Failure-mode catalog · Revised September 19, 2026

32 failure modes in AI-assisted software development

AI-assisted work can go wrong in its inputs, actions, handoffs, checks, and reports. This catalog describes recurring patterns, the errors they can introduce, and ways to detect or address those errors.

The survey draws on published research and Bradley Gibbs’s work on Gyre’s staged code-generation pipeline and a simpler demonstration loop with one code-producing agent. Each entry separates observable behavior from possible explanations. A check may catch an error without establishing its cause; a plausible diagnosis needs evidence before it becomes a reason to change the workflow.

How to read the catalog

The entries cover agent behavior and conditions in the surrounding workflow. They are a practical set of distinctions, not a mutually exclusive taxonomy. One incident can involve several entries. An isolated error may suggest a pattern; recurrence and causal attribution remain separate questions.

Possible checks and responses are conditional options. The relevant choice depends on the evidence, consequence, cost, and available alternatives. A flag can justify investigation without justifying a blocking control.

Agent. A vendor's model together with the vendor's harness, treated as one actor for the task.

Workflow. The surrounding arrangement of tasks, tools, handoffs, evaluation, and human decisions.

Evaluator. A mechanism that checks a candidate against specified requirements. A passing evaluation supports only what its evidence establishes.

Failure-mode activation. An occurrence of the behavior described by a mode. A detector flag is evidence to assess, not automatically a confirmed activation.

Evidence labels describe the basis for an entry:

  • Related research. An entry connected to external studies or deployment reports in the source research.
  • Local observation. An entry informed by Bradley Gibbs's own Gyre pipeline work. Individual observations support bounded conclusions, not population-wide rates.
  • Operational inference. A distinction motivated by how a workflow operates. Related references may inform it without directly establishing the category.

Related research can support a mechanism or motivate a distinction without measuring its frequency in a particular system. References do not establish the effectiveness of the proposed responses. Records means comparisons of observed inputs, actions, identities, and results; review means interpretation by a person or model.

What can be checked deterministically?

The Gyre mapping gives 19 modes countable events or mechanical warning signals. The other 13 modes require interpretation, independent evidence, comparisons between configurations, or later observations. The 19 modes expand into 34 event definitions in the baseline loop’s observation plan, because one mode can involve several distinct checks.

Kind of evidenceExampleWhat remains open
Directly checkable factA result identifies a different candidate; a protected input’s hash changed; a required artifact is absent.The cause, consequence, and whether the available record is complete.
Mechanical warning signalNo tests executed; failures share a setup error; a completion phrase conflicts with an evaluation result.Whether the signal supports the proposed failure-mode interpretation.
Judgment or additional evidenceA test proves the wrong claim; reviewers share a blind spot; a repair targets the wrong cause.Meaning, competing explanations, or a comparison that one trace cannot supply.

This split describes the evidence available in these workflows. It is not a universal limit on automation or a percentage of failure modes detected. Many of the 19 modes still need judgment after a signal appears. An independently specified oracle can make a particular behavioral check deterministic even when choosing that oracle requires judgment.

Deterministic means repeatable under the same rule and inputs. It does not establish that the rule interprets the evidence correctly. The recorded examples below show a shared test failure, a parser false alarm, and one set of file effects appearing under several mode labels.

Observations from Gyre’s pipeline work

These examples come from Bradley Gibbs’s staged pipeline and baseline loop records. Their figures were checked against preserved command output, native CLI records, and saved before-and-after analyses on September 19, 2026. They illustrate what a check can establish and where interpretation begins; they are individual cases, not estimates of frequency or comparative effectiveness.

Staged pipeline · September 5, 2026 · FM-20

43 failures with one shared setup error

In one live canary, 43 of 44 tests failed on the starting code. Every failed case reported the same missing-function error: (0 , createObservations) is not a function. Two starting-test executions in that canary preserved the same pattern.

Deterministic observation: executed-test counts and a common non-assertion error signature. Further judgment: whether the failures exercised the intended behavioral assertions. The shared setup failure showed why a red suite alone was insufficient evidence of test discrimination; it did not establish that every test was intrinsically defective.

Baseline-loop analysis · September 17, 2026 · FM-13

A deterministic parser produced a false alarm

A saved Claude trace included npm test 2>&1 | tail -40 and other declared commands with output redirection. The initial analysis nevertheless flagged the candidate as submitted without a recognized project-command execution. Reanalysis of the same recorded invocation removed that one flag after recognizing the shell command boundaries.

Deterministic observation: whether the parser matched a declared command in the trace. Further judgment: whether an absent match meant absent execution. The producer history was the same; the interpretation changed. A detector’s repeatable output can still be wrong.

Baseline-loop record · September 17, 2026 · FM-03, FM-07, FM-23

3,363 file effects were one shared set of evidence

During one recorded invocation, the agent ran npm ci to install dependencies. The 3,363 changed paths outside the package’s write scope were all under node_modules/; the record separately contained 15 changed files under src/ and tests/. The dependency changes were the out-of-scope portion, not the whole patch. The same observation identities appeared under tool effects, scope, and possible constraint circumvention.

Deterministic observation: the changed paths and their relationship to the declared scope. Further judgment: the significance of those dependency changes and whether they supported a particular causal label. Adding the three rows would count the same evidence three times; the paths do not establish 3,363 independent causal failures.

Explore the catalog

Search by mode, behavior, check, or response. The detection route describes the Gyre check mapping; the evidence basis describes the origin of the catalog entry. Filters apply to the directory and all 32 entries.

