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Round 72: Linux CI fix, clock inspection tests, app simulation tests, db_version investigation
TASK-156: Fix Linux CI - Disabled std.log in changes_vtab.zig and sqlite/vtab.zig (segfaults on Linux) - Added debug counter to site_identity.zig for db_version investigation - 365 tests now passing on Linux TASK-196: Clock table inspection tests (DONE) - Created test-clock-internals.sh with 14 test cases (27 assertions) - Discovered seq off-by-one divergence (Zig starts at 1, Rust at 0) - All other clock fields match exactly TASK-194: Real-world app simulation tests - Created test-app-todo.sh, test-app-chat.sh, test-app-inventory.sh - CRITICAL: Found INSERT INTO crsql_changes fails in Zig - Rust/C passes all tests, Zig fails on sync operations TASK-198: db_version investigation (IN PROGRESS) - Added crsql_debug_next_dbv_calls() debug function - Confirmed +1 divergence after ~500 ops - Root cause not yet identified New tasks: - TASK-197 (triage): Fix seq off-by-one in INSERT triggers
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‎.tasks/DELEGATE_WORK_HANDOFF.md‎

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## Round 2025-12-25 (72) — Delegation: Linux CI fix, clock inspection, app simulation, db_version investigation (4 tasks)
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**Tasks executed**
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- `.tasks/active/TASK-156-linux-ci-test-parity.md` (Linux CI fixed)
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- `.tasks/done/TASK-196-clock-table-direct-inspection.md` (completed)
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- `.tasks/active/TASK-194-real-world-app-simulation.md` (completed with critical divergence)
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- `.tasks/active/TASK-198-db-version-off-by-one.md` (investigation in progress)
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**Commits**
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- (pending commit after this round)
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**Environment**
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- OS: darwin (macOS ARM64)
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- Tooling: nix, zig (via nix), bash
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**Commands run by subagents**
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```bash
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# TASK-156: Linux CI diagnostics
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make -C zig build
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bash zig/harness/test-parity.sh
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# TASK-196: Clock table inspection
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bash zig/harness/test-clock-internals.sh
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# TASK-194: Real-world app simulation
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bash zig/harness/test-app-todo.sh
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bash zig/harness/test-app-chat.sh
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bash zig/harness/test-app-inventory.sh
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# TASK-198: db_version investigation
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STRESS_ITERATIONS=25 STRESS_OPS=500 STRESS_SEED=2025 bash zig/harness/test-fuzz-stress.sh
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```
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**Outputs (paste)**
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<details>
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<summary>TASK-156: Linux CI fix (RESOLVED)</summary>
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**Root cause**: Zig's `std.log` (used in `changes_vtab.zig` and `sqlite/vtab.zig`) internally uses `std.io.getStdErr()` which can segfault when called from a dynamically loaded shared library on Linux because the Zig runtime isn't properly initialized in that context.
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**Fixes applied**:
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1. `zig/src/ffi/init.zig` — Disabled `debugLog()` function
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2. `zig/src/site_identity.zig` — Replaced `std.crypto.random` with xorshift64 PRNG
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3. `zig/src/changes_vtab.zig` — Disabled `std.log.scoped()`
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4. `zig/src/sqlite/vtab.zig` — Disabled `std.log.scoped()`
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5. `zig/harness/test-parity.sh` — Fixed unset `ROOT_DIR` variable
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**Results**: All 9 `rows_impacted` tests that were previously failing on Linux now PASS. 365 tests passing overall.
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</details>
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<details>
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<summary>TASK-196: Clock table inspection (14 tests, seq divergence found)</summary>
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```text
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PASSED: 27
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FAILED: 0
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seq divergences: 7 (known issue)
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```
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**Tests created**: 14 test cases covering:
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- Single/bulk INSERT, UPDATE, DELETE
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- Resurrection (DELETE + INSERT same PK)
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- ALTER ADD COLUMN
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- Sync receive
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- Compound primary keys
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**Divergence discovered**: `seq` value off-by-one
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- **Rust/C**: INSERT triggers start `seq` at 0
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- **Zig**: INSERT triggers start `seq` at 1
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All other clock fields (key, col_name, col_version, db_version) match exactly.
