docs: add spec for configurable summary length

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-03-26-summary-length-design.md

@@ -0,0 +1,86 @@
+# Design: Configurable Summary Length
+
+**Date**: 2026-03-26
+**Scope**: Add a user setting to control summary detail level (court/moyen/detaille)
+
+---
+
+## Context
+
+Currently, article summaries are fixed at 4-5 lines based on 500 chars of article body. Users want longer summaries to avoid opening articles when the summary is sufficient.
+
+---
+
+## 1. New setting: `summary_length`
+
+**Column:** `summary_length INTEGER NOT NULL DEFAULT 3` in the `settings` table.
+
+Values and their effect on the classify prompt:
+
+| Value | Label | Summary instruction | Body snippet size |
+|-------|-------|--------------------|--------------------|
+| 1 | Court | "un resume de 3 a 4 lignes" | 500 chars |
+| 2 | Moyen | "un resume de 6 a 8 lignes" | 2000 chars |
+| 3 | Detaille | "un resume de 12 a 15 lignes" | 4000 chars (full scrape) |
+
+Default: **3 (Detaille)** — generates comprehensive summaries by default.
+
+Validation: value must be 1, 2, or 3.
+
+---
+
+## 2. Prompt change
+
+`build_article_classify_prompt` receives `summary_length: i32` as a new parameter. It adjusts the prompt instruction:
+
+- Current: `"Genere un titre clair et un resume de 4 a 5 lignes."`
+- New: dynamically selects the line count based on `summary_length`
+
+The body snippet parameter (`body_snippet`) is already passed by the caller — the caller controls the truncation length.
+
+---
+
+## 3. Pipeline change
+
+In `synthesis.rs`, the body snippet truncation in both Phase 1 and Phase 2 Brave classify loops changes from:
+
+```rust
+let body_snippet: String = body_text.chars().take(500).collect();
+```
+
+To a dynamic value based on `settings.summary_length`:
+
+```rust
+let snippet_size = match settings.summary_length {
+    1 => 500,
+    2 => 2000,
+    _ => 4000,
+};
+let body_snippet: String = body_text.chars().take(snippet_size).collect();
+```
+
+---
+
+## 4. Frontend
+
+A slider in Settings with 3 positions labeled "Court", "Moyen", "Detaille". Default position: "Detaille" (rightmost).
+
+Placed in the generation settings section, near `max_items_per_category`.
+
+---
+
+## 5. Files to modify
+
+- **Create:** `backend/migrations/20260326000023_add_summary_length.sql`
+- **Modify:** `backend/src/models/settings.rs` — add `summary_length` to `UserSettings`, `UpdateSettingsRequest`, `Default`, validation (1-3)
+- **Modify:** `backend/src/db/settings.rs` — add `summary_length` to `SettingsRow`, queries, binds
+- **Modify:** `backend/src/services/prompts.rs` — `build_article_classify_prompt` takes `summary_length`, adjusts instruction
+- **Modify:** `backend/src/services/synthesis.rs` — dynamic snippet size based on `settings.summary_length`
+- **Modify:** `frontend/src/types.ts` — add `summary_length: number` to `UserSettings` and `DEFAULT_SETTINGS`
+- **Modify:** `frontend/src/pages/Settings.tsx` — add slider component
+- **Modify:** `frontend/src/i18n/fr.ts` — labels for slider
+- **Modify:** `CLAUDE.md` — migration count
+- **Modify:** `backend/src/services/prompts.rs` tests — update `test_settings()` fixture, add test for summary_length
+- **Modify:** `backend/tests/api_syntheses_test.rs` — add `summary_length` to settings payload
+- **Modify:** `backend/tests/pipeline_test.rs` — add `summary_length` to settings payload
+- **Modify:** `e2e/tests/generation-live.spec.ts` — add `summary_length` to settings payload