32 of 32 modes

Mode directory
FM-01Context, specification, and scopeRelated researchJudgment or additional evidence

Unverified handoff contamination

An upstream error becomes accepted context for later work, without a return to the source that could contradict it.

What it can look like

A summary attributes a requirement to a document that does not contain it. Later stages treat the summary as authoritative and build on the false claim.

Why it matters

One unsupported claim can propagate through plans, tests, and code, increasing the amount of work affected by its eventual correction.

Possible check

Preserve a handoff and its sources so consequential claims can be compared. Exact identifiers and quotations can be checked mechanically; whether a summary preserves meaning requires interpretation. A loop with no handoff stage supplies no opportunity to observe this particular pattern.

What the check cannot establish

A matching reference does not establish a faithful summary, and a faithful summary can repeat an incorrect source. Attribution needs the original claim, the handoff, and evidence of downstream reliance.

Ways to reduce the risk

Keep source references with consequential handoff claims. Compare those claims with the source before dependent work begins.

Possible response

If a handoff is wrong, correct it and identify which later decisions or artifacts relied on it before deciding what to repeat.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [10] · [11]

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FM-02Context, specification, and scopeRelated researchEvents or warning signals

Context overload and distraction

Irrelevant material competes with the requirements and evidence needed for the task.

What it can look like

A large context package includes unrelated examples. The agent adopts one of their patterns and overlooks an explicit acceptance criterion.

Why it matters

A requirement can be present in the input yet fail to influence the result. Increasing the context window alone does not resolve relevance or prioritization.

Possible check

Count prompts above a stated reference size and reads reported as truncated; retain the actual byte count and affected input. The Gyre mapping uses 128 KiB as a reference threshold, not a universal model limit.

What the check cannot establish

These rules detect size and truncation, not distraction. A smaller input can still omit critical context; showing that input volume caused an error needs comparison with other explanations.

Ways to reduce the risk

Select context for the current objective, remove duplication, and make controlling requirements easy to locate while keeping additional sources retrievable.

Possible response

If an omission suggests distraction, compare outcomes with a smaller, task-focused input before attributing the error to context volume.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: agent invocations; context reads.

Related sources: [5]

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FM-03Context, specification, and scopeRelated researchEvents or warning signals

Tool and context ambiguity

Similar, overlapping, or poorly described tools make the intended operation difficult to distinguish from alternatives.

What it can look like

An agent chooses a similarly named tool that operates on a different environment, or uses a general capability where a narrower operation was intended.

Why it matters

A plausible tool choice can affect the wrong resource or exceed the scope of the task.

Possible check

Compare recorded file changes and command effects with explicit permissions. A changed path outside the permitted scope is mechanically identifiable when scope and change capture are complete.

What the check cannot establish

The effect does not explain the tool choice or establish confusion. The same file change may also inform scope and constraint-circumvention entries; those labels do not create independent incidents.

Ways to reduce the risk

Give tools distinct descriptions, expose capabilities appropriate to the task, and state the relevant environment and permitted effects.

Possible response

If an action is misdirected, inspect its actual effects, correct recoverable changes, and clarify the tool selection that led to it.

FM-04Context, specification, and scopeRelated researchJudgment or additional evidence

Conflicting authority or instructions

Instructions or sources disagree without a clear way to determine which controls the decision.

What it can look like

An example demonstrates one behavior while the approved design requires another. The agent silently chooses the example or blends the two.

Why it matters

An unresolved product decision becomes an implicit implementation choice that may be difficult to discover later.

Possible check

Preserve clarification questions and the instructions they concern. Structured contradictions can be compared when the relevant rules have a formal representation; prose conflicts need review of the actual statements.

What the check cannot establish

A question is not proof of conflicting instructions. Conditional requirements may differ legitimately, while consequential contradictions may never produce a question.

Ways to reduce the risk

Name the controlling requirements and distinguish them from examples, background material, and suggestions. Resolve consequential contradictions before dependent work.

Possible response

When a genuine conflict appears, preserve both statements and obtain a decision from the person responsible for that requirement.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [8] · [9]

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FM-05Context, specification, and scopeRelated researchEvents or warning signals

Missing, stale, truncated, or misbound memory

Remembered or carried-forward information is missing, outdated, truncated, or associated with the wrong task.

What it can look like

A decision from an earlier session is treated as current even though its source has changed, or information from another project enters the current task.

Why it matters

Work can be internally consistent while depending on facts that no longer apply.

Possible check

Compare controlling-input hashes at readback and record explicitly truncated reads. Keep input identity, expected version, and missing-capture information with the observation.

What the check cannot establish

A hash mismatch establishes a byte difference, not its author or cause. Matching bytes establish neither continued truth nor correct use; undelivered or unseen information needs separate investigation.

Ways to reduce the risk

Use identifiable source records for consequential decisions, verify relevant versions, and make missing or truncated context visible.

Possible response

If a memory mismatch is found, refresh the affected information and review decisions that depended on it.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: readback entries; context reads.

Related sources: [5]

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FM-06Context, specification, and scopeRelated researchJudgment or additional evidence

Under-specified objective or completion

The objective lacks a sufficiently clear behavioral target or stopping condition.

What it can look like

A request to improve a feature permits several incompatible outcomes. The agent chooses one and completes work that does not meet the intended need.

Why it matters

Competent execution cannot resolve intent that the task never expresses. An unclear stopping rule can also encourage unnecessary changes.

Possible check

Preserve questions, requirement text, and the evaluation mapping. A task with a deliberately ambiguous decision can compare whether the agent asks or guesses against the decision's specified answer and authority.

