diff --git a/packages/cli/src/ingest.ts b/packages/cli/src/ingest.ts
index deaa9d77..53d28f42 100644
--- a/packages/cli/src/ingest.ts
+++ b/packages/cli/src/ingest.ts
@@ -195,6 +195,9 @@ function writeReportStatus(report: IngestReportSnapshot, io: KtxIngestIo): void
   io.stdout.write(`Report: ${report.id}\n`);
   io.stdout.write(`Run: ${report.runId}\n`);
   io.stdout.write(`Job: ${report.jobId}\n`);
+  if (report.body.tracePath) {
+    io.stdout.write(`Trace: ${report.body.tracePath}\n`);
+  }
   io.stdout.write(`Status: ${reportStatus(report)}\n`);
   io.stdout.write(`Source: ${reportSourceLabel(report.sourceKey)}\n`);
   io.stdout.write(`Connection: ${report.connectionId}\n`);
diff --git a/packages/context/src/ingest/ingest-trace.test.ts b/packages/context/src/ingest/ingest-trace.test.ts
new file mode 100644
index 00000000..88b56a37
--- /dev/null
+++ b/packages/context/src/ingest/ingest-trace.test.ts
@@ -0,0 +1,85 @@
+import { mkdtemp, readFile } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { describe, expect, it, vi } from 'vitest';
+import { FileIngestTraceWriter, ingestTracePathForJob, traceTimed } from './ingest-trace.js';
+
+describe('FileIngestTraceWriter', () => {
+  it('persists structured trace events as JSONL', async () => {
+    const root = await mkdtemp(join(tmpdir(), 'ktx-trace-'));
+    const tracePath = ingestTracePathForJob(root, 'job-1');
+    const trace = new FileIngestTraceWriter({
+      tracePath,
+      jobId: 'job-1',
+      connectionId: 'metabase-main',
+      sourceKey: 'metabase',
+      level: 'debug',
+    });
+
+    await trace.event('debug', 'snapshot', 'input_snapshot', {
+      baseSha: 'abc123',
+      rawFileCount: 2,
+      diffSummary: { added: 1, modified: 1, deleted: 0, unchanged: 3 },
+    });
+
+    const lines = (await readFile(tracePath, 'utf-8'))
+      .trim()
+      .split('\n')
+      .map((line) => JSON.parse(line));
+    expect(lines).toHaveLength(1);
+    expect(lines[0]).toMatchObject({
+      schemaVersion: 1,
+      jobId: 'job-1',
+      connectionId: 'metabase-main',
+      sourceKey: 'metabase',
+      level: 'debug',
+      phase: 'snapshot',
+      event: 'input_snapshot',
+      data: {
+        baseSha: 'abc123',
+        rawFileCount: 2,
+        diffSummary: { added: 1, modified: 1, deleted: 0, unchanged: 3 },
+      },
+    });
+    expect(typeof lines[0].at).toBe('string');
+  });
+
+  it('records timing and error context for postmortem inspection', async () => {
+    vi.useFakeTimers();
+    vi.setSystemTime(new Date('2026-05-17T12:00:00.000Z'));
+    const root = await mkdtemp(join(tmpdir(), 'ktx-trace-'));
+    const tracePath = ingestTracePathForJob(root, 'job-2');
+    const trace = new FileIngestTraceWriter({
+      tracePath,
+      jobId: 'job-2',
+      connectionId: 'c1',
+      sourceKey: 'fake',
+      level: 'trace',
+    });
+
+    await expect(
+      traceTimed(trace, 'integration', 'apply_patch', { unitKey: 'wu-1' }, async () => {
+        vi.advanceTimersByTime(17);
+        throw new Error('patch conflict');
+      }),
+    ).rejects.toThrow('patch conflict');
+
+    const lines = (await readFile(tracePath, 'utf-8'))
+      .trim()
+      .split('\n')
+      .map((line) => JSON.parse(line));
+    expect(lines.map((line) => line.event)).toEqual(['apply_patch_started', 'apply_patch_failed']);
+    expect(lines[1]).toMatchObject({
+      level: 'error',
+      phase: 'integration',
+      data: { unitKey: 'wu-1' },
+      error: { name: 'Error', message: 'patch conflict' },
+    });
+    expect(lines[1].durationMs).toBe(17);
+    vi.useRealTimers();
+  });
+
+  it('uses the documented trace path layout', () => {
+    expect(ingestTracePathForJob('/project/.ktx', 'job-3')).toBe('/project/.ktx/ingest-traces/job-3/trace.jsonl');
+  });
+});
diff --git a/packages/context/src/ingest/ingest-trace.ts b/packages/context/src/ingest/ingest-trace.ts
new file mode 100644
index 00000000..eed0cfd5
--- /dev/null
+++ b/packages/context/src/ingest/ingest-trace.ts
@@ -0,0 +1,158 @@
+import { appendFile, mkdir } from 'node:fs/promises';
+import { dirname, join } from 'node:path';
+
+export type IngestTraceLevel = 'info' | 'debug' | 'trace' | 'error';
+
+const TRACE_LEVEL_RANK: Record<IngestTraceLevel, number> = {
+  error: 0,
+  info: 1,
+  debug: 2,
+  trace: 3,
+};
+
+export interface IngestTraceContext {
+  tracePath: string;
+  jobId: string;
+  connectionId: string;
