
Context Compression
- 165 installs
- 941 repo stars
- Updated August 5, 2026
- guanyang/antigravity-skills
Shrink large prompts, logs, and histories into dense summaries so agents stay within token limits without losing decisions, constraints, or task state.
About
Antigravity skill focused on compressing conversational and codebase context for LLM agents. Reduces token usage while retaining critical instructions, decisions, and task state for reliable long-horizon automation.
- Token budget optimization
- History summarization
- State-preserving compression
- Long-session agent support
- Prompt footprint reduction
Context Compression by the numbers
- 165 all-time installs (skills.sh)
- Ranked #3,173 of 16,546 AI & Agent Building skills by installs in the Skillselion catalog
- Data as of Aug 5, 2026 (Skillselion catalog sync)
npx skills add https://github.com/guanyang/antigravity-skills --skill context-compressionAdd your badge
Show developers this skill is listed on Skillselion. Paste this into your README.
| Installs | 165 |
|---|---|
| repo stars | ★ 941 |
| Last updated | August 5, 2026 |
| Repository | guanyang/antigravity-skills ↗ |
What it does
Shrink large prompts, logs, and histories into dense summaries so agents stay within token limits without losing decisions, constraints, or task state.
Files
Context Compression Strategies
When agent sessions generate millions of tokens of conversation history, compression becomes mandatory. The naive approach is aggressive compression to minimize tokens per request. The correct optimization target is tokens per task: total tokens consumed to complete a task, including re-fetching costs when compression loses critical information.
When to Activate
Activate this skill when:
- Agent sessions exceed context window limits
- Codebases exceed context windows (5M+ token systems)
- Designing conversation summarization strategies
- Debugging cases where agents "forget" what files they modified
- Building evaluation frameworks for compression quality
- Creating durable handoff summaries that preserve decisions, files, risks, and next actions
Do not activate this skill for adjacent work owned by other skills:
- General token-efficiency tactics such as masking, prefix caching, or partitioning:
context-optimization. - Diagnosing why a long context is failing before choosing a mitigation:
context-degradation. - Writing raw outputs, logs, or plans to files without summarizing them:
filesystem-context. - Designing long-term semantic memory across sessions:
memory-systems.
Core Concepts
Context compression trades token savings against information loss. Select from three production-ready approaches based on session characteristics:
1. Anchored Iterative Summarization: Implement this for long-running sessions where file tracking matters. Maintain structured, persistent summaries with explicit sections for session intent, file modifications, decisions, and next steps. When compression triggers, summarize only the newly-truncated span and merge with the existing summary rather than regenerating from scratch. This prevents drift that accumulates when summaries are regenerated wholesale — each regeneration risks losing details the model considers low-priority but the task requires. Structure forces preservation because dedicated sections act as checklists the summarizer must populate, catching silent information loss.
2. Opaque Compression: Reserve this for short sessions where re-fetching costs are low and maximum token savings are required. It produces compressed representations optimized for reconstruction fidelity, achieving 99%+ compression ratios but sacrificing interpretability entirely. The tradeoff matters: there is no way to verify what was preserved without running probe-based evaluation, so never use this when debugging or artifact tracking is critical.
3. Regenerative Full Summary: Use this when summary readability is critical and sessions have clear phase boundaries. It generates detailed structured summaries on each compression trigger. The weakness is cumulative detail loss across repeated cycles — each full regeneration is a fresh pass that may deprioritize details preserved in earlier summaries.
Detailed Topics
Optimize for Tokens-Per-Task, Not Tokens-Per-Request
Measure total tokens consumed from task start to completion, not tokens per individual request. When compression drops file paths, error messages, or decision rationale, the agent must re-explore, re-read files, and re-derive conclusions — wasting far more tokens than the compression saved. A strategy saving 0.5% more tokens per request but causing 20% more re-fetching costs more overall. Track re-fetching frequency as the primary quality signal: if the agent repeatedly asks to re-read files it already processed, compression is too aggressive.
Solve the Artifact Trail Problem First
Artifact trail integrity is often the weakest dimension in compression evaluations (claim-context-compression-factory-benchmark). Address this proactively because general summarization cannot reliably maintain it.
Preserve these categories explicitly in every compression cycle:
- Which files were created (full paths)
- Which files were modified and what changed (include function names, not just file names)
- Which files were read but not changed
- Specific identifiers: function names, variable names, error messages, error codes
Implement a separate artifact index or explicit file-state tracking in agent scaffolding rather than relying on the summarizer to capture these details. Even structured summarization with dedicated file sections struggles with completeness over long sessions.
Structure Summaries with Mandatory Sections
Build structured summaries with explicit sections that prevent silent information loss. Each section acts as a checklist the summarizer must populate, making omissions visible rather than silent.
## Session Intent
[What the user is trying to accomplish]
## Files Modified
- auth.controller.ts: Fixed JWT token generation
- config/redis.ts: Updated connection pooling
- tests/auth.test.ts: Added mock setup for new config
## Decisions Made
- Using Redis connection pool instead of per-request connections
- Retry logic with exponential backoff for transient failures
## Current State
- 14 tests passing, 2 failing
- Remaining: mock setup for session service tests
## Next Steps
1. Fix remaining test failures
2. Run full test suite
3. Update documentationAdapt sections to the agent's domain. A debugging agent needs "Root Cause" and "Error Messages"; a migration agent needs "Source Schema" and "Target Schema." The structure matters more than the specific sections — any explicit schema outperforms freeform summarization.
Choose Compression Triggers Strategically
When to trigger compression matters as much as how to compress. Select a trigger strategy based on session predictability:
| Strategy | Trigger Point | Trade-off |
|---|---|---|
| Fixed threshold | 70-80% context utilization | Simple but may compress too early |
| Sliding window | Keep last N turns + summary | Predictable context size |
| Importance-based | Compress low-relevance sections first | Complex but preserves signal |
| Task-boundary | Compress at logical task completions | Clean summaries but unpredictable timing |
Default to sliding window with structured summaries for coding agents — it provides the best balance of predictability and quality. Use task-boundary triggers when sessions have clear phase transitions (e.g., research then implementation then testing).