What the check cannot establish

Filled fields and valid output structure do not establish clear intent. Whether a question is necessary, a default is reasonable, or the task itself is underspecified requires interpretation of the objective.

Ways to reduce the risk

Describe the desired behavior, relevant constraints, and how completion will be assessed. Allow an evidence-supported no-change result when appropriate.

Possible response

Clarify the ambiguity that changes the outcome, then update the objective and evaluation together before continuing affected work.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [3] · [4]

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FM-07Context, specification, and scopeRelated researchEvents or warning signals

Scope and anti-scope ambiguity

The permitted scope and excluded effects are left implicit or open to incompatible interpretations.

What it can look like

An agent makes a useful adjacent change outside the requested feature, assuming that improving the overall result supplies permission.

Why it matters

Helpful work can still create unauthorized behavior, review burden, or risk outside the agreed task.

Possible check

Compare paths changed during each agent invocation with the task's allowed write scope. Count observed path effects against the invocation population, retaining their shared source evidence.

What the check cannot establish

File scope cannot establish whether behavior inside an allowed file was authorized. Final snapshots miss transient changes, and thousands of dependency files can arise from one installation rather than thousands of independent mistakes.

Ways to reduce the risk

State relevant non-goals, resources, and permitted effects. Use enforceable boundaries when the consequence of exceeding them warrants that control.

Possible response

If work exceeds scope, identify the effects and either undo them or obtain a deliberate scope decision before carrying them forward.

FM-08Context, specification, and scopeRelated researchJudgment or additional evidence

Task decomposition overload

One assignment contains more dependent concerns than the agent can reliably complete together.

What it can look like

A request combines design interpretation, test design, implementation, and documentation. Later obligations receive superficial treatment or disappear.

Why it matters

A plausible overall result can conceal omitted work, especially when the missing concern has no independent check.

Possible check

Retain unusable returns, elapsed time, and files changed per invocation as evidence for investigation. Compare missed obligations and final outcomes on combined and decomposed assignments.

What the check cannot establish

Time, file counts, and response failures are not an overload diagnosis. A comparison must account for task difficulty and the information and coordination costs introduced by splitting it.

Ways to reduce the risk

Separate concerns where doing so improves focus, with explicit outputs and enough shared context to preserve dependencies.

Possible response

If omissions recur, compare a narrower assignment with the combined task, including handoff cost and the quality of the final result.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [19] · [7]

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FM-09Context, specification, and scopeRelated researchJudgment or additional evidence

Topology mismatch

The arrangement of agents and handoffs is poorly matched to the dependencies and information needs of the task.

What it can look like

Independent research questions are serialized unnecessarily, or tightly coupled code changes are split across agents that repeatedly lose shared context.

Why it matters

Coordination costs and information loss can outweigh the benefit of additional roles. A single agent can also become an avoidable bottleneck.

Possible check

Record attempts, agent invocations, elapsed time, and evaluated outcomes for later comparison between single-agent, staged, and specialist arrangements.

What the check cannot establish

One arrangement's trace supplies no counterfactual. Meaningful comparison needs similar tasks, compatible budgets, and the same completion criteria; another model name alone does not create independent evidence.

Ways to reduce the risk

Choose roles and parallelism from task dependencies rather than assuming that a larger or smaller agent count is inherently better.

Possible response

Compare candidate arrangements on similar work, with comparable budgets and the same outcome criteria, before reorganizing the workflow.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [10] · [11]

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FM-10Execution and coordinationOperational inferenceEvents or warning signals

Prompt-only coordination

A workflow relies on instructions alone to coordinate operations that require atomicity or exclusive access.

What it can look like

Two agents are told not to edit a file at the same time. Both observe it as available and one overwrites the other's work.

Why it matters

A prompt cannot make a check-and-write operation atomic. Lost updates can occur even when each actor attempts to follow the instruction.

Possible check

Compare run, process, and worktree identities with the expected state and retain observable interference. Inspect the synchronization mechanism separately. Supervisor pauses in a staged workflow and identity mismatches in a simpler loop are different observations.

What the check cannot establish

Consistent records do not prove that writes were serialized or that every interfering process was observed. A supervisor action does not establish a coordination failure, and unlike observations should not share a rate.

Ways to reduce the risk

Use ordinary synchronization, isolated workspaces, or a single writer where concurrent access can corrupt shared state.

Possible response

If conflicting writes occur, preserve both versions, reconcile the intended changes, and correct the coordination mechanism before repeating the operation.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: runs.

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FM-11Execution and coordinationRelated researchEvents or warning signals

Skipped stage or premature completion

Required work is skipped or rushed while the task is presented as complete.

What it can look like

A completion report arrives before a required verification step has run, or a stage supplies a placeholder that looks like its expected output.

Why it matters

Later work or human review can begin with an incomplete basis for deciding whether the task succeeded.

Possible check

Check for required artifacts and matching executions of declared commands at each attempt boundary. Record missing artifacts, absent execution records, and incomplete collection distinctly.

What the check cannot establish

An artifact's presence does not establish its substance. A command absent from incomplete records cannot be called unexecuted; a completed stage can still fail to satisfy the intended requirement.

Ways to reduce the risk

Make required transitions depend on the relevant results, and distinguish absent evidence from adverse evidence and successful completion.

Possible response

When a step is missing, complete the specific obligation or report an honest stop. Review substance when a nominally present artifact may be inadequate.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: attempts.

