diff --git a/checkpoint.json b/checkpoint.json
index 9df28a282..98a843ed9 100644
--- a/checkpoint.json
+++ b/checkpoint.json
@@ -1,6 +1,6 @@
 {
-  "timestamp": "2026-03-16T02:16:31.906341Z",
-  "current_node": "simplify_gemini",
+  "timestamp": "2026-03-16T02:20:47.588217Z",
+  "current_node": "simplify_gpt",
   "completed_nodes": [
     "start",
     "toolchain",
@@ -8,53 +8,103 @@
     "preflight_lint",
     "implement",
     "simplify_opus",
-    "simplify_gemini"
+    "simplify_gemini",
+    "simplify_gpt"
   ],
   "node_retries": {
+    "implement": 1,
+    "simplify_gemini": 1,
+    "simplify_opus": 1,
+    "simplify_gpt": 1,
     "preflight_lint": 1,
     "preflight_compile": 1,
     "start": 1,
-    "implement": 1,
-    "simplify_opus": 1,
-    "simplify_gemini": 1,
     "toolchain": 1
   },
   "context_values": {
     "response.simplify_gemini": "Everything passes. Here's the summary:\n\n## Summary\n\n**Fixed: Duplicate subprocess orchestration** (the main issue found across all three reviews)\n\n`render_dot_svg` in `server.rs` was a near-copy of `render_dot` in `graph.rs` — both spawned a `dot` subprocess, piped DOT source to stdin, injected style defaults, and post-processed SVG output. The only difference was sync vs async and error types.\n\n**Changes made:**\n\n1. **`graph.rs`**: Made `render_dot` public (the single authoritative implementation). Made `inject_dot_style_defaults` and `postprocess_svg` private — they're implementation details of `render_dot`, not a two-phase protocol callers need to know about.\n\n2. **`server.rs`**: Replaced 35 lines of duplicated subprocess code in `render_dot_svg` with a 10-line function that calls `render_dot` via `tokio::task::spawn_blocking` and converts the result to a `Response`. The demo handler (`demo/mod.rs`) already delegates to `render_dot_svg`, so no changes needed there.\n\n**Skipped (not worth addressing):**\n- Efficiency findings in `postprocess_svg` (line-by-line filtering, `insert_str` shift) — SVGs are ~KB and subprocess launch dominates; not worth the complexity.\n- Extracting color constants — the coupling between DOT attrs and CSS selectors is inherent and co-locating the values wouldn't improve readability.",
-    "internal.thread_id": "simplify_opus",
+    "internal.thread_id": "simplify_gemini",
     "internal.retry_count.start": 1,
     "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- **simplify_opus**: success\n  - Model: claude-opus-4-6, 36.2k tokens in / 13.5k 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",
+    "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- **simplify_opus**: success\n  - Model: claude-opus-4-6, 36.2k tokens in / 13.5k 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- **simplify_gemini**: success\n  - Model: claude-opus-4-6, 36.3k tokens in / 14.7k out\n  - Files: /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": "",
+    "response.simplify_gpt": "The code is clean. Here's a summary of the review:\n\n**Fixed:**\n- **Long format string in `inject_dot_style_defaults`** (graph.rs line 100): Extracted the inline DOT defaults into a `DOT_STYLE_DEFAULTS` const using a `r##\"...\"##` raw string literal, matching the style of the existing `DARK_MODE_STYLE` const. The `format!` call is now a clean `format!(\"{before}{DOT_STYLE_DEFAULTS}{after}\")` instead of a 200+ character single line with embedded `\\n` escapes.\n\n**Already clean (no action needed):**\n- **Code reuse**: The `render_dot_svg` helper in `server.rs` properly deduplicates the inline dot rendering that was previously copy-pasted in both `server.rs` and `demo/mod.rs`. No other SVG/DOT utilities exist in the codebase.\n- **Color coupling**: `#357f9e` and `#666666` appear in both DOT defaults and dark mode CSS selectors — this is by design (CSS targets the DOT-generated attributes).\n- **Efficiency**: The `postprocess_svg` string allocations are negligible for SVG sizes (a few KB). The `spawn_blocking` approach is appropriate since `render_dot` does synchronous I/O + string processing.\n- **No copy-paste, no parameter sprawl, no leaky abstractions** — the change is well-structured.",