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</details>
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<details>
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<summary>TASK-194: Real-world app simulation (CRITICAL DIVERGENCE)</summary>
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**Scripts created**:
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1. `zig/harness/test-app-todo.sh` — Todo app with subtasks
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2. `zig/harness/test-app-chat.sh` — Chat with offline edits
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3. `zig/harness/test-app-inventory.sh` — Inventory management
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**Results**:
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| App | Rust/C | Zig | Parity |
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|-----|--------|-----|--------|
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| Todo | PASS | FAIL | **DIVERGENCE** |
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| Chat | PASS | FAIL | **DIVERGENCE** |
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| Inventory | PASS | FAIL | **DIVERGENCE** |
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**CRITICAL BUG FOUND**: `INSERT INTO crsql_changes` fails in Zig with "SQL logic error"
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```
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debug(changes_vtab): changesUpdate INSERT: table=todos, cid=title...
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debug(changes_vtab): changesUpdate: no local row, inserting new row
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debug(changes_vtab): changesUpdate: insertOrUpdateColumn failed
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Error: stepping, SQL logic error
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```
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This completely breaks cross-device sync — the core functionality of cr-sqlite.
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</details>
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<details>
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<summary>TASK-198: db_version investigation (NOT FIXED)</summary>
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**Investigation summary**:
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- Divergence: Zig db_version is +1 ahead of Rust/C after ~500 operations
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- First divergence point: Rust db_version 111 → Zig skips 111, uses 112
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- Zig has exactly 1 more "gap" (57 vs 56 unused db_version values)
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**Ruled out**:
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- No-op UPDATE handling (both call `nextDbVersion()` unconditionally)
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- INSERT OR REPLACE (both fire INSERT trigger once)
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- Resurrection (matches between implementations)
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**Debug instrumentation added**: `crsql_debug_next_dbv_calls()` SQL function in `zig/src/site_identity.zig`
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**Root cause NOT definitively identified**. Needs further investigation with binary search of operation sequence.
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</details>
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**Files created**
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- `zig/harness/test-clock-internals.sh` (new, ~21KB)
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- `zig/harness/test-app-todo.sh` (new, ~20KB)
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- `zig/harness/test-app-chat.sh` (new, ~27KB)
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- `zig/harness/test-app-inventory.sh` (new, ~29KB)
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**Files modified**
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- `zig/src/site_identity.zig` — Added debug call counter
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- `zig/src/changes_vtab.zig` — Disabled std.log
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- `zig/src/sqlite/vtab.zig` — Disabled std.log
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**New follow-up tasks created**
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- `.tasks/triage/TASK-197-fix-seq-off-by-one.md` — seq starts at 1 instead of 0 (LOW priority)
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**Reproduction steps (clean checkout)**
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1. `git clone <repo> && cd cr-sqlite`
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2. `make -C zig build`
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3. `bash zig/harness/test-clock-internals.sh` — verify 27 pass with seq divergence notes
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4. `bash zig/harness/test-app-todo.sh` — see Zig sync failure vs Rust success
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**Known gaps / unverified claims**
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- **CRITICAL**: `INSERT INTO crsql_changes` fails in Zig — breaks all cross-device sync
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- db_version off-by-one not fixed (TASK-198 still in progress)
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- seq off-by-one (TASK-197) is separate issue from db_version
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- Linux CI changes not yet pushed to verify in actual CI
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---
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## Round 2025-12-23 (69) — Fix 64-column limit bug (1 task)
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**Tasks executed**

‎.tasks/active/TASK-194-real-world-app-simulation.md‎

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# TASK-194 — Real-World Application Simulation Tests
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## Goal
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Simulate realistic application patterns to invalidate "Zig parity is complete".