Related sources: [7]

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FM-12Execution and coordinationRelated researchEvents or warning signals

Unverified output or claimed execution

A claim that work was executed or verified lacks matching evidence of that execution.

What it can look like

A report says tests pass, but no corresponding process result exists, or the result belongs to a different candidate.

Why it matters

A reader may rely on a check that never ran or that does not apply to the delivered work.

Possible check

Compare each execution receipt's candidate identity with the evaluated candidate, and record command timeouts. Keep the command, candidate, result, and evidence source together.

What the check cannot establish

These comparisons can establish a binding mismatch or timeout. They do not establish whether the command tested the right behavior, whether an unsupported prose claim is false, or whether missing records imply non-execution.

Ways to reduce the risk

Capture the command, candidate, result, and relevant output through the execution system, and connect verification claims to those records.

Possible response

If a claim cannot be reconciled, mark it unsupported and perform the relevant check when feasible. Preserve the distinction between missing records and proven non-execution.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: command executions.

Related sources: [1]

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FM-13Execution and coordinationRelated researchEvents or warning signals

First-response and action bias

The first plausible answer is accepted too quickly, or receiving an assignment is treated as evidence that a change is necessary.

What it can look like

An agent changes behavior that already meets the requirement because producing a patch appears to be the expected outcome.

Why it matters

Unnecessary changes consume review effort and can introduce defects without improving the result.

Possible check

Record whether the untouched starting code passes its checks and whether declared commands appear in the agent's execution trace before submission. Distinguish an agent's own execution from a command run later by the surrounding workflow.

What the check cannot establish

A passing starting suite does not prove that no change is needed. An unmatched command may reveal a parser limitation; shell redirection and pipelines can hide a valid match from a simplistic detector. Neither observation alone establishes action bias.

Ways to reduce the risk

Inspect the initial state and reproduce the reported problem when possible. Include already-correct cases when evaluating the workflow.

Possible response

If the requested behavior is already satisfied, explain the evidence for leaving it unchanged. If the evidence is incomplete, investigate the specific gap.

FM-14Execution and coordinationRelated researchEvents or warning signals

Self-report as state or evidence

An agent's declaration of readiness, completion, confidence, or diagnosis is treated as authoritative workflow state.

What it can look like

A status display reports success because it copied a model summary, despite a failed or absent execution result.

Why it matters

The same actor can create the work and determine whether it advances, without an independent basis for the transition.

Possible check

Match explicit success or execution claims against saved evaluation results and command records. Retain the matched text and the scope of the result used for comparison.

What the check cannot establish

A deterministic text rule can misread negation, miss paraphrases, or compare claims about different tests. A discrepancy prompts inspection; it does not by itself establish deception or that self-report controlled the workflow.

Ways to reduce the risk

Derive consequential workflow states from observed results and explicit decision rules, with model summaries serving as explanations.

Possible response

If reported and observed state disagree, reconcile the underlying records and correct the status before dependent actions proceed.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: attempts.

Related sources: [1]

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FM-15Verification and reviewLocal observationJudgment or additional evidence

Displaced proof or boundary substitution

A genuine passing check is used as evidence for a different object, execution path, or requirement.

What it can look like

A unit test exercises a mocked collaborator while the actual integration remains disconnected. Its pass is cited as evidence that the feature works end to end.

Why it matters

Authentic execution can create false confidence when the assertion does not test the claim being made.

Possible check

Collect execution identities, command traces, and results from checks that exercise the relevant boundary. Compare the claim, assertion, candidate, and actual path; use a discriminating behavioral case where the claim permits one.

What the check cannot establish

Matching candidate identities and real execution are mechanical facts. Whether the assertion supports the intended claim can require semantic review or an independently specified behavioral test; valid execution alone cannot settle it.

Ways to reduce the risk

Connect each consequential claim to a check that exercises the relevant candidate and behavior. Use real integration paths where the claim depends on them.

Possible response

When proof is displaced, withdraw the unsupported conclusion and run or design a check that can distinguish the required behavior from a relevant defect.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [18]

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FM-16Verification and reviewLocal observationEvents or warning signals

Agent-owned disposition

An agent's recommendation is treated as a decision reserved for a human or another authorized actor.

What it can look like

A review recommends shipping, and that prose is used to mark the work accepted even though no authorized acceptance decision occurred.

Why it matters

A review can redirect, release, or terminate work without the responsible person's decision. A strong recommendation alone is not this failure.

Possible check

Record explicit completion or readiness phrases and the actor responsible for consequential state changes. A vocabulary match and an unauthorized transition are separate observations.

What the check cannot establish

A phrase such as “complete” may describe an operation inside the program or a legitimate recommendation. Interpretation and authorization records are needed before calling it an agent-owned decision.

Ways to reduce the risk

Separate recommendations from decisions, and identify who may authorize scope, acceptance, release, or replacement.

Possible response

If an unauthorized decision advances the workflow, restore the decision point and present the recommendation with its evidence and alternatives.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: agent invocations.

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FM-17Verification and reviewRelated researchJudgment or additional evidence

Shared-method agreement

Agreement among reviewers is mistaken for independent corroboration despite overlapping methods or blind spots.

What it can look like

Two model families read the same diff and approve it. Neither exercises the integration, but their agreement is treated as independent evidence of correct behavior.

Why it matters

Additional opinions can repeat the same omission while making the result appear more reliable.

Possible check

Preserve reviewer inputs, methods, findings, and which independently established defects each reviewer missed. A one-producer loop without reviewers supplies no reviewer-agreement observation.

