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Robin
Robin

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Coding Is Forward. Debugging Is Backward.

Coding starts with an intention. Debugging starts with a failure.

Most AI coding workflows follow a forward loop:

Idea → Code → Test → Ship

Production debugging starts from the opposite direction:

Failure → Evidence → Hypothesis → Reproduction → Fix → Validation

That difference matters.

Coding Starts With a Known Outcome

When you ask an AI coding agent to build something, the goal is usually clear.

You know what the system should do.

The agent can:

  • inspect the repository
  • understand the requirements
  • write code
  • run tests
  • iterate

The workflow moves toward an intended result.

Debugging doesn't have that luxury.

Debugging Starts With a Symptom

Consider:

500 errors increased after the latest deployment.
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That's a signal.

It doesn't tell you the root cause.

You still need to determine:

  • What changed?
  • Which requests fail?
  • Can the failure be reproduced?
  • Which component is responsible?
  • Is the visible exception the actual cause?
  • Does the failure disappear after the fix?

A stack trace tells you where execution failed.

It doesn't automatically tell you why.

Where it failed ≠ why it failed.

Reproduction Is the Critical Step

Suppose an AI says:

The root cause is X.

The next question should be:

Can you reproduce it?

If the current code fails under the same conditions, you have evidence.

If the same reproduction passes after the fix, you have stronger evidence that the fix actually addressed the problem.

The chain becomes:

Root Cause
    ↓
Reproduction
    ↓
Fix
    ↓
Validation
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Without reproduction, the root cause is still a hypothesis.

Green Tests Aren't Automatically Proof

An AI can change several files and make the test suite pass.

That doesn't necessarily mean the production bug is fixed.

The tests may not reproduce the original failure.

The test may not cover the affected behavior.

The patch may fix a symptom rather than the cause.

Or the change may introduce a regression.

The better question isn't:

Did the tests pass?

It's:

Did the same failure disappear after the fix?

An Evidence-First Debugging Loop

A stronger AI debugging workflow looks like this:

Signal
  ↓
Evidence
  ↓
Hypothesis
  ↓
Reproduction
  ↓
Fix
  ↓
Validation
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Signal

An alert, exception, customer report, timeout, crash, or test failure.

Evidence

Logs, traces, metrics, recent changes, repository state, runtime information, issue history, and environment details.

Hypothesis

A possible explanation.

Not a conclusion.

Reproduction

Recreate the original failure.

Fix

Make the smallest appropriate change.

Validation

Run the reproduction again and check for regressions.

AI Coding Agents vs AI Debugging Agents

A coding workflow can look like:

Create → Execute → Iterate
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A debugging workflow needs to look more like:

Investigate → Reproduce → Explain → Fix → Validate
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The same model can potentially perform both jobs.

But the workflow and success criteria are different.

A plausible patch isn't the same thing as a proven fix.

The Standard Should Be Higher

The future of AI debugging shouldn't simply be:

AI generated a patch.

It should be:

AI investigated the failure, reproduced it, identified the root cause, fixed it, and validated that the original failure disappeared.

That's the difference between generating a fix and proving one.

Root Cause → Reproduction → Fix → Validation

What should an AI debugger prove before changing production code?

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