canvas-update

Canvas Update

Preflight: Read target canvas file(s) before any Write/Edit

Hard rule. Before issuing Write or Edit against any .claude/canvas/*.yml, use the Read tool on that file in this session. Claude Code's Read-before-Write check requires the Read tool specifically — cat/head/grep via Bash do NOT satisfy it.

Edit vs Write — different cost profiles (verified 2026-05-14):

• Edit (exact-string replacement): Read with limit: 1 satisfies the check at ~50 tokens. State-tracking is per-file, not per-byte — subsequent Edit calls work anywhere in the file. Use this for partial updates against large canvas files (e.g., purpose.yml at 800+ lines).
• Write (full replacement): do a full Read first. Write obliterates the file; you should see what you're about to replace. The limit:1 shortcut is not appropriate here.

ID-bearing entries — scan the ID space before assigning (added 2026-05-15, v0.23.19): When adding a new component, opportunity, solution, or any other ID-bearing entry to a canvas file, run a Bash grep first to confirm the next ID in your prefix sequence is actually free:

grep "^  - id: <prefix>-" .claude/canvas/<file>.yml | sort -u

Replace <prefix> with the canvas's ID prefix (comp for landscape, opp for opportunities, sol for solutions, ht for human-tasks, etc.). Then pick the next free integer. validate_canvas.py has a duplicate-ID check (lines 230-239) that catches the failure on CI, but a duplicate can persist in the working tree for days if CI isn't run between edit and discovery — see roadmap-repo corrections.md 2026-05-15 "Duplicate canvas ID created in landscape.yml" for the worked example.

Original failure mode: anti-pattern #7 instance #5, 2026-05-09 — agent conflated Bash head with the Read tool, lost ~14k tokens to a Write-fail → remedial-full-Read → re-Write loop. The limit:1 discipline (graduated 2026-05-14, v0.23.18) prevents the second-order cost where the agent correctly follows the rule but full-Reads every time. The ID-scan discipline (graduated 2026-05-15, v0.23.19) prevents the related class where the agent reads enough of the file to satisfy the Edit check but not enough to see existing ID assignments — kin to anti-pattern #8 (Stale State Read).

If this skill writes to multiple canvas files, register each one first (limit:1 for Edit-only paths; full Read for Write paths) AND ID-scan any prefix you intend to assign.

See CLAUDE.md Canvas writes — Read before Write for the canonical rule.

Rules

1. Never update without evidence -- every canvas change must have a source
2. Maintain cross-file consistency -- if you update opportunities.yml, check if north-star.yml or gist.yml need updates too
3. Log the update -- add an entry to .claude/harness/decision-log.md explaining what changed and why

Which Canvas File for Which Information

| Information Type | Canvas File | Source | |-----------------|-------------|--------| | Purpose, mission, why | purpose.yml | Sinek | | North Star metric, inputs | north-star.yml | North Star Framework | | BVSSH health scores | bvssh-health.yml | Smart | | Value chain, competitive | landscape.yml | Wardley | | Team structure | team-shape.yml | Skelton | | User opportunities, OST | opportunities.yml | Torres | | User needs map | user-needs.yml | Allen | | Goals, ideas, steps | gist.yml | Gilad | | Service quality scores | services.yml | Downe | | Go-to-market, positioning | go-to-market.yml | Lauchengco | | Delivery performance | dora-metrics.yml | Forsgren | | Security threats | threat-model.yml | OWASP | | Privacy assessment | privacy-assessment.yml | GDPR/PbD | | Trust architecture | trust-signals.yml | Digital Trust | | Jobs to be done | jobs-to-be-done.yml | Christensen | | Bounded contexts | bounded-contexts.yml | Evans (DDD) | | Value stream map | value-stream.yml | Rother & Shook (VSM) | | Content delivery metrics | content-metrics.yml | v0.11.0 | | AI tool delivery metrics | ai-tool-metrics.yml | v0.11.0 | | Service delivery metrics | service-metrics.yml | v0.11.0 | | Human task tracking | human-tasks.yml | v0.11.0 | | Archived/discarded solutions | archived-solutions.yml | v0.12.0 | | Leaf lifecycle calibration | cycle-history.yml | v0.12.0 | | Adaptive thresholds | thresholds.yml | v0.12.0 | | User scenarios (Hoskins) | scenarios.yml | Hoskins |

Workflow

1. Identify which canvas file(s) need updating
2. Read current state
3. Make the update with evidence citation
4. Check cross-file consistency
5. Log in .claude/harness/decision-log.md

Counter-Argument Check (Bias Mitigation)

Before applying the canvas update, draft a one-line counter-argument: "What's the strongest case AGAINST this update — what evidence or perspective would invalidate it?" If you can't articulate one, run /mycelium:devils-advocate before proceeding.

This addresses the bias cluster documented in corrections.md (L5 sycophancy 2026-04-20, eval overfitting 2026-04-30, sharper-framing-isn't-righter 2026-05-03). Common shape: agent prefers what feels right over what evidence supports under competing pressure (be helpful vs. be honest, sharpen framing vs. preserve evidence base). The counter-argument step forces the missing perspective explicit, so the bias surfaces before it lands in canvas.

Especially important when interpolating user-supplied content (already untrusted per ${CLAUDE_PLUGIN_ROOT}/harness/security-trust.md#prompt-injection-defense) AND when increasing a confidence value — both contexts where the agent is most likely to default toward the optimistic read.