Evaluate Compression with Probes, Not Metrics
Traditional metrics like ROUGE or embedding similarity fail to capture functional compression quality. A summary can score high on lexical overlap while missing the one file path the agent needs to continue.
Use probe-based evaluation: after compression, pose questions that test whether critical information survived. If the agent answers correctly, compression preserved the right information. If not, it guesses or hallucinates.
| Probe Type | What It Tests | Example Question |
|---|---|---|
| Recall | Factual retention | "What was the original error message?" |
| Artifact | File tracking | "Which files have we modified?" |
| Continuation | Task planning | "What should we do next?" |
| Decision | Reasoning chain | "What did we decide about the Redis issue?" |
Score Compression Across Six Dimensions
Evaluate compression quality for coding agents across these dimensions. Accuracy and artifact-trail preservation tend to separate methods more clearly than lexical similarity (claim-context-compression-factory-benchmark), so compression needs specialized handling beyond general summarization.
1. Accuracy: Are technical details correct — file paths, function names, error codes? 2. Context Awareness: Does the response reflect current conversation state? 3. Artifact Trail: Does the agent know which files were read or modified? 4. Completeness: Does the response address all parts of the question? 5. Continuity: Can work continue without re-fetching information? 6. Instruction Following: Does the response respect stated constraints?
Practical Guidance
Apply the Three-Phase Compression Workflow for Large Codebases
For codebases or agent systems exceeding context windows, compress through three sequential phases. Each phase narrows context so the next phase operates within budget.
1. Research Phase: Explore architecture diagrams, documentation, and key interfaces. Compress exploration into a structured analysis of components, dependencies, and boundaries. Output: a single research document that replaces raw exploration.
2. Planning Phase: Convert the research document into an implementation specification with function signatures, type definitions, and data flow. A 5M-token codebase compresses to approximately 2,000 words of specification at this stage.
3. Implementation Phase: Execute against the specification. Context stays focused on the spec plus active working files, not raw codebase exploration. This phase rarely needs further compression because the spec is already compact.
Use Example Artifacts as Compression Seeds
When provided with a manual migration example or reference PR, use it as a template to understand the target pattern rather than exploring the codebase from scratch. The example reveals constraints static analysis cannot surface: which invariants must hold, which services break on changes, and what a clean implementation looks like.
This matters most when the agent cannot distinguish essential complexity (business requirements) from accidental complexity (legacy workarounds). The example artifact encodes that distinction implicitly, saving tokens that would otherwise go to trial-and-error exploration.
Implement Anchored Iterative Summarization Step by Step
1. Define explicit summary sections matching the agent's domain (debugging, migration, feature development) 2. On first compression trigger, summarize the truncated history into those sections 3. On subsequent compressions, summarize only newly truncated content — do not re-summarize the existing summary 4. Merge new information into existing sections rather than regenerating them, deduplicating by file path and decision identity 5. Tag which information came from which compression cycle — this enables debugging when summaries drift
Select the Right Approach for the Session Profile
Use anchored iterative summarization when:
- Sessions are long-running (100+ messages)
- File tracking matters (coding, debugging)
- Verification of preserved information is needed
Use opaque compression when:
- Maximum token savings are required
- Sessions are relatively short
- Re-fetching costs are low (e.g., no file system access needed)
Use regenerative summaries when:
- Summary interpretability is critical for human review
- Sessions have clear phase boundaries
- Full context review is acceptable on each compression trigger
Calibrate Compression Ratios by Method
| Method | Compression Ratio | Quality Score | Trade-off |
|---|---|---|---|
| Anchored Iterative | 98.6% | 3.70 | Best quality, slightly less compression |
| Regenerative | 98.7% | 3.44 | Good quality, moderate compression |
| Opaque | 99.3% | 3.35 | Best compression, quality loss |
Use these as source-specific benchmark figures, not universal constants (claim-context-compression-factory-benchmark). For any task where re-fetching costs exist, this tradeoff generally favors structured approaches.
Examples
Example 1: Debugging Session Compression
Original context (89,000 tokens, 178 messages):
- 401 error on /api/auth/login endpoint
- Traced through auth controller, middleware, session store
- Found stale Redis connection
- Fixed connection pooling, added retry logic
- 14 tests passing, 2 failing
Structured summary after compression:
## Session Intent
Debug 401 Unauthorized error on /api/auth/login despite valid credentials.
## Root Cause
Stale Redis connection in session store. JWT generated correctly but session could not be persisted.
## Files Modified
- auth.controller.ts: No changes (read only)
- middleware/cors.ts: No changes (examined)
- config/redis.ts: Fixed connection pooling configuration
- services/session.service.ts: Added retry logic for transient failures
- tests/auth.test.ts: Updated mock setup
## Test Status
14 passing, 2 failing (mock setup issues)
## Next Steps
1. Fix remaining test failures (mock session service)
2. Run full test suite
3. Deploy to stagingExample 2: Probe Response Quality
After compression, asking "What was the original error?":
Good response (structured summarization):
"The original error was a 401 Unauthorized response from the /api/auth/login endpoint. Users received this error with valid credentials. Root cause was stale Redis connection in session store."
Poor response (aggressive compression):
"We were debugging an authentication issue. The login was failing. We fixed some configuration problems."
The structured response preserves endpoint, error code, and root cause. The aggressive response loses all technical detail.
Guidelines
1. Optimize for tokens-per-task, not tokens-per-request 2. Use structured summaries with explicit sections for file tracking 3. Trigger compression at 70-80% context utilization 4. Implement incremental merging rather than full regeneration 5. Test compression quality with probe-based evaluation 6. Track artifact trail separately if file tracking is critical 7. Accept slightly lower compression ratios for better quality retention 8. Monitor re-fetching frequency as a compression quality signal
Gotchas
1. Never compress tool definitions or schemas: Compressing function call schemas, API specs, or tool definitions destroys agent functionality entirely. The agent cannot invoke tools whose parameter names or types have been summarized away. Treat tool definitions as immutable anchors that bypass compression.
