AI-Assisted Debuggingon the JVM

run(application)→Unexpected behavior→Why?

Nikita KovalAppGlass @ JetBrains

What to expect

Experience & intuition

Debugging approaches

What not to expect

A model leaderboard

One universal recipe

Beyond the JVM

My path to debugging

Algorithms

Kotlin Coroutines
IDE tooling

PLDI · PPoPP

→

Concurrency
Testing

Lincheck

Concurrent JVM code

CAV · ISSTA

→

Debugging

Execution traces
Failing schedules

AI-Assisted Debugging
Debugging production

I start with `println()`

OrderDemo.java→PricingService.java

3PricingService pricing = new PricingService(args.length == 0);

4Order order = new Order();

5Money result = pricing.price(order);

6if (!order.currency.equals(result.currency)) {

7 throw new AssertionError("expected " + order.currency + ", got " + result.currency);

8}

Console

AssertionError: expected EUR, got USD
  at OrderDemo.main(OrderDemo.java:7)

OrderDemo.java→PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

4 if (cached != null) {

5 return useCached(cached);

6 } else {

7 return fetchPrice(order);

8 }

9}

Console

AssertionError: expected EUR, got USD

Which branch?

OrderDemo.java→PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

4 if (cached != null) {

+ println("useCached");

6 return useCached(cached);

7 } else {

+ println("fetchPrice");

9 return fetchPrice(order);

10 }

11}

Console

useCached
AssertionError: expected EUR, got USD

Which call?

OrderDemo.java→PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

+ println("sku=" + order.sku +

+ ", requested=" + order.currency +

+ ", cached=" + cached);

7 if (cached != null) {

+ println("useCached");

9 return useCached(cached);

10 } else {

+ println("fetchPrice");

12 return fetchPrice(order);

13 }

14}

Console

sku=JVM-1, requested=EUR, cached=90 USD
useCached
AssertionError: expected EUR, got USD

Which values?

Agents add logs too

CURSOR · 10 DECEMBER 2025

Introducing Debug Mode

ReLog

Generate diagnostic logs
Refine them after execution

Debugging framework · ASE 2026

A developer and an AI robot point at each other, each holding the same log printout — MeAI

An agent runs the same loop

PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

4 if (cached != null) {

5 return useCached(cached);

6 } else {

7 return fetchPrice(order);

8 }

9}

Console

AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Locating the price calculation

✓Read PricingService.java

PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

4 if (cached != null) {

+ println("useCached " + cached);

6 return useCached(cached);

7 } else {

+ println("fetchPrice " + order);

9 return fetchPrice(order);

10 }

11}

Console

useCached 90 USD
AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Checking both price sources

✓Add call + result logs

PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

4 if (cached != null) {

+ println("useCached " + cached);

6 return useCached(cached);

7 } else {

+ println("fetchPrice " + order);

9 return fetchPrice(order);

10 }

11}

Console

useCached 90 USD
AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Checking which currency was requested

✓Inspect the request and cache key

PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

+ println("sku=" + order.sku +

+ ", requested=" + order.currency +

+ ", cached=" + cached);

7 if (cached != null) {

+ println("useCached " + cached);

9 return useCached(cached);

10 } else {

+ println("fetchPrice " + order);

12 return fetchPrice(order);

13 }

14}

Console

sku=JVM-1, requested=EUR, cached=90 USD
useCached 90 USD
AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Comparing request and cached price

✓Log SKU, currency and cached value

PricingService.java

1class PricingService {

2Money price(Order order) {

3 Money cached = prices.get(order.sku);

4 println("sku=" + order.sku +

5 ", requested=" + order.currency +

6 ", cached=" + cached);

7 if (cached != null) {

8 println("useCached " + cached);

9 return useCached(cached);

10 } else {

11 println("fetchPrice " + order);

12 return fetchPrice(order);