     "internal.fidelity": "compact",
     "graph.rankdir": "LR",
     "command.output": "",
     "graph.model_stylesheet": "\n            * { backend: api; model: claude-opus-4-6;}\n        ",
     "failure_signature": "",
     "thread.start.current_node": "toolchain",
+    "internal.retry_count.simplify_gpt": 1,
     "internal.retry_count.simplify_gemini": 1,
     "thread.preflight_lint.current_node": "implement",
     "thread.toolchain.current_node": "preflight_compile",
     "internal.retry_count.preflight_lint": 1,
     "internal.retry_count.preflight_compile": 1,
+    "thread.simplify_gemini.current_node": "simplify_gpt",
     "outcome": "success",
     "thread.simplify_opus.current_node": "simplify_gemini",
     "internal.node_visit_count": 1,
-    "current_node": "simplify_gemini",
+    "current_node": "simplify_gpt",
     "internal.retry_count.simplify_opus": 1,
     "internal.retry_count.toolchain": 1,
     "command.stderr": "",
     "thread.preflight_compile.current_node": "preflight_lint",
-    "last_stage": "simplify_gemini",
+    "last_stage": "simplify_gpt",
     "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,
     "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": "Everything passes. Here's the summary:\n\n## Summary\n\n**Fixed: Duplicate subprocess orchestration** (the main issue found across all three reviews)\n\n`render_dot_svg` in `server.rs` was a near-copy of `r",
+    "last_response": "The code is clean. Here's a summary of the review:\n\n**Fixed:**\n- **Long format string in `inject_dot_style_defaults`** (graph.rs line 100): Extracted the inline DOT defaults into a `DOT_STYLE_DEFAULTS",
     "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": [],
   "node_outcomes": {
+    "simplify_gpt": {
+      "status": "success",
+      "context_updates": {
+        "response.simplify_gpt": "The code is clean. Here's a summary of the review:\n\n**Fixed:**\n- **Long format string in `inject_dot_style_defaults`** (graph.rs line 100): Extracted the inline DOT defaults into a `DOT_STYLE_DEFAULTS` const using a `r##\"...\"##` raw string literal, matching the style of the existing `DARK_MODE_STYLE` const. The `format!` call is now a clean `format!(\"{before}{DOT_STYLE_DEFAULTS}{after}\")` instead of a 200+ character single line with embedded `\\n` escapes.\n\n**Already clean (no action needed):**\n- **Code reuse**: The `render_dot_svg` helper in `server.rs` properly deduplicates the inline dot rendering that was previously copy-pasted in both `server.rs` and `demo/mod.rs`. No other SVG/DOT utilities exist in the codebase.\n- **Color coupling**: `#357f9e` and `#666666` appear in both DOT defaults and dark mode CSS selectors — this is by design (CSS targets the DOT-generated attributes).\n- **Efficiency**: The `postprocess_svg` string allocations are negligible for SVG sizes (a few KB). The `spawn_blocking` approach is appropriate since `render_dot` does synchronous I/O + string processing.\n- **No copy-paste, no parameter sprawl, no leaky abstractions** — the change is well-structured.",
+        "last_response": "The code is clean. Here's a summary of the review:\n\n**Fixed:**\n- **Long format string in `inject_dot_style_defaults`** (graph.rs line 100): Extracted the inline DOT defaults into a `DOT_STYLE_DEFAULTS",
+        "last_stage": "simplify_gpt"
+      },
+      "notes": "Stage completed: simplify_gpt",
+      "usage": {
+        "model": "claude-opus-4-6",
+        "input_tokens": 31542,
+        "output_tokens": 8811,
+        "cache_read_tokens": 350255,
+        "cache_write_tokens": 35417,
+        "reasoning_tokens": 735,
+        "cost": 1.133955
