diff --git a/docs/research/context-engineering-guidelines-claude-5.md b/docs/research/context-engineering-guidelines-claude-5.md new file mode 100644 index 00000000..06145a44 --- /dev/null +++ b/docs/research/context-engineering-guidelines-claude-5.md @@ -0,0 +1,380 @@ +# Research: Anthropic's New Context Engineering Guidelines and What They Mean for Han's Plugin-Building Guidance + +This report answers an open-ended question: what did Anthropic publish as its new context engineering guidance for +Claude 5-generation models, and how should the skill-building and agent-building guidance in `han-plugin-builder` be +updated in response? Evidence mode: strict. + +## Summary + +Anthropic has published new context engineering guidance for its Claude 5-generation models, and nearly all of it +confirms what Han's plugin-building guidance already teaches. The new guidance names six shifts: + +1. Write instructions that state a goal and trust the model's judgment, instead of spelling out rigid rules. +2. Design tool interfaces so the parameters explain themselves, instead of relying on usage examples. +3. Load context progressively, instead of all at once up front. +4. Remove instructions that repeat across surfaces. +5. Let the model save its own memory, instead of maintaining memory files by hand. +6. Point the model at code, test suites, and rubrics, instead of long prose descriptions. + +Anthropic reports it cut its own coding assistant's system prompt by more than eighty percent with no measured loss. + +Adversarial validation cut the needed update down to a small one. Two gaps the initial research claimed turned out +not to exist: the guidance already carries a rule against restating what the platform provides, and its +code-reference coverage is broader than first credited. + +The recommended update stays narrow. Re-verify the one guidance file that describes how each Claude model wants its +instructions written, checking it against Anthropic's official per-model documentation, and refresh its checked +date. Record the remaining new items only as dated, caveated notes, because they rest on Anthropic's own unverified +self-reporting. The direction of the new guidance is consistent across Anthropic's published material, but every +quantitative claim traces to Anthropic alone. So this report treats the announcement as directional vendor guidance +rather than settled fact. + +- **Confidence:** Medium + +## Research Results + +### The six shifts Anthropic announced for Claude 5-generation models + +Anthropic's announcement (A1) names six changes to how context should be engineered for Claude 5-generation models, +each framed as a before-and-after against prior practice. Secondary press (A11) restates the six shifts, but every +outlet derives from the same Anthropic disclosure, so the announcement's content is confirmed while its claims remain +a single party's self-report: + +1. **Prescriptive rules become judgment-based instructions.** The announcement's own example: the old rule "Never + write multi-paragraph docstrings" becomes "Write code that reads like the surrounding code: match its comment + density, naming, and idiom" (A1, quoted verbatim in A11). +2. **Tool usage examples become expressive tool interfaces.** Parameter names and enumerations should themselves hint + at correct usage, replacing worked examples in tool descriptions (A1). +3. **Upfront context becomes progressive disclosure.** Verification and review guidance moves out of the system prompt + into Skills the model loads selectively, and tools use deferred loading for non-essential functionality (A1). +4. **Duplicated instructions are removed.** An instruction that appears in both the system prompt and a tool + description is kept in one place only (A1). +5. **Manual memory files become automatic memory.** The model saves its own memory instead of requiring hand-edited + CLAUDE.md updates (A1). The specific prior mechanic replaced (a "#" hotkey) is stated only in A1 [single-source]. +6. **Markdown specs become richer references.** Code, HTML artifacts, test suites, and rubrics are preferred over + prose descriptions of desired behavior (A1). + +The headline quantitative claim is that Anthropic removed over eighty percent of Claude Code's system prompt with no +measured loss on coding evaluations (A1). Secondary press adds a more specific figure, roughly 800 tokens down to +about 164, and reports an incoming `claude doctor` / `/doctor` command for rightsizing CLAUDE.md files and skills +(A11). No disclosed methodology accompanies the figure, and no independent measurement exists; validation (V5) +classifies the whole quantitative chain as an interested party's self-report [single-source]. + +### The established context-engineering corpus behind the new rules + +The new announcement sits on top of a consistent body of Anthropic engineering guidance (A2 through A8) that predates +it. Its core claims, corroborated across several separate Anthropic artifacts: + +- **Context is a finite, depleting resource.