2. Compressed summaries hallucinate facts: When an LLM summarizes conversation history, it may introduce plausible-sounding details that never appeared in the original. Always validate compressed output against source material before discarding originals — especially for file paths, error codes, and numeric values that the summarizer may "round" or fabricate.
3. Compression breaks artifact references: File paths, commit SHAs, variable names, and code snippets get paraphrased or dropped during compression. A summary saying "updated the config file" when the agent needs config/redis.ts causes re-exploration. Preserve identifiers verbatim in dedicated sections rather than embedding them in prose.
4. Early turns contain irreplaceable constraints: The first few turns of a session often contain task setup, user constraints, and architectural decisions that cannot be re-derived. Protect early turns from compression or extract their constraints into a persistent preamble that survives all compression cycles.
5. Aggressive ratios compound across cycles: A 95% compression ratio seems safe once, but applying it repeatedly compounds losses. After three cycles at 95%, only 0.0125% of original tokens remain. Calibrate ratios assuming multiple compression cycles, not a single pass.
6. Code and prose need different compression: Prose compresses well because natural language is redundant. Code does not — removing a single token from a function signature or import path can make it useless. Apply domain-specific compression strategies: summarize prose sections aggressively while preserving code blocks and structured data verbatim.
7. Probe-based evaluation gives false confidence: Probes can pass despite critical information being lost, because the probes test only what they ask about. A probe set that checks file names but not function signatures will miss signature loss. Design probes to cover all six evaluation dimensions, and rotate probe sets across evaluation runs to avoid blind spots.
Integration
This skill connects to several others in the collection:
- context-degradation - Compression is a mitigation strategy for degradation
- context-optimization - Compression is one optimization technique among many
- evaluation - Probe-based evaluation applies to compression testing
- memory-systems - Compression relates to scratchpad and summary memory patterns
References
Internal reference:
- Evaluation Framework Reference - Read when: building or calibrating a probe-based evaluation pipeline, or when needing scoring rubrics and LLM judge configuration for compression quality assessment
Related skills in this collection:
- context-degradation - Read when: diagnosing why agent performance drops over long sessions, before applying compression as a mitigation
- context-optimization - Read when: compression alone is insufficient and broader optimization strategies (pruning, caching, routing) are needed
- evaluation - Read when: designing evaluation frameworks beyond compression-specific probes, including general LLM-as-judge methodology
External resources:
- Factory Research: Evaluating Context Compression for AI Agents (December 2025) - Read when: needing benchmark data on compression method comparisons or the 36,000-message evaluation dataset
- Research on LLM-as-judge evaluation methodology (Zheng et al., 2023) - Read when: implementing or validating LLM judge scoring to understand bias patterns and calibration
- Netflix Engineering: "The Infinite Software Crisis" - Three-phase workflow and context compression at scale (AI Summit 2025) - Read when: implementing the three-phase compression workflow for large codebases or understanding production-scale context management
---
Skill Metadata
Created: 2025-12-22 Last Updated: 2026-05-15 Author: Agent Skills for Context Engineering Contributors Version: 1.3.0
Context Compression Evaluation Framework
This document provides the complete evaluation framework for measuring context compression quality, including probe types, scoring rubrics, and LLM judge configuration.
Probe Types
Recall Probes
Test factual retention of specific details from conversation history.
Structure:
Question: [Ask for specific fact from truncated history]
Expected: [Exact detail that should be preserved]
Scoring: Match accuracy of technical detailsExamples:
- "What was the original error message that started this debugging session?"
- "What version of the dependency did we decide to use?"
- "What was the exact command that failed?"
Artifact Probes
Test file tracking and modification awareness.
Structure:
Question: [Ask about files created, modified, or examined]
Expected: [Complete list with change descriptions]
Scoring: Completeness of file list and accuracy of change descriptionsExamples:
- "Which files have we modified? Describe what changed in each."
- "What new files did we create in this session?"
- "Which configuration files did we examine but not change?"
Continuation Probes
Test ability to continue work without re-fetching context.
Structure:
Question: [Ask about next steps or current state]
Expected: [Actionable next steps based on session history]
Scoring: Ability to continue without requesting re-read of filesExamples:
- "What should we do next?"
- "What tests are still failing and why?"
- "What was left incomplete from our last step?"
Decision Probes
Test retention of reasoning chains and decision rationale.
Structure:
Question: [Ask about why a decision was made]
Expected: [Reasoning that led to the decision]
Scoring: Preservation of decision context and alternatives consideredExamples:
- "We discussed options for the Redis issue. What did we decide and why?"
- "Why did we choose connection pooling over per-request connections?"
- "What alternatives did we consider for the authentication fix?"
Scoring Rubrics
Accuracy Dimension
| Criterion | Question | Score 0 | Score 3 | Score 5 |
|---|---|---|---|---|
| accuracy_factual | Are facts, file paths, and technical details correct? | Completely incorrect or fabricated | Mostly accurate with minor errors | Perfectly accurate |
| accuracy_technical | Are code references and technical concepts correct? | Major technical errors | Generally correct with minor issues | Technically precise |
Context Awareness Dimension
| Criterion | Question | Score 0 | Score 3 | Score 5 |
|---|---|---|---|---|
| context_conversation_state | Does the response reflect current conversation state? | No awareness of prior context | General awareness with gaps | Full awareness of conversation history |
| context_artifact_state | Does the response reflect which files/artifacts were accessed? | No awareness of artifacts | Partial artifact awareness | Complete artifact state awareness |
Artifact Trail Dimension
| Criterion | Question | Score 0 | Score 3 | Score 5 |
|---|---|---|---|---|
| artifact_files_created | Does the agent know which files were created? | No knowledge | Knows most files | Perfect knowledge |
| artifact_files_modified | Does the agent know which files were modified and what changed? | No knowledge | Good knowledge of most modifications | Perfect knowledge of all modifications |
| artifact_key_details | Does the agent remember function names, variable names, error messages? | No recall | Recalls most key details | Perfect recall |
Completeness Dimension
| Criterion | Question | Score 0 | Score 3 | Score 5 |
|---|---|---|---|---|
| completeness_coverage | Does the response address all parts of the question? | Ignores most parts | Addresses most parts | Addresses all parts thoroughly |
| completeness_depth | Is sufficient detail provided? | Superficial or missing detail | Adequate detail | Comprehensive detail |
Continuity Dimension
| Criterion | Question | Score 0 | Score 3 | Score 5 |
|---|---|---|---|---|
| continuity_work_state | Can the agent continue without re-fetching previously accessed information? | Cannot continue without re-fetching all context | Can continue with minimal re-fetching | Can continue seamlessly |
| continuity_todo_state | Does the agent maintain awareness of pending tasks? | Lost track of all TODOs | Good awareness with some gaps | Perfect task awareness |
| continuity_reasoning | Does the agent retain rationale behind previous decisions? | No memory of reasoning | Generally remembers reasoning | Excellent retention |
Instruction Following Dimension
| Criterion | Question | Score 0 | Score 3 | Score 5 |
|---|---|---|---|---|
| instruction_format | Does the response follow the requested format? | Ignores format | Generally follows format | Perfectly follows format |
| instruction_constraints | Does the response respect stated constraints? | Ignores constraints | Mostly respects constraints | Fully respects all constraints |
LLM Judge Configuration
System Prompt
You are an expert evaluator assessing AI assistant responses in software development conversations.
