diff --git a/checkpoint.json b/checkpoint.json
index f3ddb7e66..4440181c5 100644
--- a/checkpoint.json
+++ b/checkpoint.json
@@ -1,13 +1,15 @@
 {
-  "timestamp": "2026-03-19T15:20:46.286203Z",
-  "current_node": "preflight_lint",
+  "timestamp": "2026-03-19T15:24:47.113617Z",
+  "current_node": "implement",
   "completed_nodes": [
     "start",
     "toolchain",
     "preflight_compile",
-    "preflight_lint"
+    "preflight_lint",
+    "implement"
   ],
   "node_retries": {
+    "implement": 1,
     "start": 1,
     "toolchain": 1,
     "preflight_lint": 1,
@@ -16,21 +18,26 @@
   "context_values": {
     "thread.toolchain.current_node": "preflight_compile",
     "internal.fidelity": "compact",
-    "internal.thread_id": "preflight_compile",
+    "internal.thread_id": "preflight_lint",
     "internal.retry_count.preflight_compile": 1,
     "command.output": "",
     "internal.retry_count.preflight_lint": 1,
+    "last_response": "Here's a summary of all changes made:\n\n### `lib/crates/fabro-util/src/telemetry/sender.rs` — rewritten\n\n**Writer side:**\n- Renamed `send(track: Track)` → `emit(tracks: &[Track])` — accepts a sli",
     "graph.goal": "# Plan: JSONL analytics event file format\n\n## Context\n\nCurrently each CLI invocation writes a single `Track` event as a standalone JSON file (`~/.fabro/tmp/fabro-event-{uuid}.json`) and spawns a detached subprocess to send it. We want to switch to JSONL format (one JSON event per line) so a single file can contain multiple events. Filenames keep a UUID for uniqueness. This enables callers to batch multiple events into one file/subprocess.\n\nThe panic sender (`__send_panic`) is unaffected — it stays single-JSON-per-file.\n\n## Changes\n\n### 1. `lib/crates/fabro-util/src/telemetry/sender.rs` — rewrite\n\n**Writer — rename `send()` to `emit()`, accept multiple events:**\n- `pub fn emit(tracks: &[Track])` (was `pub fn send(track: Track)`)\n- Early return if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty\n- Generate a UUID for the filename: `fabro-events-{uuid}.jsonl`\n- Serialize each `Track` as a compact JSON line (`serde_json::to_string`), join with `\\n`\n- Pass the bytes to `spawn_fabro_subcommand(\"__send_analytics\", &filename, &json)` as before\n\nNo file locking needed — each invocation writes its own uniquely-named file.\n\n**Reader — rename `send_to_segment()` to `upload()`:**\n- Read file contents as string\n- Parse each non-empty line as `serde_json::Value`, inject `\"type\": \"track\"`, collect into batch array\n- Skip malformed lines with `tracing::warn!`\n- If no valid events, return `Ok(())`\n- POST to `https://api.segment.io/v1/batch` with payload `{\"batch\": [...]}`\n- Keep Basic auth the same\n\nExtract a pure `fn build_segment_batch(content: &str) -> Option<Value>` for testability.\n\n**Constants:**\n- Change `SEGMENT_API_URL` from `.../v1/track` to `.../v1/batch`\n\n### 2. `lib/crates/fabro-cli/src/main.rs`\n\n**`send_telemetry_event()` (~line 428):** Change call from `sender::send(track)` to `sender::emit(&[track])`.\n\n**`SendAnalytics` handler (~line 910):** Change call from `sender::send_to_segment(&path)` to `sender::upload(&path)`.\n\n### 3. `lib/crates/fabro-util/src/telemetry/spawn.rs` — no changes\n\n`spawn_fabro_subcommand` is generic (takes raw bytes). It continues to work for both JSONL analytics files and single-JSON panic files.\n\n### 4. No changes to these files\n- `event.rs` — `Track` struct unchanged\n- `panic.rs` — stays single-JSON-per-file\n- `mod.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — unchanged\n\n## Implementation order (red/green TDD)\n\nWrite each test first (red), then implement just enough to make it pass (green).