From 5d73b89e5f0898d2cc322da1e9d52f9091c05e88 Mon Sep 17 00:00:00 2001
From: Fabro <noreply@fabro.sh>
Date: Sun, 15 Mar 2026 22:10:49 -0400
Subject: [PATCH] checkpoint
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

⚒️ Generated with [Fabro](https://fabro.sh)
---
 checkpoint.json                        |  70 +++++---
 nodes/implement/diff.patch             | 219 +++++++++++++++++++++++++
 nodes/simplify_opus/prompt.md          | 135 +++++++++++++++
 nodes/simplify_opus/provider_used.json |   5 +
 nodes/simplify_opus/response.md        |  14 ++
 nodes/simplify_opus/status.json        |   6 +
 6 files changed, 429 insertions(+), 20 deletions(-)
 create mode 100644 nodes/implement/diff.patch
 create mode 100644 nodes/simplify_opus/prompt.md
 create mode 100644 nodes/simplify_opus/provider_used.json
 create mode 100644 nodes/simplify_opus/response.md
 create mode 100644 nodes/simplify_opus/status.json

diff --git a/checkpoint.json b/checkpoint.json
index f26b96136..923524f04 100644
--- a/checkpoint.json
+++ b/checkpoint.json
@@ -1,46 +1,51 @@
 {
-  "timestamp": "2026-03-16T02:04:55.416450Z",
-  "current_node": "implement",
+  "timestamp": "2026-03-16T02:10:49.291808Z",
+  "current_node": "simplify_opus",
   "completed_nodes": [
     "start",
     "toolchain",
     "preflight_compile",
     "preflight_lint",
-    "implement"
+    "implement",
+    "simplify_opus"
   ],
   "node_retries": {
     "preflight_lint": 1,
     "preflight_compile": 1,
     "start": 1,
     "implement": 1,
+    "simplify_opus": 1,
     "toolchain": 1
   },
   "context_values": {
-    "last_stage": "implement",
-    "thread.preflight_lint.current_node": "implement",
-    "internal.thread_id": "preflight_lint",
+    "internal.thread_id": "implement",
     "internal.retry_count.start": 1,
-    "thread.toolchain.current_node": "preflight_compile",
-    "current.preamble": "Goal: # Style SVG output from `fabro graph` and API\n\n## Context\n\nSVGs from `fabro graph` use raw Graphviz defaults (black strokes, white bg, Times-serif). The docs SVGs look much better: teal nodes, gray edges, Helvetica font, transparent bg, dark mode CSS. The goal is to make `fabro graph` and the API `get_graph` endpoint produce the same styled output without building a layout engine.\n\n## Approach: DOT defaults + SVG post-processing\n\n### Step 1: `inject_dot_style_defaults(source: &str) -> String` in `graph.rs`\n\nFind first `{`, insert after it:\n```dot\n    bgcolor=\"transparent\"\n    node [color=\"#357f9e\", fontname=\"Helvetica\", fontsize=12, fontcolor=\"#1a1a1a\"]\n    edge [color=\"#666666\", fontname=\"Helvetica\", fontsize=10, fontcolor=\"#666666\"]\n```\nThese are DOT defaults — per-node/edge attrs override them. Applies to both SVG and PNG.\n\n### Step 2: `postprocess_svg(raw: Vec<u8>) -> Vec<u8>` in `graph.rs`\n\nSVG-only. Two string operations:\n1. Remove line containing `<polygon fill=\"white\" stroke=\"none\"` (the white background)\n2. Insert dark mode `<style>` block after the `<svg ...>` closing `>`\n\n### Step 3: Wire into `render_dot()` in `graph.rs`\n\n- Call `inject_dot_style_defaults` on source before piping to `dot`\n- Call `postprocess_svg` on output when format is SVG\n\n### Step 4: Wire into `get_graph()` in `server.rs` (line ~1440, ~1467, ~1472)\n\n- Wrap `dot_source` with `inject_dot_style_defaults`\n- Wrap `output.stdout` with `postprocess_svg`\n\n### Step 5: Wire into `get_run_graph()` in `demo/mod.rs` (line ~227, ~248, ~252)\n\nSame two wraps.\n\n### Step 6: Tests in `graph.rs`\n\n- `inject_dot_style_defaults` inserts expected attrs\n- `inject_dot_style_defaults` returns unchanged if no `{`\n- `postprocess_svg` removes white background\n- `postprocess_svg` injects dark mode style block\n- Update `graph_valid_workflow_svg` to assert styled output\n\n## Files to modify\n\n1. `lib/crates/fabro-workflows/src/cli/graph.rs` — add 2 pub fns, modify `render_dot`, add tests\n2. `lib/crates/fabro-api/src/server.rs` — 2-line change in `get_graph`\n3. `lib/crates/fabro-api/src/demo/mod.rs` — 2-line change in `get_run_graph`\n\n## Verification\n\n1. `cargo test -p fabro-workflows -- graph` — unit tests pass\n2. `cargo test -p fabro-api` — API tests pass\n3. `cargo clippy --workspace -- -D warnings` — no warnings\n4. `fabro graph fabro/workflows/implement/workflow.fabro -o /tmp/test.svg` — visually inspect:\n   - Teal node strokes, gray edges, Helvetica font\n   - No white background\n   - Dark mode `<style>` block present\n   - Compare with `docs/images/tutorial-plan-implement.svg`\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",
+    "thread.implement.current_node": "simplify_opus",
