docs(spike): deep research report on Jupyter as LLM execution layer

Expands on issue #155 spike with deeper coverage of:
- JupyterHub vs JupyterLab vs Notebook product suite distinction
- Papermill production execution (parameterization, Python API, CLI, scrapbook)
- nbformat file format internals for programmatic agent manipulation
- The full PR model for notebooks (nbstripout + nbdime + nbval)
- NotebookExecutor tool design sketch with structured result API
- hermes_runtime injection architecture for tool access in kernels
- JupyterHub multi-agent isolation with DockerSpawner/KubeSpawner

Refs #155

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/jupyter-as-execution-layer-research.md

@@ -0,0 +1,678 @@
+# Jupyter Notebooks as Core LLM Execution Layer — Deep Research Report
+
+**Issue:** #155
+**Date:** 2026-04-06
+**Status:** Research / Spike
+**Prior Art:** Timmy's initial spike (llm_execution_spike.ipynb, hamelnb bridge, JupyterLab on forge VPS)
+
+---
+
+## Executive Summary
+
+This report deepens the research from issue #155 into three areas requested by Rockachopa:
+1. The **full Jupyter product suite** — JupyterHub vs JupyterLab vs Notebook
+2. **Papermill** — the production-grade notebook execution engine already used in real data pipelines
+3. The **"PR model for notebooks"** — how agents can propose, diff, review, and merge changes to `.ipynb` files similarly to code PRs
+
+The conclusion: an elegant, production-grade agent→notebook pipeline already exists as open-source tooling. We don't need to invent much — we need to compose what's there.
+
+---
+
+## 1. The Jupyter Product Suite
+
+The Jupyter ecosystem has three distinct layers that are often conflated. Understanding the distinction is critical for architectural decisions.
+
+### 1.1 Jupyter Notebook (Classic)
+
+The original single-user interface. One browser tab = one `.ipynb` file. Version 6 is in maintenance-only mode. Version 7 was rebuilt on JupyterLab components and is functionally equivalent. For headless agent use, the UI is irrelevant — what matters is the `.ipynb` file format and the kernel execution model underneath.
+
+### 1.2 JupyterLab
+
+The current canonical Jupyter interface for human users: full IDE, multi-pane, terminal, extension manager, built-in diff viewer, and `jupyterlab-git` for Git workflows from the UI. JupyterLab is the recommended target for agent-collaborative workflows because:
+
+- It exposes the same REST API as classic Jupyter (kernel sessions, execute, contents)
+- Extensions like `jupyterlab-git` let a human co-reviewer inspect changes alongside the agent
+- The `hamelnb` bridge Timmy already validated works against a JupyterLab server
+
+**For agents:** JupyterLab is the platform to run on. The agent doesn't interact with the UI — it uses the Jupyter REST API or Papermill on top of it.
+
+### 1.3 JupyterHub — The Multi-User Orchestration Layer
+
+JupyterHub is not a UI. It is a **multi-user server** that spawns, manages, and proxies individual single-user Jupyter servers. This is the production infrastructure layer.
+
+```
+[Agent / Browser / API Client]
+         |
+      [Proxy]  (configurable-http-proxy)
+      /      \
+   [Hub]    [Single-User Jupyter Server per user/agent]
+ (Auth,      (standard JupyterLab/Notebook server)
+  Spawner,
+  REST API)
+```
+
+**Key components:**
+- **Hub:** Manages auth, user database, spawner lifecycle, REST API
+- **Proxy:** Routes `/hub/*` to Hub, `/user/<name>/*` to that user's server
+- **Spawner:** How single-user servers are started. Default = local process. Production options include `KubeSpawner` (Kubernetes pod per user) and `DockerSpawner` (container per user)
+- **Authenticator:** PAM, OAuth, DummyAuthenticator (for isolated agent environments)
+
+**JupyterHub REST API** (relevant for agent orchestration):
+
+```bash
+# Spawn a named server for an agent service account
+POST /hub/api/users/<username>/servers/<name>
+
+# Stop it when done
+DELETE /hub/api/users/<username>/servers/<name>
+
+# Create a scoped API token for the agent
+POST /hub/api/users/<username>/tokens
+
+# Check server status
+GET /hub/api/users/<username>
+```
+
+**Why this matters for Hermes:** JupyterHub gives us isolated kernel environments per agent task, programmable lifecycle management, and a clean auth model. Instead of running one shared JupyterLab instance on the forge VPS, we could spawn ephemeral single-user servers per notebook execution run — each with its own kernel, clean state, and resource limits.