\n\n### Step 1: `build_segment_batch` — pure function, no I/O\n\n1. **Red:** Write test `build_segment_batch_empty_content` — empty string returns `None`\n2. **Green:** Add `fn build_segment_batch(content: &str) -> Option<Value>` stub returning `None`\n3. **Red:** Write test `build_segment_batch_single_event` — one JSONL line produces `{\"batch\": [{\"type\": \"track\", ...}]}`\n4. **Green:** Implement line parsing, `\"type\": \"track\"` injection, batch wrapping\n5. **Red:** Write test `build_segment_batch_multiple_events` — two lines produce batch of 2\n6. **Green:** Should already pass\n7. **Red:** Write test `build_segment_batch_skips_malformed_lines` — one good + one bad line produces batch of 1\n8. **Green:** Add `continue` on parse error\n\n### Step 2: `emit()` — writer side\n\n9. **Red:** Update existing `send_noops_without_write_key` to use `emit(&[track])` signature\n10. **Green:** Rename `send` to `emit`, change signature to `&[Track]`, serialize as JSONL (one JSON line per track, joined with `\\n`), generate `fabro-events-{uuid}.jsonl` filename\n\n### Step 3: `upload()` — reader side\n\n11. **Red:** Write test `upload_noops_without_write_key` — same pattern as existing `send_panic_noops_without_dsn`\n12. **Green:** Rename `send_to_segment` to `upload`, change internals to read file as string, call `build_segment_batch`, POST to `/v1/batch`\n\n### Step 4: Wire up call sites in `main.rs`\n\n13. Update `send_telemetry_event()` to call `sender::emit(&[track])`\n14. Update `SendAnalytics` handler to call `sender::upload(&path)`\n\n### Step 5: Final checks\n\n```bash\ncargo fmt --check --all\ncargo clippy --workspace -- -D warnings\ncargo test -p fabro-util\ncargo test --workspace\n```\n",
-    "current.preamble": "Goal: # Plan: JSONL analytics event file format\n\n## Context\n\nCurrently each CLI invocation writes a single `Track` event as a standalone JSON file (`~/.fabro/tmp/fabro-event-{uuid}.json`) and spawns a detached subprocess to send it. We want to switch to JSONL format (one JSON event per line) so a single file can contain multiple events. Filenames keep a UUID for uniqueness. This enables callers to batch multiple events into one file/subprocess.\n\nThe panic sender (`__send_panic`) is unaffected — it stays single-JSON-per-file.\n\n## Changes\n\n### 1. `lib/crates/fabro-util/src/telemetry/sender.rs` — rewrite\n\n**Writer — rename `send()` to `emit()`, accept multiple events:**\n- `pub fn emit(tracks: &[Track])` (was `pub fn send(track: Track)`)\n- Early return if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty\n- Generate a UUID for the filename: `fabro-events-{uuid}.jsonl`\n- Serialize each `Track` as a compact JSON line (`serde_json::to_string`), join with `\\n`\n- Pass the bytes to `spawn_fabro_subcommand(\"__send_analytics\", &filename, &json)` as before\n\nNo file locking needed — each invocation writes its own uniquely-named file.\n\n**Reader — rename `send_to_segment()` to `upload()`:**\n- Read file contents as string\n- Parse each non-empty line as `serde_json::Value`, inject `\"type\": \"track\"`, collect into batch array\n- Skip malformed lines with `tracing::warn!`\n- If no valid events, return `Ok(())`\n- POST to `https://api.segment.io/v1/batch` with payload `{\"batch\": [...]}`\n- Keep Basic auth the same\n\nExtract a pure `fn build_segment_batch(content: &str) -> Option<Value>` for testability.\n\n**Constants:**\n- Change `SEGMENT_API_URL` from `.../v1/track` to `.../v1/batch`\n\n### 2. `lib/crates/fabro-cli/src/main.rs`\n\n**`send_telemetry_event()` (~line 428):** Change call from `sender::send(track)` to `sender::emit(&[track])`.