+    "current.preamble": "Goal: # Style SVG output from `fabro graph` and API\n\n## Context\n\nSVGs from `fabro graph` use raw Graphviz defaults (black strokes, white bg, Times-serif). The docs SVGs look much better: teal nodes, gray edges, Helvetica font, transparent bg, dark mode CSS. The goal is to make `fabro graph` and the API `get_graph` endpoint produce the same styled output without building a layout engine.\n\n## Approach: DOT defaults + SVG post-processing\n\n### Step 1: `inject_dot_style_defaults(source: &str) -> String` in `graph.rs`\n\nFind first `{`, insert after it:\n```dot\n    bgcolor=\"transparent\"\n    node [color=\"#357f9e\", fontname=\"Helvetica\", fontsize=12, fontcolor=\"#1a1a1a\"]\n    edge [color=\"#666666\", fontname=\"Helvetica\", fontsize=10, fontcolor=\"#666666\"]\n```\nThese are DOT defaults — per-node/edge attrs override them. Applies to both SVG and PNG.\n\n### Step 2: `postprocess_svg(raw: Vec<u8>) -> Vec<u8>` in `graph.rs`\n\nSVG-only. Two string operations:\n1. Remove line containing `<polygon fill=\"white\" stroke=\"none\"` (the white background)\n2. Insert dark mode `<style>` block after the `<svg ...>` closing `>`\n\n### Step 3: Wire into `render_dot()` in `graph.rs`\n\n- Call `inject_dot_style_defaults` on source before piping to `dot`\n- Call `postprocess_svg` on output when format is SVG\n\n### Step 4: Wire into `get_graph()` in `server.rs` (line ~1440, ~1467, ~1472)\n\n- Wrap `dot_source` with `inject_dot_style_defaults`\n- Wrap `output.stdout` with `postprocess_svg`\n\n### Step 5: Wire into `get_run_graph()` in `demo/mod.rs` (line ~227, ~248, ~252)\n\nSame two wraps.\n\n### Step 6: Tests in `graph.rs`\n\n- `inject_dot_style_defaults` inserts expected attrs\n- `inject_dot_style_defaults` returns unchanged if no `{`\n- `postprocess_svg` removes white background\n- `postprocess_svg` injects dark mode style block\n- Update `graph_valid_workflow_svg` to assert styled output\n\n## Files to modify\n\n1. `lib/crates/fabro-workflows/src/cli/graph.rs` — add 2 pub fns, modify `render_dot`, add tests\n2. `lib/crates/fabro-api/src/server.rs` — 2-line change in `get_graph`\n3. `lib/crates/fabro-api/src/demo/mod.rs` — 2-line change in `get_run_graph`\n\n## Verification\n\n1. `cargo test -p fabro-workflows -- graph` — unit tests pass\n2. `cargo test -p fabro-api` — API tests pass\n3. `cargo clippy --workspace -- -D warnings` — no warnings\n4. `fabro graph fabro/workflows/implement/workflow.fabro -o /tmp/test.svg` — visually inspect:\n   - Teal node strokes, gray edges, Helvetica font\n   - No white background\n   - Dark mode `<style>` block present\n   - Compare with `docs/images/tutorial-plan-implement.svg`\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- **implement**: success\n  - Model: claude-opus-4-6, 37.6k tokens in / 7.8k out\n  - Files: /home/daytona/workspace/lib/crates/fabro-api/src/demo/mod.rs, /home/daytona/workspace/lib/crates/fabro-api/src/server.rs, /home/daytona/workspace/lib/crates/fabro-workflows/src/cli/graph.rs\n",
     "internal.run_id": "01KKT5VWYY8VQFETNRC7RTYKDW",
     "failure_class": "",
-    "outcome": "success",
-    "internal.retry_count.preflight_compile": 1,
-    "internal.retry_count.preflight_lint": 1,
-    "internal.node_visit_count": 1,
     "internal.fidelity": "compact",
-    "current_node": "implement",
     "graph.rankdir": "LR",
-    "internal.retry_count.toolchain": 1,
     "command.output": "",
-    "command.stderr": "",
     "graph.model_stylesheet": "\n            * { backend: api; model: claude-opus-4-6;}\n        ",
-    "thread.preflight_compile.current_node": "preflight_lint",
-    "graph.goal": "# Style SVG output from `fabro graph` and API\n\n## Context\n\nSVGs from `fabro graph` use raw Graphviz defaults (black strokes, white bg, Times-serif). The docs SVGs look much better: teal nodes, gray edges, Helvetica font, transparent bg, dark mode CSS. The goal is to make `fabro graph` and the API `get_graph` endpoint produce the same styled output without building a layout engine.\n\n## Approach: DOT defaults + SVG post-processing\n\n### Step 1: `inject_dot_style_defaults(source: &str) -> String` in `graph.rs`\n\nFind first `{`, insert after it:\n```dot\n    bgcolor=\"transparent\"\n    node [color=\"#357f9e\", fontname=\"Helvetica\", fontsize=12, fontcolor=\"#1a1a1a\"]\n    edge [color=\"#666666\", fontname=\"Helvetica\", fontsize=10, fontcolor=\"#666666\"]\n```\nThese are DOT defaults — per-node/edge attrs override them. Applies to both SVG and PNG.\n\n### Step 2: `postprocess_svg(raw: Vec<u8>) -> Vec<u8>` in `graph.rs`\n\nSVG-only. Two string operations:\n1. Remove line containing `<polygon fill=\"white\" stroke=\"none\"` (the white background)\n2. Insert dark mode `<style>` block after the `<svg ...>` closing `>`\n\n### Step 3: Wire into `render_dot()` in `graph.rs`\n\n- Call `inject_dot_style_defaults` on source before piping to `dot`\n- Call `postprocess_svg` on output when format is SVG\n\n### Step 4: Wire into `get_graph()` in `server.rs` (line ~1440, ~1467, ~1472)\n\n- Wrap `dot_source` with `inject_dot_style_defaults`\n- Wrap `output.stdout` with `postprocess_svg`\n\n### Step 5: Wire into `get_run_graph()` in `demo/mod.rs` (line ~227, ~248, ~252)\n\nSame two wraps.