Prompt Change Management

The Core Problem

Prompt changes have blast radius. A change to Parser prompt affects sub-question phrasing, which affects what Critic reads, which affects sufficiency judgment — even though you only touched one file. Silent regressions are the norm, not the exception.

Rule: Never commit a prompt change without a validation run.

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Step 0: Before You Touch Anything

Answer these questions first. If you can't answer them, do not proceed.

1. What behavior are you trying to change? (specific, observable)
2. What is the current behavior? (with a concrete example from logs)
3. Which node's prompt are you changing?
4. Which other nodes read output from that node? (these are your blast radius)
5. What test cases will you run to confirm the change worked?
6. What test cases will you run to confirm nothing else broke?

Write these down before opening any prompt file.

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Step 1: Document the Change Before Committing

Every prompt change MUST have a log entry in docs/prompt-change-log.md BEFORE the commit. Format:

| # | Commit | Task | What Changed | Why | Validation Log |
|---|--------|------|-------------|-----|---------------|
| P7 | pending | [task name] | [exact diff in plain language] | [root cause this fixes] | pending |

Fill in commit hash and validation log path after the run completes.

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Step 2: Scope the Change

Prefer the smallest possible change that fixes the problem.

Before writing new prompt text, ask:

• Is this a prompt problem or an input structure problem? (Input structure problems cannot be fixed by prompt changes — see critic-judge-design skill)
• Can a few-shot example fix this instead of a new rule?
• Will adding this rule conflict with any existing rule in the same prompt?
• Is this prompt already too long? (>100 lines is a warning sign — rules start competing for attention)

If the prompt is already long: consider whether the new rule is truly necessary, or whether it's patching a structural problem that needs a different fix.

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Step 3: Identify Downstream Effects

For each node whose prompt you're changing, identify what downstream nodes consume its output:

Parser prompt change
  → affects sub_question text
    → affects Generator SQL strategy
    → affects Critic sufficiency judgment (Critic reads sub_question text)
      → affects whether follow-up rounds trigger
        → affects Synthesizer input

Generator prompt change
  → affects SQL quality
    → affects Executor row counts
      → affects Critic coverage assessment

Critic prompt change
  → affects retrieval_outcome routing
  → affects feedback object quality
    → affects follow-up Parser decomposition

Known high-risk pattern: Parser prompt examples that use entity names from your actual test data will prime the LLM to copy those phrasings, causing consistent sub-question phrasing shifts that propagate to Critic judgment.

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Step 4: Run Validation

Minimum validation required for any prompt change:

python terminal_app.py \
  --batch-file test-inputs/critic/core.txt \
  --logs-dir logs/<change-name>/<timestamp> \
  --max-critic-rounds 3 \
  --sleep-seconds 5 \
  --retry-cooldown-seconds 30

Save a _metadata.txt in the log directory:

commit: <hash> <message>
command: <full command>
batch_file: <path>
max_critic_rounds: <N>
model: <model name>
temperature: <N>
seed: <N>
started_at: <ISO timestamp>
results: <N/M sufficient>
notes: <what you changed and why>

Controlled comparison rules:

When comparing before/after runs, these MUST be identical:

• Batch file (same cases, same order)
• --max-critic-rounds
• All other CLI parameters
• Model, temperature, seed

If any parameter differs, the comparison is not valid for causal claims.

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Step 5: Evaluate Results

After the run, check:

1. Did the target behavior change? (the thing you were trying to fix)
2. Did any previously-passing cases regress?
3. Is the result stable? (run twice — if results differ significantly, the change introduced instability)

Passing threshold: All previously-stable cases must still pass. If any regression appears, the change is not safe to ship regardless of whether it fixed the target behavior.

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Step 6: Rollback Protocol

If a regression is detected:

1. git revert <commit> immediately
2. Document the regression in the prompt change log with the validation log path
3. Analyze root cause before attempting the fix again (see regression-testing skill for bisect protocol)

Do not attempt to fix the regression with another prompt change. Stacked prompt changes make root cause analysis impossible.

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Known High-Risk Prompt Patterns

Pattern	Risk	Mitigation
Entity-specific examples in prompt	LLM copies entity names into outputs, causing phrasing drift	Use generic examples only
Rules added after 100+ line prompt	Rules compete for attention, critical rules get ignored	Simplify or split the prompt
Same node doing judgment + planning	Reasoning quality degrades when doing two conflicting things at once	Split into two nodes
Fixing a structural problem with a prompt rule	Prompt says one thing, data structure says another — data structure wins	Fix the structure, not the prompt