\n\n**`SendAnalytics` handler (~line 910):** Change call from `sender::send_to_segment(&path)` to `sender::upload(&path)`.\n\n### 3. `lib/crates/fabro-util/src/telemetry/spawn.rs` — no changes\n\n`spawn_fabro_subcommand` is generic (takes raw bytes). It continues to work for both JSONL analytics files and single-JSON panic files.\n\n### 4. No changes to these files\n- `event.rs` — `Track` struct unchanged\n- `panic.rs` — stays single-JSON-per-file\n- `mod.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — unchanged\n\n## Implementation order (red/green TDD)\n\nWrite each test first (red), then implement just enough to make it pass (green).\n\n### Step 1: `build_segment_batch` — pure function, no I/O\n\n1. **Red:** Write test `build_segment_batch_empty_content` — empty string returns `None`\n2. **Green:** Add `fn build_segment_batch(content: &str) -> Option<Value>` stub returning `None`\n3. **Red:** Write test `build_segment_batch_single_event` — one JSONL line produces `{\"batch\": [{\"type\": \"track\", ...}]}`\n4. **Green:** Implement line parsing, `\"type\": \"track\"` injection, batch wrapping\n5. **Red:** Write test `build_segment_batch_multiple_events` — two lines produce batch of 2\n6. **Green:** Should already pass\n7. **Red:** Write test `build_segment_batch_skips_malformed_lines` — one good + one bad line produces batch of 1\n8. **Green:** Add `continue` on parse error\n\n### Step 2: `emit()` — writer side\n\n9. **Red:** Update existing `send_noops_without_write_key` to use `emit(&[track])` signature\n10. **Green:** Rename `send` to `emit`, change signature to `&[Track]`, serialize as JSONL (one JSON line per track, joined with `\\n`), generate `fabro-events-{uuid}.jsonl` filename\n\n### Step 3: `upload()` — reader side\n\n11. **Red:** Write test `upload_noops_without_write_key` — same pattern as existing `send_panic_noops_without_dsn`\n12. **Green:** Rename `send_to_segment` to `upload`, change internals to read file as string, call `build_segment_batch`, POST to `/v1/batch`\n\n### Step 4: Wire up call sites in `main.rs`\n\n13. Update `send_telemetry_event()` to call `sender::emit(&[track])`\n14. Update `SendAnalytics` handler to call `sender::upload(&path)`\n\n### Step 5: Final checks\n\n```bash\ncargo fmt --check --all\ncargo clippy --workspace -- -D warnings\ncargo test -p fabro-util\ncargo test --workspace\n```\n\n\n## Completed stages\n- **toolchain**: success\n  - Script: `command -v cargo >/dev/null || { curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y && sudo ln -sf $HOME/.cargo/bin/* /usr/local/bin/; }; cargo --version 2>&1`\n  - Stdout:\n    ```\n    cargo 1.94.0 (85eff7c80 2026-01-15)\n    ```\n  - Stderr: (empty)\n- **preflight_compile**: success\n  - Script: `cargo check -q --workspace 2>&1`\n  - Stdout: (empty)\n  - Stderr: (empty)\n",
+    "current.preamble": "Goal: # Plan: JSONL analytics event file format\n\n## Context\n\nCurrently each CLI invocation writes a single `Track` event as a standalone JSON file (`~/.fabro/tmp/fabro-event-{uuid}.json`) and spawns a detached subprocess to send it. We want to switch to JSONL format (one JSON event per line) so a single file can contain multiple events. Filenames keep a UUID for uniqueness. This enables callers to batch multiple events into one file/subprocess.\n\nThe panic sender (`__send_panic`) is unaffected — it stays single-JSON-per-file.