feat(http): add SSR overrides and time until the app is stable

[santoshyadavdev]

What and why

This finishes what's left of #32, after #240 and #241: Phase 2 (intervene) and the last Phase 1 item (time until the page is interactive).

SSR overrides. These are dev-only and set from a new SSR overrides section in the SSR & HTTP tab. They're stored in the devframe server's memory (ssrRegistry().overrides), cleared on restart, and written only through set-ssr-overrides, which is gated by actions.http and listed in RPC_INSPECTOR.

Override	How it works	Needs
Render error	providePangularHttp() throws in an environment initializer during a traced server render of a matching page, so the server's real error path runs (in the demo, Express's 500 page).	providePangularHttp() and a page the engine renders
Force Client render	ssrMiddleware serves index.csr.html instead of calling next(), as RenderMode.Client would.	browserDistFolder, a new initPangularHub() option
Edit TransferState	ssrMiddleware holds back the HTML of a matching page and sets or removes one entry of the {appId}-state script before sending it. The JSON is escaped the way Angular's TransferState.toJson() does (< and /), so a value can't close the script tag.	A page with a TransferState script

• Each traced request lists the overrides that matched and what they did, under Overrides from the panel.
• Such requests are marked overridden in the table, and explain-ssr-request says the response was changed on purpose.
• Overriding a server HttpClient response and simulating API errors or timeouts were already covered by fault rules on SSR only, so this PR doesn't add them again.

Time until stable. providePangularHttp() records when ApplicationRef.whenStable() first resolves in the browser, measured from navigation start. The Hydration section shows it as App stable after, and explain-ssr-request includes it.

Not done: forcing the Prerender fallback mode. The engine reads render modes from the route tree inside the user's server bundle. The devtools can't change it without patching that bundle's copy of @angular/ssr, so the docs say so.

Refs #32

How it was verified

• pnpm commit:check
• pnpm format:check
• pnpm typecheck
• pnpm test:devtools (1402) and pnpm test:panel (164)
  • New ssr-overrides.test.ts covers sanitizing, glob matching, the escaped TransferState edit, forced Client mode with and without the shell, a page with no TransferState, the render error, time until stable, the actions.http gate and the tool output.
  • New network-ssr-overrides.test.ts covers the panel form and the overridden tag.
• pnpm docs:build passes
• pnpm extension:build and extension/ui committed
• pnpm test:axe passes on every view
• Manual, against the SSR build, adding overrides through the real panel form:
  • Render error on /examples/ssr/product/3: 500 from Express, shown as Not rendered and overridden, with "Render error: applied, database is down".
  • Force Client render on /destinations: 200 with x-pangular-override: client-render, the index.csr.html shell, shown as Client.
  • Edit TransferState of the /api/products entry on /examples/ssr: the hydrated page showed "1 products", read from the edited entry, instead of 4.
  • App stable after: 171 ms.

Notes for reviewers

• A state edit holds back only the responses of pages that match an override. All other responses still stream.
• Overrides apply from the next full page load, which the panel says each time it saves one.

Summary by CodeRabbit

• New Features
  • Added development-only SSR overrides to trigger render errors, force client rendering, and edit or remove TransferState entries. Manage overrides in the Network Inspector and see whether they were applied.
  • Added app stability timing to hydration details when available.
• Documentation
  • Documented SSR overrides, their requirements, and app stability timing.

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📒 Files selected for processing (3)

• packages/devtools/src/__tests__/ssr-overrides.test.ts
• packages/devtools/src/ssr-middleware.ts
• packages/devtools/src/ssr-overrides.ts

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🚧 Files skipped from review as they are similar to previous changes (2)

• packages/devtools/src/ssr-middleware.ts
• packages/devtools/src/ssr-overrides.ts

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📝 Walkthrough

Walkthrough

This change adds development-only SSR overrides for render errors, client rendering, and TransferState edits. It adds override controls and request-level results to the HTTP inspector. It also reports browser app stability timing in hydration statistics.

Changes

SSR overrides and hydration timing

Layer / File(s)	Summary
Override data and matching rules packages/devtools/src/ssr-overrides.ts, packages/devtools/src/ssr-registry.ts, packages/devtools/src/types.ts, packages/devtools/src/__tests__/ssr-overrides.test.ts	Adds override types, input sanitization, URL matching, TransferState editing, and applied-override records. Tests cover sanitization, matching, and state edits.
SSR request override handling packages/devtools/src/ssr-middleware.ts, packages/devtools/src/http.ts, packages/devtools/src/hub.ts, packages/devtools/src/rpc/ssr-tools.ts, src/server.ts, packages/devtools/src/__tests__/ssr-overrides.test.ts	Applies matching overrides to SSR requests, serves index.csr.html for client-render overrides when available, and includes override results in request explanations.
Override RPC and inspector controls packages/devtools/src/devframe.ts, packages/devtools/src/config.ts, app/src/pages/network-inspector.ts, app/src/__tests__/network-ssr-overrides.test.ts, apps/docs/src/content/inspectors/ssr-http.md, apps/docs/src/content/getting-started/*, extension/ui/*	Adds the HTTP RPC and inspector controls to configure overrides. The inspector displays override results for requests, and documentation describes override settings and prerequisites.
Browser stability timing packages/devtools/src/http.ts, packages/devtools/src/http-rules.ts, packages/devtools/src/http-overlay.ts, packages/devtools/src/http-payload.ts, packages/devtools/src/rpc/ssr-tools.ts, app/src/pages/network-inspector.ts, packages/devtools/src/__tests__/ssr-overrides.test.ts, apps/docs/src/content/inspectors/ssr-http.md	Records time until the browser app first becomes stable and adds the optional value to hydration reports and the inspector. Documentation describes the timing and provider requirement.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~45 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant NetworkInspector
  participant devframe
  participant SSRRegistry
  participant ssrMiddleware
  participant BrowserShell
  NetworkInspector->>devframe: send set-ssr-overrides
  devframe->>SSRRegistry: store sanitized overrides
  ssrMiddleware->>SSRRegistry: match overrides for request
  alt client-render shell is available
    ssrMiddleware->>BrowserShell: read index.csr.html
    BrowserShell-->>ssrMiddleware: return HTML shell
  else TransferState edit matches
    ssrMiddleware->>ssrMiddleware: edit buffered HTML response
  end