13 }

14}

Console

sku=JVM-1, requested=EUR, cached=90 USD
useCached 90 USD
AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Connecting the observations

✓Read request and cached currency

Currency is missing from the cache key

A EUR order gets a USD price

0:00 / 0:19

Logs need a feedback loop

ReLog · ASE 2026 · revised 26 August 2026

DeepSeek-V3 · 311 faulty Java methods · correct repairs

One round of logging

Add logs → Run → Diagnose

26.0%

Improve the observations

Add logs → Run → Read output

31.2%

`println()` has limits

Change a log

Recompile + rerun

Inside a dependency

No source edits

A skeleton still waiting for its laptop to finish compiling

`println()` has limits

Change a log

Recompile + rerun

Inside a dependency

No source edits

A frustrated man pleading to get through a locked fence

Let’s use a debugger
for debugging

Run, pause, inspect, resume

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4 if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Debug session not started

Console

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4 if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Waiting for a breakpoint

Console

PricingService.java

●1class PricingService {

●2Money price(Order order) {order: Order@402

●3 Money cached = prices.get(order.sku);90 USD

●4 if (cached != null) {cached ≠ null

●▶5 return useCached(cached);cached: 90 USD

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Frames

main ▾

price:5PricingService

main:5OrderDemo

Variables

▸

this = {PricingService@401}

▾

order = {Order@402}

id = 42

▸

sku = "JVM-1"

▸

currency = "EUR"

▾

cached = {Money@403}"90 USD"

amount = 90

▸

currency = "USD"

Console

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4 if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Console

Exception in thread "main" java.lang.AssertionError:
  expected EUR, got USD
  at OrderDemo.main(OrderDemo.java:7)

Tests: 1 failed

Connect your agent to IntelliJ

✓ Enable MCP Server

Your AI agentAuto-Configure

Other MCP clients → Copy Config

Restart the agent

Debugger tools are available

xdebug_set_breakpointxdebug_control_sessionxdebug_get_frame_values

MCP Server setup · Debugger tools · IDEA 2026.1.3+

An agent uses the debugger

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4 if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Debug session not started

Console

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Choosing where to pause

✓Set breakpoints · lines 5 and 7

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4 if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Waiting for a breakpoint

Console

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Waiting for either branch

✓Start OrderDemo

PricingService.java

●1class PricingService {

●2Money price(Order order) {order: Order@402

●3 Money cached = prices.get(order.sku);90 USD

●4 if (cached != null) {cached ≠ null

●▶5 return useCached(cached);cached: 90 USD

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Frames

main ▾

price:5PricingService

main:5OrderDemo

Variables

▸

this = {PricingService@401}

▾

order = {Order@402}

id = 42

▸

sku = "JVM-1"

▸

currency = "EUR"

▾

cached = {Money@403}"90 USD"

amount = 90

▸

currency = "USD"

Console

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Inspecting the cached-price branch

✓Read order and cached

PricingService.java

●1class PricingService {

●2Money price(Order order) {order: Order@402

●3 Money cached = prices.get(order.sku);90 USD

●4 if (cached != null) {cached ≠ null

●▶5 return useCached(cached);cached: 90 USD

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Frames

main ▾

price:5PricingService

main:5OrderDemo

Variables

▸

this = {PricingService@401}

▾

order = {Order@402}

id = 42

▸

sku = "JVM-1"

▸

currency = "EUR"

▾

cached = {Money@403}"90 USD"

amount = 90

▸

currency = "USD"

Console

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Checking the cache key

✓Read prices.get(order.sku)

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4 if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Console

Exception in thread "main" java.lang.AssertionError:
  expected EUR, got USD
  at OrderDemo.main(OrderDemo.java:7)

Tests: 1 failed

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Connecting the observations

✓Resume the test

Currency is missing from the cache key

A EUR order gets a USD price

0:00 / 0:19

Does debugger access help?