\n\n### Step 6: Tests in `graph.rs`\n\n- `inject_dot_style_defaults` inserts expected attrs\n- `inject_dot_style_defaults` returns unchanged if no `{`\n- `postprocess_svg` removes white background\n- `postprocess_svg` injects dark mode style block\n- Update `graph_valid_workflow_svg` to assert styled output\n\n## Files to modify\n\n1. `lib/crates/fabro-workflows/src/cli/graph.rs` — add 2 pub fns, modify `render_dot`, add tests\n2. `lib/crates/fabro-api/src/server.rs` — 2-line change in `get_graph`\n3. `lib/crates/fabro-api/src/demo/mod.rs` — 2-line change in `get_run_graph`\n\n## Verification\n\n1. `cargo test -p fabro-workflows -- graph` — unit tests pass\n2. `cargo test -p fabro-api` — API tests pass\n3. `cargo clippy --workspace -- -D warnings` — no warnings\n4. `fabro graph fabro/workflows/implement/workflow.fabro -o /tmp/test.svg` — visually inspect:\n   - Teal node strokes, gray edges, Helvetica font\n   - No white background\n   - Dark mode `<style>` block present\n   - Compare with `docs/images/tutorial-plan-implement.svg`\n",
     "failure_signature": "",
     "thread.start.current_node": "toolchain",
+    "thread.preflight_lint.current_node": "implement",
+    "thread.toolchain.current_node": "preflight_compile",
+    "internal.retry_count.preflight_lint": 1,
+    "internal.retry_count.preflight_compile": 1,
+    "outcome": "success",
+    "internal.node_visit_count": 1,
+    "current_node": "simplify_opus",
+    "internal.retry_count.simplify_opus": 1,
+    "internal.retry_count.toolchain": 1,
+    "command.stderr": "",
+    "thread.preflight_compile.current_node": "preflight_lint",
+    "last_stage": "simplify_opus",
+    "graph.goal": "# Style SVG output from `fabro graph` and API\n\n## Context\n\nSVGs from `fabro graph` use raw Graphviz defaults (black strokes, white bg, Times-serif). The docs SVGs look much better: teal nodes, gray edges, Helvetica font, transparent bg, dark mode CSS. The goal is to make `fabro graph` and the API `get_graph` endpoint produce the same styled output without building a layout engine.\n\n## Approach: DOT defaults + SVG post-processing\n\n### Step 1: `inject_dot_style_defaults(source: &str) -> String` in `graph.rs`\n\nFind first `{`, insert after it:\n```dot\n    bgcolor=\"transparent\"\n    node [color=\"#357f9e\", fontname=\"Helvetica\", fontsize=12, fontcolor=\"#1a1a1a\"]\n    edge [color=\"#666666\", fontname=\"Helvetica\", fontsize=10, fontcolor=\"#666666\"]\n```\nThese are DOT defaults — per-node/edge attrs override them. Applies to both SVG and PNG.\n\n### Step 2: `postprocess_svg(raw: Vec<u8>) -> Vec<u8>` in `graph.rs`\n\nSVG-only. Two string operations:\n1. Remove line containing `<polygon fill=\"white\" stroke=\"none\"` (the white background)\n2. Insert dark mode `<style>` block after the `<svg ...>` closing `>`\n\n### Step 3: Wire into `render_dot()` in `graph.rs`\n\n- Call `inject_dot_style_defaults` on source before piping to `dot`\n- Call `postprocess_svg` on output when format is SVG\n\n### Step 4: Wire into `get_graph()` in `server.rs` (line ~1440, ~1467, ~1472)\n\n- Wrap `dot_source` with `inject_dot_style_defaults`\n- Wrap `output.stdout` with `postprocess_svg`\n\n### Step 5: Wire into `get_run_graph()` in `demo/mod.rs` (line ~227, ~248, ~252)\n\nSame two wraps.\n\n### Step 6: Tests in `graph.rs`\n\n- `inject_dot_style_defaults` inserts expected attrs\n- `inject_dot_style_defaults` returns unchanged if no `{`\n- `postprocess_svg` removes white background\n- `postprocess_svg` injects dark mode style block\n- Update `graph_valid_workflow_svg` to assert styled output\n\n## Files to modify\n\n1. `lib/crates/fabro-workflows/src/cli/graph.rs` — add 2 pub fns, modify `render_dot`, add tests\n2. `lib/crates/fabro-api/src/server.rs` — 2-line change in `get_graph`\n3. `lib/crates/fabro-api/src/demo/mod.rs` — 2-line change in `get_run_graph`\n\n## Verification\n\n1. `cargo test -p fabro-workflows -- graph` — unit tests pass\n2. `cargo test -p fabro-api` — API tests pass\n3. `cargo clippy --workspace -- -D warnings` — no warnings\n4. `fabro graph fabro/workflows/implement/workflow.fabro -o /tmp/test.svg` — visually inspect:\n   - Teal node strokes, gray edges, Helvetica font\n   - No white background\n   - Dark mode `<style>` block present\n   - Compare with `docs/images/tutorial-plan-implement.svg`\n",
     "internal.retry_count.implement": 1,
-    "last_response": "Everything looks good. Let me provide a summary of all changes made:\n\n## Summary\n\n### Changes made across 3 files:\n\n**1. `lib/crates/fabro-workflows/src/cli/graph.rs`** — Core implementation + tests",
