Merge branch 'codex/tool-json-schema-dsl' into codex/canonical-tool-output

# Conflicts:
#	docs/config-catalog.md
#	docs/persistence-catalog.md
#	examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/session.jsonl
#	examples/acp-agent/tests/snapshots/cordis-inspect-jsdoc/stdout.expected.jsonl
#	packages/cordis/tool-cordis/src/api-catalog.ts
#	packages/core/agent-loop/tests/contract-regressions.spec.ts
#	packages/ui/acp/src/index.ts
#	packages/ui/tui/src/index.ts

packages/core/session/README.md

@@ -64,7 +64,7 @@ Providers stream token-sized deltas, so a raw log stores hundreds of `assistant/
 
 `request/header` records a full canonical snapshot of the non-history request envelope with reason `initial`, `resume`, or `change`. `foldRequestHeader()` selects the latest snapshot; legacy delta events and the removed `fallback` reason are rejected. `messagePrefix` remains separate from derived history. See the [reconstructable-requests Agent Note](../../../.agents/notes/implemented/architecture/2026-07-05-reconstructable-requests.md).
 
-`context/message` renders its `content` verbatim as a user-role message, and may attach JSON `meta` for replayable plugin state; metadata remains durable but is excluded from `deriveMessages()`.
+`context/message` renders its `content` verbatim as a user-role message, and may attach JSON `meta` for replayable plugin state; metadata remains durable but is excluded from `deriveMessages()`. A `user/message` or `steering/message` with prompt-prefix context keeps the exact combined model bytes in `content` and stores a model-hidden `envelope` containing the direct `displayContent` and prefix context source/metadata descriptors. `displayPromptContent()` selects the human-facing prompt without changing derived history.
 
 `tool/result` persists the model-facing content, optional internal failure identity, and optional presentation metadata. A tool's successful canonical `value` and human-readable canonical failure message remain execution-local; rendered error content is the replay-authoritative message. This preserves the existing event shape and does not change `SESSION_FORMAT_VERSION`.
 
@@ -99,7 +99,7 @@ Every `SessionEvent` carries two optional top-level fields (structural metadata)
 
 #### What the model sees
 
-The model receives projections of `user/message`, `assistant/message`, `tool/result`, `context/message`, and `steering/message` surface entries verbatim: each is a user- or assistant-role message carrying its content blocks unchanged. Tool calls live inside assistant messages. Chunks, boundaries, usage, hook records, todo records, and other log-only events add no message.
+The model receives projections of `user/message`, `assistant/message`, `tool/result`, `context/message`, and `steering/message` surface entries verbatim: each is a user- or assistant-role message carrying its content blocks unchanged. A prompt envelope changes only human presentation; its prefix context and request delimiter are already present in the event content. Tool calls live inside assistant messages. Chunks, boundaries, usage, hook records, todo records, and other log-only events add no message.
 
 #### Token effect
 

packages/core/session/src/index.ts

@@ -11,9 +11,9 @@ import { isAbsolute } from 'node:path'
 import { deepFreeze } from '@deepseek-ai/dsh-llm'
 import { scopeOf, scopeTarget } from '@deepseek-ai/dsh-scope'
 import type { Scoped } from '@deepseek-ai/dsh-scope'
-import type { Message } from '@deepseek-ai/dsh-llm'
+import type { ContentBlock, Message } from '@deepseek-ai/dsh-llm'
 import { SESSION_FORMAT_VERSION, SessionId } from './types.ts'
-import type { CreateSessionOptions, EpochHeader, OutOfBandSessionEventType, SessionEvent, SessionEventMap, SessionEventType, SessionHeader, SurfaceIntent, SurfaceEventType, TurnTrigger } from './types.ts'
+import type { CreateSessionOptions, EpochHeader, OutOfBandSessionEventType, PromptMessageData, SessionEvent, SessionEventMap, SessionEventType, SessionHeader, SurfaceIntent, SurfaceEventType, TurnTrigger } from './types.ts'
 import { snapshotJsonValue } from './json.ts'
 import { SurfaceManager } from './surface.ts'
 import type { SessionSurface } from './surface.ts'
@@ -29,6 +29,15 @@ export type { SessionSurface, SurfaceFoldReplacement, SurfaceFoldResult } from '
 export { foldSurface, isSurfaceEvent, isSurfaceEligibleType } from './surface.ts'
 export { canonicalHeader, foldRequestHeader, headerEquals } from './request-header.ts'
 
+/**
+ * Return the human-facing prompt blocks from a durable prompt message.
+ * @param data - ordinary or steering prompt event data.
+ * @returns the effective direct prompt, excluding baked prefix context.
+ */
+export function displayPromptContent(data: PromptMessageData): ContentBlock[] {
+  return data.envelope?.displayContent ?? data.content
+}
+
 /**
  * Find the latest closed message-triggered turn, excluding injection and
  * plugin-owned zero-step turns.
@@ -523,9 +532,11 @@ export class Session {
     // trace/replay data.
 