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## Status
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- State: **DONE**
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- Priority: HIGH (tests real usage, not contrived scenarios)
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- Discovered: 2025-12-23 (hypothesis invalidation request)
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- Completed: 2025-12-25
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## Hypothesis to Invalidate
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"Zig behaves correctly under realistic application workloads."
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## Test Scenarios
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### 1. Todo App Sync
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- Create tasks with nested subtasks
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- Mark complete/incomplete in different order on two devices
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- Sync and verify convergence
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### 2. Chat/Notes App
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- Long-running conversation with edits
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- Offline edits on multiple devices
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- Reconnect and merge
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### 3. Shopping Cart
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- Add/remove items rapidly
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- Update quantities concurrently
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- Apply discount codes (triggers)
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### 4. Collaborative Document
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- Multiple users editing same "document" (row with text blob)
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- Concurrent field updates
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- History/versioning queries
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### 5. Inventory Management
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- Stock count adjustments
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- Transfer between locations
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- Audit trail preservation
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## Test Approach
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1. **Script realistic operation sequences**
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2. **Simulate multi-device with separate DBs**
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3. **Sync via crsql_changes protocol**
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4. **Verify final state matches on all "devices"**
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5. **Compare Zig vs Rust/C behavior**
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## Files to Create
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- `zig/harness/test-app-todo.sh` (new)
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- `zig/harness/test-app-chat.sh` (new)
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- `zig/harness/test-app-inventory.sh` (new)
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## Acceptance Criteria
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1. Each app simulation runs without error
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2. All "devices" converge to same state
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3. Zig and Rust/C produce identical final state
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4. Either find divergence OR confirm real-world readiness
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## Parent Docs / Cross-links
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- Existing realistic tests: `test-realistic-sync.sh`, `test-realistic-offline.sh`, `test-realistic-collab.sh`
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- Gap backlog: `research/zig-cr/92-gap-backlog.md`
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## Progress Log
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- 2025-12-23: Created from hypothesis invalidation request.
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- 2025-12-25: Created 3 app simulation test scripts.
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- 2025-12-25: Fixed schema issue (NOT NULL columns need DEFAULT values for cr-sqlite).
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- 2025-12-25: Discovered **critical Zig bug**: INSERT INTO crsql_changes fails with "SQL logic error".
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## Completion Notes
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### Scripts Created
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1. `zig/harness/test-app-todo.sh` - Todo app with subtasks and concurrent edits
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2. `zig/harness/test-app-chat.sh` - Chat app with offline edits and message conflicts
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3. `zig/harness/test-app-inventory.sh` - Inventory system with multi-location sync
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### Test Results
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#### Rust/C Oracle: ALL PASS
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- Todo app: 2/2 tests pass
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- Chat app: 4/4 tests pass
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- Inventory: 4/4 tests pass
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#### Zig Implementation: CRITICAL FAILURE
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- **Root Cause**: `INSERT INTO crsql_changes` fails with "SQL logic error"
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- Debug output shows: `insertOrUpdateColumn failed`
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- This breaks ALL sync operations (changes from one device cannot be applied to another)
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### Specific Divergence Found
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```
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=== Rust/C INSERT INTO crsql_changes ===
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Todo count: 1 (row created successfully)
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=== Zig INSERT INTO crsql_changes ===
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debug(changes_vtab): changesUpdate INSERT: table=todos, cid=title...
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debug(changes_vtab): changesUpdate: no local row, inserting new row
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debug(changes_vtab): changesUpdate: insertOrUpdateColumn failed
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Error: stepping, SQL logic error
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Todo count: 0 (FAILED - no row created)
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```
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### Hypothesis Result
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**INVALIDATED**: "Zig behaves correctly under realistic application workloads."
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The Zig implementation has a fundamental bug that prevents cross-device sync from working. When Device A creates data and sends changes to Device B, Device B cannot apply them via `INSERT INTO crsql_changes`.
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### Recommended Follow-up
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Create a new task to fix the `insertOrUpdateColumn` function in the Zig changes vtab implementation. The bug appears to be in `zig/src/changes-vtab.zig` in the `changesUpdate` path when handling new rows.

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