+    "response.simplify_opus": "All checks pass. Here's a summary of the review and fixes:\n\n## Summary\n\n**3 issues found and fixed:**\n\n1. **Code duplication eliminated** — The async DOT→SVG rendering logic was copy-pasted across `server.rs::get_graph` and `demo/mod.rs::get_run_graph` (spawn `dot -Tsvg`, pipe stdin, collect stdout, apply style defaults + SVG post-processing). Extracted a shared `render_dot_svg()` async helper in `server.rs` (as `pub(crate)`). The demo handler now calls `crate::server::render_dot_svg(dot_source).await` — a single line replacing ~25 lines of duplicated code.\n\n2. **Unnecessary allocation removed** — `String::from_utf8_lossy(&raw).into_owned()` in `postprocess_svg` always clones the buffer, even when the input is valid UTF-8 (which Graphviz always outputs). Changed to `String::from_utf8(raw)` which reuses the original `Vec<u8>` backing buffer zero-copy, with a `unwrap_or_else` fallback for the impossible non-UTF-8 case.\n\n3. **Redundant `format!` eliminated** — `format!(\"\\n{DARK_MODE_STYLE}\")` allocated a new `String` on every call just to prepend a newline. Folded the leading newline into the `DARK_MODE_STYLE` constant and replaced with a direct `insert_str(_, DARK_MODE_STYLE)`.\n\n**Skipped (not worth fixing):**\n- The `lines().filter().collect::<Vec<_>>().join(\"\\n\")` pattern in `postprocess_svg` — micro-optimization for ~200 lines of SVG that takes microseconds vs. the ~50ms `dot` subprocess. Not worth the readability cost.",
+    "last_response": "All checks pass. Here's a summary of the review and fixes:\n\n## Summary\n\n**3 issues found and fixed:**\n\n1. **Code duplication eliminated** — The async DOT→SVG rendering logic was copy-pasted across",
     "response.implement": "Everything looks good. Let me provide a summary of all changes made:\n\n## Summary\n\n### Changes made across 3 files:\n\n**1. `lib/crates/fabro-workflows/src/cli/graph.rs`** — Core implementation + tests\n\n- Added `DARK_MODE_STYLE` constant — CSS `<style>` block with `@media (prefers-color-scheme: dark)` that adjusts text fill, stroke colors, and polygon fills for dark mode viewing\n- Added `pub fn inject_dot_style_defaults(source: &str) -> String` — Inserts DOT graph-level defaults (`bgcolor=\"transparent\"`, teal node styling with `#357f9e`, gray edge styling with `#666666`, Helvetica font) after the first `{` in DOT source. Returns unchanged if no `{` found.\n- Added `pub fn postprocess_svg(raw: Vec<u8>) -> Vec<u8>` — Removes the white background `<polygon>` line and inserts the dark mode `<style>` block after the opening `<svg ...>` tag\n- Modified `render_dot()` — Calls `inject_dot_style_defaults` on source before piping to `dot`, and calls `postprocess_svg` on output when format is SVG\n- Added 4 new unit tests: `inject_dot_style_defaults_inserts_attrs`, `inject_dot_style_defaults_no_brace`, `postprocess_svg_removes_white_bg`, `postprocess_svg_injects_dark_mode`\n- Updated `graph_valid_workflow_svg` test to assert dark mode style block is present and white background is removed\n\n**2. `lib/crates/fabro-api/src/server.rs`** — API `get_graph` endpoint\n\n- Wrapped `dot_source` with `inject_dot_style_defaults` before piping to `dot`\n- Wrapped `output.stdout` with `postprocess_svg` in the success response\n\n**3. `lib/crates/fabro-api/src/demo/mod.rs`** — Demo `get_run_graph` endpoint\n\n- Same two wraps: `inject_dot_style_defaults` on the DOT source, `postprocess_svg` on the output\n\n### Verification results:\n- ✅ `cargo test -p fabro-workflows -- graph` — 108 tests pass (including 4 new + 1 updated)\n- ✅ `cargo test -p fabro-api` — 76 tests pass (62 unit + 14 integration)\n- ✅ `cargo clippy --workspace -- -D warnings` — zero warnings"
   },
   "logs": [],
@@ -96,17 +101,42 @@
       "notes": "Script completed: cargo check -q --workspace 2>&1",
       "duration_ms": 72647
     },
+    "simplify_opus": {
+      "status": "success",
+      "context_updates": {
+        "last_stage": "simplify_opus",
+        "response.simplify_opus": "All checks pass. Here's a summary of the review and fixes:\n\n## Summary\n\n**3 issues found and fixed:**\n\n1. **Code duplication eliminated** — The async DOT→SVG rendering logic was copy-pasted across `server.rs::get_graph` and `demo/mod.rs::get_run_graph` (spawn `dot -Tsvg`, pipe stdin, collect stdout, apply style defaults + SVG post-processing). Extracted a shared `render_dot_svg()` async helper in `server.rs` (as `pub(crate)`). The demo handler now calls `crate::server::render_dot_svg(dot_source).await` — a single line replacing ~25 lines of duplicated code.\n\n2. **Unnecessary allocation removed** — `String::from_utf8_lossy(&raw).into_owned()` in `postprocess_svg` always clones the buffer, even when the input is valid UTF-8 (which Graphviz always outputs). Changed to `String::from_utf8(raw)` which reuses the original `Vec<u8>` backing buffer zero-copy, with a `unwrap_or_else` fallback for the impossible non-UTF-8 case.\n\n3. **Redundant `format!` eliminated** — `format!(\"\\n{DARK_MODE_STYLE}\")` allocated a new `String` on every call just to prepend a newline. Folded the leading newline into the `DARK_MODE_STYLE` constant and replaced with a direct `insert_str(_, DARK_MODE_STYLE)`.\n\n**Skipped (not worth fixing):**\n- The `lines().filter().collect::<Vec<_>>().join(\"\\n\")` pattern in `postprocess_svg` — micro-optimization for ~200 lines of SVG that takes microseconds vs. the ~50ms `dot` subprocess. Not worth the readability cost.",
