diff --git a/CLAUDE.md b/CLAUDE.md
index e51d3d6e..f4e720bf 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -311,7 +311,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Git status indicator** (`showGitStatus`, per-device, default OFF; `src/git-workspace-status.ts`, `routes/git-status-routes.ts`, `git-status-ui.js`): the bottom-bar indicator and its panel read `GET /api/sessions/:id/git-status` and `/git-diff`, read-only and offline (it never fetches and never writes). ⚠️ git never runs on a repository at or inside a Docker case workspace (walk-up, scan and diff alike, and a cached repository list is re-checked against the CURRENT Docker roots), since a container could plant a clean filter that runs on the host; remote and Docker sessions answer `unsupported`. ⚠️ `git-diff` takes `repo`/`path`/`kind` only as keys matched against the workspace's own repository list (`findWorkspaceRepo()`) and that repository's current status, never as paths. ⚠️ Keep `--no-optional-locks`, `core.fsmonitor=false` and `log.showSignature=false` on every call and `--no-ext-diff --no-textconv` on diffs; clean filters still run, which is why the Docker rule exists. ⚠️ An enclosing repository at `$HOME` or above is ignored (`isUnrelatedAncestor()`), and is identified by one cached `rev-parse` before any full status runs. Everything git supplies renders via `textContent`. Tests: `test/git-workspace-status.test.ts`, `test/routes/git-status-routes.test.ts`, and `test/git-status.browser.test.ts` (browser suite, not in the gate).
 
-**Raw file bodies are streamed and range-aware**: `file-raw`, the attachments `/raw` route and `GET /api/download` share `sendFileBody()`, advertise `Accept-Ranges: bytes` and answer `Range` with `206` + `Content-Range` (single-range, parser in `src/web/http-range.ts`); without it `<video>` cannot seek. The size cap (`MAX_FILE_DOWNLOAD_BYTES`, default 2GB, env `CODEMAN_MAX_DOWNLOAD_BYTES`, `0` = unlimited) is a sanity bound, not memory protection; never reintroduce a whole-file buffer. ⚠️ Bodies go out via `reply.hijack()`, so `sendRawStream` must copy the status onto `reply.raw` by hand or a partial body ships as `200`. ⚠️ Closing the preview must pause and unload media (`_stopFilePreviewMedia`), since a detached `HTMLMediaElement` keeps playing. → [architecture-invariants#raw-file-bodies-streamed-and-range-aware](docs/architecture-invariants.md#raw-file-bodies-streamed-and-range-aware)
+**Raw file bodies are streamed and range-aware**: `file-raw`, the attachments `/raw` route, `GET /api/download` and the rendered-HTML route `GET /html-view/<cap>/...` share `sendFileBody()`, advertise `Accept-Ranges: bytes` and answer `Range` with `206` + `Content-Range` (single-range, parser in `src/web/http-range.ts`); without it `<video>` cannot seek. The size cap (`MAX_FILE_DOWNLOAD_BYTES`, default 2GB, env `CODEMAN_MAX_DOWNLOAD_BYTES`, `0` = unlimited) is a sanity bound, not memory protection; never reintroduce a whole-file buffer. ⚠️ Bodies go out via `reply.hijack()`, so `sendRawStream` must copy the status onto `reply.raw` by hand or a partial body ships as `200`. ⚠️ Closing the preview must pause and unload media (`_stopFilePreviewMedia`), since a detached `HTMLMediaElement` keeps playing. → [architecture-invariants#raw-file-bodies-streamed-and-range-aware](docs/architecture-invariants.md#raw-file-bodies-streamed-and-range-aware)
 