Your task is to grade responses against specific rubric criteria. For each criterion:
1. Read the criterion question carefully
2. Examine the response for evidence
3. Assign a score from 0-5 based on the scoring guide
4. Provide brief reasoning for your score
Be objective and consistent. Focus on what is present in the response, not what could have been included.Judge Input Format
{
"probe_question": "What was the original error message?",
"model_response": "[Response to evaluate]",
"compacted_context": "[The compressed context that was provided]",
"ground_truth": "[Optional: known correct answer]",
"rubric_criteria": ["accuracy_factual", "accuracy_technical", "context_conversation_state"]
}Judge Output Format
{
"criterionResults": [
{
"criterionId": "accuracy_factual",
"score": 5,
"reasoning": "Response correctly identifies the 401 error, specific endpoint, and root cause."
}
],
"aggregateScore": 4.8,
"dimensionScores": {
"accuracy": 4.9,
"context_awareness": 4.5,
"artifact_trail": 3.2,
"completeness": 5.0,
"continuity": 4.8,
"instruction_following": 5.0
}
}Benchmark Results Reference
Performance across compression methods (based on 36,000+ messages):
| Method | Overall | Accuracy | Context | Artifact | Complete | Continuity | Instruction |
|---|---|---|---|---|---|---|---|
| Anchored Iterative | 3.70 | 4.04 | 4.01 | 2.45 | 4.44 | 3.80 | 4.99 |
| Regenerative | 3.44 | 3.74 | 3.56 | 2.33 | 4.37 | 3.67 | 4.95 |
| Opaque | 3.35 | 3.43 | 3.64 | 2.19 | 4.37 | 3.77 | 4.92 |
Key Findings:
1. Accuracy gap: 0.61 points between best and worst methods 2. Context awareness gap: 0.45 points, favoring anchored iterative 3. Artifact trail: Universally weak (2.19-2.45), needs specialized handling 4. Completeness and instruction following: Minimal differentiation
Statistical Considerations
- Differences of 0.26-0.35 points are consistent across task types and session lengths
- Pattern holds for both short and long sessions
- Pattern holds across debugging, feature implementation, and code review tasks
- Sample size: 36,611 messages across hundreds of compression points
Implementation Notes
Probe Generation
Generate probes at each compression point based on truncated history: 1. Extract factual claims for recall probes 2. Extract file operations for artifact probes 3. Extract incomplete tasks for continuation probes 4. Extract decision points for decision probes
Grading Process
1. Feed probe question + model response + compressed context to judge 2. Evaluate against each criterion in rubric 3. Output structured JSON with scores and reasoning 4. Compute dimension scores as weighted averages 5. Compute overall score as unweighted average of dimensions
Blinding
The judge should not know which compression method produced the response being evaluated. This prevents bias toward known methods.
"""
Context Compression Evaluation
Public API for evaluating context compression quality using probe-based
assessment. This module provides three composable components:
- **ProbeGenerator**: Extracts factual claims, file operations, and decisions
from conversation history, then generates typed probes for evaluation.
Use when: building a compression evaluation pipeline and needing to
automatically derive test questions from raw conversation history.
- **CompressionEvaluator**: Scores probe responses against a multi-dimensional
rubric (accuracy, context awareness, artifact trail, completeness,
continuity, instruction following). Use when: comparing compression methods
or validating that a compression strategy preserves critical information.
- **StructuredSummarizer**: Implements anchored iterative summarization with
explicit sections for session intent, file tracking, decisions, and next
steps. Use when: compressing long-running coding sessions where file
tracking and decision rationale must survive compression.
Top-level convenience function:
- **evaluate_compression_quality**: End-to-end pipeline that generates probes,
collects model responses, evaluates them, and returns a scored summary with
recommendations. Use when: running a one-shot compression quality check
without wiring up individual components.
PRODUCTION NOTES:
- The LLM judge calls are stubbed for demonstration. Production systems
should implement actual API calls to a frontier model.
- Token estimation uses simplified heuristics. Production systems should
use model-specific tokenizers.
- Ground truth extraction uses pattern matching. Production systems may
benefit from more sophisticated fact extraction.
"""
from dataclasses import dataclass, field
from typing import List, Dict, Optional, Callable
from enum import Enum
import json
import re
__all__ = [
"ProbeType",
"Probe",
"CriterionResult",
"EvaluationResult",
"RUBRIC_CRITERIA",
"ProbeGenerator",
"CompressionEvaluator",
"StructuredSummarizer",
"evaluate_compression_quality",
]
class ProbeType(Enum):
"""Types of evaluation probes for compression quality assessment."""
RECALL = "recall"
ARTIFACT = "artifact"
CONTINUATION = "continuation"
DECISION = "decision"
@dataclass
class Probe:
"""A probe question for evaluating compression quality.
