diff --git a/packages/context/time-context/src/index.ts b/packages/context/time-context/src/index.ts
index 064af060bd..917c2937ee 100644
--- a/packages/context/time-context/src/index.ts
+++ b/packages/context/time-context/src/index.ts
@@ -214,21 +214,19 @@ export function apply(ctx: Context, config: Config): () => void {
     const formatter = sessionTimeZone === undefined
       ? fallbackFormatter
       : formatterFor(sessionTimeZone)
+    const text = renderText(
+      now,
+      turn,
+      step,
+      previous,
+      formatter,
+      displayTimeZone,
+      sessionTimeZone,
+      requestMessages(agent, turn, messages),
+    )
     return createUserMessage({
-      content: [{
-        type: 'text',
-        text: renderText(
-          now,
-          turn,
-          step,
-          previous,
-          formatter,
-          displayTimeZone,
-          sessionTimeZone,
-          requestMessages(agent, turn, messages),
-        ),
-      }],
-      source: { kind: 'plugin', plugin: name },
+      content: [{ type: 'text', text }],
+      source: { kind: 'plugin', plugin: name, form: 'snapshot', sections: [{ name, text }] },
     })
   }
 
diff --git a/packages/context/time-context/src/invariant.ts b/packages/context/time-context/src/invariant.ts
index 0fdd953508..79917ad6bf 100644
--- a/packages/context/time-context/src/invariant.ts
+++ b/packages/context/time-context/src/invariant.ts
@@ -82,8 +82,24 @@ function validateReading(
   if (turn !== expected.turn || step !== expected.step) {
     fail(`time-context reading names turn ${turn}/step ${step}, expected turn ${expected.turn}/step ${expected.step}`)
   }
-  if (Object.keys(event.data.source).length !== 2) {
-    fail('time-context source must not duplicate request authority')
+  const source = event.data.source
+  /* v8 ignore next 2 -- replay and dispatch callers select this exact package-owned source before validation. */
+  if (source.kind !== 'plugin' || source.plugin !== SOURCE_NAME) {
+    fail('time-context source must retain package ownership')
+  }
+  const sections: unknown = 'sections' in source ? source.sections : undefined
+  const section: unknown = Array.isArray(sections) ? sections[0] : undefined
+  if (Object.keys(source).length !== 4
+    || source.form !== 'snapshot'
+    || !Array.isArray(sections)
+    || sections.length !== 1
+    || typeof section !== 'object'
+    || section === null
+    || !('name' in section)
+    || section.name !== SOURCE_NAME
+    || !('text' in section)
+    || section.text !== block.text) {
+    fail('time-context source must carry only the exact snapshot text, not request authority')
   }
   const renderedAuthority = `Session time zone: ${match[4]}.\nClient time zone for this request: ${match[5]}.`
   const expectedAuthority = renderTimeZoneContext(
diff --git a/packages/context/time-context/tests/invariant.spec.ts b/packages/context/time-context/tests/invariant.spec.ts
index e303553e38..926af82227 100644
--- a/packages/context/time-context/tests/invariant.spec.ts
+++ b/packages/context/time-context/tests/invariant.spec.ts
@@ -32,6 +32,8 @@ function event(
         ? {
           kind: 'plugin',
           plugin,
+          form: 'snapshot',
+          sections: [{ name: plugin, text }],
         }
         : { kind: 'plugin', plugin },
     }),
@@ -77,6 +79,8 @@ function appendReading(session: Session, text: string): void {
     source: {
       kind: 'plugin',
       plugin: 'time-context',
+      form: 'snapshot',
+      sections: [{ name: 'time-context', text }],
     },
   }), { surfaceOp: 'append' })
 }
@@ -148,7 +152,22 @@ describe('time-context invariants', () => {
     }
     expect(() => {
       ctx.emit('session/event', preparing(1, 1), duplicate)
-    }).toThrow(/must not duplicate request authority/)
+    }).toThrow(/must carry only the exact snapshot text/)
+  })
+
+  it('rejects package-owned provenance without snapshot sections', async () => {
+    const ctx = await setup()
+    const base = event(reading())
+    const unformed: SessionEvent<'user/message'> = {
+      ...base,
+      data: {
+        ...base.data,
+        source: { kind: 'plugin', plugin: 'time-context' },
+      },
+    }
+    expect(() => {
+      ctx.emit('session/event', preparing(1, 1), unformed)
+    }).toThrow(/must carry only the exact snapshot text/)
   })
 
   it('validates each existing reading against its preceding durable prefix', async () => {
diff --git a/packages/schedule/tool-schedule/src/tools.ts b/packages/schedule/tool-schedule/src/tools.ts
index d0a57907b4..93848c3954 100644
--- a/packages/schedule/tool-schedule/src/tools.ts
+++ b/packages/schedule/tool-schedule/src/tools.ts
@@ -222,16 +222,23 @@ interface AtTimeZoneContext {
 function isTimeContextReading(event: SessionEvent): boolean {
   if (event.type !== 'user/message') return false
   const source = event.data.source
+  if (source.kind !== 'plugin'
+    || source.plugin !== 'time-context'
+    || Object.keys(source).length !== 4
+    || source.form !== 'snapshot') return false
   const [block] = event.data.content
+  const sections: unknown = source.sections
+  const section: unknown = Array.isArray(sections) ? sections[0] : undefined
   return event.data.content.length === 1
     && block?.type === 'text'
-    && source.kind === 'plugin'
-    && source.plugin === 'time-context'
-    && Object.keys(source).length === 4
-    && source.form === 'snapshot'
-    && source.sections.length === 1
-    && source.sections[0]?.name === 'time-context'
-    && source.sections[0].text === block.text
+    && Array.isArray(sections)
+    && sections.length === 1
+    && typeof section === 'object'
+    && section !== null
+    && 'name' in section
+    && section.name === 'time-context'
+    && 'text' in section
+    && section.text === block.text
 }
 
 /** Derive request zones only while the current open turn contains a time-context reading. */