Issue
Output Breaks After Model Change
Output that previously worked begins failing after a model, mode, runtime, or product behavior changes.
What This Looks Like
A prompt, workflow, structured output, parser-facing response, or generated artifact worked before, but starts failing after the model, mode, runtime, or product behavior changes. The user may see different formatting, missing structure, new wording, parser failures, changed refusal behavior, or different assumptions after the change.
Why It Matters
Model changes can break working workflows even when the user did not change the prompt. If the output contract depends on behavior that shifts across versions or modes, downstream systems may fail without an obvious local cause. Users need to distinguish prompt failure from compatibility drift.
Structural Signal
The output contract remains expected by the user or workflow, but the model behavior that produced it has changed. The issue is not simply that a new output is different; it is that the new behavior no longer fits a previously working compatibility envelope.
Common Triggers
- A model update changes formatting, reasoning style, or default structure
- The runtime switches models or modes without clear notice
- Prompt examples no longer constrain the new model the same way
- A parser expects old output behavior
- Product changes alter tool use, refusal behavior, or response structure
- A workflow depends on undocumented model behavior
When to Use This Issue
Use this Issue when output that previously worked begins failing after a model, mode, runtime, or product behavior change.
When Not to Use This Issue
Do not use this Issue when the prompt, schema, or workflow changed at the same time and is the clearer cause. Do not use it for ordinary output variation unless the model or runtime change is central to the break.
Category
Primary Pattern
Declared Patterns
Compatibility Violation
A structural condition where a graph, object, behavior, or runtime state exceeds a declared compatibility envelope without an authorized exception.
Contract Drift
A structural condition where a declared contract changes but connected structures, implementations, consumers, or expectations do not update in sync.
Divergent Outputs
A structural condition where parallel evaluations under comparable scope and shared authority produce non-equivalent outputs.
Derived Primary Lenses
Compatibility Envelope Lens
Determines whether structure fits within declared runtime, platform, version, or support constraints.
Convergence Lens
Compares parallel structural systems to determine whether they align under shared authority.
Reconciliation Lens
Evaluates whether structural changes align with declared authority updates, version changes, or reconciliation rules.
Variance / Entropy Lens
Measures structural variability across repeated or comparable evaluations and identifies divergence beyond expected bounds.
Derived Secondary Lenses
Boundary Compliance Lens
Evaluates observed structure against declared boundary posture, including allow, block, and exception rules.
Compression Lens
Reduces structural graphs into stable minimal representations for comparison, redundancy detection, and diffing.
Determinism Lens
Evaluates whether identical structural inputs produce equivalent structural outputs across repeated executions.
Related AI-Adjacent Issues
AI Works in One Environment Not Another
The same AI task appears to work in one app, mode, model, account, workspace, or runtime but fails or behaves differently in another.
Guardrail Applies to One Model Path Only
A guardrail, policy, validation rule, safety check, or workflow constraint applies to one model path, mode, runtime, or route but not another.
Search Intents
- output breaks after model change
- AI output changed after model update
- model change broke output format
- prompt worked before model update
- output no longer works after upgrade
- model version changed output