diff --git a/.planning/ROADMAP.md b/.planning/ROADMAP.md
index 8ca65cc..cde808b 100644
--- a/.planning/ROADMAP.md
+++ b/.planning/ROADMAP.md
@@ -122,7 +122,7 @@ Plans:
 | 17. Single Track Edit | v1.2 | 2/2 | Complete | 2026-03-18 |
 | 18. Batch Edit | v1.2 | 2/2 | Complete | 2026-03-18 |
 | 19. WAV Tag Writer | 2/2 | Complete    | 2026-03-19 | - |
-| 20. OGG Vorbis Tag Writer | 2/2 | Complete   | 2026-03-19 | - |
+| 20. OGG Vorbis Tag Writer | 2/2 | Complete    | 2026-03-19 | - |
 | 21. Cleanup | v1.2.1 | 0/? | Not started | - |
 
 ---
diff --git a/.planning/STATE.md b/.planning/STATE.md
index efeda5d..20977de 100644
--- a/.planning/STATE.md
+++ b/.planning/STATE.md
@@ -2,11 +2,11 @@
 gsd_state_version: 1.0
 milestone: v1.0
 milestone_name: milestone
-status: in-progress
-last_updated: "2026-03-19T18:02:38Z"
+status: unknown
+last_updated: "2026-03-19T18:07:52.236Z"
 progress:
-  total_phases: 1
-  completed_phases: 1
+  total_phases: 2
+  completed_phases: 2
   total_plans: 4
   completed_plans: 4
 ---
diff --git a/.planning/phases/20-ogg-vorbis-tag-writer/20-VERIFICATION.md b/.planning/phases/20-ogg-vorbis-tag-writer/20-VERIFICATION.md
new file mode 100644
index 0000000..4f560da
--- /dev/null
+++ b/.planning/phases/20-ogg-vorbis-tag-writer/20-VERIFICATION.md
@@ -0,0 +1,100 @@
+---
+phase: 20-ogg-vorbis-tag-writer
+verified: 2026-03-19T18:15:00Z
+status: passed
+score: 13/13 must-haves verified
+---
+
+# Phase 20: OGG Vorbis Tag Writer Verification Report
+
+**Phase Goal:** Users can edit metadata and cover art on OGG Vorbis files with the same experience as MP3/FLAC/WAV
+**Verified:** 2026-03-19T18:15:00Z
+**Status:** passed
+**Re-verification:** No — initial verification
+
+## Goal Achievement
+
+### Observable Truths
+
+#### Plan 01 Truths
+
+| # | Truth | Status | Evidence |
+|---|-------|--------|----------|
+| 1 | writeOggTags function compiles and is reachable from the pipeline switch | ✓ VERIFIED | `go build ./backend/tagwriter/` passes; pipeline.go:149-150 dispatches `case FormatOGG: err = writeOggTags(...)` |
+| 2 | OGG pages are parsed with lenient CRC and re-serialized with correct MSB-first CRC32 | ✓ VERIFIED | ogg.go:152-158 logs CRC mismatch warnings but continues; TestOggCRC_KnownVectors passes with 3 independent vectors + self-consistency check |
+| 3 | Vorbis Comment fields are preserved byte-for-byte when not edited | ✓ VERIFIED | ogg_vorbis.go uses `[][]byte` for raw entries; TestWriteOggTags_PartialUpdate confirms unchanged fields survive |
+| 4 | Edited fields use uppercase field names and replace all existing entries for that field | ✓ VERIFIED | ogg_vorbis.go:118 uses `strings.ToUpper(field)`, line 122 filters case-insensitively with `bytes.ToUpper` |
+| 5 | Cover art is written as base64-encoded METADATA_BLOCK_PICTURE; legacy COVERART/COVERARTMIME fields are stripped | ✓ VERIFIED | ogg_vorbis.go:244-246 strips all 3 field types; line 256 base64-encodes; TestWriteOggTags_CoverArt and _ClearCoverArt pass |
