diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5a86a307..f8b15c8a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,14 @@
 
 ## [Unreleased]
 
+### Added
+
+- **PR #2482** by @Michaelyklam (refs #2453) — Add a durable source/API boundary inventory for the WebUI's remaining Hermes Agent source dependencies: chat execution, runtime events, profiles, goals, slash/plugin commands, provider/auth/model catalogs, redaction parity, and imported Agent/Gateway sessions. The new RFC tracks replacement API contracts before the source mount can be removed.
+
+### Changed
+
+- **PR #2482** by @Michaelyklam (refs #2453) — Make the multi-container source boundary more explicit: Docker docs and README now link the boundary inventory, and `docker_init.bash` emits a startup warning when the WebUI sees a writable agent-source mount instead of the default read-only `hermes-agent-src` mount.
+
 ## [v0.51.85] — 2026-05-17 — Release BI (stage-378 — 3-PR batch — workspace-prefix display leakage fix + release-tag update banner + Slice 3a cancel-control gate RFC)
 
 ### Fixed
diff --git a/README.md b/README.md
index 1a941b9e..9d2d2169 100644
--- a/README.md
+++ b/README.md
@@ -208,6 +208,8 @@ docker compose -f docker-compose.three-container.yml up -d
 Both compose files use **named Docker volumes** by default, which solves the UID/GID problem by construction. If you need bind mounts to share an existing host directory, see [`docs/docker.md`](docs/docker.md) for the full migration recipe.
 
 > **Known limitation (#681)**: in the two-container setup, tools triggered from the WebUI run in the **WebUI container**, not the agent container. If you need git/node/etc. on the WebUI's filesystem, either use the single-container setup, extend the WebUI Dockerfile, or use the community [all-in-one image](https://github.com/sunnysktsang/hermes-suite).
+>
+> **Source boundary note (#2453)**: the multi-container setup mounts `hermes-agent-src` read-only into the WebUI by default. This prevents WebUI-side source rewrites but is still an implementation-coupling bridge, not a stable Agent API boundary. See [`docs/rfcs/agent-source-boundary.md`](docs/rfcs/agent-source-boundary.md) for the current source/API decoupling inventory.
 
 ### Common failure modes
 
diff --git a/docker_init.bash b/docker_init.bash
index 4cbc4467..e70a0889 100644
--- a/docker_init.bash
+++ b/docker_init.bash
@@ -391,6 +391,15 @@ else
     fi
   done
   if [ -n "$_agent_src" ]; then
+    if [ -w "$_agent_src" ]; then
+      echo ""
+      echo "!! WARNING: hermes-agent source mount is writable from the WebUI container."
+      echo "!!   Path: $_agent_src"
+      echo "!! The multi-container compose defaults use a read-only mount for defence-in-depth."
+      echo "!! If this is not an intentional local development checkout, switch the WebUI"
+      echo "!! agent source volume/bind mount to read-only. See docs/rfcs/agent-source-boundary.md."
+      echo ""
+    fi
     uv pip install "$_agent_src[all]" --trusted-host pypi.org --trusted-host files.pythonhosted.org || error_exit "Failed to install hermes-agent's requirements"
   else
     echo ""
diff --git a/docs/docker.md b/docs/docker.md
index 4d1a5944..f238773b 100644
--- a/docs/docker.md
+++ b/docs/docker.md
@@ -211,6 +211,8 @@ What multi-container does **not** isolate:
 
 If you need **filesystem isolation** between the chat UI and the agent (e.g. you don't trust the WebUI to read agent state), the multi-container setup is not enough — run the agent on a separate host and connect the WebUI to it via the gateway HTTP API. If you don't need any boundary, the single-container setup is simpler.
 