+
+### 1.4 Jupyter Kernel Gateway — Minimal Headless Execution
+
+If JupyterHub is too heavy, `jupyter-kernel-gateway` exposes just the kernel protocol over REST + WebSocket:
+
+```bash
+pip install jupyter-kernel-gateway
+jupyter kernelgateway --KernelGatewayApp.api=kernel_gateway.jupyter_websocket
+
+# Start kernel
+POST /api/kernels
+# Execute via WebSocket on Jupyter messaging protocol
+WS /api/kernels/<kernel_id>/channels
+# Stop kernel
+DELETE /api/kernels/<kernel_id>
+```
+
+This is the lowest-level option: no notebook management, just raw kernel access. Suitable if we want to build our own execution layer from scratch.
+
+---
+
+## 2. Papermill — Production Notebook Execution
+
+Papermill is the missing link between "notebook as experiment" and "notebook as repeatable pipeline task." It is already used at scale in industry data pipelines (Netflix, Airbnb, etc.).
+
+### 2.1 Core Concept: Parameterization
+
+Papermill's key innovation is **parameter injection**. Tag a cell in the notebook with `"parameters"`:
+
+```python
+# Cell tagged "parameters" (defaults — defined by notebook author)
+alpha = 0.5
+batch_size = 32
+model_name = "baseline"
+```
+
+At runtime, Papermill inserts a new cell immediately after, tagged `"injected-parameters"`, that overrides the defaults:
+
+```python
+# Cell tagged "injected-parameters" (injected by Papermill at runtime)
+alpha = 0.01
+batch_size = 128
+model_name = "experiment_007"
+```
+
+Because Python executes top-to-bottom, the injected cell shadows the defaults. The original notebook is never mutated — Papermill reads input, writes to a new output file.
+
+### 2.2 Python API
+
+```python
+import papermill as pm
+
+nb = pm.execute_notebook(
+    input_path="analysis.ipynb",     # source (can be s3://, az://, gs://)
+    output_path="output/run_001.ipynb",  # destination (persists outputs)
+    parameters={
+        "alpha": 0.01,
+        "n_samples": 1000,
+        "run_id": "fleet-check-2026-04-06",
+    },
+    kernel_name="python3",
+    execution_timeout=300,           # per-cell timeout in seconds
+    log_output=True,                 # stream cell output to logger
+    cwd="/path/to/notebook/",        # working directory
+)
+# Returns: NotebookNode (the fully executed notebook with all outputs)
+```
+
+On cell failure, Papermill raises `PapermillExecutionError` with:
+- `cell_index` — which cell failed
+- `source` — the failing cell's code
+- `ename` / `evalue` — exception type and message
+- `traceback` — full traceback
+
+Even on failure, the output notebook is written with whatever cells completed — enabling partial-run inspection.
+
+### 2.3 CLI
+
+```bash
+# Basic execution
+papermill analysis.ipynb output/run_001.ipynb \
+  -p alpha 0.01 \
+  -p n_samples 1000
+
+# From YAML parameter file
+papermill analysis.ipynb output/run_001.ipynb -f params.yaml
+
+# CI-friendly: log outputs, no progress bar
+papermill analysis.ipynb output/run_001.ipynb \
+  --log-output \
+  --no-progress-bar \
+  --execution-timeout 300 \
+  -p run_id "fleet-check-2026-04-06"
+
+# Prepare only (inject params, skip execution — for preview/inspection)
+papermill analysis.ipynb preview.ipynb --prepare-only -p alpha 0.01
+
+# Inspect parameter schema
+papermill --help-notebook analysis.ipynb
+```
+
+**Remote storage** is built in — `pip install papermill[s3]` enables `s3://` paths for both input and output. Azure and GCS are also supported. For Hermes, this means notebook runs can be stored in object storage and retrieved later for audit.
