Merge remote-tracking branch 'origin/master' into codex/truncated-design

# Conflicts:
#	docs/capability-seams.md
#	docs/config-catalog.md
#	docs/cordis-catalog/services.md
#	docs/core-data-structures/core.md
#	docs/event-producer-consumer.md
#	docs/module-graph.md
#	docs/rfc/INDEX.md
#	docs/tool-catalog.md
#	examples/acp-agent/README.md
#	packages/README.md
#	packages/bash/bash/README.md
#	packages/core/tools/tests/gen-tool-catalog.spec.ts
#	packages/support/acp-snapshot/src/harness.ts
#	pnpm-lock.yaml
#	scripts/gen-doc-graphs.ts
#	scripts/gen-tool-catalog.ts
#	scripts/type-equiv.manifest.json

packages/support/acp-snapshot/tests/normalize.spec.ts

@@ -1,5 +1,11 @@
 import { describe, expect, it } from 'vitest'
-import { type NormalizeContext, normalizeSessionLog, normalizeStdout, scrubRequestHeaders } from '../src/normalize.ts'
+import {
+  type NormalizeContext,
+  normalizeSessionLog,
+  normalizeStdout,
+  scrubRequestHeaders,
+  scrubSystemPrompts,
+} from '../src/normalize.ts'
 
 /**
  * Unit tests for the pure snapshot normalizers. Live as a *.spec.ts (runs in
@@ -201,6 +207,38 @@ describe('scrubRequestHeaders', () => {
     expect(toolsOnly).not.toContain('{{system}}')
   })
 
+  it('scrubs the header session prefix to one token per message, keeping the count', () => {
+    const ev = headerEvent({
+      config: { model: 'm' },
+      messagePrefix: [
+        { role: 'user', content: [{ type: 'text', text: 'workspace AGENTS digest' }] },
+        { role: 'user', content: [{ type: 'text', text: 'skills catalog' }] },
+      ],
+    })
+    const out = scrubRequestHeaders(`${headerLine}\n${ev}\n`)
+    expect(out).toContain('"messagePrefix":["{{messagePrefix}}","{{messagePrefix}}"]')
+    expect(out).not.toContain('AGENTS digest')
+    expect(out).not.toContain('skills catalog')
+    // Absence stays absent — a prefix-less header gains no token…
+    expect(scrubRequestHeaders(`${headerLine}\n${headerEvent({ system: 's' })}\n`)).not.toContain('{{messagePrefix}}')
+    // …and a non-array shape passes through untouched.
+    const odd = JSON.stringify({ type: 'request/header', seq: 4, time: 9, data: { header: { config: { model: 'm' }, messagePrefix: 'weird' }, reason: 'initial' } })
+    expect(scrubRequestHeaders(`${headerLine}\n${odd}\n`)).toContain('"messagePrefix":"weird"')
+  })
+
+  it('scrubs a header-delta prefix replacement to one token per message', () => {
+    const delta = JSON.stringify({
+      type: 'request/header-delta', seq: 8, time: 9,
+      data: { messagePrefix: [{ role: 'user', content: [{ type: 'text', text: 'leaked opener' }] }] },
+    })
+    const out = scrubRequestHeaders(`${headerLine}\n${delta}\n`)
+    expect(out).toContain('"messagePrefix":["{{messagePrefix}}"]')
+    expect(out).not.toContain('leaked opener')
+    // The empty-array transition-to-absence stays a structural fact.
+    const toNone = JSON.stringify({ type: 'request/header-delta', seq: 9, time: 9, data: { messagePrefix: [] } })
+    expect(scrubRequestHeaders(`${headerLine}\n${toNone}\n`)).toContain('"messagePrefix":[]')
+  })
+
   it('leaves a delta with no scrubbable payload byte-identical (config-only, or non-array shapes)', () => {
     const configOnly = JSON.stringify({ type: 'request/header-delta', seq: 8, time: 9, data: { config: { model: 'm2' } } })
     const oddShapes = JSON.stringify({ type: 'request/header-delta', seq: 9, time: 9, data: { system: { insert: 'not-an-array' }, tools: null } })
@@ -274,3 +312,43 @@ describe('scrubRequestHeaders', () => {
     expect(scrubRequestHeaders(once)).toBe(once)
   })
 })
+
+describe('scrubSystemPrompts', () => {
+  it('scrubs only system prompt payloads while keeping tools and prefixes verbatim', () => {
+    const header = JSON.stringify({
+      type: 'request/header', seq: 1, time: 2,
+      data: {
+        header: {
+          system: 'full prompt',
+          tools: [{ name: 'read', description: 'full schema' }],
+          messagePrefix: [{ role: 'user', content: [{ type: 'text', text: 'full prefix' }] }],
+        },
+        reason: 'initial',
+      },
+    })
+    const delta = JSON.stringify({
+      type: 'request/header-delta', seq: 2, time: 3,
+      data: {
+        system: { keepStart: 1, keepEnd: 2, insert: ['new prompt line'] },
+        tools: { changed: [{ name: 'read', description: 'changed schema' }] },
+        messagePrefix: [{ role: 'user', content: [{ type: 'text', text: 'changed prefix' }] }],
+      },
+    })
+    const toolsOnly = JSON.stringify({
+      type: 'request/header', seq: 3, time: 4,
+      data: { header: { tools: [{ name: 'read', description: 'schema only' }] }, reason: 'resume' },
+    })
+
+    const out = scrubSystemPrompts(`${header}\n${delta}\n${toolsOnly}\n`)
+    expect(out).toContain('"system":"{{system}}"')
+    expect(out).toContain('"insert":["{{system}}"]')
+    expect(out).not.toContain('full prompt')
+    expect(out).not.toContain('new prompt line')
+    expect(out).toContain('full schema')
+    expect(out).toContain('full prefix')
+    expect(out).toContain('changed schema')
+    expect(out).toContain('changed prefix')
+    expect(out.split('\n')[2]).toBe(toolsOnly)
+    expect(scrubSystemPrompts(out)).toBe(out)
+  })
+})