+The direct source mount is a compatibility bridge, not the long-term API contract. The current source/API boundary inventory and decoupling task list live in [`docs/rfcs/agent-source-boundary.md`](rfcs/agent-source-boundary.md) for [#2453](https://github.com/nesquena/hermes-webui/issues/2453). If you customize the compose files with bind mounts, keep the WebUI-side agent source mount read-only unless you are intentionally doing local development; `docker_init.bash` warns at startup when that path is writable.
+
 ## Bind-mount migration (advanced)
 
 If you really need to bind-mount an existing host `~/.hermes` (e.g. you're keeping config in dotfiles, sharing with a non-Docker `hermes` install, etc.):
diff --git a/docs/rfcs/agent-source-boundary.md b/docs/rfcs/agent-source-boundary.md
new file mode 100644
index 00000000..4cb527cd
--- /dev/null
+++ b/docs/rfcs/agent-source-boundary.md
@@ -0,0 +1,70 @@
+# Agent Source Boundary and API Decoupling Inventory
+
+- **Status:** Proposed
+- **Created:** 2026-05-17
+- **Tracking issue:** [#2453](https://github.com/nesquena/hermes-webui/issues/2453)
+
+## Problem
+
+The WebUI currently depends on Hermes Agent Python source being importable at
+runtime. In local installs this usually means a neighboring checkout; in the
+multi-container Docker setup it means the WebUI reads the `hermes-agent-src`
+volume that the agent container also uses.
+
+That source mount is a compatibility bridge, not the desired long-term contract.
+Even when mounted read-only on the WebUI side, it couples WebUI releases to
+Hermes Agent internal module layout and makes the multi-container setup look more
+isolated than it really is.
+
+## Current safety posture
+
+- The multi-container compose files mount `hermes-agent-src` read-only into the
+  WebUI service by default.
+- `docker_init.bash` prunes the agent source subtree from `chown` so read-only
+  mounts do not break startup.
+- If an operator overrides the compose files with a mutable agent-source mount,
+  startup now emits a notable warning. The WebUI still starts because local dev
+  checkouts and custom deployments may intentionally be writable, but the warning
+  makes the reduced boundary explicit.
+
+## Source-access inventory
+
+These are the current WebUI capabilities that still rely on Agent source or
+`hermes_cli`/`agent` modules being importable. Each item should eventually move
+behind an explicit, versioned Agent API or a packaged library contract that does
+not require mounting the live source checkout.
+
+| WebUI capability | Current dependency | Desired API / contract | Notes |
+|---|---|---|---|
+| Browser chat execution | `run_agent.AIAgent` imported by `api/streaming.py` | Run lifecycle API: start, observe, status, cancel, approval, clarify, final usage | Covered by the runtime-adapter migration in [#1925](https://github.com/nesquena/hermes-webui/issues/1925), but still source-backed today. |
+| Runtime event rendering | WebUI callbacks around Agent token/reasoning/tool events | Stable event envelope for tokens, reasoning, progress, tool lifecycle, approvals, clarify, errors, and final usage | The existing run-adapter RFC describes the browser-facing shape; Agent still needs a durable producer contract. |
+| Profile list/create/delete/seed | `hermes_cli.profiles` from `api/profiles.py` | Profile management API with profile metadata, env/runtime context, seed/delete operations, and validation errors | WebUI has fallback filesystem handling for some operations, but feature parity follows Hermes CLI internals. |
+| Goal command state | `hermes_cli.goals` from `api/goals.py` | Goal CRUD/control API: get, save, pause/resume/clear, and status | Should preserve current `/goal` WebUI behavior without direct module import. |
+| Slash command registry and plugin commands | `hermes_cli.commands` and `hermes_cli.plugins` from `api/commands.py` | Command/plugin capability discovery API scoped by active profile | WebUI should render command help from a stable capability response. |
+| Provider/auth/model catalogs | `hermes_cli.models`, `hermes_cli.auth`, and `agent.credential_pool` from `api/config.py` | Provider registry, model catalog, auth status, OAuth/credential-pool status APIs | WebUI has static fallbacks, but exact parity and custom provider state come from Agent internals. |