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Merge Risk: ⚪ Minimal · up to 5d210

This adds dev-only SSR overrides and app-stable timing. Earlier review concerns were addressed, and no outstanding merge-blocking risk is evident.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 71874

Existing access and action controls constrain who can configure overrides. However, client-render and state-edit overrides are not automatically disabled by a production Angular build if the developer tools remain mounted. Buffered state edits can also conflict with response headers already sent.

Retained concerns

• Medium · security · observed: The new client-render and TransferState response mutations are described as development-only, but their middleware execution does not check development mode. If the hub and SSR middleware remain mounted with a production build, an HTTP-action RPC caller can configure mutations affecting matching visitors. Production hub mounting already existed, but this PR adds response-mutating authority outside the existing Angular development-mode enforcement.
• Medium · reliability · inferred: TransferState buffering rewrites the response body but recalculates Content-Length only before headers are sent. A downstream SSR consumer that commits an original length first can therefore produce mismatched HTTP framing after a length-changing edit, compromising response integrity and failure containment. The normal unsent-header path is handled correctly; precise effects on clients or intermediaries were not verified.

Security review details

Security Blast Radius

• inferred — An HTTP-action RPC caller can configure a wildcard override affecting every eligible matching HTML request handled by the process registry, not just that caller's browser session. Exposure is bounded by installed middleware/provider capabilities and connection access; actual tenant, environment, and network reach were not established.

Security Findings and Attack Paths

• inferred — If developer tools remain mounted in production, a caller admitted to the HTTP action RPC can replace TransferState consumed by visitors or force the client shell before downstream handlers execute. The new response sinks make this consequential even when Angular's existing HTTP fault interceptor is disabled. An unrestricted remote attack or transport authorization bypass was not demonstrated.

Trust Boundaries and Controls

• observed — The RPC is assigned to the HTTP inspector, filtered during registration, and independently checks actions.http before mutation. Render-error additionally requires development mode, server platform, and an active request identity. Hub origin and MCP token configuration remain in the existing connection setup; their external enforcement implementation was not inspected.

Resilience and Maintainability Implications

• inferred — Request-local cleanup limits cross-request state leakage, but successful buffering depends on coordination with the downstream response writer. Once headers are committed, a length-changing edit cannot be made safe merely by skipping header updates; this leaves an unresolved response-containment failure state.

Hardening Proposals

• proposed — Enforce an explicit server-side development-only precondition for response overrides, rather than relying solely on production callers omitting the hub. Coordinate body rewriting with header commitment, or decline edits when committed framing cannot remain valid.

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Pre-merge checks | 4 | 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 27 functions across 17 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely summarizes the two main changes: SSR overrides and tracking the time until the app becomes stable.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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Actionable comments posted: 3

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🤖 Prompt to fix review comments

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Inline comments:
Review comments at @packages/devtools/src/ssr-middleware.ts:
- Around line 185-187: Update the note-generation conditional in the edit loop
so a failed removal retains the “no entry” note, while a failed set reports that
the TransferState script could not be edited for the key. Preserve the existing
successful-edit notes and the behavior for responses without a TransferState
script.
- Around line 190-199: Update the response buffering flow around the
middleware’s write and end overrides to defer res.flushHeaders() while state
edits are being buffered, then restore the original flushHeaders behavior before
sending the edited response.

Review comments at @packages/devtools/src/ssr-overrides.ts:
- Around line 111-114: Update the assignment in the TransferState edit logic so
keys such as `__proto__` become enumerable own properties rather than changing
the state object's prototype. Preserve the parsed value and ensure the property
is included by `JSON.stringify`, keeping the existing applied-key behavior.

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📥 Commits

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⛔ Files ignored due to path filters (1)

• extension/ui/assets/index-BEfrZ0QX.js is excluded by !**/assets/index-[0-9a-z_-][0-9a-z_-][0-9a-z_-][0-9a-z_-][0-9a-z_-][0-9a-z_-][0-9a-z_-][0-9a-z_-].js

📒 Files selected for processing (21)

• app/src/__tests__/network-ssr-overrides.test.ts
• app/src/pages/network-inspector.ts
• apps/docs/src/content/getting-started/configuration.md
• apps/docs/src/content/getting-started/express.md
• apps/docs/src/content/inspectors/ssr-http.md
• extension/ui/assets/browser-agent-rpc-BXhoSh1z-C_twCiPD.js
• extension/ui/index.html
• packages/devtools/src/__tests__/ssr-overrides.test.ts
• packages/devtools/src/config.ts
• packages/devtools/src/devframe.ts
• packages/devtools/src/http-overlay.ts
• packages/devtools/src/http-payload.ts
• packages/devtools/src/http-rules.ts
• packages/devtools/src/http.ts
• packages/devtools/src/hub.ts
• packages/devtools/src/rpc/ssr-tools.ts
• packages/devtools/src/ssr-middleware.ts
• packages/devtools/src/ssr-overrides.ts
• packages/devtools/src/ssr-registry.ts
• packages/devtools/src/types.ts
• src/server.ts

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