\n\n## Changes\n\n### 1. `lib/crates/fabro-util/src/telemetry/sender.rs` — rewrite\n\n**Writer — rename `send()` to `emit()`, accept multiple events:**\n- `pub fn emit(tracks: &[Track])` (was `pub fn send(track: Track)`)\n- Early return if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty\n- Generate a UUID for the filename: `fabro-events-{uuid}.jsonl`\n- Serialize each `Track` as a compact JSON line (`serde_json::to_string`), join with `\\n`\n- Pass the bytes to `spawn_fabro_subcommand(\"__send_analytics\", &filename, &json)` as before\n\nNo file locking needed — each invocation writes its own uniquely-named file.\n\n**Reader — rename `send_to_segment()` to `upload()`:**\n- Read file contents as string\n- Parse each non-empty line as `serde_json::Value`, inject `\"type\": \"track\"`, collect into batch array\n- Skip malformed lines with `tracing::warn!`\n- If no valid events, return `Ok(())`\n- POST to `https://api.segment.io/v1/batch` with payload `{\"batch\": [...]}`\n- Keep Basic auth the same\n\nExtract a pure `fn build_segment_batch(content: &str) -> Option<Value>` for testability.\n\n**Constants:**\n- Change `SEGMENT_API_URL` from `.../v1/track` to `.../v1/batch`\n\n### 2. `lib/crates/fabro-cli/src/main.rs`\n\n**`send_telemetry_event()` (~line 428):** Change call from `sender::send(track)` to `sender::emit(&[track])`.\n\n**`SendAnalytics` handler (~line 910):** Change call from `sender::send_to_segment(&path)` to `sender::upload(&path)`.\n\n### 3. `lib/crates/fabro-util/src/telemetry/spawn.rs` — no changes\n\n`spawn_fabro_subcommand` is generic (takes raw bytes). It continues to work for both JSONL analytics files and single-JSON panic files.\n\n### 4. No changes to these files\n- `event.rs` — `Track` struct unchanged\n- `panic.rs` — stays single-JSON-per-file\n- `mod.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — unchanged\n\n## Implementation order (red/green TDD)\n\nWrite each test first (red), then implement just enough to make it pass (green).\n\n### Step 1: `build_segment_batch` — pure function, no I/O\n\n1. **Red:** Write test `build_segment_batch_empty_content` — empty string returns `None`\n2. **Green:** Add `fn build_segment_batch(content: &str) -> Option<Value>` stub returning `None`\n3. **Red:** Write test `build_segment_batch_single_event` — one JSONL line produces `{\"batch\": [{\"type\": \"track\", ...}]}`\n4. **Green:** Implement line parsing, `\"type\": \"track\"` injection, batch wrapping\n5. **Red:** Write test `build_segment_batch_multiple_events` — two lines produce batch of 2\n6. **Green:** Should already pass\n7. **Red:** Write test `build_segment_batch_skips_malformed_lines` — one good + one bad line produces batch of 1\n8. **Green:** Add `continue` on parse error\n\n### Step 2: `emit()` — writer side\n\n9. **Red:** Update existing `send_noops_without_write_key` to use `emit(&[track])` signature\n10. **Green:** Rename `send` to `emit`, change signature to `&[Track]`, serialize as JSONL (one JSON line per track, joined with `\\n`), generate `fabro-events-{uuid}.jsonl` filename\n\n### Step 3: `upload()` — reader side\n\n11. **Red:** Write test `upload_noops_without_write_key` — same pattern as existing `send_panic_noops_without_dsn`\n12. **Green:** Rename `send_to_segment` to `upload`, change internals to read file as string, call `build_segment_batch`, POST to `/v1/batch`\n\n### Step 4: Wire up call sites in `main.rs`\n\n13. Update `send_telemetry_event()` to call `sender::emit(&[track])`\n14. Update `SendAnalytics` handler to call `sender::upload(&path)`\n\n### Step 5: Final checks\n\n```bash\ncargo fmt --check --all\ncargo clippy --workspace -- -D warnings\ncargo test -p fabro-util\ncargo test --workspace\n```\n\n\n## Completed stages\n- **toolchain**: success\n  - Script: `command -v cargo >/dev/null || { curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y && sudo ln -sf $HOME/.cargo/bin/* /usr/local/bin/; }; cargo --version 2>&1`\n  - Stdout:\n    ```\n    cargo 1.94.0 (85eff7c80 2026-01-15)\n    ```\n  - Stderr: (empty)\n- **preflight_compile**: success\n  - Script: `cargo check -q --workspace 2>&1`\n  - Stdout: (empty)\n  - Stderr: (empty)\n- **preflight_lint**: success\n  - Script: `cargo clippy -q --workspace -- -D warnings 2>&1`\n  - Stdout: (empty)\n  - Stderr: (empty)\n",
