diff --git a/.tasks/backlog/TASK-057-fix-github-actions-test-failures.md b/.tasks/backlog/TASK-057-fix-github-actions-test-failures.md
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@@ -0,0 +1,48 @@
+# TASK-057: Fix GitHub Actions Test Failures
+
+## Status
+- [x] Planned
+- [ ] Assigned
+- [ ] In Progress
+- [ ] Blocked (reason: ...)
+- [ ] Complete
+
+## Priority
+high
+
+## Assigned To
+subagent (general)
+
+## Parent Docs / Cross-links
+- Gap backlog: `research/zig-cr/92-gap-backlog.md`
+- GitHub Actions workflows: `.github/workflows/`
+- Zig tests workflow: `.github/workflows/zig-tests.yaml`
+- Test infrastructure: `zig/harness/`
+
+## Description
+GitHub Actions tests are consistently failing on the main branch. The `zig-tests` workflow has been failing since at least December 14, 2025 (run #20210398182 and subsequent runs through #20238288233).
+
+This task investigates and fixes the root cause of these test failures to restore CI health.
+
+## Files to Modify
+- `.github/workflows/zig-tests.yaml` (if workflow configuration is the issue)
+- `zig/` (if Zig implementation has issues)
+- `zig/harness/` (if test harness setup is the issue)
+- Any other files identified during investigation
+
+## Acceptance Criteria
+- [ ] Identify the root cause of the GitHub Actions test failures
+- [ ] Document the root cause in the `Progress Log`
+- [ ] Implement fixes to resolve the failures
+- [ ] All GitHub Actions workflows pass on the main branch
+- [ ] CI remains green after the fix
+- [ ] Document the fix and verification steps in `Completion Notes`
+
+## Progress Log
+### 2025-12-17
+- Task created to address ongoing CI failures
+- GitHub Actions runs show `zig-tests` workflow failing consistently
+- Latest failing run: #20238288233 (2025-12-15)
+
+## Completion Notes
+[fill in when done]
diff --git a/.tasks/backlog/TASK-058-ensure-zig-functionality-complete.md b/.tasks/backlog/TASK-058-ensure-zig-functionality-complete.md
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@@ -0,0 +1,57 @@
+# TASK-058: Ensure All Zig Functionality is Fully Implemented
+
+## Status
+- [x] Planned
+- [ ] Assigned
+- [ ] In Progress
+- [ ] Blocked (reason: ...)
+- [ ] Complete
+
+## Priority
+high
+
+## Assigned To
+subagent (general)
+
+## Parent Docs / Cross-links
+- Feature matrix: `research/zig-cr/90-feature-matrix.md`
+- MVP roadmap: `research/zig-cr/91-mvp-roadmap.md`
+- Gap backlog: `research/zig-cr/92-gap-backlog.md`
+- Phased execution proposal: `research/zig-cr/93-phased-execution-proposal.md`
+- Zig implementation: `zig/`
+- Core C implementation (reference): `core/`
+
+## Description
+Systematically verify that all cr-sqlite functionality documented in the feature matrix and research docs is fully implemented in the Zig port. This includes:
+
+1. All core replication surfaces (init, as_crr/as_table, write capture, crsql_changes vtab, merge semantics)
+2. Serialization and wire formats (PK blob format, pack_columns)
+3. All SQLite extension APIs (UDFs, writable virtual tables, hooks, triggers)
+4. Clock versioning and ordering semantics
+5. Fractindex support (currently stubbed: crsql_fract_as_ordered)
+6. Any other functionality identified in the feature matrix
+
+Cross-reference the Zig implementation against the C/Rust reference implementation to identify any missing or incomplete features.
+
+## Files to Modify
+- `zig/src/` (implement missing functionality)
+- `research/zig-cr/90-feature-matrix.md` (update status)
+- `research/zig-cr/92-gap-backlog.md` (update completion status)
+
+## Acceptance Criteria
+- [ ] Complete audit of all features in `research/zig-cr/90-feature-matrix.md` against Zig implementation
+- [ ] Identify all missing or incomplete features
+- [ ] Implement missing functionality or create separate task cards for complex features
+- [ ] All core replication features are fully functional
+- [ ] All C oracle tests pass (including fract suite if implemented)
+- [ ] Documentation updated to reflect implementation status
+- [ ] Completion notes include a comprehensive list of what was implemented or deferred
+
+## Progress Log
+### 2025-12-17
+- Task created to ensure Zig parity with C/Rust implementation
+- Known gap: crsql_fract_as_ordered is currently a stub (causes 1/20 C oracle tests to fail)
+- Reference: Round 20 notes indicate 153/154 tests passing (99.4%)
+
+## Completion Notes
+[fill in when done]
diff --git a/.tasks/backlog/TASK-059-design-tests-expose-unimplemented-zig.md b/.tasks/backlog/TASK-059-design-tests-expose-unimplemented-zig.md
new file mode 100644
index 00000000..c1146f1e
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+++ b/.tasks/backlog/TASK-059-design-tests-expose-unimplemented-zig.md
@@ -0,0 +1,65 @@
+# TASK-059: Design and Add Tests to Expose Unimplemented Zig Functionality
+
+## Status
+- [x] Planned
+- [ ] Assigned
+- [ ] In Progress
+- [ ] Blocked (reason: ...)
+- [ ] Complete
+
+## Priority
+medium
+
+## Assigned To
+subagent (general)
+
+## Parent Docs / Cross-links
+- Test oracle design: `research/zig-cr/10-test-oracle.md`
+- Feature matrix: `research/zig-cr/90-feature-matrix.md`
+- Gap backlog: `research/zig-cr/92-gap-backlog.md`
+- Existing test harnesses: `zig/harness/`
+- C oracle tests: `core/c/`
+
+## Description
+Design and implement additional tests to systematically expose any gaps in the Zig implementation that aren't caught by existing test suites.
+
+Focus areas:
+1. **Edge cases and error conditions**: Test boundary conditions, error handling, and failure modes
+2. **Multi-table scenarios**: Complex interactions between multiple CRR tables
+3. **Merge conflict resolution**: All tie-breaker paths (cl/col_version/value/site_id)
+4. **Clock semantics**: dbVersion/pendingDbVersion/seq invariants across transactions
+5. **Serialization formats**: PK blob packing/unpacking edge cases
+6. **Virtual table operations**: xUpdate paths, transaction boundaries, best-index scenarios
+7. **Hook chaining**: Commit/rollback hook interactions with other extensions
+8. **Schema evolution**: as_crr/as_table with different table configurations
+9. **Performance characteristics**: Large UNION query scaling, statement cache effectiveness
+
+Each test should:
+- Be deterministic and reproducible
+- Have clear pass/fail criteria
+- Document what functionality it's validating
+- Run quickly (avoid long-running stress tests in CI)
+
+## Files to Modify
+- `zig/harness/` (new test scripts or extensions to existing ones)
+- `zig/src/` (add unit tests in relevant modules)
+- `research/zig-cr/92-gap-backlog.md` (document test coverage improvements)
+
+## Acceptance Criteria
+- [ ] Identify at least 5-10 additional test scenarios not covered by existing tests
+- [ ] Document the test design in the `Progress Log` with rationale
+- [ ] Implement the new tests
+- [ ] Tests successfully expose at least one previously undetected gap (if any exist)
+- [ ] All new tests pass (or are marked as expected failures with task cards created for fixes)
+- [ ] Test documentation explains what each test validates and why it's important
+- [ ] Tests are integrated into existing test harness (make test-* targets)
+
+## Progress Log
+### 2025-12-17
+- Task created to improve test coverage and expose implementation gaps
+- Current test status: 154/154 MVP tests passing per gap backlog
+- C oracle harness: 19/20 tests pass (fract_as_ordered stub causes 1 failure)
+- Need to design tests that go beyond existing coverage
+
+## Completion Notes
+[fill in when done]
diff --git a/research/zig-cr/92-gap-backlog.md b/research/zig-cr/92-gap-backlog.md
index f9cffea3..ff1c84fb 100644
--- a/research/zig-cr/92-gap-backlog.md
+++ b/research/zig-cr/92-gap-backlog.md
@@ -1,6 +1,6 @@
 # 92-gap-backlog
 