+
+### 2.4 Scrapbook — Structured Output Collection
+
+`scrapbook` is Papermill's companion for extracting structured data from executed notebooks. Inside a notebook cell:
+
+```python
+import scrapbook as sb
+
+# Write typed outputs (stored as special display_data in cell outputs)
+sb.glue("accuracy", 0.9342)
+sb.glue("metrics", {"precision": 0.91, "recall": 0.93, "f1": 0.92})
+sb.glue("results_df", df, "pandas")  # DataFrames too
+```
+
+After execution, from the agent:
+
+```python
+import scrapbook as sb
+
+nb = sb.read_notebook("output/fleet-check-2026-04-06.ipynb")
+metrics = nb.scraps["metrics"].data   # -> {"precision": 0.91, ...}
+accuracy = nb.scraps["accuracy"].data # -> 0.9342
+
+# Or aggregate across many runs
+book = sb.read_notebooks("output/")
+book.scrap_dataframe  # -> pd.DataFrame with all scraps + filenames
+```
+
+This is the clean interface between notebook execution and agent decision-making: the notebook outputs its findings as named, typed scraps; the agent reads them programmatically and acts.
+
+### 2.5 How Papermill Compares to hamelnb
+
+| Capability | hamelnb | Papermill |
+|---|---|---|
+| Stateful kernel session | Yes | No (fresh kernel per run) |
+| Parameter injection | No | Yes |
+| Persistent output notebook | No | Yes |
+| Remote storage (S3/Azure) | No | Yes |
+| Per-cell timing/metadata | No | Yes (in output nb metadata) |
+| Error isolation (partial runs) | No | Yes |
+| Production pipeline use | Experimental | Industry-standard |
+| Structured output collection | No | Yes (via scrapbook) |
+
+**Verdict:** `hamelnb` is great for interactive REPL-style exploration (where state accumulates). Papermill is better for task execution (where we want reproducible, parameterized, auditable runs). They serve different use cases. Hermes needs both.
+
+---
+
+## 3. The `.ipynb` File Format — What the Agent Is Actually Working With
+
+Understanding the format is essential for the "PR model." A `.ipynb` file is JSON with this structure:
+
+```json
+{
+  "nbformat": 4,
+  "nbformat_minor": 5,
+  "metadata": {
+    "kernelspec": {"display_name": "Python 3", "language": "python", "name": "python3"},
+    "language_info": {"name": "python", "version": "3.10.0"}
+  },
+  "cells": [
+    {
+      "id": "a1b2c3d4",
+      "cell_type": "markdown",
+      "source": "# Fleet Health Check\n\nThis notebook checks system health.",
+      "metadata": {}
+    },
+    {
+      "id": "e5f6g7h8",
+      "cell_type": "code",
+      "source": "alpha = 0.5\nthreshold = 0.95",
+      "metadata": {"tags": ["parameters"]},
+      "execution_count": null,
+      "outputs": []
+    },
+    {
+      "id": "i9j0k1l2",
+      "cell_type": "code",
+      "source": "import sys\nprint(sys.version)",
+      "metadata": {},
+      "execution_count": 1,
+      "outputs": [
+        {
+          "output_type": "stream",
+          "name": "stdout",
+          "text": "3.10.0 (default, ...)\n"
+        }
+      ]
+    }
+  ]
+}
+```
+
+The `nbformat` Python library provides a clean API for working with this:
+
+```python
+import nbformat
+
+# Read
+with open("notebook.ipynb") as f:
+    nb = nbformat.read(f, as_version=4)
+
+# Navigate
+for cell in nb.cells:
+    if cell.cell_type == "code":
+        print(cell.source)
+
+# Modify
+nb.cells[2].source = "import sys\nprint('updated')"
+
+# Add cells
+new_md = nbformat.v4.new_markdown_cell("## Agent Analysis\nInserted by Hermes.")
