docs(01): capture phase context

.planning/phases/01-architecture-foundation/01-CONTEXT.md

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+# Phase 1: Architecture Foundation - Context
+
+**Gathered:** 2026-03-27
+**Status:** Ready for planning
+
+<domain>
+## Phase Boundary
+
+Two-project solution scaffold with WASM/API split and shared models. Establishes the tutorial commenting convention. The critical boundaries (no API key in WASM, no file I/O in WASM, no direct OpenAI calls from WASM) are architecturally enforced before any feature code is written.
+
+</domain>
+
+<decisions>
+## Implementation Decisions
+
+### Solution Structure
+- **D-01:** Solution named `ChatAgent.sln` at repo root with three projects: `ChatAgent.Client` (Blazor WASM), `ChatAgent.Api` (ASP.NET Core backend), `ChatAgent.Shared` (shared models/DTOs)
+- **D-02:** Projects live in `src/` subfolders: `src/ChatAgent.Client/`, `src/ChatAgent.Api/`, `src/ChatAgent.Shared/`
+- **D-03:** Solution file at repo root for easy `dotnet build` from project root
+
+### API Communication
+- **D-04:** Typed HttpClient pattern — a `ChatApiClient` class in the Client project wraps all backend API calls, registered via DI
+- **D-05:** Backend uses traditional MVC Controllers (not Minimal API) — more structure, familiar pattern for tutorial
+- **D-06:** CORS configured on the API to allow the WASM client origin during development
+
+### Tutorial Comments
+- **D-07:** Full tutorial-style inline comments — explain everything including basic patterns, treat every file as a teaching moment
+- **D-08:** Comments go inline (XML doc comments and `//` comments right next to the code), no separate companion docs
+- **D-09:** Every Blazor concept introduced must have a comment explaining WHAT it is and WHY it's used
+
+### UI Framework
+- **D-10:** Start with plain HTML/CSS in Phase 1 — no MudBlazor yet. Learn raw Blazor rendering first, add component library later
+- **D-11:** Light theme as default look and feel
+
+### Claude's Discretion
+- CORS configuration details (origins, headers, methods)
+- Base URL configuration approach (appsettings.json vs environment variables)
+- Project file (.csproj) configuration details
+- Test project structure (if any placeholder tests needed)
+- .NET version targeting (9 vs 10 based on current stability)
+
+</decisions>
+
+<canonical_refs>
+## Canonical References
+
+**Downstream agents MUST read these before planning or implementing.**
+
+### Project context
+- `.planning/PROJECT.md` — Project vision, constraints, core value (tutorial-style build)
+- `.planning/REQUIREMENTS.md` — CODE-01 and CODE-02 requirements for this phase
+- `.planning/ROADMAP.md` — Phase 1 success criteria and dependencies
+
+### Research
+- `.planning/research/STACK.md` — Recommended .NET 9 stack, OpenAI SDK, Markdig, version compatibility
+- `.planning/research/ARCHITECTURE.md` — WASM/API split architecture, component boundaries, data flow
+- `.planning/research/PITFALLS.md` — Critical pitfalls: streaming transport, API key exposure, DI lifetimes, IL trimming
+
+</canonical_refs>
+
+<code_context>
+## Existing Code Insights
+
+### Reusable Assets
+- No existing application code — greenfield project
+
+### Established Patterns
+- No patterns yet — this phase establishes the foundational patterns all subsequent phases will follow
+
+### Integration Points
+- `.planning/` directory exists with research and project docs
+- `.claude/` directory has GSD workflow tooling (do not modify)
+- Git repo already initialized with planning commits
+
+</code_context>
+
+<specifics>
+## Specific Ideas
+
+- ChatAgent.* namespace convention for all projects
+- Controllers over Minimal API for more structured, tutorial-friendly code
+- Plain HTML/CSS first to understand raw Blazor before adding component libraries
+- Full verbose comments — this is a learning project, not a production codebase
+
+</specifics>
+
+<deferred>
+## Deferred Ideas
+
+None — discussion stayed within phase scope
+
+</deferred>
+
+---
+
+*Phase: 01-architecture-foundation*
+*Context gathered: 2026-03-27*