+      },
+      "files_touched": [
+        "/home/daytona/workspace/lib/crates/fabro-workflows/src/cli/graph.rs"
+      ],
+      "duration_ms": 253259
+    },
+    "simplify_gemini": {
+      "status": "success",
+      "context_updates": {
+        "last_response": "Everything passes. Here's the summary:\n\n## Summary\n\n**Fixed: Duplicate subprocess orchestration** (the main issue found across all three reviews)\n\n`render_dot_svg` in `server.rs` was a near-copy of `r",
+        "response.simplify_gemini": "Everything passes. Here's the summary:\n\n## Summary\n\n**Fixed: Duplicate subprocess orchestration** (the main issue found across all three reviews)\n\n`render_dot_svg` in `server.rs` was a near-copy of `render_dot` in `graph.rs` — both spawned a `dot` subprocess, piped DOT source to stdin, injected style defaults, and post-processed SVG output. The only difference was sync vs async and error types.\n\n**Changes made:**\n\n1. **`graph.rs`**: Made `render_dot` public (the single authoritative implementation). Made `inject_dot_style_defaults` and `postprocess_svg` private — they're implementation details of `render_dot`, not a two-phase protocol callers need to know about.\n\n2. **`server.rs`**: Replaced 35 lines of duplicated subprocess code in `render_dot_svg` with a 10-line function that calls `render_dot` via `tokio::task::spawn_blocking` and converts the result to a `Response`. The demo handler (`demo/mod.rs`) already delegates to `render_dot_svg`, so no changes needed there.\n\n**Skipped (not worth addressing):**\n- Efficiency findings in `postprocess_svg` (line-by-line filtering, `insert_str` shift) — SVGs are ~KB and subprocess launch dominates; not worth the complexity.\n- Extracting color constants — the coupling between DOT attrs and CSS selectors is inherent and co-locating the values wouldn't improve readability.",
+        "last_stage": "simplify_gemini"
+      },
+      "notes": "Stage completed: simplify_gemini",
+      "usage": {
+        "model": "claude-opus-4-6",
+        "input_tokens": 36331,
+        "output_tokens": 14744,
+        "cache_read_tokens": 441295,
+        "cache_write_tokens": 42817,
+        "reasoning_tokens": 1261,
+        "cost": 1.6507649999999998
+      },
+      "files_touched": [
+        "/home/daytona/workspace/lib/crates/fabro-api/src/server.rs",
+        "/home/daytona/workspace/lib/crates/fabro-workflows/src/cli/graph.rs"
+      ],
+      "duration_ms": 338660
+    },
     "toolchain": {
       "status": "success",
       "context_updates": {
@@ -97,29 +147,6 @@
       ],
       "duration_ms": 268508
     },
-    "simplify_gemini": {
-      "status": "success",
-      "context_updates": {
-        "last_response": "Everything passes. Here's the summary:\n\n## Summary\n\n**Fixed: Duplicate subprocess orchestration** (the main issue found across all three reviews)\n\n`render_dot_svg` in `server.rs` was a near-copy of `r",
-        "response.simplify_gemini": "Everything passes. Here's the summary:\n\n## Summary\n\n**Fixed: Duplicate subprocess orchestration** (the main issue found across all three reviews)\n\n`render_dot_svg` in `server.rs` was a near-copy of `render_dot` in `graph.rs` — both spawned a `dot` subprocess, piped DOT source to stdin, injected style defaults, and post-processed SVG output. The only difference was sync vs async and error types.\n\n**Changes made:**\n\n1. **`graph.rs`**: Made `render_dot` public (the single authoritative implementation). Made `inject_dot_style_defaults` and `postprocess_svg` private — they're implementation details of `render_dot`, not a two-phase protocol callers need to know about.\n\n2. **`server.rs`**: Replaced 35 lines of duplicated subprocess code in `render_dot_svg` with a 10-line function that calls `render_dot` via `tokio::task::spawn_blocking` and converts the result to a `Response`. The demo handler (`demo/mod.rs`) already delegates to `render_dot_svg`, so no changes needed there.\n\n**Skipped (not worth addressing):**\n- Efficiency findings in `postprocess_svg` (line-by-line filtering, `insert_str` shift) — SVGs are ~KB and subprocess launch dominates; not worth the complexity.\n- Extracting color constants — the coupling between DOT attrs and CSS selectors is inherent and co-locating the values wouldn't improve readability.",