debug-gym · Microsoft Research · March 2025

Claude 3.7 Sonnet · 300 SWE-bench Lite Python tasks

TASKS SOLVED · MEAN OF 3 RUNS

Edit + run

37.2%

+ interactive debugger

48.4%

The workflow matters too

Debug2Fix · Garg & Huang, Microsoft · February 2026

186 GitBug-Java tasks · pass rate

	GPT-5	Haiku 4.5	Sonnet 4.5
Baseline	60.2%	71.0%	75.7%
+ debugger tools	60.8%	70.4%	64.5%
+ debugging subagent	64.0%	76.1%	78.0%
Mandatory first debugger call	73.1%	82.3%	85.5%

Edits locked→Call debug subagent→Edits enabled

Logpoint: Debugger in `println` style

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

●4● if (cached != null) {

●5 return useCached(cached);

●6 } else {

●7 return fetchPrice(order);

●8 }

●9}

Logpoint PricingService.java:4

"sku=" + order.sku +
", requested=" + order.currency +
", cached=" + cached

Done

Console

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

Logpoint"sku=" + order.sku + ", requested=" + order.currency + ", cached=" + cached

●4● if (cached != null) {

Logpoint"useCached"

●5● return useCached(cached);

●6 } else {

Logpoint"fetchPrice"

●7● return fetchPrice(order);

●8 }

●9}

Console

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

Logpoint"sku=" + order.sku + ", requested=" + order.currency + ", cached=" + cached

●4● if (cached != null) {

Logpoint"useCached"

●5● return useCached(cached);

●6 } else {

Logpoint"fetchPrice"

●7● return fetchPrice(order);

●8 }

●9}

Console

sku=JVM-1, requested=EUR, cached=90 USD
useCached
AssertionError: expected EUR, got USD

Completed
without
suspension

Logpoints, ready for agents

JETBRAINS · INTELLIJ IDEA 2026.2

JetBrains Println Debugging Done Right article cover

Set observations

Run once

Read the output

No step / resume loop

The agent sets logpoints

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

Logpoint"sku=" + order.sku + ", requested=" + order.currency + ", cached=" + cached

●4● if (cached != null) {

Logpoint"useCached"

●5● return useCached(cached);

●6 } else {

Logpoint"fetchPrice"

●7● return fetchPrice(order);

●8 }

●9}

Console

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Preparing the observations

✓Set all logpoints · lines 4, 5 and 7

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

Logpoint"sku=" + order.sku + ", requested=" + order.currency + ", cached=" + cached

●4● if (cached != null) {

Logpoint"useCached"

●5● return useCached(cached);

●6 } else {

Logpoint"fetchPrice"

●7● return fetchPrice(order);

●8 }

●9}

Console

sku=JVM-1, requested=EUR, cached=90 USD
useCached
AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Running without pauses

✓Completed without suspension

PricingService.java

●1class PricingService {

●2Money price(Order order) {

●3 Money cached = prices.get(order.sku);

Logpoint"sku=" + order.sku + ", requested=" + order.currency + ", cached=" + cached

●4● if (cached != null) {

Logpoint"useCached"

●5● return useCached(cached);

●6 } else {

Logpoint"fetchPrice"

●7● return fetchPrice(order);

●8 }

●9}

Console

sku=JVM-1, requested=EUR, cached=90 USD
useCached
AssertionError: expected EUR, got USD

AI ChatDemo

You · OrderDemo.java:7

Test failed: expected EUR, got USD

Connecting the observations

✓Read values and executed branch

Currency is missing from the cache key

A EUR order gets a USD price

0:00 / 0:11

Logpoints or breakpoints?

Know what to observe?

Logpoints

Set → Run → Read

Need to explore?

Breakpoints

Pause → Inspect → Choose next

Logpoints first · pause when needed

The bundled ij-debugger skill follows this strategy

Debugging
without a debugger?