Use when: constructing evaluation inputs for CompressionEvaluator.
Each probe targets a specific information category that compression
may have lost.
"""
probe_type: ProbeType
question: str
ground_truth: Optional[str] = None
context_reference: Optional[str] = None
@dataclass
class CriterionResult:
"""Result for a single evaluation criterion."""
criterion_id: str
score: float
reasoning: str
@dataclass
class EvaluationResult:
"""Complete evaluation result for a probe response.
Contains per-criterion scores, per-dimension aggregates, and an
overall aggregate score.
"""
probe: Probe
response: str
criterion_results: List[CriterionResult]
aggregate_score: float
dimension_scores: Dict[str, float] = field(default_factory=dict)
# Evaluation Rubrics
RUBRIC_CRITERIA: Dict[str, List[Dict]] = {
"accuracy": [
{
"id": "accuracy_factual",
"question": "Are facts, file paths, and technical details correct?",
"weight": 0.6
},
{
"id": "accuracy_technical",
"question": "Are code references and technical concepts correct?",
"weight": 0.4
}
],
"context_awareness": [
{
"id": "context_conversation_state",
"question": "Does the response reflect current conversation state?",
"weight": 0.5
},
{
"id": "context_artifact_state",
"question": "Does the response reflect which files/artifacts were accessed?",
"weight": 0.5
}
],
"artifact_trail": [
{
"id": "artifact_files_created",
"question": "Does the agent know which files were created?",
"weight": 0.3
},
{
"id": "artifact_files_modified",
"question": "Does the agent know which files were modified?",
"weight": 0.4
},
{
"id": "artifact_key_details",
"question": "Does the agent remember function names, variable names, error messages?",
"weight": 0.3
}
],
"completeness": [
{
"id": "completeness_coverage",
"question": "Does the response address all parts of the question?",
"weight": 0.6
},
{
"id": "completeness_depth",
"question": "Is sufficient detail provided?",
"weight": 0.4
}
],
"continuity": [
{
"id": "continuity_work_state",
"question": "Can the agent continue without re-fetching information?",
"weight": 0.4
},
{
"id": "continuity_todo_state",
"question": "Does the agent maintain awareness of pending tasks?",
"weight": 0.3
},
{
"id": "continuity_reasoning",
"question": "Does the agent retain rationale behind previous decisions?",
"weight": 0.3
}
],
"instruction_following": [
{
"id": "instruction_format",
"question": "Does the response follow the requested format?",
"weight": 0.5
},
{
"id": "instruction_constraints",
"question": "Does the response respect stated constraints?",
"weight": 0.5
}
]
}
class ProbeGenerator:
"""Generate typed probes from conversation history.
Use when: automatically deriving evaluation questions from raw
conversation history at compression points. Extracts facts, file
operations, and decisions via pattern matching, then produces
one probe per category.
For production systems, replace the regex-based extraction with
an LLM-based extractor for higher recall.
"""
def __init__(self, conversation_history: str) -> None:
self.history = conversation_history
self.extracted_facts = self._extract_facts()
self.extracted_files = self._extract_files()
self.extracted_decisions = self._extract_decisions()
def generate_probes(self) -> List[Probe]:
"""Generate all probe types for evaluation.
Use when: preparing evaluation inputs at a compression point.
Returns one probe per category (recall, artifact, continuation,
decision) based on extractable content from the history.
"""
probes: List[Probe] = []
# Recall probes
if self.extracted_facts:
probes.append(Probe(
probe_type=ProbeType.RECALL,
question="What was the original error or issue that started this session?",
ground_truth=self.extracted_facts.get("original_error"),
context_reference="session_start"
))
# Artifact probes
if self.extracted_files:
probes.append(Probe(
probe_type=ProbeType.ARTIFACT,
question="Which files have we modified? Describe what changed in each.",
ground_truth=json.dumps(self.extracted_files),
context_reference="file_operations"
))
# Continuation probes
probes.append(Probe(
probe_type=ProbeType.CONTINUATION,
question="What should we do next?",
ground_truth=self.extracted_facts.get("next_steps"),
context_reference="task_state"
))
# Decision probes
if self.extracted_decisions:
probes.append(Probe(
probe_type=ProbeType.DECISION,
question="What key decisions did we make and why?",
ground_truth=json.dumps(self.extracted_decisions),
context_reference="decision_points"
))
return probes
def _extract_facts(self) -> Dict[str, str]:
"""Extract factual claims from history."""
facts: Dict[str, str] = {}
# Extract error patterns
error_patterns = [
r"error[:\s]+(.+?)(?:\n|$)",
r"(\d{3})\s+(Unauthorized|Not Found|Internal Server Error)",
r"exception[:\s]+(.+?)(?:\n|$)"
]
for pattern in error_patterns:
match = re.search(pattern, self.history, re.IGNORECASE)
if match:
facts["original_error"] = match.group(0).strip()
break
# Extract next steps
next_step_patterns = [
r"next[:\s]+(.+?)(?:\n|$)",
r"TODO[:\s]+(.+?)(?:\n|$)",
r"remaining[:\s]+(.+?)(?:\n|$)"
]
for pattern in next_step_patterns:
match = re.search(pattern, self.history, re.IGNORECASE)
if match:
facts["next_steps"] = match.group(0).strip()
break
return facts
def _extract_files(self) -> List[Dict[str, str]]:
"""Extract file operations from history."""
files: List[Dict[str, str]] = []
# Common file patterns
file_patterns = [
r"(?:modified|changed|updated|edited)\s+([^\s]+\.[a-z]+)",
r"(?:created|added)\s+([^\s]+\.[a-z]+)",
r"(?:read|examined|opened)\s+([^\s]+\.[a-z]+)"
]
for pattern in file_patterns:
matches = re.findall(pattern, self.history, re.IGNORECASE)
for match in matches:
if match not in [f["path"] for f in files]:
files.append({
"path": match,
"operation": "modified" if "modif" in pattern else "created" if "creat" in pattern else "read"
})
return files
def _extract_decisions(self) -> List[Dict[str, str]]:
"""Extract decision points from history."""
decisions: List[Dict[str, str]] = []
decision_patterns = [
r"decided to\s+(.+?)(?:\n|$)",
r"chose\s+(.+?)(?:\n|$)",
r"going with\s+(.+?)(?:\n|$)",
r"will use\s+(.+?)(?:\n|$)"
]
for pattern in decision_patterns:
matches = re.findall(pattern, self.history, re.IGNORECASE)
for match in matches:
decisions.append({
"decision": match.strip(),
"context": pattern.split("\\s+")[0]
})
return decisions[:5] # Limit to 5 decisions
class CompressionEvaluator:
"""Evaluate compression quality using probes and LLM judge.