+nb.cells.insert(3, new_md)
+
+# Write
+with open("modified.ipynb", "w") as f:
+    nbformat.write(nb, f)
+
+# Validate
+nbformat.validate(nb)  # raises nbformat.ValidationError on invalid format
+```
+
+---
+
+## 4. The PR Model for Notebooks
+
+This is the elegant architecture Rockachopa described: agents making PRs to notebooks the same way they make PRs to code. Here's how the full stack enables it.
+
+### 4.1 The Problem: Raw `.ipynb` Diffs Are Unusable
+
+Without tooling, a `git diff` on a notebook that was merely re-run (no source changes) produces thousands of lines of JSON changes — execution counts, timestamps, base64-encoded plot images. Code review on raw `.ipynb` diffs is impractical.
+
+### 4.2 nbstripout — Clean Git History
+
+`nbstripout` installs a git **clean filter** that strips outputs before files enter the git index. The working copy is untouched; only what gets committed is clean.
+
+```bash
+pip install nbstripout
+nbstripout --install   # per-repo
+# or
+nbstripout --install --global  # all repos
+```
+
+This writes to `.git/config`:
+```ini
+[filter "nbstripout"]
+    clean = nbstripout
+    smudge = cat
+    required = true
+
+[diff "ipynb"]
+    textconv = nbstripout -t
+```
+
+And to `.gitattributes`:
+```
+*.ipynb filter=nbstripout
+*.ipynb diff=ipynb
+```
+
+Now `git diff` shows only source changes — same as reviewing a `.py` file.
+
+**For executed-output notebooks** (where we want to keep outputs for audit): use a separate path like `runs/` or `outputs/` excluded from the filter via `.gitattributes`:
+```
+*.ipynb filter=nbstripout
+runs/*.ipynb !filter
+runs/*.ipynb !diff
+```
+
+### 4.3 nbdime — Semantic Diff and Merge
+
+nbdime understands notebook structure. Instead of diffing raw JSON, it diffs at the level of cells — knowing that `cells` is a list, `source` is a string, and outputs should often be ignored.
+
+```bash
+pip install nbdime
+
+# Enable semantic git diff/merge for all .ipynb files
+nbdime config-git --enable
+
+# Now standard git commands are notebook-aware:
+git diff HEAD notebook.ipynb          # semantic cell-level diff
+git merge feature-branch              # uses nbdime for .ipynb conflict resolution
+git log -p notebook.ipynb            # readable patch per commit
+```
+
+**Python API for agent reasoning:**
+
+```python
+import nbdime
+import nbformat
+
+nb_base = nbformat.read(open("original.ipynb"), as_version=4)
+nb_pr   = nbformat.read(open("proposed.ipynb"), as_version=4)
+
+diff = nbdime.diff_notebooks(nb_base, nb_pr)
+
+# diff is a list of structured ops the agent can reason about:
+# [{"op": "patch", "key": "cells", "diff": [
+#     {"op": "patch", "key": 3, "diff": [
+#         {"op": "patch", "key": "source", "diff": [...string ops...]}
+#     ]}
+# ]}]
+
+# Apply a diff (patch)
+from nbdime.patching import patch
+nb_result = patch(nb_base, diff)
+```
+
+### 4.4 The Full Agent PR Workflow
+
+Here is the complete workflow — analogous to how Hermes makes PRs to code repos via Gitea:
+
+**1. Agent reads the task notebook**
+```python
+nb = nbformat.read(open("fleet_health_check.ipynb"), as_version=4)
+```
+
+**2. Agent locates and modifies relevant cells**
+```python
+# Find parameter cell
+params_cell = next(
+    c for c in nb.cells
+    if "parameters" in c.get("metadata", {}).get("tags", [])
+)
+# Update threshold
+params_cell.source = params_cell.source.replace("threshold = 0.95", "threshold = 0.90")
+
+# Add explanatory markdown
+nb.cells.insert(
+    nb.cells.index(params_cell) + 1,
+    nbformat.v4.new_markdown_cell(
+        "**Note (Hermes 2026-04-06):** Threshold lowered from 0.95 to 0.90 "
+        "based on false-positive analysis from last 7 days of runs."