+  sourceKey: string;
+  runId?: string;
+  syncId?: string;
+  level?: IngestTraceLevel;
+}
+
+export interface IngestTraceEvent {
+  schemaVersion: 1;
+  at: string;
+  level: IngestTraceLevel;
+  jobId: string;
+  connectionId: string;
+  sourceKey: string;
+  runId?: string;
+  syncId?: string;
+  phase: string;
+  event: string;
+  durationMs?: number;
+  data?: Record<string, unknown>;
+  error?: {
+    name: string;
+    message: string;
+    stack?: string;
+  };
+}
+
+export interface IngestTraceWriter {
+  readonly tracePath: string;
+  readonly context: IngestTraceContext;
+  withContext(context: Partial<Pick<IngestTraceContext, 'runId' | 'syncId'>>): IngestTraceWriter;
+  event(
+    level: IngestTraceLevel,
+    phase: string,
+    event: string,
+    data?: Record<string, unknown>,
+    error?: unknown,
+    durationMs?: number,
+  ): Promise<void>;
+}
+
+export function ingestTracePathForJob(homeDir: string, jobId: string): string {
+  return join(homeDir, 'ingest-traces', jobId, 'trace.jsonl');
+}
+
+function serializeError(error: unknown): IngestTraceEvent['error'] | undefined {
+  if (error === undefined || error === null) {
+    return undefined;
+  }
+  if (error instanceof Error) {
+    return {
+      name: error.name,
+      message: error.message,
+      ...(error.stack ? { stack: error.stack } : {}),
+    };
+  }
+  return { name: 'Error', message: String(error) };
+}
+
+function shouldWrite(configured: IngestTraceLevel, incoming: IngestTraceLevel): boolean {
+  return TRACE_LEVEL_RANK[incoming] <= TRACE_LEVEL_RANK[configured];
+}
+
+export class FileIngestTraceWriter implements IngestTraceWriter {
+  readonly tracePath: string;
+  readonly context: IngestTraceContext;
+
+  constructor(context: IngestTraceContext) {
+    this.context = { ...context, level: context.level ?? 'debug' };
+    this.tracePath = context.tracePath;
+  }
+
+  withContext(context: Partial<Pick<IngestTraceContext, 'runId' | 'syncId'>>): IngestTraceWriter {
+    return new FileIngestTraceWriter({ ...this.context, ...context, tracePath: this.tracePath });
+  }
+
+  async event(
+    level: IngestTraceLevel,
+    phase: string,
+    event: string,
+    data?: Record<string, unknown>,
+    error?: unknown,
+    durationMs?: number,
+  ): Promise<void> {
+    if (!shouldWrite(this.context.level ?? 'debug', level)) {
+      return;
+    }
+    const serializedError = serializeError(error);
+    const payload: IngestTraceEvent = {
+      schemaVersion: 1,
+      at: new Date().toISOString(),
+      level,
+      jobId: this.context.jobId,
+      connectionId: this.context.connectionId,
+      sourceKey: this.context.sourceKey,
+      ...(this.context.runId ? { runId: this.context.runId } : {}),
+      ...(this.context.syncId ? { syncId: this.context.syncId } : {}),
+      phase,
+      event,
+      ...(durationMs !== undefined ? { durationMs } : {}),
+      ...(data ? { data } : {}),
+      ...(serializedError ? { error: serializedError } : {}),
+    };
+    await mkdir(dirname(this.tracePath), { recursive: true });
+    await appendFile(this.tracePath, `${JSON.stringify(payload)}\n`, 'utf-8');
+  }
+}
+
+export class NoopIngestTraceWriter implements IngestTraceWriter {
+  readonly tracePath = '';
+  readonly context: IngestTraceContext = {
+    tracePath: '',
+    jobId: '',
+    connectionId: '',
+    sourceKey: '',
+    level: 'error',
+  };
+
+  withContext(): IngestTraceWriter {
+    return this;
+  }
+
+  async event(): Promise<void> {}
+}
+
+export async function traceTimed<T>(
+  trace: IngestTraceWriter,
+  phase: string,
+  event: string,
+  data: Record<string, unknown>,
+  fn: () => Promise<T>,
+): Promise<T> {
+  await trace.event('debug', phase, `${event}_started`, data);
+  const started = Date.now();
+  try {
+    const result = await fn();
+    await trace.event('debug', phase, `${event}_finished`, data, undefined, Date.now() - started);
+    return result;
+  } catch (error) {
+    await trace.event('error', phase, `${event}_failed`, data, error, Date.now() - started);
+    throw error;
+  }
+}
diff --git a/packages/context/src/ingest/local-bundle-runtime.ts b/packages/context/src/ingest/local-bundle-runtime.ts
index 4f52684e..d8fffc3b 100644
--- a/packages/context/src/ingest/local-bundle-runtime.ts
+++ b/packages/context/src/ingest/local-bundle-runtime.ts
@@ -76,6 +76,7 @@ import { createEmitHistoricSqlEvidenceTool } from './adapters/historic-sql/evide