+| 6 | Multi-stream and non-Vorbis OGG files are rejected with clear error messages | ✓ VERIFIED | ogg.go:189 checks serial count >1 or bosCount >1; ogg.go:195-198 checks `\x01vorbis`; TestWriteOggTags_RejectNonVorbis and _RejectMultiStream pass |
+| 7 | File writes use AtomicWrite for crash safety | ✓ VERIFIED | ogg.go:459 calls `fileutil.AtomicWrite`; TestWriteOggTags_AtomicSafety verifies corrupt files untouched |
+
+#### Plan 02 Truths
+
+| # | Truth | Status | Evidence |
+|---|-------|--------|----------|
+| 8 | All 8 text fields round-trip correctly through writeOggTags and dhowden/tag read-back | ✓ VERIFIED | TestWriteOggTags_TextFields passes — all 9 values (8 fields + composer) verified via metadata.ExtractTags |
+| 9 | Non-edited Vorbis Comment fields survive a partial update | ✓ VERIFIED | TestWriteOggTags_PartialUpdate: writes all fields, updates 2, verifies remaining 7 unchanged |
+| 10 | Audio page data is byte-identical after tag write | ✓ VERIFIED | TestWriteOggTags_AudioPreservation: captures audio bytes before/after, `bytes.Equal` assertion passes |
+| 11 | Cover art can be embedded, replaced, and cleared via METADATA_BLOCK_PICTURE | ✓ VERIFIED | TestWriteOggTags_CoverArt (embed+verify JPEG), TestWriteOggTags_ClearCoverArt (add→verify→clear→verify nil) |
+| 12 | Failed writes leave the original file untouched (atomic safety) | ✓ VERIFIED | TestWriteOggTags_AtomicSafety: corrupt file unchanged after error, valid file unchanged after unrelated failure |
+| 13 | CRC32 implementation produces correct checksums (validated against known vectors) | ✓ VERIFIED | TestOggCRC_KnownVectors: empty→0x0, "OggS"→0x5fb0a94f, {1..8}→0x7d0f3681, plus fixture page self-consistency |
+
+**Score:** 13/13 truths verified
+
+### Required Artifacts
+
+| Artifact | Expected | Status | Details |
+|----------|----------|--------|---------|
+| `backend/tagwriter/ogg.go` | OGG page parser/writer, CRC32, writeOggTags (min 200 lines) | ✓ VERIFIED | 575 lines; CRC table, page parser/writer, packet extraction/splitting, writeOggTags pipeline, AtomicWrite |
+| `backend/tagwriter/ogg_vorbis.go` | Vorbis Comment parse/serialize, field manipulation, cover art (min 100 lines) | ✓ VERIFIED | 259 lines; parseVorbisCommentPacket, serializeVorbisCommentPacket, replaceField, removeField, buildMetadataBlockPicture, applyOggCoverArt |
+| `backend/tagwriter/tagwriter.go` | FormatOGG constant and .ogg case in DetectFormat | ✓ VERIFIED | Line 42: `FormatOGG AudioFormat = "ogg"`, lines 59-60: `case ".ogg": return FormatOGG, nil` |
+| `backend/tagwriter/pipeline.go` | case FormatOGG dispatch to writeOggTags | ✓ VERIFIED | Lines 149-150: `case FormatOGG: err = writeOggTags(tw.logger, audioFile.FilePath, changes)` |
+| `backend/tagwriter/ogg_test.go` | Round-trip tests, CRC validation, fixture builder (min 300 lines) | ✓ VERIFIED | 659 lines; 10 test functions, programmatic OGG fixture builder, 3 CRC known vectors + self-consistency |
+
+### Key Link Verification
+
+| From | To | Via | Status | Details |
+|------|----|-----|--------|---------|
+| pipeline.go | ogg.go | `case FormatOGG` → `writeOggTags` | ✓ WIRED | pipeline.go:149-150 dispatches to writeOggTags |