+    )
+)
+```
+
+**3. Agent writes and commits to a branch**
+```bash
+git checkout -b agent/fleet-health-threshold-update
+nbformat.write(nb, open("fleet_health_check.ipynb", "w"))
+git add fleet_health_check.ipynb
+git commit -m "feat(notebooks): lower fleet health threshold to 0.90 (#155)"
+```
+
+**4. Agent executes the proposed notebook to validate**
+```python
+import papermill as pm
+
+pm.execute_notebook(
+    "fleet_health_check.ipynb",
+    "output/validation_run.ipynb",
+    parameters={"run_id": "agent-validation-2026-04-06"},
+    log_output=True,
+)
+```
+
+**5. Agent collects results and compares**
+```python
+import scrapbook as sb
+
+result = sb.read_notebook("output/validation_run.ipynb")
+health_score = result.scraps["health_score"].data
+alert_count = result.scraps["alert_count"].data
+```
+
+**6. Agent opens PR with results summary**
+```bash
+curl -X POST "$GITEA_API/pulls" \
+  -H "Authorization: token $TOKEN" \
+  -d '{
+    "title": "feat(notebooks): lower fleet health threshold to 0.90",
+    "body": "## Agent Analysis\n\n- Health score: 0.94 (was 0.89 with old threshold)\n- Alert count: 12 (was 47 false positives)\n- Validation run: output/validation_run.ipynb\n\nRefs #155",
+    "head": "agent/fleet-health-threshold-update",
+    "base": "main"
+  }'
+```
+
+**7. Human reviews the PR using nbdime diff**
+
+The PR diff in Gitea shows the clean cell-level source changes (thanks to nbstripout). The human can also run `nbdiff-web original.ipynb proposed.ipynb` locally for rich rendered diff with output comparison.
+
+### 4.5 nbval — Regression Testing Notebooks
+
+`nbval` treats each notebook cell as a pytest test case, re-executing and comparing outputs to stored values:
+
+```bash
+pip install nbval
+
+# Strict: every cell output must match stored outputs
+pytest --nbval fleet_health_check.ipynb
+
+# Lax: only check cells marked with # NBVAL_CHECK_OUTPUT
+pytest --nbval-lax fleet_health_check.ipynb
+```
+
+Cell-level markers (comments in cell source):
+```python
+# NBVAL_CHECK_OUTPUT   — in lax mode, validate this cell's output
+# NBVAL_SKIP           — skip this cell entirely
+# NBVAL_RAISES_EXCEPTION  — expect an exception (test passes if raised)
+```
+
+This becomes the CI gate: before a notebook PR is merged, run `pytest --nbval-lax` to verify no cells produce errors and critical output cells still produce expected values.