+        "last_response": "All checks pass. Here's a summary of the review and fixes:\n\n## Summary\n\n**3 issues found and fixed:**\n\n1. **Code duplication eliminated** — The async DOT→SVG rendering logic was copy-pasted across"
+      },
+      "notes": "Stage completed: simplify_opus",
+      "usage": {
+        "model": "claude-opus-4-6",
+        "input_tokens": 36237,
+        "output_tokens": 13475,
+        "cache_read_tokens": 634699,
+        "cache_write_tokens": 41947,
+        "reasoning_tokens": 714,
+        "cost": 1.5541800000000001
+      },
+      "files_touched": [
+        "/home/daytona/workspace/lib/crates/fabro-api/src/demo/mod.rs",
+        "/home/daytona/workspace/lib/crates/fabro-api/src/server.rs",
+        "/home/daytona/workspace/lib/crates/fabro-workflows/src/cli/graph.rs"
+      ],
+      "duration_ms": 351417
+    },
     "start": {
       "status": "success",
       "duration_ms": 0
     }
   },
-  "next_node_id": "simplify_opus",
+  "next_node_id": "simplify_gemini",
   "node_visits": {
     "preflight_lint": 1,
     "implement": 1,
     "start": 1,
     "toolchain": 1,
-    "preflight_compile": 1
+    "preflight_compile": 1,
+    "simplify_opus": 1
   }
 }
\ No newline at end of file
diff --git a/nodes/implement/diff.patch b/nodes/implement/diff.patch
new file mode 100644
index 000000000..575a8d5e6
--- /dev/null
+++ b/nodes/implement/diff.patch
@@ -0,0 +1,219 @@
+diff --git a/lib/crates/fabro-api/src/demo/mod.rs b/lib/crates/fabro-api/src/demo/mod.rs
+index d056854..d724e32 100644
+--- a/lib/crates/fabro-api/src/demo/mod.rs
++++ b/lib/crates/fabro-api/src/demo/mod.rs
+@@ -226,6 +226,8 @@ pub async fn get_run_graph(
+     // Use graphviz to render the demo DOT source
+     let dot_source = "digraph demo {\n  graph [goal=\"Demo\"]\n  rankdir=LR\n  start [shape=Mdiamond, label=\"Start\"]\n  detect [label=\"Detect\\nDrift\"]\n  exit [shape=Msquare, label=\"Exit\"]\n  propose [label=\"Propose\\nChanges\"]\n  review [label=\"Review\\nChanges\"]\n  apply [label=\"Apply\\nChanges\"]\n  start -> detect\n  detect -> exit [label=\"No drift\"]\n  detect -> propose [label=\"Drift found\"]\n  propose -> review\n  review -> propose [label=\"Revise\"]\n  review -> apply [label=\"Accept\"]\n  apply -> exit\n}";
+ 
++    let styled_source = fabro_workflows::cli::graph::inject_dot_style_defaults(dot_source);
++
+     let mut child = match tokio::process::Command::new("dot")
+         .arg("-Tsvg")
+         .stdin(std::process::Stdio::piped())
+@@ -245,14 +247,14 @@ pub async fn get_run_graph(
+ 
+     if let Some(mut stdin) = child.stdin.take() {
+         use tokio::io::AsyncWriteExt;
+-        let _ = stdin.write_all(dot_source.as_bytes()).await;
++        let _ = stdin.write_all(styled_source.as_bytes()).await;
+     }
+ 
+     match child.wait_with_output().await {
+         Ok(output) if output.status.success() => (
+             StatusCode::OK,
+             [("content-type", "image/svg+xml")],
+-            output.stdout,
++            fabro_workflows::cli::graph::postprocess_svg(output.stdout),
+         )
+             .into_response(),
+         _ => ApiError::new(StatusCode::BAD_GATEWAY, "Dot rendering failed.").into_response(),
+diff --git a/lib/crates/fabro-api/src/server.rs b/lib/crates/fabro-api/src/server.rs
+index 59debde..ddb460a 100644
+--- a/lib/crates/fabro-api/src/server.rs
++++ b/lib/crates/fabro-api/src/server.rs
+@@ -1445,6 +1445,8 @@ async fn get_graph(
+         }
+     };
+ 
++    let styled_source = fabro_workflows::cli::graph::inject_dot_style_defaults(&dot_source);
++
+     let mut child = match tokio::process::Command::new("dot")
+         .arg("-Tsvg")
+         .stdin(std::process::Stdio::piped())
+@@ -1464,7 +1466,7 @@ async fn get_graph(
+ 
+     if let Some(mut stdin) = child.stdin.take() {
+         use tokio::io::AsyncWriteExt;
+-        let _ = stdin.write_all(dot_source.as_bytes()).await;
++        let _ = stdin.write_all(styled_source.as_bytes()).await;
+         // stdin is dropped here, closing the pipe
+     }
+ 
+@@ -1472,7 +1474,7 @@ async fn get_graph(
+         Ok(output) if output.status.success() => (
+             StatusCode::OK,
+             [("content-type", "image/svg+xml")],
+-            output.stdout,
++            fabro_workflows::cli::graph::postprocess_svg(output.stdout),
+         )
+             .into_response(),
+         Ok(output) => {
+diff --git a/lib/crates/fabro-workflows/src/cli/graph.rs b/lib/crates/fabro-workflows/src/cli/graph.rs
+index daab1c6..0b21fdf 100644
+--- a/lib/crates/fabro-workflows/src/cli/graph.rs
++++ b/lib/crates/fabro-workflows/src/cli/graph.rs
+@@ -76,8 +76,62 @@ pub fn graph_command(args: &GraphArgs, styles: &Styles) -> anyhow::Result<()> {
+     Ok(())
+ }
+ 
++/// Dark mode CSS injected into SVG output.