A confused suited man looking around for the missing debugger

Two invoices, one number

Webshop example · Igor Kulakov, JetBrains · May 2026

Request A

INV-00001

Request B

INV-00002

Passing run · sequential requests

Request A

INV-00001

Request B

INV-00001

Rare failure · overlapping requests

A shocked hamster reacting to the duplicate invoice number

Same lines, different hit counts

IntelliJ coverage · two controlled JVM runs

InvoiceService.java	Pass	Fail
19`if (generator == null) {`	✓	✓
20 `generator = createGenerator();`	✓	✓
22`number = generator.nextNumber();`	✓	✓
28`max = repository.findMaxInvoiceNumber();`	✓	✓

100% line coverage in both runs

InvoiceService.java	Pass	Fail
19`if (generator == null) {`	2	2
20 `generator = createGenerator();`	1	2
22`number = generator.nextNumber();`	2	2
28`max = repository.findMaxInvoiceNumber();`	1	2

Inspect generator initialization

Sampling gives us a direction

Sampling profiler

ILLUSTRATIVE STACK SAMPLES

AppDBAppDBDBAppAppDBApp

InvoiceService.createGenerator()

A clue where to look

Rare calls may be missed

An option in production

Every execution has a history

price(order) EUR

prices.get("JVM-1") → 90 USD

cached != null → true

useCached(cached) → 90 USD

AssertionError: expected EUR, got USD

Every event is too much

1 secondof execution

≈1 GBof full trace

Calls · arguments · locals · reads · writes

Order of magnitude · varies with the program

What deserves the detail?

A frantic investigator connecting far too many log printouts on a conspiracy board

Keep the useful parts

First 2 + last 2 · preserve selected failures

0199

Iteration 0USD → USD

Iteration 1USD → USD

196 more iterations

Iteration 198USD → USD

Iteration 199EUR → USD

First 2 + last 2 · preserve selected failures

0199

Iteration 0USD → USD

Iteration 1USD → USD

196 iterations omitted

Iteration 198USD → USD

Iteration 199EUR → USD

Illustrative trace 200 iterations · 1,409 events

Batch@401.run()

loadCatalog()

decode("90 USD") → Money@403

String.split(" ") → ["90", "USD"]

Integer.parseInt("90") → 90

normalize(Money@403) → Money@403

index(Money@403)

prices.put("JVM-1", Money@403) → null

for each order

iteration 0

price(Order@404) → Money@403

prices.get("JVM-1") → Money@403

useCached(Money@403) → Money@403

validateCurrency(Order@404, Money@403)

expected = "USD", actual = "USD"

passed = 1

… iterations 1–198 …

iteration 199

price(Order@603) → Money@403

prices.get("JVM-1") → Money@403

useCached(Money@403) → Money@403

validateCurrency(Order@603, Money@403)

expected = "EUR", actual = "USD"

throw AssertionError

Selected view 1 event · Failure

throw AssertionError

Start with failures or logs

Throw · catch · assertion

Logging · stdout · stderr

Illustrative trace 200 iterations · 1,409 events

Batch@401.run()

loadCatalog()

decode("90 USD") → Money@403

String.split(" ") → ["90", "USD"]

Integer.parseInt("90") → 90

normalize(Money@403) → Money@403

index(Money@403)

prices.put("JVM-1", Money@403) → null

for each order

iteration 0

price(Order@404) → Money@403

prices.get("JVM-1") → Money@403

useCached(Money@403) → Money@403

validateCurrency(Order@404, Money@403)

expected = "USD", actual = "USD"

passed = 1

… iterations 1–198 …

iteration 199

price(Order@603) → Money@403

prices.get("JVM-1") → Money@403

useCached(Money@403) → Money@403

validateCurrency(Order@603, Money@403)

expected = "EUR", actual = "USD"

throw AssertionError

Selected view 5 events · + call path

Batch@401.run()

for each order

iteration 199

validateCurrency(Order@603, Money@403)

throw AssertionError

Illustrative trace 200 iterations · 1,409 events

Batch@401.run()

loadCatalog()

decode("90 USD") → Money@403

String.split(" ") → ["90", "USD"]

