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/agent-loop/src/agent.ts

@@ -252,7 +252,6 @@ export class ReactLoopAgent implements Agent {
     const context = {
       content,
       source,
-      ...options?.envelope !== undefined ? { envelope: options.envelope } : {},
       ...options?.meta !== undefined ? { meta: options.meta } : {},
     }
     if (isTurnOpen(this.session)) {

packages/core/agent-loop/src/loop.ts

@@ -260,11 +260,10 @@ async function runTurn(
       session.append('user/message', { content, source: message.source }, { surfaceOp: 'append' })
       // Every `allow.additionalContexts` entry is a separate context/message the
       // next request also sees. The turn is open, so inject() appends each one
-      // into THIS turn without flattening provenance, framing, or metadata.
+      // into THIS turn without flattening provenance or metadata.
       for (const context of decision.additionalContexts ?? []) {
         agent.inject(context.content, {
           source: context.source,
-          ...context.envelope !== undefined ? { envelope: context.envelope } : {},
           ...context.meta !== undefined ? { meta: context.meta } : {},
         })
       }

packages/core/agent-loop/tests/interception.spec.ts

@@ -99,7 +99,6 @@ describe('agent/prompt-submit', () => {
         additionalContexts: [{
           content: [{ type: 'text', text: '<system-reminder>extra ctx</system-reminder>' }],
           source: { kind: 'plugin', plugin: 'test' },
-          envelope: 'raw',
           meta,
         }],
       }))
@@ -113,7 +112,6 @@ describe('agent/prompt-submit', () => {
     expect(userMsg).toBeDefined()
     expect(ctxMsg?.type === 'context/message' && ctxMsg.data.content).toEqual([{ type: 'text', text: '<system-reminder>extra ctx</system-reminder>' }])
     expect(ctxMsg?.type === 'context/message' && ctxMsg.data.source).toEqual({ kind: 'plugin', plugin: 'test' })
-    expect(ctxMsg?.type === 'context/message' && ctxMsg.data.envelope).toBe('raw')
     expect(ctxMsg?.type === 'context/message' && ctxMsg.data.meta).toEqual(meta)
     const sent = JSON.stringify(adapter.requests[0]!.messages)
     expect(sent).toContain('extra ctx')
@@ -556,7 +554,6 @@ describe('tool additionalContexts buffering across a step', () => {
         additionalContexts: [{
           content: [{ type: 'text', text: `ctx-${exec.callId}` }],
           source: { kind: 'plugin', plugin: 'p' },
-          envelope: 'raw',
           meta: { callId: exec.callId },
         }],
       }))
@@ -580,7 +577,6 @@ describe('tool additionalContexts buffering across a step', () => {
       .map(b => (b.type === 'text' ? b.text : ''))
     expect(ctxTexts).toEqual(['ctx-c1', 'ctx-c2'])
     const contextEvents = events(agent).filter(e => e.type === 'context/message')
-    expect(contextEvents.map(e => e.type === 'context/message' && e.data.envelope)).toEqual(['raw', 'raw'])
     expect(contextEvents.map(e => e.type === 'context/message' && e.data.meta)).toEqual([{ callId: 'c1' }, { callId: 'c2' }])
   })
 
@@ -591,7 +587,7 @@ describe('tool additionalContexts buffering across a step', () => {
       name: 'composite', description: 'composite', parameters: {},
       async execute(_args, exec) {
         exec.deferContext({ content: [{ type: 'text', text: 'nested-a' }], source: { kind: 'plugin', plugin: 'a' }, meta: { order: 1 } })
-        exec.deferContext({ content: [{ type: 'text', text: 'nested-b' }], source: { kind: 'plugin', plugin: 'b' }, envelope: 'raw', meta: { order: 2 } })
+        exec.deferContext({ content: [{ type: 'text', text: 'nested-b' }], source: { kind: 'plugin', plugin: 'b' }, meta: { order: 2 } })
         return [{ type: 'text', text: 'outer result' }]
       },
     }))

packages/core/agent-loop/tests/loop.spec.ts

@@ -385,10 +385,10 @@ describe('agent loop', () => {
     await waitForIdle(ctx, agent)
     const flat = JSON.stringify(adapter.requests[0]!.messages)
     expect(flat).toContain('file changed: a.ts')
-    expect(flat).toContain('<context source=\\"plugin\\">')
+    expect(flat).not.toContain('<context source=')
   })
 
-  it('inject() can persist raw structured context without the generic context envelope', async () => {
+  it('inject() persists structured context content verbatim with durable hidden meta', async () => {
     const adapter = new MockAdapter([textResponse('ok')])
     const ctx = await harness(adapter)
     const agent = ctx.agentLoop.create(SessionId('raw-context'), { provider: 'mock', model: 'mock' })
@@ -401,14 +401,13 @@ describe('agent loop', () => {
 
     agent.inject([{ type: 'text', text }], {
       source: { kind: 'plugin', plugin: 'workspace-context' },
-      envelope: 'raw',
       meta,
     })
     send(agent, 'go')
     await waitForIdle(ctx, agent)
 
     const contextEvent = agent.session.events.find(event => event.type === 'context/message')
-    expect(contextEvent?.type === 'context/message' && contextEvent.data).toMatchObject({ envelope: 'raw', meta })
+    expect(contextEvent?.type === 'context/message' && contextEvent.data).toMatchObject({ meta })
     const requestText = JSON.stringify(adapter.requests[0]!.messages)
     expect(requestText).toContain('Additional instructions from: pkg/AGENTS.md')
     expect(requestText).not.toContain('<context source=')
@@ -432,7 +431,6 @@ describe('agent loop', () => {
         const first = { type: 'text' as const, text: 'mid-turn notice' }
         agent.inject([first], {
           source: { kind: 'plugin', plugin: 'x' },
-          envelope: 'raw',
           meta,
         })
         first.text = 'mutated after inject'
@@ -458,7 +456,6 @@ describe('agent loop', () => {
     expect(contexts).toHaveLength(2)
     expect(result.seq).toBeLessThan(contexts[0]!.seq)
     expect(contexts[0]?.type === 'context/message' && contexts[0].data).toMatchObject({
-      envelope: 'raw',
       meta,
     })
     expect(contexts.flatMap(event => event.type === 'context/message' ? event.data.content : []))