++const DARK_MODE_STYLE: &str = r##"<style>
++  @media (prefers-color-scheme: dark) {
++    text { fill: #e0e0e0 !important; }
++    [stroke="#357f9e"] { stroke: #5bb8d8; }
++    [stroke="#666666"] { stroke: #999999; }
++    polygon[fill="#357f9e"] { fill: #5bb8d8; }
++    polygon[fill="#666666"] { fill: #999999; }
++  }
++</style>"##;
++
++/// Inject DOT graph-level style defaults (transparent background, teal nodes,
++/// gray edges, Helvetica font) right after the first `{` in the DOT source.
++/// Per-node/edge attributes override these defaults.
++pub fn inject_dot_style_defaults(source: &str) -> String {
++    let Some(pos) = source.find('{') else {
++        return source.to_string();
++    };
++    let (before, after) = source.split_at(pos + 1);
++    format!(
++        "{before}\n    bgcolor=\"transparent\"\n    node [color=\"#357f9e\", fontname=\"Helvetica\", fontsize=12, fontcolor=\"#1a1a1a\"]\n    edge [color=\"#666666\", fontname=\"Helvetica\", fontsize=10, fontcolor=\"#666666\"]\n{after}"
++    )
++}
++
++/// Post-process raw SVG output from Graphviz:
++/// 1. Remove the white background `<polygon>` element
++/// 2. Insert a dark-mode `<style>` block after the opening `<svg ...>` tag
++pub fn postprocess_svg(raw: Vec<u8>) -> Vec<u8> {
++    let mut svg = String::from_utf8_lossy(&raw).into_owned();
++
++    // Remove white background polygon (single line containing it)
++    svg = svg
++        .lines()
++        .filter(|line| {
++            !(line.contains("<polygon")
++                && line.contains("fill=\"white\"")
++                && line.contains("stroke=\"none\""))
++        })
++        .collect::<Vec<_>>()
++        .join("\n");
++
++    // Insert dark mode style block after the opening <svg ...> tag
++    if let Some(svg_close) = svg
++        .find("<svg")
++        .and_then(|start| svg[start..].find('>').map(|end| start + end))
++    {
++        svg.insert_str(svg_close + 1, &format!("\n{DARK_MODE_STYLE}"));
++    }
++
++    svg.into_bytes()
++}
++
+ /// Spawn the `dot` command to render DOT source into the given format.
+ fn render_dot(source: &str, format: GraphFormat) -> anyhow::Result<Vec<u8>> {
++    let styled_source = inject_dot_style_defaults(source);
++
+     let mut child = match Command::new("dot")
+         .arg(format!("-T{format}"))
+         .stdin(std::process::Stdio::piped())
+@@ -95,7 +149,7 @@ fn render_dot(source: &str, format: GraphFormat) -> anyhow::Result<Vec<u8>> {
+     };
+ 
+     if let Some(mut stdin) = child.stdin.take() {
+-        stdin.write_all(source.as_bytes())?;
++        stdin.write_all(styled_source.as_bytes())?;
+     }
+ 
+     let output = child.wait_with_output()?;
+@@ -105,7 +159,12 @@ fn render_dot(source: &str, format: GraphFormat) -> anyhow::Result<Vec<u8>> {
+         bail!("dot failed: {stderr}");
+     }
+ 
+-    Ok(output.stdout)
++    let raw = output.stdout;
++    if matches!(format, GraphFormat::Svg) {
++        Ok(postprocess_svg(raw))
++    } else {
++        Ok(raw)
++    }
+ }
+ 
+ /// Check whether the `dot` command is available on PATH.