 **Ultracode / workflow-run visualization** (opt-in, default OFF): the Workflow tool writes a completion artifact only at run *end*, so live in-flight runs exist solely as transcript dirs. `workflow-run-watcher.ts` therefore synthesizes ACTIVE runs from transcripts until the completion artifact appears and supersedes them. It is **STANDALONE** and deliberately never imports or touches `subagent-watcher.ts`, despite reading the same tree. Two independent toggles: `showUltracodeAgents` (docked panel) and `ultracodeFloatingWindows` (floating windows); the watcher starts if **either** is on. → [architecture-invariants#ultracode--workflow-run-visualization](docs/architecture-invariants.md#ultracode-and-workflow-run-visualization)
 
diff --git a/docs/architecture-invariants.md b/docs/architecture-invariants.md
index 383bc138..0cf43de7 100644
--- a/docs/architecture-invariants.md
+++ b/docs/architecture-invariants.md
@@ -658,7 +658,7 @@ Matching semantics: a query containing `/` matches the relative path, otherwise
 
 ### Raw file bodies: streamed and range-aware
 
-**Raw file bodies are streamed and range-aware**: `file-raw`, the attachments `/raw` route and `GET /api/download` always advertise `Accept-Ranges: bytes` and answer a `Range` header with `206` + `Content-Range` (single-range only; parser is pure + unit-tested in `src/web/http-range.ts`, a malformed spec is ignored → 200 while an out-of-bounds one is a 416).
+**Raw file bodies are streamed and range-aware**: `file-raw`, the attachments `/raw` route, `GET /api/download` and the rendered-HTML route `GET /html-view/<cap>/...` (so a rendered page's own `<video>`/`<audio>` can seek) always advertise `Accept-Ranges: bytes` and answer a `Range` header with `206` + `Content-Range` (single-range only; parser is pure + unit-tested in `src/web/http-range.ts`, a malformed spec is ignored → 200 while an out-of-bounds one is a 416).
 
 ⚠️ **The size cap on all three is a sanity bound, not memory protection** (`MAX_FILE_DOWNLOAD_BYTES` in `config/buffer-limits.ts`, default 2GB, env `CODEMAN_MAX_DOWNLOAD_BYTES`, `0` = unlimited): the bodies stream, so size costs a read stream and not RSS (measured: a 600MB download moved peak RSS by ~37MB). Its predecessor was a hardcoded 50MB whose comment still said "prevent memory exhaustion" long after the `readFile()` it described was replaced by `sendFileBody()`, so all it did was refuse legitimate downloads of build artifacts, videos and archives. `/api/download` was the last route that really did buffer the whole file, and now shares `sendFileBody()` with the other two.
 
diff --git a/src/web/routes/file-routes.ts b/src/web/routes/file-routes.ts
index e9549b3d..0474270f 100644
--- a/src/web/routes/file-routes.ts
+++ b/src/web/routes/file-routes.ts
@@ -200,8 +200,8 @@ interface FileBodySource {
   cleanup?: () => void;
 }
 
-/** Byte source for a LOCAL file (the historical, only path). */
-function localFileSource(resolvedPath: string) {
+/** Byte source for a LOCAL file (the historical, only path). Shared with html-view-routes.ts. */
+export function localFileSource(resolvedPath: string) {
   return (range?: { start: number; end: number }): FileBodySource => ({
     content: createReadStream(resolvedPath, range ? { start: range.start, end: range.end } : undefined),
   });
@@ -221,8 +221,11 @@ function localFileSource(resolvedPath: string) {
  * `open` supplies the bytes for the (optional) range, which is what lets a remote
  * case reuse this instead of re-implementing the 206/416 contract: same headers,
  * same status codes, whether the file sits on this host or behind an ssh pipe.
+ *
+ * Exported for the rendered-HTML route (html-view-routes.ts), so a page's own
+ * `<video>`/`<audio>` can seek as well.
  */
-function sendFileBody(
+export function sendFileBody(
   reply: FastifyReply,
   size: number,
   rangeHeader: string | string[] | undefined,
diff --git a/src/web/routes/html-view-routes.ts b/src/web/routes/html-view-routes.ts
index d440c00d..6fa90df3 100644
--- a/src/web/routes/html-view-routes.ts
+++ b/src/web/routes/html-view-routes.ts
@@ -25,7 +25,7 @@
  */
 