+
+---
+
+## 5. Gaps and Recommendations
+
+### 5.1 Gap Assessment (Refining Timmy's Original Findings)
+
+| Gap | Severity | Solution |
+|---|---|---|
+| No Hermes tool access in kernel | High | Inject `hermes_runtime` module (see §5.2) |
+| No structured output protocol | High | Use scrapbook `sb.glue()` pattern |
+| No parameterization | Medium | Add Papermill `"parameters"` cell to notebooks |
+| XSRF/auth friction | Medium | Disable for local; use JupyterHub token scopes for multi-user |
+| No notebook CI/testing | Medium | Add nbval to test suite |
+| Raw `.ipynb` diffs in PRs | Medium | Install nbstripout + nbdime |
+| No scheduling | Low | Papermill + existing Hermes cron layer |
+
+### 5.2 Short-Term Recommendations (This Month)
+
+**1. `NotebookExecutor` tool**
+
+A thin Hermes tool wrapping the ecosystem:
+
+```python
+class NotebookExecutor:
+    def execute(self, input_path, output_path, parameters, timeout=300):
+        """Wraps pm.execute_notebook(). Returns structured result dict."""
+
+    def collect_outputs(self, notebook_path):
+        """Wraps sb.read_notebook(). Returns dict of named scraps."""
+
+    def inspect_parameters(self, notebook_path):
+        """Wraps pm.inspect_notebook(). Returns parameter schema."""
+
+    def read_notebook(self, path):
+        """Returns nbformat NotebookNode for cell inspection/modification."""
+
+    def write_notebook(self, nb, path):
+        """Writes modified NotebookNode back to disk."""
+
+    def diff_notebooks(self, path_a, path_b):
+        """Returns structured nbdime diff for agent reasoning."""
+
+    def validate(self, notebook_path):
+        """Runs nbformat.validate() + optional pytest --nbval-lax."""
+```
+
+Execution result structure for the agent:
+```python
+{
+    "status": "success" | "error",
+    "duration_seconds": 12.34,
+    "cells_executed": 15,
+    "failed_cell": {       # None on success
+        "index": 7,
+        "source": "model.fit(X, y)",
+        "ename": "ValueError",
+        "evalue": "Input contains NaN",
+    },
+    "scraps": {            # from scrapbook
+        "health_score": 0.94,
+        "alert_count": 12,
+    },
+}
+```
+
+**2. Fleet Health Check as a Notebook**
+
+Convert the fleet health check epic into a parameterized notebook with:
+- `"parameters"` cell for run configuration (date range, thresholds, agent ID)
+- Markdown cells narrating each step
+- `sb.glue()` calls for structured outputs
+- `# NBVAL_CHECK_OUTPUT` markers on critical cells
+
+**3. Git hygiene for notebooks**
+
+Install nbstripout + nbdime in the hermes-agent repo:
+```bash
+pip install nbstripout nbdime
+nbstripout --install
+nbdime config-git --enable
+```
+
+Add to `.gitattributes`:
+```
+*.ipynb filter=nbstripout
+*.ipynb diff=ipynb
+runs/*.ipynb !filter
+```
+
+### 5.3 Medium-Term Recommendations (Next Quarter)
+
+**4. `hermes_runtime` Python module**
+
+Inject Hermes tool access into the kernel via a module that notebooks import:
+
+```python
+# In kernel cell: from hermes_runtime import terminal, read_file, web_search
+import hermes_runtime as hermes
+
+results = hermes.web_search("fleet health metrics best practices")
+hermes.terminal("systemctl status agent-fleet")
+content = hermes.read_file("/var/log/hermes/agent.log")
+```
+
+This closes the most significant gap: notebooks gain the same tool access as skills, while retaining state persistence and narrative structure.
+
+**5. Notebook-triggered cron**
+
+Extend the Hermes cron layer to accept `.ipynb` paths as targets:
+```yaml
+# cron entry
+schedule: "0 6 * * *"
+type: notebook
+path: notebooks/fleet_health_check.ipynb
+parameters:
+  run_id: "{{date}}"
+  alert_threshold: 0.90
+output_path: runs/fleet_health_{{date}}.ipynb
+```
+
+The cron runner calls `pm.execute_notebook()` and commits the output to the repo.
+
+**6. JupyterHub for multi-agent isolation**
+
+If multiple agents need concurrent notebook execution, deploy JupyterHub with `DockerSpawner` or `KubeSpawner`. Each agent job gets an isolated container with its own kernel, no state bleed between runs.
