reference log
The complete record: definitions, measurements, mitigation patterns, field notes, and bridges to adjacent disciplines.
Definitions
A hallucination cascade is what happens when a fabrication produced by one agent in a multi-agent pipeline is consumed, restated, and built upon by the next agent as if it were verified fact. What 2026 propagation studies show about how cascades amplify or attenuate depending on architecture, why fabrications get harder to catch the further they travel, and how to contain them.
Definitions
Proactive interference is the failure mode where an agent asked for the current value of something updated multiple times in its own context retrieves an earlier, superseded value instead, a decline that holds even when input length is fixed and the correct value sits right next to the query. Grounded in a 2026 benchmark testing 35 models from 0.6B to 637B parameters, with detection and mitigation patterns distinct from context rot and memory poisoning.
Field Notes
Compacting a long-running agent's context to control token cost has a measured side effect: the agent starts re-fetching, re-checking, and re-exploring facts it already established before the compaction happened. What the 2026 evidence shows about why this happens, how to spot it in a trajectory log before it shows up as a bigger invoice, and how to bound it.
Definitions
Memory poisoning is the injection of false or adversarial content into an agent's persistent memory store, where it survives across sessions and is later retrieved as if it were verified fact. How it differs from context rot and drift, and why aggressive memory write policies make it worse.
Bridges
Marketing science spent decades inferring silent customer dropout from behavior alone. A guide to which of its habits, cohort curves, survival analysis, hazard thinking, transfer usefully to measuring agent drift, and which assumptions do not.
Mitigation
Anything an agent must not forget should live outside the context window. How to externalize goals, plans, decisions, and facts into files, ledgers, and checkpoints that survive compaction and session death.
Definitions
Calibration drift is the failure mode where an agent's expressed confidence in its own output separates from that output's actual correctness over the course of a session, growing more confident, less confident, or simply noisier without any change in how right the agent actually is. Distinct from sycophantic drift and context rot, grounded in multi-turn calibration research spanning self-anchoring, reasoning-budget effects, and mechanistic circuit analysis, with detection and mitigation patterns.
Definitions
Context handoff loss is the failure mode where a constraint, fact, or instruction established by one agent fails to survive the boundary into the next agent's context, silently producing a downstream action built on an incomplete picture. Distinct from coordination drift and context rot, grounded in a 150-trace human-annotated multi-agent failure taxonomy, with detection and mitigation patterns.
Measurement
Teams use an LLM judge to score drift regression suites at scale, but the judge carries its own unreliability and can silently change out from under a monitoring pipeline. What the 2026 evaluation literature measures, and how to tell a real system regression from a judge that moved.
Definitions
Tool-use drift is the failure mode where an agent's tool selection degrades over a session: it reaches for a recently-used or memory-favored tool instead of the one the current step actually needs, even when the correct tool is sitting in its own retrieved context. Grounded in 2026 benchmarks isolating selection failure from retrieval failure, with detection and mitigation patterns distinct from goal drift and role drift.
Definitions
Sycophantic drift is the failure mode where an agent's stated assessment reverses under user pushback rather than new evidence, and does so faster the more pressure it receives. Distinct from goal drift and role drift, grounded in multi-turn sycophancy benchmarks showing accuracy collapses of up to 47% under sustained disagreement, with detection and mitigation patterns.
Mitigation
Re-anchoring re-injects an agent's goal, role, and constraints mid-run to counter drift without discarding session progress. The main patterns, a concrete procedure, and the failure modes to avoid.
Definitions
Instruction fragmentation is the failure mode where an agent forms a premature synthesis from partial requirements and never revises it as later turns correct or complete the picture. Distinct from context rot and goal drift, grounded in a 200,000-conversation sharded-prompt study, with detection and mitigation patterns.
Definitions
Role drift is the gradual loosening of an agent's assigned persona, voice, and permission boundaries over a long session, distinct from goal drift. What causes it, how to detect it, and role pinning, the pattern of re-anchoring identity independent of context growth.
Measurement
Ordinary evals test a model on fresh state. Drift regression tests replay a fixed golden-task suite against an agent's aged state to catch degradation over session lifetime. Design, pseudocode, and pitfalls.
Measurement
A neutral walkthrough of the Agent Stability Index from arXiv 2601.04170: the four weighted categories and composite drift threshold, and how to adapt the framework to your own telemetry.
Definitions
Plan decay is the growing mismatch between an agent's multi-step plan and the current state of the world. Why plans rot even when no failure is immediately visible, how to detect staleness, and how to design plans that age well.
Definitions
Goal drift is the gradual divergence of an agent's operative objective from its assigned objective. How it develops without any single failure, how to detect it with goal probes, and how to correct it.
Definitions
Context rot is the degradation, and increasingly non-uniform reliability, of model performance as context grows longer. What causes it, the behavioral signals that reveal it, and how it differs from context drift.
Definitions
Agent drift has three manifestations proposed in arXiv 2601.04170, semantic, coordination, and behavioral, plus a set of finer practitioner labels. A working taxonomy with measurement hooks for each type.
Definitions
This site's working definition of behavioral state decay in long-running AI agents: what degrades, why the decay does not require a model-weight or model-version change, how to measure it, and the mitigation patterns that help.