Integer.parseInt("90") → 90

normalize(Money@403) → Money@403

index(Money@403)

prices.put("JVM-1", Money@403) → null

for each order

iteration 0

price(Order@404) → Money@403

prices.get("JVM-1") → Money@403

useCached(Money@403) → Money@403

validateCurrency(Order@404, Money@403)

expected = "USD", actual = "USD"

passed = 1

… iterations 1–198 …

iteration 199

price(Order@603) → Money@403

prices.get("JVM-1") → Money@403

useCached(Money@403) → Money@403

validateCurrency(Order@603, Money@403)

expected = "EUR", actual = "USD"

throw AssertionError

Selected view 7 events · + nearby state

Batch@401.run()

for each order

iteration 199

price(Order@603) → Money@403

validateCurrency(Order@603, Money@403)

expected = "EUR", actual = "USD"

throw AssertionError

Keep the useful parts

Measured example · Kotlin compiler · KT-75831

16.4Mrecorded events

756selected events

128 kB of text for the agent

Trace Recorder: lower cost

Our internal experiments · combined results

AVERAGE MODEL COST · REPORTED UNITS

Without trace

7.806

Trace Recorder

3.336

57%lower cost

SOLVED46.7% → 50.9%

Uncertain gain
p = 0.15 · interval −1.5 to +9.9 pp

AVERAGE TIME541 → 588 s

Lower cost
Longer runs

Would you do any of this
in production?

A calm cartoon dog with coffee and a laptop surrounded by flames

Production changes the rules

Extra println	Rebuild + redeploy
Remote debugger	Pauses · mutable state · JDWP
IDE logpoints	Debug connection · mutable state
Coverage comparison	No controlled reruns
Execution traces	Too much to record
Sampling profiler	Can run continuously · partial evidence

×Extra println	Rebuild + redeploy
Remote debugger	Pauses · mutable state · JDWP
IDE logpoints	Debug connection · mutable state
Coverage comparison	No controlled reruns
Execution traces	Too much to record
Sampling profiler	Can run continuously · partial evidence

×Extra println	Rebuild + redeploy
×Remote debugger	Pauses · mutable state · JDWP
IDE logpoints	Debug connection · mutable state
Coverage comparison	No controlled reruns
Execution traces	Too much to record
Sampling profiler	Can run continuously · partial evidence

×Extra println	Rebuild + redeploy
×Remote debugger	Pauses · mutable state · JDWP
×IDE logpoints	Debug connection · mutable state
Coverage comparison	No controlled reruns
Execution traces	Too much to record
Sampling profiler	Can run continuously · partial evidence

×Extra println	Rebuild + redeploy
×Remote debugger	Pauses · mutable state · JDWP
×IDE logpoints	Debug connection · mutable state
×Coverage comparison	No controlled reruns
Execution traces	Too much to record
Sampling profiler	Can run continuously · partial evidence

×Extra println	Rebuild + redeploy
×Remote debugger	Pauses · mutable state · JDWP
×IDE logpoints	Debug connection · mutable state
×Coverage comparison	No controlled reruns
×Execution traces	Too much to record
Sampling profiler	Can run continuously · partial evidence

×Extra println	Rebuild + redeploy
×Remote debugger	Pauses · mutable state · JDWP
×IDE logpoints	Debug connection · mutable state
×Coverage comparison	No controlled reruns
×Execution traces	Too much to record
✓Sampling profiler	Can run continuously · partial evidence

Keep the values
Keep the app running

Live request→→Response

Snapshot

order.currency = "EUR"
cached.currency = "USD"