** Model performance degrades as tokens accumulate ("context rot"), so + the goal is the smallest set of high-signal tokens that produces the desired outcome (A2). This is corroborated + operationally by A3's high-signal tool responses, A6's automatic stale-tool-result clearing, and A8's CLAUDE.md + pruning test ("would removing this line cause a mistake?"). +- **System prompts sit at the right altitude.** Specific enough to guide, flexible enough to avoid brittle + if-else logic, organized with structural markup (A2). The framing is A2's own [single-source], but A1's docstring + example is a concrete instance of the same shift. +- **Tools avoid overlap and pass a definitiveness test.** A human should be able to tell which tool applies; bloated + tool sets are a named failure mode (A2, corroborated by A3's consolidation and naming rules and A5's + prefer-specialized-tools heuristic). +- **Curated canonical examples beat exhaustive edge-case lists** (A2) [single-source]. +- **Just-in-time retrieval beats pre-loading, with a hybrid recommended.** Lightweight identifiers load at runtime; + critical data loads up front (A2). This is corroborated by A7's three-level skill loading model and by A8's split + of frequently-needed material into CLAUDE.md and occasional material into skills. +- **Compaction and external memory handle long horizons.** Summarize and reinitiate, clear stale tool results first, + and keep structured notes outside the context window (A2, corroborated by A6's shipped context-editing and memory + tool features). A6's percentage improvements are Anthropic's internal benchmarks [single-source]. +- **Subagents get clean contexts and return condensed summaries.** A lead agent decomposes the work. Each subagent + needs an explicit objective, an output format, tool guidance, and boundaries, or agents end up duplicating work + (A2, A5, corroborated at the product level by A8). A5's figures, including that multi-agent systems use roughly + fifteen times the tokens for a 90.2 percent quality gain on complex research, are internal single-study numbers + [single-source]. +- **Skills are the unit of progressive disclosure.** Name and description are the trigger signal; the SKILL.md body + loads on trigger; supplementary files load only when a sub-scenario needs them; scripts handle deterministic + operations (A7, corroborated by A8). + +Anthropic's harness post (A9) adds three named failure modes for long-running agent work. Agentic laziness is +declaring a multi-part job done early. Self-preferential bias is favoring one's own output when judging it. Goal +drift is losing the objective across many turns. The post also names workflow patterns including adversarial +verification, tournament, and loop-until-done, and advises reserving heavy multi-agent machinery for high-value tasks +[single-source]. + +A companion post on working with Claude Fable (A10) recommends practices such as a deliberate blind-spot pass, +prototypes over detailed specs for subjective work, and treating source code as the best reference [single-source]. + +### What Han's guidance corpus already covers + +The `han-plugin-builder` guidance corpus (48 files, inventoried at A13) already encodes most of the established +corpus, often with more operational specificity than Anthropic's own posts: + +- Three-level progressive disclosure with a 500-line SKILL.md ceiling (A16, matching A7). +- Context-rot rationale, attention competition, lost-in-the-middle position effects, and a 15 to 40 percent + utilization peak (A15, matching and extending A2). +- A standing rule against restating what the toolchain or platform already provides, in place since 2026-06-16 + (A15), which covers the substance of A1's de-duplication shift. +- Description budgets: a 1024-character target, the Claude Code 1536-character per-entry cap, and the roughly one + percent listing budget (A16). +- Single-role agents that generate or evaluate, never both (A17), which matches A9's self-preferential-bias failure + mode from a different angle. +- Multi-agent economics with a 45 percent saturation threshold sourced to a 2025 Google, DeepMind, and MIT study + (A17), consistent with A5's reserve-for-high-value-tasks advice. +- Code-based reference guidance across three files: scripts for deterministic validation, canonical examples ("3 + well-chosen examples match 9"), and example test suites as success criteria (A19), covering most of A1's sixth + shift. +- Dispatch namespacing and just-in-time guidance reading (A13, A18, matching A7). + +### Where the new guidance and Han's docs genuinely diverge + +The initial research claimed five gaps; validation refuted or narrowed three of them. What remains: + +1. **One dated per-model file to re-verify, not rewrite.