fix(tools): preserve canonical output boundaries

packages/core/session/README.md

@@ -58,7 +58,7 @@ Durable values need one accepted representation, not a check followed by a secon
 
 `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()`.
 
-`tool/result` persists the model-facing content, canonical failure detail, and optional presentation metadata. A tool's successful canonical `value` is deliberately execution-local and never enters the session event, so replay reconstructs the Native/model presentation but cannot recover intermediate programmatic values. This does not change `SESSION_FORMAT_VERSION`: the persisted projection remains authoritative.
+`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`.
 
 ### Session event vocabulary (`types.ts`)
 

packages/core/session/src/repair.ts

@@ -92,10 +92,7 @@ export function interruptedTurnClosers(events: readonly SessionEvent[]): Session
         callId,
         content: [{ type: 'text', text: 'Tool call interrupted by a crash; no result was recorded.' }],
         isError: true,
-        error: {
-          message: 'Tool call interrupted by a crash; no result was recorded.',
-          info: { name: 'InterruptedError', code: 'interrupted' },
-        },
+        error: { name: 'InterruptedError', code: 'interrupted' },
       },
       surfaceOp: 'append',
       ...callSeq !== undefined ? { sourceEventSeqs: [callSeq] } : {},

packages/core/session/src/types.ts

@@ -243,12 +243,13 @@ export interface SessionEventMap {
    */
   'tool/call': { turn: number; step: number; callId: CallId; name: string; arguments: string }
   /**
-   * A completed tool call's model-facing result, canonical failure detail, and
-   * optional tool-private `meta` presentation payload. `meta` is opaque to the
-   * core (the producing tool owns its shape and reads it back in `presentResult`)
-   * but MUST be JSON-serializable: `Session.append` runtime-validates all event
-   * data with `isJsonValue`, so a non-serializable `meta` is rejected at the
-   * source, and the durable log reproduces the identical card on replay. Absent
+   * A completed tool call's model-facing result, optional internal failure
+   * identity, and optional tool-private `meta` presentation payload. `meta` is
+   * opaque to the core (the producing tool owns its shape and reads it back in
+   * `presentResult`) but MUST be JSON-serializable: `Session.append`
+   * runtime-validates all event data with `isJsonValue`, so a non-serializable
+   * `meta` is rejected at the source, and the durable log reproduces the
+   * identical card on replay. Absent
    * unless the tool attaches one (e.g. `dsh-tool-fs` carries its result-time
    * contextual diff here).
    */
@@ -258,7 +259,7 @@ export interface SessionEventMap {
     callId: CallId
     content: ContentBlock[]
     isError: boolean
-    error?: { message: string; info?: { name: string; code: string } }
+    error?: { name: string; code: string }
     meta?: JsonValue
   }
   /** Steering content injected between steps of a running turn. */

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

@@ -64,7 +64,7 @@ describe('interruptedTurnClosers', () => {
     expect(closers.map(e => e.seq)).toEqual([3, 4, 5])
     const result = closers[0]!
     expect(result.type === 'tool/result' && result.data).toMatchObject({
-      turn: 2, step: 1, callId: CallId('call-1'), isError: true, error: { info: { code: 'interrupted' } },
+      turn: 2, step: 1, callId: CallId('call-1'), isError: true, error: { code: 'interrupted' },
     })
   })