Verify the root cause
of production incidents

appglass.org

How AppGlass makes it possible

AppGlass Java agent installed in the JVM

Production restrictionAppGlass mechanism

Rebuild + redeploy→Install tracepoints at runtime

Production restrictionAppGlass mechanism

Rebuild + redeploy→Install tracepoints at runtime

Thread pauses→Capture values, then continue

Production restrictionAppGlass mechanism

Rebuild + redeploy→Install tracepoints at runtime

Thread pauses→Capture values, then continue

Mutable state→Validated read-only expressions

Production restrictionAppGlass mechanism

Rebuild + redeploy→Install tracepoints at runtime

Thread pauses→Capture values, then continue

Mutable state→Validated read-only expressions

JDWP connection→Connect through the AppGlass Java agent

Production restrictionAppGlass mechanism

Rebuild + redeploy→Install tracepoints at runtime

Thread pauses→Capture values, then continue

Mutable state→Validated read-only expressions

JDWP connection→Connect through the AppGlass Java agent

No controlled reruns→Capture the next matching live request

Production restrictionAppGlass mechanism

Rebuild + redeploy→Install tracepoints at runtime

Thread pauses→Capture values, then continue

Mutable state→Validated read-only expressions

JDWP connection→Connect through the AppGlass Java agent

No controlled reruns→Capture the next matching live request

Too much to record→Selected snapshots + capture limits

Expression safety checker

order.id == 42

Expression

→

Compile

Application types

→

Check

Bytecode + callees

→

Install

Validated only

MutationI/OLocksLong loopsDeep recursionBlocked

Unsafe at runtime → tracepoint disabled

Gandalf blocks the way for unsafe expressions

Control plane

AI agent

IntelliJ IDEA

→

Control plane

←

Application JVM

Java agent

No inbound port needed on the application

Live demo

demo.appglass.org

A hopeful cat clasping its paws in prayer behind a laptop

Runtime evidence for debugging

Approach	Runtime evidence	Production
println	Chosen events + values	Code change + redeploy
Debugger	Frames + object state	Pauses · can change state
IDE logpoints	Chosen events + values	Debug connection required
Coverage	Lines + execution counts	Comparable runs needed
Profiler	Sampled call stacks	Available in production
Execution trace	Calls + state over time	Full capture is too large
AppGlass	Selected runtime snapshots	Read-only, without pauses

Give the AI agent runtime evidence

Thank you!

Try AppGlass yourselfdemo.appglass.org

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AI-Assisted Debuggingon the JVM

What to expect

What not to expect

My path to debugging

Algorithms

ConcurrencyTesting

Debugging

I start with println()

Agents add logs too

Introducing Debug Mode

ReLog

An agent runs the same loop

Logs need a feedback loop

One round of logging

Improve the observations

println() has limits

println() has limits

Let’s use a debuggerfor debugging

Run, pause, inspect, resume

Connect your agent to IntelliJ

Restart the agent

An agent uses the debugger

Does debugger access help?

The workflow matters too

Logpoint: Debugger in println style

Logpoints, ready for agents

The agent sets logpoints

Logpoints or breakpoints?

Know what to observe?

Need to explore?

Debuggingwithout a debugger?

Two invoices, one number

Same lines, different hit counts

Sampling gives us a direction

Every execution has a history

Every event is too much

Keep the useful parts

Start with failures or logs

Keep the useful parts

Trace Recorder: lower cost

Would you do any of thisin production?

Production changes the rules

Keep the valuesKeep the app running

How AppGlass makes it possible

Expression safety checker

Compile

Check

Install

Control plane

AI agent

IntelliJ IDEA

Control plane

Application JVM

Java agent

Live demo

Runtime evidence for debugging

Thank you!

Concurrency
Testing

I start with `println()`

`println()` has limits

`println()` has limits

Let’s use a debugger
for debugging

Logpoint: Debugger in `println` style

Debugging
without a debugger?

Would you do any of this
in production?

Keep the values
Keep the app running