 import { HistoricSqlProjectionPostProcessor } from './adapters/historic-sql/post-processor.js';
 import { ContextEvidenceIndexService, SqliteContextEvidenceStore } from './context-evidence/index.js';
 import { DiffSetService } from './diff-set.service.js';
+import { ingestTracePathForJob } from './ingest-trace.js';
 import { IngestBundleRunner } from './ingest-bundle.runner.js';
 import { PageTriageService } from './page-triage/index.js';
 import { createWarehouseVerificationTools } from './tools/warehouse-verification/index.js';
@@ -151,6 +152,10 @@ class LocalIngestStorage implements IngestStoragePort {
   resolveTranscriptDir(jobId: string): string {
     return join(this.project.projectDir, '.ktx/ingest-transcripts', jobId);
   }
+
+  resolveTracePath(jobId: string): string {
+    return ingestTracePathForJob(this.homeDir, jobId);
+  }
 }
 
 class LocalIngestLock implements IngestLockPort {
@@ -671,6 +676,8 @@ export function createLocalBundleIngestRuntime(
       workUnitMaxConcurrency: options.project.config.ingest.workUnits.maxConcurrency,
       workUnitStepBudget: options.project.config.ingest.workUnits.stepBudget,
       workUnitFailureMode: options.project.config.ingest.workUnits.failureMode,
+      isolatedDiffSourceKeys: ['metabase'],
+      ingestTraceLevel: 'debug',
     },
     skillsRegistry: new SkillsRegistryService({ skillsDir, logger }),
     promptService,
diff --git a/packages/context/src/ingest/ports.ts b/packages/context/src/ingest/ports.ts
index 6f0e9f1e..3527d29c 100644
--- a/packages/context/src/ingest/ports.ts
+++ b/packages/context/src/ingest/ports.ts
@@ -16,6 +16,7 @@ import type {
 import type { ToolContext, ToolSession, TouchedSlSource } from '../tools/index.js';
 import type { KnowledgeIndexPort, KnowledgeWikiService } from '../wiki/index.js';
 import type { CanonicalPin } from './canonical-pins.js';
+import type { IngestTraceLevel } from './ingest-trace.js';
 import type { IngestReportSnapshot } from './reports.js';
 import type {
   ReconcileCandidateForPrompt,
@@ -142,6 +143,8 @@ export interface IngestSettingsPort {
   workUnitMaxConcurrency?: number;
   workUnitStepBudget?: number;
   workUnitFailureMode?: 'abort' | 'continue';
+  isolatedDiffSourceKeys?: string[];
+  ingestTraceLevel?: IngestTraceLevel;
 }
 
 export interface IngestGitAuthor {
@@ -155,6 +158,7 @@ export interface IngestStoragePort {
   resolveUploadDir(uploadId: string): string;
   resolvePullDir(jobId: string): string;
   resolveTranscriptDir(jobId: string): string;
+  resolveTracePath(jobId: string): string;
 }
 
 export interface IngestCommitMessagePort {
diff --git a/packages/context/src/ingest/report-snapshot.ts b/packages/context/src/ingest/report-snapshot.ts
index de377dd5..9d2e1062 100644
--- a/packages/context/src/ingest/report-snapshot.ts
+++ b/packages/context/src/ingest/report-snapshot.ts
@@ -137,6 +137,18 @@ export const ingestReportSnapshotSchema = z
         diffSummary: ingestDiffSummarySchema,
         fetch: sourceFetchReportSchema.optional(),
         commitSha: z.string().nullable(),
+        tracePath: z.string().optional(),
+        isolatedDiff: z
+          .object({
+            enabled: z.boolean(),
+            integrationWorktreePath: z.string().optional(),
+            ingestionBaseSha: z.string().optional(),
+            projectionSha: z.string().nullable().optional(),
+            acceptedPatches: z.number().int().min(0),
+            textualConflicts: z.number().int().min(0),
+            semanticConflicts: z.number().int().min(0),
+          })
+          .optional(),
         workUnits: z.array(
           z.object({
             unitKey: z.string().min(1),
diff --git a/packages/context/src/ingest/reports.ts b/packages/context/src/ingest/reports.ts
index 672c5bfb..95d610f2 100644
--- a/packages/context/src/ingest/reports.ts
+++ b/packages/context/src/ingest/reports.ts
@@ -53,6 +53,16 @@ export interface IngestReportBody {
   diffSummary: IngestDiffSummary;
   fetch?: SourceFetchReport;
   commitSha: string | null;
+  tracePath?: string;
+  isolatedDiff?: {
+    enabled: boolean;
+    integrationWorktreePath?: string;
+    ingestionBaseSha?: string;
+    projectionSha?: string | null;
+    acceptedPatches: number;
+    textualConflicts: number;
+    semanticConflicts: number;
+  };
   workUnits: IngestReportWorkUnit[];
   failedWorkUnits: string[];
   reconciliationSkipped: boolean;