+| ogg.go | ogg_vorbis.go | `parseVorbisCommentPacket` / `serializeVorbisCommentPacket` | ✓ WIRED | ogg.go:417 calls parseVorbisCommentPacket, ogg.go:429 calls serializeVorbisCommentPacket |
+| ogg.go | fileutil/atomicwrite.go | `fileutil.AtomicWrite` | ✓ WIRED | ogg.go:459 calls fileutil.AtomicWrite(logger, filePath, func...) |
+| ogg_test.go | ogg.go | `writeOggTags`, `parseOggPages`, `oggCRC` | ✓ WIRED | 27 references across all test functions |
+| ogg_test.go | metadata/tags.go | `metadata.ExtractTags` for read-back | ✓ WIRED | 10 references for dhowden/tag read-back verification |
+
+### Requirements Coverage
+
+| Requirement | Source Plan | Description | Status | Evidence |
+|-------------|------------|-------------|--------|----------|
+| OGG-01 | 20-01, 20-02 | Edit all 8 text metadata fields on OGG Vorbis | ✓ SATISFIED | ogg_vorbis.go field mappings (lines 148-162), TestWriteOggTags_TextFields passes with all 9 values verified |
+| OGG-02 | 20-01, 20-02 | Preserve non-edited Vorbis Comment fields | ✓ SATISFIED | Raw byte preservation ([][]byte entries), TestWriteOggTags_PartialUpdate verifies 7 unchanged fields |
+| OGG-03 | 20-01, 20-02 | Preserve audio data identically (lossless round-trip) | ✓ SATISFIED | Audio pages copied byte-for-byte (ogg.go:451), TestWriteOggTags_AudioPreservation compares bytes |
+| OGG-04 | 20-01, 20-02 | Embed, replace, remove cover art via METADATA_BLOCK_PICTURE | ✓ SATISFIED | buildMetadataBlockPicture + base64 + legacy stripping, TestWriteOggTags_CoverArt and _ClearCoverArt pass |
+| OGG-05 | 20-01, 20-02 | Crash-safe atomic writes | ✓ SATISFIED | fileutil.AtomicWrite at ogg.go:459, TestWriteOggTags_AtomicSafety verifies file integrity on failure |
+| OGG-06 | 20-02 | Round-trip tests verify via dhowden/tag read-back | ✓ SATISFIED | All 7 TestWriteOggTags_* functions use metadata.ExtractTags (dhowden/tag); 10 read-back call sites |
+
+**No orphaned requirements.** All 6 OGG requirements (OGG-01 through OGG-06) are mapped in REQUIREMENTS.md to Phase 20 and accounted for in plan frontmatters.
+
+### Anti-Patterns Found
+
+| File | Line | Pattern | Severity | Impact |
+|------|------|---------|----------|--------|
+| — | — | None found | — | — |
+
+No TODOs, FIXMEs, placeholders, stub implementations, or console.log patterns found in any OGG files.
+
+### Human Verification Required
+
+None. All phase requirements are verifiable through automated build, vet, and test checks. The round-trip tests use dhowden/tag as an independent reader, providing strong evidence that written files are valid OGG Vorbis.
+
+### Gaps Summary
+
+No gaps found. All 13 must-have truths are verified, all 5 artifacts pass all three levels (exists, substantive, wired), all 5 key links are wired, all 6 requirements are satisfied, and no anti-patterns were detected.
+
+**Build:** `go build ./backend/tagwriter/` — passes clean
+**Vet:** `go vet ./backend/tagwriter/` — passes clean
+**Tests:** All 10 OGG test functions pass (0.03s), full tagwriter suite passes with zero regressions (0.41s)
+
+---
+
+_Verified: 2026-03-19T18:15:00Z_
+_Verifier: Claude (gsd-verifier)_