     "graph.model_stylesheet": "\n            * { backend: api; model: claude-opus-4-6;}\n        ",
     "failure_signature": "",
     "internal.node_visit_count": 1,
     "internal.retry_count.toolchain": 1,
     "command.stderr": "",
+    "thread.preflight_lint.current_node": "implement",
+    "response.implement": "Here's a summary of all changes made:\n\n### `lib/crates/fabro-util/src/telemetry/sender.rs` — rewritten\n\n**Writer side:**\n- Renamed `send(track: Track)` → `emit(tracks: &[Track])` — accepts a slice of events\n- Early returns if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty\n- `spawn_sender` serializes each `Track` as a compact JSON line, joins with `\\n`, generates a `fabro-events-{uuid}.jsonl` filename\n\n**Reader side:**\n- Renamed `send_to_segment()` → `upload()` — reads file as string, delegates to `build_segment_batch`, POSTs to `/v1/batch`\n- New pure function `build_segment_batch(content: &str) -> Option<Value>` — parses each non-empty JSONL line, injects `\"type\": \"track\"`, wraps in `{\"batch\": [...]}`, skips malformed lines with `tracing::warn!`\n\n**Constants:**\n- `SEGMENT_API_URL` changed from `.../v1/track` to `.../v1/batch`\n- Added `use uuid::Uuid` (removed unused `Track.message_id` dependency for filename)\n\n**Tests (9 total, all passing):**\n1. `build_segment_batch_empty_content` — empty string returns `None`\n2. `build_segment_batch_single_event` — one line produces batch with `\"type\": \"track\"`\n3. `build_segment_batch_multiple_events` — two lines produce batch of 2\n4. `build_segment_batch_skips_malformed_lines` — bad JSON lines are skipped\n5. `build_segment_batch_all_malformed` — all bad lines returns `None`\n6. `build_segment_batch_skips_blank_lines` — blank lines are ignored\n7. `emit_noops_without_write_key` — no-ops without compile-time key\n8. `emit_noops_with_empty_tracks` — no-ops on empty slice\n9. `upload_noops_without_write_key` — errors without compile-time key\n\n### `lib/crates/fabro-cli/src/main.rs` — two call sites updated\n\n- Line 429: `sender::send(track)` → `sender::emit(&[track])`\n- Line 911: `sender::send_to_segment(&path)` → `sender::upload(&path)`\n\n### Unchanged files (as planned)\n- `event.rs`, `panic.rs`, `mod.rs`, `spawn.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — no changes needed",
     "thread.preflight_compile.current_node": "preflight_lint",
     "internal.run_id": "01KM3AVN0Z99W7AX4PCVEB8C9J",
+    "last_stage": "implement",
+    "internal.retry_count.implement": 1,
     "graph.rankdir": "LR",
-    "current_node": "preflight_lint",
+    "current_node": "implement",
     "internal.retry_count.start": 1,
     "outcome": "success",
     "failure_class": "",
@@ -51,6 +58,29 @@
       "status": "success",
       "duration_ms": 0
     },
+    "implement": {
+      "status": "success",
+      "context_updates": {
+        "last_response": "Here's a summary of all changes made:\n\n### `lib/crates/fabro-util/src/telemetry/sender.rs` — rewritten\n\n**Writer side:**\n- Renamed `send(track: Track)` → `emit(tracks: &[Track])` — accepts a sli",