Use when: comparing compression methods or validating that a specific
compression pass preserved critical information. Scores responses
across six dimensions (accuracy, context awareness, artifact trail,
completeness, continuity, instruction following) and produces an
aggregate quality score.
The evaluate() method is the primary entry point. Call it once per
probe, then call get_summary() to retrieve aggregated results.
"""
def __init__(self, model: str = "gpt-5.2") -> None:
self.model = model
self.results: List[EvaluationResult] = []
def evaluate(self,
probe: Probe,
response: str,
compressed_context: str) -> EvaluationResult:
"""Evaluate a single probe response against the rubric.
Use when: scoring how well a model's response (given compressed
context) answers a probe question. Returns per-criterion scores,
per-dimension aggregates, and an overall score.
Args:
probe: The probe question with expected ground truth.
response: The model's response to evaluate.
compressed_context: The compressed context that was provided
to the model when generating the response.
Returns:
EvaluationResult with scores and reasoning across all
applicable dimensions.
"""
# Get relevant criteria based on probe type
criteria = self._get_criteria_for_probe(probe.probe_type)
# Evaluate each criterion
criterion_results: List[CriterionResult] = []
for criterion in criteria:
result = self._evaluate_criterion(
criterion,
probe,
response,
compressed_context
)
criterion_results.append(result)
# Calculate dimension scores
dimension_scores = self._calculate_dimension_scores(criterion_results)
# Calculate aggregate score
aggregate_score = sum(dimension_scores.values()) / len(dimension_scores) if dimension_scores else 0.0
result = EvaluationResult(
probe=probe,
response=response,
criterion_results=criterion_results,
aggregate_score=aggregate_score,
dimension_scores=dimension_scores
)
self.results.append(result)
return result
def get_summary(self) -> Dict:
"""Get summary of all evaluation results.
Use when: all probes have been evaluated and an aggregate
report is needed to compare methods or make a go/no-go
decision on a compression strategy.
Returns:
Dictionary with total evaluations, average score,
per-dimension averages, and weakest/strongest dimensions.
"""
if not self.results:
return {"error": "No evaluations performed"}
avg_score = sum(r.aggregate_score for r in self.results) / len(self.results)
# Average dimension scores
dimension_totals: Dict[str, float] = {}
dimension_counts: Dict[str, int] = {}
for result in self.results:
for dim, score in result.dimension_scores.items():
dimension_totals[dim] = dimension_totals.get(dim, 0) + score
dimension_counts[dim] = dimension_counts.get(dim, 0) + 1
avg_dimensions = {
dim: dimension_totals[dim] / dimension_counts[dim]
for dim in dimension_totals
}
return {
"total_evaluations": len(self.results),
"average_score": avg_score,
"dimension_averages": avg_dimensions,
"weakest_dimension": min(avg_dimensions, key=avg_dimensions.get) if avg_dimensions else None,
"strongest_dimension": max(avg_dimensions, key=avg_dimensions.get) if avg_dimensions else None,
}
def _get_criteria_for_probe(self, probe_type: ProbeType) -> List[Dict]:
"""Get relevant criteria for probe type."""
criteria: List[Dict] = []
# All probes get accuracy and completeness
criteria.extend(RUBRIC_CRITERIA["accuracy"])
criteria.extend(RUBRIC_CRITERIA["completeness"])
# Add type-specific criteria
if probe_type == ProbeType.ARTIFACT:
criteria.extend(RUBRIC_CRITERIA["artifact_trail"])
elif probe_type == ProbeType.CONTINUATION:
criteria.extend(RUBRIC_CRITERIA["continuity"])
elif probe_type == ProbeType.RECALL:
criteria.extend(RUBRIC_CRITERIA["context_awareness"])
elif probe_type == ProbeType.DECISION:
criteria.extend(RUBRIC_CRITERIA["context_awareness"])
criteria.extend(RUBRIC_CRITERIA["continuity"])
criteria.extend(RUBRIC_CRITERIA["instruction_following"])
return criteria
def _evaluate_criterion(self,
criterion: Dict,
probe: Probe,
response: str,
context: str) -> CriterionResult:
"""
Evaluate a single criterion using LLM judge.
PRODUCTION NOTE: This is a stub implementation.
Production systems should call the actual LLM API:
```python
result = openai.chat.completions.create(
model="gpt-5.2",
messages=[
{"role": "system", "content": JUDGE_SYSTEM_PROMPT},
{"role": "user", "content": self._format_judge_input(criterion, probe, response, context)}
]
)
return self._parse_judge_output(result)
```
"""
# Stub implementation - in production, call LLM judge
score = self._heuristic_score(criterion, response, probe.ground_truth)
reasoning = f"Evaluated {criterion['id']} based on response content."
return CriterionResult(
criterion_id=criterion["id"],
score=score,
reasoning=reasoning
)
def _heuristic_score(self,
criterion: Dict,
response: str,
ground_truth: Optional[str]) -> float:
"""
Heuristic scoring for demonstration.
Production systems should use LLM judge instead.