+@@ -194,6 +253,14 @@ mod tests {
+ 
+         let content = std::fs::read_to_string(&output_path).unwrap();
+         assert!(content.contains("<svg"), "expected SVG content");
++        assert!(
++            content.contains("prefers-color-scheme: dark"),
++            "expected dark mode style block"
++        );
++        assert!(
++            !content.contains("fill=\"white\""),
++            "white background should be removed"
++        );
+     }
+ 
+     #[test]
+@@ -258,6 +325,52 @@ mod tests {
+         assert!(!content.is_empty(), "output file should not be empty");
+     }
+ 
++    #[test]
++    fn inject_dot_style_defaults_inserts_attrs() {
++        let source = "digraph G {\n    a -> b\n}";
++        let styled = inject_dot_style_defaults(source);
++        assert!(styled.contains("bgcolor=\"transparent\""));
++        assert!(styled.contains("node [color=\"#357f9e\""));
++        assert!(styled.contains("fontname=\"Helvetica\""));
++        assert!(styled.contains("edge [color=\"#666666\""));
++        // Original content preserved
++        assert!(styled.contains("a -> b"));
++    }
++
++    #[test]
++    fn inject_dot_style_defaults_no_brace() {
++        let source = "no brace here";
++        let result = inject_dot_style_defaults(source);
++        assert_eq!(result, source);
++    }
++
++    #[test]
++    fn postprocess_svg_removes_white_bg() {
++        let svg = b"<svg xmlns=\"...\" width=\"100\">\n<polygon fill=\"white\" stroke=\"none\" points=\"0,0 100,0 100,100 0,100\"/>\n<g>content</g>\n</svg>";
++        let result = postprocess_svg(svg.to_vec());
++        let result_str = String::from_utf8(result).unwrap();
++        assert!(
++            !result_str.contains("fill=\"white\""),
++            "white background polygon should be removed"
++        );
++        assert!(result_str.contains("<g>content</g>"));
++    }
++
++    #[test]
++    fn postprocess_svg_injects_dark_mode() {
++        let svg = b"<svg xmlns=\"...\" width=\"100\">\n<g>content</g>\n</svg>";
++        let result = postprocess_svg(svg.to_vec());
++        let result_str = String::from_utf8(result).unwrap();
++        assert!(
++            result_str.contains("prefers-color-scheme: dark"),
++            "dark mode style block should be present"
++        );
++        // Style block should come after <svg ...>
++        let svg_tag_end = result_str.find('>').unwrap();
++        let style_pos = result_str.find("<style>").unwrap();
++        assert!(style_pos > svg_tag_end);
++    }
++
+     #[test]
+     fn graph_toml_path() {
+         if !dot_is_available() {
diff --git a/nodes/simplify_opus/prompt.md b/nodes/simplify_opus/prompt.md
new file mode 100644
index 000000000..6064688da
--- /dev/null
+++ b/nodes/simplify_opus/prompt.md
@@ -0,0 +1,135 @@
+Goal: # Style SVG output from `fabro graph` and API
+
+## Context
+
+SVGs from `fabro graph` use raw Graphviz defaults (black strokes, white bg, Times-serif). The docs SVGs look much better: teal nodes, gray edges, Helvetica font, transparent bg, dark mode CSS. The goal is to make `fabro graph` and the API `get_graph` endpoint produce the same styled output without building a layout engine.
+
+## Approach: DOT defaults + SVG post-processing
+
+### Step 1: `inject_dot_style_defaults(source: &str) -> String` in `graph.rs`
+
+Find first `{`, insert after it:
+```dot
+    bgcolor="transparent"
+    node [color="#357f9e", fontname="Helvetica", fontsize=12, fontcolor="#1a1a1a"]
+    edge [color="#666666", fontname="Helvetica", fontsize=10, fontcolor="#666666"]
+```
+These are DOT defaults — per-node/edge attrs override them. Applies to both SVG and PNG.
+
+### Step 2: `postprocess_svg(raw: Vec<u8>) -> Vec<u8>` in `graph.rs`
+
+SVG-only. Two string operations:
+1. Remove line containing `<polygon fill="white" stroke="none"` (the white background)
+2. Insert dark mode `<style>` block after the `<svg ...>` closing `>`
+
+### Step 3: Wire into `render_dot()` in `graph.rs`
+
+- Call `inject_dot_style_defaults` on source before piping to `dot`
+- Call `postprocess_svg` on output when format is SVG
+
+### Step 4: Wire into `get_graph()` in `server.rs` (line ~1440, ~1467, ~1472)
+
+- Wrap `dot_source` with `inject_dot_style_defaults`
+- Wrap `output.stdout` with `postprocess_svg`
+
+### Step 5: Wire into `get_run_graph()` in `demo/mod.rs` (line ~227, ~248, ~252)
+
+Same two wraps.
+
+### Step 6: Tests in `graph.rs`
+
+- `inject_dot_style_defaults` inserts expected attrs
+- `inject_dot_style_defaults` returns unchanged if no `{`
+- `postprocess_svg` removes white background
+- `postprocess_svg` injects dark mode style block
+- Update `graph_valid_workflow_svg` to assert styled output
+
+## Files to modify
+
+1. `lib/crates/fabro-workflows/src/cli/graph.rs` — add 2 pub fns, modify `render_dot`, add tests
+2. `lib/crates/fabro-api/src/server.rs` — 2-line change in `get_graph`
+3. `lib/crates/fabro-api/src/demo/mod.rs` — 2-line change in `get_run_graph`
+
+## Verification
+
+1. `cargo test -p fabro-workflows -- graph` — unit tests pass
+2. `cargo test -p fabro-api` — API tests pass
+3. `cargo clippy --workspace -- -D warnings` — no warnings
+4. `fabro graph fabro/workflows/implement/workflow.fabro -o /tmp/test.svg` — visually inspect:
+   - Teal node strokes, gray edges, Helvetica font
+   - No white background
+   - Dark mode `<style>` block present
+   - Compare with `docs/images/tutorial-plan-implement.svg`
+
+
+## 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)
+- **implement**: success
+  - Model: claude-opus-4-6, 37.6k tokens in / 7.8k out
+  - Files: /home/daytona/workspace/lib/crates/fabro-api/src/demo/mod.rs, /home/daytona/workspace/lib/crates/fabro-api/src/server.rs, /home/daytona/workspace/lib/crates/fabro-workflows/src/cli/graph.rs
+
+
+# Simplify: Code Review and Cleanup
+
+Review all changed files for reuse, quality, and efficiency. Fix any issues found.