+        "response.implement": "Here's a summary of all changes made:\n\n### `lib/crates/fabro-util/src/telemetry/sender.rs` — rewritten\n\n**Writer side:**\n- Renamed `send(track: Track)` → `emit(tracks: &[Track])` — accepts a slice of events\n- Early returns if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty\n- `spawn_sender` serializes each `Track` as a compact JSON line, joins with `\\n`, generates a `fabro-events-{uuid}.jsonl` filename\n\n**Reader side:**\n- Renamed `send_to_segment()` → `upload()` — reads file as string, delegates to `build_segment_batch`, POSTs to `/v1/batch`\n- New pure function `build_segment_batch(content: &str) -> Option<Value>` — parses each non-empty JSONL line, injects `\"type\": \"track\"`, wraps in `{\"batch\": [...]}`, skips malformed lines with `tracing::warn!`\n\n**Constants:**\n- `SEGMENT_API_URL` changed from `.../v1/track` to `.../v1/batch`\n- Added `use uuid::Uuid` (removed unused `Track.message_id` dependency for filename)\n\n**Tests (9 total, all passing):**\n1. `build_segment_batch_empty_content` — empty string returns `None`\n2. `build_segment_batch_single_event` — one line produces batch with `\"type\": \"track\"`\n3. `build_segment_batch_multiple_events` — two lines produce batch of 2\n4. `build_segment_batch_skips_malformed_lines` — bad JSON lines are skipped\n5. `build_segment_batch_all_malformed` — all bad lines returns `None`\n6. `build_segment_batch_skips_blank_lines` — blank lines are ignored\n7. `emit_noops_without_write_key` — no-ops without compile-time key\n8. `emit_noops_with_empty_tracks` — no-ops on empty slice\n9. `upload_noops_without_write_key` — errors without compile-time key\n\n### `lib/crates/fabro-cli/src/main.rs` — two call sites updated\n\n- Line 429: `sender::send(track)` → `sender::emit(&[track])`\n- Line 911: `sender::send_to_segment(&path)` → `sender::upload(&path)`\n\n### Unchanged files (as planned)\n- `event.rs`, `panic.rs`, `mod.rs`, `spawn.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — no changes needed",
+        "last_stage": "implement"
+      },
+      "notes": "Stage completed: implement",
+      "usage": {
+        "model": "claude-opus-4-6",
+        "input_tokens": 38607,
+        "output_tokens": 4625,
+        "cache_read_tokens": 268156,
+        "cache_write_tokens": 40280,
+        "reasoning_tokens": 113,
+        "cost": 0.92598
+      },
+      "files_touched": [
+        "/home/daytona/workspace/lib/crates/fabro-cli/src/main.rs",
+        "/home/daytona/workspace/lib/crates/fabro-util/src/telemetry/sender.rs"
+      ],
+      "duration_ms": 237748
+    },
     "toolchain": {
       "status": "success",
       "context_updates": {
@@ -70,10 +100,11 @@
       "duration_ms": 71459
     }
   },
-  "next_node_id": "implement",
+  "next_node_id": "simplify_opus",
   "node_visits": {
     "start": 1,
     "preflight_lint": 1,
+    "implement": 1,
     "toolchain": 1,
     "preflight_compile": 1
   }
diff --git a/nodes/implement/prompt.md b/nodes/implement/prompt.md
new file mode 100644
index 000000000..4cc08f71e
--- /dev/null
+++ b/nodes/implement/prompt.md
@@ -0,0 +1,108 @@
+Goal: # Plan: JSONL analytics event file format
+
+## Context
+
+Currently each CLI invocation writes a single `Track` event as a standalone JSON file (`~/.fabro/tmp/fabro-event-{uuid}.json`) and spawns a detached subprocess to send it. We want to switch to JSONL format (one JSON event per line) so a single file can contain multiple events. Filenames keep a UUID for uniqueness. This enables callers to batch multiple events into one file/subprocess.
+
+The panic sender (`__send_panic`) is unaffected — it stays single-JSON-per-file.