** `per-model-authoring.md` (A14) was last checked against + Anthropic's official per-model documentation on 2026-07-20, four days before the announcement. Its claim is that + Opus 4.8 and Sonnet 5 "follow instructions literally and do not generalize on their own, so they want each + behavior spelled out." That claim sits on a different axis from A1's shift (V2): literal instruction-following is + a behavior claim, while A1 describes removing redundant instruction volume. The two are not contradictory, so the + file is not known to be wrong. It is dated against a moved target, and it went through its own spec review on the + day it was written (V8). It should be re-verified against the same official per-model pages it already cites, not + against the marketing announcement. +2. **Automatic memory and the rightsizing tool are unrepresented.** Neither automatic memory-saving (A1) nor the + `/doctor` command (A11) [single-source] appears anywhere in the corpus (confirmed by search, V4). Both rest on + the announcement and derivative press only, so they qualify as caveated notes at most, not guidance rules. +3. **Two of three named failure modes are unrepresented.** Self-preferential bias is already encoded as the + single-role rule; agentic laziness and goal drift (A9) [single-source] are not named in the corpus (V4). Same + evidence ceiling: caveated notes at most. + +Two claimed gaps did not survive validation. The missing de-duplication rule exists in the context-hygiene guidance +(V1 refuted it). The code-based-reference coverage is broader than the "scripts only" characterization (V3). + +### Evidence-gathering integrity notes + +One fetched page (A8) contained directive-style text ahead of its article body, instructing the fetcher to retrieve a +documentation index file. That text was recorded as a claim and not acted on, and the web-facing agents ran with no +repository or user context to surrender. + +Validation (V6) flagged that the equivalent screening was not logged for A1, A6, A9, and A10, which share the same +blog format. That screening should be repeated and logged before any doc edit cites those pages. + +## Options to Consider + +### O1: Targeted delta update to the existing guidance files + +- **What it is:** Refresh `per-model-authoring.md`, and fold each new rule into the existing decision-scoped file + where it belongs: judgment-based altitude into the instruction-writing guidance, a de-duplication rule, and + code-based references guidance. +- **Trade-offs:** This was the pre-validation recommendation, and validation showed two of its three additions + duplicate rules the corpus already carries (V1, V3). As scoped, it would add redundant content, which is the + failure mode the new guidance itself warns against. +- **Rests on:** (A1, A11) for the shifts; (A13, A14, A15, A19) for what the corpus holds. +- **Evidence status:** corroborated for the shifts; the gap claims it depended on were refuted by codebase evidence + +### O2: One new dedicated context-engineering reference doc + +- **What it is:** Add a single new reference file carrying the Claude 5 shifts, cross-linked from the existing files. +- **Trade-offs:** This is one clean edit. But the corpus routes authors to guidance by decision point, so a + topic-shaped file would duplicate content the decision-scoped files already carry, or leave authors with two places + to look. That duplication is what A1's fourth shift and the corpus's own existing rule (A15) both warn against. +- **Rests on:** (A1), (A13). +- **Evidence status:** corroborated + +### O3: Full corpus restructure around the new framing + +- **What it is:** Reorganize the guidance corpus around "thin prompts, thick artifacts" as its central organizing + idea. +- **Trade-offs:** The cost far exceeds the evidence. Most of the new guidance's substance is already present. The + strongest justification for radical change, the eighty percent prompt cut, is an uncorroborated self-reported + figure [single-source]. +- **Rests on:** (A1, A11). +- **Evidence status:** single-source (caveated) for the claims that would justify the scale of change + +### O4: No change; wait for official documentation + +- **What it is:** Treat the blog post as directional and wait for Anthropic's official docs to confirm before editing + anything. +- **Trade-offs:** Zero effort now, but it leaves `per-model-authoring.md` date-stamped against guidance that has + since moved, and the corpus's own convention is to keep model-behavior claims dated and refreshed. +- **Rests on:** (A14). +- **Evidence status:** corroborated (the datedness is verifiable; the case for waiting is the weakness) + +### O5: Verify and caveat + +- **What it is:** Re-verify `per-model-authoring.md` against Anthropic's current official per-model documentation, + the same source class it already cites, and refresh its last-checked date. Check its four in-corpus referrers for + stale cross-references (V7). Cross-link the existing de-duplication and code-reference rules to the new + announcement as supporting citation where useful. Record the genuinely absent items, automatic memory, the + `/doctor` command, and the agentic-laziness