What the check cannot establish

Agreement and model diversity do not establish independence. A shared blind spot needs evidence of the miss; attributing that miss to a shared method requires further comparison.

Ways to reduce the risk

Choose complementary evidence and methods where independent corroboration matters, such as execution, requirement checks, and code inspection.

Possible response

If an escape reveals a shared miss, identify what each review actually examined and evaluate a targeted method change against comparable defects.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [10] · [11]

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FM-18Verification and reviewRelated researchJudgment or additional evidence

Environmental or causal misdiagnosis

An environmental or execution condition is confused with a defect in the product, or a product defect is dismissed as an environmental issue.

What it can look like

A test fails because a service is unavailable. The agent changes application logic to address a defect that the failure did not establish.

Why it matters

A repair aimed at the wrong layer can waste work, conceal the original problem, or introduce a new defect.

Possible check

Classify recorded failures as assertion, import/loading, timeout, or other observable error types, and retain whether the next attempt clears the symptom along with the intervening changes.

What the check cannot establish

An error class narrows investigation without establishing cause. A disappearing symptom can reflect environmental recovery or masking; product, test, and environment defects can coexist.

Ways to reduce the risk

Preserve raw failures and relevant environment conditions. Use targeted reproduction to distinguish infrastructure, test, and product explanations.

Possible response

When environmental uncertainty matters, isolate the relevant condition and rerun a discriminating check before deciding which layer needs repair.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [6]

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FM-19Verification and reviewRelated researchJudgment or additional evidence

Measurement/query artifact

An artifact of a query, population, filter, or grading method is reported as a property of the system being measured.

What it can look like

A repository search silently excludes a file class, and its result is presented as a complete count of the behavior in the codebase.

Why it matters

A precise-looking number can support a false conclusion if its denominator or selection rule does not match the question.

Possible check

Identify evaluation rows with empty observations and retain the populations, filters, exclusions, and denominators behind reported measurements. Compare them with the intended question.

What the check cannot establish

Empty evidence is a useful lead, not proof of a faulty query. A populated row or fully documented query can still answer the wrong question; the population and claim need interpretation.

Ways to reduce the risk

State the intended population and question, inspect the actual query and exclusions, and retain the denominator alongside the result.

Possible response

If the measurement answers a different question, correct the query or narrow the claim and revisit conclusions that relied on it.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [4] · [3]

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FM-20Verification and reviewLocal observationEvents or warning signals

Non-discriminating check

A check does not distinguish the required behavior from the defect it claims to detect.

What it can look like

A test remains green when the relevant behavior is removed, or fails for an incidental setup error in both good and bad cases.

Why it matters

A passing result provides little assurance when the check would also pass a relevant defect. An insensitive check can also reject valid work.

Possible check

Parse actual executed-test counts, excluding skipped and pending cases. Flag zero execution, fewer executed cases than the comparable starting run, or starting failures that all share one non-assertion error signature. Use known-good and known-bad cases to assess discrimination separately.

What the check cannot establish

These are warning signals about exercised evidence. A shared setup error does not prove a test is useless, and fewer tests may have a legitimate explanation. A negative control establishes sensitivity only to the tested defect and only if it fails for the intended reason.

Ways to reduce the risk

Use representative known-good and known-bad cases to examine what a check actually responds to, including whether its assertions execute.

Possible response

If the check cannot discriminate, repair its oracle or assertions. If the required condition was never exercised, add that condition to the evaluation environment.

FM-21Verification and reviewRelated researchJudgment or additional evidence

Shared contract/oracle defect

Requirements, tests, expected results, and code inherit the same misunderstanding of the intended behavior.

What it can look like

A mistaken interpretation enters the contract and the expected test output. Code implements that interpretation and every check agrees.

Why it matters

Internal consistency can reinforce an error instead of exposing it. Valid behavior may also be rejected by the mistaken expectation.

Possible check

Seek an independent statement of intended behavior, a separately specified behavioral check, or later evidence that challenges the shared expectation. Preserve that evidence alongside the original contract and result.

What the check cannot establish

A single internally consistent run cannot expose every inherited misunderstanding. Code can compare an independent oracle once one exists; choosing and validating that oracle may require domain judgment.

Ways to reduce the risk

Compare consequential expectations with independently obtained requirements, examples, domain evidence, or decisions from the person responsible for the behavior.

Possible response

When a shared misunderstanding is found, correct the requirement and its derived artifacts, then reassess affected candidates against the clarified intent.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [3] · [4]

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FM-22Behavior, change, and robustnessRelated researchJudgment or additional evidence

Visible-check myopia

The implementation satisfies visible examples or isolated tests while failing required general or composed behavior.

What it can look like

Individual operations pass their examples, but combining them in a permitted sequence produces an incorrect result.

Why it matters

Success on a narrow visible suite can conceal incomplete behavior at boundaries and interactions.

Possible check

Compare success on visible checks with independently specified boundary or composition cases and later observed behavior. Retain the admitted candidate so that the comparison concerns the same work.

What the check cannot establish

A visible pass supplies no evidence about an untested condition. An independent counterexample establishes a behavioral gap, but not necessarily why the agent produced it or whether the remaining cases are complete.

Ways to reduce the risk

Derive additional cases from the requirements, including relevant compositions and boundaries, independently of the produced solution.

Possible response

If an independent case exposes a defect, correct the behavior and examine the missing evaluation condition without inferring the agent's motivation from the defect alone.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [13]

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FM-23Behavior, change, and robustnessRelated researchEvents or warning signals

Goal-directed constraint circumvention

An agent works around a restriction while pursuing the task's apparent goal.