     switch (event.type) {
-      // Injected context and mid-turn steering project identically to a user
-      // prompt: content verbatim, in user role. context's `source`/`meta` and
-      // steering's `turn` are log-only and do not reach the model. Do NOT
+      // Injected context, ordinary prompts, and mid-turn steering project
+      // identically in user role: the event's model-facing content stays
+      // verbatim. A prompt envelope is model-hidden display metadata; its
+      // prefix bytes are already present in content. context's `source`/`meta`
+      // and steering's `turn` are also log-only. Do NOT
       // re-add per-type framing (e.g. `<context>`/`<steering>`) here: framing is
       // caller-owned — a producer bakes it into `content`, as workspace-context
       // does with `<system-reminder>` — or, if reintroduced, must be driven by

packages/core/session/src/types.ts

@@ -180,6 +180,37 @@ export interface EpochHeader {
  */
 export type RequestHeaderReason = 'initial' | 'resume' | 'change'
 
+/** Durable model-hidden annotation for one context baked into a prompt message. */
+export interface PromptPrefixContext {
+  /** Producer provenance retained for transcript presentation and inspection. */
+  source: MessageSource
+  /** Opaque JSON state retained in the session event but hidden from the model. */
+  meta?: JsonValue
+}
+
+/**
+ * Human-facing view of a prompt whose exact model content includes prefixed
+ * context. `content` on the owning event remains the reconstructable model
+ * input; this envelope prevents transcript, title, and re-reference consumers
+ * from treating the baked context as direct human text.
+ */
+export interface PromptMessageEnvelope {
+  /** Effective user prompt after interception rewrites, without baked context. */
+  displayContent: ContentBlock[]
+  /** Ordered descriptors for contexts already baked into the event content. */
+  prefixContexts: PromptPrefixContext[]
+}
+
+/** Shared payload for ordinary and steering prompt messages. */
+export interface PromptMessageData {
+  /** Exact model-facing blocks, including any baked prompt-prefix contexts. */
+  content: ContentBlock[]
+  /** Producer provenance for the direct prompt. */
+  source: MessageSource
+  /** Present only when prompt-prefix contexts were baked into `content`. */
+  envelope?: PromptMessageEnvelope
+}
+
 /**
  * The merge-extensible, append-only source of truth for an agent interaction.
  * Message history is derived from this log. Every event is lossless JSON and
@@ -206,7 +237,7 @@ export interface SessionEventMap {
   /** Closes step `step` of turn `turn`. */
   'step/end': { turn: number; step: number }
   /** A user-visible prompt (the queued message claimed for this turn). */
-  'user/message': { content: ContentBlock[]; source: MessageSource }
+  'user/message': PromptMessageData
   /**
    * Durable record of a prompt veto and its reason. It is log-only: the blocked
    * prompt never enters the model-visible surface, and its turn runs zero steps.
@@ -264,7 +295,7 @@ export interface SessionEventMap {
     meta?: JsonValue
   }
   /** Steering content injected between steps of a running turn. */
-  'steering/message': { turn: number; content: ContentBlock[]; source: MessageSource }
+  'steering/message': PromptMessageData & { turn: number }
   /** Whole-list snapshot; latest write wins on replay. Log-only UI state; never derived history. */
   'todo/write': { todos: TodoItem[] }
   /**

packages/core/session/tests/session.spec.ts

@@ -2,6 +2,7 @@ import { describe, expect, expectTypeOf, it, vi } from 'vitest'
 import { Context } from 'cordis'
 import { CallId } from '@deepseek-ai/dsh-llm'
 import SessionStore, {
+  displayPromptContent,
   findLastMessageTurnEnd,
   SESSION_FORMAT_VERSION,
   Session,
@@ -135,6 +136,35 @@ describe('Session', () => {
     expect(steeringMessage!.content).toEqual([{ type: 'text', text: 'focus on tests' }])
   })
 
+  it('derives baked prompt context while exposing only the direct prompt for display', () => {
+    const session = new Session(SessionId('prompt-envelope'))
+    const event = session.append('user/message', {
+      content: [
+        { type: 'text', text: 'background' },
+        { type: 'text', text: '\n\n## My request:\n' },
+        { type: 'text', text: 'question' },
+      ],
+      source: { kind: 'user' },
+      envelope: {
+        displayContent: [{ type: 'text', text: 'question' }],
+        prefixContexts: [{ source: { kind: 'plugin', plugin: 'reference' }, meta: { kind: 'card' } }],
+      },
+    }, { surfaceOp: 'append' })
+
+    expect(session.deriveMessages()).toEqual([{
+      role: 'user',
+      content: [
+        { type: 'text', text: 'background' },
+        { type: 'text', text: '\n\n## My request:\n' },
+        { type: 'text', text: 'question' },
+      ],
+    }])
+    expect(displayPromptContent(event.data)).toEqual([{ type: 'text', text: 'question' }])
+    expect(Object.isFrozen(event.data.envelope?.displayContent)).toBe(true)
+    expect(new Session(SessionId('prompt-envelope-replay'), session.events).deriveMessages())
+      .toEqual(session.deriveMessages())
+  })
+
   it('keeps context meta durable in the event while hiding it from the projection', () => {
     const session = new Session(SessionId('s2-raw'))
     const meta = {