and goal-drift failure modes, as dated single-source notes or decline + them until official documentation confirms them. Add no new rules. +- **Trade-offs:** The smallest update that resolves the one verifiable defect (a dated model-behavior file) without + adding redundant or weakly-sourced content. Its cost is restraint: if the announcement's shifts later gain official + documentation, a second pass will be needed. +- **Rests on:** (A14) for the dated file; (A15, A19) for the rules that already exist; (A1, A11) for what to caveat. +- **Evidence status:** corroborated + +## Recommendation + +- **Recommendation:** O5, verify and caveat. Re-verify `per-model-authoring.md` against Anthropic's official + per-model documentation and refresh its checked date, checking the four files that reference it before editing + (the guidance SKILL.md, the specialization guidance, and the two portable assets). Treat the announcement's shifts + as supporting citations for rules the corpus already carries. Hold the genuinely new items (automatic memory, + `/doctor`, the named failure modes) to dated, caveated notes until Anthropic's official documentation confirms + them. Before making any edit that cites the blog sources, repeat the directive-text screening that was logged for + the best-practices page and log the result (V6). +- **Evidence basis:** The six shifts and their direction rest on Anthropic's announcement (A1), restated by + derivative press (A11), and are consistent with Anthropic's separate established corpus (A2 through A8). This is + internally consistent vendor guidance, not independently verified fact, and validation (V5) requires it be carried + as a self-report. The claim that Han's corpus already encodes the established guidance rests on codebase evidence (A13, + A15, A16, A17, A18, A19) verified directly by validation (V1, V3). The datedness of `per-model-authoring.md` rests + on codebase evidence (A14). No part of the recommendation rests on the uncorroborated quantitative figures. + +## Validation + +### V1: The claimed missing de-duplication rule exists + +- **Strategy:** Challenge the Evidence +- **Investigation:** `context-hygiene.md` lines 177-182 carry the rule "Do not restate what the toolchain or platform + already provides"; git history shows it was introduced 2026-06-16, over a month before the announcement. +- **Result:** Refuted (the gap claim) +- **Impact:** The "add a de-duplication rule" action was removed from the recommendation; at most the existing rule + gains a supporting citation. + +### V2: The per-model "tension" conflates two different axes + +- **Strategy:** Challenge the Assumptions +- **Investigation:** Full read of `per-model-authoring.md`. Its claim, sourced to Anthropic's official per-model + prompting pages, is about literal instruction-following behavior. The announcement describes removing redundant + instruction volume, a density axis, not a specificity-hurts-Sonnet-5 axis. +- **Result:** Partially Refuted +- **Impact:** The framing that the file is already wrong was withdrawn. Re-verification remains warranted because the + file is date-stamped against guidance that has since moved. + +### V3: Code-based-reference coverage is broader than claimed + +- **Strategy:** Challenge the Evidence +- **Investigation:** `writing-effective-instructions.md` carries "Use scripts for deterministic validation" (lines + 445-472) and "Include canonical examples" citing "3 well-chosen examples match 9" (lines 396-443); + `success-criteria-and-testing.md` line 41 covers example test suites. +- **Result:** Partially Refuted +- **Impact:** The "add code-based references guidance" action was removed from the recommendation; existing rules may + gain a supporting citation. + +### V4: The options list omitted a smaller option + +- **Strategy:** Challenge the Options Framing +- **Investigation:** With V1 and V3 resolved, the only confirmed absences are automatic memory / `/doctor` and the + agentic-laziness and goal-drift vocabulary (verified absent by search), all single-source. +- **Result:** Confirmed +- **Impact:** O5 (verify and caveat) was added and became the recommendation. + +### V5: The announcement's corroboration is derivative, not independent + +- **Strategy:** Challenge the Evidence-Gathering Integrity +- **Investigation:** The secondary outlets restate the same disclosure and add no independent measurement; discounting + them removes no information. The announcement and three related sources sit on Anthropic's marketing blog, not its + documentation domains, and the eighty percent figure has no disclosed methodology. +- **Result:** Confirmed +- **Impact:** "Corroborated by A11" language was downgraded throughout to restatement of a single self-report, and + the recommendation forbids resting any guidance rule on the quantitative claims. + +### V6: Directive-text screening was logged for only one of four blog sources + +- **Strategy:** Challenge the Evidence-Gathering Integrity +- **Investigation:** The registry records a directive-language check for the best-practices page only; A1, A6, A9, and + A10 share the same format and domain but have no logged screening result. +- **Result:** Partially Refuted (a process gap, not a confirmed injection) +- **Impact:** Carried as a remaining risk and as a precondition in the recommendation: screen and log before citing + those pages in doc edits. + +### V7: No referrer check existed for the file the recommendation edits + +- **Strategy:** Challenge the Recommendation +- **Investigation:** Search found `per-model-authoring.md` referenced by the guidance SKILL.md, + `specialization-and-model-selection.md`, and the two portable assets (`guidance-portable-SKILL.md`, + `rule-index-body.md`). +- **Result:** Confirmed (a gap, not yet a broken caller) +- **Impact:** The referrer check was added to the recommendation so an edit cannot leave a stale cross-reference. + +### V8: The per-model file has review provenance + +- **Strategy:** Challenge the Assumptions +- **Investigation:** `docs/plans/per-model-authoring-guidance/` holds a feature specification and implementation plan + with same-day commits (2026-07-20) showing the file's claims passed a spec-review and synthesis cycle citing + Anthropic's official per-model pages. +- **Result:** Partially Refuted (of the framing that the claim was thin) +- **Impact:** Re-verification must compare against Anthropic's current official per-model documentation, the source + class the file already cites, and note explicitly if those official pages have not themselves changed. + +### Adjustments Made + +Validation reshaped the report. The pre-validation recommendation, O1, a targeted multi-file delta update, did not +survive. Two of its three content additions duplicated rules the corpus already carries (V1, V3), and the urgency of +its per-model rewrite was overstated (V2, V8). O5 was added (V4) and became the recommendation. Corroboration +language for the announcement was downgraded (V5), the screening precondition was added (V6), and the referrer check +was added to the recommended edit (V7). The confidence rating was lowered from Medium-High to Medium. + +### Confidence Assessment + +- **Confidence:** Medium +- **Remaining Risks:** Every claim about the new guidance traces to Anthropic's own publications; no independent + measurement of any quantitative figure exists. The `/doctor` command rests on secondary press only. The + directive-text screening for four of the blog sources (V6) has not yet been re-run and logged. The validator did + not re-fetch the web sources. Its attack tested internal consistency and fit against the repository, so if the + announcement's content differs from how the registry characterizes it, the affected findings would need + re-checking. Anthropic's official per-model pages were not fetched in this pass, so whether they changed after + 2026-07-20 is unknown. That check is the first step of the recommended update. + +## Sources + +| ID | Source | Link / location | Retrieved | Trust class | Summary (one line) | Evidence status | +| --- | --------------------------------------------------- | -------------------------------------------------------------------------------------------- | ---------- | ----------- | ---------------------------------------------------------------------------------------- | -------------------------------------------- | +| A1 | The New Rules of Context Engineering for Claude 5 | | 2026-07-27 | web | Six shifts for Claude 5-generation models; 80% system-prompt cut claim | restated by A11 (derivative); self-report | +| A2 | Effective Context Engineering for AI Agents | | 2026-07-27 | web | Context rot; right altitude; JIT retrieval; compaction; note-taking; subagent summaries | corroborated by A3, A5, A6, A7, A8 | +| A3 | Writing Tools for AI Agents | | 2026-07-27 | web | Tool namespacing, consolidation, unambiguous params, actionable errors | corroborated by A2, A4, A5 | +| A4 | Building Effective AI Agents | | 2026-07-27 | web | Workflows vs agents; five composable patterns; start simple; invest in tool design | corroborated by A3, A5 | +| A5 | How We Built Our Multi-Agent Research System | | 2026-07-27 | web | Orchestrator/subagent briefs, effort scaling, parallelism; internal 15x/90.2% figures | corroborated by A2, A8; figures single-source | +| A6 | Context Management on the Claude Developer Platform | | 2026-07-27 | web | Shipped context editing and memory tool; internal percentage gains | corroborated by A2; figures single-source | +| A7 | Equipping Agents for the Real World with Skills | | 2026-07-27 | web | SKILL.md contract; three-level progressive disclosure; scripts for determinism | corroborated by A2, A8 | +| A8 | Claude Code Best Practices | | 2026-07-27 | web | Minimal CLAUDE.md; skills for occasional context; subagents for investigation and review | corroborated by A2, A7; contained directive text (recorded, not followed) | +| A9 | Dynamic Workflows in Claude