fix(#2549,#2550,#2552): bound discuss-phase context reads, add phase-type map selection, prohibit split reads (#2590)

#2549: load_prior_context was reading every prior *-CONTEXT.md file,
growing linearly with project phase count. Cap to the 3 most recent
phases. If .planning/DECISIONS-INDEX.md exists, read that instead.

#2550: scout_codebase claimed to select maps "based on phase type" but
had no classifier — agents read all 7 maps. Replace with an explicit
phase-type-to-maps table (2–3 maps per phase type) with a Mixed fallback.

#2552: Add explicit instruction not to split-read the same file at two
different offsets. Split reads break prompt cache reuse and cost more
than a single full read.

Closes #2549
Closes #2550
Closes #2552

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/bug-2549-2550-2552-discuss-phase-context.test.cjs

@@ -0,0 +1,78 @@
+'use strict';
+
+/**
+ * Bugs #2549, #2550, #2552: discuss-phase context bloat and cache invalidation.
+ *
+ * #2549: load_prior_context must cap prior CONTEXT.md reads (was O(phases))
+ * #2550: scout_codebase must select maps by phase type (was always all 7)
+ * #2552: scout_codebase must not instruct split reads of the same file
+ */
+
+const { test, describe } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const DISCUSS_PHASE = path.join(
+  __dirname, '..', 'get-shit-done', 'workflows', 'discuss-phase.md',
+);
+
+describe('discuss-phase context fixes (#2549, #2550, #2552)', () => {
+  let src;
+  test('discuss-phase.md source exists', () => {
+    assert.ok(fs.existsSync(DISCUSS_PHASE), 'discuss-phase.md must exist');
+    src = fs.readFileSync(DISCUSS_PHASE, 'utf-8');
+  });
+
+  // ─── #2549: load_prior_context cap ──────────────────────────────────────
+  test('#2549: load_prior_context must NOT instruct reading ALL prior CONTEXT.md files', () => {
+    if (!src) src = fs.readFileSync(DISCUSS_PHASE, 'utf-8');
+    assert.ok(
+      !src.includes('For each CONTEXT.md where phase number < current phase'),
+      'load_prior_context must not unboundedly read all prior CONTEXT.md files',
+    );
+  });
+
+  test('#2549: load_prior_context must reference a bounded read (3 phases or DECISIONS-INDEX)', () => {
+    if (!src) src = fs.readFileSync(DISCUSS_PHASE, 'utf-8');
+    const hasBound = src.includes('3') && src.includes('prior CONTEXT.md');
+    const hasIndex = src.includes('DECISIONS-INDEX.md');
+    assert.ok(
+      hasBound || hasIndex,
+      'load_prior_context must reference a bounded read (e.g., most recent 3 phases) or DECISIONS-INDEX.md',
+    );
+  });
+
+  // ─── #2550: scout_codebase phase-type selection ──────────────────────────
+  test('#2550: scout_codebase must not instruct reading all 7 codebase maps', () => {
+    if (!src) src = fs.readFileSync(DISCUSS_PHASE, 'utf-8');
+    assert.ok(
+      !src.includes('Read the most relevant ones (CONVENTIONS.md, STRUCTURE.md, STACK.md based on phase type)'),
+      'scout_codebase must not use the old vague "most relevant" instruction without a selection table',
+    );
+  });
+
+  test('#2550: scout_codebase must include a phase-type-to-maps selection table', () => {
+    if (!src) src = fs.readFileSync(DISCUSS_PHASE, 'utf-8');
+    // The table maps phase types to specific map selections
+    assert.ok(
+      src.includes('Phase type') && src.includes('Read these maps'),
+      'scout_codebase must include a phase-type to map-selection table',
+    );
+    // Key phase types must be covered
+    assert.ok(src.includes('UI') || src.includes('frontend'), 'Table must cover UI/frontend phases');
+    assert.ok(src.includes('Backend') || src.includes('API'), 'Table must cover backend phases');
+    assert.ok(src.includes('Testing'), 'Table must cover testing phases');
+    assert.ok(src.includes('Mixed'), 'Table must have a fallback for mixed/unclear phases');
+  });
+
+  // ─── #2552: no split reads ───────────────────────────────────────────────
+  test('#2552: scout_codebase must explicitly prohibit split reads of the same file', () => {
+    if (!src) src = fs.readFileSync(DISCUSS_PHASE, 'utf-8');
+    const prohibitsSplit = src.includes('split reads') || src.includes('split read');
+    assert.ok(
+      prohibitsSplit,
+      'scout_codebase must explicitly warn against split reads (same file, two offsets) that break prompt cache',
+    );
+  });
+});