diff --git a/docs_dev/issue-604/findings.md b/docs_dev/issue-604/findings.md
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+# Findings: GitHub issue #604
+
+- `AGENTS.md:324-342` already records Keystone's six transport invariants; the new
+  Design Philosophy should explain the engineering decision lens rather than
+  repeat or rename those invariants.
+- `AGENTS.md:10-16` and ADR-015 establish that Keystone is pure transport and that
+  agent/orchestration concerns moved to ProjectAgamemnon.
+- ProjectOdyssey's `AGENTS.md` carries KISS, YAGNI, DRY, SOLID, modularity, and
+  POLA as the inherited development-principle set.
+- Hephaestus issue #2111 is the completed ecosystem precedent: it adds a
+  repository-specific `## Design Philosophy` section, explicitly attributes
+  ProjectOdyssey, and protects the contract with a focused regression check.
+- Keystone-specific evidence for those principles exists in ADR-015's
+  single-responsibility extraction, `core::IMessageSink` dependency inversion,
+  transparent local/remote routing, centralized NATS subject ownership, and
+  pull-based durable backpressure.
+- Keystone has no Python runtime/test harness. Documentation contract checks are
+  shell-based (`justfile:100-113`), and Markdown syntax is gated by the
+  `markdownlint` job in `.github/workflows/_required.yml:338-354`.
diff --git a/docs_dev/issue-604/progress.md b/docs_dev/issue-604/progress.md
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+# Progress: GitHub issue #604
+
+- Read the planning skill and isolated its scratch files from an existing issue plan.
+- Inspected the complete root `AGENTS.md` and repository documentation gates.
+- Located and reviewed the completed Hephaestus implementation-plan precedent.
+- Mapped ProjectOdyssey principles to Keystone's current pure-transport architecture.
+- Drafted the exact `AGENTS.md` section, focused shell regression check, `just`
+  entry point, CI integration, and per-criterion verification commands.
diff --git a/docs_dev/issue-604/task_plan.md b/docs_dev/issue-604/task_plan.md
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+# Task Plan: GitHub issue #604
+
+## Goal
+
+Produce a repository-grounded implementation plan for adding Keystone's
+ProjectOdyssey-heritage Design Philosophy section to `AGENTS.md`.
+
+## Phases
+
+- [x] Read applicable repository and planning instructions.
+- [x] Inspect `AGENTS.md`, documentation checks, and related ecosystem precedent.
+- [x] Determine the exact documentation and regression-check changes.
+- [x] Draft the complete implementation plan and runnable verification commands.
+
+## Key Questions
+
+- How should ProjectOdyssey's development principles be adapted to a pure transport library?
+- Where should the section live without duplicating Keystone's existing Key Principles?
+- Which repository-native check should enforce the documentation contract?
+
+## Errors Encountered
+
+_None._