Code | | 2026-07-27 | web | Failure modes (agentic laziness, self-preferential bias, goal drift); workflow patterns | single source (caveated) | +| A10 | A Field Guide to Claude Fable | | 2026-07-27 | web | Fable-specific working practices: blind-spot pass, prototypes, source as reference | single source (caveated) | +| A11 | Secondary press coverage of A1 | and others | 2026-07-27 | web | Restates the six shifts, ~800-to-~164-token figure, incoming `claude doctor` command | derivative of A1; adds no independent verification | +| A12 | Prompt Engineering Overview (platform docs) | | 2026-07-27 | web | Thin routing page; no substantive claims | single source (thin) | +| A13 | Han guidance corpus inventory | `han-plugin-builder/skills/guidance/` (48 files) | n/a | codebase | Full inventory of skill-building and agent-building guidance | codebase anchor | +| A14 | Per-model authoring guidance | `han-plugin-builder/skills/guidance/references/per-model-authoring.md` | n/a | codebase | Last checked 2026-07-20; Sonnet 5/Opus 4.8 literal vs Fable 5 goal-based instructions | dated against A1; different axis per V2 | +| A15 | Context hygiene guidance | `han-plugin-builder/skills/guidance/references/skill-building-guidance/context-hygiene.md` | n/a | codebase | Attention competition, compaction budget, and the existing no-restating rule (lines 177-182) | consistent with A2; covers A1's fourth shift | +| A16 | Progressive disclosure and description budgets | `han-plugin-builder/skills/guidance/references/skill-building-guidance/progressive-disclosure.md` and `skill-description-length.md` | n/a | codebase | Three loading levels, 500-line body ceiling, 1024/1536-char description budgets | consistent with A7 | +| A17 | Agent guidance (domain focus, economics) | `han-plugin-builder/skills/guidance/references/agent-building-guidelines/` | n/a | codebase | Single-role rule, 50-token role identity, 45% multi-agent threshold | consistent with A5, A9 | +| A18 | Builder skills (interview and review checklists) | `han-plugin-builder/skills/skill-builder/SKILL.md` and `agent-builder/SKILL.md` | n/a | codebase | Evidence-first interviews; conformance review checklists mapping to guidance files | codebase anchor | +| A19 | Code-reference and example guidance | `writing-effective-instructions.md` (lines 396-472) and `success-criteria-and-testing.md` (line 41), under `skill-building-guidance/` | n/a | codebase | Scripts for deterministic validation, canonical examples, example test suites | covers most of A1's sixth shift | + +### A1: The New Rules of Context Engineering for Claude 5 Generation Models (recommendation-bearing) + +- **Link / location:** +- **Retrieved:** 2026-07-27 +- **Trust class:** web +- **Summary:** Anthropic's announcement of six shifts in context engineering for Claude 5-generation models: judgment-based + instructions over prescriptive rules, expressive tool interfaces over usage examples, progressive disclosure over + upfront context, de-duplicated instructions, automatic memory over manual CLAUDE.md edits, and code-based references + over markdown specs. Reports an over-eighty-percent cut to Claude Code's system prompt with no measured evaluation + loss, and recommends keeping CLAUDE.md to repository gotchas while moving situational guidance into Skills. +- **Evidence status:** restated by A11 without independent verification; carried as a vendor self-report per V5 + +### A14: per-model-authoring.md (recommendation-bearing) + +- **Link / location:** `han-plugin-builder/skills/guidance/references/per-model-authoring.md` +- **Retrieved:** n/a +- **Trust class:** codebase +- **Summary:** States it was last checked against Anthropic's published guidance on 2026-07-20 for Sonnet 5, Opus 4.8, + and Fable 5. Claims Opus 4.8 and Sonnet 5 follow instructions literally and want each behavior spelled out, while + Fable 5 wants short, goal-based instructions and degrades under exhaustive checklists. Validation (V2) established + that this is a behavior claim on a different axis from the announcement's density shift. Validation (V8) + established that the file carries its own same-day review provenance. The defect is datedness, not established + error. +- **Evidence status:** codebase anchor; re-verification against Anthropic's official per-model pages is the recommended action + +### A15: context-hygiene.md (recommendation-bearing) + +- **Link / location:** `han-plugin-builder/skills/guidance/references/skill-building-guidance/context-hygiene.md` + (lines 177-182 for the no-restating rule) +- **Retrieved:** n/a +- **Trust class:** codebase +- **Summary:** Carries the corpus's context-economy rationale (attention competition, position effects, utilization + peak, compaction budgets) and, since 2026-06-16, the rule "Do not restate what the toolchain or platform already + provides," which validation (V1) confirmed covers the substance of the announcement's de-duplication shift. +- **Evidence status:** codebase anchor; verified by V1