"""
score = 3.0 # Base score
# Adjust based on response length and content
if len(response) < 50:
score -= 1.0 # Too short
elif len(response) > 500:
score += 0.5 # Detailed
# Check for technical content
if any(ext in response for ext in [".ts", ".py", ".js", ".md"]):
score += 0.5 # Contains file references
overlap_ratio = self._ground_truth_overlap_ratio(response, ground_truth)
if overlap_ratio >= 0.75:
score += 1.0
elif overlap_ratio >= 0.4:
score += 0.5
elif ground_truth:
score -= 0.5
return min(5.0, max(0.0, score))
def _ground_truth_overlap_ratio(self,
response: str,
ground_truth: Optional[str]) -> float:
if not ground_truth:
return 0.0
terms = self._extract_ground_truth_terms(ground_truth)
if not terms:
return 1.0 if ground_truth.lower() in response.lower() else 0.0
response_lower = response.lower()
matches = sum(1 for term in terms if term in response_lower)
return matches / len(terms)
def _extract_ground_truth_terms(self, ground_truth: str) -> List[str]:
try:
parsed = json.loads(ground_truth)
except json.JSONDecodeError:
return [ground_truth.lower()] if ground_truth.strip() else []
terms: List[str] = []
def collect(value) -> None:
if isinstance(value, str):
normalized = value.strip().lower()
if normalized:
terms.append(normalized)
elif isinstance(value, dict):
for nested in value.values():
collect(nested)
elif isinstance(value, list):
for nested in value:
collect(nested)
collect(parsed)
return list(dict.fromkeys(terms))
def _calculate_dimension_scores(self,
criterion_results: List[CriterionResult]) -> Dict[str, float]:
"""Calculate dimension scores from criterion results."""
dimension_scores: Dict[str, float] = {}
for dimension, criteria in RUBRIC_CRITERIA.items():
criterion_ids = [c["id"] for c in criteria]
relevant_results = [
r for r in criterion_results
if r.criterion_id in criterion_ids
]
if relevant_results:
# Weighted average
total_weight = sum(
c["weight"] for c in criteria
if c["id"] in [r.criterion_id for r in relevant_results]
)
weighted_sum = sum(
r.score * next(c["weight"] for c in criteria if c["id"] == r.criterion_id)
for r in relevant_results
)
dimension_scores[dimension] = weighted_sum / total_weight if total_weight > 0 else 0.0
return dimension_scores
class StructuredSummarizer:
"""Generate structured summaries with explicit sections.
Use when: implementing anchored iterative summarization for
long-running coding sessions. Maintains a persistent summary
with dedicated sections for session intent, file modifications,
decisions, current state, and next steps.
Call update_from_span() each time a new content span is truncated.
The summarizer merges new information into existing sections rather
than regenerating, preventing cumulative detail loss.
"""
TEMPLATE = """## Session Intent
{intent}
## Files Modified
{files_modified}
## Files Read (Not Modified)
{files_read}
## Decisions Made
{decisions}
## Current State
{current_state}
## Next Steps
{next_steps}
"""
def __init__(self) -> None:
self.sections: Dict = {
"intent": "",
"files_modified": [],
"files_read": [],
"decisions": [],
"current_state": "",
"next_steps": []
}
def update_from_span(self, new_content: str) -> str:
"""Update summary from newly truncated content span.
Use when: a compression trigger fires and a portion of
conversation history is about to be discarded. Pass the
content that will be truncated; the summarizer extracts
structured information and merges it with prior state.
Args:
new_content: The conversation span being truncated.
Returns:
Formatted summary string with all sections populated.
"""
# Extract information from new content
new_info = self._extract_from_content(new_content)
# Merge with existing sections
self._merge_sections(new_info)
# Generate formatted summary
return self._format_summary()
def _extract_from_content(self, content: str) -> Dict:
"""Extract structured information from content."""
extracted: Dict = {
"intent": "",
"files_modified": [],
"files_read": [],
"decisions": [],
"current_state": "",
"next_steps": []
}
# Extract file modifications
mod_pattern = r"(?:modified|changed|updated|fixed)\s+([^\s]+\.[a-z]+)[:\s]*(.+?)(?:\n|$)"
for match in re.finditer(mod_pattern, content, re.IGNORECASE):
extracted["files_modified"].append({
"path": match.group(1),
"change": match.group(2).strip()[:100]
})
# Extract file reads
read_pattern = r"(?:read|examined|opened|checked)\s+([^\s]+\.[a-z]+)"
for match in re.finditer(read_pattern, content, re.IGNORECASE):
file_path = match.group(1)
if file_path not in [f["path"] for f in extracted["files_modified"]]:
extracted["files_read"].append(file_path)
# Extract decisions
decision_pattern = r"(?:decided|chose|going with|will use)\s+(.+?)(?:\n|$)"
for match in re.finditer(decision_pattern, content, re.IGNORECASE):
extracted["decisions"].append(match.group(1).strip()[:150])
return extracted
def _merge_sections(self, new_info: Dict) -> None:
"""Merge new information with existing sections."""
# Update intent if empty
if new_info["intent"] and not self.sections["intent"]:
self.sections["intent"] = new_info["intent"]
# Merge file lists (deduplicate by path)
existing_mod_paths = [f["path"] for f in self.sections["files_modified"]]
for file_info in new_info["files_modified"]:
if file_info["path"] not in existing_mod_paths:
self.sections["files_modified"].append(file_info)
# Merge read files
for file_path in new_info["files_read"]:
if file_path not in self.sections["files_read"]:
self.sections["files_read"].append(file_path)
# Append decisions
self.sections["decisions"].extend(new_info["decisions"])
# Update current state (latest wins)
if new_info["current_state"]:
self.sections["current_state"] = new_info["current_state"]
# Merge next steps
self.sections["next_steps"].extend(new_info["next_steps"])
def _format_summary(self) -> str:
"""Format sections into summary string."""
files_modified_str = "\n".join(
f"- {f['path']}: {f['change']}"
for f in self.sections["files_modified"]
) or "None"
files_read_str = "\n".join(
f"- {f}" for f in self.sections["files_read"]
) or "None"
decisions_str = "\n".join(
f"- {d}" for d in self.sections["decisions"][-5:] # Keep last 5
) or "None"
next_steps_str = "\n".join(
f"{i+1}. {s}" for i, s in enumerate(self.sections["next_steps"][-5:])
) or "None"
return self.TEMPLATE.format(
intent=self.sections["intent"] or "Not specified",
files_modified=files_modified_str,
files_read=files_read_str,
decisions=decisions_str,
current_state=self.sections["current_state"] or "In progress",
next_steps=next_steps_str
)
def evaluate_compression_quality(
original_history: str,
compressed_context: str,
model_response_fn: Callable[[str, str], str],
) -> Dict:
"""Evaluate compression quality for a conversation end-to-end.