+| Redaction helper parity | `agent.redact.redact_sensitive_text` from `api/helpers.py` | Redaction service/library contract with signature/version compatibility | WebUI keeps a fallback redactor because this import has changed before. |
+| CLI/Gateway session bridge | Agent `state.db` schema and gateway metadata read by sidebar/session helpers | Session listing/transcript/metadata API for non-WebUI-originated sessions | Direct SQLite/schema coupling should narrow over time, especially for messaging/email/gateway sessions. |
+
+## Decoupling task list
+
+1. Keep the Docker default safe: WebUI-side `hermes-agent-src` stays read-only in
+   two- and three-container compose files.
+2. Keep documenting the boundary honestly: multi-container isolates process,
+   network, and resources, not filesystem/source compatibility.
+3. Warn loudly when the WebUI container sees a writable agent-source mount in
+   Docker, because that weakens the defense-in-depth posture.
+4. Convert runtime execution first through the #1925 RuntimeAdapter path instead
+   of adding new direct imports.
+5. For each inventory row, file or link a follow-up that defines the Agent API
+   response shape before replacing the import.
+6. Do not claim the source mount can be removed until chat execution, provider
+   catalogs/auth status, profiles, goals, commands/plugins, redaction, and
+   imported Agent/Gateway sessions all have stable replacement contracts.
+
+## Non-goals for this slice
+
+- Do not remove `HERMES_WEBUI_AGENT_DIR`.
+- Do not break local source-checkout development.
+- Do not fail startup solely because the agent source is writable.
+- Do not replace the runtime adapter or Hermes Agent API in this document-only
+  inventory slice.
diff --git a/tests/test_issue2453_agent_source_boundary.py b/tests/test_issue2453_agent_source_boundary.py
new file mode 100644
index 00000000..8aa93b36
--- /dev/null
+++ b/tests/test_issue2453_agent_source_boundary.py
@@ -0,0 +1,67 @@
+"""Regression coverage for issue #2453 agent-source boundary docs/warnings."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+REPO = Path(__file__).resolve().parents[1]
+
+
+def test_agent_source_boundary_rfc_inventories_import_coupling():
+    """The #2453 source-boundary work must keep a concrete import inventory.
+
+    The risk in #2453 is not just a Docker mount mode; it is that WebUI behavior
+    still relies on Hermes Agent internals. Pinning these rows prevents the docs
+    from degrading into a vague security note without the follow-up task list.
+    """
+    doc = REPO / "docs" / "rfcs" / "agent-source-boundary.md"
+    assert doc.exists(), "#2453 needs a durable source/API boundary RFC"
+    src = doc.read_text(encoding="utf-8")
+
+    required_terms = [
+        "run_agent.AIAgent",
+        "hermes_cli.profiles",
+        "hermes_cli.goals",
+        "hermes_cli.commands",
+        "hermes_cli.plugins",
+        "hermes_cli.models",
+        "hermes_cli.auth",
+        "agent.credential_pool",
+        "agent.redact.redact_sensitive_text",
+        "state.db",
+    ]
+    for term in required_terms:
+        assert term in src, f"agent source-boundary RFC must inventory {term}"
+
+    for api_phrase in (
+        "Run lifecycle API",
+        "Profile management API",
+        "Command/plugin capability discovery API",
+        "Provider registry, model catalog, auth status",
+        "Session listing/transcript/metadata API",
+    ):
+        assert api_phrase in src, f"RFC must name replacement contract: {api_phrase}"
+
+
+def test_docker_startup_warns_when_agent_source_mount_is_writable():
+    """Mutable WebUI-side agent source mounts should be visibly discouraged.
+
+    The compose default is read-only, but custom bind mounts can still make the
+    WebUI's agent source path writable. The entrypoint should warn instead of
+    silently accepting a weakened boundary.
+    """
+    src = (REPO / "docker_init.bash").read_text(encoding="utf-8")
+
+    assert "agent source mount is writable" in src
+    assert "read-only mount" in src
+    assert "$_agent_src" in src
+    assert "-w \"$_agent_src\"" in src
+
+
+def test_docker_docs_link_source_boundary_inventory():
+    """Docker docs should link the #2453 inventory from the boundary section."""
+    src = (REPO / "docs" / "docker.md").read_text(encoding="utf-8")
+
+    assert "agent-source-boundary.md" in src
+    assert "source/API boundary inventory" in src
+    assert "#2453" in src