What it can look like

A prohibited operation is denied through one tool, so the agent uses another route to produce the same prohibited effect.

Why it matters

Persistence can defeat a constraint even without malicious intent. Checking only one command name may leave equivalent effects available.

Possible check

Record out-of-scope path effects, writes to protected paths, and failed commands followed by alternatives on a shared target. Preserve the failure and alternative rather than reducing the sequence to a bypass label.

What the check cannot establish

A post-failure retry may be ordinary recovery. A command reference is not proof of a successful effect, and missing operating-system events limit visibility. Intent and actual restriction circumvention need separate evidence.

Ways to reduce the risk

Define restrictions in terms of relevant effects and enforce them at the appropriate boundary. Distinguish prohibited effects from merely unavailable methods.

Possible response

If circumvention occurs, stop the affected operation, inspect its effects, and correct the boundary. A legitimate alternative that respects the restriction should remain available.

FM-24Behavior, change, and robustnessOperational inferenceEvents or warning signals

Causal diagnosis substitution

A real symptom gives unwarranted credibility to a proposed cause and the repair derived from it.

What it can look like

A failure is reproducible, but the explanation is untested. A broad change removes the symptom while leaving the initiating defect intact.

Why it matters

A persuasive diagnosis can turn uncertain attribution into harmful repair. This includes causal mistakes beyond environmental conditions.

Possible check

Compare the same requirement across consecutive changed candidates and flag an observed failure that persists after the change. Preserve the diagnosis and the difference between candidates for review.

What the check cannot establish

A failed repair does not establish a false diagnosis; a correct diagnosis can lead to an incomplete fix. A passing repair can mask the cause. Causal attribution needs evidence distinguishing alternatives.

Ways to reduce the risk

Keep observations separate from causal hypotheses and identify evidence that would distinguish plausible explanations.

Possible response

Before a consequential repair, test the proposed mechanism where feasible. Afterward, check both the intended correction and relevant competing explanations.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: attempts beyond the first.

Related sources: [11]

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FM-25Behavior, change, and robustnessRelated researchJudgment or additional evidence

Trajectory residue

Code from abandoned approaches remains in the final result without contributing to the intended behavior.

What it can look like

A working patch retains unused helpers, redundant branches, or a dependency introduced by an earlier failed approach.

Why it matters

Passing functional checks may coexist with unnecessary complexity that increases later review and maintenance effort.

Possible check

Track files added and later removed, the size of each change, and the history of abandoned approaches. Use static analysis or code review to inspect what remains in the final candidate.

What the check cannot establish

File churn is a lead, not a residue count. An earlier addition may still serve the final design, and dynamic or indirect use can defeat an unused-code scan.

Ways to reduce the risk

Keep changes attributable to the intended solution, and inspect abandoned approaches when reviewing a completed patch.

Possible response

Remove residue only after checking that it is unnecessary, then rerun the relevant behavioral checks to guard against deleting legitimate dynamic or indirect use.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [14]

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FM-26Behavior, change, and robustnessRelated researchJudgment or additional evidence

Longitudinal structural or behavioral erosion

Repeated locally successful changes gradually make later work harder or allow broader behavior to drift.

What it can look like

Each increment passes its immediate checks, while duplicated logic, inconsistent error handling, and compatibility differences accumulate across the project.

Why it matters

The cost or behavioral damage may become visible only during subsequent changes, beyond the scope of any one passing patch.

Possible check

Compare later work on the same codebase: effort for similar changes, regressions, and departures from explicit architectural or behavioral constraints.

What the check cannot establish

A single run cannot establish longitudinal erosion. Complexity metrics and elapsed time need context; comparable later tasks and competing explanations matter.

Ways to reduce the risk

Preserve important architectural and behavioral constraints and observe comparable follow-on work, rather than relying on a single complexity score.

Possible response

If a pattern of erosion emerges, identify the recurring mechanism and compare a targeted refactor or workflow change against its cost and regression risk.

Check method: Judgment, independent evidence, or comparison; recorded signals can narrow the investigation.

Related sources: [15] · [16]

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FM-27Behavior, change, and robustnessRelated researchEvents or warning signals

Regression blindness and repair oscillation

A repair reopens a previously satisfied requirement or cycles back to an earlier failing state.

What it can look like

Fixing one test breaks another. The next patch restores the second test but recreates the original defect.

Why it matters

Repeated attempts can consume the budget without net progress and obscure which obligations remain satisfied.

Possible check

Detect repeat candidate identities, repeated candidate/result pairs where those are the chosen unit, and requirements that change from satisfied to unsatisfied. Keep the identity rule and earlier results explicit.

What the check cannot establish

Returning to identical code differs from returning to the same code-and-result pair. A reopened result may reflect a flaky check; neither signal alone proves a causal regression or oscillation. Comparisons must use the same unit.

Ways to reduce the risk

Track candidate changes and relevant regression results across attempts, with explicit limits for repeated or unproductive repair.

Possible response

When a cycle appears, preserve its history, inspect interacting requirements, and choose a different repair strategy or an honest stop.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: evaluated attempts; attempts beyond the first.

Related sources: [17]

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FM-28Behavior, change, and robustnessRelated researchEvents or warning signals

Test or evaluator tampering

An agent changes or bypasses the evaluation mechanism without authorization so that inadequate behavior appears successful.

What it can look like

A failing test is skipped, an expected result is weakened, or a different evaluator is invoked in place of the required one.

