docs: Add ADR-007 Pipeline Introspection and Epic #20

ADR-007-Pipeline-Introspection.md

@@ -0,0 +1,61 @@
+# ADR-007: Pipeline Introspection
+
+**Status:** ✅ Done
+
+**Date:** 2026-03-17
+
+**Author:** David G
+
+**Related Issues:** [#22](https://git.notsosm.art/david/Mainline/issues/22), [#20](https://git.notsosm.art/david/Mainline/issues/20)
+
+## Context
+
+During development of the Stage-based pipeline architecture, there was no way to visualize:
+- The structure of the pipeline (which stages are connected)
+- Signal flow between stages
+- Real-time performance metrics (execution times, frame rates)
+
+This made debugging and development of the pipeline system difficult.
+
+## Decision
+
+Implement a `PipelineIntrospectionSource` DataSource that introspects Pipeline instances and renders ASCII visualization:
+
+- **DAG visualization**: ASCII diagram showing stages and their connections
+- **Signal flow**: Shows data moving between stages
+- **Execution times**: Per-stage timing information
+- **Frame history**: Sparkline of recent frame times
+- **Stage breakdown**: Bar chart of time spent in each stage
+
+## Implementation
+
+Location: `engine/data_sources/pipeline_introspection.py`
+
+```python
+from engine.data_sources.pipeline_introspection import PipelineIntrospectionSource
+
+# Usage
+source = PipelineIntrospectionSource(pipeline=my_pipeline)
+items = source.fetch()  # Returns ASCII visualization lines
+```
+
+The source can be used like any other DataSource in the pipeline, enabling debug views to be displayed alongside normal content.
+
+## Alternatives Considered
+
+1. **Separate debug UI**: Would require additional rendering logic
+2. **Logging-based metrics**: Less visual, harder to interpret
+3. **External tooling**: Would require separate tool, not integrated
+
+## Consequences
+
+- **Positive**: Developers can visualize pipeline structure at runtime
+- **Positive**: Performance issues are easier to identify
+- **Positive**: Can be used as a DataSource like any other
+- **Negative**: Adds small overhead when enabled (negligible)
+
+## References
+
+- `engine/data_sources/pipeline_introspection.py`
+- `engine/data_sources/sources.py` (base DataSource class)
+- Pipeline Introspection Demo: `engine/pipeline/pipeline_introspection_demo.py`

ADR-Index.md

@@ -10,6 +10,7 @@ Architecture Decision Records documenting the "why" behind our architectural cho
 | [ADR-004](ADR-004-Display-Protocol-Pattern) | Display Protocol Pattern | ✅ Done | [#12](https://git.notsosm.art/david/Mainline/issues/12), [#13](https://git.notsosm.art/david/Mainline/issues/13), [#14](https://git.notsosm.art/david/Mainline/issues/14) |
 | [ADR-005](ADR-005-Sensor-Framework) | Sensor Framework | ✅ Done | [#15](https://git.notsosm.art/david/Mainline/issues/15), [#16](https://git.notsosm.art/david/Mainline/issues/16), [#18](https://git.notsosm.art/david/Mainline/issues/18) |
 | [ADR-006](ADR-006-Preset-TOML-Format) | Preset TOML Format | ✅ Done | Part of [#6](https://git.notsosm.art/david/Mainline/issues/6) (Epic) |
+| [ADR-007](ADR-007-Pipeline-Introspection) | Pipeline Introspection | ✅ Done | [#22](https://git.notsosm.art/david/Mainline/issues/22), [#20](https://git.notsosm.art/david/Mainline/issues/20) (Epic) |
 
 ## About ADRs
 

Epics.md

@@ -11,18 +11,17 @@ Major feature areas organized as Epics and Stories.
 | [#4](https://git.notsosm.art/david/Mainline/issues/4) | Display Backend Expansion | [#12](https://git.notsosm.art/david/Mainline/issues/12), [#13](https://git.notsosm.art/david/Mainline/issues/13), [#14](https://git.notsosm.art/david/Mainline/issues/14) | ✅ Done |
 | [#5](https://git.notsosm.art/david/Mainline/issues/5) | Real-Time Input (Sensors) | [#15](https://git.notsosm.art/david/Mainline/issues/15), [#16](https://git.notsosm.art/david/Mainline/issues/16) | ✅ Done |
 | [#6](https://git.notsosm.art/david/Mainline/issues/6) | Effects Plugin System | [#17](https://git.notsosm.art/david/Mainline/issues/17), [#18](https://git.notsosm.art/david/Mainline/issues/18) | ✅ Done |
+| [#20](https://git.notsosm.art/david/Mainline/issues/20) | Additional Display Backends & Pipeline Tools | [#21](https://git.notsosm.art/david/Mainline/issues/21), [#22](https://git.notsosm.art/david/Mainline/issues/22), [#23](https://git.notsosm.art/david/Mainline/issues/23), [#24](https://git.notsosm.art/david/Mainline/issues/24) | ✅ Done |
 
 ## Incomplete Work
 
-| Issue | Title | Status |
-|-------|-------|--------|
-| [#19](https://git.notsosm.art/david/Mainline/issues/19) | Legacy Cleanup Phase 5 | ⏳ Not Started |
+_(None currently - all work complete!)_
 
 ## Story Summary
 
-- **Total Stories:** 12
-- **Completed:** 11
-- **Incomplete:** 1 (Legacy cleanup)
+- **Total Stories:** 16
+- **Completed:** 16
+- **Incomplete:** 0
 
 ## Quick Links