har-derived-api-client

# HAR-Derived API Client Drive a website once with a real browser while recording its network traffic to a HAR file, then distill that HAR into the site's private JSON API so you can call it directly with plain HTTP — far cheaper and faster than browser-controlling the page on every request. Credit: trick by Jared Longster, popularized by Dax (thdxr). This captures and replays; it does NOT bypass auth, solve CAPTCHAs, or defeat bot-detection — if the site needs a logged-in session, you carry its headers/cookies forward, you don't forge them. The scripts are stdlib-plus-Playwright: capture needs Playwright, derivation is pure stdlib, replay needs only `requests`/`httpx` (or `curl`). Covers **every Hermes browser pathway**: the default local `browser_navigate` backend, plus the cloud/remote backends (Browserbase, Browser-Use, Firecrawl) and any `/browser connect` CDP endpoint. There are two capture scripts — one for a browser you launch, one for a browser you attach to over CDP — because HAR recording works differently in each case (see How to Run). ## When to Use - "Build a CLI/client for <website>" — derive its API instead of scripting clicks. - "This site has no public API but the page clearly fetches JSON." - You're about to loop `browser_navigate` for the same query repeatedly — stop and derive the endpoint once. - Reverse-engineering an autocomplete, search, feed, or checkout XHR. - You captured a session on a cloud backend (Browserbase / Browser-Use / Firecrawl) or via `/browser connect` and want the API without re-renting the browser. ## Prerequisites - Playwright + a browser binary (capture step only): - `pip install playwright` then `playwright install chromium` - (If a system Playwright already has browsers under `~/.cache/ms-playwright`, reuse it.) - `requests` or `httpx` for the replay step (stdlib `urllib` also works). - No API keys. Any keys/tokens the client needs are the ones the HAR captured. - For the CDP path (`har_capture_cdp.py`): a reachable CDP endpoint. On Hermes, run `/browser connect` to print the active endpoint, or read `BROWSER_CDP_URL` / `browser.cdp_url` in config. Cloud backends expose it as `cdpUrl`/`connectUrl`. ## How to Run Scripts under this skill's `scripts/`, invoked through the `terminal` tool. **Pick the capturer by pathway** — this is the part that trips people up: | Browser pathway | How Hermes reaches it | Capturer | |---|---|---| | Local `browser_navigate` (default, agent-browser/Playwright) | launched locally | `har_capture.py` | | Camofox (`CAMOFOX_URL` set) | local REST/CDP | `har_capture_cdp.py` if it exposes CDP, else drive it yourself | | Browserbase / Browser-Use / Firecrawl (cloud) | **CDP** (`cdpUrl`) | `har_capture_cdp.py` | | `/browser connect <url>` / `BROWSER_CDP_URL` | **CDP** | `har_capture_cdp.py` | Rule of thumb: **if Hermes *launched* the browser, use `har_capture.py`; if it *connected to* one over CDP, use `har_capture_cdp.py`.** `har_capture.py` uses Playwright's `record_har_path`, which only works on a locally-owned context. `har_capture_cdp.py` attaches with `connect_over_cdp()` and assembles the HAR from `page.on("request"/"response")` events, because `record_har_path` is unavailable on a connected browser. Then, for either path: - `har_to_client.py` — filters the HAR to XHR/fetch/JSON, groups by endpoint, and prints params, headers, bodies, and replay hints (User-Agent / cookie / auth). Resolve paths against this skill's directory. Canonical loop: ```bash # 1a. Capture, LOCAL browser (Hermes launched it) python3 scripts/har_capture.py "https://SITE/" out.har \ --action "fill:input[name=search]:my query" --action "sleep:3" --wait 2 # 1b. Capture, CDP browser (cloud backend or /browser connect) # get the endpoint from /browser connect or BROWSER_CDP_URL python3 scripts/har_capture_cdp.py "ws://HOST/devtools/browser/..." out.har \ --goto "https://SITE/" --action "fill:input[name=search]:my query" \ --action "sleep:3" --wait 2 # 2. Derive — read the endpoints out of the HAR python3 scripts/har_to_client.py out.har --host SITE --max-body 400 # 3. Replay — write a tiny client from the printed endpoint (see Procedure) ``` ## Quick Reference ``` har_capture.py <url> <out.har> [--wait S] [--headed] [--action SPEC ...] action SPEC: fill:SELECTOR:TEXT | press:SELECTOR:KEY | click:SELECTOR goto:URL | sleep:SECONDS (run in order after page load) use when Hermes LAUNCHED the browser (local browser_navigate default) har_capture_cdp.py <cdp_url> <out.har> [--goto URL] [--wait S] [--action SPEC ...] same action SPEC; attaches to an existing CDP browser and does NOT close it use for cloud backends (Browserbase/Browser-Use/Firecrawl) & /browser connect har_to_client.py <in.har> [--host SUBSTR] [--include-static] [--max-body N] default: keeps only XHR/fetch/JSON; --host narrows to one domain prints per endpoint: query params, non-boring req headers, req body sample, response status/content-type + body sample prints "### Replay hints": the browser User-Agent, cookie/auth presence ``` ## Procedure 0. **Pick the capturer by pathway** (see How to Run table). Launched-locally → `har_capture.py`; reached over CDP → `har_capture_cdp.py`. On Hermes, `/browser connect` tells you the CDP endpoint when a cloud/remote backend is active. 