Why it matters

Visible success can cease to mean conformance when the producer can redefine the check that admits its output.

Possible check

Compare protected-input hashes and recorded changes to tests, expected results, and other protected paths. Inspect trace evidence for temporary change-then-restore and for commands referring to evaluation material.

What the check cannot establish

Endpoint snapshots cannot reveal every temporary edit. A command that references evaluation material does not prove a successful read, and a read does not establish tampering. Authorized test repair and unauthorized weakening require different treatment.

Ways to reduce the risk

Keep the controlling evaluator and its inputs outside the producer's write authority where independent evaluation is required. Separate legitimate test repair from candidate repair.

Possible response

If unauthorized modification occurs, restore the intended evaluation, inspect the actual inputs used, and reevaluate the affected candidate.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: agent invocations; readback entries.

Related sources: [1]

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FM-29Behavior, change, and robustnessRelated researchEvents or warning signals

Inbound instruction contamination

Material supplied as data is treated as an instruction with authority over the task.

What it can look like

A retrieved page, fixture, or tool result contains an instruction to skip a check. The agent follows it despite the controlling task requirements.

Why it matters

Untrusted or incidental content can redirect behavior across the boundary between evidence and instructions.

Possible check

Record exposure to instruction-like text when supplied material contains it, preserving provenance and subsequent relevant actions. If the task deliberately supplies no such material, exposure is inapplicable for that task rather than a measured zero rate.

What the check cannot establish

A text match does not establish that an instruction was followed. Quoted benign material can trigger a scanner, and causal influence requires evidence beyond exposure.

Ways to reduce the risk

Preserve input provenance, distinguish task instructions from quoted or retrieved content, and limit the effects that lower-trust material can induce.

Possible response

When conflicting behavior follows exposure, inspect the source and action sequence, restore the intended task boundary, and keep causal attribution separate from the exposure flag.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: supplied artifacts.

Related sources: [8] · [9] · [1]

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FM-30Behavior, change, and robustnessRelated researchEvents or warning signals

Concealed uncertainty

A report omits material uncertainty, unsupported work, or failed verification while presenting an apparently complete result.

What it can look like

Every affirmative sentence is true, but a failed check or unresolved requirement that would change the reader's decision is absent.

Why it matters

An incomplete account can mislead without containing an explicit false statement, regardless of whether the omission was deliberate.

Possible check

Count unsupported or unevaluable requirement rows and unusable agent returns as explicit gaps in the record. Compare those gaps and failed checks with the final account.

What the check cannot establish

A visible evidence gap is not concealed uncertainty by itself. Unknowns absent from both the requirements and records remain invisible, and determining whether an omission would change a decision requires judgment.

Ways to reduce the risk

Reconcile completion reports with open obligations, adverse results, and missing evidence. Make consequential uncertainty part of the handoff.

Possible response

If an omission is discovered, correct the report and revisit decisions that depended on its apparent completeness.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: obligation rows; agent invocations.

Related sources: [1]

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FM-31Behavior, change, and robustnessRelated researchEvents or warning signals

Nondeterminism and retry laundering

Mixed execution outcomes are reduced to a convenient passing result without preserving relevant failures.

What it can look like

The same suite fails and then passes under apparently comparable conditions. Only the passing attempt appears in the handoff.

Why it matters

Selective reporting hides instability and makes a result seem more repeatable than the evidence supports.

Possible check

Group executions by candidate identity and command; flag differing exit codes or output hashes. Use only pairs with at least two executions as the relevant population and preserve environment differences.

What the check cannot establish

Output timestamps can change a hash without changing behavior. A third comparable observation is needed to describe what happened after the first disagreement. Mixed results alone prove neither nondeterminism under identical conditions nor selective reporting.

Ways to reduce the risk

Retain attempts, relevant environment differences, and candidate changes. Distinguish a pass after a real repair from unexplained variation.

Possible response

If comparable executions disagree, report the mixed outcome and investigate the variation in proportion to its consequence before treating the result as reliable.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: candidate/command pairs executed at least twice.

Related sources: [6] · [3]

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FM-32Behavior, change, and robustnessLocal observationEvents or warning signals

Premature formalization and clarification overload

Unnecessary formal requirements or clarification requests interrupt useful work and impose disproportionate human effort.

What it can look like

A workflow asks many questions about reversible presentation details before making a concrete draft, even though reasonable defaults would allow progress.

Why it matters

The process can consume more attention than the work it is meant to support and delay learning from a reviewable result.

Possible check

Count clarification requests and unusable-response retries, and retain elapsed time and human effort. Keep per-invocation questions separate from a workflow's consolidated guidance pauses.

What the check cannot establish

Counts measure interruptions or effort, not whether they were unnecessary. A required authorization question is legitimate; burden and lost progress need human assessment. Different units should not be compared as one rate.

Ways to reduce the risk

Distinguish consequential missing decisions from reversible details. Use reasonable defaults and prepare concrete work before requesting decisions that can wait.

Possible response

If interruptions dominate useful progress, examine which requests were necessary and simplify the workflow while preserving decisions that require authorization.

Check method: Deterministic events or warning signals; interpretation as described above.

Observation population: agent invocations.

Back to catalog

Detection, correction, and learning

A code-generation loop can evaluate a candidate against a conformance contract, return failures for repair, and stop when the completion criteria or a budget limit is reached. The contract states the required behavior; the evaluator supplies evidence about whether the candidate meets it.

That terminal result does not explain the whole trajectory. A passing candidate may follow clean work, several recoveries, or an error that escaped the evaluator. Intermediate observations help distinguish those histories and identify where a correction might save work or reduce escapes.