+
+---
+
+## 6. Architecture Vision
+
+```
+┌─────────────────────────────────────────────────────────────────┐
+│                        Hermes Agent                             │
+│                                                                  │
+│  Skills (one-shot)          Notebooks (multi-step)              │
+│  ┌─────────────────┐       ┌─────────────────────────────────┐  │
+│  │ terminal()      │       │ .ipynb file                     │  │
+│  │ web_search()    │       │  ├── Markdown (narrative)       │  │
+│  │ read_file()     │       │  ├── Code cells (logic)         │  │
+│  └─────────────────┘       │  ├── "parameters" cell          │  │
+│                             │  └── sb.glue() outputs          │  │
+│                             └──────────────┬────────────────┘  │
+│                                            │                    │
+│                             ┌──────────────▼────────────────┐  │
+│                             │   NotebookExecutor tool        │  │
+│                             │  (papermill + scrapbook +      │  │
+│                             │   nbformat + nbdime + nbval)   │  │
+│                             └──────────────┬────────────────┘  │
+│                                            │                    │
+└────────────────────────────────────────────┼────────────────────┘
+                                             │
+                         ┌───────────────────▼──────────────────┐
+                         │          JupyterLab / Hub             │
+                         │  (kernel execution environment)       │
+                         └───────────────────┬──────────────────┘
+                                             │
+                         ┌───────────────────▼──────────────────┐
+                         │           Git + Gitea                 │
+                         │  (nbstripout clean diffs,            │
+                         │   nbdime semantic review,            │
+                         │   PR workflow for notebook changes)   │
+                         └──────────────────────────────────────┘
+```
+
+**Notebooks become the primary artifact of complex tasks:** the agent generates or edits cells, Papermill executes them reproducibly, scrapbook extracts structured outputs for agent decision-making, and the resulting `.ipynb` is both proof-of-work and human-readable report. Skills remain for one-shot actions. Notebooks own multi-step workflows.
+
+---
+
+## 7. Package Summary
+
+| Package | Purpose | Install |
+|---|---|---|
+| `nbformat` | Read/write/validate `.ipynb` files | `pip install nbformat` |
+| `nbconvert` | Execute and export notebooks | `pip install nbconvert` |
+| `papermill` | Parameterize + execute in pipelines | `pip install papermill` |
+| `scrapbook` | Structured output collection | `pip install scrapbook` |
+| `nbdime` | Semantic diff/merge for git | `pip install nbdime` |
+| `nbstripout` | Git filter for clean diffs | `pip install nbstripout` |
+| `nbval` | pytest-based output regression | `pip install nbval` |
+| `jupyter-kernel-gateway` | Headless REST kernel access | `pip install jupyter-kernel-gateway` |
+
+---
+
+## 8. References
+
+- [Papermill GitHub (nteract/papermill)](https://github.com/nteract/papermill)
+- [Scrapbook GitHub (nteract/scrapbook)](https://github.com/nteract/scrapbook)
+- [nbformat format specification](https://nbformat.readthedocs.io/en/latest/format_description.html)
+- [nbdime documentation](https://nbdime.readthedocs.io/)
+- [nbdime diff format spec (JEP #8)](https://github.com/jupyter/enhancement-proposals/blob/master/08-notebook-diff/notebook-diff.md)
+- [nbconvert execute API](https://nbconvert.readthedocs.io/en/latest/execute_api.html)
+- [nbstripout README](https://github.com/kynan/nbstripout)
+- [nbval GitHub (computationalmodelling/nbval)](https://github.com/computationalmodelling/nbval)
+- [JupyterHub REST API](https://jupyterhub.readthedocs.io/en/stable/howto/rest.html)
+- [JupyterHub Technical Overview](https://jupyterhub.readthedocs.io/en/latest/reference/technical-overview.html)
+- [Jupyter Kernel Gateway](https://github.com/jupyter-server/kernel_gateway)