+
+## Phase 1: Identify Changes
+
+Run git diff (or git diff HEAD if there are staged changes) to see what changed. If there are no git changes, review the most recently modified files that the user mentioned or that you edited earlier in this conversation.
+
+## Phase 2: Launch Three Review Agents in Parallel
+
+Use the Agent tool to launch all three agents concurrently in a single message. Pass each agent the full diff so it has the complete context.
+
+### Agent 1: Code Reuse Review
+
+For each change:
+
+1. Search for existing utilities and helpers that could replace newly written code. Use Grep to find similar patterns elsewhere in the codebase — common locations are utility directories, shared modules, and files adjacent to the changed ones.
+2. Flag any new function that duplicates existing functionality. Suggest the existing function to use instead.
+3. Flag any inline logic that could use an existing utility — hand-rolled string manipulation, manual path handling, custom environment checks, ad-hoc type guards, and similar patterns are common candidates.
+
+Note: This is a greenfield app, so focus on maximizing simplicity and don't worry about changing things to achieve it.
+
+### Agent 2: Code Quality Review
+
+Review the same changes for hacky patterns:
+
+1. Redundant state: state that duplicates existing state, cached values that could be derived, observers/effects that could be direct calls
+2. Parameter sprawl: adding new parameters to a function instead of generalizing or restructuring existing ones
+3. Copy-paste with slight variation: near-duplicate code blocks that should be unified with a shared abstraction
+4. Leaky abstractions: exposing internal details that should be encapsulated, or breaking existing abstraction boundaries
+5. Stringly-typed code: using raw strings where constants, enums (string unions), or branded types already exist in the codebase
+
+Note: This is a greenfield app, so be aggressive in optimizing quality.
+
+### Agent 3: Efficiency Review
+
+Review the same changes for efficiency:
+
+1. Unnecessary work: redundant computations, repeated file reads, duplicate network/API calls, N+1 patterns
+2. Missed concurrency: independent operations run sequentially when they could run in parallel
+3. Hot-path bloat: new blocking work added to startup or per-request/per-render hot paths
+4. Unnecessary existence checks: pre-checking file/resource existence before operating (TOCTOU anti-pattern) — operate directly and handle the error
+5. Memory: unbounded data structures, missing cleanup, event listener leaks
+6. Overly broad operations: reading entire files when only a portion is needed, loading all items when filtering for one
+
+## Phase 3: Fix Issues
+
+Wait for all three agents to complete. Aggregate their findings and fix each issue directly. If a finding is a false positive or not worth addressing, note it and move on — do not argue with the finding, just skip it.
+
+When done, briefly summarize what was fixed (or confirm the code was already clean).
\ No newline at end of file
diff --git a/nodes/simplify_opus/provider_used.json b/nodes/simplify_opus/provider_used.json
new file mode 100644
index 000000000..c1905ff10
--- /dev/null
+++ b/nodes/simplify_opus/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/simplify_opus/response.md b/nodes/simplify_opus/response.md
new file mode 100644
index 000000000..13eb3f340
--- /dev/null
+++ b/nodes/simplify_opus/response.md
@@ -0,0 +1,14 @@
+All checks pass. Here's a summary of the review and fixes:
+
+## Summary
+
+**3 issues found and fixed:**
+
+1. **Code duplication eliminated** — The async DOT→SVG rendering logic was copy-pasted across `server.rs::get_graph` and `demo/mod.rs::get_run_graph` (spawn `dot -Tsvg`, pipe stdin, collect stdout, apply style defaults + SVG post-processing). Extracted a shared `render_dot_svg()` async helper in `server.rs` (as `pub(crate)`). The demo handler now calls `crate::server::render_dot_svg(dot_source).await` — a single line replacing ~25 lines of duplicated code.
+
+2. **Unnecessary allocation removed** — `String::from_utf8_lossy(&raw).into_owned()` in `postprocess_svg` always clones the buffer, even when the input is valid UTF-8 (which Graphviz always outputs). Changed to `String::from_utf8(raw)` which reuses the original `Vec<u8>` backing buffer zero-copy, with a `unwrap_or_else` fallback for the impossible non-UTF-8 case.
+
+3. **Redundant `format!` eliminated** — `format!("\n{DARK_MODE_STYLE}")` allocated a new `String` on every call just to prepend a newline. Folded the leading newline into the `DARK_MODE_STYLE` constant and replaced with a direct `insert_str(_, DARK_MODE_STYLE)`.
+
+**Skipped (not worth fixing):**
+- The `lines().filter().collect::<Vec<_>>().join("\n")` pattern in `postprocess_svg` — micro-optimization for ~200 lines of SVG that takes microseconds vs. the ~50ms `dot` subprocess. Not worth the readability cost.
\ No newline at end of file
diff --git a/nodes/simplify_opus/status.json b/nodes/simplify_opus/status.json
new file mode 100644
index 000000000..fb290f23f
--- /dev/null
+++ b/nodes/simplify_opus/status.json
@@ -0,0 +1,6 @@
+{
+  "status": "success",
+  "notes": "Stage completed: simplify_opus",
+  "failure_reason": null,
+  "timestamp": "2026-03-16T02:10:49.290485+00:00"
+}
\ No newline at end of file