fix(session): drop the <context> envelope and project context verbatim

context/message previously defaulted to a <context source="…">…</context>
wrapper. No model is trained on a <context> tag either, and message
framing does not belong on the session surface: the surface projects the
durable log, and a caller that wants a frame formats its own content —
which the one heavy producer (workspace-context) already does with its own
<system-reminder> frame, opting out via 'raw'. The tag only added
machinery — ContextEnvelope plus an envelope field threaded through
InjectOptions, HookContext, the context/message event, and the agent-loop
inject/additionalContexts plumbing.

context/message now projects its content verbatim as a user-role message,
sharing one deriveEventMessage case with user/message and steering/message.
ContextEnvelope and every envelope field are removed; context/message.meta
still carries durable, model-hidden JSON state. Regenerated catalogs and
website API; refreshed the three affected keyless snapshots (envelope field
only; timestamps unchanged).

Broadens and renames the steering Agent Note to cover both envelope
removals as one decision.

Agent Note: .agents/notes/implemented/simplification/2026-07-20-unwrap-injected-content-envelopes.md

packages/core/session/README.md

@@ -56,7 +56,7 @@ Durable values need one accepted representation, not a check followed by a secon
 
 `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` defaults to the canonical tagged context projection. A producer may set `envelope: 'raw'` when its `content` already contains the complete model-facing frame, 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()`.
 
 ### Session event vocabulary (`types.ts`)
 
@@ -87,7 +87,7 @@ 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`, and `steering/message` surface entries verbatim. A `context/message` is a user-role message containing exactly `<context source="<source-kind>">`, its content blocks, and `</context>`. 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. 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 { ContentBlock, Message, MessageSource } from '@deepseek-ai/dsh-llm'
+import type { Message } from '@deepseek-ai/dsh-llm'
 import { SESSION_FORMAT_VERSION, SessionId } from './types.ts'
-import type { ContextEnvelope, CreateSessionOptions, EpochHeader, SessionEvent, SessionEventMap, SessionEventType, SessionHeader, SurfaceIntent, SurfaceEventType } from './types.ts'
+import type { CreateSessionOptions, EpochHeader, SessionEvent, SessionEventMap, SessionEventType, SessionHeader, SurfaceIntent, SurfaceEventType } from './types.ts'
 import { snapshotJsonValue } from './json.ts'
 import { SurfaceManager } from './surface.ts'
 import type { SessionSurface } from './surface.ts'
@@ -80,19 +80,6 @@ declare module 'cordis' {
   }
 }
 
-/**
- * Render injected context as tagged synthetic user-role content, keeping the
- * canonical session vocabulary provider-neutral. Adapter-specific exceptions
- * belong in the adapter.
- */
-function renderContextEnvelope(content: ContentBlock[], source: MessageSource): ContentBlock[] {
-  return [
-    { type: 'text', text: `<context source=${JSON.stringify(source.kind)}>` },
-    ...content,
-    { type: 'text', text: '</context>' },
-  ]
-}
-
 /** Detach, validate, and freeze the creation metadata published by a session. */
 function snapshotSessionHeader(id: SessionId, source?: SessionHeader): SessionHeader {
   const input: unknown = source === undefined
@@ -226,22 +213,6 @@ interface SessionEntry {
 /** Store attachment for the append path; module-private to keep Session store-agnostic publicly. */
 const attachments = new WeakMap<Session, SessionEntry>()
 
-/**
- * Render one context contribution exactly as it will appear in model history.
- * @param content - content blocks supplied by the context producer.
- * @param source - attribution used by the canonical context envelope.
- * @param envelope - canonical tagged framing or caller-owned raw framing.
- * @returns a detached block list ready for the derived model transcript.
- */
-export function renderContextContent(
-  content: ContentBlock[],
-  source: MessageSource,
-  envelope: ContextEnvelope = 'context',
-): ContentBlock[] {
-  const cloned = structuredClone(content)
-  return envelope === 'raw' ? cloned : renderContextEnvelope(cloned, source)
-}
-
 /**
  * An event-sourced session: an append-only log of {@link SessionEvent}s.
  *
@@ -507,7 +478,18 @@ export class Session {
     // trace/replay data.
 