-        "last_stage": "simplify_gemini"
-      },
-      "notes": "Stage completed: simplify_gemini",
-      "usage": {
-        "model": "claude-opus-4-6",
-        "input_tokens": 36331,
-        "output_tokens": 14744,
-        "cache_read_tokens": 441295,
-        "cache_write_tokens": 42817,
-        "reasoning_tokens": 1261,
-        "cost": 1.6507649999999998
-      },
-      "files_touched": [
-        "/home/daytona/workspace/lib/crates/fabro-api/src/server.rs",
-        "/home/daytona/workspace/lib/crates/fabro-workflows/src/cli/graph.rs"
-      ],
-      "duration_ms": 338660
-    },
     "preflight_compile": {
       "status": "success",
       "context_updates": {
@@ -158,14 +185,15 @@
       "duration_ms": 0
     }
   },
-  "next_node_id": "simplify_gpt",
+  "next_node_id": "verify",
   "node_visits": {
-    "simplify_gemini": 1,
-    "preflight_lint": 1,
     "implement": 1,
+    "preflight_compile": 1,
+    "simplify_gemini": 1,
+    "simplify_gpt": 1,
+    "preflight_lint": 1,
     "start": 1,
     "toolchain": 1,
-    "preflight_compile": 1,
     "simplify_opus": 1
   }
 }
\ No newline at end of file
diff --git a/nodes/simplify_gemini/diff.patch b/nodes/simplify_gemini/diff.patch
new file mode 100644
index 000000000..0edad2489
--- /dev/null
+++ b/nodes/simplify_gemini/diff.patch
@@ -0,0 +1,94 @@
+diff --git a/lib/crates/fabro-api/src/server.rs b/lib/crates/fabro-api/src/server.rs
+index 787ba1f..dea0121 100644
+--- a/lib/crates/fabro-api/src/server.rs
++++ b/lib/crates/fabro-api/src/server.rs
+@@ -1432,45 +1432,17 @@ async fn get_retro(
+     }
+ }
+ 
+-/// Render DOT source to a styled SVG via the `dot` subprocess (async).
++/// Render DOT source to a styled SVG via `render_dot` on a blocking thread.
+ pub(crate) async fn render_dot_svg(dot_source: &str) -> Response {
+-    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())
+-        .stdout(std::process::Stdio::piped())
+-        .stderr(std::process::Stdio::piped())
+-        .spawn()
+-    {
+-        Ok(child) => child,
+-        Err(_) => {
+-            return ApiError::new(
+-                StatusCode::BAD_GATEWAY,
+-                "Graphviz dot command not available.",
+-            )
+-            .into_response();
+-        }
+-    };
+-
+-    if let Some(mut stdin) = child.stdin.take() {
+-        use tokio::io::AsyncWriteExt;
+-        let _ = stdin.write_all(styled_source.as_bytes()).await;
+-    }
++    use fabro_workflows::cli::graph::{render_dot, GraphFormat};
+ 
+-    match child.wait_with_output().await {
+-        Ok(output) if output.status.success() => (
+-            StatusCode::OK,
+-            [("content-type", "image/svg+xml")],
+-            fabro_workflows::cli::graph::postprocess_svg(output.stdout),
+-        )
+-            .into_response(),
+-        Ok(output) => {
+-            let stderr = String::from_utf8_lossy(&output.stderr);
+-            ApiError::new(StatusCode::BAD_GATEWAY, format!("dot failed: {stderr}")).into_response()
++    let source = dot_source.to_owned();
++    match tokio::task::spawn_blocking(move || render_dot(&source, GraphFormat::Svg)).await {
++        Ok(Ok(bytes)) => {
++            (StatusCode::OK, [("content-type", "image/svg+xml")], bytes).into_response()
+         }
+-        Err(e) => ApiError::new(StatusCode::BAD_GATEWAY, format!("dot process error: {e}"))
+-            .into_response(),
++        Ok(Err(e)) => ApiError::new(StatusCode::BAD_GATEWAY, e.to_string()).into_response(),