+
+## Changes
+
+### 1. `lib/crates/fabro-util/src/telemetry/sender.rs` — rewrite
+
+**Writer — rename `send()` to `emit()`, accept multiple events:**
+- `pub fn emit(tracks: &[Track])` (was `pub fn send(track: Track)`)
+- Early return if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty
+- Generate a UUID for the filename: `fabro-events-{uuid}.jsonl`
+- Serialize each `Track` as a compact JSON line (`serde_json::to_string`), join with `\n`
+- Pass the bytes to `spawn_fabro_subcommand("__send_analytics", &filename, &json)` as before
+
+No file locking needed — each invocation writes its own uniquely-named file.
+
+**Reader — rename `send_to_segment()` to `upload()`:**
+- Read file contents as string
+- Parse each non-empty line as `serde_json::Value`, inject `"type": "track"`, collect into batch array
+- Skip malformed lines with `tracing::warn!`
+- If no valid events, return `Ok(())`
+- POST to `https://api.segment.io/v1/batch` with payload `{"batch": [...]}`
+- Keep Basic auth the same
+
+Extract a pure `fn build_segment_batch(content: &str) -> Option<Value>` for testability.
+
+**Constants:**
+- Change `SEGMENT_API_URL` from `.../v1/track` to `.../v1/batch`
+
+### 2. `lib/crates/fabro-cli/src/main.rs`
+
+**`send_telemetry_event()` (~line 428):** Change call from `sender::send(track)` to `sender::emit(&[track])`.
+
+**`SendAnalytics` handler (~line 910):** Change call from `sender::send_to_segment(&path)` to `sender::upload(&path)`.
+
+### 3. `lib/crates/fabro-util/src/telemetry/spawn.rs` — no changes
+
+`spawn_fabro_subcommand` is generic (takes raw bytes). It continues to work for both JSONL analytics files and single-JSON panic files.
+
+### 4. No changes to these files
+- `event.rs` — `Track` struct unchanged
+- `panic.rs` — stays single-JSON-per-file
+- `mod.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — unchanged
+
+## Implementation order (red/green TDD)
+
+Write each test first (red), then implement just enough to make it pass (green).
+
+### Step 1: `build_segment_batch` — pure function, no I/O
+
+1. **Red:** Write test `build_segment_batch_empty_content` — empty string returns `None`
+2. **Green:** Add `fn build_segment_batch(content: &str) -> Option<Value>` stub returning `None`
+3. **Red:** Write test `build_segment_batch_single_event` — one JSONL line produces `{"batch": [{"type": "track", ...}]}`
+4. **Green:** Implement line parsing, `"type": "track"` injection, batch wrapping
+5. **Red:** Write test `build_segment_batch_multiple_events` — two lines produce batch of 2
+6. **Green:** Should already pass
+7. **Red:** Write test `build_segment_batch_skips_malformed_lines` — one good + one bad line produces batch of 1
+8. **Green:** Add `continue` on parse error
+
+### Step 2: `emit()` — writer side
+
+9. **Red:** Update existing `send_noops_without_write_key` to use `emit(&[track])` signature
+10. **Green:** Rename `send` to `emit`, change signature to `&[Track]`, serialize as JSONL (one JSON line per track, joined with `\n`), generate `fabro-events-{uuid}.jsonl` filename
+
+### Step 3: `upload()` — reader side
+
+11. **Red:** Write test `upload_noops_without_write_key` — same pattern as existing `send_panic_noops_without_dsn`
+12. **Green:** Rename `send_to_segment` to `upload`, change internals to read file as string, call `build_segment_batch`, POST to `/v1/batch`
+
+### Step 4: Wire up call sites in `main.rs`
+
+13. Update `send_telemetry_event()` to call `sender::emit(&[track])`
+14. Update `SendAnalytics` handler to call `sender::upload(&path)`
+
+### Step 5: Final checks
+
+```bash
+cargo fmt --check --all
+cargo clippy --workspace -- -D warnings
+cargo test -p fabro-util
+cargo test --workspace
+```
+
+
+## Completed stages
+- **toolchain**: success
+  - Script: `command -v cargo >/dev/null || { curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y && sudo ln -sf $HOME/.cargo/bin/* /usr/local/bin/; }; cargo --version 2>&1`
+  - Stdout:
+    ```
+    cargo 1.94.0 (85eff7c80 2026-01-15)
+    ```
+  - Stderr: (empty)
+- **preflight_compile**: success
+  - Script: `cargo check -q --workspace 2>&1`
+  - Stdout: (empty)
+  - Stderr: (empty)
+- **preflight_lint**: success
+  - Script: `cargo clippy -q --workspace -- -D warnings 2>&1`
+  - Stdout: (empty)
+  - Stderr: (empty)
+
+
+Read the plan file referenced in the goal and implement every step. Make all the code changes described in the plan. Use red/green TDD.