     switch (event.type) {
-      case 'user/message': {
+      // 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
+      // 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
+      // the event `meta` map and a dedicated renderer, keeping this projection a
+      // verbatim pass-through. See the deferred design note in
+      // ../../../../.agents/notes/implemented/simplification/2026-07-20-unwrap-injected-content-envelopes.md
+      case 'user/message':
+      case 'context/message':
+      case 'steering/message': {
         return { role: 'user', content: event.data.content }
       }
       case 'assistant/message': {
@@ -524,13 +506,6 @@ export class Session {
           content: [{ type: 'tool-result', toolCallId: callId, content, isError }],
         }
       }
-      case 'context/message': {
-        const { content, source, envelope } = event.data
-        return { role: 'user', content: renderContextContent(content, source, envelope) }
-      }
-      case 'steering/message': {
-        return { role: 'user', content: event.data.content }
-      }
       default:
         // A non-surface event (boundary, chunk, log-only record) projects to
         // no message. Merge-extensible union: no assertNever here.

packages/core/session/src/types.ts

@@ -2,9 +2,6 @@ import type { Branded } from '@deepseek-ai/dsh-brand'
 import type { AssistantProvenance, CallId, ContentBlock, LlmCallConfig, Message, MessageSource, StreamChunk, TokenUsage, ToolSchema } from '@deepseek-ai/dsh-llm'
 import type { JsonValue } from './json.ts'
 
-/** Canonical context-tag framing, or caller-owned framing rendered verbatim. */
-export type ContextEnvelope = 'context' | 'raw'
-
 /** Identifies one session in the store (and its persistence artifacts). */
 export type SessionId = Branded<'SessionId'>
 
@@ -205,14 +202,17 @@ export interface SessionEventMap {
   /**
    * In-session context injection (file-change notices, subdir AGENTS.md,
    * skill content, cron notifications, …). Rendered into the derived history
-   * as synthetic context — NOT a user prompt. `envelope: 'raw'` lets a caller
-   * own the complete model-facing frame; `meta` is durable JSON state omitted
-   * from the model projection.
+   * as a synthetic user-role message carrying `content` verbatim — NOT a
+   * user prompt. `meta` is durable JSON state omitted from the model
+   * projection; it is also the intended channel for any future framing
+   * directive (a producer declares the frame, a dedicated renderer applies it —
+   * see the deferred note in
+   * ../../../../.agents/notes/implemented/simplification/2026-07-20-unwrap-injected-content-envelopes.md),
+   * so the surface keeps projecting `content` verbatim rather than wrapping it.
    */
   'context/message': {
     content: ContentBlock[]
     source: MessageSource
-    envelope?: ContextEnvelope
     meta?: JsonValue
   }
   /** Raw stream chunk — token-level replay fidelity. */

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

@@ -48,7 +48,7 @@ describe('Session', () => {
     expect(structuredClone(turnEnd.data.reason)).toEqual({ kind: 'max-tokens' })
   })
 
-  it('renders context messages tagged and steering messages as plain user content', () => {
+  it('renders context and steering messages as plain user content', () => {
     const session = new Session(SessionId('s2'))
     session.append('context/message', {
       content: [{ type: 'text', text: 'file changed: a.ts' }],
@@ -62,13 +62,12 @@ describe('Session', () => {
 
     const [contextMessage, steeringMessage] = session.deriveMessages()
     expect(contextMessage!.role).toBe('user')
-    expect(contextMessage!.content[0]).toMatchObject({ type: 'text', text: '<context source="plugin">' })
-    expect(contextMessage!.content.at(-1)).toMatchObject({ type: 'text', text: '</context>' })
+    expect(contextMessage!.content).toEqual([{ type: 'text', text: 'file changed: a.ts' }])
     expect(steeringMessage!.role).toBe('user')
     expect(steeringMessage!.content).toEqual([{ type: 'text', text: 'focus on tests' }])
   })
 
-  it('renders raw context without a generic envelope while preserving structured metadata', () => {
+  it('keeps context meta durable in the event while hiding it from the projection', () => {
     const session = new Session(SessionId('s2-raw'))
     const meta = {
       kind: 'workspace-instructions',
@@ -78,7 +77,6 @@ describe('Session', () => {
     session.append('context/message', {
       content: [{ type: 'text', text: '<system-reminder>Additional instructions from: pkg/AGENTS.md</system-reminder>' }],
       source: { kind: 'plugin', plugin: 'workspace-context' },
-      envelope: 'raw',
       meta,
     }, { surfaceOp: 'append' })
 

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

@@ -369,7 +369,7 @@ describe('deriveMessages with surface', () => {
     s.append('steering/message', { turn: 1, content: [{ type: 'text', text: 'focus' }], source: { kind: 'user' } }, { surfaceOp: 'append' })
     const messages = s.deriveMessages()
     expect(messages).toHaveLength(2)
-    expect(messages[0]!.content[0]).toMatchObject({ type: 'text', text: '<context source="plugin">' })
+    expect(messages[0]!.content).toEqual([{ type: 'text', text: 'file changed' }])
     expect(messages[1]!.content).toEqual([{ type: 'text', text: 'focus' }])
   })
 })