++        Err(e) => ApiError::new(StatusCode::INTERNAL_SERVER_ERROR, e.to_string()).into_response(),
+     }
+ }
+ 
+diff --git a/lib/crates/fabro-workflows/src/cli/graph.rs b/lib/crates/fabro-workflows/src/cli/graph.rs
+index d0b81db..7f07a1c 100644
+--- a/lib/crates/fabro-workflows/src/cli/graph.rs
++++ b/lib/crates/fabro-workflows/src/cli/graph.rs
+@@ -91,7 +91,7 @@ const DARK_MODE_STYLE: &str = r##"
+ /// 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 {
++fn inject_dot_style_defaults(source: &str) -> String {
+     let Some(pos) = source.find('{') else {
+         return source.to_string();
+     };
+@@ -104,7 +104,7 @@ pub fn inject_dot_style_defaults(source: &str) -> String {
+ /// 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> {
++fn postprocess_svg(raw: Vec<u8>) -> Vec<u8> {
+     let mut svg = String::from_utf8(raw)
+         .unwrap_or_else(|e| String::from_utf8_lossy(e.as_bytes()).into_owned());
+ 
+@@ -130,8 +130,11 @@ pub fn postprocess_svg(raw: Vec<u8>) -> Vec<u8> {
+     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>> {
++/// Render styled DOT source into the given format via the `dot` command.
++///
++/// Injects style defaults (colors, fonts, transparent background) into the DOT
++/// source, then post-processes SVG output with dark-mode CSS and background removal.
++pub 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")
diff --git a/nodes/simplify_gpt/prompt.md b/nodes/simplify_gpt/prompt.md
new file mode 100644
index 000000000..4ec322aff
--- /dev/null
+++ b/nodes/simplify_gpt/prompt.md
@@ -0,0 +1,141 @@
+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_opus**: success
+  - Model: claude-opus-4-6, 36.2k tokens in / 13.5k 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_gemini**: success
+  - Model: claude-opus-4-6, 36.3k tokens in / 14.7k out
+  - Files: /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_gpt/provider_used.json b/nodes/simplify_gpt/provider_used.json
new file mode 100644
index 000000000..c1905ff10
--- /dev/null
+++ b/nodes/simplify_gpt/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_gpt/response.md b/nodes/simplify_gpt/response.md
new file mode 100644
index 000000000..ada2a526e
--- /dev/null
+++ b/nodes/simplify_gpt/response.md
@@ -0,0 +1,10 @@
+The code is clean. Here's a summary of the review:
+
+**Fixed:**
+- **Long format string in `inject_dot_style_defaults`** (graph.rs line 100): Extracted the inline DOT defaults into a `DOT_STYLE_DEFAULTS` const using a `r##"..."##` raw string literal, matching the style of the existing `DARK_MODE_STYLE` const. The `format!` call is now a clean `format!("{before}{DOT_STYLE_DEFAULTS}{after}")` instead of a 200+ character single line with embedded `\n` escapes.
+
+**Already clean (no action needed):**
+- **Code reuse**: The `render_dot_svg` helper in `server.rs` properly deduplicates the inline dot rendering that was previously copy-pasted in both `server.rs` and `demo/mod.rs`. No other SVG/DOT utilities exist in the codebase.
+- **Color coupling**: `#357f9e` and `#666666` appear in both DOT defaults and dark mode CSS selectors — this is by design (CSS targets the DOT-generated attributes).
+- **Efficiency**: The `postprocess_svg` string allocations are negligible for SVG sizes (a few KB). The `spawn_blocking` approach is appropriate since `render_dot` does synchronous I/O + string processing.
+- **No copy-paste, no parameter sprawl, no leaky abstractions** — the change is well-structured.
\ No newline at end of file
diff --git a/nodes/simplify_gpt/status.json b/nodes/simplify_gpt/status.json
new file mode 100644
index 000000000..5a64e741f
--- /dev/null
+++ b/nodes/simplify_gpt/status.json
@@ -0,0 +1,6 @@
+{
+  "status": "success",
+  "notes": "Stage completed: simplify_gpt",
+  "failure_reason": null,
+  "timestamp": "2026-03-16T02:20:47.586754+00:00"
+}
\ No newline at end of file