diff --git a/.planning/phases/01-foundation/01-CONTEXT.md b/.planning/phases/01-foundation/01-CONTEXT.md
new file mode 100644
index 0000000..15e8339
--- /dev/null
+++ b/.planning/phases/01-foundation/01-CONTEXT.md
@@ -0,0 +1,70 @@
+# Phase 1: Foundation - Context
+
+**Gathered:** 2026-02-09
+**Status:** Ready for planning
+
+<domain>
+## Phase Boundary
+
+Establish architectural foundation by reorganizing the monolithic Flutter app into a modular directory structure, extracting data models, centralizing behavioral constants, and replacing raw print statements with a proper logger. All existing functionality must remain identical after reorganization.
+
+</domain>
+
+<decisions>
+## Implementation Decisions
+
+### Directory conventions
+- Layer-first structure directly under lib/: screens/, widgets/, providers/, services/, models/, config/
+- Flat widget structure — all widget files directly in widgets/, no subdirectories
+- Overlay-specific code lives within the layer folders (overlay widgets in widgets/, overlay services in services/) rather than a dedicated overlay/ directory
+- File names match class names exactly: GpsDataManager → gps_data_manager.dart
+
+### Model extraction
+- ProcessedGpsData, OverlayMessage, and a Theme model to be extracted
+- Models are immutable — all fields final, changes via copyWith()
+- Theme model holds all available color palettes internally, exposes only the current palette's named colors, a "current set name" label, and a rotate() method for cycling themes
+- Persistence (SharedPreferences) handled separately from the theme model itself
+
+### Claude's Discretion
+- Whether models include formatting/serialization helpers (toMap, fromMap) based on current usage patterns
+- Exact fields and structure of each model based on existing code analysis
+- How theme palette rotation wraps (circular vs bounded)
+
+### Constants organization
+- Split by domain into separate files: config/gps_constants.dart, config/ui_constants.dart, config/timing_constants.dart, etc.
+- Extract behavioral constants only (timeouts, thresholds, GPS settings, speed limits) — leave UI padding/sizing as inline values
+- SCREAMING_SNAKE naming convention: GPS_TIMEOUT_SECONDS, SPEED_THRESHOLD_HIGH
+- Grouped into abstract classes with static members: GpsConfig.TIMEOUT_SECONDS, TimingConfig.HEARTBEAT_INTERVAL
+
+### Migration strategy
+- Incremental migration — app must compile and run after each execution wave
+- When files move, all imports updated immediately (no temporary re-exports)
+- No intermediate broken states; each wave is a working checkpoint
+
+### Debug logging
+- Semi-proper logger with 4 verbosity levels: error, warn, info, debug
+- Include caller name and timestamp in log output
+- Replaces all existing unconditional print statements
+
+</decisions>
+
+<specifics>
+## Specific Ideas
+
+- Theme model mental model: "holds all possible colour palettes, exposing only the current set of colours (with their nametags), informative 'current set name', and a method for rotating themes"
+- App must be runnable on a bench phone after each session/wave — this is a hard verification constraint
+- Logger should feel like a proper utility, not just a debugPrint wrapper
+
+</specifics>
+
+<deferred>
+## Deferred Ideas
+
+None — discussion stayed within phase scope
+
+</deferred>
+
+---
+
+*Phase: 01-foundation*
+*Context gathered: 2026-02-09*