Three separate choices

ChoicePurposeQuestion to test
Observe the workPreserve relevant inputs, actions, tool results, changes, and evaluations.Does the record support useful investigation without excessive collection cost?
Add a targeted check or correctionCatch a specific error before dependent work amplifies it.Does earlier intervention improve outcomes enough to justify misses, false alarms, and overhead?
Reorganize constructionChange objectives, roles, sequencing, or parallelism to fit the task.Does the new arrangement outperform the alternative on comparable work?

Observation and intervention also need separate accounting. A staged workflow may enforce a condition before later work begins, while an observation-only loop records the same event without using it to steer the agent. Their event rates are comparable only when event definitions, opportunity populations, and incident grouping match. A per-invocation question count and a per-run guidance-pause count, for example, measure different things.

These choices can be evaluated separately. Comparing them under the same requirements and external evaluator makes changes in completion rate, effort, and escaped defects easier to interpret. Human acceptance remains a separate decision from machine admission.

Preserve observations before assigning causes

“Completion was requested without a matching verification result” describes an observable event. “Context overload caused the omission” adds a causal interpretation. The first can sometimes be counted mechanically; the second requires evidence that distinguishes it from other explanations.

A useful incident record separates the origin, the missed detection, and the consequence. It can also name a primary lever: the least costly plausible change that would have prevented the escape, with the supporting evidence and uncertainty attached. Mechanism and responsibility for the intervention are different fields.

Possible dispositions include repairing the specific defect, observing further, relying on an existing correction, changing task conditions, adding a targeted control, accepting residual risk, or recording insufficient evidence. A regression test covers the behavior it exercises; it does not establish that the whole failure class is eliminated.

Count events and outcomes carefully

Measure the total cost

There is no single runtime for checking all 32 modes. Identity and counter checks can reuse recorded metadata. File analysis depends on the amount of material examined; behavioral checks inherit test runtime. Semantic review, causal experiments, and comparisons of agent arrangements require different kinds of work. Longitudinal erosion may become visible only during later development.

Several checks can share the same observations. Capture transient evidence when it occurs, then analyze it afterward when timely intervention is unnecessary. Measure wall time, compute, tokens, storage, and human effort separately, including the burden of false alarms on healthy work.

The comparison is against what would otherwise have happened. An agent may recover unaided, or an existing evaluator may catch the defect later. Earlier correction is valuable when its benefit exceeds its total cost under comparable conditions.

What research measurements can establish

Real-Time Detection and Repair of LLM Agent Failures reports approximately 200 microseconds per step for monitor scoring, plus telemetry extraction with a median of 674 microseconds and p95 of 1,045 microseconds across 491 timed steps. Separate task-specific checks reportedly caught 93% of failures in a later 120-episode evaluation, with zero flags among 64 healthy episodes. Those results concern particular checks and tasks; zero observed false positives does not establish a zero false-positive rate. Paper, sections 4 and 10.

StepFinder selects an annotated root-cause step from an already-failed, completed multi-agent trace. The authors report exact-step accuracy of 29.63% and 22.99% on two test subsets, with processing times of 0.61 and 3.56 seconds per trajectory, including encoding, using an NVIDIA RTX 3080 Ti. Faster attribution can still leave substantial uncertainty. This task differs from recognizing an error online or classifying it into the 32 categories here. Paper, section 5.4 and tables 2 and 6.

Evaluate a candidate check

  1. Define the exact event, required evidence, observation point, legitimate lookalikes, known blind spots, and expected cost.
  2. Apply the check to successful, failed, stopped, and recovered runs.
  3. Review flagged cases and a sample of unflagged cases. Reviewing flags alone cannot estimate missed events.
  4. Use known-positive and legitimate-negative cases to test discrimination. Synthetic cases assess the check; they do not establish natural incidence.
  5. Measure the added work separately from evaluation already required by the task.
  6. Compare a proposed intervention with observation alone under the same completion criteria, including natural recovery, regressions, false blocks, and wasted work.

The learning loop uses these observations to choose a proportionate change, evaluate its effect, and retain or revise it. Evidence that a check recognizes an event is one result; evidence that intervening improves the whole workflow is another.

Related research

Numbered references connect to the mode entries above. The detection and attribution studies are linked beside their reported findings.

  1. OpenAI — How we monitor internal coding agents for misalignment (2026)
  2. OpenAI — GPT-5.6 System Card (2026)
  3. OpenAI — Separating signal from noise in coding evaluations (2026)
  4. OpenAI — Why SWE-bench Verified no longer measures frontier coding capabilities (2026)
  5. Anthropic — Effective context engineering for AI agents
  6. Anthropic — Quantifying infrastructure noise in agentic coding evals (2026)
  7. Anthropic — Effective harnesses for long-running agents
  8. IHEval — Evaluating Language Models on Following the Instruction Hierarchy
  9. ManyIH — Many-Tier Instruction Hierarchy in LLM Agents
  10. MAST — Why Do Multi-Agent LLM Systems Fail? (NeurIPS 2025)
  11. Who & When — failure attribution in multi-agent systems
  12. FixedBench — Coding Agents Don't Know When to Act
  13. SpecBench — visible versus compositional checks
  14. TRIM — trajectory residue and minimization
  15. SlopCodeBench — iterative code erosion
  16. CodeThread — follow-on change cost
  17. TDAD — test-driven agent development and regressions
  18. Agent-generated test over-mocking study
  19. METR — Task-completion time horizons