Use when: running a one-shot quality check on a compression pass.
Generates probes from original history, collects model responses
using the compressed context, evaluates each response, and returns
a scored summary with actionable recommendations.
Args:
original_history: The full conversation before compression.
compressed_context: The compressed version to evaluate.
model_response_fn: Callable that takes (compressed_context, question)
and returns the model's response string.
Returns:
Dictionary with total evaluations, average score, per-dimension
averages, weakest/strongest dimensions, and recommendations list.
"""
# Generate probes
generator = ProbeGenerator(original_history)
probes = generator.generate_probes()
# Evaluate each probe
evaluator = CompressionEvaluator()
for probe in probes:
# Get model response using compressed context
response = model_response_fn(compressed_context, probe.question)
# Evaluate response
evaluator.evaluate(probe, response, compressed_context)
# Get summary
summary = evaluator.get_summary()
# Add recommendations
summary["recommendations"] = []
if summary.get("weakest_dimension") == "artifact_trail":
summary["recommendations"].append(
"Consider implementing separate artifact tracking outside compression"
)
if summary.get("average_score", 0) < 3.5:
summary["recommendations"].append(
"Compression quality is below threshold - consider less aggressive compression"
)
return summary
if __name__ == "__main__":
# Demo: generate probes and evaluate a sample compression
sample_history = """
User reported error: 401 Unauthorized on /api/auth/login endpoint.
Examined auth.controller.ts - JWT generation looks correct.
Examined middleware/cors.ts - no issues found.
Modified config/redis.ts: Fixed connection pooling configuration.
Modified services/session.service.ts: Added retry logic for transient failures.
Decided to use Redis connection pool instead of per-request connections.
Modified tests/auth.test.ts: Updated mock setup for new config.
14 tests passing, 2 failing (mock setup issues).
Next: Fix remaining test failures in session service mocks.
"""
sample_compressed = """
## Session Intent
Debug 401 Unauthorized on /api/auth/login.
## Root Cause
Stale Redis connection in session store.
## Files Modified
- config/redis.ts: Fixed connection pooling
- services/session.service.ts: Added retry logic
- tests/auth.test.ts: Updated mock setup
## Test Status
14 passing, 2 failing
## Next Steps
1. Fix remaining test failures
"""
# Stub model response function
def mock_model_response(context: str, question: str) -> str:
if "error" in question.lower():
return "The original error was a 401 Unauthorized on /api/auth/login."
if "files" in question.lower():
return "Modified config/redis.ts, services/session.service.ts, tests/auth.test.ts."
if "next" in question.lower():
return "Fix remaining test failures in session service mocks."
if "decision" in question.lower():
return "Decided to use Redis connection pool instead of per-request connections."
return "No specific information available."
# Run evaluation
result = evaluate_compression_quality(
original_history=sample_history,
compressed_context=sample_compressed,
model_response_fn=mock_model_response,
)
print("=== Compression Quality Evaluation ===")
print(f"Total evaluations: {result['total_evaluations']}")
print(f"Average score: {result['average_score']:.2f}")
print()
print("Dimension averages:")
for dim, score in result.get("dimension_averages", {}).items():
print(f" {dim}: {score:.2f}")
print()
print(f"Weakest dimension: {result.get('weakest_dimension')}")
print(f"Strongest dimension: {result.get('strongest_dimension')}")
print()
if result.get("recommendations"):
print("Recommendations:")
for rec in result["recommendations"]:
print(f" - {rec}")
else:
print("No recommendations - compression quality looks acceptable.")
import importlib.util
import unittest
from pathlib import Path
MODULE_PATH = (
Path(__file__).resolve().parents[1] / "scripts" / "compression_evaluator.py"
)
MODULE_SPEC = importlib.util.spec_from_file_location(
"compression_evaluator", MODULE_PATH
)
if MODULE_SPEC is None or MODULE_SPEC.loader is None:
raise RuntimeError(f"Unable to load compression_evaluator.py from {MODULE_PATH}")
COMPRESSION_EVALUATOR = importlib.util.module_from_spec(MODULE_SPEC)
MODULE_SPEC.loader.exec_module(COMPRESSION_EVALUATOR)
class CompressionEvaluatorTests(unittest.TestCase):
def test_json_ground_truth_terms_score_when_response_mentions_artifacts(
self,
) -> None:
evaluator = COMPRESSION_EVALUATOR.CompressionEvaluator()
rich_score = evaluator._heuristic_score(
{"id": "artifact_files_modified"},
"We modified src/app.py and updated README.md during the session.",
'[{"path": "src/app.py", "operation": "modified"}, {"path": "README.md", "operation": "updated"}]',
)
poor_score = evaluator._heuristic_score(
{"id": "artifact_files_modified"},
"We changed some files but I do not remember which ones.",
'[{"path": "src/app.py", "operation": "modified"}, {"path": "README.md", "operation": "updated"}]',
)
self.assertGreater(rich_score, poor_score)
self.assertGreaterEqual(rich_score, 4.0)
def test_plain_text_ground_truth_still_uses_substring_match(self) -> None:
evaluator = COMPRESSION_EVALUATOR.CompressionEvaluator()
exact_score = evaluator._heuristic_score(
{"id": "continuity_work_state"},
"Next: fix the websocket timeout before rerunning tests.",
"fix the websocket timeout",
)
missing_score = evaluator._heuristic_score(
{"id": "continuity_work_state"},
"Next: inspect logs again.",
"fix the websocket timeout",
)
self.assertGreater(exact_score, missing_score)
if __name__ == "__main__":
unittest.main()
Related skills
Forks & variants (1)
Context Compression has 1 known copy in the catalog totaling 135 installs. They canonicalize to this original listing.
- muratcankoylan - 135 installs