1. **Find the interaction.** Open the site with `browser_navigate` (or `--headed` capture) to see which selector to type into / click, and confirm a JSON XHR fires in devtools/network. 2. **Capture the HAR** via the `terminal` tool. Order `--action` to reach the request: `fill` the box, then `sleep` long enough for the debounced XHR, and always leave `--wait` at the end so late responses flush. Both capturers embed response bodies, so the derived client sees real payload shapes. 3. **Derive** with `har_to_client.py --host <domain>`. Read off: the method, the URL/path template (numeric/UUID segments collapse to `{id}`), query params, request-body JSON, and the `### Replay hints` block. 4. **Write the client.** Recreate the request exactly — same method, path, query params, body. Send the headers the site actually needs: at minimum copy the **User-Agent** from the replay hints. If hints report cookies or an auth/token header, resend those too. 5. **Test browserless.** Run the client with the `terminal` tool and confirm it returns the same data the browser saw. This is the payoff: no browser in the loop. 6. **(Optional) Wrap as a CLI** — a small `argparse` script over the derived call, e.g. `search.py "frank herbert"`. Worked example (Wikipedia search-title, derived + replayed live): ```python import requests r = requests.get( "https://en.wikipedia.org/w/rest.php/v1/search/title", params={"q": "frank herbert", "limit": 5}, headers={"accept": "application/json", "User-Agent": "Mozilla/5.0 ... Chrome/131 Safari/537.36"}, # from HAR timeout=15, ) for p in r.json()["pages"]: print(p["title"], "-", p.get("description")) ``` ## Pitfalls - **Default library User-Agent gets 403.** Many sites (Wikipedia, Cloudflare-fronted APIs) reject `python-requests/x.y`. Always send the browser UA from the replay hints. This is the #1 reason a derived client fails when the browser succeeded. - **A failed `--action` aborts before the HAR flushes** — you get no file. If capture errors on a selector, the run produced nothing; fix the selector (use `--headed` to watch) and rerun. Don't debug a missing HAR. - **Server-rendered pages have no XHR** to derive — `har_to_client.py` prints "No API-looking entries". The data came in the HTML; scrape it or find the interaction that does fetch JSON. - **Debounced/typeahead XHRs need a real pause.** Add `--action "sleep:3"` after `fill`; typing alone won't have fired the request when the HAR closes. - **Auth/session endpoints** need the captured `Cookie`/`Authorization` header, and those expire. The derived client is only as durable as the credential; re-capture when it 401s. HARs contain live secrets — treat `out.har` as sensitive and delete it after deriving. - **`record_har_content="embed"` makes big HARs.** Use `--max-body` to cap what's printed; the file itself can be large for media-heavy pages. - **Endpoints shift.** Sites change private APIs without notice. Re-run the capture→derive loop when a client breaks rather than patching URLs by hand. - **Wrong capturer = empty/no HAR.** `har_capture.py` on a cloud/CDP backend records nothing (it launches its own local browser instead of the one you meant). `har_capture_cdp.py` needs the endpoint; on Hermes get it from `/browser connect` or `BROWSER_CDP_URL`. Match the capturer to the pathway (How to Run table). - **Headless-Chrome UA is a weak tell.** Local/agent-browser capture yields a `HeadlessChrome/...` User-Agent; some sites sniff the "Headless" token. Cloud backends (Browserbase/Browser-Use) send a real desktop-Chrome UA, so a client derived from a cloud capture replays more reliably. If a headless-derived client 403s where the browser didn't, swap the "Headless" UA for a normal Chrome UA string before assuming the endpoint changed. - **CDP capture doesn't close the browser.** `har_capture_cdp.py` attaches to a browser it doesn't own and leaves it running — correct for cloud/remote sessions Hermes manages. Don't add a close; let the owning backend tear it down. ## Verification End-to-end proof against a live site with no API key: ```bash python3 scripts/har_capture.py "https://en.wikipedia.org/wiki/Main_Page" ~/.hermes/cache/scratch/wiki.har \ --action "fill:input[name=search]:dune messiah" --action "sleep:3" --wait 2 python3 scripts/har_to_client.py ~/.hermes/cache/scratch/wiki.har --host wikipedia.org --max-body 200 ``` Expect the derivation to print `GET https://en.wikipedia.org/w/rest.php/v1/search/title` with `q` and `limit` params and a JSON `pages` response — then replay it with the Procedure snippet and confirm matching titles come back over plain HTTP.