 import type { FastifyInstance } from 'fastify';
-import { createReadStream, realpathSync } from 'node:fs';
+import { realpathSync } from 'node:fs';
 import fs from 'node:fs/promises';
 import { homedir, tmpdir } from 'node:os';
 import { basename, dirname, extname, isAbsolute, relative, resolve, sep } from 'node:path';
@@ -34,6 +34,7 @@ import { isBlockedAttachmentPath, isUnderTree, loadAttachmentGuardConfig } from
 import { HTML_VIEW_PREFIX, htmlViewCapabilities } from '../../html-view-capabilities.js';
 import { CASES_DIR, findSessionOrFail, ownerFor, parseBody, validateSessionFilePath } from '../route-helpers.js';
 import { HtmlViewOpenSchema } from '../schemas.js';
+import { localFileSource, sendFileBody } from './file-routes.js';
 import { getUserSpacesDir } from '../../config/multiuser.js';
 import { exceedsDownloadLimit } from '../../config/buffer-limits.js';
 import type { SessionPort } from '../ports/index.js';
@@ -254,7 +255,6 @@ export function registerHtmlViewRoutes(app: FastifyInstance, ctx: SessionPort):
 
     reply.header('Content-Security-Policy', SANDBOX_CSP);
     reply.header('Content-Type', contentType);
-    reply.header('Content-Length', String(stat.size));
     reply.header('Cache-Control', 'no-store');
     reply.header('Referrer-Policy', 'no-referrer');
     // The sandboxed page is opaque-origin, so even its fetch() of a sibling
@@ -262,6 +262,10 @@ export function registerHtmlViewRoutes(app: FastifyInstance, ctx: SessionPort):
     // enough, and widens nothing: these bytes are already readable by anyone
     // holding the capability URL.
     reply.header('Access-Control-Allow-Origin', '*');
-    return reply.send(createReadStream(resolvedPath));
+    // The file routes' body sender: Content-Length, and `Range` answered with 206
+    // (or 416), so a page's own <video>/<audio> can seek. It hijacks the reply, and
+    // carries every header set above across to it.
+    sendFileBody(reply, stat.size, req.headers.range, localFileSource(resolvedPath));
+    return reply;
   });
 }
diff --git a/test/routes/html-view-routes.test.ts b/test/routes/html-view-routes.test.ts
index a8671c75..87050f19 100644
--- a/test/routes/html-view-routes.test.ts
+++ b/test/routes/html-view-routes.test.ts
@@ -94,6 +94,28 @@ describe('html-view routes', () => {
     expect(res.body).toBe('<h1>hi</h1>');
   });
 
+  it('answers Range requests, so a page can seek its own media', async () => {
+    writeFileSync(join(workspace, 'clip.mp4'), '0123456789');
+    const base = (await openUrl()).replace(/index\.html$/, '');
+    const full = await harness.app.inject({ method: 'GET', url: `${base}clip.mp4` });
+    expect(full.statusCode).toBe(200);
+    expect(full.headers['accept-ranges']).toBe('bytes');
+    expect(full.headers['content-length']).toBe('10');
+
+    const part = await harness.app.inject({ method: 'GET', url: `${base}clip.mp4`, headers: { range: 'bytes=2-5' } });
+    expect(part.statusCode).toBe(206);
+    expect(part.headers['content-range']).toBe('bytes 2-5/10');
+    expect(part.body).toBe('2345');
+    // Every header the route sets survives the hijacked body sender.
+    expect(part.headers['content-type']).toBe('video/mp4');
+    expect(String(part.headers['content-security-policy'])).toMatch(/^sandbox /);
+    expect(part.headers['access-control-allow-origin']).toBe('*');
+    expect(part.headers['cache-control']).toBe('no-store');
+
+    const beyond = await harness.app.inject({ method: 'GET', url: `${base}clip.mp4`, headers: { range: 'bytes=50-' } });
+    expect(beyond.statusCode).toBe(416);
+  });
+
   it('serves sibling assets, including subdirectories', async () => {
     const base = (await openUrl()).replace(/index\.html$/, '');
     expect((await harness.app.inject({ method: 'GET', url: `${base}assets/app.css` })).statusCode).toBe(200);