', ...) — the 500 we see in production.
2. image-processor.service.ts was instantiating Sharp with animated: true only when source content-type was image/gif. Animated WebP (ANIM chunk) and APNG (acTL chunk) were read single-frame, so animation was silently stripped on first encode. Side effect: the Q50 animated-WebP cap added in the optimization sweep (#2, commit 52bfe6d) never fired on real WebP sources because metadata.pages was always 1.

Fixes:

4a7cec5 — BUG-01: serve ICO sources verbatim, bypassing Sharp

ICO is a multi-resolution container, not a single-frame raster. Sharp can't decode it and re-encoding would discard the bundled sizes anyway — serve the source bytes verbatim.

• origin-fetcher.ts: whitelist image/x-icon and image/vnd.microsoft.icon; add ICO magic bytes (00 00 01 00) to validateImageMagicNumbers so content-type/buffer mismatches are still caught.
• image-processor.service.ts: after fetch, if sourceImageContentType is an ICO type, short-circuit the transformation pipeline — set response.contentType to the source type, log an ico_passthrough event, return the buffer unchanged. Same shape as the existing empty-transformations branch.
• auto-optimizer.ts: skip the format optimization for ICO sources so it doesn't appear in transformation logs as if it were applied.

Unblocks: every .ico URL currently 500-ing (e.g. /static/par-favicon.ico, /development/redeemables/.../631addc5537f2622da5e5c13718223267097c82e.ico).

0cdbcba — BUG-02 + BUG-03: preserve animation for WebP and APNG

Broaden isExpectedToBeAnimated:

ANIMATION_CAPABLE_SOURCE_TYPES = new Set(['image/gif', 'image/webp', 'image/png']);

Two implementation subtleties:

1. The metadata probe must be animation-aware. sharp(buf).metadata() without animated: true returns pages: 1 for APNG (the acTL chunk isn't surfaced). The existing pages <= 1 reset would then incorrectly fire and undo the fix. Compute isExpectedToBeAnimated first, then pass it into the metadata probe.

2. The auto-optimizer guard widens alongside. The old sourceIsGif check generalizes to any animation-capable source — when client only accepts a non-animation-capable target (jpeg, etc.) we skip the format conversion so any animation in the source survives. The image-processor verifies multi-frame downstream; static sources still emit the source format unchanged via the same pages <= 1 reset path.

Unblocks: animated WebP at /development/redeemables/.../1e60f883869f60656cbd9868ca16c9f95ff8114a.webp and APNG at /development/subscription_plans/.../83d8b62a7733dec4275e3062c6a24f20a3c1e02a.png. Also activates the dormant Q50 animated-WebP cap from PR #2.

Test plan

• origin-fetcher.test.ts — 19/19 passing (3 new: accepts ICO content-types; ICO magic bytes accepted with both ICO content types; mismatch caught when ICO bytes are labeled as image/png)
• image-processor.service.test.ts — 30/30 passing (3 new for ICO passthrough; 8 new for animation-capable source detection including single-frame WebP/PNG regression coverage)
• auto-optimizer.test.ts — 25/25 passing (2 new for ICO passthrough; 5 new for generalized animation guard covering WebP and PNG; one existing test revised because the non-GIF sources assertion no longer reflects current behavior)
• edit-applicator.test.ts — 27/27 passing (regression check)
• Smoke-test against a real origin: confirm par-favicon.ico returns 200 with Content-Type: image/x-icon; confirm the animated WebP and APNG redeemables animate in browser; confirm a static PNG/WebP still produces output (reset path)
• Post-deploy: watch the new operation: ico_passthrough log line for unexpected volume

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes production issues in the image transformation pipeline by (1) supporting ICO sources safely (bypass Sharp and serve bytes verbatim) and (2) preserving animation for animation-capable source containers (WebP/APNG) by making Sharp metadata probing and instantiation animation-aware and widening auto-optimizer guards accordingly.

Changes:

• Add ICO support in origin fetching (Content-Type allowlist + ICO magic bytes validation) and bypass Sharp processing for ICO in the processor.
• Preserve animation for WebP/APNG by treating image/webp and image/png as animation-capable sources and probing metadata with animated: true.
• Update auto-optimizer to skip format conversion for ICO sources and to conservatively avoid converting animation-capable sources to non-animation-capable targets; expand/adjust tests.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
source/container/src/services/transformation-resolver/auto-optimization/auto-optimizer.ts	Generalizes animation-related format-selection guard and skips format optimization for ICO sources.
source/container/src/services/transformation-resolver/auto-optimization/auto-optimizer.test.ts	Adds/updates tests for generalized animation guard and ICO passthrough behavior.
source/container/src/services/image-processing/origin-fetcher.ts	Accepts ICO Content-Types and validates ICO magic bytes.
source/container/src/services/image-processing/origin-fetcher.test.ts	Adds tests for ICO Content-Type acceptance and ICO magic-number validation/mismatch behavior.
source/container/src/services/image-processing/image-processor.service.ts	Adds ICO passthrough and makes metadata probing/Sharp instantiation animation-aware for WebP/APNG.
source/container/src/services/image-processing/image-processor.service.test.ts	Adds tests for ICO passthrough and broadened animation-capable source detection (incl. single-frame WebP/PNG regression coverage).

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

source/container/src/services/image-processing/origin-fetcher.ts:201

• WebP magic-number validation currently treats any RIFF container (52494646 / "RIFF") as WebP. RIFF is a generic container (e.g. WAV/AVI), so a non-WebP RIFF payload labeled image/webp will incorrectly pass magic-number validation and fail later in Sharp (often as a 500). Consider validating the WebP fourCC at offset 8 ("WEBP") before classifying RIFF as WebP.

    const fileHeader = buffer.subarray(0, 4).toString('hex').toUpperCase();
    let detectedFormat: string | undefined;
    
    for (const [magic, format] of Object.entries(magicToFormat)) {
      if (fileHeader.startsWith(magic)) {

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.