-> Last updated: 2025-12-15 (Round 34 — Zig parity fixed, browser tests green)
+> Last updated: 2025-12-17 (Added CI health + Zig completeness tasks)
 
 ## Status
 
@@ -12,9 +12,11 @@
 
 Pick disjoint tasks from `.tasks/backlog/`:
 
-- **Tests now green**
-  - Zig parity: 52/52 passing (TASK-051 done)
-  - Browser tests: 18/18 passing (TASK-052 done — was port conflict, not code bug)
+- **CI and Zig implementation health**
+  - Fix GitHub Actions test failures: `.tasks/backlog/TASK-057-fix-github-actions-test-failures.md`
+  - Ensure all Zig functionality fully implemented: `.tasks/backlog/TASK-058-ensure-zig-functionality-complete.md`
+  - Design tests to expose unimplemented Zig functionality: `.tasks/backlog/TASK-059-design-tests-expose-unimplemented-zig.md`
+  - *(Note: Local tests passing - 154/154 MVP, 52/52 parity, but CI is red)*
 
 - **Unblock browser specs (to unblock TS work)**
   - Tom decision: browser spec naming + package boundary: `.tasks/backlog/TASK-056-tom-browser-spec-naming.md`
@@ -55,7 +57,15 @@ Pick disjoint tasks from `.tasks/backlog/`:
 
 ## Gaps (only what’s still open)
 
-### Test infrastructure (resolved)
+### CI and Zig implementation gaps
+
+Source: GitHub Actions workflow failures + feature matrix audit
+
+- [ ] Fix GitHub Actions test failures → `.tasks/backlog/TASK-057-fix-github-actions-test-failures.md` (2025-12-17)
+- [ ] Ensure all Zig functionality fully implemented → `.tasks/backlog/TASK-058-ensure-zig-functionality-complete.md` (2025-12-17)
+- [ ] Design tests to expose unimplemented Zig functionality → `.tasks/backlog/TASK-059-design-tests-expose-unimplemented-zig.md` (2025-12-17)
+
+### Test infrastructure (previously resolved)
 
 Source: `.tasks/DELEGATE_WORK_HANDOFF.md` (Round 34)