\ No newline at end of file
diff --git a/nodes/implement/provider_used.json b/nodes/implement/provider_used.json
new file mode 100644
index 000000000..c1905ff10
--- /dev/null
+++ b/nodes/implement/provider_used.json
@@ -0,0 +1,5 @@
+{
+  "mode": "agent",
+  "provider": "anthropic",
+  "model": "claude-opus-4-6"
+}
\ No newline at end of file
diff --git a/nodes/implement/response.md b/nodes/implement/response.md
new file mode 100644
index 000000000..bf27710b8
--- /dev/null
+++ b/nodes/implement/response.md
@@ -0,0 +1,35 @@
+Here's a summary of all changes made:
+
+### `lib/crates/fabro-util/src/telemetry/sender.rs` — rewritten
+
+**Writer side:**
+- Renamed `send(track: Track)` → `emit(tracks: &[Track])` — accepts a slice of events
+- Early returns if `SEGMENT_WRITE_KEY` is `None` or `tracks` is empty
+- `spawn_sender` serializes each `Track` as a compact JSON line, joins with `\n`, generates a `fabro-events-{uuid}.jsonl` filename
+
+**Reader side:**
+- Renamed `send_to_segment()` → `upload()` — reads file as string, delegates to `build_segment_batch`, POSTs to `/v1/batch`
+- New pure function `build_segment_batch(content: &str) -> Option<Value>` — parses each non-empty JSONL line, injects `"type": "track"`, wraps in `{"batch": [...]}`, skips malformed lines with `tracing::warn!`
+
+**Constants:**
+- `SEGMENT_API_URL` changed from `.../v1/track` to `.../v1/batch`
+- Added `use uuid::Uuid` (removed unused `Track.message_id` dependency for filename)
+
+**Tests (9 total, all passing):**
+1. `build_segment_batch_empty_content` — empty string returns `None`
+2. `build_segment_batch_single_event` — one line produces batch with `"type": "track"`
+3. `build_segment_batch_multiple_events` — two lines produce batch of 2
+4. `build_segment_batch_skips_malformed_lines` — bad JSON lines are skipped
+5. `build_segment_batch_all_malformed` — all bad lines returns `None`
+6. `build_segment_batch_skips_blank_lines` — blank lines are ignored
+7. `emit_noops_without_write_key` — no-ops without compile-time key
+8. `emit_noops_with_empty_tracks` — no-ops on empty slice
+9. `upload_noops_without_write_key` — errors without compile-time key
+
+### `lib/crates/fabro-cli/src/main.rs` — two call sites updated
+
+- Line 429: `sender::send(track)` → `sender::emit(&[track])`
+- Line 911: `sender::send_to_segment(&path)` → `sender::upload(&path)`
+
+### Unchanged files (as planned)
+- `event.rs`, `panic.rs`, `mod.rs`, `spawn.rs`, `anonymous_id.rs`, `context.rs`, `git.rs`, `sanitize.rs` — no changes needed
\ No newline at end of file
diff --git a/nodes/implement/status.json b/nodes/implement/status.json
new file mode 100644
index 000000000..a539eca8f
--- /dev/null
+++ b/nodes/implement/status.json
@@ -0,0 +1,6 @@
+{
+  "status": "success",
+  "notes": "Stage completed: implement",
+  "failure_reason": null,
+  "timestamp": "2026-03-19T15:24:47.113112+00:00"
+}
\ No newline at end of file